JPH0722275B2 - Shortwave data communication system - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION When data communication is performed between a mobile station and a land fixed station using a short-wave band that uses spatial propagation and whose quality fluctuates greatly, frequency selection or various types of Although the transmission quality has been improved by using the diversity technique, the present invention selects the frequency as the mobile station device is as small as possible, and improves the transmission quality by using the diversity technique. The present invention relates to a short-wave band data communication system for performing half-duplex communication as illustrated.

(Prior Art and its Problems) FIG. 1 is an explanatory diagram of a conventional short-wave band data communication system. In the figure, A is a fixed station on the ground and D is a mobile station.
The frequency is changed from f ₁ to f ₂ , f _{3 to} f _{3 in} sequence from the fixed station A and transmitted, and the mobile station D sequentially measures the S / N for each frequency while sequentially changing the received frequency. The N best frequency (for example, f ₂ ) is selected and notified to the ground fixed station, and the subsequent communication is performed using this frequency. However, the drawbacks of this method are as follows.

Since S / N is measured by changing the frequency sequentially, it takes time to select the optimum frequency.

Due to the time difference between the time of S / N measurement and the time of communication, it cannot always be said that the optimum frequency is used during actual communication.

Even if the optimum frequency changes due to the temporal fluctuation of the line quality and the line quality deteriorates, there is no means for relieving it.

Equipment is required for the mobile station to select the frequency.

(Object of the Invention) The present invention prevents the deterioration of the line quality and the loss of the time required for the frequency investigation due to the difference between the selection time of these frequencies and the actual communication time, and minimizes the equipment for the mobile station, and the fixed station. Is to provide a short-wave band data communication system with improved transmission quality using both frequency diversity technology and space diversity technology while selecting frequencies.

(Structure and Operation of the Invention) In the short-wave band data communication system of the present invention, one key station and a mobile station selected from a plurality of terrestrial fixed stations connected to each other by a terrestrial communication network and distributedly arranged mutually. In order to perform short-wave band data communication, the same terrestrial fixed stations send different short-wave band transmission frequencies to the mobile station 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 by a plurality of receivers provided corresponding to different short-wave band transmission frequencies of the plurality of ground fixed stations, and the frequency diversity The demodulated data is taken out, and the frequency of the line with the best S / N is selected by S / N comparison judgment, and that frequency is used as the transmission frequency and modulated by the transmission data. The plurality of ground fixed stations transmitted to the plurality of ground fixed stations, the plurality of ground fixed stations distributed, among the plurality of receivers provided in each of the plurality of ground fixed stations, of the reception radio wave from the mobile station. Radio waves from the mobile station are received and detected by the receiver corresponding to the frequency, demodulated data and S / N
The signal is detected and collected in the key station via the terrestrial communication network, and demodulated data by space diversity is taken out by a combiner provided in the key station. .

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

FIG. 2 is an explanatory diagram of an embodiment of the present invention, and shows a configuration of a communication system between a land fixed station and a mobile station. Here, an example is shown in which the land fixed station has three cylinders and the frequency is three waves. In the figure, A, B, and C represent the land fixed stations of the three cylinders,
Each station has one transmission system and three reception systems, which are connected to each other by a ground communication system L. And three fixed stations A,
One of B and C is used as a key station, and transmission data is sent to another fixed station via the ground communication line L,
Received data is received from another fixed station. The mobile station D independently has one transmission system and three reception systems, and selects the frequency and
Diversity composition is possible.

FIG. 3 is a block diagram showing the configuration of the land fixed station apparatus of the present invention. In the figure, 1 transmitter (Tx), 2, 3 and 4 are receivers (Rx1, Rx2, Rx3), which have different reception frequencies. Reference numeral 5 represents a modulator (MOD), and 6 represents a detector (DET). 8
Is a synthesizer (DIV) provided only in the key station.

The operation of the land fixed station is performed as follows.

The transmission data input at the key station is sent to other fixed stations through the own station and the ground communication line L, and is modulated by the modulator 5 for digital transmission at each fixed station.
It is amplified by (Tx), converted into different transmission frequencies assigned to each fixed station, and transmitted.

On the other hand, in the case of reception, the receiver 2 (Rx1), 3 (Rx2), 4 (Rx3) with different reception frequencies in the always standby state receives the radio wave from the mobile station and detects it with the detector 6 at the same time. The S / N of the radio wave is obtained, and at the same time as the received data, the S / N signal required for diversity combination is sent to the key station through the land communication system L.

One fixed station serving as a key station performs diversity combining by the combiner 8 based on the data from another fixed station and the S / N signal, and outputs the 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 the mobile station of the present invention. In the figure, 1 is a transmitter (Tx), 2 (Rx1), 3 (Rx
2) and 4 (Rx3) are receivers with different reception frequencies. S is a transmission / reception changeover switch, which is normally connected to the reception side, and is switched to the transmission side only when transmitting and is half 2
Perform heavy communication. Reference numeral 5 is a transmission data modulator (MOD), and 6 is a detector (DET), which simultaneously demodulates the data and at the same time receives S of signals received by the receivers 2 (Rx1), 3 (Rx2), 4 (Rx3). / N
And output each. Reference numeral 7 is a comparator (COM) that compares the S / Ns of the respective reception systems from the detector 6 and finds which reception wave is the best S / N. Reference numeral 8 denotes a combiner that combines and demodulates the data of each receiving system input from the detector 6 with the input from the comparator 7 by using the diversity technique and outputs the final received data.

The operation of the mobile station is performed as follows.

The radio waves f ₁ , f ₂ , and f ₃ from the three ground fixed stations A, B, and C are respectively received by the receivers 2, 3, and 4 in the receiving state, and the wave demodulator 6 detects and demodulates each reception frequency. Then, the combiner 8 performs diversity combining, and then outputs the final received data. At this time, the S / N (signal-to-noise ratio) is obtained by the detector 6 for each reception frequency, and the frequency having a good S / N is obtained by the comparator 7. One of the outputs is output to the combiner 8 and used for diversity combining, and the other is sent to the transmitter 1 to set the transmission frequency of the transmitter 1 to the frequency obtained by the comparator 7. That is, the transmission frequency of switching the switch S to the transmission side and transmitting to the fixed land station is the highest among the received frequencies.
You will use a good S / N frequency.

Next, the overall operation of the communication system of the present invention will be described with reference to FIG.

Ground fixed stations A, B and C modulate f ₁ , f ₂ and f ₃ having different frequencies by the transmission data input from the key station and transmit them simultaneously. The control of the emission time of the radio wave at this time is controlled by using the communication line L of the land fixed station from the fixed station A, B, or C which becomes the key station.

On the other hand, the mobile station is the radio wave sent from each fixed station on the ground.
f ₁ , f ₂ , and f ₃ are independently received by the three receivers ₂ , _3, and 4, respectively, and combined and demodulated using frequency diversity.
At the same time, the highest quality (S / N) of the radio waves of f ₁ , f ₂ and f ₃
Find out what's good. For example, the result transmission if f ₂ is determined to best to the ground fixed station performs switching to transmit the switch S using f _2. At the ground fixed station, the radio wave of the frequency of f ₂ is received by any one of the corresponding receivers of Rx1, Rx2, and Rx3, and it is sent to the key station by the land-based communication system L, where it is combined using space diversity and finally Get the received data.

In the embodiment described above, there are three ground fixed stations, but the same method can be adopted when there are four or more ground fixed stations.

(Effects of the Invention) The advantages of implementing the present invention are as follows.

A mobile station, which has a problem of power consumption, can prevent an increase in power consumption by independently providing one transmission system and multiple reception systems.

For the 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 reception system, and the mobile station uses frequency diversity technology to improve quality. It is possible to obtain good demodulation data. (Combined use of frequency diversity technology and transmission space diversity technology).

From the mobile station to the terrestrial fixed station, it is transmitted at the frequency with the best line quality selected by the mobile station, and the result received by each terrestrial fixed station is used to obtain high-quality demodulated data by the space diversity technology. Capable of (space diversity technology with selected frequency).

When the moving speed of the mobile station is high, for example, in the case of an airplane, a remarkable effect is obtained.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a conventional communication configuration, FIG. 2 is a diagram illustrating a communication configuration to which the present invention is applied, FIG. 3 is a diagram illustrating a configuration of a land fixed station according to the present invention, and FIG. 4 is a mobile station according to the present invention. It is a structural example figure. 1 ... Transmitter, 2-4 ... Receiver, 5 ... Modulator, 6 ...
… Detector, 7 …… Comparator, 8 …… Combiner.

Claims (1)

[Claims] 1. A plurality of terrestrial fixed stations connected to each other by a terrestrial communication network and distributed among the fixed terrestrial stations, wherein one selected key station and a mobile station perform short-wave band data communication with each other. Simultaneous emission of radio waves from the fixed station on the ground to the mobile station, which are modulated by the same transmission data sent from the key station via the terrestrial communication network to the mobile stations, The station receives the radio waves by a plurality of receivers provided corresponding to different short-wave band transmission frequencies of the plurality of terrestrial fixed stations, extracts demodulated data by frequency diversity, and S / N by S / N comparison determination. Select the frequency of the best line of / N and transmit it to the plurality of terrestrial fixed stations by modulating the frequency with transmission data as the transmission frequency, The plurality of terrestrial fixed stations that are distributed are the radio waves from the mobile station that are received by the receivers corresponding to the frequencies of the radio waves received from the mobile station among the plurality of receivers provided in the plurality of terrestrial fixed stations. Received and detected, demodulated data and S / N
A signal in the short-wave band, which is configured to detect signals and collect them in the key station via the terrestrial communication network, and to extract demodulated data by space diversity by a combiner provided in the key station.