JPH03198535A - Mobile object digital communication system - Google Patents

Abstract

PURPOSE:To attain high-speed digital transmission even in mobile object communication by constituting a line without using a free space but with a leakage coaxial cable as a transmission medium of a radio wave. CONSTITUTION:A radio wave sent from a base station 1 toward a mobile station 3 passes through an LCX 9 different from the case of the space wave system and reaches the vicinity of an antenna for the mobile station and passes through a very short space section of several meters or the like and reaches an antenna for the mobile station. When the mobile station runs through a homogeneous electric field generated by the LCX as above, the received electric fields by the antenna for the mobile station and the base station are excellent less in the fluctuation than the case of the free space. Moreover, in the case of the LCX system, since the path length of the passing free space is short, the influence of multi-path is very less. Furthermore, in the case of the high speed digital transmission through the line of the LCX system, a bit error rate is much more improved than the case with the space wave system and high speed digital transmission is attained in the mobile object communication.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to high-speed digital transmission in mobile communications.

[Conventional technology]

Figure 7 is a system diagram of the Shinkansen train radio using the space wave method described on pages 103 to 105 of Shinkansen Electronic Control and Communication System (written by Hisao Watanabe, edited by the Institute of Electronics and Communication Engineers). (1) is the base station, (2) is the base station antenna, (3) is the mobile station, (4) is the mobile station antenna, (5)
) is a railway line, (6) is a building such as a building, (7) is a direct wave among the radio waves between the base station and the mobile station, and (8) is a reflected wave.

Next, the operation will be explained. The radio waves emitted from the base station (1) toward the mobile station (3) are sent to the base station antenna (2).
) and becomes a direct wave (7) and a reflected wave (8).
and reaches the mobile station antenna (4). Since the direct wave and the reflected wave have different path lengths, a delay time difference (multi-path phenomenon) occurs when they arrive. Furthermore, the ratio of the reflected wave to the direct wave and the delay opening/closing change depending on the location of the mobile station.

Furthermore, the arrival level of the direct wave also changes depending on the location of the mobile station.

For the above reasons, when the mobile station runs on the track (5), a standing wave is generated in the received electric field of the mobile station antenna, resulting in a Rayleigh distribution as shown in FIG. The same applies to the received field strength at the base station of the radio waves emitted from the mobile station toward the base station.

When performing high-speed digital transmission over such a wireless line, the input electric field strength increases, as shown by the solid line in Figure 5, mainly due to the effect of multi-path phenomena, but the bit error rate (BER) increases. ) exhibited floor characteristics that could not be improved beyond a certain point.

[Problem to be solved by the invention]

High-speed digital transmission lines in conventional mobile communications are
With the above configuration, the bit error rate exhibits a floor characteristic due to the multi-path phenomenon, and there were problems such as not being able to obtain the required BER required for digital transmission.

The present invention was made to solve the above-mentioned problems, and its purpose is to obtain a high-speed digital transmission line with a good bit error rate in mobile communications.

[Means to solve the problem] A mobile digital communication system according to the present invention is as follows.

It uses a leaky coaxial cable instead of free space as the transmission medium, takes advantage of its radiation characteristics, reduces the effects of multi-path phenomena, and enables high-speed digital transmission in mobile communications.

[Effect]

The high-speed digital communication in this invention realizes a high-quality line by having a mobile station run in a homogeneous, equal-phase electric field radiated from a leaky coaxial cable.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (1) is the base station, (3) is the mobile station, and (4) is the base station.
is an antenna for a mobile station, (5) is a railway line, (6) is a building such as a building, (9) is an LCX placed on both sides of the railway line, and α1 is an LC
These are repeaters installed at regular intervals to compensate for the insertion loss of X.

The operation will be explained in detail below. Unlike the case of the space wave method, the radio waves emitted from the base station (1) to the mobile station (3) pass through the L CX (9) and reach the vicinity of the mobile station antenna. After passing through an extremely short space wave section of several meters, it reaches the mobile station antenna. This few meters of LCX
FIG. 3 shows the radio wave radiation mode between the mobile station antenna and the mobile station antenna.

In FIG. 3, a is a signal source, (a) is a terminator, and (to) is a slot. LCX slot pitch P1
If the wavelength shortening rate is λ and the wavelength of the radio wave to be used is λ, then there is a distance of 1 λ 1 r from the radiation angle θ.

e08θ■---(1-,-) PKf However, there is a relationship where f is the frequency of the radio wave to be used and fo is the resonance frequency of the LCX.

If fo is made a little higher than f, the radiation angle θ will be directed toward the signal source. Furthermore, the equiphase front of radio waves.

As shown by the broken lines, they occur at regular intervals perpendicular to the radiation direction of the radio waves. If °Cro is slightly lower than f, the radiation angle θ
will be directed in the opposite direction from the signal source.

In order to ensure reliable communication with both directions of θ and C, it is desirable that the radiation characteristics of the mobile station antenna be heart-shaped. FIG. 4 shows an example of heart-shaped radiation characteristics.

When a mobile station runs in a homogeneous electric field generated by the LCX in this way, the received electric field of the mobile station antenna and the base station is as shown in Fig. 2, and in the case of free space (Fig. 7). It is of high quality and has less fluctuation compared to . (The reason why the electric field suddenly changes in the middle is because the amount of coupling between the LCX and the mobile station antenna is changed.) In addition, in the case of the LCX method, the free space path length is short, so multi-path The effect of the phenomenon is also very small (possible).

Therefore, when high-speed digital transmission is performed over a line using the LCX system, the bit error rate is better than when using the space wave system, as shown by the broken line in Figure 5. High-speed digital transmission becomes possible.

In addition, in the above embodiment, C was described about high-speed digital transmission in train radio such as Shinkansen, but it is not limited to trains.
As shown in the figure, the same effects as in the above embodiment can be achieved even in digital transmission with a C-car or the like using LCX as a transmission medium.

In Figure 6, (1) is the base station, (2) is the antenna for the base station, (9) is the LCX, α0 is the repeater, α→ is the transmitting and receiving equipment outside the tunnel, αQ is the transmitting and receiving equipment outside the tunnel and the LC
X is the antenna for the terminal, 0Q is the feeder cable, C is the car, and (to) is the tunnel, which performs high-speed digital transmission between the base station and the car.

〔Effect of the invention〕

As described above, according to the present invention, the radio wave transmission medium can be used as a radio wave transmission medium.
Since the line is constructed using a leaky coaxial cable rather than a free space, high-speed digital transmission is also possible in mobile communication.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the mobile digital communication system of the present invention, Fig. 2 is a received electric field diagram by a leaky coaxial cable, Fig. 3 is a diagram showing the radiation characteristics of the leaky coaxial cable, and Fig. 4 is a diagram showing the radiation characteristics of the leaky coaxial cable. Figure 5 is a radiation characteristic diagram of the antenna of a mobile station, Figure 5 is a characteristic diagram showing the relationship between electric field strength and bit error rate, Figure 6 is a system diagram showing another embodiment of the present invention, and Figure 7 is a conventional diagram. FIG. 8 is a system diagram of the space wave method high-speed digital transmission, and FIG. 8 is a receiving electric field diagram of the space wave method. (1) is the base station, (2) is the antenna for the base station, (31 is the mobile station, (4) is the antenna for the mobile station, (5) is the line, (6)
is a building such as a building, (7) is a direct wave, (8) is a reflected wave, (
9) is the leaky coaxial cable, 00 is the repeater, 0υ is the signal source, (2) is the terminator, (to) is the slot, α4 is the transmission and reception equipment outside the tunnel, (g) is the transmission and reception equipment outside the tunnel and LC
Antenna for X terminal, αQ is feeder cable, αη is car, (to) is tunnel. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A mobile station equipped with an antenna having heart-shaped radiation characteristics, a leaky coaxial cable installed along the moving path of this mobile station and radiating radio waves with an equal phase electric field to the moving path, and A mobile digital communication system comprising a repeater that compensates for loss and a base station that transmits digital data to the mobile station via the leaky coaxial cable.