JPH1093531A - Code division multiplex communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid an error in the case of estimating a multiplicity by receiving a code division multiplex signal. SOLUTION: A received signal is given to an automatic gain control circuit 22, in which the power of signal is converted to have a constant power and its output is given to correlators 23-1-23-n, in which the signal is in correlation with spread codes PN-1-PN-n. A multiplicity estimate section 28 compares a plurality of threshold levels in response to the multiplex number with outputs from the correlators 23-1-23-n to estimate the multiplicity. A demodulation circuit 24 and a parallel serial converter 25 select any of outputs from the collerators 23-1-23-n and provide an output of the selected output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a code division multiplex communication apparatus for performing synchronous multiplexing and transmission using a plurality of spreading codes.

[0002]

2. Description of the Related Art In a spread spectrum communication system, a signal having a much wider bandwidth than original data is generated from a normally transmitted digital signal by using a spread code sequence such as a pseudo noise code (PN code). It is converted into an RF (radio frequency) signal and transmitted.

[0003] Therefore, under the condition that the transmission bandwidth is originally limited, spread spectrum communication can realize only a very low transmission speed as compared with ordinary narrow band communication.

In order to increase the transmission speed, there is a code division multiplex communication in which a plurality of spread codes having a small correlation are synchronously multiplexed and transmitted.

In the code division multiplex communication, a signal modulated with m effective data is selected from n modulation outputs according to an input transmission speed, added, and transmitted. On the receiving side, after synchronization is established, a correlation operation is performed between the received signal and the n spread codes, and the number of channels whose absolute value of the n correlation values is equal to or greater than a predetermined value or less than a predetermined value is detected. m is detected, and m effective outputs are selected from the n demodulation means outputs.

[0006]

In code division multiplex communication, if automatic gain control is ideally operated on the receiving side, the correlation value of the signal of the data-modulated channel is inversely proportional to the square root of the number of multiplexes.

Therefore, in order to detect the multiplex number,
The threshold value needs to be set to a value according to the maximum multiplex number. However, when the difference between the maximum multiplexing number and the minimum multiplexing number is large, when the multiplexing number is small, correlation is detected on a channel where correlation is not originally detected by multipath or the like, and erroneous determination of the multiplexing number may occur. Conceivable.

[0008]

According to the present invention, a correlation means for correlating a received signal with each of a plurality of spreading codes, and a multiplex number estimating means for estimating a multiplex number based on an output from the correlation means. And demodulating means for demodulating data based on the output of the multiplex number estimating means, wherein the multiplex number estimating means has a plurality of thresholds according to the number of multiplexes, and The number of multiplexes is estimated from the output from the means.

With this configuration, it is possible to reduce the multiplexing number estimation error and increase the throughput.

[0010]

FIG. 1 is a block diagram showing a configuration of a transmitting section according to an embodiment of the present invention. FIG.
FIG. 3 is a block diagram illustrating a configuration of a receiving unit according to the embodiment of the present invention.

In FIG. 1, reference numeral 11 denotes a serial / parallel converter for converting input serial data into parallel data. The serial-parallel converter 11 converts a multiplexed information signal input from the outside into parallel data of a number corresponding to the multiplexed information, and outputs data to some or all of the n parallel output lines. 12-1,
.., 12-n are spread modulators. 13 is a synthesizing circuit for synthesizing the output of the spread modulator 12, 14 is a gain control circuit for amplifying or attenuating the output of the synthesizing circuit 13 according to multiplexed information input from the outside, and 15 is a frequency for transmitting an input signal. A high-frequency section for converting, amplifying, filtering, etc., 16 is composed of n synchronized spreading codes P
N1,..., PNn.

In FIG. 2, reference numeral 21 denotes a high-frequency unit for converting the frequency of a received signal and performing amplification, filtering, and the like.
Are automatic gain control circuits for keeping the output signal level constant, 23-1,..., 23-n are correlators for calculating the correlation of two input signals, and 24 are correlators 3-1,.
.. a demodulation circuit which receives outputs of 23-n and judges data for each of them; 28 is a correlator 3-1,..., 23
Multiplex number estimating unit for estimating the multiplex number by receiving the output of -n, 2
5 receives the input from the multiplex number estimating unit 28 and
Is a parallel-to-serial converter that selects some or all of the n parallel data from the data and converts the data into serial data. 26
Is a synchronizing circuit for synchronizing the received signal with the spreading code output from the code generator 27, and 27 is a code generator for generating n synchronized spreading codes PN1,..., PNn.

The operation of the transmitting section will be described with reference to FIG. The serial transmission data is input to the serial-parallel converter 11 whose number of parallels is variable. The multiplex number information signal is input to the serial / parallel converter 11, the data is subjected to parallel processing based on the multiplex number information, and the input data is distributed to part or all of the n parallel outputs and output. I do. N of the serial-parallel converter 11
Are output from the spread modulators 12-1 and 12-, respectively.
, 12-n, are spread-modulated by one of n synchronized spreading codes PN1,..., PNn output from the code generator 16. Here, a spread-modulated signal is output from a spread modulator to which a signal to which data is distributed among the n output signals of the serial-parallel converter 11 is input. Spreading modulators 12-1, 12-2,.
, 12-n are input to the synthesis circuit 13.
By the combining circuit 13, the spread modulators 12-1, 12-2,
.., The signals of which the data are spread-modulated among the outputs from 12-n are linearly added. The output of the synthesis circuit 13 is linearly amplified by the gain control circuit 14 so that the transmission power is constant regardless of the number of multiplexes, converted to a desired frequency by the high frequency circuit 15, and amplified, filtered, etc. Is performed and output (transmitted).

Next, the operation of the receiving section will be described with reference to FIG. The received signal is converted to a desired frequency by the high-frequency circuit 21 and subjected to processing such as amplification and filtering. Next, the signal is linearly converted into a signal having a constant power by the automatic gain control circuit 22, and the n correlators 23-1, 23-
, 23-n and the synchronization circuit 26. The synchronization circuit 26 performs code synchronization and clock synchronization between the received signal and n synchronized spread codes PN1,..., PNn output from the code generator 27. , PNn synchronized with the received signal are input to correlators 23-1, 23-2, ..., 23-n, respectively, and are subjected to a correlation operation. Here, the n spreading codes PN1,..., PNn are the same code sequence as the code used for spreading modulation on the transmitting side.

The received signal is converted into a baseband signal by a carrier reproduced by a carrier reproducing circuit (not shown), or is converted into a baseband signal by a carrier having a frequency substantially equal to the carrier frequency of the received signal. , And then the correlators 23-1, 23-2,.
-It is desirable to input to 23-n. However, when converting to a signal in the baseband using a carrier having a frequency substantially equal to the carrier frequency of the received signal, it is necessary to perform a correlation operation on each of the in-phase component and the quadrature component.

The n correlators 23-1, 23-2,...
The outputs of 23-n are output from the multiplex number estimating unit 28 and the demodulation circuit 2
4 is input. The multiplex number estimating unit 28 estimates the multiplex number from the outputs of the n correlators 23-1, 23-2,..., 23-n.

FIG. 3 shows an example of the relationship between the number of multiplexes and the absolute value of the correlation value for the channel spread modulated by data. FIG. 3 shows a case where the number of multiplexes is 1, 2, 4, 8, and 16, and the absolute values of the correlation values at that time are 4, 2, √2, 2, √2, 1 (relative values), respectively. Becomes Therefore, a threshold value is provided near the middle of the absolute value of each correlation value (that is, 3.4, 2.4, 1.7, 1.2), and n correlators 23-1, 23-2,. .. Count the number exceeding each threshold value among the absolute values of the outputs of 23-n, and determine the multiplexing number according to the number. For example, if the number of multiplexes is 4, the absolute value of four of the outputs of the correlators 23-1, 23-2,..., 23-n should be 2 (relative value). There should be no outputs exceeding the threshold value (2.4) between 4 and four outputs exceeding the threshold value (1.4) between the multiplex numbers 4 and 8.

Therefore, in such a case, the multiplex number estimating section 28 estimates that the multiplex number is four.

The n correlators 23-1, 23-2,...
The outputs of 23-n are data-demodulated by the demodulation circuit 24 and input to the parallel / serial converter 25. In the parallel-to-serial converter 25, the multiplex number estimation unit 28
Is selected according to the number of multiplexes determined by the above, converted into serial data and output.

The data modulation method is not limited to the two-phase modulation method. Such as four-phase modulation
A polyphase modulation method may be used. Alternatively, the spread-modulated two-phase modulated signal may be combined with the in-phase component and the quadrature component of the carrier wave separately.

The number of multiplexes is 1, 2, 4, 8, 16,
.. Is not limited to 2 n times, and may be, for example, 1, 4, 16,. In this case, the absolute value of the correlation value is 4, 2, 1,... (Relative value), and the interval between the thresholds for estimating the number of multiplexes is widened. Become.

[0022]

As described above, according to the present invention,
Since the number of multiplexes is estimated based on a plurality of thresholds according to the number of multiplexes, it is possible to reduce errors in estimating the number of multiplexes and increase the throughput.

Further, by making the number of multiplexes variable by a factor of 2 to the power of n or by a factor of 4 to the power of m (n and m are integers of 0 or more), the interval between threshold values according to the number of multiplexes can be widened Therefore, the multiplex number estimation error can be further reduced. In particular, it is effective when the multiplex number is estimated by digital processing.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a transmission unit according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a receiving unit according to the embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between the number of multiplexes and a correlation value.

[Explanation of symbols]

 Reference Signs List 22 automatic gain control circuit 23 correlator 24 demodulation circuit 25 parallel-serial conversion circuit 28 multiplex number estimation unit

Claims (17)

[Claims] 1. A correlation means for correlating a received signal with each of a plurality of spreading codes, and a plurality of thresholds corresponding to the number of multiplexing signals. Code division multiplex communication comprising: estimating means for estimating a multiplex number from a correlation output and the plurality of thresholds; and demodulating means for demodulating a received signal according to the multiplex number estimated by the estimating means. apparatus. 2. The apparatus further comprises level adjusting means for adjusting the level of the received signal, wherein the correlating means correlates each of the plurality of spreading codes with the received signal whose level has been adjusted by the level adjusting means. The code division multiplex communication device according to claim 1, wherein: 3. The code division multiplex communication apparatus according to claim 1, wherein the reception signal is spread-modulated by one or more of a plurality of spread codes on a transmission side. 4. The code division multiplex communication apparatus according to claim 1, wherein the number of multiplexes is variable by an n-th power of 2 (n is an integer of 0 or more). 5. The code division multiplex communication apparatus according to claim 1, wherein the number of multiplexes is variable by an n-th power of 4 (n is an integer of 0 or more). 6. A code division multiplexing communication apparatus for synchronously multiplexing and transmitting a signal spread spectrum modulated by a plurality of spread codes from a transmitting side to a receiving side and transmitting the signal, the receiving side comprising: Correlation means for taking each correlation, and a plurality of thresholds according to the number of multiplexing, the number of multiplexing from the correlation output of each of the received signal and a plurality of spreading codes by the correlation means and the plurality of thresholds A code division multiplex communication apparatus comprising: estimating means for estimating; and demodulating means for demodulating a received signal according to the number of multiplexes estimated by the estimating means. 7. The receiving side further includes level adjusting means for adjusting the level of the received signal, and the correlating means correlates each of the plurality of spreading codes with the received signal whose level has been adjusted by the level adjusting means. 7. The code division multiplex communication device according to claim 6, wherein: 8. The code division multiplex communication apparatus according to claim 6, wherein the transmitting side spreads and modulates the signal by using one or more of a plurality of spreading codes and transmits the spread code. 9. The code division multiplex communication apparatus according to claim 6, wherein the transmission side further comprises a power control means for controlling power per channel. 10. The code division multiplex communication apparatus according to claim 9, wherein said power control means controls power per channel substantially in inverse proportion to a multiplex number. 11. The code division multiplex communication apparatus according to claim 6, wherein said multiplexing number is variable by an n-th power of 2 (n is an integer of 0 or more). 12. The code division multiplex communication apparatus according to claim 6, wherein said multiplexing number is variable by an n-th power of 4 (n is an integer of 0 or more). 13. A correlation between a received signal and a plurality of spreading codes, and a multiplex number is estimated from a correlation output of each of the received signal and a plurality of spreading codes and a threshold value according to the multiplex number. A code division multiplex communication method comprising demodulating a received signal according to a multiplex number. 14. The code division multiplex communication method according to claim 1, wherein the level of the received signal is adjusted, and then the level-adjusted received signal is correlated with each of the plurality of spreading codes. 15. The code division multiplex communication method according to claim 1, wherein the received signal is spread-modulated by one or more of a plurality of spread codes on a transmission side. 16. The code division multiplex communication method according to claim 1, wherein the number of multiplexes is variable by an n-th power of 2 (n is an integer of 0 or more). 17. The code division multiplex communication method according to claim 1, wherein the number of multiplexes is variable by an n-th power of 4 (n is an integer of 0 or more).