JPH0229250B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a mobile communication system that accommodates many mobile stations on a limited frequency and services a wide area.
The present invention relates to a channel switching method during a call to maintain continuity of a call when a mobile station moves from one wireless zone to another.

Conventionally, in this type of system, a mobile station, a base radio station, and a switching center are configured as shown in FIG. 1 is a handset, 2 is a transmission/reception control circuit, 3 is a sequence control circuit, 4 is a modulation/demodulation device, and 5 is a transmitter/receiver.
These 1 to 5 constitute mobile station equipment. 6
The base transceiver 7 is the exchange, 8 is the communication path from the exchange 7 to the base transceiver 6, 9 is the communication path from the base transceiver 6 to the exchange 7, and 10 is the communication path from the exchange 7 to the base transceiver 6. 11 is a control line from the base transceiver 6 to the exchange 7.

In this system, when the mobile station moves during a call and the S/N of the channel it is using drops, the base transceiver 6 detects the S/N drop, and the control line 1
1 to inform exchange 7. The switching station 7 collects the field strength data of the corresponding channel from the radio stations placed around the corresponding radio station, and from among the data, sends a channel switching signal (hereinafter referred to as EX) that specifies the channel number to be newly used by the mobile station. ) is converted into a digital signal and sent to the mobile station.

In the conventional mobile station configuration, the voice band is used for digital signals, so the signal that enters the transceiver 5 is not only passed to the modem 4 but also goes to the transmitting/receiving control circuit 2 and is transmitted to the user as noise from the handset 1 during a call. I could hear it and it was interfering with calls. Furthermore, the mobile station receives the channel switching signal EX, moves to a new channel, and sends a second response signal (hereinafter referred to as EA).
The signal shown in the example in the figure was sent multiple times. In FIG. 2, 101 is a preamplifier signal, 102 is a synchronization signal, 103 is an information signal including a mobile station number, and 104 is a check code.

The exchange side sends EX to the old channel and at the same time sends a channel reserve signal (hereinafter referred to as
RB) is transmitted, and the EA from the mobile station is
When the mobile station receives the signal, it determines whether the signal is from the corresponding mobile station and then disconnects the RB.The mobile station determines that the RB has been disconnected and determines that the channel switching has been successful, and the exchange side then transmits the EA. It is determined that the channel switching of the mobile station has been successful in the sequence of signal reception - EA signal disconnection.

As described above, the channel switching sequence has a long signal length, which is a major cause of communication interference.

In the present invention, in order to eliminate these drawbacks,
When a mobile station receives a channel switching command signal during a call, a means is provided to silently interrupt the call and eliminate the control signal as noise from the receiving circuit. By simply mutually receiving a synchronization signal between the base station and the mobile station as a mutual confirmation signal between the stations and restarting the communication path, it is possible to shorten the channel switching time during a call. This will be explained below along with examples.

FIG. 3 shows an embodiment to which the present invention is applied, in which 1 to 5 and 20 are mobile station equipment, and 1 to 11 correspond to the same reference numerals in FIG. 20 is a tone transmitting/receiving circuit, and 21 is a tone transmitting/receiving device.

In this embodiment, when the mobile station moves during a call and the S/N of the channel being used drops, the base transceiver 6 detects the S/N drop and transmits it to the exchange 7 via the signal control line 11. The exchange 7 collects field strength data of the corresponding channel from wireless stations around the corresponding wireless station, and sets a new channel number for the mobile station to use from among the data. At that stage, first, a signal is sent through the control line 10 to activate the tone transmitter/receiver 21 attached to the base transceiver 6, and with that signal, the tone transmitter/receiver 21 generates a low frequency tone of 150 Hz for a specified time, and the base transceiver 6 The signal is sent to the transmitter/receiver 5 via the transmitter/receiver 5, and is transmitted to the tone transmitter/receiver circuit 20 through the transmitter/receiver 5. When the tone transmitting/receiving circuit 20 receives the tone, it starts the transmitting/receiving control circuit 2 and disconnects the receiving circuit to the handset 1. Exchange 7 will switch to EX after a specified time has elapsed after sending the activation signal.
Send out. Therefore, the EX digital signal tone can be prevented from entering the handset 1 as noise because the transmitter/receiver control circuit 2 controls the disconnection of the receiver circuit.

The details will be explained below according to the signal sequence shown in FIG.

In the same figure, BS shows the base stations that cover the wireless zone, S1 and R1 are the channel transmission and reception sequences during the call of the first base station, and S2 and R2 are the new base station after channel switching of the second base station. This is the transmission and reception sequence of the different channels. MS indicates a mobile station, S3 and R3 are the transmission and reception sequences of the active channel, and S4 and R4 are the transmission and reception sequences of the new channel. 2
01 is a channel switching command signal, 202 is a signal for disconnecting the reception circuit, 203 is a synchronization signal transmitted by the base station, and 204 is a synchronization signal transmitted by the mobile station.

The transmission sequence of the base station in the first wireless zone is shown in S1. Reference numeral 201 is a speech channel switching command signal, and this signal includes the switching destination speech channel number, etc. Before the signal 201, a signal 202 is transmitted from the base station, and the receiving circuit of the mobile station is disconnected from the speaking circuit, thereby making the mobile station silent. 1st
The communication channel of the mobile station in the radio zone is a sequence in which S3 is the transmitting side and R3 is the receiving side. Upon reception of signal 201 at R3, a speech channel switch is performed, switching to new speech channels S4 and R4. Since the new communication channel in the second wireless zone has already transmitted the synchronization signal 203 as the S4 transmission signal, the mobile station receives the signal 203 as the R4 reception signal.
When it receives and recognizes that it is a synchronization signal, S
A synchronization signal 204 is transmitted as a transmission signal of No. 4.
After receiving signal 204, the base station stops signal 203. The mobile station detects the stop of the signal 203, stops the signal 204, connects the communication path to the receiver circuit, and releases the silent state. The base station stops signal 204 and reconnects the call path.

The synchronization signal between the base station and the mobile station is, for example, a second
As shown in the figure, the signal is a 16-bit constant pattern repeating signal, but the signals 203 and 204 may have different patterns.

In this way, after the call channel is switched to a new call channel, the base station and mobile station mutually confirm the call channel using a predetermined simple signal pattern, and the call can be continued. By restarting, the channel switching times T1 and T2 during a call can be shortened.

Also, by applying the signal 202 before transmitting the channel change command signal, the control signal can be removed from the subscriber's listening circuit until the synchronization signal is mutually verified as described above.

As explained above, according to the present invention, there are advantages such as being able to eliminate a control signal from the receiving circuit for a subscriber when switching channels during a call and shortening the switching time, and the effects thereof are significant.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a device using a conventional mobile communication system, Fig. 2 is a schematic diagram of a conventional channel switching response signal, and Fig. 3 is a block diagram of a communication device using a channel switching system during a call according to the present invention. FIG. 4 is a diagram showing the same sequence, and FIG. 5 is a schematic diagram of a synchronization signal. 5... Transmitter/receiver, 6... Base transceiver, 20...
...Tone transmitter/receiver circuit, 21...Tone transmitter/receiver.

Claims (1)

[Claims] 1. When the mobile station detects that the reception level during a call has fallen below a certain value and instructs the mobile station to make a new call through the channel in use, the mobile station Even if you move to different wireless service areas,
In a channel switching method during a call that maintains the continuation of a call, before transmitting a new channel switching signal from the base station to the mobile station, a low frequency signal is sent to temporarily disconnect the receiver circuit, and the receiver circuit Channel switching during a call, characterized in that the mobile station issues a channel switching instruction after determining the timing of disconnection, and at the same time, the mobile station moves to a new channel and continues the call after receiving a certain synchronization signal. method.