WO2008067721A1

WO2008067721A1 - Synchronization process method, base-station, user device and communication system

Info

Publication number: WO2008067721A1
Application number: PCT/CN2007/003382
Authority: WO
Inventors: Zhenglei Hu
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2006-12-04
Filing date: 2007-11-29
Publication date: 2008-06-12
Also published as: CN101197804A; CN101197804B

Abstract

A synchronization process method for resolving the problem in prior art that it does not support the coherent detecting due to the P-SCH channel estimation does not match with the real unicast channel when using single PSC; and the problem that the synchronization detecting is hardly realized due to the power of the multi-cells is not able to be enhanced when using multi-PSC; the method includes: mapping the sequence PSC used by the P-SCH to the sub-carrier wave of the OFDM signal, wherein, the first part of P-SCH of each frame uses a public PSC to realize map, and the second part of P-SCH selects one PSC from multi PSC to realize map; and forms the OFDM signals of the time region according to all the sub-carrier waves of each frame and then sending them. A base-station, a user device and a communication system are also provided.

Description

Synchronous processing method, base station, user equipment and communication system

The present invention relates to the field of communications technologies, and in particular, to a synchronization processing method, a base station, a user equipment, and a communication system. Background technique

In the fourth generation wireless mobile communication system, the main physical layer technology OFDM (Orthogonal Frequency Division Multiplexing) is a mobile communication technology that utilizes parallel transmission to increase the communication data rate. In order to ensure orthogonality between subcarriers, OFDM systems require very accurate time-frequency synchronization. Therefore, synchronization technology is one of the key technologies of OFDM systems. In the wireless communication system, when the user initially accesses the network, the downlink synchronization process is mainly performed through a synchronization channel (SCH, Synchronization Channel).

In an OFDM system, the SCH occupies part of the bandwidth of the system center in the frequency domain, and occupies one or more OFDM symbols in the frame structure in the time domain (two in the 3GPP LTE). OFDM system The functions of downlink slot timing, frame timing, frequency offset estimation and cell search can be realized by SCH-specific structure. When the timing frequency offset function and the cell search function are implemented by the same SCH symbol, it is called non-hierarchical SCH; when the timing frequency offset function and the cell identification function are respectively implemented by different SCH symbols, Is a hierarchical SCH (hierarchical SCH).

3GPP LTE is designed with a layered SCH, where P-SCH (primary SCH) is used for timing frequency offset estimation, and S-SCH (secondary SCH) carries cell identity (cell ID) information for cell search.

The P-SCH occupies one or more OFDM symbols in the time domain, and the first half of the OFDM symbol containing the P-SCH is the same as the second half. After receiving the signal, the UE first implements the coarse timing frequency offset through differential correlation, and then achieves precise synchronization through sequence correlation and matching processing.

The number of sequences used on the P-SCH directly affects the time and performance of the synchronization. One implementation in the prior art is that all cells use a common P-SCH sequence as the primary synchronization channel, for example in Asynchronous system In a WCDMA system, since each cell uses the same PSC (the sequence used by the P-SCH), the UE only needs to use one sequence to search for the synchronization signal, and the timing complexity is low. In addition, in a synchronous system, the same PSC of each cell is equivalent to a multipath component, thereby enhancing energy and being easy to detect.

However, when all cells use the same P-SCH, the P-SCH-based channel estimation is a superposition of the multi-cell propagation channel, which may cause a mismatch with the actual unicast channel, that is, the actual channel condition of the cell cannot be characterized. Therefore, the scheme cannot use the P-SCH for coherent detection to obtain the information of the S-SCH. Especially in a synchronous system, for a UE at a large cell edge, such a mismatch can seriously deteriorate the cell search performance. Many implementations of LTE and TDD-based communication systems are implemented as synchronous systems. Therefore, this mismatch problem needs to be solved.

In order to solve the above problem, another implementation in the prior art is to use multiple PSCs as primary synchronization channels to distinguish neighboring cells by a group of multiple PSCs. Considering the search time, the number of PSCs is controlled to a small range. The industry analysis indicates that the number of PSCs ranges from 3 to 7. Considering the computational complexity and solving the problem of P-SCH and S-SCH channel mismatch, the number of PSCs is chosen to be 3.

Although the above implementation improves the problem of channel mismatch, multiple PSCs cannot achieve the effect of multi-cell energy enhancement, which is not conducive to detecting synchronization signals, and the increase in the number of PSCs also brings the complexity of synchronous detection. Summary of the invention

Embodiments of the present invention provide a synchronization processing method, a base station, a user equipment, and a communication system, to implement coherent detection of an S-SCH, improve cell search performance, and facilitate detection of a synchronization signal.

The embodiments of the present invention provide the following technical solutions:

A synchronization processing method, the method comprising the steps of:

The sequence PSC used by the primary synchronization channel P-SCH is mapped to the subcarriers of the OFDM symbol, wherein the first partial P-SCH in each frame is mapped using a common PSC, and the second partial P-SCH is selected from multiple PSCs. Mapping by a PSC;

A time domain OFDM symbol is formed and transmitted according to all subcarriers in each frame. A synchronization processing method, the method comprising the steps of:

Receiving a plurality of OFDM symbols, wherein a partial OFDM symbol in each frame carries a first partial P-SCH mapped using a common PSC, and a partial OFDM symbol carries a second partial P-SCH mapped using one of a plurality of PSCs ;

Demodulating the first partial P-SCH, the second partial P-SCH, and the S-SCH information from the received OFDM symbols;

Performing coarse timing or frame timing by using the demodulated first partial P-SCH and the demodulated second partial P-SCH, and performing timing offset estimation using the demodulated first partial P-SCH, The demodulated second partial P-SCH and the demodulated S-SCH information are used for cell search.

A base station comprising:

A unit for mapping a sequence PSC used by a primary synchronization channel P-SCH to a subcarrier of an OFDM symbol, wherein a first partial P-SCH in each frame is mapped using a common PSC, and a second partial P-SCH is from a plurality Select one PSC for mapping in each PSC;

a unit for forming an OFDM symbol of a time domain according to all subcarriers in each frame;

A unit for transmitting OFDM symbols.

A user equipment, including:

Means for receiving a plurality of OFDM symbols, wherein a partial OFDM symbol in each frame carries a first partial P-SCH mapped using a common PSC, and a partial OFDM symbol carries a second mapping using one of a plurality of PSCs Partial P-SCH;

Means for demodulating the first partial P-SCH, the second partial P-SCH, and the S-SCH information from the received OFDM symbols;

And performing coarse timing or frame timing by using the demodulated first partial P-SCH and the demodulated second partial P-SCH, and performing timing offset estimation by using the demodulated first partial P-SCH. The demodulated second partial P-SCH and the demodulated S-SCH information perform cell search.

A communication system comprising:

a base station, configured to map a sequence PSC used by the primary synchronization channel P-SCH to an OFDM symbol On the subcarrier, where the first part of the P-SCH in each frame is mapped using a common PSC, and the second part of the P-SCH selects one PSC from the plurality of PSCs for mapping; and, according to all subcarriers in each frame Time domain OFDM symbols and sent;

a user equipment, configured to demodulate the first partial P-SCH, the second partial P-SCH, and the S-SCH information from the received OFDM symbol, using the demodulated first portion P-SCH and demodulating The second part of the P-SCH performs coarse timing or frame timing, and uses the demodulated first partial P-SCH to perform timing frequency offset estimation, and uses the demodulated second partial P-SCH and the demodulated S. The -SCH information is used for cell search.

The beneficial effects of the embodiments of the present invention are as follows:

In the embodiment of the present invention, when mapping the PSC to the subcarrier of the OFDM symbol, the first part of the P-SCH in each frame is mapped by using a common PSC, and the second part of the P-SCH is selected by selecting one PSC from the plurality of PSCs. The advantages of the synchronization signal energy gain and the low sequence complexity when mapping with a common PSC in the prior art are retained, and the prior art only uses a common PSC for mapping, resulting in P-SCH and S. The -SCH channel is not matched, and the problem of coherent detection of the S-SCH cannot be performed, thereby improving the timing synchronization performance and the cell search performance of the synchronization system without increasing the system resource occupation and the detection complexity. DRAWINGS

1 is a schematic structural diagram of a communication system according to an embodiment of the present invention;

2 is a schematic diagram of mapping and converting a first part of a P-SCH according to an embodiment of the present invention;

3 is a schematic diagram of a second part P-SCH mapping and conversion according to an embodiment of the present invention;

4 is a schematic diagram of a time domain structure of a hierarchical SCH in an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a base station according to an embodiment of the present invention;

6 is a flowchart of synchronization processing of a base station according to an embodiment of the present invention;

FIG. 7 is a schematic structural diagram of a user equipment according to an embodiment of the present invention;

FIG. 8 is a flowchart of synchronization processing of a user equipment according to an embodiment of the present invention. detailed description

In the embodiment of the present invention, the P-SCH in each frame is divided into two parts. The first part of the P-SCH is mapped to the subcarriers of the OFDM symbol by using a common PSC, and the second part of the P-SCH is selected from the multiple PSCs. A PSC is mapped to the subcarriers of the OFDM symbol, and then converted into a time domain OFDM symbol and sent to the user equipment for processing, which improves the timing synchronization performance and the cell search performance of the synchronization system.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Referring to FIG. 1, a communication system in this example includes: a base station 100 and a user equipment 101. The base station 100 is located in the E-UTRAN of the universal terrestrial radio access network, and is configured to receive uplink data sent by the user equipment 101 and send downlink data to the user equipment 101. When the base station 100 transmits the downlink data to the user equipment 101, the primary synchronization channel P-SCH in each frame is divided into two parts, and the first part of the P-SCH is mapped to the subcarriers of the OFDM symbol by using a common PSC. And the second part of the P-SCH selects one PSC from the plurality of PSCs to be mapped to the subcarriers of the OFDM symbol; and forms an OFDM symbol of the time domain according to all the subcarriers in each frame and sends the OFDM symbol to the user equipment 101. The user equipment 101 is configured to receive downlink data sent by the base station 100 and send uplink data to the base station 100, where the user equipment 101 receives an OFDM symbol sent by the base station 100, and demodulates the first part P from the user equipment 101. -SCH, second part P-SCH and S-SCH information, performing coarse timing or frame timing by using the first part P-SCH and the second part P-SCH, and performing timing frequency offset estimation by using the first part P-SCH And performing cell search by using the second part of the P-SCH and the demodulated S-SCH information.

When the PSC is mapped onto a subcarrier, the P-SCH maps the elements of the PSC used by it to the subcarriers of the OFDM symbol at equal intervals.

Referring to FIG. 2, the first part P-SCH 釆 uses a common sequence P _c , and the common sequence P _c is N symbols long. In the frequency domain, on subcarrier 0 to subcarrier 2N-1, each element of P 映射 is mapped to an even-numbered subcarrier, and an odd-numbered subcarrier is an empty subcarrier. And, all the subcarriers in each frame are subjected to inverse discrete fast Fourier transform (IFFT), and the cyclic prefix CP is added to form an OFDM symbol with the same characteristics in the front and back of the time domain and transmitted.

Referring to FIG. 3, the second part P-SCH uses a set of sequences {P } , ( 1 , M ); The system selects one sequence from the M sequences according to the number of the cell group and the PSC, and uses the sequence transmitted on the P-SCH of the second part of the cell to map the elements of the sequence to the subcarriers with the even number. The subcarriers whose odd number is odd are empty subcarriers. And, all subcarriers in each frame are subjected to inverse discrete fast Fourier transform IFFT, and after the cyclic prefix CP is formed, an OFDM symbol having exactly the same characteristics in the front and rear regions is formed and transmitted.

In FIG. 2 and FIG. 3, when the PSC is mapped to the subcarrier, each element of the PSC is mapped to an even-numbered subcarrier, and the odd-numbered subcarrier is an empty subcarrier, so that the processing is for the time. The OFDM symbols with the same characteristics of the two parts are obtained on the domain. Of course, the elements of the PSC can be mapped to the subcarriers with odd ordinal numbers, and the subcarriers with even numbers are null subcarriers. The two parts of the domain OFDM symbol are identical after modulo.

For example, as shown in FIG. 4, the time domain structure of the layered SCH in the present embodiment is as shown in FIG. 4, where the P-SCH is repeated twice in a frame. The slot spacing between the OFDM symbols is the same; and, in order to facilitate the coherent detection, the OFDM symbol carrying the secondary synchronization channel S-SCH information or the broadcast channel BCH information and the OFDM symbol carrying the second partial P-SCH are in the time domain Adjacent.

As shown in FIG. 5, the structure of the base station 100 in this embodiment includes: a mapping unit 500, a converting unit 501, and a sending unit 502. The mapping unit 500 is configured to map a sequence PSC used by the primary synchronization channel P-SCH. Going to the subcarrier of the OFDM symbol, wherein the first part of the P-SCH in each frame is mapped using a common PSC, and the second part of the P-SCH is selected from a plurality of PSCs for mapping; the converting unit 501 is used And forming, according to all subcarriers in each frame, a unit of an OFDM symbol in a time domain; and the sending unit 502, configured to send an OFDM symbol.

Referring to Figure 6, the synchronization process of the base station is as follows:

Step 600: Divide the primary synchronization channel P-SCH in each frame into two parts. The first part of the P-SCH is mapped to the subcarriers of the OFDM symbol by using a common PSC, and the second part of the P-SCH is selected from the multiple PSCs. One PSC is mapped onto the subcarriers of the OFDM symbol.

Step 601: Perform inverse inverse fast Fourier transform IFFT on all subcarriers in each frame, and add a cyclic prefix CP to form an OFDM symbol with the same characteristics in the front and back of the time domain. Step 602: Send an OFDM symbol.

After demodulating the first partial P-SCH and the second partial P-SCH from the received OFDM symbols, the user equipment 101 performs coarse timing by using the first partial P-SCH and the second partial P-SCH. Since the first part P-SCH and the second part P-SCH are both repeating structures, the correlation peak of the received signal can be detected by using a differential correlation method, and the intra-frame average can also be used (ie, the first part P- The correlation peaks of the SCH and the second part of the P-SCH are superimposed after modulo or multi-frame averaging to detect the correlation peak of the received signal.

The user equipment 101 performs frame timing by using the demodulated first part P-SCH and the second part P-SCH, and performs matching with the PSC corresponding to the first part P-SCH at the peak of the received signal, and finds The frame timing is implemented when the first portion of the P-SCH is located.

Preferably, when the number of OFDM symbols carrying the P-SCH included in one frame is greater than two, the OFDM symbol carrying the first part of the P-SCH and the second part P- Different timing arrangements of the OFDM symbols of the SCH carry related information of other demodulated OFDM symbols, such as indicating the length of the CP symbol or the number of antennas.

Preferably, in order to avoid the complexity of detection when multiple PSCs are matched, and the inter-cell enhancement effect is utilized, the user equipment 101 performs timing offset estimation using the demodulated first partial P-SCH.

Further, since the second part of the P-SCH uses multiple PSCs, part of the cell identity information may also be carried to improve the cell search function. In addition, since the sequence detection of the second partial P-SCH does not affect the synchronization time, it is possible to appropriately carry more information (not limited to the maximum number of sequences in the prior art).

Further, since the second part of the P-SCH can better correspond to the propagation environment of the target cell, the OFDM symbol carrying the S-SCH information in the time domain is adjacent to the OFDM symbol carrying the second part of the P-SCH, It is advantageous for S-SCH coherent demodulation, that is, the identification information of a specific cell is obtained from the S-SCH detection.

Further, after the synchronization and cell search are completed by using the layered SCH, the BCH information can be read. A structure of the user equipment 101 in this embodiment is as shown in FIG. 7, and includes: a receiving unit 700, and a solution The modulating unit 701 is configured to receive a plurality of OFDM symbols, where a part of the OFDM symbols in each frame carries a first part of the P-SCH that is mapped using a common PSC, and the part of the OFDM symbol is carried. a second part P-SCH mapped by one of the plurality of PSCs; the demodulation unit 701, configured to demodulate the first part P-SCH and the second part P-SCH from the received OFDM symbols The processing unit 702 is configured to perform coarse timing or frame timing by using the first part P-SCH and the second part P-SCH, perform timing frequency offset estimation by using the first part P-SCH, and use the second A unit for performing cell search by the partial P-SCH and the demodulated S-SCH information.

The processing unit 702 also performs coherent detection using the second portion P-SCH.

Referring to Figure 8, the synchronization process of the user equipment is as follows:

Step 800: Receive multiple OFDM symbols, where a partial OFDM symbol in each frame carries a first partial P-SCH mapped using one common PSC, and a partial OFDM symbol carries a second portion mapped using one of a plurality of PSCs P-SCH.

Step 801: Demodulate the first partial P-SCH and the second partial P-SCH from the received OFDM symbols.

Step 802: Perform coarse timing or frame timing by using the first part P-SCH and the second part P-SCH, perform timing frequency offset estimation by using the first part P-SCH, and utilize the second part P-SCH and demodulation The generated S-SCH information is used for cell search.

Step 802 can also include performing coherent detection using the second portion of the P-SCH.

As can be seen from the above embodiments, when mapping a PSC to a subcarrier of an OFDM symbol, the first part of the P-SCH in each frame is mapped using a common PSC, and the second part of the P-SCH is selected from a plurality of PSCs. Performing the mapping preserves the advantages of the synchronization signal energy gain and the low sequence complexity when mapping with a common PSC in the prior art, and solves the problem that the prior art only uses a common PSC for mapping and causes P-SCH. If the S-SCH channel does not match, the problem of coherent detection of the S-SCH cannot be performed, thereby improving the timing synchronization performance and the cell search performance of the synchronization system without increasing the system resource occupation and detection complexity; further, The second part of the P-SCH carries partial cell identification information, which reduces inter-cell interference, and the grouping ratio is only Carrying cell identification information with S-SCH is more conducive to improving detection accuracy and speed. The spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and the modifications of the invention

Claims

Rights request

A synchronization processing method, characterized in that the method comprises:

A time domain OFDM symbol is formed and transmitted according to all subcarriers in each frame.

The method according to claim 1, wherein the P-SCH maps elements of the PSC used by it to the subcarriers of the OFDM symbol at equal intervals.

The method according to claim 2, wherein the P-SCH maps each element of the PSC used by the P-SCH to an even-numbered subcarrier in the OFDM symbol.

The method according to claim 1, wherein in the time domain, in a plurality of PSC-bearing OFDM symbols, time slot intervals between adjacent two OFDM symbols are the same.

The method according to claim 1, wherein the OFDM symbol carrying the secondary synchronization channel S-SCH information or the broadcast channel BCH information is adjacent to the OFDM symbol carrying the second partial P-SCH in the time domain.

The method according to any one of claims 1 to 5, further comprising: the receiving end demodulating the first partial P-SCH, the second partial P-SCH and the S-SCH from the received OFDM symbols And performing the coarse timing or the frame timing by using the demodulated first partial P-SCH and the demodulated second partial P-SCH, and performing timing frequency offset estimation by using the demodulated first partial P-SCH, The cell search is performed by using the demodulated second partial P-SCH and the demodulated S-SCH information.

7. The method according to claim 6, wherein the receiving end further performs coherent detection by using the demodulated second partial P-SCH.

8. A synchronization processing method, characterized in that the method comprises:

Receiving a plurality of OFDM symbols, wherein a partial OFDM symbol in each frame carries a first partial P-SCH mapped using a common PSC, and a partial OFDM symbol carries a plurality of PSCs a PSC that is mapped by a PSC;

9. The method of claim 8, further comprising:

Coherent detection is performed using the second portion of the P-SCH.

The method according to claim 8, wherein when the first part P-SCH and the second part P-SCH are used for coarse timing, the method uses differential correlation, intra-frame average or multi-frame average detection. Receive signal correlation peaks.

The method according to claim 8, wherein when the first partial P-SCH is used for frame timing, the PSC corresponding to the first partial P-SCH is matched at the received signal correlation peak.

12. The method according to claim 8, wherein the second part of the P-SCH further carries cell identity information.

The method according to claim 8, wherein the OFDM symbol carrying the first partial P-SCH and the OFDM symbol carrying the second partial P-SCH in each frame indicate demodulation through different timing arrangements Information about OFDM symbols.

A base station, comprising:

A unit for transmitting OFDM symbols.

15. A user equipment, comprising:

Means for receiving a plurality of OFDM symbols, wherein a portion of the OFDM symbols in each frame are carried a first partial P-SCH mapped by a common PSC, the partial OFDM symbol carrying a second partial P-SCH mapped using one of the plurality of PSCs;

The user equipment of claim 15, further comprising:

A unit for coherent detection using the second portion of the P-SCH.

17. A communication system, comprising:

a base station, configured to map a sequence PSC used by the primary synchronization channel P-SCH to a subcarrier of an OFDM symbol, where a first part of the P-SCH in each frame is mapped using a common PSC, and a second part of the P-SCH is from a plurality of Selecting one PSC for mapping in each PSC; and forming a time domain OFDM symbol according to all subcarriers in each frame and transmitting;

a user equipment, configured to demodulate the first partial P-SCH, the second partial P-SCH, and the S-SCH information from the received OFDM symbol, and use the demodulated first partial P-SCH and demodulation The second part of the P-SCH is subjected to coarse timing or frame timing, and the demodulated first part P-SCH is used for timing frequency offset estimation, and the demodulated second part P-SCH and the demodulated one are used. The S-SCH information performs cell search.

18. The system according to claim 17, wherein the P-SCH maps each element of the PSC used by it to an even number of subcarriers in the OFDM symbol.

The system according to claim 17, wherein in the time domain, among the plurality of PSC-bearing OFDM symbols, the slot intervals between two adjacent OFDM symbols are the same.

20. The system according to claim 17, wherein the OFDM symbol carrying the secondary synchronization channel S-SCH information or the broadcast channel BCH information is adjacent to or adjacent to the OFDM symbol carrying the second partial P-SCH.