JPH10173631A - Spread spectrum communication system and communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain secrecy, and to operate control by a base station or the like by using one spread code by diffusion modulating a signal including control information for controlling communication by a common spread code, and spread modulating a signal, including user information by a spread code specific between communication stations, and transmitting them. SOLUTION: The control information part of a packet is primary modulated by a primary modulator 110 and inputted to a multiplier 150. Then, a common spread code is generated by a spread code generator 130, the common spread code is multiplied by the signal from the primary modulator 110 by the multiplier 150, and spread modulation by the common spread code is operated. On the other hand, the data part and error-correcting part of the packet is primary modulated by the primary modulator 110, and inputted to a multiplier 140. A specific spread code is generated by a spread code generator 120, based on data indicating the spread code specific between communication stations held in an RAM 330. This code is multiplied by the signal from the primary modulator 110, and the spread modulation by the specific spread code is performed.

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 communication terminal for converting a signal into a signal having a band much wider than the band of the signal.

[0002]

2. Description of the Related Art A spread spectrum system is sometimes used for communication because of its excellent interference resistance and confidentiality.

As the spread spectrum communication system, there are a direct sequence system (DIRECT SEQUENCE) and a frequency hopping system (FREQUENCY HOPPING).

First, a communication system using the direct spreading method will be described.

FIG. 11 is a diagram showing a configuration of a conventional spread spectrum communication. In FIG. 1, reference numeral 10 denotes a transmitter, and reference numeral 20 denotes a receiver.

[0006] In the transmitter 10, the carrier wave is transmitted by the carrier wave modulation unit 11 using PSK (PHASE SHIFT K).
EYING), FM (FREQUENCY MODUL)
ATTION), AM (AMPLITUDE MODUL)
After primary modulation such as ATION), secondary modulation (spreading modulation) is performed by multiplying by a spreading code far wider than the transmission data. The spread-modulated signal is power-amplified by the transmission unit 13 and radiated from the antenna 14 as radio waves.

On the other hand, in the receiver 20, the high-frequency signal input from the antenna 21 is subjected to high-frequency amplification and band limitation in the receiving unit 22, and is spread-demodulated in the spread demodulation unit 23.
This spread demodulation is to demodulate the received signal by multiplying it by the same spread code as that on the transmitting side. Then, the carrier wave demodulation unit 24 reproduces the data except for the carrier wave.

FIG. 12 is a diagram showing a spectrum of a signal of each section in spread spectrum communication having the configuration shown in FIG.

As shown in FIGS. 1A and 1B, the spectrum of the signal after passing through the spread modulator 12 is much wider than the spectrum of the signal after passing through the carrier modulator 11. As a result, the power density per unit frequency is significantly reduced, and interference with other communications is avoided. Also, when the signal is demodulated by the spreading post-tuning unit 23 of the receiver 20 using the same spreading code as that at the time of modulation at the transmitter, the signal can be reproduced as shown in FIG. When demodulation is performed using a spreading code different from that used for modulation at the transmitter, the information remains spread and cannot be reproduced, as shown in FIG. For this reason, when signals in which a plurality of pieces of transmission information are modulated with different spreading codes are present in the same frequency band, each transmission information is demodulated with the same spreading code as in the modulation operation of each piece of transmission information. Can reproduce information.

[0010] On the other hand, the spread spectrum communication system of the frequency hopping system is a system in which a carrier frequency modulated with information is randomly and discretely switched within a given band to spread the signal over a wide band.

[0011] The spread spectrum communication as described above is a kind of encryption communication, and transmission data can be reproduced only when the sequence of spread codes on the transmitter and the receiver matches. For this reason, even if there is a violating user such as power over, it becomes difficult to specify the violating user. When a base station or the like performs communication control or maintenance management control, the base station is one of the communication stations to be controlled.
It is necessary to perform communication by performing spread modulation with a spread code unique to the base. Furthermore, it is difficult to broadcast to communication stations having different spreading codes.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and a spread spectrum signal which can be controlled by a base station using one spreading code while maintaining secrecy. It is an object to provide a communication system and a communication terminal.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention according to claim 1 is a spectrum for transmitting information between communication terminals by spreading and modulating a primary-modulated signal using a spreading code. A spread communication system, wherein the primary-modulated signal including control information for communication control is spread-modulated by a predetermined common spreading code, and the primary-modulated signal is transmitted by a user. Including the user information is spread-modulated by a unique spreading code between communication stations and transmitted.

According to a second aspect of the present invention, in the system according to the first aspect, the signal including control information for communication control is a signal for performing broadcast communication, and the signal is transmitted by the user. The signal including the user information is a signal that the communication device individually communicates.

According to a third aspect of the present invention, there is provided a communication terminal for transmitting information by spreading-modulating a primary-modulated signal using a spreading code, wherein the primary-modulated signal is used for controlling communication. Means for spreading and modulating a signal containing control information by a predetermined spreading code common to the whole; and a spreading code unique to the communication station for transmitting the primary modulated signal containing user information for user information transfer. And means for transmitting these spread-modulated signals.

According to a fourth aspect of the present invention, in the communication terminal according to the third aspect, the signal including control information for the communication control is a signal for performing a broadcast communication, and the user transfers information. Including the user information is a signal that the communication device individually communicates.

According to the present invention, a signal which is primary-modulated and includes control information for communication control is spread-modulated by a predetermined common spreading code, is primary-modulated, and is used by a user for information transfer. Since the signal including the user information is spread-modulated and transmitted between the communication stations using a unique spreading code, control and the like by the base station can be performed using one spreading code while maintaining secrecy.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a configuration of a communication apparatus according to an embodiment when a spread spectrum communication system of the present invention is realized by a direct spread system.

In the figure, 100 is a transmitter, 200 is a receiver, 300 is an antenna for inputting and outputting radio waves, 31
0 is a duplexer for sharing the antenna 300 between the transmitter 100 and the receiver 200, 320 is a control unit for performing overall control of the operation of the communication device, 330 is a RAM for storing a unique spreading code, 340 Denotes a ROM for storing a common spreading code, and 350 denotes a clock generator for generating a clock for generating a spreading code.

The transmitter 100 transmits data to be transmitted to the FS
A primary modulator 110 for performing primary modulation such as K or PSK;
Spreading code generators 120 and 130 for generating spreading codes
Multipliers 140 and 150 for performing spreading modulation by multiplying the spreading code generated by spreading code generators 120 and 130 by the signal modulated by primary modulator 110, and multiplier 14
A band-pass filter 160 that passes only a predetermined band of the signal output from the signal 0, 150;
Power amplifier 17 for performing power amplification on the signal output from 60
0.

The receiver 200 includes a high-frequency amplifier 210 that performs high-frequency amplification of a signal received from the duplexer 310, a band-pass filter 220 that passes only a predetermined band of the signal that has been high-frequency amplified by the high-frequency amplifier 210, and a band-pass filter. Correlators 230 and 240 that perform spread demodulation of the signal band-limited by the filter 220;
And a demodulator 250 that demodulates the signal spread and demodulated by 240. The correlators 230 and 240 are programmable correlators such as a SAW convolver.

FIG. 2 is a diagram showing an example of an M-sequence spread code having a code length N = 31. In this case, six types of codes are obtained. One of them may be used as a common spreading code, and the remaining five may be used as unique spreading codes.

Next, the operation of the communication apparatus having the above configuration will be described.

First, the transmission operation will be described.

The primary modulator 110 of the transmitter 100 receives a packet-like signal.

FIG. 3 is a diagram showing the structure of an example of a packet transmitted by the above-described communication device. As shown in the figure, the packet 500 has a control information section 510 for transferring control information such as ID and packet length, a data section 520 for transmitting user information to be transmitted, and an error in data. Error correction section 530 for checking whether or not
Consists of

The control information section 510 of the packet 500 is subjected to primary modulation by the primary modulator 110 and then to the multiplier 150
Is input to The ROM 340 holds data indicating a predetermined common spreading code. Based on this data, the spreading code generator 130 generates a common spreading code, and the multiplier 150 outputs the common spreading code from the primary modulator 110. Is multiplied by the common spreading code, and spread modulation is performed by the common spreading code.

On the other hand, the data section 520 and the error correction section 530 of the packet 500 are primary-modulated by the primary modulator 110 and then input to the multiplier 140. RAM33
Data indicating a spreading code unique to a system cell or a communication station is held in 0, and can be changed according to the state. The spread code generator 120 generates a unique spread code between the communication stations based on the data indicating the unique spread code between the communication stations held in the RAM 330. The signal from the next modulator 110 is multiplied to perform spread modulation by a unique spread code.

The signals spread and modulated by the multipliers 140 and 150 are band-limited by a band-pass filter 160, power-amplified by a power amplifier 170, supplied to an antenna 300 via a duplexer 310, Radiated as

FIG. 4 is a diagram showing a spectrum of control information section 510 spread by a common spreading code and a spectrum of data section 520 and error correction section 530 spread by a spreading code peculiar to communication stations.

Next, the receiving operation will be described.

A case where the packet 500 is transmitted as a radio wave from another communication station or the like by the same operation as the above-described transmission operation will be described.

This radio wave induces a high frequency signal in the antenna 300, and this high frequency signal is
After the high frequency amplification is performed, the band is limited by the band pass filter 220. Bandpass filter 22
The high-frequency signal passing through 0 is sent to the correlators 230 and 240. The correlator 230 performs correlation based on data indicating a common spreading code stored in the ROM 340,
Spread demodulation of the control information section 510 of the packet 500 is performed. The spread-demodulated control information section 510 is the demodulator 2
At 50, carrier demodulation is performed, and control information is reproduced and transferred to the control unit 320. On the other hand, the correlator 240
Correlation is taken between the communication stations stored in 30 based on a unique spreading code, and spread demodulation of the data section 520 and error correction section 530 of the packet 500 is performed. The spread demodulated data section 520 and error correction section 530 perform carrier demodulation by the demodulator 250 to reproduce communication data.

As described above, since the control information section of the packet 500 is spread-modulated by the common spread code, anyone can reproduce the ID unique to the communication device transmitting the radio wave. Further, since data to be communicated is spread-modulated with a unique spreading code between communication stations, the secrecy of communication is maintained.

In the above-described embodiment, the control information portion of one packet is spread-modulated with a common spreading code, and the other portion of the packet is spread-modulated with a spread signal unique to communication stations.
As shown in FIG. 5, an information packet (FIG. 5A) and a control packet (FIG. 5B) are used, and the information packet is spread-modulated using a spreading code unique to the system (communication station) and transmitted. The control packet may perform spread modulation using a common spread code. In this case, since the control packet can be reproduced by anyone, it is possible to specify the transmitting station, and control can be performed using one spreading code, for example, when the base station performs control. .

Further, since the information packet is spread-modulated between the communication stations by a unique spreading code, the secrecy of communication is maintained. Note that the control packet and the information packet can be transmitted independently.

FIG. 6 is a diagram showing a configuration of a communication apparatus when the frequency hopping method is used. Note that parts performing the same operations as those of the communication device shown in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

In the communication device of this embodiment, the RAM 330
The oscillation frequency of the variable frequency synthesizer 360 changes based on the data indicating the unique spreading code stored in the ROM or the data indicating the common spreading code stored in the ROM 340. And the variable frequency synthesizer 360
Is output from the spread modulator 180 of the transmitter 100a.
The signal is supplied to 190 and spread modulation of the frequency hopping method is performed. The output signal from the variable frequency synthesizer 360 is supplied to spread demodulation units 260 and 280 of the receiver 200a, and spread demodulation is performed by the frequency hopping method. The synchronization circuits 270 and 290 are circuits for synchronizing the hopping of the output signal of the bandpass filter 220 and the hopping of the output signal of the variable frequency synthesizer 360.

Next, the operation when transmitting the packet 500 shown in FIG. 3 by the communication apparatus having the above configuration will be described.

First, when transmitting packet 500, when control information section 510 of packet 500 is primary-modulated by primary modulator 110, this signal is transferred to spreading modulator 180. On the other hand, the variable frequency synthesizer 360 has a ROM
The signal of the frequency based on the data indicating the common spreading code held in 340 is sequentially oscillated, and the spread modulator 1
The signal is supplied to the spread modulator 80, and the spread modulator 180 performs spread modulation based on the frequency hopping method. Data part 5 of packet 500
When the primary modulator 20 and the error correction unit 530 are primary-modulated by the primary modulator 110, this signal is transferred to the spread modulator 190. On the other hand, the variable frequency synthesizer 360
A signal having a frequency based on the data indicating the unique spreading code held in M330 is sequentially oscillated and supplied to the spreading modulator 190, and the spreading modulator 190 performs spread hopping modulation.

When receiving packet 500 shown in FIG. 3, control information section 510 includes spread demodulator 280 and data section 5.
20 and the error correction unit 530 perform spread demodulation by the spread demodulator 260.

When transmitting using the information packet and the control packet shown in FIG. 5, the information packet may be spread-modulated by a unique spreading code, and the control packet may be spread-demodulated by a common spreading code. .

FIG. 7 shows CDMA (CODE DIVISI).
FIG. 11 is a diagram showing a negotiation procedure of a spreading code in ON MULTIPLE ACCES). 700 indicates a communication device, and 710 indicates a base station.

First, when communication apparatus 700 requests base station 710 for a spreading code using control packet 720, base station 710 allocates a spreading code to communication apparatus 700 using control packet 730. Thereafter, the communication device 70
0 executes data transmission using the assigned spreading code. By doing so, the spreading code can be used effectively, and the multiplicity can be increased. Further, when the bit error rate increases due to the cross-correlation characteristic of the spreading code and the transmission quality deteriorates, the spreading code can be changed even during the communication using the control packet.

FIG. 8 is a diagram showing a case where transmission power control is performed from the base station to the mobile station in order to solve the near-far problem. As shown in the figure, a base station 710 transmits a control packet 7 spread-modulated with a common spreading code to a mobile station 750.
Transmit 60. The mobile station 750 changes the transmission power according to the output control information sent by the control packet 760. In this case, the base station 710 can individually request the mobile stations to perform transmission power control. Requesting transmission power control from the mobile station to the base station can also be realized in a similar manner.

FIG. 9 is a diagram showing a case where an offending station is identified.

In the figure, 800 is a violating mobile station, 81
0 indicates a management station. The violating mobile station 800 includes a control packet 820 spread-modulated by a common spreading code and an information packet 83 spread-modulated by a unique spreading code.
It is assumed that 0 is transmitted. In this case, the management station 810 uses the common spreading code correlator 811 to set the offending mobile station 800.
By reproducing the ID of the control packet 820 transmitted by the mobile station 800, the violating mobile station 800 can be specified.

FIG. 10 is a diagram showing switching of base stations when a failure occurs.

Normally, base station 900 has a unique spreading code A
, And the base station 910 covers zone B communicating with a unique spreading code B, respectively. When a failure occurs in the base station 900, the zone A
By transmitting a control packet 930 spread-modulated with a common spreading code to the mobile stations 920 and 921 within the base station and notifying a unique spreading code B, a base station switching instruction can be issued. FIG. 13 shows the direct spreading method, FIG.
FIG. 1 is a block diagram illustrating a configuration of a communication device according to an embodiment when a common spreading code is used for broadcast communication realized by a frequency hopping method. In the present embodiment, regardless of control information or user information, information to be broadcast is spread-modulated with a common spreading code, and communication is simultaneously performed with a plurality of communication stations simultaneously as in the above-described base station control at the time of a failure. Enabled if

Therefore, in the above-described embodiment, it is possible to specify a station that is transmitting a signal by transmitting a signal that has been partially spread and modulated by a common spreading code. It can be performed using codes.

[0051]

As described above, according to the present invention,
Control and the like by the base station can be performed using one spreading code while maintaining secrecy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a communication apparatus according to an embodiment when a spread spectrum communication system of the present invention is realized by a direct spread method.

FIG. 2 is a diagram illustrating an example of an M-sequence spreading code having a code length N = 31.

FIG. 3 is a diagram illustrating a structure of an example of a packet transmitted by a communication device.

FIG. 4 is a diagram showing a spectrum of a control information section spread by a common spreading code and a spectrum of a data section and an error correction section spread by a spreading code unique between communication stations.

FIG. 5 uses an information packet (FIG. 5A) and a control packet (FIG. 5B), spreads and modulates the control packet using a spreading code specific to the system (communication station), and transmits the information. FIG. 3 is a diagram illustrating a case where a packet is subjected to spreading modulation using a common spreading code.

FIG. 6 is a diagram illustrating a configuration of a communication device when a frequency hopping method is used.

FIG. 7 is a diagram showing a negotiation procedure of a spreading code in CDMA.

FIG. 8 is a diagram illustrating a case where a base station requests transmission power control from a mobile station.

FIG. 9 is a diagram showing a case where an offending station is identified.

FIG. 10 is a diagram illustrating switching of base stations when a failure occurs.

FIG. 11 is a diagram showing a configuration of a conventional spread spectrum communication.

12 is a diagram illustrating a spectrum of a signal of each unit in spread spectrum communication having the configuration illustrated in FIG. 11;

FIG. 13 is a diagram illustrating a direct spread scheme in a spread spectrum communication system that performs broadcast communication.

FIG. 14 is a block diagram illustrating a configuration of a communication apparatus according to an embodiment when a spread spectrum communication system that performs broadcast communication is realized by a frequency hopping method.

[Explanation of symbols]

 100 transmitter 110 primary modulator 120, 130 spreading code generator 140, 150 multiplier 160, 220 bandpass filter 170 power amplifier 200・ Receiver 210 ・ ・ ・ High-frequency amplifier 230, 240 ・ ・ ・ Correlator 250 ・ ・ ・ Demodulator 300 ・ ・ ・ Antenna 310 ・ ・ ・ Common part 320 ・ ・ ・ Control part 330 ・ ・ ・ RAM 340 ・ ・ ・ ROM

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryuji Kono 1202-9, Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa-ken Inventor Motomitsu Yano 70, Yanagicho, Yuki-ku, Kawasaki-shi, Kanagawa

Claims (4)

[Claims] 1. A spread-spectrum communication system for transmitting information between communication terminals by spreading-modulating a primary-modulated signal using a spreading code, wherein said primary-modulated signal is control information for communication control. Is spread-modulated by a predetermined common spreading code, the signal is first-order modulated, and the signal containing user information for user information transfer is spread-modulated by a unique spreading code between communication stations. A spread-spectrum communication system, characterized in that the signal is transmitted through a transmission. 2. A signal including control information for the communication control is a signal for performing broadcast communication, and a signal including user information for the user to transfer information is a signal for a communication device to individually communicate. The spread spectrum communication system according to claim 1, wherein: 3. A communication terminal for transmitting information by spreading-modulating a primary-modulated signal using a spreading code, and transmitting a signal containing control information for controlling communication, which is primary-modulated, in advance. Means for performing spread modulation by a predetermined common spreading code; means for performing spread modulation on the primary-modulated signal including user information for transmitting information by a user using a unique spreading code between communication stations; Means for transmitting these spread-modulated signals. 4. A signal including control information for the communication control is a signal for performing broadcast communication, and a signal including user information for the user to transfer information is a signal for a communication device to individually communicate. The communication terminal according to claim 3, wherein: