JP2007124060A - Correlation peak detection circuit and method thereof, synchronization acquisition circuit using the same and method thereof, and receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of decreasing an error in a peak position caused by sampling accuracy of a correlation peak in synchronization acquisition (serial search) processed by a reception section of a terminal in a CDMA mobile communication system that detects the correlation of signals subjected to spread coding to take synchronization for data demodulation. <P>SOLUTION: A differential amount discrimination circuit 1 estimates a true maximum peak position on the basis of sampling results at a maximum peak position detected by sampling a correlation waveform denoting the correlation and a plurality of sampling positions before and after the detected maximum peak position and detects a difference 202 between the estimated maximum peak position and the detected maximum peak position. The differential amount discrimination circuit 1 controls a VCO 2 in response to the difference 202 to allow a PN code generator 3 to execute phase shift control, resulting in executing phase control of an inverse spread code 203 for demodulating the signal subjected to the spread coding. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a correlation peak detection circuit and method thereof, a synchronization acquisition circuit and method using the same, and a receiver, and more particularly to a serial search method for acquiring synchronization in a receiver in a mobile communication terminal of a CDMA mobile communication system. It is about improvement.

  In a communication system such as W-CDMA (Wideband Code Division Multiple Access) system, a spread spectrum system is used. On the receiving side of a mobile communication terminal adopting this spread spectrum communication method, it is necessary to synchronize for data demodulation. That is, on the receiving side, it is necessary to match the PN (Pseudo Noise) code for despreading with the PN code of the received signal, and this synchronization acquisition process is a method called serial search.

  In this serial search, since the clock source on the receiving side of the mobile communication terminal is different from the clock source on the communication network side, an operation for searching (searching for) a point where the synchronization can be obtained is performed. The point at which the peak of the correlation value, which is the result of demodulating the pilot channel, is maximized is searched while being shifted one by one.

Referring to Patent Document 1, the peak determination circuit first performs correlation detection while taking a large search step width, and when a peak is detected, the search step width is set after reversing 1 to 2 chips from this peak point. A technique is disclosed in which, after switching to small, the peak determination is performed again to detect the peak position of the correlation.
JP-A-11-145934

  In the serial search on the receiving side of the terminal, it is inevitable that some error occurs with respect to the true peak position depending on the sampling accuracy for the correlation peak determination. In this case, if the sampling accuracy (search step width) is set finely, the error is reduced and the characteristics are improved. However, if sampling is performed finely, it is necessary to increase the operating frequency of the LSI. An increase will be invited. Therefore, in the mobile communication terminal, the operable time and the characteristic improvement are in a so-called trade-off relationship, and therefore it is not realistic to set the sampling accuracy finely.

  In the serial search used in the current W-CDMA system, sufficient characteristics to satisfy the specifications of 3GPP (Third Generation Partnership Project) are secured. On the other hand, there is a HSDPA (High Speed Downlink Packet Access) type mobile communication system that is currently being standardized as a technique for realizing high-speed downlink. In this method, the data rate is adaptively switched according to the communication quality of the downlink. When the communication quality is high, high-speed data communication is performed using a modulation method based on 16QAM (Quadrature Amplitude Modulation). .

  In such high-speed data communication, even if data is demodulated at the peak position found as a result of the current serial search, there is a high possibility of characteristic degradation due to an error with respect to the true peak position. Become. This is because, in high-speed data communication such as 16QAM, the redundancy is set lower than in the current W-CDMA communication, so that an error such as CRC NG (Cyclic Redundancy Check No Good) is likely to occur. It is.

  In the technique of Patent Document 1, at the time of peak determination, the search step width is initially increased, and after peak detection, the peak determination is performed again by going backward from the peak point and decreasing the step width. Therefore, it is necessary to perform the peak determination twice, the search time becomes long, and in the subsequent peak determination, the step width (sampling interval) is made small, so that the operating frequency becomes large and the above-described problem of current consumption. Remains.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a correlation peak detection circuit, a method thereof, and a synchronous acquisition circuit using the same, in which an error from the true peak position caused by the sampling accuracy of serial search is reduced without increasing current consumption. It is to provide such a method as well as a receiver.

  Another object of the present invention is to provide a correlation peak detection circuit capable of improving demodulation characteristics in a setting with low redundancy such as high-speed data communication in an HSDPA communication system, a method thereof, and a synchronization acquisition circuit using the same A method and receiver are provided.

  The correlation peak detection circuit according to the present invention is a correlation peak detection circuit for detecting a correlation peak position by sampling a correlation waveform of a spread-coded signal in a receiver of a CDMA communication system. And a means for estimating a true maximum peak position based on sampling results at a detected maximum peak position and a plurality of sampling positions before and after the detected maximum peak position.

  The correlation peak detection method according to the present invention is a correlation peak detection method for detecting a correlation peak position by sampling a correlation waveform of a spread-coded signal in a receiver of a CDMA communication system. The method includes a step of estimating a true maximum peak position based on sampling results at a detected maximum peak position and a plurality of sampling positions before and after the detected maximum peak position.

  A synchronization acquisition circuit according to the present invention is a synchronization acquisition circuit that detects a correlation of spread-coded signals and obtains synchronization for data demodulation in a CDMA communication system receiver, and has a correlation waveform indicating the correlation. Maximum peak estimation means for estimating a true maximum peak position based on sampling results at a maximum peak position detected by sampling and a plurality of sampling positions before and after the detected maximum peak position, and the estimated true peak Phase difference control means for detecting a difference between a maximum peak position and the detected maximum peak position and performing phase control of a despread code for demodulating the spread coded signal according to the difference. And

  A synchronization acquisition method according to the present invention is a synchronization acquisition method for detecting a correlation of a spread-coded signal and acquiring synchronization for data demodulation in a receiver of a CDMA communication system, wherein a correlation waveform indicating the correlation is obtained. A maximum peak position estimating step for estimating a true maximum peak position based on sampling results at a maximum peak position detected by sampling and a plurality of sampling positions before and after the detected maximum peak position; and Detecting a difference between the maximum peak position of the signal and the detected maximum peak position, and performing phase control of a despread code for demodulating the spread coded signal according to the difference. Features.

  The receiver according to the present invention uses the above-described synchronization acquisition circuit.

  A program according to the present invention is a program for causing a computer to execute a correlation peak detection method for detecting a correlation peak position by sampling a correlation waveform of a spread-coded signal in a CDMA communication system receiver, The method includes a process of estimating a true maximum peak position based on sampling results at a maximum peak position detected by sampling a correlation waveform and a plurality of sampling positions before and after the detected maximum peak position.

  Another program according to the present invention is a program for causing a computer to execute a synchronization acquisition method for detecting a correlation of spread-coded signals and obtaining synchronization for data demodulation in a CDMA communication system receiver. A process for estimating a true maximum peak position based on sampling results at a maximum peak position detected by sampling the correlation waveform indicating the correlation and a plurality of sampling positions before and after the detected maximum peak position; A process for detecting a difference between the true maximum peak position and the detected maximum peak position, and a process for performing phase control of a despread code for demodulating the spread coded signal according to the difference It is characterized by including.

  The operation of the present invention will be described. In the difference determination circuit, the true maximum peak position is estimated based on the sampling results of the maximum peak position detected by sampling the correlation waveform indicating the correlation and a plurality of sampling positions before and after the detected maximum peak position. The difference between the estimated maximum peak position and the detected maximum peak position is detected. In accordance with this difference, the VCO is controlled, the phase shift control of the PN code generator is performed, and the phase control of the despread code for demodulating the spread coded signal is performed. As a result, a position closer to the true maximum peak position can be detected without increasing the operating frequency for sampling, and a search can be performed without increasing power consumption.

  According to the present invention, the true peak position where the maximum correlation can be obtained is estimated, and the phase shift control of the PN code is performed according to the difference between the estimated position and the detected peak position. As a result, the communication performance can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic functional block diagram of an embodiment of the present invention. Referring to FIG. 1, the functional block is equivalent to a general well-known DLL (delayed locked loop) model, and has a feedback loop configuration with a difference amount determination circuit 1, a VCO 2, and a PN code generator 3. is there.

  The received input signal 201 is input to the difference determination circuit 1, despread by the despread code 203 from the PN code generator 3 and demodulated, and correlation detection of this demodulated output is performed (in FIG. 4, It is shown as a correlation peak waveform 101). Then, the true peak point (shown as 107 in FIG. 4) of the detected correlation waveform is estimated, and this estimated peak position and the currently detected peak position (shown as 104 in FIG. 4). And is output as control data 202 of VCO2.

  FIG. 2 is a more detailed functional block diagram of the difference amount determination circuit 1 shown in FIG. 1. The despreading unit 11 performs despreading by multiplying the input signal 201 and the despreading code 203, and the despread output of the despread output. A correlation detection unit 12 for detecting a correlation peak waveform (see 101 in FIG. 4), a peak position estimation unit 13 for estimating the true peak position of the correlation peak waveform, and a difference between the estimated peak position and the detected peak position The difference determination unit 14 that determines and outputs the difference amount data 202 is included.

  Based on the difference data 202, the VCO 2 generates a signal for shifting the phase of the despread code 203 and inputs it to the PN code generator 3. The next signal is demodulated using the despread code 203 generated by the PN code generator 3, and a kind of DLL is formed by the above configuration.

  A feature of the present invention resides in an algorithm that executes estimation of the peak position in the peak position estimation unit 13 in the difference amount determination circuit 1 and determination of the difference amount in the difference determination unit 14.

  The operation of the embodiment of the present invention will be described using the flowchart of FIG. 3 and an example of the correlation peak 101 shown in FIG. Assume that the correlation peak waveform 101 of the demodulated output of the pilot channel is detected by the correlation detection unit 12 in FIG. The correlation peak waveform 101 is sampled as shown by points 102 to 106 in FIG. 4 at the same sampling interval as in the prior art, and the point where the correlation value is maximum is determined (step S1). The sampling point at this time is 104.

  Then, the correlation values of the sampling points immediately before and after the sampling point 104 at which the correlation value is maximum are compared (step S2). Sampling points at this time are 103 and 105. As a result of this comparison, if the correlation value of the subsequent sampling point 105 is larger than that of the previous sampling point 103 (Yes in step S3), the straight line passing through the sampling point 103 and the sampling point 104, the sampling point 105 and the subsequent sampling An intersection point with a straight line passing through the point 106 is calculated (step S4).

  If “No” in step S3, that is, if the correlation value of the previous sampling point 103 is larger than that of the subsequent sampling point 105, a straight line passing through the sampling point 103 and the immediately preceding sampling point 102, and the sampling point The intersection of 104 and the straight line passing through the sampling point 105 is calculated (step S5). Then, the calculated intersection is estimated as the true peak position, and the phase difference amount between the estimated peak position and the detected peak position 104 is calculated (step S6).

  Note that the processes in steps S3 to S5 are other than the process of detecting the slopes before and after the peak position of the correlation peak waveform 101 shown in FIG. 4 and estimating the intersection of straight lines indicating both slopes as the true peak position. Don't be.

  The difference amount obtained in this way is the difference amount data 202 shown in FIGS. 1 and 2, which becomes the control data of the VCO 2 (step S7). Accordingly, the VCO 2 generates a clock signal for shifting the phase of the despread code 203 of the PN code generator 3 according to the difference amount, and as a result, the sampling point approaches the true peak position 107. Become.

  It is apparent that the operation of the difference amount determination circuit shown in FIG. 3 can be configured such that the operation procedure is stored in advance in a recording medium such as a ROM as a program and is read and executed by a computer. Further, the present invention is suitable for use in a mobile communication terminal receiver in an HSDPA mobile communication system, but is not particularly limited to this, and can be widely applied to general CDMA communication terminal receivers. Is.

It is a functional block diagram which shows embodiment of this invention. FIG. 2 is a functional block diagram illustrating an example of a difference amount determination circuit in FIG. 1. It is a flowchart which shows operation | movement of embodiment of this invention. It is a figure which shows the relationship between a correlation peak waveform and a sampling point.

Explanation of symbols

1 Difference determination circuit 2 VCO
3 PN code generator 11 Despreading unit 12 Correlation detection unit 13 Peak position estimation unit 14 Difference determination unit

Claims (11)

A correlation peak detection circuit for detecting a correlation peak position by sampling a correlation waveform of a spread coded signal in a receiver of a CDMA communication system,
And a means for estimating a true maximum peak position based on sampling results at a maximum peak position detected by sampling the correlation waveform and a plurality of sampling positions before and after the detected maximum peak position. Correlation peak detection circuit.   The means detects an inclination of the correlation waveform before and after the maximum detected peak position based on sampling results at a plurality of sampling positions before and after the maximum detected peak position, and determines an intersection of straight lines indicating the inclination, 2. The correlation peak detection circuit according to claim 1, wherein the true maximum peak position is set. A correlation peak detection method for detecting a correlation peak position by sampling a correlation waveform of a spread coded signal in a receiver of a CDMA communication system,
Including a step of estimating a true maximum peak position based on sampling results at a maximum peak position detected by sampling the correlation waveform and a plurality of sampling positions before and after the detected maximum peak position. Correlation peak detection method.   The step includes detecting a slope of the correlation waveform before and after the maximum detected peak position based on sampling results at a plurality of sampling positions before and after the maximum detected peak position, and an intersection of straight lines indicating the slope. The correlation peak detection method according to claim 3, further comprising a step of determining the true maximum peak position. In a CDMA communication system receiver, a synchronization acquisition circuit that detects the correlation of spread-coded signals and synchronizes for data demodulation,
Maximum peak estimation means for estimating a true maximum peak position based on sampling results at a maximum peak position detected by sampling the correlation waveform indicating the correlation and a plurality of sampling positions before and after the detected maximum peak position; ,
Phase control for detecting a difference between the estimated true maximum peak position and the detected maximum peak position and performing phase control of a despread code for demodulating the spread coded signal according to the difference Means,
A synchronization acquisition circuit comprising:   The maximum peak estimating means detects a slope of the correlation waveform before and after the detected maximum peak position based on sampling results at a plurality of sampling positions before and after the detected maximum peak position, and calculates a straight line indicating the slope. 6. The synchronization acquisition circuit according to claim 5, wherein an intersection is the true maximum peak position. In a CDMA communication system receiver, a synchronization acquisition method for detecting a correlation of a spread coded signal and obtaining synchronization for data demodulation,
Maximum peak position estimation step for estimating a true maximum peak position based on sampling results at a maximum peak position detected by sampling a correlation waveform indicating the correlation and a plurality of sampling positions before and after the detected maximum peak position When,
Detecting a difference between the estimated true maximum peak position and the detected maximum peak position;
According to the difference, performing phase control of a despreading code for demodulating the spread coded signal;
Including a synchronization acquisition method.   The step includes detecting a slope of the correlation waveform before and after the maximum detected peak position based on sampling results at a plurality of sampling positions before and after the maximum detected peak position, and an intersection of straight lines indicating the slope. The synchronization acquisition method according to claim 7, further comprising the step of determining the true maximum peak position.   A receiver comprising the synchronization acquisition circuit according to claim 5. A program for causing a computer to execute a correlation peak detection method for detecting a correlation peak position by sampling a correlation waveform of a spread coded signal in a CDMA communication system receiver,
Including a process of estimating a true maximum peak position based on sampling results at a maximum peak position detected by sampling the correlation waveform and a plurality of sampling positions before and after the detected maximum peak position. program. In a CDMA communication system receiver, a program for causing a computer to execute a synchronization acquisition method for detecting a correlation of spread-coded signals and obtaining synchronization for data demodulation,
A process for estimating a true maximum peak position based on sampling results at a maximum peak position detected by sampling the correlation waveform indicating the correlation and a plurality of sampling positions before and after the detected maximum peak position;
A process of detecting a difference between the estimated true maximum peak position and the detected maximum peak position;
In accordance with this difference, a process for performing phase control of a despread code for demodulating the spread coded signal;
The program characterized by including.

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