JPH08237173A - Spread spectrum communication system - Google Patents

Abstract

PURPOSE: To start synchronization locking from any initial phase difference by providing a synchronization spread code with a period being a specific multiple of that of a code generating timing signal and a local reference signal so as to eliminate the need for modulation of information of the local reference signal. CONSTITUTION: A code generator 8 generates an inverse spread code of a code series length L and a local reference signal PNO* of a code series length 2L based on a same clock signal. A signal PN0 is a synchronizing signal included in a reception signal S1 and the signal PNO* is a signal being inverse of the PN0 on time base. In this case, a correlation peak output S4 as shown in caption 215 is a signal led by Δ/2 from a code generating timing signal S6 shown in caption 216. Then synchronization locking and synchronization tracing are attained by giving the correlation peak output S5 and the code generating timing signal S6 to a PLL 7. Since it is not required to modulate the local reference signal different from a conventional system, the correlation peak signal at out of synchronism is not lost and the synchronization locking is attained from any initial phase difference.

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 system and, more particularly, to its synchronization system.

[0002]

2. Description of the Related Art FIG. 15 is a block diagram showing a structure of a synchronizing section of a receiver for explaining a conventional synchronizing method in spread spectrum communication.

The receiver is constructed so that the spread spectrum signal S1 received by the antenna 1 is despread by the demodulation section 3 by the despreading code S2 output from the synchronization section 2 to extract information.

In the synchronizing section 2, first, the received signal S1 is SA
It is input to the W convolver 4, and the correlation calculation with the local reference signal S3 ′ is performed. The local reference signal S3 ′ is a time-reversed P of the same code as the synchronization spreading code PN0 included in the received signal.
N0 _* (* indicates an inverted signal hereinafter) is used. S
The output of the AW convolver 4 is obtained as a correlation output S4 through the detector 5.

A PLL (Phase Locked Loop) 7 has an output S5 from a peak detector 6 for detecting the peak of the correlation output S4.
Then, the speed of the code generation clock S7 is adjusted according to the phase difference between the code generation timing signal S6 and the code generation timing signal S6.

However, the code sequence length L is applied to the SAW convolver.
If the same sign is input from the left and right, the correlation peak will have a period of
Therefore, in the conventional spread spectrum communication synchronization method using the SAW convolver, as shown in FIG.
By using a local reference signal S3 ′ obtained by converting information of PN0 every other cycle by “0” and “1”, this L / 2 peak is eliminated and a correlation peak S4 appears in a cycle L. (See, for example, Japanese Patent Application No. 63-287101).

Further, when performing spread spectrum communication by converting information into frames, a transmission signal normally includes a preamble period 61 for transmitting only a spreading code for synchronization as shown in FIG. 7 in the machine
Is configured so that code synchronization can be performed at high speed during this preamble period 61.

[0008]

However, in the above-mentioned conventional example, as shown in FIG. 17, when the code synchronization between PN0 and PN0 _* is out of phase and the phase difference is L / 2, 9 in FIG.
As shown by 4, the level of both correlation peaks appearing in the period L / 2 of the correlation output S4 is halved due to the information modulation for each period of the local reference signal S3 ′, and the threshold of the peak detector 6 is reduced. Does not exceed As a result, there is no input to the PLL, and in some cases, synchronization pull-in takes a very long time.

Further, as shown in FIG. 9, when the information is framed and transmitted, if the preamble period 61 for code synchronization is not sufficiently shorter than the information transmission time 62, the substantial information transmission efficiency decreases. Therefore, in order to shorten the preamble period 61, a high-speed and high-precision PLL is required, which is disadvantageous in that the cost is high and the configuration is complicated.

It is a first object of the present invention to provide a synchronization method which does not require information modulation of a local reference signal and can start synchronization pull-in from any initial phase difference.

A second object of the present invention is to realize high-speed synchronization pull-in, and particularly to provide a synchronization method suitable for transmitting information in frame.

A third object of the present invention is to provide a more accurate synchronization method.

[0013]

The first and second inventions (claims 1 and 2) of the present application are provided with a synchronization spreading code having a period twice that of the code generation timing signal and a local reference signal. Is characterized by. The third invention of the present application (claim 3)
Is characterized by performing code synchronization by using a synchronization pilot code having a code sequence length of 2L, which is twice the code sequence length L of the spreading code PNi for spreading information.

In such a system, for example, SAW
When the same code having a code sequence length of 2L is input to the convolver from the left and right, the correlation peak appears in the cycle L and is compared with the code generation timing signal of the cycle L in the PLL. Therefore, the information modulation of the local reference signal is not necessary, and the correlation peak can be obtained at a level higher than the threshold for peak detection at any initial phase difference, so that the synchronization pull-in is possible.

Further, according to this method, the synchronization pilot signal has a doubled code sequence length, and thus a doubled process gain, and therefore a distance characteristic of 2.
^1/2 times improved.

A fourth invention of the present application (claim 4)
Is an information spreading code PNi and a synchronization pilot code P
It is characterized in that the code sequence length L of N0 is synchronized by using a code generation timing signal output in an L / 2 cycle.

In such a system, for example, the output from the SAW convolver to which the same code of the code sequence length L is input from the left and right is input to the PLL with the period L / 2 after the detection and the peak detection, and the same period. It is compared with the code generation timing signal of L / 2. Therefore, the information modulation with the local reference signal is not necessary, and the correlation peak can be obtained at a level equal to or higher than the threshold for peak detection at any initial phase difference, so that the synchronization pull-in becomes possible.

Further, in this system, the frequency of the signal input to the PLL is double that of the conventional signal, and as a result, the time required for phase pull-in is half that of the conventional signal without using a high-speed PLL.

The seventh invention of the present application (claim 7)
Since the code generation timing signal is 1/2 times the code cycle of the synchronization spreading code of the cycle and the local reference signal, it is twice the code sequence length L of the spreading code PNi for spreading the information. This is to perform code synchronization using a synchronizing pilot code having a code sequence length of 2L, which is equivalent to, for example, when the SAW convolver inputs the same code having a code sequence length of 2L from the left and right, a correlation peak appears at a cycle L and the code The reset means also compares with the code generation timing signal of the period L. Therefore, the information modulation of the local reference signal is not necessary, and the correlation peak can be obtained at a level higher than the threshold for peak detection at any initial phase difference, so that the synchronization pull-in is possible.

Further, according to this method, the synchronization pilot signal has a doubled code sequence length, and thus a doubled process gain, and therefore a distance characteristic of 2.
^1/2 times improved.

The eighth invention of the present application (claim 8)
Is an information spreading code PNi and a synchronization pilot code P
The code sequence length L of N0 is synchronized by using a code generation timing signal output in L / 2 cycles. For example, the same code of the code sequence length L is input from the left and right SAW convolvers. After the peak is detected, the output of is input to the code reset means with the period L / 2 as it is and compared with the code generation timing signal of the period L / 2. Therefore, the information modulation with the local reference signal is not necessary, and the correlation peak can be obtained at a level equal to or higher than the threshold for peak detection at any initial phase difference, so that the synchronization pull-in becomes possible.

Further, in this system, the frequency of the signal input to the code reset means is double that of the conventional signal, and as a result, the time required to establish synchronization is half that of the conventional signal.

The ninth invention of the present application (claim 9)
Detects the phase difference between the peak signal output from the peak detection means and the code timing signal and the phase difference between the peak signal and the output clock of the reference signal generation means a plurality of times, and calculates the average value of these phase differences. It is characterized in that it is provided with a phase difference calculating means. Therefore, for example, even when a synchronous circuit is formed by digital processing using a correlation signal from a device such as a SAW convolver, the jitter and the like of the correlation peak signal itself due to various fluctuation factors around the SAW convolver are averaged and accurate synchronization is achieved. It is possible to take

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a first embodiment of the present invention.

The receiver in this embodiment has an antenna 1, a synchronizing section 2 and a demodulator 3.

The demodulator 3 receives the spread spectrum signal S1 received by the antenna from the despreading code S received from the synchronizing section 2.
2 despreads and retrieves information.

In the synchronizing section 2, the SAW convolver 4 performs a correlation operation between the received signal S1 and the local reference signal S3, and the detector 5 detects the output of the SAW convolver 4.

The peak detector 6 receives the output S4 of the detector 5 and detects the correlation peak signal S5.
The L (phase locked loop) 7 is for adjusting the speed of the code generation clock S7 according to the phase difference between the correlation peak signal S5 and the code generation timing signal S6 of the code generator 8. The PLL 7 is usually composed of a phase comparator, a loop filter, and a voltage controlled oscillator.

From the code generator 8, a despreading code PNi having a code sequence length L and a local reference signal PN0 having a code sequence length 2L.
_* Is generated by the same clock. PN0 is
PN0 _* , which is a synchronization code included in the received signal S1 _.
Is a code obtained by inverting PN0 on the time axis. The code generation timing signal S6 represents the beginning of the code sequence of the despreading code S2, for example, and at the same time, the local reference signal S6.
3 shows the beginning and 1/2 position of the code sequence of No. 3.

2 and 3 are explanatory diagrams showing signal waveforms of the synchronization system in the first embodiment of the present invention.

First, in FIG. 2, with respect to the code sequence length L of the despread signal S2 shown at 201, the interaction area of the convolver in this embodiment is 2L as shown at 202. For the sake of explanation, the rising edge of a certain code generation timing signal S6 is set to t = 0.

Next, as shown in FIG. 2, when code synchronization is established, t = 2 kL (k = 0, 1, 2, ...)
Then, the signs of PN0 and PN0 _* are, as shown at 203,
Match within the interaction area of the convolver. Also, 204
As shown in, even at t = (2k + 1) L, PN0
And PN0 _{* have} the same sign in the convolver interaction region. Therefore, as indicated by 205, the correlation peak output S4 is obtained in the cycle L, so that it becomes a signal having the same cycle as the code generation timing signal S6 of 206.

Next, as shown in FIG. 3, when the code synchronization is deviated by Δ, t = 2 kL-Δ / 2 (k = 0,
, 2, ...), and the symbols of PN0 and PN0 _* are 213
As shown in, there is agreement within the interaction area of the convolver. Further, as indicated by 214, t = (2k + 1) L−
Even in Δ / 2, the signs of PN0 and PN0 _* match within the interaction area of the convolver. Therefore, as shown by 215, the correlation peak output S4 has the same period L as the code generation timing signal S6 of 216 and is a signal advanced by Δ / 2 from the code generation timing signal S6. Therefore,
P the correlation peak output S5 and the code generation timing signal S6
By inputting to LL7, synchronization pull-in and synchronization follow-up become possible.

Therefore, according to this embodiment, since it is not necessary to modulate the information of the local reference signal as in the prior art, there is no disappearance of the correlation peak signal at the time of loss of synchronization, and synchronization can be pulled in from any initial phase difference. Becomes

Further, according to the present embodiment, the spread code signal for synchronization has a doubled code sequence length, and thus a doubled process gain (indicating a degree of resistance to noise). Therefore, the distance characteristic is also improved by 2 ^1/2 times. In particular, when configuring a wireless LAN (local area network) system using spread spectrum communication, by using the synchronization method of the present embodiment in a multi-cell configuration as shown in FIG. The good synchronization signal enables code synchronization between the BS (base station) 34 and the BS 35, and between the BS 35 and the BS 36, and an effect of preventing interference between different cells can be obtained.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

In the second embodiment, the code generation timing signal S6 'is, for example, a signal of a cycle L / 2 indicating the head and the 1/2 position of the despread code S2 and the local reference signal S3'.

Then, the SAW convolver 4 performs a correlation calculation between the received signal S1 and the local reference signal S3 '. Also,
The PLL 7 adjusts the speed of the code generation clock S7 according to the phase difference between the correlation peak signal S5 and the code generation timing signal S6 'of the code generator 8.

The other structure in FIG. 5 is basically the same as that of the first embodiment (FIG. 1), and the description thereof will be omitted.

6 to 8 are explanatory diagrams showing signal waveforms of the synchronization system in the second embodiment of the present invention.

First, in FIG. 6, the interaction area of the convolver in this embodiment is L, which is the same as the code sequence length of the spreading code, as indicated by 502. In addition, for explanation,
The rising edge of a certain code generation timing signal S6 ′ is t =
Set to 0.

Next, as shown in FIG. 6, when code synchronization is achieved, t = kL (k = 0, 1, 2, ...),
The signs of PN0 and PN0 _* coincide within the interaction area of the convolver, as shown at 503. Further, as shown by 504, even at t = (k + 1/2) L, the signs of PN0 and PN0 _* match in the interaction area of the convolver. Therefore, the correlation peak output S4 is obtained at the cycle L / 2, as shown at 505, and therefore has a same cycle as the code generation timing signal S6 'at 506.

Next, as shown in FIG. 7, when the code synchronization is deviated by Δ, t = kL-Δ / 2 (k = 0, 1,
2, ...), the signs of PN0 and PN0 _* coincide within the interaction area of the convolver, as shown at 513. Also, as indicated by 514, t = (k + 1/2) L-Δ /
Also in No. 2, the signs of PN0 and PN0 _* match in the interaction area of the convolver. Therefore, the correlation peak output S
As indicated by 515, 4 has the same period L / 2 as the code generation timing signal S6 of 516 and is a signal advanced by Δ / 2 from the code generation timing signal S6.

Next, as shown in FIG. 8, when the code synchronization is shifted by L / 2, t = (k-1 / 4) L (k =
0, 1, 2, ...) and the sign of PN0 and PN0 _* is 5
As shown in 23, there is agreement within the interaction region of the convolver. Also, as indicated by 524, t = (k + 1/4)
Also in L, the signs of PN0 and PN0 _* match in the interaction area of the convolver. Therefore, the correlation peak output S
As indicated by 525, 4 has the same period L / 2 as the code generation timing signal S6 ′ of 526, and is a signal shifted by L / 4 from the code generation timing signal S6 ′.

That is, the code generation timing signal S6 '
Is a cycle L / 2, but is not stable when the code synchronization is deviated by L / 2, it is regarded as a phase lead or a lag, and the lead is performed to the correct code synchronization point.

The broken line code generation timing signal and the correlation peak signal in FIG. 14 indicate that the generation timing signal is considered to be in phase advance with respect to the correlation peak signal and the synchronization pull-in is performed.

When the phase of the generated timing signal is delayed by the PLL, the phase of the correlation peak signal, which is the result of the convolution calculation, is delayed by 1/2. Therefore, as shown in the figure, it is pulled to the correct code synchronization point. The same applies to the case of phase delay.

Therefore, according to the present embodiment, since it is not necessary to modulate the information of the local reference signal as in the conventional case, the correlation peak signal at the time of synchronization loss does not disappear and the synchronization pull-in is possible from any initial phase difference. Becomes

Furthermore, according to the present embodiment, the frequency of the signal input to the PLL is double that of the conventional signal. As a result, the time required for phase pull-in is reduced to half that of the conventional signal without using a high-speed PLL. Has the effect of being shortened. Therefore, as shown in FIG. 6, when the information is framed and transmitted, the preamble period can be shortened by using the synchronization method of the present embodiment, and as a result, the throughput of the communication system can be improved.

FIG. 10 is a block diagram showing a third embodiment of the present invention.

From the code generator 115, the despreading code PN _i having the code sequence length L and the reference code PN having the code sequence length 2L are provided.
0 _* and 0 _* are generated by the same clock. Also,
The code generation timing signal represents the beginning of the code sequence of the despreading code, and at the same time, indicates the beginning and the 1/2 position of the code sequence of the reference code.

The SAW convolver 110, which is a correlation detector, detects the correlation between the received IF (intermediate frequency) signal processed by the high frequency section and the reference spreading code used for despreading. Then, this correlation signal is the peak detector 11
It is digitized by 1 and output to the sign reset circuit 112 and the phase shift circuit 113.

When the SAW convolver 110 is used to perform processing by convolutional correlation, the code reset circuit 112 resets the code at the code phase obtained by doubling the phase delay of the peak signal with respect to the code generation timing of the reference spreading code. A signal is output to synchronize the reference code and the despreading code. The received IF signal is despread by the despreading code and information is taken out.

The phase shift circuit 113 outputs the output of the reference signal generator 114 as it is as a code generator clock before starting the synchronous operation. Then, when reception is started and a peak signal is obtained, the amount obtained by doubling the phase delay of the peak signal with respect to the output clock of the reference signal generator 114 is shifted from the reference clock to obtain the code generator clock, Synchronize the clock.

Next, FIG. 11 is an explanatory diagram showing signal waveforms of the synchronization system in the third embodiment.

With respect to the code sequence length L of the despread signal S2 shown at 121 in the figure, the interaction area of the convolver in this embodiment is 2L as shown at 122. For the sake of explanation, the rising edge of a certain code generation timing signal S6 is set to t = 0.

When code synchronization is established, t
= 2 kL (k = 0,1,2 ...), PN0 and PN0 _*
The signs of are in agreement within the interaction area of the convolver as shown at 123. Further, as indicated by 124, t = (2
Also in k + 1) L, the signs of PN0 and PN0 _* match in the interaction area of the convolver.

Therefore, the correlation peak output S4 is obtained at the cycle L as shown at 125, and thus becomes a signal having the same cycle as the code generation timing signal S6 at 126. Therefore, according to the present embodiment, since it is not necessary to modulate the reference code as in the conventional case, the correlation peak signal does not disappear when the synchronization is lost, and the synchronization can be established from any initial phase difference.

Further, according to the present embodiment, the synchronization pilot signal has a doubled code sequence length, so that the process gain is doubled, and thus the distance characteristic is also improved by 2 ^1/2 times. In particular, wireless LA using spread spectrum communication
In the case of configuring the N system, in the multi-cell configuration as shown in FIG. 4, by using the synchronization method of the present embodiment, BS34, BS35,
Code synchronization can be established between S35 and BS36, and the effect of preventing interference between different cells can be obtained.

FIG. 12 is a block diagram showing a fourth embodiment of the present invention.

From the code generator 145, the despreading code PN _i having the code sequence length L and the local reference code PN0 _* are generated by the same clock. In addition, the code generation timing signal is a half of the beginning of the despread code and the reference code.
It is a signal having a period L / 2 indicating the position. Further, the code start signal is a signal representing the beginning of the despread code and the reference code.

In FIG. 12, SAW which is a correlation detector
The convolver 140 detects the correlation between the received IF signal processed by the high frequency unit and the reference spreading code used for despreading. The correlation signal is digitized by the peak detector 141 and output to the sign reset circuit 142 and the phase shift circuit 143.

When the SAW convolver 140 is used to perform convolutional correlation, the code reset circuit 142 uses the code start signal as the delay amount obtained by doubling the phase delay of the peak signal with respect to the code generation timing of the reference spreading code. As a reference, it is delayed and output as a code reset signal, and the reference code and despread code are reset to establish code synchronization. The received IF signal is despread by the despreading code and information is taken out.

Before the synchronous operation is started, the phase shift circuit 143 outputs the output of the reference signal generator 144 as it is as a code generator clock. When reception is started and a peak signal is obtained, the amount obtained by doubling the phase delay of the peak signal with respect to the output clock of the reference signal generator 144 is shifted from the reference clock to be the code generator clock, and clock synchronization is performed. To take.

Next, FIG. 13 is an explanatory view showing signal waveforms of the synchronization system in the fourth embodiment.

The interaction area of the convolver in this embodiment is L, which is the same as the code sequence length of the spreading code, as indicated by 151. For the sake of explanation, it is assumed that the rising edge of a certain code generation timing signal S6 'is t = 0. When the codes are synchronized, t = kL (k = 0, 1, 2, ...) And PN0
The signs of PN0 _* and PN0 _* coincide within the interaction area of the convolver as shown at 152.

Further, as indicated by 153, t = (k + 1
Even in / 2) L, the signs of PN0 and PN0 _* match in the interaction area of the convolver. Therefore, the correlation peak output S4 is obtained at the cycle L / 2 as indicated by 154, and thus becomes a signal having the same cycle as the code generation timing signal S6 'of 155. Therefore, according to the present embodiment, since it is not necessary to modulate the station reference code as in the conventional case, the correlation peak signal at the time of synchronization loss does not disappear, and the synchronization can be established from any initial phase difference. .

Furthermore, according to the present embodiment, the frequency of the signal input to the code reset circuit 142 is double that of the conventional signal, and as a result, the time required for establishing synchronization is reduced to half that of the conventional signal. is there. Therefore, when the information is framed and transmitted as shown in FIG. 9, the preamble period can be shortened by using the synchronization method of the present embodiment, and as a result, the throughput of the communication system can be improved.

FIG. 14 is a block diagram showing a fifth embodiment of the present invention.

In FIG. 14, the SAW which is the correlation detector
The convolver 170 detects the correlation between the received IF signal processed by the high frequency unit and the reference spreading code used for despreading. The correlation signal is digitized by the peak detection circuit 171 and output to the phase difference detection circuit 176.

The phase difference detection circuit 176 is the peak detector 1
The phase difference between the peak signal and the code timing signal output from 71 and the phase difference between the peak signal and the output clock of the reference signal generator 174 are detected a plurality of times and output to the phase difference calculation circuit 177. A plurality of times may vary depending on the situation, but it is usually preferable to use an appropriate value of about 2 to 5 times.

The phase difference calculation circuit 177 uses the output of the phase difference detection circuit 176 to calculate the sign reset phase and the shift amount of the clock phase shift.

These phase calculation methods include, for example, a method of taking an average from a plurality of detected phase differences, a method of selecting the most phase difference among a plurality of detected phases, and the like. When the convolutional correlation is performed using 170, the code phase is reset by the code phase obtained by doubling the phase difference calculated in this way, and the clock is shifted by the clock phase shift amount obtained by doubling the code phase. .

The code reset circuit 172 receives the code reset signal and synchronizes the reference code and the despreading code with each other.

Before the synchronous operation is started, the phase shift circuit 173 outputs the output of the reference frequency generator 174 as it is as the code generator clock. When reception is started and a peak signal is obtained, a clock phase shift amount is received, and a reference signal is shifted to obtain a code generator clock, and clock synchronization is achieved.

Therefore, even when a synchronous circuit is formed by digital processing using the correlation signal from the SAW convolver 170, the jitter and the like of the correlation peak signal itself are averaged by various fluctuation factors around the SAW convolver, and the synchronization is accurately performed. It becomes possible to take

Here, as in the third embodiment, the code generator 1
75 to despread code PN _i with code sequence length L and code length 2L
If the reference code PN0 _* of 1 is generated by the same clock, as shown in FIG.
The peak signal generated by 71 has the same period as the code generation timing signal of the reference code. Therefore, even if the phase difference detection circuit 176 detects the peak signal and the code generation timing signal a plurality of times, it is possible to prevent the time required for synchronization acquisition from becoming long.

[0078]

As described above, according to the present invention,
The information modulation of the local reference signal as in the prior art is unnecessary, and the synchronization pull-in from any initial phase difference is possible. Furthermore, by using a code having a code sequence length that is twice as long as the information spreading code as the synchronizing code, the distance characteristic of the synchronizing signal is also improved. For example, in a wireless LAN system of a multi-cell configuration by spread spectrum communication, between base stations. It is possible to obtain the code synchronization of, and the effect of preventing mutual interference between different cells can be obtained.

Further, according to the present invention, it is possible to carry out synchronization pull-in from any initial phase difference without the conventional information modulation of the local spreading code.

According to claim 6 of the present invention, the PLL
Since the frequency of the signal input to is doubled as compared with the conventional one, there is an effect that the time required for phase pull-in can be reduced to half of the conventional one without using a high-speed PLL. Therefore, when the information is framed and transmitted, the preamble period can be shortened and the throughput of the communication system can be improved.

Further, according to claim 7 of the present invention, the frequency of the signal input to the code resetting means is doubled as compared with the conventional one, so that there is an effect that the time required for establishing the synchronization is reduced to half of the conventional one. . Therefore, when the information is framed and transmitted, the preamble period can be shortened and the throughput of the communication system can be improved.

According to claim 9 of the present invention, the phase difference between the peak signal output from the peak detecting means and the code timing signal is detected a plurality of times, the average value of the phase difference is calculated, and the synchronous reset is performed. Therefore, for example, even when a synchronous circuit is formed by digital processing using a correlation signal from a device such as a SAW convolver, the jitter and the like of the correlation peak signal itself due to various fluctuation factors around the SAW convolver are averaged and the accuracy is improved. It is possible to synchronize well.

Further, according to the present invention, it is possible to speed up the synchronization. Further, according to the present invention, spread spectrum communication resistant to noise can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a signal waveform of a synchronization system in the first embodiment.

FIG. 3 is an explanatory diagram showing a signal waveform of a synchronization system in the first embodiment.

FIG. 4 is an explanatory diagram showing a multi-cell configuration in a wireless LAN system.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a signal waveform of a synchronization system in the second embodiment.

FIG. 7 is an explanatory diagram showing a signal waveform of a synchronization system in the second embodiment.

FIG. 8 is an explanatory diagram showing a signal waveform of a synchronization system in the second embodiment.

FIG. 9 is an explanatory diagram showing a transmission signal for converting information into a frame and transmitting the frame.

FIG. 10 is a block diagram showing a third embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a signal waveform of a synchronization system in the third embodiment.

FIG. 12 is a block diagram showing a fourth embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a signal waveform of a synchronization system in the fourth embodiment.

FIG. 14 is a block diagram showing a fifth embodiment of the present invention.

FIG. 15 is a block diagram showing a configuration of a conventional example.

FIG. 16 is an explanatory diagram showing signal waveforms in the synchronization method of the conventional example.

FIG. 17 is an explanatory diagram showing a signal waveform at the time of synchronization pull-in in the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... Synchronization part, 3 ... Demodulator, 4 ... SAW convolver, 5 ... Detector, 6 ... Peak detector, 7 ... PLL, 8 ... Code generator.

Claims (11)

[Claims] 1. In a spread spectrum communication system for transmitting an information spreading code and a synchronization spreading code, a code generator for generating a local reference signal and a code generation timing signal, and a correlation between the local reference signal and a received signal. And a control means for controlling the code generator according to the phase difference between the correlation peak output of the correlation means and the code generation timing signal, and the spreading code for synchronization and the local reference signal A spread spectrum communication system, wherein the code period is twice the code generation timing signal period. 2. In a spread spectrum communication system for transmitting an information spreading code and a synchronization spreading code, a code generator for generating a local reference signal and a code generation timing signal, and a correlation between the local reference signal and a received signal. And a clock adjusting unit that adjusts a clock input to the code generator according to a phase difference between the correlation peak output of the correlating unit and the code generation timing signal. A spread spectrum communication system, wherein the code period of the local reference signal is twice as long as the code generation timing signal period. 3. The spread spectrum communication system according to claim 1, wherein the code period of the synchronization spreading code is twice the code period of the information spreading code. 4. The spread spectrum communication system according to claim 1, wherein the code period of the synchronization spreading code is the same as the code period of the information spreading code. 5. The spread spectrum communication system according to claim 3, wherein the synchronization spreading code is a code that is not modulated by data. 6. The phase adjusting loop circuit according to claim 2, wherein the clock adjusting means is a phase locked loop circuit including a phase comparator, a loop filter, and a voltage controlled oscillator. Spread spectrum communication system. 7. In a spread spectrum communication system for transmitting an information spreading code and a synchronization spreading code, a code generator for generating a local reference signal and a code generation timing signal, and a correlation between the local reference signal and a received signal. A correlating means, a peak detecting means for detecting a correlation peak output of the correlating means, a reference signal generating means for generating a signal having a frequency substantially equal to a clock of a received signal, and a peak signal output from the peak detecting means. And a code reset means for resetting the code generator according to the phase difference between the code generation timing signal and the reference signal according to the phase difference between the peak signal output from the peak detection means and the code generation timing signal. Phase shift means for shifting the phase of the output of the signal generation means, wherein the code generation timing signal period is for synchronization Spread spectrum communication system, which is a half of the code period of the diffusing code and the local reference signal. 8. The code generator according to claim 7, wherein the code generator outputs a code start signal together with the code generation timing signal, and the code reset means responds to a phase difference between the peak signal and the code generation timing signal. Then, the code generator is reset with the code start signal as a reference, and the code start signal period is twice the code generation timing signal period. 9. In a spread spectrum communication system for transmitting an information spreading code and a synchronization spreading code, a code generator for generating a local reference signal and a code generation timing signal, and a correlation between the local reference signal and a received signal. A correlating means, a peak detecting means for detecting a correlation peak output of the correlating means, a reference signal generating means for generating a signal having a frequency substantially equal to a clock of a received signal, and a peak signal output from the peak detecting means. And a code generation timing signal, and a phase difference detection means for detecting a phase difference between a peak signal and an output clock of the reference signal generation means a plurality of times, and an output of the phase difference detection means. A phase difference calculating means for calculating the reset phase and the shift amount of the clock phase shift, and the code generator according to the output of the phase difference calculating means. Code reset means and, a spread spectrum communication system characterized by comprising a phase shifting means for shifting the phase of the output of said reference signal generating means in response to an output of said phase difference calculation means for setting. 10. The spread spectrum communication system according to claim 1, wherein the correlating unit is a surface acoustic wave convolver. 11. A generator for generating a reference code and a timing signal, a correlator for correlating a received signal and a reference code, and a despreader for despreading a received signal according to a correlation output of the timing signal and the correlator. A spread spectrum receiving apparatus, characterized in that the cycle of the timing signal is half the cycle of the reference code.