JPH02121424A - Band narrowing system for spread spectrum radio communication - Google Patents

Abstract

PURPOSE:To narrow a occupied frequency band width when the pulse processing FM system in the spread spectrum is employed by dividing a series of transmission information string into plural lines to apply spread spectrum modulation through the use of a multiple access technology. CONSTITUTION:A serial/parallel conversion section 5 of a transmitter 1 distributes information into 3 sets of information strings having a transmission speed of 5kbps, and spread spectrum modulation is applied in the pulse processing FM (chirp) system to obtain a spread processing gain of a 27dB by a modulation section. Since the multiple access technology is employed to superimpose the split information string onto the same frequency band in such a way, the occupied frequency band width on the transmission line is 2.5MHz, then improved. Since the multiplex by the multiple access is applied in such a way, the band narrowing processing is attained in comparison with the case of applying spread modulation to each information string as it is, and sending the result.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to wireless communication using a spread spectrum communication system, and particularly to a method suitable for narrowing the occupied frequency bandwidth and a method for realizing this. Regarding equipment.

[Conventional technology]

For traditional spread spectrum communications, the spread
Spectrum Systems (1984) pp. 44-47 (SPREAD 5PEC'1”RUM
SYS'l'EMS (1984) PP44-47].

[Problem to be solved by the invention]

The above-mentioned conventional technology mainly focuses on securing processing gain during spread demodulation obtained by wideband communication of spread spectrum communication, and narrows the occupied frequency bandwidth necessary for transmitting a series of information sequences. Furthermore, no consideration was given to multiple access to compensate for this, and the problem of expanding the occupied frequency bandwidth, which is currently a bottleneck to the practical application of spread spectrum communications in relation to Japan's Radio Law, has been resolved. It has not been.

The purpose of the present invention is to apply multiple access technology to narrow the occupied frequency band by one inch when using the pulsed FM method in spread spectrum, and to do so under the constraints of the current domestic radio law. The goal is to learn about the path to practical application of spread spectrum communications.

[Means to solve the problem]

The above purpose is to divide a series of transmission information strings into multiple lines,
This is achieved by applying Lamb spread modulation to spectrum 1 using multiple access techniques.

[Effect]

A series of digital information strings to be transmitted is divided into a plurality of information strings by performing serial/parallel conversion. The divided information strings are subjected to spread spectrum modulation (chirp modulation) by changing the carrier frequency in a predetermined manner using control signals having different phases. The bandwidth after modulation at this time may be narrower because the information transmission speed is slower than when spread modulation is performed to obtain the same processing gain without dividing the original information string. In order to completely transmit the original information, it is necessary to multiplex each divided information string and transmit it to the receiving side, but by performing multiplexing using multiple access, each divided information If the information sequence is spread-modulated and transmitted as it is, it becomes possible to narrow the band.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram schematically showing a transmission system to which the present invention is applied. For example, the input data in Figure 1 is 15k.
This is an information string of bps.

The serial/parallel converter 5 of the transmitter 1 distributes the information into three information streams having a transmission rate of 5 kbps. To this, the modulation section 3
When spreading modulation is applied using a pulsed FM (chirp) method to obtain a spreading processing gain of 7 dB, the occupied frequency bandwidth becomes 2.5 MHz.

This is transmitted on a transmission path, but multiple access technology is used here and each divided information string is superimposed on the same frequency band, so the occupied frequency bandwidth on the transmission path is 2.5MHz.
That's fine.

In addition, the conventional Speci-Lamb spread modulation (pulsed 1"
In a wireless communication system using M-spread modulation, for example, the above-mentioned 15 kbps transmission rate information requires 27 dB.
When spreading modulation is applied using a pulsed FM (chirp) method so as to obtain a spreading processing gain of , the occupied frequency bandwidth on the transmission path becomes 7.5 MHz.

In the receiver 2, the received waves are sent to a demodulator 4 prepared for three channels. The demodulator 4 demodulates the information string that has been spread-modulated by the transmitter (a number of modulators 3) using a chirb signal having a 2/3π phase shift for each customer channel.

The demodulated information string is converted to the original 15k by the parallel/serial converter 6.
It is restored to an information string of bps and output.

FIG. 2 is a specific configuration diagram of the transmitter 1 shown in FIG. 1. The transmitter 1 includes a serial/parallel converter 5. Modulation section 3. High frequency section7. It is composed of 8 CPUs.

The serial/parallel converter 5 converts the input serial data into 3bi
Convert to t parallel data. With this, 15k
Divide the information string that has been manually generated in bps into three 5kb pieces.
Create an information string of ps (15 kbps ÷ 3). The three divided information strings are sent to the modulation section 3. Modulation section 3 is CP
Control of U8 (by No. W, timing generator 9
Create a timing pulse. The spreading code generator 10 generates a control signal that generates a pulsed chirp No. 6, and according to this signal, the VCO II generates a pulsed FM (chirp) No. 4.
11, and spread modulation is applied to the three information streams sent from the serial/parallel converter 5. The modulation section 3 includes spreading modulators 1.2. 3 VCOIIs and 3 spreading code generators 10 each.
The timing generator 9 generates a pulse signal for each channel at a time with a phase shift of 2/3 of the period of the control signal. The bandwidth after modulation is 2.5 MHz when the processing gain is 27 dB. Each information string that has undergone spread modulation and has become a 2.5 MHz signal is sent to the high frequency section 7. Here, first of all, 33
The 2.5 MHz information stream is mixed into one transmission band with a bandwidth of 2.5 MHz by the mixer 13. Since the pulsed FM (chirp) signal of each information string used for modulation has a 2/3π position shift for each channel, interference will occur even if the pulsed FM (chirp) signal is mixed in the same frequency band without widening the bandwidth. Demodulation is possible without any problems. The demodulation can be separated for each channel by correlating with the pulsed FM (chirp) signal for each channel. The multiplexed transmission signal is sent to a high frequency power amplifier 14 to obtain the required transmission power. The signal is emitted as a radio wave through an antenna filter 15 which removes noise in unnecessary bands and an antenna 16 which sends the signal into the air as an electromagnetic wave. High frequency power amplifier 1 used in this high frequency section 7
4. Antenna filter 15. The antenna 16 may be one for ordinary high frequency circuits as long as it can be applied to a wide band by spread spectrum. CP'tJ8 controls the timing generator 9 and the like based on the settings of switches and the like on the operation panel.

FIG. 3 shows the configuration of the receiver 2. This device has a high frequency section 7.
', demodulator 4. Parallel/serial converter 6. It is composed of a CPU 8'.

The reception wave caught by the antenna 16' is subjected to reception band restriction by a reception band filter 17, noise in unnecessary bands is cut, and after being amplified by a low noise amplifier 18, it is sent to the demodulator 4. Each component used here may be one for ordinary high frequency circuits as long as it can be applied to a wide band by spectrum spread, similar to the high frequency section 7 of the transmitter 1.

The demodulating section 4 spreads the received wave sent from the high frequency section 7' based on the pulsed FM (chirp) signal through the same generation process as the modulating section 3 of the transmitter 1 using the control signal of CI) U8'. Demodulate.

The received wave is divided into three parts between the high frequency section 7' and the demodulation section 4, and the synchronous detector 19 of the demodulation section 4 corresponds to this. The spreading demodulator 20 includes a VCOII' and a spreading code generator 10'.
for each channel in parallel. Each distributed received wave is synchronized with a transmitted wave pulsed FM (chirp) signal by a synchronization detector 19 and sent to a spreading demodulator 20, but here, some of the distributed received waves are still 3 each
Contains information for channels. Here, like the modulation section 3 of the transmitter 1, a timing pulse having a 2/3π phase shift is generated for each channel. The spreading code generator 10' of each channel receives the timing pulse and simultaneously generates a control signal in the same way as the modulator 3 of the transmitter 1. Based on the control signal, a pulsed FM (chirp) signal is generated at Co11'. Demodulation is possible because the control signal, which is the key to demodulating the special channel, has a 2/3π phase shift for each channel. The three information streams thus dispersively demodulated are sent to the parallel/serial converter 6, where they are converted to the original 15kbp.
The information string of s is restored and output.

According to this embodiment, the conventional system requires a radio frequency bandwidth of 7.5 MHz as the occupied frequency bandwidth, but this can be narrowed down to 2.5 MHz.

In the embodiment, since the information string was divided into three, the occupied frequency bandwidth could be reduced to 1/3, but theoretically, if the number of information divisions is increased, the band can be made narrower. In other words, according to the present invention, if the number of divisions of the original information string is Tl, the occupied frequency bandwidth is 1/11 of that without using the present invention.
It can be done.

〔Effect of the invention〕

According to the present invention, it is possible to narrow the occupied frequency bandwidth in wireless communication using spread spectrum.

As a result, it is possible to effectively utilize radio wave resources by narrowing the band of the wireless line, and it is also possible to put spread spectrum communication into practical use even under the restrictions of the current radio law. Furthermore, due to this narrow band,
Spread spectrum communications can also be used in lower frequency bands.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of a transmission system to which the present invention is applied, FIG. 2 is a configuration diagram of a transmitter of this embodiment, and FIG.
It is a block diagram of g machine. ]...Transmitter, 2...Receiver, 3・Modulation unit, 4・
...Demodulation section, 5...Serial/parallel conversion section, 6...Parallel/serial conversion section, 7.7'...High frequency section, 8.8'...C
PU, 9,9...timing generator, 10.10'.
... Spreading code generator, 11.11'... VCO (voltage controlled oscillator) 12... Spreading modulator, 13... Mixer,
14... High frequency power amplifier, 15... Antenna filter, 16, 16'... Antenna, 17... Reception band filter, 18... Low noise power amplifier, 19... Synchronization detector, 20. - Spreading demodulator. vine] Figure 1... 尼 (I wo Ukishi ( 4-・I 笈j [かんまる 2 ... うい菖 4) ( s,, -1/*Retsushi #Okibe 3... 斐Pigeon axis 4-, tAtsu・3・support key sound figure 3

Claims (1)

[Claims] 1. In a spread spectrum communication method that sweeps a carrier wave using a control signal, spread-modulates the signal wave using the carrier wave, and uses an occupied frequency bandwidth that is wider than the absolutely necessary occupied frequency bandwidth, transmission information can be transmitted in multiple ways. A method for narrowing the band of spread spectrum wireless communication, which is characterized by splitting the carrier wave sweep signal, shifting the phase of each carrier wave sweep signal, applying chirp modulation, and transmitting in the same radio frequency band using multiple access technology.