JPH10112672A - Receiver for spread spectrum communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a required time till synchronization acquisition by conducting synchronization acquisition and synchronization tracing based on a peak of a correlation characteristic after a spread code included in a reception signal and a reference spread code are averaged. SOLUTION: A reference spread code S8 is multiplied with a spread spectrum signal S1 obtained from a reception signal S0 at a multiplier 7 and a modulation signal S9 obtained thereby is demodulated by a demodulator 8. A timewise mean correlation value is stored in a memory of an averaging arithmetic section 4, the mean correlation value is sequentially given to a discrimination section 5 to detect a synchronization peak and to conduct the synchronization acquisition and synchronization tracing. The discrimination section 5 conducts delay to compensate a require time till the end of synchronization peak retrieval and gives a synchronization timing pulse S6 to a spread code generating circuit 6, in which production of a reference spread code is started. Furthermore, when a synchronization peak is retrieved, the discrimination section 5 stops averaging arithmetic operation to the arithmetic section 4 to reset the stored content of the storage section 3 and the arithmetic section 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct sequence / spread spectrum (DS / SS) system.
The present invention relates to a spread spectrum communication receiver for despreading a trummed signal and demodulating the despread signal into an original signal. In particular, it relates to synchronization acquisition and synchronization tracking, a diversity reception system, and a mobile reception system.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open Publication No. Hei 8-97748 discloses a correspondence relationship between a reproduced spread code reproduced from a spread spectrum signal (received signal) and a reference spread code stored in advance.
The correlation value of both spreading codes is calculated by shifting one chip at a time, a peak in the correlation value group is obtained and adopted as a synchronization peak, and the reference spreading code is converted to the spread spectrum signal at a timing based on the synchronization peak. A receiver for spread spectrum communication that performs synchronization acquisition by multiplying and despreading is disclosed.

Japanese Unexamined Patent Publication No. 6-177805 discloses a diversity receiver for selecting and demodulating a signal having a good reception condition from spread spectrum signals received by a plurality of reception systems. A receiver that switches a receiving system according to the signal power level after despreading is disclosed. This switching method is based on the fact that the signal power level before despreading increases when the noise level alone increases, and that the signal power level after despreading does not increase. Are increased together.

A diversity receiver for selecting and demodulating a signal having a good reception condition from spread spectrum signals received by a plurality of reception systems, wherein a peak in a correlation value group has a maximum value instead of a received signal intensity. Diversity receivers for selecting a receiving system to be used are known. This is described as a known technique in, for example, the above-mentioned Japanese Patent Application Laid-Open No. 6-177805.

A mobile type spread spectrum communication receiver for receiving and demodulating a plurality of spread spectrum signals which are spread spectrum by a direct spreading method using a plurality of different spreading codes, respectively. A mobile-type spread-spectrum communication receiver that determines that its own current position is present in a cell of a transmitting station of a spread-spectrum signal having a maximum peak in a correlation value group is known.

[0006]

A spread spectrum signal received by a spread spectrum communication receiver includes an error due to noise or interference from another station. JP-A-8-97
In the method of calculating the correlation value between the spread code included in the received signal and the reference spread code and obtaining the peak in the calculated value, as in the technique described in Japanese Patent No. 748, the degree of the error increases. In this case, a peak (pseudo peak) caused by the error may be erroneously recognized as a synchronization peak position, and synchronization acquisition may be erroneously performed. The present invention is capable of accurately performing synchronization acquisition even when errors due to noise, interference, and the like included in a received spread spectrum signal increase, and performing synchronization acquisition at high speed when the errors are small. It is an object of the present invention to provide a receiver for spread spectrum communication capable of performing the following. Another object of the present invention is to provide a receiver for spread spectrum communication that can accurately perform synchronous tracking.

When a signal wave is reflected by an obstacle such as a building and a multipath is generated, a fading phenomenon in which the intensity of a received signal fluctuates remarkably occurs. Fading is particularly pronounced in mobile communications. As a countermeasure against fading, a known technique described in JP-A-6-177805, that is, a diversity receiving system that selects a receiving system that maximizes the peak of the correlation value between the spread code of the received signal and the reference spread code is adopted. In the case where the degree of noise or interference from other stations is large and the signal strength fluctuates greatly in terms of location or time, the switching operation of the receiving system frequently occurs, and as a result, the degree of noise generated at the time of the switching is reduced. The problem that it becomes large arises. The present invention provides a diversity spread spectrum communication receiver that can reduce the switching operation of the reception system when the signal strength fluctuates greatly in place or time, and can select the best reception system. Aim.

A mobile communication system for spread spectrum communication which determines that its current position is within a cell of a base station of a spread spectrum signal having a maximum correlation value peak between a spread code included in a received signal and a reference spread code. When the current position of the receiver is near the midpoint between the two base stations, the magnitude of the peak of the correlation value of the signal from the two base stations frequently fluctuates depending on the situation. The location information is frequently updated, and it is difficult to determine which base station is in the cell. An object of the present invention is to provide a mobile type spread spectrum communication receiver that can easily determine which base station is in a cell even when the current position is near the boundary of a plurality of base stations. And

[0009]

According to the present invention, there is provided a spread spectrum communication receiver for demodulating a spread spectrum signal which is spread spectrum by a direct spread method, wherein a spread code included in the spread spectrum signal is stored in advance. Calculating means for calculating a correlation value characteristic having the same cycle as the cycle of both spreading codes by calculating the correlation value of both spreading codes in each case where the correspondence relationship with the reference spreading code is shifted one chip at a time. And calculating the average value of the correlation value and its past value for each time position within the cycle of the correlation value characteristic, and updating the corresponding correlation value of the correlation value characteristic with the calculation result. Averaging means for averaging the correlation value characteristic, and comparing the time distance between each peak appearing in the correlation value characteristic with the period of the correlation value characteristic to search for a synchronous peak where both coincide. Control means for providing the reference spreading code synchronized with the spread spectrum signal based on the synchronization peak as a signal source for despreading and stopping the function of the averaging means. And a receiver for spread spectrum communication having:

[0010] The correlation value characteristic between the spread code included in the received spread spectrum signal and the reference spread code is obtained by the arithmetic means. When the noise included in the received signal and the interference from other stations are large, the correlation value characteristic has several peaks (pseudo peaks that are not true synchronization peaks) due to the noise and the interference, as shown in FIG. . Such spurious peaks
The correlation value characteristic is reduced by averaging over a certain period (averaging the correlation value at each time position in the period with each past value). The degree of reduction increases as the number of cycles for performing the averaging operation increases, but as the number of cycles increases,
There is a problem that the time required until the completion of synchronization acquisition becomes longer. Therefore, in the present invention, the averaging operation is performed until a true synchronization peak whose distance between peaks matches the period of the correlation function is searched. FIG. 1c shows a state in which the synchronization peak has been searched. If the pseudo peak due to noise or interference is small and a synchronous peak is searched for in the first cycle, the averaging operation is not performed.

The present invention relates to a diversity spread spectrum communication receiver for receiving a spread spectrum signal, which has been spread spectrum by a direct spread method, in a plurality of receiving systems and demodulating the spread spectrum signal having a good reception condition. , The correspondence between the spread code included in the spread spectrum signal and the previously stored reference spread code is set to 1
The operation of calculating the correlation value of both spread codes in each case shifted by each chip is performed for each of the plurality of reception systems, so that the correlation value characteristic having the same cycle as the cycle of both spread codes is obtained. Calculating means for calculating each of the reception systems, and performing an operation of calculating an average value of the correlation value and its past value for each time position in the cycle of the correlation value characteristic, for each of the plurality of reception systems. Averaging means for respectively averaging the correlation value characteristics of the plurality of reception systems by updating the corresponding correlation values of the correlation value characteristics with the result, and the time distance between each peak appearing in the correlation value characteristics. Searching means for executing, for each of the plurality of reception systems, an operation of searching for a synchronization peak in which the two coincide with each other by comparing with the cycle of the correlation value characteristic; When a search is performed for the reception system, a reception system having the maximum synchronization peak value (or a reception system in which the synchronization peak is searched first) is selected, the spread spectrum signal received by the reception system is subjected to demodulation, and the averaging is performed. And a control means for stopping the function of the converting means.

[0012] Correlation value characteristics between the spreading code and the reference spreading code included in the received spread spectrum signal are obtained for each receiving system. When the noise included in the received signal or the interference of another station greatly fluctuates, the peak value of the correlation value characteristic of each receiving system also fluctuates greatly due to the influence of the noise or interference, and becomes inaccurate. When diversity is performed based on an incorrect and fluctuating peak value, the switching operation of the receiving system is frequently performed, and noise accompanying the switching operation increases. The peak value of the correlation value characteristic can be made closer to an accurate value by averaging the correlation value characteristic over a certain period. As the number of cycles of the averaging operation increases, the peak value approaches an accurate value. However, when the number of cycles increases, the time required until an optimal receiving system is selected becomes longer. Therefore, in the present invention, the averaging operation is performed until a true synchronization peak whose distance between peaks matches the period of the correlation function is searched.
If the pseudo peak due to noise or interference is small and the peak value is relatively accurate, a synchronization peak is searched for in the first cycle, and in this case, the averaging operation is not performed.

The present invention relates to a mobile type spread spectrum communication receiver for receiving and demodulating a plurality of spread spectrum signals which are spread spectrum by a direct spreading method using a plurality of different spreading codes. In each case, the correspondence between the plurality of spread codes included in the plurality of spread spectrum signals and the plurality of reference spread codes stored in advance corresponding to the plurality of spread codes is shifted one chip at a time. Calculating means for respectively calculating, for each of the plurality of spread spectrum signals, a correlation value characteristic having the same cycle as the cycle of both spread codes by performing operations for calculating the correlation values of the codes for each of the plurality of spread spectrum signals, The operation of calculating the average value of the correlation value and its past value for each time position within the cycle of the correlation value characteristic is performed by the plurality of operations. An averaging means for respectively averaging the correlation characteristic of the spread-spectrum signal of the plurality of by the spread spectrum signal with each run to update each of the corresponding correlation value of the correlation characteristic in the operation result,
Search means for executing, for the correlation value characteristics of the plurality of spread spectrum signals, an operation of comparing the time distance between each peak appearing in the correlation value characteristics with the period of the correlation value characteristics and searching for a synchronization peak where both coincide with each other. And the cell of the base station of the spread spectrum signal whose synchronization peak value is maximized when the synchronization peak is searched for at least one spread spectrum signal (or the cell of the base station of the spread spectrum signal whose synchronization peak is searched first) ) Is determined to be the current position and a control means for stopping the function of the averaging means is provided.

The correlation value characteristic of the spread code included in the received spread spectrum signal and the reference spread code is obtained for each spread spectrum signal. In the area near the boundary between the two base stations, the peak values of the correlation value characteristics of the spread spectrum signals from the two base stations are substantially equal, and the base station giving the maximum peak value is frequently switched. For this reason, if the data of the current belonging cell is obtained based on the peak value of the correlation value characteristic, the data indicating the current belonging cell is frequently switched, and it is difficult to determine the current position. The peak value of the correlation value characteristic can be made closer to an accurate value by averaging the correlation value characteristic over a certain period. As the number of cycles of the averaging operation increases, the peak value approaches an accurate value. However, when the number of cycles increases, a problem arises that the time required for acquiring the current position data becomes longer. Therefore, in the present invention, the averaging operation is performed until a true synchronization peak whose distance between peaks matches the period of the correlation function is searched. If the radio wave from a single transmitting station has sufficient strength and the interference of other stations is slight, a synchronization peak is searched for in the first cycle. In this case, the averaging operation is not performed. I can't.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments will be described with reference to the drawings.

(1) First Embodiment (Synchronization Supplement / Tracking) FIGS. 2 to 6 show a receiver for spread spectrum communication according to a first embodiment. 2 is a block diagram showing the overall circuit configuration, FIG. 3 is a block diagram showing details of the correlator unit 2 in FIG. 2, and FIG. 4 is a data storage method and averaging operation in the correlation value storage unit 3 in FIG. FIG. 5 is an explanatory diagram showing a data averaging method in the unit 4, FIG. 5 is a diagram showing an outline of a function of the determining unit 5 in FIG. 2 and a procedure for realizing the function, and FIG. FIG.

The receiver for spread spectrum communication shown in FIG.
The spread-spectrum signal S1 obtained from the received signal S0 by passing through the band-pass filter 1 is despread by multiplying the spread-spectrum signal S1 by the reference spreading code S8 in the multiplier 7, and the modulated signal S9 obtained by the despreading is demodulated. This is a device for demodulating the original information signal in the device 8. The reference spread code S8 is a reproduced spread code S reproduced from the spread spectrum signal S1 in the correlator unit 2.
The signal is supplied from the spreading code generator 6 to the multiplier 7 so as to synchronize with the phase of 1 '.

The correlator unit 2 outputs a correlation value S3 between the spread spectrum signal S1 and a reference spread code S2 stored in advance, and has a delay detector 21 and a digital correlator 25 in the present embodiment. An example will be described. Delay detector
At 21, the process of reproducing the spread code multiplied by the spread spectrum signal S1 and outputting the reproduced spread code S1 'is performed. That is, as shown in FIG. 3, the received spread spectrum signal S1 is converted into a digital signal by an AD converter 211, and then delayed by a predetermined chip length by a shift register 212. The delayed digital signal is multiplied by the undelayed digital signal in a multiplier 213, and then input to a low-pass filter 214 to output only a low-frequency component. Thus, the reproduction spread code S1 'is obtained.

In the digital correlator 25, the reproduction spread code S
For 1 ′ and the reference spreading code S2 stored in the apparatus in advance, the correlation value between the two spreading codes S1 ′ and S2 in each case where the correspondence between them is shifted by one chip is calculated. . This set of correlation values gives the correlation value characteristics. The reference spread code S2 is the same code as the spread code multiplied by the spread spectrum signal S1 on the transmitter side (not shown). For example, the reference spread code S2 is in an ideal state, such as an M sequence or a Gold code sequence. A code sequence whose auto-correlation function approaches the characteristic shown in FIG.

The reproduction spreading code S1 'has a spreading speed (1 / T
The data is input to the shift register 252 one chip at a time in synchronization with the clock SK having the same frequency as that of c). Here, Tc is a chip cycle. On the other hand, the shift register 254 is loaded with the reference spread code S2 in advance. This shift register
After the exclusive OR of each chip of the shift register 252 and the exclusive OR of the shift register 252 is calculated by the Ex-OR circuit 253, these are added by the adder 255, and further, the absolute value circuit 256
The absolute value is calculated at the correlation value storage unit 3 as the correlation value S3.
Output to For example, when the M-sequence of the a-stage is used, the maximum value of the correlation value S3 is “2 ^a −1”. In addition,
The operation in the Ex-OR circuit 253 and the subsequent operation until the correlation value S3 is output are performed one chip at a time in synchronization with the clock SK. Therefore, the correlation value S3 is also output in time series, and has the same cycle as the two spreading codes S1 ′ and S2. Note that the correlator unit 2 is not limited to the above configuration, and may use the following known technology. That is, a method using a sliding correlator that calculates the correlation value between the spread code in the received signal and the reference spread code by sequentially shifting the phases of the spread spectrum received signal and the previously stored reference spread code, or A method of obtaining a correlation value by inputting a received signal and a reference spreading code to a convolver using a SAW (Surface Acoustic Wave) device and outputting a signal corresponding to the degree of phase matching between the two. And so on.

The correlation value S3 input to the correlation value storage unit 3 is
As shown in FIG. 4, the correlation value characteristic is sequentially stored at a time position (chip position) within a cycle and an address determined according to the cycle. For example, the correlation value output from the absolute value circuit 256 in synchronization with the first clock SK in the first cycle is
It is stored in the address 11 at the time position 1 of the cycle. When the storage of the first cycle is completed, the storage of the correlation value of the second cycle is started on the condition that no synchronization peak is searched for in the first cycle. Note that when a synchronous peak (a peak whose peak-to-peak distance matches the period of the correlation function) is searched for in the first cycle, the averaging operation is not required, so that storage after the second cycle is not performed.

Specifically, the processing is performed as follows. First, the correlation value output from the absolute value circuit 256 in synchronization with the first clock SK in the first cycle is stored in the first value stored in the correlation value storage unit 3.
The address M (1) for the time position 1 of the averaging operation unit 4 is stored in the address 11 for the time position 1 of the cycle.
Is also stored. Hereinafter, similarly, the correlation value of the first cycle is
It is stored in the correlation value storage unit 3 at an address below time position 2 and in the averaging operation unit 4 at an address below time position 2.

If the synchronization peak is not found in the first cycle, the storage of the correlation value in the second cycle and the averaging operation are started. That is, the correlation value output from the absolute value circuit 256 in synchronization with the first clock SK in the second cycle is stored in the address 21 for the time position 1 in the second cycle of the correlation value storage unit 3, and An average value of the correlation value and the correlation value of the address 11 is calculated, and the content of the address M (1) for the time position 1 of the averaging calculation unit 4 is updated based on the calculation result. That is, the address M (1) for the time position 1 of the averaging operation unit 4 stores the correlation value of the time position 1 of the second cycle which is the current cycle and the correlation value of the time position 1 of the first cycle which is the past value. The average value with the correlation value is stored. Hereinafter, similarly, the correlation value at the time position 2 or less in the second cycle is stored in the address for the corresponding time position in the correlation value storage unit 3, and the correlation between the corresponding time position in the second cycle and the first cycle is stored. The average of the values is stored in the corresponding time position address of the averaging operation unit 4.

If no synchronization peak is found in the second cycle, the same processing as described above is performed for the third cycle. That is, the correlation value output from the absolute value circuit 256 in synchronization with the first clock SK in the third cycle is stored in the correlation value storage unit.
3 is stored in the address 31 for the time position 1 in the third period, and an arithmetic average of the correlation value and the correlation values of the addresses 11 and 21 is calculated. The contents of the address M (1) for the time position 1 of the conversion operation unit 4 are updated. Note that here, the first
The arithmetic mean of the period to the third period is calculated. Instead of this, the correlation value of the third period and the past average stored at the corresponding time position address of the averaging calculation unit 4 are calculated. The arithmetic mean with the correlation value may be calculated, and the content of the address for the corresponding time position of the averaging calculation unit 4 may be updated based on the calculation result. In that case, there is an effect that pseudo peaks in the past cycle can be reduced more quickly.

Thus, the memory of the averaging operation unit 4 has
An average correlation value (correlation value in the case of the first period) of each time position is stored, and these average correlation values M (1), M
(2),..., M (n), that is, the correlation value S5 is sequentially determined by the determination unit.
5 and is used for synchronous peak detection and synchronous acquisition and synchronous tracking based on the detection.

In the determination section 5, as shown in FIG. 5, the procedure of synchronization acquisition and the procedure of synchronization tracking after completion of synchronization acquisition are performed by the arithmetic section. Further, the calculated synchronization peak PS and the number k of cycles of the averaging calculation until the detection of the synchronization peak PS are sent to the delay circuit 55. The delay circuit 55 sends the synchronization timing pulse S6 to the spreading code generator 6 (FIG. 2) after a delay for compensating the time required until the search for the synchronization peak PS is completed, and starts the generation of the reference spreading code as described above. Let it. When the synchronization peak PS is searched, the calculation unit of the determination unit 5 stops the averaging calculation to the averaging calculation unit 4 to stop the correlation value storage unit 3.
And an instruction to reset the storage contents of the averaging unit 4 is sent. Note that, when an out-of-synchronization occurs, the procedure of synchronization acquisition is performed again.

The above-described synchronization acquisition procedure is executed, for example, as shown in FIG. First, a variable i indicating a time position in a cycle, a variable j indicating a number when the average correlation value is a peak exceeding a predetermined threshold, and a variable k indicating the number of the cycle after the start of the averaging operation , An initial value is set (S101).

Next, the average correlation value M (i) at the time position i
Is compared with a predetermined threshold value SH. As a result, if the average correlation value M (i) exceeds the threshold value SH, it is a peak (true peak or pseudo peak), j is incremented, and a variable P (j) indicating the time position of the peak is set.
Is set to the time position i (S103, S105). If the average correlation value M (i) does not exceed the threshold value SH, the process returns to the step S103 after incrementing i, provided that it is not the time position next to the last time position n of the cycle (S103).
103, S117, S119). If the end of the cycle is exceeded, i is reset, the variable k indicating the number of cycles is incremented, and the process returns to step S103 (S119,
S121).

Thereafter, when the number of peaks (true peaks or pseudo peaks) detected as described above becomes two or more (S10
7; YES), all the time distances between the peaks detected up to that point are calculated and set to a variable τ (h) (S109),
It is determined whether or not the τ (h) matches the period τ of the correlation function (S111). As a result, if present, the peak time position P (j) giving the matching τ (h) is set to the synchronous peak time position PS.
(S113).

Also, as described above, the time position of the synchronization peak
The PS is sent to the delay circuit 55, and based on this, the timing pulse S6 is generated in the delay circuit 55. Further, thereby, the spreading code S8 is sent to the multiplier 7, and despreading is performed. Further, a signal S7 indicating that the averaging operation should be stopped is sent to the averaging operation unit 4.

When the synchronization acquisition procedure is completed,
Returning to the flowchart of FIG. 5B, next, a synchronization tracking procedure is performed. The procedure for synchronization tracking can be configured in substantially the same manner as the procedure for synchronization acquisition described above. In the synchronization tracking procedure, the number of averaging operations may be fixed to, for example, the number in the latest synchronization acquisition procedure.

(2) Second Embodiment (Diversity Receiver) FIG. 7 is a block diagram showing a circuit configuration of a diversity receiver for spread spectrum communication according to a second embodiment. The illustrated receiver receives spread spectrum signals, which have been spread spectrum by the direct spread method, in receiving systems A and B, and demodulates the spread spectrum signal having a good reception condition.

Each of the receiving systems A and B has a correlator unit 2, a correlation value storage unit 3, an averaging operation unit 4 and a judgment unit 5 of the receiver according to the first embodiment. When a synchronization peak is searched for by both reception systems A and B based on the average correlation value, the determination unit 91 compares the synchronization peak values of both systems, and as a result, the reception system with the larger synchronization peak value is determined. A control signal is transmitted from the determination unit 91 to the switch unit SW so as to be selected.

Thus, the switch unit SW sends the spread spectrum signal of the selected receiving system to the signal processing unit 92, and performs the despreading process and the demodulation process of demodulating the modulated signal generated by the despreading process. . The switch SW
It is also possible to carry out despreading up to the preceding stage, and to send the resulting modulated signal to the signal processing unit 92. In that case, the signal processing unit is constituted by a demodulator.

As described above, in the second embodiment, since the peak value of the correlation value characteristic is obtained by averaging the correlation value characteristic over a certain period, noise and other noises included in the received signal are obtained. A relatively accurate peak value can be obtained even when the station interference fluctuates greatly. As a result, it is possible to prevent a problem that the receiving system is frequently switched and noise caused by the switching is increased. Further, since the number of averaging operations is limited until a true synchronous peak whose distance between peaks matches the period of the correlation function is searched for, as in the receiver of the first embodiment, The above effects can be achieved with a minimum required time.

(3) Third Embodiment (Mobile System Receiver) FIG. 8 is a block diagram showing a circuit configuration of a mobile system spread spectrum communication receiver according to a third embodiment. is there. The illustrated receiver receives a spread spectrum signal which is spread spectrum by a direct spreading method and transmitted from each of a plurality of base stations, and determines a synchronization peak of a correlation value of each spread spectrum signal in the first and second embodiments. Is determined by the same method as in the above embodiment, and it is determined that the mobile station itself is within the area of the base station of the spread spectrum signal in which the synchronization peak is maximum.

The correlator section 95 of FIG. 8 includes the correlator section 2, the correlation value storage section 3, the averaging operation section 4 and the judgment section 5 of the receiver according to the first embodiment. They are provided corresponding to the spread spectrum signals from AC. Instead of this configuration, two sets of the correlator unit 2, the correlation value storage unit 3, the averaging operation unit 4 and the judgment unit 5 of the receiver according to the first embodiment are provided. Alternatively, the reference spread code S2 corresponding to each spread spectrum signal may be selected and supplied.

When the wireless terminal m is in the cell (area) of the base station A as shown in the figure, the radio wave transmitted from the base station A is strong, so that the correlation value does not need to be averaged but is calculated. As for the peak value, the spread spectrum signal from the base station A has the maximum value. Thereby, the wireless terminal m determines that the wireless terminal m is within the area of the base station A.

When the radio terminal m moves and reaches near the boundary between the base station A and the base station B, the intensity of the radio waves transmitted from both base stations becomes substantially balanced. The peak value of the correlation value characteristic of the spread spectrum signal becomes substantially equal, the transmitting station giving the maximum peak value is frequently switched, and it becomes difficult to determine the current position. For this reason, in the receiver of the third embodiment, a relatively accurate maximum peak value is obtained by averaging the correlation value characteristics over a certain period, thereby making it possible to determine the current position. It's easier. Also, in the receiver of the third embodiment, the number of averaging operations is set to be the same as that of the receivers of the first and second embodiments, so that the distance between peaks matches the period of the correlation function. Therefore, the above effect can be achieved with a minimum required time since the synchronization peak is limited until the synchronization peak is searched.

[0040]

According to the invention in which synchronization acquisition and synchronization tracking are performed based on the peak of the correlation value characteristic after averaging the spreading code and the reference spreading code included in the received signal, the pseudo peak caused by noise or interference is erroneously detected. Since there is no possibility of determining a synchronization peak, accurate synchronization acquisition and synchronization tracking can be performed. In addition, a peak whose distance between peaks matches the period of the correlation function is searched for as a synchronization peak, and the averaging operation is stopped at that time.
The time required for synchronization acquisition is also minimized.

According to the invention, for each receiving system, synchronization peaks are respectively obtained from the averaged correlation value characteristics of the spreading code and the reference spreading code included in the reception signal, and diversity is performed based on the comparison result of the synchronization peak values. The effect of significantly fluctuating noise and interference on the synchronization peak value is sufficiently reduced, so that an accurate synchronization peak value can be obtained, thereby preventing frequent switching of the receiving system. This also prevents an increase in noise due to the switching operation. Also,
The peak whose distance between peaks matches the period of the correlation function is searched for as a synchronization peak, and the averaging operation is stopped at that time.Therefore, the number of periods for performing the averaging operation is minimized. Time is also minimized.

For each of the received signals from a plurality of base stations, a synchronization peak is obtained from the correlation value characteristic of the spread code and the reference spread code after averaging, and based on the comparison result of the synchronization peak values, the mobile station itself belongs to the mobile station. In the invention for obtaining the data of the cell in which the cell is located, the data indicating the cell is prevented from being frequently switched near the boundary between a plurality of base stations. Therefore, it is easy to determine the current position. In addition, a peak whose distance between peaks matches the cycle of the correlation function is searched for as a synchronization peak, and the averaging operation is stopped at that time. Therefore, the number of cycles for performing the averaging operation is minimized, and the cell to which the current cell belongs is determined. The time required to do so is also minimal.

[Brief description of the drawings]

FIG. 1 shows correlation value characteristics between a reproduced spreading code and a reference spreading code, where (a) is an ideal state with no noise or interference, (b) is a case where noise or interference is large, and (c) is an averaging operation Are shown.

FIG. 2 is a block diagram showing a circuit configuration of the receiver for spread spectrum communication according to the first embodiment;

FIG. 3 is a block diagram showing a circuit configuration of a correlator unit 2 of the receiver in FIG. 2;

FIG. 4 is an explanatory diagram showing a storage position of a correlation value stored in a correlation value storage unit 3 of the receiver in FIG. 2 and a storage position of a correlation value after averaging calculation stored in an averaging calculation unit 4;

5 is a block diagram (a) showing a function of a judgment unit 5 of the receiver in FIG. 2 and a flow chart showing an outline of a procedure for realizing the function.
Chart (b).

FIG. 6 is a flowchart showing a synchronization acquisition procedure which is a function of the judgment unit 5 of the receiver in FIG. 2;

FIG. 7 is a block diagram showing a circuit configuration of a diversity spread spectrum communication receiver according to a second embodiment;

FIG. 8 is a block diagram showing a circuit configuration of a mobile-system spread-spectrum communication receiver according to a third embodiment;

[Explanation of symbols]

 3 Correlation value storage unit 4 Averaging operation unit 5 Judgment unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Chisato Endo 41 Toyota Chuo Research Institute, Inc. 41 at Yokomichi, Toyota Central Research Laboratory, Inc.

Claims (1)

[Claims] 1. A spread-spectrum communication receiver for demodulating a spread-spectrum signal subjected to spread-spectrum by a direct-spreading method, wherein a correspondence between a spread code included in the spread-spectrum signal and a reference spread code stored in advance is provided. Calculating means for calculating a correlation value characteristic having the same period as the period of both spreading codes by calculating the correlation value of both spreading codes in each case of shifting the relationship one chip at a time; By calculating the average value of the correlation value and its past value for each time position in the cycle, and updating the corresponding correlation value of the correlation value characteristic with the calculation result,
Averaging means for averaging the correlation value characteristic, and a search means for comparing a time distance between each peak appearing in the correlation value characteristic with a cycle of the correlation value characteristic, and searching for a synchronization peak where both match. When the synchronization peak is searched, the reference spreading code synchronized with the spread spectrum signal based on the synchronization peak is used as a signal source for despreading, and control means for stopping the function of the averaging means, A receiver for spread spectrum communication having: