JPH0637735A - Spread spectrum communication equipment - Google Patents

Abstract

PURPOSE:To enhance ciphering performance of information by sending an element for disturbing signal transmission in precedence over an element for information transmission. CONSTITUTION:A transmission system 1A is provided with a transmission system for disturbing wave transmission in addition to a basic transmission for information transmission, and the transmission system 21A for disturbing wave transmission has a disturbing coding section 5A generating, e.g., a disturbance transmission frequency hopping pattern different from a frequency hopping pattern generated from a coding section 5 acting like a master section in the information transmission system and generates the disturbance transmission frequency hopping pattern in precedence over an element for information transmission. Then an information transmission wave is transmitted by an antenna 6A and a disturbance transmission wave being outputs of a spread spectrum modulation section 4 and a disturbance spread spectrum modulation section 4A. Thus, an AGC of a receiver of a 3rd party causes an invalid time from the reply for a period of the precedence disturbance to the restoration to a demodulation enable state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency hopping type spread spectrum communication device, and more particularly to a device for improving the confidentiality of its communication contents.

[0002]

2. Description of the Related Art FIG. 7 shows, for example, "Spread Spectrum Communication System" by Mitsuo Yokoyama (published by Science and Technology Publishing Company, Showa 63).
FIG. 1 is a basic system diagram of a conventional spread-spectrum communication device of a frequency hopping system shown in the first edition of the year). In the figure, 1 is a transmission system for transmitting information 2, 2 is information to be transmitted by this transmission system 1, 3 is an information modulator for modulating information 2, and 4 is information modulated by this information modulator 3. Of the spread spectrum modulation unit, 5 is a coding unit for generating a code for determining a frequency hopping pattern when performing the spread spectrum modulation, and 6A is an antenna for transmitting the spread spectrum modulated radio wave.
The transmission system 1 includes the information modulator 3, the spread spectrum modulator 4, and the encoder 5.

Further, 7 is a receiving system for receiving radio waves from the transmission system 1, 8 is a spread spectrum demodulation unit for performing spread spectrum demodulation of the radio waves from the transmission system 1 received by the antenna 6B, and 9 is this. A synchronization unit 10 used for performing spread spectrum demodulation, which generates a code synchronized with a code generated by the coding unit 5 of the transmission system 1, is an information demodulator that demodulates the signal spread spectrum demodulated by the spread spectrum demodulation unit 8. The parts 2 are information demodulated by the information demodulator 10, and the receiving system 7 includes the spread spectrum demodulator 8, the synchronizer 9 and the information demodulator 10.

Next, the operation of the conventional method will be described. First, the operation of the transmission system 1 will be described with reference to FIG. Information 2 to be transmitted, such as a voice signal or a data signal, is input to the information modulator 3 where it is information-modulated. Amplitude modulation (AM), phase shift keying (PSK), frequency shift keying (FSK), etc. are used as the information modulation method in the information modulator 3. The modulated information-modulated wave further enters the spread spectrum modulation unit 4, and spread spectrum modulation is performed to spread the spectrum.

In the spread spectrum modulation of the frequency hopping system, the carrier frequency is not fixed to one, but FIG.
As shown in an example thereof, according to the frequency hopping pattern (hereinafter referred to as FH-1) generated by the encoding unit 5, the carrier frequency is switched in time series such as F1 → F3 → F8 → F5 → F6 → F2. ing. Hereinafter, the switched carriers are referred to as F1 element to F8 element, respectively. Then, in this way, the spread spectrum modulated transmission wave is radiated into the air from the antenna 6A.

Next, the operation of the receiving system 7 will be described. Antenna 6
The radio wave received by B is converted by the spread spectrum demodulation unit 8 into a narrow band signal wave by a reverse operation of the spread spectrum modulation performed by the spread spectrum modulation unit 4 of the transmission system 1. To be done. That is, the local oscillation frequency supplied to the frequency converter in the spread spectrum demodulation unit 8 is switched in synchronization with the hopping pattern (FH-1) of the received signal wave by the control of the synchronization unit 9.

The signal wave converted into the narrow band signal wave by the spread spectrum demodulation section 8 is subjected to information processing by the information demodulation section 10 by the reverse operation of the same modulation method as that performed by the information modulation section 3. Information 2 can be obtained by demodulation.

As described above, generally, the receiving side can demodulate the received wave only when it knows the frequency hopping pattern of the transmitting side, and the information transmitted by the transmitting side can be obtained. Therefore, even if you intercept in the usual way,
It is considered that the confidentiality of the communication content is secured almost perfectly.

[0009]

The conventional frequency hopping spread spectrum communication apparatus is configured as described above, and the spread spectrum modulated signal transmitted from the transmission system via the antenna is shown in FIG. As shown in FIG. 1, the switching is performed based on the frequency hopping pattern (FH-1) in which the cycle created by the code unit is one cycle.

However, when a plurality of receiving (intercepting) devices are prepared and an intercepting system exists in which each receiving device can receive the frequencies F1 to F8, the receiving device having the reception output is sequentially switched. As a result, a third party can easily intercept the communication content, and there is a problem that confidentiality of the communication content is lost, which is a characteristic of spread spectrum communication.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a frequency hopping spread spectrum communication apparatus in which communication contents are not easily intercepted.

[0012]

In order to achieve the above object, a spread spectrum communication device according to the present invention is a transmission system of a frequency hopping spread spectrum communication device, which is a basic transmission system for information transmission. In addition, a transmission system for interfering wave transmission with different frequency hopping patterns is provided, and the interfering transmission wave is transmitted at the frequency corresponding to the frequency transmitting each element of the information transmission wave, and then the original information transmission wave is transmitted. It is designed to be sent.

[0013]

In the transmission system of the spread spectrum communication apparatus of the frequency hopping system according to the present invention, the elements of the interference transmission wave are transmitted at a timing slightly earlier than the transmission of each element of the information transmission wave. Therefore, the receiving device of the third party who tried to intercept the
Since C responds to this during the period of the preceding disturbance and returns to the state where it can be demodulated, an invalid time occurs, and the original communication is performed during this period, so that the possibility of interception is reduced.

[0014]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a basic system diagram of a frequency hopping spread spectrum communication apparatus according to an embodiment of the present invention.

In the transmission system 1A of FIG. 1, the basic transmission system for information transmission is the information 2 to be transmitted, the information modulator 3 that modulates the information 2, and the information modulator 3 that modulates the information 2. It is composed of a spread spectrum modulator 4 for performing spread spectrum of the information modulated wave, and a coding unit 5 for generating a frequency hopping pattern used when the spread spectrum modulator 4 performs spread spectrum.

On the other hand, the transmission system 21A for transmitting the interference wave includes the interference information 2A which is information different from the original information 2, the interference information modulator 3A which modulates the interference information 2A, and the interference information modulator 3A. An interference spread spectrum modulation unit 4A that performs spectrum spread of the modulated interference information modulated wave, and an interference code unit 5A that generates a frequency hopping pattern used when the interference spread spectrum modulation unit 4A performs spread spectrum. The interference code part 5
A is based on the code generated by the encoding unit 5 of the original transmission system,
A code for interference different from this is generated.

In the transmission system 1A, the information 2 to be transmitted, the information modulator 3, the spread spectrum modulator 4, and the encoder 5 are the same as those in FIG. 7 of the basic system diagram of the conventional spread spectrum communication apparatus of the frequency hopping system. Since it is a thing and has already been explained, it will be omitted. In addition, the transmission system for interference transmission, other than the components described below, is the same as the configuration of each part of the transmission system for information transmission, and the description thereof will be omitted.

The embodiment of FIG. 1 differs from the conventional example of FIG. 7 in that a transmission system 1A is provided with a set of transmission systems for transmission of disturbing waves in addition to a transmission system for basic information transmission. In addition, the transmission system 21A for transmitting the interference wave is different from the frequency hopping pattern (FH-1) generated by the encoding unit 5 by using the encoding unit 5 of the transmission system for information transmission as a master. The interference code part 5A for generating the frequency hopping pattern (FH-2) as shown is provided, and the frequency hopping pattern (FH-2) for interference transmission is generated prior to the element for information transmission. .
Then, the information transmission wave and the interference transmission wave, which are the outputs of the spread spectrum modulation section 4 and the interference spread spectrum modulation section 4A, are transmitted from the antenna 6A.

FIG. 2 shows an example of the hopping pattern of the carrier frequency of the transmission wave transmitted from the antenna 6A. The carrier frequencies of the transmission wave for information transmission are F1, F3 and
Hopping is performed periodically by the frequency hopping pattern (FH-1) like F8, F5, F6, F2, while the carrier frequency of the transmission wave for interference transmission is FH-
Although similar to the 1st pattern, it occurs at a timing slightly earlier than each element of the FH-1 pattern and precedes this.

The system diagram of the receiving system 7 is the same as that of the conventional frequency hopping spread spectrum communication device shown in FIG. 7, and the synchronizing unit 9 has the same frequency hopping pattern as the encoding unit 5 of the transmitting system for information transmission ( Since it is generated in synchronization with FH-1), the target information transmission wave can be selected from the reception waves and spread spectrum demodulation can be performed without being affected by the transmission waves for interference transmission.

As described above, in the present embodiment, the elements of the interfering transmission wave are transmitted before transmitting the respective elements of the information transmission wave, whereby the first attempt is made to intercept the information transmission wave. The receiving devices of the three parties act as follows, and it becomes difficult for the third party to receive the information of the information transmission wave.

First, the general operation of the receiver will be described. Radio waves coming from the antenna are subjected to high-frequency amplification and intermediate-frequency amplification by the receiving device, enter the demodulation section, and are demodulated there. Therefore, the user (third party) will hear this demodulated output. Further, when the input state is changed to the non-input state, the demodulated output is naturally cut off. In this series of receiving operations, the receiving device is provided with an AGC function for keeping the demodulated output substantially constant even when the strength of the incoming radio wave changes and ensuring the dynamic range of the received input.

The operation of the AGC function is changed depending on the strength of the incoming radio wave so as to keep the demodulation output substantially constant. For this reason, a certain amount of invalid time is required from the arrival of the incoming radio wave to the stabilization of the output of the demodulated signal. Also, if the state changes from the touched state to the no input state, the AGC
The function works and requires some invalid time before the demodulated signal appears.

This invalid time is essentially generated when the AGC function fluctuates, and there is a characteristic that normal reception cannot be performed during this invalid time.

Therefore, in this embodiment, as described above, A
Paying attention to the characteristics of the receiver having the GC function, the element of the information transmission wave is transmitted after transmitting the interference transmission wave, and while the invalid time is generated in the receiving device by the interference transmission wave, The element of the transmission wave is transmitted to secure the confidentiality of the communication content.

Embodiment 2 In the above-described embodiment, the interference code section 5A for generating the interference code for interference transmission is provided by using the information transmission code section 5 as a master, but this is as shown in FIG. Interfering code 5
A to the frequency hopping pattern (FH-
The information of 1) may be input, and the interference coding unit 5A may be configured to configure the transmission system 21B for interference wave transmission so as to generate the frequency hopping pattern (FH-2) shown in FIG. As a result, in addition to the effects similar to those of the first embodiment,
This has the effect of making the device slightly smaller.

Embodiment 3 In the embodiment of FIGS. 1 and 3, the transmission system for each interference transmission is also provided with the interference information 2A and the interference information modulator 3A, but as shown in FIG. In addition, the transmission system 21C for transmitting the interference wave is configured by only the interference spread spectrum modulation unit 4A and the interference code unit 5A, and only the carrier wave whose frequency fluctuates according to the frequency hopping pattern (FH-2) shown in FIG. You may make it transmit as an interference signal. At this time, the AGC function acts on the intercepting side to mitigate the change from the no-input state to the touched state,
Invalid time occurs. Therefore, it is possible to conceal the content by performing the original information transmission according to the frequency hopping pattern (FH-1) during the invalid time.
In addition to the same effects as those of the above-described first embodiment, there is an effect that the device can be small in scale.

Embodiment 4 Further, as shown in FIG. 6, the interference spread spectrum modulator 4
A transmission system for interference transmission is configured only by the transmission system 1D for transmission of an interference wave, which has only the A and the interference code unit 5A and does not have a transmission system for information transmission, and is installed near the interception side. For example, the interception side may be only interfered with, and the same effect as that of the above-described embodiment can be obtained. The hopping pattern of the interference code unit 5A in this embodiment may be the frequency hopping pattern (FH-2) shown in FIG. 4 or may be other than this.

[0029]

As described above, according to the spread spectrum communication apparatus of the frequency hopping system according to the present invention, in addition to the basic information transmission transmission system, the interference hopping transmission is used as the transmission system. Since a system is provided and the element for interference transmission is transmitted before the element for information transmission, the reception of the interference wave is invalid in the receiving device of the third party who is trying to intercept the carrier wave. Since time is required and the element for information transmission is transmitted during that time, it becomes difficult to receive the information for information transmission. As a result, the spread spectrum demodulation cannot be performed. Therefore, the information demodulation cannot be performed, and the confidentiality of information is improved.

[Brief description of drawings]

FIG. 1 is a system diagram of a spread spectrum communication device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a frequency hopping pattern of a transmission wave transmitted by the spread spectrum communication device of FIG.

FIG. 3 is a system diagram of a spread spectrum communication device according to another embodiment of the present invention.

4 is a frequency hopping pattern (F corresponding to FIG.
It is a figure which shows H-2).

FIG. 5 is a system diagram of a spread spectrum communication device according to another embodiment of the present invention.

FIG. 6 is a system diagram of a spread spectrum transmitter according to another embodiment of the present invention.

FIG. 7 is a system diagram of a conventional spread spectrum communication device.

FIG. 8 is a diagram showing an example of a frequency hopping pattern of a transmission wave transmitted by a conventional spread spectrum communication device.

[Explanation of symbols]

1, 1A, 1B, 1C, 1D Transmission system 2 Information 2A Interference information 3 Information modulation section 3A Interference information modulation section 4 Spread spectrum modulation section 4A Interference spread spectrum modulation section 5 Code section 5A Interference code section 6A, 6B Antenna 7 Reception system 8 spread spectrum demodulation unit 9 synchronization unit 10 information demodulation unit 11 frequency hopping pattern of information transmission wave (FH-
1) 12 Frequency hopping pattern (FH-
2) 21A transmission system for interference wave transmission 21B transmission system for interference wave transmission 21C transmission system for interference wave transmission

Claims (1)

[Claims] 1. A transmission system of a spread spectrum communication device of a frequency hopping system, comprising: a transmission system for transmitting an interfering wave having a frequency hopping pattern different from that for original information transmission, the same as a carrier frequency element for an information transmission wave. A spread spectrum communication device, wherein an interference transmission wave is transmitted prior to an information transmission wave using a carrier frequency element for frequency interference.