JPH10233753A - Spread spectrum communication method and equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a mean output and to extend the communication distance by modulating a plurality of carriers with signals modulated by spread spectrum processing before the signals are linearly added. SOLUTION: In the case that signals subject to spread spectrum modulation are multiplexed by N sets of orthogonal spread codes and the resulting signal is communicated, spread codes PN1 -PNn from a code generator 15 are used for applying spread modulation (11-1-11-n) to transmission data #1-#n. N-sets of spread modulation signals are phase-modulated (13-1-13-n) with N-sets of carriers with a different phase from a signal generator 12 and N-sets of phase modulated signals are synthesized (14) and outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication method and apparatus, and more particularly, to a multiplexed spread spectrum communication method and apparatus.

[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 digital signal to be transmitted by using a spread code sequence such as a pseudo-noise code (PN code). (Radio frequency) signal and transmit.

As a method for realizing high-speed transmission by this method, Japanese Patent Application No. 5-344920 discloses a multiplexed spread spectrum communication apparatus. This Japanese Patent Application 5-3
The device of No. 44920 uses a plurality of orthogonal spreading codes.
First, transmission data is spread-modulated, linearly added, and then modulated by a carrier for transmission.

[0004] A transmitting unit and a receiving unit of a conventional spread spectrum communication apparatus will be described below.

FIG. 5 is a block diagram showing a configuration of a conventional transmitting section. First, the n pieces of parallel data are transmitted to the spread modulator 51-.
After being spread-modulated by n different spreading codes PN1 to PNn output from the code generator 54 at 1 to 51-n, they are linearly added by the adder 52. And
The carrier is modulated by the output of the adder 52 by the modulator 53, and after being subjected to processing such as amplification, filtering, and frequency conversion as necessary, is transmitted.

FIG. 6 is a block diagram showing a configuration of a conventional receiving unit. First, the received signal r (t) is subjected to processing such as amplification, filtering, and frequency conversion as required, and is branched. A part of the received signal is input to the synchronization circuit 63, and the received signal and the code generator 64 are input. Clock synchronization and code synchronization with the spreading code generated from. Further, a part of the received signal is further branched into n pieces, and is correlated with one of the spreading codes PN1 to PNn output to the correlator 61-1 to 61-n and output from the code generator 64, respectively. Will be Here, assuming that the spreading codes PN1 to PNn are orthogonal when code synchronization is established, that is, if the cross-correlation is 0, the correlation output of each of the correlators 61-1 to 61-n is output by another spreading code. The modulated component is removed, and only the component modulated by the spread code input to the correlator is extracted. Accordingly, the determiners 62-1 to 62-2
At -n, data demodulation is performed from the correlation results at the correlators 61-1 to 61-n by a phase modulation signal demodulation technique known to those skilled in the art.

Here, by inserting a serial-to-parallel converter in the transmitting section and a parallel-to-parallel converter in the receiving section, it is possible to realize high-speed transmission n times as compared with the case without multiplexing.

[0008]

However, in the above conventional example, since a plurality of spread-modulated signals are linearly added and then modulated by a carrier, the amplitude fluctuation is large and the maximum peak power is very small with respect to the average power. It becomes big. For example, when 8 multiplexing is performed, the maximum peak power is eight times (9 dB) the average power. Therefore, there has been a problem that the average output becomes small and the communication distance becomes short.

[0009] Further, in order to secure a predetermined communication distance, a high-output power amplifier is required, and there is a problem that power consumption is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to increase the average output and extend the communication distance by performing modulation with a plurality of carriers before linearly adding spread-modulated signals. It is an object of the present invention to provide a spread spectrum communication method and apparatus.

[0011]

In order to achieve the above object, the present invention provides a code generating means for generating N (N is an integer of 3 or more) spread codes, and a spread code by the N spread codes. Spreading modulating means for performing modulation, signal generating means for generating N carrier waves having different phases, phase modulating means for performing phase modulation by the N carrier waves, and synthesizing the N phase modulated signals. And output means for outputting.

According to another aspect of the present invention, there is provided a spread spectrum communication method for multiplexing and transmitting a signal subjected to spread spectrum modulation using N orthogonal spreading codes. The N parallel data is spread-modulated using N spreading codes, and the spread-modulated N signals are phase-modulated by N carrier waves having different phases from each other. It is characterized by combining and outputting N signals subjected to phase modulation.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 1 is a diagram showing a schematic configuration of a transmission section of a spread spectrum communication apparatus. In the figure, reference numerals 11-1 to 11-n denote spread modulators, which spread-modulate transmission data by a spread code. A signal generator 12 generates n carrier waves having different phases.
13-1 to 13-n are modulators which modulate the carrier outputted from the signal generator 12 by the outputs of the spread modulators 11-1 to 11-n. Reference numeral 14 denotes a synthesizer, and the modulator 13
The outputs of -1 to 13-n are combined. A code generator 15 generates a spreading code.

In the above configuration, n pieces of transmission data #
1 to #n are n spread codes PN1 to PN output from the code generator 15 in the spread modulators 11-1 to 11-n, respectively.
Nn performs spread modulation. Spreading modulators 11-1 to 11-1
The outputs of 11-n are input to modulators 13-1 to 13-n, respectively, and are phase-modulated by n different carrier waves output from the signal generator 12, respectively. The n signals are combined and output. The signal output from the synthesizer 14 is amplified, filtered,
The data is transmitted after being subjected to processing such as frequency conversion.

Here, the case where n = 8 will be specifically described. In the case of n = 8, as shown in FIG. 4, eight carriers are generated by shifting the phase by 22.5 degrees.
The spread modulated signals are phase-modulated by a plurality of carriers and then combined. Here, the amplitude of the synthesized signal changes according to the values of the eight spread modulation signals to be synthesized, but the maximum is obtained when the phases of all the signals after the phase modulation are within 180 degrees. Is about 5.1 A, where A is the amplitude of one modulation signal. Assuming that eight spreading codes used for spreading modulation are orthogonal, the average power is obtained by the sum of the powers of the respective modulated signals, so that the peak power with respect to the average power can be suppressed to about 5.2 dB.

FIG. 2 is a diagram showing a schematic configuration of a receiving section of the spread spectrum communication apparatus. In FIG.
Reference numerals -1 to 21-n denote correlators that perform a correlation operation between a received signal and a spread code output from a code generator described later.
22-1 to 22-n are decision units, each of which is a correlator 2
Data determination is performed based on outputs from 1-1 to 21-n. Reference numeral 23 denotes a synchronization circuit that synchronizes clocks and codes between a received signal and a spread code output from a code generator described later. Reference numeral 24 denotes a code generator, which is a spread code PN1 to PN1.
Generate PNn.

In the above configuration, the received signal r (t) is subjected to processing such as amplification, filtering, and frequency conversion as necessary, and then branched, and a part of the received signal is input to the synchronization circuit 23. Clock synchronization and code synchronization between the received signal and the spread code generated from the code generator 24 are established. Examples of the synchronous circuit include a sliding correlator, a delay locked loop, Japanese Patent Application No. 6-332715 and Japanese Patent Application No.
There is a circuit using a surface acoustic wave device as described in JP-A-3-287101.

A part of the received signal is further branched into n parts, and is correlated with one of spread codes PN1 to PNn which are input to correlators 21-1 to 21-n and output from code generator 24, respectively. An operation is performed. For example, the first correlator 2
In 1-1, the correlation operation with the first spreading code PN1 is performed, and in the second correlator 21-2, the second spreading code PN2
Is calculated. Here, the spreading codes PN1 to PN
Nn are orthogonal when the code is synchronized, that is, if the cross-correlation is 0, each of the correlators 21-1 to 21-n
In the correlation output at, the component modulated by another spreading code is removed, and only the component modulated by the spreading code input to the correlator is extracted. Therefore, the decision unit 2 is determined from the correlation results in the correlators 21-1 to 21-n.
Data demodulation is performed in 2-1 to 22-n.

As described above, a carrier having a phase different by the number equal to the number of codes to be multiplexed is provided, a signal spread and modulated by each code is modulated by a carrier having a different phase, and then combined and transmitted. Therefore, it is possible to reduce the amplitude fluctuation of the multiplexed signal. Therefore, the average output can be increased, and the communication distance can be increased. Further, the output of the power amplifier for securing a predetermined communication distance can be reduced, and power consumption can be reduced.

[Second Embodiment] Next, as a second embodiment, a case where a correlation operation is performed after conversion to a quasi-baseband in a receiving unit will be described. Note that the configuration of the transmitting unit of the spread spectrum communication apparatus is the same as that of the first embodiment, and the receiving unit will be described here.

FIG. 3 is a diagram showing a schematic configuration of a receiving section according to the second embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals.

In the configuration shown in FIG. 3, the output signal from the oscillator 31 is a signal whose frequency is substantially equal to the received signal, is directly input to the baseband converter 32, and is supplied to the baseband converter 34 with a 90-degree phase. Input via the device 33. With this configuration, a baseband signal of the in-phase component and a baseband signal of the quadrature component are obtained, and the phase relationship between the received signals can be stored by both.

Here, the outputs rI and rQ from the baseband converters 32 and 34 are input to the correlators 21-1a and 21-1b for the spreading code PN1, respectively, and are correlated with the spreading code PN1 synchronized with the received signal. . Then, the spreading code PN1
And the spread codes PN2 to PNn are orthogonal or have a small cross-correlation, so that the spread code PN1 correlators 21-1a and 21-1
An in-phase component and a quadrature component of the component modulated by the spreading code PN1 are extracted from the output of b. Therefore,
By inputting these to the determiner 22-1, the components modulated by the spreading code PN1 are demodulated.

Similarly, outputs rI and rQ from baseband converters 32 and 34 are respectively assigned to spreading codes PN2 to PNn.
Correlators 21-2a, 21-2b to 21-na, 21-
nb and spread codes PN2 to P synchronized with the received signal.
Correlate with Nn. Then, each spreading code PN1 to PNn
Since each has a small orthogonal or cross-correlation, an in-phase component and a quadrature component of a component modulated by each spreading code are extracted from each correlator. Therefore, by inputting these to the determiners 22-2 to 22-n, the components modulated by the respective spread codes are demodulated.

In the above-described embodiment, the synchronization circuit operates by a signal before being converted into the baseband band. However, the synchronization circuit may be configured to operate by a signal in the baseband band.

In the above-described embodiment, one spreading code is associated with one bit of transmission data. However, the present invention is not limited to this, and for example, a set of spreading codes is used for a plurality of data. A so-called parallel combination method can be used.

An object of the present invention is to supply a storage medium storing program codes of software for realizing the functions of the above-described embodiments to a system or an apparatus, and to provide a computer (CPU or MP) of the system or apparatus.
It goes without saying that U) can also be achieved by reading and executing the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also an OS (Operating System) running on the computer based on the instruction of the program code. ) May perform some or all of the actual processing, and the processing may realize the functions of the above-described embodiments.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, based on the instruction of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

[0033]

As described above, according to the present invention,
By performing modulation with a plurality of carriers before linearly adding signals spread and modulated with a plurality of spread codes, the average output can be increased, and the communication distance can be lengthened.

Further, the output of the power amplifier for securing a predetermined communication distance can be suppressed low, and the power consumption can be reduced.

[0035]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a transmission unit according to a first embodiment.

FIG. 2 is a diagram illustrating a configuration of a receiving unit according to the first embodiment.

FIG. 3 is a diagram illustrating a configuration of a receiving unit according to the first embodiment.

FIG. 4 is a diagram showing a phase of a carrier output from a signal generator.

FIG. 5 is a diagram showing a configuration of a transmitter in a conventional example.

FIG. 6 is a diagram showing a configuration of a receiver in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Spreading modulator 12 Signal generator 13 Modulator 14 Synthesizer 15 Code generator 21 Correlator 22 Judgment device 23 Synchronization circuit 24 Code generator

Claims (7)

[Claims] 1. A code generating means for generating N (N is an integer of 3 or more) spreading codes; a spreading modulating means for performing spread modulation with the N spreading codes; Spread spectrum communication, comprising: a signal generating means for generating; a phase modulating means for performing phase modulation with the N carrier waves; and an output means for synthesizing and outputting the N phase modulated signals. apparatus. 2. The phase of each of the N carriers is 180
2. The spread spectrum communication apparatus according to claim 1, wherein the spread spectrum communication apparatus differs by / N degrees. 3. The apparatus according to claim 1, further comprising: N correlation means for obtaining a correlation between said N spread codes and a received signal; and demodulation means for performing demodulation based on a correlation result by said N correlation means. The spread spectrum communication apparatus according to claim 1, wherein: 4. The spread spectrum communication apparatus according to claim 2, wherein the N spreading codes are codes having a small correlation with each other. 5. The spread spectrum communication apparatus according to claim 2, wherein the N spread codes are codes orthogonal to each other. 6. The spread spectrum communication apparatus according to claim 3, wherein after the received signal is converted into a signal in a baseband, a correlation with a spread code is obtained by a correlation unit. 7. A spread spectrum communication method for multiplexing and communicating signals spread spectrum modulated by N orthogonal spreading codes, wherein the transmission data is converted into N parallel data, and the transmission data is converted into the N parallel data. On the other hand, the spread modulation is performed using N spread codes, and the spread modulated N signals are N
A phase spread communication method, comprising: performing phase modulation with a plurality of carrier waves; combining and outputting the N phase-modulated signals.