HK1185729B - Wireless communication system, pilot sequence allocation apparatus, pilot sequence allocating method used for the system and apparatus, and mobile station used in the method - Google Patents

Abstract

The present invention provides a wireless communication system, a pilot sequence allocation apparatus and method, and a mobile station. The method can obtain effect of reducing interference by combining received pilot blocks when sequence such as the CAZAC sequence as a pilot sequence is used. In the present invention, the pilot sequences by the number of 2K are divided into K sets of {C_1, C_2}, {C_3, C_4}, ..., {C_(2K-1), C_2K} and allocated a set of the pilot sequences to each of the cells #1 to #K. For example, pilot sequences: {C_1, C_2} are allocated to pilot blocks (SB #1, #2) of the cell #1, pilot sequences: {C_3, C_4} are allocated to pilot blocks (SB #1, #2) of the cell #2, pilot sequences: {C_5, C_6} are allocated to pilot blocks (SB #1, #2) of the cell #3, and pilot sequences {C_7, C_8} are allocated to two pilot blocks (SB #1, #2) of the cell #4.

Description

Wireless communication system, pilot sequence allocation apparatus and method, and mobile station

The present application is a divisional application of chinese patent application No.200710097731.2 entitled "wireless communication system, pilot sequence allocation apparatus and method, and mobile station" filed on 28/04/2007.

Technical Field

The present invention relates to a wireless communication system, a pilot sequence allocation apparatus, a method for allocating a pilot sequence for the system and apparatus, and a mobile station used in the method, and more particularly to allocation of a pilot sequence in a single carrier transmission system used in a wireless access method.

Background

As an uplink radio access method in the next-generation wireless communication system, a single-carrier transmission method is effective (for example, refer to non-patent document 1 "physical layer spectrum for evolution utra" (3 gpp tr25.814v1.2.2 (2006-3), chapter 9.1) — the configuration of a frame format used in the single-carrier transmission method proposed in non-patent document 1 is shown in fig. 19.

In fig. 19, it is assumed that data signals are transmitted in six LB (long block) #1 to #6 of a subframe, and pilot signals are transmitted in two SB (short block) #1, # 2.

CP (cyclic prefix) is added to the first half of LB #1 to #6 and SB #1 and #2 in order to effectively perform frequency domain equalization at the receiving side. The addition of the CP is to copy the latter part of the block to the first part, as shown in fig. 20.

As a pilot signal used in uplink radio access in the next generation wireless communication system, the Zadoff-Chu sequence is currently drawing attention, and the Zadoff-Chu sequence is a CAZAC (constant amplitude zero autocorrelation) sequence (refer to, for example, non-patent document 2, k.fazel and s.keiser, "Multi-carrier spread spectra systems" (john willyyandsons, 2003)).

Zadoff-Chu is represented by the following equation:

C_k(n)＝exp[-(j2πk/N)(n(n+1)/2+qn)...(1)

in formula (1), N =0, 1.

The CAZAC sequence is a sequence having a constant amplitude in both time and frequency domains, and its autocorrelation is always zero for a time displacement other than a cyclic autocorrelation value of 0. Since CAZAC has a constant amplitude in the time domain, it can keep the PAPR (peak-to-average power ratio) low. Since the CAZAC sequence also has a constant amplitude in the frequency domain, it is a sequence suitable for propagation path estimation in the frequency domain. Here, a small PAPR means that it can keep power consumption low. This feature is preferred in mobile communications.

In addition, since the "CAZAC sequence" has a characteristic of complete autocorrelation, it is advantageously applicable to detecting the time of a received signal, and attracts attention as a pilot sequence applicable to single carrier transmission, which is an uplink radio access method in a next-generation wireless communication system.

In a cellular environment (a wireless communication network having a service area divided into a plurality of cells), a base station receives not only an uplink signal of a mobile station in a cell managed by the base station as an uplink reception signal but also an uplink signal of a mobile station of another cell (particularly, a neighboring cell) (see fig. 1). The mobile station receives not only a downlink signal from the base station of the cell managed by the base station but also a downlink signal of the base station of another cell because the base station of the other cell receives an uplink signal. Herein, communication from a mobile station to a base station is referred to as an uplink, and communication from a base station to a mobile station is referred to as a downlink. The above-mentioned cells are also called sectors.

Since the base station captures the pilot signal from the mobile station in the cell managed by the base station in the uplink communication, the pilot signal transmitted from the mobile station of another cell needs to be greatly reduced. Thus, it is desirable to allocate a small set of correlation value sequences as pilot sequences of cells adjacent to each other. In downlink communication, it is also desirable to allocate a small set of correlation value sequences as pilot sequences of cells adjacent to each other for the same reason as in uplink communication.

The correlation properties of CAZAC sequences depend largely on the sequence length. That is, if the sequence length includes one prime number or a large prime number, the correlation characteristic is very good (the correlation value is small). In contrast, if the sequence length is a combined number (e.g., a power of 2 or 3) including only a small prime number, the correlation characteristic is greatly reduced (a larger value is included in the correlation value).

Specifically, if the sequence length of the Zadoff-Chu sequence is a prime number, the correlation value of any sequence is always maintained at(N is the sequence length and the root is a prime number) (see, for example, non-patent document 2). If the sequence length N =127, the correlation value is always kept atAnd if the sequence length is N =128, the worst value (maximum value) of the correlation value is

Correlation value ofUp to (N-1). From the viewpoint of correlation values, it is proposed to assign CAZAC sequences, which have the same sequence length and are prime numbers and different parameters (parameters in expression (1)), to each cell as pilot sequences. The result of this assignment is a number of sequences of (N)-1), so that, for each of the (N-1) cells, the same pilot sequence needs to be re-executed. Hereinafter, (N-1) will be referred to as the number of repetitions of the pilot sequence.

On the other hand, if pilot sequences are transmitted in a plurality of blocks (two SB #1, #2 in the frame format shown in fig. 19) as in the frame format of the uplink radio access considered in the next-generation wireless communication system (see fig. 19), and if one pilot sequence is allocated to each cell as described above (that is, if the pilot sequences transmitted in a plurality of pilot blocks of a frame are common and the pilot sequences used in SB #1, #2 in the frame format shown in fig. 19 are the same), on the receiving side, the interference pattern from another cell is the same in each pilot block.

This causes a problem that the effect of reducing interference of other cells by combining (averaging) a plurality of pilot blocks cannot be obtained at the receiving side. This is because since the pilot sequences transmitted in a plurality of pilot blocks are the same, interference from other cells is received in the same manner (interference pattern) in all the pilot blocks to combine (average) them, and thus the effect of reducing interference of other cells cannot be obtained (see fig. 21).

If a pilot sequence common to a plurality of pilot blocks in a frame is used in conventional W-CDMA (wideband code division multiple access) or the like, a random sequence called a scrambling code is transmitted, and the sequence is multiplied by the frame. Thus, the pattern of the pilot sequence to be transmitted is different for each pilot block, so that the effect of reducing interference of other cells can be obtained by combining (averaging) a plurality of pilot blocks at the receiving side.

In the above-described conventional uplink wireless access system, if a sequence such as the above-described CAZAC sequence is used as a pilot sequence, there is a limitation that a scrambling code cannot be applied. This is because a unique characteristic is lost as a result of multiplying a sequence such as a CAZAC sequence by a random sequence such as a scrambling code (for example, a CAZAC characteristic (a characteristic favorable for reception, for example, constant in amplitude in the time and frequency domains, and a cyclic autocorrelation value is always 0 except in the case where the time shift is 0)).

If a sequence such as a CAZAC sequence is used as a pilot sequence and only one code is allocated to each cell, a problem that an effect of reducing interference cannot be obtained by combining (averaging) the received pilot blocks in the above-described frame cannot be avoided.

An object of the present invention is to provide a wireless communication system, a pilot sequence allocation apparatus, and a method for allocating pilot sequences to be used in the apparatus and a mobile station using the method, which eliminate the above-mentioned problems and obtain an effect of reducing interference by combining received pilot blocks in the case where a sequence such as a CAZAC sequence is used as a pilot sequence.

Disclosure of Invention

A first wireless communication system of the present invention is a wireless communication system including a plurality of cells, a pilot sequence allocating apparatus for allocating a pilot sequence used in communication between a base station and a mobile station to each cell, and the mobile station, the wireless communication system including:

a pilot sequence allocating means provided in the pilot sequence allocating apparatus for allocating a different pilot sequence to each of a plurality of pilot blocks in a frame for one of the plurality of cells, an

Signal transmission means provided in the mobile station for allocating a different pilot sequence to each of a plurality of pilot blocks in a frame for the base station.

In the second wireless communication system of the present invention, at least one of the plurality of pilot sequences allocated to one of the plurality of cells is different from at least one of the plurality of pilot sequences allocated to another cell.

In the third wireless communication system of the present invention, the pilot sequence allocation apparatus divides the pilot sequences into sets, the number of pilot sequences in each set being equal to the number of pilot blocks in the frame, and allocates the sets to each of the plurality of cells.

The fourth wireless communication system of the present invention includes N (N is an integer equal to or greater than 2) pilot blocks in a frame, and

wherein the pilot sequence allocating apparatus performs allocation of the pilot sequences such that the pilot sequences are reused by the number M of repeated cells (M is an integer equal to or greater than 2), and pilot sequences to be allocated to a j-th pilot block (j =1, 2.... N) of a cell i (i =1, 2.... M) are different for different cells.

In the fifth wireless communication system of the present invention, the pilot sequence allocation device performs allocation of pilot sequences such that a pilot sequence to be allocated to a j-th pilot block of the cell i is different from a pilot sequence to be allocated to a j '-th pilot block of the cell i (j' ≠ j).

In the sixth wireless communication system of the present invention, the pilot sequence assignment device makes the pilot sequence assigned to the j-th pilot block of the cell i a candidate for the sequence of the j '(j' ≠ j) pilot block to be reassigned to another cell i '(i' ≠ i).

In the seventh wireless communication system of the present invention, the pilot sequence allocation apparatus allocates a sequence C _ ({ i + j-2}) modM } +1 to the jth pilot block of cell i so that the total number of sequences C _ (1), C _ (2),.., C _ (M) is equal to the number M of repeated cells, and the number N of pilot blocks in one frame is equal to or smaller than the number M of repeated cells (N ≦ M).

In the eighth wireless communication system of the present invention, the pilot sequence is a CAZAC (constant amplitude zero autocorrelation) sequence.

In the ninth wireless communication system of the present invention, the sequence length of the pilot sequence is a prime number length.

A first pilot sequence allocation apparatus of the present invention is a pilot sequence allocation apparatus for allocating a pilot sequence used in communication between a base station and a mobile station for each of a plurality of cells of a wireless communication system, the pilot sequence allocation apparatus comprising:

pilot sequence allocating means for allocating a different pilot sequence to each of a plurality of pilot blocks in a frame for one of a plurality of cells.

In the second pilot sequence allocation apparatus of the present invention, at least one of the plurality of pilot sequences allocated to one of the plurality of cells is different from at least one of the plurality of pilot sequences allocated to another cell.

In the third pilot sequence allocation apparatus of the present invention, the apparatus divides the pilot sequences into sets, the number of pilot sequences in each set is equal to the number of pilot blocks in a frame, and allocates the sets to each of a plurality of cells.

When a pilot sequence is reused by the number M of repeated cells (M is an integer equal to or greater than 2), in a frame configuration including N (N is an integer equal to or greater than 2) pilot blocks in a frame, the fourth pilot sequence allocating apparatus of the present invention allocates pilot sequences such that a pilot sequence to be allocated to a j-th pilot block (j =1, 2.... prot., N) of a cell i (i =1, 2.. prot., M) and a pilot sequence to be allocated to a j-th pilot block of another cell are different from each other.

The fifth pilot sequence allocation apparatus of the present invention performs allocation of pilot sequences such that a pilot sequence to be allocated to a j-th pilot block of the cell i is different from a pilot sequence to be allocated to a j '-th pilot block of the cell i (j' ≠ j).

The sixth pilot sequence allocation apparatus of the present invention makes the pilot sequence allocated to the j-th pilot block of the cell i a candidate for the sequence of the j '(j' ≠ j) pilot block to be allocated to another cell i '(i' ≠ i).

The seventh pilot sequence allocation apparatus of the present invention allocates a sequence C _ ({ i + j-2}) modM } +1 to the jth pilot block of cell i such that the total number of sequences C _ (1), C _ (2),.., C _ (M) is equal to the number M of repeated cells, and the number N of pilot blocks in one frame is equal to or less than the number M of repeated cells (N ≦ M).

In the eighth pilot sequence allocation apparatus of the present invention, the pilot sequence is a CAZAC (constant amplitude zero autocorrelation) sequence.

In the ninth pilot sequence allocation apparatus of the present invention, the sequence length of the pilot sequence is a prime number length.

A first method for allocating a pilot sequence of the present invention is a method for allocating a pilot sequence used in a wireless communication system including a plurality of cells, a pilot sequence allocating apparatus for allocating a pilot sequence used in communication between a base station and a mobile station to each cell, and the mobile station, the method comprising performing the following steps in the pilot sequence allocating apparatus:

each of a plurality of pilot blocks in a frame for one of a plurality of cells is assigned a different pilot sequence.

In the second method for allocating pilot sequences of the present invention, at least one of a plurality of pilot sequences allocated to one of a plurality of cells is different from at least one of a plurality of pilot sequences allocated to another cell.

In the third method for allocating pilot sequences of the present invention, the pilot sequence allocating apparatus divides the pilot sequences into sets, the number of pilot sequences in each set is equal to the number of pilot blocks in a frame, and the pilot sequence allocating apparatus allocates the sets to each of the plurality of cells.

The fourth method for allocating pilot sequences of the present invention includes N (N is an integer equal to or greater than 2) pilot blocks in a frame, and

wherein the pilot sequence allocating apparatus performs allocation of the pilot sequences such that the pilot sequence allocating apparatus reuses the pilot sequences by the number M of repeated cells (M is an integer equal to or greater than 2), and pilot sequences to be allocated to a jth pilot block (j =1, 2...., N) of a cell i (i =1, 2...., M) are different for different cells.

In the fifth method for allocating pilot sequences of the present invention, the pilot sequence allocation apparatus performs allocation of pilot sequences such that a pilot sequence to be allocated to a j-th pilot block of the cell i is different from a pilot sequence to be allocated to a j '-th pilot block of the cell i (j' ≠ j).

In the sixth method for allocating pilot sequences of the present invention, the pilot sequence allocation apparatus makes the pilot sequence allocated to the j-th pilot block of the cell i a candidate for a sequence of j '(j' ≠ j) pilot blocks to be reallocated to another cell i '(i' ≠ i).

In the seventh method for allocating pilot sequences of the present invention, the pilot sequence allocation apparatus allocates a sequence C _ ({ i + j-2}) modM } +1 to the jth pilot block of cell i so that the total number of sequences C _ (1), C _ (2),.., C _ (M) is equal to the number M of repeated cells, and the number N of pilot blocks in one frame is equal to or less than the number M of repeated cells (N ≦ M).

In the eighth method for allocating pilot sequences of the present invention, the pilot sequences are CAZAC (constant amplitude zero autocorrelation) sequences.

In the ninth method for allocating pilot sequences of the present invention, the sequence length of the pilot sequences is a prime number length.

A first mobile station of the present invention is a mobile station for communicating with a base station of a wireless communication system, comprising:

signal transmission means for transmitting a signal in which a different pilot sequence is allocated to each of a plurality of pilot blocks in a frame for a base station.

In the second mobile station of the present invention, the transmission apparatus decides pilot sequences to be allocated to the plurality of pilot blocks based on the index of the pilot sequence received from the base station.

In the third mobile station of the present invention, at least one of the plurality of pilot sequences allocated to one of the plurality of pilot blocks is different from at least one of the plurality of pilot sequences allocated to a mobile station of another cell.

According to the present invention, when the above-described configuration and operation are used and a sequence such as a CAZAC sequence is used as a pilot sequence, by combining received pilot blocks, a significant effect of reducing interference can be obtained.

Drawings

Fig. 1 is a block diagram showing the configuration of a wireless communication system according to a first embodiment of the present invention;

fig. 2 is a diagram showing a cell arrangement pattern used in the first embodiment of the present invention;

fig. 3 is a block diagram showing a configuration example of the pilot sequence allocation server of fig. 1;

fig. 4 is a diagram showing a configuration example of the mobile station of fig. 1;

fig. 5 is a diagram showing a configuration of an allocation correspondence table, in which pilot sequence allocation according to the first embodiment of the present invention is shown;

fig. 6 is a diagram illustrating a pilot sequence notification in a wireless communication system according to a first embodiment of the present invention;

fig. 7 is a diagram for illustrating the effect of pilot sequence allocation in a wireless communication system according to a first embodiment of the present invention;

fig. 8 is a diagram showing a configuration of an allocation correspondence table, in which pilot sequence allocation according to a second embodiment of the present invention is shown;

fig. 9 is a diagram for illustrating the effect of pilot sequence allocation in a wireless communication system according to a second embodiment of the present invention;

fig. 10 is a diagram showing a configuration of an allocation correspondence table, in which pilot sequence allocation according to a third embodiment of the present invention is shown;

fig. 11 is a diagram showing a configuration of an allocation correspondence table, in which pilot sequence allocation according to a fourth embodiment of the present invention is shown;

fig. 12 is a diagram showing a configuration of an allocation correspondence table, in which pilot sequence allocation according to a fifth embodiment of the present invention is shown;

FIG. 13 is a block diagram illustrating a system model of a simulation in connection with the present invention;

FIG. 14 is a diagram showing a simulation result in the present invention;

fig. 15A to 15C are diagrams showing examples of allocation of pilot sequences to pilot blocks (SB #1, SB # 2) used in the simulation of the present invention;

fig. 16A to 16C are diagrams showing examples of allocation of pilot sequences to pilot blocks (SB #1, SB # 2) used in the simulation of the present invention;

FIG. 17 is a diagram showing exemplary parameters used in simulations in connection with the present invention;

fig. 18 is a diagram showing a case where a data signal and a pilot signal are multiplexed in a frequency domain of a simulation of the present invention;

fig. 19 is a diagram showing a configuration example of a frame format used in the single carrier transmission method;

fig. 20 is a diagram illustrating the addition of a cyclic prefix;

fig. 21 is a diagram for illustrating a problem caused by conventional pilot sequence allocation.

Detailed Description

Embodiments of the present invention will now be described with reference to the accompanying drawings.

[ example 1]

Fig. 1 is a block diagram showing the configuration of a wireless communication system according to a first embodiment of the present invention. In fig. 1, a wireless communication system according to a 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 # 3) 3-1 to 3-3.

At cells #1 to #3 managed by each of the base stations (# 1 to # 3) 2-1 to 2-3, signals of pilot sequences allocated in a method to be described below are transmitted as communications between the base stations (# 1 to # 3) 2-1 to 2-3 and the mobile stations (# 1 to # 3) 3-1 to 3-3. 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 referred to as uplink communication, and communication from the base stations to the mobile stations (# 1 to # 3) 3-1 to 3-3 is referred to as downlink communication.

A general wireless communication network having a service area divided into a plurality of cells #1 to #3 is assumed as a wireless communication system according to the first embodiment of the present invention. A plurality of base stations (# 1 to # 3) 2-1 to 2-3 are combined together and connected to a pilot sequence allocation server 1. The pilot sequence allocation server 1 need not exist independently of the base stations (# 1 to # 3) 2-1 to 2-3, but may be provided in any one of the plurality of base stations (# 1 to # 3) 2-1 to 2-3. In addition, the pilot sequence allocation server 1 may be provided in a higher-level device (e.g., 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.

Fig. 2 is a diagram showing a cell arrangement pattern used in the first embodiment of the present invention. Fig. 2 shows a seven-cell repetition pattern of seven base stations from #1 to # 7. The pilot sequence allocation server 1 allocates any one of seven indexes from #1 to #7 shown in fig. 2 to each connected base station. Based on the index, the pilot sequence allocation server 1 performs pilot sequence allocation, which will be described later, for each of the seven base stations thereunder.

The frame format to be used to transmit 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 has a configuration as shown in fig. 19. It is considered that the data signal is transmitted in six LB (long block) #1 to #6 using one subframe, and the pilot sequence is transmitted in two SB (short block) #1 and # 2.

That is, in the present embodiment, it is assumed that the number of pilot blocks in one frame is 2, the cell repetition factor in the pilot sequence is 7, the pilot sequence used for transmission is a Zadoff-Chu sequence represented by equation (1), and the number of sequences used is 7, the same as the number of cell repetition factors. Assume that the sequence is { C _1, C _2, C _3, C _4, C _5, C _6, C _7 }.

In addition, it is assumed that the pilot sequence allocation server 1 stores in advance cell repetition patterns of base stations (# 1 to # 3) 2-1 to 2-3 each connected to the server 1 (this means a cell arrangement pattern in which the same pilot patterns are not adjacent to each other; in the present embodiment, a seven-cell repetition pattern as shown in fig. 2 is assumed).

Fig. 3 is a block diagram showing a configuration example of the pilot sequence allocation server 1 of fig. 1. In fig. 3, the pilot sequence allocation server 1 includes a CPU (central processing unit)) 11, a main memory 12 for storing a control program 12a executed by the CPU11, a storage device 13 for storing data and the like used during execution of the control program 12a by the CPU11, and a communication control device 14 for controlling communication with each of the base stations (# 1 to # 3) 2-1 to 2-3.

The storage device 13 includes a cell repetition pattern storage area 131 for storing the above-described cell repetition pattern, a pilot sequence storage area 132 for storing a pilot sequence, and an allocation correspondence relation storage area 133 for storing an allocation correspondence relation table showing the correspondence relation between each of the base stations (cells #1 to # K) and the pilot sequence to be allocated to the base station.

Fig. 4 is a block diagram showing a configuration example of the mobile stations (# 1 to # 3) 3-1 to 3-3 of fig. 1. In fig. 4, the mobile station 3 includes a CPU31, a main memory 32 for storing a control program 32a executed by the CPU31, a storage device 33 for storing data and the like used when the CPU31 executes the control program 32a, and a communication control device 34 for controlling communication with each of the base stations (# 1 to # 3) 2-1 to 2-3. The mobile stations (# 1 to # 3) 3-1 to 3-3 have the same configuration as the mobile station.

Fig. 5 is a diagram showing an allocation correspondence table in which pilot sequence allocation according to the first embodiment of the present invention is shown. Fig. 6 is a diagram illustrating pilot sequence notification in a wireless communication system according to a first embodiment of the present invention. Fig. 7 is a diagram for illustrating the effect of pilot sequence allocation in a wireless communication system according to a first embodiment of the present invention. Referring to fig. 1 to 7, an operation of pilot sequence allocation in a wireless communication system according to a first embodiment of the present invention will now be described.

The wireless communication system according to the first embodiment of the present invention employs a pilot sequence allocation method that divides 2K pilot sequences into K sets of { [ C _1, C _2], [ C _3, C _4],., [ C _ (2K-1), C _2K ] }, and allocates one set of pilot sequences to each of the cells #1 to # K (see fig. 5).

That is, in fig. 5, two pilot sequences { C _1, C _2} are allocated to two pilot blocks (SB #1, # 2) of cell #1, two pilot sequences { C _3, C _4} are allocated to two pilot blocks (SB #1, # 2) of cell #2, two pilot sequences { C _5, C _6} are allocated to two pilot blocks (SB #1, # 2) of cell #3, and two pilot sequences { C _7, C _8} are allocated to two pilot blocks (SB #1, # 2) of cell # 4.

Similarly, in fig. 5, two pilot sequences { C _ (2K-3), C _ (2K-2) } are allocated to two pilot blocks (SB #1, # 2) of cell # (K-1), and two pilot sequences { C _ (2K-1), C _2K } are allocated to two pilot blocks (SB #1, # 2) of cell # K.

As shown in fig. 5, the pilot sequence allocation server 1 transmits a pilot sequence allocation information notification to each of the base stations (# 1 to # 3) 2-1 to 2-3, and allocates one pilot sequence to each of the base stations (# 1 to # 3) 2-1 to 2-3) based on the set allocation correspondence table. Each of the base stations (# 1 to # 3) 2-1 to 2-3 notifies the mobile stations (# 1 to # 3) 3-1 to 3-3 (pilot sequence notification to the mobile stations (# 1 to # 3) 3-1 to 3-3) by transmitting a downlink notification channel including an index of an assigned pilot sequence or the like to a service area in the cells #1 to #3 (see fig. 6).

Each of the mobile stations (# 1 to # 3) 3-1 to 3-3) in the service area obtains indexes of two pilot blocks (SB #1, # 2) used in the cells (# 1 to # 3) where the self-station exists (self-station) by receiving a downlink announcement channel or the like. When each of the mobile stations (# 1 to # 3) 3-1 to 3-3 transmits data to each of the base stations (# 1 to # 3) 2-1 to 2-3, the mobile station transmits different pilot sequences for SB #1 and #2 based on the indexes of two pilot blocks obtained from a downlink notification channel or the like.

At this time, the interference pattern received by SB #1 from the mobile station of another cell and the interference pattern received by SB #2 from the mobile station of another cell are different. This is effective for reducing interference of another cell by combining (averaging) SB #1 and #2 when allocating pilot sequences in the present embodiment (see fig. 7).

In this way, in the present embodiment, different pilot sequences can be transmitted in different pilot blocks (SB #1, # 2) of a frame, so that a significant effect such as a plurality of received pilot blocks being combined together (averaged) at the receiving side to reduce interference of another cell can be obtained.

As described above, since this embodiment is changed to allocate two sequences to one cell instead of one sequence, the reuse cell repetition factor of the pilot sequence is reduced. Each of the embodiments to be described later is designed based on this point, and also improves because the amount of interference from cells using the same code increases as the distance between base stations using the same pilot sequence decreases. Although the method for allocating an uplink pilot sequence to each cell is described in the present embodiment, a similar pilot sequence allocation method is also applicable to the method for allocating a downlink pilot sequence to each cell.

[ example 2]

Fig. 8 is a diagram showing an allocation correspondence table in which pilot sequence allocation according to a second embodiment of the present invention is shown. Fig. 9 is a diagram for illustrating the effect of pilot sequence allocation in a wireless communication system according to a second embodiment of the present invention.

The wireless communication system according to the second embodiment of the present invention has the same configuration as the wireless communication system according to the first embodiment of the present invention shown in fig. 1 except for a method for allocating pilot sequences. The pilot sequence allocation server according to the second embodiment of the present invention also has the same configuration as the pilot sequence allocation server 1 according to the first embodiment of the present invention shown in fig. 3. In addition, 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. 4. 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. 2.

The pilot sequence allocation server 1 allocates one of seven indexes from #1 to #7 shown in fig. 2 to each of the connected base stations (# 1 to # 3) 2-1 to 2-3. Based on the index, the pilot sequence allocation server 1 allocates one pilot sequence to each of the seven base stations thereunder.

Fig. 8 shows an assignment correspondence table for assigning two pilot sequences { C _ K, C _ (K +1) } (K =1, 2.., 6) to each of the cells having an index # K (K =1, 2.., 7). In the case of K =7, { C _7, C _1} is allocated. The pilot sequence allocation server 1 transmits a pilot sequence allocation information notification to each of the base stations (# 1 to # 3) 2-1 to 2-3, and allocates one pilot sequence to each of the base stations (# 1 to # 3) 2-1 to 2-3 based on the allocation correspondence table set shown in fig. 8.

Each of the base stations (# 1 to # 3) 2-1 to 2-3 notifies the mobile stations (# 1 to # 3) 3-1 to 3-3 (pilot sequence notification to the mobile stations (# 1 to # 3) 3-1 to 3-3) by transmitting a downlink notification channel or the like including an index of the assigned pilot sequence to a service area directed from the station. The mobile stations (# 1 to # 3) 3-1 to 3-3) in the service area obtain indexes of two pilot blocks (SB #1, # 2) used in a cell in which the own station exists by receiving a downlink notification channel or the like. Then, 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, it transmits pilot sequences different for SB #1 and #2 based on the indexes of two pilot blocks obtained from a downlink notification channel or the like.

That is, in fig. 8, two pilot sequences { C _1, C _2} are allocated to two pilot blocks (SB #1, # 2) of cell #1, two pilot sequences { C _2, C _3} are allocated to two pilot blocks (SB #1, # 2) of cell #2, two pilot sequences { C _3, C _4} are allocated to two pilot blocks (SB #1, # 2) of cell #3, and two pilot sequences { C _4, C _5} are allocated to two pilot blocks (SB #1, # 2) of cell # 4.

Similarly, in fig. 8, two pilot sequences { C _ (K-1), C _ K } are allocated to two pilot blocks (SB #1, # 2) of cell # (K-1), and two pilot sequences { C _ K, C _1} are allocated to two pilot blocks (SB #1, # 2) of cell # K.

Thus, in the present embodiment, by reassigning the pilot sequence of SB #2 assigned to a certain base station (cell) to SB #1 of another base station (cell), different pilot sequences can be transmitted in different pilot blocks (SB #1, # 2) of a frame without reducing the cell repetition factor for reusing the pilot sequences. Thus, in the present embodiment, by combining (averaging) a plurality of pilot blocks at the receiving side, a significant effect of reducing interference of another cell can be achieved without reducing the cell repetition factor for reusing the pilot sequence.

[ example 3]

Fig. 10 is a diagram showing an allocation correspondence table in which pilot sequence allocation according to a third embodiment of the present invention is shown. The wireless communication system according to the third embodiment of the present invention has the same configuration as the wireless communication system according to the first embodiment of the present invention shown in fig. 1 except for a method for allocating pilot sequences. The pilot sequence allocation server according to the third embodiment of the present invention also has the same configuration as the pilot sequence allocation server 1 according to the first embodiment of the present invention shown in fig. 3. In addition, 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. 4. 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. 2.

The pilot sequence allocation server 1 allocates one of seven indexes from #1 to #7 shown in fig. 2 to each of the connected base stations (# 1 to # 3) 2-1 to 2-3. Based on the index, the pilot sequence allocation server 1 allocates one pilot sequence to each of the seven base stations thereunder.

Fig. 10 shows an allocation correspondence table for dividing K cells to perform pilot allocation in some regions (groups) and allocating one set of pilot sequences to each divided region. The pilot sequence allocation server 1 transmits a pilot sequence allocation information notification to each of the base stations (# 1 to # 3) 2-1 to 2-3, and allocates one pilot sequence to each of the base stations (# 1 to # 3) 2-1 to 2-3 based on the allocation correspondence table set shown in fig. 10.

Each of the base stations (# 1 to # 3) 2-1 to 2-3 notifies the mobile stations (# 1 to # 3) 3-1 to 3-3 (pilot sequence notification to the mobile stations (# 1 to # 3) 3-1 to 3-3) by transmitting a downlink notification channel or the like including an index of the assigned pilot sequence to a service area directed from the station. The mobile stations (# 1 to # 3) 3-1 to 3-3) in the service area obtain indexes of two pilot blocks (SB #1, # 2) used in a cell in which the own station exists by receiving a downlink notification channel or the like. Then, 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, it transmits pilot sequences different for SB #1 and #2 based on the indexes of two pilot blocks obtained from a downlink notification channel or the like.

That is, in fig. 10, cell #1 and cell #2 belong to a first divided region, and two pilot sequences { C _1, C _2} are allocated to the two cells #1 and # 2. Two pilot sequences { C _1, C _2} are allocated to two pilot blocks (SB #1, # 2) of the cell #1 in the order of C1, C2. On the other hand, __ plane, 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 divided region, and two pilot sequences { C _3, C _4} are allocated to the two cells #3 and # 4. Two pilot sequences { C _3, C _4} are allocated to 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 allocated to two pilot blocks (SB #1, # 2) of cell #4 in the order of C _4, C _ 3.

Similarly, cell # (K-1) and cell # K belong to the K/2 th division area, and two pilot sequences { C _ (K-1), C _ K } are allocated to the two cells # (K-1) and # K. Two pilot sequences { C _ (K-1), C _ K } are allocated to two pilot blocks (SB #1, # 2) of the cell # (K-1) in the order of C _ (K-1), C _ K. 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).

Thus, in the present embodiment, by reassigning the pilot sequences of SB #1 and SB #2 assigned to a certain base station to SB #2 and SB #1 of another base station, different pilot sequences can be transmitted in different pilot blocks (SB #1, # 2) of a frame without reducing the cell repetition factor for reusing the pilot sequences. Thus, in the present embodiment, by combining (averaging) a plurality of received pilot blocks at the receiving side, a significant effect of reducing interference of another cell can be achieved without reducing the cell repetition factor for reusing the pilot sequence.

[ example 4]

Fig. 11 is a diagram showing an allocation correspondence table in which pilot sequence allocation according to a fourth embodiment of the present invention is shown. The wireless communication system according to the fourth embodiment of the present invention has the same configuration as the wireless communication system according to the first embodiment of the present invention shown in fig. 1 except that the number of pilot blocks in a frame is different. The pilot sequence allocation server according to the fourth embodiment of the present invention also has the same configuration as the pilot sequence allocation server 1 according to the first embodiment of the present invention shown in fig. 3. In addition, 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. 4. The cell arrangement pattern used in the fourth 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. 2. In addition, the method for allocating pilot sequences according to the fourth embodiment of the present invention is the same as the method for allocating pilot sequences according to the second embodiment of the present invention shown in fig. 8.

That is, in fig. 11, three pilot sequences { C _1, C _2, C _3} are allocated to three pilot blocks (SB #1, #2, # 3) of cell #1, and three pilot sequences { C _2, C _3, C _4} are allocated to three pilot blocks (SB #1, #2, # 3) of cell # 2.

In fig. 11, three pilot sequences { C _3, C _4, C _5} are allocated to three pilot blocks (SB #1, #2, # 3) of cell #3, and three pilot sequences { C _4, C _5, C _6} are allocated to three pilot blocks (SB #1, #2, # 3) of cell # 4.

Similarly, in fig. 11, three pilot sequences { C _ (K-1), C _ K, C _1} are allocated to three pilot blocks (SB #1, #2, # 3) of cell # (K-1), and three pilot sequences { C _ K, C _1, C _2} are allocated to three pilot blocks (SB #1, #2, # 3) of cell # K.

Thus, in the present embodiment, by reassigning the pilot sequences of SB #2 and SB #3 assigned to 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) of a frame without reducing the cell repetition factor for reusing the pilot sequences. Thus, in the present embodiment, by combining (averaging) a plurality of received pilot blocks at the receiving side, a significant effect of reducing interference of another cell can be achieved without reducing the cell repetition factor for reusing the pilot sequence.

[ example 5]

Fig. 12 is a diagram showing an allocation correspondence table in which pilot sequence allocation according to a fifth embodiment of the present invention is shown. The wireless communication system according to the fifth embodiment of the present invention has the same configuration as the wireless communication system according to the first embodiment of the present invention shown in fig. 1 except that the number of pilot blocks in a frame is different. The pilot sequence allocation server according to the fifth embodiment of the present invention also has the same configuration as the pilot sequence allocation server 1 according to the first embodiment of the present invention shown in fig. 3. In addition, 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. 4. The cell arrangement pattern used in the fifth 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. 2. In addition, the method for allocating pilot sequences according to the fifth embodiment of the present invention is the same as the method for allocating pilot sequences according to the second embodiment of the present invention shown in fig. 8.

That is, in fig. 12, four pilot sequences { C _1, C _2, C _3, C _4} are allocated to four pilot blocks (SB #1, #2, #3, # 4) of cell #1, and four pilot sequences { C _2, C _3, C _4, C5} are allocated to four pilot blocks (SB #1, #2, #3, # 4) of cell # 2.

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, and four pilot sequences { C _4, C _5, C _6, C7} are allocated to four pilot blocks (SB #1, #2, #3, # 4) of cell # 4.

Similarly, in fig. 12, four pilot sequences { C _ (K-1), C _ K, C _1, C _2} are allocated to four pilot blocks (SB #1, #2, #3, # 4) of cell # (K-1), and four pilot sequences { C _ K, C _1, C _2, C3} are allocated to four pilot blocks (SB #1, #2, #3, # 4) of cell # K.

Thus, in the present embodiment, by reassigning the pilot sequences of SB #2, SB #3, and SB #4 assigned to a certain base station to SB #1, SB #2, and SB #3 of another base station, different pilot sequences can be transmitted in different pilot blocks (SB #1, #2, #3, # 4) of a frame without reducing the cell repetition factor for reusing the pilot sequences. Thus, in the present embodiment, by combining (averaging) a plurality of received pilot blocks at the receiving side, a significant effect of reducing interference of another cell can be achieved without reducing the cell repetition factor for reusing the pilot sequence.

FIG. 13 is a block diagram illustrating a system model of a simulation in connection with the present invention. Fig. 14 is a diagram showing a simulation result relating to the present invention. Fig. 15A to 15C and fig. 16A to 16C are diagrams showing examples of allocation of pilot sequences to pilot blocks (SB #1, SB # 2) used in simulations relating to the present invention. Fig. 17 is a diagram showing exemplary parameters used in simulations related to the present invention. Fig. 18 is a diagram showing a case where a data signal and a pilot signal are multiplexed in a frequency domain of a simulation related to the present invention. The effects of the present invention will now be described with reference to fig. 13 to 18.

As shown in fig. 13, the simulated wireless communication system related to the present invention includes two cells, i.e., a self-cell (self-cell) a and another cell B. The local cell a includes a local cell base station 2 and a local cell user (mobile station (UE) 3 a). The other cell B has another cell user (mobile station (UE) 3B). The own-cell base station 2 receives a signal from a user (mobile station (UE) 3 a) of the own cell and also receives a signal as interference from a user (mobile station (UE) 3 b) of another cell. In addition, in the simulation related to the present invention, it is assumed that a frame of communication between a base station and a mobile station has two pilot blocks SB #1 and SB # 2.

Fig. 14 shows block error rate characteristics of a signal received by the own-cell base station 2 from the own-cell user (mobile station (UE) 3 a). The dotted line shows the result of the case where the same pilot sequence is used in SB #1 and SB #2 (table #1 in fig. 15A). The solid line shows the results for the case where different pilot sequences are used for SB #1 and SB #2 (table #2 in fig. 15B).

Simulations related to the present invention used localized FDM as a data multiplexing method, using a distributed FDM pilot [1] (9.1.1.2.2 uplink reference signal structure). SRF (symbol repetition factor) =4 for the pilot is set. In addition, the interfering user from another cell is set as one user, and the average interference power is set to-6 dB for the average power of the user of the own cell, and it is assumed that the frame timing between the user of the own cell and the user of another cell (interfering user) is synchronized.

In addition, the pilot sequence uses the sequence described in the above equation (1) (where "k" is a parameter), and the pilot sequence assignment to each user and each SB (assignment of the parameter "k") is shown in each of tables #1 to #6 in fig. 15A to 15C and fig. 16A to 16C. For reference, the case of multiplexing data and pilot in the frequency domain at this time is shown in fig. 18, and parameters used in the simulation are shown in fig. 17.

As shown in fig. 14, it is apparent that the block error rate =10 is satisfied^-1The required Eb/No improvement is nearly 1db, it is clear that the block error rate =3 × 10 is satisfied^-2The required Eb/No is increased by 2dB or more.

It is assumed that table #2 shown in fig. 15B shows the pilot allocation of the second embodiment of the present invention described above, but the pilot allocation of the third embodiment of the present invention, i.e., the allocation in table #3 shown in fig. 15C can achieve the same effect. The same effect can be achieved for pilot allocation of the first embodiment of the present invention (such as the pilot sequence allocation of table #4 shown in fig. 16A).

With tables #5 and #6 shown in fig. 16B, 16C, if the sequences used in SB #2 are different, the effect of reducing the interference of another cell can be achieved even if the pilot sequence used in SB #1 is the same as that in another cell. Similarly, if a sequence different from the adjacent cell is used in SB #1, the same effect as described above can be achieved even if SB #2 uses the same sequence as the adjacent cell. That is, if at least one of the pilot sequences allocated to the own cell is different from at least one of the pilot sequences allocated to another cell, the same effect can be achieved. This is also true for the case where the number of SBs in a frame is three or more.

In the present invention, the case where the number of pilot blocks in a frame is two or four is described above, respectively. However, the present invention is also applicable to the case where the number of pilot blocks is five or more, as in the case where the number of blocks is two or four.

Claims (22)

1. A mobile station in a communication system, the mobile station comprising:

an apparatus for transmitting a frame to a base station,

wherein a first Zadoff-Chu sequence is assigned to a first block of a frame and a second Zadoff-Chu sequence is assigned to a second block of the frame, and the first Zadoff-Chu sequence is different from the second Zadoff-Chu sequence.

2. The mobile station of claim 1, wherein the communication system comprises a plurality of cells,

wherein the first Zadoff-Chu sequence assigned to one of the plurality of cells is different from the first Zadoff-Chu sequence assigned to another one of the plurality of cells.

3. The mobile station of claim 1, wherein a value of a parameter in the first Zadoff-Chu sequence is different from a value of the parameter in the second Zadoff-Chu sequence.

4. The mobile station of claim 3, wherein the first and second Zadoff-Chu sequences are represented by the following equation:

c _ k (N) ═ exp [ - (j2 pi k/N) (N (N +1)/2+ qn) ], and

in the formula, N is 0, 1.

5. A communication system, the communication system comprising:

a base station; and

a mobile station transmitting a frame to the base station,

wherein a first Zadoff-Chu sequence is assigned to a first block of a frame and a second Zadoff-Chu sequence is assigned to a second block of the frame, and the first Zadoff-Chu sequence is different from the second Zadoff-Chu sequence.

6. The communication system of claim 5, wherein the communication system comprises a plurality of cells,

wherein the first Zadoff-Chu sequence assigned to one of the plurality of cells is different from the first Zadoff-Chu sequence assigned to another one of the plurality of cells.

7. The communication system of claim 5, wherein a value of a parameter in the first Zadoff-Chu sequence is different from a value of the parameter in the second Zadoff-Chu sequence.

8. The communication system of claim 7, wherein the first and second Zadoff-Chu sequences are represented by the following equation:

c _ k (N) ═ exp [ - (j2 pi k/N) (N (N +1)/2+ qn) ], and

in the formula, N is 0, 1.

9. A base station in a communication system, the base station comprising:

a unit that receives a frame from a mobile station,

wherein a first Zadoff-Chu sequence is assigned to a first block of a frame and a second Zadoff-Chu sequence is assigned to a second block of the frame, and the first Zadoff-Chu sequence is different from the second Zadoff-Chu sequence.

10. The base station of claim 9, wherein the communication system comprises a plurality of cells,

wherein the first Zadoff-Chu sequence assigned to one of the plurality of cells is different from the first Zadoff-Chu sequence assigned to another one of the plurality of cells.

11. The base station of claim 9, wherein a value of a parameter in the first Zadoff-Chu sequence is different from a value of the parameter in the second Zadoff-Chu sequence.

12. The base station of claim 11, wherein the first and second Zadoff-Chu sequences are represented by the following equation:

C_k(n)＝exp[-(j2πk/N)(n(n+1)/2+qn)]，

in the formula, N is 0, 1.

13. A method for a mobile station in a communication system, the method comprising:

a frame is sent to the mobile station and,

wherein a first Zadoff-Chu sequence is assigned to a first block of a frame and a second Zadoff-Chu sequence is assigned to a second block of the frame, and the first Zadoff-Chu sequence is different from the second Zadoff-Chu sequence.

14. The method of claim 13, wherein the communication system comprises a plurality of cells,

wherein the first Zadoff-Chu sequence assigned to one of the plurality of cells is different from the first Zadoff-Chu sequence assigned to another one of the plurality of cells.

15. The method of claim 13, wherein a value of a parameter in the first Zadoff-Chu sequence is different from a value of the parameter in the second Zadoff-Chu sequence.

16. The method of claim 15, wherein the first and second Zadoff-Chu sequences are represented by the following equation:

C_k(n)＝exp[-(j2πk/N)(n(n+1)/2+qn)]，

in the formula, N is 0, 1.

17. A method for a communication system comprising a mobile station and a base station, the method comprising:

transmitting a frame from the mobile station to the base station,

wherein a first Zadoff-Chu sequence is assigned to a first block of a frame and a second Zadoff-Chu sequence is assigned to a second block of the frame, and the first Zadoff-Chu sequence is different from the second Zadoff-Chu sequence.

18. The method of claim 17, wherein the communication system comprises a plurality of cells,

wherein the first Zadoff-Chu sequence assigned to one of the plurality of cells is different from the first Zadoff-Chu sequence assigned to another one of the plurality of cells.

19. The method of claim 17, wherein a value of a parameter in the first Zadoff-Chu sequence is different from a value of the parameter in the second Zadoff-Chu sequence.

20. The method of claim 19, wherein the first and second Zadoff-Chu sequences are represented by the following equation:

C_k(n)＝exp[-(j2πk/N)(n(n+1)/2+qn)]，

in the formula, N is 0, 1.

21. A method for a base station in a communication system, the method comprising:

a frame is received from a mobile station and,

wherein a first Zadoff-Chu sequence is assigned to a first block of a frame and a second Zadoff-Chu sequence is assigned to a second block of the frame, and the first Zadoff-Chu sequence is different from the second Zadoff-Chu sequence.

22. The method of claim 21, wherein a value of a parameter in the first Zadoff-Chu sequence is different from a value of the parameter in the second Zadoff-Chu sequence.