SHORT CELL MULTIPLEXED ATM TRANSMISSION SYSTEM AND TRANSMISSION METHOD

SYSTEME ET METHODE DE TRANSMISSION MTA MULTIPLEXEE A CELLULES DE COURTE DUREE

English Abstract

A short cell multiplexing is provided for chiefly transmitting data shorter than the payload of a standard ATM cell (basically the data of less than 48 bytes, but the data more than 48 bytes can be allowed). A standard ATM cell assembler 1 converts various forms of input information into short cells, places the short cells in standard ATM cells efficiently considering their information length, and output them to a B/ISDN network 7. The standard ATM cell disassembler 2 disassembles the standard ATM cells, which are assembled by the standard ATM cell assembler 1 and is input through the B-ISDN network 7, into short cells, converts the short cells into those with the original input information forms, and outputs them to channels. The configuration makes it possible for the short cell ATM cell multiplexing to improve channel efficiency with small delay, and matching to the standard ATM system.

French Abstract

Un multiplexage des cellules courtes est fourni principalement pour la transmission de données plus courtes que la charge d'une cellule ATM standard (principalement des données de moins de 48 octets, mais les données de plus de 48 octets peuvent être autorisées). Un assembleur de cellules ATM standard 1 convertit différentes formes d'information d'entrée en cellules courtes, place ces cellules courtes dans des cellules ATM standard de manière efficace, en tenant compte de la longueur de l'information et les envoie en sortie dans un réseau B/ISDN 7. Le désassembleur de cellules ATM standard 2 sépare les cellules ATM standard, qui ont été assemblées par l'assembleur 1 puis envoyées dans le réseau B-ISDN 7, les transforme en cellules courtes, convertit les cellules courtes en cellules ayant la forme d'information d'origine puis les envoie en sortie dans des canaux. La configuration permet au multiplexage des cellules ATM courtes d'améliorer l'efficacité des canaux tout en garantissant un délai très court, en conformité avec le système ATM standard.

Claims

WHAT IS CLAIMED IS:
1. A standard ATM cell assembler comprising:
means for forming short cells from various types of
input data; and
means for multiplexing the short cells in standard
ATM cells,
wherein said means for multiplexing can divide one
short cell into two or more partial short cells, and
store the two or more partial short cells in two or more
standard ATM cells.
2. A standard ATM cell disassembler comprising:
means for receiving standard ATM cells in which
short cells are multiplexed;
means for disassembling the standard ATM cells into
the short cells; and
means for converting the short cells into output
data,
wherein said means for disassembling can generate
one short cell from two or more partial short cells stored
in two or more standard ATM cells.
3. A short cell multiplexing ATM transmission method
comprising the steps of:
forming short cells from various types of input
data;
multiplexing the short cells in standard ATM cells;
transmitting the standard ATM cells;
receiving the standard ATM cells;
disassembling the standard ATM cells into short
cells; and


converting the short cells obtained by the
disassembling step into output data,
wherein said step of multiplexing can divide one
short cell into two or more partial short cells, and
store the two or more partial short cells in two or more
standard ATM cells, and
said step of disassembling can generate one short
cell from two or more partial short cells stored in two or
more standard ATM cells.
4. A standard ATM cell assembler/disassembler
comprising the standard ATM cell assembler as claimed in
claim 1, and the standard ATM cell disassembler as
claimed in claim 2.
5. The standard ATM cell assembler/disassembler as
claimed in claim 4, wherein said short cell accommodates
multiplexed sub-short cells.
6. A short cell multiplexing ATM transmission system,
in which the standard ATM cell assembler as claimed in
claim 1 is linked with the standard ATM cell disassembler
as claimed in claim 2 via a standard ATM cell switching
network.
7. The short cell multiplexing ATM transmission system
as claimed in claim 6, wherein said short cell
accommodates multiplexed sub-short cells.

Description

CA 02489644 1996-10-11
SPECIFICATION
TITLE OF THE INVENTION
SHORT CELL MULTIPLEXED ATM TRANSMISSION SYSTEM AND
TRANSMISSION METHOD
TECHNICAL FIELD
The present invention relates to ATM
transmission, and particularly to a short cell
multiplexing for transmitting, over an ATM network,
data shorter than the payload of a standard ATM cell
(basically less than 48 bytes, but more than 48
bytes can be allowed) which is transmitted through a
network such as an ATM network, private short cell
network, STM (Synchronous Transport Module) network,
radio, packet network, or FR (Frame Relay) network.
BACKGROUND ART
Forming ATM cells from low bit rate. highly real
time information like voice will cause a large delay
time if the information is stored fully in the
payload of the standard ATM cell, resulting in the
degradation in the information. To prevent this, a
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CA 02489644 1996-10-11
partial fill method is proposed which loads the
information partially (into part of the ATM cell) to
be transmitted.
On the other hand, in a local environment like
premises, a short cell using a payload shorter than
the 48-byte payload of the standard ATM cell is
proposed, which is expected to match better to the
low bit rate data.
Figs. 30A and 30B illustrate the partial fill
method and short cell method.
In the partial fill method as shown in Fig. 30A,
a partial fill cell assembler 12 forms a standard
ATM cell by adding dummy data to input data, and
outputs it to a B-ISDN network. A partial fill cell
disassembles 13 extracts the data from the partial
fill cell received from the B-ISDN network, and
outputs it.
In the short cell method as shown in Fig. 30B, a
short cell assembler 14 forms from input data a
short cell matching to an intended data length, and
outputs it to an exclusive network having a unique
cell slot structure. A short cell disassembles 15
extracts the data from the short cell received from
the exclusive network, and outputs it.
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CA 02489644 1996-10-11
DISCLOSURE OF THE INVENTION
The partial fill method described as the
conventional techniques has a problem in that it
impairs efficiency of utilizing the payload of the
standard ATM cell and hence the transmission
efficiency accompanying that because it uses only
part of the payload of the standard ATM cell.
The short cell method, on the other hand,
requires the exclusive network with a unique cell
slot structure, which causes a problem of bad
matching with the standard ATM switching network (B-
ISDN network).
In view of these, a short cell multiplex
transmission method is proposed which multiplexes
information from multiple users to a single ATM cell
(ISS' 95 Nakajima). This method multiplexes short
packets received from different users within a
predetermined time period into the payload of an ATM
cell. This has advantages of limiting the delay
below a certain fixed amount, thereby improving the
efficiency.
In connection with the transmission method, a
Shinagawa patent is disclosed. Besides, a Mita
patent application has been filed which increases
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CA 02489644 1996-10-11
the degree of freedom in combining the users to be
multiplexed.
In handling variable length user data, the
following two methods can be considered: A first
method fills the variable length user data into a
predetermined fixed length short cell and fills
dummy information into the remainder of the cell;
and a second method forms variable length short
cells in accordance with the user data, thereby
multiplexing/demultiplexing them into or from the
ATM cell. Although the second method is superior to
the first method in efficiency, it requires a
technique to decide the length of the variable short
cells which vary for each ATM cell to extract them.
The second method has another problem in that its
payload efficiency is somewhat impaired as compared
with the method which transmits the payload after
filling it completely, because the second method, if
higher transmission efficiency is required,
transmits the ATM payload after loading it with the
dummy information when its occupation ratio reaches
to a certain level and no new short cell can be
expected to be multiplexed into the ATM cell. Thus,
a cell overlapping technique is effective which
allows a variable length short cell to undergo
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CA 02489644 1996-10-11
multiplexing/demultiplexing across more than one ATM
cell (Docomo, ATM-F).
In connection with one of the technique of
multiplexing/demultiplexing variable short cells
into or from one or more ATM cells, ATT filed a
letter to ITU. According to the ATT letter, each
short cell is provided with length information and
user identifier (LLN: logical link number) to
implement the extraction of variable length short
cells. The first half of a short cell extending
over two ATM cells is provided with the length
information indicating the entire length of the
short cell, and the second half multiplexed at the
initial position of the next ATM cell is provided
with the length information indicating only the
length of the latter part of the short cell. A
receiving end, when the length information of the
short cell exceeds the end of the payload of the ATM
cell, decides that it continues to the next ATM
cell, and combines the first half and second half of
the short cell overlapping the two ATM cell when the
length of the remainder of the short cell equals the
length indicated by the length information of the
latter half multiplexed into the initial position of
the next received ATM cell.
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CA 02489644 1996-10-11
This method, however, has the following two
problems if the synchronization for the extraction
processing of the short cell is lost owing to the
loss of the ATM cell during its transmission.
First, if the length information of the second half
of the short cell multiplexed into the initial
position of the ATM cell received after the cell
loss disagrees with the length of the remainder
expected from the previously received first half of
the overlapping short cell, it is impossible to
decide whether or not the short cell multiplexed at
the initial position of the next received ATM cell
is a complete short cell or the continued short cell
from the lost ATM cell, even though the cell loss
can be detected (problem 1). Second, in spite of
the cell loss, if the expected length of the
remainder happens to agree with the length
information of the latter half of the short cell
multiplexed into the initial position of the ATM
cell received after the cell loss, not only the cell
loss is undetected, but also erroneous short cells
are combined (problem 2).
The present invention features the following
three aspects in connection with the variable short
cell multiplexed transmission system and method.
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CA 02489644 1996-10-11
(1) A multiplex transmission method providing
each short cell with information for multiplexing
and demultiplexing (embodiment 1).
(2) A multiplex transmission method providing
each ATM cell collectively with information for
multiplexing and demultiplexing (embodiment 2).
(3) A multiplex transmission method providing
no information for multiplexing and demultiplexing
(embodiment 3).
Although the item (1) has a similar
characteristic to that of the ATT letter in that
multiplexing and demultiplexing is carried out by
providing each short cell with the length
information, it solves the problem 1 of the ATT
letter by deciding the cell overlapping not by the
length information but by proving short cell status
information. Furthermore, it can add control
information on the ATM transmission to the
multiplexed data of the short cells to achieve more
reliable detection of the cell loss for each ATM
cell as an option to solve the problem 2.
The foregoing items (2) and (3) relate to novel
short cell multiplex transmission methods which have
not yet been disclosed.


CA 02489644 1996-10-11
According to the first aspect of the present
invention, a short cell multiplexing ATM
transmission system comprises:
a standard ATM cell assembler (1) for forming
short cells from various types of input information,
and for multiplexing the short cells to be placed in
a payload of one or more standard ATM cells to be
output to an ATM switching network;
an ATM switching network (7) for transmitting
the standard ATM cells; and
a standard ATM cell disassembler (2) for
receiving a short cell multiplexed ATM cell, and for
disassembling the short cell multiplexed ATM cell
into short cells which are converted into an output
data format of a channel and output to the channel.
According to the second aspect of the present
invention, a standard ATM cell assembler comprises:
a data receiver/short cell assembler (3) for
receiving various types of input information such as
private short cells, ATM cells, STM frames,
information packets of a frame relay or a packet
network, TDMA/FDMA radio frames, and CDMA radio
packets, and for forming short cells for each type
of the information;
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CA 02489644 1996-10-11
a short cell multiplexer (4) for multiplexing
short cells onto a payload of one or more standard
ATM cells;
a standard ATM cell generator (5) for receiving
multiplexed data as a standard ATM payload, and for
forming a standard ATM cell by adding an AAL and a
header; and
an ATM cell transmitter (6) for outputting the
standard ATM cell to an ATM switching network.
In the standard ATM cell assembler (1), the
standard ATM cell generator (5) may form the
standard ATM cell by inputting data other than the
multiplexed data fed from the short cell multiplexer
(4) .
In the standard ATM cell assembler (1), the data
receiver/short cell assembler (3) may comprise:
a data receiving portion (3-1) for receiving
various types of data such as private short cells,
ATM cells, STM frames, information packets of a
frame relay or a packet network, TDMA/FDMA radio
frames, and CDMA radio packets;
an SC-PL assembler (3-2) for forming a payload
of a short cell (SC-PL) by extracting input data
frame by frame or packet by packet;
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CA 02489644 1996-10-11
an SC-AAL provider (3-3) for providing an AAL of
the short cell based on attributes of the data as
needed; and
an SC-H provider (3-4) for providing a header of
the short cell by converting address information of
the data.
In the standard ATM cell assembler (1), the
short cell multiplexer (4) may comprise:
a multiplexing combination determiner A (4A-1)
for deciding a combination and order of multiplexing
parties of a plurality of input short cells with a
free length in accordance with purposes (such as
multiplexing data for each data attribute, for each
identical cell length, for each identical route);
a short cell information provider A (4A-2) for
providing each short cell with short cell
information including length information of the
short cell; and
a short cell multiplexing portion A (4A-3) for
linking the short cells provided with the short cell
information in accordance with a decision of the
multiplexing combination determiner A (4A-1).
In the standard ATM cell assembler (1), the
short cell multiplexer (4) may comprise:
a multiplexing combination determiner B (4B-1)
for deciding a combination and order from among
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CA 02489644 1996-10-11
predetermined multiplexing parties of a plurality of
input short cells with a free length in accordance
with purposes (such as multiplexing data for each
data attribute, for each identical cell length, for
each identical route);
a multiplexing information generator B (4B-2)
for generating multiplexing information including
information on lengths and a number of short cells
to be multiplexed; and
a short cell multiplexing portion B (4B-3) for
linking the short cells and the multiplexing
information in accordance with a decision of the
multiplexing combination determiner B (4B-1).
In the standard ATM cell assembler (1), the
short cell multiplexer (4) may comprise:
a multiplexing combination determiner C (4C-1)
for deciding a combination and order from among
predetermined multiplexing parties of a plurality of
input short cells with a free length in accordance
with purposes (such as multiplexing data for each
data attribute, for each identical cell length, for
each identical route); and
a short cell multiplexing portion C (4C-2) for
linking the short cells in accordance with a
decision of the multiplexing combination determiner
C ( 4C-1 ) .
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CA 02489644 1996-10-11
In the standard ATM cell assembler (1), the
multiplexing information may include multiplex
pattern identifiers (PI) representing a multiplexed
data structure to make correspondence between the
multiplex pattern identifiers and the multiplexed
data structures, and wherein the short cell
multiplexer (4) provides multiplexing information
corresponding to the multiplexed data structure.
In the standard ATM cell assembler (1), the
multiplexing information may include:
multiplexed cell number information (N)
indicating a number of identical length short cells
multiplexed onto a payload of a standard ATM cell;
and
short cell length information (L) indicating a
length of multiplexed short cells, and
wherein the short cell multiplexer (4) provides
multiplexing information corresponding to a
multiplexed data structure.
In the standard ATM cell assembler (1), the
multiplexing information may include:
multiplexed cell number information (N)
indicating a number of short cells multiplexed onto
a payload of a standard ATM cell, and short cell
length information (LI1-LIN) indicating a length of
each of the multiplexed short cells, and
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CA 02489644 1996-10-11
wherein the short cell multiplexer (4) provides
multiplexing information corresponding to a
multiplexed data structure.
According to the third aspect of the present
invention, a standard ATM cell disassembler
comprises:
an ATM cell receiver (8) for receiving standard
ATM cells sent from a B-ISDN network (7);
a standard ATM cell processor (9) for obtaining
payloads by carrying out disassembly/processing of
the received standard ATM cells;
a short cell disassembler (10) for disassembling
obtained payloads into short cells; and
a short cell processor/data transmitter (11) for
carrying out a predetermined processing of each of
the short cells to convert them into various types
of output information such as private short cells,
ATM cells, STM cells, information packets of a frame
relay or a packet network, TDMA/FDMA radio frames,
and CDMA radio packets, and for outputting the
converted data to respective channels.
In the standard ATM cell disassembler (2), the
standard ATM cell processor (9) may output data
other than to the short cell disassembler (10) to
have the ATM standard cells processed.
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CA 02489644 1996-10-11
In the standard ATM cell disassembler (2), the
short cell disassembler (10) may extract short cell
information sequentially beginning from an initial
position of multiplexed data, and disassembles the
multiplexed data into short cells by analyzing the
short cell information.
In the standard ATM cell disassembler (2), the
short cell disassembler (10) may comprise:
a multiplexing information analyzer B (10B-1)
for extracting and analyzing multiplexing
information; and
a short cell disassembler B (10B-2) for
disassembling multiplexed data into short cells in
accordance with analyzed results given by the
multiplexing information analyzer B (10B-1).
In the standard ATM cell disassembler (2), the
short cell disassembler (10) may disassemble
multiplexed data into short cells in accordance with
a predetermined structure.
In the standard ATM cell disassembler (2), the
short cell processor/data transmitter (11) may
comprise:
an SC-H processor (11-1) for processing a of a
received short cell SC-H;
an SC-AAL processor (11-2) for carrying out an
AAL processing if the short cell includes an AAL;
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CA 02489644 1996-10-11
an SC-PL processor (11-3) for processing a
payload of the short cell; and
a data transmitter (11-4) for converting the
short cell to each format of output data to be
output to a channel.
In the standard ATM cell disassembler (2), the
multiplexing information of the standard ATM cell
may include multiplex pattern identifiers (PI)
representing a multiplexed data structure to make
correspondence between the multiplex pattern
identifiers and the multiplexed data structures, and
wherein the short cell disassembler (10)
disassembles into the multiplexed data structure
corresponding to the multiplexing information.
In the standard ATM cell disassembler (2), the
multiplexing information of the standard ATM cell
may include:
multiplexed cell number information (N)
indicating a number of identical length short cells
multiplexed onto a payload of the standard ATM cell;
and
short cell length information (L) indicating a
length of the multiplexed short cells, and
wherein the short cell disassembler (10)
disassembles into a multiplexed data structure
corresponding to the multiplexing information.
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CA 02489644 1996-10-11
In the standard ATM cell disassembler (2), the
multiplexing information may include:
multiplexed cell number information (N)
indicating a number of short cells multiplexed onto
a payload of a standard ATM cell, and short cell
length information (LI1-LIN) indicating a length of
each of the multiplexed short cells, and
wherein the short cell disassembler (10)
disassembles into a multiplexed data structure
corresponding to the multiplexing information.
Here, the standard ATM cell
assembler/disassembler may comprise the standard ATM
cell assembler (1) and the standard ATM cell
disassembler (2).
In the standard ATM cell assembler/disassembler,
the short cell hierarchically may multiplex sub-
short cells.
According to the fourth aspect of the present
invention, a short cell multiplexing ATM
transmission method comprises the steps of:
assembling one or more standard ATM cells to be
output to an ATM switching network, each the
standard ATM cell including a payload including one
or more multiplexed short cells formed from various
types of input information;
transmitting the standard ATM cells; and
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CA 02489644 1996-10-11
receiving short cell multiplexed ATM cells,
disassembles them into short cells, and output them
to a channel after converting into an output data
format .
In the short cell multiplexing ATM transmission
method, the short cell may hierarchically multiplex
sub-short cells.
According to the fifth aspect of the present
invention, a short cell multiplexing ATM
transmission method comprises the steps of:
forming short cells from various types of input
information, multiplexing the short cells to be
placed in a payload of one or more standard ATM
cells, receiving multiplexed data as a standard ATM
payload, assembling a standard ATM cell by adding an
AAL and a header to be sent to an ATM switching
network;
receiving a short cell multiplexed ATM cell,
disassembling the received short cell multiplexed
ATM cell to obtain its payload, disassembles the
obtained payload into short cells which are
converted into an output data format to be output to
a channel.
According to the sixth aspect of the present
invention, a short cell multiplexing ATM
transmission method comprising the steps of:
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CA 02489644 1996-10-11
forming short cells from various types of input
information, providing each short cell with
information which must be individually provided for
the short cells as a short cell multiplexing
individual AAL, forming multiplexed data by
multiplexing the short cells, providing the
multiplexed data with a short cell multiplexing
common AAL shared by ATM cells assembled, providing
the standard ATM cells with an ATM header and sends
the standard ATM cells to an ATM switching network;
receiving the short cell multiplexed ATM cells,
and routing them to processors in accordance with
the ATM headers;
extracting short cells through processing of the
multiplexed data in accordance with a combination of
the short cell multiplexing common AAL and the short
cell multiplexing individual AAL; and
individually processing the short cells in
accordance with the short cell multiplexing
individual AAL, and converting the short cells into
output data to be output.
Tn the short cell multiplexing ATM transmission
method, the combination of the short cell
multiplexing common AAL and the short cell
multiplexing individual AAL may comprise, in the
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CA 02489644 1996-10-11
short cell multiplexing individual AAL, length
information and overlapping information.
In the short cell multiplexing ATM transmission
method, the combination of the short cell
multiplexing common AAL and the short cell
multiplexing individual AAL may comprise, in the
short cell multiplexing common AAL, length
information and overlapping information.
In the short cell multiplexing ATM transmission
method, the combination of the short cell
multiplexing common AAL and the short cell
multiplexing individual AAL may comprise overlapping
information in the short cell multiplexing common
AAL, and length information in the short cell
multiplexing individual AAL.
According to the seventh aspect of the present
invention, a standard ATM cell assembler which
receives various types of input information such as
private short cells, ATM, STM frames, information
packets of a frame relay or a packet network,
TDMA/FDMA radio frames, and CDMA radio packets, and
assembles standard ATM cells, the standard ATM cell
assembler comprises:
means for providing an AAL common to the
assembled standard ATM cell as a short cell
multiplexing common AAL; and
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CA 02489644 1996-10-11
means for providing information which must be
individually provided for the short cells as a short
cell multiplexing individual AAL.
In the standard ATM cell assembler, the short
cell multiplexing individual AAL may be provided
with :length information for short cell multiplexing.
In the standard ATM cell assembler, the length
information may provide a length of a short cell to
be multiplexed before dividing the short cell.
In the standard ATM cell assembler, the length
information may provide a length of a short cell
divided into units each corresponding to the
standard ATM cell.
In the standard ATM cell assembler, the short
cell multiplexing common AAL may be provided with
length information for short cell multiplexing.
In the standard ATM cell assembler, the short
cell multiplexing common AAL may be provided with
overlapping information indicating that the short
cell is multiplexed onto standard ATM cells in an
overlapped manner.
In the standard ATM cell assembler, the short
cell multiplexing individual AAL may be provided
with overlapping information indicating that the
short cell is multiplexed onto standard ATM cells in
an overlapped manner.
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CA 02489644 1996-10-11
In the standard ATM cell assembler, the short
cell multiplexing individual AAL may be provided
with information for individually processing the
short cells.
In the standard ATM cell assembler, the
information for individually processing the short
cells may be provided with information identifying
switched points of speech burst/mute.
In the standard ATM cell assembler, the
information for individually processing the short
cells may be provided with information indicating
individuality of contents of data included in the
short cells, or with information indicating quality.
According to the eighth aspect of the present
invention, a standard ATM cell assembler comprises
providing a short cell multiplexing individual AAL
which is provided with length information after
division.
According to the ninth aspect of the present
invention, a standard ATM cell disassembler which
receives standard ATM cells assembled from various
types of input data such as private short cells,
ATM, STM frames, information packets of a frame
relay or a packet network, TDMA/FDMA radio frames,
and CDMA radio packets, and disassembles the
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CA 02489644 1996-10-11
standard ATM cells into short cells, the standard
ATM cell disassembler comprises:
means for disassembling into short cells using a
short cell multiplexing common AAL which is provided
in common to the standard ATM cells and a short cell
multiplexing individual AAL which is provided
individually for the short cells; and
means for carrying out processing of
disassembled individual short cells.
In the standard ATM cell disassembler, the short
cell multiplexing individual AAL may be provided
with length information for short cell multiplexing.
In the standard ATM cell disassembler, the
length information may be provided with a length of
the multiplexed short cells before division.
In the standard ATM cell disassembler, the
length information may be provided with lengths
after divided into units each corresponding to the
standard ATM cell.
According to the tenth aspect of the present
invention, a standard ATM cell disassembler
comprises providing a short cell multiplexing
individual AAL which is provided with length
information after division.
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CA 02489644 1996-10-11
In the standard ATM cell disassembles, the short
cell multiplexing common AAL may be provided with
length information for short cell multiplexing.
In the standard ATM cell disassembles, the short
cell multiplexing common AAL may be provided with
overlapping information indicating that the short
cell is multiplexed onto standard ATM cells in an
overlapped manner.
In the standard ATM cell disassembles, the short
cell multiplexing individual AAL may be provided
with overlapping information indicating that the
short cell is multiplexed onto standard ATM cells in
an overlapped manner.
In the standard ATM cell disassembles, the short
cell multiplexing individual AAL may be provided
with information for individually processing the
short cells.
In the standard ATM cell disassembles, the
information for individually processing the short
cells may be provided with information identifying
switched points of speech burst/mute.
In the standard ATM cell disassembles, the
information for individually processing the short
cells may be provided with information indicating
individuality of contents of data included in the
short cells, or with information indicating quality.
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CA 02489644 1996-10-11
Here, the short cell multiplexing ATM
transmission system, in which a standard ATM cell
assembler may be linked with a standard ATM cell
disassembler via a standard ATM cell switching
network.
In the short cell multiplexing ATM transmission
system, the short cell may hierarchically multiplex
sub-short cells.
In the SC-AAL provider (3-3, 3-3') of a data
receiver/short cell assembler (3) in the standard
ATM cell assembler (1), the SC-AAL provider may
provide a last one or a first one of divided user
data with a final identifier or an initial
identifier as the SC-AAL.
In the SC-AAL provider of a data receiver/short
cell assembler (3), the final identifier may
comprise an identifying bit indicating that the
divided user data is the last one.
In the SC-AAL provider of a data receiver/short
cell assembler (3), the initial identifier may
comprise an identifying bit indicating that the
divided user data is the first one.
BRIEF DESCRIPTION OF THE DRAWINGS
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CA 02489644 1996-10-11
Fig. 1 is a diagram showing a relationship
between Figs. 1A and 1B;
Fig. 1A is a block diagram showing a
configuration of a fundamental system employing a
short cell multiplexed ATM transmission method in
accordance with the present invention;
Fig. 1B is a block diagram showing the
configuration of the fundamental system employing
the short cell multiplexed ATM transmission method
in accordance with the present invention;
Fig. 2 is a block diagram showing a detailed
configuration and operational example of a data
receiver/short cell assembler;
Fig. 3 is a block diagram showing a detailed
configuration and operational example of a short
cell processor/data transmitter;
Fig. 4 is a block diagram showing a detailed
configuration and operational example of a short
cell multiplexer;
Fig. 5 is a diagram illustrating patterns
depending on a multiplexed data length;
Fig. 6 is a block diagram showing a detailed
configuration and operational example of a short
cell disassembler;
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CA 02489644 1996-10-11
Fig. 7 is a block diagram showing a detailed
configuration and operational example of another
embodiment of the short cell multiplexer;
Fig. 8 is a diagram illustrating patterns
depending on a multiplexed data length;
Fig. 9 is a block diagram showing a detailed
configuration and operational example of another
embodiment of the short cell disassembler;
Fig. 10 is a diagram illustrating a data
assembling method 1 of multiplexing information;
Fig. 11A is a diagram illustrating a data
assembling method 2 of the multiplexing information;
Fig. 11B is a diagram illustrating the data
assembling method 2 of the multiplexing information;
Fig. 12A is a diagram illustrating a data
assembling method 3 of the multiplexing information;
Fig. 12B is a diagram illustrating the data
assembling method 3 of the multiplexing information;
Fig. 13 is a diagram illustrating an example of
the data assembling method 3 of the multiplexing
information;
Fig. 14 is a block diagram showing a detailed
configuration and operational example of still
another embodiment of the short cell multiplexer;
Fig. 15A is a diagram illustrating patterns
depending on a multiplexed data length;
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CA 02489644 1996-10-11
Fig. 15B is a diagram illustrating patterns
depending on the multiplexed data length;
Fig. 16 is a block diagram showing a detailed
configuration and operational example of still
another embodiment of the short cell disassembler;
Fig. 17 is a diagram showing the relationship
between Figs. 17A and 17B;
Fig. 17A is a block diagram showing a combined
transmission of the short cell multiplexed
transmission and other transmissions;
Fig. 17B is a block diagram showing the combined
transmission of the short cell multiplexed
transmission and other transmissions;
Fig. 18A is a diagram illustrating a format of
the short cell multiplexing;
Fig. 18B is a diagram illustrating the format of
the short cell multiplexing;
Fig. 19A is a diagram illustrating a format of
the short cell multiplexing;
Fig. 19B is a diagram illustrating the format of
the short cell multiplexing;
Fig. 20 is a diagram showing the relationship
between Figs. 20A and 20B;
Fig. 20A is a diagram illustrating a short cell
multiplexing processing;
- 27 -


CA 02489644 1996-10-11
Fig. 20B is a diagram illustrating the short
cell multiplexing processing;
Fig. 21 is a diagram showing the relationship
between Figs. 21A and 21B;
Fig. 21A is a diagram illustrating a short cell
multiplexing processing;
Fig. 21B is a diagram illustrating the short
cell multiplexing processing;
Fig. 22 is a diagram showing the relationship
between Figs. 22A and 22B;
Fig. 22A is a diagram illustrating a short cell
multiplexing processing;
Fig. 22B is a diagram illustrating the short
cell multiplexing processing;
Fig. 23 is a diagram illustrating a system
configuration for implementing the short cell
multiplexing processing;
Fig. 24 is a diagram illustrating a system
configuration for implementing the short cell
multiplexing processing;
Fig. 25 is a diagram illustrating a system
configuration for implementing the short cell
multiplexing processing;
Fig. 26 is a diagram showing the relationship
between Figs. 26A and 26B;
- 28 -


CA 02489644 1996-10-11
Fig. 26A is a block diagram illustrating a
system configuration for implementing the short cell
multiplexing processing;
Fig. 26B is a block diagram illustrating the
system configuration for implementing the short cell
multiplexing processing;
Fig. 27 is a diagram showing the relationship
between Figs. 27A and 27B;
Fig. 27A is a block diagram illustrating a
system configuration for implementing the short cell
multiplexing processing;
Fig. 27B is a block diagram illustrating the
system configuration for implementing the short cell
multiplexing processing;
Fig. 28 is a diagram showing the relationship
between Figs. 28A and 28B;
Fig. 28A is a block diagram illustrating a
system configuration for implementing a sub-short
cell multiplexing;
Fig. 28B is a block diagram illustrating the
system configuration for implementing the sub-short
cell multiplexing;
Fig. 29 is a diagram illustrating a double-layer
short cell multiplexing;
- 29 -


CA 02489644 1996-10-11
Fig. 30A is a block diagram illustrating a
conventional partial fill method and short cell
method;
Fig. 30B is a block diagram illustrating a
conventional partial fill method and short cell
method;
Fig. 31A is a diagram illustrating a method for
adding to a payload a short cell multiplexing common
AAL, a short cell multiplexing individual AAL, and
an AAL of an SC-AAL;
Fig. 31B is a diagram illustrating a method for
adding to the payload the short cell multiplexing
common AAL, the short cell multiplexing individual
AAL, and the AAL of the SC-AAL;
Fig. 31C is a diagram illustrating a method for
adding to the payload the short cell multiplexing
common AAL, the short cell multiplexing individual
AAL, and the AAL of the SC-AAL;
Fig. 31D is a diagram illustrating a method for
adding to the payload the short cell multiplexing
common AAL, the short cell multiplexing individual
AAL, and the AAL of the SC-AAL;
Fig. 31E is a diagram illustrating a method for
adding to the payload the short cell multiplexing
common AAL, the short cell multiplexing individual
AAL, and the AAL of the SC-AAL;
- 30 -


CA 02489644 1996-10-11
Fig. 32 is a diagram showing the relationship
between Figs. 32A and 32B;
Fig. 32A is a block diagram illustrating a data
receiver/short cell assembler and a short cell
processor/data transmitter when dividing user data;
Fig. 32B is a block diagram illustrating the
data receiver/short cell assembler and the short
cell processor/data transmitter when dividing user
data;
Fig. 33 is a diagram illustrating protocol stack
of the AAL for the short cell multiplexing;
Fig. 34 is a diagram illustrating the
correspondence between sublayers and a processor
when carrying out the processing associated with
Fig. 33;
Fig. 35 is a flowchart illustrating the outline
of a short cell multiplexed ATM transmission method;
Fig. 36 is a flowchart illustrating the details
of the short cell multiplexed ATM transmission
method;
Fig. 37 is a flowchart illustrating a particular
combination of the short cell multiplexing common
AAL and the short cell multiplexing individual AAL
in the short cell multiplexed ATM transmission
method;
- 31 -


CA 02489644 1996-10-11
Fig. 38 is a flowchart illustrating a particular
combination of the short cell multiplexing common
AAL and the short cell multiplexing individual AAL
in the short cell multiplexed ATM transmission
method; and
Fig. 39 is a flowchart illustrating a particular
combination of the short cell multiplexing common
AAL and the short cell multiplexing individual AAL
in the short cell multiplexed ATM transmission
method.
BEST MODE FOR CARRYING OUT THE INVENTION
The embodiments in accordance with the invention
will now be described with reference to the
accompanying drawings.
Figs. 1A and 1B shows an embodiment in
accordance with the present invention. In Figs. lA
and 1B, the reference numeral 1 designates a
standard ATM cell assembler, 7 designates a B-ISDN
network on which a standard ATM switching network is
constructed, and 2 designates a standard ATM cell
disassembler. The standard ATM cell assembler 1 is
composed of a data receiver/short cell assembler 3,
a short cell multiplexer 4, a standard ATM cell
generator 5 and an ATM cell transmitter 6. The
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CA 02489644 1996-10-11
standard ATM cell disassembler 2 is composed of an
ATM cell receiver 8, a standard ATM cell processor
9, a short cell disassembler 10, and a short cell
processor/data transmitter 11. These blocks will be
described in more detail later.
The standard ATM cell assembler 1 converts into
short cells various input information such as a
private short cell, ATM cell, STM frame, information
packet of a frame relay or packet network, TDMA/FDMA
radio frame, CDMA radio packet, loads the standard
ATM cell with the short cells effectively
considering their information length, and outputs it
to the B-ISDN network 7. In this case, the source
data can be longer than the payload of the standard
cell (equal to or greater than 48 bytes).
The B-ISDN network 7 transmits and switches the
standard ATM cell, thereby routing it in accordance
with the address set in its ATM header (ATM-H).
The standard ATM cell disassembler 2
disassembles into short cells the standard ATM cell
which is assembled by the standard ATM cell
assembler 1 and fed through the B-ISDN network 7,
converts the short cells into a private short cell,
ATM cell, STM frame, information packet of a frame
relay or packet network, TDMA/FDMA radio frame or
- 33 -


CA 02489644 1996-10-11
CDMA radio packet, and outputs them to corresponding
channels.
The output of the standard ATM cell disassembler
2 may undergo processing (data processing) followed
by switching, and be further input to the standard
ATM cell assembler 1.
A plurality of standard ATM cell assemblers 1
can be interconnected with a plurality of standard
ATM cell disassemblers 2 through the B-ISDN network.
The standard ATM cell assembler 1 and standard
ATM cell disassembler 2 can be combined into a
standard ATM cell assembler/disassembler.
The standard ATM cell assembler 1 will now be
described in more detail. The standard ATM cell
assembler 1 is composed of the data receiver/short
cell assembler 3, short cell multiplexer 4, standard
ATM cell generator 5 and ATM cell transmitter 6.
The data receiver/short cell assembler 3
receives various input information such as a private
short cell, ATM cell, STM frame, information packet
of a frame relay or packet network, TDMA/FDMA radio
frame, CDMA radio packet, and converts it into short
cells.
The short cell multiplexer 4 multiplexes the
short cells formed by the data receiver/short cell
- 34 -


CA 02489644 1996-10-11
assembler 3 to generate multiplexed data (that is,
the payload excluding the AAL of the standard ATM).
The standard ATM cell generator 5 provides the
multiplexed data fed from the short cell multiplexer
4 with the AAL (ATM Adaptation Layer) of the
standard ATM, and with the standard ATM header,
thereby forming the standard ATM cell from the
multiplexed data. The standard ATM cell is sent to
the ATM cell transmitter 6.
It is possible to provide a plurality of ATM
cell transmitters 6, in which case, an ATM switch is
placed between the standard ATM cell generator 5 and
the ATM cell transmitters 6 to select one of the ATM
cell transmitters 6 using the standard ATM header.
Alternatively, it is possible to provide a
plurality of sets each consisting of the data
receiver/short cell assembler 3, short cell
multiplexer 4 and standard ATM cell generator 5, and
to connect them to the single ATM cell transmitter
6. In this case also, an ATM switch must be placed
between the plurality of the standard ATM cell
generators 5 and the ATM cell transmitter 6.
The standard ATM cell generator 5 communicates
with the standard ATM cell processor 9 during path
setting, and sets an address translation table
(which will be described later) used for routing the
- 35 -


CA 02489644 1996-10-11
standard ATM cell, by way of the address translation
in each ATM switch included in B-ISDN network 7, in
the case where the B-ISDN network 7 includes the ATM
switches. The processing for setting the address
translation table through the communication at the
time of path setting can be obviated if the address
translation table has been set in advance.
The ATM cell transmitter 6 has an interface
function with the B-ISDN network, and transmits the
standard ATM cell formed by the standard ATM cell
generator 5 to the B-ISDN network 7.
Next, the standard ATM cell disassembler 2 will
be described in detail. The standard ATM cell
disassembler 2 is composed of the ATM cell receiver
8, standard ATM cell processor 9, short cell
disassembler 10 and short cell processor/data
transmitter 11.
The ATM cell receiver 8, having an interface
function with the B-ISDN network, receives the
standard ATM cell from the B-ISDN network 7 and
sends the received standard ATM cell to the standard
ATM cell processor 9.
It is possible to provide a plurality of sets
each consisting of the standard ATM cell processor
9, short cell disassembler 10 and short cell
processor/data transmitter, in which case, an ATM
- 36 -


CA 02489644 1996-10-11
switch is placed between the ATM cell receiver 8 and
the standard ATM cell processors ~9 to select one of
the standard ATM cell processors 9 using the
standard ATM header.
Alternatively, it is possible to provide a
plurality of ATM cell receivers 8. In this case
also, an ATM switch must be placed between the
plurality of the ATM cell receivers 8 and the
standard ATM cell processor 9.
The standard ATM cell processor 9 processes the
ATM header of the standard ATM cell fed from the
standard ATM cell receiver 8, and then carries out
the AAL (ATM Adaptation Layer) processing. The
multiplexed data in the form of the payload is
delivered to the short cell disassembler 10.
The short cell disassembler 10 disassembles the
multiplexed data fed from the standard ATM cell
processor 9 into the short cells, combines them and
supplies them to the short cell processor/data
transmitter 11.
The short cell processor/data transmitter 11
converts the short cells fed from the short cell
disassembler 10 in accordance with the format of the
output channel, and outputs them to various channels
such as a private short cell, ATM cell, STM frame,
- 37 -


CA 02489644 1996-10-11
information packet of a frame relay or packet
network, TDMA/FDMA radio frame, CDMA radio packet.
The data receiver/short cell assembler 3 and
short cell processor/data transmitter 11 will now be
described in detail with reference to Figs. 2 and 3.
In Fig. 2 and the following drawings, the SC-AAL
is drawn as if it were placed only at the head of
data. This, however, is a mere example, and it can
be placed at the final position, initial position,
or both final and initial positions of the data just
as the AAL standardized by the ITU-T.
It may be possible to add to a payload a short
cell multiplexing common AAL, a short cell
multiplexing individual AAL, and an AAL of a SC-AAL
as a header (Fig. 31A), a trailer (Fig. 31B), or
both header and trailer (Fig. 31C).
The data receiver/short cell assembler 3
receives various input information such as a private
short cell, ATM cell, STM frame, information packet
of a frame relay or packet network, TDMA/FDMA radio
frame, CDMA radio packet, and converts them into
short cells.
In Fig. 2, the data receiver/short cell
assembler 3 is composed of a data receiver 3-1, an
SC-PL (Short Cell-Payload) generator 3-2, an SC-AAL
- 38 -


CA 02489644 1996-10-11
(Short Cell-AAL) provider 3-3, and an SC-H (Short
Cell-Header) provider 3-4.
The data receiver 3-1 carries out different
processings depending on whether it terminates a
particular transmission method of the input data to
begin a new ATM transmission, or continues to
transmit the received data of the data receiver 3-1
transparently using the same transmission method of
the transmitted data of the data transmitter 11-4.
First, the processing involved in terminating
the transmission method of the input data and begins
the new ATM transmission will be described. The
data receiver 3-1 includes a hardware interface
matching the transmission method of the input data,
and divides the input data into individual frames or
packets.
In the course of this, it carries out diverse
control for terminating the transmission method of
the input data. (For example, if the input is the
ATM method, it carries out the ALL processing, and
if the input is the frame relay or packet method, it
carries out the delivery control or frame check
processing).
After that, the data receiver 3-1 obtains from
the divided input data the user data and address
information for transmitting the data. The
- 39 -


CA 02489644 1996-10-11
following are examples of acquiring the user data
and the address information from the input data.
Example 1:
When the input is a private short cell or
the ATM cell, it is possible to adopt the payload as
the user data, and the ATM header as the address
information.
Example 2:
When the input is an STM frame or TDMA/FDMA
radio frame information, the entire frame
information is adopted as the user data, and the
address information is newly generated from a
line/CH number and a time slot position.
Example 3:
When the input is an information packet of a
frame relay or packet network, it is possible to
adopt the whole user data section in the information
packet as the user data, and the address or header
of the packet as the address information.
Example 4:
When the input is a CDMA radio information
packet, it is possible to adopt the entire user data
section in the information packet as the user data,
and the CDMA code number in the packet as the
address information.
- 40 -


CA 02489644 1996-10-11
Thus, a physical line number, time slot position
information or the like is adopted as the address
information if the input has no logical address as
the STM.
Secondly, when transmitting the received data of
the data receiver 3-1 transparently to the data
transmitter 11-4, the data receiver 3-1 has a
hardware interface matching the transmission method
of the input data, and divides the input data to
individual frames or packets.
The divided input data are entirely adopted as
the user data, and the address information is
obtained from the input data as described above.
The address information obtained by the data
receiver 3-1 is used by the SC-H provider 3-4 as
address information 1.
The SC-PL assembler 3-2 adopts the user data
extracted from the input data by the data receiver
3-1 as the SC-PL.
The SC-AAL provider 3-3 determines the AAL type
from a data attribute obtained over an out-channel
during setting of the short cell connection, and
adds required AAL information to the SC-PL. It may
further add new information needed for SC-PL
processing (such as control information needed for
mute compression control of the voice data, or
- 41 -


CA 02489644 1996-10-11
control information for diversity handover of the
mobile communication data) as the~SC-AAL. If no AAL
control is required for the user data, this
processing can be omitted. When determining the
short cell header, the SC-H provider 3-4 and an SC-H
processor 11-1 in the standard ATM cell disassembles
2 are notified of the AAL type set here, and
corresponds it to the process in an SC-AAL processor
11-2.
The SC-H provider 3-4 communicates with the SC-H
processor 11-1 in the standard ATM cell disassembles
2 during the short cell path setting, and sets the
address translation table for routing.
The address translation table 1 which is set and
referred to by the SC-H provider 3-4 stores the
correspondence between the address information 1 of
the input data and the short cell header, and stores
the short cell AAL type decided by the SC-AAL
provider 3-3.
The address translation table 2 which is set and
referred to by the SC-H processor 11-1 stores the
correspondence between the short cell header and the
address information 2 of the output data, and stores
the short cell AAL type decided by the SC-AAL
provider 3-3.
- 42 -


CA 02489644 1996-10-11
The setting of the address translation tables 1
and 2 through the communication during the path
setting can be omitted if the relationships of the
address information 1, SC-H, address information 2
and short cell AAL types have been set in advance in
the address translation tables 1 and 2 using office
data or the like.
The short cell header can have the same
structure as that of the standard ATM cell header,
or a different structure from it.
Having the same structure as the standard ATM
header offers advantages that the short cell header
can be used without change as the standard ATM
header for conveying the multiplexed data as will be
described later in connection with an embodiment 3,
or that better matching can be obtained when the
data transmitter 11-4 in the short cell
processor/data transmitter 11 outputs data according
to the ATM.
The short cell completed by the SC-H provider 3-
4 is sent to the short cell multiplexer 4.
The short cell processor/data transmitter 11
will now be described in more detail with reference
to Fig. 3.
The short cell completed by the SC-H provider 3-
4 is recovered to the data in accordance with the
- 43 -


CA 02489644 1996-10-11
original transmission method, or converted to the
data complying with another transmission method by
the short cell processor/data transmitter 11 in the
standard ATM cell disassembler 2.
The short cell processor/data transmitter 11
converts the received short cell into various
transmission forms such as a private short cell, ATM
cell, STM frame, information packet of a frame relay
or packet network, TDMA/FDMA radio frame or CDMA
radio packet, and outputs it.
In Fig. 3, the short cell processor/data
transmitter 11 is composed of the SC-H (Short Cell-
Header) processor 11-1, the SC-AAL (Short Cell-AAL)
processor 11-2, an SC-PL (Short Cell-Payload)
processor 11-3 and the data transmitter 11-4.
The SC-H processor 11-1 sets the above-mentioned
address translation table 2 through the
communication with the SC-H provider 3-4 during the
path setting.
The SC-H processor 11-1 analyzes the short cell
header of the short cell fed from the short cell
disassembler 10, and obtains the address information
of the output data and the AAL type of the short
cell using the address translation table 2.
The SC-AAL processor 11-2 carries out, when the
AAL is set in the short cell, the AAL processing in
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CA 02489644 1996-10-11
accordance with the AAL type of the short cell
obtained by the SC-H processor 11-1. This
processing is omitted if the AAL is not set in the
short cell.
The SC-PL processor 11-3 extracts the payload
out of the short cell as the user data of the output
data.
The data transmitter 11-4 has a hardware
interface matching the transmission modes of the
output data, and transfers the output data frame by
frame or packet by packet to each channel in
accordance with the transmission mode.
The output data is generated in different manner
depending on whether the data receiver 3-1
terminates the current transmission mode of the
input data to begin a new ATM transmission, or
continues to transmit its received data
transparently according to the transmission mode of
the data transmitter.
First, when employing the method of terminating
the transmission mode of the input data to begin the
new ATM transmission, the data transmitter 11-4
forms the output data from the address information 2
obtained by the SC-H processor 11-1, the data
attribute obtained by the SC-A.AL processor 11-2 and
the user data obtained by the SC-PL processor 11-3.
- 45 -


CA 02489644 1996-10-11
Example 1:
When the output is a private short cell or
the ATM cell, it is possible to adopt the user data
as the payload, the address information 2 as the ATM
header, and the AAL in the short cell as the AAL of
the ATM cell without change.
Example 2:
When the output is an STM frame or TDMA/FDMA
radio frame information, the user data is adopted as
the frame information, and the line/channel number
and a time slot position are decided from the
address information 2.
Example 3:
When the output is an information packet of
a frame relay or packet network, it is possible to
adopt the user data as the user data in the
information packet, and to generate the address or
header of the packet from the address information 2.
Example 4:
When the output is a CDMA radio information
packet, it is possible to adopt the user data as the
user data in the information packet, and to decide
the CDMA code number of the packet from the address
information 2.
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CA 02489644 1996-10-11
In this case also, the physical line number,
time slot position information or the like is used
if no logical address is provided as in the STM.
Secondly, when the transmission method is
employed, in which the received data by the data
receiver 3-1 is transmitted transparently to the
data transmitter 11-4 in accordance with the
transmission mode of the data transmitter 11-4, the
user data obtained by the SC-PL processor 11-3 is
adopted as the output data including the address
information. However, if the output is the STM
frame or TDMA/FDMA radio frame, the user data is
adopted as the frame information, and the
line/channel number and time slot position
information are decided from the address information
2.
The short cell multiplexer and short cell
disassembler will now be described with reference to
Figs. 4-16.
EMBODIMENT 1
An embodiment 1 (a short cell multiplexer A and
short cell disassembler A) will now be described
referring to Figs. 4-6.
The embodiment 1 adds the length information to
each short cell.
- 47 -


CA 02489644 1996-10-11
In Fig. 4, the short cell multiplexer A (4A) is
composed of a multiplexing combination determiner A
(4A-1), a short cell information provider A (4A-2)
and a short cell multiplexing portion A (4A-3).
First, the short cell multiplexer A (4A) has the
multiplexing combination determiner A (4A-1) decide
the combination and order in multiplexing a
plurality of input short cells into the payload of
the standard ATM cell.
In making this decision, the multiplexing
combination determiner A (4A-1) obtains beforehand
the byte length of the short cell information given
by the short cell information provider A (4A-2), and
the byte length of the AAL of the standard ATM given
by the standard ATM cell generator 5 so that it can
obtain the data byte length actually available for
multiplexing the short cells, that is, the byte
length obtained by subtracting from the 48 bytes of
the standard ATM payload the byte length of its
control information.
The decision can be made as follows to minimize
the waiting time in the system: First, the
multiplexing is carried out by combining the data in
the received order. Second, the multiplexing is
carried out by having the received short cells wait
in a buffer within allowed waiting times
- 48 -


CA 02489644 1996-10-11
corresponding to their attributes (SC-AAL types),
and by selecting suitable ones from the short cells
stored in the buffer, which match in their
attribute, length and address (SC-H).
Example 1:
With regard to the cell attribute,
multiplexing the cells of the same attribute will
facilitate the delay control or the like by the
standard ATM management.
Example 2:
With regard to the cell length, a
combination can be selected which will minimize the
remainder (of the partial fill) in the payload of
the standard ATM cell, or which will prevent a
single short cell from overlapping across multiple
standard ATM cells, as much as possible.
Example 3:
With regard to the cell address,
multiplexing the short cells conveyed through the
same route makes it possible to transmit them to a
farther common destination without changing the
multiplexed standard cell.
The combinations of multiplexing thus determined
are divided into the following three multiplexed
data length patterns in accordance with the
multiplexed data length as shown in Fig. 5.
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CA 02489644 1996-10-11
Here, the multiplexed data length is defined as
the sum total of the sum of the lengths of the short
cells to be multiplexed, the sum of the short cell
information given to the individual short cells by
the short cell information provider A (4A-2) and the
AAL information length given by the standard ATM
cell generator 5.
(Pattern 1) The multiplexed data length equals
48 bytes.
(Pattern 2) The multiplexed data length is less
than 48 bytes.
(Pattern 3) The multiplexed data length exceeds
48 bytes.
In the case of the pattern 3, since the data
cannot be accommodated in a single standard ATM
cell, the overflowed data of the short cell at the
final position (that is, data beyond 48 bytes) must
be transferred by the next standard ATM cell. Thus,
the overflowed data is separated as a new short cell
(having no SC-H and SC-AAL), and placed in the next
standard ATM cell as the first short cell to be
multiplexed.
The short cell information provider A (4A-2)
generates the short cell information from each short
cell fed from the multiplexing combination
- 50 -


CA 02489644 1996-10-11
determiner A (4A-1), and puts it at the initial
position of the short cell.
The short cell information includes short cell
length information (LI), short cell status
information (ST: Short cell Type), error
detecting/error correcting bits (parity bits, CRC,
etc.) against transmission error when transmitting
these information.
The short cell status information is for
indicating whether the short cell is complete
(ST="00"), lacking only the latter part (ST="01"),
lacking only the former part (ST="10") or lacking
both the former and latter parts (ST="11").
The short cell multiplexing portion A (4A-3)
carries out different processings in accordance with
the multiplexed data length patterns described
above.
In the case of the multiplexed data length
pattern 1 in which the multiplexed data length is 48
bytes, the short cell multiplexing portion A (4A-3)
links the short cells to which the short cell
information is added in accordance with the
combination and multiplexing order of the short
cells decided by the multiplexing combination
determiner A (4A-1).
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CA 02489644 1996-10-11
In the case of the pattern 2 in which the
multiplexed data length is less than 48 bytes, the
short cell multiplexing portion A (4A-3) links the
short cells in a manner similar to those of the
multiplexed data length pattern 1, and then adds
null information (NULL) to the final position of the
multiplexed data so that the total data length
becomes 48 bytes considering the AAL information
length provided by the standard ATM cell generator
5.
In the case of the pattern 3 in which the
multiplexed data length exceeds 48 bytes, the
multiplexed data length is adjusted to 48 bytes
because the data exceeding 48 bytes is delivered to
the next standard ATM cell as the first short cell
to be multiplexed. Accordingly, the short cell
multiplexing portion A (4A-3) links the short cells
in a manner similar to those of the multiplexed data
length pattern 1.
The multiplexed data (with a length of 48 bytes
- the AAL information length of the standard ATM)
assembled by the short cell multiplexing portion A
(4A-3) is sent to the standard ATM cell generator 5.
The multiplexed data thus assembled is
disassembled into the original data by the short
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CA 02489644 1996-10-11
cell disassembler A. This will be described
referring to Fig. 6.
The short cell disassembler A (10A) is composed
of the short cell disassembling portion A (10A-1).
It disassembles the multiplexed data which is
assembled by the short cell multiplexing portion A
(4A-3) and fed from the standard ATM cell processor
9, and combines the disassembled data.
The short cell disassembling portion A (10A-1),
extracting the short cell information from the
initial position of the multiplexed data assembled
by the short cell multiplexing portion A (4A-3), and
analyzing the information, can extract the short
cell following the short cell information. This
process is repeated until the last short cell of the
multiplexed data is extracted.
The short cell disassembling portion A (10A-1)
obtains the short cell length information (LI),
short cell status information (ST) and error
detecting/error correcting bits (C) by analyzing the
short cell information.
First, the short cell disassembling portion A
(10A-1) makes a decision from the error
detecting/error correcting bits (C) whether or not
any transmission error occurs in the short cell
information, and corrects the error if it is
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CA 02489644 1996-10-11
correctable. If the error cannot be corrected
because only the error detecting function is
provided, or the error is not correctable, the
multiplexed data after the error is relinquished
because it is difficult to extract the short cell on
the basis of the erroneous information.
(Alternatively, it may be possible to continue the
processing without relinquishing, allowing the
possibility of erroneous extraction).
Second, the short cell disassembling portion A
(10A-1) can extract the short cell following the
short cell information using the short cell length
information (LI). For example, when the short cell
length information indicates 8 bytes, the 8-byte
data following the short cell information is
extracted as the short cell.
Third, the short cell disassembling portion A
(10A-1) can obtain from the short cell status
information (ST) the overlapping information about
whether the short cell extracted in accordance with
the short cell length information is a complete
cell, lacking only a first half, lacking only the
second half, or both the first and second half (that
is, a single short cell overlaps across three or
more multiplexed data). As illustrated in the
flowcharts of Figs. 35, 36 and 37, the multiplexing
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CA 02489644 1996-10-11
individual AAL includes the length information and
the overlapping information in the embodiment 1.
The following processings are carried out in
accordance with the short cell status information
(ST) .
If ST="00", the short cell disassembling portion
A (l0A-1) decides that the short cell is complete,
and transfers the extracted short cell to the short
cell processor/data transmitter 11.
If ST="01", the short cell disassembling portion
A (l0A-1) decides that only the second half is
lacking, and temporarily stores the extracted short
cell to be combined with the second half, thereby
waiting for the short cell in the next multiplexed
data.
If ST="10", the short cell disassembling portion
A (10A-1) decides that only the first half is
lacking, and combines the second half with the short
cell stored to be combined, thereby transferring the
combined short cell to the short cell processor/data
transmitter 11.
If ST="11", the short cell disassembling portion
A (10A-1) decides that both the former and latter
portions are lacking, combines the extracted one
with the short cell stored to be combined, restores
55 _


CA 02489644 1996-10-11
the combined one, and waits for the short cell in
the next multiplexed data.
If the short cell status information of the
final short cell of multiplexed data (multiplexed
data 1) is ST="01" or ST="11", the short cell status
information of the first short cell of the next
incoming multiplexed data (multiplexed data 2) must
be ST="10" or ST="11", Otherwise, it is possible to
decide that although one or more multiplexed data
were present between the multiplexed data 1 and 2,
some cell lose occurs in the standard ATM cells
conveying the multiplexed data.
On the contrary, if the short cell status
information of the first short cell of multiplexed
data (multiplexed data 4) is ST="10" or ST="11", and
the short cell status information of the final short
cell of the preceding multiplexed data (multiplexed
data 3) is ST="00" or ST="10", and no short cell is
stored to be combined, it is also possible to decide
that although one or more multiplexed data were
present between the multiplexed data 3 and 4, some
cell lose occurs in the standard ATM cells conveying
the multiplexed data.
To obtain the presence and absence of the cell
loss or the accurate number thereof, it is necessary
to apply the AAL (AAL type 1, for example) having
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CA 02489644 1996-10-11
the order information in the standard ATM cells
conveying the multiplexed data.
Using the function of the AAL of the standard
ATM cells to have the standard ATM cell processor 9
notify the short cell disassembling portion A (10A-
1) of the occurrence of the cell loss makes it
possible to prevent erroneous short cell combining
(combining of the first half and the second half of
different short cells) due to the cell loss which
cannot be detected only from the ST.
The short cell components are relinquished which
are unrecoverable to a complete short cell owing to
the omission of the multiplexed data due to the cell
loss or the cancelling of the multiplexed data due
to transmission error.
Thus, the first half of the short cell stored to
be combined with the second half is relinquished if
the expected second half cannot be obtained.
On the other hand, if the first half of the
short cell has not been stored which is to be
combined with the second half of the short cell
extracted from the initial position of the
multiplexed data, the second half of the short cell
is relinquished. In this case, the second and the
following short cells in the multiplexed data are
effective.
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CA 02489644 1996-10-11
EMBODIMENT 2
Another short cell multiplexer will now be
described referring to Figs. 7-9.
This embodiment 2 adds the number of the
multiplexed short cells and the lengths of
individual short cells as a piece of multiplexing
information.
In Fig. 7, the short cell multiplexer B (4B) is
composed of a multiplexing combination determiner B
(B-1), a multiplexing information generator B (4B-2)
and a short cell multiplexing portion B (4B-3).
First, the short cell multiplexer B (4B) has the
multiplexing combination determiner B (4B-1) decide
the combination and order in multiplexing a
plurality of input short cells into the payload of
the standard ATM cell. This decision processing is
the same as that of the multiplexing combination
determiner A (4A-1).
In making this decision, the multiplexing
combination determiner B (4B-1) obtains beforehand
the byte length of the multiplexing information
generated by the multiplexing information generator
B (4B-2), and the byte length of the AAL of the
standard ATM given by the standard ATM cell
generator 5 so that it can obtain the data byte
length actually available for the short cell
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CA 02489644 1996-10-11
multiplexing, that is, the byte length obtained by
subtracting the byte length for the control
information from the 48 bytes of the standard ATM
payload.
The combinations to be multiplexed thus
determined are divided into the following three
multiplexed data length patterns in accordance with
the multiplexed data length as shown in Fig. 8.
Here, the multiplexed data length is defined as
the sum total of the sum of the lengths of the short
cells to be multiplexed, the length of the
multiplexing information formed by the multiplexing
information generator B (4B-2) and the AAL
information length given by the standard ATM cell
generator 5.
(Pattern 1) The multiplexed data length equals
48 bytes.
(Pattern 2) The multiplexed data length is less
than 48 bytes.
(Pattern 3) The multiplexed data length exceeds
48 bytes.
In the case of the pattern 3, since the data
cannot be accommodated in a single standard ATM
cell, the overflowed data of the short cell at the
final position (that is, data beyond 48 bytes) must
be transferred by the next standard ATM cell. Thus,
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CA 02489644 1996-10-11
the overflowed data is separated as a new short cell
(having no SC-H and SC-AAL), and placed in the next
standard ATM cell as the first short cell to be
multiplexed.
The multiplexing information generator B (4B-2)
generates the multiplexing information from the
short cells fed from the multiplexing combination
determiner B (4B-1).
The multiplexing information, which can take
various data structures, indicates the way in which
the plurality of the short cells are arranged into
the multiplexed data.
The short cell multiplexing portion B (4B-3)
carries out somewhat different processings in
accordance with the multiplexed data length patterns
described above.
In the case of the multiplexed data length
pattern 1 in which the multiplexed data length is 48
bytes, the short cell multiplexing portion B (4B-3)
links the short cells in accordance with the
combination and multiplexing order of the short
cells decided by the multiplexing combination
determiner B (4B-1), and adds the multiplexed data
generated by the multiplexing information generator
B (4B-2) to the initial position of the multiplexed
data.
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CA 02489644 1996-10-11
In the case of the pattern 2 in which the
multiplexed data length is less than 48 bytes, the
short cell multiplexing portion B (4B-3) links the
short cells in a manner similar to that of the
multiplexed data length pattern 1, adds the
multiplexed data generated by the multiplexing
information generator B (4B-2) to the initial
position of the multiplexed data, and then adds null
information (NULL) to the final position of the
multiplexed data so that the total data length
becomes 48 bytes considering the AAL information
length provided by the standard ATM cell generator
5.
In the case of the pattern 3 in which the
multiplexed data length exceeds 48 bytes, the
multiplexed data length is adjusted to 48 bytes
because the data exceeding 48 bytes is delivered to
the next standard ATM cell as the first short cell
to be multiplexed. Accordingly, the short cell
multiplexing portion B (4B-3) links the short cells
in a manner similar to that of the multiplexed data
length pattern 1, and adds the multiplexed data
generated by the multiplexing information generator
B (4B-2) to the initial position of the multiplexed
data.
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CA 02489644 1996-10-11
The multiplexed data (with a length of (48 bytes
- the AAL information length of the standard ATM))
assembled by the short cell multiplexing portion A
(4A-3) is sent to the standard ATM cell generator 5.
The data structure of the multiplexing
information will now be described with reference to
Figs. 10-12.
Example 1 of Multiplexing information Data
Structure.
The structure as illustrated in Fig. 10 includes
a multiplexed pattern identifier (PI), and error
detecting/error correcting bits (C) (parity bits,
CRC etc.) for the transmission error that might
occur during the transmission of the PI.
With this data structure, if the number of the
multiplexed data structures determined by the
multiplexing combination determiner B (4B-1) is
limited, the multiplexed pattern identifier PI is
associated with the multiplexed data structures in
advance.
For example, the following steps a)-c) can be
taken.
a) If the multiplexed pattern identifier PI is
"000001", the short cells of the same length are
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CA 02489644 1996-10-11
multiplexed in such a way that two 23-byte short
cells are multiplexed.
b) If the multiplexed pattern identifier PI is
"000010", the short cells of different lengths are
multiplexed in such a way that one 16-byte short
cell and one 30-byte cell are combined.
c) If the multiplexed pattern identifier PI is
"000011", the short cells are multiplexed in such a
way that at least one of them is placed across the
two or more multiplex data such as one 30-byte short
cell and the former 16 bytes of another 30-byte
short cell are multiplexed, first. Then, if the
multiplexed pattern identifier PI is "000100", the
remaining 14 bytes of the 30-byte short cell, still
another 30-byte short cell and 2-byte null
information are multiplexed. Thus, the multiplexed
data structure includes an overlapped short cell.
In the case of employing the example 1 of the
multiplexing information data structure, the
multiplexing information generator B (4B-2) forms
the multiplexing information by selecting the
multiplexed pattern identifier (PI) corresponding to
the multiplexed data structure which is associated
with a short cell disassembler B (10B-1) in advance
in accordance with the combination and order of the
short cells fed from the multiplexing combination
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CA 02489644 1996-10-11
determiner B (4B-1). The multiplexing information
may have additional error detecting/error correcting
bits (C) for the transmission error.
Example 2 of the Multiplexing information Data
Structure.
The structure as shown in Fig. 11A includes
multiplexed cell number information (N), short cell
length information (L), multiplexing sequence number
tSN) and error detecting/error correcting bits (C)
(parity bits, CRC, etc.) for the transmission error
which might occur during the transmission of these
data.
This data structure is employed when
multiplexing the short cells of the same length.
The multiplexed cell number information (N)
indicates the number of short cells multiplexed into
the multiplexed data. It is an integer number
(including zero) such as 0, 1, 2, 3,...
For example, the multiplexed cell number zero
indicates that the multiplexed data is dummy data
including no short cell. The multiplexed cell
number one indicates that the multiplexed data
includes one short cell.
The short cell length information indicates the
number of bytes of each short cell.
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CA 02489644 1996-10-11
The multiplexing sequence number is used, when
the short cell at the final position of the
multiplexed data overflows, for controlling
deliverance of the overflowed data to the next
multiplexed data.
For example, if the multiplexed data length (48
bytes - the multiplexing information length - the
AAL length of the standard ATM) available for
multiplexing the short cells is 45 bytes, and 36-
byte short cells are multiplexed, four multiplexed
data (45 bytes x 4 - 180 bytes) can convey five
short cells (36 bytes x 5 - 180 bytes), which
indicates that there are four patterns of the
multiplexed data structure. Accordingly, if the
four multiplexed data are provided with the numbers
1-4 cyclically as the multiplexing sequence numbers
(SN), it is possible to decide the manner in which
the short cells are overlapped across the
multiplexed data. That is, the boundary of each
short cell can be decided from the short cell length
information (L) and the multiplexing sequence number
(SN). This makes it possible to decide the number
of complete short cells in each multiplexed data
from the number of the multiplexed short cells.
(The partial fill can be implemented by setting the
multiplexed cell number to less than that which
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CA 02489644 1996-10-11
would causing a cell overlapping across two
multiplexed data, in which case, the next
multiplexing sequence number is returned to one).
Fig. 11B illustrates a case in which three 36-
byte short cells are sent. The first cell has a
multiplexing sequence number 1, the second cell has
a multiplexing sequence number 2 and the final cell
has a multiplexing sequence number 3.
The multiplexing sequence numbers may not cycle
depending on the length of the short cells. In such
a case, the multiplexed data can be made partial
fill at the multiplexing sequence number M which
will minimize the dummy data added for the partial
fill to that multiplexed data so that the
multiplexing sequence numbers 1-M are repeated again
from the next multiplexed data.
When the example 2 of the multiplexing
information data structure is employed, the
multiplexing information generator B (4B-2) forms,
as the multiplexing information, the multiplexed
cell number information (N) and short cell length
information (L) (of the complete short cell without
omission) from the combination and order of the
short cells fed from the multiplexing combination
determiner B (4B-1).
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CA 02489644 1996-10-11
Tf the relationship, multiplexed cell number x
short cell length S multiplexed data length
available for multiplexing the short cells (that is,
48 bytes - multiplexing information length - AAL
length of the standard ATM) is satisfied, no cell
overlapping will occur.
In contrast, in the case of multiplexed cell
number x short cell length > multiplexed data length
available for multiplexing the short cells (that is,
48 bytes - multiplexing information length - AAL
length of the standard ATM), the cell overlapping
will occur, and hence the control must be carried
out for delivering the overflowed data of the short
cell at the final position to the next multiplexed
data. In this case, the multiplexing sequence
numbers (SN) are provided as the multiplexing
information depending on the number of repetitions
of the overlapping of the multiplexed data as
described above. If no overlapping of the
multiplexed data occurs, the multiplexing sequence
number (SN) is basically unnecessary. However, it
can be set to zero to distinguish the absence of the
overlapping from the presence thereof if they are
mixed.
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CA 02489644 1996-10-11
The multiplexing information may be further
provided with the error detecting/error correcting
bits (C) to detect the transmission error and
prevent it.
Example 3 of the Multiplexing information Data
Structure.
The structure as shown in Figs. 12 and 13
includes multiplexed cell number information (N),
composite type information (CT: Cell Type), short
cell length information (LI1-LIn) and error
detecting/error correcting bits (C) (parity bits,
CRC, etc.) for the transmission error when
transferring these data.
This data structure is employed when
multiplexing the short cells of the same and
different lengths.
The multiplexed cell number information (N)
indicates the number of short cells multiplexed into
the multiplexed data. It takes an integer number
(including zero) such as 0, 1, 2, 3,... as in the
example 2 of the multiplexing information data
structure.
The composite type information (CT) is for
indicating whether the entire short cells are
complete (CT="00"), lacking only the second half of
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CA 02489644 1996-10-11
the cell at the final position (N-th one of the
multiplexed cells) (CT="01"), lacking only the first
half of the cell at the initial position (first one
of the multiplexed cells) (CT="10") or lacking both
the first half of the first short cell and the
second half of the N-th short cell (CT="11").
The short cell length information (LI1-LIn),
including the same number of pieces of information
as that of the multiplexed cells, indicates the
number of bytes of each short cell. For example, if
the number of multiplexed cells is five, there are
five pieces of short cell length information.
In the example 3 of the multiplexing information
data structure, the multiplexing information
generator B (4B-2) forms the multiplexed cell number
information (N), composite type information (CT) and
N pieces of short cell length information (LI1-LIn)
in accordance with the combination and order of the
short cells fed from the multiplexing combination
determiner B (4B-1). The multiplexing information
can further include the error detecting/error
correcting bits (C) for detecting and preventing its
transmission error.
The multiplexing information can take a variable
information length corresponding to the multiplexed
cell number information (N), and a short cell
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CA 02489644 1996-10-11
disassembling portion B (10B-1) can decide the data
structure and information length of the multiplexed
data.
The short cell disassembler B will now be
described referring to Fig. 9.
In Fig. 9, the short cell disassembler B (10B)
is composed of the multiplexing information analyzer
B (108-1) and the short cell disassembling portion B
(lOB-2). The short cell disassembler B disassembles
the multiplexed data which is assembled by the short
cell multiplexing portion B (4B-3) and fed from the
standard ATM cell processor 9, and combines the
disassembled data into short cells.
The multiplexing information analyzer B (10B-1)
extracts the multiplexing information from the
initial position of the multiplexed data assembled
by the short cell multiplexing portion B (4B-3), and
analyzes the information, thereby extracting the
information for extracting the multiplexed short
cells.
The short cell disassembling portion B (10B-2)
carries out extracting processing of the multiplexed
short cells in accordance with the multiplexing
information obtained. The processing, however,
differs depending on the multiplexing information
data structure, and hence it will be described for
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CA 02489644 1996-10-11
respective examples of the multiplexing information
data structure, separately.
In the example 1 of the multiplexing information
data structure, the short cell disassembling portion
B (lOB-2) obtains the multiplexed pattern identifier
(PI) and error detecting/error correcting bits (C)
as the multiplexing information.
First, the short cell disassembling portion B
(10B-2) makes a decision from the error
detecting/error correcting bits (C) whether or not
any transmission error occurs in the multiplexing
information, and corrects the error if it is
correctable. If the error cannot be corrected
because only the error detecting function is
provided, or the error is not correctable, the
multiplexed data is relinquished because it is
difficult to extract the short cell on the basis of
the erroneous information. (Alternatively, it may
be possible to continue the processing without
relinquishing, allowing the possibility of error
extraction).
Second, the short cell disassembling portion B
(lOB-2) can extract the short cells because it can
decide the multiplexed data structure of the short
cells from the multiplexed pattern identifier
information (PI).
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CA 02489644 1996-10-11
If the short cell is placed across a plurality
of multiplexed data, a complete short cell can be
recovered by combining its stored first half and its
second half contained in the next multiplexed data.
For example, if the multiplexed pattern
identifier is "000011", one 30-byte short cell and
the first 16 bytes of a second 30-byte short cell
are multiplexed, and if the multiplexed pattern
identifier is "000100", the second 14 bytes of the
second 30-byte short cell, a third 30-byte short
cell and 2-byte null information are multiplexed.
With such a multiplexed data structure including
short cells across the plurality of multiplexed
data, the complete short cell can be recovered by
combining its components across the multiplexed data
when receiving the multiplexed pattern identifier
information "000011" followed by the multiplexed
pattern identifier information "000100".
If some contradiction occurs in the multiplexed
pattern information (for example, the multiplexed
pattern identifier information "000011" is
successively received twice in the foregoing
example), it can be found that the cell loss occurs
in the standard ATM cell conveying the multiplexing
information.
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CA 02489644 1996-10-11
The short cell is relinquished if a complete
short cell cannot be recovered owing to the omission
of the multiplexed data due to the cell loss or
owing to the cancellation of the multiplexed data
due to the transmission error.
In other words, the first half of the short cell
stored to be combined with its second half is
relinquished if the expected second half cannot be
obtained.
In contrast, if the first half of the short cell
has not been stored to be combined with its second
half extracted from the initial position of the
multiplexed data, the extracted second half of the
short cell is cancelled. Thus, the second and the
following short cells in the multiplexed data are
made valid.
To determine the presence or absence of the cell
loss or the accurate number of the lost cells, it is
necessary to apply the AAL (AAL type 1, for example)
having order information in the standard ATM cells
conveying the multiplexed data.
Using the function of the AAL of the standard
ATM cells and having the standard ATM cell processor
9 notify the short cell disassembling portion B
(10B-2) of the occurrence of the cell loss make it
possible to prevent erroneous short cell combining
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CA 02489644 1996-10-11
(combining of the first half and the second half of
different short cells) due to the cell loss
undetectable from the multiplexing information.
The short cells the short cell disassembling
portion B (10B-2) produces are delivered to the
short cell processor/data transmitter 11.
In the example 2 of the multiplexing information
data structure, the short cell disassembling portion
B (10B-2) obtains the multiplexed cell number
information (N), short cell length information (L),
multiplexing sequence number (SN), and error
detecting/error correcting bits (C), as the
multiplexing information.
First, the short cell disassembling portion B
1.5 (10B-2) makes a decision from the error
detecting/error correcting bits (C) whether or not
any transmission error occurs in the multiplexing
information, and corrects the error if it is
correctable. If the error cannot be corrected
because only the error detecting function is
provided, or the error is not correctable, the
multiplexed data is relinquished because it is
difficult to extract the short cell on the basis of
the erroneous information. (Alternatively, it may
be possible to continue the processing without
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CA 02489644 1996-10-11
relinquishing, allowing the possibility of error
extraction).
Second, the short cell disassembling portion B
(10B-2), analyzing the multiplexing sequence number
(SN), makes a decision that no cell overlapping is
present if SN=0, and extracts N-short cells with a
length of LI bytes in accordance with the
multiplexed cell number information (N) and the
short cell length information (L).
If SN=1, the short cell disassembling portion B
(10B-2), recognizing that a new cell overlapping
begins, extracts the short cells with a length of LI
bytes as many as possible, and stores the remaining
incomplete short cell to be combined with the second
half of that short cell obtained from the next
multiplexed data (in which SN=2).
The extraction processings are carried out N
times including that of the incomplete short cell.
If there further remains some multiplexed data, it
is cancelled out as the null information.
If SN>1, the short cell disassembling portion B
(10B-2) determines the boundaries between the short
cells in the multiplexed data in accordance with the
SN, and extracts the short cells. The first short
cell extracted is the second half of the short cell
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CA 02489644 1996-10-11
whose first half has been stored. Thus, they are
combined to a complete short cell.
The short cell disassembling portion B (10B-2)
extracts the short cells with the length of LI bytes
as many as possible beginning from the second short
cell, and stores the remaining incomplete short cell
to be combined with its second half which will be
obtained from the next multiplexed data.
The extraction processings are carried out N
times including that of the incomplete short cell.
If there further remains some multiplexed data, it
is cancelled out as the null information.
For example, in the case where the multiplexed
data length available for multiplexing the short
cells is 45 bytes, and when 36-byte short cell are
multiplexed across the multiplexed data, the
multiplexed data with the multiplexing sequence
number 1 (multiplexed data 1) indicates that it
includes a first 36-byte short cell (short cell A)
and a 9-byte short cell (a first half of a second
short cell B). Likewise, the multiplexed data with
the multiplexing sequence number 2 (multiplexed data
2) indicates that it includes a 27-byte short cell
(the second half of the second short cell B) and an
18-byte short cell (a first half of a third short
cell C). Accordingly, the short cell disassembling
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CA 02489644 1996-10-11
portion B (lOB-2) stores the first half of the
second short cell B at the time i~t receives the
multiplexed data 1, and combines it with the second
half of the second short cell B at the time it
receives the multiplexed data 2 to obtain the
complete short cell.
In this example, if the multiplexed cell number
N of the multiplexed data 2 is one, only the second
half of the short cell B is extracted, and the
remaining data is cancelled out as the null
information. In this case, the multiplexing
sequence number is reset to the next new number
SN=1.
If the received multiplexing sequence number
skips (such as the multiplexing sequence number 1 is
followed by the multiplexing sequence number 3), it
can be found that the cell loss occurs in the
standard ATM cell conveying the multiplexing
information.
The short cell is relinquished if a complete
short cell cannot be recovered owing to the omission
of the multiplexed data due to the cell loss or
owing to the cancellation of the multiplexed data
due to the transmission error.
In other words, the first half of the short cell
stored to be combined with its second half is
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CA 02489644 1996-10-11
relinquished if the expected second half cannot be
obtained.
In contrast, if the first half of the short cell
has not been stored to be combined with its second
half extracted from the initial position of the
multiplexed data, the extracted second half of the
short cell is cancelled. Thus, the second and the
following short cells in the multiplexed data are
made valid.
Although the cell loss within one cycle of the
sequence can be detected using the multiplexing
sequence number, to determine the presence or
absence of the cell loss or the accurate number of
the lost cells beyond that range, it is necessary to
apply the AAL (AAL type 1, for example) having the
order information in the standard ATM cells
conveying the multiplexed data.
Using the function of the AAL of the standard
ATM cells and having the standard ATM cell processor
9 notify the short cell disassembling portion B
(10B-2) of the occurrence of the cell loss make it
possible to prevent erroneous short cell combining
(combining of the first half and the second half of
different short cells) due to the cell loss
undetectable from the multiplexing information.
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CA 02489644 1996-10-11
The short cells the short cell disassembling
portion B (10B-2) produces are delivered to the
short cell processor/data transmitter 11.
In the example 3 of the multiplexing information
data structure, the short cell disassembling portion
B (10B-2) obtains the multiplexed cell number
information (N), composite type information (CT:
Cell Type), N pieces of short cell length
information (LI1-LIn) and error detecting/error
correcting bits (C). As will be described in
connection with Figs. 35, 36 and 38, the example 3
of the multiplexing information data structure
includes the length information and overlapping
information in the common AAL for multiplexing.
Figs. 35, 36 and 38 are flowcharts of the processing
mentioned above.
First, the short cell disassembling portion B
(10B-2) makes a decision from the error
detecting/error correcting bits (C) whether or not
any transmission error occurs in the multiplexing
information, and corrects the error if it is
correctable. If the error cannot be corrected
because only the error detecting function is
provided, or the error is not correctable, the
multiplexed data is relinquished because it is
difficult to extract the short cell on the basis of
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CA 02489644 1996-10-11
the erroneous information. (Alternatively, it may
be possible to continue the processing without
relinquishing, allowing the possibility of error
extraction).
Second, the short cell disassembling portion B
(10B-2) extracts N short cells in accordance with
the multiplexed cell number information, the
composite type information (CT) and the short cell
length information (LI1-LIn). Specifically, after
extracting the multiplexing information, it extracts
N short cells in accordance with the lengths
indicated by the short cell length information
(short cell length information (LI1-LIn)) beginning
from the initial position of the multiplexed data,
and relinquishes the remaining data, it there is
any, as the null information.
In this case, the composite type information CT
is referred to for carrying out the extracting
processing of the first and N-th short cells (where
N=1 is possible).
If CT="00", the short cell disassembling portion
B (10B-2) decides that the entire short cells are
complete, and carried out the normal extracting
processing.
If CT="01", the short cell disassembling portion
B (10B-2) decides that only the second half of the
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CA 02489644 1996-10-11
N-th short cell is lacking, and stores the N-th
short cell to be combined with the first short cell
in the next multiplexed data.
If CT="10", the short cell disassembling portion
B (10B-2) decides that only the first half of the
first short cell is lacking, and obtains a complete
short cell by combining the first short cell with
the stored final short cell in the previous
multiplexed data.
If CT="11", the short cell disassembling portion
B (10B-2) decides that both the first half of the
first short cell and the second half of the N-th
short cell are lacking, and combines the stored
final short cell in the previous multiplexed data
with the received first short cell to restore a
complete short cell (if N=1, a complete short cell
cannot be obtained and hence it is stored again).
In addition, the received N-th short cell is stored
to be combined with the first short cell in the next
2'0 multiplexed data.
It can be found that the cell loss occurs in the
standard ATM cell conveying the multiplexing
information, if some contradiction occurs in the
received composite type information (for example,
although the received multiplexing information of
multiplexed data is CT="00" or CT="10", that of the
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CA 02489644 1996-10-11
next multiplexed data is CT="10" or CT="11"; or
reversely, although CT="10" or CT="11" is received
as the multiplexing information of multiplexed data,
the multiplexing information of the previous
multiplexed data is CT="00" or CT="10" and there is
no stored short cell to be combined).
The short cell is relinquished if a complete
short cell cannot be recovered owing to the omission
of the multiplexed data due to the cell loss or
owing to the cancellation of the multiplexed data
due to the transmission error.
In other words, the first half of the short cell
stored to be combined with its second half is
relinquished if the expected second half cannot be
obtained.
In contrast, if the first half of the short cell
has not been stored to be combined with its second
half extracted from the initial position of the
multiplexed data, the extracted second half of the
short cell is cancelled. Thus, the second and the
following short cells in the multiplexed data are
valid.
To determine the presence or absence of the cell
loss or the accurate number of the lost cells, it is
necessary to apply the AAL (AAL type 1, for example)
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CA 02489644 1996-10-11
having the order information in the standard ATM
cells conveying the multiplexed data.
Using the function of the AAL of the standard
ATM cells and having the standard ATM cell processor
9 notify the short cell disassembling portion B
(10B-2) of the occurrence of the cell loss make it
possible to prevent erroneous short cell combining
(combining of the first half and the second half of
different short cells) due to the cell loss
undetectable from the multiplexing information.
The short cells the short cell disassembling
portion B (10B-2) produces are delivered to the
short cell processor/data transmitter 11.
EMBODIMENT 3
An embodiment 3 of the short cell multiplexer
and short cell disassembler will now be described
with reference to Figs. 14-16.
zn the present embodiment 3, since the
multiplexed data structure is known by a short cell
multiplexer C (4C) and a short cell disassembler C
(10C) in advance, it is only necessary to combine
short cells in accordance with the known multiplexed
pattern.
Thus, the present embodiment is characterized in
that it is unnecessary for the short cell
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CA 02489644 1996-10-11
multiplexes C (4C) to add the foregoing short cell
information or multiplexing information by matching
the multiplexed data structure and the header
address of the standard ATM cell conveying the
multiplexed data to those of the short cell
disassembles C (10C) in advance. This offers the
advantage that the data bytes in the payload of the
standard ATM cell, which have been occupied by the
short cell information or the multiplexing
information, can be used for multiplexing the short
cells.
In addition, the short cell multiplexes C (4C)
can employ the header of the short cell multiplexed
onto the initial position of multiplexed data as the
header of the standard ATM cell conveying the
multiplexed data without change, if the structure of
the short cell header provided to the short cell by
the SC-H provider 3-4 is the same as that of the
standard ATM cell, and if the short cell multiplexes
C (4C) has made the above-mentioned matching in
advance, that is, the matching of the address of the
short cell header and the multiplexed data structure
with those of the short cell disassembles C (lOC),
when providing the short cell header. This presents
the advantage that the five bytes occupied by the
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CA 02489644 1996-10-11
standard ATM header can be utilized for multiplexing
the short cells.
The short cell multiplexer C (4C) is composed of
a multiplexing combination determiner C (4C-1) and a
short cell multiplexing portion C (4C-2), and
carries out different processings according to the
following cases.
(1) When the standard ATM cell generator 5
gives the header of the standard ATM cell conveying
the multiplexed data.
(2) When the short header given by the SC-H
provider 3-4 is used as the header of the standard
ATM cell conveying the multiplexed data.
The processings will now be described with
reference to Figs. 15A and 15B.
(1) When the standard ATM cell generator 5
gives the header of the standard ATM cell conveying
the multiplexed data (see, Fig. 15A).
When multiplexing a plurality of input short
cells into the payload of the standard ATM cell, the
multiplexing combination determiner C (4C-1) in Fig.
14 makes a decision of the combination and order of
the multiplexing.
In making this decision, the multiplexing
combination determiner C (4C-1) decides the
multiplexing in such a way that the multiplexed data
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CA 02489644 1996-10-11
structure is obtained which agrees with the address
of the standard ATM header provided by the standard
ATM cell generator 5. (Alternatively, the standard
ATM cell generator 5 provides the standard ATM
header corresponding to the multiplexed data
structure in accordance with the decision on
multiplexing by the multiplexing combination
determiner C (4C-1)).
The combinations of multiplexing thus determined
falls into the following three multiplexed data
length patterns in accordance with the multiplexed
data length.
(Pattern 1) The multiplexed data length equals
48 bytes.
(Pattern 2) The multiplexed data length is less
than 48 bytes.
(Pattern 3) The multiplexed data length exceeds
48 bytes.
Here, the multiplexed data length is defined as
the sum total of the sum of the lengths of the short
cells to be multiplexed and the AAL information
length given by the standard ATM cell generator 5.
In the case of the pattern 3, since the data
cannot be accommodated in a single standard ATM
cell, the overflowed data of the short cell at the
final position (that is, data beyond 48 bytes) must
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CA 02489644 1996-10-11
be transferred by the next standard ATM cell. Thus,
the overflowed data is separated ~as a new short cell
(having no SC-H and SC-AAL), and placed in the next
standard ATM cell as the first short cell to be
multiplexed.
The short cell multiplexing portion C (4C-2)
carries out the different processings in accordance
with the multiplexed data length patterns as
mentioned above.
In the case of the pattern 1 in which the
multiplexed data length is 48 bytes, the short cell
multiplexing portion C (4C-2) links the short cells
in accordance with the combination and multiplexing
order of the short cells decided by the multiplexing
combination determiner C (4C-1).
In the case of the pattern 2 in which the
multiplexed data length is less than 48 bytes, the
short cell multiplexing portion C (4C-2) links the
short cells in a manner similar to those of the
multiplexed data length pattern 1, and adds the null
information (NULL) to the final position of the
multiplexed data so that the total data length
becomes 48 bytes considering the AAL information
length provided by the standard ATM cell generator
5.
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CA 02489644 1996-10-11
In the case of the pattern 3 in which the
multiplexed data length exceeds 48 bytes, the
multiplexed data length is adjusted to 48 bytes by
delivering the data exceeding 48 bytes to the next
standard ATM cell as the first short cell to be
multiplexed. Accordingly, the short cell
multiplexing portion C (4C-2) links the short cells
in a manner similar to those of the multiplexed data
length pattern 1.
The multiplexed data with a length of 48 bytes
assembled by the short cell multiplexing portion C
(4C-2) is sent to the standard ATM cell generator 5.
(2) When the short header given by the SC-H
provider 3-4 is used as the header of the standard
ATM cell conveying the multiplexed data (see, Fig.
15B ) .
When multiplexing a plurality of input short
cells into the same form as the standard ATM cell,
the multiplexing combination determiner C (4C-1) in
Fig. 14 makes a decision of the combination and
order of the multiplexing.
In making this decision, the multiplexing
combination determiner C (4C-1) decides the
multiplexing in such a way that the multiplexed data
structure is obtained which agrees with the address
of the short cell header which is provided by the
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CA 02489644 1996-10-11
SC-H provider 3-4 and has the same structure as the
standard ATM header. (Alternatively, the SC-H
provider 3-4 provides the short cell header of the
same structure as the standard ATM header
corresponding to the multiplexed data structure,
prior to the decision on multiplexing by the
multiplexing combination determiner C (4C-1)).
In the B-ISDN network 7, the SC-H of the first
short cell in the multiplexed data functions as the
header of the standard ATM, and its SC-AAL functions
as the AAL of the standard ATM.
The combinations of multiplexing thus determined
falls into the following three patterns in
accordance with the multiplexed data length.
(Pattern 1) The multiplexed data length equals
53 bytes.
(Pattern 2) The multiplexed data length is less
than 53 bytes.
(Pattern 3) The multiplexed data length exceeds
53 bytes.
Here, the multiplexed data length is defined as
the sum of the lengths of the short cells to be
multiplexed.
In the case of the pattern 3, since the data
cannot be accommodated in a single standard ATM
cell, the overflowed data of the short cell at the
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CA 02489644 1996-10-11
final position (that is, data beyond 53 bytes) must
be transferred by the next standard ATM cell. Thus,
the overflowed data is separated as a new short cell
(having no SC-H and SC-AAL), and placed in the next
standard ATM cell as the short cell to be
multiplexed. (In this case, since it has no SC-H,
it must be multiplexed in a position other than the
initial position. Alternatively, it can be placed
at the initial position as the first short cell by
providing the same SC-H and SC-AAL as those of the
original cell by copying them when making the new
short cell from the overflowed data.) The short
cell multiplexing portion C (4C-2) carries out the
different processings in accordance with the
multiplexed data length patterns as mentioned above.
In the case of the pattern 1 in which the
multiplexed data length is 53 bytes, the short cell
multiplexing portion C (4C-2) links the short cells
in accordance with the combination and multiplexing
order of the short cells decided by the multiplexing
combination determiner C (4C-1).
In the case of the pattern 2 in which the
multiplexed data length is less than 53 bytes, the
short cell multiplexing portion C (4C-2) links the
short cells in a manner similar to that of the
multiplexed data length pattern 1, and then adds the
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CA 02489644 1996-10-11
null information (NULL) to the final position of the
multiplexed data so that the total data length
becomes 53 bytes.
In the case of the pattern 3 in which the
multiplexed data length exceeds 53 bytes, the
multiplexed data length is adjusted to 53 bytes by
delivering the data exceeding 53 bytes to the next
standard ATM cell as the short cell to be
multiplexed. Accordingly, the short cell
multiplexing portion C (4C-2) links the short cells
in a manner similar to that of the multiplexed data
length pattern 1.
The multiplexed data with a length of 53 bytes
assembled by the short cell multiplexing portion C
(4C-2) is sent to the ATM cell transmitter 6. (The
processing by the standard ATM cell generator 5 is
omitted).
The short cell disassembles C will now be
described with reference to Fig. 16.
The short cell disassembles C (10C) carries out
different processings according to the following
cases taken by the short cell multiplexes C (4C) to
assemble the multiplexed data.
(1) When the standard ATM cell generator 5
gives the header of the standard ATM cell conveying
the multiplexed data.
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CA 02489644 1996-10-11
(2) When the short header given by the SC-H
provider 3-4 is used as the header of the standard
ATM cell conveying the multiplexed data.
The case will now be described where standard
ATM cell generator 5 gives the header of the
standard ATM cell conveying the multiplexed data.
In Fig. 16, the short cell disassembler C (10C)
is composed of a short cell disassembling portion C
(10C-1). It disassembles the multiplexed data which
is assembled by the short cell multiplexing portion
C (4C-2) and fed from the standard ATM cell
processor 9, and combines the disassembled data into
short cells.
The short cell disassembling portion C (10C-1)
makes a decision of the corresponding multiplexed
data structure from the address of the standard ATM
header processed by the standard ATM cell processor
9, and extracts the short cells from the multiplexed
data.
2'0 If the previously known multiplexed data
structure allows a short cell overlapping across a
plurality of multiplexed data, the received short
cell (the first half) is stored to be combined with
the second half in the next multiplexed data when it
is received to form a complete short cell.
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CA 02489644 1996-10-11
To determine the presence or absence of the cell
loss or the accurate number of the lost cells, it is
necessary to apply the AAL (AAL type 1, for example)
having the order information in the standard ATM
cells.
The short cell is relinquished if a complete
short cell cannot be recovered owing to the omission
of the multiplexed data due to the cell loss or
owing to the cancellation of the multiplexed data
due to the transmission error.
In other words, the first half of the short cell
stored to be combined with its second half is
relinquished if the expected second half cannot be
obtained.
In contrast, if the first half of the short cell
has not been stored to be combined with its second
half extracted from the initial position of the
multiplexed data, the extracted second half of the
short cell is cancelled. Thus, the second and the
following short cells in the multiplexed data are
made valid.
(2) When the short header given by the SC-H
provider 3-4 is used as the header of the standard
ATM cell conveying the multiplexed data.
In Fig. 16, the short cell disassembler C (10C)
is composed of the short cell disassembling portion
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CA 02489644 1996-10-11
C (lOC-1). Tt disassembles the multiplexed data
which is assembled by the short cell multiplexing
portion C (4C-2) and fed from the ATM cell receiver
8, and combines the disassembled data into short
cells. (The processing in the standard ATM cell
processor 9 is omitted.)
The short cell disassembling portion C (10C-1)
makes a decision of the corresponding multiplexed
data structure from the address of the short cell
header, and extracts the short cells from the
multiplexed data.
If the previously known multiplexed data
structure allows a short cell overlapping across a
plurality of multiplexed data, the received short
cell (the first half) is stored to be combined with
the second half in the next multiplexed data when it
is received to form a complete short cell.
To determine the presence or absence of the cell
loss or the accurate number of the lost cells, it is
necessary to apply the AAL (AAL type 1, for example)
having the order information in the standard ATM
cells.
The short cell is relinquished if a complete
short cell cannot be recovered owing to the omission
of the multiplexed data due to the cell loss or
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CA 02489644 1996-10-11
owing to the cancellation of the multiplexed data
due to the transmission error.
In other words, the first half of the short cell
stored to be combined with its second half is
relinquished if the expected second half cannot be
obtained.
In contrast, if the first half of the short cell
has not been stored to be combined with its second
half extracted from the initial position of the
multiplexed data, the extracted second half of the
short cell is cancelled.
OTHER EMBODIMENTS
Referring to Figs. 17A and 17B, other
embodiments will now be described which carries out
transmission by an integrated method of the
foregoing short cell multiplexed ATM transmission
method and other transmission methods.
In Figs. 17A and 17B, the standard ATM cell
assembler 1 can comprise, besides a short cell
multiplexing payload assembler 16 including the data
receiver/short cell assembler 3 and short cell
multiplexer 4, payload assemblers 18, 20, 22 and 24
employing other ATM transmission methods.
The conventional ATM type payload assembler 18
assembles the payload (except for the AAL
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CA 02489644 1996-10-11
information) of the existing ATM cell according to
the specifications on AAL type 1 - type 5 defined by
ITU-T international standard.
The partial fill type payload assembler 20
assembles the payload (except for the AAL
information) of the ATM cell, in which only part of
the payload is used for user data and the remaining
portion is filled with the null information to
reduce the delay involved in assembling the cell.
The path clad type payload assembler 22
assembles the payload (except for the AAL
information) of the ATM cell by dividing the payload
of an ATM cell into several subslots so that a
plurality of user data are put into respective
subslots of the payload of the single ATM cell.
This method enables a mechanical fast processing by
associating the time slots of the STM channel with
the subslots of the ATM cell, for example.
The other ATM type payload assembler 24
assembles the payload (except for the AAL
information) of an ATM cell other than the foregoing
ATM cells.
The standard ATM cell disassembler 2 can
comprise, besides a short cell multiplexing type
payload disassembler 17 including the short cell
disassembler 10 and the short cell processor 11,
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CA 02489644 1996-10-11
payload disassemblers 19, 21, 23 and 25 employing
other ATM transmission methods.
The conventional type ATM payload disassembler
19 disassembles and processes the payload (except
for the AAL information) assembled by the
conventional ATM type payload assembler 18.
The partial fill type payload disassembler 21
disassembles and processes the payload (except for
the AAL information) assembled by the partial fill
type payload assembler 20.
The path clad type payload assembler 23
disassembles and processes the payload (except for
the AAL information) assembled by the path clad type
payload assembler 22.
The other ATM type payload disassembler 25
disassembles the payload (except for the AAL
information) assembled by the other ATM type payload
assembler 24.
The standard ATM cell generator 5 receives the
payloads of the standard ATM with various internal
structures formed by the payload assemblers 16, 18,
20, 22 and 24, and assembles the standard ATM cell
by adding the needed AAL information and ATM header.
The standard ATM cell processor 9, receiving
from the ATM cell receiver 8 the mixed standard ATM
cells having various internal structures formed by
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CA 02489644 1996-10-11
the payload assemblers 16, 18, 20, 22 and 24,
processes the ATM header of each received standard
ATM cell, and carries out the AAL processing. The
payloads thus obtained are delivered separately to
the payload disassemblers 17, 19, 21, 23 and 25.
The standard ATM cell generator 5 and standard
ATM cell processor 9 each have a branching means:
The standard ATM cell generator 5 employs it for
mixing the plurality of ATM transmission methods to
carry out transmission over the common B-ISDN
network 7; and the standard ATM cell processor 9
employs it for branching the standard ATM cells into
corresponding payload disassemblers.
There are two branching methods as follows, and
the two can be combined.
(1) Branching method 1 that employs the routing
bits (VPI and VCI) of the ATM header.
The standard ATM cell processor 9 decides the
payload disassemblers 17, 19, 21, 23 and 25 to which
the branched cells are delivered by analyzing the
routing bits (VPI and VCI) of the ATM header.
For this purpose, when providing the ATM header
during ATM path setting, the standard ATM cell
generator 5 communicates with the standard ATM cell
processor 9 to establish correspondence between the
routing bits of the provided ATM header and the
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CA 02489644 1996-10-11
types of the transmission methods. The
correspondence can be omitted if it is set in
advance as the office data or the like.
(2) Branching method 2 that possesses the
transmission method information as part of the AAL
information of the ATM payload.
The standard ATM cell processor 9 decides the
payload disassemblers 17, 19, 21, 23 and 25 to which
the branched cells are to be delivered by analyzing,
during the AAL processing, the transmission method
information included in the part of the AAL
information.
For this purpose, the standard ATM cell
generator 5 places the transmission method
information indicating the transmission methods into
the part of the AAL information when providing the
AAL. The payload assemblers 16, 18, 20, 22 and 24
each assemble the payload with a length taking
account of the length of the AAL information.
EMBODIMENT 4
The relationships between the AAL information
and information for multiplexing the short cells
will be considered again.
2'S The AAL information is the information for the
adaptation to the ATM. Furthermore, considering the
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CA 02489644 1996-10-11
short cell multiplexing in the embodiments of the
present invention, all the information for
adaptation needed to transmit a plurality of short
cells by multiplexing them into a single ATM
connection can be generally termed short cell
multiplexing AAL information.
This will be described with reference to Figs.
18 and 19. Fig. 18 corresponds to the foregoing
embodiment 1 and Fig. 19 corresponds to the
foregoing embodiment 2.
As described in the embodiment 1 in connection
with Figs. 4-6, when the length information is
provided for each short cell, the short cell header
(SC-H) and/or the individual short cell information,
combined with the SC-AAL, and the AAL in the
standard ATM cell can be called the short cell
multiplexing AAL. In this case, the AAL in the
standard ATM cell is the short cell common AAL which
can be distinguished from the short cell individual
AAL provided for each short cell like the short cell
information, SC-H and SC-AAL.
In Fig. 18 illustrating the foregoing
relationships concretely, the symbols represent the
following.
Short cell multiplexing common AAL
SN: Sequence Number
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CA 02489644 1996-10-11
OID: Overlapping Identifier
C: Check bit
Short cell multiplexing individual AAL
(Short cell information)
LI: Length Information
(SC-H)
SCI: Short cell Connection Identifier
PT: Payload Type
C: Check bit
(SC-AAL)
FN: Frame Number
Vb: Voice activation bit
CON: Confidentiality Information
As described in the embodiment 2 in connection
with Figs. 7-13, when a format is used representing
the short cells multiplexed into the standard ATM
with a single piece of multiplexing information, the
combination of each short cell header (SC-H) and the
SC-AAL can be called the short cell multiplexing
AAL. In addition, the AAL information added to each
multiplexed data, which is assembled by
multiplexing the short cells in the AAL layer (ATM
Adaptation Layer) carrying out the short cell
multiplexing, is called "short cell multiplexing
common AAL", and the AAL information added to each
short cell in the AAL layer (ATM Adaptation Layer)
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CA 02489644 1996-10-11
carrying out the short cell multiplexing is called
"short cell multiplexing individual AAL".
In Fig. 19 illustrating the foregoing
relationships concretely, the symbols represent the
following.
Short cell multiplexing common AAL
SN: Sequence Number
OID: Overlapping IDentifier (multiplexing
information)
N: Number of short cells
LI1-LIn: Length Information
C: Check bit
Short cell multiplexing individual AAL
(SC-H)
SCI: Short cell Connection Identifier
PT: Payload Type
C: Check bit
(SC-AAL)
FN: Frame Number
Vb: Voice activation bit
CON: Confidentiality Information
Taking the embodiment 3 described in connection
with Figs. 14-16, the AAL provided by the standard
ATM cell generator 5 can be called the short cell
multiplexing AAL information.
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CA 02489644 1996-10-11
Figs. 20A and 20B - 22A and 22B illustrate this
in connection with the short cell multiplexing
processing. In these figures, "Layers" represent
the processing layers, and the "Data Formats"
represent the data formats generated by the
multiplexing processing.
The "Application" in the "Layers" represents
layers for carrying out input and output processings
of the user data from various sources. SDU is the
abbreviation for "Service Data Unit".
Next, CS refers to "Convergence Sublayer", a
layer for completing the short cell. The CS is
divided into two: SSCS (Service Specific CS) which
carries out individual processings corresponding to
the attributes of individual data constituting the
short cells so as to provide or deprive the SC-AAL;
and CPCS (Common Part CS) which provides the short
cell connection identifier or the like (SC-H) for
multiplexing the short cells to be transmitted, and
deprives it from the SC-H by processing the SC-H.
Here, PDU is the abbreviation for the "Protocol Data
Unit".
Next to the short cell processings, a MAD
(Multiplexed And Demultiplexed) layer for
multiplexing the assembled short cells into the
standard ATM cell. This layer is also divided into
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two: SSAR (Short cell Segmentation And Reassembly)
for segmenting the short cells in accordance with
the standard ATM cell or for reassembling the short
cells from the standard ATM cell; and MAD (Multiplex
And Demultiplex) for assembling or disassembling the
standard ATM cell. The SSAR makes a division
(segmentation) of the short cells as needed, so that
they are adjusted to become 48 bytes when
multiplexed in the MAD.
Figs. 20A, 20B, 21A and 21B illustrate the case
in which the length information is provided for each
short cell as described in the embodiment 1 shown in
Figs. 4-6.
Figs. 22A and 22B illustrate the case in which a
single piece of multiplexing information represents
the short cells multiplexed into the standard ATM
cell as described in the embodiment 2 shown in Figs.
7-13.
Referring to Figs. 20A and 20B, the process from
the input of the user data to the assembly of the
standard ATM cell will be described. The process
from the input of the standard ATM cell to the
disassembly of the user data is carried out
reversely.
In Figs. 20A and 20B, when various data with a
variable length are input, individual processings
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corresponding to the attributes of individual data
are carried out (SSCS). As the result of the
individual processing, the SC-AAL is provided.
Besides, the SC-H including the short cell
connection identifier or the like (SC-H) is also
provided (CPCS).
The SSAR segments the short cell (into short
cell segments) as needed for multiplexing them onto
the standard ATM cell (when the short cell is placed
across the standard ATM cells), and provides the
individual data units (SSAR-PDU) with the length
information after the segmentation.
The MAD assembles the standard ATM cell by
multiplexing the plurality of the SSAR-PDU. In
addition, it inserts the null information or a dummy
short cell into the remainder of the payload of the
standard ATM cell. It further generates and
provides the sequence number or overlapping
information (MAD).
In this case, since the length information is
provided for each SSAR-PDU after division, its
indication never exceed 48 bytes.
Figs. 21A and 21B differ from Figs. 20A and 20B
in a method for providing the length of the short
cell. In Figs. 20A and 20B, it is provided for each
unit (SSAR-PDU) generated by dividing the short
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cells to multiplex them in accordance with the
standard ATM cell (MAD layer). In contrast, in
Figs. 21A and 21B, the short cell length is provided
for each short cell (CPCS), and if the short cell is
divided for multiplexing it across the standard ATM
cells, the divided second half is also provided with
the length information (MAD).
In this case, since the length information is
provided for each short cell, it can exceed 48
bytes.
In Figs. 22A and 22B, to provide each standard
ATM cell with the length information of the short
cells, the number of the SSAR-PDUs multiplexed into
the standard ATM cell and their individual length
information and overlapping information are
generated to be provided at the final stage of
forming the standard ATM cell.
Considering the AAL of the standard ATM together
with the information for the short cell multiplexing
makes it possible to arrange the role assignment of
the blocks of the system as shown in Figs. 11-16 as
in Figs. 23-25.
The short cell information provider A (4A-2) in
Fig. 4, together with the SC-AAL provider 3-3 and
SC-H provider 3-4 shown in Fig. 2, handles the
information for ATM adaptation of the short cell
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CA 02489644 1996-10-11
multiplexing, which provides the SC-AAL, SC-H and
short cell information to be given to each short
cell (see, Figs. 23 and 24).
In Fig. 7, the multiplexing information
generator B (4B-2) provides each multiplexed data
with multiplexing information when multiplexing the
short cells (Fig. 25)
The standard ATM cell generator 5 in Fig. 1A and
1B common to all the embodiments handles the
information for ATM adaptation of the short cell
multiplexing, which is to be given to each ATM
payload after multiplexing. It is easy to alter the
structure so that the standard ATM cell generator 5
can freely provide, as the AAL information, not only
information defined by the Type 1 - Type 5 which are
now subjected to standardization in ITU-T, but also
the information for the ATM adaptation (such as the
SN or OID) satisfying diverse requirements.
Considering the foregoing arrangement, the
system portion for generating and providing the
short cell multiplexing AAL can be made as follows
from the viewpoints of effective allocation of the
short cell multiplexing AAL and simplifying the
system configuration.
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EMBODIMENT 4-1
The application will now be described of the
foregoing idea to the case where the short cell
information is provided for each short cell as in
the embodiment 1 shown in Figs. 4-6. In this case,
it is possible in Fig. 4 to replace the short cell
status information (ST) provided by the short cell
information provider A (4A-2) by the overlapping
identifier (OID) provided for each ATM payload by
the standard ATM cell generator 5.
This obviates the need for giving the short cell
status information (ST) which is provided for each
short cell. Fig. 18 shows an example of the
information structure of the short cell multiplexing
AAL using the OID instead of the short cell status
information (ST), and Figs. 26A and 26B show the
system configuration for implementing this. The
following description is made when the processings
as shown in Figs. 21A and 21B are carried out by the
system assignment as shown in Fig. 24. The SC-H
provider 3-4 provides each short cell with the short
cell connection identifier (SCI), the short cell
information provider A (4A-2) provides each short
cell with the length information (LI) and the check
bits (parity) (C2 and C3), and the standard ATM cell
generator 5 provides each ATM payload with the ATM
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CA 02489644 1996-10-11
cell sequence number (SN), cell overlapping
identifier (OID), and parity (C1).
This is achieved by a simplified configuration
formed by integrating the SC-H provider 3-4 and
short cell information provider A (4A-2) as shown in
Fig. 26A, and by providing each short cell with the
information. In this arrangement, the multiplexing
combination determiner A (4A-1) is placed after the
short cell information provider A (4A-2). If the
short cell is divided by the multiplexing
combination determiner A (4A-1) because the ATM
payload has only insufficient space, the separated
second half is also provided with the length
information, and is multiplexed by the short cell
multiplexing portion A (4A-3).
Receiving the ATM cell having the information
structure of the short cell multiplexing AAL, the
standard ATM cell disassembler 2 disassembles the
short cell in the following procedure, which will
now be described with reference to Fig. 26A and 26B.
The standard ATM cell processor 9 obtains from the
AAL the ATM cell sequence number (SN), cell
overlapping identifier (OID) and parity (C), and
checks the information error using the parity bits
(C). Subsequently, it detects for each cell whether
any cell loss occurs or not with the ATM cell
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CA 02489644 1996-10-11
sequence number (SN). The detection of the cell
loss provides important decision information for
extracting the overlapped short cell. The cell
overlapping identifier (OID) has a similar function
as that of the composite type information (CT)
described in connection with the short cell
disassembler B (10B) in Fig. 9. Therefore, the
standard ATM cell processor 9 which processes the
cell overlapping identifier (OID) cooperates with
the short cell disassembling portion A (10A).
The description about the OID will be omitted
here because it is the same as that about the CT in
Fig. 9. Using the OID enables the cell loss to be
detected as when using the CT, without using the
sequence number (SN).
Next, the extraction of the short cells from the
standard ATM payload can be achieved by the short
cell disassembler A (10A) which looks into the LI of
the short cell information provided for each short
cell as in Fig. 6, and the extracted short cell are
delivered to the short cell processor/data
transmitter 11. In the embodiment 4-1, the length
information and the overlapping information are
included in the multiplexing individual AAL and the
multiplexing common AAL, respectively, as shown in
the flowcharts of Figs. 35, 36 and 39.
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EMBODIMENT 4-2
The application will now be described of the
foregoing idea to the case where the multiplexing
information is provided for each standard cell as in
the embodiment 2 shown in Figs. 7-13. In this case,
as shown in Fig. 19, the short cell information is
collected and placed as the multiplexing information
of the standard AAL. The processing of Fig. 25 will
now be described with reference to Fig. 24.
As shown in Figs. 27A and 27B, the multiplexing
information generator B (4B-2) and the standard ATM
cell generator 5 are integrated. The multiplexing
information the multiplexing information generator B
(4B-2) forms for each multiplexed data can be
1.5 partially or entirely included into the AAL which is
provided for each ATM payload by the standard ATM
cell generator 5. In this case, the short cell
length information of each short cell is prepared by
the multiplexing information generator B (4B-2)
after the multiplexing combination determiner B (4B-
1) decides the combination of the short cells, and
is provided for the multiplexed data by the short
cell multiplexing portion B (4B-3).
In the course of this, the ATM sequence number
(SN), cell overlapping identifier (OID) and parity
(C1) are also provided for each ATM payload by the
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CA 02489644 1996-10-11
multiplexing information generator B (4B-2) or the
standard ATM cell generator 5.
The disassembling procedure in the standard ATM
cell disassembler 2 is basically the same as that of
the foregoing embodiment 1. In this case, since the
information for extracting the short cells is
included in the multiplexing information or the
standard AAL, the multiplexing information analyzer
B (10B-1) and standard ATM cell processor 9 are
integrated to extract the information.
Then, the short cell disassembling portion B
(10B-2) disassembles the multiplexed data into the
short cells, delivers them to the short cell
processor/data transmitter 11.
EMBODIMENT 5
If there is some constraint on the short cell
length handled by the CPCS, SSCS divides the user
data into a plurality of data with a length within
the allowed short cell length, and provides each
divided data with such information that will enable
them to be reassembled at the receiving end.
In the foregoing case, the SC-PL assembler and
the SC-AAL provider in the data receiver/short cell
assembler carry out the following processings.
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The SC-PL assembler and the SC-AAL provider
cooperate.
When there is constraint on the short cell
payload length, the SC-PL assembler divides the user
data of the input data obtained by the data
receiving portion into a plurality of data with a
length within the short cell payload length.
The SC-AAL provider carries out one of the
following processings from (1) to (3) or a
combination thereof.
(1) It provides a divided user data sequence
number as the SC-AAL so as to detect the order or
omission of the divided user data. Methods for
providing it when dividing the user data into three
parts, for example, are: a) providing individual
divided user data with 1, 2 and 3; b) providing them
with 1/3, 2/3 and 3/3; and c) providing with 1, 2,
3, 4, ..., N in the arriving order of the divided
user data at a certain interval without considering
the individual user data.
This processing (1) can be omitted if the
divided user data can be controlled to arrive at the
short cell processor/data transmitter at regular
time intervals by controlling the short cell
multiplexer and ATM cell transmitter or the like.
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(2) It provides the final divided user data or
the initial divided user data with d) final
identifier or e) initial identifier, as the SC-AAL.
As the final identifier, identification bits
indicating that the divided user data is the last
one are given. The number of division can be added.
As the initial identifier, identification bits
indicating that the divided user data is the first
one is given. The number of division can also be
added.
3) It provides the error detecting/correcting
information for f) the final divided user data or g)
the initial divided user data. The error
detecting/correcting information has been computed
with the whole user data before division.
The type of the SC-AAL information (SC-AAL type)
which is set here is notified when the short cell
header is determined by the SC-H provider 3-4 or the
SC-H processor 11-1 in the standard ATM cell
disassembler 2, thus to be related to the
processings in the SC-AAL processor 11-2.
The SC-AAL processor and SC-PL processor in the
short cell processor/data transmitter carry out the
following processings in correspondence to the
processings of the foregoing SC-PL assembler and the
SC-AAL provider.
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CA 02489644 1996-10-11
The SC-AAL processor and the SC-PL processor
cooperate.
The SC-PL processor reassembles the divided user
data by the SC-PL assembler to recover the original
user data. For this purpose, the SC-A.AL processor
analyze the information provided by the SC-AAL
provider.
The processing of the SC-AAL processor is
decided by the SC-H processor (11-1) which searches
for the correspondence of the SC-AAL from the short
cell header using the address translation table 2.
The SC-AAL processor carries out one of the
following processings (1)-(3) or a combination
thereof, in correspondence to the processings in the
SC-AAL provider.
(1) The SC-AAL processor reads the SC-AAL
information, and confirms from the divided user data
sequence number the validity of the order and the
presence or absence of the omission of the divided
user data, and thus the arrival of the entire
divided user data. With regard to a), returning of
the sequence number to one ensures that the divided
user data up to that time are the divided units.
with regard to b), the sequence number includes the
number of divisions. With regard to c), since the
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CA 02489644 1996-10-11
division units cannot be recognized, the following
(2) or (3) are used together.
(2) The SC-AAL processor reads the SC-AAL
information, and with regard to d), it decides the
final divided unit from the final identifier, and
identifies that the final one together with the
divided data stored up to that time constitutes the
whole divided user data. If the divided number
information is added, confirmation is made whether
the number information agrees with the total number
of the divided user data. With regard to e), the
SC-AAL processor decides from the initial identifier
that the data is the initial divided unit, and
identifies that the divided user data stored up to
that time constitute the whole divided user data.
If the divided number information is added to the
initial identifier, the entire user data can be
obtained by counting the number of received divided
user data up to the divided number.
(3) The SC-AAL processor reads the SC-AAL
information, and with regard to f), it carries out
the error detecting/correcting computation
sequentially for the divided user data which have
been received and stored, and decides the final
divided user data when the computed value coincides
with the error detecting/correcting information that
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CA 02489644 1996-10-11
would be placed in a specific position of the
received divided user data. With~regard to g), it
stores the error detecting/correcting information
placed in a specific position of the initial divided
user data, carries out the error
detecting/correcting computation for the divided
user data received sequentially, and decides the
final divided user data when the computed value
coincides with the stored value.
Using the error detecting/correcting computation
information in common to f) and g) makes it possible
to confirm the validity of the entire user data, and
to correct the error data.
The SC-PL processor recovers the original user
data by combining the entire divided user data
decided by the SC-AAL processor.
EMBODIMENT 6
One of the methods for identifying the length of
the variable short cell in the present invention is
to use the short cell status information ST and the
short cell length information LI which are provided
for each short cell as described in the embodiment 1
in connection with Fig. 5. In the embodiment 2, the
length is identified using the multiplexed cell
number information, short cell length LI and the
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composite type information as shown in Figs. 12 and
13, and they are collectively provided for each
standard ATM cell as the multiplexing information.
Summarizing the methods for representing the
short cell length, they can be roughly divided into
three.
In the following description, the length "before
division" refers to the length of the short cell in
its entirety before division in the case where the
short cell is divided into two or more parts to be
loaded on a plurality of ATM cells because of the
cell overlapping. On the other hand, the length
"after division" refers to the length of the short
cell after division in the case where the short cell
is divided into two or more parts to be loaded on a
plurality of ATM cells because of the cell overlap.
It corresponds to the length "before division"
when there is no cell overlap.
Method 1: A method which represents the length
of the short cells before the division for the cell
overlap independently of the standard ATM cells,
into which the short cells are multiplexed (see,
Figs. 21A and 21B and Figs. 22A and 22B).
This method corresponds to the providing method
described in connection with Figs. 21A and 21B. In
Figs. 21A and 21B, the length information is also
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CA 02489644 1996-10-11
provided for the latter half after division which
overlaps to the next standard ATM cell. However, it
is also possible not to provided it with the length
information. In this case, the length of the
successive short cell can be calculated, after
completing processing of the standard ATM cell, by
detecting the length of the remainder of the
incomplete short cell with a predetermined length,
thereby recognizing that the short cell is divided.
In this case the ST or CT (represented as OID above)
can be omitted. A similar method can be applied to
Figs. 22A and 22B.
Method 2: A method which represents the length
of respective short cells after division which are
multiplexed within the 48-byte payload of the
standard ATM cell by means of the ST or CT (which is
also denoted as OID above) (see, Figs. 20A and 20B
and Figs. 22A and 22B).
For example, with a short cell of 100 bytes, the
LI does not indicate 100 bytes, but the LI of the
first standard ATM cell indicates LI=47 (due to the
multiplexing information length and the standard AAL
length), that of the second standard ATM cell
indicates LI=47, and that of the third standard ATM
cell indicates LI=6.
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Method 3: A method which identifies the short
cell length from the patterns when the short cell
length has some patterns.
In Fig. 10, the PI bits are provided for
identifying the patterns of the short cells
multiplexed into the standard ATM cell. The method
3 represents the short cell length using such
patterns. In connection with this, the length
information LI provided for each short cell as shown
in Figs. 18, 19 and others can also be used as a
method for indicating the patterns of the short cell
length.
This method can shorten the length information
if the short cell length is discrete and its number
is limited even though it is variable. For example,
if there are five types of short cells with the
length of 5 bytes, 10 bytes, 15 bytes, 20 bytes and
bytes, 3-bit LI is sufficient for identifying
them by relating the 5 bytes to a first, the 10
20 bytes to a second, ... etc. because eight patterns
can be identified by the 3-bit LI. Accordingly, the
LI can be made shorter than when it represents the
actual length of the short cell in the binary
notation.
25 Thus, the LI can be represented with the
patterns of the short cell length. This method is
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CA 02489644 1996-10-11
applicable only when the transmitting end and the
receiving end know the patterns of the short cell
length in advance.
EMBODIMENT 7
The concrete structure of the short cell AAL
will be described with reference to Figs. 18 and 19.
Structure 1 of the short cell AAL.
The short cell AAL can be provided with the
attributes or processing information associated with
the payload.
If the processing information associated with
the payload is placed in the short cell AAL, the
short cell AAL processor can decide the attributes
or necessary processing of the payload without
reading and analyzing the payload. As a result,
fast and accurate processing of the payload is
possible. If the processing information is placed
in the payload, it is necessary to make a decision
by analyzing the information after obtaining the
payload by disassembling.
To explain more specifically, the diversity
combining handover processing will be described when
the CDMA is employed as a radio system in the mobile
communications. In this case, it is necessary for
the handover trunk in a switching office to select
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and combine higher quality information from incoming
information packets (corresponding to the short
cells of the present invention) sent from a
plurality of base stations by comparing the
reliability information added to each packet.
A frame number FN and reliability information
CON as shown in the short cell AAL in Fig. 18 can be
used for the selecting and combining control in the
handover trunk. The frame number FN can be used to
identify the information packets of the incoming
information sent from the base stations. The
reliability information CON is generated by the base
stations depending on the quality of the radio
packets (which is decided from the receiving level,
CRC check or the like). The information is placed
into the short cell AAL.
The short cell AAL processor in the handover
trunk can decide the quality of the information
using the frame number FN and the reliability
information CON in the short cell AAL. Thus, the
fast and accurate processing of the payload becomes
possible without reading and analyzing the payload.
Structure 2 of the short cell AAL
In the voice communications, the mute
compression of the voice data can be carried out (a
technique for compressing/removing the voice
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CA 02489644 1996-10-11
transmitted data in mute sections in the voice
information during conversation). In this case,
speech spurt/mute information about the voice is
needed for deciding switching positions of the
speech spurt/mute, thereby switching the voice data
processings.
This information can be provided in the short
cell AAL as the Vb (Voice activation bit) as
illustrated in the short cell AAL of Fig. 18. The
speech spurt/mute can be decided using the Vb.
For example, a voice data processor (CODEC) can
make a fast decision of the switching of the speech
spurt/mute by looking up the Vb in the short cell
AAL without reading and analyzing the payload,
thereby handling the payload accurately.
EMBODIMENT 8
The short cell (of a variable length) input to
the standard ATM cell assembler 1 as shown in Figs.
lA and 1B can accommodate multiplexed sub-short
cells in its payload, and wait for them.
As a method for multiplexing such sub-short
cells into the short cell, the method for
multiplexing the plurality of short cells into the
ATM cell as described above can be applied. A
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system configuration for the sub-short cell
multiplexing is shown in Fig. 29.
In Figs. 28A and 28B, a data receiver/sub-short
cell assembler 52 receives diverse input information
and forms the sub-short cells. The detailed
configuration and operation of the data
receiver/sub-short cell assembler 52 are the same as
those of the data receiver/short cell assembler 3 as
shown in Figs. 1A and 1B.
A sub-short cell multiplexes 53 has a function
of multiplexing the sub-short cells into the payload
of one or more short cells. The detailed
configuration and operation of the sub-short cell
multiplexes 53 are the same as those of the short
cell multiplexes 4 as shown in Figs. 1A and 1B.
A short cell generator 54 has a function for
generating the short cell by receiving the
multiplexed data as the payload of the short cell,
and by adding the short cell AAL and short cell
header. The detailed configuration and operation of
the short cell generator 54 are the same as those of
the standard ATM cell generator 5 as shown in Figs.
1A and 1B.
A short cell transmitter 55 has a function of
outputting the generated short cell to a short cell
transmission network 60, the standard ATM cell
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assembler 1, and so on. The detailed configuration
and operation of the short cell transmitter 55 are
the same as those of the ATM cell transmitter 6 as
shown in Figs. 1A and 1B.
As described above, the blocks in a multiplex
short cell assembler 50 as shown in Figs. 28A and
28B are basically the same as those of the standard
ATM cell assembler 1 as shown in Figs. lA and 1B.
However, although the assembled standard ATM cells
have a fixed length in Figs. 1A and 1B because the
short cells are multiplexed into the standard ATM
cells, the short cells assembled by the multiplexed
short cell assembler 50 as shown in Fig. 28 can be
either a fixed or variable length.
If the short cell assembled by the multiplexed
short cell assembler 50 as shown in Figs. 28A and
28B has a fixed length, it is also necessary in
Figs. 28A and 28B to carry out the overlapping
control to the next cell, or the null information
addition control (partial fill) which is required
because the standard ATM cell has a fixed 48-byte
length.
If the short cell assembled by the multiplexed
short cell assembler 50 as shown in Figs. 28A and
28B has a variable length, the length obtained by
multiplexing the sub-short cells can be made the
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payload length of the short cell, or the overlapping
control can be performed to the next short cell of a
suitable length. The variable length short cell,
however, must be provided with additional
information so that the receiving portion can decide
its length.
The short cell thus assembled which includes the
multiplexed sub-short cells is delivered to a short
cell receiver 56 through the short cell transmission
network 60 and a standard ATM cell disassembler 2.
The short cell receiver 56 has a function of
receiving from the short cell transmission network
60 and standard ATM cell disassembler 2. The
detailed configuration and operation of the short
cell receiver 56 are the same as those of the ATM
cell receiver 8 as shown in Figs. 1A and 1B.
A short cell processor 57 has a function of
obtaining the payload by disassembling and
processing the received short cell. The detailed
configuration and operation of the short cell
processor 57 are the same as those of the standard
ATM cell processor 9 as shown in Figs. 1A and 1B.
A sub-short cell disassembler 58 has a function
of disassembling the obtained payload into sub-short
cells. The detailed configuration and operation of
the sub-short cell disassembler 58 are the same as
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those of the short cell disassembles 10 as shown in
Figs. 1A and 1B.
A sub-short cell processor/data transmitter 59
carries out specific processing for each sub-short
cell, thereby achieving conversion and output in
accordance with the diverse data formats of output
channels. The detailed configuration and operation
thereof are the same as those of the short cell
processor/data transmitter 11.
As described above, the blocks in a multiplex
short cell disassembles 51 are basically the same as
those of the standard ATM cell disassembles 2. The
incoming short cells can be either a fixed or
variable length.
If the short cell has a fixed length, it is also
necessary to carry out the overlapping control to
the next cell, or the null information addition
control (partial fill) which is required because the
standard ATM cell has a fixed 48-byte length.
If the short cell has a variable length, the
short cell length is decided from the information
added to the short cell for determining its length
by the multiplexed short cell assembler 50 so as to
process the short cell.
The payload of the sub-short cell can be
provided with further multiplexed sub-short cells.
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Thus, it is possible to implement multilayer short
cell multiplexing in the ATM cell.
As a concrete example of a double layer short
cell multiplexing, multiplexing will now be
described of respective channels (B1-CH, B2-CH and
D-CH) of the 2B+D ISDN into the short cell, as the
sub-short cells.
Fig. 29 illustrates the multiplexing in which
the data of the three channels of the ISDN are
segmented into sub-short cells at every 2 ms time
frame interval to be multiplexed into short cells
which in turn are multiplexed into the ATM cell.
In Fig. 29, the data on channels B1-CH, B2-CH
and D-CH are each segmented into sub-short cells at
2 ms intervals, multiplexed in that order, and
provided with short cell headers. The sub-short
cell multiplexer 53 in Figs. 28A and 28B carries out
similar processing as that of short cell multiplexer
C (4C) in Fig. 14.
The provision of the sub-short cell header by
the data receiverlsub-short cell assembler 52 can be
omitted if the combination and multiplexing
structure of the sub-short cells to be multiplexed
into the short cell are fixed.
The data length of the short cells can exceed 48
bytes which are input to the ATM cell supplied to
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CA 02489644 1996-10-11
the data receiver/short cell assembler 3 of the
standard ATM cell assembler 1 shown in Figs. 1A and
1B. In addition, it is possible to input thereto
the standard ATM cells including various types of
payloads which can be transmitted by the standard
ATM cells, or the ATM cells employing the Type 1 -
Types 5 AAL.
Likewise, the data length of the short cells can
exceed 48 bytes which are output in the form of the
ATM cell from the short cell processor/data
transmitter 11 of the standard ATM cell disassembles
2 shown in Figs, lA and 1B. In addition, it is
possible to output not only the partial fill ATM
cells, but also the standard ATM cells including
various types of payloads which can be transmitted
by the standard ATM cells, or the ATM cells
employing the Type 1 - Types 5 AAL. For example, in
the standard ATM cell, the Type 5 can transmit up to
64 Kbyte variable length data. Although the short
cell multiplexes in the embodiments 1 and 2 carries
out the overlapping control to enable the standard
ATM cell generator to employ the adaptation for
implementing the fixed bit rate communication such
as Type 1, the overlapping control can be omitted if
the standard ATM cell generator employs the
adaptation for implementing the variable bit rate
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CA 02489644 1996-10-11
communication like Type 5, and the variable length
multiplexed data can be delivered to the standard
ATM cell generator.
According to the present invention, low bit rate
data, which are received from the ATM network
(partial or private short cell), STM network, radio,
packet network, or FR (frame relay) network, can be
transmitted by ATM with a minimum delay time, and
high payload efficiency.
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Representative Drawing