United States Patent (19)
`Trompower
`
`54 CELLULAR COMMUNICATION SYSTEM
`WITH DEDICATED REPEATER CHANNELS
`
`75 Inventor: Michael L. Trompower, Navarre, Ohio
`73 Assignee: Cisco Systems, Inc., San Jose, Calif.
`
`Appl. No.: 08/625,421
`21
`22 Filed:
`Mar. 29, 1996
`Related U.S. Application Data
`63 Continuation-in-part of application No. 08/566,502, Dec. 4,
`1995, Pat. No. 5,950,124, which is a continuation-in-part of
`application No. 08/523.942, Sep. 6, 1995, abandoned.
`(51) Int. Cl. .................................................. H04J 3/22
`52 U.S. Cl. ............................................ 453/11.1; 455/450
`58 Field of Search .................................... 455/11.1, 450,
`455/422, 63,524,517,572, 561, 426, 446,
`447, 448, 466; 370/335, 342, 468; 375/140,
`146, 147, 141, 220
`
`56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,041,389 8/1977 Oades ........................................ 455/17
`4,041,391
`8/1977 Deerkoski.
`4,456,793
`6/1984 Baker et al..
`4,509,199 4/1985 Ichihara ...................................... 455/7
`4,534,061
`8/1985 Ulug .......................................... 455/17
`4,539,706 9/1985 Mears et al. ........................... 455/11.1
`4,665,404 5/1987 Christy et al..
`... 379/63
`4,672,658 6/1987 Kavehrad et al.
`4,799,252
`1/1989 Eizenhoffer et al. ................... 370/330
`4,856,046 8/1989 Strecket al..
`4,882,765 11/1989 Maxwell et al. ....................... 455/11.1
`4,907,224 3/1990 Scoles et al..
`4,930,140 5/1990 Cripps et al..
`5,025,486 6/1991 Klughart.
`... 375/1
`5,042,050 8/1991 Owen ..
`... 455/15
`5,133,080 7/1992 Borras .....
`5,152,002 9/1992 Leslie et al. ........................... 455/11.1
`5,164,958 11/1992 Omura.
`5,177,766
`1/1993 Holland et al..
`5,204.876 4/1993 Bruckert et al. ............................ 375/1
`5,223,923
`6/1993 Morales-Garza.
`5,241,410 8/1993 Strecket al..
`
`USOO61323.06A
`Patent Number:
`11
`(45) Date of Patent:
`
`6,132,306
`Oct. 17, 2000
`
`5,258,867 11/1993 Iggulden et al..
`5,267,244 11/1993 Messerchmitt et al. ............... 370/95.3
`5,291,516 3/1994 Dixon et al..
`5,321,721 6/1994 Yamaura et al. ........................... 375/1
`5,327,580 7/1994 Vignali et al..
`5,335,249 8/1994 Krueger et al. ............................. 375/1
`5,341,396 8/1994 Higgins et al..
`5,353,300 10/1994 Lee et al..
`5,363,404 11/1994 Kotzin et al. ............................... 375/1
`5,377,256 12/1994 Franklin et al..
`5,425,051 6/1995 Mahany.
`5,442,625 8/1995 Giltin et al. .............................. 370/18
`5,450,616 9/1995 Rom.
`5,490,284 2/1996 Itoh et al. .............................. 455/11.1
`5,493,436 2/1996 Karasawa et al. .
`5,509,050 4/1996 Berland.
`5,511,073
`4/1996 Padovani et al..
`5,565,982 10/1996 Lee et al..
`5,574,771 11/1996 Driessen et al. .......................... 379/57
`
`(List continued on next page.)
`
`FOREIGN PATENT DOCUMENTS
`579372 1/1994 European Pat. Off..
`622911 11/1994 European Pat. Off..
`WO 94/11957 5/1994 WIPO.
`
`Primary Examiner Nay Maung
`Assistant Examiner Tracy M. Legree
`Attorney, Agent, or Firm Arter & Hadden LLP
`57
`ABSTRACT
`A cellular communication System in which dedicated
`repeater controller transceivers are included in base Stations
`and wireleSS base Stations. The repeater controller transceiv
`erS are configured to operate on a different channel as
`compared to communications received by or transmitted
`directly from mobile terminals. By utilizing a dedicated
`channel for communications between the base Stations and
`wireleSS base Stations, the contention areas formed by over
`lapping cell areas is effectively eliminated. The different
`channels may be based on differences in parameterS Such as
`frequency and/or data encoding techniques.
`
`26 Claims, 19 Drawing Sheets
`
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`
`Qualcomm Incorporated
`Exhibit 1003
`Page 1 of 44
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`

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`6,132,306
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`5,613,225
`5,614.914
`5,673,260
`5,687,166
`
`3/1997 Charas .................................... 455/103
`3/1997 Bolgiano et al..
`9/1997 Umeda et al. .
`11/1997 Natali et al. .
`
`5,689.524
`5,694,417
`5,715,236
`5,724,665
`5,802,173
`
`11/1997
`12/1997
`2/1998
`3/1998
`9/1998
`
`Takaki et al. .
`Andren et al. .
`Gilhousen et al. ..................... 370/209
`Abassi et al. .
`Hamilton-Piercy et al..
`
`Page 2 of 44
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`U.S. Patent
`
`Oct. 17, 2000
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`Sheet 1 of 19
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`6,132,306
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`Page 3 of 44
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`

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`U.S. Patent
`
`Oct. 17, 2000
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`Sheet 2 of 19
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`6,132,306
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`Page 4 of 44
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`U.S. Patent
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`Oct. 17, 2000
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`Sheet 3 of 19
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`
`Page 5 of 44
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`

`U.S. Patent
`
`Oct. 17, 2000
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`Sheet 4 of 19
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`U.S. Patent
`
`Oct. 17, 2000
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`Sheet 5 of 19
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`Oct. 17, 2000
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`Sheet 6 of 19
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`6,132,306
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`Page 8 of 44
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`U.S. Patent
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`Oct. 17, 2000
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`Sheet 7 of 19
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`6,132,306
`
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`Page 9 of 44
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`U.S. Patent
`US. Patent
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`Oct. 17, 2000
`Oct. 17, 2000
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`Sheet 8 of 19
`Sheet 8 0f 19
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`Oct. 17, 2000
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`U.S. Patent
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`Oct. 17, 2000
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`Sheet 10 of 19
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`U.S. Patent
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`Oct. 17, 2000
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`Sheet 11 of 19
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`6,132,306
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`Page 13 of 44
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`U.S. Patent
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`Oct. 17, 2000
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`Sheet 12 of 19
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`6,132,306
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`U.S. Patent
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`Oct. 17, 2000
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`

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`U.S. Patent
`
`Oct. 17, 2000
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`Sheet 17 of 19
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`6,132,306
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`START
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`Page 19 of 44
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`U.S. Patent
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`Oct. 17, 2000
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`Sheet 18 of 19
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`6,132,306
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`Page 20 of 44
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`U.S. Patent
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`Oct. 17, 2000
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`Sheet 19 of 19
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`6,132,306
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`CHAL 901,
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`Page 21 of 44
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`6,132,306
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`1
`CELLULAR COMMUNICATION SYSTEM
`WITH DEDICATED REPEATER CHANNELS
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`This application is a Continuation-In-Part of Ser. No.
`08/566,502, filed Dec. 4, 1995 now U.S. Pat. No. 5,950,124,
`which is a Continuation-In-Part of Ser. No. 08/523,942, filed
`Sep. 6, 1995 now abandoned, the entireties of which are
`incorporated herein by reference.
`
`TECHNICAL FIELD
`The present invention relates a cellular communication
`System utilizing dedicated repeater channels and modifiable
`transmission parameters to enhance System performance.
`
`15
`
`2
`that interfere with the transmission and reception of a
`transmitted Signal are collectively referred to as noise Sig
`nals. A useful quantitative measure of relative noise in a
`communication System is the Signal-to-noise ratio (SNR).
`The SNR is the ratio of the amplitude of a desired signal at
`any given time to the amplitude of noise signals at that same
`time.
`Generally, when a mobile terminal is powered up, it
`“registers” with a base station through which the mobile
`terminal can maintain wireleSS communication with the
`network. In order to register, the mobile terminal must be
`within the cell range of the base Station and the base Station
`must likewise be situated within the effective cell range of
`the mobile terminal. It is generally not possible to have one
`base Station Service a large area by itself. This is due to
`transmission power restrictions governed by the FCC and
`the fact that the extra hardware needed to provide a mobile
`terminal with Such a large cell range would add significantly
`to the size and weight of the mobile terminal thereby making
`it leSS desirable to use. Thus, cellular communication Sys
`tems generally have Several base Stations Spaced apart Such
`that the collective cell area coverage of the base Stations is
`Sufficient to cover the entire area in which a mobile terminal
`may roam. AS the location of the mobile terminal changes,
`the base station with which the mobile terminal was origi
`nally registered may fall outside of the geographic cell range
`of the mobile terminal. Therefore, the mobile terminal may
`"de-register' with the base Station it was originally regis
`tered to and register with another base Station which is
`within its communication range.
`When designing a cellular communication System for a
`region, an appropriate number of base Stations must be
`Selected and their locations determined to assure cell cov
`erage for the region. Each additional base Station increases
`the cost of the communication System by the incremental
`cost of the base station itself and installation fees. When
`hardwiring a new base Station to the network, both a data
`line and a power line must be provided. The data line allows
`the base Station to transmit and receive information from the
`System backbone while the power line provides continual
`power to Support the operations of the base Station. Although
`wireleSS base Stations do not require data lines Since all data
`is communicated wirelessly, they do require power.
`However, providing power lines to wireleSS base Stations
`can often be difficult. This is especially true in the common
`Situation where a wireleSS base Station is situated in a large
`outdoor Storage facility having a concrete foundation, Such
`as areas near a shipyard or loading dock. Typically, electrical
`outlets are not readily accessible in Such areas and therefore
`power lines must be Supplied to the wireleSS base Station
`from the network or elsewhere. Power lines could be located
`on the Surface of the concrete foundation, however, this
`provides an undesirable obstacle that must be avoided by
`heavy loading vehicles typically found operating at Such
`facilities. Consequently, a trench is often created through the
`concrete in order to house the power lines. Unfortunately,
`providing Such a trench adds a significant amount of extra
`time and cost to the installation process. Another method of
`Supplying power to wireleSS base Stations could involve
`Suspending power lines from power poles. However, this
`method has been found implausible given the difficulty
`involved with erecting Such power poles in the concrete
`foundation. As a result, there is a strong need in the art for
`a manner of Supplying power to a wireleSS base Station that
`is not unduly burdensome or costly.
`WireleSS communication Systems. Such as those described
`above often involve spread spectrum (SS) technology. An SS
`
`BACKGROUND
`In recent years, the use of cellular communication SyS
`tems having mobile terminals which communicate with a
`hardwired network, Such as a local area network (LAN) and
`a wide area network (WAN), has become widespread. Retail
`Stores and warehouses, for example, may use cellular com
`munications Systems to track inventory and replenish Stock.
`25
`The transportation industry may use Such Systems at large
`outdoor Storage facilities to keep an accurate account of
`incoming and outgoing Shipments. In manufacturing
`facilities, Such Systems are useful for tracking parts, com
`pleted products and defects.
`A typical cellular communication System includes a num
`ber of fixed base Stations interconnected by a cable medium
`to form a hardwired network. The hardwired network is
`often referred to as a System backbone. Also included in
`many cellular communication Systems are intermediate base
`Stations which are not directly connected to the hardwired
`network. Intermediate base Stations, often referred to as
`wireleSS base Stations, increase the area within which base
`Stations connected to the hardwired network can communi
`cate with mobile terminals. Unless otherwise indicated, the
`term “base station' will hereinafter refer to both base
`Stations hardwired to the network and wireleSS base Stations.
`ASSociated with each base Station is a geographic cell. A
`cell is a geographic area in which a base Station has Sufficient
`Signal Strength to transmit data to and receive data from a
`mobile terminal with an acceptable error rate. The error rate
`for transmitted data is defined as the ratio of the number of
`transmitted data bits received in error to the total number of
`bits transmitted. It is economically inefficient to design a
`communications System with a “Zero’ error rate. Rather,
`depending on the requirements of users of the System, an
`acceptable error rate is determined. For example, an accept
`able error rate may be set at a maximum error correcting rate
`capability of an error correcting code utilized by the System.
`The shape of each cell is primarily determined by the type
`of antenna associated with a given base Station. For instance,
`base Stations which communicate with mobile terminals
`often have omnidirectional type antennas which provide for
`generally circular shaped cells and allow for a wide area of
`coverage. In many instances, however, the cell of a base
`Station is not completely Symmetrical because physical
`Structures within the cell may partially block data Signals
`emanating from the base Station or create “dead Spots”
`where no signals can pass. Further, the cell Size may be
`decreased by machinery located in the vicinity of the base
`Station which generates excessive noise levels that degrade
`a signal transmitted by the base Station. Undesirable signals
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`communication System is one in which the transmitted
`frequency spectrum or bandwidth is much wider than abso
`lutely necessary. Generally, SS technology is utilized for
`communications in the unlicensed bands provided by the
`FCC. These bands include the 902-928 MHZ and 2.4-2.48
`GHz ranges in the U.S. The FCC requires that information
`transmitted in these bands be spread and coded in order to
`allow multiple user access to these bands at the same time.
`One type of a digital SS communication System is known
`as a direct sequence spread spectrum (DSSS) System. The
`coding Scheme of a SS digital communication System uti
`lizes a pseudo-random binary sequence (PRBS). In a DSSS
`System, coding is achieved by converting each original data
`bit (Zero or one) with a predetermined repetitive pseudo
`noise (PN) code. The PN code is used to convert effectively
`each data bit into a series of Sub-bits often referred to as
`“chips”. The rate of transmission of chips by a transmitter is
`defined as the “chipping rate”. A type of PN code is
`illustrated in FIG. 1. For this example, the digital data Signal
`110 is made up of a binary “1” bit and a “0” bit. APN code
`120 representing the digital data Signal 110 is comprised of
`a sequence of ten sub bits or chips, namely, “1”; “0”; “1”,
`“1”, “0”, “1”, “1”, “1”, “0”, “1”.
`The digital data signal 110 is coded or spread by modulo
`2 multiplying (e.g., via an “EXCLUSIVE NOR” (XNOR)
`function) of the digital data signal 110 with the PN code 120.
`If the data bit is a “1”, then the resulting spread data Signal
`(PN coded signal) in digital form corresponds to the PN code
`120. However, if the data bit to be coded is a “0”, then the
`Spread data Signal in digital form will correspond to a code
`130. AS can be seen, the code 130 is the inverse of PN code
`120. That is, the PN code and its inverse are used to
`represent data bits “1” and “0” respectively.
`APN code length refers to a length of the coded Sequence
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`(the number of chips) for each original data bit. AS noted
`above, the PN code length effects the processing gain. A
`longer PN code yields a higher processing gain which results
`in an increased communication range. The PN code chipping
`rate refers to the rate at which the chips are transmitted by
`a transmitter System. A receiver System must receive,
`demodulate and despread the PN coded chip Sequence at the
`chipping rate utilized by the transmitter System. At a higher
`chipping rate, the receiver System is allotted a Smaller
`amount of time to receive, demodulate and despread the chip
`45
`Sequence. AS the chipping rate increases So to will the error
`rate. Thus, a higher chipping rate effectively reduces com
`munication range. Conversely, decreasing the chipping rate
`increases communication range.
`The spreading of a digital data Signal by the PN code does
`not effect overall signal Strength (or power) the data being
`transmitted or received. However, by Spreading a signal, the
`amplitude at any one point typically will be less then the
`original (non-spread) signal.
`It will be appreciated that increasing the PN code length
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`or decreasing the chipping rate to achieve a longer commu
`nication range will result in a slower data transmission rate.
`Correspondingly, decreasing the PN code length or increas
`ing the chipping rate will increase data transmission rate at
`a price of reducing communication range.
`Additional methods of coding information in a SS system
`also exist. For example, in a frequency hopping (FH)
`System, data bits are spread and transmitted using a pSuedo
`random hop Sequence. The hop Sequence involves Switching
`between different frequency channels in a given bandwidth.
`Only transmitters and receivers hopping on the same
`Sequence are capable of communication with one another.
`
`4
`Thus, multiple users can share the same bandwidths without
`Significant interference by Selecting different pseudo
`random hop Sequences with which to communicate. This is
`similar to DS systems where multiple users select different
`PN codes to avoid interference.
`FIG. 1A schematically illustrates a transmitter system or
`assembly 100 of a DSSS system. Original data bits 101 are
`input to the transmitter system 100. The transmitter system
`includes a modulator 102, a spreading function 104 and a
`transmit filter 106. The modulator 102 modulates the data
`onto a carrier using, for example, a binary phase shift keying
`(BPSK) modulation technique. The BPSK modulation tech
`nique involves transmitting the carrier in-phase with the
`oscillations of an oscillator or 180 degrees out-of-phase with
`the oscillator depending on whether the transmitted bit is a
`“0” or a “1”. The spreading function 104 converts the
`modulated original data bits 101 into a PN coded chip
`Sequence, also referred to as Spread data. The PN coded chip
`Sequence is transmitted via an antenna So as to represent a
`transmitted PN coded sequence as shown at 108.
`FIG. 1A also illustrates a receiver System or assembly,
`shown generally at 150. The receiver system 150 includes a
`receive filter 152, a despreading function 154, a bandpass
`filter 156 and a demodulator 158. The PN coded data 108 is
`received via an antenna and is filtered by the filter 152.
`Thereafter, the PN coded data is decoded by a PN code
`despreading function 154. The decoded data is then filtered
`and demodulated by the filter 156 and the demodulator 158
`respectively to reconstitute the original data bits 101. To
`receive the transmitted spread data, the receiver system 150
`must be tuned to the same predetermined carrier frequency
`and be set to demodulate a BPSK signal using the same
`predetermined PN code.
`More Specifically, to receive a SS transmission Signal, the
`receiver System must be tuned to the same frequency as the
`transmitter assembly to receive the data. Furthermore, the
`receiver assembly must use a demodulation technique which
`corresponds to the particular modulation technique used by
`the transmitter assembly (i.e. same PN code length, same
`chipping rate, BPSK). Because mobile terminals communi
`cate with a common base Station, each device in the cellular
`network must use the same carrier frequency and modula
`tion technique.
`An important aspect of any cellular communication Sys
`tem is the ability to optimize overall System performance.
`System performance may be optimized, for example, by
`communicating information at the fastest possible rates
`while minimizing packet errors, collisions and/or the need to
`re-transmit information among devices.
`A drawback associated with current cellular communica
`tion systems is that PN code parameters such as PN code
`length and chipping rate must be Selected to provide per
`formance based on average communication range and aver
`age noise conditions. The data rate/range tradeoff leads to a
`cell size/throughput tradeoff in the communication System.
`The rate that each transmission occurs will limit the size of
`each cell. Thus, it would be desirable to have a cellular
`communication System wherein PN code parameter, modu
`lation complexity and other transmitting and receiving
`parameters could be dynamically modified for each trans
`mission based on distance between the transmitter and
`receiver and noise conditions Such that an improved data
`transmission rate for that transmission could be achieved
`thereby enhancing System performance.
`A further drawback associated with cellular communica
`tion Systems is related to those Systems utilizing wireleSS
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`base Stations. More particularly, the cell area of a wireleSS
`base Station typically overlaps to a large extent the cell area
`asSociated with a base Station hardwired to the network.
`Mobile terminals which roam into the overlapping areas
`transmit signals which are received or “heard” by both the
`base Station and the wireleSS base Station. This can occur
`despite the fact that the mobile terminal will typically be
`registered to only one of the devices, namely the mobile
`terminal is registered to communicate with either the base
`Station or the wireleSS base Station. Since many Systems
`operate under a Collision Sense Multiple Access (CSMA)
`protocol, each base station (wireless and hardwired) and
`mobile terminal “listens' to the signal traffic in the air before
`transmitting information in order to avoid packet collisions.
`If the air is busy with signal traffic, the device performs a
`random back off in order to allow time for the air to clear.
`Unfortunately, in areas where there is overlapping cell
`coverage each transmission from a mobile terminal will
`cause the air signal traffic to be busy for both the wireless
`base Station and the base Station hardwired to the network.
`Thus, extra delays will occur due to the random backoff.
`Similarly, the mobile terminals will also experience addi
`tional delays due to their internal random backoff protocol
`when attempting to transmit information in areas of conten
`tion. Further, even in systems not implementing CSMA or
`other similar protocol, there will be many times where two
`devices transmit information simultaneously. When this
`happens, both packets collide and each device must retrans
`mit its packet, thereby also causing a loSS in overall System
`performance.
`Accordingly, it is also highly desirable to have a cellular
`communication System and method in which System perfor
`mance can be optimized by eliminating unnecessary delays
`and packet collisions caused by overlapping cell areas of
`base Stations and wireleSS base Stations.
`
`SUMMARY OF THE INVENTION
`The present invention includes an apparatus and a proceSS
`for enhancing the performance capabilities of a cellular
`communication System. The cellular communication System
`of the present invention includes a plurality of mobile
`terminals and a plurality of base Stations. The base Stations
`may be connected to a hardwired network backbone or Serve
`as wireleSS base Stations. Each base Station can transmit and
`receive data in its respective cell. For a given communica
`tion between a mobile terminal and a base Station, the
`mobile terminal and the base Station according to one feature
`of the invention can adjust the PN code length and the
`chipping rate depending on communication conditions to
`increase the transmission rate while retaining an acceptable
`error rate. Moreover, the System also provides that System
`components can adjust between other cellular communica
`tion System transmission parameterS Such as between dif
`ferent modulation Schemes and/or different transmitter
`power levels in conjunction with PN code adjustments to
`further enhance the performance capabilities of the System.
`According to another feature of the invention, dedicated
`repeater controller transceivers are coupled to the base
`Stations and wireleSS base Stations. The repeater controller
`transceivers are configured to typically operate on a different
`communication channel as compared to communications
`received by or transmitted directly from the mobile termi
`nals. For example, a wireleSS base Station may include two
`transceivers, one to be used for communicating directly with
`base stations hardwired to the backbone or other wireless
`base stations while the other transceiver handles all direct
`
`6
`communications with mobile terminals. This reduces or
`avoids the number of random backoffs and/or packet colli
`Sions which may occur in overlapping cell areas. By utiliz
`ing a dedicated channel for communications between the
`base Stations and wireleSS base Stations, the contention areas
`formed by overlapping cell areas is effectively eliminated.
`The different channels may be based on different parameters
`such as frequency and/or PN code parameters including PN
`code Sequences and PN code lengths.
`According to one particular aspect of the invention, a
`cellular communication System is provided including a base
`Station coupled to a System backbone; a mobile terminal for
`communicating with the System backbone by way of the
`base Station; and a wireleSS base Station Serving as an
`intermediary for communications between the mobile ter
`minal and the base Station; wherein the base Station includes
`a base Station transceiver for wirelessly communicating with
`the mobile terminal directly on a first communication
`channel, and a repeater controller transceiver for wirelessly
`communicating with the wireleSS base Station on a Second
`communication channel, the first communication channel
`being different from the Second communication channel.
`In accordance with another aspect, in a cellular commu
`nication System comprising a base Station coupled to a
`System backbone, a mobile terminal for communicating with
`the System backbone by way of the base Station, and a
`wireleSS base Station Serving as an intermediary for com
`munications between the mobile terminal and the base
`Station, a method of communication is provided including
`the Steps of the base Station wirelessly communicating with
`the mobile terminal directly on a first communication
`channel, and wirelessly communicating with the wireleSS
`base Station on a second communication channel, the first
`communication channel being different from the Second
`communication channel.
`According to yet another aspect, a base Station is provided
`for use in a cellular communication System having a System
`backbone, at least one mobile terminal and at least one
`wireleSS base Station. The base Station includes a commu
`nication circuit coupling the base Station to the System
`backbone; a base Station transceiver for wirelessly commu
`nicating with the at least one mobile terminal directly on a
`first communication channel, and a repeater controller trans
`ceiver for wirelessly communicating with the at least one
`wireleSS base Station on a Second communication channel,
`the first communication channel being different from the
`Second communication channel.
`According to yet another aspect, a wireleSS base Station is
`provided for use in a cellular communication System having
`a System backbone, at least one mobile terminal and at least
`one base Station coupled to the backbone. The wireleSS base
`Station includes a wireleSS base Station transceiver for wire
`lessly communicating with the mobile terminal on a first
`communication channel; and a wireleSS base Station repeater
`controller transceiver for wirelessly communicat