JPH0614006A - Spread spectrum communication system and transmitter-receiver - Google Patents

Abstract

PURPOSE:To prevent the S/N from deteriorating and to save power consumption by detecting a communication quantity between a base station and a terminal equipment and controlling a band of a spread spectrum signal in response to the communication quantity detection output. CONSTITUTION:Plural terminal equipments 21-2n are provided to a base station 1 of the spread spectrum communication system. The base station 1 detects the communication quantity of each terminal equipment to discriminate whether or not the communication quantity is larger than a prescribed threshold level. When the communication quantity is larger than the threshold level, it is instructed to a terminal equipment to widen a band width of a spread spectrum signal and each terminal equipment selects a clock so that the inverse processing is implemented for the band. When the communication quantity is less than the threshold level, it is instructed to the terminal equipment that the band width for the spread spectrum signal is made narrow and each terminal equipment selects the clock. The deterioration in the S/N is prevented and the power consumption is reduced by controlling the band width of the spread spectrum signal in response to the communication quantity in this way.

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 a spread spectrum transmitter / receiver, and more particularly to a spread spectrum communication system and a transmitter / receiver capable of adaptively changing the clock rate of a spread spectrum signal.

[0002]

2. Description of the Related Art In a spread spectrum communication system,
The carrier is modulated (spread) by a pseudo noise (PN) code sequence on the transmitter side, and the receiver side undergoes a correlation (despread) process by a PN code generated by a code generator having the same structure as the transmitter, and then the base. Data is obtained by band demodulation. In the case of such a spread spectrum method, since the power density per unit frequency is low, even if it looks like a slight increase in noise for other communication, if the communication volume increases, the S / N (signal to noise ratio) will increase. However, there is a problem that it becomes a hindrance when communicating using a desired signal.

Further, in order to solve the problem, if the frequency band of the spread spectrum signal is widened and the power density per unit frequency is lowered, it is necessary to speed up the clock on the receiving device side, resulting in a large power consumption. Therefore, when the communication amount is small, the clock is unnecessarily increased, resulting in a waste of power.

FIG. 13 shows a modulator of a direct spread spectrum transmission system. In FIG. 13, the carrier fc from the carrier generator 201 is PSK.
The (phase shift keying) modulator 202 is supplied, and the carrier fc is two-phase PSK modulated by the transmission signal (binary modulation signal) d (t) from the input terminal 203.
The PSK modulation signal from the PSK modulator 202 is supplied to the spread modulator 204. This spread modulator 204 has a PN
The spread signal p (t) is supplied from the PN generator 205 that generates a (pseudo noise) code sequence, and the PSK modulated signal is spread modulated.

FIG. 14A shows an example of the signal change of the transmission signal d (t), and FIG. 14B shows the frequency spectrum of the PSK modulation signal output from the PSK modulator 202. In FIG. 14, Td is the period of the transmission signal d (t), and the frequency width Bd is 1 / Td. Further, A of FIG. 15 shows an example of a signal change of the spread signal p (t), and B of FIG.
Indicates the frequency spectrum of the spread spectrum signal output from the spread modulator 203. Tp is the spread signal
It shows the period of p (t). As is clear from FIG. 15, since the period Tp of the spread signal p (t) is short and changes greatly with respect to the period Td of the transmission signal d (t), the spread modulator 203 spreads the frequency spectrum in a wide band. (Frequency width B
p = 1 / Tp).

FIG. 16 shows a demodulation section of a direct spread system reception system. In the figure, an antenna and the like (not shown)
The spread spectrum signal received at the terminal 211 is supplied to a bandpass filter (BPF) 212 having a center frequency fc and a passband of 2Bp,
Components other than the required band are removed. The spread spectrum signal extracted by the BPF 212 is supplied to the despreader 213 including a multiplier, for example. The despreader 213 is supplied with the same signal p (t) ′ as the above-described spread signal p (t) from the PN (pseudo noise) generator 214 to perform despreading.
In this case, the signal p (t) 'from the PN generator 214 is controlled so that its phase matches the phase of the spread signal p (t), and p (t) p (t)' =
It is set such that p (t) ² = 1.

The output signal from the despreader 213 is supplied to a BPF (bandpass filter) 215 having a center frequency of fc and a passband of 2Bd, and a PSK modulated signal is extracted. This PSK modulated signal is a PSK demodulator 216.
To be demodulated to obtain the original signal d (t)
Is taken out from the output terminal 217. As described above, the spread spectrum communication is a method of spreading the frequency spectrum in a wide band to perform communication, and has characteristics of excellent confidentiality and interference resistance.

[0008]

By the way, in order to maintain a normal spread spectrum communication system, it is necessary that the received power at the base station side is uniform in the communication channel with each mobile station. Is. Therefore, the transmission power to the base station must be controlled according to the movement of the mobile station and changes in the external environment, and the control accuracy must be 0.5 dB or less near the upper limit of the system line capacity. Is theoretically calculated. However, it is difficult to realize this accuracy, and it has been a problem of the code division multiplexing system by the spread spectrum communication system.

Here, in A, B, and C of FIG. 17, a signal sent from the input terminal 211 of FIG. 16 to the BPF 212, a signal sent from the despreader 213 to the BPF 215, and BPF2.
Each frequency spectrum of the signal sent from 15 to the PSK demodulator 216 is shown. In FIG. 17A, a narrow band interference component is mixed in a spread spectrum signal having a bandwidth of 2Bp. The power of the signal at this time is P _r ,
When the power of the interference wave is P _I , the signal-to-interference wave power ratio (S / I) _{A at A} is (S / I) _A = P _r / P _I. In FIG. 17B, the relationship is the reverse of that of the above A, and the result becomes like C by passing through the BPF 215 having a bandwidth of 2Bd. The signal-to-interference wave power ratio (S / I) _C here is (S / I) _C = (P _r / P _I ) (B p / B _d ) = (S / I) _A (B p / B d) = ( S / I) _A G. Here, G is called a processing gain, and G = Bp /
Bd. That is, by applying spread spectrum modulation to the input signal, the signal-to-interference wave power ratio becomes (S /
As a result, only G is improved from I) _A to (S / I) _C , and when such a spread spectrum system is used, the effect of being less susceptible to the interference signal component can be obtained.

Next, consider the case where white noise (white noise) is included instead of the narrow band interference signal component. Considering the same as above, the spectrum of the signal of each part in FIG.
It becomes like A, B, C of 8. (S / N) _A , which is the S / N of A in FIG. 18, is (S / N) _A = P _r / (N ₀ .2Bp) where N ₀ is the power of the white noise signal component. Similarly, the S / N of C in FIG. 18 (S / N
N) _C becomes (S / N) _A = P _r / (N ₀ .2Bd) = (S / N) _A (Bp / Bd) = (S / N) _A G, and in this case also, FIG. The result is similar to the case of the narrow band interference signal described with reference to FIG.

In the case of communication in the same system using the same PN code, all communication performed by other terminals becomes noise close to white noise, and narrow band interference occurs in communication other than spread spectrum communication. It becomes a component close to the signal component. That is, if the communication volume increases anyway, C in FIG.
Also, the noise indicated by each shaded area in C of FIG. 18 increases, which hinders communication.

To solve this problem, if Bp is increased to increase the processing gain G, that is, the band of the spread spectrum signal is widened, the spread signal p (t) 'in FIG.
It is necessary to speed up the clock when multiplying by and despreading, resulting in further consumption of power, and when G is not so large, waste occurs.

The present invention has been made in view of such circumstances, and S / N can be improved when the communication amount is large or when the transmission quality is poor, and when the communication amount is small or the transmission quality is high. In this case, it is an object of the present invention to provide a spread spectrum communication system and a transmission / reception apparatus that can save power and allow a margin for power control accuracy of a mobile station near the upper limit of communication line capacity.

[0014]

A spread spectrum communication system according to one aspect of the invention is a communication system in which a pseudo noise signal is superimposed on a transmission signal between a transmission device and a reception device to perform spread spectrum communication. By including means for detecting the amount of communication between the device and the receiving device, and means for changing the clock frequency of the pseudo noise signal according to the output from the communication amount detecting means, Solve the problem.

A spread spectrum communication system according to another invention is a communication system for performing spread spectrum communication by superimposing a pseudo noise signal on a transmission signal between a transmission device and a reception device. It is characterized by comprising transmission quality judging means for judging the transmission quality, and means for changing the clock frequency of the pseudo noise signal according to the transmission quality judged by the transmission quality judging means.

A spread spectrum transmitter / receiver according to still another invention is a transmission quality judging means for judging the transmission quality of a received signal, and a clock of a spreading code for transmission based on the transmission quality judged by this transmission quality judging means. The data synthesizing means for synthesizing the speed change data into the transmission signal and the clock control means for controlling the clock speed of the spreading code for transmission are provided.

A spread spectrum transmission / reception system according to still another invention is a transmission quality determination means for determining the quality of a received signal from the first spread spectrum transmission / reception apparatus, and a transmission quality determined by this transmission signal quality determination means. Control data creating means for creating clock control data for controlling the clock speed of the spread code for transmission of the first spread spectrum transmitter / receiver, and the clock control data created by this control data creating means are combined with the transmission signal. And a band-pass filter circuit capable of controlling the bandwidth to be passed along with the change of the clock speed of the spread code of the received signal from the first spread spectrum transmitter / receiver. From the received signal from the second spread spectrum transmitter / receiver. The first spread spectrum transmitter / receiver comprises data extraction means for extracting the control data and clock control means for controlling the clock speed of the spread code for transmission based on the clock control data extracted by the data extraction means. It is a thing.

[0018]

According to the spread spectrum communication system of the present invention, for example, by controlling the band of the spread spectrum signal according to the communication amount between the terminal and the base station, the band can be widened when the communication amount is large and the S / It is possible to prevent deterioration of N and to narrow the band to save power when the amount is small.

According to another invention, for example, by controlling the band of the spread spectrum signal according to the transmission quality of the received signal on the receiving side, deterioration of the S / N is prevented when the transmission quality is low, and saved when it is high. Electricity can be achieved.

According to still another aspect of the invention, for example, in the vicinity of the upper limit of the capacity of the communication line, the mobile station determines that the transmission quality is lower than a predetermined value, and changes the clock speed of the spreading code for transmission by changing the communication partner. The clock speed of the spread code for transmission is increased after the clock speed change data is combined with the transmission signal and transmitted in order to notify the. Therefore, the processing gain due to spread spectrum is improved, it becomes possible to have a margin in power control accuracy without lowering the data rate of communication data, and the high frequency power control circuit of the mobile station is made simple. And the line capacity can be brought closer to the theoretical upper limit.

According to still another aspect of the invention, for example, in the vicinity of the upper limit of the capacity of the communication line, the base station determines that the transmission quality is lower than a predetermined value, and increases the clock speed of the spreading code for transmission of the mobile station. The clock control data for controlling is generated, combined with the base station transmission signal, and transmitted.
In the mobile station, the clock speed of the spread code for transmission is increased based on the clock control data extracted from the received signal. Therefore, the processing gain due to spread spectrum is improved, it becomes possible to have a margin in power control accuracy without lowering the data rate of communication data, and the high frequency power control circuit of the mobile station is made simple. And the line capacity can be brought closer to the theoretical upper limit.

[0022]

1 is a block diagram showing a schematic configuration for explaining the basic concept of a spread spectrum communication system according to the present invention. Spread spectrum communication is performed using the same PN (pseudo noise) code sequence. I am assuming that

In FIG. 1, there are a plurality (n) of terminals 2 ₁ , 2 ₂ , ..., 2 _n for the base station 1 of the spread spectrum communication system. The communication status is grasped and the communication is carried out. When the number of terminals actually communicating exceeds a certain threshold, the processing gain G is increased, that is, the bandwidth of the spread spectrum signal is increased and the S / N is improved. Conversely, when the number of terminals that are communicating is small, the clock for despreading can be delayed by narrowing the bandwidth of the spread spectrum signal to the communicable width, thus saving power. Becomes

That is, in FIG. 2, A shows the distribution of the spectrum of the spread spectrum signal in the case of a normal communication amount, and the bandwidth is 2B _A. When the B 2 a large number of terminals communicating, also C represents the time number of terminals in communication is small, respectively, each of 2B _B the bandwidth of each case, 2
B _C. Relationship of each of these bandwidth is _{B B> B A> B C} .

As another application example, the S / N of the signal from each terminal is detected by the base station in the same system, and S / N is detected.
There is also a method of determining that the narrow band interference signal has increased because the communication volume of a completely different system has increased when N is rented out as a whole and similarly changing the spread spectrum signal bandwidth. For example, in the morning and in the evening, since the communication volume of the mobile phone increases, noise increases, which is detected to widen the bandwidth of the spread spectrum signal and increase the processing gain G to prevent the deterioration of S / N. , Is.

In any of the above cases, when varying the bandwidth of the spread spectrum signal, the base station instructs the terminal when, at what timing, and how much the bandwidth should be changed. , A clock must be prepared to despread the spread spectrum signal of that bandwidth. As for the plurality of types of clocks, a method of dividing the clocks, a method of holding a plurality of oscillators and switching with a switch, and the like can be considered.

FIGS. 3 and 4 show flowcharts of the above processes. First, in the first step S11 of FIG. 3, the base station detects the current communication amount T. In the next step S12, it is determined whether or not the communication amount T is larger than a predetermined threshold value T _{A. If} NO, the process proceeds to step S13, and if YES, the process proceeds to step S14. In step S14, the base station instructs each terminal as to when and how wide the bandwidth of the spread spectrum signal should be. Specifically, a signal including bandwidth switching instruction data is transmitted from the base station to each terminal. As shown in step S15, each terminal side switches the clock in response to the instruction from the base station so that the despreading process can be performed in that bandwidth.

In step S13, it is determined whether or not the detected current traffic amount T is smaller than another predetermined threshold value T _B (T _B <T _A ). If YES, step S16
Proceed to. In step S16, the base station instructs each terminal as to when and how narrow the bandwidth of the spread spectrum signal should be. In the next step S15, as described above, each terminal performs a process of switching the clock according to an instruction from the base station. N in step S13
When it is determined to be O, the communication amount T is between the two thresholds T _A and T _B (T _B ≦ T ≦ T _A ),
In step S17, the normal bandwidth is set. In this case, on the terminal side, when the previous clock is a clock corresponding to the above wide band width or narrow band width, it is switched to the clock corresponding to the original normal bandwidth.

In the case of detecting another communication amount and switching the bandwidth and clock, for example, a processing flow as shown in FIG. 4 can be considered. Steps S21 to S of FIG.
23 is different from the processing flow of FIG. 3 above, and the other steps S14 to S17 are the same as those in FIG.

In FIG. 4, the first step S21
Then, the base station detects the S / N value x of the signal from each terminal, determines in step S22 whether it is smaller than the first threshold x _A , and in the next step S23 it is larger than the second threshold x _B. Whether or not each is detected. YES in step S22
If NO, go to step S14; if NO, go to step S2
If NO in step S23, the process proceeds to step S16. If NO in step S23, the process proceeds to step S17.

Next, an example of each configuration on the base station side and the terminal side where such processing is performed is shown in FIGS. That is, FIG. 5 is a block circuit diagram showing a schematic configuration example on the base station side, and FIG. 6 is a block circuit diagram showing a schematic configuration example on the terminal side.

In FIG. 5, on the side of the base station, the signal transmitted from each terminal is received by the receiving antenna 31, and the received high frequency (RF) signal is sent to the frequency conversion circuit 32 to output the intermediate frequency (IF). Convert to signal. In the case of digital processing configuration, A / D conversion is also performed here. It is then sent to several demodulation blocks 33 ₁ , 33 ₂ , ... On the base station side, some demodulators 3
It has 3 ₁ , 33 ₂ , ... Each demodulator 33 ₁ ,
33 ₂ , ... Performs despreading processing using the PN code sequence from the pseudo noise (PN) generation circuit 38, and then
Performs data demodulation. If the communication data is encoded, it is decoded here. The demodulated data is sent to the data processing / control circuit unit 34 such as a so-called baseband processor. In the data processing / control circuit unit 34, data processing, transmission / reception control, clock rate switching control of the pseudo noise (PN), and the like are performed.

For the transmission from the base station to each terminal, the data processing / control circuit section 34 such as a baseband processor sends the desired data to the modulation sections 35 ₁ , 35 ₂ ,.
After performing modulation or coding here, pseudo noise (P
N) Spreading processing is performed with the PN code from the generation circuit 39. The signal is converted (amplified) into a transmission output signal by the high power amplifier 36, and a radio wave is transmitted from the transmission antenna 47 to each terminal. In the case of the present invention, data processing /
The control circuit unit 34 changes the communication amount T to, for example, the demodulation unit 3
The number of operating circuits among 3 ₁ , 33 ₂ , ... Is grasped by monitoring and the like, and the despreading is performed by each demodulation unit 33 ₁ , 33 ₂ , ... In accordance with the flowchart shown in FIG. , Or the clock of the pseudo noise (PN) code sequence at the time of spreading by each of the modulators 35 ₁ , 35 ₂ , ...

As another example, when performing clock control according to the S / N value of the signal from each of the terminals, for example, the S of the received signal is received by each of the demodulation units 33 ₁ , 33 ₂ ,. /
N is detected, and the detection signal is sent to the data processing / control circuit unit 34 such as a baseband processor to change the clock of the PN code at the time of despreading or spreading.

Next, the terminal side shown in FIG. 6 is also the same. The RF signal received by the receiving antenna 41 is sent to the frequency conversion circuit 42 to be converted into an IF signal, and the demodulation section 43 carries out a PN (pseudo noise) code. Demodulation processing including despreading processing by the data processing / control circuit unit 44 such as a baseband processor.
To perform data processing and transmission / reception control. The transmission data from the data processing / control circuit unit 44 is sent to the modulation unit 45, where it is subjected to modulation, PN coding processing, etc., and is converted (amplified) into a transmission signal by the high power amplifier 46, and the transmission antenna 47. Is transmitted to the base station via. On the terminal side, the data processing / control circuit unit 44 switches the PN clock for despreading in the demodulation unit 43 or the spreading process in the modulation unit 45 in response to the clock switching instruction signal from the base station side.

Here, in FIG. 7, the modulators 33 ₁ , 33
₂ shows a concrete example of 45. This Figure 7
Performs BPSK (binary phase modulation) on the data and then
An example of conversion into a spread spectrum signal is shown. Figure 7
In, the transmission data from the data processing / control circuit unit 34 (or 44) is sent to the multiplier 53 via the input terminal 51 and is multiplied by the carrier signal from the input terminal 52. It becomes a BPSK modulated signal. Next, this BPSK signal is multiplied by the PN code generated by the PN code generator 54 by the multiplier 57, and the spread spectrum signal is taken out from the output terminal 58.
Further, in the embodiment of the present invention, the PN code generator 54
, One of the clocks from the plurality of clock oscillators 56 ₁ , 56 ₂ , ... Is switched and selected by the changeover selection switch 55. The changeover selection switch 55 is controlled by the data processing / control circuit unit 34 detecting the communication amount and the like and supplying the signal to the control terminal 57. Also, on the terminal side,
The data processing / control circuit unit 44 sends a control signal corresponding to the clock switching instruction data transmitted from the base station to the terminal 57.
To send to. In addition, spreading on the base station side and the terminal side,
Of course, the same clock must be selected for despreading.

According to the embodiment as described above, by controlling the band of the spread spectrum signal according to the communication amount between the terminal and the base station, S /
It is possible to prevent deterioration of N and save power when the amount is small.

Next, another embodiment of the present invention will be described with reference to FIG. This embodiment is an example of performing spread spectrum communication between a base station and a mobile station. Figure 8
FIG. 3 is a block diagram showing a configuration of a mobile station. In the figure, at the input terminal, a digital audio signal or the like is transmitted signal d.
It is supplied as T (t), and this transmission signal dT (t)
Is sent to the clock rate change information synthesizer 101. When it is necessary to change the clock rate of the transmission spreading code, the clock rate change information synthesizer 1 synthesizes the transmission signal dT (t) and the clock rate change information.

The transmission signal output from the clock rate change information synthesizer 101 is error correction coded by the encoder 102, and then the PSK (phase shift keying) modulator 10 is provided.
3 is supplied. The carrier fc is supplied to the PSK modulator 103 from a carrier generator (not shown), and the carrier fc is modulated by the two-phase phase shift keying (BPSK) by the transmission signal.

PSK output from PSK modulator 103
The modulated signal is supplied to the spread modulator 104. The spread code p (t) is supplied to the spread modulator 104, whereby the PSK modulation signal is spread modulated. The spread spectrum signal output from the spread modulator 104 is the frequency converter 1
After the center frequency is converted to high frequency by 07,
The signal is supplied to the transmission / reception antenna 110 via the output amplifier (high power amplifier) 108, the antenna duplexer 109, and transmitted to the base station.

The spread spectrum signal from the base station is transmitted from the transmitting / receiving antenna 110 to the antenna duplexer 109,
It is supplied to a frequency converter 112 via an amplifier (low noise amplifier) 111, and the center frequency is frequency-converted to the operating frequency of the demodulation unit 113. The spread spectrum signal output from the frequency converter 112 is supplied to the demodulation unit 113 to be subjected to despreading and PSK demodulation.

The error-correction-coded signal output from the demodulation unit 113 is subjected to error correction processing in the decoding unit 114 and supplied to the receiving system in the subsequent stage. Further, the input signal and the output signal of the decoding unit 114 are supplied to the BER (bit error rate) detection unit 115, and the BER is calculated and determined. Here, in the upper limit of the communication line capacity of the system,
The BER of the received signal of the mobile station may exceed a threshold value of about 3.0 × 10.

When the BER detector 115 exceeds the threshold value of about 3.0 × 10, the BER detector 115 controls the spread code clock generator 106 to increase the clock rate of the spread code applied to the transmission signal. To be

The present embodiment is configured as described above, and since the transmission quality of the received signal deteriorates at the upper limit of the communication line capacity, the transmission code from the transmission spread code clock generator 106 is controlled by the BER detection unit 115. The spread code clock rate is increased. Therefore, at the upper limit of the communication channel capacity, the cycle Tp of change of the spreading code p (t) for transmission becomes short,
The processing gain of spread spectrum is improved, and there is a margin in power control accuracy.

FIG. 9 shows the relationship between the clock rate and the processing gain. Let G be the processing gain and Bd (the signal period is Td) be the data rate of the transmission signal. In the case of FIG. 9A, if the clock rate of the spreading code is B ₁ (cycle T ₁ ), G = B ₁ / Bd, and in the case of FIG. 9B, the clock rate of the spreading code is B ₂ (Period T ₂ ) G = B
₂ / Bd. By increasing the clock rate of the spreading code from B ₁ to B ₂ , the signal is spread over a wider band, and the processing gain is improved by B ₂ / B ₁ .

FIG. 10 shows the relationship between the rate of increase in the clock rate of the spreading code for transmission and the increase in the margin of power control accuracy that occurs at this time. Therefore, as described above, by increasing the clock rate of the transmission spread code near the upper limit of the communication line capacity, it is possible to allow the control accuracy of the output high power amplifier 108 to have a margin as shown in FIG.

In the spread spectrum communication system, in order to keep about 90% of the theoretical communication line capacity, 0.5d
It has been calculated that B-precision power control is required. For example, the spread code clock rate is 1.2.
By doubling it, a margin of 0.8 dB is generated, so it is possible to maintain the line capacity by power control with 1.3 dB accuracy, and to make the power control circuit of the mobile station transmitter simple Will be able to.

Incidentally, even if not mentioned above, the processing gain increases by increasing the clock rate of the spreading code for transmission, and therefore, under the control of the BER detection unit 115, the gain of the output amplifier 108 does not deteriorate below the required BER. May be reduced. Thereby, power consumption can be saved.

Next, referring to FIGS. 11 and 12,
Still another embodiment of the present invention will be described. FIG. 11 is a block diagram showing the configuration of the base station. In the figure,
Spread spectrum signals from mobile stations are transmitted and received by antenna 1
The signal is supplied from the antenna 30 to the frequency converter 132 via the antenna duplexer 129 and the amplifier (low noise amplifier) 131, and the center frequency is frequency-converted to the operating frequency of the demodulator 133. The spread spectrum signal output from the frequency converter 132 passes through the band pass filter 136 having the bandwidth of the spread spectrum signal and is supplied to the demodulation unit 133.
Despreading and PSK demodulation are performed.

The error-correction-coded signal output from the demodulation unit 133 is subjected to error correction processing in the decoding unit 134 and supplied to the receiving system in the subsequent stage. Further, the input signal and the output signal of the decoding unit 134 are supplied to the BER (bit error rate) detection unit 135, and the BER is calculated and determined. Here, in the upper limit of the communication line capacity of the system,
The BER of the received signal of the base station may exceed a threshold value of about 3.0 × 10.

Mobile station spreading code clock control information creation unit 1
From 37, clock rate control information for controlling the clock rate of the spreading code for transmission of the mobile station is created and output. When the BER detection unit 135 detects that the threshold value exceeds about 3.0 × 10, the BER detection unit 135 controls the creation unit 137, and the spread code for transmission of the mobile station is controlled as mobile station spread code clock control information. Information is created to increase the clock rate. At this time, the clock control information creation unit 137 controls the band pass filter 136,
The pass band width of the filter 136 is switched to the one corresponding to the clock rate designated by the control information in accordance with the next mobile station transmission.

In FIG. 11, a transmission signal d such as voice is transmitted.
T (t) (which is already a digital signal) is supplied to the clock rate control information synthesizer 121. The synthesizer 121 is supplied with the control information of the mobile station transmission spreading code created by the creating unit 137, and transmits the transmission signal dT.
is synthesized into (t). The transmission signal output from 121 is subjected to error correction coding by the encoder 122, and then the PSK modulator 1
23. A carrier fc is supplied from a carrier generator (not shown) to the PSK modulator 123, and the carrier fc is two-phase PSK modulated by a transmission signal.

PSK output from PSK modulator 123
The modulation signal is supplied to the spread modulator 124. The spread code p (t) is supplied to the spread modulator 124, whereby the PSK modulation signal is spread modulated. The spread spectrum signal output from the spread modulator 124 is the frequency converter 1
After the center frequency is converted to a high frequency by 27,
It is supplied to the transmission / reception antenna 130 via the output amplifier (high power amplifier) 128, the antenna duplexer 129, and transmitted to the mobile station.

FIG. 12 is a block diagram showing the structure of the mobile station. 12, parts corresponding to those in FIG. 8 are designated by the same reference numerals, and detailed description thereof will be omitted. The received signal from the base station is processed up to the decoding unit 114 exactly as in the case of FIG. The reception signal combined with the mobile station transmission spread code clock rate control information output from the decoding unit 114 is supplied to the clock control information extraction unit 116. The signal dR (t) from which the clock control information has been removed, which is output from the extraction unit 116, is supplied to the receiving system in the subsequent stage.

The clock control information extracted by the extraction unit 116 is supplied to the spread code clock generator to control the clock rate of the spread code for transmission. Other configurations of the mobile station in FIG. 12 are the same as those in the example in FIG.

In the configuration of such an embodiment, since the transmission quality of the received signal of the base station deteriorates at the upper limit of the communication channel capacity, the clock of the spread code for transmission of the mobile station is output according to the output of the BER detection unit 135 of the base station. Clock control information for increasing the rate is created, and this is combined with the transmission signal dT (t) and transmitted to the mobile station. In the mobile station which has received this, the clock rate of the spread code for transmission from the spread code clock generator for transmission 106 is increased by the clock control information extracted by the clock control information extraction unit 116. When the base station receives the signal from the mobile station whose clock of the spread code is changed, the bandwidth of the band pass filter 136 controlled by the clock control information creation unit 137 becomes the clock rate of the spread code for transmission of the mobile station. The demodulation unit 133 correctly performs despreading and demodulation.

By performing the control as described above, the cycle Tp of the change of the spreading code p (t) for transmission is shortened at the upper limit of the communication line capacity, the processing gain of the spread spectrum is improved, and the power control accuracy is improved. Has a margin,
Similar to the example of FIG. 8, the structure of the power control circuit of the mobile station can be simplified.

The present invention is not limited to the above-mentioned embodiment, and for example, the processing gain is increased by increasing the clock rate of the spreading code for transmission.
Based on the clock control information detected by the extraction unit 30,
The gain of the output amplifier 8 may be reduced to such an extent that it does not become worse than the required BER. Thereby, power consumption can be saved. In the above embodiment, the BER
However, the transmission quality may be determined using an S / N detection circuit.

Further, in the above embodiment, the two-phase PSK modulation is used as the modulation method, but other modulation methods such as QPSK may be used.

[0060]

As is apparent from the above description, according to the spread spectrum communication system of the present invention, the communication amount between the transmitting device and the receiving device is detected, and this communication amount detection output is output. Accordingly, since the clock frequency of the pseudo noise signal for spread spectrum is changed, for example, when there is a large amount of communication between the base station and the terminal, the clock rate is increased to widen the spread spectrum signal band and S
It is possible to prevent deterioration of / N and reduce the clock rate to narrow the spread spectrum signal band when the communication amount is small, thereby achieving power saving.

Further, according to another invention, since the clock frequency of the pseudo noise signal is changed according to the transmission quality of the received signal, it is possible to effectively prevent the deterioration of S / N and save power. it can.

Next, according to a spread spectrum transmission / reception apparatus according to still another invention, for example, in the vicinity of the upper limit of the capacity of the communication line, the mobile station determines that the transmission quality is lower than a predetermined value, and the spread code for transmission is transmitted. The clock rate of the spread code for transmission is increased after the clock rate change data is combined with the transmission signal and transmitted in order to notify the other party of the change of the clock rate. Therefore, the processing gain due to spread spectrum is improved, it becomes possible to have a margin in power control accuracy without lowering the data rate of communication data, and the high frequency power control circuit of the mobile station is made simple. And the line capacity can be brought closer to the theoretical upper limit.

According to still another aspect of the invention, for example, in the vicinity of the upper limit of the capacity of the communication line, the base station determines that the transmission quality is lower than a predetermined value, and raises the clock rate of the spreading code for transmission of the mobile station. The clock control data for controlling is generated, combined with the base station transmission signal, and transmitted. In the mobile station, the clock rate of the spread code for transmission is increased based on the clock control data extracted from the received signal. Therefore, the processing gain due to spread spectrum is improved, it becomes possible to have a margin in power control accuracy without lowering the data rate of communication data, and the high frequency power control circuit of the mobile station is made simple. And the line capacity can be brought closer to the theoretical upper limit.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a transmission side and a reception side for explaining an embodiment of a spread spectrum system according to the invention.

FIG. 2 is a spectrum diagram used for explaining the operation of the embodiment.

FIG. 3 is a flowchart used for explaining the operation of the embodiment.

FIG. 4 is a flowchart used for explaining another operation of the embodiment.

FIG. 5 is a transmission side (base station side) of the communication system of the embodiment.
3 is a block diagram showing a specific example of the configuration of FIG.

FIG. 6 is a block diagram showing a specific example of a configuration of a receiving side (terminal side) of the communication system of the example.

FIG. 7 is a block circuit diagram showing a specific configuration example of a modulation block circuit diagram used in the embodiment.

FIG. 8 is a block diagram showing a configuration of a mobile station according to another embodiment of the invention.

FIG. 9 is a diagram for explaining a processing gain of spread spectrum communication.

FIG. 10 is a diagram showing a relationship between an increase in the clock rate of the spread code for transmission and a margin of power control accuracy which increases accordingly.

FIG. 11 is a block diagram showing a specific example of the configuration of a base station.

FIG. 12 is a block diagram showing a specific example of the configuration of a mobile station.

FIG. 13 is a diagram showing a configuration of a direct diffusion modulation unit.

FIG. 14 is a diagram showing a signal change and a frequency spectrum in the PSK modulator.

FIG. 15 is a diagram showing a signal change and a frequency spectrum in a direct spread spectrum modulator.

FIG. 16 is a diagram showing a direct spread spectrum demodulation unit.

FIG. 17 is a diagram showing a frequency spectrum of each unit on the receiving device side when a narrowband interference signal component is included.

FIG. 18 is a diagram showing a frequency spectrum of each unit on the receiving device side when a white noise signal component is included.

[Explanation of symbols]

1 ... Base station 2 ₁ , 2 ₂ , ... Terminal (mobile station) 31, 41 ... Receiving antenna 32, 42 ... Frequency conversion circuit 33 ₁ , 33 ₂ , ..., 43 ... Demodulation unit 34, 44 ... Data processing / control circuit 35 ₁ , 35 ₂ , ..., 45 ... Modulation unit 36, 46 ... ( High power) amplifier 37, 47 ... Transmission antenna 38, 39 ... Pseudo noise generating circuit 53, 57 ... Multiplier 54 ... PN (pseudo noise) code generator 56 ₁ , 56 ₂ , ..... clock oscillator 57 .. control signal input terminal

Claims (12)

[Claims] 1. In a communication system for performing spread spectrum communication by superimposing a pseudo noise signal on a transmission signal, means for detecting the communication amount of the transmission signal, and the pseudo noise according to the output from the communication amount detecting means. And a means for changing the clock frequency of a signal. 2. In a communication system for carrying out spread spectrum communication by superimposing a pseudo noise signal on a transmission signal, a transmission quality judgment means for judging the transmission quality of the reception signal, and a transmission quality judged by this transmission quality judgment means. And a means for changing the clock frequency of the pseudo noise signal in response thereto. 3. The spread spectrum communication system according to claim 2, wherein said transmission quality judging means comprises S / N detecting means for said received signal. 4. The spread spectrum communication system according to claim 2, wherein said transmission quality judging means comprises bit error rate detecting means for said received signal. 5. In a spread spectrum transmission / reception apparatus for transmitting a transmission signal by superimposing a transmission spreading code on the transmission signal and receiving the transmission signal on which the transmission spreading code is superimposed, a transmission quality judging means for judging the transmission quality of the reception signal. And a spread spectrum transmission / reception device which controls the clock rate of the transmission spread code based on the transmission quality determined by the transmission quality determination means. 6. A spread spectrum transmitter / receiver for transmitting a transmission signal by superimposing a transmission spreading code on the transmission signal and receiving the transmission signal on which the transmission spreading code is superimposed, and detecting a communication amount of the transmission signal. Means for controlling the clock rate of the spread code for transmission according to the output from the communication amount detecting means. 7. A transmission quality judging means for judging the quality of a received signal from the other party spread spectrum transmitter / receiver, and a transmitter for transmitting to the other party spread spectrum transmitter / receiver based on the transmission quality judged by this transmission quality judging means. Control data creating means for creating clock control data for controlling the clock rate of the spread code, data synthesizing means for synthesizing the clock control data created by the control data creating means with a transmission signal, and the other party spread spectrum transmission / reception device And a band pass filter circuit capable of controlling a bandwidth to be passed according to a change of a clock rate of a spread code of a received signal from the spread spectrum transmitter / receiver. 8. A data extracting means for extracting the clock control data from a received signal from the spread spectrum transmitter / receiver according to claim 7, and a spread code for transmission based on the clock control data extracted by the data extracting means. Spread spectrum transmitter / receiver comprising a clock control means for controlling the clock rate of the. 9. A communication amount detecting means for detecting a communication amount of a received signal from the other party spread spectrum transmitting / receiving device, and a spread code for transmission of the other party spread spectrum transmitting / receiving device according to an output from this communication amount detecting means. Control data creating means for creating the clock control data for controlling the clock rate of, the data synthesizing means for synthesizing the clock control data created by the control data creating means with the transmission signal, A spread spectrum transmission / reception device, comprising: a band pass filter circuit capable of controlling a bandwidth to be passed along with a change of a clock rate of a spread code of a received signal. 10. A transmission quality judging means for judging the quality of a received signal from the first spread spectrum transmitter / receiver, and a transmission of the first spread spectrum transmitter / receiver based on the transmission quality judged by this transmission quality judging means. Second spread spectrum including control data creating means for creating clock control data for controlling the clock rate of the credit spread code, and data synthesizing means for synthesizing the clock control data created by the control data creating means into a transmission signal. A transmitter / receiver, a data extraction means for extracting the clock control data from a received signal from the second spread spectrum transmitter / receiver, and a clock rate of a spread code for transmission based on the clock control data extracted by the data extraction means. And a clock control means for controlling the first spread spectrum transmission Spread spectrum transmission and reception system, characterized by comprising more the communication apparatus. 11. A communication amount detecting means for detecting a communication amount of a received signal from the first spread spectrum transmitting / receiving device, and a transmission spread of the first spread spectrum transmitting / receiving device based on an output from the communication amount detecting means. A second spread spectrum transmitter / receiver including control data creating means for creating clock control data for controlling the clock rate of the code, and data combining means for combining the clock control data created by the control data creating means with a transmission signal. And data extraction means for extracting the clock control data from the received signal from the second spread spectrum transmitter / receiver, and controlling the clock rate of the spread code for transmission based on the clock control data extracted by the data extraction means. And a clock control means for Spread spectrum transmission and reception system, characterized by comprising. 12. The second spread spectrum transmitter / receiver has a band pass filter capable of controlling a bandwidth to be passed according to a change of a clock rate of a spread code of a received signal from the first spread spectrum transmitter / receiver. The spread spectrum transmission / reception system according to claim 10 or 11, characterized in that.