United States Patent [19J
`Gorsuch et al.
`
`[54]
`
`DYNAMIC BANDWIDTH ALLOCATION TO
`TRANSMIT A WIRELESS PROTOCOL
`ACROSS A CODE DIVISION MULTIPLE
`ACCESS (CDMA) RADIO LINK
`
`[75]
`
`Inventors: Thomas E. Gorsuch, Indialantic; Carlo
`Amalfitano, Melbourne Beach, both of
`Fla.
`
`[73] Assignee: Tantivy Communications, Inc.,
`Melbourne, Fla.
`
`[21] Appl. No.: 08/992,760
`
`[22] Filed:
`
`Dec. 17, 1997
`
`Related U.S. Application Data
`[60] Provisional application No. 60/050,277, Jun. 20, 1997, and
`provisional application No. 60/050,338, Jun. 20, 1997.
`Int. Cl? ..................................................... H04L 12/28
`[51]
`[52] U.S. Cl. .......................... 370/468; 370/335; 370/342;
`370/465; 370/338; 455/452; 455/500; 455/509;
`455/422
`[58] Field of Search ..................................... 455/450, 452,
`455/509, 500, 422, 447; 370/335, 342,
`441, 209, 468, 433, 465, 338
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`6/1987 Paneth eta!. ............................. 370/50
`3/1989 Paneth eta!. ............................. 370/95
`3/1990 Paneth eta!. .......................... 370/95.1
`6/1991 Paneth eta!. ............................. 370/50
`5/1992 Wellhausen et a!. ................... 446/246
`1!1994 Fattouche et a!. .......................... 375/1
`6/1994 Connolly et a!. ......................... 379/60
`10/1994 Hester eta!. ............................. 370/84
`5/1995 Glover .................................... 348/398
`11/1995 Hulbert ..................................... 370/18
`12/1996 Schwaller ................................ 348/388
`1!1997 Rudrapatna et a!. ................... 370/320
`1!1997 Rudrapatna et a!. ................... 370/320
`4/1997 Li eta!. .................................. 370/426
`8/1997 Cline eta!. ............................. 370/328
`8/1997 Paneth eta!. ........................... 375/356
`
`4,675,863
`4,817,089
`4,912,705
`5,022,024
`5,114,375
`5,282,222
`5,325,419
`5,355,374
`5,412,429
`5,471,463
`5,585,850
`5,592,470
`5,592,471
`5,617,423
`5,655,001
`5,657,358
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006081536A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,081,536
`Jun.27,2000
`
`5,687,194
`5,697,059
`5,793,744
`5,881,060
`5,893,376
`5,956,332
`5,966,374
`6,002,690
`6,011,800
`
`11/1997 Paneth et a!. ........................... 375/283
`12/1997 Carney ................................... 455/34.1
`8/1998 Kanerva et a!. ........................ 370/209
`3/1999 Morrow et a!. ......................... 370/337
`4/1999 Alperovich et a!. .................... 370/348
`9/1999 Rasanen et a!. ........................ 370/342
`10/1999 Rasanen .................................. 370/337
`..................... 370/437
`12/1999 Takayama et a!.
`1!2000 Nadgauda et a!. ...................... 370/437
`
`FOREIGN PATENT DOCUMENTS
`
`0 526 106 A2
`0 682 423 A2
`0 719 062 A2
`wo 96/08934
`wo 96/37081
`wo 97/23073
`wo 97/46044
`
`2/1993
`11/1995
`6/1996
`3/1996
`11/1996
`6/1997
`12/1997
`
`European Pat. Off ..
`European Pat. Off. . ........ H04J 13/00
`European Pat. Off ..
`WIPO.
`WIPO.
`WIPO.
`WIPO.
`
`OTHER PUBLICATIONS
`
`Melanchuk, et al., "CDPD and Emerging Digital Cellular
`Systems," Digest of Papers of COMPCON, Computer Soci(cid:173)
`ety Conference 1996, Technologies for the Information
`Superhighway, Santa Clara, CA., no. Conf. 41, pp. 2-8 (Feb.
`25, 1996), XP000628458 Institute of Electrical and Elec(cid:173)
`tronics Engineers.
`
`Primary Examiner-William G. Trost
`Assistant Examiner-Joy Redmon
`Attorney, Agent, or Firm--Hamilton, Brook, Smith &
`Reynolds, P.C.
`
`[57]
`
`ABSTRACT
`
`A technique for transmission of wireless signals across
`CDMA radio links. Bandwidth is allocated dynamically
`within a session to specific CDMA subscriber unit based
`upon data rate determinations. Specifically, a dynamic band(cid:173)
`width allocation algorithm operates from limits calculated
`based upon available ports per subscriber, expected user
`bandwidth, and parallel user bandwidth versus throughput.
`Provisions for priority service, unbalanced forward and
`reverse spectrum utilization, voice prioritization, and band
`switching are also made .
`
`8 Claims, 7 Drawing Sheets
`
`100
`
`/
`
`170
`
`110
`
`180
`
`t IS-634
`@
`
`BWmgt.
`
`174
`
`V5.2
`
`Cisco Systems, Inc., Exhibit 1011
`Page 1
`
`

`
`, _______________ [ ______ ,
`
`101
`
`100
`
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`
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`160-1
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`I
`1 ~
`150
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`I
`_j
`
`160-2
`
`170
`
`172
`
`COMA
`Transceiver(s)
`
`BWmgt.
`
`174
`
`V5.2
`
`t IS-634
`
`6ff 112-1
`
`I
`I
`112-2 :
`
`<@
`
`..)-. -=-:,.,.
`
`110
`
`2B+D
`
`130
`
`140
`
`ISDN
`Modem
`
`11U 11 Protocol Cpnvert
`
`Spoof BW mgt
`
`COMA
`Transceiver
`
`1
`ll------1 -II
`I
`I
`120
`192Kbps
`132
`134
`L-------------------
`
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`
`102
`r - - - - - - - - - - _____ _( __ -----,
`nB+D
`130
`140
`I
`I
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`I 150
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`I
`(134
`(132
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`
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`Modem
`
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`
`Transceiver
`
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`
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`
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`
`FIG. 1
`
`d •
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`Ul
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`0\
`
`Cisco Systems, Inc., Exhibit 1011
`Page 2
`
`

`
`22 o-....
`
`App I ications
`223
`-
`
`End to End
`User
`Signalling
`228 - -
`Q.931 X 25
`227
`-
`
`LAPD 0.921
`226
`
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`
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`
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`225
`
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`Line I
`Line 2 __......
`(TE) 110, 112
`
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`dio Link
`0
`16
`X~
`
`bps y
`
`230\
`
`Bandwidth
`Management 235
`
`u
`Interface
`ISDN
`
`192 Kbps
`
`LAPD 0.921 EW[X]
`232
`234
`-
`
`1.430 (BRI) COMA
`231
`233
`-
`
`-
`
`Call Processing
`247
`-
`-
`BWmgt 0.931
`V5.2
`243
`246
`
`EW·X
`242
`-
`
`COMA
`241
`-
`
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`0.921
`245 - -
`1.430
`(BRI)
`244
`
`v240
`
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`180
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`
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`
`.... = 00
`
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`Ul
`~
`0\
`
`ISDN Modem 120
`
`Protocol Converter 130
`
`Base Station 140
`
`FIG.2
`
`Cisco Systems, Inc., Exhibit 1011
`Page 3
`
`

`
`U.S. Patent
`
`Jun.27,2000
`
`Sheet 3 of 7
`
`6,081,536
`
`~
`
`-....---
`N :c
`~
`L()
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`N
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`
`Cisco Systems, Inc., Exhibit 1011
`Page 4
`
`

`
`------,
`r---- --------=.---=-=--~----=---=--=--- - - - - l I
`I ~---------
`Control
`I I
`t
`0
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`Detect
`
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`I
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`-1 Fwd Spoof Data
`- - -+
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`
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`
`from COMA
`Transceiver
`150
`
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`Ch. N
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`on . .
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`Modem
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`
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`
`d •
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`from COMA
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`FIG. 4 L _________ - - - - - - - - - - - -
`
`- - t -
`, - - - - , . - - - - - - - - - - - - .L:::::423-
`
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`
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`
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`Detect
`
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`
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`
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`424
`
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`
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`
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`BW Request
`Channel Set-Up
`Channel Tear-Down
`Error Correction
`Packet Buffering
`BER Measurements
`
`Cisco Systems, Inc., Exhibit 1011
`Page 5
`
`

`
`--
`-
`-----
`-- -----
`....-----~ ---------
`,.--(cid:173)
`
`,., ....,.. ..,-
`
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`to Transmit
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`
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`Released
`
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`Timer Expired
`
`/
`
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`
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`
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`
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`Timer Expired
`
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`Exceeded
`
`FIG. 5
`
`d •
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`
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`0\
`
`Cisco Systems, Inc., Exhibit 1011
`Page 6
`
`

`
`r-------------------------
`--.
`~ I
`Sub-
`I
`Ch. I ---:-1
`Contra
`I
`Ch. 2--.!-- Channa
`: I
`Inverse
`Data
`Ch.N~ Multiplexer
`i
`J
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`I
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`
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`
`FIG.6
`
`0\
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`.... = 00
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`Ul
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`
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`
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`
`I
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`L ________________ '636 ___ ReverseLi~63~
`
`Cisco Systems, Inc., Exhibit 1011
`Page 7
`
`

`
`U.S. Patent
`
`Jun.27,2000
`
`Sheet 7 of 7
`
`6,081,536
`
`MAIN:
`DO Always
`Process Port Request
`Process Bandwidth Release
`Process Bandwidth Requests
`Locate and tear down unused sub-channels
`END DO
`
`710
`
`PORT REQUEST:
`Make reservation in least ~tmzed sub-band
`Reservation decision based on °/o of available Sub-Channels to
`assign (Based on parallel user BWvs. throughput efficiency}
`IF reservation was made
`Send frequency and code assignment
`Update allocations
`ELSE
`Add port request to port queue
`Calculate expected wait time
`Send wait message to user
`ENDIF
`
`720
`
`BANDWIDTH RELEASE:
`Notify channel-bonding function
`Return frequency and code to available pool
`Update radio record
`
`730
`
`BANDWIDTH REQUEST:
`Select highest priority with lowest bandwidth utilization,
`including need-allocation gap
`Check other sub-bands for greatest available sub channels
`(Switch sub-bands if difference in sub-band space
`exceeds payback threshold)
`Assign sub channels based on need, priority, availability
`Notify channel bonding function
`Update radio record
`
`740
`
`FIG. 7
`
`Cisco Systems, Inc., Exhibit 1011
`Page 8
`
`

`
`6,081,536
`
`1
`DYNAMIC BANDWIDTH ALLOCATION TO
`TRANSMIT A WIRELESS PROTOCOL
`ACROSS A CODE DIVISION MULTIPLE
`ACCESS (CDMA) RADIO LINK
`
`5
`
`CROSS REFERENCE TO RELATED
`APPLICATION(S)
`This application claims the benefit of a prior pending U.S.
`Provisional Application No. 60/050,338 filed Jun. 20, 1997
`entitled "Dynamic Bandwidth Allocation to Transmit a 10
`Wireless ISDN Protocol Across a Code Division Multiple
`Access (CDMA) Radio Link" and a prior pending U.S.
`Provisional Application No. 60/050,277 filed Jun. 20, 1997
`entitled "Protocol Conversion and Bandwidth Reduction
`Technique Providing Multiple nB+D ISDN Basic Rate Inter(cid:173)
`face Links Over a Wireless Code Division Multiple Access
`Communication System."
`
`2
`certain wire line networks, called Integrated Services Digital
`Networks (ISDN), capable of higher speed data access have
`been known for a number of years, their costs have only
`been recently reduced to the point where they are attractive
`to the residential customer, even for wireline service.
`Although such networks were known at the time that cellular
`systems were originally deployed, for the most part, there is
`no provision for providing ISDN-grade data services over
`cellular network topologies.
`ISDN is an inherently circuit switched protocol, and was,
`therefore, designed to continuously send bits in order to
`maintain synchronization from end node to end node to
`maintain a connection. Unfortunately, in wireless
`environments, access to channels is expensive and there is
`15 competition for them; the nature of the medium is such that
`they are expected to be shared. This is dissimilar to the usual
`wireline ISDN environment in which channels are not
`intended to be shared by definition.
`
`25
`
`BACKGROUND OF THE INVENTION
`The increasing use of wireless telephones and personal
`computers by the general population has led to a correspond(cid:173)
`ing demand for advanced telecommunication services that
`were once thought to only be meant for use in specialized
`applications.
`For example, in the late 1980's, wireless voice commu-
`nication such as available with cellular telephony had been
`the exclusive province of the businessman because of
`expected high subscriber costs. The same was also true for
`access to remotely distributed computer networks, whereby
`until very recently, only business people and large institu- 30
`tions could afford the necessary computers and wireline
`access equipment.
`However, the general population now increasingly wishes
`to not only have access to networks such as the Internet and
`private intranets, but also to access such networks in a 35
`wireless fashion as well. This is particularly of concern for
`the users of portable computers, laptop computers, hand(cid:173)
`held personal digital assistants and the like who would
`prefer to access such networks without being tethered to a
`telephone line.
`There still is no widely available satisfactory solution for
`providing low cost, high speed access to the Internet and
`other networks using existing wireless networks. This situ(cid:173)
`ation is most likely an artifact of several unfortunate cir(cid:173)
`cumstances. For example, the typical manner of providing 45
`high speed data service in the business environment over the
`wireline network is not readily adaptable to the voice grade
`service available in most homes or offices. In addition, such
`standard high speed data services do not lend themselves
`well to efficient transmission over standard cellular wireless 50
`handsets.
`Furthermore, the existing cellular network was originally
`designed only to deliver voice services. At present, the
`wireless modulation schemes in use continue their focus on
`delivering voice information with maximum data rates only 55
`in the range of 9.6 kbps being readily available. This is
`because the cellular switching network in most countries,
`including the United States, uses analog voice channels
`having a bandwidth from about 300 to 3600 Hertz. Such a
`low frequency channel does not lend itself directly to 60
`transmitting data at rates of 28.8 kilobits per second (kbps)
`or even the 56.6 kbps that is now commonly available using
`inexpensive wire line modems, and which rates are now
`thought to be the minimum acceptable data rates for Internet
`access.
`Switching networks with higher speed building blocks are
`just now coming into use in the United States. Although
`
`20
`
`SUMMARY OF THE INVENTION
`The present invention provides high speed data and voice
`service over standard wireless connections via an unique
`integration ofiSDN protocols and existing cellular signaling
`such as is available with Code Division Multiple Access
`(CDMA) type modulated systems. The present invention
`achieves high data rates through more efficient allocation of
`access to the CDMA wireless channels. In particular, a
`number of subchannels are defined within a standard CDMA
`channel bandwidth, which is normally necessary to support
`the ISDN protocol, such as by assigning different codes to
`each subchannel. The instantaneous bandwidth needs of
`each on-line subscriber unit are met by dynamically allo(cid:173)
`cating multiple subchannels of the RF carrier on an as
`needed basis for each session. For example, multiple sub(cid:173)
`channels are granted during times when the subscriber
`bandwidth requirements are relatively high, such as when
`downloading Web pages and released during times when the
`line content is relatively light, such as when the subscriber
`is reading a Web page which has been previously down-
`40 loaded or is performing other tasks.
`Subchannel assignment algorithms may be implemented
`to offer various levels of priority service to particular sub(cid:173)
`scribers. These may be assigned based upon available ports
`per subscriber, expected user bandwidth, service premium
`payments, and so on.
`In accordance with another aspect of the invention, some
`portion of the available bandwidth is initially allocated to
`establish a communication session. Once the session has
`been established, if a subscriber unit has no data to present
`for transmission, namely, if the data path remains quiescent
`for some period of time, the previously assigned bandwidth
`is deallocated. In addition, it is preferable that not all of the
`previously assigned bandwidth be deallocated, but rather at
`least some portion be kept available for use by an in-session
`subscriber. If the inactivity continues for a further period of
`time, then even the remaining portion of the bandwidth can
`be deallocated from the session. A logical session connec(cid:173)
`tion at a network layer protocol is still maintained even if no
`subchannels are assigned.
`In a preferred arrangement, a single subchannel is main(cid:173)
`tained for a predetermined minimum idle time for each
`network layer connection. This assists with more efficient
`management of channel setup and tear down.
`
`65
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`The foregoing and other objects, features and advantages
`of the invention will be apparent from the following more
`
`Cisco Systems, Inc., Exhibit 1011
`Page 9
`
`

`
`6,081,536
`
`3
`particular description of preferred embodiments of the
`invention, as illustrated in the accompanying drawings in
`which like reference characters refer to the same parts
`throughout the different views.
`FIG. 1 is a block diagram of a wireless communication
`system making use of a bandwidth management scheme
`according to the invention.
`FIG. 2 is an Open System Interconnect (OSI) type layered
`protocol diagram showing where the bandwidth manage(cid:173)
`ment scheme is implemented in terms of communication
`protocols.
`FIG. 3 is a diagram showing how subchannels are
`assigned within a given radio frequency (RF) channel.
`FIG. 4 is a more detailed block diagram of the elements 15
`of a subscriber unit.
`FIG. 5 is a state diagram of the operations performed by
`a subscriber unit to request and release subchannels dynami(cid:173)
`cally.
`FIG. 6 is a block diagram of a portion of a base station
`unit necessary to service each subscriber unit.
`FIG. 7 is a high level structured English description of a
`process performed by the base station to manage bandwidth
`dynamically according to the invention.
`
`4
`134, a CDMA transceiver 140, and subscriber unit antenna
`150. The various components of the subscriber unit 101 may
`be realized in discrete devices or as an integrated unit. For
`example, an existing conventional ISDN modem 120 such
`5 as is readily available from any number of manufacturers
`may be used together with existing CDMA transceivers 140.
`In this case, the unique functions are provided entirely by the
`protocol converter 130 which may be sold as a separate
`device. Alternatively, the ISDN modem 120, protocol con-
`10 verter 130, and CDMA transceiver 140 may be integrated as
`a complete unit and sold as a single subscriber unit device
`101.
`The ISDN modem 120 converts data and voice signals
`between the terminal equipment 110 and 112 to format
`required by the standard ISDN "U" interface. The U inter(cid:173)
`face is a reference point in ISDN systems that designates a
`point of the connection between the network termination
`(NT) and the telephone company.
`The protocol converter 130 performs spoofing 132 and
`20 basic bandwidth management 134 functions, which will be
`described in greater detail below. In general, spoofing 132
`consists of insuring that the subscriber unit 101 appears to
`the terminal equipment 110, 112 that is connected to the
`public switched telephone network 180 on the other side of
`25 the base station 170 at all times.
`The bandwidth management function 134 is responsible
`for allocating and deallocating CDMAradio channels 160 as
`required. Bandwidth management also includes the dynamic
`management of the bandwidth allocated to a given session
`30 by dynamically assigning sub-portions of the CDMA chan(cid:173)
`nels 160 in a manner which is more fully described below.
`The CDMA transceiver 140 accepts the data from the
`protocol converter 130 and reformats this data in appropriate
`35 form for transmission through a subscriber unit antenna 150
`over CDMA radio link 160-1. The CDMA transceiver 140
`may operate over only a single 1.25 MHZ radio frequency
`channel or, alternatively, in a preferred embodiment, may be
`tunable over multiple allocatable radio frequency channels.
`CDMA signal transmissions are then received at the base
`station and processed by the base station equipment 170.
`The base station equipment 170 typically consists of mul(cid:173)
`tichannel antennas 171, multiple CDMA transceivers 172,
`and a bandwidth management functionality 174. Bandwidth
`management controls the allocation of CDMA radio chan(cid:173)
`nels 160 and subchannels. The base station 170 then couples
`the demodulated radio signals to the Public Switch Tele(cid:173)
`phone Network (PSTN) 180 in a manner which is well
`known in the art. For example, the base station 170 may
`50 communicate with the PSTN 180 over any number of
`different efficient communication protocols such as primary
`rate ISDN, or other LAPD based protocols such as IS-634 or
`V5.2.
`It should also be understood that data signals travel
`bidirectionally across the CDMA radio channels 160, i.e.,
`data signals originate at the portable computer 110 are
`coupled to the PSTN 180, and data signals received from the
`PSTN 180 are coupled to the portable computer 110.
`Other types of subscriber units such as unit 102 may be
`used to provide higher speed data services. Such subscriber
`units 102 typically provide a service referred to as nB+D
`type service that may use a so-called Primary Rate Interface
`(PRI) type protocol to communicate with the terminal equip(cid:173)
`ment 110, 112. These units provide a higher speed service
`65 such as 512 kbps across the U interface. Operation of the
`protocol converter 130 and CDMA transceiver 140 are
`similar for the nB+D type subscriber unit 102 as previously
`
`DETAILED DESCRIPTION OF 1HE
`INVENTION
`
`Turning attention now to the drawings more particularly,
`FIG. 1 is a block diagram of a system 100 for providing high
`speed data and voice service over a wireless connection by
`seamlessly integrating a digital data protocol such as, for
`example, Integrated Services Digital Network (ISDN) with
`a digitally modulated wireless service such as Code Division
`Multiple Access (CDMA).
`The system 100 consists of two different types of
`components, including subscriber units 101, 102 and base
`stations 170. Both types of these components 101 and 170
`cooperate to provide the functions necessary in order to
`achieve the desired implementation of the invention. The 40
`subscriber unit 101 provides wireless data services to a
`portable computing device 110 such as a laptop computer,
`portable computer, personal digital assistant (PDA) or the
`like. The base station 170 cooperates with the subscriber unit
`101 to permit the transmission of data between the portable 45
`computing device 110 and other devices such as those
`connected to the Public Switched Telephone Network
`(PSTN) 180.
`More particularly, data and/or voice services are also
`provided by the subscriber unit 101 to the portable computer
`110 as well as one or more other devices such as telephones
`112-1, 112-2 (collectively referred to herein as telephones
`112. (The telephones 112 themselves may in turn be con(cid:173)
`nected to other modems and computers which are not shown
`in FIG. 1). In the usual parlance of ISDN, the portable 55
`computer 110 and telephones 112 are referred to as terminal
`equipment (TE). The subscriber unit 101 provides the func(cid:173)
`tions referred to as a network termination type 1 (NT-1 ). The
`illustrated subscriber unit 101 is in particular meant to
`operate with a so-called basic rate interface (BRI) type 60
`ISDN connection that provides two bearer or "B" channels
`and a single data or "D" channel with the usual designation
`being 2B+D.
`The subscriber unit 101 itself consists of an ISDN modem
`120, a device referred to herein as the protocol converter 130
`that performs the various functions according to the inven(cid:173)
`tion including spoofing 132 and bandwidth management
`
`Cisco Systems, Inc., Exhibit 1011
`Page 10
`
`

`
`6,081,536
`
`5
`
`5
`described for subscriber unit 101, with the understanding
`that the number of radio links 160 to support subscriber unit
`102 are greater in number or each have a greater bandwidth.
`Turning attention now to FIG. 2, the invention may be
`described in the context of a Open Systems Interconnect
`multilayer protocol diagram. The three protocol stacks 220,
`230, and 240 are for the ISDN modem 120, protocol
`converter 130, and base station 170, respectively.
`The protocol stack 220 used by the ISDN modem 120 is
`conventional for ISDN communications and includes, on the
`terminal equipment side, the analog to digital conversion
`(and digital to analog conversion) 221 and digital data
`formatting 222 at layer one, and an applications layer 223 at
`layer two. On the U interface side, the protocol functions
`include Basic Rate Interface (BRI) such as according to
`standard 1.430 at layer one, a LAPD protocol stack at layer 15
`two, such as specified by standard Q.921, and higher level
`network layer protocols such as Q.931 or X.227 and high
`level end to end signaling 228 required to establish network
`level sessions between modes.
`The lower layers of the protocol stack 220 aggregate two 20
`bearer (B) channels to achieve a single 128 kilobits per
`second (kbps) data rate in a manner which is well known in
`the art. Similar functionality can be provided in a primary
`rate interface, such as used by subscriber unit 102, to
`aggregate multiple B channels to achieve up to 512 kbps 25
`data rate over the U interface.
`The protocol stack 230 associated with the protocol
`converter 130 consists of a layer one basic rate interface 231
`and a layer two LAPD interface 232 on the U interface side,
`to match the corresponding layers of the ISDN modem stack
`220.
`At the next higher layer, usually referred to as the network
`layer, a bandwidth management functionality 235 spans both
`the U interface side and the CDMA radio link side of the 35
`protocol converter stack 230. On the CDMA radio link side
`160, the protocol depends upon the type of CDMA radio
`communication in use. An efficient wireless protocol
`referred to herein as EW[x] 234, encapsulates the layer one
`231 and layer two 232 ISDN protocol stacks in such a
`manner that the terminal equipment 110 may be discon(cid:173)
`nected from one or more CDMA radio channels without
`interrupting a higher network layer session.
`The base station 170 contains the matching CDMA 241
`and EW[ x] 242 protocols as well as bandwidth management 45
`243. On the PSTN side, the protocols may convert back to
`basic rate interface 244 and LAPD 245 or may also include
`higher level network layer protocols as Q.931 or V5.2 246.
`Call processing functionality 247 allows the network
`layer to set up and tear down channels and provide other 50
`processing required to support end to end session connec(cid:173)
`tions between nodes as is known in the art.
`The spoofing function 132 performed by the EW[ x]
`protocol 234 includes the necessary functions to keep the U
`interface for the ISDN connection properly maintained, even 55
`in the absence of a CDMA radio link 160 being available.
`This is necessary because ISDN, being a protocol originally
`developed for wire line connections, expects to send a
`continuous stream of synchronous data bits regardless of
`whether the terminal equipment at either end actually has 60
`any data to transmit. Without the spoofing function 132,
`radio links 160 of sufficient bandwidth to support at least a
`192 kbps data rate would be required throughout the dura(cid:173)
`tion of an end to end network layer session, whether or not
`data is actually presented.
`EW[x] 234 therefore involves having the CDMA trans(cid:173)
`ceiver 140 loop back these synchronous data bits over the
`
`6
`ISDN communication path to spoof the terminal equipment
`110, 112 into believing that a sufficiently wide wireless
`communication link 160 is continuously available.
`However, only when there is actually data present from the
`terminal equipment to the wireless transceiver 140 is wire(cid:173)
`less bandwidth allocated. Therefore, unlike the prior art, the
`network layer need not allocate the assigned wireless band(cid:173)
`width for the entirety of the communications session. That
`is, when data is not being presented upon the terminal
`10 equipment to the network equipment, the bandwidth man(cid:173)
`agement function 235 deallocates initially assigned radio
`channel bandwidth 160 and makes it available for another
`transceiver and another subscriber unit 101.
`In order to better understand how bandwidth management
`235 and 243 accomplish the dynamic allocation of radio
`bandwidth, turn attention now to FIG. 3. This figure illus(cid:173)
`trates one possible frequency plan for the wireless links 160
`according to the invention. In particular, a typical transceiver
`170 can be tuned on command to any 1.25 MHZ channel
`within a much larger bandwidth, such as up to 30 MHZ. In
`the case of location in an existing cellular radio frequency
`bands, these bandwidths are typically made available in the
`range of from 800 to 900 MHZ. For personal communica(cid:173)
`tion systems (PCS) type wireless systems, the bandwidth is
`typically allocated in the range from about 1.8 to 2.0
`GigaHertz (GHz). In addition, there are typically two match-
`ing bands active simultaneously, separated by a guard band,
`such as 80 MHZ; the two matching bands form forward and
`reverse full duplex link.
`Each of the CDMA transceivers, such as transceiver 140
`in the subscriber unit 101 and transceivers 172 in the base
`station 170, are capable of being tuned at any given point in
`time to a given 1.25 MHZ radio frequency channel. It is
`generally understood that such 1.25 MHZ radio frequency
`carrier provides, at best, a total equivalent of about 500 to
`600 kbps maximum data rate transmission within acceptable
`bit error rate limitations.
`In the prior art, it was thus generally understood that in
`order to support an ISDN type like connection which may
`contain information at a rate of 128 kbps that, at best, only
`about (500 kbps/128 kbps) or only 3 ISDN subscriber units
`could be supported at best.
`In contrast to this, the present invention subdivides the
`available approximately 500 to 600 kbps bandwidth into a
`relatively large number of subchannels. In the illustrated
`example, the bandwidth is divided into 64 subchannels 300,
`each providing an 8 kbps data rate. A given subchannel 300
`is physically implemented by encoding a transmission with
`one of a number of different assignable pseudorandom
`codes. For example, the 64 subchannels 300 may be defined
`within a single CDMA RF carrier by using a different
`orthogonal Walsh codes for each defined subchannel 300.
`The basic idea behind the invention is to allocate the
`subchannels 300 only as needed. For example, multiple
`subchannels 300 are granted during times when a particular
`ISDN subscriber unit 101 is requesting that large amounts of
`data be transferred. These subchannels 300 are released
`during times when the subscriber unit 101 is relatively
`lightly loaded.
`Before discussing how the subchannels are preferably
`allocated and deallocated, it will help to understand a typical
`subscriber unit 101 in greater detail. Turning attention now
`to FIG. 4, it can be seen that an exemplary protocol
`65 converter 130 consists of a microcontroller 410, reverse link
`processing 420, and forward link processing 430. The
`reverse link processing 420 further includes ISDN reverse
`
`30
`
`40