JPH08237169A - Preamble synchronization system - Google Patents

Abstract

PURPOSE: To obtain the system where correction of the stability of synchronization acquisition in deteriorated channel quality and of Doppler shift is simplified in the mobile communication equipment employing the spread spectrum system. CONSTITUTION: A transmitter is made up of a primary data modulator 6, a secondary spread spectrum modulator 7, and a preamble generator 5, the preamble generator 5 generates consecutive data of '1' or '0' for a preamble period, generates a non-modulation wave for the preamble period by giving the data to the primary modulator 6. The non-modulation data only for the preamble period are given to the spread spectrum modulator 7, in which spread spectrum modulation is conducted to improve the reception S/N by minimizing a demodulation signal band at synchronization acquisition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronization system for performing burst-like synchronization by a spread spectrum communication system on a wireless transmission line.

[0002]

2. Description of the Related Art Conventionally, a spread spectrum communication system has been used for a wireless LAN and a mobile communication device. According to this, data can be multiplexed, the communication capacity can be increased, and since it is strong against interference and has excellent confidentiality, it is useful for effective use of frequencies.

However, in order to make full use of the characteristics of spread spectrum communication, it is necessary to synchronize spread codes for performing spread spectrum modulation, and it is necessary to consider a synchronization method based on the required specifications of all the systems used.

In the prior art, PS is used as the primary modulation method.
When the K modulation method is used, the carrier recovery circuit of FIG. 3 is used to configure an AFC circuit to take measures against Doppler shift. (Refer to GPS by Japan Surveyors Association) In the figure, 11 is an amplifier unit, 12 is a frequency multiplier 1, 13 is a phase comparator, 14 is a loop filter, 15 is a voltage controlled oscillator, and 16 is a frequency multiplier 2. is there. In the system using this carrier recovery circuit, PS is used as the primary modulation system.
This is only possible when the K method is used, and there is a problem that the time constant of the carrier recovery circuit is limited to some extent.

As another related technique, Japanese Patent Laid-Open No. Hei 1-198.
133, JP-A-4-172727, JP-A-6-177858 and the like.

[0006]

As described above, when performing synchronization acquisition of spread spectrum communication, correlation detection is performed using a primary modulation signal, but since it is a data modulation wave, the signal is detected at the data modulation speed. There is a drawback that the level is lowered and the band of the correlation detection filter is widened to lower the correlation detection S / N.

Further, in the method using the carrier wave reproducing circuit,
This is only possible when the PSK method is used as the primary modulation method, and there is a problem that the time constant of the carrier recovery circuit is limited to some extent.

An object of the present invention is to provide a synchronization system capable of reliably performing spread code synchronization by considering the influence of Doppler shift within a band determined in a radio device using a spread spectrum communication system. .

[0009]

The above-mentioned object is to make primary modulation data within the preamble period into a continuous non-modulation state of "1" or "0" and reduce the demodulation signal bandwidth after primary demodulation to a narrow band. By doing so, the correlation detection S / N can be improved.

That is, it is achieved by providing a preamble period at the beginning of the data and maintaining an unmodulated state for a certain period of time to improve the S / N at the time of synchronous acquisition and ensure the synchronous acquisition. To be done.

This is also achieved by setting the primary modulation data in the preamble period to "1" or "0" to facilitate detection of the phase rotation amount due to Doppler shift.

[0012]

With the above means, the preamble generator converts the primary modulation data in the preamble period to "1" or "1".
It is generated as continuous data of 0 ". This data is input to the primary modulator to generate an unmodulated signal.

The unmodulated signal is demodulated after the primary demodulation (spectrum despreading) is performed on the receiving side by generating the unmodulated signal during the preamble period.

Since the demodulation signal for synchronization acquisition is a non-modulated wave, it becomes a narrow band signal and the S / N ratio at the time of synchronization acquisition can be improved.
Even if the line quality deteriorates, the synchronization can be reliably acquired.

Further, since the primary modulation data is continuous data of "1" or "0" during the preamble period, the phase rotation amount due to the Doppler shift can be easily detected.

[0016]

EXAMPLES The present invention will be described below with reference to examples.

FIG. 1 shows a data format according to an embodiment of the present invention, which comprises a preamble 1, a start word 2, a slave station address 3 and data 4.

FIG. 2 is a block diagram on the transmitter side according to one embodiment of the present invention. The preamble generator 5, the primary modulator 6, the spread spectrum modulator 7, the frequency converter 8, the power amplifier unit 9, It is composed of a spread code generator 10.

The circuit operation will be described below. The preamble generator 5 generates continuous data of "1" or "0" in the preamble 1 period as shown in FIG. 1, and the start word 2 which is the first word of the data after the end of the preamble period. Then, a slave station address 3 for designating a partner device to be transmitted next is connected, and finally a data format in which data 4 to be transmitted is connected is generated.

The data generated by the preamble generator 5 is input to the primary modulator 6, and PSK modulation or FSK modulation is performed to generate a non-modulated modulated wave only during the preamble period. Data that is not modulated only during this preamble period is input to the spread spectrum modulator 7, spread spectrum modulation is performed by the spread code generated from the spread code generation base 10 up to the required bandwidth, and then up to the required frequency band. The frequency converter 8 performs frequency conversion, the power amplifier unit 9 amplifies power to a required transmission level, and transmits from a transmission antenna.

On the receiver side (not shown), the preamble 1
During the period, the spread code generated by the spread code generator on the receiving side is used to perform spectrum despreading in the primary demodulation section using a matched filter or a sliding correlator to detect correlation. By the way, in the spread spectrum communication system, a demodulated output can be obtained only when the spreading codes on the transmitting side and the receiving side match, and when the spreading codes on the receiving side do not match due to deviation, the noise level is reached.

Therefore, there is no particular problem when the line quality is good, but when the spread spectrum communication system is used for mobile communication, when the line quality is deteriorated due to the influence of external noise or interference, S at the time of correlation detection is used. / N decreases, which causes erroneous synchronization.

However, since the transmission data in the preamble period is continuous data of "1" or "0" as described above, a narrow band unmodulated wave signal is demodulated as a demodulation output and the filter at the time of correlation detection is narrow band. By doing so, the correlation detection output S / N after time integration is improved, and even in a state where the line quality is deteriorated due to interference, external noise, etc., false synchronization can be prevented and correlation detection can be reliably performed, and spread code synchronization can be completed.

Further, when the receiver side is provided with a data demodulator and a Doppler shift amount detector to detect the Doppler shift amount, the transmission data in the preamble period is continuous data of "1" or "0". Therefore, even if a Doppler shift occurs on the transmission line, it is an unmodulated wave within the preamble period, the phase shift amount is easier to detect than the modulated wave, and the phase rotation amount due to the Doppler shift can be detected more easily than the demodulated data. By correcting the demodulated data with the amount of phase rotation due to the Doppler shift detected during the preamble period, the influence of the Doppler shift generated on the transmission path can be removed.

As described above, when the spread code synchronization is completed within the preamble period, the modulated wave which is primary-modulated by data or the like is demodulated, and the PSK or FSK method which is a demodulation method corresponding to the primary modulation method is used. Next demodulation is performed and the start word is detected to detect the start of data.

After detecting the status word, the slave station address for distinguishing whether it is the transmission data to the own station or different is detected, and if it is the transmission data to the own station, the receiving operation is continued.

According to the present embodiment, since the unmodulated wave is used for the preamble period synchronization acquisition, the S / N at the time of synchronization acquisition is improved regardless of the primary modulation method, unlike the prior art. The effect of Doppler shift occurring on the transmission line can be easily corrected.

[0028]

As described above, according to the present invention, since the non-modulated wave is used for the synchronization acquisition during the preamble period, the S / N at the acquisition of the synchronization is improved and the synchronization is stably acquired even when the line quality is deteriorated. Can be done. Moreover, since the non-modulated wave is used, the effect of easily correcting the influence of the Doppler shift generated on the transmission line can be obtained.

[Brief description of drawings]

FIG. 1 is a data format diagram of the present invention.

FIG. 2 is a block diagram of a transmitter according to an embodiment of the present invention.

FIG. 3 is a block diagram of a conventional carrier recovery circuit.

[Explanation of symbols]

1 ... Preamble part, 2 ... Start word part, 3 ...
... Slave station address, 4 ... Data section, 5 ... Preamble generator, 6 ... Primary modulator, 7 ... Spread spectrum modulator, 8 ... Frequency converter, 9 ... Power amplifier section, 10
... Spread code generator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukihiro Maruyama 216 Totsuka-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi Advanced Systems Co., Ltd.

Claims (2)

[Claims] 1. In a radio device for transmitting data in bursts, a transmitter side comprises a primary data modulator, a secondary spread spectrum modulator, and a preamble generator for generating a preamble for synchronization acquisition, and a receiver. The side is composed of a narrow band reception filter for synchronization acquisition and a reception filter switcher, and the transmitter side converts only the primary modulation data in the preamble period into all "1" or "0" continuous data and only the secondary modulation. A preamble synchronization system characterized in that the reception S / N is improved by minimizing the demodulation signal band after synchronization acquisition. 2. In a radio device for transmitting data in bursts, a transmitter side is composed of a primary data modulator, a secondary spread spectrum modulator and a preamble generator for generating a preamble for synchronization acquisition, and a receiver. The side is composed of a data demodulator and a detector for detecting the amount of Doppler shift. At the transmitter side, all the primary modulation data within the preamble period are treated as continuous data of "1" or "0".
A preamble synchronization method characterized by performing only the next modulation and minimizing the demodulation signal band after synchronization acquisition to facilitate detection of the Doppler shift amount.