WO2014166264A1

WO2014166264A1 - Correlator for mobile terminal and implementation method

Info

Publication number: WO2014166264A1
Application number: PCT/CN2013/087839
Authority: WO
Inventors: 程健; 徐鑫昌; 倪海峰
Original assignee: 中兴通讯股份有限公司
Priority date: 2013-04-09
Filing date: 2013-11-26
Publication date: 2014-10-16
Also published as: CN104104408B; CN104104408A

Abstract

A correlator for a mobile terminal and an implementation method. The method comprises: a mobile terminal performing segmentation correlation processing on received downlink pilot signals and pre-stored training signals, so as to obtain various local correlation values; according to a plurality of preset attempt frequency offset values, performing frequency attempt correlation and segment weighting processing on the various local correlation values, so as to obtain a plurality of global correlation values corresponding to the plurality of attempt frequency offset values; and by comparing the plurality of global correlation values, determining the maximum global correlation value used as an actual correlation value of the mobile terminal and a corresponding attempt frequency offset value used as an actual frequency offset value of the mobile terminal. The correlator in the embodiments of the present invention can have good working performance under large frequency offset, and does not increase the operational complexity basically.

Description

Correlator and implementation method of mobile terminal

Technical field

The present invention relates to a mobile terminal, and in particular, to a correlator having a large frequency offset in a mobile terminal and related implementation methods.

Background technique

In a mobile terminal, correlation operations need to be performed frequently. For example, in a 3G communication system, TD-SCDMA needs to perform DwPCH channel correlation on a downlink pilot time slot DwPTS time slot, and WCDMA needs to perform correlation operation on a primary synchronization channel P-SCH. To get the initial time synchronization of the downlink reception.

When the mobile terminal starts to receive the linear signal, there may be a frequency offset in the receiver. Especially with the low cost requirement, after the crystal replaces the temperature compensated TC-VCXO oscillator, the receiver will have a large frequency offset when initially receiving. For example, there is a frequency offset of 20k ~ 30kHz in the initial reception, so that when the initial correlation operation is performed at the initial reception, the possible frequency offset may be too large, or the related performance may be degraded.

Summary of the invention

It is an object of the present invention to provide a correlator and implementation method for a mobile terminal, which can better solve the problem that the mobile terminal fails to close first or the related performance decreases under a large frequency offset.

According to an aspect of the present invention, a method for implementing a correlator of a mobile terminal is provided, including:

The mobile terminal performs segmentation correlation processing on the received downlink pilot signal and the pre-stored training signal to obtain respective local correlation values;

Performing a frequency attempt correlation and a segmentation weighting process on the respective local correlation values according to a preset plurality of trial frequency offset values, to obtain a plurality of global correlation values corresponding to the plurality of trial frequency offset values;

And determining, by comparing the plurality of global correlation values, a maximum total preference for the actual correlation value of the mobile terminal, before performing the segmentation correlation processing, the method further includes: Obtaining a phase rotation maximum value of the mobile terminal according to a maximum frequency offset of the mobile terminal; determining, by using the phase rotation maximum value and a preset phase rotation threshold value, the number of segments of the downlink pilot signal and the training signal M. Preferably, the step of the segment correlation processing comprises:

And dividing the downlink pilot signal and the training signal into M parts of equal length according to the number of segments M;

The M parts of the downlink pilot signal are locally correlated with the M parts of the corresponding training signal to obtain M local correlation values.

Preferably, before performing the frequency attempt correlation and segment weighting processing steps, the method further includes: determining a frequency offset range of the mobile terminal according to a maximum frequency offset of the mobile terminal;

Within the frequency offset range, a plurality of trial frequency offset values are selected for use in determining the actual correlation value and the actual frequency offset value of the mobile terminal.

Preferably, the steps of the frequency attempt correlation and the segmentation weighting process comprise:

Performing phase rotation processing on each of the local correlation values by using the selected one of the trial frequency offset values to obtain respective local phase rotation correlation values;

And weighting each of the partial phase rotation correlation values to obtain a global correlation value corresponding to the trial frequency offset value.

According to another aspect of the present invention, a correlator for a mobile terminal is provided, including: a segmentation correlation module, configured to: perform segmentation correlation processing on a received downlink pilot signal and a pre-stored training signal to obtain each part Related value

The frequency attempting module is configured to: perform frequency trial correlation and segment weighting processing on each of the local correlation values according to a preset plurality of trial frequency offset values, to obtain multiple global responses corresponding to the plurality of trial frequency offset values Related value

The peak search module is configured to: determine to use as a mobile frequency offset value by comparing the plurality of global correlation values.

Preferably, the method further comprises: a segment number determining module, configured to: obtain a phase rotation maximum value of the mobile terminal according to a maximum frequency offset of the mobile terminal, and determine the downlink pilot by using the phase rotation maximum value and a preset phase rotation threshold value The number of segments of the signal and the training signal M.

Preferably, the segment correlation module comprises:

The segmentation sub-module is configured to: divide the downlink pilot signal and the training signal into M parts of equal length according to the number of segments M;

The correlation submodule is configured to: perform partial correlation processing on the M parts of the downlink pilot signal and the M parts of the corresponding training signal to obtain M local correlation values.

Preferably, the method further comprises:

The frequency offset value determining module is configured to: determine a frequency offset range of the mobile terminal according to a maximum frequency offset of the mobile terminal, and select a plurality of trial frequency offset values in the frequency offset range, so as to determine the mobile terminal Actual correlation value and actual frequency offset value.

Preferably, the frequency attempting module comprises:

The phase rotation sub-module is configured to: perform phase rotation processing on each of the local correlation values by using the selected one of the trial frequency offset values to obtain respective local phase rotation correlation values;

The weighting processing sub-module is configured to: perform weighting processing on each of the local phase rotation correlation values to obtain a global correlation value corresponding to the trial frequency offset value.

Compared with the prior art, the beneficial effects of the embodiments of the present invention are:

1. By transforming the structure of the correlator, it has good working performance under a large frequency offset;

2. On the basis of ensuring relevant performance, the complexity associated with the attempt can be greatly reduced. BRIEF abstract

1 is a schematic block diagram of a method for implementing a correlator of a mobile terminal according to an embodiment of the present invention; FIG. 2 is a schematic diagram of a downlink pilot signal in a mobile communication system according to an embodiment of the present invention; FIG. 3 is a mobile terminal according to an embodiment of the present invention; FIG. 4 is a relationship diagram of phase rotation and signal to noise ratio according to an embodiment of the present invention; FIG. FIG. 5 is a schematic diagram of segmentation related according to an embodiment of the present invention; FIG.

Figure; ; " , , , , ,

FIG. 7 is a schematic diagram of a complexity comparison of the present invention according to an embodiment of the present invention; FIG. 8 is a block diagram of a correlator of a mobile terminal according to an embodiment of the present invention.

Preferred embodiment of the invention

The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

1 is a schematic block diagram of a method for implementing a correlator of a mobile terminal according to an embodiment of the present invention. As shown in FIG. 1, the method includes: Step 101: A mobile terminal segments a received downlink pilot signal and a pre-stored training signal. Correlation processing yields individual local correlation values.

Before performing the segmentation correlation process, the number of segments is determined in advance, that is, the phase rotation maximum value of the mobile terminal is obtained according to the maximum frequency offset of the mobile terminal, and the phase rotation maximum value and the preset phase are utilized. a rotation threshold value, the number of segments M of the downlink pilot signal and the training signal is determined. Then, the mobile terminal divides the downlink pilot signal and the training signal into M parts of equal length according to the number of segments M, respectively, and separately respectively respectively M parts of the downlink pilot signal The M parts of the training signal are subjected to local correlation processing to obtain M local correlation values. The maximum frequency offset of the mobile terminal is determined by the device type of the mobile terminal. For example, when the mobile terminal uses a crystal, the maximum frequency offset is 20k ~ 30kHz.

Step 102: Perform frequency trial correlation and segment weighting processing on each of the local correlation values according to a preset plurality of trial frequency offset values, to obtain a plurality of global correlation values corresponding to the plurality of trial frequency offset values.

Before performing the frequency attempt correlation and segment weighting processing steps, a plurality of trial frequency offset values are preset, that is, determining a frequency offset range of the mobile terminal according to a maximum frequency offset of the mobile terminal; Within the frequency offset range, a plurality of trial frequency offset values are selected for use in determining the actual correlation value and the actual frequency offset value of the mobile terminal. Then, using the selected one of the trial frequency offset values, performing phase rotation processing on the respective local correlation values to obtain respective local phase rotation correlation values; and weighting the respective local phase rotation correlation values to obtain the attempt A global correlation value corresponding to the frequency offset value.

Step 103: Determine, by comparing the plurality of global correlation values, a maximum global correlation value used as an actual correlation value of the mobile terminal and a corresponding trial frequency offset value used as a real frequency offset value of the mobile terminal.

The intensive description will be made below with reference to Figs. 2 to 7.

In a general mobile communication system, downlink pilot signals are transmitted in the entire cell in a broadcast form and periodically repeated. Taking FIG. 2 as an example, r(n) is a received pilot signal, and s(n) is locally known. The training signal, n is the sample point number, and N is the length of the pilot signal/training signal. The general correlation operation is performed according to the following formula:

R = ∑r(n) *s*(n) ( 1 ) The above formula is accurate in the scene without frequency offset or small frequency offset, but when the system exists in the scene with unknown unknown frequency offset The conventional approach is to try the frequency offset compensation method. For example, if the unknown frequency offset is within 20 kHz, then try to correlate the frequency offsets such as 0, ±5 kHz, ±10 kHz, ±15 kHz, and ±20 kHz. It is necessary to try 9 correlations. Let the frequency offset of the attempt be f, the symbol rate be fs, the symbol period be Ts=l/fs, and the pilot last for N symbol periods. Then the conventional attempt correlation is performed according to the following formula:

From the above formula, j denotes an imaginary factor, ie j = , s*(n) denotes a conjugate operation on s(n). It can be seen here that the complexity is greatly improved when multiple correlation attempts at different frequencies are performed:

a. First, it is necessary to perform multiple correlation operations in accordance with a certain compensation within the maximum frequency offset range; b. Second, in the received pilot signal, each symbol needs to be multiplied by a phase rotation _e j ^f *( ⁿ - ^1)Ts . The present invention can greatly reduce the complexity associated with the attempt and substantially achieve the same performance associated with the attempt. The process of the present invention is shown in FIG. 3, and the steps include:

Step one, data segmentation.

There are two links in the data segmentation: segment the received pilot signal, set the pilot signal length to N, and divide it into M parts of equal length, each length being L=N/M. Similarly, the locally pre-stored training signals are segmented.

The criterion of segmentation first analyzes the possible range of large frequency offset. For example, under the crystal scheme, the maximum frequency offset is about ±30 kHz. Secondly, the length and symbol rate of the training signal need to be considered. Finally, the phase rotation before and after segmentation is converted. How many other conditions are considered together. After the segmentation, the phase-to-tail data rotates too much under the frequency offset, which will affect the related performance. If the phase rotation is too small, it means that the length of the whole training signal is too thin, which will lead to more complexity, such as requiring a minute. The maximum phase rotation of the first and last data in the segment does not exceed π/4. An example is given below:

In the P-SCH pilot channel of WCDMA, the length of the crystal is 256 chips, and the maximum frequency deviation of the crystal is ±30 kHz. If it is +30 kHz, if it is not segmented, the phase rotation caused by the frequency offset on the first and last symbols of the training code is:

2nx30kx256x ~ - ~ = 4π ( 3 )

3.84Μ

That is to say, due to the possible large frequency offset, the phase rotation of the P-SCH pilot channel in the 256 chip time will reach 4π. If the correlation is directly performed, the correlation peak will not be obtained, resulting in detection failure. .

According to the phase rotation threshold value is π/4, the number of segments to be segmented is 4π÷ π/4 = 16 , and the length of each segment is

256/16=16 chips.

Let us derive the relationship between phase rotation and channel ratio.

Assume that the length of the pilot signal received in the post-segment segment is 2χΑ, the phase rotation of the first and last symbols is Θ and -Θ, and then the training code is all 1, then the signal strength S and the noise intensity Ν are respectively ^ , 2i + 1„,

s=∑|ex _P (^e) 2*cos( Θ) (4)

2A-1 2A-1

SNR = S/N (6) When A is large, the signal-to-noise ratio SNR is independent of A, and the signal-to-noise ratio values of different values are calculated as shown in Fig.

4 is shown.

When calculating the correlation peak, it is generally only necessary to find the relevant peak. In combination with the simulation, the general phase rotation is between π/4 and π/2, and the correlation performance has little effect.

Then, after segmentation, the phase rotation of the first and last symbols in the segment does not exceed the range between π/4 and π/2.

Step 2, segmentation related, that is, local correlation.

The local correlation diagram is shown in Figure 5. In Figure 5, the received downlink pilot signals are segmentally correlated to obtain a local correlation value R(l), R(2) R(M), and the local correlation is as follows: Formula to execute:

L

R( _m ) = ^r(l + (ml)*L) *s*(l + (ml)*L),m = l,2,..., M (7)

1=1

Where R(m) is a complex form, which is the local correlation value of the mth part, L is the segment length, and r(l + (ml)*L) is the l + (ml)*L of the mth part The pilot symbol or pilot code of the bit, s*(l+(ml)*L) is the conjugate of the training symbol or training code of the l + (ml) * L bits of the mth part.

Step 3. Frequency trial correlation and segmentation weighting

In this step, the global correlation of the phase rotation of the frequency offset value to be tried based on the local correlation value is shown as follows:

J*27i: *f*(m-i;)*L*Ts

∑R(m)* (7) where |x| denotes the modulo operation on the complex number X, f is the trial frequency offset value, and Ts is the symbol period Or chip period.

After the above steps, the correlation operation is realized, and the global correlation value R is obtained. For different trial frequency offset values f, multiple global correlation values R can be obtained.

Step four, peak search.

For the above step 3, according to different trial frequency offset values, multiple global correlation values R are obtained, and the global correlation values are compared, the maximum value is selected as the actual correlation value, and the actual frequency offset value existing in the system is output.

Next, let's analyze the complexity comparison between traditional correlation and our proposed local correlation and global correlation to achieve correlation operations:

Traditionally related, assuming that F frequency attempts are required, then it needs to be performed according to equation (2).

F times full correlation, and each time the correlation operation, if the frequency f of the attempt is not 0, a phase-by-symbol phase rotation operation is required;

The correlation method we propose here needs to perform the local correlation of M times L according to formula (3). The overall complexity of this step is the same as the complexity of a full correlation operation (formula (1)); then the frequency is tried according to the formula. (8), perform the correlation accumulation of length F of length M, because M=N/L<N, the complexity is much smaller than the traditional frequency trial method.

The present invention will be described below by taking the P-SCH correlation in the WCDMA system as an example. P-SCH length is N=256 chips, M is 16 segments, each length L=N/M=16 chips, assuming the initial frequency offset of the system is 18kHz, try to correlate every 5kHz, try 0, ± There are 13 points of 5 kHz, ±10 kHz, ±15 kHz, ±20 kHz, ±25 kHz, and ±30 kHz. According to the above conventional correlation method and the local correlation method proposed by the present invention, the correlation values are as shown in FIG. 6. As can be seen from the table, both algorithms can find the correlation peak, around 0.96, and the corresponding frequency offset is at 20 kHz.

According to the above example, according to the 13-time frequency offset attempt, the traditional correlation and the segment correlation method of the present invention are compared as shown in Fig. 7.

FIG. 8 is a block diagram of a correlator of a mobile terminal according to an embodiment of the present invention. As shown in FIG. 8, the method includes: The segment number determining module is configured to obtain a maximum phase offset of the mobile terminal according to the maximum frequency offset of the mobile terminal, and determine the downlink pilot by using the phase rotation maximum value and a preset phase rotation threshold value. The number of segments of the signal and the training signal M.

The segmentation correlation module is configured to perform segmentation-related processing on the received downlink pilot signal and the pre-stored training signal to obtain respective local correlation values. Further, the segmentation correlation module includes a segmentation submodule and a related submodule, and the segmentation submodule is configured to divide the downlink pilot signal and the training signal into equal lengths according to the number of segments M, respectively. The M sub-sections are configured to perform partial correlation processing on the M parts of the downlink pilot signal and the M parts of the corresponding training signal to obtain M local correlation values.

The trial frequency offset value determining module is configured to determine a frequency offset range of the mobile terminal according to a maximum frequency offset of the mobile terminal, and select a plurality of trial frequency offset values in the frequency offset range, so as to be used to determine the mobile terminal. Actual correlation value and actual frequency offset value.

The frequency attempting module is configured to perform frequency trial correlation and segment weighting processing on the respective local correlation values according to a preset plurality of trial frequency offset values, to obtain multiple global corresponding to the multiple trial frequency offset values. Relevant value. Further, the frequency attempting module includes a phase rotation sub-module and a weighting processing sub-module, and the phase rotation sub-module is configured to perform phase rotation processing on each of the local correlation values by using the selected one of the trial frequency offset values. Obtaining respective local phase rotation correlation values; the weighting processing sub-module is configured to perform weighting processing on each of the local phase rotation correlation values to obtain a global correlation value corresponding to the trial frequency offset value.

A peak search module is configured to determine to be used as a mobile terminal value by comparing the plurality of global correlation values.

The correlator of the mobile terminal in the embodiment of the present invention has good working performance and low complexity in a large random frequency offset scenario. After segmentation, the first and last phase rotation does not exceed a certain threshold, such as pi/4 to Between pi/2. Although the invention has been described in detail above, the invention is not limited thereto, and various modifications may be made by those skilled in the art in accordance with the principles of the invention. Therefore, modifications made in accordance with the principles of the invention should be construed as falling within the scope of the invention.

Industrial applicability

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

2. On the basis of ensuring relevant performance, the complexity associated with the attempt can be greatly reduced.

Claims

Claim

A method for implementing a correlator of a mobile terminal, comprising:

Determining the maximum value of the actual correlation value used as the mobile terminal by comparing the plurality of global correlation values

2. The method according to claim 1, wherein before performing the segmentation related processing, the method further includes:

Obtaining a maximum phase rotation of the mobile terminal according to a maximum frequency offset of the mobile terminal;

The downlink pilot signal and the number of segments M of the training signal are determined using the phase rotation maximum value and a preset phase rotation threshold value.

The method according to claim 2, wherein the step of segmentation correlation processing comprises: dividing the downlink pilot signal and the training signal into equal length M according to the number of segments M, respectively Part

The method according to claim 3, wherein before the performing the frequency attempt correlation and the segmentation weighting processing step, the method further includes:

Determining the frequency offset range of the mobile terminal according to the maximum frequency offset of the mobile terminal;

5. The method according to claim 4, wherein the steps of the frequency attempt correlation and the segmentation weighting process comprise: Performing phase rotation processing on each of the local correlation values by using the selected one of the trial frequency offset values to obtain respective local phase rotation correlation values;

6. A correlator for a mobile terminal, comprising:

The segmentation correlation module is configured to: perform segmentation correlation processing on the received downlink pilot signal and the pre-stored training signal to obtain respective local correlation values;

7. The correlator according to claim 6, further comprising:

a segment number determining module, configured to: obtain a phase rotation maximum value of the mobile terminal according to a maximum frequency offset of the mobile terminal, and determine the downlink pilot by using the phase rotation maximum value and a preset phase rotation threshold value The number of segments of the signal and the training signal M.

The correlator according to claim 7, wherein the segmentation correlation module comprises: a segmentation submodule, configured to: respectively, according to the number of segments M, respectively, the downlink pilot signal and the training signal Divided into M parts of equal length;

9. The correlator according to claim 8, further comprising:

The frequency offset value determining module is configured to: determine a frequency offset range of the mobile terminal according to a maximum frequency offset of the mobile terminal, and select a plurality of trial frequency offset values in the frequency offset range to be used for determining The actual correlation value and the actual frequency offset value of the mobile terminal.

The correlator according to claim 9, wherein the frequency attempting module comprises: a phase rotation sub-module, configured to: perform phase rotation on each of the local correlation values by using the selected one of the trial frequency offset values Processing, obtaining respective local phase rotation correlation values;