JP2935358B2 - Method of switching channel during communication in mobile communication system and mobile terminal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for switching a busy channel of a mobile communication system in a small zone system (cellular system) and a mobile terminal for realizing the method.

[0002]

2. Description of the Related Art The small zone system (cellular system) is a system in which a service area is divided into a number of wireless zones, and the same frequency is reused in distant wireless zones to increase the number of accommodations per frequency. Used in telephone systems. However, the potential demand for car phones far exceeds the capacity of current systems,
It is necessary to realize a larger capacity system. As a method of further increasing the capacity in a limited frequency band, minimization of a wireless zone can be considered. For example, if the radius of the wireless zone is 1 /
If it is 10, the frequency utilization factor will be 100 times.

[0003] When the radio zone is minimized in this way, the mobile station moves between radio zones one after another during a call.
The frequency of channel switching during a call increases. As for the current channel switching method of the Nippon Telegraph and Telephone Corporation's automobile telephone system during a call, as described in detail in the automobile telephone issued by the IEICE (supervised by Moriya Kuwahara), pp. 197 to 200, base stations Constantly monitors the reception level of the uplink traffic channel from the mobile station, and when the reception level falls below the threshold, the adjacent base station measures the uplink traffic channel of this mobile station, and the radio network controller compares these measurement results. By doing so, the movement of the mobile station between the wireless zones is detected.

[0004]

In the conventional method of switching channels during a call, the detection of movement of a mobile station between radio zones is performed intensively by a base station and a radio network controller. If this is done, the frequency of channel switching during a call increases, the control amount increases locally, and a device with a large processing capability is required.

It is an object of the present invention to provide a method of switching channels during a call in which a control amount is not locally concentrated, and a mobile terminal realizing the method.

[0006]

According to the method of switching a busy channel of a mobile communication system according to the present invention, each radio base station transmits a signal including a flag indicating the presence or absence of an idle talk channel, and the mobile terminal that is talking is dedicated. Using the receiver, receiving the signal transmitted from the connected radio base station and the radio base station adjacent to the radio base station, and comparing the reception level of the base station having an idle communication channel based on the flag Monitoring the movement between the wireless zones, and when the movement is detected, transmits a switching request signal to switch the connection to a destination wireless base station having an idle communication channel, thereby enabling the mobile terminal during the communication On the side, the connection can be switched to a destination radio base station having an empty communication channel, and control of channel switching during communication is decentralized.

A mobile terminal according to the present invention includes a measuring device for measuring a reception level of a signal transmitted from a connected radio base station and a radio base station adjacent to the radio base station, an output of the level measuring device and the signal. A memory for storing a flag indicating the presence or absence of a free communication channel contained therein is monitored by comparing the contents of the memory with the contents of the memory, and when the movement is detected, the movement having a free communication channel is performed. And a control circuit for transmitting a switching request signal for requesting switching to a destination radio base station. It is characterized in that channel switching control is decentralized.

[0008]

When the base station compares the reception level of the uplink signal of the mobile station and monitors the movement between the radio zones,
Since it is necessary to perform observations at a plurality of base stations and collect and compare these results somewhere, if the switching frequency increases, the control amount locally increases. On the other hand, in the present invention, the mobile station side compares the reception level of the downlink signal of each base station and monitors the movement between the wireless zones to achieve decentralized control. Therefore, a dedicated measurement receiver for receiving a downlink signal from another base station without disturbing a call is provided. The downlink signal received by the receiver may be a communication channel, but is preferably a control channel that is constantly transmitted. Further, if the control channel is common to all zones and is time-division multiplexed by each base station, there is no need to change the reception frequency of the receiver, and the apparatus is simplified. In addition, the base station transmits a flag indicating the presence or absence of the idle communication channel in advance in the downlink signal, and the mobile station compares only the reception level of the downlink signal of the base station with the idle communication channel based on this flag. This prevents selection of a base station having no idle communication channel as a switching destination. In this way, the mobile station monitors the movement between the wireless zones during a call, and when the movement is detected, transmits a switching request signal to switch to the destination base station having an empty communication channel. In addition, it is possible to avoid local concentration of the control amount due to the switching of the busy channel.

[0009]

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

FIG. 1 is a block diagram showing an embodiment of a method of switching channels during a call according to the present invention. The mobile communication system includes an exchange 10, a base station 20, and a mobile terminal 30, and the N base stations communicate with the mobile terminal through their own communication channels and control channels. The downlink signal of each control channel includes a flag 40 indicating the presence or absence of an idle communication channel of the base station. Flag 4
If 0 is, for example, “1”, it indicates that there is an available communication channel, and if the flag 40 is “0”, it indicates that there is no available communication channel. These communication channels and control channels are assigned frequencies so as not to interfere with each other. In FIG. 1, the frequency fd is allocated to the downlink traffic channel of the base station 3, the frequency fu is allocated to the uplink traffic channel, and I frequencies are reused and allocated to the downlink control channel. A case is shown where frequencies f1, f2, f3 and fI are assigned to I, respectively. Other frequency assignments are omitted. The mobile terminal 30 includes an antenna 31, a duplexer 32, a call transmitter 33, a call receiver 34, a measurement receiver 35, and a control circuit 36. The mobile terminal 30 communicates with the nearest base station by the call transmitter 33 and the call receiver 34, and transmits the downlink control channel of each base station, that is, the frequency f 1 to fI 1 by the measurement receiver 35.
, Are sequentially switched and received, and based on the flag 40, the reception level of the base station having an idle communication channel is compared to monitor the movement between wireless zones. When movement is detected, a switching request signal is transmitted on the uplink communication channel to inform the exchange of the destination base station.

For example, the mobile terminal 30 connected to the base station 3 by the downlink communication channel of the frequency fd and the uplink communication channel of the frequency fu moves from the radio zone of the base station 3 to the radio zone of the base station 2 having an empty communication channel. Consider moving. With the movement, the output of the measurement receiver 35 has the highest reception level at the frequency f2 instead of the frequency f3. The control circuit 36 compares the reception level of the base station having the idle communication channel based on the flag 40, and finds that the mobile station has moved to the wireless zone of the base station 2,
A switching request signal for requesting switching to the base station 2 is transmitted on the uplink traffic channel. Upon receiving this signal, the base station 3
This is reported to the exchange 10. The exchange 10 selects a free communication channel of the base station 2 and indicates the number to the mobile terminal 30 via the base station 3. The mobile terminal 30 switches to the communication channel of the base station 2 according to this instruction. By monitoring the movement between wireless zones on the mobile terminal side and decentralizing the control of channel switching during a call, local concentration of control amounts can be avoided. In the present embodiment, different frequencies are assigned as control channels, but it is also possible to assign the same frequency by time division multiplexing. In this case, it is not necessary to change the receiving frequency of the measuring receiver.

FIG. 2 is a block diagram of an embodiment of the mobile terminal according to the present invention. The mobile terminal is an antenna 31, a duplexer 3
2. Mixer 331 and modulator 332 forming a call transmitter, mixer 341 and demodulator 342 forming a call receiver, mixer 351, demodulator 352, level measuring device 353 and oscillator forming a measurement receiver 350,
An oscillator 330 for the mixers 331 and 341, a control circuit 36, and a telephone 37 are provided. Antenna 3
1 is distributed to the mixer 341 and the mixer 351 via the duplexer 32. The RF signal of the downlink communication channel is supplied to the oscillator 3 by the mixer 341.
After being mixed with the output of 30 and converted into an IF signal, it is demodulated by the demodulator 342 and the speech signal is sent to the telephone 37, and the control signal included in the speech channel is sent to the control circuit 36. In addition, the call signal and control circuit 3
The control signal output from 6 is converted into an IF signal by the modulator 332, mixed with the output of the oscillator 330 by the mixer 331, and then transmitted from the antenna 31 via the duplexer 32 as an RF signal of a communication channel. . The method of modulation and demodulation may be any commonly used method and will not be described in detail here. Also, one communication channel may be assigned to one frequency, or a plurality of communication channels may be assigned by time division multiplexing. on the other hand,
The RF signal of the downlink control channel is mixed with the output of the oscillator 350 by the mixer 351 and then distributed to the demodulator 352 and the level measuring device 353. The output of the mixer 351 is demodulated by the demodulator 352 and sent to the control circuit 36 as a control signal including a base station identification code, a flag indicating the presence or absence of an idle communication channel, and the like.
3, the level is measured and sent to the memory 354. The control circuit 36 changes the oscillation frequency of the oscillator 350 so that the downlink control channel of each base station can be sequentially received. When recognizing the base station identification code in the output of the demodulator 352, the control circuit 36 controls the level measuring device 353 at that time. The output and the flag indicating the presence or absence of the idle communication channel are stored in the memory 354 for each base station identification code. The control circuit 36
Monitors the movement between the radio zones by comparing the reception level of the base station having the idle communication channel in the contents of the memory 354, and when the movement is detected, generates a switching request signal including the identification code of the base station of the movement destination. Send. Also, by storing a plurality of reception levels for each base station and comparing their average values, the effect of measurement errors due to fading can be reduced. In this case, a flag indicating the presence or absence of a plurality of available communication channels is stored, but the reception level may be compared based on the latest flag. If the mobile station monitors the movement between the wireless zones in this way, it is possible to avoid concentration of the control amount due to the channel switching during the call.

[0013]

As described above, according to the present invention, it is possible to provide a method and a mobile terminal for switching a busy channel of a mobile communication system in which the control amount hardly increases locally with an increase in the frequency of switching the busy channel. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a method of switching a busy channel according to the present invention.

FIG. 2 is a block diagram showing one embodiment of the mobile terminal of the present invention.

[Explanation of symbols]

 Reference Signs List 20 base station 30 mobile terminal 36 control circuit 353 level measuring device 354 memory

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-131703 (JP, A) JP-A-58-191542 (JP, A) JP-A-58-9442 (JP, A) 273028 (JP, A) Masaya Yamauchi, “New Edition Mobile Communication Method”, Kagaku Shimbun, May 10, 1979, p. ) Surveyed field (Int.Cl. ⁶ , DB name) H04B 7/24-7/26 H04Q 7/00-7/38

Claims (6)

(57) [Claims] A wireless base station transmits a signal including a flag indicating the presence or absence of an idle communication channel using control channels allocated to different frequencies in a plurality of zones, and a mobile terminal during a call transmits a signal to a dedicated receiver. Using the control channel to receive the signal transmitted from the wireless base station and the wireless base station connected with the wireless base station using the control channel,
The mobile station monitors movement between wireless zones by comparing the reception level of the base station having the idle communication channel based on the flag, and when the movement is detected, switches the switching request signal to the destination radio having the idle communication channel. By transmitting to the base station and switching the connection, the mobile terminal during the call can switch the connection to the destination radio base station having an idle communication channel, thereby decentralizing the control of channel switching during the call. A method for switching channels during a call in a mobile communication system. 2. A measuring device for measuring a reception level of a signal transmitted from a connected radio base station and a radio base station adjacent to the radio base station using control channels assigned to different frequencies in a plurality of zones. And a memory for storing the output of the level measuring device and a flag indicating the presence or absence of an idle communication channel included in the signal, and monitoring the movement between the wireless zones by comparing the contents of the memory to perform the movement. A control circuit for transmitting a switching request signal for requesting switching to a destination radio base station having an idle communication channel when the mobile terminal has an idle communication channel. A mobile terminal characterized in that connection can be switched to a radio base station and control of channel switching during a call is decentralized. 3. A radio base station transmits a signal including a flag indicating the presence or absence of an idle communication channel in a plurality of zones on the same frequency by using a control channel allocated by time division multiplexing. The terminal receives, using the control channel, the signal transmitted from the connected radio base station using a dedicated receiver and the radio base station adjacent to the radio base station, and uses the idle communication channel based on the flag. Monitoring the movement between the wireless zones by comparing the reception levels of the base stations having the same, and when the movement is detected, transmits a switching request signal to the movement-destination wireless base station having the idle communication channel to establish the connection. By switching the connection, the mobile terminal on the call side can switch connection to a destination radio base station having an idle communication channel, thereby controlling the channel switching during the call. Busy channel switching method for a mobile communication system, characterized in that decentralized. 4. Receiving a signal transmitted from a connected radio base station and a radio base station adjacent to said radio base station using a control channel allocated by time division multiplexing on the same frequency in a plurality of zones. A measuring device for measuring a level, a memory for storing an output of the level measuring device and a flag indicating the presence or absence of an idle communication channel included in the signal, and comparing the contents of the memory to determine the movement between wireless zones. And a control circuit for transmitting a switching request signal for requesting switching to a destination radio base station having an idle communication channel when monitoring and detecting movement, and A mobile terminal characterized in that connection can be switched to a destination radio base station having a channel and control of channel switching during a call is decentralized. 5. Each radio base station transmits a signal including a flag indicating the presence or absence of an idle communication channel using the communication channel,
The mobile terminal during a call receives the signal transmitted from the connected radio base station using the dedicated receiver and the radio base station adjacent to the radio base station using the communication channel, and based on the flag, Monitoring the movement between the wireless zones by comparing the reception levels of the base stations having the idle communication channels, and transmitting the switching request signal to the destination wireless base station having the idle communication channel when the movement is detected. The connection is switched to the destination wireless base station having a free communication channel on the side of the mobile terminal during the communication, and control of channel switching during the communication is decentralized. A method for switching channels during a call in a communication system. 6. A measuring device for measuring a reception level of a signal transmitted from a connected radio base station and a radio base station adjacent to the radio base station by using a communication channel, an output of the level measuring device, and A memory for storing a flag indicating the presence or absence of a free communication channel included in the signal, and monitoring of movement between wireless zones by comparing the contents of the memory, and having a free communication channel when the movement is detected. A control circuit for transmitting a switching request signal for requesting switching to a destination wireless base station, and enabling a connection to a destination wireless base station having an idle communication channel to be switched on the side of a mobile terminal during a call to enable a call. A mobile terminal characterized by decentralized control of channel switching.