JPH0767102B2 - Wireless communication system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a digital wireless communication system having a secret talking function.

(Prior Art) Conventionally, a wireless device of this type includes an interface circuit between a memory for storing encrypted data and a special jig for changing the data in the memory from the outside, and a terminal station is stolen. When there is, to prevent eavesdropping on the contents of communication,
The encryption code data in the memory is changed by hand using a special jig all over the system. Alternatively, a means such as exchanging the memory element itself storing the cryptographic code data for a memory element storing another cryptographic code has been taken.

FIG. 4 shows the configuration of a conventional digital radio apparatus. In the figure, 21 is a voice input terminal, and a voice encoder 22
It is connected to the. 23 is an encoder, a voice encoder
The output data of 22 (which is a digital signal string) is encrypted according to the encryption code data in the memory 24. With this encrypted digital data, the modulator
Modulate the carrier wave at 25. This modulated wave is a power amplifier
It is amplified to a predetermined electric power at 26 and radiated from the antenna 28 via the antenna switch 27. On the other hand, the received wave received by the antenna 28 reaches the receiver 29 via the antenna switch 27. The output of the receiver 29 is demodulated into a digital signal by a demodulator 30, and the demodulated digital signal is decrypted by an encryption / decryption unit 31 in accordance with the encryption code data in the memory 24. The decoded digital data is decoded by the audio decoder 32, and audio is output from the output terminal 33.

On the other hand, 34 is an interface circuit for changing the encryption code data in the memory 24 from the outside by using a special jig. As described above, even in the case of theft of the terminal device according to the above-mentioned conventional example, a special jig is used through the interface circuit 34,
It is possible to change the encryption code manually,
The call was kept secret.

(Problems to be Solved by the Invention) In the above-described conventional digital wireless system, when the terminal station is stolen, the encryption code must be manually changed,
Since it is very complicated, and the encryption codes of all command stations and terminal stations belonging to the same system must be changed at the same time, there is a drawback that it takes a huge amount of time and labor.

An object of the present invention is to overcome the drawbacks of the prior art and, when attempting to eavesdrop on a stolen terminal station, automatically delete the encryption code of the stolen station prior to making a call, which is an excellent wireless system capable of preventing eavesdropping. It is to provide a communication system.

(Means for Solving the Problems) In the wireless communication system of the present invention, on the transmitting side, the transmitted voice is converted into a digital signal sequence by a voice encoder, and this signal sequence is subjected to encryption processing to obtain an encryption code. The carrier wave is FM- or PM-modulated with the converted digital signal sequence, and the receiving side uses a digital modulation method that demodulates the transmitted voice by the reverse processing of the transmitting side. Command station, relay station, multiple terminal stations (fixed Station, mobile station, vehicle-mounted station, etc.), which is a digital wireless communication system that mainly communicates between the command station and the terminal station by the dual frequency simplex method. Prior to, the header for taking the bit period and for indicating the transmission of the encryption code data erasing signal, the ID signal indicating the individual number of the stolen terminal station and the call instruction sound prompting the caller to call Stealing It has a function to send a voice control signal to open the voice circuit of a general terminal station that is not difficult, while the terminal station mutes the voice when it receives the header and continues to output the ID signal. If the ID signal matches with its own ID, as a result, it has a function to erase the code data for encryption built in the terminal station, and if the ID number does not match, Ignore the ID signal and continue to receive,
When the voice control signal is detected, the voice circuit is opened to enter the call mode.

(Operation) According to the present invention, when a command station sends a cryptographic code data erasing signal to a terminal station stolen prior to a call and the stolen terminal station tries to steal, the stolen terminal The encryption code of the station can be erased, and even if the terminal station is stolen, it can be prevented from being eavesdropped.

If the transmission rate of the encrypted code data erasing signal is designed to be high, there is no fear that the erasing of the encrypted code will fail in the weak electric field region and only the voice will be decrypted.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 shows the operation of the wireless communication system of the present invention. In the figure, (a) shows the operation of the command station,
(B) shows the operation of a general terminal station, and (c) shows the operation of a stolen terminal station. In (a), the command station presses the talk button to set a bit period for each terminal station, to indicate that an encryption code data erasing signal is to be sent, and to mute the voice circuit. The header as a control signal is sent out, and subsequently the ID signal of the terminal station that has been stolen is sent out (it is possible for a plurality of stolen terminal stations, ID ₁ and ID ₂ in this embodiment), and then the terminal station. The voice control signal for opening the voice circuit is sent, and at the same time, a voice sending instruction sound for prompting the talker to speak is issued and the voice sending mode is entered. In the general terminal station of (b), when the header is received, bit synchronization is achieved, and noise is heard until the header is detected, but when the header is detected, the voice is muted. Continue to receive the ID signal, but ignore it if the ID signal is not your own number. The audio circuit remains muted during ID reception. When the voice control signal is subsequently received and detected, the voice circuit is opened and the reception mode is set. In the stolen terminal station of (c), when the header is received, bit synchronization is established, and noise is heard until the header is detected, but when the header is detected, the audio circuit is muted. Continuing, when the ID signal is detected and the transmitted ID signal matches the ID number of its own station (ID _{1 in} this embodiment)
Delete the encryption code data. After that, even if the voice control signal is received, since the cipher code data does not match, the voice control signal cannot be detected, the voice circuit does not open, and the silent state continues.

FIG. 2 is a block diagram showing an embodiment of the command station of the wireless communication system of the present invention. In the figure, 1 is a voice input terminal, 2 is a voice encoder, 3 is an encoder, 4 is a modulator, 5 is a power amplifier, 6 is an antenna, 7 is an interface circuit, 8 is an encryption code memory, and 9 is Switch, 10 is an antenna switch, 11 is a receiver, 12 is a demodulator, 13 is a decryption device, 14 is a voice decoder, 15 is a voice output terminal, 16 is a control circuit, 17 is an ID number memory, and 18 is It is a transmission instruction sound generator.

Next, the transmission operation of the command station will be described with reference to FIG. The receiving operation is the same as in the conventional example, and will not be repeated. In FIG. 2, when the terminal station is stolen, the ID number of the terminal station is written in the ID number memory 17. When the operator of the command station who intends to communicate presses the talk button, the control circuit 16 is activated by this talk signal and the control circuit 16 switches the switch 9 to connect the control circuit 16 and the encryptor 3. When this connection is completed, the control circuit 16 sends a header signal to the encryption device 3, and subsequently all of the ID number memory 17 stores.
Send the ID signal. When the control circuit 16 finishes sending the ID number, it sends the voice control signal and at the same time sends the voice instruction sound generator.
18 is activated, and the voice signal output terminal 15 outputs a voice transmission instruction sound to prompt the caller to make a call, and at the same time, the switch 9 is switched to the voice encoder 2 side to start a call. In this embodiment, the header, the ID signal, and the voice are all encrypted, but the header and the ID signal may not be encrypted.

FIG. 3 is a block diagram showing an embodiment of the terminal station of the present invention. In the figure, parts that are the same as those shown in FIG. 2 are given the same reference numerals, and descriptions thereof will be omitted. Reference numeral 19 is a decoder, 20 is a local ID number memory, 41 is a mute circuit, and 42 is a memory erasing circuit.

Next, the receiving operation of the terminal station will be described. The transmission operation is the same as that of the conventional example, and thus the description of the operation is omitted.

In FIG. 3, the mute circuit 41 is open during standby, and noise is output from the audio output terminal 15 during standby. When the receiver 11 receives the radio wave of its own station, the demodulator 12
The digital signal is demodulated by (1), and the demodulated digital signal is decrypted by the encryption / decryption device 13 (hereinafter, abbreviated as data). The decoder 19 verifies the header in the data, and when it detects the header, it activates the mute circuit 41 to mute the voice, continuously monitor the ID signal sent, and monitor the own station in the own station ID number memory 20. When the ID signal that matches the ID number is detected, the memory erasing circuit 42 is activated, and the memory erasing circuit 42 erases the cipher code in the cipher code memory 8 via the interface circuit 7, and all the codes are "H" or "L".
To If the local ID number cannot be detected, the data will be ignored. Subsequently, when the decoder 19 detects the voice control signal, the decoder 19 opens the mute circuit 41 to enter the reception mode, and the reception voice is output from the voice output terminal 15.

(Effects of the Invention) According to the present invention, since it is a two-wave frequency simplex system, a stolen terminal station cannot eavesdrop on a transmission from the terminal station. Further, since the encryption code deletion signal is sent to the theft terminal station each time the command station is transmitted, the stolen terminal station cannot eavesdrop on the call contents of the command station. In addition, since a general terminal station gives a call instruction using a voice control signal, the call is not cut off, the same operation as a normal wireless communication system can be performed, and more than one ID number memory capacity can be used. It is possible to deal with the theft of the terminal station, and its practical effect is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing the operation of a wireless communication system according to an embodiment of the present invention, FIG. 2 is a block diagram of the command station, FIG. 3 is a block diagram of the terminal station, and FIG. 4 is a conventional digital radio. It is a block diagram of an apparatus. 1 ... voice input terminal, 2 ... voice encoder, 3 ... encryption device, 4 ... modulator, 5 ... power amplifier, 6 ... antenna, 7 ... interface circuit, 8 ... encryption code Memory, 9 ... Switch, 10 ... Antenna switch, 11 ...
Receiver, 12-demodulator, 13-encryption decoder, 14-voice decoder, 15-voice output terminal, 16-control circuit, 17 ---
ID number memory, 18 …… Sending instruction tone generator, 19 …… Decoder, 20 …… Self ID number memory, 41 …… Mute circuit, 42
...... Memory erase circuit.

Claims (1)

[Claims] 1. A transmitting side converts a transmitted voice into a digital signal sequence by a voice encoder, performs an encryption process on the digital signal sequence, and uses a carrier wave as an FM or FM in the encrypted digital signal sequence. PM modulation is performed, and the receiving side is composed of a command station, a relay station, and a plurality of terminal stations using a digital modulation method that demodulates a transmission voice by a process reverse to that of the transmitting side. A digital wireless communication system for performing communication between a command station and a terminal station, wherein the command station uses a talk button to take a bit period before transmitting when transmitting a voice and to indicate transmission of an encryption code data erase signal. At the same time as issuing a header, an ID signal indicating the individual number of the stolen terminal station and a call instruction sound that prompts the caller to call, open the voice circuit of the general terminal station that has not been stolen Has a function of transmitting a voice control signal for, on the other hand, in the terminal station, when the header is received, the voice is muted, and subsequently the ID signal is tested, and as a result, the ID signal is its own. If it matches the ID, it has a function to erase the code data for encryption built in the terminal station.If the ID number does not match, the terminal signal is ignored and reception continues. Continuing, when the voice control signal is detected, the circuit is opened,
A wireless communication system characterized in that a call mode is entered.