JP2023099053A - mobile station - Google Patents

Abstract

To provide an allocation method capable of obtaining interference suppression effect by combining a reception pilot block in a case of using a sequence such as a CAZAC sequence as a pilot sequence.SOLUTION: According to an embodiment, an allocation method includes dividing 2K pilot sequences into K groups like {[C_1,C_2], [C_3,C_4],..., [C_(2K-1),C_2K]}, and allocating one pair of pilot sequence to each cell #1 to #K. For example, the pilot sequence {C_1,C_2} is allocated to a pilot block (SB#1,#2) in the cell #1, the pilot sequence {C_3,C_4} is allocated to a pilot block (SB#1,#2) of the cell #2, the pilot sequence {C_5,C_6} is allocated to a pilot block (SB#1,#2) of the cell #3, and the pilot sequence {C_7,C_8} is allocated to a pilot block (SB#1,#2) of the cell #4.SELECTED DRAWING: Figure 5

Description

The present invention relates to a mobile station, a base station, an allocation device, a system using them, and a method for using them, and more particularly to allocation of pilot sequences in a single-carrier transmission system used in a radio access system.

A single-carrier transmission scheme is likely to be an uplink radio access scheme in next-generation wireless communication systems (see, for example, Non-Patent Document 1). FIG. 19 shows a configuration example of a frame format used in the single-carrier transmission system proposed in Non-Patent Document 1. In FIG.

In FIG. 19, in one sub-frame (sub-frame), data signals are transmitted in six LB (Long Block) #1 to #6, and two SB (Short Block) #1, It is assumed that the pilot signal is transmitted at #2.

In addition, a CP (Cyclic Prefix) is added in front of these LB#1 to #6 and SB#1, #2 in order to effectively perform frequency domain equalization on the receiving side. there is Here, adding a 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 next-generation mobile communication systems, at present, a Zadoff-Chu sequence (for example, non-patented Reference 2) is attracting attention.

The Zadoff-Chu sequence is
C_k(n)=exp[-(j2πk/N)(n(n+1)/2+qn)] (1)
is represented by the formula (1), n=0, 1, . . . , N, q is an arbitrary integer, and N is the sequence length.

A CAZAC sequence is a sequence that has a constant amplitude in both the time and frequency domains and has a periodic autocorrelation value that is always 0 (zero auto-correlation) with respect to a time lag 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. Also, since the CAZAC sequence has a constant amplitude even 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, the "CAZAC sequence" has perfect autocorrelation characteristics, so it has the advantage of being suitable for timing detection of received signals, and is the uplink radio access scheme in the above-mentioned next-generation wireless communication system. It is attracting 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 receives uplink signals not only from mobile stations in its own cell but also from other cells (especially , adjacent cells) are also received (see FIG. 1). As for the downlink signal, the mobile station receives not only the downlink signal from the base station of its own cell but also the downlink signal from the base stations of other cells, 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. Also, the above cells can be read as sectors.

Therefore, in the uplink, in order for the base station to acquire pilot signals from mobile stations in its own cell, it is necessary to sufficiently suppress pilot signals transmitted from mobile stations in other cells. It is desirable to assign the set of sequences with lower values as pilot sequences for neighboring cells. Also in the downlink, for the same reason as in the uplink, it is desirable to allocate a set of sequences with small cross-correlation values as pilot sequences for adjacent cells.

Here, the cross-correlation property of the CAZAC sequence greatly depends on its 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 composite numbers (for example, powers of 2 and 3) composed only of small prime numbers, the cross-correlation characteristics are significantly degraded (cross-correlation values include large values).

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, now a prime number) (for example, See 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 cross-correlation value (maximum value ) becomes 1/√2.

In addition, there are (N−1) sequences with a cross-correlation value of 1/√N. Therefore, from the viewpoint of the cross-correlation value, it is proposed to allocate one CAZAC sequence having the same prime number length and different parameters [parameters in equation (1)] to each cell as a pilot sequence. With such allocation, (N−1) sequences can be obtained, so the same pilot sequence can be reused for each (N−1) cells. Hereinafter, this (N-1) will be referred to as the number of repetitions of the pilot sequence.

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

As a result, there arises a problem that the other-cell interference suppression effect 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 the manner of receiving interference (interference pattern) from other cells is the same in any pilot block, and they are combined (averaged). This is because the interference suppression effect cannot be obtained.

Regarding this point, in conventional W-CDMA (Wideband-Code Division Multiple Access), etc., 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 used for one frame. Since the multiplied sequence is transmitted, the pattern of the transmitted pilot sequence differs for each pilot block. Therefore, by combining (averaging) a plurality of pilot blocks on the receiving side, interference from other cells can be reduced. You can get the suppression effect.

WO2005/015797

"Physical Layer Aspects for Evolved UTRA" (3GPP TR25.814 v0.5.0 (2005-11), Chapter 9.1) K. Fazel and S. Keiser, "Multi-Carrier and Spread Spectrum Systems" (John Willey and Sons, 2003) Texas Instruments, On Uplink Pilot EUTRA SC-FDMA, 3GPP TSG RAN WG1 Ad Hoc LTE, Oct. 14, 2005, R1-051062, URL, http://www. 3 gpp. org/ftp/tsg_ran/WG1_RL1/TSGR1_42bis/Docs/R1_051062. zip Freescale Semiconductor, Inc. , Considerations 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, in the conventional uplink radio access scheme described above, there is a limitation that scrambling codes cannot be applied when a sequence such as the CAZAC sequence described above is used as a pilot sequence. As a result of multiplying a sequence such as a CAZAC sequence by a random sequence such as a scrambling code, a characteristic characteristic [for example, CAZAC property (constant amplitude in the time/frequency domain and a periodic autocorrelation value with a time lag other than 0 is always 0, etc., which is very advantageous for reception)] 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. It is not possible to avoid the problem of no

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above problems, and to obtain an interference suppression effect by synthesizing received pilot blocks when a sequence such as a CAZAC sequence is used as a pilot sequence. It is to provide a station, an allocation device, a system using them, and a method for using them.

A mobile station according to the present invention comprises:
having means for transmitting frames to a base station;
The frame is characterized by being a frame in which a plurality of predetermined sequences having different values of predetermined variables included in the predetermined sequences are assigned to one frame.

A base station according to the present invention comprises:
having means for receiving frames from a mobile station;
The frame is characterized by being a frame in which a plurality of predetermined sequences having different values of predetermined variables included in the predetermined sequences are assigned to one frame.

The allocation device according to the invention comprises:
One frame is characterized by being a frame to which a plurality of predetermined sequences having different values of predetermined variables included in the predetermined sequences are assigned.

A system according to the present invention comprises:
A system comprising a base station and a mobile station,
the mobile station has means for transmitting frames to the base station;
said base station having means for receiving said frame;
The frame is characterized by being a frame in which a plurality of predetermined sequences having different values of predetermined variables included in the predetermined sequences are assigned to one frame.

The method according to the invention comprises:
transmitting the frame;
The frame is characterized by being a frame in which a plurality of predetermined sequences having different values of predetermined variables included in the predetermined sequences are assigned to one frame.
Another method according to the invention comprises:
receiving a frame;
The frame is characterized by being a frame in which a plurality of predetermined sequences having different values of predetermined variables included in the predetermined sequences are assigned to one frame.
Yet another method according to the invention comprises:
One frame is characterized by being a frame to which a plurality of predetermined sequences having different values of predetermined variables included in the predetermined sequences are assigned.

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, it is possible to obtain an interference suppression effect by combining received pilot blocks. A remarkable effect is obtained.

1 is a block diagram showing the configuration of a radio communication system according to a first embodiment of the present invention; FIG. FIG. 4 is a diagram showing a cell arrangement pattern used in the first embodiment of the present invention; FIG. 2 is a block diagram showing a configuration example of a pilot sequence allocation server in FIG. 1; FIG. 2 is a block diagram showing a configuration example of a mobile station in FIG. 1; FIG. FIG. 4 is a diagram showing the configuration of an assignment correspondence table showing assignment of pilot sequences according to the first embodiment of the present invention; FIG. 4 is a diagram showing notification of pilot sequences in the radio communication system according to the first embodiment of the present invention; FIG. 4 is a diagram for explaining the effect of pilot sequence allocation in the radio communication system according to the first embodiment of the present invention; FIG. 10 is a diagram showing the configuration of an allocation correspondence table showing allocation of pilot sequences according to the second embodiment of the present invention; FIG. 10 is a diagram for explaining the effect of pilot sequence allocation in the radio communication system according to the second embodiment of the present invention; FIG. 10 is a diagram showing the configuration of an assignment correspondence table showing assignment of pilot sequences according to the third embodiment of the present invention; FIG. 10 is a diagram showing the configuration of an assignment correspondence table showing assignment of pilot sequences according to the fourth embodiment of the present invention; FIG. 12 is a diagram showing the configuration of an allocation correspondence table showing allocation of pilot sequences according to the fifth embodiment of the present invention; FIG. 2 is a block diagram showing a system model for simulation related to the present invention; It is a figure which shows the simulation result in this invention. (a) to (c) are diagrams showing examples of assignment of pilot sequences to pilot blocks (SB#1, SB#2) used in simulations in the present invention. (a) to (c) are diagrams showing examples of assignment of pilot sequences to pilot blocks (SB#1, SB#2) used in simulations in the present invention. FIG. 5 is a diagram showing an example of parameters used for simulation in the present invention; FIG. 4 is a diagram showing how data signals and pilot signals are multiplexed in the frequency domain for simulation in the present invention; FIG. 2 is a diagram showing a configuration example of a frame format used in a single-carrier transmission system; FIG. FIG. 4 is a diagram for explaining addition of a cyclic prefix; FIG. FIG. 4 is a diagram for explaining problems caused by conventional pilot sequence allocation;

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

FIG. 1 is a block diagram showing the configuration of a radio 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, mobile stations (#1 to #3) Consists of 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 and 3-3, signals of pilot sequences assigned by the method described below are 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. #1 to #3) Communication to 3-1 to 3-3 is called downstream.

As a radio communication system according to the first embodiment of the present invention, a general radio 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 a pilot sequence allocation server 1. FIG. Note that the pilot sequence allocation server 1 does not necessarily need to exist separately from the base stations (#1 to #3) 2-1 to 2-3. 2-3 may be provided in any one base station. Furthermore, 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 a plurality of base stations (#1 to #3) 2-1 to 2-3. may

FIG. 2 shows a cell layout 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 allocation server 1 allocates one of seven indices #1 to #7 as shown in FIG. 2 to each connected base station. Based on the index, the pilot sequence allocation server 1 allocates pilot sequences as will be described later for each of the seven base stations under its control.

It is also used to transmit communication data and pilot signals between base stations (#1 to #3) 2-1 to 2-3 and mobile stations (#1 to #3) 3-1 to 3-3. The frame format has a configuration as shown in FIG. By one sub-frame (sub-frame), a data signal is transmitted in six LB (Long Block) #1 to #6, two SB (Short Block) #1, pilot in #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 cell repetitions of the pilot sequence is 7, the pilot sequence used for transmission is the Zadoff-Chu sequence represented by equation (1), and the number of sequences used is is 7, which is equal to the number of cell repetitions. Let the sequence be {C_1, C_2, C_3, C_4, C_5, C_6, C_7}.

Further, the pilot sequence allocation server 1 determines the 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 the present embodiment, a 7-cell repetition pattern as shown in FIG. 2 is assumed) has already been stored.

FIG. 3 is a block diagram showing a configuration example of the pilot sequence allocation server 1 of 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 comprises a storage device 13 and a communication control device 14 for controlling communication with each base station (#1 to #3) 2-1 to 2-3.

Storage device 13 stores a cell repetition pattern storage area 131 for storing the above cell repetition patterns, a pilot sequence storage area 132 for storing pilot sequences, base stations (cells #1 to #K) and pilot sequences assigned to them. and an assignment correspondence table storage area 133 for storing an assignment correspondence table showing the correspondence between.

FIG. 4 is a block diagram showing a configuration example of mobile stations (#1 to #3) 3-1 to 3-3 in FIG. 4, the mobile station 3 has a CPU 31, a main memory 32 for storing a control program 32a executed by the CPU 31, a storage device 33 for storing data used when the CPU 31 executes the control program 32a, and each base station. (#1 to #3) and a communication control device 34 for controlling communication with 2-1 to 2-3. Mobile stations (#1 to #3) 3-1 to 3-3 have the same configuration as the mobile station 3. FIG.

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 pilot sequence notification in the wireless communication system according to the first embodiment of the present invention. FIG. 7 is a diagram for explaining the effect of allocating pilot sequences in the wireless communication system according to the first embodiment of the present invention. The pilot sequence allocation operation in the radio communication system according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 7. FIG.

In the radio 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 assignment method is adopted in which the pilot sequences are divided into K sets and one set of pilot sequences is assigned to each cell #1 to #K (see FIG. 5).

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

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

Pilot sequence allocation server 1 transmits a pilot sequence allocation information notification to 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 stations (#1 to #3) 2-1 to 2-3. Each base station (#1 to #3) 2-1 to 2-3 transmits a downlink broadcast channel or the like including the index of the assigned pilot sequence to the service area within the cells #1 to #3, thereby enabling movement. Stations (#1 to #3) 3-1 to 3-3 [pilot sequence notification to mobile stations (#1 to #3) 3-1 to 3-3] (see FIG. 6).

Mobile stations (#1 to #3) 3-1 to 3-3 within the service area receive the downlink broadcast channel, etc., and use two Get the index of the pilot block (SB#1, #2). When transmitting data to the base stations (#1 to #3) 2-1 to 2-3, the mobile stations (#1 to #3) 3-1 to 3-3 use two data obtained from the downlink broadcast channel or the like. Based on the pilot block index, SB#1 and #2 transmit different pilot sequences.

At this time, the interference pattern that SB#1 receives from mobile stations in other cells differs from the interference pattern that SB#2 receives from mobile stations in other cells. , #2 are combined (averaged) to suppress other-cell interference (see FIG. 7).

Thus, in this embodiment, different pilot sequences can be transmitted in different pilot blocks (SB #1, #2) within one frame, thereby combining (combining) a plurality of received pilot blocks on the receiving side. averaging) yields a significant effect of suppressing other-cell interference.

As described above, in the present embodiment, instead of allocating one sequence per cell as in the past, two sequences are allocated per cell. It is conceivable that the number of cell repetitions is reduced. In each embodiment described below, this point is devised, and the distance between base stations using the same pilot sequence decreases, so that the amount of interference from cells using the same code increases. are also improving. Although the method of allocating uplink pilot sequences to each cell has been described with the present embodiment, the same pilot sequence allocation method as described above can be applied to the method of allocating downlink pilot sequences to each cell.

FIG. 8 is a diagram showing an allocation correspondence table showing allocation of pilot sequences according to the second embodiment of the present invention, and FIG. 9 shows 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 that of 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. A pilot sequence allocation server according to the second embodiment of the present invention also has the same configuration as 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 also 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 also 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 indices #1 to #7 as shown in FIG. 2 to each of the connected base stations (#1 to #3) 2-1 to 2-3. assigning. Based on the index, the pilot sequence allocation server 1 performs the following pilot sequence allocation for each of the seven base stations under its control.

In FIG. 8, for each cell with index #K (K=1, 2, . . . , 7), two pilot sequences: {C_K, C_(K+1)} (K=1, 2, 6) shows an allocation correspondence table when allocating . However, {C_7, C_1} are assigned only when K=7. Pilot sequence allocation server 1 transmits pilot sequence allocation information notification to 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 base stations (#1 to #3) 2-1 to 2-3.

Each of the base stations (#1 to #3) 2-1 to 2-3 transmits a downlink broadcast channel or the like including the index of the assigned pilot sequence to the service area of the own station, thereby enabling the mobile station (#1 to #3) Notify 3-1 to 3-3 [notify pilot sequence to mobile stations (#1 to #3) 3-1 to 3-3]. The mobile stations (#1 to #3) 3-1 to 3-3 within the service area receive downlink broadcast channels and the like, thereby creating two pilot blocks (SB#1 , #2). 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, Based on the indices of the two pilot blocks, SBs #1 and #2 transmit different pilot sequences, as shown in FIG.

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

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

Thus, in the present 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 of pilot sequence reuse can be achieved. Different pilot sequences can be transmitted in different pilot blocks (SB#1, #2) within one frame without reducing the number. As a result, by combining (averaging) a plurality of received pilot blocks on the receiving side, it is possible to obtain a significant effect of suppressing other-cell interference without reducing the number of cell repetitions for pilot sequence reuse.

FIG. 10 is a diagram showing an assignment correspondence table showing assignment of pilot sequences 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 that of 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. A pilot sequence allocation server according to the third embodiment of the present invention also has the same configuration as 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 also 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 also 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 indices #1 to #7 as shown in FIG. 2 to each of the connected base stations (#1 to #3) 2-1 to 2-3. assigning. Based on the index, the pilot sequence allocation server 1 performs the following pilot sequence allocation for each of the seven base stations under its control.

FIG. 10 shows an allocation correspondence table in which K cells to which pilots are allocated are divided into several areas (groups) and a set of pilot sequences is allocated to each divided area. Pilot sequence allocation server 1 transmits a pilot sequence allocation information notification to 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 base stations (#1 to #3) 2-1 to 2-3.

Each of the base stations (#1 to #3) 2-1 to 2-3 transmits to its own service area on a downlink channel or the like including the index of the assigned pilot sequence, so that the mobile station (#1 to #3) Notify 3-1 to 3-3 [notify pilot sequence to mobile stations (#1 to #3) 3-1 to 3-3]. The mobile stations (#1 to #3) 3-1 to 3-3 within the service area receive downlink broadcast channels and the like, thereby creating two pilot blocks (SB#1 , #2). 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 indices of the two pilot blocks.

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

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

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

As described above, in the present embodiment, pilot sequences can be reused 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) within one frame without reducing the number of cell repetitions. As a result, in the present embodiment, by combining (averaging) a plurality of received pilot blocks on the receiving side, there is a remarkable effect of suppressing other-cell interference without reducing the number of cell repetitions for pilot sequence reuse. 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. be. A pilot sequence allocation server according to the fourth embodiment of the present invention also has the same configuration as pilot sequence allocation server 1 according to the first embodiment of the present invention shown in FIG. Furthermore, the mobile station according to the fourth embodiment of the present invention also has the same configuration as the mobile station 3 according to the first embodiment of the present invention shown in FIG. Also, 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 method of allocating pilot sequences according to the fourth embodiment of the present invention is the same as the method of allocating pilot sequences according to the second embodiment of the present invention shown in FIG.

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

Also, in FIG. 11, three pilot sequences (SB #1, #2, #3) of cell #3 are assigned three pilot sequences: {C_3, C_4, C_5}, and three pilot sequences of cell #4 are assigned Pilot blocks (SB#1, #2, #3) are assigned three pilot sequences: {C_4, C_5, C_6}.

Similarly, in FIG. 11, three pilot blocks (SB #1, #2, #3) of cell # (K-1) include three pilot sequences: {C_(K-1), C_K, C_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 cell #K.

As described above, in the present embodiment, pilot sequences that have been allocated to SB#2 and SB#3 of a certain base station are reassigned to SB#1 and SB#2 of another base station, thereby achieving pilot sequence reuse. Different pilot sequences can be transmitted in different pilot blocks (SB #1, #2, #3) within one frame without reducing the number of cell repetitions. As a result, in the present embodiment, by combining (averaging) a plurality of received pilot blocks on the receiving side, there is a remarkable effect of suppressing other-cell interference without reducing the number of cell repetitions for pilot sequence reuse. 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. be. A pilot sequence allocation server according to the fifth embodiment of the present invention also has the same configuration as 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 also has the same configuration as the mobile station 3 according to the first embodiment of the present invention shown in FIG. Also, 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 method of allocating pilot sequences according to the fifth embodiment of the present invention is the same as the method of allocating pilot sequences 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 four pilot blocks (SB #1, #2, #3, #4) of cell #1, and the cell Four pilot sequences: {C_2, C_3, C_4, C_5} are assigned to the four pilot blocks of #2 (SB #1, #2, #3, #4).

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

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

Thus, in this embodiment, 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 another base station. Thus, different pilot sequences can be transmitted in different pilot blocks (SB #1, #2, #3, #4) within one frame without reducing the number of cell repetitions for pilot sequence reuse. As a result, in the present embodiment, by combining (averaging) a plurality of received pilot blocks on the receiving side, there is a remarkable effect of suppressing other-cell interference without reducing the number of cell repetitions for pilot sequence reuse. is obtained.

FIG. 13 is a block diagram showing a system model for simulation 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. is a diagram showing an example of assigning pilot sequences to pilot blocks (SB#1, SB#2) used in simulations related to the present invention, and FIG. 17 is a diagram showing an example of parameters used in simulations related to the present invention, FIG. 18 is a diagram showing how data signals and pilot signals are multiplexed in the frequency domain in a simulation related to the present invention. The effect of the present invention will be described with reference to FIGS. 13 to 18. FIG.

As shown in FIG. 13, the simulated wireless communication system related to the present invention is composed of two cells, the own cell A and the other cell B. As shown in FIG. Own cell A has own cell base station 2 and own cell users [mobile station (UE) 3a]. Also, the other cell B has another cell user [mobile station (UE) 3b]. The own cell base station 2 receives signals from its own cell user [mobile station (UE) 3a], and also receives signals from other cell users [mobile station (UE) 3b] as interference. Furthermore, in the simulations relating 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 the block error rate characteristics of the signal received by the own cell base station 2 from the own cell user [mobile station (UE) 3a]. The dotted line is the result when the same pilot sequence is used for SB#1 and SB#2 [FIG. 15(a) table #1], and the solid line is the case when different pilot sequences are used for SB#1 and SB#2. This is the result of [FIG. 15(b) table #2].

In simulations related to the present invention, Localized FDM is used as a data multiplexing method, and Distributed-FDM pilot [1] (9.1.1.2.2 Uplink reference-signal structure) is used as a pilot multiplexing method. . In addition, the SRF (Symbol Repetition Factor) of the pilot is set to 4. Furthermore, the number of interfering users from other cells is assumed to be 1 user, the average interference power is set to -6 dB relative to the average power of own cell users, and the frame timing of own cell users and other cell users (interfering users) is synchronized. Assume that

Furthermore, as the pilot sequence, the sequence described in the above equation (1) (where “k” is a parameter) is used, and pilot sequence assignment (assignment of parameter “k”) to each user and each SB is shown in FIG. Tables #1 to #6 shown in (a) to (c) and FIGS. 16(a) to (c) are as follows. For reference, FIG. 18 shows how data and pilots are multiplexed in the frequency domain at this time, and FIG. 17 shows parameters used in the simulation.

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

Table #2 shown in FIG. 15(b) assumes the pilot allocation of the second embodiment of the present invention described above. ) yields the same effect as the above. Moreover, the pilot allocation [pilot sequence allocation such as Table #4 shown in FIG. 16(a)] according to the first embodiment of the present invention has the same effect as above.

Furthermore, as in tables #5 and #6 shown in FIGS. 16(b) and 16(c), even if the pilot sequences used in SB#1 are the same as those of other cells, if the sequences used in SB#2 are different, , the effect of being able to suppress other-cell interference can be obtained. Similarly, even if SB#2 uses the same sequence as the adjacent cell, if SB#1 uses a sequence different from that of the adjacent cell, the same effect as above can be obtained. In other words, 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 other cells, the same effect as 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 explained. However, the present invention is applicable to the case of 5 or more pilot blocks as well as to the case of 2 to 4 pilot blocks.

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 own cell user [mobile station (UE)]
3b Other Cell User [Mobile Station (UE)]
11, 31 CPU
12, 32 Main memories 12a, 32a Control programs 13, 33 Storage devices 14, 34 Communication control device 131 Cell repetition pattern storage area 132 Pilot series storage area 133 Allocation correspondence table storage area A Own cell B Other cells

Claims (2)

having means for transmitting frames to a base station;
A mobile station, wherein the frame is a frame to which a plurality of different predetermined sequences are assigned. the frame has at least two blocks;
2. The mobile station according to claim 1, wherein said predetermined sequence is assigned to said two blocks.

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