JP3280197B2 - 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 direct spread type spread spectrum communication apparatus, and more particularly to a communication apparatus having a transmission identification function in a code division multiplex communication system for multiplexing and transmitting a plurality of spread code channels.

[0002]

2. Description of the Related Art Generally, in a spread spectrum communication system using a direct spread system, a transmitting side uses a spread code sequence such as a pseudo noise code (PN code) from a baseband signal of a digital signal to be normally transmitted. A baseband signal having a much wider bandwidth than the original data is generated. Furthermore, PSK (phase shift keying), FS
K (frequency shift keying) modulation and RF
(Radio frequency) signal and transmit.

[0003] On the other hand, the receiving side performs despreading for correlation with the received signal using the same spreading code as that of the transmitting side, and converts the received signal into a narrow band signal having a bandwidth corresponding to the original data. Subsequently, normal data demodulation is performed to reproduce the original data.

As described above, in the spread spectrum communication system, since the transmission bandwidth is extremely wide with respect to the information bandwidth,
Under the condition that the transmission bandwidth is constant, only a very low transmission rate can be realized as compared with the normal narrow band modulation method.

[0005] To solve this problem, there is a method called code division multiplexing. This method reduces the spreading factor of the spread modulation by converting a high-speed information signal into low-speed parallel data, spreading and modulating each with a different spreading code sequence, and then converting it to an RF signal for transmission. It realizes high-speed data transmission under the condition that the transmission bandwidth is constant without any data.

FIG. 3 is a block diagram showing a configuration of a transmitter in this system.

In the figure, input data is converted by a serial-parallel converter 301 into n parallel data. Each converted data is divided into n multiplier groups 302-1 to 302
At -2, the signals are multiplied by n different spreading code outputs of the spreading code generator 303 and converted into n-channel wideband spread signals.

Next, the outputs of the multipliers 302-1 to 302-2 are added in an adder 304 and output to a high frequency stage 305 as a baseband broadband spread signal. In the high frequency stage 305, the baseband broadband spread signal is converted into a transmission frequency signal having an appropriate center frequency S, and transmitted from the transmission antenna 306.

FIG. 4 is a block diagram showing the configuration of the receiver.

The signal received by the antenna 401 is appropriately filtered and amplified by the high-frequency signal processing unit 402, and is converted into an intermediate frequency signal. This intermediate frequency signal is distributed to channels corresponding to n parallelly connected spreading codes.

In each channel, the input signal is
In 03-1 to 03-n, despreading is performed in which correlation is detected with the outputs of the spreading code generator groups 404-1 to 40n corresponding to the channel. This despread signal is transmitted to the synchronization circuit group 405-1.
.About.n, synchronization is established for each channel, and the code phases and clocks of the respective spread code generators are matched. The despread signal is demodulated by demodulator groups 406-1 to 406-n, and data is reproduced. Subsequently, the reproduced data is converted to serial data by the parallel / serial converter 407, and the original information is reproduced.

[0012]

The object of the invention is to be Solved However, the above-mentioned slave
In the past case, the receiver is notified of the identification data unique to the transmitter.
In order to do so, the sender and the receiver
Must be sent and received.

[0013]

The present invention provides k spreads selected on the transmitting side.
Spectrum expansion for discriminating transmission identification data from code sequence
It is an object of the present invention to provide a communication device .

[0015]

According to the present invention, a serial / parallel conversion means for converting an input serial data string into a parallel data string having a predetermined number of symbols (k symbols) and the same serial data conversion means according to input transmission identification data. Code sequence selecting means for selecting and outputting k parallel sequences from n data spreading code sequences having a period and having the same code phase, and k data spreading code sequences from the code sequence selecting device A modulating means for modulating each of the signals, an adding means for adding the k outputs of the modulating means and the synchronization-dedicated spreading code sequence, an output of the adding means being converted into a predetermined transmission frequency band signal and transmitted to a transmission path. Spread signal transmitting means for transmitting a signal from a transmission path, an output of the receiving means and n
Correlation means for performing a correlation operation with the number of data spreading code sequences, demodulation means for demodulating n-symbol data from a correlation value output from the correlation means, and an absolute value of the correlation value being equal to or greater than a predetermined value or It is determined whether
Transmission code channel detection means for detecting the number of spread code sequences, transmission identification data for determining transmission identification data from the k spread code sequences, reproducing and outputting transmission identification data on the transmission side, and demodulation. Demodulated data selecting means for selecting and outputting k symbol data for the k spread codes detected by the transmission channel detecting means from n symbol data output from the means, and an output of the demodulated data selecting means. And a parallel-serial conversion means for converting a parallel data string of a certain k symbol into a serial data string.

[0016]

According to the present invention, in the above arrangement, the receiving means
The absolute value of the correlation value between the output and the n data spreading code sequences is
Judge whether the value is above or below the specified value, and
K spread code sequences are detected, and the k spread code systems are detected.
The transmission identification data is determined from the transmission
The data is reproduced and output.

[0017]

FIG. 1 is a block diagram showing a configuration of a transmitter in one embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a receiver in this embodiment.

In FIG. 1, a serial-parallel converter 101 converts serially input data into k parallel data, and a spreading code generator 102 includes n different spreading codes and a dedicated synchronization code. To generate a spread code of

The code sequence selection circuit 103 outputs n from the spread code generator 102 based on the input transmission identification data.
The multipliers 104-1 to 104-k select and output k spread code sequences from among the spread code sequences, and each of the data parallelized by the serial-parallel converter 101 and the code sequence selection. The multiplication is performed by k spread codes output from the circuit 103.

The adder 105 includes a synchronization-specific spreading code output from the spreading code generator 103 and multipliers 104-1 to 104-1.
The high-frequency stage 106 adds k outputs.
The output of the adder 105 is converted into a transmission frequency signal and transmitted to the transmission antenna 107.

In FIG. 2, the high-frequency signal processing unit 2
Numeral 02 is for appropriately filtering and amplifying the signal from the receiving antenna 201 and converting the signal into a predetermined frequency band signal. The synchronizing circuit 203 is for acquiring and maintaining synchronization with the spread code on the transmitting side and the clock. It is.

The spreading code generator 204 includes a synchronization circuit 203
The carrier reproduction circuit 205 generates the same n + 1 spread codes as the spread code group on the transmission side based on the input code synchronization signal and clock signal. The carrier signal is reproduced from the spread code for use and the output of the high-frequency signal processing unit 202.

The baseband demodulation circuit 206 performs demodulation in baseband using the output of the carrier reproduction circuit 205, the output of the high-frequency signal processing unit 202, and the n spread codes output from the spread code generator 204. And the transmission code channel detection circuit 207 is a baseband demodulation circuit 2
It detects k spread code channels transmitted from the correlation value group of 06.

The transmission identification circuit 208 discriminates and outputs transmission identification data from the detected k spread code channels, and the demodulation data selection circuit 209 outputs n transmission data which is the output of the baseband demodulation circuit. , And selects k demodulated data corresponding to the detected k spread code channels from the demodulated data.

The parallel / serial converter 210 converts the k parallel demodulated data output from the demodulated data selection circuit 209 into parallel / serial data.

In the above configuration, on the transmission side, the input transmission identification data is first input to the code sequence selection circuit 103. In the code sequence selection circuit 103, according to a rule uniquely determined from the transmission identification data, the spreading code generator 1
The k spreading code sequences are selected and output from the n data spreading code sequences which are the outputs of 02.

The data to be subsequently transmitted is the serial-to-parallel converter 1
01 is converted to k parallel data equal to the number of code division multiplexes. The k parallel data are multiplied by k spread code sequences output from the code sequence selection circuit 103 by multiplier groups 104-1 to 104-k, respectively.
5 is input.

Also, among the outputs of the spreading code generator 102,
PN0 is exclusively for synchronization and carrier reproduction, and is directly input to the adder 105 without passing through a multiplier. Adder 105
Linearly adds the input k + 1 signals, and outputs the baseband signal added to the high frequency stage 106. The baseband signal is subsequently converted into a high-frequency signal having an appropriate center frequency in the high-frequency stage 106 and transmitted from the transmitting antenna 107.

On the receiving side, the signal received by the receiving antenna 201 is appropriately filtered and amplified by the high-frequency signal processing unit 202, and is output as it is in the transmission frequency band signal or converted into an appropriate intermediate frequency band signal. .

This signal is input to the synchronization circuit 203,
The synchronization circuit 203 establishes spread code synchronization and clock synchronization for the transmission signal, and outputs the code synchronization signal and the clock signal to the spread code generator 204.

For the configuration of the synchronous circuit, for example, a circuit using a surface acoustic wave (SAW) matched filter as shown in FIG. 7 is used.

In FIG. 7, the received intermediate frequency band signal is
Input to the SAW matched filter 701. The SAW matched filter 701 has an integration region length corresponding to one period of the spreading code, and integrates a product of the received signal and a preset tap coefficient, that is, a synchronization-specific spreading code sequence, over one period of the spreading code. Thing (correlation integral value)
And outputs a voltage signal having a center frequency equal to the carrier frequency of the input signal.

This output is then passed to the matched filter 70
1 as a center frequency, passing through a band-pass filter 702 that blocks signals other than the correlation integration signal,
After being appropriately amplified by the amplifier 703, the envelope detector 7
At 04, the envelope is detected.

Since this envelope signal is the absolute value of the correlation integral value, the envelope signal is designed so that the autocorrelation characteristic of the synchronization-dedicated spreading code has a sharp peak at the synchronization point and has a sufficiently low side lobe at the other points. If the received signal contains a spread code component dedicated for synchronization, the envelope detector 70
In the output of No. 4, a steep peak appears. Therefore, the peak detection circuit 705 detects the steep peak and outputs the peak to the phase detector 706.

A phase detector 706 detects a phase difference between the peak and a code start signal output from the code generator 204 and indicating a start point of a cycle of a spread code, and detects a voltage corresponding to the phase difference. Output level. This voltage level is smoothed by loop filter 707 and output to voltage controlled oscillator 708.

The voltage controlled oscillator 708 generates a clock signal having a frequency corresponding to the input voltage level, and outputs it as a clock for the spread code generator 204. The spread code start signal is used as a code synchronization signal by the code generator 204.
And output to the baseband demodulation circuit 206.

The synchronizing circuit 203 and the code generator 204 constitute a kind of phase lock loop as a whole. When synchronization is not established, the phase detector 706
Since there is a phase difference between the correlation peak signal, which is the input of the signal, and the spreading code start signal, the spreading code clock is advanced (or delayed), and thereby the synchronization-specific spreading code component included in the received signal and the spreading code start The phase difference with the signal gradually decreases. When the two phases match, the phase difference of the phase detector 706 becomes 0, and thereafter, this phase difference becomes 0.
It is controlled so that

After the synchronization is established, the spreading code generator 204 generates a spreading code group in which the clock and the spreading code phase match the spreading code group on the transmitting side. The spreading code PN0 dedicated to synchronization among these code groups is provided by the carrier reproducing circuit 20.
5 is input.

The carrier reproducing circuit 205 despreads the received signal converted into the transmission frequency band or the intermediate frequency band, which is the output of the high frequency signal processing unit 202, using the synchronization-dedicated spreading code PN0. Regenerate the carrier. The configuration of the carrier reproduction circuit 205 is as follows.
For example, a circuit using a phase locked loop as shown in FIG. 5 is used.

In FIG. 5, a received signal is multiplied by a synchronization-dedicated spreading code PN0 in a multiplier 501. After the synchronization is established, the clock and code phase of the synchronization-only spreading code in the received signal and the synchronization-only spreading code for reference match, and the synchronization-only spreading code on the transmitting side is not modulated with data.
The signal is despread by the multiplier 501, and a carrier component appears at the output. This output is subsequently input to the band pass filter 502, where only the carrier component is extracted and output.

This output is then input to a well-known phase locked loop composed of a phase detector 503, a loop filter 504, and a voltage controlled oscillator 505.
The signal whose phase is locked to the output carrier component is output as a reproduced carrier. This regenerated carrier is
Input to baseband demodulation circuit 206.

The baseband demodulation circuit 206 generates a baseband signal from the reproduced carrier and the output of the high-frequency signal processing section 202. The baseband signal is distributed to n branches, despread for each code division channel by spreading code groups PN1 to PNn output from the spreading code generator 204, and then data demodulation is performed. The baseband demodulation circuit 206 is configured, for example, as shown in FIG.

In FIG. 6, a received signal and a reproduced carrier are multiplied by a multiplier 601 and unnecessary signals are removed by a low-pass filter 602 to convert the received signal into a baseband signal. This baseband signal is converted into a digital signal having a single-bit or multiple-bit resolution in an AD converter 603 using a reproduction clock as a sampling period.

The digital signal is distributed to n branches, and in each branch, the most significant bit of the digital signal is a spreading code group PN1 to PN1 to Pn which is an output of a spreading code generator.
Nn and exclusive-OR operation in exclusive-OR circuit groups 604-1 to 60n, and adder group 6 together with other bits
05-1 to n. In the adder group 605-1 to n, the input signal and the register group
06-1 to 06-n are added, and a register group 606-
1 to 1n.

The register groups 606-1 to n are reset when the first bit of each spreading code is input.
Thereafter, the result obtained by adding the product of the received signal and the spread code over one cycle of the spread code is stored. Therefore,
When the last bit of one cycle of the spread code is input, the register group 606-1-n stores the correlation value between one cycle of each spread code and the received signal.

Then, the correlation value is determined by the following judgment circuit group 6
By performing data determination in 07-1 to 07-n, n pieces of parallel demodulated data are obtained. Further, the correlation value is subsequently input to the transmission code channel detection circuit 207. When the absolute value of the correlation value of each code channel is equal to or smaller than a certain value, the transmission code channel detection circuit 207 determines that the signal is not transmitted on the channel. That is, it determines k code channels whose absolute value of the correlation value is equal to or greater than a certain value, and outputs the determination result to the transmission identification circuit 208 and the demodulation data selection circuit 209.

The transmission identification circuit 208 determines and outputs transmission identification data corresponding to the determined k code channels on a one-to-one basis. The demodulation data selection circuit 209 outputs the demodulation data corresponding to the k code channels detected by the transmission code channel detection circuit 207 to the baseband demodulation circuit 2
The demodulated data is selected from the n pieces of demodulated data which is the output of 06 and output to the parallel / serial converter 210. The selected k pieces of parallel demodulated data are converted into serial data by the parallel / serial converter 210 and output.

[0048]

As described above, according to the present invention,
Notify the receiver of transmitter-specific identification data with a combination of spreading code sequences used for spreading code channels to be multiplexed
be able to. In addition, the received signal is
Since it can be converted to a baseband signal, a correlator for demodulating the data channel can be constituted by a digital signal processing circuit, and a spread code channel selected on the transmission side is converted from the digital correlation output. It is possible to easily detect, and the circuit scale can be easily reduced, and the correlator can be easily integrated into an IC. Further, even when the number of code division multiplexing is large, there is an effect that a small and inexpensive communication device can be provided.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a configuration of a receiver in the embodiment.

FIG. 3 is a block diagram showing a configuration of a transmitter in a conventional example.

FIG. 4 is a block diagram showing a configuration of a receiver in a conventional example.

FIG. 5 is a block diagram showing a carrier reproducing circuit in the embodiment.

FIG. 6 is a block diagram showing a baseband demodulation circuit in the embodiment.

FIG. 7 is a block diagram showing a synchronization circuit in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Serial-parallel converter, 102 ... Spread code generator, 103 ... Code sequence selection circuit, 104-1 ... k ... Multiplier, 105 ... Adder, 106 ... High frequency stage, 107 ... Transmit antenna, 201 ... Receive antenna, 202: high-frequency signal processing unit, 203: synchronization circuit, 204: spreading code generator, 205: carrier recovery circuit, 206: baseband demodulation circuit, 207: transmission code channel detection circuit, 208: transmission identification circuit, 209: demodulated data Selection circuit, 210 ... parallel-to-serial converter.

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

Claims (2)

(57) [Claims] 1. A serial-parallel conversion means for converting an input serial data sequence into a parallel data sequence having a predetermined number of symbols (k symbols), and having the same cycle according to input transmission identification data and having the same code phase. code sequence selecting means for selecting and outputting k parallel sequences from the n data spreading code sequences, and modulating means for modulating each of the k data spreading code sequences from the code sequence selecting device. An adding means for adding the k outputs of the modulating means and the synchronization-dedicated spreading code sequence, and a transmitting means for converting the output of the adding means into a predetermined transmission frequency band signal and transmitting the signal to a transmission path. A spread-spectrum transmitting apparatus; a received signal for receiving a signal from a transmission path, a correlating means for performing a correlation operation between an output of the receiving means and n data spread code sequences, and a correlation value which is an output of the correlating means From n Demodulating means for demodulating the data of Bol, and transmits code channel detecting means absolute value of the correlation value is determined whether a predetermined value or more or less, to detect a k-number of spreading code sequences which are selected on the transmitting side, Transmission identification means for discriminating transmission identification data from the k spread code sequences, reproducing and outputting transmission identification data on the transmission side, and transmission channel detection means from n-symbol data output from the demodulation means. A demodulated data selecting means for selecting and outputting data of k symbols for the k spread codes detected in the step (a), and a parallel data string for converting a parallel data string of k symbols output from the demodulated data selecting means into a serial data string. A spread spectrum receiving apparatus having a serial conversion means; and a spread spectrum communication apparatus. 2. The method according to claim 1, The receiving means includes: a reproducing means for reproducing the carrier;
The output of the receiving means is transmitted to the baseband
First converting means for converting the baseband signal into
A second conversion unit for converting the digital signal into a digital signal; The correlating means outputs the output of the second converting means and n
It performs correlation calculation with a number of data spreading code sequences.
Spread spectrum communication equipment.