JPH1051836A - Congestion control system for mobile communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of times of forces hand-over when the inside of a radio zone reaches a congestion state. SOLUTION: Each of base stations 1, 2 has a means that detects a moving direction and a moving speed of a mobile station 3 during communication based on a fading pitch of a communication radio wave. An exchange 5 has a forced hand-over discrimination means using a reception electric field intensity of a radio wave of a peripheral base station to be measured by each mobile station 3, a moving speed and a moving direction of each mobile station 3 for a discrimination condition. In the case that the congestion state is detected based on a channel use rate, when the reception electric field intensity of the peripheral base station is a prescribed level or over and the moving direction is parted from the base stations 1, 2 or the moving direction cannot be specified, a mobile station whose speed is smaller than a predetermined speed threshold level is extracted and a mobile station 3 with a largest reception electric field intensity is highest is sequentially and forcibly handed over among the mobile stations.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system, and more particularly to a mobile communication system in which a plurality of mobile stations are concentrated in a radio zone of a certain base station and a congestion state occurs in which a communication channel is insufficient. The present invention relates to a congestion control method for a mobile communication system in which a mobile station capable of handover is forcibly handed over to eliminate a congestion state.

[0001]

2. Description of the Related Art In a conventional mobile communication system, a method of forcibly handing over a mobile station located near a boundary of a radio zone has been adopted.

For example, Japanese Patent Application Laid-Open No. 4-344723 discloses a base station having a function of calculating the difference between the received field strength of its own base station and the received field strength of an adjacent base station for each mobile station, and recording and holding the difference. There is disclosed a technique provided in a control device, and among mobile stations capable of handover, a mobile station having the largest difference is set as a candidate for forced handover.

[0003]

However, in the prior art, there is a possibility that the mobile station that has performed the forced handover is moving at a high speed, so the handover is performed before and after the handover. There was a possibility that the state changed greatly after that, and the mobile station that performed the forced handover needed to immediately perform the handover process again.

[0004]

SUMMARY OF THE INVENTION The present invention provides a congestion control system which solves the above-mentioned problems and minimizes handover performed during congestion.

[0005] The present invention provides an exchange for controlling mobile communication,
In a mobile communication system including a plurality of base stations connected to the exchange and a plurality of mobile stations that move and communicate in a wireless zone provided by each base station, the base station includes:
The mobile station is provided with speed detecting means for detecting a moving direction and a moving speed of a mobile station during communication based on a fading pitch of a communication radio wave. A forced handover determination unit that uses a received electric field strength value of a peripheral base station radio wave, a moving direction and a moving speed of each mobile station detected by the base station as a determination material, and the forced handover determination unit includes: If the state is detected based on the channel utilization, the received electric field strength of the peripheral base station is larger than a predetermined level threshold, and if the moving direction is not the direction approaching the base station and the moving direction cannot be specified, the moving speed Mobile stations that are smaller than the predetermined speed threshold are extracted as forced handover candidate mobile stations, and the reception electric field is extracted from those candidate mobile stations. Wherein the degree value to perform sequentially forced handover from the biggest mobile station.

Further, the forced handover determination means detects a congestion state each time one mobile station is forcibly handed over, and terminates the forced handover when it detects the elimination of the congestion state.

[0007] The forced handover determination means is periodically activated, and when the forced handover of all the mobile stations extracted as the forced handover candidate mobile stations cannot detect the elimination of the congestion state, the processing is performed. It is characterized by terminating and waiting for the next activation cycle.

As described above, according to the present invention, a mobile station is selected under such a condition that a handover can be reliably performed even if a forced handover is performed. The condition considers the moving direction and moving speed of the mobile station detected by the base station in addition to the received electric field strength of the peripheral base station.

[0009]

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

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention. The base stations 1 and 2, each of which forms a wireless zone 7, 8, are connected to a switch 5 for controlling mobile communication via a transmission line 9. The exchange 5 has a reception field strength level threshold for permitting communication, a congestion threshold based on a channel usage rate for judging congestion, a moving speed threshold of a mobile station permitting forced handover, and a moving direction. It has a forced handover determination means 6. Base stations 1 and 2 are speed detecting means 4 for detecting the moving speed and moving direction of mobile station 3 during communication by fading pitch.
have.

Next, the operation of the embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a flowchart for explaining the operation of the congestion control system of the present invention. This operation is periodically executed in the exchange 5 to identify a congestion state, and in the case of congestion, execute a forced handover to try to eliminate the congestion.

As described with reference to FIG.
Indicates the channel usage rate of each base station, the received electric field intensity value of the radio wave radiated from the neighboring base station measured by each mobile station received via the base station, and the base station measures and transmits by the forced handover determination means. The moving direction and moving speed of each mobile station are used as the determination data.

The moving direction and the moving speed of the mobile station are measured at the base station using the fading pitch of the communication radio wave. Therefore, the direction and speed that can be measured are basically values of a linear direction component connecting the base station and the mobile station. In particular, it is determined whether the moving direction is toward or away from the base station.

When the operation shown in FIG. 2 is started by the exchange 5, the channel utilization of each base station is compared with a predetermined congestion threshold, and when the channel utilization exceeds the congestion threshold, the congestion is reduced. (Step 101: Ye
s). When not in a congestion state (Step 101: No)
Ends the process and waits for the next startup cycle.

If it is determined that the mobile station is in a congested state, a mobile station that has a possibility of performing a forced handover is extracted from all mobile stations communicating with the base station (step 102). This extraction condition is when the received electric field level of the peripheral base station measured and notified by the mobile station is larger than a predetermined level threshold, the moving direction is not the direction approaching the base station, and the moving direction cannot be specified. Is assumed to have a moving speed smaller than a predetermined speed threshold, and all mobile stations satisfying these conditions are extracted as forced handover candidates.

[0017] Among the mobile stations extracted in this way, the mobile station having the maximum received electric field level of the neighboring base station is selected as a target mobile station for forced handover (step 10).
3).

A handover is performed by giving an instruction for forced handover to the selected mobile station (step 1).
04).

Here, the exchange 5 determines again whether or not the congestion state has been eliminated by the forced handover based on the channel utilization (step 105). if,
If the congestion state has been resolved, the processing is terminated and the next activation cycle is waited (step 105: No).

However, when the congestion state has not been resolved even by the forced handover (step 105: Ye
In s), the target mobile station to be subjected to the next forced handover is selected from the forced handover candidate mobile stations extracted earlier under the same conditions as in step 103 to perform the forced handover. At this time, if there is no mobile station that matches the extraction condition (step 106: No),
End the process and wait for the next startup cycle.

In this way, the forced handover candidate mobile stations are sequentially forced to perform a handover to check the change in the congestion state, and the same operation is repeated until the congestion state is eliminated. If the forced handover candidate mobile station no longer exists in the process, the process is terminated and the next activation cycle is waited.

[0022]

As described above, according to the congestion control method of the mobile communication system of the present invention, when a mobile station as a candidate for forced handover is extracted, it can be determined that the mobile station is clearly going away from the base station. If a forced handover is performed, such as when a mobile station or a mobile station that moves in the tangential direction of the circumference around the base station with no change in the distance from the base station but has a slower moving speed, the hand is surely handed over. Mobile stations that can be over-selected are selected as candidates, and forced handover is performed sequentially from those having the highest received electric field strength value of radio waves of peripheral base stations from among them, so there is no need to perform handover again for the same mobile station. Also, there is an effect that the congestion state can be surely eliminated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a flowchart illustrating the operation of the present invention.

[Explanation of symbols]

 1, 2 base station 3 mobile station 4 speed detection means 5 exchange 6 forced handover determination means 7, 8 wireless zone 9 transmission path

Claims (3)

[Claims] 1. A switching system for controlling mobile communication, a plurality of base stations connected to the switching system, and a plurality of mobile stations which communicate within a wireless zone provided by each base station. In a mobile communication system, the base station includes speed detecting means for detecting a moving direction and a moving speed of a mobile station during communication by a fading pitch of a communication radio wave. The received electric field intensity value of the surrounding base station radio wave measured by each mobile station received via the station, the moving direction and moving speed of each mobile station detected by the base station comprising a forced handover determination means using as a determination material, The forced handover determination means, when detecting the congestion state of the base station based on the channel usage rate, makes the reception electric field strength of the neighboring base stations larger than a predetermined level threshold. If the moving direction is not the direction approaching the base station and the moving direction cannot be specified, mobile stations whose moving speed is smaller than a predetermined speed threshold are extracted as the forced handover candidate mobile stations, and the candidate mobile stations are extracted. A congestion control method for a mobile communication system, wherein forced handover is performed sequentially from the mobile station having the largest received electric field strength value. 2. The forced handover determination means detects a congestion state each time one mobile station is forcibly handed over, and terminates the forced handover when it detects the elimination of the congestion state. A congestion control method for a mobile communication system according to claim 1. 3. The forcible handover determination means is periodically activated, and when it is not possible to detect the elimination of the congestion state even when forcibly handing over all the mobile stations extracted as the forcible handover candidate mobile stations, 3. The process according to claim 2, wherein the process is terminated and a next start cycle is waited.
Congestion control method for a mobile communication system according to claim 1.