JPH08316935A - Communication system - Google Patents

Abstract

PURPOSE: To improve the error at the time of detecting the validity of data by giving a difference between the transmission power level of a preamble signal for synchronism acquisition and that of a data signal. CONSTITUTION: In a demodulation part, the validity of demodulated data is discriminated by the signal power of a spread spectrum signal (PN 0). In this case, the signal PN 0 used in the preamble period from a time t1 to a time t2 of data to be transmitted is multiplexed even during transmission of data, and the power of the signal PN 0 during data transmission (from the time t2 to a time t3 ) is made smaller than that in the preamble period and is made larger than the power of the other data channels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system for performing communication by a code division multiplex communication system using a spread spectrum communication system.

[0002]

2. Description of the Related Art Generally, in a synchronous information transmission system which does not have a channel dedicated to synchronization, a preamble for supplementing synchronization is transmitted for a certain period of time prior to transmission of notification data, and then transmission of data is started. In such a system, the receiver side needs to identify the invalid data and the report data from the demodulated data by some means after performing the synchronization supplement during the preamble period.

As a means for recognizing the start of this effective data, for example, there is a method of inserting a start frame delimiter (SFD) having a specific bit pattern in the data stream. In this method, the start of data can be identified by detecting the SFD code string on the receiver side. However, in the data stream
When D is inserted, in packet type data transmission, the data transmission efficiency significantly decreases.

Therefore, in the code division multiplex communication system using the spread spectrum (SS) communication system, the start of data is determined by the code correlation value obtained after despreading in the receiving section.

FIG. 5 is a block diagram showing the structure of a demodulation section of a conventional code division multiplex communication device. In the digital code division multiplex signal shown in the figure, an analog code division multiplex baseband signal is converted into a digital value by an A / D converter (not shown). The digital code division multiplexed signal and a plurality of different pseudo-random code sequences generated by the despreading code generator 21 are subjected to correlation calculation by a plurality of digital correlators 22. The code correlation value obtained by each digital correlator 22 is converted into demodulated data by the P / S converter 24 into a time series data stream.

[0006] Here, by comparing the code correlation value output obtained from at least one digital correlator 22 with the discrimination reference value in the comparator 23, the determination value for discriminating the validity of the demodulated data can be obtained.

FIG. 6 is a diagram showing the concept of determining the validity of data from the output of the code correlation value.

[0008] Theoretically, in an SS communication device using a spread spectrum code of N code length, the code correlation value when demodulation is performed by the receiving section is N or − if there is inter-code correlation. N (negative values are not shown in FIG. 6), or 0 if no intersymbol correlation exists.

In an actual system, the code correlation value exists with a certain distribution near N or 0 because it is affected by noise, interference, and other factors. In the demodulation of data in the spread spectrum communication system, in order to discriminate between the code correlation values N and -N when there is an inter-code correlation, 0 is used as a reference value, and if the code correlation value is negative, the data is "0". Is positive, the data is demodulated to "1". In such a demodulation method, even if there is no report data, the sign correlation value is negative or positive, and some demodulation data is obtained. Therefore, it is impossible to determine whether or not the data is correct.

Therefore, as shown in FIG. 6, an appropriate reference value S1 is provided between the code correlation value N and 0 in order to judge the validity of the data, and when the code correlation value is larger than the reference value S1. Assumes that there is inter-code correlation and recognizes the demodulated data as valid. Further, when the code correlation value is smaller than the reference value S1, it can be considered that there is no inter-code correlation and it can be determined that the demodulated data is not valid. This method is very effective for a high-speed data transmission method because it does not require a specific bit pattern such as SFD and does not reduce the data transmission efficiency.

[0011]

However, if the validity of the data is determined by the code correlation value of the data signal as in the above-mentioned conventional method, a sufficient code correlation value cannot be obtained, and therefore a determination error may occur. It is highly likely. In particular, in the code division multiplex communication system, there is a problem that the determination error has a great influence in order to determine the validity of all the multiplexed data by detecting the validity of the data.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a sufficient difference in code correlation value during a preamble transmission period, a data transmission period, and a non-signal period. Thus, it is an object of the present invention to provide a communication system capable of determining the validity of demodulated data with few errors.

[0013]

[Means for Solving the Problems] and

In order to achieve the above object, the present invention is a communication system for transmitting a preamble signal for synchronization supplementation prior to transmission of a data signal in a code division multiplex communication system in a spread spectrum communication system, comprising: On the side, means for modulating the preamble signal and the data signal by a specific spread spectrum code, means for controlling the transmission period of the preamble signal and the transmission period of the data signal, and the transmission period for the modulated signal And means for transmitting by multiplexing with different power in the transmission period, means for demodulating the multiplexed signal into a data signal using a predetermined despreading code and digital correlation calculation at the receiving side, and a code correlation value And a discriminating means for discriminating the validity of the demodulated data signal.

The above structure functions to reduce errors in determining the validity of demodulated data.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of a communication system according to an embodiment of the present invention. In the figure, in the transmission unit 1, the SS modulator 11 performs serial / parallel conversion on a series of transmission data, then modulates the data in SS format in digital form, and multiplexes. Further, reference numeral 12 is a control SS code generator that generates a specific SS code to be multiplexed during preamble or data transmission, and 14 is a timing of data transmission of the SS modulator 11 and the control SS code generator 12. It is a controller unit that controls.

Reference numeral 13 is an adder for adding the digital output from the SS modulator 11 and the digital output from the control SS code generator, and 15 is a D / A (not shown) for obtaining a required high frequency signal. Converter, modulator, frequency converter,
A transmission RF unit including a power amplification unit and the like.

Next, in the receiving unit 2, reference numeral 16 is a receiving RF unit which performs frequency conversion from the received high frequency signal, demodulates it to a baseband signal, and then performs digital conversion by A / D conversion. , 17 are despreading code generators that generate the SS code of each channel. Reference numeral 18 is a correlator that digitally correlates the SS code for each channel, and reference numeral 19 is a determiner that determines whether there is code correlation and the demodulated data is valid.

The operation of the communication system according to this embodiment having the above configuration will be described below.

First, prior to the data transmission, the controller section 14 controls the preamble transmission period for synchronization supplement. The control SS code generator 12 sends out a preamble for a fixed period. The spread spectrum code used at this time is hereinafter referred to as PN0.

FIG. 2 is a diagram showing the power of PN0 in this embodiment. As shown in the figure, here, PN0 is transmitted at power P0 from t1 to t2 during the preamble period.

Next, during the data transmission period, the controller section 14 enables the SS modulator 11 to perform SS modulation on the transmission data. Further, for the control SS code generator 12, PN0 is generated with power shorter than the preamble period and higher than that of other data channels. That is, as shown in FIG. 2, during the data transmission period t2 to t3,
PN0 is transmitted with power P1.

In the receiver 2, the correlator 18 detects the power of PN0. FIG. 3 is a diagram showing the concept of determining valid data based on the obtained code correlation value. As described above, during the preamble transmission period, the power of P0 causes PN
Since 0 is transmitted, the code correlation is M. Further, during the data transmission period, PN0 is transmitted by the power of P1, so the code correlation value becomes L. In an actual system, because of being affected by noise, interference, and the like, the code correlation value exists with a certain distribution in the vicinity of L, M, or 0 (there is no inter-code correlation) as shown in FIG. To do.

Therefore, in this embodiment, in order to determine the validity of the data, an appropriate reference value S2 (reference value 1) is provided between the code correlation values L and 0, and the code correlation values L and M are set. Between them, an appropriate reference value S3 (reference value 2) is provided. If the code correlation value is larger than the reference value S2 and smaller than the reference value S3, it is considered that there is inter-code correlation and the demodulated data is recognized as valid.

On the other hand, when the code correlation value is smaller than the reference value S2, it is considered that there is no inter-code correlation, the demodulated data is recognized as invalid, and the code correlation value is the reference value S3.
If it is larger than the above, it is regarded as the preamble period and it is determined that the demodulated data is not valid.

FIG. 4 is a circuit diagram showing an example of the configuration of a reference value determination circuit (determination device) in the communication system according to this embodiment. In this embodiment, the code correlation values are D0 to D11.
Is given as a digital value, and the effective data is discriminated using the circuit shown in FIG.

As described above, according to this embodiment,
When the demodulation unit determines the validity of the demodulated data by the signal power of the spread spectrum code (PN0), the PN0 used in the preamble period of the transmitted data is multiplexed even during the data transmission, and the power of PN0 during the data transmission. Is smaller than the preamble period and larger than the power of other data channels, there is an effect that the discrimination error is reduced as compared with the conventional method of discriminating the validity of the demodulated data by the data channel.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0029]

As described above, according to the present invention,
By transmitting the preamble signal and the data signal with different transmission power levels for the synchronization supplement, it is possible to improve the error in detecting the validity of the data and enable the high speed data transmission.

[0030]

[Brief description of drawings]

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

FIG. 2 is a diagram showing the power of PN0 in the embodiment.

FIG. 3 is a diagram showing a concept of determining valid data from a code correlation value.

FIG. 4 is a circuit diagram showing a configuration example of a determiner in the communication system according to the example.

FIG. 5 is a block diagram showing a configuration of a demodulation unit of a conventional code division multiplexing communication device.

FIG. 6 is a diagram showing the concept of determining the validity of data from the sign correlation value output.

[Explanation of symbols]

 1 Transmitter 2 Receiver 11 SS Modulator 12 Control SS Code Generator 13 Adder 14 Controller 15 Transmit RF 16 Receive RF 17 Despread Code Generator 18 Correlator 19 Evaluator

Claims (3)

[Claims] 1. A communication system for transmitting a preamble signal for synchronization supplementation prior to transmission of a data signal in a code division multiplex communication system in a spread spectrum communication system, wherein the preamble signal and the data signal are transmitted on a transmission side. Means for modulating the transmission period of the preamble signal and the transmission period of the data signal by a specific spread spectrum code, and the modulated signal is multiplexed by different power in the transmission period and the transmission period. And means for transmitting at the receiving side, means for demodulating the multiplexed signal, means for obtaining a code correlation value from the demodulated signal and a predetermined despread code, and a predetermined value for the code correlation value. A reference value is provided, and a determination means for determining the validity of the demodulated signal based on the reference value is provided. Communication system to be. 2. The communication system according to claim 1, wherein the determining means determines the validity of the demodulated signal by a multi-level code correlation reference value. 3. The communication system according to claim 1, wherein the power of the preamble signal in the transmission period is larger than the power of the data signal in the transmission period.