JP2000252867A - Spread spectrum communciation equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain high-speed spread code synchronization by reducing a time required for searching multi path. SOLUTION: A code generating timing control circuit 21 estimates a time region, where a multi-path signal is received with high probability on the basis of generating timing information of a spread code generated for inverse spread processing of a maximum path during reception in a second correlators 16a-16n. Then the generating timing of a spread code replica is controlled so as to allow a 1st correlation 13 to receive this time region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication apparatus used in a radio communication system employing, for example, a CDMA system as a radio access system, and more particularly to an apparatus for speeding up synchronization of spread codes.

[0002]

2. Description of the Related Art In a radio communication system using a direct spread spectrum (DS-SS) system, a RAKE reception technique can be applied to a spread spectrum communication apparatus.
RAKE reception is a technique for stabilizing communication quality with high quality by using a plurality of correlation circuits called fingers, receiving a multipath signal time-dispersed by multiple reflection by the plurality of fingers, and performing in-phase synthesis. is there.

In order to perform RAKE reception, it is necessary to accurately measure a multipath delay time and signal strength, that is, a delay profile, and to determine a path effective for combining. However, conventionally, this multi-path search is always performed uniformly over the entire area to be searched. For this reason, the search may be started first from an area where the possibility of receiving the multipath signal is low. In this case, it takes a lot of time to determine an effective multipath signal.

[0004] In order to efficiently measure the occurrence of multipath on the receiving side, a known spreading code having a fixed code pattern is time-multiplexed or code-multiplexed on a transmission signal so as to be received from the transmitting side. A method of periodically transmitting data to the side has been considered. This method can be realized by, for example, providing a matched filter corresponding to a known fixed spreading code on the receiving side and measuring a delay profile of a multipath signal using the matched filter. However, since a known fixed spreading code generally has a low signal energy, a multipath search cannot be accurately determined only by measuring a delay profile using a matched filter.

Further, in a system adopting the CDMA system, it is necessary to identify the timing of the spreading code and the type of the spreading code at the time of initial capture of the spreading code. Among them, the code timing can be identified by multiplexing the fixed spreading code known from the transmitting side to the main signal and transmitting the signal, as described above. However, in order to identify the type of the spreading code, it is necessary to perform a code search by sequentially matching the spreading code of the synchronization candidate to the received signals of all the paths.

[0006]

As described above, in the prior art, since the multipath search is always performed uniformly over the entire area to be searched, many multipath searches are required when specifying an effective multipath signal. It may take time.

[0007] Further, a known fixed spreading code is multiplexed on the main signal from the transmitting side and transmitted, and the receiving side receives the known fixed spreading code using a matched filter. In the measurement method, a high-speed search can be performed over a wide range, but is susceptible to noise and is not suitable for a high-precision search.

Further, when identifying the type of the spreading code,
Since the search is performed on the received signals of all the paths in the same procedure, it takes much time for the search.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. It is an object of the present invention to provide a spread spectrum communication apparatus which shortens the time required for multipath search and speeds up spread code synchronization. To provide.

[0010]

In order to achieve the above object, according to the present invention, a multipath signal of a spread spectrum signal transmitted from a transmitting station is searched, and a code for the multipath signal is searched based on the search result. In the spread spectrum communication apparatus for establishing synchronization, search means for detecting a reception state of the multipath signal, determination means for determining a valid multipath signal based on a detection result of the search means, A correlation means for performing despreading processing to selectively receive the effective multipath signal based on the determination result; and a search control means. The search control means allows the correlation means to perform the despreading processing. Based on the generation timing information of the spread code generated in It is obtained so as to control the generation timing of the spread code replica.

More specifically, the search control means estimates a time region in which the multipath signal is highly likely to be received based on the spread code generation timing information of the correlation means, and calculates a spread code replica in the search means. By controlling the generation timing based on this estimation result,
The multipath signal search operation is performed in the estimated time domain.

With this configuration, the search means preferentially searches a time region where the probability of receiving a multipath signal is high, and as a result, uniformly searches all search target regions. Compared with the case, the search for the multipath signal can be performed in a short time, and thereby, the speed of code synchronization can be increased.

According to another aspect of the present invention, a multipath signal of a spread spectrum signal transmitted from a transmitting station is searched, and code synchronization with the multipath signal is established based on the search result. In the spread spectrum communication apparatus, when the transmitting station periodically multiplexes and transmits a known fixed spreading code to the spread spectrum signal, the delay profile of the multipath signal is calculated using the known fixed spreading code. First search means having a matched filter for detection, second search means for detecting the reception state of the multipath signal, and multipath effective based on the detection results of the first and second search means Determining means for determining a signal; and despreading processing for selectively receiving the effective multipath signal based on the determination result of the determining means. Performing correlation, and estimating a time region having a high probability of receiving the multipath signal based on generation timing information of a spreading code generated for the despreading process in the correlation, Search control means for controlling the generation timing of the spreading code replica based on the estimation result. And
The determination means selects the detection result of the second search means in a time domain where the probability of receiving a multipath signal is high based on the estimation result of the search control means, and selects the first search result in other time domains. The search result of the search means is selected.

With this configuration, a high-precision search is performed by the second search means in the time domain where the probability of receiving the multipath signal is high, and the first search using the matched filter is performed in other time domains. The high-speed search is performed by the search means. Therefore, high-precision and high-speed code synchronization can be performed.

Further, another object of the present invention is to search for a multipath signal of a spread spectrum signal spread and transmitted by different transmitting codes at a plurality of transmitting stations, and based on the search result. In a spread spectrum communication apparatus for establishing code synchronization with the multipath signal, a search means for detecting a reception state of the multipath signal, and a determination for determining a valid multipath signal based on a detection result of the search means Means, correlation means for performing despreading processing to selectively receive the effective multipath signal based on the result of the determination by the determination means, and search control means. In the above, based on the information indicating the type and generation timing of the spreading code generated for the despreading process, It is obtained to perform the identification spread code by controlling the type and generation timing of the spread code replica to be generated in order to receive the multipath signal in means.

More specifically, the search control means estimates a time region having a high probability of receiving a multipath signal arriving from the same transmitting station based on the spread code generation timing information of the correlation means, In the estimated time domain, a spread code replica of the same type as the spread code generated by the correlation means is generated by the search means.

In general, in the time domain where the probability of receiving a multipath signal is high, there is a high possibility that spread spectrum signals from the same transmitting station are received with delay dispersion. For this reason, as described above, by performing a multipath search using the same type of spreading code as the multipath signal being received by the correlation means, the time required for the search can be reduced, and identification of the code type can be performed at high speed. It can be carried out. In contrast,
In the time domain where the probability of receiving a multipath signal is low,
A search is performed using all candidate spreading codes. By doing so, it is possible to identify the type of spreading code for the multipath signal at high speed and with high accuracy.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a circuit block diagram showing a first embodiment of a spread spectrum communication apparatus according to the present invention.

In FIG. 1, a direct spread spectrum spread signal (DS-SS signal) transmitted from a transmitting station (not shown) is received by an antenna 10 and then received by a radio receiving unit (R).
F) 11, where it is frequency converted to a received baseband signal. Then, the received baseband signal is converted into a digital signal by an analog / digital converter (ADC) 12, and a first correlator 13 having a function as a searcher and a plurality of first correlators for performing RAKE reception are provided. Are input to the two correlators 16a to 16n.

The first correlator 13 has a spreading code generator for generating a spreading code replica, and performs a multipath search by despreading the received received digital baseband signal using the spreading code replica. I do. Then, the output signal of the multipath search is output to an intensity determiner 14.
To enter. The intensity determiner 14 is provided with the first correlator 13
The effective multipath is determined by measuring the received electric field strength of the output signal from.

The composite finger control circuit 15, to which the result of the determination by the intensity determiner 14 is input, converts the multipath determined to be valid by the intensity determiner 14 into a second correlator 16a.
-16n to be selectively received by the second correlator 16
On / off control of a to 16n and the generation timing of the spread code generated by these correlators are controlled.

Each of the second correlators 16a to 16n has a spread code generator, and generates a spread code from the spread code generator in accordance with the timing specified by the combining finger control circuit 15. Then, the input received digital baseband signal is despread by the spreading code, and the received signal of each path obtained by the despreading is input to the adder 19 via the multipliers 17a to 17n. The adder 19 performs in-phase synthesis on the input reception signals of the respective paths and outputs the combined signals to the decision unit 20. The determiner 20 determines the received signal supplied from the adder 19.

The multipliers 17a to 17n combine the transmission path response estimators 18a to 18n for in-phase combining the received signals of the respective paths output from the correlators 16a to 16n.
The complex weight calculated in 18n is reflected on the received signal of each path.

The spread spectrum communication apparatus according to the present embodiment includes a code generation timing control circuit 21. The code generation timing control circuit 21 basically has a function of controlling the generation timing of the spread code replica generated by the spread code generator of the first correlator 13. 2 correlators 16
This is performed in accordance with the generation timings of spreading codes a to 16n. That is, based on the spread code generation timing of the second correlators 16a to 16n, a time domain where the probability of receiving a multipath signal is estimated is high, and the first correlator 13 performs multipath estimation in the estimated time domain. In order to perform a signal search, the generation timing of the spread code replica is controlled.

Next, the operation of the apparatus configured as described above will be described. When the code synchronization acquisition procedure is started, the apparatus first searches for a known fixed spreading code inserted into each slot of the spread spectrum signal transmitted by the transmitting station by, for example, a matched filter (not shown) as shown in FIG. Measure the multipath delay profile.

In general, the pilot signal added after the data sequence is also a known signal, but since the pilot signal is scrambled by a code called a scramble code, the type and phase of the scramble code are specified. Only after that, the multipath reception status cannot be measured. The portion of the fixed spreading code is a code sequence that has not been subjected to scramble processing, and delay profile measurement can be performed even when scramble code identification is not performed.

When the delay profile is measured, a path having the highest received electric field strength is detected based on the measurement result, and this path is allocated to the second correlator 16a for reception. This assignment is performed by adjusting the timing of generating the spreading code of the second correlator 16a to the timing of the path to be received.

Now, when the maximum path is allocated to the second correlator 16a, the apparatus subsequently receives the pilot signal inserted in the latter half of each slot as shown in FIG. Perform a detailed search for multipath signals.

That is, this search is performed by the first correlator 13
It is performed in. At this time, the code generation timing control circuit 21 determines a time region having a high probability of receiving a multipath signal in accordance with the maximum path being received by the second correlator 16a, for example, the reception timing of P11 shown in FIG. presume. Then, only this time domain is used as the first correlator 1
No. 3 designates the generation timing of the spread code replica to be received. For example, in FIG. 2, a certain period T1 from the reception timing of the maximum path P11 is designated to the first correlator 13 as a search period. Therefore, the first correlator 1
In 3, the search for the multipath signal is performed in the period T1 designated by the code generation timing control circuit 21.

With this configuration, the multipath signals P12 and P13 to be detected can be searched in a short time. That is, a multipath signal is generated due to a difference in a propagation path due to multiple reflection of a radio wave. Therefore, if there is a path having the strongest signal strength, the timing around the path timing is a timing candidate having a high probability that a multipath having the next highest strength exists. Therefore, as described above, a multipath search can be performed in a short time by performing a path search from the periphery of the receiving path P11 having the highest received electric field strength. Code synchronization can be realized.

(Second Embodiment) FIG. 3 is a circuit block diagram showing a second embodiment of the spread spectrum communication apparatus according to the present invention. In this figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description is omitted.

The received digital baseband signal output from the ADC 12 is supplied to a first correlator 13 and a plurality of second
Are input to the matched filters 31 as well as the correlators 16a to 16n.

When a transmitting station (not shown) periodically multiplexes and transmits a known fixed spreading code to a spread spectrum signal, the matched filter 31 converts the multipath signal using the known fixed spreading code. Search, thereby measuring the multipath delay profile. The delay profile is information including a multipath delay time and a received electric field strength. The measurement result of the delay profile obtained by the matched filter 31 is input to the intensity determiner 32 together with the multipath detection signal obtained by the first correlator 13.

The code generation timing control circuit 33 for controlling the multi-path search operation in the first correlator 13 has a first correlation function similar to the code generation timing control circuit 21 described in the first embodiment. A function of controlling the generation timing of the spreading code replica generated by the spreading code generator of the correlator 13.
This is performed according to the respective spread code generation timings 6a to 16n. That is, based on the respective spread code generation timings in the second correlators 16a to 16n, a time domain in which a multipath signal is highly likely to be received is estimated, and the first correlator 13 in the estimated time domain. In order to search the multipath signal in detail, the generation timing of the spread code replica is controlled.

In accordance with the information indicating the time domain estimated by the code generation timing control circuit 33, the intensity judgment unit 32 uses the multipath detection signal obtained by the first correlator 13 and the matched filter 31 The obtained delay profile measurement results are selectively used, and effective multipath determination is performed based on the selected detection results.

With such a configuration, when the code synchronization establishment procedure is started, a known fixed spreading code is first searched for by the matched filter 31 as in the first embodiment, and as a result, a multipath The delay profile is measured. Then, based on the measurement result, the path having the highest received electric field intensity is detected by the intensity determiner 32,
The spread code generation timing for receiving this path is determined by the synthesizing finger control circuit 15 from the second correlators 16a to 16a.
n.

For example, in the matched filter 31, multipaths P41 to P43 and P51 to P43 as shown in FIG.
If the delay profiles of P53 and P61 are detected, the paths P41 and P41 having the higher received electric field strength are selected from the delay profiles.
51 is selected, and these paths P41 and P51 are assigned to the second correlator 16a (finger 1) and the second correlator 16b (finger 2), respectively.

Now, the second correlators 16a, 16
After the maximum path is assigned to b, a detailed search for a multipath signal is performed by receiving a pilot signal. That is, the code generation timing control circuit 33 determines the time domain in which the second correlators 16a and 16b should search the multipath signal in detail based on the reception timing of the paths P41 and P51 being received (see FIG. 4). The detailed search ranges T2 and T3) shown are set.
Then, in order for the first correlator 13 to receive the detailed search ranges T2 and T3, the generation timing of the spread code replica is designated to the first correlator 13. Therefore, in the first correlator 13, the code generation timing control circuit 3
In a period corresponding to the detailed search ranges T2 and T3 designated from No. 3, a search for a multipath signal is performed.

At this time, in the intensity judgment unit 32,
During the period corresponding to the detailed search ranges T2 and T3, the first
Multipath P4 to be detected output from the correlator 33
2, the detection signals of P52 and P53 are selected, while the delay profiles of the multipaths P43 and P61 output from the matched filter 31 are selected in other periods.

In general, a path search using a matched filter is suitable for a high-speed search over a wide range, but is not suitable for a high-precision search with little influence of noise. On the other hand, in the method in which the generation timing of the spread code is shifted by the correlator, the search takes time,
By using the averaging over a plurality of symbols, a highly accurate search can be performed. Therefore, as in the present embodiment, an area having a high probability of existence of a path is intensively searched using the first correlator 13 capable of searching with high accuracy, and other areas can be searched at high speed. By performing a search using the matched filter 31, a high-precision and high-speed multipath search can be performed.

(Third Embodiment) FIG. 5 is a circuit block diagram showing a third embodiment of the spread spectrum communication apparatus according to the present invention. In this figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description is omitted.

The code generation timing control circuit 51 performs the code search of the multipath signal by receiving the pilot signal.
Incorporates information indicating the generation timing of the spreading code and the type of the spreading code being generated, and based on these information, a time domain in which the probability of receiving a multipath signal arriving from the same transmitting station is high, that is, The same code search range is estimated. Then, in order to cause the first correlator 13 to search for a multipath signal in the estimated same code search range, the generation timing and type of the spread code replica are designated to the first correlator 13.

With such a configuration, when the code synchronization establishment procedure is started, a known fixed spreading code is first searched for by a matched filter (not shown), as in the first embodiment described above. Measure the multipath delay profile. Then, based on the measurement result, the path having the highest received electric field strength is detected by the intensity determiner 14, and the spread code generation timing for receiving this path is determined by the combining finger control circuit 15 from the second correlators 16a to 16a. 16n.

For example, in a matched filter, multipaths P71 to P73, P81 to P8 as shown in FIG.
3, when the delay profile of P91 is detected,
Of these, paths P71 having a large received electric field strength are selected, and these paths P71 are assigned to the second correlator 16a (finger 1).

When the maximum path is assigned to the second correlator 16a, a detailed search for a multipath signal is performed by receiving a pilot signal.

That is, the code generation timing control circuit 51 determines the time domain in which the multipath signal is to be searched in detail based on the reception timing of the path P71 being received by the second correlator 16a (the same as shown in FIG. 6). Code search range T
4) Set. Then, in order for the first correlator 13 to receive the detailed search range T4, the generation timing of the spread code replica is designated to the first correlator 13.

At the same time, the code generation timing control circuit 51 fetches information indicating the type of the spreading code generated by the second correlator 16a, and the second correlator 16a generates the code based on this information. The first correlator 13 is controlled so that the first correlator 13 generates the same type of spreading code replica as the spreading code being performed.

Therefore, in the first correlator 13, the same code as the spread code generated by the second correlator 16a is used in the period corresponding to the same code search range T4 specified by the code generation timing control circuit 51. Various kinds of spreading code replicas are generated, and the received digital baseband signal is despread by the spreading code replicas.

Generally, in a region where the multipath existence probability is high, there is a high possibility that the same transmission signal is received with delay dispersion. Therefore, when performing a code search in this area, if the search is performed using the same spreading code as the spreading code of the maximum path P71 already received, the time required for the search can be reduced.

Therefore, as in the present embodiment, in the code generation timing control circuit 51, the second correlator 16a
To estimate the search range of the same code based on the reception timing of the maximum path P71 being received, and
And the same type of spreading code as the spreading code generated by the second correlator 16a is specified to the first correlator 13, so that the type of code of the multipath signal is high. It is possible to identify the speed.

In a region other than the same code search range T4, the possibility of receiving the same multipath as the path P71 is low.
Performs a search for all candidate spreading codes.

The present invention is not limited to the above embodiments. For example, in the first and third embodiments, the case where the measurement of the multipath delay profile in the initial synchronization process is performed using the matched filter as in the second embodiment has been described as an example. Other delay profile measuring means may be used.

Further, a spread spectrum apparatus having all the components of the first to third embodiments may be constituted. Other, synchronization establishment procedure, second correlator (finger)
, The configuration of the spread spectrum communication apparatus, the type of system to be applied, and the like, can be variously modified without departing from the gist of the present invention.

[0054]

As described above in detail, according to the present invention, the search control unit uses the correlation unit based on the generation timing information of the spreading code generated for the despreading process.
The search means controls the generation timing of the spread code replica generated for receiving the multipath signal.

According to another aspect of the present invention, when a transmitting station periodically multiplexes a known fixed spreading code with a spread spectrum signal and transmits the multiplexed signal, a delay profile of a multipath signal is detected using the known fixed spreading code. First search means having a matched filter that performs matching, second search means for detecting the reception state of the multipath signal, and a multipath signal effective based on the detection results of the first and second search means. Determining means for determining whether or not the effective multipath signal is to be selectively received based on the determination result of the determining means; and correlating means for performing the despreading processing in the correlating means. Based on the generated spread code generation timing information, a time region in which the multipath signal is highly likely to be received is estimated, and a spread code replica The formation timing and a search control means for controlling on the basis of the estimation result, the in the determination means, under high time probability of multipath signals are received in the region estimation result of said search control means the second
And the detection result of the first search means is selected in other time regions.

In still another invention, the search control means uses the information indicating the type and generation timing of the spreading code generated for the despreading process in the correlation means.
The search means controls the type and generation timing of the spread code replica generated to receive the multipath signal to identify the spread code.

Therefore, according to these inventions, it is possible to provide a spread spectrum communication apparatus which shortens the time required for multipath search and speeds up spread code synchronization.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing a first embodiment of a spread spectrum communication apparatus according to the present invention.

FIG. 2 is a view for explaining a multipath search operation by the device shown in FIG. 1;

FIG. 3 is a main part configuration diagram showing a second embodiment of the spread spectrum communication apparatus according to the present invention.

FIG. 4 is a view for explaining a multipath search operation by the device shown in FIG. 3;

FIG. 5 is a main part configuration diagram showing a third embodiment of the spread spectrum communication apparatus according to the present invention.

FIG. 6 is a view for explaining a spread code search operation performed by the device shown in FIG. 5;

FIG. 7 is a diagram showing an example of a configuration of a signal transmitted by a transmitting station.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Antenna 11 ... Radio receiver 12 ... Analog / digital converter (ADC) 13 ... 1st correlator 14 ... Intensity judgment device 15 ... Synthetic finger control circuit 16a-16n ... 2nd correlator 17a-17n ... Multiplication Units 18a to 18n Transmission line response estimator 19 Adder 20 Judge 21, 33, 51 Code generation timing control circuit 31 Matched filter 32 Strength determiner

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Ogura, Inventor Koji Komukai Toshiba-cho, Kawasaki City, Kanagawa Prefecture, Japan Inside the R & D Center of Toshiba Corporation (72) Inventor Manabu Mukai Toshiba Komukai, Sachi-ku, Kawasaki City, Kanagawa Prefecture 1-cho, Toshiba R & D Center (72) Inventor Hiroshi Asanuma 3-1-1 Asahigaoka, Hino-shi, Tokyo In-house Toshiba Hino Plant (72) Inventor Hidehiro Takahashi 3-chome, Asahigaoka, Hino-shi, Tokyo F-term (reference) at Toshiba Hino Plant, No. 1 5K022 EE02 EE33 EE36 5K047 AA02 BB01 GG34 HH15 MM11 MM33 5K052 AA01 BB01 CC06 FF31 GG51

Claims (5)

[Claims] 1. A spread spectrum communication apparatus for searching for a multipath signal of a spread spectrum signal transmitted from a transmitting station and establishing code synchronization with the multipath signal based on the search result. Searching means for detecting a reception state; determining means for determining a valid multipath signal based on the detection result of the searching means; and selectively selecting the valid multipath signal based on the determination result of the determining means. A correlation unit for performing a despreading process for receiving, based on generation timing information of a spreading code generated for the despreading process in the correlation unit, a search unit for generating a multipath signal received by the search unit. And search control means for controlling the generation timing of the spread code replica. Distributed communication device. 2. The search control unit estimates a time domain in which the multipath signal is highly likely to be received based on spread code generation timing information of the correlation unit, and generates a spread code replica in the search unit. 2. The spread spectrum communication apparatus according to claim 1, wherein by controlling timing based on the estimation result, a search operation of the multipath signal is performed in the estimated time domain. 3. A spread spectrum communication apparatus for searching for a multipath signal of a spread spectrum signal transmitted from a transmission station and establishing code synchronization with the multipath signal based on the search result. A first search unit having a matched filter for detecting a delay profile of the multipath signal using the known fixed spreading code, when the fixed spreading code is periodically multiplexed with the spread spectrum signal and transmitted. A second search means for detecting a reception state of a multipath signal using a spread spectrum signal other than the known fixed spread code, and an effective multipath based on a detection result of the first and second search means. Determining means for determining a path signal; and selectively receiving the valid multipath signal based on a determination result of the determining means. A correlation means for performing a despreading process; and estimating a time region having a high probability of receiving the multipath signal based on generation timing information of a spreading code generated for the despreading process in the correlation means. A search control unit that controls the generation timing of the spreading code replica in the search unit based on the estimation result, wherein the determination unit receives a multipath signal based on the estimation result of the search control unit. A spread spectrum communication apparatus, wherein a detection result of the second search means is selected in a time domain having a high probability of occurrence, and a detection result of the first search means is selected in other time domains. 4. A spectrum for searching for a multipath signal of a spread spectrum signal transmitted by being spread by different spreading codes at a plurality of transmitting stations, and establishing code synchronization with the multipath signal based on the search result. In the spread communication apparatus, a search means for detecting a reception state of the multipath signal; a determination means for determining a valid multipath signal based on a detection result of the search means; and a determination result based on the determination result of the determination means. Correlation means for performing despreading processing to selectively receive the effective multipath signal, based on information indicating the type and generation timing of a spreading code generated for the despreading processing in the correlation means. , The type and generation timing of a spreading code replica generated for receiving a multipath signal in the search means. Spread spectrum communication system being characterized in that includes a search control unit that controls the grayed conducting the identification spread code. 5. The search control means estimates a time domain in which a multipath signal arriving from the same transmitting station is highly likely to be received, based on the spread code generation timing information of the correlation means, 5. The spread spectrum communication apparatus according to claim 4, wherein, in said time domain, said search means generates a spread code replica of the same type as a spread code generated by said correlation means.