CN108494715A - A kind of primary synchronization signal catching method of lte-a system - Google Patents

Abstract

A kind of primary synchronization signal catching method of LTE A systems is claimed in the present invention.It is related to the correlation computations of synchronizing sequence in mobile communication system.Terminal needs, the i.e. capture and processing of synchronizing signal synchronous with the time into line frequency to received signal in mobile communication system.Frequency Synchronization mainly carries out Digital Down Convert operation to signal, and time synchronization mainly carries out sliding correlation by the synchronizing sequence for being from a locally generated baseband signal, to determine the initial position of synchronizing signal, to reach time synchronization.With the development of technology, high-speed, low delay character is presented in mobile communication system, and how quickly and accurately processing signal becomes the hot spot for research, the synchronous first step as mobile communication system, and synchronous efficiency directly determines the processing of follow-up signal with performance.Therefore, it herein by taking LTE A systems as an example, proposes that a kind of low complex degree based on FFT slides correlation technique, can significantly reduce the computation complexity in synchronizing process.

Description

A primary synchronization signal acquisition method for an LTE-A system

technical field

The invention belongs to the technical field of LTE-A, and in particular relates to the processing technology of the main synchronization signal of the LTE-A system.

Background technique

Autocorrelation and cross-correlation are important in statistical communication and digital signal processing. In digital signal processing, correlation is used to describe the similarity of two signals. In a communication system, in order to accurately find out the special sequence sent by the base station at a specific location, a correlation algorithm is usually used to correlate the locally constructed sequence with the received sequence to determine the location of the time-frequency resource. Therefore, the research on related algorithms is of great significance.

LTE-A is an evolved version of LTE. Compared with LTE, the system parameters of LTE-A are greatly improved, and can provide larger system capacity and lower system delay. With the performance improvement of LTE-A, it has become a new generation mainstream mobile communication standard in the world after 3G. In the LTE-A system, after the terminal is turned on, it first performs a cell search, finds the cell in the area where the terminal is located, and performs frequency and time synchronization. After the terminal is synchronized with the cell, it can receive and process subsequent signals. Therefore, synchronization is very important in the LTE-A system.

In the LTE-A system, the primary synchronization signal adopts a Zadoff-Chu (ZC) sequence. In the TD-LTE system, the primary synchronization signal PSS is mapped to the third OFDM symbol of subframe 1 and subframe 6. Therefore, as long as the terminal can calculate the starting position of the PSS, it can synchronize half the frame. The position of the synchronization signal SSS is one step closer to frame synchronization, so as to achieve the effect of time synchronization, so it is very important to accurately find the position of the PSS. The existing PSS correlation algorithm mainly performs sliding correlation in the time domain, but its large amount of calculation does not conform to the concept of future green communication, so a correlation algorithm with lower complexity is required for synchronous calculation.

Contents of the invention

The present invention aims to solve the above problems of the prior art. A method of primary synchronization signal acquisition for LTE-A system with reduced complexity is proposed. Technical scheme of the present invention is as follows:

A method for acquiring a primary synchronization signal of an LTE-A system, comprising the following steps:

Step 1: Divide the received signal r(t) into n pieces of data, the length of each piece is k, k{{r(1),r(2),...,r(k)},...,{r(nk) +1),r(nk+2),…,r((n+1)k)}}, where n=0,1,2,…;

Step 2: Splicing and merging the adjacent two sections of data equally divided in step 1, and then performing N-point FFT (fast Fourier transform) operation; wherein N represents the number of points for performing FFT;

Step 3: Divide the main synchronization sequence into pieces of data with a length of k, perform FFT on each piece of data, and then take the conjugate;

Step 4: Multiply the data of the received sequence after the FFT of step 2 with the corresponding point of the data of the local sequence after the FFT to obtain the intermediate value of the correlation result;

Step 5: Accumulate the intermediate values of the relevant parts of the results in step 4, then do N-point IFFT, and finally keep the first k points, which is the correlation result;

Step 6: Repeat the above operations until the correlation ends and the acquisition of the main synchronization signal ends.

Further, the step 3 divides the local sequence into pieces of data with a length of k, and performs FFT on each piece of data, and then takes the conjugate, which specifically includes the steps: by Perform FFT operation on the received data.

Further, the step four: multiply the data a+bi after the FFT of the received sequence by the corresponding point of the data c+di after the FFT of the local sequence to obtain the intermediate value of the correlation result, specifically including the steps:

The real part of the intermediate value of the correlation result is ac-bd, and the imaginary part is ad+bc.

Further, in the step five, the results in the step four are accumulated in the intermediate values of the relevant parts, and then N-point IFFT is performed, and the first k points are finally retained, which is the correlation result, which specifically includes the steps:

①Through type Perform IFFT operation

② Retain the first k points of the IFFT result as the relevant result

Advantage of the present invention and beneficial effect are as follows:

The method of the invention transforms the sliding correlation into the frequency domain, uses the knowledge of the circular correlation theorem, and replaces the linear correlation with the circular correlation, thereby significantly reducing the calculation amount of the sliding correlation. At the same time, the method of segmenting the received sequence and then adjacently merging the received sequence can reduce resource consumption in the implementation process. In the present invention, the main calculation amount is concentrated in the FFT and IFFT process, and the FFT operation calculation amount of N points is: the number of times of complex number addition is Nlog ₂ N, and the number of times of complex number multiplication is Therefore, it is deduced that the correlation value calculation complexity of the present invention is o(Nlog ₂ N), while the traditional time domain sliding correlation calculation complexity is o(Nk), and k is the number of correlation value calculation points. It can be seen that as the number of correlations increases, the calculation amount of the present invention is significantly reduced.

Description of drawings

Fig. 1 is a structural block diagram related to traditional sliding of a preferred embodiment provided by the present invention;

Fig. 2 is a structural block diagram of the present invention;

Fig. 3 is a simulation diagram of correlation results of 4 frames of data in the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be described clearly and in detail below with reference to the drawings in the embodiments of the present invention. The described embodiments are only some of the embodiments of the invention.

In the traditional sliding correlation method, the baseband signal is correlated with the local PSS, and the maximum value of the sliding correlation result is found by comparison, so as to determine As well as the location of the PSS, the specific implementation scheme is shown in FIG. 1 . Although the steps of this solution are simple, the computational complexity increases linearly with the number of correlations, and the implementation complexity is still high.

Taking the LTE-A system as an example, the description is as follows in combination with Figure 2 and examples:

Step 1: Segment the received signal r(t) with a length of 1024, and divide the baseband signal into many segments of 1024 data.

Step 2: Merge the data in Step 1 adjacent to each other, that is, 1st and 2nd segments, 2nd and 3rd segments, 3rd and 4th segments, and so on.

Step 3: Perform a 2048-point FFT operation on each piece of data spliced in Step 2 to obtain the frequency domain expression after the baseband signal is segmented.

Step 4: Divide the local synchronization sequence into two pieces of data with a length of 1024, perform 2048-point FFT processing on each piece of data, and then take the conjugate to obtain the segmented frequency expression of the local synchronization sequence.

Step 5: Multiply the corresponding points of the results obtained in Step 3 and Step 4 to obtain the intermediate value of the relevant results.

Step 6: When the correlation median value of two or more splicing results is calculated, add the correlation median values of two adjacent times, and then proceed to Step 7. Otherwise, go to step three.

Step 7: Perform 2048-point IFFT on the addition result, and keep the first 1024 values as the correlation result. Repeat the above steps until 153600 point (field) correlation values are calculated.

Fig. 3 is a simulation diagram of correlation results of 4 frames of data according to the present invention. The dotted line in the figure indicates the half-frame boundary. According to the time domain position of the main synchronization signal, it can be known that each half-frame data contains a synchronization signal. Within each half-frame range, find out the peak and position of the largest correlation peak by comparison, so as to determine the number within the cell group The coordinates in the figure indicate the peak value and position of the largest correlation peak in each field.

The above embodiments should be understood as only for illustrating the present invention but not for limiting the protection scope of the present invention. After reading the contents of the present invention, skilled persons can make various changes or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims (4)

1. a kind of primary synchronization signal catching method of lte-a system, which is characterized in that include the following steps：

Step 1：Signal r (t) will be received and be divided into n segment datas, every section of length is k, k { { r (1), r (2) ..., r (k) } ..., r (nk+1), r (nk+2) ..., r ((n+1) k) }, wherein n=0,1,2 ...；

Step 2：Adjacent two segment data that step 1 is divided equally, which is spliced, to be merged, and N point FFT Fast Fourier Transform (FFT)s behaviour is then carried out Make；Wherein N indicates to carry out the points of FFT；

Step 3：Main synchronizing sequence is divided into the data that every segment length is k, and FFT is carried out to every segment data, then takes conjugation；

Step 4：Data of the sequence after step 2 FFT will be received to be multiplied with the data corresponding points after local sequence FFT, obtained To the median of correlated results；

Step 5：Result in step 4 is carried out relevant portion median to add up, is then N point IFFT again, it is final to retain preceding k It is a, as correlated results；

Step 6：Aforesaid operations are repeated, until correlation terminates, primary synchronization signal is obtained and terminates.

2. a kind of primary synchronization signal catching method of lte-a system according to claim 1, which is characterized in that the step Rapid three are divided into local sequence the data that every segment length is k, and carry out FFT to every segment data, then take conjugation, specifically include step Suddenly：Pass throughFFT operations are carried out to receiving data.

3. a kind of primary synchronization signal catching method of lte-a system according to claim 1, which is characterized in that the step Rapid four：Data a+bi of the sequence after step 2 FFT will be received to be multiplied with the data c+di corresponding points after local sequence FFT, The median of correlated results is obtained, step is specifically included：

The real part of median is ac-bd, imaginary part ad+bc.

4. a kind of primary synchronization signal catching method of lte-a system according to claim 1, which is characterized in that the step Result in step 4 is carried out relevant portion median by rapid five to add up, and is then N point IFFT again, final to retain preceding k point, i.e., For correlated results, step is specifically included：

1. passing through formulaCarry out IFFT operations；

2. k point is as correlated results before the result of IFFT is retained.