USOO8411557B2
`
`(12) United States Patent
`US 8,411,557 B2
`(10) Patent N0.:
`Imamura et al.
`
`(45) Date of Patent: *Apr. 2, 2013
`
`(54)
`
`(75)
`
`MOBILE STATION APPARATUS AND
`RANDOM ACCESS METHOD
`
`Inventors: Daichi Imamura, Kanagawa (JP);
`Sadaki Futagi, Ishikawa (JP); Atsushi
`Matsumoto, Ishikawa (JP); Takashi
`Iwai, Ishikawa (JP); Tomofumi Takata,
`Ishikawa (JP)
`
`(73)
`
`Assignee: Panasonic Corporation, Osaka (JP)
`
`(*)
`
`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. N0.: 13/333,805
`
`(22)
`
`Filed:
`
`Dec. 21, 2011
`
`(65)
`
`Prior Publication Data
`
`US 2012/0087329 A1
`
`Apr. 12, 2012
`
`Related US. Application Data
`
`(63)
`
`Continuation of application No. 12/293,530, filed as
`application No. PCT/JP2007/055695 on Mar. 20,
`2007, now Pat. No. 8,139,473.
`
`(30)
`
`Foreign Application Priority Data
`
`Mar. 20, 2006
`
`(JP) ................................. 2006-076995
`
`Int. Cl.
`
`(51)
`
`(52)
`(58)
`
`(2006.01)
`H04J11/00
`(2006.01)
`H043 7/216
`US. Cl.
`......................... 370/208; 370/335; 370/342
`Field of Classification Search .................. 370/208,
`370/335, 342, 441
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`6,519,462 B1
`6,859,445 B1
`2002/0041578 A1
`2007/0165567 A1
`
`2/2003 Lu et a1.
`2/2005 Moon et a1.
`4/2002 Kim et a1.
`7/2007 Tan et a1.
`
`(Continued)
`
`CN
`WO
`
`FOREIGN PATENT DOCUMENTS
`1381107 A
`11/2002
`01/05050 Al
`1/2001
`
`(Continued)
`OTHER PUBLICATIONS
`
`“3rd Generation Partnership Project; Technical Specification Group
`Radio Access Network; Physical layer procedures (FDD) (Release
`6),” 3GPP TS 25.214 V6.7.1, Dec. 2005, 60 pages.
`
`(Continued)
`
`Primary Examiner 7 Andrew Lee
`(74) Attorney, Agent, or Firm 7 Seed IP Law Group PLLC
`
`ABSTRACT
`(57)
`A mobile station apparatus includes a receiving unit config-
`ured to receive control information; a selecting unit config-
`ured to randomly select a sequence from a plurality of
`sequences contained in one group of a plurality of groups,
`into which a predetermined number of sequences generated
`from a plurality of base sequences are grouped and which are
`respectively associated with different amounts of data or
`reception qualities; and a transmitting unit for transmitting
`the selected sequence. The predetermined number of
`sequences are grouped by partitioning the predetermined
`number of sequences, in which sequences generated from the
`same base sequence and having different cyclic shifts are
`arranged in an increasing order ofthe cyclic shifts. A position
`at which the predetermined number of sequences are parti-
`tioned is determined based on the control information, and a
`number of sequences contained in each of the plurality of
`groups varies in accordance with the control information.
`
`10 Claims, 11 Drawing Sheets
`
`11 EACH GENERATING SECTION
`
`
`I EIEGLEATT‘UfiGE I MODULATING I
` CONTROL
`I SECTION I 350110“ I
`
`
`
` NOLLOEISONIXEI‘IdLI'InlN
`‘I 3
`1 4
`
`
` 31
`
`
`INFORMATION
`
`USER DATA
`
`CODING SECTION
`
`33
`
`CONTROL SECTION
`
`
`
`
`
`
`
`MODULATING
`SECTION
`
`32
`
`DEMODULATING
`SECTION
`
`RADIO
`TRANSMITTING
`SECTION
`
`
`
`RADIO RECEIVING
`SECTION
`
`APPLE 1001
`
`APPLE 1001
`
`

`

`US 8,411,557 B2
`Page 2
`
`U.S. PATENT DOCUMENTS
`2008/0192678 A1*
`8/2008 Bertrandetal.
`.............. 370/328
`2009/0003308 A1*
`l/2009 Baxley et al.
`370/350
`.
`2010/0278114 A1* 11/2010 Kwon et al.
`370/328
`
`2011/0007825 A1 *
`l/2011 Hao et al.
`...................... 375/259
`9/2011 Zetterberg et al.
`............ 370/248
`2011/0235529 A1 *
`2011/0310940 A1* 12/2011 Ozluturk ............
`375/219
`2012/0079330 A1 *
`3/2012 Kawaguchi et al.
`.......... 714/718
`FOREIGN PATENT DOCUMENTS
`2006/019710 Al
`2/2006
`
`WO
`
`OTHER PUBLICATIONS
`
`Chinese Office Action, for Chinese Application No. 200780010212.
`6, dated Jun. 11,2010, 5 pages.
`International Search Report, for International Application No. PCT/
`JP2007/055695, mailed Jun. 12, 2007, 2 pages.
`Motorola, “RACH Design for EUTRA,” Rl-060025, Agenda Item:
`5.2.3.1, 3GPP TSG RAN1#43, Helsinki, Finland, Jan. 23-25, 2006,
`11 pages.
`
`Motorola, “RACH Design for EUTRA,” Rl-060387, Agenda Item:
`13.2.3.1, 3GPPTSGRAN1#44, Denver, CO,USA, Feb. 13-17, 2006,
`13 pages.
`Notice of the Reasons for Rejection, for Japanese Application No.
`2010-265294, 5 pages.
`NTT DoCoMo, NEC, Sharp, “Orthogonal Pilot Channel Structure in
`E-UTRA Uplink,” R1-060046, Agenda Item: 5.2.2.2, 3GPP TSG-
`RAN WGl LTE Ad Hoc Meeting, Helsinki, Finland, Jan. 23-25,
`2006, 8 pages.
`NTT DoCoMo, NEC, Sharp, “Random Access Transmission in
`E-UTRA Uplink,” R1-060047, Agenda Item: 5.2.3.1, 3GPP TSG-
`RAN WGl LTE Ad Hoc Meeting, Helsinki, Finland, Jan. 23-25,
`2006, 8 pages.
`NTT DoCoMo, Fujitsu, Mitsubishi Electric, NEC, Panasonic, Sharp,
`Toshiba Corporation, “Orthogonal Pilot Channel Structure for
`E-UTRA Uplink,” R1-060319, Agenda Item: 13.2.2.2, 3GPP TSG
`RAN WGl Meeting #44, Denver, CO, USA, Feb. 13-17, 2006, 7
`pages.
`Qualcomm Europe, “Principles of RACH,” Rl-060480, Agenda
`Item: 13.2.3.1, 3GPP TSG-RAN WGl LTE, Denver, CO, USA, Feb.
`13-17, 2006, 7 pages.
`
`* cited by examiner
`
`

`

`U.S. Patent
`
`Apr. 2, 2013
`
`Sheet 1 of 11
`
`US 8,411,557 B2
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`U.S. Patent
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`Apr. 2, 2013
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`Sheet 2 of 11
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`US 8,411,557 B2
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`US. Patent
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`Apr. 2, 2013
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`Sheet 3 of 11
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`US 8,411,557 B2
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`U.S. Patent
`
`Apr. 2, 2013
`
`Sheet 4 of 11
`
`US 8,411,557 B2
`
`CONTROL
`INFORMATION
`
`CAZAC SEQUENCE
`NUMBER: k
`
`
`
`SHIFT: m
`
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`US. Patent
`
`Apr. 2, 2013
`
`Sheet 5 of 11
`
`US 8,411,557 B2
`
`CONTROL
`INFORMATION
`
`
`
`FIG.5
`
`

`

`U.S. Patent
`
`Apr. 2, 2013
`
`Sheet 6 of 11
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`US 8,411,557 B2
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`U.S. Patent
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`Apr. 2, 2013
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`Sheet 7 of 11
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`US 8,411,557 B2
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`US. Patent
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`Apr. 2, 2013
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`Sheet 8 of 11
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`US 8,411,557 B2
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`
`TABLE
`
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`
`

`

`US. Patent
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`Apr. 2, 2013
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`Sheet 9 of 11
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`US 8,411,557 B2
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`
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`

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`U.S. Patent
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`Apr. 2, 2013
`
`Sheet 10 0f 11
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`US 8,411,557 132
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`US. Patent
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`Apr. 2, 2013
`
`Sheet 11 of 11
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`US 8,411,557 B2
`
`
`
`

`

`US 8,411,557 B2
`
`1
`MOBILE STATION APPARATUS AND
`RANDOM ACCESS METHOD
`
`TECHNICAL FIELD
`
`The present invention relates to a radio communication
`mobile station apparatus and a radio communication method.
`
`BACKGROUND ART
`
`Presently, studies are underway to use RACH (Random
`Access Channel) for initial access from a radio communica-
`tion mobile station apparatus (hereinafter simply “mobile
`station”) to a radio communication base station apparatus
`(hereinafter simply “base station”), in 3GPP RAN LTE (Long
`Term Evolution) (see Non-Patent Document 1). The RACH is
`utilized, for example, to make an association request and a
`resource request to the base station, and in initial access upon
`acquiring uplink transmission timing synchronization.
`A mobile station transmitting a RACH signal selects one of
`a plurality of unique signatures in the RACH and transmits
`the selected signature to the base station to distinguish itself
`from other mobile stations transmitting RACH signals.
`Moreover, in the RACH, taking into account that a plurality
`of signatures are transmitted from a plurality of mobile sta-
`tions at the same time, studies are underway to use code
`sequences having low cross-correlation and high autocorre-
`lation as signatures so as to demultiplex and detect those
`signatures in the base station. As a code sequence having such
`characteristics, the CAZAC (Constant Amplitude Zero Auto-
`Correlation) sequence is known, which is one of GCL (Gen-
`eralized Chirp-Like) sequences (see Non-Patent Document
`2).
`
`Furthermore, to reduce the processing delay after the initial
`access, studies are underway to report, in the RACH, control
`information including the mobile station ID, the reason for
`RACH transmission, bandwidth allocation request informa-
`tion (QoS information, the amount of data, and so on), and
`downlink received quality information (see Non-Patent
`Document 3).
`Non-patent Document 1: 3GPP TSG-RAN WGl LTE Ad
`Hoc Meeting, Rl-060047, NTT DoCoMo, NEC, Sharp,
`“Random Access Transmission in E-UTRA Uplink,” Hels-
`inki, Finland, 23-25 Jan., 2006
`Non-patent Document 2: 3GPP TSG-RAN WGl LTE Ad
`Hoc Meeting, Rl-060046, NTT DoCoMo, NEC, Sharp,
`“Orthogonal Pilot Channel Structure in E-UTRA Uplink,”
`Helsinki, Finland, 23-25 Jan., 2006
`Non-patent Document 3: 3GPP TSG-RAN WGl LTE Ad
`Hoc Meeting, Rl-060480, Qualcomm,
`“Principles of
`RACH,” Denver, USA, 13-17 Feb., 2006
`
`DISCLOSURE OF INVENTION
`
`Problems to be Solved by the Invention
`
`Various studies are presently conducted for a method for
`reporting control information in the RACH, and efficient
`reporting of control information in the RACH meets a strong
`demand.
`
`It is therefore an object of the present invention to provide
`a mobile station and radio communication method for effi-
`
`ciently reporting control information in the RACH.
`
`Means for Solving the Problem
`
`The mobile station of the present invention adopts a con-
`figuration including: a selecting section that selects one code
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`
`sequence from a base code sequence associated with control
`information to be reported and a plurality of derived code
`sequences derived from the associated base code sequence, or
`from a plurality of derived code sequences derived from the
`base code sequence associated with the control information to
`be reported; and a transmitting section that transmits the
`selected code sequence in a random access channel.
`The radio transmission method of the present invention
`includes steps of: selecting one code sequence from a base
`code sequence associated with control information to be
`reported and a plurality of derived code sequences derived
`from the corresponding base code sequence, or from a plu-
`rality of derived code sequences derived from the base code
`sequence associated with the control
`information to be
`reported; and transmitting the selected code sequence in a
`random access channel.
`
`Advantageous Effect of the Invention
`
`The present invention provides an advantage of reporting
`control information efficiently in the RACH.
`
`BRIEF DESCRIPTION OF DRAWINGS
`
`FIG. 1 is a block diagram showing the configuration of the
`mobile station according to Embodiment 1;
`FIG. 2 illustrates the CAZAC sequences according to
`Embodiment 1;
`FIG. 3 shows the control
`Embodiment 1;
`FIG. 4 is the reference table (table example 1) according to
`Embodiment 1;
`FIG. 5 is the reference table (a simplified version of the
`reference table in FIG. 4) according to Embodiment 1;
`FIG. 6 shows an example of control information multiplex-
`ing according to Embodiment 1;
`FIG. 7 shows the rate of occurrence of control information
`
`information according to
`
`according to Embodiment 1;
`FIG. 8 shows the reference table (table example 2) accord-
`ing to Embodiment 1;
`FIG. 9 shows the reference table (table example 3) accord-
`ing to Embodiment 2;
`FIG. 1 0 is a block diagram showing the configuration ofthe
`mobile station according to Embodiment 3; and
`FIG. 11 is the reference table (table example 4) according
`to Embodiment 3.
`
`BEST MODE FOR CARRYING OUT THE
`INVENTION
`
`invention will be
`Now, embodiments of the present
`described in detail with reference to the accompanying draw-
`ings.
`Embodiment 1
`
`FIG. 1 shows the configuration of mobile station 10 of the
`present embodiment.
`RACH generating section 11 is constructed of signature
`selecting section 111 and modulating section 112, and gen-
`erates a RACH signal as follows.
`Signature selecting section 111 selects one of a plurality of
`unique code sequences as a signature, according to inputted
`control information, and outputs the selected code sequence
`to modulating section 112.
`The signature selection (code sequence selection) will be
`described later in detail.
`
`

`

`US 8,411,557 B2
`
`4
`
`according to equation 6, the base code sequence found by
`equation 4, with CAZAC sequences
`similar
`to GCL
`sequences, a plurality of derived code sequences Ck,m(n) of
`respective numbers of cyclic shifts can be acquired from a
`base code sequence Ck(n).
`
`3
`Modulating section 112 modulates the signature (code
`sequence) to generate a RACH signal and outputs the RACH
`signal to multiplexing section 12.
`On the other hand, encoding section 13 encodes user data
`and outputs the encoded user data to modulating section 14.
`Modulating section 14 modulates the encoded user data
`and outputs the modulated user data to multiplexing section
`12.
`
`Multiplexing section 12 time-domain-multiplexes the
`RACH signal and the user data, and outputs the time-domain-
`multiplexed RACH signal and user data to radio transmitting
`section 15. That is, after the RACH signal transmission is
`completed, multiplexing section 12 outputs the user data to
`radio transmitting section 15.
`Radio transmitting section 15 performs radio processing
`including up-conversion on the RACH signal and user data,
`and transmits the result to the base station Via antenna 16.
`
`5
`
`10
`
`15
`
`(Equation 4)
`
`(Equation 5)
`
`
`'27rk
`+ 1
`Ck(n)=exp(jN (n+”(”2 U]
`where N is an odd number
`
`
`n2
`,5an
`Ck(n)=exp N n+3
`where N is an even number
`
`4
`[]
`
`[5]
`
`[6]
`
`Next, the signature selection (code sequence selection) will
`be described in detail.
`
`20
`
`(Equation 6)
`
`
`j27rk
`Ck,m(”) = exp N
`
`(n+m-A)modN+
`(n + m-A)modN - ((n + m-A)modN +1)
`2
`
`
`
`Although an example of cases will be explained below
`where the CAZAC sequence is used as a signature (code
`sequence), it is obvious from the above explanation that the
`present
`invention is also implemented when the GCL
`sequence is used as a signature (a code sequence).
`FIG. 2 shows, in CAZAC sequences, eight derived code
`sequences C1,O(n) to C1,7(n) of the numbers of cyclic shifts
`m:0 to 7 (i.e., shift 0 to 7) that can be generated from a single
`base code sequence (CAZAC sequence #1), given that the
`sequence length N is 293, the cyclic shift value A is 36 and k
`is 1. If k is 2 or greater, equally, eight derived code sequences
`may be generated from a single base code sequence. That is,
`if CAZAC sequences #1 to #8 are used as the base code
`sequences, sixty four code sequences in total can be utilized
`as signatures. A base code sequence and a derived code
`sequence where the shift is zero are the same. Moreover, the
`cyclic shift value A needs to be set greater than the maximum
`propagation delay time of signatures. This results from occur-
`ring error detection of signatures in the base station, if a
`plurality of mobile stations transmit a plurality of signatures
`at the same time and delay waves are received with delays
`beyond the cyclic shift value A, the base station is unable to
`decide whether it received signature with large delay time or
`it received signatures of different cyclic shift values. This
`maximum propagation delay time depends on the cell radius,
`that
`is,
`the distance of the maximum propagation path
`between the mobile station and the base station.
`
`In the present embodiment, the base code sequences and
`derived code sequences acquired as such associated with
`control information are used as the signatures.
`Signature selecting section 111 receives received quality
`information as, for example, control information shown in
`FIG. 3. Pieces of control information “000” to “111” are
`
`associated with received quality (i.e., SINRs) shown in FIG.
`3, respectively, and one of pieces of the control information
`“000” to “111” is inputted to signature selecting section 111
`as the control information to be reported.
`Signature selecting section 111, which has the table shown
`in FIG. 4, selects one of the signatures (code sequences) with
`reference to the table shown in FIG. 4 based on the inputted
`control information to be reported.
`
`In the present embodiment, GCL sequences or CAZAC
`sequences are used as signatures (code sequences).
`GCL sequence Ck(n) is given by equations 1 and 2. GCL
`sequence is a code sequence having high autocorrelation and
`low cross-correlation and having frequency response charac-
`teristics of constant amplitude. Here, N is an arbitrary integer
`and represents the sequence length. Moreover, k is an integer
`between 1 and N-1.
`
`Further, n represents the n-th in the code sequence length N
`and is an integer between 0 and N-1. The GCL sequence
`found by equations 1 and 2 serves as the base code sequence.
`
`(Equation 1)
`
`(Equation 2)
`
`
`CM”) = z)z-exp(j21\7lflC (fi-n+ ”(”24- DD
`where N is an odd number
`
`
`j27rk
`n2
`Ck(n) 2 oz - exp[
`N [47]]
`where N is an even number
`
`25
`
`30
`
`35
`
`40
`
`[2]
`
`45
`
`50
`
`55
`
`60
`
`65
`
`Here, to acquire a large number of GCL sequences of low
`cross-correlations, the sequence length N is preferably an odd
`number and a prime number. Then, if the sequence length N
`is an odd number, by cyclically shifting, according to equa-
`tion 3, the base code sequence given by equation 1, a plurality
`of derived code sequences Ck,m(n) of respective numbers of
`cyclic shifts, can be acquired from a base code sequence
`Ck(n).
`
`fi-(n+m-A)modN+
`
`[(n+m-A)modN-((n+m-A)modN +1) ]]
`
`2
`
`[3]
`
`(Equation 3)
`
`N
`
`j27rk
`
`0mm) = a-exp[
`
`Then, the GCL sequence where (X and [3 are 1 in equations
`1 to 3 is a CAZAC sequence, and the CAZAC sequences are
`code sequences of the lowest cross-correlation among GCL
`sequences. That
`is,
`the base code sequence of CAZAC
`sequence Ck(n) is found by equations 4 and 5. When the code
`sequence length N is an odd number, by cyclically shifting,
`
`

`

`US 8,411,557 B2
`
`5
`In this table, as shown in FIG. 4, control information “000”
`to “1 1 1” are provided in association with CAZAC sequences
`#1 to #8, which are the base code sequences. Furthermore, for
`each CAZAC sequence #1 to #8, control information “000” to
`“111” are provided in association with derived code
`sequences of shifts 0 to 7 derived from each CAZAC
`sequence #1 to #8. FIG. 5 shows a simplified version of the
`table shown in FIG. 4.
`
`In the table shown in FIG. 4, for example, the control
`information “000” is provided in association with CAZAC
`sequence #1 and derived code sequences of shifts 0 to 7
`derived from CAZAC sequence #1. The derived code
`sequences of shifts 0 to 7 of CAZAC sequence #1 correspond
`to signatures #1 to #8, respectively. Moreover, control infor-
`mation “001” is provided in association with CAZAC
`sequence #2 and derived code sequences of shifts 0 to 7
`derived from CAZAC sequence #2. The derived code
`sequences of shifts 0 to 7 of CAZAC sequence #2 correspond
`to signatures #9 to #16, respectively. The same applies to
`control information “010” to “111.” That is, in the present
`embodiment, one piece of control information is associated
`with a single base code sequence and a plurality of unique
`derived code sequences derived from this single base code
`sequence. Moreover, the unique 64 code sequences are asso-
`ciated with signatures #1 to #64.
`Then, when, for example, “000” is inputted as the control
`information to be reported, signature selecting section 111
`selects one code sequence from code sequences of shifts 0 to
`7 of CAZAC sequence #1 as the signature. The base code
`sequence and a derived code sequence of shift 0 are the same,
`so that signature selecting section 111 selects one code
`sequence as a signature from the base code sequence corre-
`sponding control information to be reported and a plurality of
`derived code sequences derived from the corresponding base
`code sequence, or from a plurality of derived code sequences
`derived from the base code sequence corresponding to the
`control information to be reported.
`Consequently, according to the present embodiment, the
`mobile station utilizes signatures as control information upon
`reporting control information in the RACH, so that the mobile
`station does not need to transmit control information in addi-
`tion to signatures.
`Moreover, the base station that receives a signature can
`detect control information by detecting the signature at the
`same time. In this way, according to the present embodiment,
`control information can be reported efficiently in the RACH.
`In the present embodiment, taking into account that a plu-
`rality of mobile stations transmit the identical control infor-
`mation at the same time, it is preferable that signature select-
`ing section 111 selects one of the eight code sequences
`corresponding to the inputted control information on a ran-
`dom basis. For example, when the control information “000”
`is inputted, taking into account that a plurality of mobile
`stations report identical control information “000” at the
`same time, signature selecting section 111 preferably selects
`one of code sequences (signatures #1 to #8) of shifts #0 to #7
`of CAZAC sequence #1 corresponding to the control infor-
`mation “000” on a random basis. Even when a plurality of
`mobile stations transmit the identical control information at
`the same time, this random selection reduces the likelihood of
`selecting the same code sequence between separate mobile
`stations, so that the base station is more likely to improve the
`likelihood of demultiplexing and detecting the signatures
`transmitted from the individual mobile stations.
`Moreover, a configuration may also be employed where
`signature selecting section 111 may select the code sequence
`associated with the control information to be reported from
`the code sequences prepared in advance (here, 64 code
`sequences #1 to #64), or select the CAZAC sequence number
`k and the number of shifts m associated with the control
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`information to be reported to generate a code sequence Cb,"
`(n) from equation 6 every selection.
`Whichever configuration is employed, as a result, signature
`selecting section 111 selects one of signatures
`(code
`sequences) based on control information to be reported.
`Here, a plurality of derived code sequences derived from a
`single base code sequence are completely orthogonal, and the
`cross-correlation is
`zero between these derived code
`sequences.
`On the other hand, although cross-correlation between a
`plurality of base code sequences is relatively low, these base
`code sequences are not completely orthogonal, and the cross-
`correlation is not zero. The same applies to derived code
`sequences derived from different code sequences.
`That is, a plurality of derived code sequences derived from
`a single base code sequence have a feature of having a lower
`cross-correlation than the cross-correlation between a plural-
`ity of base code sequences and the cross-correlation between
`derived code
`sequences derived from different code
`sequences.
`in the table shown in FIG. 4, with CAZAC
`That is,
`sequence #1 corresponding to control information “000” and
`CAZAC sequence #2 corresponding to control information
`“001,” the cross-correlation between the code sequences of
`shifts 0 to 7 of CAZAC sequence #1 is lower than the cross-
`correlation between CAZAC sequence #1 and CAZAC
`sequence #2 and the cross-correlation between the code
`sequences of shifts 0 to 7 of CAZAC sequence #1 and the
`code sequences of shifts 0 to 7 of CAZAC sequence #2. That
`is, the cross-correlation between the identical control infor-
`mation can be lower than the cross-correlation between dif-
`ferent control
`information by adopting the associations
`shown in FIG. 4.
`That is, as shown in FIG. 6, even when identical control
`information (“000”) is reported at the same time from a plu-
`rality of mobile stations (mobile stations A to C) and a plu-
`rality of signatures are multiplexed in the RACH, if code
`sequences with unique numbers of shifts (shifts 0, 3 and 7)
`derived from the same base code sequence (CAZAC
`sequence #1) are multiplexed as signatures,
`intersymbol
`interference between the signatures is ideally zero, and the
`performance of demultiplexing and detecting signatures in
`the base station hardly degrades compared with a case where
`multiplexing is not performed, even when the number of
`multiplexing increases.
`On the other hand, as shown in FIG. 6, when there is a
`mobile station (mobile station D) reporting different control
`information (“001”), code sequence (shift 2) derived from the
`different base code sequence (CAZAC sequence #2) is mul-
`tiplexed as a signature, and so the performance of demulti-
`plexing and detecting signatures in the base station degrades
`when the number of multiplexing increases.
`That is, the present embodiment is effective particularly
`when the identical control information is reported from a
`plurality ofmobile stations at the same time. The specific and
`identical control information is more likely to be reported
`from a plurality of mobile stations at the same time when the
`rate of occurrence of the pieces of control information is less
`uniform.
`For example, in a situation where there is a train station in
`the cell and there are always a large number ofmobile stations
`in a specific location in the cell, the mobile stations in this
`specific location are likely to have nearly uniform received
`quality, so that the specific and identical control information
`is likely to have a high rate of occurrence and are reported
`from a plurality of mobile stations at the same time.
`Moreover, received quality in a mobile station increases
`closer to the center of a cell where the base station is located
`and gradually decreases farther from the center of the cell.
`Further, this area increases as farther from the center of the
`
`

`

`US 8,411,557 B2
`
`5
`
`10
`
`20
`
`7
`cell. Accordingly, in the situation where mobile stations are
`uniformly distributed in the cell, as shown in FIG. 7, it is
`possible that when the rate of occurrence is high at lower
`received quality (SINR), there are a large number of mobile
`stations
`reporting control
`information showing lower
`received quality (SINR). Accordingly,
`in the situation as
`such, for control information showing lower received quality,
`the identical control information is likely to be reported from
`a plurality of mobile stations at the same time.
`That is, in this situation, the specific and identical control
`information is likely to be reported from a plurality ofmobile
`stations at the same time.
`it is
`In this way, according to the present embodiment,
`possible to keep the rate of detection of signatures and control
`information at the base station high, in the situation where 15
`there are a large number of mobile stations reporting the
`identical control information in the RACH.
`When the cell radius is small, the table shown in FIG. 8 may
`be used instead of the table shown in FIG. 4. That is, the
`maximum propagation delay time of the signatures is small
`and the cyclic shift value A can be less when the cell radius is
`small, so that, to decrease the cross-correlation between dif-
`ferent pieces of control information, as shown in FIG. 8, a
`plurality of pieces of control information may be associated
`with a single base code sequence. In the table shown in FIG.
`8, control information “000” to “011” are associated with 25
`CAZAC sequence #1, and control information “000” is asso-
`ciated with the code sequence of shifts 0 to 7 of CAZAC
`sequence #1 , control information “001” is associated with the
`code sequence of shifts 8 to 15 of CAZAC sequence #1,
`control
`information “010” is associated with the code 30
`sequence of shifts 16 to 23 of CAZAC sequence #1, and
`control
`information “011” is associated with the code
`sequence of shifts 24 to 31 of CAZAC sequence #1. More-
`over, control information “100” to “1 11” are associated with
`CAZAC sequence #2, control information “100” is associ- 35
`ated with the code sequence of shifts 0 to 7 of CAZAC
`sequence #2, control information “101” is associated with the
`code sequence of shifts 8 to 15 of CAZAC sequence #2,
`control
`information “110” is associated with the code
`sequence of shifts 16 to 23 of CAZAC sequence #2, and
`control
`information “111” is associated with the code
`sequence of shifts 24 to 31 of CAZAC sequence #2. These
`associations make it possible to associate different pieces of
`control information with derived code sequences of different
`shift values derived from a single base code sequence, so that
`it is possible to decrease the cross-correlation between differ- 45
`ent pieces of control information and keep the rate of detec-
`tion of signatures and control information at the base station
`high even when there are a large number of mobile stations
`reporting the different control information at the same time.
`Embodiment 2
`As shown in FIG. 7 above, there are cases where the rate of
`occurrence is not uniform between control information in the
`cell. That is, in such a case, it is preferable to assign more code
`sequences to control information occurred much.
`Now, the present embodiment does not employ tables
`(FIGS. 4, 5 and 8) that provide various pieces of control
`information in association with the same number of code
`sequences as in Embodiment 1. Instead, the present embodi-
`ment employs a table that associates control information of a
`higher rate of occurrence with more base code sequences or
`more derived code sequences, as shown in FIG. 9.
`When control information of high rate of occurrence is
`reported from a plurality of mobile stations at the same time,
`use ofthis table reduces the rate oftransmitting the same code
`sequences from a plurality of mobile stations, so that it is
`possible to reduce the rate of collisions between code 65
`sequences and to keep the rate of detection of signatures and
`control information at the base station high.
`
`40
`
`50
`
`55
`
`60
`
`8
`Moreover, at this time, when one piece of control informa-
`tion is provided in association with a plurality of base code
`sequences, to keep the cross-correlationbetween the identical
`control information low, it is preferable to associate derived
`code sequences derived from a single base code sequence
`preferentially. For example, when one piece of control infor-
`mation like control information “000” in FIG. 9 is provided in
`association with CAZAC sequences #1 and #2, control infor-
`mation “000” is preferentially associated with all derived
`code sequences derived from CAZAC sequence #1 and, the
`rest of the piece is associated with part of the derived code
`sequences derived from CAZAC sequence #2. That is, in the
`table shown in FIG. 9, one piece of control information is
`provided in association with a plurality of base code
`sequences and all of the derived code sequences derived from
`at least one of a plurality of the base code sequences.
`Moreover, although a case has been described above with
`the present embodiment where the number of code sequences
`assigned to each control information is determined according
`to the rate of occurrence of each control information, the
`number of code sequences assigned to each control informa-
`tion is determined according to, for example, the significance,
`priority, the number of retransmissions, and QoS of each
`control
`information. That
`is,
`the present embodiment
`employs the table that provides the pieces of control informa-
`tion in association with different numbers of base code
`sequences or different numbers of derived code sequences.
`Embodiment 3
`The rate of occurrence of control information changes in a
`cell. For example, at a single place in a cell, there are a number
`ofmobile stations in daytime larger than in nighttime, and the
`rate of occurrence for the specific and identical control infor-
`mation is higher in daytime than nighttime in such a case.
`Then, according to the present embodiment, the number of
`base code sequences or the number ofderived code sequences
`associated with pieces of control information change accord-
`ing to changes of the rate of occurrence of control informa-
`tion.
`FIG. 10 shows the configuration of mobile station 30
`according to the present embodiment. In FIG. 10, the same
`reference numerals will be assigned to the same component in
`FIG. 1 (Embodiment 1), and description thereof will be omit-
`ted.
`Radio receiving section 31 receives control signal trans-
`mitted from the base station via antenna 16, performs radio
`processing including d