United States Patent [191
`Cheng
`
`llllllllllllllllllllllllllllllllllllllllllllllllllllIllllllllllllllllllllll
`5,563,883
`Oct. 8, 1996
`
`USOO5563883A
`[11] Patent Number:
`[45] Date of Patent:
`
`[54] DYNAMIC CHANNEL MANAGEMENT AND
`SIGNALLIN G lVlETHOD AND APPARATUS
`
`[76] Inventor: Alexander L. Cheng, ll Sprindale
`Ave., White Plains, NY. 10604
`
`[21] Appl. No.: 276,534
`[22] Filed:
`Jul. 18, 1994
`
`[51] Int. Cl.6 ..................................................... .. H04H 1/04
`[52] US. Cl. ........................... .. 370/73; 348/12; 370/857;
`370/858; 455/42; 455/51
`[58] Field of Search ............................. .. 348/6, 9, 12, 13;
`455/3.1, 4.2, 5.1, 6.1, 34.1; 379/71, 73,
`76, 80, 85.3, 85.7, 85.8, 95.1, 95.2
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,573,206
`5,132,680
`5,224,097
`
`2/1986 Grauel et al. ........................ .. 455/341
`7/1992 Tezuka et al. ..
`370/858
`6/1993 Kaneshima .... ..
`370/858
`
`5,331,316
`
`7/1994 Mestdagh . . . . . . . .
`
`. . . . . .. 370/857
`
`5,355,375 10/1994 Christensen . . . . .
`. . . . . .. 370/858
`5,374,952 12/1994 Flohr ....................................... .. 348/12
`5,434,611
`7/1995 Tamura ................................... .. 348/12
`
`Primary Examiner-Benedict V. Safourek
`
`[57]
`
`ABSTRACT
`
`There is provided a dynamic and adaptable method and
`apparatus to support two-way multi-media communication
`
`services on a multiple access communication system, which
`comprises a central controller, a shared transmission media
`and a plurality of remote terminals dispersed throughout the
`network. The central controller comprises switch and con
`trol apparatus and a pool of transmitters and receivers. The
`communication channels between the central controller and
`remote terminals are arranged for signalling data and traf?c
`bearer channels in the forward and reverse directions. The
`number of signalling data channels is adjusted to satisfy the
`traf?c requirements and for redundancy purposes. The for
`ward and reverse signalling data channels are coupled in
`di?erent mappings to support terminal grouping. Multiple
`access of the remote terminals for the upstream tra?ic are
`mitigated by separating remote terminals in groups via the
`channel allocation and the terminal assignment process.
`Communication between the central controller and the
`remote terminals follows a multiple access scheme con
`trolled by the central controller via polling procedure on
`each of the forward signalling data channels independently.
`In case of collision, the central controller engages the remote
`terminals in a selective polling process to resolve the con
`tention. The overlapping polling method of the controlled
`access scheme increases the utilization of the signalling
`channel and reduces the time required to gain access to the
`shared transmission media. By dynamically adjusting the
`load on signalling data channels, the signalling process is
`greatly improved for e?iciency and redundancy against
`anomalies with the added bene?t of improved ?exibility and
`extensibility. The system is especially useful in a two-way
`CATV network.
`
`20 Claims, 16 Drawing Sheets
`
`(
`
`)
`
`controller
`
`initialization
`
`clear all
`
`'
`
`lists
`
`terminal
`response
`
`contention
`resolution
`
`ARRIS883IPRI0000001
`
`

`
`U.S. Patent
`
`Oct. 8, 1996
`
`Sheet 1 of 16
`
`5,563,883
`
`in
`I'—(
`
`C3
`Gu-1
`
`S1
`
`.4
`CD
`4-)
`
`remote
`
`
`
`centralcontroller
`
`guard band
`
`ARRIS883IPRI0000002
`
`

`
`US. Patent
`
`Oct. 8, 1996
`
`Sheet 2 of 16
`
`5,563,883
`
`FD RD
`h—-—k
`z—-——l
`j-——-m
`Figure 3a
`
`FD RD
`
`71 $0 p
`q
`Figure 3b
`
`FD RD
`I‘
`U
`
`S
`
`I
`
`v
`
`Figure 3c
`
`controller
`initialization
`i
`clear all
`
`FD-x
`
`terminal
`response
`on RD-x'
`
`contention
`resolution
`
`Figure 4
`
`ARRIS883IPRI0000003
`
`

`
`US. Patent
`
`Oct. 8, 1996
`
`Sheet 3 0f 16
`
`5,563,883
`
`command
`on FD-x
`
`terminal
`response
`on RD~x'
`
`retry
`count
`exceeded
`
`successful '
`transmission
`
`terminal
`failure
`processing
`
`Figure 5
`
`ARRIS883IPRI0000004
`
`

`
`US. Patent
`
`Oct. 8, 1996
`
`Sheet 4 of 16 '
`
`5,563,883
`
`terminal
`request
`
`registration
`message
`
`newly
`registering
`terminal
`
`signalling
`processing
`
`reassign
`
`channel failure
`processing
`
`available
`capacity
`on other
`
`terminal
`disable
`
`allocate new
`Channel
`
`terminal
`assignment
`V
`
`Figure 6
`
`terminal
`disable
`
`ARRIS883IPRI0000005
`
`

`
`U.S. Patent
`
`Oct. 8, 1996
`
`of 16
`Sheet 5
`
`5,563,883
`
`regi s
`tration
`
`controller
`
`registration
`frame on RD-x
`
`toggle x
`between 1 2
`
`terminal
`disable
`
`channel
`assignment
`set x and x‘
`
`l
`
`operatio
`
`Figure 7
`
`toggle x‘
`between
`V
`
`2
`
`ARRIS883IPRI0000006
`
`

`
`US. Patent
`
`0a. 8, 1996
`
`Sheet 6 6f 16
`
`5,563,883
`
`operation
`
`A
`
`request on
`RD-x'
`I
`
`controller
`response
`
`collision or
`error retry
`
`successful
`transmission
`
`terminal
`confirmation
`
`1
`
`Figure 8
`
`ARRIS883IPRI0000007
`
`

`
`U.S.
`Patent
`
`Oct. 8, 1996
`
`Sheet 7 0f 16
`
`5,563,883
`
`Signalling data frame in the reverse
`direction sent by remote terminals:
`bytes
`1
`1
`3
`1
`I PMB I TID 1
`SRT
`| FCS I
`
`Signalling data frame in the forward
`direction sent by central controller:
`1
`1
`3
`1
`IPMBITIDI
`[PCS]
`SAT
`preamble (PMB)
`sequence to indicate the start of message frame transmission and aid detection of
`collision
`Terminal IDentifier (TID)
`terminal identifier for command
`lower TID of the range for the selective poll
`0 (hexadecimal 00) is an invalid TID used for disabling terminal during the
`registration process (SAT/SRT contains the serial number)
`255 (hex FF) for registration process (SAT/SRT contains the serial number)
`Signalling Action Type (SAT)
`serial number of the remote terminal for channel assignment during registration
`process
`selective poll including higher TID of the range (used also for general/speci?c poll)
`selective poll with collision alert including higher range (used also for specific poll)
`in-coming call command on the indicated channel number
`release command
`disable command
`test command
`channel re-assignment command
`Signalling Request Type (SRT)
`serial number of the remote terminal for terminal registration process
`on-hook
`off-hook
`switch-hook
`ringing
`release
`dial-digits
`incoming call blocking
`incoming call unblocking
`feature code (e.g., conference)
`test report
`alarm message (fault and fraud)
`multiple channel request (bandwidth-on-demand)
`channelized services (sub-rate & multiple channels)
`Fr
`ame Check Sequence (FCS)
`protection, which covers TID and SAT/SRT fields, against transmission error or
`collision
`Figure 9
`
`C
`
`ARRIS883IPRI0000008
`
`

`
`US. Patent
`
`Oct. 8, 1996
`
`Sheet 8 of 16
`
`5,563,883
`
`ranges of remote terminals
`
`r01
`
`r11
`
`r21
`
`r12
`
`r23
`
`r24
`
`N level of
`halving
`0th
`
`D
`
`1st
`
`2nd
`
`m 3
`
`Figure
`
`10
`
`CO
`lines
`
`central
`controller
`
`remote
`terminals
`
`e ‘ h 4”
`
`V 2a.:
`
`wnmmmmmum mm mm
`
`Figure 11
`
`ARRIS883IPRI0000009
`
`

`
`US. Patent
`
`Oct. 8, 1996
`
`Sheet 9 of 16
`
`5,563,883
`
`first poll
`range r11
`
`next poll
`range rl 2
`
`collision
`
`M) response
`
`processing res-
`ponse from r11
`
`next poll
`range r21
`
`processing res- V next poll next poll
`ponse from r12
`range r23 range r22
`
`collision ‘YES
`
`'
`tx. error
`processing
`+
`
`polling
`cycle
`
`000‘
`
`processing res-
`ponse from r21
`
`next poll
`range r31
`
`polling
`
`Cycle
`
`é
`
`‘
`,
`continued in
`Figure 12b
`
`polling
`cycle m
`from r23
`
`next poll
`range r24
`+
`:
`
`Continued in
`-
`7
`Figure l -b
`
`Figure 12a
`
`ARRIS883IPRI0000010
`
`

`
`US. Patent
`
`Oct. 8, 1996
`
`Sheet 10 of 16
`
`5,563,883
`
`from
`Figure 12a
`
`from
`Figure 12a
`
`collision
`
`processing res
`ponse from r23
`
`next poll
`range r35
`
`polling
`cycle
`
`next poll
`range r36
`
`response
`from r35
`
`response
`from r31
`
`next poll
`range r32
`* processing res
`ponse from r31
`:
`
`next poll
`range r41
`
`00. 4
`
`processing res
`ponse from r35
`
`polling
`cycle
`
`next poll
`range r49
`
`+
`
`Figure
`
`12b
`
`ARRIS883IPRI0000011
`
`

`
`US. Patent
`
`Oct. 8, 1996
`
`Sheet 11 0f 16 .
`
`5,563,883
`
`k XE
`
`.SZPSEZ
`2223
`
`2535:“
`23:3
`
`$29355
`295:3
`
`2.22:3
`33:2
`
`Figure 13a
`
`Figure 13b
`
`ARRIS883IPRI0000012
`
`

`
`US. Patent
`
`Oct. 8, 1996
`
`Sheet 12 of 16
`
`5,563,883
`
`selective
`polling
`
`first poll
`range rll
`
`repeated
`collisio
`
`next poll
`range r12
`
`tx' em?
`Processmg
`
`polling
`cycle
`
`next poll
`range r23
`
`.
`.
`colhslon
`
`YES
`
`processing res-
`ponse from r11
`
`next poll
`range r21
`
`polling
`cycle
`
`continued in
`Figure 14b
`
`continued in
`Figure 14b
`
`Figure 14a
`
`ARRIS883IPRI0000013
`
`

`
`US. Patent
`
`Oct. 8, 1996
`
`Sheet 13 0f 16
`
`5,563,883
`
`from
`Figure 14a
`
`from
`Figure 1 4a
`
`processing res-
`ponse from r12
`
`next poll
`range r24
`
`first poll
`range r22
`
`YES
`
`'
`
`next poll
`range r3 7
`
`next poll
`E processing res-
`ponse from r12 range r23
`
`YES
`
`next poll
`range r35
`
`first poll
`range r24
`
`next poll
`range r36
`
`l
`
`Figure 14b
`
`ARRIS883IPRI0000014
`
`

`
`Oct. 8, 1996
`
`Sheet 14 of 16'
`
`5,563,883
`
`15
`
`U:
`To
`§
`E
`x...
`<9
`dd
`
`remote
`
`.
`
`5-‘
`°"
`:-
`H
`=
`G
`Q)
`
`1T c
`
`central
`
`ARRIS883IPRI0000015
`
`

`
`US. Patent
`
`Oct. 8, 1996
`
`Sheet 15 of 16
`
`5,563,883
`
`micro
`processor
`
`EPRO
`
`switching
`matrix
`
`demod.
`;
`164
`VFdata demod.
`164
`VF
`163 '
`VF data mod.
`163
`
`li?er
`
`?lter
`166
`demodulator 165
`
`.
`
`receiver
`
`12
`
`buffer
`
`modulator
`
`166
`165
`
`transmltter
`
`Figure 16
`
`ARRIS883IPRI0000016
`
`

`
`U.S. Patent
`
`Oct. 8, 1996
`
`Sheet 16 0f 16
`
`5,563,883
`
`f
`
`1
`
`fnicro-
`
`EPROM
`
`processor
`
`1/72
`(
`
`r
`
`6
`RF data
`demod.
`|
`Y
`
`V
`g
`g libeaker } ) { demodulator H ampli?er Hfilterl
`
`E
`
`12
`g
`
`\mlcrophone
`
`k
`
`{ modulator HbufferH ampli?er]
`
`J
`
`J
`
`L
`
`)
`
`Figure 17
`
`ARRIS883IPRI0000017
`
`

`
`5,563,883
`
`1
`DYNAMIC CHANNEL MANAGEMENT AND
`SIGNALLING METHOD AND APPARATUS
`
`FIELD OF THE INVENTION
`
`The present invention pertains generally to methods and
`apparatus for facilitating the two-way multi-media commu
`nication based on a shared transmission media such as
`coaxial cable-TV network, and more speci?cally to methods
`and apparatus for signalling channel management and pro
`tocol.
`
`BACKGROUND OF THE INVENTION
`
`A multiple access communication system comprises a
`central controller, a shared transmission media and a plu
`rality of remote terminals dispersed geographically. To pro
`vide the means for multiple access is a classical problem in
`communication systems with a shared common transmission
`media. Some of the well known schemes are frequency
`division multiple access or FDMA, time division multiple
`access or TDMA, and code division multiple access or
`CDMA. These multiple access schemes deal with the tech
`niques of separating the communication bandwidth into
`tra?ic-bearing channels. In a FDMA scheme, the commu
`nication bandwidth is divided into the frequency bands. The
`TDMA scheme separates the communication bandwidth into
`time slots. The traffic is encoded and then decoded using
`different code in a CDMA scheme.
`In all these multiple access schemes the contention for
`access is resolved through signalling protocols on a pre
`determined and ?xed signalling channel. There are propos
`als to dynamically allocate tra?ic-bearing channels to meet
`the service requirements in terms of lower blocking prob
`ability. However, in addition to availability, bandwidth and
`delay of the tra?ic-bearing channel, the traffic requirements
`should include responsiveness of the signalling process and
`the quality of the transmission means.
`The signalling protocols for multiple access communica
`tion systems fall in two general categories for resolving the
`possible contention: scheduled access via polling or other
`means, and random access contention. In radiotelephony and
`local-area-network (CSMA/CD) environment, the conten
`tion is resolved by monitoring the signal during transmis
`sion, which requires synchronization and/or means to moni
`tor activities amongst all remote terminals and the central
`controller. In the CATV network, remote terminals have
`different distance from the central controller making syn
`chronization difficult. It is also not feasible to detect colli
`sion, i.e., multiple remote terminals transmit at the same
`time, on the CATV network since the remote terminals are
`attached to different branches of the network. The poll and
`response method is often used to schedule the multiple
`access from plurality of remote terminals, but it has the
`disadvantage of ine?iciency due to wasteful interaction with
`remote terminals that are not in need of servicing.
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`2
`units to balance the tra?ic load over the available channels.
`U.S. Pat. No. 5,010,329 discloses a method for dynamically
`grouping terminals in blocks for which the central unit
`performs block polling on a common data channel. The
`present invention presents a method to dynamically allocate
`both signalling data and tra?ic-bearing channels and to
`dynamically assign remote terminals to these channels.
`The polling scheme is commonly used to resolve conten
`tion in a multiple access system. U.S. Pat. No. 4,385,314
`proposes a system to sequentially poll all terminals. Due to
`the inherent ine?iciency with sequential polling method,
`some proposals with the following variations for perfor
`mance improvement have been presented. U.S. Pat. No.
`4,754,426 proposes a two-level polling scheme with distrib
`uted control. U.S. Pat. No. 4,829,297 proposes use of a high
`priority group. U.S. Pat. No. 4,868,816 proposes a binary
`polling scheme, sirrrilar to the polling scheme in the present
`invention, with terminal address in each poll. U.S. Pat. No.
`4,924,461 proposes a method to register other pending
`request on a second channel to interrupt sequential polling.
`U.S. Pat. No. 4,942,572 proposes a dual rate polling method
`using pseudo random sequence at high rate to poll all
`terminals resulting possibly in contention with a small
`number of terminals, and following the high rate poll by
`speci?c poll at lower rate in case of collision. This invention
`diifers from the prior art in that multiple access is controlled
`through overlapping polling sequence executing on multiple
`channels in a parallel fashion. Only when collision occurs,
`this method will enter a selective polling sequence for
`contention resolution. The added bene?t of this method is
`e?iciency and redundancy against anomalies such as inter
`ference and component failure.
`
`OBJECTS OF THE INVENTION
`
`To overcome the problems mentioned above, the objec
`tive of the present invention is to present
`A ?exible and extensible method for signalling channel
`management;
`A ?exible and extensible method for assigning remote
`terminals to the signalling channels;
`An e?icient asynchronous signalling protocol.
`In the present invention, a dynamic process is disclosed to
`adjust the number of signalling channels to meet the require
`ments of varying tra?ic demand and the system growth. This
`is important in carrying multi-media tra?‘ic with different
`requirements in both the traffic-bearing charmel bandwidth
`and the time required to setup a traffic-bearing channel. This
`dynamic signalling channel allocation and terminal assign
`ment method also aids in system redundancy for anomalies
`such as interference and component failure. Integrated with
`the channel allocation and terminal assignment process, the
`present invention also presents an e?icient controlled mul
`tiple access method. The central controller initiates the
`general polling on each signalling data channel in parallel to
`solicit request from all terminals assigned to the signalling
`data channel. Only when collision is detected, the central
`controller starts to poll selectively for resolution.
`Further objects and advantages of my invention will
`become apparent from considerations of the drawings and
`ensuing description thereof.
`
`DESCRIPTION OF THE RELATED ART
`
`There are many proposals of means for dynamically
`adjusting the number of traf?c-bearing channels according
`to varying trailic demands or the transmission quality in the
`radio telephony environment, e.g., U.S. Pat. Nos. 5,134,709,
`5,235,631 and 5,276,908. In addition U.S. Pat. No. 4,868,
`811 discusses the protocol over the common signalling
`channel for allocation of tra?ic-bearing channels. U.S. Pat.
`No. 4,870,408 proposes a process of re-assigning subscriber
`
`BRIEF SUMMARY OF THE INVENTION
`
`65
`
`The multiple access communication system architecture
`depicted in FIG. 1 comprises a plurality of remote terminals,
`a common shared transmission media, a central controller
`
`ARRIS883IPRI0000018
`
`

`
`3
`and interface to wide area networks. There are provided a
`number of communication channels (L) to the wide area
`networks, a number of communication channels (M) for
`supporting a plurality of remote terminals (N). The M
`number of channels to support communication between the
`central controller and the remote terminals are separated into
`four categories as depicted in FIG. 2, for carrying signalling
`data and user tra?ic in the forward and reverse directions,
`i.e., forward signalling data or FD channel, forward traffic
`bearer or FB channel, reverse signalling data or RD channel,
`and reverse tra?ic bearer or RB channel. All communication
`signals between the central controller and the remote termi
`nals are multiplexed onto the shared transmission media.
`The remote terminals are equipment supporting the users’
`communication need and are distributed throughout the
`network. For simplicity reason, the summing device for
`signals from remote terminals are shown as a single device
`in FIG. 1. Each of the remote terminals has one RF data
`demodulator capable of receiving data on the assigned FD
`channel, one frequency agile receiver capable of tuning to
`the assigned FB channel, one RF data modulator capable of
`transmitting data on the assigned RD channel, and one
`frequency agile transmitter capable of tuning to the assigned
`RB channel. The central controller comprises a switch and
`control mechanism, and a pool of transmitters and receivers
`for the communication channels. The central controller
`provides concentration and control function to meet the
`communication demand of the remote terminals much the
`same way as a Private Automated Branch eXchange or
`PABX. The central controller also translates the signalling
`information according to the requirement of the network.
`There are two levels of concentrations provided with this
`system: contention in the shared transmission media via the
`signalling protocol, and through the switching matrix of the
`central controller.
`The signalling channels are dynamically adjusted for
`efficiency and redundancy. This also adds to the extensibility
`of the system for the increasing tra?ic load and system
`growth. The downstream tra?ic on these channels are sched
`uled by the central controller. Multiple access of the remote
`terminals for the upstream tra?ic are mitigated by separating
`remote terminals in groups via the channel allocation and the
`terminal assignment process. Prompted by the remote ter
`minals at startup, or through the failure recovery procedure,
`or deemed necessary by the central controller, the channel
`allocation and terminal assignment process are initiated and
`controlled by the central controller. Through the registration
`process, the central controller assigns the remote terminal to
`a group supported by coupling of the speci?c forward and
`reverse signalling data channels. Afterwards, the communi
`cation between the central controller and the remote termi
`nals follows a two-phase process. The controlled multiple
`access method is used, on each forward signalling data
`channel in parallel, for sporadic user data transfer or sig
`nalling purpose. The central controller either sends com
`mand to a speci?c remote terminal or solicits requests via a
`general poll from remote terminals assigned to the forward
`signalling data channel. The remote terminals respond to the
`controller’s poll to request services. The selective polling
`process is used to identify the remote terminals involved in
`case of collision. The traf?c bearer channel is used once the
`circuit is established via signalling protocol over the signal
`ling data channels. The controlled multiple access scheme
`using overlapping polling method represents an el?cient
`asynchronous signalling method and the decision process is
`designed to improve the effectiveness of the selective poll
`ing coverage during the contention resolution process.
`
`40
`
`45
`
`55
`
`60
`
`65
`
`5,563,883
`
`15
`
`20
`
`25
`
`30
`
`35
`
`4
`Accordingly the achieved bene?ts of the present invention
`are:
`General communication channels management architec
`ture;
`Flexible and extensible scheme’ for signalling channel
`management;
`Flexible and extensible scheme for assigning remote
`terminals to the signalling channels;
`Flexible and extensible scheme for supporting system
`growth and new services requirements;
`Improved system redundancy;
`E?‘icient asynchronous signalling protocol.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Other objects, features and advantages of the invention
`will be apparent from the following Description of the
`Preferred Embodiment taken together with the accompany
`ing drawings in which:
`FIG. 1 is a illustration of a multiple access communication
`system architecture with interconnections between the
`remote terminals, the central controller which comprises the
`switch and control module and a number of transmitters and
`receivers, and the wide-area network.
`FIG. 2 shows the channelization of the communication
`bandwidth of the shared transmission media between the
`central controller and the remote terminals for different
`functions.
`FIG. 3 depicts the possible mappings of forward and
`reverse signalling data channels.
`FIG. 4 depicts the logic ?ow diagram for polling and
`registration process at the central controller.
`FIG. 5 depicts the logic ?ow diagram for command
`process at the central controller.
`FIG. 6 is the logic flow diagram for registration, terminal
`reassignment, channel allocation, and terminal assignment
`process at the central controller.
`FIG. 7 depicts the logic ?ow diagram for registration
`process at the remote terminals.
`FIG. 8 depicts the logic ?ow diagram for signalling
`process at the remote terminals.
`FIG. 9 details the message format for the signalling
`protocol between the central controller and the remote
`temiinals.
`FIG. 10 shows the ranges of remote terminals for selective
`polling during the contention resolution process.
`FIG. 11 is a message exchange diagram for signalling
`protocol between the central controller and the remote
`terminals illustrating a scenario of collision and its resolu
`tion.
`FIG. 12 is the decision graph for contention resolution
`process using polling ranges as de?ned in FIG. 10 using the
`regular polling method.
`FIG. 13 contains signalling message exchange diagrams
`for comparison of two methods using the regular and the
`overlapping polling cycle.
`FIG. 14 is the decision graph for contention resolution
`process using polling ranges as de?ned in FIG. 10 using the
`overlapping polling method.
`FIG. 15 is a message exchange diagram using the over
`lapping polling method for signalling protocol between the
`central controller and the remote terminals illustrating a
`scenario of collision and its resolution.
`
`ARRIS883IPRI0000019
`
`

`
`5,563,883
`
`5
`FIG. 16 is the system block diagram of the central
`controller for supporting telephone services.
`FIG. 17 is the system block diagram of a remote terminal
`for supporting telephone services.
`
`DESCRIPTION OF PREFERRED EMBODIMENT
`
`6
`in the reverse direction, i.e., from the remote terminals to the
`central controller, numbered from l to c. RB-y’ is traffic
`bearer channel 50 in the reverse direction numbered from 1
`to d. A guard band 42 is also shown to separate the signals
`traveling in the forward and the reverse directions if they are
`to be put side-by-side. As explained later a and c should be
`greater than or equal to 2 for redundancy reason. Note that
`if the channels are of equal size, then a+b and c+d shall
`remain constant if all channels are available free of inter—
`ference problem, i.e., there are a pool of channels from the
`central controller to the remote terminals, and a separate
`pool of channels from the remote terminals to the central
`controller. These pools are set aside for a ?exible allocation
`scheme to be described in detail later.
`Although it is not necessary to have all channel to have
`equal bandwidth, the communication process can be man
`aged more easily if the channels have simpli?ed structure
`with equal bandwidth. In case of equal size of the FD and FB
`channels, the management scheme can relocate the FD to a
`channel that is better suited for data transmission while FB
`channel carrying normal voice communication can tolerate
`a considerable more noisy channel than FD charmel is able
`to. Similarly, the management process can take advantage of
`the ?exibility afforded by the equal size of the RD and RB
`channels. If the bandwidth of the communication charmels
`to the wide area network is equivalent to the channels of the
`shared transmission media, the number L is less than or
`equal to the number M, which in turn is less than or equal
`to the number N. In case of channels with different sizes the
`central controller needs to have the additional intelligence
`for managing these channels e?iciently, and to perform
`segmentation and reassembly. Note that communication
`with asymmetric bandwidth requirement such as multi-cast
`can be e?iciently supported in this system.
`The FB-y and RB~y’ channels are allocated according to
`the signalling protocol communicated over the FD-x and
`RD-x’ channels. There is no contention in the forward
`direction, i.e., the tra?ic on each FD-x channel is scheduled
`independently. The number of signalling data channels are
`used to improve the e?iciency servicing groups of remote
`terminals and the system redundancy. In case of transmis
`sion failure (detected through a number of retries without
`receiving acknowledgment), the central controller reverts
`back to FD-l and then FD-2 for transmission to the speci?c
`remote terminal, while the remote terminals reverts back to
`RD-1 and then RD-2 for transmission and to FD-l and FD~2
`for reception. The FD~1 and FD-2 channels are called
`primary forward signalling data channel and backup forward
`signalling data channel respectively. These RD-l and RD-2
`channels are called primary reverse signalling data channel
`and backup reverse signalling data channel respectively.
`With this general channelization architecture, a ?exible
`management scheme is possible for channel arrangement
`and remote terminals grouping. For example, channel
`arrangement can be adjusted according to traffic pattern mix
`and/or more intelligent management scheme can be imple
`mented with various priority lists. The channelization is
`shown to follow a FDMA scheme for ease of understanding,
`but this can also be easily adopted for TDMA or CDMA
`schemes.
`Multiple access of the remote terminals for the upstream
`tra?ic are mitigated by separating remote terminals in
`groups via the channel allocation and the terminal assign
`ment process to be described later. The contention among
`remote terminals in each group is resolved through a con
`trolled multiple access followed by selective polling in case
`of collision on each of the signalling data channel. The
`
`The multiple access communication system architecture
`as depicted in FIG. 1 comprises a central controller 10, a
`shared transmission media 12, and plurality of remote ter
`minals 14 dispersed geographically throughout the network.
`A pool of communication channels 16 (L) are provided to
`the wide area networks 18, a pool of communication chan
`nels 20 (M) for supporting a plurality of remote terminals 14
`(N). The M number of channels to support communication
`between the central controller 10 and the remote terminals
`1.4 are separated into four categories for carrying signalling
`data and user tra?ic in the forward and reverse directions,
`i.e., forward signalling data or FD channel 22, forward tra?ic
`bearer or F8 channel 24, reverse signalling data or RD
`channel 26, and reverse tra?ic bearer or RB channel 28. All
`communication signals between the central controller 10 and
`the remote terminals 14 are multiplexed onto the shared
`transmission media 12. All remote terminals 14 are equip
`ment supporting the users’ communication need and are
`distributed throughout the network. For simplicity reason,
`the summing device 30 for signals from remote terminals are
`shown as a single device in FIG. 1. In a CATV network, this
`summing device 30 represents the splitters and taps con
`necting the branches that make up the network.
`The central controller 10 comprises a switch and control
`' mechanism 32, and a pool of transmitters, called forward
`signalling data channel (FD) 22 and forward tra?ic bearer
`channel (FB) 24, and a pool of receivers, called reverse
`signalling data channel (RD) 26 and reverse tra?ic bearer
`channel (RB) 28. The central controller provides concentra
`tion and control function to meet the communication
`demand of the remote terminals much the same way as a
`Private Automated Branch exchange or PABX. The central
`controller also translates the signalling information accord
`ing to the requirement of the network. In addition to con
`centration provided through the switching matrix of the
`central controller, contention in the shared transmission
`media via the signalling protocol provides another level of
`concentration with this system.
`Each of the remote terminals has one radio frequency
`(RF) agile data demodulator capable of receiving on the
`assigned FD channel 34, one RF agile receiver tuned to the
`assigned FB channel 36, one RF agile data modulator
`capable of transrrritting on the assigned RD channel 38, and
`one RF agile transmitter tuned to the assigned RB channel
`40.
`Although the present invention is useful for interworking
`with a variety of different wide area networks, the telephone
`network will be used hereinafter to illustrate the present
`invention.
`As depicted in FIG. 2, the bandwidth is channelized for
`carrying tra?ic in the forward and the reverse direction. Data
`channels are used for carrying signalling or data tra?ic while
`bearer channels are used for carrying user traf?c similar to
`circuits in telephony. Therefore, there are altogether 4 types
`of channels as depicted in FIG. 2. FD-x is the signalling data
`channel in the forward direction 44, i.e., from the central
`controller to the remote terminals, numbered from 1 to a.
`FB-y is tra?ic bearer channel 46 in the forward direction
`numbered from 1 to b. RD-x’ is signalling data channel 48
`
`25
`
`35
`
`45
`
`50
`
`55
`
`65
`
`ARRIS883IPRI0000020
`
`

`
`5,563,883
`
`7
`number of remote terminals assigned to each of the RD
`channel is to be evenly distributed according to the trafiic
`demand. In the case of identical traffic requirements from all
`users, the number of remote terminals assigned to each of
`the RD channel will be equal.
`The mapping of forward and reverse signalling data
`channels is under the control of the central controller
`dynamically. The mapping of part (a) of FIG. 3 depicts the
`simplest arrangement with each pair of forward and reverse
`signalling data channels forming a terminal group. For
`example, the terminal group receiving on FD-h channel will
`transmit on RD—k. The part (b) depicts the one-to-many
`mapping where the central controller transmits on one FD-n
`channel while the remote terminals belonging to the same
`group respond in their assigned RD—o, RD—p, and RD—q
`channel respectively. In part (c) with the many-to-one map-
`ping shows that the central controller transmits on several
`FD (r, s and t) channels each reaching a subset of the group
`of the remote terminals, which respond in the same RD-u
`charmel. Depending on the traflic pattern, some mapping
`will be more eflicient in utilizing the bandwidth, e.g., the
`many-to-one mapping as depicted in part (b) of FIG. 3 is
`suitable for case where the trafiic coming from the remote
`terminals far exceeds the trafiic in the forward direction.
`Note that the mapping of part (c) can cause collision from
`remote terminals in dilferent subsets of the same terminal
`group. This is the only mapping that will
`require the
`contention resolution process, described later, to be coordi-
`nated between multiple signalling data charmels. Different
`types of mapping can be used at the same time (but not
`combined) for different segments of remote terminals when
`deemed appropriate by the