CN101729158B - Method and system estimating common-frequency multi-cell joint channels - Google Patents

Abstract

The invention relates to method and system estimating common-frequency multi-cell joint channels. The method comprises the following steps of: (a) a high layer (physical layer) distributes common-frequency multi-cell spreading codes and pilot frequency sequence midamble codes shift so as to enable the window period of each user channel to be repeatedly arranged; (b) in target time slot, different offset are added to midamble code sequences transmitted by transmitting terminals in different cells; (c) in a certain target cell in the common-frequency cell, the receiving terminals make FFT conversion on the midamble code part of a receiving signal sequence to obtain frequency domain sequences; (d) the receiving terminals carry out interval value selection on the frequency domain sequences by taking the common-frequency cell number N as a cycle so as to separate the frequency domain sequences which correspond to different cells; and (e) the receiving terminals solve the channel estimation value of each common-frequency cell by adopting the frequency domain sequences of different cells, respectively acquired in the step (d), for multi-cell joint detection. The method and the system can accurately estimate the user channel, improve the performance of multi-cell joint detection and restrain the common-frequency interference.

Description

Method and system for same-frequency multi-cell joint channel estimation

Technical Field

The present invention relates to the field of wireless communication, and in particular, to a method and system for estimating a co-frequency multi-cell joint channel in a TD-SCDMA (time division synchronous code division multiple access) system.

Background

In the field of wireless communications, the demand for high capacity systems raises the problem of how to increase the spectrum utilization as much as possible. In dense population occasions, such as squares, stadiums and other large-scale meeting occasions, dozens of cells may need to be configured for coverage, limited frequency band resources do not satisfy so many cells, and only a plurality of cells can use the same frequency band, which is the same frequency networking.

In addition, the requirement of high data rate data service makes the user occupy multiple code channel resources of multiple time slots when performing a certain service, and the time slot resources and code channel resources of one cell are limited, so that only a few users can be accommodated. In order to meet the requirements of users as many as possible, the number of cells can be increased, which also makes the same-frequency networking a necessary means.

The same frequency is used by a plurality of cells, the same code word is used in the same time slot, the means that the CDMA system inhibits the intersymbol interference by the orthogonality of the spread spectrum codes fails in the same frequency cells, the same frequency interference becomes a very serious problem, and the inhibition of the same frequency interference is particularly urgent. Different scrambling codes are used for distinguishing among cells, a multi-cell joint detection technology is adopted to inhibit co-channel interference, and with the development of a communication technology and the introduction of an MIMO technology, the co-channel interference is inhibited on one hand, and the cell throughput is improved on the other hand. Multi-cell joint detection technology, MIMO technology, etc. all rely on accurate channel estimation, and channel estimation performance is not ideal, which may seriously affect multi-cell joint detection performance. How to perform accurate multi-cell channel estimation is a primary problem in the co-channel interference suppression technology.

The currently adopted multi-cell channel estimation depends on the orthogonality among different code words used by pilot frequencies in multiple cells. The TD-SCDMA system is used for the midamble code (pilot frequency sequence code) of the channel estimation, different cells use different code words, when carrying on the channel estimation, carry on the channel estimation to the target cell first, consider the received signal when the midamble code of other co-frequency cells reaches the base station as the noise at this moment, then use channel estimation value and midamble code of this cell obtained to produce the signal of this cell, it is called the reconstructed signal here, subtract this reconstructed signal from the received signal, carry on the channel estimation to the next co-frequency cell, the reconstructed signal of the next cell of the same method of producing, subtract from the received signal, estimate another co-frequency cell, analogize. Finally, after the channel estimation of all the same-frequency cells is finished, the reconstructed signals of all the same-frequency cells except the target cell are subtracted from the original received signals, and the channel estimation is carried out on the target cell again, so that the purpose of improving the precision is achieved. The channel estimation method completely depends on the orthogonality among different midamble codewords of different cells, but the orthogonality among different midamble codewords is not ideal, and the performance loss of channel estimation is quite large.

There is also a channel estimation method, which judges whether the user is activated according to the power, then constructs a signal matrix only by using the pilot code of the activated user, and performs channel estimation in a way of solving an equation by a matrix.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for estimating a same-frequency multi-cell joint channel so as to accurately estimate a user channel value, improve the performance of multi-cell joint detection and inhibit same-frequency interference.

In order to solve the above problem, the present invention provides a method for estimating a co-frequency multi-cell joint channel, which comprises:

(a) the high layer distributes the same-frequency multi-cell spread spectrum code and pilot frequency sequence midamble code sequence shift to ensure that each user channel window is periodically and repeatedly arranged;

(b) in a target time slot, different offsets are added to midamble code sequences transmitted by transmitting terminals of different cells;

(c) in a certain target cell in the same-frequency cells, a receiving end carries out Fast Fourier Transform (FFT) on a midamble code part of a received signal sequence to obtain a frequency domain sequence;

(d) the receiving end carries out interval value taking on the frequency domain sequences by taking the same frequency cell number N as a period so as to separate the corresponding frequency domain sequences of different cells;

(e) and (d) the receiving end respectively uses the frequency domain sequences of different cells obtained in the step (d) to calculate the channel estimation value of each cell with the same frequency for multi-cell joint detection.

Further, in step (a), the shift of the same user is divided into l_kAnd in each group, the values of N shifts are taken at intervals in 8/N periods, and the corresponding channel windows are also arranged at intervals in 8/N periods, wherein N is the number of cells with the same frequency.

Further, in step (a), in the same timeslot of each cell, the number of shift groups l occupied by all users is the same_kThe sum of (a) and (b) is equal to 8/N; in the same time slot of the same-frequency cells, the total number K of users distributed by all the cells is not more than 8; the number of users K allocated in the same time slot of each cell_nNot more than 8/N, wherein N is the number of co-frequency cells.

Further, the method for adding different offsets when the midamble code sequences are transmitted by the cells with the same frequency in step (b) is as follows:

in the nth cell, if a user occupies the mth channel window, the transmitted midamble code signal of the mth channel window is:

${\mathrm{mid}}_{n,m,\mathrm{shift}}={\mathrm{mid}}_{n,m,0}\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2008101673662E00021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{16\mathrm{mn}}{128}\right)$

where j is a complex factor, mid_n，m，0For the original mth midamble code shift sequence, mid, of the nth cell_{n，m，shift}Are appended phase shifted sequences.

Further, in step (e), the channel estimation values of the cells with the same frequency are calculated as follows: ${\hat{h}}_n=\mathrm{ifft}(\mathrm{fft}\_{\mathrm{rmid}}_n/\mathrm{fft}(\mathrm{ori}\_{\mathrm{mid}}_n)),$ n＝0，1，...，N-1

wherein,ori _ mid, a channel estimate for the nth cell_nFor midamble code original sequence transmitted by the nth cell, fft _ rmid_nIs the frequency domain sequence corresponding to the nth cell, and N is the number of the co-frequency cells.

In order to solve the above technical problem, the present invention also provides a co-frequency multi-cell joint channel estimation system, which comprises a high layer, a transmitting end and a receiving end, wherein,

the high layer comprises a resource allocation module and a phase shift value definition module, wherein the resource allocation module is used for carrying out shift allocation on a spreading code and a pilot frequency sequence midamble code sequence of an accessed user so as to lead the channel windows of all users to be arranged repeatedly in a period; the phase shift value definition module is used for defining different phase shift values for the cells with the same frequency;

the transmitting end is used for adding the phase shift defined by the high layer to the midamble code part of the user signal and then transmitting the midamble code part to the receiving end;

the receiving end is used for carrying out Fast Fourier Transform (FFT) on midamble code parts of user signals sent by the sending end, carrying out interval value taking by taking the number of co-frequency cells as a period, and calculating channel estimation values of all the cells.

Further, after the resource allocation module performs resource allocation, the resource allocation module has the following characteristics: shift of the same user is divided into l_kAnd in each group, the values of N shifts are taken at intervals in 8/N periods, and the corresponding channel windows are also arranged at intervals in 8/N periods, wherein N is the number of cells with the same frequency.

Further, after the resource allocation module performs resource allocation, the resource allocation module further has the following characteristics: in the same time slot of each cell, the shift group number l occupied by all users_kThe sum of (a) and (b) is equal to 8/N; in the same time slot of the same-frequency cells, the total number K of users distributed by all the cells is not more than 8; the number of users K allocated in the same time slot of each cell_nNot more than 8/N, wherein N is the number of co-frequency cells.

Further, the phase shift value defined by the phase shift value definition module for each cell is: 2 × pi × 16 × n × m/128, where n is a cell number, m is a midamble code shift value occupied by a transmitting end, and in the nth cell, if a transmitting end occupies an mth channel window, a midamble code signal of the mth channel window transmitted is:

${\mathrm{mid}}_{n,m,\mathrm{shift}}={\mathrm{mid}}_{n,m,0}\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2008101673662E00021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{16\mathrm{mn}}{128}\right)$

where j is a complex factor, mid_n，m，0For the original mth midamble code shift sequence, mid, of the nth cell_{n，m，shift}Are appended phase shifted sequences.

Further, in step (e), the channel estimation value of each cell with the same frequency is the same ${\hat{h}}_n=\mathrm{ifft}(\mathrm{fft}\_{\mathrm{rmid}}_n/\mathrm{fft}(\mathrm{ori}\_{\mathrm{mid}}_n)),$ n＝0，1，...，N-1

Wherein,

ori _ mid, a channel estimate for the nth cell_nFor midamble code original sequence transmitted by the nth cell, fft _ rmid_nIs the frequency domain sequence corresponding to the nth cell, and N is the number of the co-frequency cells.

Compared with the prior art, the method and the system have the advantages that the channel windows of all users are arranged repeatedly in the period by reasonably configuring the code channel resources in the TD-SCDMA system, different offsets are added to different cells, the method and the system are used for optimizing the joint channel estimation of the same-frequency multi-cell, the accurate estimation of the channel values of the users can be achieved, the performance of joint detection of the multi-cell is improved, the same-frequency interference is inhibited, and the spectrum efficiency is improved; meanwhile, the channel estimation of the invention is simple to realize, the channels of all the cells with the same frequency are estimated at one time without repeated serial interference elimination, the calculation amount is small, and the realization is easy.

Drawings

Fig. 1 is a schematic diagram of the periodic interval arrangement of user channel windows of the co-frequency cells under the condition that N is 2 and K is 5.

Fig. 2 is a schematic diagram of the periodic interval arrangement of the user channel windows of the co-frequency cells under the condition that N is 4 and K is 7.

Detailed Description

The same-frequency multi-cell joint channel estimation method provided by the invention is simultaneously suitable for an uplink and a downlink, when the same-frequency multi-cell joint channel estimation method is used for the uplink, the transmitting end is a user terminal, the receiving end is a base station, and when the same-frequency multi-cell joint channel estimation method is used for the downlink, the transmitting end is the base station, and the receiving end is the user terminal.

The invention provides a same-frequency multi-cell joint channel estimation method, which comprises the following steps:

the method comprises the following steps: the high layer distributes the same-frequency multi-cell spread spectrum code and midamble (namely pilot frequency sequence) code sequence shift to lead the channel window period of each user to be repeatedly arranged;

resource allocation is done on the network side, referred to as the upper layer for the physical layer.

The total channel estimation window length 128 of the TD-SCDMA system in a single time slot is divided into 8 user channel windows, each window being 16. When the TD-SCDMA system distributes code channel resources to users, a plurality of different shifts of midamble codes of a cell are distributed to the users according to the number of the code channels, and different shift values correspond to different channel windows.

When the high layer carries out code channel and midamble code shift resource allocation, the property of FFT (fast Fourier transform) of the repeated sequence, namely the FFT transform of a new sequence formed after an original sequence is repeated for N times, is utilized to insert N-1 zeros between FFT transform value sampling points of the original sequence. According to the property, users of some data services (needing to occupy a plurality of midamble code shift numbers and corresponding to a plurality of channel windows) are selected and distributed to the same-frequency cells, and the shifts of the users are subjected to periodic interval value taking to form periodic repeated arrangement of the channel windows of the users so as to obtain the zero point of a channel sequence in a frequency domain.

The number of cells is N, the number of cells is {1, 2, 4, 8}, and the number of users allocated to the same time slot by different cells is K_nEach user is assigned l of the same midamble code_kN shift, l_kIs an integer greater than or equal to 1, different users l_kThe values are not exactly the same; of the same user_kN shift divisions into l_kEach group of N shift values are alternately taken at 8/N period; in the shift of the interval value, the corresponding channel windows are also arranged at 8/N periodic intervals, and fig. 1 and fig. 2 are an example of periodic intervals of user channel windows when N is 2 and N is 4, respectively.

The number K of users accommodated in the same-frequency cell and the number K of users in a single cell in the same time slot_nAnd the number of shift groups l occupied by the user_kThe following 3-point relationship must be satisfied:

a. in the same time slot of each cell, l of all users_kIs equal to 8/N:

b. in the same time slot of the same-frequency cells, the total number K of users distributed by all the cells is not more than 8: $K=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{K}_n\&le;8$

c. the number of users K allocated in the same time slot of each cell_nNot more than 8/N: k_n≤8/N

Step two: in a target time slot, different offsets are added to midamble code sequences transmitted by transmitting terminals of different cells;

the frequency-shifted sequence of the FFT has the following characteristics: the time domain sequence is added with a unit phase shift, and the corresponding frequency domain sequence is shifted forward or backward by one bit. According to the characteristic, when midamble code sequences are transmitted to different cells, different offsets are added, so that the channel sequences of different cells are staggered on a frequency domain.

The method for adding different offsets when transmitting midamble code sequences in N cells specifically includes:

in the nth cell, if the user occupies the mth channel window, the midamble code signal of the mth channel window transmitted is:

${\mathrm{mid}}_{n,m,\mathrm{shift}}={\mathrm{mid}}_{n,m,0}\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2008101673662E00021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{16\mathrm{mn}}{128}\right)$

where j is a complex factor, mid_n，m，0For the original mth midamble code shift sequence, mid, of the nth cell_{n，m，shift}Are appended phase shifted sequences.

Step three, in a certain target cell in the same-frequency cells, the receiving end carries out FFT (fast Fourier transform) on a midamble code part of a received signal sequence to obtain a frequency domain sequence;

the baseband model of the midamble code part of the received signal on a single antenna is:

recv_mid＝mid_0，shift*h₀+mid_1，shift*h₁+...+mid_N，shift*h_N

wherein,

recv _ mid is a midamble code partial signal sequence of a received signal sequence on a single antenna;

mid_n，shiftis a midamble code phase-shifted sequence of the nth cell;

h_nan nth cell channel vector;

is the convolution operator.

The receiving end performs FFT on recv _ mid to obtain a frequency domain sequence FFT _ recv _ mid:

fft_recv_mid＝fft(recv_mid)

step four, the receiving end performs interval value taking on the obtained frequency domain sequence fft _ recv _ mid by taking N as a period so as to separate the frequency domain sequences corresponding to different cells:

fft_rmid_n＝fft_recv_mid(n:N:128-N+n)_n＝0，1，...，N-1

wherein fft _ rmid_nIs a frequency domain sequence corresponding to the nth cell.

Step five, the receiving end respectively uses the frequency domain sequences fft _ rmid of different cells_nAnd solving channel estimation values of N cells for multi-cell joint detection:

${\hat{h}}_n=\mathrm{ifft}(\mathrm{fft}\_{\mathrm{rmid}}_n/\mathrm{fft}(\mathrm{ori}\_{\mathrm{mid}}_n)),$ n＝0，1，...，N-1

wherein,

ori _ mid, a channel estimate for the nth cell_nAnd transmitting the original sequence of the midamble code for the nth cell.

The invention can achieve the purposes of accurately estimating the user channel value, improving the performance of multi-cell joint detection and inhibiting same frequency interference.

The channel estimation, joint detection and resource allocation are all carried out by taking a time slot as a unit, and the processes are processing processes in a certain time slot.

Examples of the applications

The process of the present invention is described in further detail below with specific examples.

Example 1: n-4 co-frequency cell, having K-7 user distributed on a certain time slot

The method comprises the following specific operation steps:

1. the high layer (i.e. network layer) performs code channel allocation and midamble sequence shift allocation to the cell users:

the number of users in each cell is not more than 8/N, 2, 2 and 1 for the number of users accessed in 4 cells; the shift allocation of midamble of user is configured with period of 8/N ═ 2, as follows:

2. meanwhile, the higher layer defines different phase shifts for different cells, 2 × pi × 16 × n × m/128, where n is 0, 1, 2, 3 are cell numbers, m is different midamble code shift values of users, and the higher layer notifies all base stations and users in the same-frequency cell of the different phase shift values as system messages.

3. When a base station is used as a receiving end to establish a cell, or when a terminal is used as the receiving end to access the cell, the base station carries out FFT (fast Fourier transform) on midamble code original sequences used by 4 cells to obtain 4 sequences: fft _ ori _ mid₀、fft_ori_mid₁、fft_ori_mid₂、fft_ori_mid₄And stored.

The midamble original sequence is configured in advance by a higher layer.

4. The transmitting terminals of different cells add phase shift to the midamble code part when generating the frame signal of the user according to the phase shift defined by the high layer: according to the shift value m of the midamble code occupied by the transmitting terminal, the shift sequence of the midamble code is multiplied by the phase deviation value 2 × pi × 16 × n × m/128 of the cell where the user is located.

The transmitting end stores the result of resource allocation of the high layer.

5. Before the receiving end starts receiving, a frequency domain receiving sequence storage space is opened up for 4 cells, and initialization zero clearing is carried out:

fft_rmid₀＝[0，0，...，]_1×128

fft_rmid₁＝[0，0，...，]_1×128

fft_rmid₂＝[0，0，...，]_1×128

fft_rmid₃＝[0，0，...，]_1×128

6. a receiving end receives a signal in a target time slot, and FFT (fast Fourier transform) is carried out on a midamble code part of the signal received by a single antenna to obtain a frequency domain sequence FFT _ recv _ mid;

7. the receiving end performs dislocation splitting on the obtained frequency domain sequence fft _ recv _ mid, that is, performs interval value taking with N as a period, to obtain respective frequency domain sequences of 4 cells:

fft_rmid₀(0:4:124)＝fft_recv_mid(0:4:124)

fft_rmid₁(1:4:125)＝fft_recv_mid(1:4:125)

fftrmd₂(2:4:126)＝fft_recv_mid(2:4:126)

fft_rmid₃(3:4:127)＝fft_recv_mid(3:4:127)

8. the receiving end processes the 4 cell frequency domain sequences obtained in the last step, combines the FFT value of the midamble original sequence, and utilizes IFFT to solve the channel estimation value of the 4 cells:

${\hat{h}}_0=\mathrm{ifft}(\mathrm{fft}\_{\mathrm{<figure-callout\; id="0"\; label="rmid"\; filenames="H2008101673662E00011.png,H2008101673662E00021.png"\; state="\{\{state\}\}">rmid</figure-callout>}}_0/\mathrm{fft}\_\mathrm{ori}\_{\mathrm{mid}}_0)$

${\hat{h}}_1=\mathrm{ifft}(\mathrm{fft}\_{\mathrm{<figure-callout\; id="1"\; label="rmid"\; filenames="H2008101673662E00011.png,H2008101673662E00021.png"\; state="\{\{state\}\}">rmid</figure-callout>}}_1/\mathrm{fft}\_\mathrm{ori}\_{\mathrm{mid}}_1)$

${\hat{h}}_2=\mathrm{ifft}(\mathrm{fft}\_{\mathrm{<figure-callout\; id="2"\; label="rmid"\; filenames="H2008101673662E00021.png"\; state="\{\{state\}\}">rmid</figure-callout>}}_2/\mathrm{fft}\_\mathrm{ori}\_{\mathrm{mid}}_2)$

${\hat{h}}_3=\mathrm{ifft}(\mathrm{fft}\_{\mathrm{<figure-callout\; id="3"\; label="rmid"\; filenames="H2008101673662E00021.png"\; state="\{\{state\}\}">rmid</figure-callout>}}_3/\mathrm{fft}\_\mathrm{ori}\_{\mathrm{mid}}_3)$

if the receiving end has multiple antennas, the calculation of the steps 4-6 is repeated for other antennas.

In order to realize the method, the same-frequency multi-cell joint channel estimation system comprises a high layer, a transmitting end and a receiving end, wherein:

the high layer comprises a resource allocation module and a phase shift value definition module, wherein the resource allocation module is used for carrying out shift allocation on a spreading code and a midamble code sequence of an accessed user so as to lead the channel windows of all users to be arranged repeatedly in a period; the phase shift value definition module is used for defining different phase shift values for the cells with the same frequency;

the transmitting end is used for adding the phase shift defined by the high layer to the midamble code part of the user signal and then transmitting the midamble code part to the receiving end;

the receiving end is used for carrying out FFT (fast Fourier transform) on a midamble code part of a user signal sent by the sending end, carrying out interval value taking by taking the number of co-frequency cells as a period, and calculating a channel estimation value of each cell.

After the resource allocation module performs resource allocation, the resource allocation module has the following characteristics: shift of the same user is divided into l_kAnd in each group, the values of N shifts are taken at intervals in 8/N periods, and the corresponding channel windows are also arranged at intervals in 8/N periods, wherein N is the number of cells with the same frequency.

In addition, in the same time slot of each cell, the number l of shift groups occupied by all users_kThe sum of (a) and (b) is equal to 8/N; in the same time slot of the same-frequency cells, the total number K of users distributed by all the cells is not more than 8; the number of users K allocated in the same time slot of each cell_nNot more than 8/N, wherein N is the number of co-frequency cells.

The phase shift value defined by the phase shift value definition module for each cell is as follows: 2 × pi × 16 × n × m/128, where n is a cell number, m is a midamble code shift value occupied by a transmitting end, and in the nth cell, if a transmitting end occupies an mth channel window, a midamble code signal of the mth channel window transmitted is:

${\mathrm{mid}}_{n,m,\mathrm{shift}}={\mathrm{mid}}_{n,m,0}\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2008101673662E00021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\frac{16\mathrm{mn}}{128}\right)$

where j is a complex factor, mid_n，m，0For the original mth midamble code shift sequence, mid, of the nth cell_{n，m，shift}Are appended phase shifted sequences.

The channel estimation value of the same frequency cells at the receiving end is calculated:

${\hat{h}}_n=\mathrm{ifft}(\mathrm{fft}\_{\mathrm{rmid}}_n/\mathrm{fft}(\mathrm{ori}\_{\mathrm{mid}}_n)),$ n＝0，1，...，N-1

wherein,ori _ mid, a channel estimate for the nth cell_nFor midamble code original sequence transmitted by the nth cell, fft _ rmid_nIs a frequency domain sequence corresponding to the nth cell.

It should be understood that the foregoing description of specific embodiments is in such an effort not to limit the scope of the patent claims, which should be limited only by the language of the accompanying claims.

The method and the system of the invention can ensure that the channel windows of each user are periodically and repeatedly arranged by reasonably configuring the code channel resources in the TD-SCDMA system, and different offsets are added to different cells for the optimization of the joint channel estimation of the same-frequency multi-cell, thereby achieving the purposes of accurately estimating the channel value of the user, improving the performance of the joint detection of the multi-cell, inhibiting the same-frequency interference and improving the frequency spectrum efficiency; meanwhile, the channel estimation of the invention is simple to realize, the channels of all the cells with the same frequency are estimated at one time without repeated serial interference elimination, the calculation amount is small, and the realization is easy.

Claims (6)

1. A co-frequency multi-cell joint channel estimation method is characterized by comprising the following steps:

(a) the high layer distributes the same-frequency multi-cell spread spectrum code and pilot frequency sequence midamble code sequence shift to ensure that each user channel window is periodically and repeatedly arranged;

(b) in a target time slot, different offsets are added to midamble code sequences transmitted by transmitting terminals of different cells;

(c) in a certain target cell in the same-frequency cells, a receiving end carries out Fast Fourier Transform (FFT) on a midamble code part of a received signal sequence to obtain a frequency domain sequence;

(d) the receiving end carries out interval value taking on the frequency domain sequences by taking the same frequency cell number N as a period so as to separate the corresponding frequency domain sequences of different cells;

(e) the receiving end respectively uses the frequency domain sequences of different cells obtained in the step (d) to calculate the channel estimation value of each cell with the same frequency for multi-cell joint detection;

wherein, step (a) specifically includes:

the number of cells is N, the number of cells is {1, 2, 4, 8}, and the number of users allocated to the same time slot by different cells is K_nEach user is assigned l of the same midamble code_kN shift, l_kIs an integer greater than or equal to 1, different users l_kThe values are not exactly the same; of the same user_kN shift divisions into l_kEach group of N shift values are alternately taken at 8/N period; the number K of users accommodated in the same-frequency cell and the number K of users in a single cell in the same time slot_nAnd the number of shift groups l occupied by the user_kThe following 3-point relationship must be satisfied:

a. in the same time slot of each cell, l of all users_kIs equal to 8/N:

b. in the same time slot of the same-frequency cells, the total number K of users distributed by all the cells is not more than 8: $K=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{K}_n\&le;8;$

c. the number of users K allocated in the same time slot of each cell_nNot more than 8/N: k_n≤8/N。

2. The method of claim 1, wherein: the method for adding different offsets when the same-frequency cells transmit midamble sequences in step (b) is as follows:

in the nth cell, if a user occupies the mth channel window, the transmitted midamble code signal of the mth channel window is:

${\mathrm{mid}}_{n,m,\mathrm{shift}}={\mathrm{mid}}_{n,m,0}\exp \left(j2\mathrm{\&pi;}\frac{16\mathrm{mn}}{128}\right)$

where j is a complex factor, mid_n，m，0For the original mth midamble code shift sequence, mid, of the nth cell_n,m,shiftAre appended phase shifted sequences.

3. The method of claim 1, wherein: in step (e), the channel estimation value of each cell with the same frequency is calculated as follows: ${\hat{h}}_n=\mathrm{ifft}(\mathrm{fft}\_\mathrm{rmi}{d}_n/\mathrm{fft}(\mathrm{ori}\_\mathrm{mi}{d}_n)),$ n＝0，1，...，N-1

wherein,

ori _ mid, a channel estimate for the nth cell_nFor midamble code original sequence transmitted by the nth cell, fft _ rmid_nIs the frequency domain sequence corresponding to the nth cell, and N is the number of the co-frequency cells.

4. A co-frequency multi-cell joint channel estimation system comprises a high layer, a sending end and a receiving end, and is characterized in that:

the high layer comprises a resource allocation module and a phase shift value definition module, wherein the resource allocation module is used for carrying out shift allocation on a spreading code and a pilot frequency sequence midamble code sequence of an accessed user so as to lead the channel windows of all users to be arranged repeatedly in a period; the phase shift value definition module is used for defining different phase shift values for the cells with the same frequency;

the transmitting end is used for adding the phase shift defined by the high layer to the midamble code part of the user signal and then transmitting the midamble code part to the receiving end;

the receiving end is used for performing Fast Fourier Transform (FFT) on a midamble code part of the user signal sent by the sending end, performing interval value taking by taking the number of co-frequency cells as a period, and calculating a channel estimation value of each cell;

the resource allocation module performs spreading code and pilot sequence midamble code shift allocation on the accessed users, and specifically includes:

the number of cells is N, the number of cells is {1, 2, 4, 8}, and the number of users allocated to the same time slot by different cells is K_nEach user is assigned l of the same midamble code_kN shift, l_kIs an integer greater than or equal to 1, different users l_kThe values are not exactly the same; of the same user_kN shift divisions into l_kEach group of N shift values are alternately taken at 8/N period; the number K of users accommodated in the same frequency cell in the same time slotNumber of users K of cell_nAnd the number of shift groups l occupied by the user_kThe following 3-point relationship must be satisfied:

a. in the same time slot of each cell, l of all users_kIs equal to 8/N:

b. in the same time slot of the same-frequency cells, the total number K of users distributed by all the cells is not more than 8: $K=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{K}_n\&le;8;$

c. the number of users K allocated in the same time slot of each cell_nNot more than 8/N: k_n≤8/N。

5. The system of claim 4, wherein: the phase shift value defined by the phase shift value definition module for each cell is as follows: 2 × pi × 16 × n × m/128, where n is a cell number, m is a different midamble code shift value occupied by the transmitting end, and in the nth cell, if a certain transmitting end occupies the mth channel window, the midamble code signal of the mth channel window transmitted is:

${\mathrm{mid}}_{n,m,\mathrm{shift}}={\mathrm{mid}}_{n,m,0}\exp \left(j2\mathrm{\&pi;}\frac{16\mathrm{mn}}{128}\right)$

where j is a complex factor, mid_n,m,0For the original mth midamble code shift sequence, mid, of the nth cell_n,m,shiftAre appended phase shifted sequences.

6. The system of claim 4, wherein: the channel estimation value of each cell with the same frequency is calculated as follows: ${\hat{h}}_n=\mathrm{ifft}(\mathrm{fft}\_\mathrm{rmi}{d}_n/\mathrm{fft}(\mathrm{ori}\_\mathrm{mi}{d}_n)),$ n＝0，1，...，N-1

wherein,

ori _ mid, a channel estimate for the nth cell_nFor midamble code original sequence transmitted by the nth cell, fft _ rmid_nIs the frequency domain sequence corresponding to the nth cell, and N is the number of the co-frequency cells.

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