JPH0648800B2 - Base station selection method - Google Patents

Description

The present invention relates to a base station selection system, and more particularly to a base station that selects an optimum base station from the viewpoint of a terminal station trying to communicate in a mobile communication system using distributed base stations. Regarding selection method.

[Prior Art] Conventionally, this type of base station selection system compares reception levels of signals from terminal stations between base stations and selects a base station having a high reception level, or receives reception level information. The central equipment was used to select the optimum base station.

[Problems to be solved by the invention]

The above-mentioned conventional base station selection method is to mutually compare the reception levels of the signals from the terminal stations in the plurality of base stations,
There is a drawback that the base station or central device base station selection processing and the connection between base stations or between each base station and the central device are complicated and uneconomical.

[Means for solving problems]

The base station selection method of the present invention includes a plurality of base stations each having a small zone service area and arranged two-dimensionally or three-dimensionally to construct one operation service area, and the operation service areas. A plurality of terminal stations moving in the inside, and using a two-frequency FM or PA communication system for a wireless line between the base station and the terminal station,
In a base station selection method in a mobile communication system in which the base station cannot always transmit, the terminal station transmits an ambiguous call signal that does not specify the other base station as a means to know the nearest base station in a burst manner. However, each of the base stations that have received the ambiguous call signal transmits in burst to the terminal station a response signal to which the address of its own station has been added, and the terminal station receives a plurality of incoming response signals. Among them, the demodulation of the modulation signal having the highest input level due to the co-channel interference characteristic in FM communication or PM communication is used to detect the response signal from the nearest base station and add it to the detected response signal. By storing the address of the nearest base station that has been stored, and thereafter by specifying the stored address of the nearest base station. Serial and performs a one-to-one individual communication between the terminal station and the nearest of the base station.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sequence diagram showing an embodiment of the present invention, and FIG. 2 is a system configuration diagram showing a mobile communication system using the embodiment shown in FIG.

In the mobile communication system shown in FIG. 2, the base station A1
2 to base station C14 are connected to the central unit 11 by signal lines. The base station A12 has a service area 15, and hereinafter the base station B13 also has a service area 16,
The base station C14 has a service area 17. The service areas 15 to 17 may or may not overlap as shown in FIG.

The terminal stations a18 to c20 are mobile terminals of a mobile type or a vehicle type, and can freely move inside and outside the service areas 15 to 17.

FIG. 3 is a device system diagram of the terminal stations a18 to c20.

When there is a call request or data input from the input unit 21, the control unit 23 sends a call signal and other signals to the data modem unit 24. The data modem unit 24 frequency-modulates the carrier wave by the signal sent from the control unit 23 and sends it to the sending unit 26. The transmitting unit 26 transmits the above-mentioned calling signal and other signals from the antenna 29 as radio waves to the base station via the antenna switching unit 28.

On the other hand, the response signal received from the base station and the modulation signal frequency-modulated by other signals are the antenna 29 and the antenna switching unit 2
It is input to the receiving unit 27 via 8. The response signal and other signals demodulated by the receiving unit 27 are the data modem unit 2
It is converted into logical data at 4 and passed to the control unit 23. The control unit 23 processes the response signal and other signals and outputs them to the output unit 22 as necessary.

Further, the control unit 23 performs channel switching from the control channel of the transmission unit 26 and the reception unit 27 to the data channel by controlling the synthesizer 25.

FIG. 4 is a device system diagram of the base stations A12 to C14, and the operation is almost the same as that of the terminal station.

FIG. 5 is an explanatory diagram showing signal formats of a calling signal and other signals. Bit synchronization is a preamble signal for stabilizing the system, and frame synchronization is a flag indicating that data follows. The calling address is the address of the side that first calls the other party by a calling signal or the like, and the response address is the address of the called side. The command indicates a signal type such as a calling signal and a response signal. The information is various data according to the signal at that time, and the erroneous correction code is a self-correction code or an erroneous detection code for retransmission correction.

The sequence diagram of FIG. 1 shows a case where the terminal station b19 moves and the nearest base station becomes unknown.

In order for the terminal station b19 to know the nearest base station, the call origination signal 1 (hereinafter, such an address of such an address is used) in which the calling address is b of the own station and the response address is an unspecified wild address (hereinafter referred to as *). The combination is referred to as F (b, *)) is transmitted in a burst on the control channel. The base stations A12 to C14, which have received the calling signal 1, assign their addresses to F (b,
A), F (b, B), F (b, C) response signals 2
4 are similarly transmitted in bursts on the control channel.

At this time, the terminal station b19 receives the response signals 2 to 4 from the base stations A12 to C14 almost at the same time, but here, the co-channel interference characteristic of FM communication is used. That is, the characteristic that the modulation signal with the highest input level is demodulated when a plurality of modulation signals having the same carrier frequency are received is used. In the case of this example, the response signal 3 of the base station B13 closest in distance is the terminal station b1.
It will be received (demodulated) at 9.

Therefore, the calling terminal station b19 can know that the nearest base station is "B" from the address F (b, B) of the response signal 3 of the base station B13.

At this time, each base station switches to the data channel immediately after transmitting the response signal, while the terminal station b19 switches to the data channel after receiving the response signal 3. A method of selecting a predetermined data channel is preferably such that the calling station first applies for the calling signal and the responding station confirms with the response signal.

After that, the terminal station b19 and the base station B13 assign the address F
By setting (b, B), mutual data communication can be performed.

〔The invention's effect〕

As described above, according to the present invention, a mobile terminal station that has lost sight of the nearest base station burstly transmits an ambiguous call signal that does not specify a responding station, and the corresponding base station receives the ambiguous call signal. Then, the response signal is transmitted in a burst manner, and the mobile terminal station demodulates the modulated signal having the highest input level from the plurality of received response signals according to the co-channel interference characteristic of FM or PM communication, thereby nearest the base station. Since it is possible to know the station and does not require the mutual comparison of the reception levels of the signals from the mobile terminal stations at each base station, the base station selection processing at the base station or the central unit is not necessary, and the base station selection There is no need for connection between base stations for processing or between each base station and a central unit, which is advantageous in that it is economical.

[Brief description of drawings]

FIG. 1 is a sequence diagram showing an embodiment of the present invention, FIG. 2 is a system configuration diagram of a mobile communication system using the embodiment shown in FIG. 1, and FIG. 3 is a device system diagram of the terminal station. FIG. 4 is a device system diagram of the base station, and FIG. 5 is an explanatory diagram showing a signal format between the terminal station and the base station. 1 ... Calling signal, 2-4 ... Response signal, 5 ... Transmission data, 6 ... Response data, 11 ... Central unit, 12-14
... base stations A to C, 15 to 17 ... service areas of the base stations A to C, 18 to 20 ... terminal stations a to c.

Claims (1)

[Claims] 1. A plurality of base stations each of which has a small zone service area and is arranged two-dimensionally or three-dimensionally to form one operation service area as a whole, and moves within the operation service area. Base station selection in a mobile communication system in which the base station cannot always transmit, using a two-frequency FM or PA communication system in a wireless line between the base station and the terminal station. In the method, the terminal station burst-transmits an ambiguous call signal that does not specify the other base station as means for knowing the nearest base station, and each of the base stations that has received the ambiguous call signal. Transmits a response signal to which the address of its own station is added in a burst manner to the terminal station, and the terminal station performs FM communication or PM communication from among the plurality of incoming response signals. Using the demodulation of the modulation signal with the highest input level due to the co-channel interference characteristic in, the response signal from the closest base station is detected, and the closest base station added to the detected response signal is detected. By storing the address of the station, and thereafter by specifying the stored address of the nearest base station, one-to-one individual communication is performed between the terminal station and the nearest base station. A base station selection method characterized by the above.