JP3187304B2 - 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 communication apparatus using a spread spectrum system, and more particularly, to an improvement in the performance of capturing despread synchronization on the receiving side.

[0002]

2. Description of the Related Art In recent years, as one of LANs, a wireless LAN for transmitting terminal data and the like by wireless has been actively used. At this time, when the data bit rate is high and the data cannot be accommodated in a desired bandwidth if it is transmitted as it is, the data is serial-parallel converted and multiplexed using a plurality of channels to transmit the data.

[0003] A spread spectrum system is used as the wireless transmission system. In this case, the transmitting side modulates the signal of each channel using a spreading code independently assigned to each channel, and modulates and transmits the multiplexed wave, while the receiving side demodulates the information. By despreading with each spreading code, the signal of each channel is reproduced.

[0004] In this conventional spread spectrum communication apparatus, as shown in FIG.
Mutually different spreading codes 20-1 to 4-1 to 4-k
A spreading code generating circuit 19 for simultaneously outputting 20-k and a spreading code 21 for detecting the despread synchronization timing is multiplied by each of the information channels 4-1 to 4-k and the spreading codes 20-1 to 20-k. Multiplication circuits 5-1 to 5-k, an addition circuit 6 for adding k outputs of the multiplication circuits 5-1 to 5-k and a spread code 21 for detecting a despread synchronization timing, and an output of the addition circuit 6 An information modulation circuit 7 for multiplying and modulating information by a carrier wave and an antenna 8 for transmitting an output of the information modulation circuit 7 are provided.

[0005] The receiver 9 includes an antenna 10 for receiving a signal, an information demodulation circuit 11 for multiplying the output of the antenna 10 by a carrier wave and demodulating information, and a spread code 20-
1 to 20-k and spread code 21 for detecting despread synchronization timing
And a correlator 22-correlating the output of the information demodulation circuit 11 with the spreading codes 20-1 to 20-k.
And a correlator 22- (k) for correlating the output of the information demodulation circuit 11 with the spread code 21 for detecting the despread synchronization timing.
+1), a peak value detection circuit 23 for detecting the timing at which the output of the correlator 22- (k + 1) indicates a peak, and a despread synchronization timing signal 24 output from the peak value detection circuit 23 when enabled. Each correlator 22-1
Data holding circuit 25-1 for latching the output values of .about.22-k
25-k, and a decoding circuit 27 for reproducing the data of the information channels 4-1 to 4-k into reproduction channels 26-1 to 26-k based on the outputs of the data holding circuits 25-1 to 25-k. It has.

When the value of the bit data of the information channels 4-1 to 4-k is "1", the multiplying circuits 5-1 to 5-k in the transmitter 1 of this communication device have their spreading codes 20-1. ~
20-k is output with the same polarity, and when the value of the bit data of the information channels 4-1 to 4-k is "0",
The positive and negative polarities of the spreading codes 20-1 to 20-k are inverted and output. The outputs of the multiplication circuits 5-1 to 5-k are added to the despreading synchronization timing detection spreading code 21 by the addition circuit 6 and multiplexed, and then multiplied by the carrier in the information modulation circuit 7 to be information-modulated. Transmitted from the antenna 8.

The transmitted signal is received by the antenna 10 of the receiver 9, multiplied by a carrier in the information demodulation circuit 11, demodulated and input to the correlators 22-1 to 22- (k + 1). Each of the correlators 22-1 to 22-k despreads the spread codes 20-1 to 20-k with respect to the information demodulated signal, and correlates the demodulated signal with the spread codes 20-1 to 20-k. I take the. The correlator 22- (k + 1) despreads the information-demodulated signal with the despread synchronization timing detection spreading code 21, and obtains a correlation between the demodulated signal and the despread synchronization timing detection spreading code 21. .

At this time, the correlator 22- (k + 1) suppresses the components related to the spread codes 20-1 to 20-k in the input signal, and the spread code 21 for detecting the despread synchronization timing of this signal.
The autocorrelation with the component related to is obtained, and the peak value is output. This peak value is detected by the peak value detection circuit 23,
It is output as a despread synchronization timing signal 24 to each of the data holding circuits 25-1 to 25-k.

The correlators 22-1 to 22-k also have
At the time of despreading synchronization, each spreading code
The peak value of the autocorrelation for 20-1 to 20-k is output. This peak value is determined by each of the data holding circuits 25-1 to 25-k
Then, when the despread synchronization timing signal 24 is enabled, it is latched, and the value is held and output until the next despread synchronization timing signal 24 is enabled. The decoding circuit 27 reproduces the data of the information channels 4-1 to 4-k on the reproduction channels 26-1 to 26-k based on the outputs of the data holding circuits 25-1 to 25-k.

[0010]

However, in the conventional spread spectrum communication apparatus, when the spreading ratio cannot be sufficiently obtained due to the limitation of the used bandwidth, when the phases of the spreading codes match in despreading. However, the autocorrelation value does not increase so much. Therefore, as the number of spreading codes multiplexed and transmitted increases, it becomes more difficult to identify the peak in the output of the correlator for detecting the despread synchronization timing, and when the despread synchronization timing is obtained, There is a problem that it becomes difficult to determine when it is not performed, and the despreading synchronization timing acquisition performance deteriorates.

The present invention solves such a conventional problem. Even when the number of spread codes to be multiplexed and transmitted is increased, the deterioration of despread synchronization timing acquisition performance is suppressed, and excellent transmission quality is achieved. It is an object of the present invention to provide a spread spectrum communication device that can be secured.

[0012]

Therefore, according to the present invention, on the transmitting side, a plurality of channel data is spread with a spreading code assigned to each channel, and then multiplexed and transmitted. In the spread spectrum communication apparatus that performs despreading with each spreading code and decodes each channel data based on the despreading result at the despreading synchronization timing, as a spreading code assigned to each channel on the transmission side,
An orthogonal code generating means for outputting a plurality of orthogonal codes having orthogonality to each other is provided, and the receiving side outputs orthogonal codes for detecting the despread synchronization timing having orthogonality with these orthogonal codes, together with the same orthogonal code as the transmitting side. Orthogonal code generating means,
Correlation means for obtaining a correlation between the received signal and the orthogonal code for detecting the despread synchronization timing, and detection means for detecting the time point at which the minimum value is output from the correlation means as the despread synchronization timing are provided.

With this configuration, it is possible to prevent deterioration of the despread synchronization timing acquisition performance and to ensure excellent transmission quality.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, the transmitting side spreads a plurality of channel data with a spreading code assigned to each channel, and then multiplexes and transmits the data. In a spread spectrum communication apparatus that despreads a received signal with each spreading code and decodes each channel data based on the result of despreading at the despread synchronization timing, as a spreading code to be assigned to each channel on the transmission side. The orthogonal code generating means for outputting a plurality of orthogonal codes having orthogonality to each other is provided.On the receiving side, together with the same orthogonal code as that on the transmitting side, orthogonal codes for detecting despread synchronization timing having orthogonality with these orthogonal codes are provided. Orthogonal code generating means for outputting, correlation means for correlating the received signal with the orthogonal code for detecting the despread synchronization timing, and when the minimum value is output from the correlation means It is provided detecting means for detecting the despread synchronization timing.

The orthogonal code is a plurality of spreading codes having no correlation with each other. When correlation between the codes is obtained, the correlation value becomes zero when the despread synchronization timing is obtained. However, when the despread synchronization timing is not obtained, there is no guarantee that the cross-correlation value becomes zero.

The output of the correlation means for detecting the despread synchronization timing of the communication device becomes theoretically zero regardless of the number of orthogonal codes multiplexed from the transmitter when the despread synchronization timing is obtained. On the other hand, when the despread synchronization timing has not been obtained, the cross-correlation value between each orthogonal code multiplexed and transmitted from the transmitter and the orthogonal code for detecting the despread synchronization timing is output. Therefore, the despread synchronization timing can be captured by detecting the time point at which the output of the despread synchronization timing detection correlation means takes the minimum value.

According to a second aspect of the present invention, the orthogonal code generating means on the receiving side outputs a plurality of types of orthogonal codes for detecting the despread synchronization timing, and as a correlating means, a received signal and the inverse of each type are output. Providing a plurality of correlation means for taking a correlation with the orthogonal code for detecting the spread synchronization timing, the detection means,
It is configured to detect the point in time when the sum of the absolute values of the outputs of the correlating means is minimum.

In this case, when the despreading synchronization timing has not been obtained, the positive and negative correlation value outputs of the respective correlation means are added without canceling each other, so that the number of orthogonal codes multiplex-transmitted from the transmitter is reduced. The larger the number, and the larger the number of despread synchronization timing detection correlating means, the larger the added value becomes, and when the despread synchronization timing is obtained,
It is easy to distinguish when not taken.

An embodiment of the spread spectrum communication apparatus according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the communication device outputs, to the transmitter 1, mutually different orthogonal codes 3-1 to 3-k corresponding to the information channels 4-1 to 4-k at the same time. An orthogonal code generation circuit 2 and a multiplication circuit 5-1 for multiplying each information channel 4-1 to 4-k by the orthogonal code 3-1 to 3-k
5-k, an addition circuit 6 for adding k outputs of the multiplication circuits 5-1 to 5-k, an information modulation circuit 7 for modulating the output of the addition circuit 6, and an output of the information modulation circuit 7 And an antenna 8 to be used.

Further, the receiver 9 includes an antenna 10 for receiving a signal, an information demodulation circuit 11 for demodulating information of the output of the antenna 10, an orthogonal code 3-1 to 3-k and despreading same as the transmitter 1. An orthogonal code generation circuit 12 for generating orthogonal codes 13-1 to 13-m for detecting synchronization timing, and a correlator 14- for correlating the output of the information demodulation circuit 11 with the orthogonal codes 3-1 to 3-k. 1
14-k, correlators 15-1 to 15-m for correlating outputs of the information demodulation circuit 11 and orthogonal codes 13-1 to 13-m for detecting despread synchronization timing, and correlators 15-1 To 16-m, and an adder 17 to add the outputs of the absolute-value circuits 16-1 to 16-m.
And a minimum value detection circuit 18 for outputting a despread synchronization timing signal 24 indicating the timing when the output of the adder circuit takes the minimum value, and despread synchronization of the output values of the correlators 14-1 to 14-k. Data holding circuits 25-1 to 25-k which latch when the timing signal 24 is enabled, and an information channel 4-1 based on the outputs of the data holding circuits 25-1 to 25-k.
And a decoding circuit 27 for reproducing the data of .about.4-k into reproduction channels 26-1 to 26-k.

The orthogonal code is, for example, a code "1, 1,-"
A plurality of spreading codes having orthogonality to each other (that is, having no cross-correlation) such as "1, -1" and code "1, -1, 1, -1", and are in a synchronized state. , The sum of the inner products of those codes (1 × 1 + 1 ×
(−1) + (− 1) × 1 + (− 1) × (−1) = 0) becomes 0.

The orthogonal code generation circuit 2 of the transmitter 1 generates orthogonal codes 3-1 to 3-k having orthogonality to each of the information channels 4-1 to 4-k and a multiplication circuit. When the value of the bit data of the information channels 4-1 to 4-k is "1", the orthogonal codes 5-5-1 to 5-k are used.
1 to 5-k are output with the same polarity, and when the value of the bit data of the information channels 4-1 to 4-k is "0", the positive and negative of the orthogonal codes 5-1 to 5-k are output. The polarity is inverted and output. The outputs of the multiplication circuits 5-1 to 5-k are multiplexed by the addition circuit 6, modulated by the information modulation circuit 7, and transmitted from the antenna 8.

On the other hand, in the receiver 9, the reception signal demodulated through the information demodulation circuit 11 is divided into correlators 15-1 to 15-m for detecting the despread synchronization timing and the correlator 14 for data reproduction.
-1 to 14-k. Also, the orthogonal code generation circuit 12
Generates the same orthogonal codes 3-1 to 3-k as those of the transmitter 1, and detects a plurality of types of orthogonal codes 13-1 to 13-m for detecting despread synchronization timing having orthogonality with the orthogonal codes.
And the orthogonal codes 13-1 to 13-m are correlated with the correlators 15-1 to 15-15.
-M, and the orthogonal codes 3-1 to 3-k are
Output to the corresponding correlators 14-1 to 14-k.

Correlator 15- for detecting despread synchronization timing
Numerals 1 to 15-m despread orthogonal codes 13-1 to 13-m for detecting despread synchronization timing with respect to the information-demodulated received signal, and take a correlation therebetween. At this time, in the state where the despread synchronization timing is obtained, the number k of the orthogonal codes 3-1 to 3-k multiplexed and transmitted from the transmitter 1 depends on the nature of the orthogonal code.
Irrespective of the above, the outputs of the correlators 15-1 to 15-m theoretically become zero, and the output of the adding circuit 17 for adding the outputs of the correlators 15-1 to 15-m also becomes zero.

On the other hand, when the despread synchronization timing has not been obtained, the orthogonal code 3-1 multiplexed from the transmitter 1 is transmitted.
３−3-k and orthogonal code for detecting despread synchronization timing 13-
The cross-correlation values with 1 to 13-m are output from the correlators 15-1 to 15-m, passed through absolute value circuits 16-1 to 16-m, and added to an adder circuit.
It is added by 17.

The minimum value detecting circuit 18 detects the minimum value of the output of the adding circuit 17 and outputs a despread synchronization timing signal 24 indicating the timing of despreading to the data holding circuits 25-1 to 25-k.

The correlators 14-1 to 14-k are used to demodulate the information-demodulated received signal and the orthogonal codes 3-1 to 3-
Correlate with m and output the result. This output is output to each of the orthogonal codes 3-1 to 3-1 at the synchronization timing of the despreading.
The peak value of the 3-k autocorrelation is shown.

Each of the data holding circuits 25-1 to 25-k operates when the despread synchronization timing signal 24 is enabled.
The peak values output from the correlators 14-1 to 14-k are latched, and the values are held and output until the despread synchronization timing signal 24 is enabled next.

The decoding circuit 27 includes data holding circuits 25-1 to 25-1.
The data of the reproduction channels 26-1 to 26-k is reproduced based on the output of 25-k.

The receiver 9 of this communication device takes the absolute values of the values output from the correlators 15-1 to 15-m for detecting the despread synchronization timing, and adds the absolute values by the adding circuit 17. When the despread synchronization timing is not obtained, the positive and negative correlation value outputs of the correlators 15-1 to 15-m are added without canceling each other. Therefore, as the number k of the orthogonal codes 3-1 to 3-k multiplexed and transmitted from the transmitter 1 increases, and as the number m of the correlators 15-1 to 15-m increases, the despreading synchronization timing is obtained. When not performed, the output of the adding circuit 17 can take a large value. Therefore, the addition circuit
The difference from the state where the output of 17 is 0 and the despread synchronization timing is obtained is increased, and the minimum value detection circuit 18 can accurately identify the point where the despread synchronization timing is obtained. .

Thus, in this spread spectrum communication apparatus, when the despread synchronization timing is obtained,
When the output of the adding means becomes zero and the despread synchronization timing is not obtained, the output value of the adding means becomes large. Then, it is easier to distinguish between when the timing is obtained and when the timing is not obtained, as the number of orthogonal codes multiplexed and transmitted from the transmitter is larger and the number of despread synchronization timing detection correlators is larger. become. Therefore, it is possible to suppress the deterioration of the despread synchronization acquisition performance with respect to the increase of the multiplexed spreading code.

[0032]

As is apparent from the above description, the spread spectrum communication apparatus of the present invention suppresses deterioration of despread synchronization acquisition performance even when the number of multiplexed and transmitted spreading codes increases. And high transmission quality can be ensured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a spread spectrum communication apparatus according to the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional spread spectrum communication apparatus.

[Explanation of symbols]

Reference Signs List 1 transmitter 2 orthogonal code generation circuit 3-1 to 3-k, 13-1 to 13-m orthogonal code 4-1 to 4-k information channel 5-1 to 5-k multiplication circuit 6, 17 addition circuit 7 information Modulation circuit 8, 10 Antenna 9 Receiver 11 Information demodulation circuit 12 Orthogonal code generation circuit 14-1 to 14-k, 15-1 to 15-m, 22-1 to 22- (k +
1) Correlator 16-1 to 16-m Absolute value conversion circuit 18 Minimum value detection circuit 19 Spread code generation circuit 20-1 to 20-k Spread code 21 Spread code for detecting despread synchronization timing 23 Peak value detection circuit 24 Reverse Spread synchronization timing signal 25-1 to 25-k Data holding circuit 26-1 to 26-k Reproduction channel 27 Decoding circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 1/69-1/713 H04J 13/00-13/06 H04L 7/00

Claims (2)

(57) [Claims] 1. A transmitting side spreads a plurality of channel data with a spreading code allocated to each channel, and then multiplexes and transmits the data. A receiving side despreads a received signal with each of the spreading codes, In a spread spectrum communication apparatus that decodes each channel data based on a result of despreading at a spread synchronization timing, a plurality of orthogonal codes having orthogonality to each other are output to a transmitting side as spreading codes assigned to the respective channels. Orthogonal code generation means for outputting orthogonal codes for detecting a despread synchronization timing having orthogonality to these orthogonal codes, together with the orthogonal codes, on the receiving side; a reception signal and the despread synchronization timing A correlation means for taking a correlation with the orthogonal code for detection, and detecting a time point at which the minimum value is output from the correlation means as a despread synchronization timing. A spread spectrum communication apparatus, comprising: 2. The orthogonal code generating means on the receiving side outputs a plurality of types of orthogonal codes for detecting the despread synchronization timing, and the correlating means outputs the received signal and the respective types of despread synchronization timing detection. 2. The method according to claim 1, further comprising a plurality of correlation units that take a correlation with an orthogonal code, wherein the detection unit detects a time point at which an addition value in an absolute value of an output of each of the correlation units becomes a minimum. Spread spectrum communication equipment.