CN108183726B - Synchronization detection method for multi-antenna communication system based on spatial filtering - Google Patents

Abstract

The invention discloses a synchronous detection method of a multi-antenna communication system based on spatial filtering. The invention aims at the problem that the receiver detects the synchronous signal of the target cell base station easily to be interfered by the cell base stations in other directions under the condition that the base stations are densely distributed in the mobile communication system environment. The implementation method of the invention comprises the following steps: receiving signals in different wave beam directions by adopting parallel multi-channel mutually independent spatial filters, and then performing correlation with a local synchronization sequence by using a correlator to detect a synchronization signal; the synchronous detection judging unit obtains a synchronous signal detection result according to the output of the parallel multi-path correlator and determines whether to adjust the spatial filtering direction; if the synchronous signal is not detected in a period of time, the receiving beam direction of each spatial filtering unit is adjusted, and then the synchronous signal detection process of the parallel multi-path spatial filtering is repeated. The invention can effectively improve the synchronous signal detection capability of the target direction base station.

Description

Synchronization detection method for multi-antenna communication system based on spatial filtering

technical field

The present invention relates to the field of mobile communication, in particular to a synchronization detection method of a multi-antenna communication system.

Background technique

The synchronization process is an indispensable part of all digital communication systems, and the synchronization signal plays a vital role in the normal operation of the mobile communication system. In the process of accessing the cellular network, the mobile communication system first needs to detect the downlink synchronization signal sent by the cell base station, so as to obtain synchronization with the corresponding base station, and then realize the follow-up work such as cell search.

With the continuous increase of users' demand for the capacity of mobile communication systems, in order to increase the bandwidth, the carrier frequency of wireless signals used in mobile communication systems is constantly increasing, and the corresponding electromagnetic wave wavelengths are constantly decreasing. The size of the antenna can also be reduced. Small. Multi-antenna technology has a wide range of applications and an important position in today's and future mobile communication systems, including user terminals and relay systems. Especially for the relay system, there is no restriction on the size of the user terminal, and it is easier to implement the multi-antenna technology. At the same time, we have noticed that higher frequency wireless carriers and the demand for larger communication capacity make mobile cells smaller and smaller, and corresponding base stations are becoming more and more dense.

Before the user terminal or the relay system accesses the cell, that is, before the synchronization with the target base station is obtained, the synchronization signal in the downlink direction needs to be detected. Since there is no prior information about the cell base station before the detection of the synchronization signal, the omnidirectional reception method is usually used to receive the signal. After analog-to-digital conversion, low-pass filtering and downsampling, the cross-correlation algorithm is used to detect the synchronization signal in the digital baseband. . In a cell environment where the surrounding base stations are increasingly dense, the detection of the synchronization signal of the target cell base station by the receiver is easily interfered by the surrounding cell base stations in other directions.

SUMMARY OF THE INVENTION

Objective of the invention: In view of the technical problem that synchronization signal detection in a dense cell environment is easily interfered by surrounding cells in the prior art, the present invention provides a synchronization detection method for a multi-antenna communication system. The synchronization detection method of the multi-antenna communication system utilizes the receiving antenna array to reduce the signal interference of the surrounding cells and enhance the detection capability of the synchronization signal sent by the target base station by combining the multi-channel parallel spatial filtering and the synchronization signal detection method. , and is easy to implement in practical engineering.

Technical scheme: In order to realize the above-mentioned technical effect, the technical scheme proposed by the present invention is:

A synchronization detection method for a multi-antenna communication system based on spatial filtering, comprising the following steps:

S1, the multi-antenna array of the receiver simultaneously receives M channels of signals as data to be processed;

S2, dividing the multi-antenna received signals into N parallel paths to perform spatial filtering processing in different beam directions to obtain the output of the spatial filtering unit;

S3, use a cross-correlation algorithm to cross-correlate the received signal after each spatial domain filter with the local synchronization sequence, and detect the synchronization signal to obtain the output of the correlator;

S4, according to the output of the cross-correlation operation, determine the detection result of the synchronization signal, and determine whether the spatial filtering direction needs to be adjusted;

S5, if it is determined in step S4 that the detection of the synchronization signal is successful, the spatial filtering direction does not need to be adjusted; otherwise, the beam direction of the parallel N-path spatial filtering is adjusted and the process returns to step S2.

Specifically, the step S1 includes the steps:

S1-1, the multi-antenna array of the receiver simultaneously receives M channels of wireless signals;

S1-2, performing analog-to-digital conversion, low-pass filtering and down-sampling on the wireless signal, and using the obtained digital baseband signal as the data to be processed.

Specifically, the step S2 includes the steps:

S2-1, calculate the spatial filtering vector w _i according to the target beam direction θ _i and in combination with the antenna shape feature, where _wi is the spatial filtering vector of the ith spatial filtering unit, i=1,2,...,N,N is the number of parallel spatial filtering units;

S2-2, calculate the output x _i (n) of the ith spatial filtering unit at time n as:

Among them, r _i (n) is the received signal vector of length M before the ith spatial filtering at time n; S2-3, defines the synchronization signal detection counter CNT, which starts counting from the completion of the calculation of the spatial filtering vector, and is used to measure the The synchronization signal detection time of each target receiving beam direction.

Specifically, the step S3 includes: using a cross-correlation algorithm to cross-correlate the received signal with the locally stored synchronization sequence, and according to the step S2-2, it can be known that the input signal of the ith correlator at time n is x _i (n), Then the output of the ith correlator whose time index is d is P _i (d):

Among them, s(n) represents the local synchronization sequence of length L, s*(n) is the sequence calculated by taking the conjugate of s(n); x _i (d+n) represents the i-th path when the time is d+n Correlator input signal.

Specifically, the step S4 includes the steps:

S4-1, set the correlation peak detection threshold of the i-th synchronization signal to THR _i , and limit the detection duration of the synchronization signal in each beam direction to MaxCNT; when the value CNT of the counter in step S2 does not exceed the limited duration MaxCNT, and in step S3 If the correlator output exceeds the threshold THR _i , that is, a correlation peak is detected, it is considered that a synchronization signal is detected in the current beam direction;

S4-2, if the counter CNT in step S2 reaches the limited duration MaxCNT, and the outputs of the M channels of correlators do not exceed the respective correlation detection thresholds THR _i , then it is determined that the synchronization signal detection fails and the previous spatial filtering direction needs to be adjusted.

Specifically, the step S5 includes the steps:

S5-1, if step S4 determines that the synchronization signal detection fails and requires adjustment of the spatial filtering direction, the spatial filtering direction adjustment unit simultaneously adjusts each spatial filtering unit described in step S2, and modifies its corresponding receiving beam direction;

S5-2, returning to step S2 and clearing the counter CNT in step S2, and repeating the foregoing steps to detect the synchronization signal.

Specifically, during adjustment, the high-value step angle Δθ ₁ and the low-value step angle Δθ ₂ are preset; when the correlator output is less than k% of the correlation peak threshold value THR, the high-value step angle Δθ ₁ is used ; When the correlator output is greater than k% of the correlation peak threshold value THR, a low value step angle Δθ ₁ is used, where the percentage k% is an empirical value, adjusted according to the false alarm probability requirement of the system corresponding to the synchronization signal detection.

Specifically, in the step S2-1, the antenna arrays are arranged in an equidistant linear arrangement, and the calculation formula of the spatial filtering vector w(θ) is:

为天线阵列中相邻天线接收信号的相位差。Among them, θ is the incident direction angle of the wireless signal of the target base station to the receiving antenna array, λ is the wavelength corresponding to the carrier frequency of the wireless signal,

is the phase difference of signals received by adjacent antennas in the antenna array.

通过下式求得：Specifically, the phase difference of signals received by adjacent antennas in the antenna array

Obtained by the following formula:

where d is the distance between adjacent antennas.

Beneficial effects: the present invention is applied to the synchronization signal detection of the multi-antenna mobile communication system, using the receiving antenna array and the method of combining parallel multi-path spatial filtering and synchronization signal detection, and can effectively resist the interference of surrounding cells in the environment of dense cells Signal, to quickly and effectively realize the detection of the synchronization signal of the target cell.

Description of drawings

1 is a schematic structural diagram of an embodiment of the present invention;

FIG. 2 is a schematic diagram of the relationship between the received signal and the direction angle of the equidistant linear antenna array according to the embodiment of the present invention;

3 is a schematic structural diagram of a spatial filter according to an embodiment of the present invention;

Detailed ways

The present invention will be further explained below in conjunction with the accompanying drawings.

Figure 1 is a schematic structural diagram of an embodiment of the present invention, which includes the following steps:

S1, the multi-antenna array of the receiver simultaneously receives M channels of signals as data to be processed, which specifically includes the steps:

S1-1, the multi-antenna array of the receiver simultaneously receives M channels of wireless signals;

S1-2, performing analog-to-digital conversion, low-pass filtering and down-sampling on the wireless signal, and using the obtained digital baseband signal as the data to be processed.

S2: Divide the multi-antenna received signals into N parallel channels to perform spatial filtering processing in different beam directions to obtain the output of the spatial filtering unit, which specifically includes the steps:

S2-1, define _wi as the spatial filtering vector of the ith spatial filtering unit, the target beam direction is θ _i , and the spatial filtering vector _wi is calculated according to the target beam direction θ _i and the antenna shape feature.

即为：As shown in FIG. 2 , in the embodiment of the present invention, the antenna arrays are arranged in an equidistant linear arrangement. Assuming that the antenna spacing is d, and the incident direction angle of the wireless signal of the target base station to the receiving antenna array is θ, then the wireless signal transmission distance between adjacent antennas The difference is dsinθ, then the phase difference of the signals received by adjacent antennas in the antenna array

That is:

Among them, λ is the wavelength corresponding to the carrier frequency of the wireless signal. In the embodiment of the present invention, the calculation formula of the spatial filtering vector w(θ) corresponding to the θ beam direction is:

S2-2, define r _i (n) as the received signal vector of length M before the ith spatial filtering at time n, and the corresponding output of the ith spatial filtering unit at time n is:

Among them, i=1,2,...,N, where N is the number of parallel spatial filtering units.

As shown in FIG. 3 , in the embodiment of the present invention, the parallel N spatial filters are independent of each other, and each corresponds to a beam receiving direction. The algorithm described in step S2-2 is implemented in each spatial filtering unit to strengthen the received signal corresponding to the direction angle and suppress signals in other directions, thereby obtaining the maximum received signal-to-noise ratio.

S2-3, define a synchronization signal detection counter CNT, which starts counting from the completion of the calculation of the spatial filter vector, and is used to measure the synchronization signal detection time for each target receiving beam direction.

S3, use a cross-correlation algorithm to perform cross-correlation between the received signal after each spatial domain filtering and the local synchronization sequence, and detect the synchronization signal to obtain the output of the correlator. According to the step S2-2, it can be known that the ith path, the input signal of the correlator whose time is n is x _i (n), the local synchronization sequence whose length is defined as L is s(n), and s*(n) represents a pair of s(n). n) Take the sequence obtained by the conjugate calculation, and the output of the correlator with the time subscript d of the i-th channel is P _i (d):

S4, according to the output of the cross-correlation operation, determine the synchronization signal detection result, and determine whether it is necessary to adjust the spatial filtering direction, which specifically includes the steps:

S4-1, define the correlation peak detection threshold of the i-th synchronization signal as THR _i , and limit the detection duration of the synchronization signal in each beam direction as MaxCNT. If the correlator output P _i (d) exceeds this threshold, that is, if a correlation peak is detected, it is considered that a synchronization signal is detected in the current beam direction;

S4-2, if the counter CNT in step S2 reaches or exceeds the limited duration MaxCNT, and the outputs of the M channels of correlators do not exceed the respective correlation detection thresholds THR _i , then it is determined that the detection of the synchronization signal has failed and the previous spatial filtering direction needs to be adjusted .

S5, if step S4 determines that the synchronization signal detection is successful, then the spatial filtering direction does not need to be adjusted, otherwise the beam directions of the parallel N-path spatial filtering are adjusted and return to step S2:

S5-1, if it is determined in step S4 that the detection of the synchronization signal fails and the spatial filtering direction is required to be adjusted, the spatial filtering direction adjustment unit adjusts each spatial filtering unit described in step S2 at the same time, and modifies its corresponding receiving beam direction. The beam direction angle is adjusted to Δθ;

Here, according to a plurality of preset adjustment angles, and according to the magnitude relationship between the output of the correlator and the correlation peak detection threshold THR, different adjustment angles can be used for adjustment.

For example, two kinds of step angles Δθ ₁ and Δθ ₂ may be preset, wherein Δθ ₁ is larger and Δθ ₂ is smaller. When the correlator output is less than k% of the correlation peak threshold value THR, a larger step angle Δθ ₁ is used; when the correlator output is greater than k% of the correlation peak threshold value THR, a smaller step angle Δθ is used ₂ , where the percentage k% is an empirical value, which can be adjusted according to the false alarm probability requirement of the system corresponding to the detection of the synchronization signal.

Through different adjustment angles, faster synchronization detection can be achieved.

S5-2, recalculate the spatial filtering vector according to the modified beam direction, clear the counter CNT described in step S2 to zero, and repeat the foregoing steps to perform synchronization signal detection.

In the present invention, the synchronization signal correlation peak detection threshold THR _i , the synchronization signal detection limited duration MaxCNT in each beam direction, and the beam direction angle adjustment size Δθ of the spatial filter are all empirical values and can be adjusted appropriately.

The synchronization detection method of a multi-antenna communication system of the present invention can be used in a relay system or a user terminal of a mobile cell. The multi-antenna signals received by the antenna array are processed by parallel multi-path spatial filtering. It can cancel the surrounding interference and improve the detection ability of the synchronization signal of the target cell base station in the environment of the target cell.

The above content is a further detailed description of the present invention in conjunction with the specific embodiments, but should not be construed as a limitation on the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (8)

1. a synchronous detection method based on a multi-antenna communication system of spatial filtering, is characterized in that, comprises the following steps: S1, the multi-antenna array of the receiver simultaneously receives M channels of signals as data to be processed; S2, dividing the multi-antenna received signals into N parallel paths to perform spatial filtering processing in different beam directions to obtain the output of the spatial filtering unit; S3, use a cross-correlation algorithm to cross-correlate the received signal after each spatial domain filter with the local synchronization sequence, and detect the synchronization signal to obtain the output of the correlator; S4, according to the output of the cross-correlation operation, determine the detection result of the synchronization signal, and determine whether the spatial filtering direction needs to be adjusted; S5, if it is determined in step S4 that the detection of the synchronization signal is successful, the spatial filtering direction does not need to be adjusted; otherwise, the beam direction of the parallel N-path spatial filtering is adjusted and the process returns to step S2. 2. The method for synchronizing detection of a multi-antenna communication system based on spatial filtering according to claim 1, wherein the step S1 comprises the steps of: S1-1, the multi-antenna array of the receiver simultaneously receives M channels of wireless signals; S1-2, performing analog-to-digital conversion, low-pass filtering and down-sampling on the wireless signal, and using the obtained digital baseband signal as the data to be processed. 3. The method for synchronizing detection of a multi-antenna communication system based on spatial filtering according to claim 1, wherein the step S2 comprises the steps of: S2-1, calculate the spatial filtering vector w _i according to the target beam direction θ _i and in combination with the antenna shape feature, where _wi is the spatial filtering vector of the ith spatial filtering unit, i=1,2,...,N,N is the number of parallel spatial filtering units; S2-2, calculate the output x _i (n) of the ith spatial filtering unit at time n as:

Wherein, r _i (n) is the received signal vector of length M before the ith spatial filtering at time n; S2-3, define a synchronization signal detection counter CNT, which starts counting from the completion of the calculation of the spatial filter vector, and is used to measure the synchronization signal detection time for each target receiving beam direction. 4. The method for synchronizing detection of a multi-antenna communication system based on spatial filtering according to claim 3, wherein the step S3 comprises, adopting a cross-correlation algorithm to cross-correlate the received signal with the locally stored synchronization sequence, According to the step S2-2, it can be known that the input signal of the ith correlator at time n is x _i (n), then the output of the ith correlator whose time subscript is d is P _i (r):

Among them, s(n) represents the local synchronization sequence of length L, s*(n) is the sequence calculated by taking the conjugate of s(n); x _i (r+n) represents the ith path when the time is r+n Correlator input signal. 5. The method for synchronizing detection of a multi-antenna communication system based on spatial filtering according to claim 3, wherein the step S4 comprises the steps of: S4-1, set the correlation peak detection threshold of the i-th synchronization signal to THR _i , and limit the detection duration of the synchronization signal in each beam direction to MaxCNT; when the value CNT of the counter described in step S2 does not exceed the limited duration MaxCNT, and step The output of the correlator in S3 exceeds the threshold THR _i , that is, if a correlation peak is detected, it is considered that a synchronization signal is detected in the current beam direction; S4-2, if the counter CNT in step S2 reaches the limited duration MaxCNT, and the outputs of the N correlators do not exceed the respective correlation detection thresholds THR _i , then it is determined that the synchronization signal detection fails and the previous spatial filtering direction needs to be adjusted. 6. The method for synchronizing detection of a multi-antenna communication system based on spatial filtering according to claim 5, wherein the step S5 comprises the steps of: S5-1, if step S4 determines that the synchronization signal detection fails and requires adjustment of the spatial filtering direction, the spatial filtering direction adjustment unit simultaneously adjusts each spatial filtering unit described in step S2, and modifies its corresponding receiving beam direction; S5-2, returning to step S2 and clearing the counter CNT in step S2, repeating the steps S2-S4 for synchronization signal detection. 7 . The method for synchronous detection of a multi-antenna communication system based on spatial filtering according to claim 6 , wherein, when adjusting, a high-value step angle Δθ ₁ and a low-value step angle Δθ ₂ are preset in advance. 8 . ; When the correlator output is less than k% of the correlation peak threshold value THR, the high value step angle Δθ ₁ is used; when the correlator output is greater than k% of the correlation peak threshold value THR, the low value step angle Δθ ₁ is used , where the percentage k% is an empirical value, which is adjusted according to the false alarm probability requirement of the system corresponding to the detection of the synchronization signal. 8. the synchronous detection method of a kind of multi-antenna communication system based on spatial filtering according to claim 3, is characterized in that, in described step S2-1, the antenna array is equidistant linear arrangement, and spatial filtering vector w ( The calculation formula of θ) is:

Among them, θ is the incident direction angle of the wireless signal of the target base station to the receiving antenna array, λ is the wavelength corresponding to the carrier frequency of the wireless signal,

is the phase difference of signals received by adjacent antennas in the antenna array, and d is the distance between adjacent antennas.

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