JP2537517B2 - Spread spectrum communication device - Google Patents

Description

The present invention relates to a spread spectrum communication device, and more particularly to a spread spectrum communication device used for wireless communication.

[Prior Art] In a spread spectrum communication system, a baseband signal such as digitized voice or image data that is generally transmitted has a very wide bandwidth compared to the original data by using a spread code such as a pseudo noise code. Convert to band signal,
Further, modulation is performed by a method such as PSK or FSK modulation to form and transmit a high frequency signal.

On the receiving side, the original data is demodulated by performing despreading to obtain a correlation with the received signal using the same spreading code as that on the transmitting side.

The spreading code used for demodulation is set and assigned so that the mutual correlation is sufficiently small for each communication channel. Therefore, even if the signals spread by different codes are despread and demodulated, they become wide band noise, and only the target signal can be extracted. Therefore, multiple access by code division is possible.

A conventional multiple access device using a spread spectrum communication system is configured as shown in FIG. This multiple access device is used as a transmitting / receiving device for a fixed station capable of communicating with many mobile stations.

The spread signal received by the antenna 1 in FIG. 4 is converted into an intermediate frequency signal by the transceiver 2 and input to the multiple access processing unit 3. Here, the communication channel number of each mobile communication device and the synchronization signal for demodulation are detected. The detected channel number is supplied to the tap selectors 41, 42 ... Which are composed of a decoder circuit and the like.

The tap selector generates code generators 51, 52 ...
Select the feedback tap of. On the other hand, the synchronization signals detected by the multiple access processing unit 3 are code generators 51, 52.
Is input to the code generator, and the code generator generates a spread code with a phase corresponding to the synchronizing signal.

This spread code is multiplied by the received signal by the despread demodulators 61, 62 ... And further subjected to baseband demodulation,
The transmitted data is reproduced.

On the other hand, the transmission system is configured as follows. Different input data to be transmitted to each mobile station is input to the multiple access control unit 7. The control unit 7 determines a channel number for each communication channel and outputs the data to the tap selector 81,
Enter in 82. The tap selectors 81, 82 ... Select the feedback taps of the code generators 91, 92 ... In the subsequent stage so as to generate different spreading codes according to the input channel numbers. The code generators 91, 92, ... Supply the spread codes according to the phase information of the spread codes output by the multiple access control unit 7 to the spread modulators 101, 102.

The data input to the multiple access control unit 7 is the spread modulator.
Are input to 101, 102, respectively, and the respective code generators 91, 92, ...
The spread code is modulated according to the spread code input from
Entered in 13. The combiner 13 combines the outputs of the respective spread modulators to generate a multiplexed spread modulation signal, and outputs it to the transceiver 2. The transceiver 2 converts the multiplexed spread signal into a high frequency signal and transmits it from the antenna 1.

On the other hand, the mobile station used with the fixed station having the configuration of FIG. 4 is configured as shown in FIG.

In FIG. 5, the digital data to be transmitted is modulated by the spread modulator 30 with a predetermined spread code output from the code generator 29. The output of the spread modulator 30 is multiplied by a mixer 32 with a signal of a predetermined frequency generated by the local oscillator 31.

Since the output of the mixer 32 becomes a signal having a predetermined intermediate frequency, it is amplified by the intermediate frequency amplifier 33, and further subjected to frequency conversion by the mixer 35 and the local oscillator 34.

The output of the mixer 35 is input to the transmission filter 36, where only the necessary band component is extracted and transmitted from the antenna 14 via the duplexer 15.

On the other hand, in the reception system, the reception signal output from the duplexer 15 is input to the mixer 19. The signal combined by the mixer 18 is input to the other input of the mixer 19. The mixer 18 is supplied with a predetermined spread code output from the spread code generator 17 and a signal having a frequency deviated from the reception frequency generated by the local oscillator 16 by an intermediate frequency.

At the output of the mixer 19, an intermediate frequency signal having a bandwidth corresponding to the original data can be obtained if the spread code used for modulation and demodulation is synchronized between the transmitter and the receiver.
The intermediate frequency signal output from the mixer 19 is amplified by the variable gain amplifier 20 and input to the intermediate frequency filter 22.
The variable amplifier 20 can control the gain voltage by the AGC voltage output from the AGC (automatic gain control) voltage generation circuit 21. The AGC voltage generation circuit 21 inputs and outputs the variable amplifier 20 and controls the amplifier 20 so that its level becomes constant.

The output of the variable amplifier 20 is input to the intermediate frequency filter 22. This intermediate frequency filter 22 has a bandwidth corresponding to the original data. The output of the intermediate frequency filter 22 is input to the demodulator 23, and the original data is reproduced.

[Problems to be Solved by the Invention] In order to enable communication between fixed stations and mobile stations using different channels in the above configuration,
Since different spreading codes are used for all mobile radios, when transmitting common data to all mobile stations, the same data is sent from the fixed station using different spreading codes for each mobile station. There was a problem of having to send.

[Means for Solving Problems] In order to solve the above problems, according to the present invention, in a spread spectrum communication apparatus including a fixed station and a plurality of mobile stations, the fixed station is common to each mobile station. Common transmission means for transmitting data common to each mobile station by using the spreading code and multiple transmissions for each mobile station transmitting data for each mobile station by using different spreading codes for each mobile station A plurality of mobile stations, each of the plurality of mobile stations, a common demodulation means for demodulating a synchronization signal from the received signal in accordance with the common spreading code, in synchronization with the synchronization signal demodulated by the common demodulation means, A configuration having demodulation means for demodulating received data from a received signal according to a spread code for each mobile station is adopted.

[Operation] In the above configuration, for each of the plurality of mobile stations,
The fixed station transmits common data to each mobile station using a common spreading code, and also transmits data to each mobile station using a different spreading code, while each mobile station uses a common spreading code. The received data can be reproduced in synchronization with the common synchronization signal demodulated by the spread code.

[Examples] Hereinafter, details of the present invention will be described based on examples shown in the drawings.

FIG. 1 shows a fixed station of a spread spectrum communication apparatus according to the present invention, and FIG. 2 shows a mobile station. In the following description, the same or corresponding members as those in the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted.

First, FIG. 1 is different from the conventional example of FIG. 4 in that a common spreading code generator 11 for generating a spreading code common to each mobile station and a common spreading code generated by this common spreading code generator 11 are used. The point is that a spread modulator 12 that spread-modulates the common transmission data input from the multiple access control unit 7 using a code is provided. Since other structures of the transmission system and the reception system are the same as those of the conventional example, the description thereof will be omitted here.

On the other hand, the difference in FIG. 2 is that a code generator 24 for generating the same common spreading code as the common spreading code generator 11 in FIG. 1 is provided, and the spreading code generated by this code generator 24 is provided. The point is that a circuit for restoring received data based on the above is provided.

That is, the received data branched from the duplexer 15 is the mixer.
Entered in 26. The output signal of the local oscillator 16 and the output of the common spreading code generator 24 are input to the mixer 26. Mixer 26
Is output to the intermediate frequency filter 27, and only the intermediate frequency component is extracted and input to the demodulator 28.

It is assumed that all mobile stations have the configuration shown in FIG. 2, and in this embodiment, time information is transmitted as common data to be transmitted to each mobile station.

The time information to be transmitted is the transmission multiple access control unit 7 in FIG.
Is input to the spread modulator 12 via the common spread code generator.
11 is spread-modulated by the spreading code generated by 11
To the antenna 1 from the transceiver 2 as a multiplexed signal.
Sent to. This time data is always output.

On the other hand, in the mobile station shown in FIG. 2, the transmitted time data and communication data are input to the duplexer 15, where they are branched to the mixer 19 and the mixer 26.

Since the result of multiplication of the output signal of the local oscillator 16 and the output of the common spreading code generator 24 is input to the mixer 26, the received signal is converted to an intermediate frequency as a result and the mixer 26
Only the time information is obtained by the despreading in the demodulator 28
And the final reception time data is generated.

The data other than the time data which is the common data is restored to the received data by the receiving circuit after the mixer 19 in the same circuit as the conventional one.

As described above, it is possible to set a different communication channel for each mobile station, transmit and receive data, simultaneously transmit common data that has been spread and modulated using a common spreading code, and have all mobile stations receive at the same time. .

Therefore, when transmitting data common to all mobile stations, there is no need to transmit the same data multiple times by time division using different spreading codes as in the conventional case.

Further, in the spread spectrum communication device, a technique is conceivable in which a frame synchronization signal is transmitted from a multiple access device of a fixed station and demodulated in synchronization with this frame synchronization signal.

Therefore, in the embodiment of the present invention, by changing the configuration of the mobile station as shown in FIG. 3, a frame synchronization signal is transmitted from the fixed station as data common to each mobile station.

The difference between FIG. 3 and FIG. 2 is that the demodulator 28
The other configuration is exactly the same in that the output of is input to the demodulator 23 as a synchronization signal.

The frame synchronization signal is transmitted to the mobile station as described above by using the common spreading code generator 11 and the spreading modulator 12 of the fixed station shown in FIG. 1 as data common to all mobile stations. The signal is modulated by the demodulator 28 and input to the demodulator 23.

With such a configuration, it is possible to reproduce the received data by using the frame synchronization signal common to all mobile stations.

EFFECTS OF THE INVENTION According to the present invention, for each of a plurality of mobile stations, common data is transmitted from a fixed station to each mobile station using a common spreading code, and different spreading codes are used. Data is transmitted to each mobile station on the other hand, and on the other hand, each mobile station reproduces the received data in synchronization with a common synchronization signal demodulated by a common spreading code. Can transmit different data in parallel to multiple mobile stations, and multiple mobile stations can immediately demodulate the data for each mobile station. Also, each mobile station receives using a common synchronization signal. It has an excellent effect that data can be reproduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a multiple access device adopting the present invention,
2 is a block diagram showing the configuration of a communication device, FIG. 3 is a block diagram showing the configuration of a communication device used in the device of FIG. 1, and FIG. 4 is a block diagram of a conventional multiple access device, FIG. 5 is a block diagram showing a conventional configuration of a communication device used with the device of FIG. 1, 14 ... Antenna, 3 ... Multiple access processing unit 11, 24 ... Common spreading code generator 12 ... Spreading modulator 16, 31, 34 ... Local oscillator 17 ... Spreading code generator 22, 27 ... … Intermediate frequency filter 23, 28 …… Demodulator

Claims (1)

(57) [Claims] 1. A spread spectrum communication apparatus comprising a fixed station and a plurality of mobile stations, wherein the fixed station uses a common spreading code for each mobile station to transmit common data to each mobile station. Means and
And a plurality of mobile station-specific transmitting means for transmitting data to each mobile station by using a separate spreading code for each mobile station, each of the plurality of mobile stations to the common spreading code In response to the common demodulation means for demodulating the synchronization signal from the received signal, and the synchronization signal demodulated by the common demodulation means,
A spread spectrum communication device, comprising: demodulation means for demodulating received data from a received signal according to a spread code for each mobile station.