JP5348281B2 - RADIO COMMUNICATION SYSTEM, ALLOCATION DEVICE, AND ALLOCATION METHOD USED FOR THEM - Google Patents

Description

  The present invention relates to a radio communication system, an allocation apparatus, an allocation method used therefor, and a mobile station using the same, and more particularly to pilot sequence allocation in a single carrier transmission scheme used in a radio access scheme.

  As an uplink radio access system in the next-generation radio communication system, a single carrier transmission system is dominant (see, for example, Non-Patent Document 1). FIG. 19 shows a configuration example of a frame format used in the single carrier transmission method proposed in Non-Patent Document 1.

  In FIG. 19, in one subframe (sub-frame), data signals are transmitted in six LBs (Long Blocks) # 1 to # 6, and two SBs (Short Blocks) # 1, It is assumed that a pilot signal is transmitted in # 2.

  Further, CP (Cyclic Prefix) is added to the preceding stage of LB # 1 to # 6 and SB # 1 and # 2 in order to effectively perform frequency domain equalization on the receiving side. Yes. Here, the addition of the CP means copying the rear part of the block to the front part of the block as shown in FIG.

  By the way, as a pilot signal used for uplink radio access in the next generation mobile communication system, currently, a Zadoff-Chu sequence (for example, non-patent) is one of CAZAC (Constant Amplitude Zero Auto-Correlation) sequences. Reference 2) is drawing attention.

Zadoff-Chu series is
C_k (n) = exp [− (j2πk / N) (n (n + 1/2) + qn)] (1)
It is expressed by the formula. In equation (1), n = 0, 1,..., N, q is an arbitrary integer, and N is a sequence length.

  The CAZAC sequence is a sequence that always has a constant amplitude in both time and frequency domains, and that the periodic autocorrelation value is always 0 (Zero Auto-Correlation) with respect to a time shift other than 0. Since this CAZAC sequence has a constant amplitude in the time domain, the PAPR (Peak to Average Power Ratio) can be kept small. Further, since the CAZAC sequence has a constant amplitude in the frequency domain, it is a sequence suitable for channel estimation in the frequency domain. Here, a small PAPR means that power consumption can be kept low, and this property is particularly preferred in mobile communications.

  Furthermore, since the “CAZAC sequence” has perfect autocorrelation characteristics, it has the advantage of being suitable for timing detection of received signals, and is a single carrier that is an uplink radio access method in the next-generation radio communication system. It attracts attention as a pilot sequence suitable for transmission.

  By the way, in a cellular environment (a wireless communication network having a service area divided into a plurality of cells), a base station can receive not only an uplink signal of a mobile station in its own cell but also another cell (particularly, an uplink received signal). The uplink signal of the mobile station in the adjacent cell is also received (see FIG. 1). As for the downlink signal, the mobile station receives not only the downlink signal from the base station of the own cell but also the downlink signal of the base station of the other cell, similarly to the uplink signal. Here, communication from the mobile station to the base station is called uplink, and communication from the base station to the mobile station is called downlink. Further, the above cell can be read as a sector.

  Therefore, in the uplink, in order for the base station to capture the pilot signal from the mobile station in its own cell, it is necessary to sufficiently suppress the pilot signal transmitted from the mobile station in the other cell, and the cross correlation It is desirable to assign a set of sequences having a small value as a pilot sequence of adjacent cells. Also in the downlink, for the same reason as in the above uplink, it is desirable to assign a set of sequences having a small cross-correlation value as a pilot sequence of cells adjacent to each other.

  Here, the cross-correlation characteristic of the CAZAC sequence greatly depends on the sequence length. That is, when the sequence length includes a prime number or a large prime number, the cross-correlation characteristics are very good (the cross-correlation value is small). Conversely, in the case of a composite number composed only of small prime numbers (for example, a power of 2 or 3), the cross-correlation characteristics are greatly degraded (a large value is included in the cross-correlation value).

  Specifically, when the sequence length of the Zadoff-Chu sequence is a prime number, the cross-correlation value between arbitrary sequences is always kept at 1 / √N (N is the sequence length and is now a prime number) (for example, Non-patent document 2). Therefore, for example, when the sequence length is N = 127, the cross-correlation value is always 1 / √127, whereas when the sequence length is N = 128, the worst value (maximum value) of the cross-correlation value. ) Becomes 1 / √2.

  In addition, there are abundant (N-1) sequences with cross-correlation values of 1 / √N. Therefore, from the viewpoint of cross-correlation values, it has been proposed to assign one CAZAC sequence for each cell as a pilot sequence with the same prime length and different parameters [parameters in equation (1)]. If such an assignment is made, the number of sequences can be (N−1), and the same pilot sequence can be reused for each (N−1) cells. Hereinafter, (N-1) is referred to as the number of pilot sequence repetitions.

  On the other hand, as in the uplink radio access frame format considered in the next generation radio communication system (see FIG. 19), the pilot sequence is composed of a plurality of blocks (two SBs # 1, # in the frame format shown in FIG. 19). In the case of transmission in 2), as described above, when one pilot sequence is assigned to each cell (that is, the transmission pilot sequence is common to a plurality of pilot blocks in the frame), the frame format shown in FIG. When the pilot sequences used for SB # 1 and # 2 are the same), the interference pattern from other cells is the same in any pilot block on the receiving side.

  As a result, there arises a problem that the effect of suppressing interference with other cells cannot be obtained by combining (averaging) a plurality of pilot blocks on the receiving side. This is because the pilot sequences transmitted in a plurality of pilot blocks are the same, so in any pilot block, the way of receiving interference (interference pattern) from other cells is the same, and they are combined (averaged) This is because the interference suppression effect cannot be obtained.

  In this regard, in the conventional W-CDMA (Wideband-Code Division Multiple Access) or the like, even if a common pilot sequence is used in a plurality of pilot blocks in a frame, a random sequence called a scrambling code is one frame. Therefore, the pattern of the transmitted pilot sequence is different for each pilot block. Therefore, by combining (averaging) a plurality of pilot blocks on the receiving side, interference with other cells A suppression effect can be obtained.

International Publication No. 2005/015797

"Physical Layer Aspects for Evolved UTRA" (3GPP TR25.814 v0.5.0 (2005-11), Chapter 9.1) K. Fazel and S.M. Keiser, “Multi-Carrier and Spread Spectrum Systems” (John Willy and Sons, 2003) Texas Instruments, On Uplink Pilot EUTRA SC-FDMA, 3GPP TSG RAN WG1 Ad Hoc LTE, October 14, 2005, R1-051062, URL, http: // www. 3 gpp. org / ftp / tsg_ran / WG1_RL1 / TSGR1_42bis / Docs / R1_051062. zip Freescale Semiconductor, Inc. , Connections on SC-FDMA Pilot Design, 3GPP TSG RAN WG1 Ad Hoc LTE, January 25, 2006, Tdoc R1-060153, URL, http: // www. 3 gpp. org / ftp / tsg_ran / WG1_RL1 / TSGR1_AH / LTE_AH_January-06 / Docs / R1_060153. zip

  However, the above-described conventional uplink radio access scheme has a restriction that a scrambling code cannot be applied when a sequence such as the CAZAC sequence is used as a pilot sequence. This is because, as a result of multiplying a sequence such as a CAZAC sequence by a random sequence such as a scrambling code, a specific characteristic [for example, CAZAC characteristics (a constant amplitude in the time / frequency domain and a periodic autocorrelation value other than zero) This is because a characteristic that is always very advantageous for reception, such as 0, is lost.

  Therefore, when a sequence such as a CAZAC sequence is used as a pilot sequence and only one code is assigned to one cell, an interference suppression effect can be obtained by combining (averaging) the received pilot blocks in one frame. The problem of not being able to be avoided.

  Therefore, an object of the present invention is to solve the above-described problems, and when a sequence such as a CAZAC sequence is used as a pilot sequence, a radio communication system capable of obtaining an interference suppression effect by combining received pilot blocks, An allocation apparatus, an allocation method used for the allocation apparatus, and a mobile station using the allocation method are provided.

A wireless communication system according to the present invention includes:
A wireless communication system including a plurality of cells, a mobile station, an allocation device that allocates a Zadoff-Chu sequence used for communication between a base station and a mobile station for the plurality of cells,
The allocation apparatus allocates a plurality of Zadoff-Chu sequences having different values of predetermined variables included in a Zadoff-Chu sequence to a plurality of blocks in one subframe, to one of the plurality of cells. ,
The mobile station transmits, to the base station, the subframe in which a plurality of Zadoff-Chu sequences having different values of predetermined variables included in the Zadoff-Chu sequence are assigned to a plurality of blocks in the subframe. And
A pilot sequence assigned to the block is different among a plurality of cells .

An allocation device according to the present invention comprises:
An allocation device that allocates a Zadoff-Chu sequence used for communication between a base station and a mobile station to each of a plurality of cells of a wireless communication system,
Means for assigning, to one of the plurality of cells, a plurality of Zadoff-Chu sequences having different values of predetermined variables included in the Zadoff-Chu sequence, to a plurality of blocks in one subframe;
A pilot sequence assigned to the block is different among a plurality of cells .

The allocation method according to the present invention comprises:
An allocation method for use in a wireless communication system, comprising: a plurality of cells; an allocation apparatus that allocates Zadoff-Chu sequences used for communication between a base station and a mobile station to the plurality of cells; and a mobile station. ,
The allocation apparatus allocates a plurality of Zadoff-Chu sequences having different values of predetermined variables included in the Zadoff-Chu sequence to a plurality of blocks in one subframe, to one of the plurality of cells. The pilot sequence assigned to the block is different among a plurality of cells that execute processing.

The mobile station according to the present invention
A mobile station that communicates with a base station of a wireless communication system,
To the base station, a plurality of blocks in one subframe, transmitting means for transmitting the subframe value of a predetermined variable in the Zadoff-Chu sequence is assigned a different Zadoff-Chu sequences, respectively I have a,
A pilot sequence assigned to the block is different among a plurality of cells .

  According to the present invention, with the configuration and operation as described above, when a sequence such as a CAZAC sequence is used as a pilot sequence, an interference suppression effect can be obtained by combining received pilot blocks. A remarkable effect is obtained.

It is a block diagram which shows the structure of the radio | wireless communications system by the 1st Embodiment of this invention. It is a figure which shows the cell arrangement pattern used for the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the pilot sequence allocation server of FIG. FIG. 2 is a block diagram illustrating a configuration example of a mobile station in FIG. 1. It is a figure which shows the structure of the allocation corresponding table which shows allocation of the pilot sequence by the 1st Embodiment of this invention. It is a figure which shows the notification of the pilot sequence in the radio | wireless communications system by the 1st Embodiment of this invention. It is a figure for demonstrating the effect by the allocation of the pilot sequence in the radio | wireless communications system by the 1st Embodiment of this invention. It is a figure which shows the structure of the allocation corresponding table which shows allocation of the pilot sequence by the 2nd Embodiment of this invention. It is a figure for demonstrating the effect by the allocation of the pilot sequence in the radio | wireless communications system by the 2nd Embodiment of this invention. It is a figure which shows the structure of the allocation corresponding table which shows allocation of the pilot sequence by the 3rd Embodiment of this invention. It is a figure which shows the structure of the allocation corresponding table which shows allocation of the pilot sequence by the 4th Embodiment of this invention. It is a figure which shows the structure of the allocation corresponding table which shows allocation of the pilot sequence by the 5th Embodiment of this invention. It is a block diagram which shows the system model of the simulation regarding this invention. It is a figure which shows the simulation result in this invention. (A)-(c) is a figure which shows the example of allocation of the pilot sequence to the pilot block (SB # 1, SB # 2) used for the simulation in this invention. (A)-(c) is a figure which shows the example of allocation of the pilot sequence to the pilot block (SB # 1, SB # 2) used for the simulation in this invention. It is a figure which shows the example of a parameter used for the simulation in this invention. It is a figure which shows the mode of the multiplexing of the data signal and pilot signal in the frequency domain of the simulation in this invention. It is a figure which shows the structural example of the frame format used for a single carrier transmission system. It is a figure for demonstrating addition of a cyclic prefix. It is a figure for demonstrating the problem by the allocation of the pilot sequence in the past.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a wireless communication system according to the first embodiment of the present invention. 1, the radio communication system according to the first embodiment of the present invention includes a pilot sequence allocation server 1, base stations (# 1 to # 3) 2-1 to 2-3, and mobile stations (# 1 to # 1). # 3) 3-1 to 3-3.

  In cells # 1 to # 3 managed by base stations (# 1 to # 3) 2-1 to 2-3, base stations (# 1 to # 3) 2-1 to 2-3 and mobile stations (# 1 ~ # 3) As communication between 3-1 to 3-3, a pilot sequence signal assigned by the method described below is transmitted. Here, communication from the mobile stations (# 1 to # 3) 3-1 to 3-3 to the base stations (# 1 to # 3) 2-1 to 2-3 is called uplink, and the mobile station ( # 1 to # 3) Communication to 3-1 to 3-3 is called downlink.

  As a wireless communication system according to the first embodiment of the present invention, a general wireless communication network having a service area divided into a plurality of cells # 1 to # 3 is assumed. A plurality of base stations (# 1 to # 3) 2-1 to 2-3 are bundled and connected to the pilot sequence allocation server 1. The pilot sequence allocation server 1 does not necessarily have to exist separately from the base stations (# 1 to # 3) 2-1 to 2-3, and a plurality of base stations (# 1 to # 3) 2-1 to It may be provided in any one of the base stations 2-3. Further, the pilot sequence allocation server 1 is provided in a host device (for example, a base station control device or a core network) (not shown) of the plurality of base stations (# 1 to # 3) 2-1 to 2-3. May be.

  FIG. 2 is a diagram showing a cell arrangement pattern used in the first embodiment of the present invention. FIG. 2 shows a 7-cell repetition pattern by seven base stations # 1 to # 7. The pilot sequence assignment server 1 assigns one of seven indexes # 1 to # 7 as shown in FIG. 2 to each connected base station. Based on the index, the pilot sequence allocation server 1 performs pilot sequence allocation as will be described later for every seven subordinate base stations.

  Further, it is used for transmitting communication data and pilot signals between the base stations (# 1 to # 3) 2-1 to 2-3 and the mobile stations (# 1 to # 3) 3-1 to 3-3. The frame format is configured as shown in FIG. In one subframe (sub-frame), data signals are transmitted in six LBs (Long Blocks) # 1 to # 6, and pilots are transmitted in two SBs (Short Blocks) # 1 and # 2. A signal shall be transmitted.

  That is, in the present embodiment, the number of pilot blocks in one frame is 2, the number of pilot sequence cell repetitions is 7, and the pilot sequence used for transmission is a Zadoff-Chu sequence expressed by equation (1). Is 7 equal to the number of cell repetitions. The sequence is {C_1, C_2, C_3, C_4, C_5, C_6, C_7}.

  Further, the pilot sequence allocation server 1 has cell repetition patterns of the connected base stations (# 1 to # 3) 2-1 to 2-3 (this means a cell arrangement pattern in which the same pilot patterns are not adjacent to each other). In this embodiment, it is assumed that a 7-cell repetitive pattern as shown in FIG.

  FIG. 3 is a block diagram showing a configuration example of the pilot sequence allocation server 1 of FIG. In FIG. 3, the pilot sequence allocation server 1 stores a CPU (central processing unit) 11, a main memory 12 that stores a control program 12a executed by the CPU 11, and data used when the CPU 11 executes the control program 12a. It is comprised from the memory | storage device 13 and the communication control apparatus 14 which controls communication with each base station (# 1- # 3) 2-1 to 2-3.

  The storage device 13 includes a cell repetition pattern storage area 131 for storing the cell repetition pattern, a pilot sequence storage area 132 for storing a pilot sequence, each base station (cells # 1 to #K), and a pilot sequence assigned to them. And an allocation correspondence table storage area 133 for storing an allocation correspondence table indicating the correspondence between the two.

  FIG. 4 is a block diagram showing a configuration example of the mobile stations (# 1 to # 3) 3-1 to 3-3 in FIG. In FIG. 4, a mobile station 3 includes a CPU 31, a main memory 32 that stores a control program 32a executed by the CPU 31, a storage device 33 that stores data used when the CPU 31 executes the control program 32a, and each base station. (# 1- # 3) It is comprised from the communication control apparatus 34 which controls communication with 2-1 to 2-3. The mobile stations (# 1 to # 3) 3-1 to 3-3 have the same configuration as the mobile station 3.

  FIG. 5 is a diagram showing an allocation correspondence table showing allocation of pilot sequences according to the first embodiment of the present invention, and FIG. 6 shows notification of pilot sequences in the radio communication system according to the first embodiment of the present invention. FIG. 7 is a diagram for explaining the effect of pilot sequence assignment in the wireless communication system according to the first embodiment of the present invention. The pilot sequence assignment operation in the radio communication system according to the first embodiment of the present invention will be described with reference to FIGS.

  In the wireless communication system according to the first embodiment of the present invention, 2K pilot sequences are represented as {[C_1, C_2], [C_3, C_4],... [C_ (2K-1), C_2K]}. A pilot allocation method is adopted in which each group is divided into K groups and any one of the pilot sequences is allocated to each of cells # 1 to #K (see FIG. 5).

  That is, in FIG. 5, two pilot sequences: {C_1, C_2} are assigned to two pilot blocks (SB # 1, # 2) of cell # 1, and two pilot blocks (SB #) of cell # 2 are assigned. 1, # 2) are assigned two pilot sequences: {C_3, C_4}, and two pilot blocks (SB # 1, # 2) of cell # 3 are assigned two pilot sequences: {C_5, C_6 }, And two pilot sequences: {C_7, C_8} are assigned to the two pilot blocks (SB # 1, # 2) of the cell # 4.

  Similarly, in FIG. 5, two pilot sequences: {C_ (2K-3), C_ (2K-2)} are included in the two pilot blocks (SB # 1, # 2) of the cell # (K-1). Are assigned, and two pilot sequences: {C_ (2K-1), C_2K} are assigned to the two pilot blocks (SB # 1, # 2) of the cell #K.

  The pilot sequence allocation server 1 transmits pilot sequence allocation information notifications to the base stations (# 1 to # 3) 2-1 to 2-3 based on the allocation correspondence table set as shown in FIG. Pilot sequences are assigned to the stations (# 1 to # 3) 2-1 to 2-3. Each of the base stations (# 1 to # 3) 2-1 to 2-3 moves by transmitting a downlink broadcast channel including an index of the assigned pilot sequence to the service areas in the cells # 1 to # 3. Broadcast to the stations (# 1 to # 3) 3-1 to 3-3 [notification of pilot sequences to the mobile stations (# 1 to # 3) 3-1 to 3-3] (see FIG. 6).

  The mobile stations (# 1 to # 3) 3-1 to 3-3 in the service area receive the downlink broadcast channel and the like, and thereby use two mobile stations (# 1 to # 3) in the cell (# 1 to # 3) where the own station exists An index of the pilot block (SB # 1, # 2) is obtained. When the mobile stations (# 1 to # 3) 3-1 to 3-3 transmit data to the base stations (# 1 to # 3) 2-1 to 2-3, Different pilot sequences are transmitted in SB # 1 and # 2 based on the index of the pilot block.

  At this time, since the interference pattern received by SB # 1 from a mobile station in another cell is different from the interference pattern received by SB # 2 from a mobile station in another cell, SB # 1 is assigned in the pilot sequence allocation according to the present embodiment. , # 2 is combined (averaged) and has the effect of suppressing other-cell interference (see FIG. 7).

  Thus, in the present embodiment, different pilot sequences can be transmitted in different pilot blocks (SB # 1, # 2) in one frame, thereby combining a plurality of received pilot blocks on the receiving side ( A significant effect is obtained that interference with other cells can be suppressed by averaging.

  As described above, in the present embodiment, since one sequence is not allocated per cell as in the prior art, two sequences are allocated per cell. It is conceivable that the number of cell repetitions decreases. In each embodiment described below, this point is devised, and the amount of interference from cells using the same code increases as the distance between base stations using the same pilot sequence decreases. Is also trying to improve. In the present embodiment, the method of assigning the uplink pilot sequence to each cell has been described. However, the same pilot sequence assignment method as described above can be applied to the method of assigning the downlink pilot sequence to each cell.

  FIG. 8 is a diagram showing an allocation correspondence table indicating pilot sequence allocation according to the second embodiment of the present invention, and FIG. 9 is a diagram illustrating pilot sequence allocation in the radio communication system according to the second embodiment of the present invention. It is a figure for demonstrating an effect.

  The radio communication system according to the second embodiment of the present invention has the same configuration as the radio communication system according to the first embodiment of the present invention shown in FIG. 1 except that the pilot sequence allocation method is different. Also, the pilot sequence allocation server according to the second embodiment of the present invention has the same configuration as the pilot sequence allocation server 1 according to the first embodiment of the present invention shown in FIG. Furthermore, the mobile station according to the second embodiment of the present invention has the same configuration as the mobile station 3 according to the first embodiment of the present invention shown in FIG. Furthermore, the cell arrangement pattern used in the second embodiment of the present invention is the same as the cell arrangement pattern used in the first embodiment of the present invention shown in FIG.

  The pilot sequence allocation server 1 assigns one of seven indexes from # 1 to # 7 as shown in FIG. 2 to each of the connected base stations (# 1 to # 3) 2-1 to 2-3. Assigned. Based on the index, the pilot sequence allocation server 1 performs the following pilot sequence allocation for every seven subordinate base stations.

  In FIG. 8, two pilot sequences: {C_K, C_ (K + 1)} (K = 1, 2, 6) for each cell of index #K (K = 1, 2,..., 7). The assignment correspondence table when assigning is shown. However, {C_7, C_1} is assigned only when K = 7. The pilot sequence allocation server 1 transmits pilot sequence allocation information notifications to the base stations (# 1 to # 3) 2-1 to 2-3 based on the allocation correspondence table set as shown in FIG. Pilot sequences are allocated to the base stations (# 1 to # 3) 2-1 to 2-3.

  Each base station (# 1 to # 3) 2-1 to 2-3 transmits a mobile station (# 1 to # 3) by transmitting a downlink broadcast channel including an index of an assigned pilot sequence to its service area. # 3) Broadcast to 3-1 to 3-3 [Pilot sequence notification to mobile stations (# 1 to # 3) 3-1 to 3-3]. The mobile stations (# 1 to # 3) 3-1 to 3-3 in the service area receive two broadcast blocks (SB # 1) used in the cell where the own station exists by receiving the downlink broadcast channel and the like. , # 2). And when the mobile stations (# 1 to # 3) 3-1 to 3-3 transmit data to the base stations (# 1 to # 3) 2-1 to 2-3, they are obtained from the downlink broadcast channel or the like. Based on the indexes of the two pilot blocks, different pilot sequences are transmitted in SB # 1 and # 2 as shown in FIG.

  That is, in FIG. 8, two pilot sequences: {C_1, C_2} are assigned to two pilot blocks (SB # 1, # 2) of cell # 1, and two pilot blocks (SB #) of cell # 2 are assigned. 1, # 2) are assigned two pilot sequences: {C_2, C_3}, and two pilot blocks of cell # 3 (SB # 1, # 2) are assigned two pilot sequences: {C_3, C_4 }, And two pilot sequences: {C_4, C_5} are assigned to the two pilot blocks (SB # 1, # 2) of the cell # 4.

  Similarly, in FIG. 8, two pilot sequences: {C_ (K-1), C_K} are assigned to two pilot blocks (SB # 1, # 2) of cell # (K-1), and the cell Two pilot sequences: {C_K, C_1} are assigned to two pilot blocks (SB # 1, # 2) of #K.

  As described above, in this embodiment, by reassigning a pilot sequence assigned to SB # 2 of a certain base station (cell) to SB # 1 of another base station (cell), cell repetition for pilot sequence reuse is performed. Different pilot sequences can be transmitted in different pilot blocks (SB # 1, # 2) in one frame without reducing the number. Thus, by combining (averaging) a plurality of received pilot blocks on the receiving side, a remarkable effect of suppressing other cell interference can be obtained without reducing the number of repeated pilot sequence cells.

  FIG. 10 is a diagram showing an allocation correspondence table showing pilot sequence allocation according to the third embodiment of the present invention. The radio communication system according to the third embodiment of the present invention has the same configuration as the radio communication system according to the first embodiment of the present invention shown in FIG. 1 except that the pilot sequence allocation method is different. Also, the pilot sequence allocation server according to the third embodiment of the present invention has the same configuration as the pilot sequence allocation server 1 according to the first embodiment of the present invention shown in FIG. Furthermore, the mobile station according to the third embodiment of the present invention has the same configuration as the mobile station 3 according to the first embodiment of the present invention shown in FIG. Furthermore, the cell arrangement pattern used in the third embodiment of the present invention is the same as the cell arrangement pattern used in the first embodiment of the present invention shown in FIG.

  The pilot sequence allocation server 1 assigns one of seven indexes from # 1 to # 7 as shown in FIG. 2 to each of the connected base stations (# 1 to # 3) 2-1 to 2-3. Assigned. Based on the index, the pilot sequence allocation server 1 performs the following pilot sequence allocation for every seven subordinate base stations.

  FIG. 10 shows an assignment correspondence table in the case where K cells for pilot assignment are divided into several regions (groups) and a set of pilot sequences is assigned to each divided region. The pilot sequence allocation server 1 transmits pilot sequence allocation information notifications to the base stations (# 1 to # 3) 2-1 to 2-3 based on the allocation correspondence table set as shown in FIG. Pilot sequences are allocated to the base stations (# 1 to # 3) 2-1 to 2-3.

  Each of the base stations (# 1 to # 3) 2-1 to 2-3 transmits the mobile station (# 1 to # 1) by transmitting to the service area of the own station via a downlink broadcast channel including an index of the assigned pilot sequence. # 3) Broadcast to 3-1 to 3-3 [Pilot sequence notification to mobile stations (# 1 to # 3) 3-1 to 3-3]. The mobile stations (# 1 to # 3) 3-1 to 3-3 in the service area receive two broadcast blocks (SB # 1) used in the cell where the own station exists by receiving the downlink broadcast channel and the like. , # 2). And when the mobile stations (# 1 to # 3) 3-1 to 3-3 transmit data to the base stations (# 1 to # 3) 2-1 to 2-3, they are obtained from the downlink broadcast channel or the like. Based on the indexes of the two pilot blocks, different pilot sequences are transmitted in SB # 1 and # 2.

  That is, in FIG. 10, cell # 1 and cell # 2 belong to the first division region, and two pilot sequences: {C_1, C_2} are assigned to these two cells # 1 and cell # 2. It has been. Two pilot sequences: {C_1, C_2} are assigned to the two pilot blocks (SB # 1, # 2) of the cell # 1 in the order of C_1, C_2. On the other hand, two pilot sequences: {C_1, C_2} are assigned to the two pilot blocks (SB # 1, # 2) of the cell # 2 in order of C_2 and C_1.

  Further, cell # 3 and cell # 4 belong to the second divided region, and two pilot sequences: {C_3, C_4} are assigned to these two cells # 3 and cell # 4. Two pilot sequences: {C_3, C_4} are assigned to the two pilot blocks (SB # 1, # 2) of the cell # 3 in the order of C_3, C_4. On the other hand, two pilot sequences: {C_3, C_4} are assigned in order of C_4 and C_3 to the two pilot blocks (SB # 1, # 2) of the cell # 4.

  Similarly, cell # (K-1) and cell #K belong to the K / 2 divided region, and these two cells # (K-1) and cell #K have two pilot sequences: {C_ (K-1), C_K} is assigned. Two pilot sequences: {C_ (K-1), C_K} are assigned in order of C_ (K-1) and C_K to the two pilot blocks (SB # 1, # 2) of the cell # (K-1). It is done. On the other hand, two pilot sequences: {C_ (K-1), C_K} are assigned to the two pilot blocks (SB # 1, # 2) of the cell #K in the order of C_K, C_ (K-1).

  Thus, in this embodiment, pilot sequence reuse is performed by reassigning pilot sequences assigned to SB # 1 and SB # 2 of a certain base station to SB # 2 and SB # 1 of another base station, respectively. Different pilot sequences can be transmitted in different pilot blocks (SB # 1, # 2) in one frame without reducing the number of cell repetitions. Thereby, in the present embodiment, a remarkable effect of suppressing other cell interference without reducing the number of cell repetitions of pilot sequence reuse by combining (averaging) a plurality of received pilot blocks on the receiving side. Is obtained.

  FIG. 11 is a diagram showing an assignment correspondence table showing assignment of pilot sequences according to the fourth embodiment of the present invention. The radio communication system according to the fourth embodiment of the present invention has the same configuration as the radio communication system according to the first embodiment of the present invention shown in FIG. 1 except that the number of pilot blocks in one frame is different. is there. Also, the pilot sequence allocation server according to the fourth embodiment of the present invention has the same configuration as the pilot sequence allocation server 1 according to the first embodiment of the present invention shown in FIG. Further, the mobile station according to the fourth embodiment of the present invention has the same configuration as the mobile station 3 according to the first embodiment of the present invention shown in FIG. The cell arrangement pattern used in the fourth embodiment of the present invention is the same as the cell arrangement pattern used in the first embodiment of the present invention shown in FIG. Furthermore, the pilot sequence allocation method according to the fourth embodiment of the present invention is the same as the pilot sequence allocation method according to the second embodiment of the present invention shown in FIG.

  That is, in FIG. 11, three pilot sequences: {C_1, C_2, C_3} are assigned to the three pilot blocks (SB # 1, # 2, # 3) of the cell # 1, and the three pilot blocks of the cell # 2 Three pilot sequences: {C_2, C_3, C_4} are assigned to the pilot block (SB # 1, # 2, # 3).

  In FIG. 11, three pilot sequences: {C_3, C_4, C_5} are assigned to the three pilot blocks (SB # 1, # 2, # 3) of the cell # 3, and the three pilot blocks of the cell # 4 Three pilot sequences: {C_4, C_5, C_6} are assigned to the pilot block (SB # 1, # 2, # 3).

  Similarly, in FIG. 11, three pilot sequences ({C_ (K-1), C_K, C_1) are included in three pilot blocks (SB # 1, # 2, # 3) of cell # (K-1). Are assigned, and three pilot sequences: {C_K, C_1, C_2} are assigned to the three pilot blocks (SB # 1, # 2, # 3) of the cell #K.

  Thus, in this embodiment, pilot sequence reuse is achieved by reassigning pilot sequences assigned to SB # 2 and SB # 3 of a certain base station to SB # 1 and SB # 2 of another base station. Different pilot sequences can be transmitted in different pilot blocks (SB # 1, # 2, # 3) in one frame without reducing the number of cell repetitions. Thereby, in the present embodiment, a remarkable effect of suppressing other cell interference without reducing the number of cell repetitions of pilot sequence reuse by combining (averaging) a plurality of received pilot blocks on the receiving side. Is obtained.

  FIG. 12 is a diagram showing an assignment correspondence table showing assignment of pilot sequences according to the fifth embodiment of the present invention. The radio communication system according to the fifth embodiment of the present invention has the same configuration as the radio communication system according to the first embodiment of the present invention shown in FIG. 1 except that the number of pilot blocks in one frame is different. is there. The pilot sequence allocation server according to the fifth embodiment of the present invention has the same configuration as the pilot sequence allocation server 1 according to the first embodiment of the present invention shown in FIG. Furthermore, the mobile station according to the fifth embodiment of the present invention has the same configuration as the mobile station 3 according to the first embodiment of the present invention shown in FIG. The cell arrangement pattern used in the fifth embodiment of the present invention is the same as the cell arrangement pattern used in the first embodiment of the present invention shown in FIG. Furthermore, the pilot sequence allocation method according to the fifth embodiment of the present invention is the same as the pilot sequence allocation method according to the second embodiment of the present invention shown in FIG.

  That is, in FIG. 12, four pilot sequences: {C_1, C_2, C_3, C_4} are assigned to the four pilot blocks (SB # 1, # 2, # 3, # 4) of the cell # 1, and the cell Four pilot blocks: {C_2, C_3, C_4, C_5} are assigned to the four pilot blocks (SB # 1, # 2, # 3, # 4) of # 2.

  In FIG. 12, four pilot sequences: {C_3, C_4, C_5, C_6} are assigned to the four pilot blocks (SB # 1, # 2, # 3, # 4) of the cell # 3, and the cell Four pilot blocks: {C_4, C_5, C_6, C_7} are assigned to the four pilot blocks (SB # 1, # 2, # 3, # 4) of # 4.

  Similarly, in FIG. 12, the four pilot blocks (SB # 1, # 2, # 3, # 4) of the cell # (K-1) have four pilot sequences: {C_ (K-1), C_K , C_1, C_2} are assigned, and four pilot sequences: {C_K, C_1, C_2, C_3} are assigned to the four pilot blocks (SB # 1, # 2, # 3, # 4) of the cell #K. It has been.

  Thus, in this embodiment, the pilot sequences assigned to SB # 2, SB # 3, and SB # 4 of a certain base station are reassigned to SB # 1, SB # 2, and SB # 3 of other base stations. Thus, different pilot sequences can be transmitted in different pilot blocks (SB # 1, # 2, # 3, # 4) in one frame without reducing the number of pilot sequence reuse cells. Thereby, in the present embodiment, a remarkable effect of suppressing other cell interference without reducing the number of cell repetitions of pilot sequence reuse by combining (averaging) a plurality of received pilot blocks on the receiving side. Is obtained.

  FIG. 13 is a block diagram showing a simulation system model related to the present invention, and FIG. 14 is a diagram showing simulation results related to the present invention. FIGS. 15 (a) to (c) and FIGS. 16 (a) to (c). FIG. 17 is a diagram showing an example of assignment of pilot sequences to pilot blocks (SB # 1, SB # 2) used in the simulation related to the present invention, and FIG. 17 is a diagram showing an example of parameters used in the simulation related to the present invention; FIG. 18 is a diagram showing how data signals and pilot signals are multiplexed in the frequency domain of the simulation relating to the present invention. The effects of the present invention will be described with reference to FIGS.

  As shown in FIG. 13, the simulation wireless communication system according to the present invention includes two cells, that is, the own cell A and another cell B. The own cell A includes the own cell base station 2 and the own cell user [mobile station (UE) 3a]. The other cell B includes another cell user [mobile station (UE) 3b]. The own cell base station 2 receives a signal from the own cell user [mobile station (UE) 3a], and also receives a signal from another cell user [mobile station (UE) 3b] as interference. Further, in the simulation related to the present invention, one frame of communication between the base station and the mobile station has two pilot blocks SB # 1 and SB # 2.

  FIG. 14 shows a block error rate characteristic of a signal received by the own cell base station 2 from the own cell user [mobile station (UE) 3a]. The dotted line is the result of using the same pilot sequence for SB # 1 and SB # 2 [FIG. 15 (a) Table # 1], and the solid line is the case using different pilot sequences for SB # 1 and SB # 2. FIG. 15B shows the result of table # 2.

  In the simulation related to the present invention, Localized FDM is used as the data (Data) multiplexing method, and Distributed-FDM pilot [1] (9.1.1.2.2 Uplink reference-signal structure) is used as the pilot multiplexing method. . Also, the pilot SRF (Symbol Repetition Factor) is set to 4. Further, the interference user from another cell is one user, the average interference power is set to -6 dB with respect to the average power of the own cell user, and the frame timings of the own cell user and the other cell user (interference user) are synchronized. Assuming that

  Furthermore, the pilot sequence uses the sequence described in the above equation (1) (“k” in the equation is a parameter), and pilot sequence allocation (allocation of parameter “k”) to each user and each SB is shown in FIG. It is as each table # 1- # 6 shown to (a)-(c) and Fig.16 (a)-(c). For reference, FIG. 18 shows data and pilot multiplexing in the frequency domain at this time, and FIG. 17 shows parameters used for the simulation.

  As shown in FIG. 14, it can be seen that Eb / No necessary for satisfying the block error rate = 10 <-1> is improved by nearly 1 dB. It can also be seen that Eb / No required to satisfy the block error rate = 3 · 10 −2 is improved by 2 dB or more.

  The table # 2 shown in FIG. 15 (b) assumes the pilot assignment of the second embodiment of the present invention described above, but the pilot assignment of the third embodiment of the present invention, that is, FIG. The same effect as described above can be obtained by assigning the table # 3 shown in FIG. Also, the same effect as described above can be obtained for pilot allocation [pilot sequence allocation as in table # 4 shown in FIG. 16A] according to the first embodiment of this invention.

  Further, as in tables # 5 and # 6 shown in FIGS. 16B and 16C, even if the pilot sequence used in SB # 1 is the same as that in other cells, the sequence used in SB # 2 is different. Thus, the effect that other-cell interference can be suppressed can be obtained. Similarly, even if SB # 2 uses the same sequence as that of the adjacent cell, the same effect as described above can be obtained if a sequence different from that of the adjacent cell is used in SB # 1. That is, if at least one of the pilot sequences assigned to the own cell is different from at least one of the pilot sequences assigned to another cell, the same effect as described above can be obtained. This is the same even when the number of SBs in one frame is 3 or more.

  In the present invention, as described above, the case where the number of pilot blocks in one frame is 2 to 4 is described. However, the present invention is applicable to the case where the number of pilot blocks is 5 or more, as in the case where the number of pilot blocks is 2 to 4.

1 Pilot sequence allocation server 2, 2-1 to 2-3 Base station (# 1 to # 3)
3-1 to 3-3 Mobile station (# 1 to # 3)
3a Self-cell user [mobile station (UE)]
3b Other cell users [mobile station (UE)]
11,31 CPU
12, 32 Main memory 12a, 32a Control program
13,33 storage device
14, 34 Communication control device
131 cell repetitive pattern storage area
132 Pilot sequence storage area
133 Allocation correspondence table storage area
A own cell
B Other cells

Claims (14)

A wireless communication system including a plurality of cells, a mobile station, an allocation device that allocates a Zadoff-Chu sequence used for communication between a base station and a mobile station for the plurality of cells,
The allocation apparatus allocates a plurality of Zadoff-Chu sequences having different values of predetermined variables included in a Zadoff-Chu sequence to a plurality of blocks in one subframe, to one of the plurality of cells. ,
The mobile station transmits, to the base station, the subframe in which a plurality of Zadoff-Chu sequences having different values of predetermined variables included in the Zadoff-Chu sequence are assigned to a plurality of blocks in the subframe. And
A wireless communication system , wherein pilot sequences allocated to the block are different among a plurality of cells .   2. At least one of a plurality of Zadoff-Chu sequences assigned to one of the plurality of cells is different from at least one of a plurality of Zadoff-Chu sequences assigned to different cells. The wireless communication system according to 1.   The radio communication system according to claim 1 or 2, wherein the subframe includes two blocks to which the Zadoff-Chu sequence is allocated.   4. The radio according to claim 3, wherein the assigning device divides the Zadoff-Chu sequence into sets for each number of blocks in the subframe, and assigns the sets to the plurality of cells one by one. Communications system.   The allocating device reuses the Zadoff-Chu sequence with the cell repetition number M (M is an integer of 2 or more), and the j-th block (j = j) of the cell i (i = 1, 2,..., M). 5. The wireless communication system according to claim 3, wherein the Zadoff-Chu sequence is allocated so that Zadoff-Chu sequences allocated to 1, 2) are different from each other in different cells.   The allocating device includes the Zadoff-Chu sequence so that a Zadoff-Chu sequence allocated to the j-th block of the cell i is different from a Zadoff-Chu sequence allocated to the j ′ (j ′ ≠ j) block of the cell i. The wireless communication system according to claim 5, wherein allocation is performed.   The allocation apparatus includes: a candidate for a sequence to reassign the Zadoff-Chu sequence assigned to the j-th block of the cell i to the j ′ (j ′ ≠ j) block of another cell i ′ (i ′ ≠ i); The wireless communication system according to claim 6.   The allocation device has a total number of the Zadoff-Chu sequences C_ (1), C_ (2),..., C_ (M) equal to the cell repetition number M, and the number N of blocks in the subframe is equal to the cell number. 8. The wireless communication system according to claim 7, wherein the number of repetitions is M or less (N ≦ M), and a sequence C _ ({(i + j−2) mod M} +1) is assigned to the j-th block of the cell i. .   The radio communication system according to any one of claims 1 to 8, wherein a sequence length of the Zadoff-Chu sequence is a prime number length. An allocation device that allocates a Zadoff-Chu sequence used for communication between a base station and a mobile station to each of a plurality of cells of a wireless communication system,
Means for assigning, to one of the plurality of cells, a plurality of Zadoff-Chu sequences having different values of predetermined variables included in the Zadoff-Chu sequence, to a plurality of blocks in one subframe;
An allocation apparatus , wherein pilot sequences allocated to the block are different among a plurality of cells . An allocation method for use in a wireless communication system, comprising: a plurality of cells; an allocation apparatus that allocates Zadoff-Chu sequences used for communication between a base station and a mobile station to the plurality of cells; and a mobile station. ,
The allocation apparatus allocates a plurality of Zadoff-Chu sequences having different values of predetermined variables included in the Zadoff-Chu sequence to a plurality of blocks in one subframe, to one of the plurality of cells. An allocation method characterized in that a pilot sequence allocated to the block is different among a plurality of cells that execute processing. A mobile station that communicates with a base station of a wireless communication system,
To the base station, a plurality of blocks in one subframe, transmitting means for transmitting the subframe value of a predetermined variable in the Zadoff-Chu sequence is assigned a different Zadoff-Chu sequences, respectively I have a,
A mobile station characterized in that a pilot sequence allocated to the block is different among a plurality of cells .   The mobile station according to claim 12, wherein the subframe includes two blocks to which the Zadoff-Chu sequence is allocated. The wireless communication system has a first cell and a second cell,
The mobile station according to claim 12 or 13, wherein at least one different Zadoff-Chu sequence is assigned to each of the first cell and the second cell.

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