JPH0591084A - Decoder in cdma communication system - Google Patents

Abstract

PURPOSE:To use only one synchronization detection circuit and to make the circuit scale small and inexpensive entirely by allowing the decoder to-detect initial synchronization at a synchronization detection section and using a counter so as to synchronize a signal transfer section. CONSTITUTION:A 1st decoder 12 receives an M series signal S2 generated from a 1st code generator 14 and used by a synchronization detection section of a frame. As soon as the initial synchronization is detected, the decoder 12 decodes the signal S1 and outputs a signal S3 to a synchronization pattern detector 16. The detector 16 detects a synchronization pattern included in the signal S3, generates a synchronization timing signal S4 and inputs it to a counter 18. When the counter 18 counts pulse signals 7 corresponding to the M-series signals, the counter 18 generates an initializing signal 5 and the signal 5 is inputted to a 2nd code generator 20 and a 2nd decoder 22. The signal S1 is inputted to the decoder 22 and the signal transfer part of the signal S1 is decoded by using an M series signal S6 and a 2nd decoding signal S7 is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDMA communication system, and more particularly to a decoding technique therefor.

[0002]

2. Description of the Related Art Conventionally, a frequency division method (FDMA (Frequency D) has been used as means for performing multiplex communication.
(vision multiple access)) or time division (TDMA (Time Divisi).
on Multiple Access)), etc., and is one of the methods that has recently attracted attention from the viewpoints of being able to transmit noise-resistant signals with weak radio waves and optimizing multiplexing. CDMA (C
ode Division Multiple Acce
ss) There is a communication method.

FIG. 3 is a timing chart for explaining the principle of the direct sequence system which is one of the CDMA communication systems. FIG. 3A shows a signal to be transmitted,
(B) represents a code sequence having a code length d (for example, M sequence). Here, the signal of (a) is encoded by the signal of (b). Specifically, the exclusive OR of these signals of (a) and (b) is calculated ((c) signal). Depending on whether the signal of (c) is turned on or off, sine wave signals whose phases are different from each other by 180 ° are generated as shown in (d), and the signal shown in (d) is transmitted. This transmission wave has a frequency distribution dispersed in a considerably wide frequency band because the phase thereof is inverted on the way.

On the receiving side, the signal (d) is decoded (decoded) with the signal (f). Specifically, the exclusive OR of these signals (e) and (f) is calculated, whereby the same signal (g) as the signal (a) on the transmission side is generated. '1' / '0' for each code length of the signal in (g)
As a specific method for determining, the decoded signal of (g) is integrated within each code length as shown in (h), and at the end of each code length, the integrated value and a predetermined threshold are determined. The value Th is compared, and "1" / "0" of the decoded signal (signal of (g)) at each code length is determined according to the comparison result.

Here, by using different code sequences from each other, a large number of signals can be present in the same frequency band at the same time, so that multiplex communication can be realized.

[0006]

CDMA as described above
As described above, the communication method has an advantage that it can perform strong transmission against noise with weak radio waves, but since a code sequence that is normally used has a very long code length, the receiving side takes initial synchronization. There is a problem that it takes a long time.

In order to reduce the time required for this initial synchronization, the signaling frame is divided into a synchronization detection unit for initial synchronization detection and a signal transmission unit used for actual data transmission / reception. It has been proposed to use a code sequence that is shorter than the code sequence used by the department.
However, in order to realize this method, usually, the first decoder for the synchronization detection unit is provided to detect the initial synchronization, and the second decoder for the signal transmission unit is provided, and the signal is constantly synchronized. Will be decrypted. Here, a matched filter or a correlator is usually used as the synchronization detection circuit in the decoder, but the circuit scale is large regardless of which one is used.
If both the decoder and the decoder for synchronization are provided with the circuit for synchronization detection, the overall circuit scale becomes too large, which hinders the construction of an inexpensive device.

In view of the above-mentioned circumstances, the present invention provides a synchronization detecting section in which each frame encoded using a CDMA communication system uses a first code sequence, and the first code sequence following the synchronization detecting section. In a decoding device in a CDMA communication system that decodes a received signal configured with a signal transmission unit using a second code sequence having a longer code length than
It is an object of the present invention to provide a decoding device that requires only one synchronization detection circuit having a large circuit scale such as a matched filter or a correlator.

[0009]

The decoding device in the CDMA communication system of the present invention for achieving the above object is (1) a first code generator for generating a first code sequence, and (2) a received signal. And the first generated by the first code generator
And a code sequence of the first code sequence, and a first decoder that generates a first decoded signal by decoding the received signal using the first code sequence (3) A sync pattern detector for detecting a sync pattern included therein to generate a sync timing signal in synchronization with the received signal (4) The second using the sync timing signal as a trigger
A counter that generates an initialization signal for each code length of the code sequence of (5), a second code generator that generates a second code sequence synchronized with the initialization signal, and (6) a second code generation. A second code sequence generated by
Is provided with each element of the second decoder for generating the decoded signal of.

[0010]

According to the decoding apparatus of the present invention, the first decoder requires a synchronization detection circuit having a large circuit scale such as a matched filter or a recorrator.
Since the code length of the code sequence is relatively short, a matched filter or correlator having a relatively small circuit scale is sufficient, and initial synchronization can be achieved in a short time.

Further, since the counter for generating the initialization signal for each code length of the second code sequence is provided, this counter plays the role of the synchronization detection circuit in the signal transmission section, and thus the second signal is provided. The decoder does not need to be provided with a synchronous detection circuit having a large circuit scale such as a matched filter or a correlator, so that a decoding device having a relatively small circuit scale can be realized as a whole.

[0012]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a block diagram showing the configuration of a decoding device in a CDMA communication system according to an embodiment of the present invention, and FIG. 2 is a timing chart in the decoding device.

A signal encoded by the CDMA communication system and transmitted from a transmitter (not shown) is received by a receiver (not shown), and the decoding device 10 receives the received signal S1.
Entered in. The received signal S1 has a frame structure having a sync detecting section having a short code length d1 and a signal transmitting section having a long code length d2 following the sync detecting section as shown in FIG. It is a thing.

The received signal S1 is input to the first decoder 12, and the first decoder 12 uses the received signal S1 in the frame synchronization detector generated by the first code generator 14. An M-sequence signal S2 having a short code length d1 is also input, and in the first decoder 12, the matched filter or correlator provided in the first decoder 12 detects the initial synchronization and the received signal S1 is received. The first decoded signal S3 that is decoded and generated by this decoding is output from the first decoder 12. The first decoded signal S3 is input to the sync pattern detector 16. The synchronization pattern detector 16 detects the synchronization pattern included in the input first decoded signal S3 and detects the synchronization timing signal S4 (see FIG. 2) at the head timing of the signal transmission unit.
(B)) is generated, and the synchronization timing signal S4 is input to the counter 18. This counter 1
8 is the code length d2 of the M-sequence signal used in the signal transmission unit.
When the number of pulses of the pulse signal S7 is counted by the number of pulses corresponding to (see FIG. 2), the initialization signal S5 is generated, and the initialization signal S5 is generated by the second code generator 20.
2 is input to the second decoder 22, and the counter 18 itself is reset by the initialization signal S5. Therefore, the initialization signal S5 is provided for each code length d2 of the signal transmission unit as shown in FIG. 2C. It will be repeatedly generated.

In the second code generator 20, the M-sequence signal S6 having the code length d2 used in the signal transmission section is generated in synchronization with the input initialization signal S5, and the second decoder 22 is used.
Entered in. The second decoder 22 receives the received signal S1
Is also input, and the signal transmission portion of the received signal S1 is M
The second decoded signal S is decoded using the sequence signal S6.
7 is generated. Here, since the M-sequence signal S6 generated by the second code generator 20 is a signal synchronized with the initialization signal S5, it is also a signal synchronized with the reception signal S1, and therefore the second decoder It is not necessary to provide a synchronous detection circuit having a large circuit scale such as a matched filter or a correlator in 22 and the decoding apparatus 10 as a whole is configured with a small circuit scale. The initialization signal S5 is also input to the second signal 22 because it is necessary to determine the timing for performing the binarization processing shown in FIG. 3 (h) in the second decoder 22. .

[0016]

As described above, the CDMA of the present invention
Since the decoding device in the communication system is configured such that the synchronization detection unit detects the initial synchronization and the signal transmission unit is synchronized by the counter, there is only one large-scale synchronization detection circuit such as a matched filter or correlator. As a result, an inexpensive decoding device having a small circuit scale as a whole is realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a decoding device in a CDMA communication system according to an embodiment of the present invention.

FIG. 2 is a timing chart in the decoding device shown in FIG.

FIG. 3 is a timing chart for explaining the principle of a direct sequence method which is one of CDMA communication methods.

[Explanation of symbols]

 10 Decoding Device 12 First Decoder 14 First Code Generator 16 Synchronization Pattern Detector 18 Counter 20 Second Code Generator 22 Second Decoder

Claims (1)

[Claims] 1. A code length of each frame encoded using a CDMA communication system is longer than a synchronization detecting section using a first code sequence and the first code sequence following the synchronization detecting section. A decoding device in a CDMA communication system for decoding a received signal, comprising a signal transmission section using a second code sequence, comprising: a first code generator for generating the first code sequence; A signal and the first code sequence generated by the first code generator are input, and the received signal is decoded using the first code sequence to generate a first decoded signal. A first decoder, a sync pattern detector that detects a sync pattern included in the first decoded signal and generates a sync timing signal that is in synchronization with the received signal; A counter that generates an initialization signal for each code length of the second code sequence, a second code generator that generates the second code sequence synchronized with the initialization signal, and a second code generation And a second decoder for generating a second decoded signal by decoding the received signal using the second code sequence generated by the decoder. Device.