WO2012065413A1

WO2012065413A1 - Interference cancellation method and device in wireless communication system

Info

Publication number: WO2012065413A1
Application number: PCT/CN2011/074175
Authority: WO
Inventors: 李焱; 易立强; 李双喜
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-11-19
Filing date: 2011-05-17
Publication date: 2012-05-24
Also published as: CN102469475A; CN102469475B

Abstract

An interference cancellation method and a device in a wireless communication system. The method mainly includes following steps which are performed by a User Equipment (UE): obtaining related information of a target cell by detecting reception signals(S11); performing channel estimation according to the Secondary Synchronization Signal (SSS) of the target cell(S12); reconstructing the Primary Synchronization Signal (PSS) and the SSS by using the channel estimation(S13); cancelling the PSS and SSS of the target cell in the reception signal by using the reconstructed PSS and SSS to obtain a reception signal in which the interference from the target cell is cancelled(S14); performing the above steps repeatedly for the reception signal in which the interference from the target cell is cancelled until obtaining a reception signal in which the interferences from all target cells that can be searched out are cancelled. Thus the performance to detect cells with the same frequency can be enhanced greatly, especially to the adjacent cells with the same frequency whose signals are weak.

Description

Method and device for interference cancellation in wireless communication system

The invention relates to a method and a device for wireless communication signal interference, and is particularly suitable for a method and device for signal interference during cell measurement. Background technique

In wireless communication systems, especially in cellular communications, measurement plays a very important role in cell handover and reselection. First, the user equipment (UE, User Equipment) needs to identify the co-frequency or inter-frequency neighbor cell ID and timing information before making measurements. Secondly, the Automatic Neighbor Relation (ANR) function that needs to be supported in the next generation mobile network also places high demands on the UE's ability to detect neighboring cells. Finally, even if the Cell ID of the neighboring cell is delivered by the E-node B, the UE needs to detect the timing of the corresponding cell. When the signal strengths of two or more cells on the same frequency point are large, the detection of weak cells may be difficult due to the correlation characteristics of pseudo-random (PN, Pseudo Noise) sequences and noise.

In the Long Term Evolution (LTE) system, due to signal interference between different cells, it is easy for the UE to encounter difficulties in detecting the cell. Summary of the invention

The main object of the present invention is to solve the problem that the UE is susceptible to interference from different cell signals when detecting the cell. The present invention uses the interference cancellation method to utilize the information of the stronger cell detected first. By using the secondary synchronization sequence for channel estimation, the reconstructed frequency domain signal is converted to the time domain and then cancelled, which can greatly enhance the detection performance of the same frequency cell, especially the same frequency adjacent region with weak signal.

According to an aspect of the present invention, the present invention provides interference cancellation in a wireless communication system The method includes the following steps performed by the UE:

A) obtaining information about the target cell by detecting the received signal;

B) performing channel estimation according to the secondary synchronization signal SSS of the target cell;

C) reconstructing the primary synchronization signal PSS and the secondary synchronization signal SSS using the channel estimation;

D) using the reconstructed primary synchronization signal PSS and the secondary synchronization signal SSS to cancel the primary synchronization signal PSS and the secondary synchronization signal of the target cell in the received signal according to the timing information of the target cell.

SSS, obtaining a received signal that cancels interference of the target cell;

E) repeating the above steps for the received signal that cancels the target cell interference, A)

~D), until a received signal is obtained that cancels the interference of all target cells that can be detected.

Where step B) is:

Determining the secondary synchronization signal of the target cell by using the obtained ID and timing information of the target cell, and performing channel estimation in the frequency domain by using the secondary synchronization signal to determine an estimated channel frequency domain response.

Where step C) is:

Reconstructing the primary synchronization frequency domain signal and the secondary synchronization frequency domain signal by using the estimated channel frequency domain response and the locally generated primary synchronization signal and the secondary synchronization signal, respectively, and reconstructing the reconstructed primary synchronization frequency domain signal and the secondary synchronization The frequency domain signals are respectively converted into a primary synchronous time domain signal and a secondary synchronous time domain signal.

Where step D) is:

And using the timing information of the target cell to cancel the primary synchronization time domain signal and the secondary synchronization time domain signal respectively with the primary synchronization signal and the secondary synchronization signal of the target cell in the received signal.

In addition, step B) also includes:

Generating a local secondary synchronization signal by using the ID and timing information of the searched target cell; performing frequency domain least squares (LS) channel estimation by using the received cell secondary synchronization signal and the locally generated secondary synchronization signal; Smoothing the channel frequency domain response of the channel estimate.

The channel frequency domain response of the channel estimation is smoothed by using an FFT method for smoothing.

Wherein, step C) further includes:

Reconstructing the reconstructed primary synchronization time domain signal and the cyclic prefix of the secondary synchronization time domain signal respectively; determining the primary synchronization time domain signal and the secondary synchronization time domain signal after reconstructing the cyclic prefix.

According to another aspect of the present invention, the present invention further provides an apparatus for interference cancellation in a wireless communication system, including a UE, where the UE includes:

a detecting module, configured to obtain target cell related information by detecting the received signal; until a received signal that cancels interference of all target cells that can be detected is obtained;

a channel estimation module, performing channel estimation according to the secondary synchronization signal SSS of the target cell; a reconstruction module, reconstructing a primary synchronization signal PSS and a secondary synchronization signal SSS by using the channel estimation; and a cancellation module, using the reconstructed primary synchronization signal PSS And the secondary synchronization signal SSS, canceling the primary synchronization signal PSS and the secondary synchronization signal SSS of the target cell in the received signal according to the timing of the target cell, to obtain a received signal that cancels interference of the target cell

The channel estimation module further includes:

And a smoothing module, configured to perform smoothing on a channel frequency domain response of the channel estimation.

In addition, the reconstruction module is further configured to reconstruct a cyclic prefix of the primary synchronization time domain signal and the secondary synchronization time domain signal. Compared with the prior art, the present invention has the following advantages: The present invention is directed to the characteristics of the LTE system, and uses the method of interference cancellation to utilize the information of the stronger cell detected first. By performing channel estimation using the secondary synchronization sequence, the reconstructed frequency domain signal is converted to the time domain and then cancelled. Then, the detection is continued, and the detected secondary strong cells continue to cancel until no new cells are detected. This can greatly enhance the detection performance of the same-frequency cell, especially the intra-frequency neighboring area with weaker signals. At the same time, due to channel estimation, signal reconstruction and other steps can utilize existing modules. Therefore, it is basically unnecessary to increase hardware resources; effectively solving the problem that the UE is susceptible to interference from different cell signals when detecting a cell. DRAWINGS

1 is a flow chart of a method for implementing interference cancellation in a wireless communication system of the present invention;

2 is a block diagram of an interference cancellation scheme in a wireless communication system of the present invention;

3 is a block diagram of signal reconstruction in the wireless communication system of the present invention;

4 is a block diagram of signal cancellation in the wireless communication system of the present invention;

Fig. 5 is a block diagram showing the structure of an interference canceling apparatus in the wireless communication system of the present invention. detailed description

The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

A method for interference cancellation in a wireless communication system according to the present invention, the flow chart of which is shown in FIG. 1, includes the following steps performed by the UE:

511. Obtain target cell related information by detecting the received signal; (the obtained target related information includes the target cell ID and timing information)

512: Perform channel estimation according to the secondary synchronization signal SSS of the target cell.

513, using the channel estimation to reconstruct a primary synchronization signal PSS and a secondary synchronization signal SSS;

514. Using the reconstructed primary synchronization signal PSS and the secondary synchronization signal SSS, cancel the primary synchronization signal PSS and the secondary synchronization signal SSS of the target cell in the received signal according to the timing of the target cell, and obtain the offset of the target cell. Interference received signal;

For the received signal canceled by the target cell interference, the above steps S11) to S14) are repeatedly performed until a received signal that cancels the interference of all target cells that can be searched is obtained.

The specific plan map when it is offset, as shown in Figure 2,

Wherein, step S12) is specifically: Determining a secondary synchronization signal of the target cell by using the detected ID and timing information of the target cell, and performing channel estimation in the frequency domain by using the secondary synchronization signal to determine an estimated channel frequency domain port response.

The method further includes: generating, by using the detected ID and timing information of the target cell, a local auxiliary synchronization signal;

Performing frequency domain least squares (LS) channel estimation by using the received cell secondary synchronization signal and the locally generated secondary synchronization signal;

Smoothing the channel frequency domain response of the channel estimate.

The channel frequency domain response of the channel estimation is smoothed by using a fast Fourier transform (FFT) method for smoothing.

Wherein, step S13) is specifically:

The cyclic prefix of the reconstructed primary synchronization time domain signal and the secondary synchronization time domain signal are respectively reconstructed; and the primary synchronization time domain signal and the secondary synchronization time domain signal after the cyclic prefix is reconstructed are determined.

Wherein, step S14) is specifically:

The target cell detected in the foregoing step S11 may be one or more, and if it is multiple target cells, it is necessary to obtain related information of multiple target cells in step S11; and multiple targets in step S12 The cell separately performs channel estimation; in step S13, the primary synchronization signal PSS and the secondary synchronization signal SSS of each target cell are respectively reconstructed by channel estimation for multiple target cells in step S12; and then according to step S14 Target area The timing information simultaneously cancels the primary synchronization signal PSS and the secondary synchronization signal SSS of the plurality of target cells in the received signal; thereby achieving simultaneous cancellation of the plurality of target cells.

Finally, the above steps are repeated until a received signal is obtained that cancels the interference of all target cells that can be searched.

The specific scheme map of the interference cancellation, as shown in FIG. 2, first selects the received signal, selects the target cell signal, determines the signal reconstruction, and cancels the reconstructed signal and the received signal, and then Search for other target cells.

The above sweep method is summarized as the following work steps:

Step 1: Select the target cell ( ^Cel L' )··

At different stages, the target cell will be different. In the initial cell search state, the strongest cell needs to be detected first. After camping, the serving cell is the target cell. Usually, the serving cell is also the strongest cell. At this time, the timing information of ^Ce "», the cell ID and the CP (Cyclic Prefix) mode are all known.

Step 2: Channel estimation:

First, based on the ID and timing information of the selected cell "»«, using its secondary synchronization signal (SSS) for channel estimation, a common channel estimation method is given below (channel estimation can also be performed by other methods):

First, do the LS estimation of the received signal in the frequency domain:

H _LS = FFT(r _ssch )US _ID

Wherein, S _ro is a locally generated secondary synchronization signal, r ^ is a secondary synchronization signal of the received selected cell, FFT is a fast Fourier transform method, and H _S is a channel estimation result obtained by LS estimation.

In order to improve performance, it is necessary to further smooth the results of the above channel estimation, such as the commonly used FFT method:

FFT{W 1FFT(H _LS )} Where w is a window function, and the specific window size is related to the length corresponding to the channel impact, and may also be fixedly set to the CP length, IFFT is the inverse fast Fourier transform method, and H^ is the estimated secondary synchronization channel after smoothing. .

After channel estimation, the signal is reconstructed. The specific block diagram is shown in Figure 3.

The third step: signal reconstruction:

The frequency domain signal can be reconstructed separately using the estimated channel, and the locally generated PSS (primary synchronization signal) and SSS (secondary synchronization signal). After the IFFT, it is converted into a signal in the time domain to perform interference. The specific reconstruction method is:

―

IFFT{SJ

Where _s is a locally generated primary synchronization signal, which is a locally generated secondary synchronization signal, which is respectively subjected to inverse fast Fourier transform (IIFT), and then converted into a primary synchronous time domain signal ( _Ssp ) and a secondary synchronous time domain signal ( _Sssch ).

Among them, before the interference cancellation is performed, the cyclic prefix (CP) of the signal needs to be reconstructed as well. That is, a signal whose tail length is ^Λ ^ of the PSCH (Primary Synchronization Channel) and SSCH (Secondary Synchronization Channel) signals is placed in front of the OFDM symbol to form a sequence of length ^{V + Λ} ^. ^N cp is the length of the cyclic prefix. Specifically expressed as

- + ^ · N - + ^ · N where N is the length of the OFDM symbol, „_ is the primary synchronization time domain signal after reconstructing the cyclic prefix, and s _c is the secondary synchronous time domain signal after reconstructing the cyclic prefix.

After signal reconstruction, the interference cancellation of the signal is shown in Figure 4.

Step 4: Interference cancellation:

According to the timing information of the cell, the time of the arrival of the PSCH and the SSCH is respectively performed: γ ― γ — c

Ssch ssch cancell-ssch

Wherein the primary synchronization signal is received, ^ _¾ of a main synchronization signal after the elapse of offset of the received secondary synchronization _signal, r ssch elapsed secondary synchronization signal after cancellation.

The reconstructed signal can be used to cancel the currently received signal or to cancel the signal of the next cycle (the sync signal is sent in a 5ms cycle). The received signal can be buffered if necessary, and then cancelled after the signal is reconstructed.

Step 5: Community Search:

For the cell after canceling the interference, the cell search is performed again. If the detection detects a new cell, then go back to the first step and continue to cancel.

The selected target cell in the foregoing first step may also be multiple target cells; when multiple target cells are used, the channel estimation of the second step may be performed separately for multiple target cells; and in the third step, multiple target cells are used. Signal reconstruction is performed separately; finally, signals of multiple target cells are simultaneously cancelled in the fourth step; then the cell search of the fifth step is performed.

According to another aspect of the present invention, the present invention further provides an apparatus for interference cancellation in a wireless communication system. As shown in FIG. 5, the UE includes:

a channel estimation module, performing channel estimation according to the secondary synchronization signal SSS of the target cell; a reconstruction module, reconstructing a primary synchronization signal PSS and a secondary synchronization signal SSS by using the channel estimation; and a cancellation module, using the reconstructed primary synchronization signal PSS And the secondary synchronization signal SSS, canceling the primary synchronization signal PSS and the secondary synchronization signal SSS of the target cell in the received signal according to the timing of the target cell, to obtain a received signal that cancels the interference of the target cell.

The channel estimation module further includes:

In addition, the reconstruction module further includes a loop before the primary synchronization time domain signal and the secondary synchronization time domain signal The suffix is reconstructed. It is to be understood that the specific implementation of the invention is not limited to the description. It will be apparent to those skilled in the art that the present invention may be made without departing from the spirit and scope of the invention.

Claims

Claim

A method for interference cancellation in a wireless communication system, characterized by comprising the following steps performed by a UE:

D) using the reconstructed primary synchronization signal PSS and the secondary synchronization signal SSS to cancel the primary synchronization signal PSS and the secondary synchronization signal SSS of the target cell in the received signal according to the timing information of the target cell, respectively, a received signal of interference of the target cell;

2. A method of interference cancellation in a wireless communication system according to claim 1, wherein said step B) is:

3. A method of interference cancellation in a wireless communication system according to claim 2, wherein said step C) is:

4. The method of interference cancellation in a wireless communication system according to claim 3, wherein said step D) is:

Using the timing information of the target cell, respectively, the primary synchronization time domain signal and the secondary synchronization time domain signal are respectively offset from the primary synchronization signal and the secondary synchronization signal of the target cell in the received signal. Eliminate.

5. The method of interference cancellation in a wireless communication system according to claim 2, wherein the step B) further comprises:

Generating a local secondary synchronization signal by using the ID and timing information of the searched target cell; performing frequency domain least squares (LS) channel estimation by using the received cell secondary synchronization signal and the locally generated secondary synchronization signal;

Smoothing the channel frequency domain response of the channel estimate.

The method for interference cancellation in a wireless communication system according to claim 5, wherein the channel frequency domain response of the channel estimation is smoothed to be smoothed using a fast Fourier transform (FFT) method. .

The method of interference cancellation in a wireless communication system according to claim 3, wherein the step C) further comprises:

A device for interference in a wireless communication system, comprising a UE, wherein the UE comprises:

The apparatus for interference cancellation in a wireless communication system according to claim 8, wherein the channel estimation module further comprises: And a smoothing module, configured to perform smoothing on a channel frequency domain response of the channel estimation.

10. The apparatus for interference cancellation in a wireless communication system according to claim 8, wherein the reconstruction module is further configured to reconstruct a cyclic prefix of the primary synchronization time domain signal and the secondary synchronization time domain signal.