JP2537520B2 - Code division multiple access device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a code division multiple access device, and more particularly, to a predetermined communication channel in a reception spread signal including signals of a large number of communication channels code-divided by multiple code spreading. The present invention relates to a code division multiple access device that detects the presence or absence of a received signal.

[Prior Art] In a spread spectrum communication system, a baseband signal such as digitized voice or data that is normally transmitted is code spread by using a spread code such as a pseudo noise code.
It generates a baseband signal that has a much wider bandwidth than the original data, modulates it with PSK (phase modulation), FSK (frequency modulation), and converts it to a high-frequency signal for transmission. On the receiving side, the same spreading code as that on the transmitting side is used to perform despreading for correlating with the received signal to demodulate the original data.

Since the spreading code used here is selected and assigned so that the cross-correlation is sufficiently small for each communication channel, there is almost no interference between the communication channels,
Therefore, multiple access by code division is possible.

In such a method, there is also known a method of setting a common control channel in order to determine the communication channel and determining the communication channel to be used based on the information of this channel, but the information of the control channel is not always transmitted. However, there is a problem that the system becomes complicated. Therefore, a method that does not use such a control channel has been considered.

A conventional spread spectrum communication device for performing code division multiple access without a common control channel for detecting a communication channel is configured as shown in FIG. 2 or 3.

The circuit of FIG. 2 detects a code-divided communication channel by using a sliding correlation loop, and the circuit of FIG. 3 uses a correlation detection circuit by a fixed matched filter.

In FIG. 2, the received spread signal is multiplied by the spread code sequence corresponding to the communication channel generated from the spread code generation circuit 16 in the mixer 11. The output of the mixer 11 is a bandpass filter (BPF) 12 having a bandwidth corresponding to the original data.
Is input to Further, the output of the BPF 12 is envelope-detected by the detection circuit 13 and smoothed by the low-pass filter (LPF) 14.

If the autocorrelation is obtained, the despread signal is obtained at the output of the mixer 11, passes through the BPF 12, is envelope-detected by the detection circuit 13, and is smoothed by the LPF 14 to obtain a DC level. obtain.

If no autocorrelation is obtained, no despread signal is available at the output of mixer 11, and most of the received spread signal power is blocked by BPF 12. Subsequently, envelope detection is performed by the detection circuit 13 and smoothing is performed by the LPF 14, but the obtained DC level is sufficiently smaller than when the autocorrelation is obtained.

The DC level output of the LPF14 is the voltage controlled oscillator (VCO) 15
Is supplied to. When the autocorrelation cannot be obtained, the DC level of the output of the LPF 14 is sufficiently small, so that an output of a frequency slightly different from the frequency of the spread signal included in the received spread signal is obtained at the VCO 15.

This is supplied to the spread code generation circuit 16 as a clock. Since the clock speed of the spread code generated in the spread code generation circuit 16 is slightly different from the clock speed of the received spread signal, the phases of both will gradually shift. As a result, by the time the phases of both shift by one cycle of the spreading code, the cycle is taken and the autocorrelation is obtained.

As a result, the DC output level of LPF14 rises and VCO15
The transmission frequency is locked at the current frequency, the synchronization between the reception spread code and the spread code generated by the spread code generation circuit 16 is acquired, and the signal of the communication channel is detected.

On the other hand, in the method of FIG. 3, the received spread signal is input to the matched filter 17. The matched filter 17 is composed of a digital signal processing circuit, a charge transfer element, a surface acoustic wave element and the like. In FIG. 3, the matched filter 17 is composed of a surface acoustic wave device.

That is, the matched filter 17 has a receiving electrode structure in which the carrier is PSK-modulated with the spreading code corresponding to the receiving channel and which corresponds to one period of the spreading high frequency signal or the spreading intermediate frequency signal waveform pattern.

Therefore, when the correlation between the reception spread signal and the spread code pattern that is scheduled in advance on the matched filter 17 is obtained, the electromotive forces induced in the respective reception electrodes on the matched filter 17 are added without canceling each other. hand,
Peak level is obtained.

On the contrary, when the correlation between the received spread signal and the spread code pattern set on the matched filter 17 cannot be obtained,
Since the electromotive forces induced in the receiving electrodes on the matched filter 17 cancel each other out, no peak level can be obtained.

The output of the matched filter 17 is subjected to envelope detection by the detection circuit 18, and the subsequent determination circuit 19 determines the presence or absence of a peak generated when the autocorrelation is obtained, and at the same time, the phase synchronization of the spread code is acquired by the peak position.

[Problems to be Solved by the Invention] As shown in FIG. 2, when a sliding correlation loop is used in a code division multiple access device, the received spread signal and spread code generation circuit are gradually operated from the initial state until autocorrelation is obtained. Since it is necessary to shift the phase of the generated spreading code, the time required for autocorrelation detection is generally extremely long, and many codes are time-divided by using only one or a few sliding correlation loops. It is not appropriate to detect the correlation of the divided communication channels.

Further, as shown in FIG. 3, when a correlation detection circuit using a matched filter is used in a code division multiple access device, the electrode configuration of the matched filter is usually fixed, so that a plurality of code division channels are time-divisionally divided. It is impossible to detect the correlation of. Therefore, in this type of apparatus, a plurality of correlation detection circuits using the above-described sliding correlation loop or matched filter are operated in parallel, that is, the number of allocated communication channels, to realize multiple access.

Thus, in a conventional code division multiple access device that does not use a common control channel, it is necessary to provide a correlation detection circuit using many sliding correlation loops or matched filters in order to realize multiple access,
There is a drawback that the overall configuration becomes complicated.

[Means for Solving Problems] In order to solve the above problems, in the present invention, code division multiple access is performed in which multiple access is performed using a plurality of communication channels in which signals are spread by different spreading codes. In the connection device, a generation means for sequentially generating a plurality of reference signals corresponding to each of the plurality of communication channels by temporally switching, a reception signal, and a reference signal generated by the generation means are inputted, and both inputs are inputted. Convolver means for forming a convolution integrated signal of signals, and presence or absence of each signal of the plurality of communication channels based on the output state of the convolver means with respect to each of the plurality of reference signals sequentially switched by the generating means. A configuration is adopted in which a detection means for sequentially detecting is provided.

[Operation] According to the above configuration, a plurality of reference signals corresponding to each of a plurality of communication channels are temporally switched and sequentially generated, and the convolver means generates a received signal and a convolution integrated signal of the generated reference signals. The presence or absence of each signal of the plurality of communication channels can be sequentially detected based on the output state of the convolver means with respect to each of the plurality of reference signals that are generated and sequentially switched.

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

FIG. 1 shows an embodiment of a communication channel control unit of a code division multiple access device according to the present invention, wherein reference numeral 1 is a convolver. As is well known, the convolver 1 has a semiconductor detection element arranged on a surface acoustic wave element such as a piezoelectric element, and a plurality of signals input from the end electrodes of the surface acoustic wave element as envelope signals from the detection element. It outputs the convoluted (convolutional) signal of.

In the present embodiment, the received spread signal and the reference signal output from the mixer 9 are input to the convolver 1, and convolution signals of these are formed.

The output of the convolver 1 is amplified by the amplifier circuit 2 and input to the BPF 3 whose center frequency of the pass band is twice the center frequency of the transmission spread signal.

The output of BPF3 is input to the detection circuit 4 which performs envelope detection, and the detection output is input to the determination circuit 5. The determination circuit 5 determines the presence / absence of autocorrelation, that is, the presence / absence of a signal of a predetermined communication channel depending on whether or not the input signal exceeds a predetermined threshold value. The output of the determination circuit 5 is output to the reception processing unit having the same structure as the conventional one and used for signal reception.

On the other hand, a reference signal formed by the following circuit is input to the mixer 9.

First, reference numeral 6 denotes a channel number generation circuit that periodically generates all the channel numbers given to the assigned communication channels once in each cycle.

The channel number output by the channel number generation circuit 6 is input to the spread code selection circuit 7. In the spreading code selecting circuit 7, the spreading code corresponding to the communication channel input from the channel number generating circuit 6 is set to the spreading code generating circuit 8.
The control is performed so that The output of the channel number generation circuit 6 is also output to the receiver and used.

The spread code generation circuit 8 generates a signal obtained by inverting the spread code used in the communication channel on the time axis according to the output of the spread code selection circuit 7.

The output signal of the spread code generating circuit 8 is mixed in the mixer 9 with a carrier having the same frequency as the center frequency of the received spread signal generated by the local oscillator 10.

 Next, the operation of the above configuration will be described.

The channel number generation circuit 6 continues to generate the channel number of each assigned communication channel for a time corresponding to two cycles of the spread code or a time longer than that. The spread code selection circuit 7 includes a channel number generation circuit 6
Based on the obtained channel number, the spread code generating circuit 8 is controlled so as to generate a signal in which the spread code corresponding to the communication channel is inverted on the time axis.

The output of the spread code generating circuit 8 is mixed with the output of the local oscillator 10 by the mixer 9. The output of the mixer 9 is a time-reversed copy of the spread signal corresponding to the communication channel, and is continuous for at least the time corresponding to two cycles of the spread code, so if the received signal corresponds to the channel. If the spread signal is included, the peak of the autocorrelation appears once or more times in the convolver 1 as an envelope component having a frequency twice the center frequency of the spread signal.

This signal is amplified by the amplifier circuit 2, filtered by the BPF 3, envelope-detected by the detection circuit 4, and supplied to the determination circuit 5. The determination circuit 5 detects the peak of the autocorrelation, determines that the signal of the communication channel exists, and transmits the determination signal including the channel number generated by the channel number generation circuit 6 and the synchronization timing to the receiver. To do. On the other hand, when the received signal does not include the spread signal of the channel, the output of the mixer 9 does not obtain autocorrelation while the spread signal corresponding to the communication channel is generated. Determines that there is no signal corresponding to the channel, and does not transmit the signal to the receiver side.

The channel number generation circuit 6 generates a channel number corresponding to the next communication channel after a lapse of a predetermined time, and waits for a signal of the communication channel.

The above operation is repeated for all the assigned channels to determine the presence / absence of signals on all channels, and if signals are present, the channel number and synchronization timing are transmitted to the receiver.

As described above, by using the convolver to temporally switch the reference signal specified by the spread code corresponding to the communication channel, the signal of the predetermined communication channel can be transmitted without using the control channel for determining the communication channel. Can be detected. According to the above configuration, the second
A sliding correlation loop as shown in FIG. 3, FIG.
There is an excellent effect that a communication channel can be specified by a simple and inexpensive configuration without providing a lot of correlation detection circuits using a matched filter.

[Effects of the Invention] As is apparent from the above, according to the present invention, a plurality of reference signals corresponding to a plurality of communication channels are temporally switched and sequentially generated, and a convolver means generates a reception signal and a reception signal. It is possible to form a convolutional integrated signal of the reference signal and sequentially detect the presence or absence of each signal of the plurality of communication channels based on the output state of the convolver means with respect to each of the plurality of reference signals that are sequentially switched and generated. Therefore, there is an excellent effect that the received signal of the target communication channel can be detected at high speed with a simple and inexpensive configuration without providing a large number of correlation detection circuits as in the conventional case.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a communication channel control unit of a code division multiple access device adopting the present invention, FIG.
FIG. 3 is a block diagram showing a configuration of a conventional different communication channel detecting device. 1 ... Convolver, 2 ... Amplifier circuit 3 ... BPF, 4 ... Detection circuit 5 ... Determination circuit 6 ... Channel number generation circuit 7 ... Spread code selection circuit 8 ... Spread code generation circuit 9 ... Mixer , 10 …… Local oscillator 11 …… Mixer, 12 …… BPF 13 …… Detection circuit, 14 …… LPF 15 …… VCO 16 …… Spread code generation circuit 17 …… Matched filter 18 …… Detection circuit, 19 …… Judgment circuit

Claims (1)

(57) [Claims] 1. A code division multiple access device for performing multiple access using a plurality of communication channels in which signals are spread by different spreading codes, wherein a plurality of reference signals corresponding to each of the plurality of communication channels are timed. Generating means for sequentially generating and sequentially generating, a received signal, and a convolver means for inputting a reference signal generated by the generating means to form a convolution integral signal of both input signals, and temporally switching by the generating means. A code division multiple access device comprising: detection means for sequentially detecting the presence or absence of each signal of a plurality of communication channels based on the output state of the convolver means with respect to each of a plurality of reference signals sequentially generated.