Note: Descriptions are shown in the official language in which they were submitted.
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PACKET DATA TRANSMISSION
USING DYNAMIC CHANNEL ASSIGNMENT
Field of the tnvention
This invention involves the transmission of packet data over vacant channels
in
cellular networks.
Background of the Invention
Transmission of data over cellular networks has been accomplished with high
efficiency by transmitting the data in packetized format over vacant voice
channels.
One variant of this technique is CDPD - cellular pigital Eacket ,Qata - which
has been
implemented in analog celtutar networks such as the Advanced Mobile Ehone
system
{AMPS). See, for example, U. S. Patent 5,404,392. In this implementation, a
channel
pair is assigned to the CDPD protocol - one channel for forward transmissions
and the
other for reverse transmissions. On the forward channel, the base station
continuousty
transmits information that mobile stations monitor to detect, synchronize
with, and
register on, the CDPD channel. When powering-on, the mobile unit scans the
channels,
locates the forward channel, and registers with the system. If the mobile unit
wants to
transmit data, it uses the reverse channel which is identified during the
power-on
process. Since there is one reverse channel that is shared by a multiplicity
of mobile
users, access to the channel is obtained by use of well defined contention
resolution
mechanisms that avoid or resolve colitsians. Once a particular mobile-End
System
(M-ES), such as a cellular data tranceiver, gains access to the channel, it
may use the
channel to transmit data until it has completed its transmission or it has
used the
channel a for a system configurable maximum time period.
More advanced cellular networks will operate using digital rather than analog
transmission and suggestions have been made to transmit packetized data on
vacant
channels in these systems as well. By analogy with the application of CDPD to
anatog
systems, packetized data may be sent on an exemplary TDMA system by dedicating
specific frequencyJtime-slot channels to the transmission of the packetized
data. in
such a system, forward and reverse transmission would take place on these
dedicated
CA 02238552 1998-08-19
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channels in a manner similar to that described above for CDPD in AMPS.
Likewise, in
reverse transmission, contention resolution mechanisms would be used to avoid
or resolve
collisions.
These suggestions, however, carry with them the inherent inefficiencies of
CDPD
over AMPS. For example, an integral number of channel pairs must be dedicated
to data
transmission, and contention resolution mechanisms must be employed on the
reverse
channels that are used for data transmission to avoid or resolve collisions.
Summary of the Invention
In accordance with one aspect of the present invention there is provided a
method
of sending packetized data over a communication network, comprising: a)
transmitting,
over a packet data control channel, a request by a requester to send
packetized data; b)
determining at least one available packet data traffic channel and time
interval during which
the packetized data may be sent, the packet data traffic channel being
different from the
packet data control channel; c) transmitting to the requester, over the packet
data control
channel, an identification of the at least one available packet data traffic
channel and the
time interval during which the packetized data may be sent; and d)
transmitting the
packetized data from the requester over the at least one available packet data
traffic
channel during the time interval.
In accordance with another aspect of the present invention there is provided a
method of transmitting data over unused channels in a Time Division Multiple
Access
(TDMA) cellular communications network comprising: a) transmitting, by a
mobile end
system, over a reverse packet data control channel, a request to send
packetized data; b)
determining in a base station at least one available reverse TDMA traffic
channel and time
interval during which the packetized data may be sent, the packet traffic
channel being
different from the packet data control channel; c) transmitting, by the base
station to the
mobile end system, over a forward packet data control channel, the
identification of the at
least one available reverse TDMA data traffic channel and the time interval
during which
the data may be sent; and d) transmitting, by the mobile end system, the
packetized data
over the at least one available reverse TDMA data traffic channel during the
time interval.
In accordance with yet another aspect of the present invention there is
provided a
method of transmitting data over unused channels in a Time Division Multiple
Access
(TDMA) cellular communications network comprising: a) transmitting, by a base
station,
over a forward packet data control channel, a request to send packetized data;
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b) determining in the base station at least one available forward TDMA data
traffic channel
and time interval during which the packetized data may be sent, the packet
data traffic
channel being different from the packet data control channel; c) transmitting,
by the base
station, over a forward packet data control channel, the identification of the
at least one
available forward TDMA data traffic channel and the time interval during which
the data
may be sent; and d) transmitting, by the base station, the packetized data
over the at least
one available forward TDMA data traffic channel during the time interval.
Specifically, in one aspect of this invention, packetized data is transmitted
in a
cellular communication system using a dynamic channel assignment scheme. In
this
aspect of the invention a data control channel is used in addition to the data
traffic channel.
The mobile end system uses the data control channel to send a request for
assignment of
a channel for transmission of data - such as a particular frequencyltime-slot
in a TDMA
system. The network responds with the identification of a particular channel
that may be
used for a particular time period to transmit data. In this aspect of the
invention there is no
dedicated channel that is used for data transmission. Rather, the network
determines a
channel that will be free for the specified time period and assigns it to a
specific mobile end
system for data transmission. This aspect of the invention - which we call
"dynamic
channel assignment" - permits much more efficient use of the available
communication
channels.
In addition to dynamic channel assignment, another aspect of the invention
permits
assignment of more than one channel for data transmission, if more than one is
available.
This aspect of the invention - which we call "dynamic multi-channel
availability" - permits
more flexible use of the communications channels for data transmission when
they are
available. One implementation of this aspect of the invention contemplates
simultaneous
use of at least two of the available channels for data transmission to
increase the efficiency
of the network. These at least two channels may be used by different mobile
end systems,
or may be used at the same time by one mobile end system to transmit data more
rapidly
and make even more efficient use of the multiple available channels.
Other aspects of the invention include a packet data traffic channel Automatic
Retry
Request (ARQ) algorithm which significantly increases the efficiency of the
packet
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data control channel, and the use of a priority faetd to allow for selective
treatment of the
~ data request. Additionally, the data control function may be performed on
the available
voice control channel or may be performed on a dedicated data control channel.
' Although the invention has been introduced, and may be discussed in sections
of
this specification, in terms of a TDMA embodiment, those skilled in the art
will recognize
that the principles of the invention may be use advantageously with other air
interface
protocols as well, and such implementations are contemplated within the broad
scope of
the invention.
Brief Description of the Drawing
FIGURE 1 is a schematic representation of reverse channel access with dynamic
channel assignment;
FIGURE 2 is a schematic representation of forward channel access with dynamic
channel assignment;
5 FIGURE 3 is a M-ES state overview diagram of one embodiment of the
invention;
FIGURE 4 is schematic representation of the time slot format of the reverse
digital traffic channel;
FIGURE 5 is schematic representation of the time slot format of the forward
2.0 digital traffic channel;
FIGURE 6 shows the throughput performance as a function of attempted traffic
with different numbers of data tragic channels;
FIGURE 7 shows the throughput perforn~ance of a slotted Aloha and non-
persistent CSMA/CD.
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Detailed Description of the Drawina_
1. Acronyms
The following acronyms will be used in this specification.
BCCH Broadcast Control Channel (see EIA/TIA IS-136 which is hereby
incorporated by reference)
CDL . Coded Digital Control Channel Locator (see IS-136)
CDPD Cellular Digital Packet Data (see CDPD System Specification, Release
1.1, which is hereby incorporated by reference)
DS Decode Status, which indicates decode successful or failed
E-BCCH Extended Broadcast Control Channel (see IS-136)
F-BCCH Fast Broadcast Control Channel (see tS-136)
FPCCH Forward Packet Control Channel in DCCH
MDBS Mobile Data Base Station (which can be one element of a base station as
defined by CDPD)
MDLP Mobile Data Link Protocol
(see CDPD System Specification, Release 1. i , Part 403)
MNLP Mobile Network Location Protocol (see CDPD Part 501)
MNRP Mobile Network Registration Protocol (see CDPD Part 507)
PDCCH Packet Data Control Channel, which consists of FPDCCH and RPDCCH
RACH Random Access Channel (see !S-136)
RRM Radio Resource Management
RRMCH Radio Resource Management Channel in F-BCCH
SACCH' Stow Associated Control Channel (see IS-136)
S-BCCH Short Message Service-Broadcast Control Channel (see IS-i 36)
SCF Shared Control Feedback information
SMP Security Management Protocol (see CDPD Part 406)
TOMA Time Division Multiple Access
2. Overview
One aspect of the invention involves the transmission of packetized data in a
cellular communication system using a dynamic channel assignment scheme. (The
term "channel" as used in this specification refers to the set of parameters
that identify a
transmission path, for example, in TDMA, a channel is defined by a frequency,
time slot
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and transmission period.) The method involves two types of channels: a packet
data
~ control channel and a packet data traffic channel. The packet data control
channel
consists of a forward packet data control channel and a reverse packet data
control
channel. Likewise, the packet data traffc channel consists of a forward packet
data
traffrc channel and a reverse packet data traffic channel. While the invention
may be
practiced in any one of a number of protocols such as AMPS, CDMA, FDMA, etc.,
the
following description wilt often be in terms of a specific TDMA embodiment. in
such
description of a TOMA embodiment of the invention, the common terms "digital
control
channel" and "digital traffic channel" will be used. In the generic
description of the
invention however, the terms "packet data control channel" and "packet data
traffic
channel" wilt be used.
In reverse data transmission a mobile end system first sends a request message
on the reverse packet data control channel to, for example, a p~obile pigital
base
~.tation (MDBS). (It will be recognized, however, that use of the MDBS for
this function
is not necessary for the practice of the invention. Rather, this function may
be
performed, for example, anywhere in the network.) The mobile end system may
obtain
access to the reverse packet data control channel by contending with other
mobile end
systems using, for example, the slotted Aloha channel access mechanism. if the
access is successful, the mobile end system may deliver its request for data
'2:0 transmission. !n reply, the MDBS may send a response message to the
mobile end
system on the forward packet data control channel.
If the transmission request is granted, the response message may contain the
packet data traffic channel information for the mobile end system's data
transmission,
e.g., the assigned packet data traffic channel and time slots in the assigned
channel to
2:5 transmit the packet data. if the transmission request is denied, the
response message
may contain the reason for the denial.
After the mobile end system receives the response message, it switches to the
assigned packet data traffic channel at the assigned time slots, and for the
assigned
time interval, and starts data transmission. When the MDBS receives a data
block from
30 the mobile end system, it may set the decode Status (DS) flag accordingly
on the
associated forward packet data traffic channel. The mobile end system may
monitor the
decode status information on the associated forward packet data traffic
channel to
determine whether each btock is transmitted successfully or not. The mobile
end
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system may re-transmit those data blocks with a DS flag indicating that the
decode
failed during the assigned time slots. When the assigned time slots are
exhausted, the
mobile end system must cease transmission regardless of the number of
successfully
transmitted data blocks. If the mobile end system has more data blocks to
send, it may '
request permission for a new transmission through the reverse packet data
control
channel. After transmitting the data blocks, the mobile end system returns to
the
forward packet data control channel monitoring state.
In forward data transmission the MDBS sends a request message to one or
more mobile end systems on the forward packet data control channel to inform
the
mobile end systems to listen to a particular forward packet data traffic
channel at certain
time slots. Each such mobile end system switches to the packet data traffec
channel at
the assigned time slots, and receives data blocks transmitted at these time
slots. In
each of the forward packet data traffic channel blocks, there may be an
immediate
Acknowledge (IA) flag. This flag is usually only used for full-rate data
channels and
unicast data transmission. If this flag is set, the mobile end system will
send the MAC
Acknowledgment message at the next packet data traffic channel block. The
mobile
end system may or may not acknowledge all forward packet data traffic channel
blocks
in the packet data traffic channel. If not, the mobile end system may send the
MAC
Acknowledgment message in the reverse packet data control channel.
Since the MDBS dynamically assigns packet data traffcc channels for mobile end
systems to transmit data packets, these channels are contention free. Thus,
the
effective data rate on each packet data traffic channet can potentially
achieve 100% of
the effective throughput capacity. For example, a TDMA cellular sector
contains
approximately 15 30-KHz channels or 45 TDMA digital channels. If it is assumed
that
30 digital channels are used by voice services, and the packet data control to
packet
data traffic channel ratio is 1:4, then 12 reverse packet data traffic
channels are
available. Since each reverse packet data traffic channel offers a data rate
of
approximately 8 Kbps, the total reverse packet data traffic channel effective
data rate is
108 Kbps. Similarly, each forward packet data traffic channel offers a data
rate of
approximately 9 Kbps and the total forward packet data traffic channel
effective data
rate is 108 Kbps.
FIGURES 1 and 2 show reverse and forward channel access with dynamic
channel assignment. As noted in FIGURES 1 and 2, the mobile end system may use
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the reverse packet data control channel to transmit Data Channel Request
messages
{MAC DC REQ), while the MDBS may use the forward packet data control channel
to
transmit Data Change Response messages (MAC DC RESP) and forward Data
Channel Request messages (MAC DC REQ). The mobile end system and MDBS use
the packet data traffic channels to transmit data packets.
The reverse packet data control channel may reside in the digital control
channel of
standard TDMA or in a separate reverse channel. When the reverse packet data
control
channel resides in the reverse digital control channel, the reverse packet
data control
channel may employ the CSMA channel access protocol described in the RACH of
1S-
0 136, which is hereby incorporated by reference. When the reverse packet data
control
channel resides in a separate reverse channel, the reverse packet data control
channel
may employ, for example, the Slotted Aloha channel access protocol.
The above description of a particular embodiment of the invention is depicted
in
greater detail in the state diagram of FIGURE 3. in that diagram, 31 shows
that the
MAC layer entity within a mobile end system is in the Nuil state if the mobile
end system
is powered down.
When a power up occurs, the mobile end system enters the Control Channel
Scanning and Locking state depicted at 32. The MAC layer entity within a
mobile end
system is in the Control Channel Scanning and Locking state when it is in the
process of
:z0 selecting a candidate service provider (see Section 6.2.2 of IS-136.1,
which is hereby
incorporated by reference). tf the candidate packet data control channel
satisfies the
criteria described in the Control Channel Selection procedure, the mobile end
system
enters the Packet Data Control Channel Camping state, 33. Otherwise, the
mobile end
system searches for another candidate packet data control channel. if a power
down
condition occurs while in this state, the mobile end system attempts to return
to the
control channel it last used during its current power cycle and sends a Power
Down
Registration if required by that control channel.
Upon entering the Packet Data Control Channel Camping state, 33, from Control
Channel Scanning and Locking state, 32, or for the first time on the current
packet data
control channel as a result of control channel re-selection, a mobile end
system makes
an initial reading of a full cycle of F-BCCH and C-BCCH. A mobile end system
in this
state does not make an access attempt until it has completed its initial
reading of a full
cycle of F-BCCH (see Section 6.2.3 of 1S-136.1, which is hereby incorporated
by
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reference). After completing its initial reading of F-BCCH, the mobile end
system leaves
this state in response to a forward packet data control channel request, a
reverse packet
data control channel request or a RRMCH notification.
The MAC layer entity within a mobile end system is in the Waiting for Response
state, 34, after it sends a reverse packet data control channel request
massage to the
MDBS. Upon entering this state, the mobile end system sets the reverse packet
data
control channel response timer. The mobile end system responds to the
following
conditions as indicated:
forward packet data control channel response message - If the forward packet
data control channel response message with access accepted is received,
the mobile end system proceeds to the Data Transmit Proceeding state, 37.
If the forward packet data control channel response message with access
rejected is received, the mobile end system returns to the Packet Data
Control Channel Camping state.
'15 RMPDU_REQ TMR Time-out: - If the mobile end system has sent the reverse
packet data control channel request message MAC MAX ATTEMPTS times,
it returns to the Packet Data Control Channel Camping state. Otherwise, it
resets RMPDU_REQ_TMR, increments the message counter, and re-
transmits the reverse packet data control channel request message.
The MAC layer entity within a mobile end system is in the Data Receive
Proceeding state, 35, after it receives a forward packet data control channel
request
message from the MDBS. Upon entering this state, the mobile end system opens a
data packet traffic channel according to the information in the forward data
packet
control channel request message and listens to the forward packet data traffcc
channel
at the assigned time slots.
The MAC layer entity within a mobile end system is in the RRM Update
Proceeding state, 36, after it receives a RRM notification message from the
MDBS.
Upon entering this state, the mobile end system updates its radio resource
parameters.
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fteversePacket Data Traffic Channel Automatic Retrv Reaupst , ,ARQ;r~-
,laorithm
~ In the reverse packet data traffic channel access, the mobile end system
transmits a sequence of blocks in the pre-assigned channel and channel type.
After
' transmitting each data block, the mobile end system monitors the Decode
Status flag
on, for example, the forward packet data traffic channel to determine whether
the data
block is successfully transmitted. If the data block transmission fails, the
mobile end
system may re-transmit the same block until the re-transmitted data block is
successfui,~
or the assigned channel duration is exhausted, or the same data block has been
transmitted 5 times, including the frst time.
~ 0 When the MDBS receives the first attempt, it decodes the data block. If
the data
block is successfully decoded, the MDBS will set "Decode Success" in the DS
flags. If
the data block cannot be decoded successfully, the MDBS will set "Decode Fail"
in the
DS flags.
When the MDBS receives the second attempt, .it decodes the data block. tf the
data btock is successfully decoded, the MDBS will set "Decode Success" in the
DS
flags. If the data block cannot be decoded successfully, the MDBS will set
"Decode
Fail" in the DS flags.
When the MDBS receives the 3rd attempt, it decodes the data block. ff the data
block is successfully decoded, the MDBS will set "Decode Success" in the DS
Rags.
?0 Otherwise, the MDBS will combine the 3 received data blocks using a
"bitwise majority
vote" algorithm and decode the combined block. !f the combined data block is
successfully decoded, the MDBS will set "Decode Success" in the DS flags. if
the
combined data block cannot be decoded successfully, the MDBS will set "Decode
Fail"
in the DS flags.
~5 When the MDBS receives the 4th attempt, it decodes the data block. ff the
data block is successfully decoded, the MDBS will set "Decode Success" in the
DS
flags. Otherwise, the MDBS wilt combine the last 3 received data blocks using
a
"bi#wise majority vote" algorithm and decode the combined block. If the
combined data
block is successfully decoded, the MDBS will set "Decode Success" in the DS
flags. If
- 30 the combined data block cannot be decoded successfully, the MDBS will set
"Decode
Fail" in the DS flags.
When the MDBS receives the 5th attempt, it decodes the data block. !f the data
block is successfully decoded, the MDBS will set "Decode Success" in the DS
flags.
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Otherwise, the MDBS will combine the last 5 received data blocks using a
"bitwise
majority vote" algorithm and decode the combined block. If the combined data
block is ''
successfully decoded, the MDBS will set "Decode Success" in the DS flags. If
the
combined data block cannot be decoded successfully, the MDBS will set "Decode
Fail" '
in the DS flags.
In the forward packet data traffic channel access, the retransmission
algorithm is
similar to that for the reverse packet data traffic channel access, except
that the reverse
packet data traffic channel does not contain DS flags. Instead, the mobile end
system
transmits the MAC acknowledgment block to acknowledge the receiving status.
Performance An~I~rsis of a St?eclfic Embodiment
The following performance analysis for this invention in a TDMA environment is
divided into two parts: Physical and MAC layer performance analysis. In the
Physical
layer, the throughput performance is the maximum uncoded data rates on the
forward
and reverse channels. fn the MAC layer, the throughput performance is the
normalized
throughput capacity using the MAC layer protocol.
Phy i ~l ayer Performa!p,~
The practice of this invention in a TDMA environment requires the data control
channel and data traffic channel to transmit forward and reverse control and
data
packets. The frame structure of the data control channel may be the same as
that in IS-
136 The frame structure of the data traffic channel may be changed. From a
recent
analysis by Secuta (Alan Secuta, "RLP Performance Report", Contribution No.
TR45.3.2.5/93.08.23.07, August 5, 1993}. it appears that the rate 5/6
punctured
convolutional code (punctured from the rate 1/2 convotutional code} offers
substantial
throughput improvement over the rate 1/2 convolutional code. At 0% BLER, the
rate 5/6
convolutional code offers 10 Kbps in a full-rate digital channel. In the
Secuta analysis,
12% of the cell-site coverage has 17 dB CII or lower, and 81 °~ of the
cell-site coverage
has 22 dB C/I or higher. The effective throughput levels at 17 and 22 dB C/I
are
approximately 7.8 and 9.2 Kbps, respectively. In both C/1 signal levels, the
rate 5/6
convolutional code offers better throughput performance than the rate 1/2
convolutional '
code does. Moreover, the rate 516 convoiutional code offers approximately 5.3
Kbps
even at 14 dB C/1.
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The following table compares the throughput performance and BLER of different
coding schemes.
Table 1 - Uncoded Data Rate of RPVerse Digital Traffrc Ghannei
!encoded data/siotUncoded Data rate/data~LERCa~I7dB
data
(bits/bits) fbitsl channel ll
lKbns)
rate 1/2 convolutional260!324 109 5.45 -5%
rate 5l6 convolutional260/324 200 10.0 -22% '
As noted above, the mobile end systems transmit on the reverse packet data
control channel and the reverse packet data traffec channel. The mobile end
systems
use the reverse packet data control channel to transmit control and short data
packets.
The mobile end systems use the reverse packet data traffic channel to transmit
data
packets. Because the reverse packet data traffic channel access is dynamically
assigned by the MDBS, no collision occurs in the reverse packet data traffic
channel.
The mobile end system must send data blocks in the assigned TDMA slots. if the
assigned slots are not sufficient for all data blocks to be transmitted, the
mobile end
system may request another reverse packet data traffic channel access to
transmit the
rest of the data blocks. When a mobile end system requests slots for data
transmissions, the MDBS assigns a maximum of 31 TDMA slots for the full-rate
packet
data traffic channel access, or approximately 95 TDMA slots for the triple-
rate packet
data traffic channel access. .
FIGURE 4 shows the time slot format of the reverse packet data traffic
channel.
Each digital channel consists of 2 time slots in each 6-slot TDMA frame. Each
TDMA
slot consists of 324 bits or 6.67 msec, and it contains a 260-bit encoded data
field. For
the half duplex mobile end systems, each mobile end system can occupy a 2-slot
(foil
rate) data traffic channel to transmit data. For the full-duplex mobile end
systems, each
mobile end system can occupy all 6 TDMA slots (i.e. 3 reverse packet data
traffic
channels) to transmit data. Thus, the maximum data rate for the full-duplex
mobile end
systems is 30 Kbps.
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The MDBS transmits control and acknowledgment packets on the forward packet
data controt channel and transmits data packets on the packet data traffic
channel. '
FIGURE 5 shows the time slot format of the forward packet data traffic
channel. Each
TDMA slot consists of 324 bits, in which 260 bits are encoded data. The
uncoded data
rate of the forward packet data traffic channel is the same as that of the
reverse packet
data traffic channel. Some fields in the forward and reverse time slots can be
converted
to the data field, such as SACCH, CDVCC, RSVD, and CDL depending on the impact
of
such conversion on standard TDMA operation.
For both half duplex and full-duplex mobile end systems, they can receive data
on ail 6 TDMA slots (i.e. 3 forward packet data traffic channels). Thus, the
maximum
forward data rate is 30 Kbps. if the SACCH, CDVCC, RSVD and CDL fields are
converted to the data field, the maximum forward data rate is approximately
34.5 Kbps
MAC Layer
Both the MDBS and mobile end system use the packet data control channel to
transmit control and acknowledgment packets and use the packet data traffic
channel to
transmit data packets. Since the forward channel is a point-to-mufti-point
access, the
MDBS can fully utilize the forward packet data control channel and packet data
traffic
channels.
The reverse packet data control channel is a mufti-point-to-point access, the
mobile end systems contend for the reverse packet data control channel with
others
using, for example, the slotted Aloha random access scheme or the RACH access
scheme (non-persistent CSMA). When the reverse packet data control channel
resides
in the digital control channel, the RACH access scheme is used. When the
reverse
packet data control channel occupies a separate channel, the slotted Aloha
protocol can
be used to optimize the throughput performance.
FIGURE 7 depicts the throughput performance of slotted Aloha and non-
persistent CSMA/CD. it the reverse packet data control channel access is
successful,
the MDBS will send a response packet to the mobile end system and inform the
mobile
end system to go to an assigned packet data traffic channel. Then, the mobile
end
system will transmit data packets on the assigned reverse packet data traffic
channel
without any packet collision.
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The normalized throughput equation of slotted Aloha, Sri, is given as:
Src = Gel
where G is the attempted traffic on the reverse packet data control channel.
If N is the
number of data traffic channels, and Lr is the average data packet length on
the reverse
data traffic channel, the normalized throughput equation for each reverse
packet data
traffic channel, Sro, is:
S"~ = MIN~GLre-~''/N, 1.0}
FIGURE 6~shows the throughput performance of the reverse data traffic channel
with
different N where Lr is 8 slots long.
The forward packet data control channel contains Forward Request (F-Req) and
Forward Response (F-Resp) packets. The MDBS transmits F-Req to inform one or
multiple mobile end systems that one or more data blocks are sent to the
mobile end
systems through a certain forward packet data traffic channel, and it
transmits F-Resp to
respond to a mobile end system transmit request that the mobile end system may
1 a transmit on the assigned reverse packet data traffic channel.
If So is the bandwidth of the forward packet data control channel used by
other
services, such as F-BCCH, E-BCCH, and S-BCCH and L, is the average data packet
length on the forward packet data traffic channel then the normalized
throughput
equation for each forward packet data traffic channel, Sfd, is given by:
Sfa = MIN{(1-Sf~ So)Lr/N, 1.0}
There are three services primitives that may be required to practice this
invention
in the TDMA environment. These primitives are required for the MDBS and mobile
end
25 system to access the packet data control channel and packet data traffic
channel.
These primitives are: MAC DC_REQ, MAC DC RESP, MAC DT DATA.
The MAC OC_REQ primitive is used by the MDBS or mobile end system to
request a data transmission on the packet data control channel. This primitive
may
contain options to send short data frames, RR (defined in MDLP, CDPD
specification
- 30 release 1.1 which is hereby incorporated by reference), EKE and IKE
(defined in SMP,
CDPD specification release 1.1), ESH and ISC (defned in MNRP, CDPD
specifcation
release 1.1 ).
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The MAC DC REQ primitive contains the following mandatory fields: color code
(area and group colors), data packet size (in TDMA slots), data channel type
requested
(half rate, full-rate, double-rate, triple-rate, etc.).
The MAC DC RESP primitive is used by the MDBS to respond to the originating
mobile end system whether the data transmission request is accepted. If
accepted, the
MDBS will assign a packet data traffic channel for a specified duration, in
TDMA slots.
The assigned data channel type may be equal or lower than the requested data
channel
type. The primitive may contain option fields to send short data frames.
The MAC DC RESP primitive contains the following mandatory fields: color
code, assigned channel type, transmission start time, assigned data channel
(specifying
the RF channel number and digital channel(s)).
The MAC DT DATA primitive is used by the MDBS and mobile end system to
transmit a data burst at a pre-assigned RF channel, channel type, and time
slots.
Preceding this primitive, the MAC DC_REQ primitive must be sent to request the
data
transmission. The following table summarizes the MAC layer primitives.
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Table 2 - MAC Layer Primitives
~r~m~twe Path Fietds ~i~g Descri tion
~bitsl
MAC DC REQ both color code 8 area color and group
c olor codes
data packet 8 requested data packet
size size in
TDMA slots. If equal
to 0, no data
channel assignment will
be
requested
data channel3 requested data channel
type type, i.e.,
half-rate, full-rate,
double-rate, etc.
data rate 1 request data rate, i.e.,
slow or fast
priority 1 data priority, i.e.,
high or low
option < N contain short data frame
- 21 or other
information
MAC DC RESP Forward color code 8 area color and group
color codes
data packet 8 assigned data packet
size size
start time 8 assigned data transmission
start
time, i.e., no. of slots
after this
response frame
transmission8 assigned data transmission
duration duration data
channel type3 assigned data channel
type, it must
be lower than or equal
to the
request data channel
type
data rate 1 assigned data rate, must
be lower
than or equal to requested
data
rate
option < N contain short data frame
- 28 or other
information
MAC DT DATA Both color code 8 ~ area color and group
color codes
data N - data field
8
it wilt be noted that in the MAC DC REQ primitive there is a field that
permits
setting a priority code for the data that is to be transmitted. This code can
be used
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identify that data transmission for special treatment, for example, to assign
a traffic
channel to that data transmission prior to others. '
Radio Resource Manadem _nt
The MDBS sends the RRM information to mobite end systems through the
RRMCH. The RRMCH is created to offer CDPD RRM services, and it may reside in
the
Reserve Channel of the data control channel.
The RRM protocol consists of the following functions: autonomous registration;
switch channel, intra-cell transfer, inter-cell transfer; channel quality
measurement, such
as BER and RSSi; mobile station location management; adjacent channel
information
update; congestion control, and sleep control.
The RRM protocol, provided in Part 405 of CDPD specification 1.1, may be used
for the RRM protocol of CDPD/TDMA with minor modifications. This RRM protocol
may
provide the same coverage as the TDMA voice coverage in order to perform hand-
off
simultaneously between voice and data services.
Reverse Channel Access Mer~anicmc
The following table summarizes characteristics of different channel access
mechanisms.
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Summary of Characteristic~f DifEe~~nt t~t,annPr a~rPC~ l~ra~hanisms
Protoc~ Normalized ThroLlghoutCo
Ca aci ~%)
Slotted Aloha36% only fixed size packets
Slotted non-17, 28, 35, 40, altow various size packets
58% for 1,
persistent 2, 3, 4, 10-slot
DSMA packets
Slotted non-23, 37, 47, 54, allow various size packets
75% for 1,
persistent 2, 3, 4, 10-slot
packets
DSMA/CD
Slotted 1- -10-20% lower thanallow various size packets,
shorter access
persistent slotted non-persistentdelay than slotted non-persistent
DSMA/CD
DSMA/CD DSMA/CD
Slotted non-lower than slottedallow various size packets,
non- unbalance data
persistent persistent DSMAICDperformance favoring heavy users
DSMAlCD with
reservation
Virtual Timeequal or higher allow various size packets,
than much .shorter
Synchronous slotted non-persistentaccess delay than slotted non-persistent
DSMA/CD DSMA/CD DSMA/CD
Slotted Aloha/N-low capacity for allow various size packets,
short require control sub-
server packets, high capacitychannel and data sub-channels
for
5-slot or longer
packets
Dynamic high capacity fog allow various size packets,
2-slot or require control
Channel longer packets channel and data channels, use
all available
Assignment data channels to achieve high
data throughput
Advantageous Characteristics of the Invention
The following advantages are among those that accrue with practice of the
disclosed invention, for example, in a TDMA environment:
1. The physical layer and frame timing remain the same as that in lS-136.
Thus,
the IS-136 compatible mobile phone can support both voice and data services
without
hardware changes.
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2. Since the physical layer of IS-136 is used and most of CDPD's protocol
layers
are used (MDLP, SNDCP, MNRP, SMP, etc.), the design effort required for
offering data s
services over TDMA in accordance with this invention is minimal. However, the
performance analysis of tS-136 on PCS channels is required.
3. The rate 1!2 and rate 5!6 (punctured) convolutionai code may be used for
the
FEC. The effective data rate on the forward and reverse full-rate data
channels is 10
Kbps. The current TDMA mobile phone (IS-136 compliant) can be re-programmed to
support data services in accordance with this invention.
4. In CDPD~AMPS, the half-duptex CDPD modem suffers significant
't0 performance penalty because it can only transmit one block at each time
and it may
miss forward channel traffc while it is transmitting. In this invention, the
half-duplex
CDPD modem occupies a full-rate digits! channel when it transmits in the
reverse data
channel. The maximum reverse channel data rate is approximately 10 Kbps, and
the
maximum forward channel data rate is approximately 30 Kbps. Also, the modem
does
not miss forward channel traffic unless it misses the FDC-Assign packet. The
fuli-
duplex COPD modem may increase the reverse channel data rate to approximately
30
Kbps.
5. The aggregated throughput capacities of the forward and reverse channels in
this invention is 200% higher than that of the forward and reverse charnels in
CDPDlAMPS.
6. In accordance with this invention a mobile end system can simultaneously
monitor both voice and data (long and short messages) without degrading voice
or data
services.
7. An MD-tS can support the MDBSs for data transmission in AMPS, and in
accordance with this invention, in other protocols such as, for example, TOMA.
In the
TDMA embodiment no changes are required for the SNDCP layer and above. tn the
MDLP layer, only parameter values may be required to change.
8. fn CDPD/AMPS, the MAC layer's maximum blocks transmitted is 16 and
minimum idle time is 30 microslots. These parameters are tuned to offer fair
access
from all mobile users. However, these parameters lower the throughput
performance for
each mobile end system. When this invention is used in a TDMA environment, for
example, the maximum block size can be much higher than 16 and the minimum
idle
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time is not required. These new parameter values allow each mobile end system
to
maximize its reverse channel data rate.
9. In the exemplary embodiment of this invention in a TDMA environment, the
MDBS has full control of the channel arrangement. It can assign alf unused
voice
b channels for data services. If any of these unused channels is required for
voice
services, the MDBS can reassign some of these unused channels for voice
services and
block them from data services. In channel hopping CDPD/AMPS voice channels
preempt data channels causing hopping, but in this embodiment of the invention
the
data channels that are assigned are reserved for the total period of the
assignment.
10. The aggregated throughput capacity of this invention when practiced in a
TDMA environment is signifcantly higher than that of CDPDlAMPS. For example,
if 5
RF channels of a 15-RF channel sector are not used by TDMA voice services, the
aggregated throughput capacity is approximately 216 Kbps (forward + reverse
channels)
which is about 10 times of the throughput capacity of CDPD/AMPS.
