Note: Descriptions are shown in the official language in which they were submitted.
CA 02276605 1999-06-30
WO 98/30058 PCTlUS97/23968
METHOD AND APPARATUS TO INTERCONNECT TWO OR
MORE CROSS-CONNECTS INTO A SINGLE PCM NETWORK
TECHNICAL FIELD OF THE INVENTION
This invention relates in general to the field of
telecommunications, and more particularly to a method
and apparatus to interconnect two or more cross-
connects into a single pulse code modulation (PCM)
network.
BACKGROUND OF THE INVENTION
A telecommunication system may be used to
transfer data between two telecommunications systems
interfaces. Various data transmission media may be
used to transfer the data. For example, the call may
be placed by a cellular telephone using microwave
frequency electromagnetic radiation. This call may
then be connected to a land-based system which may use
copper or fiber optic conductors. The call may then
be routed through a satellite communications system
which uses high frequency electromagnetic radiation,
or through a submarine communication system that uses
copper or fiber optic conductors.
Regardless of the media used to transmit the
telecommunications data, the transfer of
telecommunications data between two telecommunication
system interfaces typically requires connection
through one or more switches. A digital cross-connect
is a specialized telecommunications switch that is
capable of connecting any of a large number of inputs
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
2
to any of a large number of outputs. An example of a
modern digital cross-connect system is provided by
U.S. Patent 5,436,890 to Read, et al., entitled
"Integrated Multi-rate Cross-Connect System," assigned
to DSC Communications Corporation, issued July 25,
1995 (hereinafter "Read"). Such digital cross-connect
systems may include a plurality of devices that define
the M network interface input ports and the N network
interface output ports of the switch
Although digital cross-connect systems provide
many advantages over prior systems, one problem that
may be encountered using digital cross-connect systems
involves the limitation of digital cross-connect
system resources that may be required to interconnect
multiple digital cross-connect systems. For example,
if a call requires routing through two digital cross-
connect systems, it is necessary to use an input port
and an output port on both digital cross-connect
switches. Thus, twice as many digital cross-connect
switch resources must be used to connect the call
through two digital cross-connect systems than would
be required if the connection could be made with a
single digital cross-connect. This problem may be
compounded when a large number of digital cross-
connect systems are interconnected. Resolution of
this problem would typically require reconnecting the
digital cross-connect systems such that digital cross-
connect switch resources may be used effectively.
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
3
SUMMARY OF THE INVENTION
Therefore a need has arisen for a method and
apparatus to interconnect two or more cross-connects
into a single pulse code modulated (PCM) network.
Accordingly, the present invention provides a
method and apparatus for interconnecting two or more
digital cross-connect systems into a single PCM
network that does not require reconfiguration of
switch connections to improve the efficient use of
system resources.
A telecommunications network is provided. The
telecommunications network includes a fiber optic
conductor and at least two digital cross-connect
systems. Each digital cross-connect system has M
network interface input ports and N network interface
output ports, where M and N are integers that are
greater than zero. The digital cross-connect systems
are interconnected by the data transmission medium.
Any one of M network interface input ports of any
digital cross-connect system may be connected to any
one of N network interface output ports of any other
digital cross-connect system through the data
transmission medium.
The present invention provides many technical
advantages. One important technical advantage of the
present invention is that two or more digital cross
connect systems may be interconnected to form a single
PCM network without reconfiguring the digital cross
connect switch input port and output port connections.
The present invention allows digital cross-connect
system resources to be used efficiently without
CA 02276605 1999-06-30
WO 98/30058 PCT1US971Z3968
4
reconfiguring the digital cross-connect system
connections.
Another important technical advantage of the
present invention is that it does not consume two
network interface ports of each digital cross connect
to make connections from an input on a first cross
connect to an output on a second cross connect. The
present invention instead uses a drop and connect
matrix fabric and ring bus configuration to route
telecommunications traffic between digital cross-
connect systems.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present
invention and the advantages thereof, reference is now
made to the following description taken in conjunction
with the accompanying drawings in which like reference
numbers indicate like features and wherein:
FIGURE 1a is a block diagram of four digital
cross-connect systems connected as a single PCM
network;
FIGURE lb is a block diagram of four digital
cross-connect systems connected as a single PCM
network in a non-blocking configuration;
FIGURE 2 shows a block diagram of a digital
cross-connect matrix connection for one plane of one
digital cross-connect matrix;
FIGURE 3 shows a detailed drawing of a block
diagram of a digital cross-connect matrix connections;
FIGURE 4 shows a schematic diagram of a digital
matrix interface card embodying concepts of the
present invention;
CA 02276605 1999-06-30
WO 98/30058 PCT/IJS97/23968
FIGURE 5 shows a schematic diagram of a digital
matrix multiplexer/demultiplexer card embodying
concepts of the present invention;
FIGURE 6 shows a schematic diagram of a digital
5 matrix card embodying concepts of the present
invention;
FIGURE 7 shows a schematic diagram of a digital
matrix interface/output card embodying concepts of the
present invention; and
FIGURE 8 shows a flow chart for a method for
interconnecting two or more digital cross-connect
systems into a single PCM network embodying concepts
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention
are illustrated in the figures, like numerals being
used to refer to like and corresponding parts of the
various drawings.
FIGURE la is an exemplary block diagram of a PCM
network 10 that includes tour interconnected digital
cross-connect systems 12, 14, 16 and 18. PCM network
10 also includes a counterclockwise data transmission
medium ring 20 and a clockwise data transmission
medium ring 22, which form counter-rotating data
transmission media rings.
Digital cross-connect systems 12, 14, 16, and 18
include high capacity switching matrices that are
operable to connect any of a large number of inputs to
any of a large number of outputs, such as shown in
Read. Digital cross-connect systems 12, 14, 16, and 18
may utilize distributed administration processing,
CA 02276605 1999-06-30
WO 98/30058 PCT/US97123968
6
such that administration processing is performed at
each digital cross-connect. Alternately, digital
cross-connect systems 12, 14, 16, and 18 may utilize
a centralized administration unit.
A system database (not explicitly shown)
containing information on the connections and status
of each digital cross-connect system 12, 14, 16, and
18 in PCM network 10 is stored at and maintained by
the administration system (not explicitly shown) of
each digital cross-connect system 12, 14, 16, and 18.
Alternately, the system database may be centrally
stored. As taught in Read, each digital cross-connect
system 12, 14, 16, and 18 may include 2 parallel
planes having redundant processing capability.
Counterclockwise data transmission medium ring 20
and clockwise data transmission medium ring 22
comprise a data transmission medium or data
transmission media that are operable to carry
digitally encoded PCM data. Counterclockwise data
transmission medium ring 20 and clockwise data
transmission medium ring 22 are characterized by a
large data bandwidth, and comprise independent
segments of data transmission media that couple each
digital cross-connect system in PCM network 10.
Counterclockwise data transmission medium ring 20 and
clockwise data transmission medium ring 22 may
comprise a copper conductor, a coaxial conductor, a
fiber optic conductor, a microwave channel, or other
suitable data transmission medium or media.
In operation, digital cross-connect systems 12,
14, 16, and 18 are used to route telecommunications
traffic. Local connections (not explicitly shown) are
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
7
made to each of digital cross-connect systems 12, 14,
16, and 18, such that any of M network interface input
connections to a digital cross-connect system may be
connected to any of N network interface output
connections of that digital cross-connect system. In
addition, any of the M network interface input
connections to one of digital cross-connect systems
12, 14, 16, or 18 may be coupled to any of the N
network interface output connections of another of
digital cross-connect systems 12, 14, 16, and 18.
For example, digital cross-connect systems 12,
14, 16, and 18 may have 1,096 inputs and 1,096
outputs. The present invention allows any of the
1,096 inputs to digital cross-connect system 12 to be
routed to any of the 1,096 outputs for digital cross-
connect system 14, 16, or 18.
In addition, this routing may be accomplished
without forming connections between the network
interfaces of digital cross-connect systems 14, 16, or
18. For example, to connect an input to digital
cross-connect system I2 to an output of digital cross-
connect system 18 in a conventional system, it may be
necessary to connect a network interface output of
digital cross-connect system 12 to a network interface
input of digital cross-connect system 14, and to
further connect a network interface output of digital
cross-connect system 14 to a network interface input
of digital cross-connect system 16, and to further
connect a network interface output of digital cross-
connect system 16 to a network interface input of
digital cross-connect system 18. The present
invention avoids these digital cross-connect system
CA 02276605 1999-06-30
WO 98/30058 PCT/IJS97/23968
8
network interface connections, and connects an input
to digital cross-connect system 12 to an output of
digital cross-connect system 18 through either
counterclockwise data transmission medium ring 20 or
clockwise data transmission medium ring 22.
FIGURE lb is an exemplary block diagram of a non-
blocking PCM network 23 that includes three "A" plane
data transmission ring interfaces 24, 26, and 28 at
each of digital cross-connect systems 12, 14, 16, and
18. Data transmission ring interfaces 24, 26, and 28
are coupled via data transmission medium ring 22a,
which comprises three separate data transmission
paths, as shown. In general, X data transmission ring
interfaces may be used, where X is an integer equal to
the number of digital cross-connect systems minus 1.
The data transmission capacity over data transmission
ring interfaces 24, 26, and 28 is approximately three
times the data transmission capacity of data
transmission medium ring 22a. PCM network 23 also
includes redundant "B" plane transmission rings (not
explicitly shown) that perform in a manner similar to
the "A" plane rings shown, with respect to data
transmission medium 22. Non-blocking PCM network 23
operates in a manner similar to blocking PCM network
10, with the modifications described below.
In operation, digital cross-connect systems 12,
14, 16, and 18 route telecommunications traffic
locally or to other remote digital cross-connect
systems. For example, digital cross connect system 12
routes traffic to remote digital cross connect system
18 over ring 24, to remote digital cross connect
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
9
system 16 over ring 26, and to remote digital cross
connect system 14 over ring 28.
At each local digital cross connect system,
telecommunications data received from the other remote
digital cross connect systems at rings 24, 26, and 28
is always retransmitted to the other remote digital
cross systems and is available at the local digital
cross connect system. Each ring is capable of
receiving and processing telecommunications data
equivalent to the M network interface input ports of
any one of the digital cross connect systems of PCM
network 23.
For example, the telecommunications traffic
routed to digital cross connect system 18 from digital
cross connect system 12 over ring 28 includes
telecommunications data received at digital cross
connect system 12 over ring 26 from digital cross
connect system 14. Likewise, the telecommunications
traffic routed to digital cross connect system 18 from
digital cross connect system 12 over ring 28 includes
telecommunications data received at digital cross
connect system 14 over ring 24 from digital cross
connect system 16.
In this manner, local telecommunications data
from digital cross connect system 16 is transmitted to
digital cross connect system 14 over ring 24 of
digital cross connect system 14. Furthermore, local
telecommunications data from digital cross connect
system 16 is transmitted to digital cross connect
system 12 over ring 26 of digital cross connect system
12, and local telecommunications data from digital
cross connect system 16 is transmitted to digital
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
cross connect system 18 over ring 28 of digital cross
connect system 18.
Rings 24, 26, and 28 thus prevent blocking from
occurring in PCM network 23. All of the data received
5 at the M network interface input ports of digital
cross connect system 12 may be transmitted to digital
cross connect system 18 without preventing the
transfer of data from digital cross connect system. l4
to digital cross connect system 16.
10 FIGURE 2 shows a block diagram 30 of digital
cross-connect matrix connections for one plane of
digital cross-connect systems 12, 14, 16, and 18 for
use in PCM network 10, as described below. Block
diagram 30 may also be applied in PCM network 23 if
insert fabric 34 is omitted, as noted in the
description of PCM network 10 below.
As previously noted, in a digital cross-connect
system such as that taught by Read, multiple redundant
planes may be used to increase system reliability.
Digital cross-connect plane 30 includes a ring
interface 32 which couples to counterclockwise data
transmission medium ring 20 and receives digitally
encoded PCM data from counterclockwise data
transmission medium ring 20. Alternately, ring
interface 32 may couple to clockwise data transmission
medium ring 22.
Ring interface 32 is also coupled to an
administration system 45, a drop fabric 38 and an
insert fabric 34. Drop fabric 38 is also coupled to
administration system 45 and to a local fabric 40.
Local fabric 40 is coupled to local interfaces 42 and
46, administration system 45, and a bridge circuit 47.
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
11
Local interfaces 42 and 46 are coupled to unit shelves
44 and administration system 45. Insert fabric 34
also couples to administration unit 45 and ring
interface 36, which transmits telecommunications data
over counterclockwise data transmission medium ring 20
to other digital cross-connect matrices (not
explicitly shown).
Ring interface 32 is a telecommunications system
that receives digitally encoded, pulse code modulated
telecommunications data from counterclockwise data
transmission medium ring 20. Ring interface 32 may
alternately receive data from other suitable data
transmission media, such as clockwise data
transmission medium ring 22. Ring interface 32
transmits telecommunications data to local fabric 40
through drop fabric 38. Ring interface also transmits
telecommunications data to other digital cross-connect
systems (not explicitly shown) by transmitting the
telecommunications data through insert fabric 34 to
ring interface 36 and counterclockwise data
transmission medium ring 20.
Drop fabric 38 is a telecommunications system
that receives telecommunications data from ring
interface 32 and transmits the telecommunications data
to local fabric 40. Drop fabric 38 may comprise a
number of digital telecommunications switches, each
having M inputs and N outputs, wherein each
telecommunications switch can connect any of M inputs
to any of N outputs. Drop fabric 38 may further
comprise time-slot interchange random access memory
coupled to a time division multiplex data bus, and may
be operable to store digitally-encoded
CA 02276605 1999-06-30
WO 98/30058 PCTlUS97/23968
12
telecommunications data on the time-slot interchange
random access memory, to retrieve digitally-encoded
telecommunications data from the time-slot interchange
random access memory, and to encode data into a
predetermined time slot of the time division multiplex
data bus.
Local fabric 40 is a digital cross-connect system
switching matrix comprising M input ports, N output
ports, and circuitry operable to couple any of the M
inputs to any of the N outputs, where M and N are
integers. Local fabric 40 may receive
telecommunications data from both drop fabric 38 and
local interface 46. Local fabric 40 transmits the
telecommunications data received at the M inputs from
local interface 46 and drop fabric 38 to local
interface 42, which are coupled to the N outputs of
local fabric 40. Local fabric 40 may also be coupled
to administration system 45, and may receive switching
control and timing data from administration system 45.
Local fabric 40 may further comprise time-slot
interchange random access memory coupled to a time
division multiplex bus. and may be operable to store
digitally-encoded telecommunications data on the time-
slot interchange random access memory. Local fabric
40 may be further operable to retrieve digitally-
encoded telecommunications data from the time-slot
interchange random access memory, and to encode data
into a predetermined time slot of the time division
multiplex data bus.
Local fabric 40 is also operable to transmit data
to and receive data from bridge circuit 47 in order to
perform additional functions such as conference
CA 02276605 1999-06-30
WO 98/30058 PCT/ITS97/23968
13
calling. For example, data received from three
outputs of local fabric 40 may be switched back
through local fabric 40 via bridge circuit 47 after
three conference outputs have been created. In this
manner, conference calling functions may be performed.
Local interface 42 and local interface 46 are
coupled to local fabric 40, unit shelves 44, and
administration system 45. Local interface 42 is
coupled to the output connections of local fabric 40,
and local interface 46 is coupled to the input
connections of local fabric 40.
Unit shelves 44 couple to local interfaces 42 and
46 and administration system 45, and are digital
cross-connect system network interfaces.
Telecommunications media carrying telecommunications
data from the external telecommunications network (not
explicitly shown) are coupled to unit shelves 44.
Administration system 45 couples to local
interfaces 42 and 46, local fabric 40, unit shelves
44, ring interfaces 32 and 36, drop fabric 38, and
insert fabric 34, and is operable to coordinate the
routing of telecommunications data received from
external telecommunications media at unit shelves 44
and ring interface 32. Administration system 45 may
receive a distributed database that contains data on
the status of components within PCM network 10. The
database for PCM network 10 may be controlled by a
publish and subscribe method, a token ring method, or
other suitable methods. Administration system 45 may
contain other suitable administration and controls
components, such as those that may be necessary to
communicate with a centralized administration unit.
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
14
Insert fabric 34 couples to ring interface 32,
local interface 46, administration unit 45, and ring
interface 36. Insert fabric 34 receives
telecommunications data from ring interface 32 for
transmission to ring interface 36. In addition,
insert fabric 34 receives telecommunications data from
local interface 46 and switches the telecommunications
data to counterclockwise data transmission medium ring
20, or other suitable data transmission media
interface.
Insert fabric 34 may comprise time-slot
interchange random access memory coupled to a time
division multiplex bus, and may be operable to store
digitally-encoded telecommunications data on the time-
slot interchange random access memory, to retrieve
digitally-encoded telecommunications data from the
time-slot interchange random access memory, and to
encode data into a predetermined time slot of the time
division multiplex data bus.
Ring interface 36 is a telecommunications system
that couples to insert fabric 34. Ring interface 36
receives digitally-encoded PCM data from insert fabric
34 and transmits the telecommunications traffic over
counterclockwise data transmission medium ring 20 to
other digital cross-connect systems. As previously
noted in regards to ring interface 32, ring interface
36 may also couple to other appropriate data
transmission media.
Bridge circuit 47 couples to local fabric 40 and
is operable to receive data from and transmit data to
local fabric 40. Bridge circuit 47 performs
additional functions on the data received from local
CA 02276605 1999-06-30
WO 98130058 PCT/US97/23968
fabric 40, such as creating conference call outputs.
For example, bridge circuit 47 may perform signal
processing on multiple data streams to create a
conference call outputs.
5 In operation, digital cross-connect plane 30
receives a plurality of channels of telecommunications
traffic via counterclockwise data transmission medium
ring 20. Digital cross-connect plane 30 also receives
local telecommunications traffic through unit shelves
10 46. Telecommunications traffic through counter-
clockwise data transmission medium ring 20 may be
addressed to other remote digital cross-connect
systems by directing it to insert fabric 34 and ring
interface 36. Otherwise, telecommunications traffic
15 from counterclockwise data transmission medium ring 20
that is received at ring interface 32 is directed to
drop fabric 38 for switching to local interface 42.
In addition to this telecommunications traffic
from other remote digital cross-connect systems, local
telecommunications traffic from connections made via
unit shelves 44 is also switched through local fabric
40. Local fabric 40, local interfaces 46, and unit
shelves 44 receive switching connection instructions
from administration system 45. As previously noted,
a central administration unit may also be used to
control switch connections for digital cross-connect
plane 30. Local fabric 40, drop fabric 38, and insert
fabric 34 then make appropriate connections between
telecommunications traffic channels from local
interface 46 and ring interface 32 to local interface
42 and ring interface 36.
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
16
For example, telecommunications traffic may be
routed from a remote digital cross-connect system
through counterclockwise data transmission medium ring
20 to ring interface 32 for connection to an output at
local interface 42. This telecommunications traffic
is routed to drop fabric 38 and local fabric 40.
Local fabric 40 receives switching commands from
administration system 45, and makes the connection
between drop fabric 38 and local interface 42.
Likewise, the telecommunications traffic received
from a remote digital cross-connect system via
counterclockwise data transmission medium ring 20 may
not require switching through local fabric 40. In
this case, the telecommunications traffic is instead
routed to insert fabric 34 and ring interface 36 for
retransmission to another remote digital cross-connect
system. From ring interface 36, the tele-
communications traffic is reinserted into
counterclockwise data transmission medium ring 20.
In addition, local telecommunications traffic may
be routed from local fabric 40 onto counterclockwise
data transmission medium ring 20 for transmission to
a remote digital cross-connect system. For example,
telecommunications data may be transmitted from local
interface 46 to insert fabric 34. From insert fabric
34, the telecommunications data is transmitted to ring
interface 36 and counterclockwise data transmission
medium ring 20. Destination information for the
telecommunications channel may be encoded into the
telecommunications channel, or may be transmitted to
the administration system of the remote digital cross-
connect systems over a dedicated data transmission
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
17
medium. For example, the switching connections for
each digital cross-connect system of PCM network 10
may be maintained in a database that is duplicated in
administration system 45 of each digital cross-connect
system in PCM network 10.
One skilled in the art will recognize that
modifications may be made to the digital cross-connect
system of FIGURE 2 without departing from the spirit
or scope of the present invention. For example, unit
shelves 44 may perform the functions of local
interfaces 42 and 46, such that unit shelves 44 couple
directly to local fabric 40. Telecommunications
traffic being routed through counterclockwise data
transmission medium ring 20 may be channeled through
drop fabric 38 directly to insert fabric 34, instead
of from ring interface 32 to insert fabric 34.
Remote sources may include telecommunications
traffic transmitted over counterclockwise data
transmission medium ring 20 or clockwise data
transmission medium ring 22. Local sources may
include hardwired connections with copper or fiber
optic cable. In particular, "local" and "remote" may
apply interchangeably to any particular digital cross
connect system in relation to a second digital cross
connect system.
For example, a connection may be formed from a
first digital cross-connect system to a second digital
cross-connect system through the ring interface of a
third digital cross-connect system. The second and
third digital cross-connect systems are "remote" from
the "local" reference frame of the first digital
cross-connect. Likewise, the first and third digital
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
18
cross-connects are "remote" from the "local" reference
frame of the second digital cross-connect system, and
the first and second digital cross-connect systems are
"remote" from the "local" reference frame of the third
digital cross-connect system.
In the example above, from the frame of reference
of the first digital cross-connect system, a signal
received at a local input port carrying
telecommunications data is being transmitted to a
first remote digital cross-connect system for
subsequent retransmission to an output port of a
second remote digital cross-connect system. From the
frame of reference of the second digital cross-connect
system, a signal carrying telecommunications data is
being transmitted from an input port of a first remote
digital cross-connect system through a second remote
digital cross-connect system to a local output port.
From the frame of reference of the third digital
cross-connect system, a signal carrying
telecommunications data is being transmitted from an
input port of a first remote digital cross-connect
system to an output port of a second remote digital
cross-connect system.
In PCM network 23 shown in FIGURE lb, insert
fabric 34 would not be required, because stages 24,
26, and 28 comprise individual data transmission paths
similar to counterclockwise data transmission medium
ring 20 and clockwise data transmission medium ring
22. Thus, data is transmitted to the local digital
cross connect system and is repeated on to the next
remote digital cross connect system, except at ring
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
19
28, where the data is not repeated to the next remote
digital cross-connect system.
For example, ring 28 of digital cross connect
system 12 comprises a ring interface 32 that is not
coupled to an insert fabric 34 of digital cross
connect system 12, and that couples to ring interface
32 of ring 26 of digital cross connect system 14, to
ring interface 32 of ring 24 of digital cross connect
system 16, and to ring interface 36 of digital cross
connect system 18 over clockwise data transmission
ring 22a.
Ring interface 32 of ring 26 of digital cross
connect system 12 couples to ring interface 32 of ring
28 of digital cross connect system I8, to ring
interface 32 of ring 24 of digital cross connect
system 14, and to ring interface 36 of digital cross
connect system 16 via clockwise data transmission
medium ring 22a.
Ring interface 32 of ring 24 of digital cross
connect system 12 couples to ring interface 32 of ring
26 of digital cross connect system 18, to ring
interface 32 of ring 28 of digital cross connect
system 16, and to ring interface 36 of digital cross
connect system 14 via clockwise data transmission
medium ring 22a.
Local interface 46 of digital cross connect
system 12 directly couples to ring interface 36. Ring
interface 36 of digital cross connect system 12
couples to ring interface 32 of ring 24 of digital
cross connect system 18, to ring interface 32 of ring
26 of digital cross connect system 16, and to ring
interface 32 of ring 28 of digital cross connect
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
system 14 via clockwise data transmission medium ring
22a.
The connections described above allow data to be
transmitted over PCM network 23 of FIGURE lb without
5 the possibility of blocking, because each clockwise
data transmission medium ring 22a is capable of
carrying the total data traffic from any of digital
cross connect systems 12, 14, 16, and 18. For
example, if digital cross connect system 12 transmits
10 all of its output data to the input ports of digital
cross connect system 16, digital cross connect systems
14, 16, and 18 are not prevented from also
transmitting data. Each digital cross connect system
also comprises similar connections to counterclockwise
15 data transmission medium rings 20a.
FIGURE 3 is a detailed block diagram of one plane
of a digital cross-connect system 50, in accordance
with the teachings of the present invention. Digital
cross-connect system 50 is similar to digital cross-
20 connect plane 30, but contains additional detail.
Digital cross connect system 50 may be used in PCM
network 10 of FIGURE la or may alternatively be used
in PCM network 23 of FIGURE lb with the modifications
described below.
Digital cross-connect system 50 includes digital
matrix interfaces 52 and digital matrix multiplexer/
demultiplexer cards 59. Digital matrix interfaces 52
and digital matrix multiplexer/demultiplexers 54
receive telecommunications traffic from remote and
local sources, respectively.
Digital matrix cards 58 and 60 are
telecommunications system components. Digital matrix
CA 02276605 1999-06-30
WO 98/30058 PCT/iJS97/23968
21
card 58 is coupled to digital matrix interface 52 and
digital matrix card 62. Digital matrix card 60 is
coupled to digital matrix interface 52, digital matrix
multiplexer/demultiplexer 54, and outbound digital
matrix interface 56. Digital matrix card 62 is
coupled to digital matrix multiplexer/demultiplexer 54
and digital matrix bridge 53. Digital matrix cards
58, 60, and 62 are time division multiplex switches
comprising time slot interchange random access memory
and time division multiplex buses, and controllably
encode digital data onto the time division multiplex
bus. Digital matrix cards 58, 60, and 62 may comprise
the same component such as shown in FIGURE 3, or may
comprise different components that are modified to
perform specialized tasks. Digital matrix cards 58
and 62 share a time division multiplex bus, and
controllably encode data onto the common time division
multiplex bus.
Digital matrix multiplexer/demultiplexer cards 54
and outbound digital matrix interfaces 56 are
telecommunications system components that are coupled
to the time division multiplex buses of digital matrix
cards 62 and 60, respectively. Digital matrix
multiplexer/demultiplexer cards 54 are used to combine
multiple lower frequency PCM data streams into a
single high frequency PCM data stream for connection
to the inputs of digital matrix cards 60 and 62, and
to separate the lower frequency PCM data streams from
the single high frequency PCM data stream received
from the output connections of digital matrix cards
62 .
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
22
Outbound digital matrix interfaces 56 are similar
to digital matrix interfaces 52, but are used to
combine telecommunications channels from digital
cross-connect system 50 for transmission to an
external media, such as counterclockwise data
transmission medium ring 20 or clockwise data
transmission medium ring 22.
Digital matrix bridge cards 53 are
telecommunications system components that couple to
digital matrix cards 62, and which are operable to
receive data from and transmit data to digital matrix
cards 62. Digital matrix bridge cards 53 controllably
receive, store, process, and transmit data to provide
additional telecommunications services, such as
conferencing. For example, digital matrix bridge
cards 53 may receive a plurality of separate channels
of data from digital matrix cards 62, create
conference call outputs, and transmit the conference
call outputs back to digital matrix cards 62.
In operation, remote and local telecommunications
data are received at digital matrix interfaces 52 and
digital matrix multiplexer/demultiplexer cards 54,
respectively. In system 10, remote telecommunications
data received at digital matrix interfaces 52 that is
routed to other digital cross-connect systems is
transferred to digital matrix cards 60 for subsequent
switching and transmission through outbound digital
matrix interfaces 56 to an external data transmission
media, such as counterclockwise data transmission
medium ring 20 or clockwise data transmission medium
ring 22. The remote telecommunications data is also
transmitted to digital matrix cards 58.
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
23
Likewise, local telecommunications traffic from
digital matrix multiplexer/demultiplexer cards 54 is
also routed to digital matrix cards 60 and 62.
Digital matrix cards 62 are operable to store and
switch digitally encoded data received from digital
matrix multiplexer/demultiplexer cards 54 onto the
time division multiplex buses provided to digital
matrix multiplexer 54. Local telecommunications data
that is to be provided to a remote cross-connect is
provided to digital matrix cards 60 for subsequent
switching and transmission through outbound digital
matrix interface 56 to an external data transmission
media, such as counterclockwise data transmission
medium ring 20 or clockwise data transmission medium
ring 22.
Digital matrix cards 58 and 62 are operable to
switch the digitally-encoded telecommunications data
received from digital matrix interfaces 52 and digital
matrix multiplexer/demultiplexer cards onto a common
time division multiplex bus, in accordance with
switching data received from an administration system
such as administration system 45 of FIGURE 2.
Telecommunications traffic routed to digital matrix
multiplexer/demultiplexer cards 54 is transmitted over
local connections (not explicitly shown) to unit
shelves that output the telecommunications traffic on
network interfaces.
Alternatively, digital cross-connect system 50
may be used in network such as PCM network 23 of
FIGURE 1b when the following modifications are made.
As noted with regard to FIGURE 2, digital matrix cards
60 are not required when additional telecommunications
CA 02276605 1999-06-30
WO 98/30058 PCT/I1S97/23968
24
media rings are included, such as rings 24, 26, and 28
of FIGURE lb. Accordingly, digital matrix
multiplexer/demultiplexer cards 54 couple directly to
outbound digital matrix interfaces 56.
Likewise, when digital cross-connect system 50 is
used in PCM network 23, connections "a" between
digital matrix interfaces 52 and digital matrix cards
60 are not present. Telecommunications data received
over clockwise data transmission medium ring 22a or
other similar telecommunications media are transmitted
through repeaters to other digital cross connect
systems, as previously described with respect to
digital cross-connect plane 30 of FIGURE 2.
FIGURE 4 is a schematic diagram of a digital
matrix interface card 52 embodying concepts of the
present invention. An external data transmission
medium, such as counterclockwise data transmission
medium ring 20, couples to optical to electric
converter 72. Optical to electrical converter 72
converts the telecommunications data stream received
from counterclockwise data transmission medium ring 20
from light signals to electrical signals, and
transmits the electrical signals to serial to parallel
converter 78 and, when used in PCM network 23, to
electrical to optical converter 74. Optical to
electrical converter 72 receives an optical signal
with digitally encoded data and converts the signal
into an electrical signal with digitally encoded data.
Optical to electric converter 72 may perform the
conversion by decoding the data in the optical signal
and encoding the data into an electrical signal.
CA 02276605 1999-06-30
WO 98/30058 PCT/LTS97/23968
In PCM network 23, electrical to optical
converter 74 receives remote telecommunications
traffic signals from optical to electrical converter
72. This remote telecommunications traffic is
5 converted from electrical to optical for transmission
to another digital cross-connect system via clockwise
data transmission medium ring 22a or other suitable
external data transmission media.
Serial to parallel converter 78 may receive
10 digitally-encoded PCM telecommunications data from
optical to electrical converter 72 and convert it to
digitally encoded PCM data transmitted in 16 bit words
at 64 MHZ frequency. This digitally encoded data is
received at demultiplexer 80. Demultiplexer 80 splits
15 the parallel 1& bit word, 64 MHZ telecommunications
data streams into two 16 bit word, 32 MHZ
telecommunications data streams. Demultiplexer 80
then transmits the parallel 32 MHZ telecommunications
data streams to two elastic store units 84 and 84' .
20 Path ID monitors 82 and 82' monitor the 16 bit, 32 MHZ
data being transmitted from demultiplexer 80 to
elastic store units 84 and 84'. Elastic store units
84 and 84' store the 16 bit, 32 MHZ data that
comprises telecommunications data and then retransmit
25 the data after the telecommunications data is
synchronized with local traffic.
The telecommunications data is then transmitted
from elastic store units 84 and 84' to alignment units
86 and 86'. The telecommunications data is also
transmitted from elastic store units 84 and 84' to a
redundant mate digital matrix interface 52 of digital
cross-connect system 50. This data from redundant
CA 02276605 1999-06-30
WO 98130058 PCT/US97123968
26
mate digital matrix interface 52 is shown in FIGURE 4
as being received at parity monitor 88 and 88'.
Parity monitors 88 and 88' receive
telecommunications data from the a redundant digital
matrix interface 52 and monitor the parity of the
digitally encoded data. Path ID is also monitored by
path ID monitors 82 and 82'. This duplicated
telecommunications data channel couples to
multiplexers 90 and 90'. Multiplexers 90 and 90'
receive the telecommunications data from alignment
units 86 and 86' and from parity monitors 88 and 88'
and select the data to create a single TDM data bus
having 16 bit words and a speed of 32 MHZ. Time slot
interchange ("TSI") RAMs 92 and 92' control the
multiplexing operation. The multiplexed
telecommunications data is transmitted to driver and
parity monitors 98 and 98' while being monitored for
path ID by path ID monitor 82 and 82'. In addition,
even parity is inserted into telecommunications
channel switched from multiplexers 90 and 90' to
driver and parity monitors 98 and 98'.
In operation, telecommunications data received
from clockwise data transmission medium ring 22a at
optical to electrical converter 72 is transmitted to
clockwise data transmission medium ring 22a in PCM
network 23. The telecommunications data is then
converted to two 16-bit 32MHz TDM buses by digital
matrix interface 52 for connection to digital matrix
cards 58. In contrast, the similar connection in PCM
network 10 provides the telecommunications data to
digital matrix cards 58 amd 60.
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
27
Telecommunications traffic that is routed to
digital cross-connect 50 for switching is split and
processed by pairs of digital matrix interface cards
52. Prior to connection with digital matrix cards 58,
the telecommunications traffic may be monitored for
parity and path ID, and may be delayed to retime the
telecommunications traffic to match local traffic
time. Telecommunications traffic is then connected
through driver and parity monitors 98 and 98' to
digital matrix cards 58. In PCM network 10,
telecommunications traffic is routed from
demultiplexer 80 to digital matrix card 60 through a
ring elastic store unit, path ID monitor and driver
and parity monitors (not explicitly shown).
FIGURE 5 is an exemplary block diagram of digital
matrix multiplexer/demultiplexer 54. Digital matrix
multiplexer/demultiplexer 54 is used in a multiplexer
capacity to connect local telecommunications traffic
from unit shelves 44 to digital matrix cards 62, and
also to digital matrix card 60 in PCM 10. In PCM 23,
digital matrix multiplexer/demultiplexer 54 is used to
connect local telecommunications traffic from unit
shelves 44 to digital matrix cards 62 and also to
outbound digital matrix interface 56. In addition,
digital matrix multiplexer/demultiplexer 54 is used in
a demultiplexer capacity to connect telecommunications
traffic from digital matrix cards 62 to unit shelves
44 in both PCM 10 and 23.
Digital matrix multiplexer/demultiplexers 54
include input devices 102. Input devices 102 receive
16 bit, 5 MHZ, digitally encoded PCM data from unit
controllers (not explicitly shown) located in unit
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
28
shelves 44 of FIGURE 2, which are used to couple unit
shelves 44 to digital cross-connect matrix 30. Path
ID monitors 100 are used to provide fault isolation
for cross-connect telecommunications data traffic,
such as to determine source address information and
routing through the cross-connect system.
Input devices 102 couple to cable equalization
circuit 104. Cable equalization circuit 104 couples
to multiplexer 106, which receives the six-16 bit, 5
MHZ, parallel PCM data from cable equalization circuit
104 and converts the telecommunications data into 32
MHZ, 16-bit digitally encoded PCM data. Cable
equalization circuit 104 also introduces appropriate
timing delays to compensate for cable length
differences in the cabling that connects unit shelves
44 to digital matrix multiplexer/demultiplexers 54
FIGURE 3. Multiplexer 106 couples to parity monitor
88. In addition, path ID monitor 100 and even parity
insertion unit 108 monitor and modify the
telecommunications data.
Digital matrix multiplexer 54 receives 16-bit, 32
MHZ outbound PCM data after it has been switched from
digital matrix cards 62 and transmits the data to
elastic store unit 112. Path ID monitor 100 and
parity monitor 88 monitor the path ID of each
telecommunications data channel prior to transmission
to elastic store unit 112. Elastic store unit lI2 is
used to control the delay of the data transmission
time in order to synchronize data transmission with
the local system data transmission rate.
Demultiplexer 114 receives the 16-bit 32 MHZ
signal and demultiplexes it into six 16-bit, 5 MHZ
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
29
signals. Parity monitor 111 and path ID monitor 100
monitor the demultiplexed signals for correct path ID
and parity. The demultiplexed signals are transmitted
to outbound PCM connections through output interfaces
116. Output interfaces 116 couple to unit controllers
in unit shelves 44 of FIGURE 2.
In operation, digital matrix multiplexer/
demultiplexers 54 are used to multiplex two or more
low speed telecommunications data streams into a
single high-speed telecommunications data stream for
switching through the digital cross-connect matrix,
and to demultiplex the high speed telecommunications
data signals that have been switched through the
digital cross-connect matrix to lower speed
telecommunications data channels for subsequent
transmission through unit shelves 44 to the
telecommunications network. Digital matrix
multiplexer/demultiplexers 54 receive control data
from administration system 45 and are operable to
controllably multiplex and demultiplex the
telecommunications data in response to the control
data.
FIGURE 6 is an exemplary schematic diagram of
digital matrix card 62 embodying concepts of the
present invention. As previously mentioned, digital
matrix cards 58, 60, and 62 may be identical, or may
comprise different components that are modified to
perform specialized tasks. Digital matrix cards 58
and 60 are identical to digital matrix card 62 with
the modifications described below.
Digital matrix card 62 includes differential
receivers 122, which are digital data transmission
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
system components that receive N input signals and
output N/2 signals. Differential receivers 122 are
operable to transfer a signal carrying digitally
encoded data from a two-conductor pair to a signal on
5 a single conductor. Administration circuitry 124
couples to differential receivers 122 and processes
the data signal to perform parity testing, frame
alignment, and signaling collection. Differential
receivers 122 also couple to elastic store units 128,
10 which couple to time-slot interchange random access
memories 126 (TSI RAMs).
Elastic store units 128 are data buffers that are
used to synchronize local telecommunications traffic
with telecommunications traffic received from remote
15 digital cross connect systems. For example, the
transmission delay caused by the length of the
telecommunications media between the local and remote
digital cross connect systems may require local
telecommunications data to be temporarily stored in
20 order to synchronize that data with remote data. This
function is performed by elastic store units 128.
Time slot interchange RAMS 126 are digital data
transmission system components that are operable to
store and retrieve digital data. Time slot
25 interchange RAMS 126 are operable to function as a
switch having M data inputs and N data outputs. For
example, time slot interchange RAMs 126 may have a
total of M input ports and N output ports, and may
read data from the M input ports and write data to the
30 N output ports.
Data is switched through time slot interchange
RAMS 126 by controlling the time slot from which data
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
31
is read for any given data output channel. Thus, any
data written to time slot interchange RAMS 126 from
the M input ports may be read from the N output ports.
Time slot interchange RAMS 126 are further grouped
into bridge row and column 130 and switching fabric
132.
In operation, digitally-encoded data is
transmitted through differential receivers 122 to time
slot interchange RAMs 126. The digitally-encoded data
is stored by writing to time slot interchange RAMS
126, and is then encoded onto a time division
multiplex bus at a predetermined time slot. The time-
slot encoded data is transmitted to differential
drivers 134 for external transmission. Data is
switched through time slot interchange RAMS 126 by
controlling the time slot that the data is encoded
into.
When the digital matrix card of FIGURE 6 is
applied to digital matrix cards 58 and 60, elastic
store units 128 and bridge row and column 130 are not
included in the circuit. Digital matrix cards 58 and
60 do not perform any of the bridging functions
described above. The buffering function for digital
matrix bridge cards 58 and 60 is performed by digital
matrix interface cards 52.
FIGURE 7 is an exemplary schematic diagram of a
outbound digital matrix interface 55 embodying
concepts of the present invention. Digital matrix
interface/output card 140 receives digitally-encoded
telecommunications data in the form of 16-bit words at
32 MHZ at parity monitors 88 from digital matrix cards
60 in PCM network 10 or from digital matrix
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
32
multiplexers/demultiplexers 54 in PCM network 23.
Path ID monitor 82 monitors administration and control
data that may be encoded into predetermined data
locations within the data format.
The digitally encoded telecommunications data is
multiplexed by multiplexer 142 into a 16 bit word, 69
MHZ signal. Parallel to serial converter 144 converts
the parallel telecommunications data transmitted from
multiplexer 142 into serial telecommunications data
for input to electrical to optical converter 146.
Electrical to optical converter 146 transmits the
digitally encoded serial telecommunications data over
counterclockwise data transmission medium ring 20 to
other digital cross-connect systems that comprise PCM
network 10, or over counterclockwise data transmission
medium ring 20a to a remote digital cross connect
system in PCM network 23.
FIGURE 8 is an exemplary flow chart 160 for a
method for interconnecting two or more digital cross
connect systems into a single PCM network embodying
concepts of the present invention. At step 162,
telecommunications data is received at a digital
cross-connect system. This telecommunications data
may comprise destination data, routing data, and the
telecommunications data that is being transmitted
between two telecommunications system interfaces. In
addition, the digital cross-connect system may
comprise two redundant parallel planes.
At step 164, it is determined whether the
telecommunications data is a local signal for
switching from an input port of the switching matrix
of the local digital cross-connect system to an output
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
33
port of the local digital cross-connect system, such
as by receiving address or path ID data from
administration system 45. If the telecommunications
data is a local signal, the method proceeds to step
166. If the telecommunications data is not a local
signal, it may be a remote signal for switching from
an input port of the local digital cross-connect
system to an output port of a remote digital cross-
connect system in PCM network 10. If the
telecommunications data is a remote signal, the method
proceeds to step 170.
At step 166, the telecommunications data is
routed through the switching matrix of the local
digital cross-connect system by forming a connection
between the input port which is coupled to the source
of the telecommunications data and the output port
that couples to the destination of the
telecommunications data. Once the connection is made
between the source and the destination for the
telecommunications data, the method proceeds to step
168 and terminates.
At step 170, the telecommunications data is
routed to at least two counter-rotating rings that
comprise at least two data transmission media that
couple all digital cross-connect systems that comprise
the single PCM network 10. For example, the single
PCM network may include four digital cross-connect
systems. These four digital cross-connect systems may
be interconnected by two counter-rotating rings of
data transmission media, as shown in FIGURE la.
Furthermore, each digital cross-connect system
may comprise two redundant parallel planes as taught
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
34
in Read, such that two independent paths may be formed
to connect the input port to the output port for the
purpose of transmitting the telecommunications data.
If each digital cross-connect system comprises two
redundant parallel planes, then the first redundant
parallel plane may be coupled to the first counter-
rotating data transmission medium ring, and the second
redundant parallel plane may be coupled to the second
counter-rotating data transmission medium ring.
The step of routing the telecommunications data
may include converting electrical signals carrying the
encoded data into light signals carrying the encoded
data. This electrical to optical conversion is
accomplished with an electrical to optical converter
that may be contained within the ring interface that
couples the digital cross-connect system to the data
transmission media.
At step 172, the telecommunications data are
received at the remote digital cross-connect systems
that are coupled to the counter-rotating data
transmission media rings. The telecommunications data
may be converted from optical to electrical signals at
this step. The remote digital cross-connect system
then proceeds to step 164, where the
telecommunications data is processed in a manner that
is similar to processing of local signals at the
remote. If the telecommunications data that has been
transmitted to the remote digital cross-connect system
is to be routed to an output port of the remote
digital cross-connect system, the method proceeds to
step 166 and the telecommunications data is routed to
the appropriate output port. Otherwise, in PCM
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
network 10 the method proceeds to step 170, and the
remote digital cross-connect system proceeds to
transmit the telecommunications data to the next
remote digital cross-connect system on the counter-
s rotating data transmission media rings.
In operation, the method shown in FIGURE 8 would
function as follows when applied to the system shown
in FIGURE la. Telecommunications data would be
received at an input port of one of the digital cross-
10 connect systems shown in FIGURE la, such as digital
cross-connect system 12. This step corresponds to
method step 162. The method would then determine at
step 164 whether the telecommunications data should be
routed to an output port of digital cross-connect
15 system 12, or whether the telecommunications data
needs to be routed to an output port of one of digital
cross-connect systems 14, 16, and 18.
If the telecommunications data is local, i.e. is
to be routed to an output port of digital cross
20 connect system 12, then the method proceeds to step
166. Otherwise, the method proceeds to step 170, and
the telecommunications data is transmitted to the
other digital cross-connect systems over counter
rotating data transmission media rings 20 and 22 in
25 PCM network 10.
In PCM network 10, the method proceeds until the
telecommunications data has been routed to the digital
cross-connect system having the appropriate output
port, such as digital cross-connect system 18. Thus,
30 the telecommunications data will be transmitted over
counterclockwise data transmission media ring 20 to
digital cross-connect system 14, 16 and 18, and over
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
36
clockwise data transmission media ring 22 to digital
cross-connect system 18. If each digital cross-
connect system is comprised of parallel planes, as
taught in Read, then counterclockwise data
transmission media ring 20 may be coupled to the first
parallel plane of each digital cross-connect system,
and clockwise data transmission media ring 22 may be
coupled to the second parallel plane of each digital
cross-connect system.
In this manner, the transmission of data between
any two digital cross-connect systems that comprise
PCM network 10 of FIGURE 1 will not be prevented in
the event of a physical break or similar disruption at
one point around the ring formed by counter-rotating
data transmission media rings 20 and 22. For example,
if a physical break occurs in the data transmission
media that comprises counterclockwise data
transmission media ring 20 and clockwise data
transmission media ring 22 between digital cross-
connect system 12 and digital cross-connect system 14,
an alternate path between digital cross-connect system
12 and digital cross-connect system 14 will remain via
digital cross-connect systems 18 and 16.
In summary, a network, system, and method has
been presented that allows multiple digital cross
connect systems to be connected into a single PCM
network. The digital cross-connect systems are
coupled via at least two counter-rotating fiber optic
conductors, such that a signal carrying
telecommunications data that is connected to an input
port of any digital cross-connect system may be
CA 02276605 1999-06-30
WO 98/30058 PCT/US97/23968
37
coupled to the output port of any other digital cross-
connect system that comprises the PCM network.
The present invention provides many technical
advantages. One important technical advantage of the
present invention is that two or more digital cross
connect systems may be interconnected to form a single
PCM network without reconfiguring the digital cross-
connect switch input port and output port connections.
Another important technical advantage of the present
invention is that it provides a method for connecting
telecommunication circuits through two or more digital
cross-connect systems without requiring switching
through each digital cross-connect system's network
interface ports. Therefore, the present method does
25 not consume revenue producing network interfaces when
telecommunications data is routed through a digital
cross-connect system to a network interface at another
digital cross-connect system
Although the present invention has been described
in detail, it should be understood that various
changes, substitutions, and alterations can be made
hereto without departing from the spirit and scope of
the invention as defined by the appended claims.
