CN102215514A - Signal joint detection method and device - Google Patents

Abstract

The invention discloses a signal joint detection method, which is used for improving the detection performance of joint detection. The method comprises the following steps of: determining whether noises are high or low according to the first power of a noise signal and a preset threshold value; when the noises are determined to be low, performing the joint detection on the signal according to a first algorithm used for eliminating multiple access interference; and when the noises are determined to be high, performing the joint detection on the signal according to a second algorithm used for suppressing the noises. The invention also discloses a device for implementing the method.

Description

Signal joint detection method and device

Technical Field

The present invention relates to the field of communications, and in particular, to a method and an apparatus for joint signal detection.

Background

In a CDMA system, due to random access of multiple users, the used spreading code sets are generally not strictly orthogonal, and a non-zero cross-correlation coefficient causes mutual interference between users, i.e., Multiple Access Interference (MAI); the presence of multiple access interference presents two problems: firstly, the capacity of the system is limited, and secondly, the near-far effect seriously affects the performance of the system. Depending on the MAI processing method, the sub-optimal multi-user detection technique can be divided into two types, interference cancellation and joint detection (also called linear detection). In comparison, the joint detection algorithm has the advantages of small calculation amount and easy implementation, and is widely applied in practice. The expression of the adopted joint detection algorithm is as follows:

$\hat{d}={\left(T\right)}^{-1}{A}^H{R}_n^{-1}e$ (formula 1)

Wherein,

referred to as minimum mean square error algorithm (MMSE). H represents conjugate transpose operation, A is system matrix, R_nAs covariance matrix of noise, R_dTo transmit the covariance matrix of the data, the received signal is e. If R is_dIf I, then equation 1 can be simplified as:

${\hat{d}}_{\mathrm{mmse}}={(A^H{R}_n^{-1}A+I)}^{-1}{A}^H{R}_n^{-1}e$ (formula 2)

The MMSE algorithm has certain noise suppression capability and can eliminate multiple access interference and intersymbol interference. Therefore, the MMSE algorithm is generally used for joint detection of signals.

At present, the joint detection algorithm only uses an MMSE detection algorithm, and when the noise is large, the anti-noise capability is weak. For example, in an Additive White Gaussian Noise (AWGN) channel environment or an AWGN-like channel environment with a direct path, MMSE cannot achieve satisfactory detection performance.

Disclosure of Invention

The embodiment of the invention provides a signal joint detection method and a signal joint detection device, which are used for improving the detection performance of joint detection.

A method for joint detection of signals, comprising the steps of:

determining whether the noise is large or small according to the first power of the noise signal and a preset threshold value;

when the noise is small, performing joint detection on signals according to a first algorithm for eliminating multiple access interference;

when the noise is large, the signals are jointly detected according to a second algorithm for suppressing the noise.

An apparatus for joint detection of signals, comprising:

the judging module is used for determining whether the noise is large or small according to the first power of the noise signal and a preset threshold value;

and the detection module is used for carrying out joint detection on the signals according to a first algorithm for eliminating the multiple access interference when the noise is small, and carrying out joint detection on the signals according to a second algorithm for suppressing the noise when the noise is large.

In the embodiment of the invention, when the noise is small, the first algorithm for eliminating the multiple access interference is adopted to carry out the joint detection on the signals, when the noise is large, the second algorithm for inhibiting the noise is adopted to carry out the joint detection on the signals, and the corresponding algorithms are adopted to carry out the joint detection aiming at different network environments, so that the detection performance of the joint detection is improved.

Drawings

FIG. 1 is a flow chart of a main method for joint detection of signals according to an embodiment of the present invention;

FIG. 2 is a flow chart of a method for joint detection of signals when a noise state is determined according to a first power and a first threshold in an embodiment of the present invention;

FIG. 3 is a flow chart of a method for joint detection of a signal when a noise condition is determined based on a first power, a second power, and a second threshold in an embodiment of the present invention;

FIG. 4 is a flowchart of a joint detection method for signals when determining a noise state according to a first power, a second power and a third threshold in an embodiment of the present invention;

FIG. 5 is a main structural view of an apparatus according to an embodiment of the present invention;

FIG. 6 is a detailed block diagram of an apparatus according to an embodiment of the present invention;

FIG. 7 is a diagram illustrating simulation results according to an embodiment of the present invention.

Detailed Description

In the embodiment of the invention, when the noise is small, the first algorithm for eliminating the multiple access interference is adopted to carry out the joint detection on the signals, when the noise is large, the second algorithm for inhibiting the noise is adopted to carry out the joint detection on the signals, and the corresponding algorithms are adopted to carry out the joint detection aiming at different network environments, so that the detection performance of the joint detection is improved.

Referring to fig. 1, the main method flow of the signal joint detection in the present embodiment is as follows:

step 101: and determining whether the noise is large or small according to the first power of the noise signal and a preset threshold value.

Step 102: when the noise is small, the signals are jointly detected according to a first algorithm for canceling multiple access interference.

Step 103: when the noise is large, the signals are jointly detected according to a second algorithm for suppressing the noise.

There are many implementations of each step in the above flow. In step 101, if the first power of the noise signal is not less than the preset first threshold, if so, determining that the noise is large, otherwise, determining that the noise is small. Or, determining whether the noise is large or small according to the first power of the noise signal, the second power of the received signal and a preset threshold value. Specifically, whether the ratio of the first power to the second power is not less than a preset second threshold value is judged, if so, the noise is determined to be large, and otherwise, the noise is determined to be small; or judging whether the ratio of the second power to the first power is not smallAnd if so, determining that the noise is small, otherwise, determining that the noise is large. Other ways of determining whether the noise is large or small are also possible and are suitable for the present embodiment, which are not listed here. In step 102, the first algorithm is minimum mean square error algorithm (MMSE), and the expression of MMSE algorithm is

A is the system matrix, R_nIs the covariance matrix of noise, H represents the conjugate transpose operation, I is the unit matrix, and e is the received signal. Or slightly deforming the expression of the MMSE algorithm, e.g.

α is a correction factor, and α is 1. The second algorithm is a matched filter algorithm (MF) or an MMSE algorithm containing a correction factor. The expression of MF is

And T is I. The expression of the MMSE algorithm containing the correction factor is

Alpha is more than 1. When the first algorithm adopts an MMSE algorithm without deformation and the second algorithm adopts an MF algorithm, the detection performance of the joint detection is better. When the first algorithm and the second algorithm both adopt an MMSE algorithm containing correction factors, alpha in the first algorithm is 1, and alpha in the second algorithm is more than 1, so that different algorithms can be realized through different values of alpha, the realization process of the algorithms is simplified, and the detection performance is improved. In order to make the T matrix in the modified MMSE algorithm degenerate into a number matrix, α can be a large value, e.g., α > 10. Alpha is also related to the signal-to-noise ratio, and the larger the signal-to-noise ratio, the smaller the value of alpha is set, and the better the detection performance is.

The following is a detailed description of three embodiments.

Referring to fig. 2, the flow of the joint detection method for determining a signal in a noise state according to a first power and a first threshold in this embodiment is as follows:

step 201: a channel impulse response of the received signal is obtained. Namely, it is

Ka, Ka being the antenna number, Ka being the total number of antennas, and W being the channel estimation window length.

Step 202: a first power Pn of the noise signal is determined from the channel impulse response.

Step 203: and judging whether the first power is not less than a first threshold value, if so, determining that the noise is in a larger state, and continuing to step 204, otherwise, determining that the noise is in a smaller state, and continuing to step 205.

Step 204: and performing joint detection on the received signals by adopting an MF algorithm.

Step 205: and performing joint detection on the received signals by adopting an undeformed MMSE algorithm.

Referring to fig. 3, the flow of the joint detection method for determining the signal in the noise state according to the first power, the second power and the second threshold in this embodiment is as follows:

step 301: a channel impulse response of the received signal is obtained. Namely, it isKa, Ka being the antenna number, Ka being the total number of antennas, and W being the channel estimation window length.

Step 302: determining a first power P of a noise signal from a channel impulse response_n。

Step 303: determining a second power P of the received signal from the channel impulse response_d. This step may be performed concurrently with step 302And (6) rows.

Step 304: and judging whether the ratio of the first power to the second power is not less than a second threshold value, if so, determining that the noise is in a larger state, and continuing to step 305, otherwise, determining that the noise is in a smaller state, and continuing to step 306. The second threshold is obtained by a simulation method, and the detection performance is better if the simulation value in TD-SCDMA is 4 dB.

Step 305: and carrying out joint detection on the received signals by adopting an MMSE algorithm containing alpha, wherein alpha is more than 1.

Step 306: and jointly detecting the received signals by adopting an MMSE algorithm containing alpha, wherein the alpha is 1.

Wherein, the steps 304-306 can be expressed as:

threshold' is the second threshold.

Referring to fig. 4, in this embodiment, a flow of the joint detection method for determining a signal in a noise state according to the first power, the second power, and the third threshold is as follows:

step 401: a channel impulse response of the received signal is obtained. Namely, it is

Ka, Ka being the antenna number, Ka being the total number of antennas, and W being the channel estimation window length.

Step 402: determining a first power P of a noise signal from a channel impulse response_n。

Step 403: determining a second power P of the received signal from the channel impulse response_d. This step may be performed simultaneously with step 402.

Step 404: and judging whether the ratio of the second power to the first power is not less than a third threshold value, if so, determining that the noise is in a smaller state, and continuing to the step 406, otherwise, determining that the noise is in a larger state, and continuing to the step 405. The third threshold is obtained by a simulation method, and the detection performance is better when the simulation value in TD-SCDMA is-4 dB. Wherein the third threshold and the second threshold are opposite numbers.

Step 405: and performing joint detection on the received signals by adopting an MF algorithm.

Step 406: and performing joint detection on the received signals by adopting an undeformed MMSE algorithm.

Wherein, the steps 404 and 406 can be expressed as:

threshold is the third threshold.

In this embodiment, the first threshold, the second threshold, and the third threshold are used to determine whether noise is large or small, and are used to balance the detection performance of the first algorithm and the second algorithm, or each threshold corresponds to a turning point of the detection performance of the first algorithm and the second algorithm, that is, when the threshold is not larger than noise corresponding to the turning point, the detection performance of the first algorithm is better than the detection performance of the second algorithm, and when the threshold is larger than noise corresponding to the turning point, the detection performance of the second algorithm is better than the detection performance of the first algorithm.

The implementation of joint detection of signals is known from the above description and can be implemented by a device, whose internal structure and function are described below.

Referring to fig. 5, the apparatus for joint signal detection in this embodiment includes: a judging module 501 and a detecting module 502. The device can be a base station or a mobile phone and other equipment which can be used as a signal receiving end.

The determining module 501 is configured to determine whether the noise is large or small according to the first power of the noise signal and a preset threshold. The determining module 501 determines whether the first power of the noise signal is not less than a preset first threshold, if so, it is determined that the noise is large, otherwise, it is determined that the noise is small. Alternatively, the determining module 501 determines the noise size according to the first power of the noise signal and the second power of the received signal. The latter method further includes: the judging module 501 judges whether the ratio of the first power to the second power is not less than a preset second threshold, if so, the noise is determined to be large, otherwise, the noise is determined to be small; or, the determining module 501 determines whether the ratio of the second power to the first power is not less than a preset third threshold, if so, the noise is determined to be low, otherwise, the noise is determined to be high.

The detection module 502 is configured to perform joint detection on the signals according to a first algorithm for canceling multiple access interference when the noise is small, and perform joint detection on the signals according to a second algorithm for suppressing the noise when the noise is large. The first algorithm is the minimum mean square error algorithm MMSE. The expression of MMSE is

α is a correction factor, and α is 1, a is a system matrix, R_nIs the covariance matrix of noise, H represents the conjugate transpose operation, I is the unit matrix, and e is the received signal. The second algorithm is a matched filtering algorithm MF; or the second algorithm is MMSE containing a correction factor. The expression for MMSE containing the correction factor is

Alpha is a correction factor and alpha > 1, A is a system matrix, R_nIs the covariance matrix of noise, H represents the conjugate transpose operation, I is the unit matrix, and e is the received signal.

The device further comprises: an estimation module 503 and a power module 504, see fig. 6.

The estimating module 503 is configured to perform channel estimation on the received signal to obtain a channel impulse response.

The power module 504 is configured to obtain a first power of the noise signal and a second power of the received signal according to the channel impulse response.

Fig. 7 shows the performance simulation result in the AWGN channel environment (which can also be understood as an environment with strong direct path power) when the scheme of fig. 3 is adopted, where BLER represents the block error rate on the ordinate, and Ior/Ioc represents the ratio of signal power to noise power on the abscissa. Line 701 represents the simulation result when the MF algorithm is used, line 702 represents the simulation result when the optimized MMSE (MMSE optimized) algorithm is used in the scheme shown in fig. 3, and line 703 represents the simulation result when the MMSE algorithm is used. According to the simulation curve, the detection performance of the receiver can be improved by adopting the scheme.

Software for implementing embodiments of the present invention may be stored in storage media such as floppy disks, hard disks, optical disks, and flash memories.

In the embodiment of the invention, when the noise is small, the first algorithm for eliminating the multiple access interference is adopted to carry out the joint detection on the signals, when the noise is large, the second algorithm for inhibiting the noise is adopted to carry out the joint detection on the signals, and the corresponding algorithms are adopted to carry out the joint detection aiming at different network environments, so that the detection performance of the joint detection is improved. The embodiment of the invention also provides a plurality of algorithms for joint detection, which not only improves the detection performance, but also simplifies the complexity of algorithm realization. In addition, the embodiment of the invention provides various methods for determining whether the noise is large or small, and is suitable for various application scenes.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (16)

1. A method for joint detection of signals, comprising the steps of:

determining whether the noise is large or small according to the first power of the noise signal and a preset threshold value;

when the noise is small, performing joint detection on signals according to a first method for eliminating multiple access interference;

when the noise is large, the signals are jointly detected according to a second method for suppressing the noise.

2. The method of claim 1, wherein the step of determining whether the noise is large or small based on the first power of the noise signal and a predetermined threshold comprises: and judging whether the first power of the noise signal is not less than a preset first threshold value, if so, determining that the noise is large, and otherwise, determining that the noise is small.

3. The method of claim 1, wherein the step of determining whether the noise is large or small based on the first power of the noise signal and a predetermined threshold comprises: and determining whether the noise is large or small according to the first power of the noise signal, the second power of the received signal and a preset threshold value.

4. The method of claim 3, wherein determining the magnitude of the noise based on the first power of the noise signal and the second power of the received signal comprises: judging whether the ratio of the first power to the second power is not less than a preset second threshold value, if so, determining that the noise is large, otherwise, determining that the noise is small; or

The step of determining the magnitude of the noise based on the first power of the noise signal and the second power of the received signal comprises: and judging whether the ratio of the second power to the first power is not less than a preset third threshold value, if so, determining that the noise is low, and otherwise, determining that the noise is high.

5. The method of claim 1, wherein the first method is a minimum mean square error algorithm, MMSE.

6. The method of claim 5, wherein MMSE specifically comprises: by passing

Determining a joint detection result, wherein: alpha is repairPositive factor, and α ═ 1, a is the system matrix, R_nIs the covariance matrix of noise, H represents the conjugate transpose operation, I is the unit matrix, and e is the received signal.

7. The method according to claim 1, characterized in that the second method is a matched filter algorithm MF; or the second method is MMSE containing a correction factor.

8. The method of claim 7, wherein the MMSE containing correction factors specifically comprises: by passing

Determining the joint detection result, wherein alpha is a correction factor and is more than 1, A is a system matrix, and R_nIs the covariance matrix of noise, H represents the conjugate transpose operation, I is the unit matrix, and e is the received signal.

9. An apparatus for joint detection of signals, comprising:

the judging module is used for determining whether the noise is large or small according to the first power of the noise signal and a preset threshold value;

and the detection module is used for carrying out joint detection on the signals according to a first method for eliminating the multiple access interference when the noise is small, and carrying out joint detection on the signals according to a second method for suppressing the noise when the noise is large.

10. The apparatus of claim 9, wherein the determining module determines whether the first power of the noise signal is not less than a preset first threshold, and if so, determines that the noise is large, otherwise, determines that the noise is small.

11. The apparatus of claim 9, wherein the determining module determines the magnitude of the noise based on a first power of the noise signal and a second power of the received signal.

12. The apparatus of claim 11, wherein the determining module determines whether a ratio of the first power to the second power is not less than a preset second threshold, if so, determining that the noise is large, otherwise, determining that the noise is small; or

The judging module judges whether the ratio of the second power to the first power is not less than a preset third threshold value, if so, the noise is determined to be small, otherwise, the noise is determined to be large.

13. The apparatus of claim 9, wherein the first method is a minimum mean square error method, MMSE.

14. The apparatus of claim 13, wherein MMSE specifically comprises: by passing

Determining a joint detection result, wherein alpha is a correction factor, alpha is 1, A is a system matrix, and R is_nIs the covariance matrix of noise, H represents the conjugate transpose operation, I is the unit matrix, and e is the received signal.

15. The apparatus of claim 9, wherein the second method is a matched filtering method MF; or the second method is MMSE containing a correction factor.

16. The apparatus of claim 15, wherein the MMSE containing correction factors specifically comprises: by passing

Determining the joint detection result, wherein alpha is a correction factor and is more than 1, A is a system matrix, and R_nIs the covariance matrix of noise, H represents the conjugate transpose operation, I is the unit matrix, and e is the received signal.

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