JP2001078243A - Branch control system and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the utilizing efficiency of a radio channel in a cellular communication system of a CDMA format. SOLUTION: In the branch control system, a mobile unit 11 enters a simultaneous communication states with 1st-3rd base stations when the mobile unit 11 is resident in a position where cells 14-18 are overlapped. In this state, a control section in the mobile unit 11 detects a frame error rate and a reception level or the like from a received signal during communication with each base station and compares them with reference values stored in the mobile unit 11. Upon detecting a base station whose reception state is poor, the control section starts open processing of communications with a corresponding base station and transmits an open request to each base station. Each base station transmits the received open request to a base station controller 12. The base station controller 12 receiving the request transmits an open request acknowledgement to delete communications between the base station and the mobile unit 11 to each base station and each base station transmits a received open request acknowledgement to the mobile unit 11 in a radio signal. Then the concerned base station and the mobile unit 11 stop their communications after conducting a predetermined procedure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CDMA (Code Division Multiple Access) type cellular communication system used for mobile phones and the like.

[0002]

2. Description of the Related Art In a CDMA cellular communication system, a service area is divided into a plurality of unit areas, cells, and one base station is provided in each cell.
A mobile station located in a certain cell in the service area communicates with a base station of the cell via a radio line, and from the base station, another mobile station or a telephone or the like via another radio line or a communication line. And can communicate.

The same frequency is used in all cells, and a frequency obtained by dividing this frequency by a spreading code is used as a carrier. Therefore, when the mobile station is located in an area where a plurality of cells overlap, communication is simultaneously performed with base stations of the plurality of cells using different spreading codes.

[0004]

In this cellular communication system, a large number of base stations need to be installed to cover a wide service area, but the number of base stations that can be installed is limited due to location problems and the like. On the other hand, in recent years, the spread of mobile phones has increased, and in places where a large number of people gather, there are cases where it is difficult to make and receive calls due to the shortage of lines due to the simultaneous use of many mobile phones.

[0005] As described above, in the cellular communication system of the CDMA system, when a mobile station is within a common cell range of a plurality of base stations, communication with the same contents is performed between the plurality of base stations. Is performed, as a result, a plurality of lines are occupied for communication of the same contents, and the line use efficiency is deteriorated.

[0006] In view of the above problems, an object of the present invention is to provide a CD.
It is an object of the present invention to provide means capable of improving the use efficiency of a radio channel in an MA cellular communication system.

[0007]

SUMMARY OF THE INVENTION A branch control system and method according to the present invention provide a CDMA cellular communication system in which, when there are a plurality of communications between a mobile station and a base station, a connection having a deteriorated communication condition occurs. In such a case, the mobile station releases communication with the corresponding base station, thereby effectively utilizing the resources of the base station.

In a CDMA cellular communication system, when a mobile station is within a common cell range of a plurality of base stations, the mobile station is simultaneously communicating with the plurality of base stations. At this time, this mobile station monitors the communication state with each base station during communication with each base station,
When a base station whose communication state has deteriorated occurs, a branch deletion request is transmitted to the base station control device via each base station in order to release communication with the corresponding base station.

The base station controller having received the branch deletion request transmits information for disconnecting the communication between the mobile station and the base station to the mobile station via each base station as a branch deletion response signal. After receiving the branch deletion response signal, the base station and the mobile station perform a predetermined procedure to stop the communication, thereby releasing the branch.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, 11 is a mobile station, 12 is a base station controller, 13 is a first base station, 14 is a cell range of a first base station, 15 is a second base station, and 16 is a second base station. Is the second
The cell range of the base station, 17 represents the third base station, and 18 represents the cell range of the third base station.

Base station controller 1 for controlling a plurality of base stations
2 is connected to base stations 13, 15, and 17. A base station having a transmitter and a receiver wirelessly communicates with a mobile station 11 also having a transmitter and a receiver. The cell ranges 14, 16, and 18 are the first base station 13 and the second
This is a range in which the mobile station can communicate with the base station 15, the third base station 17, and the like.

When the mobile station 11 is located in a cell, it can communicate with the base station of that cell. In adjacent base stations, there is a portion where cells overlap each other, and when the mobile device 11 is located in that portion, the mobile device 11 can communicate with the plurality of adjacent base stations at the same time.

In the example shown in FIG. 1, since the mobile station 11 is located at a position where three cells overlap, the first base station,
It is possible to communicate simultaneously with the second base station and the third base station. Note that the information that the mobile device 11 is communicating with each base station is all the same.

The mobile station 11 has detection means for detecting a frame error rate, a reception level, a line quality, and the like from a received signal of each base station during communication. Has a control unit that compares the values held in advance with those detected values to determine whether it is necessary to disconnect communication with the base station, and when a predetermined condition is satisfied. Has means for transmitting a request to release the connection (branch deletion request) to the base station.

The base station having received the connection release request reports to the base station controller 12, and the base station controller 12 transmits information (branch deletion response) for disconnecting the communication between the mobile station 11 and the corresponding base station. Send to the station.

FIG. 2 is a sequence chart showing the flow of control for branch deletion in the present invention. FIG. 2 shows, as an example, a process in a case where the mobile station 11 is connected to the first to third base stations and the communication state of the second base station deteriorates during branch communication and branch deletion is performed. .

The operation of the present invention will be described below with reference to FIGS.

In FIG. 1, mobile unit 11 has three cells 1
When 4, 16, and 18 are located in the overlapping cell,
The mobile station 11 includes a first base station 13, a second base station 15,
A state is established in which communication is performed simultaneously with the base station 17. In this state, the control unit in the mobile device 11 detects values such as a frame error rate, a reception level, and line quality from a received signal in communication with each base station, and stores the values in the memory of the mobile device 11. Compare with reference value.

At this time, if the reception state from the second base station deteriorates, the detected value does not match the reference value, and communication is performed with a plurality of base stations, the control unit starts the release processing of the corresponding communication. Then, a release request is transmitted to each base station.
First base station 13, second base station 15, and third base station 17
Transmits the received release request to the base station controller 12.

Upon receiving the release request signal, the base station controller 12 sends a release request response for deleting communication between the second base station 15 and the mobile station 11 to the first base station 13, the second base station 15 and the second base station 15. 3 and transmitted to the base stations 17, and each base station 13, 1
5 and 17 wirelessly transmit the received release request response to the mobile device 11. Thereafter, the second base station 15 and the mobile device 11
Stop communication after performing the prescribed procedure.

In the above embodiment, the parameters for the mobile station 11 to determine the reception status from each base station include the frame error rate, the reception level, and the channel quality. However, the present invention is not limited to these. Alternatively, another parameter may be used as a reference. It is also possible to determine by combining a plurality of parameters.

In the above embodiment, the necessity of the release request transmission is determined from the state of the received signal from the base station in the mobile station 11. However, the state of the received signal from the mobile station in the base station is determined as a reference. It may be.

[0023]

According to the present invention, there is provided means for releasing communication between a base station having a poor communication condition and a mobile station, and useless connections having a bad communication condition are eliminated, so that base station resources can be used effectively. It is possible to accommodate more mobile devices.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a cellular communication system to which the present invention is applied.

FIG. 2 is a control flow chart of branch deletion according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 mobile station 12 base station controller 13 first base station 14 cell range of first base station 15 second base station 16 cell range of second base station 17 third base station 18 cell range of third base station

Claims (5)

[Claims] 1. A service area divided into cells as a plurality of unit areas, a base station provided for each of the cells, a base station control device for controlling the base station, and In a cellular communication system of a CDMA system including a mobile station performing communication via the base station, the mobile station includes a plurality of cells when the mobile station is located in an area where a plurality of cells overlap. Means for simultaneously communicating with each of the base stations, means for determining the communication state of each of the base stations based on a received signal during communication with each of the base stations, and means for determining the reception state as a result of the determination by the determining means. Means for transmitting a branch deletion request to each base station to perform processing for releasing communication with the detected base station when a bad base station is detected, and after receiving a branch deletion response from each of the base stations, Said Means for performing an operation of stopping communication with the issued base station, the base station, the means for transmitting the branch deletion request received from the mobile device to the base station control device, Means for transmitting the branch deletion response received from the base station control device to the mobile station, the base station control device transmits a branch deletion response to the branch deletion request received from each of the base stations to the mobile station. A branch control method, comprising: means for transmitting to a base station. 2. A determining means provided in the mobile device, based on a signal received from each of the base stations, a means for detecting a frame error rate or a reception level or a channel quality, and using the detected value as a reference value. 2. The branch control system according to claim 1, further comprising means for comparing. 3. A service area divided into cells as a plurality of unit areas, a base station provided for each cell, a base station control device for controlling the base station, and In a CDMA cellular communication system including a mobile station performing communication via the base station, the mobile station simultaneously communicates with each base station of the plurality of cells when in a region where a plurality of cells overlap. Together with determining a communication state based on a received signal during communication with each of the base stations, and when a base station having a poor reception state is detected as a result of the determination, release processing of communication with the detected base station is performed. To start, transmit a branch deletion request to each base station, each base station transmits the received branch deletion request to the base station controller, the base station controller,
The base station transmits a branch deletion response to the branch deletion request toward each of the base stations, and each of the base stations transmits the received branch deletion response to the mobile station, and the mobile station receives the branch deletion response. Thereafter, the communication between the detected base station and the mobile station is stopped. 4. The communication state is determined based on a signal received from each of the base stations, by detecting a frame error rate, a reception level, or a line quality, and making a determination based on the detection result or a combination thereof. The branch control method according to claim 3, wherein 5. The branch control method according to claim 3, wherein the determination of the communication state is performed based on a state of a signal received from the mobile station in each of the base stations.