JPH044621A - Communication system for data at short wave band - Google Patents

Abstract

PURPOSE:To prevent the degradation in the quality of line due to deviation between a frequency selection time and an actual communication time and a loss of time required for the check in the frequency by sending different transmission frequencies modulated by the same transmission data simultaneously from plural ground stationary stations and selecting the frequency of a line with best S/N with a mobile station. CONSTITUTION:Different frequencies f1, f2, f3 in ground stationary stations A, B, C are modulated by a transmission data inputted from a key station (any of ground stationary stations A, B, C) respectively and the modulated signals are sent simultaneously. Independently three receivers 2, 3, 4 of a mobile station D receive respectively the radio waves f1, f2, f3 and synthesize the waves by using the frequency diversity and demodulate the waves. Simultaneously, a frequency having a best quality (S/N) among the f1, f2, f3 is checked, and when the selected frequency is f2, the transmission to the ground stationary station uses the frequency f2 and a switch S is changed over to the position of the transmission. The ground stationary station uses any of receivers Rx1, Rx2, Rx3 to receive the radio wave of the frequency f2, sends the wave to the key station via a communication system L, where the waves are synthesized by employing the space diversity to obtain a final reception data.

Description

[Detailed description of the invention] (Technical field to which the invention pertains) When data communication is performed between a mobile station and a land fixed station using a shortwave band that uses spatial propagation and has a highly variable quality, frequency selection or various Is it possible to improve transmission quality by using diversity technology? The present invention selects frequencies by making the mobile station equipment as small as possible, and improves transmission quality by using diversity technology. The invention relates to a shortwave band data communication system that performs half-duplex communication.

(Prior art and its problems) FIG. 1 is an explanatory diagram of a conventional shortwave band data communication system. In the figure, A is a terrestrial fixed station and D is a mobile station. Frequencies are sequentially fl+f2. from terrestrial fixed station A. f3-, the mobile station sequentially changes the receiving frequency and measures the S/N for each layer wave number, selects the frequency with the best S/N (for example, f2), and fixes it on the ground. The station will be notified and subsequent communications will be conducted using this frequency. However, the drawbacks of this method are as follows.

■ Since the S/N is measured by changing frequencies one after another, it takes time to select the optimum frequency.

■Due to the time difference between S/N measurement and communication, the frequency is not necessarily optimal during actual communication.

■ The optimal frequency changes due to temporal fluctuations in line quality, and even if line quality deteriorates, there is no way to remedy it.

■ Equipment for selecting frequencies at the mobile station is required.

(Objective of the Invention) The present invention prevents line quality deterioration and loss of time required for frequency investigation due to the discrepancy between frequency selection time and actual communication time. The purpose of the present invention is to provide a data communication system in the short wave band that uses both frequency diversity technology and space diversity technology to improve transmission quality by providing a certain amount of equipment and selecting frequencies.

(Structure and operation of the invention) In the shortwave band data communication system of the present invention, one key station selected from among a plurality of terrestrial fixed stations connected to each other by a terrestrial communication network and arranged in a distributed manner and a mobile station are connected to each other by a terrestrial communication network. In order to perform shortwave band data communication, the plurality of terrestrial fixed stations transmit different shortwave band transmission frequencies to the mobile station at the same frequency transmitted from the key station via the terrestrial communication network. Radio waves modulated by transmission data are simultaneously emitted, and the mobile station receives the radio waves using a plurality of receivers provided corresponding to transmission frequencies in different shortwave bands of the plurality of ground fixed stations, and transmits the radio waves by frequency diversity. While extracting the demodulated data, select the frequency of the line with the best S/N by S/N comparison judgment, use that frequency as the transmission frequency, modulate it with the transmission data, and transmit it to the plurality of terrestrial fixed stations, and perform the dispersion. The plurality of terrestrial fixed stations arranged receive the radio waves from the mobile station using a receiver corresponding to the frequency of the radio waves received from the mobile station among the plurality of receivers installed in each of the plurality of terrestrial fixed stations. Detects reception, demodulates data and S/
N signals are detected and collected at the key station via the terrestrial communication network, and demodulated data by space diversity is extracted by a synthesizer provided at the key station. be.

The present invention will be explained in detail below with reference to the drawings.

FIG. 2 is a detailed explanatory diagram of the present invention, showing the configuration of a communication system between a land fixed station and a mobile station. here,
An example is shown in which there are three land fixed stations and three frequencies.

In the figure, A, B, and C represent three land fixed stations, and each station has one transmission system.

It is equipped with three receiving systems, and is connected to each other by a ground communication system. And three fixed stations A and B.

One of C is designated as a key station, which sends transmission data to other fixed stations through a terrestrial communication line, and receives received data from other fixed stations.

The mobile station is equipped with one transmitting system and three receiving systems independently, and is capable of frequency selection and diversity combining.

FIG. 3 is a block diagram showing the configuration of a land fixed station device according to the present invention. In the figure, 1 is a transmitter (Tx), 2, 3
．． 4 is a receiver (Rxl, Rx2°Rx3), each having a different reception frequency. 5 represents a modulator (MOD), and 6 represents a detector (DET). 8 is a synthesizer (DIV) provided only in the key station.

The land fixed station operates as follows.

Transmission data input at a key station is sent to other fixed stations via its own station and terrestrial communication line, and is modulated by a modulator 5 for digital transmission at each fixed station.
(Tx), converted to different transmission frequencies assigned to each fixed station, and transmitted.

On the other hand, in the case of reception, receivers 2 (Rxl) and 3 (Rx2) with different reception frequencies are always on standby.

4 (Rx3) receives the radio wave from the mobile station and detects it using the detector 6. At the same time, the S/N of the radio wave is
is determined, and simultaneously with the received data, an S/N signal necessary for diversity combining is sent to the key station via the land communication system.

One fixed station serving as a key station performs diversity combination using a combiner 8 based on data and S/N signals from other fixed stations, and outputs final received data. That is, space diversity reception is performed by a plurality of distributed fixed stations.

FIG. 4 is a block diagram showing the configuration of a mobile station according to the present invention. In the figure, 1 is a transmitter (TX), 2 (Rxl), 3
(Rx2) and 4 (Rx3) are receivers with different reception frequencies. S is a transmitting/receiving selector switch, which is normally connected to the receiving side and switches to the transmitting side only when transmitting to perform half-duplex communication. 5 is a transmit data modulator (MOD), 6 is a detector (DET), which demodulates data and at the same time transmits data to receivers 2 (Rxl) and 3 (Rx2).
), 4 (Rx3) determines the S/N of the received signal and outputs each. 7 is S of each receiving system from the detector 6.
This is a comparator (COM) that compares S/N and determines which received wave has the best S/N.

Reference numeral 8 denotes a synthesizer that combines and demodulates the data of each receiving system input from the detector 6 using the diversity technique based on the input from the comparator 7, and outputs the final received data.

The operation of the mobile station is performed as follows.

Receiver 2 receiving radio waves of fl+f2+f3 from three terrestrial fixed stations A, B, and C. 3. 4, the detector 6 detects and demodulates each received frequency, and the synthesizer 8 performs diversity synthesis, and then outputs the final received data. At this time, a detector 6 is installed for each receiving frequency.
The S/N (signal-to-noise ratio) is determined by using the comparator 7, and a frequency with a good S/N is determined by the comparator 7. One of the outputs is sent to the combiner 8 and used for diversity combining, and the other is sent to the transmitter 1, and the transmit frequency of the transmitter 1 is changed to the comparator 7.
Set to the frequency determined by That is, switch S
is switched to the transmitting side, and the frequency with the best S/N among the received frequencies is used as the transmission frequency for transmitting to the ground fixed station.

Next, the overall operation of the communication system of the present invention will be explained using FIG.

The terrestrial fixed stations A, B, and C each have different frequencies depending on the transmission data input from the key station.
,,f2. f3 is modulated and transmitted simultaneously. At this time, the radio wave emission time is controlled from one of the fixed stations A, B, and C, which has become a key station, using the communication line of the land fixed station.

On the other hand, the mobile station receives radio waves f from each fixed station on the ground.
,,f2. f3 is independently received by three receivers 2°3.4, and combined and demodulated using frequency diversity. At the same time, f I+f2. Check the one with the best quality (S/N) among the f3 radio waves. For example,
As a result, if f2 is determined to be the best, transmission to the ground fixed station is performed by using f2 and switching the switch S to transmit.

The terrestrial fixed station transmits radio waves of frequency f2 to Rxl, Rx2.
The signals are received by any corresponding receiver of Rx3, sent to the key station via the land communication system, and synthesized there using space diversity to obtain the final received data.

In the embodiments described above, the same method can be adopted in cases where there are three terrestrial fixed stations, or when there are four or more terrestrial fixed stations.

(Effect of the invention) The advantages of implementing the invention are as follows.

■The mobile station where power consumption is an issue has only one transmission system.

By independently providing multiple receiving systems, it is possible to prevent an increase in power consumption.

■ For transmission from each terrestrial fixed station to the mobile station, the frequency with the best S/N can be selected by the mobile station's independent multiple receiving systems, and the mobile station uses frequency diversity technology. Good quality demodulated data can be obtained. (combination of frequency diversity technology and transmission space diversity technology).

■ From the mobile station to the terrestrial fixed station, data is transmitted using the frequency with the best line quality selected by the mobile station, and the results received by each terrestrial fixed station are used to generate high-quality demodulated data using space diversity technology. (space diversity technology with selected frequencies).

■ If the moving speed of the mobile station is fast, for example, a significant effect can be obtained in the case of an aircraft.

[Brief explanation of drawings]

FIG. 1 is a diagram of a conventional communication configuration, FIG. 2 is a diagram of a communication configuration to which the present invention is applied, FIG. 3 is a diagram of a configuration of a terrestrial fixed station of the present invention, and FIG. 4 is a diagram of a mobile station of the present invention. It is a configuration example diagram. DESCRIPTION OF SYMBOLS 1...Transmitter, 2-4...Receiver, 5...Modulator, 6...Detector, 7...Comparator, 8...Synthesizer.

Claims (1)

[Scope of Claims] In order for one key station selected from a plurality of terrestrial fixed stations connected to each other by a terrestrial communication network and arranged in a distributed manner to perform shortwave band data communication with each other, the plurality of Simultaneously transmitting to the mobile station from the terrestrial fixed station radio waves modulated by the same transmission data sent from the key station via the terrestrial communication network at different shortwave band transmission frequencies; The mobile station receives the radio waves using a plurality of receivers installed corresponding to different shortwave band transmission frequencies of the plurality of ground fixed stations, extracts demodulated data by frequency diversity, and performs S/N comparison judgment. Select the frequency of the line with the best S/N, use that frequency as a transmission frequency, modulate it with the transmission data, and transmit it to the plurality of terrestrial fixed stations, and the plurality of distributed terrestrial fixed stations Of the plurality of receivers installed in each of the ground fixed stations, the receiver corresponding to the frequency of the received radio waves from the mobile station receives and detects the radio waves from the mobile station, and demodulates the demodulated data and S/
A shortwave band data communication system configured to detect N signals and collect them at the key station via the terrestrial communication network, and to extract demodulated data by space diversity using a synthesizer provided at the key station.