JPH08237170A - Transmission system for spread spectrum signal and its inverse spread synchronous reception system - Google Patents

Abstract

PURPOSE: To acquire a phase of an inverse spread code in a short time even in the sliding system in the transmission reception system for the spread spectrum signal. CONSTITUTION: The transmission system for a spread spectrum signal is provided with a narrow band modulation section 11 applying narrow band modulation to transmission data, a spread code generating section 12, and a spread modulation section 13 applying spread modulation to transmission data subject to narrow band modulation with the spread code, and the spread modulation section 13 inserts a preamble being a non-spread modulation part intermittently to transmission data subject to spread modulation. On the other hand, the inverse spread synchronous reception system being the receiver side uses a narrow band preamble demodulation section 22 and a DPLL section 24 applying narrow band demodulation to the non-spread modulation part of the reception data to take rough timing, a window sliding correlation section 25 conducts sliding correlation within a range of a window of a short width set based on the rough timing, a narrow band demodulation section 26 conducts narrow band demodulation of data subject to inverse spread modulation to acquire an inverse spread code in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum signal transmission system utilizing spread spectrum and its despread synchronous receiving system.

[0002]

2. Description of the Related Art In the field of communication, conventionally, data to be transmitted is spread over a wide frequency band by a spread code, that is, the signal is buried in noise and the signal is transmitted to a person who is inconvenient to receive the signal. So-called spread spectrum communication is used in which transmission is made without awareness of its existence. In such a communication system, when the receiving side attempts to receive the spread spectrum signal, it is necessary to perform correlation reception for extracting the spread spectrum code of the desired received signal and accurately synchronizing it.

As a despreading synchronization system for obtaining the correlation of the spread spectrum signal, a correlation system called a search system or a sliding system has been conventionally used because of its simple circuit configuration and easy change of the correlation coefficient. Is widely used. In the despreading synchronization system based on this search or sliding method, it is said that the position of high correlation is searched while sliding the phase between the despreading code and the received signal on the receiving side to be referenced at intervals of one chip or less of the spreading code. It is a thing. FIG. 4 shows a state in which the despread code leads the received signal by the phase difference τ. The larger the phase difference τ, the longer it takes to capture the synchronization point. .
The arrow in the figure indicates the sliding direction.

[0004]

However, in the despreading synchronization method called the search or sliding method, which is the conventional technique, a spreading code is pulled in by a sliding correlator, but a long search time for this sliding correlation is required. It's a problem. That is, in the spread code synchronization by such sliding correlation, a reference signal is generated in the receiver, and the synchronization phase is searched while sliding this reference signal.However, since it is completely unknown where this synchronization point is, In order to supplement, it has to be slid over the entire period of the code, which has a problem that it takes time. In particular, the longer the period of the phase difference τ, the spread code, and the transmission data, the greater the synchronization supplement time until the synchronization point is supplemented.

Therefore, an object of the present invention is to solve the problem of the above-mentioned conventional technique, that is, the length of the despreading synchronization time, and to perform the despreading synchronization in a short time. It is an object of the present invention to provide a despreading synchronous receiving system.

[0006]

According to the present invention, the above object is to provide a narrow band modulator for narrow band modulating data to be transmitted by a carrier wave, and a spread code generator for generating a spread code. A spread spectrum signal transmission system comprising: a spread modulator that spread-modulates data narrow-band modulated by the narrow-band modulator with a spread code from the spread-code generator. This is achieved by a spread spectrum signal transmission system that is configured to intermittently insert a non-spreading modulator in the transmission data to be modulated.

Further, according to the present invention, also in order to achieve the above object, there is provided a despreading synchronous receiving system for receiving data transmitted by being spread-modulated by the above-mentioned spread spectrum signal transmitting system. The narrow band preamble demodulation unit for narrow band demodulating the non-spread modulation unit of the data, the despread code generation unit for generating the despread code for the despread modulation, and the data demodulated by the narrow band preamble demodulation unit. A DPLL section for obtaining a rough timing, a window sliding correlation section for setting a window having a predetermined width shorter than a data cycle on the basis of the obtained rough timing, and performing a sliding correlation within the set window range, and the window addition Despread synchronization reception of a spread spectrum signal composed of a narrow band demodulation unit that performs narrow band demodulation of data subjected to despread modulation in the sliding correlation unit. System is proposed.

[0008]

That is, according to the spread spectrum signal transmitting system and the despreading synchronous receiving system thereof according to the present invention,
As will be apparent from the following detailed description, in the transmitting system, the non-spreading part (preamble) is intermittently inserted in the spread modulation signal of the data to be transmitted, and in the receiving system, the transmission data is intermittently inserted. The despread synchronization time is shortened by narrowing the required sliding width by preliminarily performing coarse synchronization by the non-spreading portion that is inserted.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Detailed embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 2 shows the system configuration of the transmitting side of the spread spectrum signal which is an embodiment of the present invention. As is clear from the figure, this transmitting side system adopts the direct spread method. , A narrow band modulator 11 for performing a so-called narrow band modulation by a sine carrier from an oscillator (not shown), a spread code generator 12 for generating a spread code p, and a narrow code It is composed of a spread modulator 13 for further modulating the band-modulated signal with a spread code, and an antenna 14 for transmitting the spread-modulated signal. And according to the present invention,
A coarse synchronization preamble is inserted in each data frame in advance in transmission data to be transmitted.

A signal transmitted from the transmission side system having the above-described configuration is received by, for example, the antenna 21, and this reception signal is demodulated again into reception data by the reception side system having the following configuration. As shown in FIG. 1 attached hereto, this receiving side system includes a narrow band preamble demodulation unit 22 that demodulates a received signal from the antenna 21 and performs rough timing extraction, and a timing from the narrow band preamble demodulation unit 22. Hold DPLL (Digital
Phase lock loop) unit 23, despreading code generation unit 24 that generates a despreading code p ′ for performing despreading with the signal from the DPLL unit 23, the received signal and the despreading code generation unit 24 And a despreading code, the sliding correlation unit 25 with a window for performing despreading by obtaining the correlation between the received signal and the despreading code by a sliding method.
Then, it is composed of a narrow band demodulation unit 26 for performing narrow band demodulation of a carrier wave on the received signal despread by the sliding correlation unit with window 25 to obtain received data.

Next, the operation of the transmission side system and the reception side system of the spread spectrum signal having the above configuration will be described below. First, in the spread spectrum signal transmission side system of FIG. 2, at the time of transmission, the transmission data in which the coarse synchronization preamble is inserted into each data frame is subjected to narrow band modulation in the narrow band modulation unit 11. Next, the narrowband-modulated data is spread-modulated by the spreading code p generated by the spreading code generation unit 12 except for the added coarse synchronization preamble. Thereafter, the spread-modulated transmission data is transmitted via the antenna 14, and the spread-modulation transmitted data thus transmitted is spread-modulated (spread-modulated) as shown in FIG. A non-spreading preamble is intermittently inserted between the modulators and is transmitted from the transmitting side to the receiving side.

On the other hand, in the receiving side system of the spread spectrum signal shown in FIG. 1, the received signal received by the antenna 21 is first complemented by the narrow band preamble demodulation section 22 with the non-spread preamble of the received signal, that is, , Coarse timing (coarse synchronization) extraction is performed by the non-spread preamble that is not spread and modulated. Based on the extracted coarse timing, the DPLL unit 23 causes the despreading code (reference signal) generated by the despreading code generator 24.
The coarse timing in the phase is held by p '.

Further, in the spread spectrum signal reception side system, the sliding correlator with window 25 receives the phase of the despread code (reference signal) p'from the above-described sliding based on the coarse timing thus obtained. Despreading synchronization to synchronize with the spreading code of the signal will be performed,
According to the present invention, at this time, a predetermined time window is set. That is, according to the method of the present invention, coarse timing is preliminarily set by the non-spreading preamble intermittently inserted in the transmission signal. Therefore, the correlation detection for despreading synchronization is performed based on the rough timing. It is sufficient that the search is performed within the time window set by the width, and it is not necessary to search for the entire period including all symbols of the transmission signal as in the conventional case.

Then, the sliding correlation unit 2 with window
The reception signal despread in 5 is further demodulated in the narrow band demodulation unit 26, and is output as a data signal (reception data).

As described above, according to the spread spectrum signal transmission / reception system of the present invention described above, it is possible to perform despread synchronization in a short time by transmitting a non-spread narrow band signal as a preamble. Become. This makes it possible to extract the coarse timing of symbols by the non-spread preambles that are intermittently inserted between the spread modulation parts of the transmission data, and therefore, it is not necessary to perform sliding correlation in all symbol intervals, and based on the extracted coarse timing. Therefore, it is sufficient to perform the sliding correlation of the spread signal only within a time window set within a short section (for example, a predetermined width shorter than the data period).

In other words, the sliding correlation start position for obtaining (complementing) the spread code synchronization on the receiving side is preliminarily coarsely timed by the non-spread preamble inserted between the spread modulation parts. Thus, it becomes possible to keep a certain short section by the set window. Therefore, it is not necessary to search for correlation points by sliding all symbols of transmission data, and despreading synchronization can be performed in a short time. Further, according to the present invention, there is an advantage in that burst transmission using the non-spread narrow band signal as a preamble is also possible.

[0017]

As is apparent from the above detailed description, according to the spread spectrum signal transmission system and the despreading synchronous reception system thereof according to the present invention, the sliding system is adopted, but the phase search is still performed. By making it possible to shorten the supplementary time, which is the time for, it is possible to achieve a spread spectrum transmission / reception system with a simple circuit configuration and easy change of the correlation coefficient. In terms of technology, it will be extremely effective.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a spread spectrum despread synchronous reception system according to the present invention.

FIG. 2 is a block diagram showing a schematic configuration of a spread spectrum signal transmission system according to the present invention.

FIG. 3 is a diagram showing an example of a data configuration in the spread spectrum signal transmitting / receiving system according to the present invention.

FIG. 4 is a diagram illustrating the concept of sliding correlation, which is a conventional technique.

[Explanation of symbols]

 11 Narrowband Modulation Section 12 Spreading Code Generation Section 13 Spreading Modulation Section 14 Antenna 21 Antenna 22 Narrowband Preamble Demodulation Section 23 DPLL (Digital Phase Lock Loop) Section 24 Despreading Code Generation Section 25 Sliding Correlation Section with Window 26 Narrowband Demodulation Section

Claims (2)

[Claims] 1. A narrow band modulator for narrow band modulating data to be transmitted by a carrier, a spread code generator for generating a spread code, and the spread code for the data narrow band modulated by the narrow band modulator. In a spread spectrum signal transmission system including a spread modulator that spread-modulates using a spread code from a generator, the spread modulator may intermittently insert a non-spread modulator into the spread-modulated transmission data. A spread spectrum signal transmission system characterized by being configured. 2. A despreading synchronous reception system for receiving data transmitted by being spread-modulated by the spread spectrum signal transmission system according to claim 1, wherein a non-spreading modulation section of the received data is narrow-band demodulated. A narrowband preamble demodulation unit, a despreading code generation unit that generates a despreading code for despreading modulation, a DPLL unit that obtains rough timing by the data demodulated by the narrowband preamble demodulation unit,
A window with a predetermined width shorter than the data cycle is set based on the obtained coarse timing, and a windowed sliding correlation section that performs sliding correlation within the set window range, and despread modulation is performed by the windowed sliding correlation section. And a narrow-band demodulation unit for performing narrow-band demodulation of the data, and a despread synchronous reception system for spread spectrum signals.