United States Patent [19]
`Sage et al.
`
`[54] FREQUENCY AGILE TRANSCEIVER WITH
`MULTIPLE FREQUENCY SYNTHESIZERS
`PER TRANSCEIVER
`
`[75]
`
`Inventors: Gerald F. Sage. Mountain View;
`Gurbux S. Msutta. San Jose. both of
`Calif.
`
`[73] Assignee: InterWAVE Communications
`International Ltd .. Hamilton. Bermuda
`
`[21] Appl. No.: 434,597
`
`[22] Filed:
`
`May 4, 1995
`
`[51]
`
`[52]
`
`[58]
`
`Int. Cl.6
`
`............................. H04K 1/04; H04L 27/26;
`H04B 1138
`U.S. Cl ........................... 375/202: 375/222; 375/376;
`340/825.74; 379/59; 370/330; 380/34; 455/422
`Field of Search ..................................... 375/202. 200.
`375/344.356.375.219. 376; 455/33.1.
`49.1. 33.4. 50.1. 51.1. 53.1. 54.1. 57.1.
`87. 422; 380/33.21.48. 49; 395/200.19;
`364/232.2. 232.9; 379/58. 59. 62; 340/825.14.
`825.2. 825.5. 825.73. 825.74; 370/297.
`330
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,144.409
`4,777,633
`4,785,450
`4,825,448
`5224,121
`5,263,047
`5,287,384
`5,303,234
`5,448,569
`5,483,557
`5,541,954
`
`3/1979 Utano et al ............................... 379/60
`10/1988 Fletcher .................................... 370150
`ll/1988 Bo1giano et al ....................... 374/95.1
`4/1989 Critchlow et al ....................... 3751222
`6/1993 Schonnan ................................... 375/1
`11/1993 Kotzin et al ............................ 375n02
`2/1994 Avery et al ............................. 375n02
`4/1994 Kou ........................................ 370/85.2
`9/1995 Huang et al ........................... 370/95.1
`111996 Webb ...................................... 375/349
`7/1996 Emi ......................................... 375no2
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US0057815 82A
`[111 Patent Number:
`[451 Date of Patent:
`
`5,781,582
`Jul. 14, 1998
`
`FOREIGN PATENT DOCUMENTS
`
`European Pat. Off ..
`European Pat. Off ..
`France.
`France.
`United Kingdom .
`WIPO.
`
`0182762A1
`5/1986
`0565127A2
`10/1993
`2612028
`9/1988
`2699769
`6/1994
`2169477
`7/1986
`wo 93no625
`10/1993
`Prii1Ulry Examiner-Wellington Chin
`Assistant Examiner-William Luther
`Attome}; Agent, or Firm-Flehr Hohbach Test Albritton &
`Herbert LLP
`[57]
`
`ABSTRACT
`
`A base station communicates with a plurality of mobile
`stations over a cellular network. In one embodiment. the
`base station includes a receiver having a receiver synthesizer
`input. where the receiver is configured to receive inbound
`information from the mobile station on a first predetermined
`frequency. The receiver further has two programmable fre(cid:173)
`quency sources that are configured to alternately supply a
`receiver synthesizer input signal to the receiver. The base
`station also includes a transmitter having a transmitter
`synthesizer input. where the transmitter is configured to
`transmit outbound information to the mobile station on a
`second predetermined frequency. The transmitter further has
`two programmable frequency sources that are configured to
`alternately supply a transmitter synthesizer input signal to
`the transmitter. A processor is connected to the receiver and
`the transmitter and is configured to decode the inbound
`information and to encode the outbound information to
`communicate with the mobile station. This two-way com(cid:173)
`munication continues by programming and then alternately
`selecting the receive synthesizers to receive on the correct
`frequency. and by programming and then alternately select(cid:173)
`ing the transmit synthesizers to transmit on the correct
`frequency. A preferred protocol is Global Systems for
`Mobile Communication (GSM).
`
`26 Claims, 10 Drawing Sheets
`
`10~
`
`20- ' '
`
`80
`~
`DSP 84
`
`CPU
`
`82
`
`- 40
`"
`I
`___ _l_ _______ l
`
`I
`
`TRANSMITIER
`PLL #1
`
`TRANSMITIER
`PLL #2
`
`Marvell Semiconductor, Inc.
`MediaTek Inc.
`MediaTek USA, Inc.
`Exh. 1007
`IPR of U.S. Pat. No. 7,477,624
`
`0001
`
`

`

`U.S. Patent
`US. Patent
`
`Jul. 14, 1998
`Jul. 14, 1998
`
`Sheet 1 of 10
`Sheet 1 of 10
`
`5,781,582
`5,781,582
`
`/ - -
`
`/
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`0
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`0002
`
`0002
`
`

`

`U.S. Patent
`
`Jul. 14, 1998
`
`Sheet 2 of 10
`
`5,781,582
`
`915
`
`935
`
`960
`
`890
`
`I MS IT f
`
`880
`
`900
`
`920
`
`940
`
`960
`
`980 MHz
`
`FIG. 2A
`
`#
`0
`
`1
`
`2
`
`3
`
`.
`.
`.
`
`MS TRANSMIT
`mO
`
`m1
`
`m2
`
`m3
`
`.
`.
`.
`
`MS RECEIVE
`m0+45MHz
`
`m1 +45MHz
`
`m2+45MHz
`
`m3+45MHz
`.
`.
`.
`
`N-1
`
`mN-1
`
`mN-1 +45MHz
`
`FIG. 28
`
`0003
`
`

`

`U.S. Patent
`
`Jul. 14, 1998
`
`Sheet 3 of 10
`
`5,781,582
`
`FN
`HSN
`t.AA
`
`MAIO
`N
`RFCHN
`
`FRAME NUMBER
`0 ... 63
`HOPPING SEQUENCE NUMBER -
`MOBILE ALLOCATION - SET OF N FREQUENCIES
`AVAILABLE FOR USE mO ... mN-1
`MOBILE ALLOCATION
`INDEX - OFFSET IN MA TABLE
`NUMBER OF FREQUENCIES JN MA
`~DO FREQUENCY CHANNEL NUMBER
`
`NBIN BITS 6 BITS
`
`7 Bl
`TS
`
`FN
`FN
`HSN
`FN
`MA
`MAIO
`(mO ... mN-1) (0 ... N-1) T3(0 ... 50) (0 ... 83) T1 (0 ... 2047) T2(0 ... 25)
`6 BITS + 11 BITS
`5 81 TS
`REPRESENT I
`~1
`T1 R =
`T1 MOD 64
`IN 7 BITS
`t6 BITS
`I EXCLUSIVE OR I
`..
`t 6 BITS
`I
`
`I
`
`ADDITION
`7 BITS
`I LOOK-UP TABLE J
`t 7 BITS
`ADDITION
`f 8 BITS
`M'=M MOD 2-NB!D
`
`T =
`
`NBIN BITS
`
`J
`
`I
`II
`T3 MOO 2-NBIN ~NBITS
`y •
`S=M' J
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`S=(M'+ T)MOD N
`NBIN BITS~~
`I MAI=(S+MAIO)MOD N I
`+ NBIN BITS
`I
`
`I
`
`RFCHN=MA(MAI)
`
`• WHERE NBIN=INTEGER[(LOG BASE 2 OF N)+ 1]
`
`RFCN
`
`MOD= MODULO
`-=RAISED TO THE POWER OF
`
`FIG. 2C
`
`0004
`
`

`

`U.S. Patent
`US. Patent
`
`Jul. 14, 1998
`Jul. 14, 1998
`
`Sheet 4 of 10
`Sheet 4 of 10
`
`5,781,582
`5,781,582
`
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`0005
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`
`

`

`FIG. 4
`
`20mS
`
`CODED SPEECH WORD
`
`-.-
`
`---------
`
`57 CODED DATA PLUS CODING BIT
`
`GB = GUARD BITS
`TB = TALL BITS
`
`TB GB
`3
`8.25
`
`CODED DATA
`
`57
`
`-------------,
`
`I ~~I
`
`1 CONTROL BIT
`
`SEQUENCE
`TRAINING
`
`26
`
`4.615 mS
`
`;
`
`;
`
`.... ""',.'
`
`,' .....
`
`'
`
`'
`
`CODED DATA
`
`57
`
`TIME SLOT TB
`3
`
`---
`
`TDMA FRAME
`
`MULTIFRAME
`
`\J1 •
`0 •
`
`TRAFFIC
`
`0006
`
`

`

`-=
`
` :-
`
`I
`52 '-r---------,
`I
`-,
`
`00000000000
`00000000000
`
`88888888888
`
`0 90
`
`'-------j TRANSMITIER
`
`PLL #2
`
`54
`
`.------1 TRANSMITIER
`
`PLL # 1
`
`_ __ _i ______ _
`
`-40
`
`/
`
`I
`
`82
`
`CPU
`
`DSP 84
`~
`80
`
`FIG. 5
`
`88
`
`34
`
`32
`
`PLL #2
`RECEIVER
`
`PLL #1
`RECEIVER
`
`I
`I
`I
`
`______ l_ __ _
`
`' \
`
`20-
`
`23
`
`10~
`
`0007
`
`

`

`U.S. Patent
`
`Jul. 14, 1998
`
`Sheet 7 of 10
`
`5,781,582
`
`FIG. 6
`
`102
`
`TURN OFF TRANSMITTER
`
`WAIT FOR TRANSMITTER
`
`INTERRUPT
`
`104
`
`106
`
`INITIALIZE
`GET HYPERFRAME NUMBER
`COMPUTE NEXT FREQUENCY
`CODE FREQUENCY FOR PLL
`SERIAL OUTPUT TO # 1 PLL'S
`SET SWITCHES TO #2
`
`108
`
`WAIT FOR TRANSMITTER
`
`INTERRUPT
`
`110
`
`112
`
`114
`
`TURN ON
`TRANSMITTER
`
`SET TRANSMITTER
`TOGGLE TRANSMIT SWITCH
`COMPUTE NEXT FREQUENCY
`CODE FREQUENCY FOR PLL'S
`SERIAL OUTPUT TO UNUSED
`TRANSMIT PLL
`
`WAIT FOR RECEVIER
`
`INTERRUPT
`
`116
`
`118
`
`SET RECEIVER
`TOGGLE RECEIVER SWITCH
`SERIAL OUTPUT TO UNUSED
`RECEIVE PLL
`
`120
`
`I
`
`l____ __ __ _______ __j
`
`0008
`
`

`

`U.S. Patent
`
`Jul. 14, 1998
`
`Sheet 8 of 10
`
`5,781,582
`
`40A
`
`TRANSMITIER
`CARD #1
`
`408
`
`TRANSMITIER
`CARD #K
`
`10
`
`~
`
`80
`
`PROCESSOR
`
`FIG. 7
`
`22
`
`20A
`
`r
`RECEIVER
`CARD #1
`
`208
`
`,-~
`
`20J
`
`RECEIVER
`CARD #J
`
`200 1.
`
`223
`
`220 ~-
`
`' '
`
`________ _j
`
`/-- 240
`
`252~-----,
`r--------1 TRANSMITIER
`PLL
`I
`244
`L ________ _
`
`280
`
`r
`
`CPU
`
`282
`
`.-----286
`
`RAM
`
`FIG. 8
`
`290
`
`,----------, D
`
`0009
`
`

`

`U.S. Patent
`
`Jul. 14, 1998
`
`Sheet 9 of 10
`
`5,781,582
`
`RECEIVE
`Rx,Tx DATA
`
`CHECK B.E.R.
`w.r.t. FREQUENCY
`
`304
`
`310
`
`CHANGE
`FREQUENCY
`HOP TABLE
`
`CONTINUE
`
`FIG. 9A
`
`322
`RECEIVE
`Rx DATA ~
`
`...) 320
`
`1ir
`
`324
`CHECK B.E.R. l/
`w.r.t. FREQUENCY
`
`11r
`
`326
`SEND B.E.R.l--'
`TO BS
`
`FIG. 9B
`
`0010
`
`

`

`U.S. Patent
`
`Jul. 14, 1998
`
`-,
`
`Sheet 10 of 10
`
`440
`f
`......._-I
`
`5,781,582
`
`-
`
`-
`
`-
`
`l
`
`RECEIVER
`#1
`
`480 t
`
`DSP
`
`CPU
`
`TRANSMITIER
`
`RECEIVER
`#2
`
`L
`
`r--.....
`1 430
`
`_
`
`~400
`
`FIG. 10
`
`452
`
`RECEIVE Tx
`FREQUENCY
`
`CHECK B.E.R. & NOISE
`w.r.t. FREQUENCY
`
`458
`
`CONTINUE
`
`CHANGE
`FREQUENCY
`HOP TABLE
`
`462
`
`FIG. II
`
`0011
`
`

`

`5,781,582
`
`1
`FREQUENCY AGILE TRANSCEIVER WITH
`MULTIPLE FREQUENCY SYNTHESIZERS
`PER TRANSCEIVER
`
`RELATED APPUCATIONS
`
`The present application incorporates the following patent
`applications by reference: U.S. Ser. No. 081435,709. filed on
`May 4. 1995: U.S. Ser. No. 081435.838. filed on May 4,
`1995; U.S. Ser. No. 08/434.554. filed on May 4. 1995; and
`U.S. Ser. No. 08/1434,598, filed on May 4. 1995.
`
`FIELD
`
`The present invention relates to a spread spectrum com(cid:173)
`munication network with adaptive frequency agility. In
`particular, the present invention is used in a cellular com(cid:173)
`munication network to improve the information channel
`capacity by adapting the spread spectrum frequencies to
`reduce interference and improve performance.
`
`BACKGROUND
`
`Spread spectrum communication typically includes two
`type of techniques: direct sequence spread spectrum
`(FHSS), where the information signal in-phase and
`quadrature-phase are varied; and frequency hopping spread
`spectrum (FliSS). where the information carrier frequency
`is varied. Moreover. these techniques can include formats
`for what is known as time division multiple access (fDMA)
`and frequency division multiple access (FDMA). These
`formats dedicate a specific periodic time slot or frequency to
`each mobile station. Advantages of DSSS. FliSS. TDMA
`and FDMA include reduced co-channel interference and
`improved information channel capacity over a given band(cid:173)
`width. While these techniques can-be employed
`independently. they can also be combined
`One limitation of existing communication networks is
`that the base station must have a multiplicity of dedicated
`transmitters and receivers to adequately process all the
`mobile station signals. Since each base station transmitter
`and receiver can communicate only one frequency. a large
`number of transmitters and receivers are required to serve
`the communication network employing multiple frequen(cid:173)
`cies. For example, eight transmitters and eight receivers are
`required to serve eight receive frequencies and eight trans(cid:173)
`mit frequencies.
`Moreover, since existing communication networks use a
`multiplicity of dedicated transmitters and receivers. a fault
`can cause data to be lost. or even cause the network to
`malfunction. When a transmitter or receiver is broken, the
`network must operate in a reduced capacity. if it can operate
`at all.
`Another limitation of existing communication networks is
`that the FliSS protocol sequence is predetermined That is,
`the frequency hops are periodic within the same frequency
`set. This results in continual interference from other oper(cid:173)
`ating electromagnetic fields. The existing communication
`protocols do not adapt to avoid interference.
`Another limitation of existing communication networks is
`that the processing is performed within a central signal 60
`processor. A central signal processor employs software to
`perform the procedures necessary to process the data. While
`this configuration provides high flexibility. it is also slow
`and requires high computational and memory overhead.
`Another limitation of existing communication networks is 65
`that in the communication protocol. the specific periodic
`TDMA time slot is fixed. Each mobile station is entitled to
`
`5
`
`2
`a single slot and may not receive an additional slot even if
`other mobile stations are not fully utilizing their respective
`information channel capacity.
`SUMMARY
`The present invention relates to a spread spectrum com(cid:173)
`munication network with adaptive frequency agility. In
`particular, the present invention is used in a cellular com(cid:173)
`munication network to improve the information channel
`capacity by adapting the spread spectrum frequencies to
`10 reduce interference and improve performance. Exemplary
`embodiments are provided for use with the Global Systems
`for Mobile Communication (GSM) protocol.
`A base station communicates with a plurality of mobile
`stations over a cellular network. In one embodiment. the
`15 base station includes a receiver having a receiver synthesizer
`input. where the receiver is configured to receive inbound
`information from the mobile station on a first predetermined
`frequency. The receiver further has two programmable fre(cid:173)
`quency sources that are configured to alternately supply a
`20 receiver synthesizer input signal to the receiver. The base
`station also includes a transmitter having a transmitter
`synthesizer input, where the transmitter is configured to
`transmit outbound information to the mobile station on a
`second predetermined frequency. The transmitter further has
`25 two programmable frequency sources that are configured to
`alternately supply a transmitter synthesizer input signal to
`the transmitter. A processor is connected to the receiver and
`the transmitter and is configured to decode the inbound
`information and to encode the outbound information to
`30 communicate with the mobile station. This two-way com(cid:173)
`munication continues by programming and then alternately
`selecting the receive synthesizers to receive on the correct
`frequency. and by programming and then alternately select(cid:173)
`ing the transmit synthesizers to transmit on the correct
`35 frequency.
`In another embodiment, the communication frequencies
`are modified to reduce interference. The processor maintains
`statistics on the communication error rates and modifies the
`frequency hopping table (also known as a mobile allocation
`40 table) to avoid error prone frequencies. This is an adaptive
`modification based on the communication error rates with
`respect to frequency. In a first aspect of the invention. the
`base station gathers error rate statistics. In a second aspect
`of this embodiment. both the base station and the mobile
`45 station gather error rate statistics since they-each transmit
`and receive in different frequency bands. In a third aspect of
`this embodiment. the base station has an additional receiver
`that receives on the mobile station receiver frequency band.
`The additional receiver scans the available mobile station
`so receive frequencies to identify those frequencies that contain
`interference and those frequencies that are clear. Then, the
`base station processor modifies the frequency hopping table
`to avoid error prone frequencies.
`The advantages of the present invention include reduced
`55 interference. improved communication bandwidth. fault
`tolerance. and more efficient and cost-effective base stations
`and mobile stations.
`BRIEF DESCRIPTION OF THE DRAWINGS
`Additional advantages of the invention will become
`apparent upon reading the following detailed description and
`upon reference to the drawings, in which:
`FIG. 1 depicts a cellular network showing several base
`stations and several mobile stations;
`FIGS. 2A-C illustrate the frequency bands allocated to
`GSM communication. a typical frequency hopping table.
`and the GSM frequency hopping algorithm;
`
`0012
`
`

`

`5.781.582
`
`3
`FIG. 3 illustrates a speech waveform sampled and
`assembled into a digital GSM format;
`FIG. 4 illustrates a GSM frame and associated data;
`FIG. 5 depicts one embodiment of a base station archi(cid:173)
`tecture according to the invention;
`FIG. 6 is a flow-chart showing steps performed by the
`base station of FIG. 5 for controlling frequency;
`FIG. 7 depicts another embodiment of a base station
`architecture according to the invention;
`FIG. 8 depicts one embodiment of a mobile station 10
`according to the invention;
`FIGS. 9A-B are flow charts showing steps performed by
`the base station of FIG. 5 and tht~ mobile station of FIG. 8
`to gather and store statistics regarding communication error 15
`rates;
`FIG. 10 depicts another embodiment of a base station
`according to the invention, where the base station includes
`an additional receiver to scan the mobile station receive
`frequency band; and
`FIG. 11 is a flow chart showing steps performed by the
`base station of FIG. 10 to gather and store statistics regard(cid:173)
`ing communication error rates.
`DEfAll-ED DESCRIPTION
`The present invention relates to a spread spectrum com(cid:173)
`munication network with adaptive frequency agility. In
`particular. the present invention is used in a cellular com(cid:173)
`munication network to improve the information channel
`capacity by adapting the spread spectrum frequencies to
`improve performance and reduce interference. Exemplary
`embodiments are provided for us·~ with the Global Systems
`for Mobile Communication (GSM) communication proto(cid:173)
`col.
`The exemplary embodiments are described herein with
`reference to specific configurations and protocols. Those
`skilled in the art will appreciate that various changes and
`modifications can be made to tht: exemplary embodiments
`while remaining within the scope of the present inventions
`A first embodiment is described with reference to FIGS.
`1 through 6. FIG. 1 is a relatively general illustration of a
`cellular communication network. A number of base stations
`(BS) 10 are positioned to serve a number of geographically
`distinct cells. for example cell A and cell B. Each base
`station 10 is responsible for serving all the mobile stations
`(MS) 200 within its respective c:ell boundary. To perform
`this task. each base station 10 downloads a frequency
`hopping table (also known as a mobile allocation table) to
`each mobile station 200 so that the communication between
`base station 10 and mobile station 200 is on predefined
`frequencies. as explained more fully below.
`A base station controller (BSC) 12 is connected to every
`base station 10. typically via land line 92. and controls the
`communication between users. such as between mobile
`station users or existing infrastructure telephone users.
`Moveover. base station controller 12 controls the hand-off
`from one base station 10 to another base station 10 as a
`mobile station 2M moves among cells.
`A protocol selected for the embodiments is the Global
`Systems for Mobile Communication (GSM) protocol. The
`GSM protocol is lengthy and complicated. Therefore. the
`salient features are discussed with respect to the embodi(cid:173)
`ments. For additional information on the subject. the reader
`is referred to the GSM specification. One important GSM
`protocol requirement is frequency hopping spread spectrum
`(FHSS). That is. sequentially communicating over more
`than one frequency.
`
`4
`FIG. 2A shows the allocated frequency spectrum for GSM
`communication (from the mobile station standpoint). As can
`be seen. the mobile station transmit frequency band (T ) is
`disjoint from the mobile station receive frequency band (R,).
`5 Each of these frequency bands occupies approximately 15
`MHz. Within that 25 MHz. there are 124 200 KHz frequency
`steps on which the communication frequencies are permitted
`to hop. The specific hopping sequence is a function of the
`GSM hopping algorithm defined by the GSM specification
`and a given frequency hopping table that is downloaded
`from base station 10 to mobile station 200. An example
`frequency hopping table is presented in FIG. 2B. Based on
`the GSM hopping algorithm (FIG. 2C). the mobile station
`receiver and transmitter operate on specified 200KHz fre(cid:173)
`quencies in their respective frequency bands TJ' ~ Of
`course. the base station Tf and ~correspond to the mobile
`station ~and T f respectively.
`Since GSM is a digital data communication network. FIG.
`3 shows how a speech waveform is sampled and digitally
`encoded. FIG. 4 shows how the encoded data is formatted
`20 into the GSM word. Note that the information from one
`mobile station 200 is processed and placed into a specific
`time slot reserved for that particular mobile station 200
`within a TDMA frame. Further, note that after the TDMA
`frame is collected. a multiframe is constructed from 26
`25 TDMA frames. including 24 TDMA speech frames and 2
`control frames. Beyond the multiframe are superframes and
`hyperframes. There are 51 multiframes in a superframe. and
`there are 2048 superframes in a hyperframe. The hyperframe
`number is one variable used by the GSM frequency hopping
`30 algorithm to define the frequency hopping sequence.
`Based on the GSM frequency hopping algorithm (FIG.
`2C). the TDMA frames are then frequency hopped over the
`frequencies of the frequency hopping table. The mobile
`station receivers are also periodically hopped onto a fixed
`35 monitor frequency that is unique to each base station. The
`frequency hopping serves to spread the communication
`signal over the frequency bands TJ' R_r An advantage of
`spread spectrum is reduced interference effects from other
`electro-magnetic sources and other base station/mobile sta-
`40 tion communications. For the mobile station. three frequen(cid:173)
`cies are tuned onto in one 4.615ms TDMA time frame
`(transmit .. receive. monitor). Each mobile station transmitter
`and receiver synthesizer has 1 or 2 time slots (4.615 ms
`times ''"or ¥s. i.e .. 0.58 ms or 1.15 ms) to change frequen-
`45 des. Frequency hopping once per frame is easily accom(cid:173)
`plished because the synthesizers have plenty of time ( 1 or 2
`time slots) to settle before a new reception or transmission
`is required. However. the base station receiver and trans(cid:173)
`mitter have only 30 JlS to change frequencies (the time
`50 duration of the guard bits). This short time period is difficult
`to accommodate. so the invention incmporates a plurality of
`receiver synthesizers and transmitter synthesizers as now
`explained.
`FIG. 5 depicts a base station 10 having a receiver 20. a
`55 transmitter 40 and a processor 80. As shown. receiver 20 and
`transmitter 40 share common antenna 21 via diplexer 23.
`This configuration is possible since the receive frequency
`and transmit frequency are different (see FIG. 2A). Diplexer
`23 is used to permit the receive frequency to pass from
`6(1 antenna 21 to receiver 20. and to permit the transmit
`frequency to pass from transmitter 40 to antenna 21.
`Receiver 20 and transmitter 40 each employ two indepen(cid:173)
`dent synthesizers in order to facilitate fast frequency agility.
`The detail of the embodiment and the operation is explained
`65 with reference to the FIG. 6 flow chart.
`The reset step 102 is performed only at start-up. such as
`when base station 10 initially comes on-line or when recov-
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`5.781.582
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`5
`ering from a power failure. Step 104 is turns off transmitter
`40 to prevent invalid transmission before initialization of the
`base station 10. Thereafter. step 106 waits for the processor
`80 to perform its self-test and other required procedures
`before base station 10 can become operational in the cellular
`network. Step 108 calculates the required first frequency and
`the subsequent second frequency from the GSM hyperframe
`number and the frequency hopping table. Once these first
`and second frequencies are calculated. the first and second
`receiver synthesizers 32. 34. and transmitter synthesizers 52.
`54 are programmed to generate the required frequencies. At
`this point. the switches 36. 56 are set to provide the mixers
`24. 44 with the frequencies from the first synthesizers 32. 52
`respectively.
`A loop sequence begins with step 110. where processor 80
`waits for the transmitter interrupt from the CPU 82 to
`indicate that the TDMA frame should be processed. If the
`step 112 is being queried for the first time (i.e .. transmitter
`40 was turned off in step 104). step 114 is performed to turn
`transmitter 40 on. Once transmitter 40 is on. step 116
`proceeds to transmit a TDMA frame and then to toggle the
`transmitter synthesizer selector switch 56 to the other trans(cid:173)
`mitter synthesizer 54. Step 116 also calculates the next
`transmitter frequency and programs the previously active
`synthesizer 52 to generate that frequency.
`When the receiver interrupt occurs in step 118. step 120
`proceeds to receive a TDMA frame and then to toggle the
`receiver synthesizer selector switch 36 to the other receiver
`synthesizer 34. Step 120 also calculates the next receiver
`frequency and programs the previously active synthesizer 32 30
`to generate that frequency.
`Steps 110 through 120 are then repeatedly performed to
`transmit and receive the TDMA frames to and from the
`mobile stations 200 on the proper frequencies. This con(cid:173)
`figuration of the dual synthesizer receiver 20 and dual
`synthesizer transmitter 40 permits base station 10 to faith(cid:173)
`fully accomplish all the frequency hops required for proper
`communication.
`It is important to note that base station 10 of FlG. 5
`employs processor 80 to orchestrate the synthesizers 32. 34.
`52. 54 and the synthesizer switches 36. 56. Processor 80
`includes a central processing unit (CPU) 82 for performing
`many of the general procedures required to communicate
`over the network with mobile station 200; Processor 80 also
`performs procedures necessary to communicate with base
`station controller 12. A digital signal processor (DSP) 84 is
`included in processor 80 to perform many of the application
`specific and computationally intensive procedures such as
`encoding and decoding the TDMA frame data. As shown.
`the processor 80 also includes memory (RAM) 86 and bulk
`disk memory 88. Moreover. user interface 90 is provided to
`receive instructions from a user and to display requested
`information. Ground line !)2 is also provided to connect to
`base station controller 12 and other base stations 10 as
`required by the GSM specification.
`In actual implementation, it is useful to employ a plurality
`of receivers in order to perform both TDMA and FDMA. as
`provided by the GSM specification. In a conventional
`configuration, each receiver is tuned to a fixed frequency and
`frequency-hopped information from the mobile stations is
`received by various receivers depending on the specified
`communication frequency. Then the conventional processor
`must re-assemble inbound information from a plurality of
`receivers to obtain data from one mobile station. Moreover.
`the conventional processor must dis-assemble outbound
`information and deliver it to a plurality of transmitters to
`properly transmit information to a mobile station.
`
`6
`FIG. 7 depicts another embodiment of a base station 10
`according to the invention. There are provided a plurality of
`receivers 20A-J that are frequency agile (as shown in FIG.
`5). Hence. receivers 20A-J can be programmed to receive
`5 various frequencies over time and can receive information
`from each mobile station 200 on a respective one of receiv(cid:173)
`ers 20A-J. This feature permits both FDMA received signals
`and TDMA received signals associated with one mobile
`station 200 to be received by one of the receivers 20A-J.
`10 Because processor 80 programs the receiver synthesizers.
`processor 80 has a priori knowledge of which receiver
`20A-J is receiving communication signals from which
`mobile station 200. This information permits the processor
`to more efficiently process the inbound data. For example. if
`15 the signal from one mobile station 200 is always received in
`receiver card one 20A. then the processor can reduce its
`control logic (hardware. software. or both) to avoid the
`conventional step of re-assembling a mobile station's data
`from a number of different receivers. Also. configuring a
`20 plurality of frequency agile receivers 20A-J in parallel
`permits processor 80 to reconfigure receivers 20A-J at any
`time a fault is detected. If. for example, processor 80 detects
`a fault in receiver 20A (e.g .. by self-test. null data. or
`corrupted data). processor 80 re-programs another receiver.
`25 such as receiver 20J. to operate on the parameters that were
`previously assigned to receiver 20A. The feature of agile
`receivers and enhanced processing resource allocation
`reduces overhead. permits fault tolerance. and increases
`throughput since it eliminates a processing step.
`There are also provided a plurality of transmitters 40A-K
`that are frequency agile (as in FIG. 5). Hence. transmitters
`40A-K can be programmed to transmit various frequencies
`over time and can transmit information to each mobile
`station 200 on a respective one of transmitters 40A-K. This
`35 feature permits both FDMA transmitted signals and TDMA
`transmitted signals associated with one mobile station 200 to
`be transmitted by one of the transmitters 40A-K. Because
`processor 80 programs the transmitter synthesizers. proces(cid:173)
`sor 80 has a priori knowledge of which transmitter 40A-J is
`40 transmitting communication signals to which mobile station
`200. This information permits the processor to more effi(cid:173)
`ciently process the outbound data. For example. if the signal
`to one mobile station 200 is always transmitted by trans(cid:173)
`mitter one 40A. then the. processor 80 can reduce its control
`45 logic (hardware. software, or both) to avoid the conventional
`step of disassembling a mobile station's data and delivering
`it to a number of different transmitters. Also. configuring a
`plurality of frequency agile transmitters 40A-K in parallel
`permits processor 80 to reconfigure transmitters 40A-K at
`so any time a fault is detected. If. for example. processor 80
`detects a fault in transmitter 40A (e.g .. by self-test. null data
`received by the mobile station. or corrupted data), processor
`80 re-programs another transmitter, such as transmitter 40K.
`to operate on the parameters that were previously assigned
`55 to transmitter 40A. The feature of agile transmitters and
`enhanced processing resource allocation reduces overhead,
`permits fault tolerance, and increases throughput since it
`eliminates a processing step.
`As shown. receivers 20A-J and transmitters 40A-K are
`60 coupled to receive antenna 22 and transmit antenna 42
`respectively. However. a common antenna 21 can be
`employed as shown in FIG. 5. Also as shown. transmitters
`40A-K are coupled to single transmit antenna 42. However.
`if transmitters 40A-K are sensitive to back propagation of
`65 each. other's transmissions, a plurality of transmit antennas
`(42A-K) can be employed with each transmitter having its
`own transmit antenna. Moreover. corresponding receivers
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`and transmitters, e.g. 20A and 40A, 20B and 40B, 20C and
`40C. can be grouped and combined to have common anten(cid:173)
`nas 21A. 21B and 21C respectively, as shown in FIG. 5.
`Additional base station embodiments are described in
`U.S. Ser. No. 08/1434,598, filed on May 4. 1995.
`A mobile station 200 is depicted in FIG. 8. Mobile station
`200 is similar to base station 10. but requires less hardware
`since the purpose is to serve only one user. A receiver 220
`is provided connected to a common antenna 222 via diplexer
`223. Processor 280 reads the stored frequency hopping table
`and calculates the proper receive frequency for the inbound
`TDMA frame. Processor 280 then programs receiver syn(cid:173)
`thesizer 232 to generate that frequency. Receiver synthesizer
`232 provides the frequency to the receiver mixer 224. which
`down-mixes the received signal and provides an information
`signal to processor 280. Processor 280 then decodes the
`received TDMA frame. Processor 280 includes a CPU, 282.
`DSP 284. RAM 286 and user interface 290 (e.g. keypad and
`LCD display). much like base station 10. A transmitter 240
`is provided connected to the common antenna 222 via
`diplexer 223. The CPU reads the frequency hopping table
`and calculates the proper transmit frequency for the out(cid:173)
`bound TDMA frame. Processor 280 then programs the
`transmitter synthesizer 252 to generate that frequency. Pro(cid:173)
`cessor 280 encodes the transmit TDMA fram