WO2012106963A1

WO2012106963A1 - Method and device for eliminating interference and noise

Info

Publication number: WO2012106963A1
Application number: PCT/CN2011/082348
Authority: WO
Inventors: 张磊
Original assignee: 中兴通讯股份有限公司
Priority date: 2011-02-11
Filing date: 2011-11-17
Publication date: 2012-08-16
Also published as: CN102638423A

Abstract

Disclosed are a method and device for eliminating interference and noise. The method comprises: extracting a receiving pilot sequence of a user from a received signal; obtaining a spatial-feature matrix of interference and noise according to the extracted receiving pilot sequence and a local transmitting pilot sequence; determining a relative ratio of interference to noise based on the spatial-feature matrix of interference and noise; comparing the determined relative ratio of interference to noise with a predetermined threshold, and selecting a corresponding equalization algorithm for equalization according to the comparison result, thus eliminating the interference and noise. The technical solution provided in the present invention solves the problem that system performance degrades when one equalization method is robustly employed to implement equalization with the degree of interference unknown in a communication system, thereby improving the communication feature of cell-edge users, and maximally increasing the throughput of cell center users.

Description

TECHNICAL FIELD The present invention relates to the field of communications, and in particular to a method and apparatus for interference and noise cancellation. BACKGROUND OF THE INVENTION The data rate provided by the existing cellular mobile communication system is greatly different between the cell center and the cell edge, which not only affects the capacity of the entire system, but also the quality of service obtained by the user at different locations fluctuates greatly. Therefore, the new generation of broadband wireless communication systems currently under development will inevitably improve the performance of cell edge users as one of the main demand indicators. Inter-cell Interference (ICI) is an inherent problem in cellular mobile communication systems. The traditional solution is to use frequency reuse. The multiplexing factor = 1 means that neighboring cells use the same frequency resource. The interference at the edge of the cell is very serious. Larger multiplexing coefficients can effectively suppress ICI, but spectral efficiency will decrease. The existing interference cancellation scheme is mainly based on the spatial interference suppression technology of the multi-antenna receiving terminal. It does not rely on any additional transmitter configuration, so there is no need to do any additional standardization work, but does not rely on any additional signal differentiation means (such as frequency division, code division, interleaver division), but only rely on air separation means, very It is difficult to obtain a satisfactory interference cancellation effect, and the interference in the system is relatively small, and it is difficult to distinguish it by the spatial dimension, which may cause deterioration of system performance. SUMMARY OF THE INVENTION The present invention provides an interference and noise cancellation method and apparatus to solve at least one of the above problems. According to an aspect of the present invention, an interference and noise cancellation method is provided, including: extracting a received pilot sequence of a user from a received signal; and obtaining interference according to the extracted received pilot sequence and a local transmitted pilot sequence a noise space characteristic matrix; determining a relative ratio of interference and noise according to the spatial matrix of interference noise; determining a relative ratio of the interference and the noise to a predetermined threshold, and selecting a corresponding equalization algorithm to perform equalization according to the comparison result, eliminating The above interference and noise. Selecting the corresponding equalization algorithm for equalization according to the comparison result includes: when the relative ratio of the interference and the noise is greater than or equal to the predetermined threshold, selecting an equalization algorithm with interference suppression to perform equalization; and the relative ratio of the interference to the noise is less than a predetermined threshold When the value is selected, the equalization algorithm that eliminates noise is selected for equalization. Obtaining an interference noise spatial characteristic matrix according to the extracted received pilot sequence and the local transmit pilot sequence includes: performing channel estimation according to the received pilot sequence and the transmitted pilot sequence, and obtaining a channel estimation value; according to the channel estimation value, The pilot sequence is received and the pilot sequence is transmitted, and the interference noise spatial characteristic matrix is obtained. The methods for channel estimation include: Least Square (Least Square, LS for short), Linearity Minimum Mean Square Error (LMMSE), time domain noise reduction, and frequency domain noise reduction. The equalization algorithms with interference suppression include: Minimum Mean Square Error (MMSE); Noise equalization algorithms include: Zero Forcing (ZF), Maximum Ratio Combing , referred to as MRC), MMSE. According to another aspect of the present invention, there is provided an interference and noise canceling apparatus, comprising: a sequence extracting module, configured to extract a received pilot sequence of a user from a received signal; and a spatial matrix module, configured to receive, according to the received a frequency sequence and a local transmission pilot sequence, and a spatial matrix of interference noise is obtained, and a relative ratio of interference and noise is determined according to the spatial matrix of the interference noise; a decision selection module is configured to determine a relative ratio of the interference and the noise. Compared with the predetermined threshold, the corresponding equalization algorithm is selected according to the comparison result to perform equalization, and the above interference and noise are eliminated. The decision selection module includes: a decision unit configured to compare the determined relative ratio of the interference and the noise with a predetermined threshold; the interference suppression unit is configured to select the band when the relative ratio of the interference and the noise is greater than or equal to a predetermined threshold The equalization algorithm with interference suppression performs equalization; the noise cancellation unit is set to select an equalization algorithm for eliminating noise to perform equalization when the relative ratio of interference and noise is less than a predetermined threshold. The spatial matrix module includes: a channel estimation unit, configured to perform channel estimation according to the received pilot sequence and the transmitted pilot sequence, to obtain a channel estimation value; and a matrix calculation unit configured to: according to the channel estimation value, the received pilot sequence, and the transmit pilot The sequence is used to obtain a spatial characteristic matrix of interference noise; the ratio determining unit is configured to determine a relative ratio of interference and noise according to a spatial matrix of interference noise. The channel estimation unit performs channel estimation methods including: LS, LMMSE, time domain noise reduction, and frequency domain noise reduction. The equalization algorithm with interference suppression includes: MMSE; the noise elimination algorithm includes: ZF, MRC,

MMSEo uses the present invention to select a different interference noise cancellation method for equalization according to the ratio of interference and noise, and solves the problem of unknown interference size in the communication system, and robustly adopts an equalization method. The problem of system performance degradation caused by equalization is achieved, thereby improving the communication characteristics of the cell edge users and maximizing the throughput of the cell center users. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set to illustrate,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 1 is a flow chart of a method for interference and noise equalization according to an embodiment of the present invention; FIG. 2 is a schematic diagram of a structure of a pilot time domain continuous sequence according to an embodiment of the present invention; FIG. 3 is an interference according to an example of the present invention. FIG. 4 is a block diagram showing the structure of an interference and noise equalization apparatus according to an embodiment of the present invention. FIG. 5 is a block diagram showing the structure of an interference and noise equalization apparatus according to a preferred embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. 1 is a flow chart of an interference and noise equalization method in accordance with an embodiment of the present invention. As shown in FIG. 1, the interference and noise equalization method according to an embodiment of the present invention includes: Step S102: extracting a received pilot sequence of a user from a received signal; Step S104, according to the extracted received pilot sequence and a local transmit guide a frequency sequence, the interference noise spatial characteristic matrix is obtained; Step S106, determining a relative ratio of the interference and the noise according to the interference noise spatial characteristic matrix; Step S108, comparing the determined relative ratio of the interference and the noise with a predetermined threshold value, According to the comparison result, the corresponding equalization algorithm is selected for equalization to eliminate interference and noise. The above method utilizes the interference suppression combining technique, and selects different interference noise cancellation schemes for equalization according to the proportion of interference and noise, so that the communication characteristics of the cell edge users can be improved at the same time. In step S102, receiving the data information sent by the user, the pilot sequence may be extracted from the received signal according to the corresponding location, as shown in FIG. 2 . Preferably, in step S108, selecting the corresponding equalization algorithm for equalization according to the comparison result may further include the following processing: (1) selecting an equalization algorithm with interference suppression when the relative ratio of the interference and the noise is greater than or equal to a predetermined threshold. Equilibrium;

(2) When the relative ratio of interference and noise is less than the predetermined threshold, the equalization algorithm for eliminating noise is selected for equalization. The relative ratio of interference and noise reflects the difference of communication state. When the relative ratio of interference and noise is greater than or equal to the predetermined threshold, the inter-cell interference is more serious. Therefore, the equalization algorithm with interference suppression is used for equalization. When the relative ratio of interference and noise is less than the predetermined threshold, the influence of noise is more serious at this time, so the equalization algorithm with noise is used for equalization. The above predetermined threshold may be determined according to simulation statistics or may be the result of an external field test. Preferably, step S104 may further include the following processes: (1) performing channel estimation according to the received pilot sequence and the transmitted pilot sequence, and obtaining a channel estimation value;

(2) The interference noise spatial characteristic matrix is obtained based on the channel estimation value, the received pilot sequence, and the transmission pilot sequence. In order to obtain the interference noise spatial characteristic matrix, channel estimation may be first performed according to the received pilot sequence and the transmitted pilot sequence, and then the interference noise spatial characteristic matrix is finally obtained according to the channel estimation value, the received pilot sequence, and the transmitted pilot sequence. Preferably, the method for performing channel estimation may include: LS, LMMSE, time domain noise reduction, and frequency domain noise reduction. There are many methods for performing channel estimation that can be used, including but not limited to the above methods. Preferably, the foregoing equalization algorithm with interference suppression may include: MMSE; the above noise elimination equalization algorithm includes: ZF, MRC, MMSE. Similarly, algorithms that can be used here include, but are not limited to, the above algorithms. In summary, the above preferred embodiments can be summarized as: Step 1: Receive data information sent by the user, and extract a pilot sequence from the received signal according to the corresponding position; Step 2: Channel estimation, using the received pilot signal and the transmitted local pilot to perform channel estimation of the current cell; The third step: the measurement of the spatial matrix of interference and noise, according to the measured interference and noise, find their spatial feature matrix; The fourth step: Calculate the relative ratio of interference and noise according to the distribution characteristics of the interference and noise spatial matrix, And compared with the threshold; Step 5: Adaptive selection of the equalization algorithm for equalization, eliminating interference and noise. The above preferred embodiments will be described in detail below with reference to examples and FIG. As shown in FIG. 3, the interference and noise equalization method according to an example of the present invention includes the following steps: Step 302: Taking LTE as an example, the corresponding time-frequency resource location is as shown in FIG. 2, and the received time-frequency resource location is extracted according to the corresponding time-frequency resource location. Pilot information, used for channel estimation in the next step. Step 304: Perform channel estimation according to the extracted received pilot signal and the local transmit pilot sequence. The channel estimation method is not limited, and may be a channel estimation method such as LS, LMMSE, time domain noise reduction, and frequency domain noise reduction. The domain noise reduction method is taken as an example: First, the LS algorithm is used to obtain the channel estimation without noise reduction. The formula is as follows:

H _p = X~ k) .Y(k) Then perform Inverse Fast Fourier Transform (IFFT), change to the time domain to do noise reduction processing = / H^, then calculate the window length, after adding The window is denoised to obtain the channel estimation of the local cell after noise reduction. The calculation formula for the window length is as follows:

L ^JV #"

^L fore = ^mL c ' ^L post = «

J _/flre is the front window length, ^. ^ is the length of the back window, N is the number of subcarriers occupied by the target user, is 3⁄4

, / _P is the length of the cyclic prefix in the OFDM system, and "is the ratio of the length of the front window and the back window. Number. Finally, a Fast Fourier Transform (FFT) transform is performed to obtain a frequency domain channel impulse response _P = FFT(h _p ). Step 306: Calculate the spatial structure matrix of the interference noise according to the channel estimation value, the transmission and the reception pilot sequence obtained in step 304, and the method is not limited. The following method is taken as an example: First, the interference and noise sequence are calculated:

NI = Y -H _p *X where : is the received pilot sequence, including the information sent by the target user, interference information, and noise. _P is the channel estimate at the pilot, the pilot sequence sent for the target user. M is the interference noise sequence, then the interference noise spatial characteristic matrix R„ is: R _n = NI "M ^H / N where N is the number of calculated subcarriers. Step 308, according to the distribution characteristic of the interference noise spatial matrix obtained in step 306, obtain a relative ratio of interference and noise, and the distribution of noise and interference has a certain regularity in the spatial matrix. According to the regularity, the calculation can be calculated. The relative ratio of interference to noise. Step 310: Compare the relative ratio of the interference and the noise calculated in step 308 to a predetermined threshold. If the threshold is greater than or equal to the threshold, the equalization algorithm with interference suppression is used. If the threshold is smaller than the threshold, the equalization algorithm for eliminating noise is used. The threshold here may be The simulation statistics determine the result of the field test. Step 312, according to the channel estimation value obtained in step 304, the spatial characteristic matrix of the interference and noise obtained in step 304 and the received data are equalized to eliminate interference and noise, wherein the equalization formula with interference suppression is as follows, taking MMSE as an example, but Not limited to the MMSE algorithm:

X = {H ^H ■ R- · H + /)_' H ^H · R- · Y The noise equalization algorithm can be based on ZF, MRC, MMSE, etc. The following is an example of MMSE. The formula is as follows:

Χ = {Η ^Η ·Η + σ ² ΐγ ^λ Η ^Η -Y 4 is a block diagram showing the structure of an interference and noise equalization apparatus according to an embodiment of the present invention. As shown in FIG. 4, the interference and noise equalization apparatus according to an embodiment of the present invention includes: a sequence extraction module 42 configured to extract a received pilot sequence of a user from a received signal; and a spatial matrix module 44 configured to receive according to the received a pilot sequence and a local transmit pilot sequence, and a spatial matrix of interference noise is obtained, and a relative ratio of interference and noise is determined according to the interference noise spatial characteristic matrix; a decision selection module 46 is set to determine the interference and noise. The relative ratio is compared with a predetermined threshold, and the corresponding equalization algorithm is selected according to the comparison result to perform equalization to eliminate interference and noise. The above device utilizes the interference suppression combining technology, and selects different interference noise cancellation schemes for equalization according to the proportion of interference and noise (ie, adaptively performs equalization), thereby maximizing the communication characteristics of the cell edge users while maximizing Improve the throughput of community center users. Preferably, the decision selecting module 46 may further include: a determining unit 462, configured to compare the determined relative ratio of interference and noise with a predetermined threshold; the interference suppressing unit 464 is configured to have a relative ratio of interference and noise greater than or equal to When the threshold is predetermined, an equalization algorithm with interference suppression is selected for equalization; and the noise cancellation unit 466 is configured to select an equalization algorithm for canceling the noise to perform equalization when the relative ratio of the interference and the noise is less than a predetermined threshold. Through the above modules, an adaptive mechanism can be established, and the equalization processing can be selectively performed according to different network states. Preferably, the spatial matrix module 44 may further include: a channel estimation unit 442, configured to perform channel estimation according to the received pilot sequence and the transmitted pilot sequence, to obtain a channel estimation value; and a matrix calculation unit ₄₄₄ configured to determine, according to the channel estimation value, Receiving a pilot sequence and transmitting a pilot sequence to obtain an interference noise spatial characteristic matrix; the ratio determining unit 446 is configured to determine a relative ratio of interference and noise according to the interference noise spatial characteristic matrix. The calculation of the interference noise spatial characteristic matrix can be divided into two steps. After the channel estimation unit 442 obtains the channel estimation value, the matrix calculation unit 444 can obtain the interference noise spatial characteristic matrix on this basis. After the interference noise spatial characteristic matrix is obtained, the ratio determining unit 446 can determine the relative ratio of the interference and the noise according to the distribution characteristic of the interference noise spatial characteristic matrix. In summary, the working process of the foregoing preferred apparatus may be summarized as follows: First, the sequence extraction module 42 extracts the received pilot sequence of the user according to the corresponding time-frequency resource, and then the channel estimation unit 442 sends the received pilot sequence according to the received pilot sequence. The pilot sequence performs channel estimation, and the matrix calculation unit 444 calculates a spatial characteristic matrix of the interference noise. The ratio determining unit 446 calculates a relative ratio of interference and noise according to the distribution characteristic of the matrix, and then passes the interference and noise through the decision unit 462. The relative ratio is compared with the threshold. Finally, the interference suppression unit 464 and the noise cancellation unit 466 select an appropriate equalization algorithm for equalization based on the comparison result obtained by the decision unit 462 to eliminate interference and noise. Preferably, the method for performing channel estimation by the channel estimation unit 442 may include: LS, LMMSE, time domain noise reduction, and frequency domain noise reduction. There are actually many methods for channel estimation that channel estimation unit 442 can use, including but not limited to the above methods. Preferably, the foregoing equalization algorithm with interference suppression may include: MMSE; the above noise elimination equalization algorithm includes: ZF, MRC, MMSE. Similarly, algorithms that can be used here include, but are not limited to, the above algorithms. From the above description, it can be seen that the present invention designs an adaptive interference noise equalization scheme based on the interference suppression combining technology, which not only improves the communication characteristics of the cell edge users, but also maximizes the cell center. User throughput. Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general-purpose computing device, which can be concentrated on a single computing device or distributed over a network composed of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device, such that they may be stored in the storage device by the computing device and, in some cases, may be different from the order herein. The steps shown or described are performed, or they are separately fabricated into individual integrated circuit modules, or a plurality of modules or steps are fabricated as a single integrated circuit module. Thus, the invention is not limited to any specific combination of hardware and software. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

Claim

1. A method of interference and noise cancellation, comprising:

Extracting a received pilot sequence of the user from the received signal;

Obtaining an interference noise spatial characteristic matrix according to the extracted received pilot sequence and the local transmitted pilot sequence;

Determining, according to the interference noise spatial characteristic matrix, a relative ratio of the interference and the noise; comparing the determined relative ratio of the interference and the noise with a predetermined threshold, selecting a corresponding equalization algorithm according to the comparison result, performing equalization, and eliminating the Interference and noise.

2. The method according to claim 1, wherein the selecting the corresponding equalization algorithm for equalization according to the comparison result comprises:

When the relative ratio of the interference and the noise is greater than or equal to the predetermined threshold, selecting an equalization algorithm with interference suppression to perform equalization;

When the relative ratio of the interference and noise is less than the predetermined threshold, an equalization algorithm for eliminating noise is selected for equalization.

The method according to claim 2, wherein the obtaining the interference noise spatial characteristic matrix according to the extracted received pilot sequence and the local transmit pilot sequence comprises:

Performing channel estimation according to the received pilot sequence and the transmitted pilot sequence to obtain a channel estimation value;

And determining, according to the channel estimation value, the received pilot sequence, and the transmission pilot sequence, the interference noise spatial characteristic matrix.

4. The method according to claim 3, wherein the method for performing channel estimation comprises: least squares LS, linear minimum mean square error method LMMSE, time domain noise reduction, frequency domain noise reduction.

The method according to any one of claims 2 to 4, wherein

The equalization algorithm with interference suppression includes: a minimum mean square error MMSE; the noise elimination equalization algorithm includes: zero-forcing ZF, maximum ratio combining MRC, and minimum mean square error MMSE. An interference and noise cancellation device, comprising:

a sequence extraction module, configured to extract a received pilot sequence of the user from the received signal; and a spatial matrix module configured to obtain a spatial matrix of interference noise according to the extracted received pilot sequence and the local transmit pilot sequence, And determining a relative ratio of interference and noise according to the interference noise spatial characteristic matrix;

The decision selection module is configured to compare the determined relative ratio of the interference and the noise with a predetermined threshold, and select a corresponding equalization algorithm to perform equalization according to the comparison result to eliminate the interference and noise. The apparatus according to claim 6, wherein the decision selection module comprises:

a decision unit, configured to compare the determined relative ratio of the interference and noise to a predetermined threshold;

The interference suppression unit is configured to: when the relative ratio of the interference and the noise is greater than or equal to the predetermined threshold, select an equalization algorithm with interference suppression to perform equalization;

The noise canceling unit is configured to select an equalization algorithm for canceling the noise to perform equalization when the relative ratio of the interference and the noise is less than the predetermined threshold. The apparatus according to claim 7, wherein the spatial matrix module comprises:

a channel estimation unit, configured to perform channel estimation according to the received pilot sequence and the transmit pilot sequence, to obtain a channel estimation value;

a matrix calculation unit, configured to determine the interference noise spatial characteristic matrix according to the channel estimation value, the received pilot sequence, and the transmitted pilot sequence;

The ratio determining unit is configured to determine a relative ratio of the interference and the noise based on the interference noise spatial characteristic matrix. The apparatus according to claim 8, wherein the method for channel estimation by the channel estimation unit comprises: a least squares method LS, a linear minimum mean square error method LMMSE, a time domain noise reduction, and a frequency domain noise reduction. The apparatus according to any one of claims 7 to 9, wherein

The equalization algorithm with interference suppression includes: minimum mean square error MMSE;

The noise elimination equalization algorithm includes: zero forcing ZF, maximum ratio combining MRC, and minimum mean square error MMSE.