United States Patent
`
`[19]
`
`||||||l|||||l|||||||l|||||||||||l|||||||l|l|||||||l||||l|||||||||||||||l|||
`USOOS377192A
`
`[11] Patent Number:
`
`5,377,192
`
`Goodings et a1.
`[45] Date of Patent:
`Dec. 27, 1994
`
`[54] RADIO DATA COMMUNICATION SYSTEM
`HAVING MEANS FOR REDUCING
`COLLISIONS BETWEEN CONTENDING
`REMOTE STATIONS
`
`[75]
`
`Inventors: Rupert Leslie A. Goodings; Leigh
`Carter; Patrick Mitchell, all of
`Cambridge, Great Britain
`
`[73] Assignee:
`
`Cognito Limited, West Yorkshire,
`United Kingdom
`
`[21] Appl. No.:
`
`867,680
`
`[22] PCT Filed:
`
`Nov. 13, 1991
`
`[86] PCT No.:
`
`PCT/GB9l/01998
`
`§ 371 Date:
`
`Aug. 7, 1992
`
`§ 102(e) Date:
`
`Aug. 7, 1992
`
`[87] PCT Pub. No.: W092/09148
`
`PCT Pub. Date: May 29, 1992
`
`Foreign Application Priority Data
`[30]
`Nov. 13, 1990 [GB] United Kingdom ................. 9024684
`
`Int. Cl.5 ................................................ H04J 3/16
`[51]
`[52] U.S. Cl. ................................ 370/95.3; 370/110.1;
`455/321
`[58] Field of Search .................... 370/85.2, 85.7, 85.8,
`370/85.1, 94.2, 110.1, 104.1, 95.1—95.2, 95.3,
`94.1; 340/825.07, 825.08; 455/54.1, 38.3, 38.1,
`34.2, 38.2, 34.1
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4/1988 Tejima et a1.
`4,736,371
`...................... 370/94.1
`5/1988 Akashi et al.
`4,742,512
`.. 370/104.1
`......
`
`4,809,268 2/ 1989 Tejima et a1.
`..
`370/95.2
`
`4,940,974 7/1990 Sojka ..........
`340/825.08
`
`4,947,451
`8/1990 Nawata ......
`370/95.l
`5,124,985
`6/1992 Hoshikawa ............
`370/95.l
`
`5,166,675 11/1992 Amemiya et al.
`.
`370/85.8
`5,172,375 12/1992 Kou .................................. 370/104.l
`
`FOREIGN PATENT DOCUMENTS
`
`0228709 7/1987 European Pat. Off.
`
`.
`
`W089/06884 7/1989 WIPO .
`
`OTHER PUBLICATIONS
`
`“Teleterminal System”, 38th IEEE Vehicular Technol-
`09 Conference, Jun. 1988, By M. Wakao et a1., pp.
`92-99.
`
`“Satelite Databanks Using Packet Reservation and
`Combined FDMA—TDMA Technique”, International
`Conference on Communications, vol. 2, Jun. 1983, By
`B. Jabbari et al., pp. 928—931.
`
`Primary Examiner—Wellington Chin
`Assistant Examiner—Chan T. Nguyen
`Attorney, Agent, or Firm—Young & Thompson
`[57]
`ABSTRACT
`
`A radio based communication system comprises a base
`station (1) and one or more remote stations (2) each
`incorporating a radio transmitter and receiver to sup-
`port communication between the base station and each
`remote station on a down link and between each remote
`station and the base station on an up link. Each link
`comprises a plurality of frames of fixed length divided
`into a fixed number of slots. The base station includes a
`base control which transmits control data in a general
`control slot (GC) in each frame of the down link so as
`to identify to each remote station a down-setup slot
`(DSU) in each frame of the down link in which the base
`station (1) is to announce the transmission of data for it
`and identify at least one down-transfer slot (DTR) in
`the frame of the down link in which the data is to be
`transmitted. The control data further identifies an ac-
`knowledgement slot (ACK) in each frame of the down
`link and an up-setup slot (USU) divided into sub-slots
`(1/4) in each frame of the up link. Each remote station
`(2) includes a remote control which transmits a request
`to transmit data to the base station (1) in any sub-slot
`(1/4) of the up-setup slot (USU) and receives corre-
`sponding data in the acknowledgement slot (ACK) of
`the down link to identify an up-transfer slot (UTR) in
`the up link in which it is to transmit data to the base
`station.
`
`14 Claims, 22 Drawing Sheets
`
`GC
`
`
`
`UTR
`
`DTR
`
`(D LG DATA)
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 1
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 1
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 1 of 22
`
`5,377,192
`
`E
`
`STATIONS
`
`MOBILE
`
`FIG. 1
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 2
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 2
`
`

`

`US. Patent
`
`Dec. 27, 1994.
`
`Sheet 2 of 22
`
`5,377,192
`
`em
`
`41h
`be
`
`UPL|N|<lwAmas I l I
`
`
`
`
`i F
`
`FIG.2
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 3
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 3
`
`

`

`US. Patent
`
`
`
`Em—m.3m_N_ZOdawbmm¢mN0.
`
`
`
`mmmfim5.5%:
`
`=_@§%§§
` Em=@_===_fi_~wmwwm
`
`
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 4
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 4
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 4 of 22
`
`5,377,192
`
`'3 DNS
`
`m qams
`O
`
`33"”;
`
`3-
`W
`D
`
`CW!)
`
`DNkS
`
`O m
`
`m
`
`“F
`
`9 L
`
`L.
`
`M
`Z
`o
`E
`._..- 5‘- -_
`
`a
`
`Q
`
`m
`Lu.
`
`i"
`
`:1
`2
`5
`3.-
`
`Petitioner Cisco Systems - Exhibit 10175 - Page 5
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 5
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 5 of 22
`
`5,377,192
`
`9.04mS m.07..
`
`aaflgamlgafla.fla
`
`mEmmaN_Nr983_.Eammpm_05.33m
`«Em0.Liw.wm0.$1N.umonF:
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 6
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 6
`
`
`
`

`

`US. Patent
`
`Dec.27, 1994
`
`Sheet 6 of 22
`
`5,377,192
`
`WLINK
`
`N
`
`I N4 1
`
`DST
`
`ESD
`
`UPU NK
`N
`
`N+i
`
`
`
`EM-
`
`
`m
`
`'FIG.6
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 7
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 7
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 7 of 22
`
`5,377,192
`
`
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 8
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 8
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 8 of 22
`
`5,377,192
`
`um>0.>uu<uDo
`
`
`
`mug—(M...(.55
`
`
`
`hOAmHZODPQAQQHQOUZN
`
`@2500
`
`@ZS<m—._Mm._.2_ha
`
`.
`
`muggy—Ome
`
`
`
`ZOFQNMMOUNoam—m
`
`<._.<Ommm><.._
`
`m6E
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 9
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 9
`
`
`
`
`
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 9 of 22
`
`5,377,192
`
`LAYER 3 DATA
`
` FORWARD
`
`ERROR 4
`CORRECTION
`
`LAYER BDATA
`
` FORWARD
`
`ERROR -—>
`CORRECflON
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 10
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 10
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 10 of 22
`
`5,377,192
`
`Amtmmo+05n50mm»A2..3
`Elia-mlEli-EaEll-E.m8EHom
`
`-I-_Egs§—|=
`
`moIHE8'558
`
`F523,...
`
`0—GE$250«9/3
`.Ella
`
`Rate.0.+m3
`
`
`
`_mom:_EH_omh_I.lflmfi!?flnflfl:3so:zhmflnflgg.
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 11
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 11
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 11 of 22
`
`5,377,192
`
`J Ov P
`
`0.
`
`etitioner Cisco Systems - Exhibit 1015 - Page 12
`
`FIG.11
`
`fl
`
`4‘
`
`—
`. 3
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 12
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 12 of 22
`
`5,377,192
`
`FIG.12
`
`:E“
`Z I°§§
`0 [£55.I.M
`
`MOBILE
`
`BASE
`
`-—-DLGDATA
`
`l
`
`<
`‘n
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 13
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 13
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 13 of 22
`
`5,377,192
`
`m:
`
`.GE
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 14
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 14
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 14 of 22»
`
`5,377,192
`
`FIG.14
`
`lo!”
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 15
`
`In“
`
`3'.
`Mv.
`
`No.
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 15
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 15 of 22
`
`5,377,192
`
`@.
`
`£+Nm
`:IE+£
`
`twm
`
`O.
`
`0o
`
`Vmum0
`
`I~
`
`\II
`
`EBEEE
`
`9.BE
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 16
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 16
`
`
`
`
`

`

`US. Patent
`
`Dec. 27, 1994 ,
`
`Sheet 16 of 22
`
`5,377,192
`
`
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 17
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 17
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 17 of 22
`
`5,377,192
`
`Um <1O
`
`.
`
`I!
`Ll
`ll.
`U1
`
`;
`
`'—
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 18
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 18
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 18 of 22
`
`5,377,192
`
`FIG.15
`
`
`
`TRANSFERPHASE
`
`
`
`PACKET
`
`Petitioner Cisco Systems - Exhibit 1015‘ - Page 19
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 19
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 19 of 22
`
`5,377,192
`
`
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 20
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 20
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 20 of 22
`
`5,377,192
`
`)1
`
`U 4
`
`'.
`
`Z [
`
`I U m
`
`X U <
`
`FIG.20
`
`u.
`u.
`
`ou 3
`
`0 L
`
`u
`I!
`
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 21
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 21
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 21 of 22
`
`5,377,192
`
`
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 22
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 22
`
`

`

`US. Patent
`
`Dec. 27, 1994
`
`Sheet 22 of 22
`
`5,377,192
`
`
`
`FIG.22
`
`Petitioner Cisco Systems -.Exhibit 1015 - Page 23
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 23
`
`

`

`1
`
`5,377,192
`
`RADIO DATA COMl\/IUNICATION SYSTEM
`HAVING MEANS FOR REDUCING COLLISIONS
`BETWEEN CONTENDING REMOTE STATIONS
`
`TECHNICAL FIELD
`
`This invention relates to a method of and a system for
`communicating data, in particular communicating data
`across a radio based communication system.
`DISCLOSURE OF THE INVENTION
`
`The present invention consists in a method of com-
`municating data over a radio based communication
`system between a base station and one or more remote
`stations wherein the data is transmitted between the
`base station and each remote station in a down link
`comprising one or more down time-frames of fixed
`length, and data is transmitted between each remote
`station and the base station in an up link comprising one
`or more up time-frames of fixed length, each down
`frame comprising a fixed number of down slots at least
`one of which is a general control slot, at' least one other
`is a down-setup slot, at least one other is a down transfer
`slot, and at least one other is a down acknowledgement
`slot, control data in the general control slot serving to
`identify to each remote station the down-setup slot in
`which the base station is to announce the transmission
`of data for it and identify the down-transfer slot or slots
`in which said data is to be transmitted, and each up
`frame comprising a fixed number of up sloes at least one
`of which is identified by control data in the general
`control slot as an up-setup slot, at least one other is an
`up transfer slot, and at least one other is an up acknowl-
`edgement slot, the up-setup slot being divided into a
`number of sub-slots in which each remote station can
`transmit a request to transmit data to the base station,
`and the base station serving to respond to such a request
`in a down acknowledgement slot by identifying the up
`transfer slot or slots in which the remote station is to
`transmit said data.
`
`The communication of data on the down link and up
`link involves two phases: a setup phase and a data trans—
`fer phase, with a separate slot or group of slots, i.e. data
`channels, being allocated for each phase. The advantage
`of this technique is that the data transfer channel need
`not be loaded with data unless the setup phase is suc-
`cessful, and the setup messages can be very short and
`hence use very little bandwidth. This is especially ad-
`vantageous for transmissions on the up link, since the
`remote stations, which may be a mobile fleet of users,
`are necessarily uncoordinated and will therefore con-
`tend for
`channel capacity. Contention channels,
`whether operating in Aloha- or CSMA- type modes,
`have to be operated at low utilisations to avoid instabil-
`ity. By ensuring that contentions take place only be-
`tween short setup messages, even though the contention
`time-slots have to be operated at low utilisation, this has
`little impact on the overall efficiency of channel usage.
`The base station responds to a successful up-setup re-
`quest by allocating capacity on a data transfer channel,
`which thereby may be operated in a “scheduled” man-
`ner at high utilisation. Similarly, as packets arrive at a
`base station to be transmitted to a particular remote
`‘ station, the base station first executes a down-setup to
`tell the remote station to monitor the down data transfer
`channel, then schedules the data itself into the down
`data transfer channel.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`2
`Preferably, all data transmitted in the down transfer
`slot is labelled with a mobile group label by which it is
`identified by the remote station or stations to which it is
`addressed.
`
`The down-setup slot contains data which identifies
`the mobile or group of mobiles to which a message is to
`be sent,
`i.e. the mobile group label allocated to that
`message. The mobile or mobiles then identify that mes-
`sage simply by reference to the mobile group label as
`attached to data in one or more down transfer slots until
`the complete message has been received.
`In an alternative embodiment of the invention, how-
`ever, the down-setup phase may be incorporated in a
`down acknowledgement slot which the base station
`transmits in response to a message from a mobile so that
`the mobile is more rapidly setup to receive a message or
`reply, thereby shortening the response time. Further—
`more, where the reply is so long that it is divided into a
`number of separate part messages, each part message is
`adapted so as to include the relevant down setup data
`for the next part message, again avoiding the need for a
`separate down setup phase and thereby shortening the
`overall response time.
`According to a further feature of the invention, any
`transmission from a mobile station in response to a mes-
`sage received from the base station may be delayed in
`time by at least a minimum number of time-slots; and
`further a transmission from the base station in response
`to a message received from a mobile may be delayed by
`at least a minimum number of slots. By this means the
`radio subsystem of the mobile need not be capable of
`changing from transmit mode to receive mode very
`quickly; and the time available for processing signals
`and protocol messages in the mobile and base station
`can be maximised.
`According to a further feature of the invention, a
`mobile which does not have data to send during a given
`period of time, need only activate its receiving and
`decoding circuits for at least the one down-setup slot in
`each frame in which the base station announces the
`transmission of messages for the mobiles, and by this
`means the power consumed in the mobile may be mini-
`mised.
`
`Further reductions in power consumption by a factor
`of “11” may be obtained by the mobile only activating its
`receive and decoding circuits for down-setup slot of
`every “n’th” frame, provided that the base station is
`aware that this action is being followed and sends trans-
`mission announcements for such mobiles only in the
`appropriate frames.
`A further feature of the invention allows the base
`station to announce changes to the use being made of
`slots in the up and down frames using the general con-
`trol slots of the down frame, messages announcing such
`changes not requiring acknowledgement of successful
`reception by the mobiles. For example, the number of
`up-setup slots divided into sub-slots for mobiles to re-
`quest the setting-up of a data transfer channel, may be
`varied depending on the degree of load on the system,
`this change being announced via the general control
`slots of the down frame. The number of up—setup slots
`divided into subslots may be varied in accordance with
`the number of subslots in which collisions between
`mobile requests take place, and information contained in
`the request messages themselves as to the number of
`unsuccessful attempts prior to success.
`The use of a slotted ALOHA type system allows the
`use of low-cost, non-duplex radios.
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 24
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 24
`
`

`

`5,377,192
`
`3
`As with conventional radio based communication
`systems operating with a slotted ALOHA type system,
`in order to ensure efficient operation of the system it is
`important that the base station and the mobile are in
`alignment with each other. This is achieved using a
`synchronisation signal which is regularly transmitted by
`the base station and which allows the mobile to know
`exactly where it is in a frame.
`Preferably, the base station supports radio communi—
`cation with mobiles on at least one or a multiplicity of 10
`duplex information bearers, each comprising a down
`link and an up link with a frame structure as described
`earlier, where the overall structure is announced and
`controlled using the general control slot on one bearer
`designated a master bearer, all other bearers being slave
`bearers; and the synchronising information transmitted
`in the down slots of a master bearer carry information
`allowing a mobile to rapidly recognise the master
`bearer, and the synchronising information of slave bear-
`ers carry information allowing a mobile to rapidly
`retune to a master bearer in order to receive information
`on the overall use being made of down and up slots on
`all bearers.
`
`5
`
`15
`
`20
`
`4
`with it that predetermines the number of radio fre-
`quency bearers that it employs. Communication bearers
`are formed by pairs of r.f.channels one for transmission
`of data from the base station 1 to mobile station 2
`
`(downlink) and the other of which is for transmission of
`data from the mobile station 2 to the base station 1
`(uplink). Each channel is therefore simplex.
`The communication system operates according to a
`protocol which is designed using a layered approach.
`Layer 1 defines the basic radio parameters and is not
`described in any detail herein. In one embodiment of the
`system, it permits the transmission of data at a rate of
`6144 bits per second. Layer 2 defines a frame and slot
`structure that allows the bearers to carry time multi-
`plexed data between the base stations and the mobile
`stations, and also defines a Forward Error Correction
`(FEC) scheme. Layer 3 defines the allocation of slots
`into a selection of data channels. Data is sent as a con-
`nected series of one or more slots called Transmission
`Sets (TS) between Radio Multiplexing/Demultiplexing
`(RMD) means at each end. The RMD means is respon—
`sible for any retransmission of lost slots.
`Layer 2 is described in the following sections 1.1 to
`1.4. Layer 3 is described in terms of a network overview
`in the following sections 2.1 to 2.10, and in terms of
`control in the following sections 3.1 to 3.11.
`
`LAYER 2—Data Link Layer
`1.1. Frame Format
`Each of the bearers transmits data in one or more
`frames which contains data as a series of time multi-
`plexed slots, all of which slots are of the same length,
`and are grouped into predefined frames, as shown in
`FIG. 2. .
`The frame grouping is defined indirectly by the slot
`trailers, on all downlinks. Each downslot trailer (DST)
`comprises three bits, sync a, sync b and sync c, as shown
`in FIG. 4 and provides synchronisation for the individ-
`ual downslots. A particular sequence of downslot trail-
`ers defines the frame. The sequence of downslot trailers
`also provides specific bearer information detailed be-
`low.
`Uplinks also contain a series of slots that may be
`transmitted by different mobiles. Each of these mobiles
`is required to align its upslot transmission to the down-
`slot timing. A simpler upslot trailer (UST) is used on all
`upslots comprising a single bit sync and a gap, as shown
`in FIG. 4. This upslot trailer only provides slot syn-
`chronisation, and carries no frame information.
`The number of slots in a frame (the frame format)
`may lie in the following range:
`
`Minimum
`Maximum
`
`Slots/frame
`Bits/slot
`
`14
`768
`
`26 slots even numbers only
`768 bits
`
`All bearers from any one base station or site 1 are
`required to have the same frame format, with their
`frames aligned to within 1 bit in order to allow mobile
`stations 2 to switch between slots on different bearers
`yet maintain synchronisation.
`Frame alignment between different base sites is op-
`tional but desirable.
`
`In principle, the protocol allows for different frame
`formats at different base sites.
`
`DESCRIPTION OF THE DRAWINGS
`
`The invention will now be described by way of exam-
`ple with reference to the accompanying drawings, in
`which:
`FIG. 1 shows a schematic representation of a commu-
`nication system for utilising the present invention; and
`FIGS. 2 to 22 show representations of the frames
`used in the method of transmitting data in accordance
`with the present invention, in particular,
`FIG. 2 shows the frame formats,
`FIG. 3 shows frame related information (down only),
`FIG. 4 shows the protocol layer 2 structure (up and
`down),
`FIG. 5 shows the protocol layer 2 structure (up),
`FIG. 6 shows details of the upslot timing,
`FIGS. 7a and 7b show arrangements of differential
`encoding,
`FIG. 8 shows slot data encoding,
`FIGS. 9a and 9b show the encoding of [1/1] and [1/4]
`slots,
`FIG. 10 shows the interleaving process for [1/1] slot,
`FIG. 11 shows the base/mobile data flows,
`FIG. 12 shows the radio system implementation
`model,
`FIG. 13 shows the down packet set up,
`FIG. 14 shows the down packet transfer,
`FIG. 15 shows the protocol layer 3 down link slot
`contents,
`FIG. 16a to 16b shows the protocol layer 3 up slot
`contents,
`FIG. 17 shows the down link packet sementation,
`FIG. 18 shows the up link packet assembly,
`FIG. 19 shows the message segmentation,
`FIG. 20 shows a user/host interaction pattern,
`FIG. 21 shows the segmentation of an application
`message in the system of FIGS. 1 to 20, and
`FIG. 22 shows the segmentation of an application
`message in an alternative body of the invention.
`
`MODE OF GARRYING OUT THE INVENTION
`
`FIG. 1 illustrates a radio based communication sys—
`tem comprising a fixed network of radio base stations or
`sites 1 and one or more mobile stations 2. Each base
`station has a radio port controller (RPC) associated
`
`25
`
`30
`
`35
`
`45
`
`50
`
`55
`
`65
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 25
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 25
`
`

`

`5
`
`5,377,192
`
`FRAME RELATED INFORMATION
`(DOWNLINK ONLY)
`Frame related information is encoded into all the
`downlink slot trailers (DST) of a frame, as shown in
`FIG. 3. Each Radio Port Controller (RPC) transmits
`one master bearer and up to 3 slave bearers. It is impor-
`tant that mobiles can identify slot 0 of the master bearer
`as quickly as possible, and this is therefore the major
`component of frame related information. However, the
`complete frame related information uses all the encoded
`bits from every slot of a frame. This information con-
`tains:
`identification of master or slave bearer
`identification of slot 0 of a master or slave bearer
`a dotting pattern for synchronisation
`definition of the frequency offset from a slave to its
`master.
`All the information bits are encoded in the downslot
`trailers using the synchronisation codewords defined
`below. Each trailer contains 3 concatenated synchroni-
`sation codewords, and each of these codewords en-
`codes one bit of information N=NSYNC as I=ISYNC.
`The complete frame related information can either be
`viewed as 3 encoded bits per slot, or as three parallel
`sequences (seq-A, seq-B, seq-C) that repeat once per
`frame as shown in FIG. 3. FIG. 3 shows the sequences
`for the minimum frame format of 14 slots and for 4 extra
`slots for an extended frame format.
`Specifically, the frame related information is defined
`by the following combinations of the encoded bits.
`Here, the encoded bits are referred to by their sequence
`letter:
`Master/Slave
`Master and slave bearers are clearly distinguished in
`every slot trailer by the combination of seq-A and seq-
`B. The encoded bits of seq-A and seq-B in each slot of
`a master have the same polarity, whereas the encoded
`bits of seq-A and seq-B in each slot (except slot 0) of a
`slave have opposite polarity.
`Slot 0
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`The location of Slot 0 can be immediately identified
`by the combination of seq-A, seq-B and seq-C:
`An [NSYNC] in all three encoded bits identifies slot
`0 on a master bearer An [ISYNC] in all three en-
`coded bits identifies slot 0 on a slave bearer.
`Slot 0 location is used to provide frame synchronisa-
`tion. It can also be used as a confnmation of the frame
`length, since the frame length, given by the distance
`between two successive slots 0’s, must equal the prede-
`fined value.
`.
`Frame Dotting
`Frame dotting is introduced to reduce the risk of false
`frame sync acquisition. Seq-B always contains a dotting
`sequence:
`. ]
`.
`[. .
`. ,NSYNC,ISYNC,NSYNC,ISYNC, .
`This dotting pattern is a mandatory aspect of success-
`ful slot and frame acquisition.
`Frequency Offset
`The frequency offset differs from the other informa-
`tion, because it requires one encoded bit from several
`trailers (slot 1 to slot 12 inclusive). These 12 encoded
`bits are shown as F in seq-C of a slave bearer in FIG. 3.
`Together these encoded bits define the offset from that
`slave bearer to the master bearer (of the same RFC) as
`a 12 bit 2’s complement value. The most significant bit
`is at slot 1, the least significant at slot 12.
`1.2 Slot Formats
`
`45
`
`50
`
`_55
`
`65
`
`6
`The full slot length is designed for optimum segmen-
`tation of user messages up to 256 octets long. The proto-
`col also provides an option of subdividing one or more
`upslots into [1/4] subslots, as shown in FIG. 5. These
`subslots are used on the uplink only to allow for very
`short contention subslots.
`
`The slots and subslots supply the following range of
`data capacity to layer 3 of the protocol:
`[1/1] slot 510 bits (10 forward error correction FEC
`blocks of 51 bits) of layer 3 data
`[1/4] slot 102 bits (2 forward error correction FEC
`blocks of 51 bits) of layer 3 data.
`Slot Summary
`The slot formats are designed to use an exact number
`of forward error correction (FEC) blocks in all the slot
`formats. The contents of each slot are defined in the
`following components as shown in FIGS. 4 and 5:
`
` DOWNLINK UPLINK
`
`Encoded slot data (ESD)
`Padding
`Down slot trailer
`Encoded slot data (BSD)
`Up slot trailer
`Up slot Gap
`
`Padding
`A minimum of 2 bits of padding is provided on all
`uplink slots, to provide initialisation for the differential
`decoding if required. No padding is added to downslots,
`since a mobile receiver can initialise its decoding on the
`trailer of the previous slot. Padding is placed at the start
`of each upslot or upsubslot, and the padding bits are
`filled with a dotting pattern. The dotting pattern used is:
`[01] on upslots
`Transmission of this padding is mandatory. The pro-
`tocol also allows for optional transmission of further
`padding by mobiles.
`Optional Uplink Padding
`Mobiles are permitted to transmit additional padding
`bits at three points:
`‘
`during the carrier attack time.
`during the carrier release time.
`in the gap between slots, when the mobile is transmit-
`ting successive slots.
`If transmitted, this dotting must be fully synchronous
`to the encoded slot data. Optional padding can only be
`added in steps of 2 bits (i.e. an odd number of padding
`bits is not allowed).
`No other data pattern is allowed if this optional dot-
`ting is not transmitted.
`Down Slot Trailer
`
`v
`
`A down slot trailer is transmitted at each slot posi-
`tion. The down slot trailer DST uses three synchronisa-
`tion codewords that together provide a synchronisation
`sequence. Each 16 bit codeword can be used normal or
`inverted, to encode 1 bit of information. Each code-
`word is used to encode one bit of one of the frame
`sequences as follows:
`Codeword 2:1=NSYNC:0=ISYNC:(one bit of seq-
`C)
`Codeword 1:1=NSYNC:0=ISYNC:(one bit of seq-
`B)
`Codeword 0:1:NSYNC:0=ISYNC:(one bit of seq-
`A)
`The encoding uses the following complementary
`sync words:
`NSYNC (Normal sync): [1100 0100 1101 0111]
`ISYNC (Inverted sync): [0011 1011 0010 1000]
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 26
`
`Petitioner Cisco Systems - Exhibit 1015 - Page 26
`
`

`

`7
`All mobile receivers are expected to be able to ocate
`slots to an accuracy of +/—- 10 bits by simple timing
`from a previous slot where frame sync had been ac-
`quired.
`Up Slot Trailer
`An up slot trailer UST is also required at each slot
`and subslot position. This contains the single up slot
`synchronisation codeword:
`Codeword OzUSYNC
`USYNC (Up sync): [0011 1001 01]
`All mobiles are assumed to be able to transmit slots to
`
`an accuracy of +/—1 bit by timing (using the down
`slot trailer to provide slot and frame sync). The up slot
`trailer UST is designed to provide synchronisation to.
`cover three sources of error:
`the mobile timing error of +/—1 bit (just described)
`a base timing error of +/—1 bit
`0 to 2 bits of propagation delay
`This gives a total of 6 bits of timing and propagation
`errors. The overall synchronisation requirement
`is
`therefore +/—3 bits.
`Up Slot Gap
`The up slot gap is used to allow for time division
`multiplexing and timing errors on the uplink. This gap
`allows for the following elements:
`30 bits to provide carrier attack/release time (of ap-
`proximately 5 msec at 6.144 kbps)
`6 bits to allow for timing and propagation errors.
`The timing diagram for upslots (relative to down-
`slots) is shown in FIG. 6. The timing shown is all re-
`ferred to the base antenna, but the timing referenced to
`each mobile antenna will differ depending on its dis-
`tance from the base (i.e. the propagation delay).
`A11 mobiles behave as though their antenna is adja-
`cent to the base antenna, and transmit relative to their
`individual received timing, ignoring the possibility that
`this can be delayed by up to 1 bit for distant mobiles.
`Thus each mobile should attempt to align the leading
`edge of its [1/1] transmission with the leading edge of
`the base transmission. The latest reply then contains a
`double propagation delay of 2 bits (plus any timing
`errors) when viewed at the base antenna.
`All timing is referenced to the leading edge of the
`first (most significant) bit of each [1/1] downslot, shown
`as T between slot N and slot N+l in FIG. 6. FIG. 6
`shows three extreme timing examples with the carrier
`attack and release envelopes shown by the overlapping
`triangle symbols:
`I—The earliest mobile arrival occurs at [—2] bits as a
`result of a timing error of [—2] bits.
`II—The latest mobile arrival occurs at [+4] bits as a
`result of a propagation delay of [+2] bits plus a tim-
`ing error of [+2] bits.
`III—Any mobile can transmit additional padding, and
`the third example shows the maximum padding on a
`latest arrival mobile transmission.
`Encoded Slot Data
`Encoded slot data is an encoded form of the data
`supplied to/from the layer 3 protocols.
`Differential Coding Implementation
`Although the protocol defines differential coding as a
`layer 1 process, it may be preferable to consider imple-
`mentation that combine the layer 2 processes with dif-
`ferential encoding. This is suggested for ease of imple-
`mentation of the line coding (i.e. the final stage of slot
`data encoding). The principle is shown in FIGS. 70 and
`7b. FIG. 7a shows the strict layered approach; FIG. 7b
`shows an alternative arrangement with separate differ-
`
`10
`
`15
`
`20
`
`25
`
`30
`
`'
`35
`
`40
`
`4s
`
`50
`
`55
`
`65
`
`5,377,192
`
`8
`ential encoding DIFF CODE for each layer 2 element.
`Note that in both cases the differential coding must
`maintain knowledge of the most recent previous trans-
`mitted bit.
`1.3 Slot Data Encoding
`Three encoding processes are applied to the layer 3
`data:
`Forward Error Correction FEC
`Interleaving—INTL
`Line Coding (with DC carry-over DC)——LC
`The processes are applied as shown in FIG. 8. Each
`encoding process adds to the layer 3 data, as shown in
`FIG. 9a for [1/1] slots and as shown in FIG. 9b for [1/4]
`slots.
`Forward Error Correction (FEC)
`Forward error correction uses the BCH(63,51) block
`code for all slots and subslots.
`As the FEC encoding is a block structured process,
`the slot size has been arranged to contain an integral
`number of FEC blocks:
`
`Slot type
`[1/1]
`[1/4]
`
`Number of FEC blocks
`10
`2
`
`The FEC code is used to protect the complete layer
`3 data (it does not protect the slot trailer or the pad-
`ding). The FEC is only used for error correction, and
`not for error detection.
`The FEC code has the following characteristics:
`
`Code rate:
`Maximum error correction:
`Encoded block size:
`Information content:
`
`0.81
`2 errors per block
`63 bits
`51 bits per block
`
`Interleaving
`The FEC blocks will be fully interleaved over the
`complete slot, for each slot or subslot as shown in FIG.
`10. All the FEC blocks (for each slot or subslot) are
`interleaved on a bit-by—bit basis, starting with the most
`significant bit of the first block B0, and finishing with
`the least significant bit of the last block B9 to produce
`interleaved blocks IBO to IB62. This improves the burst
`error correction properties, by distributing burst errors
`across several FEC blocks.
`Line Coding
`Line coding is used to meet the modulation contraints
`of simple radios, by maintaining a zero DC content and
`a low Digital Sum Variation (DSV). This allows the
`radio modulator to operate with no DC capability and a
`limited low frequency capability. A 7:8 block code is
`used that encodes 7 bits of input into 8 bits of balanced
`output, and this operates directly on the interleaved
`data. The FEC plus interleaving always yields an exact
`number of line code blocks.
`The line coding is required to maintain a zero DC
`content in the differentially encoded data stream. This
`requires the line coder to use a ‘history’ bit that moni-
`tors the differentially encoded output.
`DC Carry Over
`Th