United States Patent [19J
`Gendel et al.
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006115407 A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,115,407
`Sep.5,2000
`
`[54] FREQUENCY HOPPING COMMUNICATION
`METHOD AND APPARATUS FOR
`MODIFYING FREQUENCY HOPPING
`SEQUENCE IN ACCORDANCE WITH
`COUNTED ERRORS
`
`[75]
`
`Inventors: Alon Gendel, Raanana; Yossi
`Waisblum, Kfar Saba, both of Israel
`
`[73] Assignee: Butterfly VSLI Ltd., Kfar Saba, Israel
`
`[21] Appl. No.: 09/054,875
`
`[22] Filed:
`
`Apr. 3, 1998
`
`[51]
`
`Int. Cl? ........................... H04L 27/30; H04B 15/00;
`H04K 1!00; H04J 1/00
`[52] U.S. Cl. .......................... 375/132; 375/131; 375/133;
`375/134; 375/135; 375/136; 375/137; 370/343;
`370/344; 370/480
`[58] Field of Search ..................................... 375/132, 136,
`375/131, 133, 134, 135, 137; 370/344,
`343, 480
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,394,433
`5,528,623
`5,737,359
`5,757,789
`5,758,290
`5,870,391
`5,937,002
`
`............................ 375/132
`2/1995 Bantz et a!.
`. .............................. 375/133
`6/1996 Foster, Jr.
`4/1998 Koivu ...................................... 375/133
`5/1998 Dent ........................................ 370/337
`5/1998 Nealon et a!. .......................... 455/464
`2/1999 Nago ....................................... 370/330
`8/1999 Andersson et a!. ..................... 375/131
`
`5,987,032 11/1999 Nadgauda et a!. ...................... 370/437
`
`Primary Examiner-Stephen Chin
`Assistant Examiner-Michael W. Maddox
`Attorney, Agent, or Firm---Ohlandt, Greeley, Ruggiero &
`Perle, L.L.P.
`
`[57]
`
`ABSTRACT
`
`The present invention is an apparatus and method thereof for
`performing frequency hopping (FH) communication with
`another party over an available spectrum of frequencies. The
`spectrum is arranged into a plurality of segments, with each
`segment corresponding to a subset of the frequencies, pref(cid:173)
`erably a contiguous subset of the frequencies. The FH
`communication apparatus includes a communication device
`for communicating with another party. The communication
`device receives data over a sequence of hopping frequencies
`from the other party, with each of the hopping frequencies
`being part of a used segment from the plurality of segments.
`A storage device stores an error value for each used segment.
`A processing unit identifies a reception error in the received
`data and an erred segment in which the reception error
`occurred. The processing unit modifies the error value
`associated with the erred segment accordingly. The process(cid:173)
`ing unit replaces the erred segment with an unused segment
`from the plurality of segments to attempt communication
`over a less error prone segment, when the error value for the
`erred segment has reached at least a predetermined thresh(cid:173)
`old. The processing unit notifies the other party of the
`unused segment, which has been newly selected, via the
`communication device.
`
`16 Claims, 11 Drawing Sheets
`
`601
`
`INITIAL STATE
`
`600
`
`606
`
`NO
`
`611
`
`MOlliFY ERR(S)=ERR(S)+INCREMENT
`
`(AS LONG AS
`ERR(S)<=lliRESHOLDtiNCREMENT)
`
`YES
`
`0001
`
`Marvell Semiconductor, Inc.
`MediaTek Inc.
`MediaTek USA, Inc.
`Exh. 1005
`IPR of U.S. Pat. No. 7,477,624
`
`

`
`U.S. Patent
`
`Sep.5,2000
`
`Sheet 1 of 11
`
`6,115,407
`
`102
`
`SEGMENT
`HANDUNG AND
`REPLACEMENT
`SUBSYSTEM
`
`SEGMENT
`HANDUNG AND
`REPLACEMENT
`SUBSYSTEM
`MAIN TRANSCEIVER
`IN THE FREQUENCY
`HOPPING
`COMMUNICA ]QN
`SYSTEM
`
`SEGMENT
`MANAGEMENT
`SUBSYSTEM
`(SEGMENT
`SUBSTITU]ON
`MECHANISM NOT
`IMPLEMENTED)
`
`122
`
`124
`
`126
`
`132
`
`134
`
`TRANSCEIVER
`EMPLOYING
`FREQUENCY HOPPING
`AND EMPLOYING
`THE SAID METHOD
`
`TRANSCEIVER
`EMPLOYING
`FREQUENCY HOPPING
`AND EMPLOYING
`THE SAID METHOD
`
`TRANSCEIVER
`EMPLOYING
`FREQUENCY HOPPING
`BUT NOT EMPLOYING
`THE SAID METHOD
`
`SEGMENT
`HANDUNG AND
`REPLACEMENT
`SUBSYSTEM
`
`SEGMENT
`HANDUNG AND
`REPLACEMENT
`SUBSYSTEM
`
`SEGMENT
`MANAGEMENT
`SUBSYSTEM
`(SEGMENT
`SUBS]TU]QN
`MECHANISM NOT
`IMPLEMENTED)
`
`136
`
`104
`
`106
`
`108
`
`FIG. 1
`
`0002
`
`

`
`""-=
`
`......::.
`
`....
`til
`~
`~
`....
`="
`
`'"""'
`'"""'
`0 ......,
`N
`~ .....
`'JJ. =-~
`
`N c c c
`~ '?
`'JJ.
`
`Ul
`
`~
`
`~ = ......
`~ ......
`~
`•
`rJJ.
`•
`Cj
`
`J
`
`FIG. 28
`
`l
`
`J
`
`FIG. 2A
`
`I
`
`c· FREQUENCY
`
`252
`
`FREQUENCY SEGMENTS NOT IN USE
`
`l SEG~ENT l
`
`=f76
`fmaJ
`
`-FREQUENCY
`
`SAMPLE USE OF SEGMENTS IN A GIVEN POINT IN TlME:
`
`:!~1~!~!::!~1~1
`
`FREQUENCIESf14 lllROUGHf20
`
`204
`
`SEGMENT 2:
`
`=fO
`fmin I
`
`202
`
`SPECTRUM
`AVAILABLE ---200
`
`SAMPLE DIVISION OF THE SPECTRUM TO SEGMENTS:
`
`0003
`
`

`
`""-=
`
`......::.
`
`....
`Ul
`~
`~
`....
`0\
`
`'"""'
`'"""'
`0 ......,
`~
`
`~ .....
`'JJ. =(cid:173)~
`
`N c c c
`~Ul
`~ '?
`'JJ.
`
`~ = ......
`~ ......
`~
`•
`\Jl
`d •
`
`FIG. J
`
`CIRCUIT
`DECODING
`
`312
`
`h---1 SYNCHRONOUS
`
`CIRCUIT
`
`309
`
`310
`
`CIRCUIT
`RECEIVE
`
`311
`
`RECEIVE DATA
`TRANSMIT DATA
`
`CONTROL UNIT
`COMMUNICATION
`
`DATA
`
`CONTROL UNIT
`SPREADING CODE
`
`SYN1HESIZER
`FREQUENCY
`
`314
`
`317
`
`308
`
`~ MO&~~~~NG H g~~~~8 1--l .. ---..
`
`CIRCUIT
`TRANSMIT
`
`~~ DUPLEXER
`
`301
`
`302
`
`/300
`
`305
`
`306
`
`0004
`
`

`
`U.S. Patent
`
`Sep.5,2000
`
`Sheet 4 of 11
`
`6,115,407
`
`502
`
`ERROR
`OCCURRENCE
`PATIIRN
`IDEN]RCAnGN
`MECHANISM
`
`518
`
`"NO ERROR FOR THIS
`SEGMENT SINCE LAST 1----1
`FULL CYCLE UPDATE"
`INDICATION
`
`520
`508
`
`ONE FULL "CYCLE" OF
`FREQUENCIES
`INDICATION
`
`INDICA ]ON OF
`ERROR
`OCCURRENCE
`IN CURRENT
`SEGMENT
`
`510
`
`FIG. 4
`
`514
`
`532
`
`534
`
`COMPARATOR
`
`0005
`
`

`
`U.S. Patent
`
`Sep.5,2000
`
`Sheet 5 of 11
`
`6,115,407
`
`INITIAL STATE
`
`INITIAUZE SEGMENT ERROR
`COU(N)TERS:
`ERRS = 0
`(FOR S=O .. N-1)
`
`INITIAUZA TION: ~X
`PARAMElERS:
`INCREMENT,
`DECREMENT, PENALTY,
`1HRESHOLD
`
`606
`
`YES
`
`PREVlOUS RECEPTION
`HAD AN ERROR
`AS 't'IELL?
`
`NO
`
`NO
`
`608
`
`NO
`
`ANY
`SEGMENT MARKED
`FOR REPLACEMENT, AND
`NO PREVlOUS REPLACEMENT
`PROCESS IN
`PROGRESS?
`
`610
`
`612
`
`MODIFY ERR(S)=ERR(S)+PENALTY
`
`MODIFY ERR(S)=ERR(S)+INCREMENT
`
`(AS LONG AS
`ERR(S)<= 1HRESHOLD+INCREMENT)
`
`(AS LONG AS
`ERR(S)<= 1HRESHOLD+INCREMENT)
`
`620
`
`YES
`
`618
`
`NO
`
`ALL FREQUENCIES
`IN ALL SEGMENTS VlSITED AT > - - - - - - - - - - - - - - - '
`LEAST ONCE?
`("ONE CYCLE")
`
`YES
`
`622
`
`FOR EACH SEGMENT S 1HAT HAD
`NO RECEPTION ERRORS, MODIFY
`ERR(S) = ERR(S)-DECREMENT
`(AS LONG AS ERR(S)>=O}
`
`FIG. 5
`
`0006
`
`

`
`U.S. Patent
`
`Sep.5,2000
`
`Sheet 6 of 11
`
`6,115,407
`
`INITIAL STATE
`
`LOCATE CANDIDATE
`SEGMENT
`FOR REPLACEMENT
`FOUND
`
`652
`
`RECEIVED REQUEST
`FROM OTHER
`TRANSCEIVER?
`
`SEND DEFECTIVE SEGMENT
`654
`INDEX ''X" AND INDEX ny"
`OF THE UNUSED SEGMENT TO 1 - - - - - - - - ,
`REPLACE IT Vv1TH
`TO THE OTHER TRANSCEIVER
`
`656
`
`RECEIVED CORRECT
`"ACKNOWLEDGE" FROM
`OTHER TRANSCEIVER?
`(SHOULD BE "X")
`
`YES
`
`662
`
`UPDATE LOCAL
`SEGMENT TABLE:
`SEGMENT nX" IS
`CHANGED TO "y"
`
`FIG. 6
`
`RECEIVED REQUEST
`FROM OTHER
`TRANSCEIVER?
`
`YES
`
`660
`
`SEND SEGMENT
`INDEX nX" TO OTHER
`TRANSCEIVER AS
`"ACKNOWLEDGE"
`
`TERMINATED
`
`0007
`
`

`
`""-=
`
`......::.
`
`....
`Ul
`~
`~
`....
`0\
`
`'"""'
`'"""'
`;
`
`252
`
`FREQUENCY !
`
`'JJ.
`
`[
`
`SEGMENT SEGMENT SEGMENT
`
`10
`
`9
`
`8
`
`FIG. 7
`
`FREQUENCY SEGMENTS NOT IN USE
`
`SEGMENT SEGMENT
`
`4
`
`3
`
`I SEG~ENT I
`
`N c c c
`~Ul
`~ '?
`'JJ.
`
`~ = ......
`~ ......
`~
`•
`\Jl
`d •
`
`-TRANSMISSION POWER LEVEL
`
`1
`
`0
`
`1
`
`3
`
`3
`
`0008
`
`

`
`""-=
`
`......::.
`
`....
`Ul
`~
`~
`....
`0\
`
`'"""'
`'"""'
`0 ......,
`00
`~ .....
`'JJ. =-~
`
`N c c c
`~Ul
`~ '?
`'JJ.
`
`~ = ......
`~ ......
`~
`•
`\Jl
`d •
`
`',_ 717
`
`I
`:
`
`I
`I
`1
`1--
`I
`I
`I
`1
`
`I
`
`I
`(724
`
`MECHANISM
`
`RESET
`
`720
`
`722
`
`VALUE
`SMALLER I
`
`L _____ L_J ______ j
`I
`I
`1 VALID RECEPTION RSSI
`I
`I
`I
`I
`l
`1 ERRED RECEPTION RSSI
`i-----.-r-------l : :
`--------, I
`718 --------,
`•
`• •
`
`RffiSTER
`
`REGISTER
`
`VALUE
`LARGER
`
`716
`
`FIG. 8
`
`L _____________ J
`I
`I
`I
`I
`I
`I
`I
`I
`I
`
`ERRED RECEPTION
`
`RECEIVER
`DIGITAL I INDICATION
`
`708
`
`[
`I
`
`I
`I
`--l
`
`[
`I
`
`CONVERTER
`ANALOG TO
`
`DIGITAL
`
`INDICATION
`
`RSSI
`
`CIRCUIT
`RECEIVER
`
`306
`
`I
`I
`I
`I __ J.. _______ _
`709-\
`
`I
`\
`
`706
`
`311
`
`700\
`
`0009
`
`

`
`U.S. Patent
`
`Sep.5,2000
`
`Sheet 9 of 11
`
`6,115,407
`
`INITIAL STATE
`
`768
`
`RESET REGISTERS FOR VALID
`.---------1 RECEP]ON AND ERRED
`RECEP]ON
`
`REGIVE PACKET OF DATA IN
`FREQUENCY f, PART OF
`SEGMENTS
`
`752
`
`OBTAIN RECEIVED SIGNAL
`STRENGTH INDICA]ON tRSSI)
`FOR LAST RECEP]ON
`
`766
`
`YES
`
`WAS A REQUEST
`FOR TRANSMISSION PO'M:R
`LEVEL CHANGE
`GENERATED?
`
`762
`
`UPDATE:
`VALID RECEP]QN REGISTER ~---~
`OF SLICE S
`\'11TH RSSI VALUE
`
`758
`
`YES
`
`UPDATE:
`ERRED RECEP]ON REGISTER 1 - - - - - - - - - - - - - - - - - - - '
`OF SLICE S
`\'11TH RSSI VALUE
`
`FIG. 9
`
`0010
`
`

`
`U.S. Patent
`
`Sep.5,2000
`
`Sheet 10 of 11
`
`6,115,407
`
`758~
`
`INITIAL STATE
`
`LOCATE NEED FOR POWER NOT FOUND
`LEVEL CHANGE REQUEST
`
`SEND REQUEST FOR
`TRANSMISSION POWER LEVEL
`CHANGE: SEGMENT "X"
`TRANSMISSIONS SHOULD USE
`POWER LEVEL "p"
`
`784
`
`782
`
`YES
`
`CHANGE LOCAL
`TRANSMISSION POWER
`FOR SEGMENT "X" TO
`BE LEVEL "p"
`
`786
`
`788
`
`800~
`
`FIG. 10
`
`MIN. RSSI
`OF GOOD
`RECEPTIONS -40dBm-
`-50dBm
`
`-50dBm-
`-60dBm
`
`-60dBm-
`-70dBm
`
`-80dBm-
`-70dBm-
`-80dBm AND LESS
`
`MAX. RSSI
`OF ERRED RECEPTI
`
`0 ERRED RECEPTIONS
`
`-40dBm - -50dBm
`
`-50dBm - -60dBm
`
`-60dBm - - 70dBm
`
`-70dBm - -80dBm
`
`-80dBm AND LESS
`
`1
`
`1
`
`2
`
`3
`
`2
`
`1
`
`0
`
`1
`
`1
`
`1
`
`0
`
`0
`
`1
`
`2
`
`1
`
`1
`
`0
`0
`FIG. 11
`
`2
`
`2
`
`3
`
`3
`
`3
`
`2
`
`3
`
`3
`
`3
`
`3
`
`3
`
`3
`
`0011
`
`

`
`""-=
`
`......::.
`
`....
`Ul
`~
`~
`....
`0\
`
`'"""'
`'"""'
`'"""' 0 ......,
`'"""'
`~ .....
`'JJ. =(cid:173)~
`
`N c c c
`
`~Ul
`'?
`~
`'JJ.
`
`~ = ......
`~ ......
`~
`•
`\Jl
`d •
`
`13
`
`(PRIOR ART)
`
`FIG. 12
`
`RECEIVE DATA
`
`CIRCUIT
`DECODING
`
`DEMODULA 11NG
`
`CIRCUIT
`
`12
`
`CIRCUIT r-----
`
`h--1 SYNCHRONOUS
`
`9
`
`10
`
`CIRCUIT
`RECEIVE
`
`11
`
`GENERA 11NG CIRCUIT
`
`FREQUENCY H SPREADING CODE
`
`SYNTHESIZER
`
`7
`
`8
`
`TRANSMIT DATA
`
`CIRCUIT
`
`l---1 MODULATING H CODING
`
`CIRCUIT
`
`2
`
`CIRCUIT
`TRANSMIT
`
`~---4 DUPLEXER
`
`4
`
`5
`
`6
`
`0012
`
`

`
`6,115,407
`
`1
`FREQUENCY HOPPING COMMUNICATION
`METHOD AND APPARATUS FOR
`MODIFYING FREQUENCY HOPPING
`SEQUENCE IN ACCORDANCE WITH
`COUNTED ERRORS
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is related to application Ser. No. 09/054,
`877, entitled "AUTOMATIC TRANSMISSION POWER
`LEVEL CONTROL METHOD IN A FREQUENCY HOP(cid:173)
`PING COMMUNICATION SYSTEM," filed same date
`herewith, by Alan Gendel et al.
`
`FIELD OF THE INVENTION
`
`The present invention relates to a frequency hopping
`communication system and, more particularly, to a fre(cid:173)
`quency hopping communication system with error detection
`capabilities. The present invention also relates to an auto(cid:173)
`matic transmission power level control method for a fre(cid:173)
`quency hopping system.
`
`BACKGROUND OF THE INVENTION
`
`2
`initiates a preliminary synchronization by selecting a fre(cid:173)
`quency ("selected frequency") from the hopping frequencies
`of a prescribed hopping pattern. The receiving side appara(cid:173)
`tus then determines whether the frequencies following the
`5 selected frequency match the received frequencies. If so, the
`receiving side apparatus continues modulating provisionally
`according to the hopping pattern (also referred herein as
`"hopping sequence"). If the received hopping frequencies
`continue to match the detected frequencies over one hopping
`10 cycle, after the preliminary synchronization, then FH com(cid:173)
`munications have been synchronized between the
`transmitting -side apparatus and the receiving -side appara(cid:173)
`tus. Thereafter, the receiving -side apparatus activates a
`synchronization holding process to maintain the synchroni-
`15 zation.
`As described above, conventional FH communication
`systems vary carrier frequencies for spreading, meaning that
`a narrow-band transmission is seen at each period of an FH
`cycle. Accordingly, when a carrier frequency coincides with
`20 an existing communication frequency, some narrow-band
`jamming frequency or a hopping frequency of other FH
`communication devices, the signals transmitted on the car(cid:173)
`rier frequency may be degraded, thereby resulting in error
`signals at the receiving side apparatus. Interference frequen-
`25 cies may also coexist in a hopping frequency, resulting in
`degradation of the transmit signals. Furthermore, conven(cid:173)
`tional FH systems may not be able to receive signals of a
`certain frequency band due to multi-path phasing.
`Accordingly, there is a need to provide error detection and
`correction techniques in FH communication systems to
`remedy the above problems. In particular, there is a need to
`modify a hopping pattern in the event of reception errors.
`One approach to remedying the above problem is found in
`U.S. Pat. No. 5,541,954 to Emi, which discloses a frequency
`hopping communication method and apparatus for changing
`a hopping frequency as a result of a counted number of
`errors. When a coding circuit informs a spreading code
`control unit of an error generation, it specifies an error prone
`40 carrier frequency and counts the errors for each hopping
`frequency. If the counted errors exceed a fixed value for a
`particular frequency, the spreading code control unit
`changes the particular frequency to another unused fre(cid:173)
`quency and informs a data communication control unit of
`45 the change. The data communication control unit notifies the
`other party apparatus of the frequency change, via control
`signal. The other party apparatus receives the control data,
`changes the particular frequency to a corresponding new
`one, and resumes data transmission with the modified hop-
`50 ping pattern.
`However, one problem with the Emi system is that errors
`affecting a particular transmission frequency may also affect
`neighboring frequencies, particularly, those that are being
`employed in the hopping pattern or are selected to replace
`55 the error-affected hopping frequency (hereinafter "erred
`frequency"). In such a case, the Emi system needs to replace
`the neighboring frequencies, thereby requiring communica(cid:173)
`tion to be stopped until a new sequence of frequencies can
`be transmitted to the other party. As a result, in such
`60 instances, the overall throughput rate of the communication
`system may be significantly degraded.
`Another problem with the Emi system and other conven(cid:173)
`tional FH communication systems is that such systems
`transmit FH modulated signals for all hopping frequencies at
`65 the same transmission power level. Furthermore, they oper(cid:173)
`ate at unnecessarily high transmission power levels to ensure
`that the transmitted signals will reach the receiving side
`
`35
`
`Spread spectrum communication systems, such as fre(cid:173)
`quency hopping (FH) communication systems, have excel(cid:173)
`lent properties, such as high resistance to interference and
`data security. Such communication systems are known to be
`used in communication fields, such as satellite communica(cid:173)
`tion and ground communication, and are progressively being 30
`applied in mobile communication and local communication.
`FH communication systems employ a wide bandwidth to
`perform communication. Such communication systems
`switch or modulate a carrier wave for data signals into
`different frequencies in accordance with spreading codes.
`An example of a conventional FH communication apparatus
`is briefly described below with reference with FIG. 12.
`In a transmission operation, transmit data are composed
`of analog signals that are encoded in a coding circuit 1. The
`encoded data are modulated in a modulating circuit 2
`through a modulating method, such as frequency shift key(cid:173)
`ing (FSK) or a phase shift keying (PSK). The modulated data
`are mixed with outputs of a frequency synthesizer 8 in a
`mixer 3. Synthesizer 8 changes its output frequency in
`accordance with spreading codes (e.g., a frequency hopping
`pattern), which are generated by a spreading code generating
`circuit 7. The mixed data are amplified in a transmit circuit
`4 and sent from an aerial 6, via a duplexer 5 that alternates
`between outputting the transmit data and inputting receive
`data from another FH communication device.
`In a receive operation, signals received via aerial 6 are
`input into a receive circuit 11 through duplexer 5, and are
`amplified through a bandpass filter of receive circuit 11. The
`amplified signals are mixed with outputs of synthesizer 8 in
`a mixer 10. The frequency output from synthesizer 8 is
`hopped in accordance with a spreading code (e.g., a fre(cid:173)
`quency hopping pattern), generated by spreading code gen(cid:173)
`erating circuit 7. Asynchronous circuit 9 is adapted to obtain
`and hold synchronization for the switching of the frequency,
`and synchronizes the received signals with the output fre(cid:173)
`quency of synthesizer 8. The synchronized outputs of mixer
`10 are demodulated into binary data in a demodulating
`circuit 13, and are decoded into analog receive data in a
`decoding circuit 12.
`A synchronizing operation of synchronous circuit 9 is
`generally described below. The receiving side apparatus
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`device at a reasonable level. As such, these systems operate
`at inefficient power consumption levels. Such systems fur(cid:173)
`ther transmit signals at transmission power levels that may
`interfere with other neighboring systems and pose a data
`security risk (e.g., the data is transmitted beyond a necessary
`transmission range, thus increasing the possibility of unau(cid:173)
`thorized access to the data).
`There is a need to provide an apparatus and method that
`performs FH communication over less error prone hopping
`frequencies. There is also a need to provide an FH commu(cid:173)
`nication apparatus and method that minimizes the number of
`frequency hopping replacement operations and, more
`specifically, provides rapid and efficient elimination of erred
`areas or portions of an available frequency spectrum.
`Furthermore, there is a need to provide an FH communica(cid:173)
`tion apparatus and method that is capable of controlling the
`transmission power levels to optimize power consumption,
`minimize communication interference with neighboring
`devices and increase data security.
`Accordingly, it is an object of the present invention to
`provide an efficient apparatus and method for error detection
`and link quality improvement in an FH communication
`system.
`It is a further object of the present invention to provide an
`FH apparatus and method that employs efficient error detec(cid:173)
`tion techniques, minimizes the amount of FH replacement
`operations and provides rapid and efficient elimination of
`erred areas or portions of an available frequency spectrum.
`Another object of the present invention is to provide an
`apparatus and method thereof for minimizing reoccurrence
`of transmission errors according to previously detected
`errors.
`A further object of the present invention is to provide an
`FH communication apparatus and method that is capable of
`controlling the transmission power levels to optimize power
`consumption, minimize interference with neighboring
`devices and increase security.
`Another object of the present invention is to provide an
`FH communication apparatus and method that optimizes
`transmission power level for each carrier frequency in a
`hopping pattern.
`It is also an object of the present invention to provide an
`FH communication apparatus and method that is capable of
`automatically controlling the transmission power levels of
`each hopping frequency.
`
`SUMMARY OF THE INVENTION
`
`Before proceeding with a summary of the present
`invention, it is well to define certain terms to be used herein.
`The term "segment" will hereinafter refer to a subset of
`available frequencies of an available frequency spectrum. In
`the context of the present invention, the frequency spectrum
`is divided into a plurality of such segments with each
`segment including a contiguous subset of the available
`frequencies. A plurality of segments ("used segments") is
`used for the FH communication, wherein carrier or hopping
`frequencies are selected from the used segments to form a
`frequency hopping pattern for data transmission. The term
`"unused segment" refers to a segment that is not in use in the
`performance of FH communication.
`A first embodiment of the present invention is a commu(cid:173)
`nication apparatus and method for performing frequency
`hopping (FH) communication with another party over an
`available spectrum of frequencies. The spectrum is arranged
`or divided into a plurality of segments, with each segment
`
`5
`
`4
`including a subset of the frequencies, preferably a contigu(cid:173)
`ous subset of the frequencies. Each segment is preferably
`arranged to include an identical number of frequencies or an
`identical bandwidth. The FH communication apparatus
`includes a communication device for communicating with
`another party. The communication device receives data over
`a sequence of hopping frequencies from the other party, with
`the hopping frequencies being selected from used segments
`from the plurality of segments. A storage device stores an
`10 error value for each used segment. A processing unit iden(cid:173)
`tifies a reception error (also referred herein as error or errors)
`in the received data, and an erred segment in which the
`reception error occurred (e.g., the used segment that includes
`the hopping frequency over which the error occurred). The
`15 processing unit modifies the error value associated with the
`erred segment according to the occurrence of a reception
`error, the non-occurrence of a reception error, a pattern of
`reception error occurrences, etc. The processing unit
`replaces the erred segment with an unused segment from the
`20 plurality of segments to attempt communication over a less
`error prone segment, when the error value for the erred
`segment has reached at least a predetermined threshold. The
`processing unit notifies the other party of the unused
`segment, which has been newly selected, via the communi-
`25 cation device, so that FH communication can be resumed
`with the substituted unused segment.
`Accordingly, a used segment that experiences reception
`errors in one (or more) of its frequencies may be completely
`eliminated from the hopping scheme, by replacing the erred
`30 segment with an unused segment from a plurality of seg(cid:173)
`ments. For example, a used segment may include 7
`frequencies, with 2 of the frequencies causing the error value
`of the used segment to reach or exceed a predetermined
`threshold. In such a case, the segment replacement process
`35 of the present invention will replace the entire used segment
`with a new unused segment, preferably also including 7
`different frequencies.
`By arranging the available frequencies into segments and
`performing FH communication over only a subset of the
`40 segments (e.g., the used segments), the present invention
`ensures a more rapid and efficient elimination of erred areas
`of the spectrum, be it a single erred frequency or several
`adjacent erred frequencies. Thus, a segment which is prone
`to reception errors is replaced at once, without the need to
`45 replace many frequencies one at a time.
`A second embodiment of the present invention is an
`apparatus and method for performing frequency hopping
`communication with another party over an available spec(cid:173)
`trum of frequencies. The spectrum is arranged into a plu-
`50 rality of segments, with each segment corresponding to a
`subset of the spectrum of frequencies, preferably a contigu(cid:173)
`ous subset of the spectrum. More specifically, the present
`invention is an apparatus and method for controlling auto(cid:173)
`matically the transmission power levels of each segment
`55 used in an FH communication system. The apparatus
`includes a communication device for communicating with
`another party. The communication device receives data (e.g.,
`data packets) over a used segment from the plurality of
`segments and received signal strength indication (RSSI)
`60 indicating a current signal reception level for the used
`segment from the other party. A processing unit analyzes the
`received data to determine an occurrence or non-occurrence
`of a reception error over the hopping frequency and notifies
`the other party to modify the current transmission power
`65 level of the used segment according to the occurrence or
`non-occurrence of a reception error, via the communication
`device.
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`ment at a point in time for performing FH communication in
`accordance with a second embodiment of the present inven(cid:173)
`tion.
`FIG. 8 illustrates a block diagram of the components for
`updating received signal strength indication (RSSI) registers
`employed for tracking the maximum and minimum recep(cid:173)
`tion power levels for a used segment, in accordance with a
`second embodiment of the present invention.
`FIG. 9 illustrates a flow diagram of a RSSI register update
`operation in accordance with a second embodiment of the
`present invention.
`FIG. 10 illustrates a flow diagram of a transmission power
`level change operation, in accordance with a second embodi(cid:173)
`ment of the present invention.
`FIG. 11 illustrates a table of transmission power levels as
`a function of values found in a erred reception RSSI register
`and a valid reception RSSI register as shown in FIG. 8, in
`accordance with the second embodiment of the present
`20 invention.
`FIG. 12 illustrates an example of an FH communication
`apparatus of the prior art.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`5
`For instance, a receiving-side apparatus may notify a
`transmitting -side apparatus to decrease a current transmis(cid:173)
`sion power level for a used segment when no reception error
`has occurred over the used segment at the current transmis(cid:173)
`sion power level (e.g., no reception errors have occurred for 5
`any one of the frequencies of the used segment).
`Alternatively, the receiving-side apparatus may notify the
`transmitting -side apparatus to increase the current transmis(cid:173)
`sion power level for the used segment when a reception error
`has occurred over the used segment at the current transmis- 10
`sian power level (e.g., reception errors have occurred for one
`or more of the frequencies of the used segment). It is
`preferred that the transmitting-side apparatus is notified
`immediately to increase the current transmission power
`levels of the used segment upon the occurrence of a recep- 15
`tion error over the used segment. On the other hand, it is
`preferred that the transmitting -side apparatus is notified,
`after a predetermined period (e.g., a delay period), to
`decrease the current transmission power level of the used
`segment if no reception error has occurred over the used
`segment at the current transmission power level.
`Through the exchange of transmission power level infor(cid:173)
`mation and error detection, the receiving-side party can
`independently control and optimize the transmission power
`level for each segment to reach a minimum transmission 25
`power level at which no reception error or an acceptable
`level of errors (i.e., correctable) has occurred for each
`segment, particularly for each used segment. That is, the
`receiving-side party would notify the transmitting-side party
`to modify (e.g., increase or decrease) the transmission power 30
`level of the used segments according to the occurrence or
`non-occurrence of reception errors, until the transmitting(cid:173)
`side party transmits data at the optimum transmission power
`level for each used segment.
`Such an arrangement minimizes power consumption,
`reduces the possibility of interference with neighboring FH
`or other communication devices, and increases data security
`by minimizing the reception z on e of the data packets. Such
`an arrangement further provides an error detection and
`monitoring implementation which responds quickly in the
`event of communication interference, and generally pro(cid:173)
`vides an overall improved communication link quality.
`
`45
`
`A first embodiment of the present invention performs FH
`communication over a sequence of segments of an available
`frequency bandwidth and, moreover, performs error detec(cid:173)
`tion and modification of used segments in the performance
`of FH communication. The present invention divides an
`available frequency spectrum into a plurality of segments,
`with each of the hopping frequency being a part of a
`frequency segment, where the segments in use are selected
`from the plurality of segments. In operation, the present
`35 invention detects an occurrence or non-occurrence of a
`reception error over the used segments and modifies (e.g.,
`increasing or decreasing) error values of the used segments
`accordingly. When the error value or a number of detected
`errors of a used segment reaches or exceeds a predetermined
`40 threshold, the used segment (e.g., erred segment) and all its
`hopping frequencies are replaced with an unused segment
`from the available spectrum. The other communicating party
`is notified of the replacement, and FH communication is
`then resumed with the modified hopping pattern.
`Accordingly, a used segment that experiences reception
`errors in one (or more) of its frequencies may be completely
`eliminated from the hopping scheme, by replacing the erred
`segment with an unused segment from a plurality of seg-
`50 ments. For example, a used segment may include 7
`frequencies, with 2 of the frequencies causing the error value
`of the used segment to reach or exceed a predetermined
`threshold. In such a case, the segment replacement process
`of the present invention replaces the entire used segment
`55 with a new unused segment, preferably having 7 different
`frequencies.
`By arranging the available frequencies into segments and
`performing FH communication over only a subset of the
`segments (e.g., the used segments), the present invention
`60 ensures a more rapid and efficient elimination of erred areas
`of the spectrum, be it a single erred frequency or several
`adjacent erred frequencies. Thus, a segment which is prone
`to reception errors is replaced at once, without the need to
`replace many frequencies one at a time.
`Referring to FIG. 1, there is provided a block diagram of
`a frequency hopping (FH) communication system 100 of the
`present invention. Communication system 100 includes a
`
`65
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 illustrates an overview of an FH communication
`system employing error detection techniques of the present
`invention.
`FIG. 2A illustrates a sample division of a spectrum to
`segments in accordance with the present invention.
`FIG. 2B illustrates a sample segment hopping pattern at a
`point in time for performing frequency hopping communi(cid:173)
`cation in accordance with the present invention.
`FIG. 3 illustrates a block diagram of a communication
`subsystem f or handling and replacing segments in accor(cid:173)
`dance with the FH communication method of the present
`invention.
`FIG. 4 illustrates a block diagram of a representative error
`counter of the present invention.
`FIG. 5 illustrates a flow diagram of a segment error
`counter update and segment replacement method of the
`present invention.
`FIG. 6 illustrates a flow diagram of a segment replace(cid:173)
`ment operation of the present invention.
`FIG. 7 illustrates a sample segment hopping pattern and
`associated transmission power levels for each hopping seg-
`
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`primary system 102, which performs FH communication
`with a plurality of secondary systems generally denoted by
`the reference numerals 104, 106 and 108, across a commu(cid:173)
`nication link(s) 110. As shown in FIG. 1, primary system
`102 includes a plurality of communication subsystems gen(cid:173)
`erally denoted by the reference numerals 122, 124 for
`performing FH communication with secondary systems 104,
`106 in accordance with the error detection method of the
`present invention. Likewise, secondary systems 104, 106
`each include communication subsystems 132, 134,
`respectively, for performing FH communication with pri(cid:173)
`mary system 102 in accordance with the error detection and
`link improvement method of the present invention.
`Each subsystem 122, 124, 132, 134 is adapted to transmit
`and receive data according to a spreading code designating
`a segment hopping sequence or pattern (e.g., S0 , S2 , S5 , S 6
`and S7 ), with the hopping frequencies being contained
`within the used segments. A hopping frequency may be
`randomly selected from a used segment or be a predeter(cid:173)
`mined frequ