INTEGRATED CIRCUIT
`
`BACKGROUND
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`Technical Field
`
`[0001]
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`The present disclosure relates to a sequence allocating method, transmitting
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`method and radio mobile station apparatus that are used in a cellular radio communication
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`system.
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`Description of the Related Art
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`[0002]
`
`In 3GPP LTE (3rd Generation Partnership Project Long Term Evolution), a
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`Zadoff-Chu sequence (“ZC sequence”’) is adopted as a reference signal (“RS”) that is used
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`10
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`in uplink. The reason for adopting a ZC sequence as an RSis that a ZC sequence has a
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`uniform frequency characteristic and has good auto-correlation and cross-correlation
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`characteristics. A ZC sequence is a kind of CAZAC (Constant Amplitude and Zero Auto-
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`correlation Code) sequence and represented by following equation 1 or equation 2.
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`[0003]
`
`In equation 1 and equation 2, “N” is the sequencelength, “r’ is the ZC
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`15
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`sequence number, and “N”and “r” are coprime. Also, “q” is an arbitrary integer. It is
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`possible to generate N-1 quasi-orthogonal sequences of good cross-correlation
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`characteristics from a ZC sequence having the sequence length N of a prime number. In
`this case, the cross-correlation is constant at VN between the N-1 quasi-orthogonal
`
`sequences generated.
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`20
`
`[0004]
`
`Here, in the RS’s that are used in uplink, the reference signal for channel
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`estimation used to demodulate data (i.e., DM-RS (Demodulation Reference Signal)) is
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`transmitted in the same bandasthe data transmission bandwidth. That is, when the data
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`transmission bandwidth is narrow, a DM-RSis also transmitted in a narrow band. For
`
`example, if the data transmission bandwidth is one RB (Resource Block), the DM-RS
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`25
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`transmission bandwidth is also one RB. Likewise, if the data transmission bandwidth is
`
`two RB’s, the DM-RStransmission bandwidth is also two RB’s. Also, in 3GPP LTE, one
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`

`

`RB is comprised of twelve subcarriers. Consequently, a ZC sequence having a sequence
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`length N of 11 or 13 is used as a DM-RSthatis transmitted in one RB, and a ZC sequence
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`having a sequence length N of 23 or 29 is used as a DM-RSthatis transmitted in two RB’s.
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`Here, when a ZC sequence having a sequence length N of 11 or 23 is used, a DM-RSof 12
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`subcarriers or 24 subcarriers 1s generated by cyclically expanding the sequence,that is, by
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`copying the head data of the sequenceto the tail end of the sequence. On the other hand,
`
`when a ZC sequence having a sequence length N of 13 or 29 is used, a DM-RSof 12
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`subcarriers or 24 subcarriers is generated by performingtruncation, that is, by deleting part
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`of the sequence.
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`10
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`[0005]
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`As a method ofallocating ZC sequences, to reduce the interference between
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`DM-RS’s that are used between different cells, that is, to reduce the inter-cell interference
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`of DM-RS, in each RB, ZC sequencesof different sequence numbersare allocated to
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`adjacent cells as DM-RS’s. The data transmission bandwidth is determined by the
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`scheduling in each cell, and therefore DM-RS’s ofdifferent transmission bandwidths are
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`15
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`multiplexed between cells. However, if ZC sequencesof different transmission
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`bandwidths, that is, ZC sequences of different sequence lengths, are multiplexed, a specific
`
`combination of ZC sequence numbershasa high cross-correlation.
`
`[0006]
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`FIG.1 is a diagram illustrating cross-correlation characteristics between ZC
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`sequences in combinations of different sequence numbers, which are acquired by computer
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`20
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`simulation, To be more specific, FIG.1 illustrates the cross-correlation characteristics
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`between a ZC sequence of a sequence length N=11 and sequence numberr=3, and ZC
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`sequences of a sequence length N=23 and sequence numbers r=1 to 6. In FIG.1, the
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`horizontal axis represents the delay time using the number of symbols, and the vertical axis
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`represents the normalized cross-correlation values, that is, the values dividing the cross-
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`25
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`correlation values by N. As shown in FIG.1, the maximum cross-correlation value is very
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`high with the combination of a ZC sequence of r=3 and N=11 and a ZC sequenceof r=6
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`and N=23, andis about three times higher than the cross-correlation value in the single
`transmission bandwidth, 1/VN,thatis, 1/V11.
`
`

`

`[0007]
`
`FIG.2 is a diagram illustrating the inter-cell interference of DM-RSin a case
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`where specific combinations of ZC sequencesthat increase cross-correlation are allocated
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`to adjacent cells. To be more specific, a ZC sequence of r=a and N=11 and a ZC sequence
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`of r=b and N=23 are allocated to cell #A, and a ZC sequence of r=c and N=23 and a ZC
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`sequence of r=d and N=11 are allocated to cell #B. In this case, the combination of the ZC
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`sequence of r=a and N=11 allocated to cell #A and the ZC sequence of r=c and N=23
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`allocated to cell #B, or the combination of the ZC sequence of r=b and N=23 allocated to
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`cell #A and the ZC sequence of r=d and N=11 allocated to cell #B, increases the inter-cell
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`interference of DM-RS, and, consequently, degrades the accuracy of channel estimation
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`10
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`and degrades the data demodulation performance degradessignificantly.
`
`[0008]
`
`To avoid such problems, the ZC sequenceallocating method disclosed in
`
`Non-Patent Document1 is used in a cellular radio communication system. To reduceinter-
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`cell interference, Non-Patent Document 1 suggests allocating a combination of ZC
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`sequences of high cross-correlation and different sequence lengths, to a single cell.
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`15
`
`[0009]
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`FIG.3 is a diagram illustrating the ZC sequenceallocating methods
`
`disclosed in Non-Patent Document 1 and Non-Patent Document 2. In FIG.3, the example
`
`shown in FIG.2 is used. As shown in FIG.3, a combination of ZC sequences of high cross-
`
`correlation, that is, a combination of a ZC sequence of r=a and N=11 and a ZC sequence of
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`r=c and N=23, is allocated to a single cell (cell #A in this case). Also, another combination
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`20
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`of ZC sequences of high cross-correlation, that is, a combination of a ZC sequence of r=d
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`and N=11 and a ZC sequence of r=b and N=23, is allocated to a single cell (cell #B in this
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`case). In the single cell, transmission bands are scheduled by oneradio basestation
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`apparatus, and, consequently, ZC sequences of high correlation allocated to the samecell,
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`are not multiplexed. Therefore, inter-cell interference is reduced.
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`25
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`[0010]
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`Also, Non-Patent Document 2 proposes a method of finding a combination
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`of ZC sequence numbers, which are used in RB’s (hereinafter referred to as a “sequence
`
`group”). ZC sequences have a feature of having higher cross-correlation when the
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`difference of r/N,that is, the difference of sequence number/ sequence length is smaller.
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`Therefore, based on a sequenceofan arbitrary RB (e.g., one RB), ZC sequences that make
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`

`

`the difference of r/N equal to or less than a predetermined threshold, are found from the ZC
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`sequences of each RB, and the multiple ZC sequences foundare allocated to a cell as one
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`sequence group.
`
`[0011]
`
`FIG.4 is a diagram illustrating a sequence group generation method
`
`disclosed in Non-Patent Document 2. In FIG.4, the horizontal axis represents r/N, and the
`
`vertical axis represents the ZC sequence of each RB. First, the reference sequence length
`
`Nb and reference sequence numberrb are set. Hereinafter, a ZC sequence having the
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`reference sequence length Nb and reference sequence numberrbis referred to as a
`
`“reference sequence.” For example, if Nb is 13 (which is the sequence length associated
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`10
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`with one RB) andrb is 1 (which is selected between 1 and Nb-1), rb/Nb is 1/13. Next, ZC
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`sequences that makethe difference of r/N from the reference rb/Nb equalto or less than a
`
`predetermined threshold, are found from the ZC sequences of each RB to generate a
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`sequence group. Also, the reference sequence numberis changed, and, in the same process
`
`as above, other sequence groups are generated. Thus, it is possible to generate different
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`15
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`sequence groups for the numberof reference sequence numbers,that1s, it 1s possible to
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`generate Nb-1 different sequence groups. Here, if ranges for selecting ZC sequences, in
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`which a difference from rb/Nb is equal to or less than a predetermined threshold, overlap
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`between adjacent sequence groups, the same ZC sequencesare includedin the plurality of
`
`sequence groups, and therefore the sequence numbers overlap between cells. Therefore, to
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`20
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`prevent ranges for selecting ZC sequences in adjacent sequence groups from overlapping,
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`the above predetermined threshold is set to, for example, a value less than 1/(2Nb).
`
`[0012]
`
`FIG.5A and FIG.5Billustrate examples of sequence groups generated by the
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`sequence group generation method disclosed in Non-Patent Document 2. Here, the
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`sequence length N is set to the prime numberthat is larger than the maximumpossible size
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`25
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`of transmission in the transmission bandwidth andthatis the closest to this size, and,
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`furthermore, the sequence length N is uniquely determined from the numberof RB’s.
`
`FIG.5A and FIG.5Billustrate sequence groups (ZC sequence group | and ZC sequence
`
`group 2) comprised of ZC sequencesthat satisfy following equation 3 in a case where the
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`reference sequence length Nb is 13 and the reference sequence numberrb is 1 or 2. In
`
`

`

`equation 3, the threshold Xth is, for example, 1/(2Nb),(7.e., 1/26) to prevent the same
`
`sequence from being included in a plurality of sequence groups.
`
`|rb/Nb-r/N| < Xth
`
`(Equation 3)
`
`[0013]
`
`Thus, according to the sequence allocating methods disclosed in Non-Patent
`
`Document 1 and Non-Patent Document 2, a sequence group comprised of ZC sequences
`
`that make a difference of r/N equal to or less than a predetermined threshold,that is, a
`
`sequence group comprised of ZC sequences having greater cross-correlation than a
`
`predetermined threshold, is generated, and the generated sequencegroupis allocated to the
`
`single cell. By this means, it is possible to allocate a combination of ZC sequences oflarge
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`10
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`cross-correlation and different sequence lengths to the single cell, and reduceinter-cell
`
`interference.
`
`Non-Patent Document 1: Huawei, R1-070367, “Sequence Allocating
`
`method for E-UTRA Uplink Reference Signal”, 3GPP TSG RAN WG1Meeting #47bis,
`
`Sorrento, Italy 15 -19 January, 2007
`
`15
`
`Non-Patent Document 2: LG Electronics, R1-071542, “Binding method for
`
`UL RSsequence with different lengths”, 3GPP TSG RAN WG1Meeting #48bis, St.
`
`Julians, Malta, March 26 — 30, 2007
`
`BRIEF SUMMARY
`
`Problems to be Solved by the Invention
`
`20
`
`[0014]
`
`However, with the sequence allocating method disclosed in Non-Patent
`
`Document2, the threshold Xth related to a difference of r/N 1s a fixed value regardless of
`
`the number of RB’s, and, consequently, the following problem arises.
`
`[0015]
`
`FIG.6 is a diagram illustrating a problem that arises when the threshold Xth
`
`is set higher. As shown in FIG.6,if the threshold Xth is set higher, ZC sequences located
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`25
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`near the boundary of adjacent sequence groups havea smaller difference of r/N, and
`
`therefore cross-correlation increases. That is, the cross-correlation between sequence
`
`groups increases.
`
`

`

`[0016]
`
`FIG.7A and FIG.7Billustrate problems that arise when the threshold Xth is
`
`set higher, using specific examples of sequence groups. In FIG.7A and FIG.7B, the
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`sequence group examples shown in FIG.SA and FIG.5B are used. In the ZC sequences
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`included in the two sequence groups (7.e., ZC sequence group 1 and ZC sequence group 2)
`
`shown in FIG.7A and FIG.7B, the hatched ZC sequences have a smaller difference of r/N
`
`from and larger cross-correlation with ZC sequences of other sequence groups. Here, as
`
`shownin FIG.4, the number of ZC sequences in each RB is N-1 at 1/N intervals in the
`
`range of r/N=0 to 1. Therefore, as shown in FIG.7A and FIG.7B, when the number of
`
`RB’s is larger, the number of ZC sequencesincreases that make a difference of r/N from a
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`10
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`reference ZC sequence smaller than a threshold. Also, when the number of RB’s is larger,
`
`that is, when the sequence length N is longer, the number of hatched ZC sequences
`
`increases.
`
`[0017]
`
`Bycontrast, when the threshold Xth is set smaller, the number of ZC
`
`sequences forming a sequence group decreases. Especially, when the number of RB’s is
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`15
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`smaller, that is, when the sequence length N is shorter, the number of sequencesthat are
`
`present in the range of r/N=0 to 1 at 1/N intervals, N-1, decreases, and, consequently, when
`
`the threshold is further smaller, the number of ZC sequences forming a sequence group
`
`further decreases. Also, to randomize the influence of interference, if sequence hopping to
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`switch sequence numbersat predetermined timeintervals is adapted and there are few
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`20
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`candidates of sequence numbersto be switched, the randomization of interference provides
`
`no effect.
`
`[0018]
`
`It is therefore an object of the present disclosure to provide a sequence
`
`allocating method that can reduce cross-correlation between different sequence groups
`
`while maintaining the number of ZC sequences forming a sequence groupthat are
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`25
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`allocated, in a cellular radio communication system.
`
`Meansfor Solving the Problem
`
`[0019]
`
`The sequence allocating method of the present disclosure for Zadoff-Chu
`
`sequences represented by equation 1 in a cellular radio communication system, includes: a
`
`

`

`referencesetting step of setting a reference sequence length Nb and a reference sequence
`
`numberrb; a first threshold setting step of setting a first threshold based on the sequence
`
`length N; a selecting step of selecting a plurality of Zadoff-Chu sequences, in which a first
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`difference representing a difference between rb/Nb and 1/N is equalto or less than the first
`
`threshold, from the Zadoff-Chu sequences generated according to the equation 1; and an
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`allocating step of allocating the plurality of Zadoff-Chu sequencesselected, to a samecell.
`
`[0020]
`
`The radio mobile station of the present disclosure that transmits Zadoff-Chu
`
`sequences represented by equation | as a reference signal, employs a configuration having:
`
`a setting section that sets a threshold based on a sequence length N signaled from a radio
`
`10
`
`base station apparatus; a selecting section that selects a Zadoff-Chu sequence, in which a
`
`difference between rb/Nb andr/N is equal to or less than the threshold, from the Zadoff-
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`Chu sequences generated according to equation 1, using a reference sequence numberrb
`
`and a reference sequence length Nb signaled from the radio base station apparatus; and a
`
`transmitting section that transmits the selected Zadoff-Chu sequenceas the reference
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`15
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`signal.
`
`[0021]
`
`The transmitting method of the present disclosure whereby a radio mobile
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`station apparatus transmits Zadoff-Chu sequences represented by equation 1 as a reference
`
`signal, in which the radio mobile station apparatus receives a sequence length N and a
`
`reference sequence numberrb signaled from the radio basestation apparatus; selects a
`
`20
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`Zadoff-Chu sequence, whichsatisfies a condition that a difference between rb/Nb (where
`
`Nb is a reference sequence length) and r/N is equalto or less than a threshold associated
`
`with the sequence length N, using the received sequence length N and the received
`
`reference sequence numberrb; and transmits the selected Zadoff-Chu sequence as the
`
`referencesignal.
`
`25
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`Advantageous Effect of Invention
`
`[0022]
`
`According to the present disclosure, it is possible to reduce cross-correlation
`
`between different groups while maintaining the number of ZC sequences forming sequence
`
`groups.
`
`

`

`BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
`
`[0023]
`
`FIG.1 is a diagram illustrating cross-correlation characteristics between ZC
`
`sequences in combinations of different sequence numbers, which are acquired by computer
`
`simulation, according to the priorart;
`
`FIG.2 is a diagram illustrating inter-cell interference between DM-RS’s in a
`
`case where specific combinations of ZC sequencesthat increase cross-correlation are
`
`allocated to adjacent cells, according to the priorart;
`
`FIG.3 is a diagram illustrating a method ofallocating ZC sequences
`
`10
`
`according to the priorart;
`
`FIG.4 is a diagram illustrating a method of generating sequence groups
`
`according to the priorart;
`
`FIG.5A is a diagram illustrating an example of a sequence group generated
`
`by a Sequence group generation method according to the prior art (ZC sequence group 1);
`
`15
`
`FIG.5B is a diagram illustrating an example of a sequence group generated
`
`by a sequence group generation method according to the prior art (ZC sequence group 2);
`
`FIG.6 is a diagram illustrating a problem with the prior art that arises when
`
`the threshold Xth is set higher;
`
`FIG.7Ais a diagram illustrating a problem with the priorart that arises
`
`20
`
`whenthe threshold Xth is set higher, using a detailed example of a sequence group (ZC
`
`sequence group 1);
`
`FIG.7B is a diagram illustrating a problem with the prior art that arises when
`
`the threshold Xth is set higher, using a detailed example of a sequence group (ZC sequence
`
`group2),
`
`25
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`FIG.8 is a flowchart showing the process of a sequence allocating method in
`
`a cellular radio communication system, according to Embodiment | of the present
`
`invention;
`
`FIG.9 is a diagram illustrating a method ofsetting a threshold in a sequence
`
`allocating method according to Embodiment | of the present invention;
`
`

`

`FIG.10A is a diagram illustrating an example of a sequence group acquired
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`by a sequence allocating method according to Embodiment1 of the present disclosure (ZC
`
`sequence group 1);
`
`FIG.10B is a diagram illustrating an example of a sequence group acquired
`
`by a sequence allocating method according to Embodiment1 of the present disclosure (ZC
`
`sequence group 2);
`
`FIG.11 is a diagram illustrating a method of setting a threshold according to
`
`a sequence allocating method according to Embodiment1 of the present invention;
`
`FIG.12A is a diagram illustrating an example of a sequence group acquired
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`10
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`by a sequence allocating method according to Embodiment1 of the present disclosure (ZC
`
`sequence group 1);
`
`FIG.12B is a diagram illustrating an example of a sequence group acquired
`
`by a sequence allocating method according to Embodiment1 of the present disclosure (ZC
`
`sequence group 2);
`
`15
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`FIG.13 is a block diagram showing the configuration of a radio base station
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`apparatus to which a sequencegroupis allocated, according to Embodiment1 of the
`
`present invention;
`
`FIG.14 is a block diagram showing the configuration inside a ZC sequence
`
`setting section according to Embodiment 1 of the present invention;
`
`20
`
`FIG.15 is a block diagram showing the configuration of a radio mobile
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`station apparatus according to Embodiment | of the present invention;
`
`FIG.16 is a diagram illustrating the cross-correlation characteristic
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`ascertained by computer simulation according to Embodiment 2 of the present invention;
`
`FIG.17 is a flowchart showing the process of a sequenceallocating method
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`25
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`in a cellular radio communication system according to Embodiment2 of the present
`
`invention;
`
`FIG.18 is a diagram illustrating a method of generating sequence groups
`
`based on the process of a sequence allocating method according to Embodiment2 of the
`
`present invention;
`
`

`

`FIG.19A is a diagram illustrating an example of a sequence group acquired
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`by a sequenceallocating method according to Embodiment2 of the present disclosure (ZC
`
`sequence group 1);
`
`FIG.19B is a diagram illustrating an example of a sequence group acquired
`
`by a sequenceallocating method according to Embodiment2 of the present disclosure (ZC
`
`sequence group8);
`
`FIG.20Ais a diagram illustrating an example of a sequence group acquired
`
`when the number of RB’s allowing sequencesto be deleted, is set 10 or greater (ZC
`
`sequence group 1); and
`
`10
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`FIG.20B is a diagram illustrating an example of a sequence group acquired
`
`when the number of RB’s allowing sequencesto be deleted, is set 10 or greater (ZC
`
`sequencegroup 8).
`
`DETAILED DESCRIPTION
`
`[0024]
`
`Embodiments of the present disclosure will be explained below in detail
`
`15
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`with reference to the accompanying drawings. Here, in these embodiments, components
`
`providing the same functions will be assigned the same reference numerals and overlapping
`
`explanations will be omitted.
`
`[0025]
`
`Embodiment 1
`
`FIG.8 is a flowchart showing the process of a sequence allocating method in
`
`20
`
`a cellular radio communication system according to Embodiment 1 of the present
`
`disclosure.
`
`[0026]
`
`First, in step (hereinafter “ST”’) 101, the reference sequence length Nb and
`
`the reference sequence numberrb are set for a generated sequence group. Here, the
`
`sequence numberrb corresponds to the sequence group numberand is lower than Nb.
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`25
`
`[0027]
`
`[0028]
`
`In ST 102, the number of RB’s, m,is initialized to 1.
`
`In ST 103, the threshold Xth(m)associated with the number of RB’s m is
`
`set. Here, the method ofsetting the threshold Xth(m) will be describedlater.
`
`10
`
`

`

`[0029]
`
`In ST 104, the ZC sequence length N associated with the number of RB’s m
`
`is set. The number of RB’s “m”and the sequence length N are uniquely associated. For
`
`example, N is a prime numberthatis larger than the maximumpossible size of
`
`transmission with the number of RB’s, m, and thatis the closest to this size.
`
`[0030]
`
`[0031]
`
`In ST 105, the sequence numberr is initialized to 1.
`
`In ST 106, whether or not r and N satisfy following equation 4 is decided.
`
`|t/N-rb/Nb|<Xth(m)
`
`(Equation 4)
`
`[0032]
`
`Following equation 5 is acquired from equation 4. Given that equation 4
`
`and equation 5 are equivalent, in ST 106, whether or not r and N satisfy equation 5 may be
`
`10
`
`decided.
`
`(rb/Nb-Xth(m))*N<r<(rb/Nb+Xth(m))*N
`
`(Equation 5)
`
`[0033]
`
`In ST 106, if r and N are decidedto satisfy equation 4 (“YES” in ST 106),
`
`the process of ST 107 is performed.
`
`[0034]
`
`In ST 107, a ZC sequence having a sequence numberofris determined as
`
`15
`
`one of ZC sequences associated with the number of RB’s m in the sequence grouprb.
`
`[0035]
`
`In ST 106, when r and N are decided notto satisfy equation 4 (“NO” in ST
`
`106), the process of ST 108 is performed.
`
`[0036]
`
`In ST 108, whether or not r<N is decided.
`
`[0037]
`
`In ST 108, if r<N is decided (“YES”in ST 108), the process of ST 109 is
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`20
`
`performed.
`
`[0038]
`
`In ST 109, the sequence numberr is incremented by 1 like r=r+1, and the
`
`process moves to ST 106.
`
`[0039]
`
`In ST 108, if r<N is not decided (‘NO”in ST 108), the process of ST 110 is
`
`performed.
`
`25
`
`[0040]
`
`In ST 110, whether or not m<Mis decided. Here, M is the maximum value
`
`of the number of RB’s in the sequence group rb and corresponds to the maximum value of
`
`the transmission bandwidth.
`
`11
`
`

`

`[0041]
`
`In ST 110, if m<M is decided (“YES”in ST 110), the process of ST 111 1s
`
`performed.
`
`[0042]
`
`In ST 111, the number of RB’s m is incremented by one, like m=m+1, and
`
`the process movesto ST 103.
`
`[0043]
`
`In ST 110, if m<M is not decided (“NO” in ST 110), the process of ST 112
`
`is performed.
`
`[0044]
`
`In ST 112, the generated sequence grouprb is allocated to a single cell, that
`
`is, a single radio base station apparatus.
`
`[0045]
`
`Next, the method ofsetting the threshold Xth(m)will be explained using
`
`10
`
`two different cases. In above ST 103, it is possible to use either of following setting
`
`method 1 andsetting method2.
`
`[0046]
`
`threshold Xth(m) setting method 1
`
`FIG.9 is a diagram illustrating threshold Xth(m) setting method | in a
`
`sequence allocating method according to the present embodiment. As shown in FIG.9, the
`
`15
`
`threshold Xth(m)is set smaller when an RB is greater. For example, as shownin following
`
`equation 6, the Xth(m) is set to decrease by a predetermined value every time the number
`
`of RB’s m increases.
`
`Xth(m)=1/(2Nb)-(m-1)*0.0012
`
`(Equation 6)
`
`[0047]
`
`Bysetting the threshold Xth(m) in this way, ZC sequences located near the
`
`20
`
`boundary of adjacent sequence groups havea greater difference ofr/N, so that it is possible
`
`to suppress an increase of cross-correlation. Also, by increasing the threshold Xth(m)
`
`associated with a smaller number of RB’s,it is possible to increase the number of ZC
`
`sequences and maintain it above a predetermined number.
`
`[0048]
`
`FIG.10A and FIG.10Billustrate examples of sequence groups acquired by
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`25
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`the sequenceallocating methods shown in FIG.8 and FIG.9. To be morespecific, the
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`sequence groups shown in FIG.10A and FIG.10B are acquired according to the following
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`conditions and process. For example, to generate ZC sequence group 1 shown in FIG.10A,
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`in ST 101, Nb=13 and rb=1 are set. Here, Nb=13 represents the sequence length associated
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`12
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`

`

`with the number of RB’s m=1, and the sequence numberrb=1 correspondsto the sequence
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`group number. Next, in the process of ST 102, the threshold Xth(m) associated with the
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`numberof RB’s is set using above equation 6, and, in the process of ST 104 to ST 107, the
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`sequence numberr that makes the difference between rb/Nb andr/N equalto or less than
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`the threshold Xth(m)is selected, to generate ZC sequence group 1. The conditions and
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`process for generating ZC sequence group 2 shown in FIG.10B differ from those in the
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`case of ZC sequencegroup 1, only in setting the reference sequence numberrb to 2 in ST
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`101.
`
`[0049]
`
`threshold Xth(m) setting method 2
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`10
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`FIG.11 is a diagram illustrating threshold Xth(m) setting method 2 in a
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`sequence allocating method according to the present embodiment. As shown in FIG.11, a
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`threshold for the number of RB’s “m”is set, and threshold Xth(m)is set higher below the
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`threshold for the number of RB’s than above the threshold for the number of RB’s. For
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`example, as shown in following equation 7, the threshold for the number of RB’s m is 10,
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`15
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`and, if the number of RB’s m is equal to or lower than 10, Xth(m)is set to 1/2 Nb, and,if
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`the number of RB’s m is higher than 10, Xth(m)is set to 1/4 Nb. Thatis, the threshold
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`Xth(m) is switched between twofixed values across the sequence length N associated with
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`the number of RB’s of 10, and the fixed value associated with the sequence lengths N’s
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`associated with the numbers of RB’s equal to or less than 10 is set lower than the fixed
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`20
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`value associated with the sequence lengths N’s associated with the numbers of RB’s
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`greater than 10.
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`Xth(m)=1/(2Nb) (in the case of 1<m<10)
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`Xth(m)=1/(4Nb)(in the case of m>11)
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`(Equation 7)
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`[0050]
`
`Bysetting the threshold Xth(m) in this way, ZC sequences located near the
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`25
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`boundary of adjacent sequence groups havea grater difference ofr/N, so that it is possible
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`to suppress an increase of cross-correlation. Also, by increasing the threshold Xth(m)
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`associated with the numbers of RB’s lower than the threshold for the number of RB’s m,it
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`13
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`

`

`is possible to increase the number of ZC sequences and maintain it above a predetermined
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`number.
`
`[0051]
`
`FIG.12A and FIG.12Billustrate examples of sequence groups acquired by
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`the sequenceallocating methods shown in FIG.8 and FIG.11. To be morespecific, the
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`conditions and process for acquiring the sequence groups shown in FIG.12A and FIG.12B
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`(i.e., ZC sequence group | and ZC sequence group 2) differ from the conditions and
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`process for acquiring the sequence groups shown in FIG.10A and FIG.10B (i.e., ZC
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`sequence group | and ZC sequencegroup 2), only in using equation 7, instead of equation
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`6, for the method of setting the threshold Xth(m).
`
`10
`
`[0052]
`
`Next, the operations of a radio base station apparatus that is present in a cell,
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`to which sequence groups generated based on the sequence allocating method according to
`
`the present embodimentare allocated, will be explained.
`
`[0053]
`
`FIG.13 is a block diagram showing the configuration of radio base station
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`apparatus 100, to which sequencegroups are allocated, according to the present
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`15
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`embodiment.
`
`[0054]
`
`Encoding section 101 encodes transmission data and control signal for a
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`radio mobile station apparatusthat is present in the samecell as that of radio base station
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`apparatus 100, and outputs the encoded data to modulating section 102. Here, the control
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`signal includes the reference sequence length Nb and the reference sequence numberrb
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`20
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`associated with the sequence group number, and the reference sequence length Nb and the
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`reference sequence numberrb are transmitted to, for example, radio mobile station
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`apparatus 200, which will be described later, via a broadcast channel. The control signal
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`also includes scheduling information showing the transmission bandwidth including, for
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`example, the number of RB’s for transmission allocated to radio mobile station 200 and the
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`25
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`sequence length N, and this scheduling information is transmitted to radio mobile station
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`apparatus 200 via a control channel.
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`[0055]
`
`Modulating section 102 modulates the encoded data received as input from
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`encoding section 101 and outputs the modulated signal to RF (Radio Frequency)
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`transmitting section 103.
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`14
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`

`

`[0056]
`
`RF transmitting section 103 performs transmission processing such as A/D
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`conversion, up-conversion and amplification on the modulated signal received as input
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`from modulating section 102, and transmits the signal subjected to transmission processing
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`via antenna 104.
`
`[0057]
`
`RF receiving section 105 performs reception processing such as down-
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`conversion and A/D conversion on a signal received via antenna 104, and outputs the
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`signal subjected to reception processing to demultiplexing section 106.
`
`[0058]
`
`Demultiplexing section 106 demultiplexes the signal received as input from
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`RF receiving section 105 into a reference signal, data signal and control signal, outputs the
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`10
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`reference signal to DFT (Discrete Fourier Transform) section 107 and outputs the data
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`signal and control signal to DFT section 114.
`
`[0059]
`
`DFT section 107 transforms the time domain reference signal received as
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`input from demultiplexing section 106 into a frequency domain signal by performing DFT
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`processing, and outputs the transformed, frequency domain reference signal to demapping
`
`15
`
`section 109 in channel estimating section 108.
`
`[0060]
`
`Channel estimating section 108 is provided with demapping section 109,
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`dividing section 110, IFFT section 111, mask processing section 112 and DFT section 113,
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`and estimates the channel based on the reference signal received as input from DFT section
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`107.
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`20
`
`[0061]
`
`Demapping section 109 extracts, from the frequency band referencesignal
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`received as input from DFT section 107, a ZC sequence correspondingto the transmission
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`band of each radio mobile station apparatus 200, and outputs the extracted ZC sequences to
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`dividing section 110.
`
`[0062]
`
`ZC sequencesetting section 1000 calculates the ZC sequences usedin radio
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`25
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`mobile station apparatuses 200, based on the reference sequence length Nb, the reference
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`sequence numberrb and the number of RB’s assignedto each radio mobile station
`
`apparatus 200, which are included in control information received as input, and outputs the
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`results to dividing section 110. Here, the internal configuration and operations of ZC
`
`sequencesetting section 1000 will be describedlater.
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`15
`
`

`

`[0063]
`
`Dividing section 110 divides the ZC sequences correspondingto each radio
`
`mobile station apparatus 200, calculated in ZC sequencesetting section 1000, by the ZC
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`sequencesactually used in each radio mobile station apparatus 200 and received as input
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`from demapping section 109, and outputs the division result to IFFT (Inverse Fast Fourier
`
`Transform) section 111.
`
`[0064]
`
`IFFT section 111 performs IFFT processing on the division result received
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`as input from dividing section 110, and outputs the signal subjected to IFFT processing to
`
`mask processing section 112.
`
`[0065]
`
`Maskprocessing section 112 extracts the correlation value in the region in
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`10
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`which the correlation value of the desired cyclic shift sequence is present, that is, extracts
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`the correlation value in the windowpart, by performing mask processing on the signal
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`received as input from IFFT section 111, and outputs the extracted correlation value to
`
`DFT section 113.
`
`[0066]
`
`DFT section 113 performs DFT processing on the correlation value received
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`15
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`as input from mask processing section 112, and outputs the correlation value subjected to
`
`DFT processing to frequency domain equalization section 116. Here, the signal subjected
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`to DFT processing outputted from DFT section 113, represents the frequency response of
`
`the channel.
`
`[0067]
`
`DFT section 114 transforms the time domain data signal and control signal
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`20
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`received as input from demultiplexing section 106, into the frequency domain by
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`performing DFT processing, and outputs the transformed, frequency domain data signal
`
`and control signal to demapping section 115.
`
`[0068]
`
`Demapping section 115 extracts the data signal and control signal
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`corresponding to the transmission band of each radio mobile st