JPH0470095A - Channel switchover controlling system for mobile communication - Google Patents

Abstract

PURPOSE:To reduce a control at a base station which is necessary for a channel switchover after sharing a load for the control at the side of a base station which is required for the channel switchover at the side of a mobile station by forecasting the destination of the channel switchover at the side of the base station, and operating the monitor of a reception level at the side of the mobile station, at the time of operating the channel switchover. CONSTITUTION:A base station 1a during communication forecasts a base station 1c being the next prime destination of the channel switchover from a probability table, based on a previous base station 1b of a mobile station 3. In this case, the forecasted base station is not always one. The forecasted base station 1c is communicated to the mobile station 3 using a control line 5. The mobile station 3 monitors the control channel of the forecast and communicated base station 1c. When the reception level from the communication base station 1a is less than a required value, and also when the reception level of the forecast base station 1c is more than the required value, the channel switchover to the base station 1a during communication is required. Thus, the load required for the control of the channel switchover at the base station is operated at the side of the mobile station so that the load for the control at the side of the base station can be reduced, and a base station device can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a channel switching control system in mobile communications.

In cellular one-way mobile communication in which a mobile station communicates in multiple zones while switching communication with base stations in the zones, the present invention predicts the next base station to switch to and Monitor the control channel reception level,
When the level exceeds a predetermined level, a channel switching request is made and the channel is switched, thereby reducing the burden of channel switching control on the base station side.

[Conventional technology]

Channel switching control in a mobile communication system in which base stations are placed in each of a plurality of zones and when a mobile station moves between base stations, switches channels to a destination base station is performed in the following procedure.

■ Detecting that the mobile station has moved from the base station area where it is currently communicating to another base station area.

■ Determine the destination base station and select an available channel at that base station.

■ Switches the base station side line to the destination base station and issues a channel switching command to the mobile station.

All of these controls from ① to ② are performed by the base station.

By the way, in the detection of mobile station migration in (2) and the determination of a base station to which to migrate (2), conventionally there have been a weak electric field channel switching method and a strong electric field channel switching method.

(1) Weak electric field channel switching method When a mobile station changes base stations, the reception level from the communication base station with which it is communicating decreases, and the transition is detected when the reception level falls below a required value.

When the reception level drops, the mobile station issues a channel switching request to the communication base station. A communication base station requests a control base station that controls a plurality of base stations to search for a base station with the highest reception level for the mobile station among surrounding base stations. As a result, the base station with the highest reception level is determined to be the transfer destination base station.

[2) Strong electric field channel switching method When controlling the transmission power so that the radio waves transmitted from the mobile station are constant to the base station of the communication partner and are received by the bell Vc, the surrounding base stations are currently communicating. It monitors the transmission channel for mobile stations other than the mobile station currently in use, and determines that a mobile station that can receive signals at a level higher than a certain level Vc has migrated to its own station, and contacts the control base station to prevent the mobile station from migrating. and determine the destination base station.

This will be explained by showing the zone configuration in mobile communication and the positional relationship between base stations in FIG. 1. Reference numeral 1a indicates the communication base stations lb, lc, and ld that are communicating with the mobile station 2.

1e is the surrounding base station, and these base stations 1a to 1e
The channel switching control is performed by the control base station 4.

[Problem to be solved by the invention]

By the way, in such conventional channel switching control,
In either case, it is necessary for neighboring base stations to monitor the reception level of the mobile station, and the burden of control required for channel switching is greater on the base station side than on the mobile station side. There is also the problem that all surrounding base stations must monitor one mobile station in the same way.

An object of the present invention is to predict the channel switching destination during channel switching, thereby eliminating the need for the base station to monitor all reception levels of each mobile station, thereby reducing the amount of control related to channel switching control, and By monitoring the reception level on the mobile station side, the control burden on the base station side required for channel switching can be shared on the mobile station side, thereby reducing the base station control required for channel switching.

[A means of promise to solve problems]

In the first invention, a service area is composed of a plurality of zones, base stations are arranged corresponding to each zone, a mobile station communicates with one of these base stations, and during communication, the mobile station In a mobile communication system in which when moving to an area of an adjacent base station, the base station being communicated with is switched to the adjacent base station and communication continues, the above base station is the base station to which the mobile station currently communicating will switch the next channel. The mobile station includes a means for predicting and notifying the predicted channel, and a monitoring means for monitoring the control channel of the base station to which the predicted channel is to be switched, and a reception level of the base station currently communicating is reduced by the monitoring means. The present invention is characterized in that it includes means for issuing a channel switching request to the predicted channel switching destination base station if the reception level of the control channel of the predicted channel switching destination base station is equal to or higher than a required value.

Further, the second invention provides a mobile station with means for predicting the next channel switching destination base station of the mobile station currently communicating, and means for monitoring the control channel of the channel switching destination base station predicted by this means. and means for issuing a channel switching request to the predicted channel switching destination base station if the reception level of the base station currently communicating decreases and the reception level of the control channel of the predicted channel switching destination base station is equal to or higher than a required value. It is characterized by having

In the second invention, the mobile station includes means for notifying other mobile stations of information about the next channel switching destination base station of the mobile station, and means for receiving channel switching destination base station information from other mobile stations. and means for predicting the next channel switching destination base station based on this information.

0 Effect] The mobile station obtains control channel frequency information of neighboring base stations from the base station with which it is currently communicating. The mobile station then monitors the received level of the control channel of the nearby base station that has been broadcast.

The communication base station predicts the next destination base station of the mobile station using a table provided for each mobile station and notifies the mobile station, or the mobile station predicts the next destination base station based on the progress of base station communication so far. Predict.

The mobile station monitors the reception level of the control channel of the predicted destination base station, and if the reception level from the communication base station with which it is currently communicating decreases, the predicted base station's J111! il
When the reception level of a channel exceeds a required value, the mobile station issues a channel switching request to the base station.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the positional relationship between base stations and control base stations in the mobile communication system according to the embodiment of the present invention, and FIG. 2 shows the system configuration according to the embodiment.
The mobile station 2 is moving in the direction of the base station IC, and the mobile station 2 is moving in the direction of the base station IC. In FIG. 2, reference numeral 5 indicates a control line, and reference numeral 6 indicates broadcast information for broadcasting channel switching destination base station information from the mobile station 2.

(Embodiment 1) This embodiment is an example of predicting the channel switching destination base station of the mobile station 3 using the base station 1a currently in communication.

First, each base station 1a-le switches the channel to its own station,
For the newly created mobile station, for example, mobile station 3, a table is created based on the base station information before channel switching, which is expressed as a statistical rate for predicting the next base station to which the channel will be switched. This probability table is shown in the table below. This probability table is based on the probability that if the base station before channel switching to base station 1a is base station 1b, the probability of channel switching to the next base station IC is 60%. represents the station.

(The following is the margin of this page) Now, when the mobile station 3 switches the channel from the base station 1b to the base station 1a, the mobile station 3 uses the control line 5 to change the channel from the previous base station 1b to the base station 1a. Notify that. The base station 1a also broadcasts the control channel frequencies of neighboring base stations to the mobile station 3 using the control line 5.

The base station 1a in communication predicts the next likely channel switching destination base station IC from the probability table based on the previous base station 1b of the mobile station 3. Note that the number of base stations to be predicted is not limited to one. This predicted base station IC is notified to the mobile station 3 using the control line 5.

The mobile station 3 monitors the predicted and notified control channel of the base station IC. When the reception level from the communication base station 1a falls below a required value, if the predicted reception level of the base station IC is equal to or higher than the required value, a channel switch is requested to the base station 1a in communication.

When the reception level from the base station 1a during communication decreases, if all the predicted reception levels from the base station are below the required value, monitor the reception level of the control channel of the surrounding base station that was not predicted, If there are base stations that exceed the required value,
A request is made to the base station 1a with which communication is being performed to switch the channel to that base station.

When the communicating base station 1a receives a channel switching request from the mobile station 3, it issues a channel switching request to the control base station 4.

Then, the mobile station 3, the communicating base station 1a, the channel switching destination base station, for example, the base station IC and the control base station 4 perform channel switching.

The channel switching operation in this embodiment 1 is shown as a flowchart in FIG.

(Example 2) In Example 1 above, the probability table was prepared in advance at base station 1, but in Example 2, the probability table at base station 1 was prepared based on the track record of actual channel switching by mobile stations. Update the table from time to time.

In FIG. 2, mobile station 2 has determined the next channel switching destination base station IC from the base station 1a with which it is communicating, and mobile station 3 is a mobile station whose next channel switching destination base station has not yet been determined. Suppose there is.

(2) When the mobile station 2 performs channel switching to the base station 1a with which it is communicating, it notifies the base station 1a of the base station 1b before the channel switching using the control line 5. Furthermore, when the base station IC in communication with the base station 1a is determined as the next base station IC of the mobile station 2 using the same procedure as in the first embodiment, the base station 1a is used together with the base station 1b before the channel switching of the mobile station 2. remember.

(2) The communicating base station 1a, like the mobile station 2, updates the probability table described in the first embodiment statistically from time to time based on information about actual channel switching.

(2) The base station 1a that is communicating with the mobile station 3 that has switched channels predicts the next base station to which the channel will be switched using the updated probability table.

■ The mobile station 3 is then notified of the predicted channel switching destination base station in the same way as in Example 1, and the mobile station 3 monitors the reception level of the control channel of the channel switching destination base station and switches the channel when the conditions are met. Make a request to switch channels.

(Third Embodiment) In the first and second embodiments described above, the communication base station predicts the next channel switching destination base station based on the probability table, but in the third embodiment, the mobile station predicts the next channel switching destination base station. The operation will be explained below.

When the mobile station 3 switches channels, the communicating base station la notifies the mobile station 3 of the control channel frequencies of the surrounding base stations and the positional relationships of the surrounding base stations using the control line 5.

(2) The mobile station 3 receives the control channel of the neighboring base station broadcast from the base station 1a with which it is communicating, and monitors its reception level. Then, the direction of movement is predicted based on the positional relationship of surrounding base stations and fluctuations in their reception levels, and the next likely channel switching destination base station is predicted. The direction of travel is predicted by weighting the probability of heading toward each neighboring base station by the increase or decrease in reception level.

FIG. 4(a) shows an example of variation in the reception level of a surrounding base station, and FIG. 4(b) shows an example of representing the direction of movement as a vector based on the variation. The magnitude of the vector is the amount of change in the reception level of the surrounding base stations, and the direction in which the surrounding base stations exist is the direction of the vector (the four arrows in Figure 4, etc.), and the direction in which these vectors are combined is the direction in which the own station is moving. Direction and prediction.

In the case of FIG. 4, the mobile station 3 is heading toward the base station IC.

■ Predicted base stations (base stations 1c and 1e in Figure 4)
) and monitors the control channel frequency of the base station 1a in communication.
If the reception level from the base station decreases below the required channel, and if the predicted reception level of the control channel of the base station is above the required value, the channel is changed to communication base station 1a in order to switch the channel to that base station. Request a switch.

(2) Hereafter, channel switching control is performed in the same manner as in the first embodiment.

(Embodiment 4) In Embodiment 4, similarly to Embodiment 3, the mobile station side predicts the next channel switching destination base station. In the third embodiment, the prediction is based on the reception level of the surrounding base stations and the positional relationship of the surrounding base stations, but in the fourth embodiment, the prediction is based on the broadcast information transmitted by the mobile station that switches channels.

The mobile station 2 has determined the next channel switching destination base station 10 from the base station 1a with which it is communicating, and the mobile station 3 is a mobile layer in which the next channel switching destination base station has not yet been determined. The vehicle following the

Q,'! The mobile station 2 determines the channel switching destination base station 1G, and broadcasts the control channel frequencies of the channel switching destination base station 1a, the channel switching destination base station 1c, and the channel switching destination base station 1c before the channel switching to neighboring switching stations. This broadcast information 6 is broadcast at a broadcast frequency f for a certain period of time with a constant transmission output. The transmission target is a subsequent mobile station, for example, a mobile station within several hundred meters on the same road, so that distant mobile stations do not receive the signal. Note that even if a distant mobile station receives the broadcast information, the broadcast information is ignored unless the communication base station is the base station 1a.

■ The mobile station 3 receives the broadcast information 6 of the mobile station 2, and if it determines that the base station before channel switching is the same as the base station 1a with which it is currently communicating, it determines the base station to which the channel will be switched and its channel. The control frequency of the switching destination base station and the reception level of broadcast information are stored. If the content of the broadcast information is that the base station before channel switching is not the base station with which communication is currently being performed, this broadcast information is ignored.

■ From among the broadcast information received in this way, the mobile station 3 extracts only the broadcast information received within a certain period of time 5, weights the broadcast information with a high reception level or the broadcast information with a high reception frequency, and then sends the next one. Predict the likely channel switching destination base station.

■ If the reception level of the base station with which you are communicating drops and the reception level of the control channel of the slave base station is higher than the required value, the channel will be switched to that base station. to request channel switching.

(2) When the mobile station 3 switches channels to the base station 1a, the base station 1a already informs it of control channel frequency information of neighboring base stations. If the predicted reception level of the control channel of the base station does not exceed the required value, monitor the reception level of other surrounding base stations, and if it exceeds the required value, send a signal to the base station 1a with which you are communicating in order to switch the channel to that base station. Make a channel switching request.

(2) Thereafter, as in the first embodiment, channel switching between the communication base station 1a and the destination base station 1c is performed under control from the control base station 4.

FIG. 5 shows an example of the TDMA slot of the fourth embodiment.

In FIG. 5, the TDMA frames of the base station 1a are shown divided into those for transmission and those for reception.

Mobile station 2 receives M2 TDMA frame, mobile station 3 receives M3 TDMA frame.
TDMA frames are used.

The transmission frame of the base station 1a is a control thrower) CB,
, a communication transmission slot TBISTB□..., and a reception frame is composed of a control slot CB2, a communication reception thrower) RnI, RJ12...

The TDMA frame of mobile station 2 has an empty slot CM2, a reception slot for communication RX2, a transmission slot for communication TX2, etc.
Similarly, mobile station 3 has an empty slot) C83.
, transmission thrower for communication) T>13, reception thrower for communication)
It is composed of Rxs...

The operation of the fourth embodiment will be further explained with such a configuration.

■ Mobile station 3 is communicating with base station 1a, and mobile station 30
Transmission thrower TI for 0 communication! , communication reception thrower) RX3
The frequencies f2 and f are selected, respectively. Note that the mobile station 2 communicates on a different frequency from that of the base station 1a.

■ The mobile station 3 receives information on the control channel frequencies of neighboring base stations that the base station 1a broadcasts in the control slot, and uses the vacant slot C.
Receive with x3.

- Mobile station 2 has determined the next base station to which it will switch channels. For this reason, the mobile station 2 uses the dedicated frequency fch for transmitting channel switching optical information in the empty slot C2 to broadcast information on the channel switching destination to neighboring mobile stations. The mobile station 3 tunes the idle slot (CX3) to the frequency fch and receives the information.

(2) When the mobile station 3 determines the next base station to which the channel will be switched, it contacts the base station 1a in an empty slot C83.

■ If the mobile station 3 cannot determine the channel switching destination base station from among the predicted base stations, it selects an empty slot (CX3).
monitor the reception level of control channels of surrounding base stations.

Through such operations, channel switching control of the mobile station 3 is performed.

In FIG. 5, for convenience of explanation, the uplink and downlink time slots of the base station 1a are described separately, and the uplink and downlink time slots of the mobile stations 2 and 3 are described together. Furthermore, the radio frequencies between the base station and other mobile stations are different.

〔Effect of the invention〕

In cellular one-way mobile communication with a zone configuration, as the number of mobile stations increases, it is necessary to increase the number of base stations by reducing the receiving area of the base station in order to use frequencies effectively. . In this case, since the base station device cannot be made large, it is necessary to reduce the equipment burden and control burden on the base station. According to the present invention, the burden required for channel switching control at the base station is carried out on the mobile station side, so that the control burden on the base station side can be reduced and the base station apparatus can be downsized.

Furthermore, since it is not necessary to monitor all base stations that are subject to channel switching, there is an effect that the number of base stations that are subject to monitoring is reduced and the amount of control for channel switching is reduced.

[Brief explanation of the drawing]

FIG. 1 shows an example of the arrangement of base stations in mobile communication according to an embodiment of the present invention and a conventional example. FIG. 2 is an example of a mobile communication system configuration according to an embodiment of the present invention. FIG. 3 is a flowchart of channel switching control in the first embodiment. FIG. 4 is a diagram showing an example of a change in reception level from a surrounding base station and a predicted direction of movement of a mobile station in the second embodiment. FIG. 5 shows an example of TDMA slots in the fourth embodiment. 1a to 1e...Base station, 2.3...Mobile station, 4...
・Control base station. Patent applicant: Nippon Telegraph and Telephone Corporation Representative Patent attorney: Naotaka Ide

Claims (1)

[Claims] 1. A service area is composed of a plurality of zones, base stations are arranged corresponding to each zone, and a mobile station communicates with one of these base stations, and during communication, the mobile station In a mobile communication system in which when a mobile station moves to the area of an adjacent base station, it switches the communicating base station to the adjacent base station and continues communication, the base station is the next channel switching destination of the currently communicating mobile station. The mobile station includes a means for predicting and notifying a base station, and a monitoring means for monitoring a control channel of a base station to which the predicted channel will be switched, and a reception level of a base station with which communication is currently being performed by the monitoring means. channel switching control in mobile communications, comprising means for requesting the predicted channel switching destination base station for channel switching if the reception level of the control channel of the predicted channel switching destination base station is equal to or higher than a required value. method. 2. The service area consists of multiple zones, base stations are placed corresponding to each zone, and a mobile station communicates with one of these base stations, and during communication, the mobile station communicates with an adjacent base station. In a mobile communication system in which when moving to an area, the base station to be communicated with is switched to an adjacent base station and communication continues, the mobile station described above predicts the base station to which the mobile station currently communicating will switch to the next channel. means for monitoring a control channel of a base station to which a channel is to be switched predicted by the means; 1. A channel switching control method in mobile communications, comprising means for requesting a channel switching to a predicted channel switching destination base station if the predicted channel switching destination is greater than or equal to a value. 3. The mobile station has means for broadcasting the next channel switching destination base station information of the mobile station to other mobile stations, means for receiving channel switching destination base station information from other mobile stations, and a means for broadcasting the channel switching destination base station information from other mobile stations, and 3. The channel switching control system in mobile communication according to claim 2, further comprising means for predicting a next channel switching destination base station.