`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 1 of 17 PageID #: 126
`
`EXHIBIT F
`
`EXHIBIT F
`
`
`
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 2 of 17 PageID #: 127
`caSGZIZO'CV'OOO’ZZ'JRG Wm“ 1"A’IIIII‘IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII'IIIIIIII”
`
`US007778310B2
`
`(12) United States Patent
`US 7,778,310 B2
`Suzuki et al.
`(45) Date of Patent:
`*Aug. 17, 2010
`
`(10) Patent No.:
`
`(54) CODE DIVISION MULTIPLE ACCESS
`MOBILE COMMUNICATION SYSTEM
`
`(75)
`
`Inventors: May Suzuki, Kokubunji (JP); Nobukazu
`Doi, Hachioji (JP); Takashi Yano,
`Tokorozawa (JP)
`
`(73) Assignee: FIPA Frohwitter Intellectual Property
`AG, Gruenwald (DE)
`
`(*)
`
`Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`This patent is subject to a terminal dis-
`claimer.
`
`(21) Appl.No.: 10/869,920
`
`(22)
`
`Filed:
`
`Jun. 18, 2004
`
`Prior Publication Data
`
`US 2004/0228316 A1
`
`NOV. 18, 2004
`
`(58) Field of Classification Search ................. 375/130,
`375/133, 134, 137, 142, 145, 149, 150, 326,
`375/356, 362,335; 370/342, 328, 335
`See application file for complete search history.
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,969,159 A
`
`11/1990 Belcher et a1.
`
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`EP
`
`693834 Al
`
`1/1996
`
`(Continued)
`OTHER PUBLICATIONS
`
`IEEE, K. Higushi et a1, “Fast Cell Research Algorithum in DS-
`CDMA Mobile Radio Using Long Spreading Codes,” May 4, 1997,
`pp. 1430-1434.
`
`(Continued)
`
`Primary ExamineriJean B Corrielus
`(74) Attorney, Agent, or FirmiMattingly & Malur, PC.
`
`Related US. Application Data
`
`(57)
`
`ABSTRACT
`
`(65)
`
`(63)
`
`Continuation of application No. 09/518,690, filed on
`Mar. 3, 2000, now Pat. No. 6,879,571, which is a
`continuation of application No. 09/257,002, filed on
`Feb. 25, 1999, now Pat. No. 6,507,576.
`
`(30)
`
`Foreign Application Priority Data
`
`May 13, 1998
`
`(JP)
`
`................................. 10-129995
`
`(51)
`
`Int. Cl.
`(2006.01)
`H04B 1/00
`(52) US. Cl.
`........................ 375/150; 370/342; 370/335
`
`In a mobile communication system using a code division
`multiple access (CDMA) method, spreading code detection
`and frame/slot timing synchronization (cell search) is con-
`ducted by using a long code masked symbol. The spreading
`factor of the long code masked symbol is set to a value lower
`than spreading factors of other ordinary symbols. As a result,
`it becomes possible to reduce the circuit scale and power
`dissipation of the mobile terminal and raise the speed of cell
`search.
`
`2 Claims, 11 Drawing Sheets
`
`. TRANSMISSION
`POWER
`
`-
`
`P1
`
`LONG CODE MASKED~131
`SYMBOL, SECTION
`
`.
`
`CHANNEL
`HI
`
`FIRST PERCH
`
`TIMEt
`
`TRANSMISSION
`
`POWER
`
`SECOND PERCH
`CHANNEL
`
`TIMEt
`
`
`
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 3 of 17 PageID #: 128
`Case 2:20-cv-00322-JRG Document 1—6 Filed 10/01/20 Page 3 of 17 PageID #: 128
`
`US 7,778,310 B2
`
`Page 2
`
`US. PATENT DOCUMENTS
`
`5/2001 Sriram et a1.
`6,226,315 B1
`4/2002 Aramaki
`..................... 370/342
`6,370,134 B1 *
`5/2002 Terashima
`6,385,232 B1
`10/2002 Yoneyama
`6,459,724 B1
`6,665,277 B1 * 12/2003 Sriram ....................... 370/324
`6/2004 Sriram et a1.
`. 375/145
`6,754,251 B1*
`
`. 370/335
`6,891,817 B2 *
`5/2005 Miya et a1.
`
`2004/0057414 A1 *
`3/2004 Sriram
`370/342
`9/2005 Iwamoto et a1.
`.
`. 375/149
`2005/0213643 A1*
`
`............. 375/149
`2005/0213644 A1*
`9/2005 Iwamoto et 31.
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`EP
`
`0825737
`838 910
`
`2/1998
`4/1998
`
`EP
`EP
`JP
`JP
`JP
`JP
`W0
`
`0388910
`0852430
`61-248698
`8-79131
`08-307316
`09-261121
`WO 99/12273
`
`4/1998
`7/1998
`5/1986
`3/1996
`11/1996
`10/1997
`3/1999
`
`OTHER PUBLICATIONS
`Translation of the Institute of Electronics, Information and Commu-
`.
`.
`.
`.
`nication Engineers, Technical Report ofIEICE DSP98-116, SAT96-
`111, RCS96-122 (Jan. 1997).
`K. Higuchi et a1, “Fast Cell Search Algorithm in DS-CDMA Mobile
`Radio Using Long Spreading Codes”, IEEE, 47th, May4-7, 1997, pp.
`1430- 1434.
`
`* cited by examiner
`
`
`
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 4 of 17 PageID #: 129
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`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 5 of 17 PageID #: 130
`Case 2:20-cv-00322-JRG Document 1—6 Filed 10/01/20 Page 5 of 17 PageID #: 130
`
`US. Patent
`
`Aug. 17, 2010
`
`Sheet 2 0111
`
`US 7,778,310 B2
`
`FIG. 2
`
`LONG CODE MASKED
`SYMBOL SECTION
`-
`H—fi
`I
`l
`I
`I
`
`
`
`
`I
`'
`
`I
`
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`I
`|
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`CSC
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`121
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`'
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`I
`:
`I
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`TRANSMISSION
`POWER
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`— —
`
`p1
`
`TRANSMISSION
`'POWER
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`I
`
`I
`
`
`
`I
`I
`
`I
`I
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`SECOND PERCH
`CHANNEL
`
`
`
`TIMEt
`
`FIG. 3
`
`LONG CODE MASKED ~131
`SYMBOL SECTION
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`
`
`. TRANSMISSION
`POWER
`
`- —
`
`mt
`
`CHANNEL
`
`FIRST PERCH
`
`TIMEt
`
`TRANSMISSION
`
`POWER SECOND PERCH
`
`CHANNEL
`
`TIMEt
`
`
`
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 6 of 17 PageID #: 131
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 6 of 17 PageID #: 131
`
`US. Patent
`
`Aug. 17, 2010
`
`Sheet 3 of 11
`
`US 7,778,310 B2
`
`FIG. 4
`
`LONG CODE MASKED
`SYMBOL SECTION
`
`TRANSMISSION
`POWER
`
`— —
`
`P1
`
`CHANNEL
`
`FIRST PERCH
`
`TIMEt
`
`TRANSMISSION
`POWER
`
`GISC
`
`
`
`
`SECOND PERCH
`CHANNEL
`
`
`TIMEt
`
`142
`
`FIG. 5
`
`LONG CODE MASKED
`SYMBOL SECTION
`
`-
`I
`
`|
`
`TRANSMISSION
`POWER
`
`— -
`
`mi
`
`CHANNEL
`
`FIRST PERCH
`
`TIMEt
`
`TRANSMISSION
`
`
`
`
`SECOND PERCH
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`
`POWER
`
`
`152
`
`TIMEt
`
`
`
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 7 of 17 PageID #: 132
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 7 of 17 PageID #: 132
`
`US. Patent
`
`Aug. 17, 2010
`
`Sheet 4 of 11
`
`US 7,778,310 B2
`
`FIG. 6
`
`LONG CODE MASKED
`SYMBOL SECTION
`
`.
`I
`
`I
`
`IIIlII
`
`TRANSMISSION
`POWER
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`mi
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`
`TIMEt
`
`TRANSMISSION
`POWER
`
`
`
`SECOND PERCH
`CHANNEL
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`
`162
`TIMEt
`
`
`
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`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 8 of 17 PageID #: 133
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`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 10 of 17 PageID #: 135
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 10 of 17 PageID #: 135
`
`US. Patent
`
`Aug. 17, 2010
`
`Sheet 7 0111
`
`US 7,778,310 B2
`
`CONTROLLERBUS
`
`FIG.9
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`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 13 of 17 PageID #: 138
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`US. Patent
`
`Aug. 17, 2010
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`Sheet 10 of 11
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`US 7,778,310 B2
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`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 14 of 17 PageID #: 139
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 14 of 17 PageID #: 139
`
`U.S. Patent
`
`Aug. 17
`
`9
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`US 7,778,310 B2
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`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 15 of 17 PageID #: 140
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 15 of 17 PageID #: 140
`
`US 7,778,310 B2
`
`1
`CODE DIVISION MULTIPLE ACCESS
`MOBILE COMMUNICATION SYSTEM
`
`This is a continuation application of US. Ser. No. 09/518,
`690, filed Mar. 3, 2000, now US. Pat. No. 6,879,571; which
`is a continuation application of US. Ser. No. 09/257,002,
`filed Feb. 25, 1999, now US. Pat. No. 6,507,576.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The present invention relates to a code division multiple
`access (CDMA) mobile communication system. In particu-
`lar, the present invention relates to a cell search method using
`a long code masked symbol (search code) in perch channels.
`2. Description of the Related Art
`When a mobile terminal starts communication, or a mobile
`terminal moves from one base station area (cell) in which the
`mobile terminal is currently conducting communication to an
`adjacent cell (i.e., in the case of hand over) in CDMA mobile
`communication systems, it is necessary to conduct spread
`code detection or frame/slot timing synchronization. Such
`processing is called cell search.
`As for an example of a conventional cell search method, a
`method of spreading only one symbol located at the end of a
`slot by using a special short code called long code masked
`symbol instead of the ordinary long code and short code is
`described in Technical Report of IEICE (the Institute of Elec-
`tronics, Information and Communication Engineers) DSP-
`96-116, SAT96-111, RCS96-122 (1997-01).
`This cell search method using the long code masked sym-
`bol will now be described. The cell search uses perch chan-
`nels shown in FIG. 1. The term “perch channels” means
`control channels for notifying reverse link interference power
`measured at the base station, system frame number, and the
`like. Furthermore, the perch channels are transmitted always
`with constant transmission power. Since a control signal of
`the perch channels is used also as a reference signal of timing
`synchronization conducted between the base station and the
`mobile terminal, the control signal of the perch channels is
`spread as described below. As for the perch channels, a first
`perch channel and a second perch channel are multiplexed. In
`a long code masked symbol position (search code position)
`101 of a first perch channel 106, a CSC (Common Short
`Code). i.e., a first search code 104 is mapped. In a long code
`masked symbol position 101 of a second perch channel 107,
`a GISC (Group Identification Short Code),
`i.e., a second
`search code 105 is mapped. In a data symbol section 102 (a
`section obtained by removing a long code masked symbol
`section (search code section) from one slot section), a control
`signal transmitted to the mobile terminal is spread by a long
`code and short code 103.
`
`The long code is a long period spreading code assigned
`uniquely to the base station. The short code is a short period
`spreading code assigned uniquely to each of channels under
`communication (including the control channel and transmis-
`sion channel). The long code has a long code length and
`includes many kinds. In order to facilitate its timing synchro-
`nization, therefore, the long code is classified into a plurality
`of groups. The GISC is a short period code provided so as to
`correspond to the classification of the long code. In the case
`where the mobile terminal is to conduct timing synchroniza-
`tion of the perch channels, the mobile terminal lightens the
`load of synchronization of the long code used by the base
`station (i.e., decreases time, circuit means, electric power, etc.
`required for the timing synchronization), by detecting the
`GISC and narrowing down the long code to a fixed range (i.e.,
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`
`by limiting candidates for the long code which may be used).
`The CSC is a short period spreading code defined uniquely to
`the mobile communication system.
`The detection of the long code and the frame/slot timing
`used by the base station, utilizing the perch channels is con-
`ducted as follows: (1) the mobile terminal despreads the perch
`channels by using the CSC, and detects the slot timing on the
`basis of the height of the correlation value; (2) the mobile
`terminal conducts despreading in all GISCs in conformity to
`the synchronized slot timing, and detects the GISC on the
`basis of the height of the correlation value; (3) the mobile
`terminal conducts despreading by using all
`long codes
`belonging to a group associated with the GISC, and detects
`the long code on the basis of the height of the correlation
`value.
`
`The format and transmission power of the perch channels
`of the conventional method are shown in FIG. 2. The symbol
`rate of the perch channels is 16 kbps (spreading factor being
`256) and constant in all sections including the long code
`masked symbol. In the long code masked symbol section in
`which the second perch channel is transmitted, transmission
`power P1 ofthe first perch channel is lowered by transmission
`power P2 ofthe second perch channel. Thereby, transmission
`power of the perch channels after multiplexing is constant.
`In the conventional system which conducts spreading pro-
`cess in the long code masked symbol section at the same
`symbol rate as in the data symbol section, it took the longest
`time in a first stage (slot timing synchronization) of the cell
`search. In order to conduct timing synchronization in a short
`time, a matched filter (MF) capable of deriving correlation
`results at a plurality oftiming instants at once is used in many
`cases.
`
`FIG. 13 shows time required in each stage ofthe cell search
`in the case where cell search is conducted by despreading the
`perch channels having a spreading factor of 256, by use of a
`MF with 64 chips. The stage requiring the longest time is slot
`timing synchronization 1301. For attaining faster cell search,
`it is an indispensable subject to shorten the time required for
`timing synchronization. In timing synchronization using the
`MF, correlation values at all timing instants in one symbol
`(256 chips) section are accumulated by using CSCs of a
`plurality of slots, thereby conducting slot timing synchroni-
`zation at high precision. For example, correlation values
`derived for CSCs of 48 slots are accumulated. In FIG. 13, one
`accumulation value with respect to timing instants of 64 chips
`which is the same in number as the number of taps of the MF
`is derived in one cycle 1301 of timing synchronization.
`Ifthe MF with 64 taps is used, coefficient mode switchover
`becomes necessary in order to derive correlation values at all
`timing instants. This results in a problem that the time
`required for timing synchronization, in turn the time required
`for cell search becomes longer. On the other hand, if a MF
`with 256 taps is used, then the received signal can be despread
`with coefficients corresponding to one symbol set in the MF
`intact. Since the coefficient mode switchover thus becomes
`
`unnecessary, correlation at all timing instants can be derived
`at high speed. However, both the gate size and power con-
`sumption of the MF become very large.
`
`SUMMARY OF THE INVENTION
`
`In order to conduct the cell search at high speed while
`suppressing the gate size and the power consumption, the
`spreading factor of the long code masked symbol is made
`smaller than spreading factors of other portions of the perch
`channels.
`
`
`
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 16 of 17 PageID #: 141
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 16 of 17 PageID #: 141
`
`US 7,778,310 B2
`
`3
`In particular, a symbol rate according to typical number of
`taps of the MF used in the mobile terminal is determined. For
`example, in the case where the spreading factor of the mask
`symbol is 64, timing synchronization is conducted by using a
`MF with 64 taps. In this case, the symbol length coincides
`with the number of taps of the MF. With coefficients corre-
`sponding to one symbol set in the MF intact, therefore, it is
`possible to conduct despreading of the received signal and
`conduct search of all timing instants in the 64 chip section.
`Without increasing the gate size and power consumption, fast
`cell search thus becomes possible.
`By referring to detailed description of preferred embodi-
`ments described below and accompanied drawing, these or
`other objects, features, and advantages will become more
`apparent.
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`FIG. 1 is a diagram showing a channel format of perch
`channels;
`FIG. 2 is a diagram showing a channel format and trans-
`mission power of perch channels of a conventional system;
`FIG. 3 is a diagram showing a channel format and trans-
`mission power of perch channels of a first embodiment;
`FIG. 4 is a diagram showing a channel format and trans-
`mission power of perch channels of a second embodiment;
`FIG. 5 is a diagram showing a channel format and trans-
`mission power of perch channels of a third embodiment;
`FIG. 6 is a diagram showing a channel format and trans-
`mission power of perch channels of a fourth embodiment;
`FIG. 7 is a diagram showing shortening of the search time,
`and reduction of the circuit scale and transmission power;
`FIG. 8 is a configuration diagram of a mobile terminal;
`FIG. 9 is a diagram showing a configuration example of a
`cell search timing synchronization unit of a mobile terminal;
`FIG. 10 is a diagram showing a configuration example of a
`cell search GISC detection unit of a mobile terminal;
`FIG. 11 is a diagram showing a configuration example of a
`first long code detection unit of a mobile terminal;
`FIG. 12 is a diagram showing a configuration example of a
`second long code detection unit of a mobile terminal; and
`FIG. 13 is a diagram showing time required at each stage of
`the cell search.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`First of all, the configuration of a mobile terminal used in a
`CDMA mobile communication system according to the
`present invention will be described by referring to FIG. 8. A
`received signal of a carrier frequency received from an
`antenna is lowered in frequency by an RF unit 801. The
`received signal of the baseband is inputted to a cell searcher
`805 and a receiver 804 via an RF interface 802. The cell
`searcher 805 conducts the above described cell search. The
`
`receiver 804 conducts despreading, error correction and the
`like of physical channels other than the perch channels. The
`decoded received signal is outputted via a user interface 807,
`and subjected to subsequent processing. A transmission sig-
`nal to be transmitted to the base station is inputted to a trans-
`mitter 803 via the user interface 807. The transmitter 803
`
`conducts coding and spreading of the transmission signal. A
`controller 806 conducts initial value setting in various units
`and timing management by using a DSP (Digital Signal Pro-
`cessor).
`FIGS. 9 to 12 show configuration examples of blocks 810-
`812 of FIG. 8. FIG. 9 shows the configuration of a timing
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`synchronizer 810. In the timing synchronizer 810, it is nec-
`essary to derive correlation values of timing corresponding to
`one symbol. Therefore, an MF 901 capable of providing
`correlation results at a plurality of timing instants at a time is
`used. As for coefficients of the MF 901, CSC generated from
`a CSC encoder 902 is used. An accumulator 903 accumulates
`
`correlation values outputted from the MF for a plurality of
`slots. A peak detector 904 detects such a timing as to maxi-
`mize the accumulated correlation values, as slot timing.
`FIG. 10 shows a configuration example of a GISC detec-
`tion unit 811. FIG. 11 shows a configuration example of a first
`long code detection unit. FIG. 12 shows a configuration
`example of a second long code detection unit. A long code
`detection unit 812 includes a first long code detection unit and
`a second long code detection unit. In these circuits, frame/slot
`timing is already known by a timing detection unit. By arrang-
`ing correlators 1001 in parallel for conducting despreading at
`one detected timing instant, high speed processing can be
`conducted efficiently.
`The GISC detection unit 811 (FIG. 10) stores a received
`signal ofa long code masked symbol in a RAM 1002. GISCs
`are specified in a GISC encoder 1003 one after another by the
`DSP. Correlation for each chip is thus derived. A correlation
`value in one symbol is derived by an accumulator 1004. Such
`processing can be conducted at high speed by suitably con-
`ducting parallel processing. By selecting the highest one of
`the derived correlation values, the GISC is detected.
`The first long code detection unit (FIG. 11) calculates
`correlation values over approximately 10 symbols, and
`detects a long code used by the base station out of long codes
`belonging to a class corresponding to the detected GISC.
`Long codes specified in a long code generator 1102 one after
`another by the DSP are multiplied by a short code ofthe perch
`channels generated by a short code generator 1103. Correla-
`tion of each timing is derived by a correlator 1001. Correla-
`tion values corresponding to 10 symbols are accumulated by
`an accumulator 1 1 01. This processing is conducted in parallel
`with different long codes. On the basis of a result of accumu-
`lation of correlation values over approximately 10 symbols, a
`probable long code is designated.
`For the long code designated by the first long code detec-
`tion unit, the second long code detection unit (FIG. 12) con-
`ducts processing similar to that ofthe first long code detection
`unit over one frame section and outputs the result to delay
`locked loop 813. In the case where a predetermined accumu-
`lation value has been obtained, the cell search is completed.
`A CDMA communication system performing a cell search
`method using the long code mask symbol will now be
`described centering around an example in which only the long
`code masked symbol portion of the perch channels typically
`transmitted at 16 Ksps (spreading factor 256) is made to have
`a spreading factor of 64.
`The spreading factor is not limited to 64. Similar effects
`can be obtained so long as the spreading factor is less than
`256.
`As a first embodiment, FIG. 3 shows a channel format and
`transmission power in the case where spreading factors of the
`CSC and GISC are made smaller (64 in the example) than
`those of other symbols of the perch channels, and the CSC
`and GISC are inserted at different timing instants. In order to
`prevent other ordinary symbol portions from being affected, a
`masked symbol section 131 is made to have 256 chips in the
`same way as the conventional system. The CSC and GISC
`may be inserted in any section of four sections (133, 134, 135
`and 136) obtained by dividing the mask symbol section at
`intervals of 64 chips. In the case where the symbol length of
`the GISC becomes short and consequently the number of
`
`
`
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 17 of 17 PageID #: 142
`Case 2:20-cv-00322-JRG Document 1-6 Filed 10/01/20 Page 17 of 17 PageID #: 142
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`US 7,778,310 B2
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`5
`GISCs is not enough for the number of classes of the long
`code which GISCs are assigned to, it is also possible to adopt
`such a method that long code identification groups are sorted
`out according to which of the tour insertion sections they are
`inserted. In the masked symbol section, sections other than
`those of CSC and GISC are provided with no symbols.
`If the symbol length is shortened, the number of times of
`possible accumulation times decreases. For obtaining the
`same receiving sensitivity, therefore, the transmission power
`must be raised. However, the perch channels are always sub-
`jected to transmission with constant power. In addition, the
`long code masked symbol portion is poor in orthogonality,
`and therefore, tends to exert interference power to other chan-
`nels. Therefore, it is desirable to suppress the transmission
`power as low as possible. In the present embodiment, there-
`fore, the CSC and GISC are not multiplexed, but the CSC and
`GISC are transmitted by time division in the long code
`masked symbol portion. Even if the spreading factor is
`reduced to 1A at this time, transmission power P3 of the CSC
`is twice the transmission power P1 of the conventional tech-
`nique and the same reception sensitivity is obtained. The
`same is true of the transmission power P4 of the GISC.
`As a second embodiment, FIG. 4 shows a channel format
`and transmission power in the case where the spreading fac-
`tors of the CSC and GISC are made sufliciently small (16 in
`the example) as compared with other symbols of the perch
`channels, and the CSC and GISC are multiplexed and trans-
`mitted. It is necessary to make transmission power P5 of the
`CSC and transmission power P6 of the GISC large so as to
`correspond to the spreading factors. If the symbol rate of
`channels other than perch channels is fast, then the number of
`perch channels which are affected by the fact that the perch
`channel power is increased will become large. In such a case,
`by multiplexing the CSC and GISC to shorten the section in
`which the transmission power becomes large as in the present
`embodiment, although the influence of the perch channels on
`other channels may be large, the shortening of the affecting
`symbol section surely causes influence as a whole to be light-
`ened.
`
`As a third embodiment, FIG. 5 shows a channel format and
`transmission power in the case where the spreading factors of
`the CSC and GISC are made sufficiently small (64 in the
`example) as compared with other symbols of the perch chan-
`nels, and the GISC is repeated a plurality oftimes (three time
`in the example). By transmitting the GISC repetitively n
`times, the number of accumulation times is increased, and
`accordingly transmission power P8 ofthe GISC of one time is
`equal to l/n of transmission power P7 ofthe CSC. As a result,
`influence on other channels is suppressed.
`As a fourth embodiment, FIG. 6 shows a channel format
`and transmissionpower in the case where the spreading factor
`of the CSC is made smaller than that of the GISC (in the
`example, the spreading factor ofthe CSC is 64 and the spread-
`ing factor of the GISC is 256). In the above described three
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`stages ofthe cell search, the GISC detection can be conducted
`by despreading only at timing designated from the CSC, and
`a correlator is used instead ofthe MF in many cases (as shown
`in FIG. 10, for example). As in the present embodiment,
`therefore, the speed of the search can be raised while sup-
`pressing the interference on other channels, by making the
`spreading factor of the CSC affecting the number of taps of
`the MF small and making the spreading factor of the GISC
`larger than it in order to suppress the transmission power.
`In FIG. 7, there is shown a list oftime required at each stage
`of the cell search obtained when the spreading factor of the
`long code masked symbol and the number of taps of the MF
`are changed.
`By thus making the spreading factor of the long code
`masked symbol small, the time required for timing synchro-
`nization can be made shorter than that of the conventional
`
`method, and the number of taps of the MF can be shortened,
`resulting in reduced gate size and power consumption.
`The present invention has been disclosed in connection
`with the preferred embodiments. Those skilled in the art can
`apply various modifications to the embodiments on the basis
`of the disclosure. All modifications existing within the true
`spirit and scope of the present invention are incorporated in
`the claims.
`What is claimed is:
`
`1. A cell search method for a code division multiple access
`mobile communication system, comprising:
`transmitting, from a base station, control signals via first
`and second perch channels, said perch channels being
`formed such that a long period code assigned to said base
`station and a first short period code are mapped in a first
`section of one slot of said first perch channel; and
`transmitting, from said base station, a predetermined short
`period code mapped in a second section of said one slot
`of said second perch channel,
`said predetermined short period code for use by a mobile
`terminal for performing cell search by calculating a cor-
`relation value for said second section of said one slot,
`wherein said predetermined short period code is transmit-
`ted plural times within said second section of said one
`slot,
`wherein said second section of said one slot of the first
`
`perch channel further includes a common short code,
`and spreading factors of said common short code and of
`said predetermined short period code are smaller than a
`spreading factor of said first short period code.
`2. A cell search method according to claim 1, wherein
`transmission power with which the transmission of said plu-
`rality of times of predetermined short period code is per-
`formed is equal to one-(n-th) transmission power with which
`the transmission of said control signal is performed in said
`first section, 11 representing a number of times said predeter-
`mined short period code is transmitted.
`*
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