CN104283628B - A kind of method of cell searching in communication system - Google Patents

Abstract

A kind of method of cell searching in communication system, methods described includes：The intersymbol intersymbol interference of orthogonal frequency division multiplex OFDM is eliminated in the first synchronizing signal and obtains the first renewal synchronizing signal, the intersymbol interference between eliminating OFDM symbol in the second synchronizing signal obtains the second renewal synchronizing signal；The original position of synchronizing signal is updated using symbol timing detection first, combining the first local synchronizing signal carries out the channel estimation value that channel estimation obtains the first renewal synchronizing signal；Synchronizing signal being updated according to first and calculating the second original position for updating synchronizing signal, the second renewal synchronous signal sequence is worth to reference to the channel estimation of the first renewal synchronizing signal；Synchronous signal sequence cycle calculations synchronizing signal correlation is updated according to second using ergodic algorithm, and small district's groups ID is determined according to the position at strongest correlation peak.After using the embodiment of the present invention, the interference between OFDM symbol can be eliminated, and then accurately determine small district's groups ID.

Description

A cell search method in a communication system

technical field

The present application relates to the field of communication technologies, and more specifically, relates to a method for cell search in a communication system.

Background technique

The authorized frequency points of the power communication network are discretely distributed in the frequency band of 223.525MHz to 231.65MHz, a total of 40, each with a bandwidth of 25KHz, called physical sub-bands. Three of them are used as synchronization subbands, and a synchronization signal is sent every other radio frame for cell search, and the remaining 37 frequency points are used as service subbands. Every 40 wireless frames is a period, and one frame is used as a synchronization frame. Synchronization signals are sent on all service subbands to maintain downlink synchronization, and the remaining 39 wireless frames are used for services.

In the current power communication system, the synchronization channel is composed of a first synchronization signal (PSC) and a second synchronization signal (SSC). In the time domain, the second synchronization signal is arranged first and occupies 462 sampling points. The first synchronization signal is placed after the second synchronization signal and occupies 463 sampling points. The two synchronization signals are connected end to end to form 925 sampling points (925 is the number of time domain sampling points of 13 OFDM symbols in each subband).

During the cell search process, the first synchronization signal is detected to obtain the symbol timing, and then the symbol timing is used to determine the starting position of the first synchronization signal, and the local first synchronization signal is used for channel estimation to obtain the channel estimation value of the first synchronization signal. The starting position of the second synchronization signal is estimated according to the first synchronization signal, and the second synchronization signal sequence is obtained by combining the channel estimation value of the first synchronization signal. A traversal algorithm is used to cyclically calculate the synchronization signal correlation value according to the second synchronization signal sequence, and the cell group ID is determined according to the position of the strongest correlation peak.

During the cell search process, whether in the channel estimation process of the first synchronization signal or in the calculation of the second synchronization sequence, the timing error of the Orthogonal Frequency Division Multiplexing (OFDM) symbol will cause inter-symbol interference, and then As a result, there is a deviation in the position of the strongest correlation peak, which reduces the accuracy of cell group ID detection.

Contents of the invention

The embodiment of the present invention proposes a cell search method in a communication system, which can eliminate interference between OFDM symbols, and then accurately determine a cell group ID.

The technical scheme of the embodiment of the present invention is as follows:

A method for cell search in a communication system, the method comprising:

Eliminating intersymbol interference between OFDM symbols in the first synchronization signal to obtain a first update synchronization signal, and eliminating intersymbol interference between OFDM symbols in the second synchronization signal to obtain a second update synchronization signal;

Using symbol timing to detect the starting position of the first updated synchronization signal, performing channel estimation in conjunction with the local first synchronization signal to obtain a channel estimation value of the first updated synchronization signal;

Estimating the starting position of the second updated synchronization signal according to the first updated synchronization signal, and combining the channel estimation value of the first updated synchronization signal to obtain a second updated synchronization signal sequence;

The traversal algorithm is used to cyclically calculate the synchronization signal correlation value according to the second updated synchronization signal sequence, and the cell group ID is determined according to the position of the strongest correlation peak.

The first update synchronization signal obtained by eliminating the intersymbol interference between OFDM symbols in the first synchronization signal includes:

A CP with a length of 3 sampling points is added before the time domain data of the first OFDM symbol, and a cyclic prefix CP with a length of 2 sampling points is added before the time domain data of other OFDM symbols.

The obtaining of the second updated synchronization signal by eliminating intersymbol interference between OFDM symbols in the second synchronization signal includes:

A CP with a length of 2 sampling points is added before the time-domain data of each OFDM symbol.

As can be seen from the above technical solution, in the embodiment of the present invention, the intersymbol interference between OFDM symbols is eliminated in the first synchronization signal to obtain the first update synchronization signal, and the intersymbol interference between OFDM symbols is eliminated in the second synchronization signal Obtain the second update synchronization signal; use symbol timing to detect the start position of the first update synchronization signal, combine the local first synchronization signal to perform channel estimation to obtain the channel estimation value of the first update synchronization signal; calculate the first update synchronization signal according to the first update synchronization signal 2. Update the initial position of the synchronization signal, and combine the channel estimation value of the first update synchronization signal to obtain the second update synchronization signal sequence; use the traversal algorithm to calculate the synchronization signal correlation value according to the second update synchronization signal sequence, and calculate the correlation value according to the strongest correlation peak The location determines the cell group ID. Since the intersymbol interference between OFDM symbols has been eliminated in the first synchronization signal and the second synchronization signal, the position of the strongest correlation peak can be more accurately located, and the cell group ID can be determined more accurately.

Description of drawings

FIG. 1 is a schematic flowchart of a method for cell search in a communication system.

detailed description

In order to make the object, technical solution and advantages of the present invention more clearly, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

In the embodiment of the present invention, firstly, the intersymbol interference between OFDM symbols of the first synchronization signal is eliminated, and the intersymbol interference between the second synchronization signals is eliminated. In the process of determining the ID of the cell group, due to the elimination of intersymbol interference and the reduction of errors during channel estimation and calculation of the second updated synchronization signal sequence, the position of the strongest correlation peak can be more accurately located, and the cell group can be determined more accurately ID.

Referring to accompanying drawing 1, it is a schematic flow diagram of a method for cell search in a communication system, which specifically includes the following steps:

101. Eliminate intersymbol interference between OFDM symbols in a first synchronization signal to obtain a first updated synchronization signal, and eliminate intersymbol interference between OFDM symbols in a second synchronization signal to obtain a second updated synchronization signal.

In the current power communication system, the first synchronization signal is generated by the Zadoff-Chu sequence, and the first synchronization signal with a length of 62 points is divided into 7 segments, and the length of each segment is 6, 10, 10, 10, 10, 10, 6 subcarriers are mapped to 7 OFDM symbols respectively, and the two ends are OFDM symbols occupying 6 subcarriers. The frequency-domain data of 7 OFDM symbols are respectively subjected to 64-point IFFT to generate time-domain data of 448 sampling points. Finally, 15 points of CP are added uniformly to a total of 463 sampling points.

The second synchronization signal is formed by interleaving and concatenating two binary sequences with a length of 31. Divide the second synchronization signal with a length of 62 points into 7 segments, and the length of each segment is 6, 10, 10, 10, 10, 10, and 6 subcarriers, which are respectively mapped to 7 OFDM symbols, and the two ends are 6 OFDM symbols of subcarriers. The frequency-domain data of 7 OFDM symbols are respectively subjected to 64-point IFFT to generate time-domain data of 448 sampling points. Finally, 14 points of CP are added uniformly for a total of 462 sampling points.

When the synchronization signal is generated, the timing error between each OFDM symbol will cause intersymbol interference, so it is necessary to eliminate the intersymbol interference between OFDM symbols before cell search. That is, a CP is added to each OFDM symbol of the synchronization signal to obtain an updated synchronization signal.

For the first synchronization signal, the CP may be added in the following manner.

The first synchronization signal is generated by the Zadoff-Chu sequence, and the first synchronization signal with a length of 62 points is divided into 7 segments, and the length of each segment is 6, 10, 10, 10, 10, 10, and 6 subcarriers, respectively mapped to On the 7 OFDM symbols, the two ends are OFDM symbols occupying 6 subcarriers. The frequency domain data of 7 OFDM symbols are respectively subjected to 64-point IFFT, 3 points are added before the time domain data of the first OFDM symbol, and 2 points of CP are added before the time domain data of each OFDM symbol to obtain the first update synchronization signal, a total of 463 Sampling point.

For the second synchronization signal, the CP can be added in the following manner.

The second synchronization signal is composed of two binary sequences with a length of 31. The second synchronization signal with a length of 62 points is divided into 7 segments, and the length of each segment is 6, 10, 10, 10, 10, 10, The 6 subcarriers are respectively mapped to 7 OFDM symbols, and the two ends are OFDM symbols occupying 6 subcarriers. The frequency domain data of 7 OFDM symbols are respectively subjected to 64-point IFFT, and 2 points of CP are added before the time-domain data of each OFDM symbol to obtain the second updated synchronization signal, with a total of 462 sampling points.

102. Determine a cell group ID according to the first update synchronization signal and the second update synchronization signal.

The symbol timing is used to detect the starting position of the first updated synchronization signal, and the channel estimation is performed jointly with the local first synchronization signal to obtain the channel estimation value of the first updated synchronization signal.

The starting position of the second updated synchronization signal is estimated according to the first updated synchronization signal, and the second updated synchronization signal sequence is obtained by combining the channel estimation value of the first updated synchronization signal.

The traversal algorithm is used to cyclically calculate the synchronization signal correlation value according to the second updated synchronization signal sequence, and the cell group ID is determined according to the position of the strongest correlation peak.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (1)

1. A method for cell search in a communication system, characterized in that the method comprises: Eliminating intersymbol interference between OFDM symbols in the first synchronization signal to obtain a first update synchronization signal, and eliminating intersymbol interference between OFDM symbols in the second synchronization signal to obtain a second update synchronization signal; Using symbol timing to detect the starting position of the first updated synchronization signal, performing channel estimation in conjunction with the local first synchronization signal to obtain a channel estimation value of the first updated synchronization signal; Estimating the starting position of the second updated synchronization signal according to the first updated synchronization signal, and combining the channel estimation value of the first updated synchronization signal to obtain a second updated synchronization signal sequence; Using a traversal algorithm to circularly calculate the synchronization signal correlation value according to the second updated synchronization signal sequence, and determine the cell group ID according to the position of the strongest correlation peak; Wherein, said eliminating the intersymbol interference between OFDM symbols in the first synchronization signal to obtain the first updated synchronization signal includes: Add a CP with a length of 3 sampling points before the time domain data of the first OFDM symbol, and add a cyclic prefix CP with a length of 2 sampling points before the time domain data of other OFDM symbols; The obtaining of the second updated synchronization signal by eliminating intersymbol interference between OFDM symbols in the second synchronization signal includes: A CP with a length of 2 sampling points is added before the time-domain data of each OFDM symbol.