JP4973282B2 - Cell selection method and communication terminal - Google Patents

Description

  The present invention relates to cell movement by selection of an appropriate cell and handover in a mobile radio communication terminal equipped with a specific service.

In mobile radio communication using W-CDMA (Wideband-Code Division Multiple Access), cell movement by handover of a communication terminal during a call is performed according to the following procedure.
(1) The reception quality of each cell is measured, and when the cell movement condition specified by the network is satisfied, the cell that satisfies the cell movement condition is reported to the network.
(2) When it is determined that the mobile radio communication terminal needs to move, the network that has received the report issues a move instruction (handover instruction) to the mobile radio communication terminal including information on the movement destination cell.
(3) The mobile radio communication terminal performs cell movement determination based on information acquired from the network, and moves to another cell, that is, performs handover.

  As an example, FIG. 6 shows the reception quality of each cell over time. An operation example of cell selection in FIG. 6 will be described below. First, it is assumed that the communication terminal moves away from the base station of the cell 1 and moves closer to the cell 2 and the cell 3 as time passes while the communication terminal is communicating with the cell 1. In this case, generally, the reception quality of the cell 1 deteriorates as shown in the cell 1 reception quality of FIG. 6, and at the same time, the reception quality of the cell 2 and the cell 3 are respectively the cell 2 reception quality and the cell 3 of FIG. Improve as shown in the reception quality. When the communication terminal receives a movement instruction (time t), the communication terminal selects the cell 2 with better reception quality and moves to the cell 2.

  Regarding such cell selection, for example, in a wireless communication system using the GSM (Global System for Mobile Communications) system, the terminal device stores information on the previous connection and is necessary for the next connection based on the information. Patent Document 1 discloses a terminal device that generates a predicted value related to a service level and selects a cell so that the terminal device matches the predicted value.

  Also, in particular, a Release 5-compatible mobile station (UE: User Equipment) capable of high-speed packet communication using the HSDPA (High Speed Downlink Packet Access) method, and a Release 99-compatible mobile station that does not support high-speed packet communication using the HSDPA method. For example, Patent Document 2 discloses a mobile communication system that performs cell selection corresponding to HSDPA using a priority in an environment in which both are mixed.

JP 2001-523422 A JP 2006-229384 A

  However, in the prior art described in Patent Documents 1 and 2, when a cell moving during communication of a mobile radio communication terminal, when a cell corresponding to a specific service and a cell not corresponding are mixed, priority is given. It was only possible to select a cell corresponding to a specific service. Therefore, even when the reception quality of the specific service compatible cell is low, there is a problem that the specific service compatible cell is selected, and as a result, the communication quality deteriorates.

  Accordingly, an object of the present invention is to provide a communication terminal and a method for solving the above-described problem that the quality of communication deteriorates as a result of selecting only a specific service-compatible cell.

  The present invention stores information about a cell in a database held by a wireless communication terminal in an environment in which compatible cells corresponding to a specific service such as HSDPA and non-compatible cells coexist, and the information and reception quality are used to store the cell. A communication terminal and method for performing selection are proposed.

  A communication terminal according to the present invention includes a cell database unit that stores information for determining whether a cell is compatible with a specific service, and a communication control unit that measures reception quality of the cell. The reception quality is corrected based on the measured reception quality of the cell and the stored information, and the handover destination cell is selected based on the corrected reception quality.

  According to the present invention, when a cell supports, for example, HSDPA, the cell information is stored in the database of the communication terminal, and the HSDPA compatible cell is given priority by using the database information and the offset value. In addition to selection, cell selection can be performed in consideration of reception quality.

  Next, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a mobile radio communication terminal according to an embodiment of the present invention.

  In FIG. 1, a mobile radio communication terminal (hereinafter referred to as a communication terminal) 100 performs radio communication with a base station. The feature includes a cell database unit 14 for storing information for determining whether or not a cell corresponds to a specific service, and a communication control unit 13 for measuring the reception quality of the cell. The communication control unit 13 corrects the reception quality based on the measured cell reception quality and the information stored in the cell database unit 14, and selects a handover destination cell based on the corrected reception quality.

Specifically, the communication device 100 is configured as follows.
The user uses the communication terminal 100 to use services such as a call with another terminal, transmission / reception of mail, and web browsing. The wireless unit 10 communicates with a base station. In particular, the radio unit 10 receives information for determining whether a cell connected to the communication terminal 100 is compatible with HSDPA. The operation unit 11 is an input device such as a button, and is used when a user operates the communication terminal 100. The display unit 12 is a screen that is made of liquid crystal or the like and is visible.

  The communication control unit 13 performs W-CDMA modulation / demodulation and HSDPA demodulation. Further, the communication control unit 13 measures the reception quality of a cell, and registers information on the cell in the cell database unit 14 when the radio unit 10 connects to a cell compatible with HSDPA and starts communication. Further, the communication control unit 13 is based on the reception quality of the cell received by the radio unit 10, the cell information of the cell database unit 14, the offset value that is the correction value of the reception quality held in the memory unit 15, the threshold value of the reception quality, and the like. , Perform cell selection.

  The cell database unit 14 stores information about cells. In particular, the cell database unit 14 stores information on whether or not a cell connected to a communication terminal in the past is compatible with HSDPA. The memory unit 15 holds a reception quality offset value used for a cell corresponding to HSDPA and a reception quality threshold value.

  Next, the overall operation of the present embodiment will be described in detail with reference to the flowchart of FIG. First, the communication terminal 100 connects to a base station and starts communication (step S01). The communication control unit 13 measures the reception quality of the cell from the signal received by the radio unit 10, and determines whether the cell is compatible with HSDPA (step S02). When the measured cell is compatible with HSDPA, cell information is registered in the cell database unit 14 (step S03). When the measured cell is not compatible with HSDPA, the cell information is not registered in the cell database unit 14.

  Next, the communication control unit 13 measures the reception quality of a movement candidate cell that is a target of cell movement by handover (step S04). The communication control unit 13 compares the measured reception quality with the threshold value read from the memory unit 15 (step S05), and if the reception quality is high, checks whether the measured cell is stored in the cell database unit 14 ( Step S06). When the measured cell is stored in the cell database unit 14, the communication control unit 13 reads the offset value of the reception quality from the memory unit 15 (step S07), and adds the offset value to the measured reception quality (step S08). . The reason for adding the offset value is to preferentially select a cell corresponding to HSDPA when selecting a cell with high reception quality. When the measured reception quality is equal to or lower than the threshold value, or when the measured reception quality is higher than the threshold value but the cell information of the measured cell is not stored in the cell database unit 14, the offset value is not added.

  Next, the communication control unit 13 determines whether or not the condition for cell movement is satisfied (step S09). When the cell movement condition is satisfied, the communication control unit 13 transmits a cell movement request to the base station via the radio unit 10 (step S10), and as a result, cell movement is performed (step S11). If the cell movement condition is not satisfied, the communication control unit 13 repeats the operation from step S04. After the cell movement is performed, the communication control unit 13 performs the operation from step S02 on the cell after the cell movement.

  As a result, when the reception quality of the cell is good, a cell corresponding to HSDPA is preferentially selected, and when the reception quality of the cell is low, there is a possibility of selecting a cell even for a cell corresponding to HSDPA. Can be reduced.

  Next, specific examples will be described with reference to FIGS. First, FIG. 3 shows a change in reception quality received by the communication terminal 100 in the first embodiment. Here, cell 1 and cell 3 are cells that support HSDPA, cell 2 is a cell that does not support HSDPA, and the communication terminal has connected to cells 1 to 3 in the past, and FIG. It is assumed that the operations from step S01 to step S03 in FIG. That is, the communication control unit 13 determines that the cells 1 and 3 are compatible with HSDPA, and stores the information of the cells 1 and 3 in the cell database unit 14. At this time, the information stored in the cell database unit 14 is as shown in FIG.

  Communication terminal 100 repeats steps S04 to S09 in FIG. That is, if the cell 2 and the cell 3 are cells to be moved, the communication control unit 13 measures the reception quality of the cell 2 and the cell 3, and stores the cell reception quality higher than a certain threshold and stored in the cell database unit 14. If the cell is a cell, the offset value of the reception quality stored in the database unit 19 is added to the measured reception quality.

  Here, the threshold value is set to, for example, −18 db, and the offset value is set to a value of 3 db.

  Next, when the cell movement condition is satisfied at time t in FIG. 3 (step S09 in FIG. 2), the communication control unit 13 transmits a cell movement request to the base station via the radio unit 10 (FIG. 3). Step S10 in 2). At this time, when only the reception quality measured at time t is compared, cell 2 has the highest reception quality. On the other hand, since cell 3 supports HSDPA, an offset value is added to the reception quality (cell 3 reception quality + offset value in FIG. 3). Therefore, the communication control unit 13 selects the cell 3 with higher reception quality as the movement destination cell (handover destination cell) and moves to the cell 3, that is, hands over (step S11 in FIG. 2, cell movement in FIG. 3). .

  However, when moving to a cell with low reception quality, there is a possibility that communication cannot be maintained. FIG. 5 is a diagram similar to FIG. 3, but the reception quality of the cell 3 at the time of cell movement is lower than the reception quality of the cell 3 at the time of cell movement in FIG. Thus, when the reception quality of cell 3 is extremely low, even if the reception quality of cell 3 plus the offset value is higher than the reception quality of cell 2 (cell 3 reception quality + offset in FIG. 5). Value), when moving to a cell having such reception quality, communication may not be maintained. 2, when the measured reception quality is higher than the threshold stored in the memory unit 15, the communication control unit 13 sets the cell as a target to which the offset value is added.

  According to the first embodiment, when there are a plurality of cells that are candidates for cell movement during cell movement, it is possible to preferentially select a cell corresponding to HSDPA, and to select a cell corresponding to HSDPA with low reception quality. It can be avoided.

  In the first embodiment, the case where the communication terminal and the base station are communicating has been described as an example. However, the same operation can be performed for cell movement in a standby state of the communication terminal. That is, while waiting, it is possible to preferentially select and move (handover) a cell corresponding to HSDPA based on information in the cell database unit 14.

  Also, the same operation can be performed at the start of the HSDPA service. For example, when data communication is performed, if the communication terminal 100 does not CampOn a cell corresponding to HSDPA, a search is performed for a cell compatible with HSDPA around the communication terminal 100, and if a corresponding cell exists. The service can be started after moving to the cell.

  According to the second embodiment, a good service can be used at a more appropriate timing.

In the first and second embodiments, an offset value is added to a cell corresponding to HSDPA and used for comparison of reception quality. However, the operation of the present invention is also applied when using a specific service other than HSDPA. be able to. That is, in an environment where cells corresponding to a specific service and cells not corresponding to each other coexist, information on the cell corresponding to the specific service is stored in the cell database unit 14 of the communication terminal 100. And when comparing reception quality, based on the value stored in the cell database part 14, what added the offset value to reception quality is utilized. Thereby, priority can be given to selection of a specific cell.

  However, when the communication terminal 100 moves to a cell that does not support a specific service when using a specific service, how to provide the service varies depending on the type of service. For example, when the specific service is a high-speed communication service, when the communication terminal 100 moves to a cell in which the high-speed communication service cannot be used, the use of the high-speed communication service may be temporarily suspended to provide a normal communication service. .

  According to the third embodiment, flexible cell selection is possible even in services other than HSDPA.

In the first to third embodiments, a cell corresponding to a specific service is stored in the cell database unit 14 of the communication terminal 100, but conversely, communication such as a cell that does not correspond to a specific service or a communication failure is performed. Alternatively, the cell in which the problem has occurred may be stored in the cell database unit 14. In this case, the communication control unit adds a negative correction value (offset value) to the cell based on the cell information stored in the cell database unit, so that selection of the cell in cell movement can be suppressed. .

  According to the fourth embodiment, it is possible to reduce the possibility of cell selection for a cell that does not support a specific service or a cell in which a communication problem such as a communication failure has occurred, and to perform flexible cell selection.

In the first to fourth embodiments, after connecting to the base station in the cell, the cell information is stored in the cell database unit 14, and cell selection is performed based on the stored information. It may be determined whether a cell is compatible with a specific service by using a system information block (System Information Block) which is control information periodically transmitted by a cell base station. Specifically, the base station includes information for identifying whether or not a specific service is supported in the System Information Block. When the radio unit 10 receives the System Information Block from the cell, the communication control unit 13 determines whether or not the cell corresponds to a specific service from the System Information Block. When corresponding to a specific service, the communication control unit 13 stores the cell information in the cell database unit 14. Thereby, the communication terminal 100 can perform cell selection based on the stored information.

  According to the fifth embodiment, it is possible to determine whether a cell supports a specific service without being connected to the cell.

  In the first to fifth embodiments, the communication terminal 100 automatically collects cell information and performs cell selection. However, the user himself / herself operates the operation unit 11 to provide a specific service. The cell may be searched, and the search result may be stored in the cell database unit 14. Further, one cell selected by the user may be selected as a moving cell from the searched cells by the user's operation.

  According to the sixth embodiment, the user can select a cell more flexibly based on the will.

It is a block diagram of the communication terminal which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the communication terminal which concerns on embodiment of this invention. It is a figure showing the reception quality at the time of adding the reception quality and offset of the cell which a communication terminal receives in the communication terminal which concerns on embodiment of this invention. It is a figure which shows the information stored in a cell database part in the communication terminal which concerns on embodiment of this invention. It is a figure showing the reception quality at the time of adding the reception quality and offset of the cell which a communication terminal receives in the communication terminal which concerns on embodiment of this invention. It is a figure showing the change of the reception quality of the cell which a communication terminal receives in the communication terminal which concerns on a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Communication terminal 10 Radio | wireless part 11 Operation part 12 Display part 13 Communication control part 14 Cell database part 15 Memory part

Claims (9)

In a communication terminal that communicates with a base station, a cell database unit that stores information for determining whether a cell is compatible with a high-speed communication service, and a communication control unit that measures reception quality of a cell,
The communication control unit adds the correction value to the measurement value of the reception quality of the cell when the cell corresponds to the high-speed communication service and the measurement value of the reception quality is larger than the threshold value, and the reception quality is the highest. A communication terminal , wherein a cell is selected as a handover destination cell . The communication control unit determines whether the cell is compatible with the high-speed communication service through communication with the base station of the cell, and stores the cell information in the cell database unit when the cell is compatible. The communication terminal according to claim 1. The communication control unit determines whether the cell is compatible with the high-speed communication service through communication with the base station of the cell, and stores the cell information in the cell database unit when the cell is not compatible The communication terminal according to claim 1 or 2. The communication terminal according to claim 3, wherein the correction value is a negative value, and the communication control unit adds the correction value to a cell that does not support the high-speed communication service. When the control information received from the base station in the cell includes information corresponding to the high-speed communication service, the communication control unit stores the cell information in the cell database unit. The communication terminal according to claim 1. 6. The communication control unit according to claim 1, wherein the communication control unit performs cell selection based on information in the cell database unit when communicating with a base station in the cell or when waiting. Communication terminal described in 1. The communication terminal according to any one of claims 1 to 5, wherein the communication control unit performs cell selection based on information in the cell database unit when a service is started. The communication terminal according to any one of claims 1 to 7, wherein the high-speed communication service is HSDPA. In a communication terminal that communicates with a base station, a step of storing information for determining whether a cell is compatible with a high-speed communication service, a step of measuring reception quality of the cell, and a cell corresponding to the high-speed communication service A correction value is added to the measurement value of the reception quality of the cell when the reception quality measurement value is greater than the threshold value, and the cell having the highest reception quality is selected as a handover destination cell. Characteristic cell selection method.

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