JP2844271B2 - Spread spectrum communication equipment - Google Patents

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 apparatus, and more particularly to a code division multiple access (CDMA) for allocating a common receiving carrier frequency to a plurality of stations, allocating a pseudo random code (PN code), and performing multiple access. ) Is performed.

[0002]

2. Description of the Related Art Generally, in a code division multiple access system, a common receiving carrier frequency is allocated to a plurality of stations and a unique PN code is allocated to each station. In such a code division multiple access system, on the transmitting side, for example, a data signal is spread spectrum by a PN code to form a transmission data signal, a transmission carrier is modulated by the transmission data signal, and transmitted as a spread spectrum signal. I have. On the other hand, on the receiving side,
Upon receiving the spread spectrum signal, the received signal spread by the own station PN code is subjected to synchronization acquisition by a so-called synchronization acquisition circuit,
After obtaining a synchronization capture output signal, a so-called synchronization tracking circuit initializes the own station PN code generator (reference PN code) with the synchronization capture output signal, and then performs synchronization tracking of the own station PN code. That is, the line to the own station is identified.

[0003]

As described above, in the conventional code division multiple access system, since a data signal is spectrum-spread by a unique PN code, any one station can use all other stations. You cannot make a batch call that calls all at once. On the other hand, when the above-mentioned own-station PN code is prepared as a reference PN code, and a collective calling PN code common to each station is prepared, and the self-station PN code and the collective calling PN code are switched as necessary. At the moment when the spread spectrum signal spread by the collective call PN code is received, each station changes the reference PN code to the collective call PN code.
It is extremely difficult to switch to a code. In addition, if each station is provided with not only a synchronization acquisition circuit and a synchronization tracking circuit corresponding to its own PN code but also a synchronization acquisition circuit and a synchronization tracking circuit corresponding to the collective calling PN code, the reception system becomes There is a problem that a system is required and the circuit scale becomes large. SUMMARY OF THE INVENTION It is an object of the present invention to provide a spread spectrum communication apparatus capable of performing a batch call without increasing the circuit scale.

[0004]

According to the present invention, there is provided a code division multiple access system comprising a plurality of stations, each of which is assigned a unique PN code, and performing code division multiple access between the stations. In a spread spectrum communication apparatus used for transmitting a spread spectrum transmission signal and receiving a spread spectrum reception signal, a common P common to all of the stations is used.
N code is assigned, a first selecting means for selectively outputting any one of the unique PN codes and the common PN code to make it a transmission reference PN code, and A transmitting means for performing spread spectrum using the spread spectrum transmission signal, and receiving the spread spectrum reception signal, the spread spectrum reception signal is spread spectrum by one of the unique PN code and the common PN code. Determining means for determining whether or not the signal has been transmitted, and selecting means for selectively outputting the unique PN code and the common PN code in accordance with the determination signal to obtain a received reference PN code; Demodulation means for demodulating the spread spectrum received signal based on the received reference PN code.

[0005]

According to the present invention, a unique PN code or a common PN code is provided as a reception reference PN code depending on whether a spread spectrum received signal is spread with a unique PN code or a common PN code. Is transmitted to demodulate the spread spectrum received signal based on the received reference PN code, so that both individual call and collective call can be handled, and the circuit scale does not increase.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. Referring to FIG. 1, the code division multiple access system according to the present invention includes first to fourth communication stations 11 to 14, and each of the communication stations 11 to 14 is a wireless communication path (hereinafter simply referred to as a communication path). 15 are connected. A unique PN code is assigned to each communication station. In addition,
Here, since each communication station performs transmission using a common carrier frequency, the communication path 15 is indicated by the sum of transmission signals (Σ). Although the first to fourth communication stations are shown here, the number of communication stations may be three or five or more.

Here, referring also to FIG. 2, each of the communication stations 11 to 14 has the transmission unit shown in FIG. A plurality of PN codes are generated from the PN code generator 20, and a PN code of a partner station (a PN code corresponding to a partner station to be transmitted) and a batch calling PN code are selectively generated according to a PN code switching signal. The PN code is provided to a band spreading circuit 21, where the transmission data is spread spectrum (the PN code has a higher transmission speed than the transmission speed of the transmission data), and is input to the modulator 22 as a spread data signal. The modulator 22 modulates the transmission carrier with the spread data signal and outputs it as a first modulation signal. Thereafter, the first modulated signal is band-limited by a band-pass filter (BPF) 23, amplified by an intermediate frequency amplifier (IFAMP) 24, and supplied to a frequency converter 25 as an amplified signal. The frequency converter 25 converts the frequency of the transmission carrier using the local oscillation frequency provided from the local oscillator 26 and supplies the converted carrier to the power amplifier (power AMP) 27 as a second modulation signal. The power amplifier 27 power-amplifies the second modulated signal and sends it out of the transmission antenna 28 as a transmission signal (spread spectrum signal).

Next, referring to FIG. 3, each of the communication stations 11 to 14 has the receiving unit shown in FIG. The transmission signal is received by the reception antenna 30 as a reception signal. This received signal is amplified by a high-frequency amplifier (high-frequency AMP) 31 and converted to an intermediate frequency signal by a frequency converter 32 using a local oscillation frequency given from a local oscillator 51. The intermediate frequency signal is band-limited by the BPF 33 and supplied to intermediate frequency amplifiers (IFAMPs) 34 and 35, where it becomes an intermediate frequency amplified signal (here, the intermediate frequency amplified signal output from the intermediate frequency amplifier 34 is The intermediate frequency amplified signal output from the intermediate frequency amplifier 35 is called a first amplified signal, and the intermediate amplified signal is called a second amplified signal.)

The first amplified signal is provided to first and second correlators 36 and 37, respectively. The first correlator 36 detects a correlation peak and outputs it as a correlation peak value when the first amplified signal is a signal subjected to spectrum spreading by the local station PN code. In this case, the second correlator 37
Of the amplified signal is detected and output as a noise level value. On the other hand, when the first amplified signal is a signal subjected to spectrum spreading by the collective calling PN code, the second correlator 37 detects a correlation peak and outputs it as a correlation peak value. In this case, the first correlator 36 outputs the first
And outputs it as a noise level value (hereinafter, the output from the first correlator 36 is the first correlation signal, and the output from the second correlator 37 is the second correlation signal). ).

First and second envelope detectors 38 and 39
In the first embodiment, the first and second correlation signals are respectively envelope-detected as first and second detection values, and the first and second comparator 40
And 41. First and second comparators 40 and 41
Then, a predetermined threshold value (Th) is compared with the first and second detection values, and first and second determination signals are transmitted. For example, in the first and second comparators 40 and 41, when the first and second detection values exceed a threshold value (Th), the first and second high-level signals are used as first and second determination signals. Is sent. The logical adder 42 logically adds the first and second determination signals to generate a logical addition signal. The logical addition signal is used as a reset signal as described later.

The second amplified signal is supplied to a synchronization tracking circuit 43 and a despreading circuit 44. The synchronization tracking circuit 43
N code generator 43a and batch calling PN code generator 43
b, when receiving the above-described logical addition signal, the local station PN code generator 43a and the collective calling PN code generator 4
3b is reset. Here, assuming that the first and second amplified signals are signals subjected to spectrum spreading with the own station PN code, the synchronization tracking circuit 43 uses the own station PN code generator 43.
own PN code from a (hereinafter referred to as oscillation own PN code)
Is synchronized with the own station PN code included in the second amplified signal.

Now, it is assumed that the terminal a and the terminal b of the switch 45 are connected. PN code switching circuit 4
In step 6, a switching signal is generated in response to the second determination signal.
Here, the second determination signal is a second determination signal indicating a noise level value.
The PN code switching circuit 46 does not generate a switching signal because the signal is generated based on the correlation signal of (i), that is, it is not generated based on the correlation peak value. When the switch 47 does not receive the switching signal, the local station PN code generator 43
a and the despreading circuit 44 are connected. That is, the oscillation own station P
The N code is provided to the despreading circuit 44 as a reference PN code. The despreading circuit 44 despreads the second amplified signal based on the oscillation local station PN code to generate a despread signal (the despread signal is equal to a signal (modulated signal) obtained by modulating a carrier with transmission data. ). This despread signal is BPF4
The signal is band-limited at 8 and provided to the data demodulator 49. The data demodulator 49 demodulates the despread signal to obtain demodulated data.

On the other hand, when the receiving section receives a transmission signal spread spectrum by the collective calling PN code as a reception signal, as apparent from the above description, the first correlation signal indicates a noise level value and the second correlation signal indicates a noise level value. Will represent the correlation peak value. As a result, the PN code switching circuit 46
Then, a switching signal is generated and transmitted. On the other hand, the logical adder 42 sends out a reset signal, whereby the own-station PN code generator 43a and the batch calling PN code generator 43b are reset. Then, the synchronization tracking circuit 43 outputs the batch calling P from the batch calling PN code generator 43b.
The N code (hereinafter, referred to as an oscillation collective calling PN code) is synchronously tracked with the collective calling PN code included in the second amplified signal.

The switch 47 connects the batch calling PN code generator 43b and the despreading circuit 44 by a switching signal. That is, the batch calling PN code is given to the despreading circuit 44. The despreading circuit 44 despreads the second amplified signal based on the PN code for oscillating batch calling to generate a despread signal. This despread signal is band-limited by the BPF 48 and supplied to the data demodulator 49. The data demodulator 49 demodulates the despread signal to obtain demodulated data.

By the way, in the switch 45, the terminal a
When the terminal c is connected to the terminal c, the switch 47 is controlled to be switched by a local PN code selection signal and a batch calling PN code selection signal provided via the switch 50, respectively. Bulk calling PN
The code will be provided to the despreading circuit 44. That is, when the terminal a and the terminal b are connected in the switch 50, a collective calling PN code selection signal is given to the switch 47, whereby the switch 47 is connected to the collective calling PN code generator 43b and the despreading circuit 44. Connect. on the other hand,
When the terminal a and the terminal c are connected in the switch 50, the own station PN code selection signal is given to the switch 47,
As a result, the switch 47 switches its own PN code generator 43b.
And the despreading circuit 44. In this way, it is possible to select the local station PN code and the PN code for collective calling as needed.

[0016]

As described above, according to the present invention, a unique PN code and a common PN code are provided, and a received reference PN code is determined depending on whether a spread spectrum received signal is spread with a unique PN code or spread with a common PN code. Since a unique PN code or a common PN code is sent out and a spread spectrum received signal is demodulated based on the received reference PN code, it is possible to cope with both individual calling and collective calling, and the circuit scale is reduced. This has the effect of not increasing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a code division multiple access system to which the present invention is applied.

FIG. 2 is a block diagram showing an embodiment of a transmission section of the spread spectrum communication apparatus according to the present invention.

FIG. 3 is a block diagram showing an embodiment of a receiving section of the spread spectrum communication apparatus according to the present invention.

[Explanation of symbols]

 11-14 Communication Station 15 Communication Path 20 PN Code Generator 21 Band Spread Circuit 22 Modulator 23 Band Pass Filter (BPF) 24 Intermediate Frequency Amplifier (IFAMP) 25 Frequency Converter 26 Local Oscillator 27 Power Amplifier 28 Transmitting Antenna 30 Receiving Antenna REFERENCE SIGNS LIST 31 high-frequency amplifier 32 frequency converter 33 band-pass filter 34, 35 intermediate-frequency amplifier 36, 37 correlator 38, 39 envelope detector 40, 41 comparator 42 logical adder 43 synchronization tracking circuit 44 despreading circuit 45 switch 46 PN Code switching circuit 47 Switch 48 Band-pass filter 49 Data demodulator 50 Switch 43a Local PN code generator 43b Batch calling PN code generator 51 Local oscillator

Claims (3)

(57) [Claims] 1. A plurality of stations, each of which is assigned a unique PN code, used in a code division multiple access system for performing code division multiple access between the stations, and transmits a spread spectrum transmission signal. In a spread spectrum communication device,
A common PN code is assigned to all of the stations, and one of the unique PN codes and the common PN code are selectively output to perform a first selection as a transmission reference PN code. And a transmitting means for performing spread spectrum using the transmission reference PN code and transmitting the spread signal as the spread spectrum transmission signal. 2. A plurality of stations, each of which is assigned a unique PN code, used in a code division multiple access system for performing code division multiple access between the stations, and receives a spread spectrum reception signal. In a spread spectrum communication device,
A common PN code is allocated to all of the stations, and the spread spectrum transmission signal according to claim 1 is received as a spread spectrum reception signal, and the spread spectrum reception signal is the unique PN code and the common PN code. A determination means for determining whether the signal has been spread by any of the codes and transmitting a determination signal;
A second selecting means for selectively outputting the N code and the common PN code to be a reception reference PN code, and a demodulation means for demodulating the spread spectrum reception signal based on the reception reference PN code. Spread spectrum communication equipment. 3. A plurality of stations, each of which is assigned a unique PN code, used in a code division multiple access system for performing code division multiple access between the stations, and transmits a spread spectrum transmission signal. In a spread spectrum communication apparatus that receives a spread spectrum reception signal together with the common PN code, a common PN code is assigned to all of the stations, and any one of the unique PN codes and the common PN code
First selecting means for selectively outputting a code to make a transmission reference PN code, transmitting means for performing spread spectrum using the transmission reference PN code and transmitting the spread spectrum transmission signal, and transmitting the spread spectrum reception signal Upon receiving the spread spectrum received signal, determines whether the spread spectrum received signal has been spread by one of the unique PN code and the common PN code, and sends a determination signal; and determines the unique PN according to the determination signal. And a demodulator for demodulating the spread spectrum received signal based on the received reference PN code based on the received reference PN code. Spread spectrum communication device.