JPS5810890B2 - Call control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a call control system in a mobile radio system based on a centralized base station system.

There are various types of mobile radio systems depending on the purpose and the like, and a centralized base station system is known as a system that aims to effectively utilize frequency bands.

In this centralized base station system, the same frequency band is used for multiple groups of mobile devices, the callable period is specified from the base station for each group, and calls between the base station and the mobile devices in the callable group are It is controlled so that it cannot be intercepted by mobile devices in other groups.

In such a conventional centralized base station system, a tone signal determined for each group is sent out from the base station as a call-ready signal as needed, and only mobile terminals in the group specified by this call-ready signal are sent. The base station, which can transmit and receive signals from the mobile station, sends out a pilot tone signal together with a call enable signal.

Generally, mobile stations are configured so that they cannot receive while transmitting, and mobile stations other than those that are transmitting are controlled so that they cannot transmit when they receive a pilot tone signal.

Therefore, even if mobile stations in a group are capable of talking, if one mobile station transmits, other mobile stations in the group will not be able to transmit, so interference will not occur.

However, there are cases where the base station sends out a call enable signal and a pilot tone signal at the same time, and since the frequency shift due to the tone signal is specified, compared to the case where a single tone signal is sent out, The S/N will be reduced by 6 dB.

The present invention improves the conventional drawbacks as described above, and its purpose is to prevent the base station from transmitting two types of tone signals at the same time, prevent S/N deterioration, and ensure reliable call control. It is about making it possible.

Examples will be described in detail below. As shown in FIG. 1, mobile station A1 of group A is located within the service area of base station BS.
．． Mobile unit B1 of A2 and B group. If B2 is present, the base station BS sends out a tone signal, as necessary, by modulating the carrier frequency f1 to enable communication between mobile stations in group A or group B.

For example, as shown in FIG.
Assuming that B is the group callable period and B is the group callable period, conventionally, as shown in Figure a, F is set in each callable period.
The A or FB tone signal is sent from the base station BS.

The speech signal sent together with the tone signal FA is sent to mobile stations A1. Only A2 can be received, and tone signal FB
The call signal sent together with the mobile station B1. Only B2 can be received.

Also, by receiving the tone signal FA, the mobile device A1 or A2 modulates the carrier frequency f2 with the audio signal and transmits the signal as shown in FIG.
Or, when the base station transmits the pilot tone signal FP as shown in FIG.
It is transmitted by modulation of 1.

A mobile station that is not transmitting is prohibited from transmitting by receiving the pilot tone signal FP.

Therefore, as mentioned above, interference is prevented.

Also, when mobile station B1 transmits as shown in Fig. 2e after receiving tone signal FB, the pilot tone signal FP is sent out from the base station in the same way as described above, and the pilot tone signal FP is transmitted to mobile stations other than mobile station B1. Sending is prohibited.

On the other hand, in the present invention, the base station transmits the tone signal FA by modulating the carrier frequency f1, and the mobile station A of group A, for example, modulates the carrier frequency f2 with an audio signal and transmits it as shown in FIG. 2C. At this time, the base station stops transmitting the tone signal FA and instead transmits the lock tone signal FL by modulating the carrier frequency f1 as shown in FIG. 2g.

The same applies when other mobile stations transmit the tone signals, so that the base station does not transmit the tone signals FA and FB at the same time as the lock tone signal FL, as shown in FIG. 2f.

Note that the lock tone signal FL corresponds to the aforementioned pilot tone signal FP.

FIG. 3 is a block diagram of main parts of a mobile device according to an embodiment of the present invention, where RX is a receiving section, TX is a transmitting section, and the receiving section R
The signals received and demodulated at X are passed through bandpass filters BPF1.X. B.P.
F2 and gate circuit G1.

The band P-wave device BPF1 is set to the pass band of the frequency of the group selection tone signal, and for a mobile station of group A, a configuration in which the tone signal FA is used as the pass band is used.

Furthermore, the bandpass filter BPF2 is set to have the lock tone signal FL as its passband.

Also, FF is a flip frog, SP is a speaker, LP is a service indicator lamp, MIC is a microphone, PB is a switch to press when transmitting a call using the microphone MIC,
TIM is a timer that is triggered by the falling edge of the output of the OR circuit OR and outputs a reset signal for the flip-flop FF for a certain period of time, for example, 500 m5, INHL and INH2 are inhibit gate circuits, and AND is an AND circuit.

In the case of group A mobile stations, the flip-flop FF is set by the tone signal FA from the base station, and the set output opens the gate circuit G1 to apply the speech signal from the base station to the speaker SP, and also to the lamp. The LP is lit to indicate that a call is possible, and the AND circuit AND is opened so that the signal when the switch PB is turned on can be applied to the transmitter TX as a transmission-on signal.

If the lock tone signal FL is not being sent out, the inhibit gate circuit INH1 is open, so when the switch PB is turned on, a transmission on signal is applied to the transmitting section TX, and the signal from the microphone MIC is sent to the transmitting section TX. The signal is modulated and sent out.

Since the mobile device does not perform a receiving operation in the receiving section RX during transmission, the output of the tone signal FA by the band P-wave device BPF1 also becomes 0 and the timer TIM is activated, but the inhibit gate is activated by the transmission ON signal. The circuit INH2 is closed and the flip-flop FF will not be reset.

Furthermore, upon receiving the signal from the mobile device, the base station stops transmitting the tone signal FA and transmits the lock tone signal FL.
In a mobile device that is not transmitting, the lock tone signal FL can be extracted by the band P wave filter BPF2. Therefore, even if the output of the band filter BPF1 becomes zero, the lock tone signal FL can be extracted immediately after that. Upon receiving the tone signal FL, the flip 71 knob FF maintains the set state without timeout (500 mS) of the timer TIM, and upon reception of the lock tone signal FL, the inhibit gate circuit INH1 is closed, and the switch of the microphone MIC is closed. Even if PB is turned on, the transmission on signal is blocked and transmission is not possible.

Then, when the transmission of the lock tone signal FL is stopped and only the tone signal FA is transmitted, the inhibit gate circuit INH1 is opened as described above, and the transmission becomes possible.

Also, when the talkable period for group A has elapsed and the tone signal FB is sent from the base station instead of the tone signal FA, and the callable period for group B begins, all mobile stations in group A will use the band P.
The output of wave generator BPF1 becomes zero, and accordingly, timer T
The IM is activated, and after a predetermined period of time, for example 500 m5, the flip-flop FF is reset, thereby closing the gate circuit G1, so that the received signal is transmitted to the speaker SP.
group, and it becomes impossible to intercept calls from other groups.

Further, the lamp LP goes out, indicating that it is not possible to make a call.

FIG. 4 is a block diagram of main parts of the base station according to the embodiment of the present invention, in which 08CA to 08CK are oscillators that generate tone signals FA to FK corresponding to groups A to 03CL, and 03CL is a lock tone signal FL. The generating oscillator, GA-GL is the gate circuit, T is the transmitting section, COM is the transmitting/receiving common section, R is the receiving section, I
A to IK are inhibit gate circuits, INV is an inverter, 5ELA-3ELK are group selection signals, TvS is a transmitted audio signal, and RVS is a received audio signal.

When the group selection signal 5ELA is turned on, an on signal is applied to the gate circuit GA via the inhibit gate circuit IA, and the tone signal FA is applied to the transmitting section T, modulated, and applied to the antenna from the transmitting/receiving section COM to generate the tone signal. Signal F
A is sent.

The transmission audio signal TVS is also added to the transmitter T and sent out together with the tone signal FA.

Therefore, only the mobile stations in group A can receive and listen to the audio signal from this base station.

When the tone signal FA is received and transmitted from a group A mobile device that is ready for a call, the receiver R outputs a demodulated received voice signal RVS indicating that it is receiving, and also outputs a receiving signal rcv. is output, thereby opening the gate circuit GL, and closing the inhibit gate circuits IA to IK by a signal inverted by the inverter INV.

Therefore, even if the group selection signal 5ELA is on, the on signal of the gate circuit GA is not applied, so the gate circuit G
A will be closed.

By closing the gate circuit GA and opening the gate circuit GL, a lock tone signal FL is generated instead of the tone signal FA.
will be sent.

When the aforementioned mobile station stops transmitting, the receiving signal rcv disappears, thereby closing the gate circuit GL and opening the gate circuit GA, and the tone signal FA is transmitted again.

The group selection signals 5ELA-8ELK can be controlled to be turned on sequentially for a certain period of time or turned on in the order of reservation registration, and the callable period of each group can be selected.

As explained above, the present invention selectively sends out a tone signal determined for a group of mobile devices from a base station, and the mobile device becomes ready for communication by receiving the tone signal corresponding to its own group. Furthermore, when a lock tone signal is received, transmission is prohibited, and if a mobile device transmits a signal while it is in a callable state, the base station stops transmitting the tone signal and sends a lock tone signal.

This prevents mobile devices other than those currently transmitting from transmitting, preventing interference, and prevents the base station from transmitting tone signals and lock tone signals at the same time, thus limiting the frequency shift caused by tone signals. Compared to the conventional example, there is an advantage that there is no deterioration in S/N.

7 Brief Description of the Drawings FIG. 1 is an explanatory diagram of a mobile radio system using a centralized base station system, and FIG. 2 is an explanatory diagram of the operation of a conventional example and an embodiment of the present invention.
3 and 4 are block diagrams of main parts of a mobile device and a base station, respectively, according to an embodiment of the present invention.

FA-FK is a tone signal, FL is a lock tone signal,
RX is a receiving section, BPFi, BrF3 are band F wave devices, TI
M is a timer, FF is a flip-flop, G1 is a gate circuit, sp is a speaker, LP is a lamp, MIC is a microphone, PB is a switch, TX is a transmitting section, COM is a transmitting/receiving section, T is a transmitting section, R is a receiving section , 08CA~08CK.

08CL is an oscillator, GA-GL is a gate circuit, IA-I
K is an inhibit gate circuit, TVS is a transmission audio signal,
RVS is a received audio signal, and 5ELA to 5ELK are group selection signals.

Claims (1)

[Claims] 1 In a mobile radio system using a centralized base station system,
The base station has means for transmitting a tone signal determined to correspond to a group of mobile stations, and means for transmitting a lock tone signal, and a mobile station is capable of talking when it receives a tone signal corresponding to its own group. and means for inhibiting the transmission after receiving the lock tone signal, the base station comprising:
A call control system characterized in that when a transmission signal is received from a mobile device of a group that is enabled to talk by the tone signal, transmission of the tone signal is stopped and the lock tone signal is sent.