JP2011124630A - Radio base station, handover method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly perform communication during handover without interruption even when it takes time to select a frequency band to be used within a cell during handover. <P>SOLUTION: When a movement detection part 101 detects that a radio terminal has moved into a cell covered by a radio base station 100-1, a handover performance part 102 performs handover processing using a preset specified frequency band and performs radio communication with the radio terminal using the specified frequency band, a scanning part 103 scans all the frequency bands usable for the radio communication within the cell covered by the radio base station 100-1 and detects the frequency band used by a radio terminal other than the radio terminal present within the cell, and a selection part 104 selects the frequency band to be used for the radio communication with the radio terminal from the frequency bands other than the frequency band detected by the scanning part 103 among all the frequency bands. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radio base station that performs radio communication with a radio terminal, a handover method, and a program.

  Currently, the frequency band of radio waves used for wireless communication is allocated for each business service, and is allocated so as not to interfere with each other between a plurality of business services.

  However, in some business services, there is a variation in each business service, such as frequent communication status congestion, and some business services being in a very good state due to a sparse communication state. Also, the usage situation of the frequency band changes depending on the place and time.

  Therefore, cognitive radio communication technology has been proposed as a technology that removes the concept of frequency band allocation by business service, monitors the availability of all frequency bands of radio waves, and performs radio communication using the available frequency bands. (For example, refer to Patent Document 1).

  In this cognitive radio communication technology, the entire frequency band is logically monitored, and the frequency utilization efficiency increases. In addition, because of the tight use of frequency resources, new service entry can be considered.

JP 2009-231976 A

  However, in the wireless communication using the cognitive wireless communication technology, in order to detect an empty frequency band, the state of the frequency band used in the surrounding wireless terminals is always investigated (scanned). Therefore, it takes time to detect an empty frequency band, and it takes time to select a frequency band to be used from the empty frequency bands.

  In mobile communication, it is necessary to perform handover when moving between cells so that communication is not interrupted. However, when the cognitive radio communication technology is used for mobile communication, it takes time to scan the entire frequency band and select an appropriate frequency band at the time of handover, so it is difficult to switch the frequency band instantaneously. There is a problem of becoming. Therefore, a technique for smoothly performing handover without interruption is indispensable.

  An object of the present invention is to provide a radio base station, a handover method, and a program that solve the above-described problems.

The radio base station of the present invention is
A wireless base station that performs wireless communication with a wireless terminal,
A movement detection unit for detecting that the wireless terminal has moved into a cell covered by the wireless base station;
When the movement detection unit detects that the wireless terminal has moved into a cell covered by the wireless base station, a handover process is performed using a predetermined specific frequency band, and the specific frequency band is A handover execution unit for performing wireless communication with the wireless terminal using,
When the movement detection unit detects that the wireless terminal has moved into a cell covered by the wireless base station, all the frequency bands that can be used for the wireless communication within the cell covered by the wireless base station A scan unit that scans and detects a frequency band used by a wireless terminal other than the wireless terminal present in the cell;
A frequency band used for wireless communication with the wireless terminal is selected from frequency bands other than the frequency band detected by the scan unit among the entire frequency bands, and the frequency band used for the wireless communication is specified. And a selector for switching from the frequency band to the selected frequency band.

The handover method of the present invention includes
A handover method executed by a wireless terminal moving between a plurality of cells respectively covered by a plurality of wireless base stations,
Detecting movement of the wireless terminal between the cells;
When detecting movement between the cells of the wireless terminal, a step of performing a handover process using a preset specific frequency band;
Performing wireless communication between the wireless terminal and a wireless base station covering a cell in which the wireless terminal exists using the specific frequency band after performing the handover process;
When the movement of the wireless terminal between the cells is detected, the entire frequency band that can be used for wireless communication is scanned in the cell in which the wireless terminal exists, and the wireless terminal other than the wireless terminal existing in the cell A scanning step to detect the frequency band being used;
A selection step of selecting a frequency band used for radio communication between the radio terminal and a radio base station covering the cell from frequency bands other than the detected frequency band out of the total frequency bands;
Switching the frequency band used for the wireless communication from the specific frequency band to the selected frequency band after selecting the frequency band.

The program of the present invention is
A program for causing a wireless base station to perform wireless communication with a wireless terminal,
A procedure for detecting that the wireless terminal has moved into a cell covered by the wireless base station;
When it is detected that the wireless terminal has moved into a cell covered by the wireless base station, a handover process is performed using a preset specific frequency band, and the wireless terminal is connected to the wireless terminal using the specific frequency band. Procedure for wireless communication between
When it is detected that the wireless terminal has moved into the cell covered by the wireless base station, the entire frequency band that can be used for the wireless communication is scanned in the cell covered by the wireless base station. A scanning procedure for detecting a frequency band used by a wireless terminal other than the wireless terminal existing in
A selection procedure for selecting a frequency band to be used for wireless communication with the wireless terminal from a frequency band other than the detected frequency band among the total frequency bands;
After selecting the frequency band, a procedure for switching the frequency band used for the wireless communication from the specific frequency band to the selected frequency band is executed.

  As described above, according to the present invention, even when it takes time to select a frequency band to be used in a cell at the time of handover, communication at the time of handover can be performed smoothly without interruption.

It is a figure which shows one Embodiment of the mobile communication system provided with the wireless base station of this invention. It is a figure which shows an example of an internal structure of the wireless base station shown in FIG. 3 is a flowchart for explaining a handover method in the radio base station shown in FIG. 2. It is a figure which shows a mode when a radio | wireless terminal exists in the cell before a hand-over. It is a figure which shows an example of the magnitude | size of the electric power used with respect to the frequency band which a radio base station can use when a radio | wireless terminal exists in the cell before a hand-over. It is a figure which shows the position of the radio | wireless terminal when the process of step S1 and S2 is performed. It is a figure which shows an example of the magnitude | size of the electric power used with respect to the frequency band when the process of step S2 is performed. It is a figure which shows a mode after a radio | wireless terminal moved to the cell after a hand-over. It is a figure which shows an example of the magnitude | size of the electric power used with respect to the frequency band after switching from the specific frequency band to the selected frequency band.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing an embodiment of a mobile communication system provided with a radio base station of the present invention.

  As shown in FIG. 1, the mobile communication system in this embodiment includes radio base stations 100-1 to 100-2 and a radio terminal 200. Further, the radio terminal 200 is moving between the cells 300-1 to 300-2 covered by the radio base stations 100-1 to 100-2. Further, FIG. 1 shows a case where the number of radio base stations is two, but three or more radio base stations may be used.

  The radio base station 100-1 performs radio communication with the radio terminal 200 when the radio terminal 200 exists in the cell 300-1. In addition, when the radio terminal 200 moves from a cell other than the cell 300-1 (for example, the cell 300-2), the radio base station 100-1 performs a handover process.

  The radio base station 100-2 performs radio communication with the radio terminal 200 when the radio terminal 200 exists in the cell 300-2. In addition, when the radio terminal 200 moves from a cell other than the cell 300-2 (for example, the cell 300-1), the radio base station 100-2 performs a handover process.

  The radio terminal 200 is a mobile terminal that performs radio communication with the radio base stations 100-1 to 100-2.

  FIG. 2 is a diagram illustrating an example of an internal configuration of the radio base station 100-1 illustrated in FIG. Note that the internal configuration of the radio base station 100-2 illustrated in FIG. 1 is the same as the internal configuration of the radio base station 100-1.

  As shown in FIG. 2, the radio base station 100-1 shown in FIG. 1 includes a movement detection unit 101, a handover execution unit 102, a scan unit 103, a selection unit 104, a radio interface unit 105, and a host device. An interface unit 106 is provided. Note that FIG. 2 shows only the constituent elements according to the present invention among the constituent elements of the radio base station 100-1 shown in FIG.

  The movement detection unit 101 detects that the wireless terminal 200 has moved into the cell 300-1 covered by the wireless base station 100-1. This detection method may be used in general handover processing. When the movement detection unit 101 detects that the radio terminal 200 has moved into the cell 300-1 covered by the radio base station 100-1, the movement detection unit 101 notifies the handover execution unit 102 and the scan unit 103 of the fact. .

  When the handover execution unit 102 is notified from the movement detection unit 101 that it has detected that the radio terminal 200 has moved into the cell 300-1 covered by the radio base station 100-1, the handover execution unit 102 sets a predetermined identification. A handover process is executed using the frequency band, and a setting for performing communication between the radio base station 100-1 and the radio terminal 200 is performed using the specific frequency band. The only difference between the handover process executed here and the generally performed handover process is whether or not a specific frequency band is used. Needless to say, when the handover process extends over the radio base stations 100-1 to 100-2, the higher-level devices of the radio base stations 100-1 to 100-2 also perform the handover process. The specific frequency band is a frequency band that is temporarily used, and is set in advance in the radio base station 100-1.

  When the scanning unit 103 is notified from the movement detecting unit 101 that it has detected that the wireless terminal 200 has moved into the cell 300-1 covered by the wireless base station 100-1, the wireless base station 100-1 The entire frequency band that can be used for wireless communication is scanned in the cell 300-1 covered by. Here, the total frequency band refers to the entire frequency band generally assigned for each business service, that is, all the frequency bands that can be used in wireless communication without restrictions imposed by the business service. And the scanning part 103 detects the frequency band currently used by radio | wireless terminals (not shown) other than the radio | wireless terminal 200 which exists in the cell 300-1 as a result of a scan. Further, the scanning unit 103 notifies the selection unit 104 of the detected frequency band.

  The selection unit 104 selects a frequency band to be used for wireless communication with the wireless terminal 200 from frequency bands other than the frequency band notified by the scanning unit 103 among all frequency bands. In addition, after selection, the selection unit 104 switches the frequency band used for wireless communication with the wireless terminal 200 from the specific frequency band to the selected frequency band.

  Then, wireless communication is performed between the wireless base station 100-1 and the wireless terminal 200 using the switched frequency band.

  Note that the scan in the scan unit 103 and the selection in the selection unit 104 described above are performed using a cognitive radio communication technique.

  Hereinafter, a handover method in this embodiment will be described. Here, the process in radio base station 100-1 when radio terminal 200 shown in FIG. 1 moves from cell 300-2 to cell 300-1 will be described as an example.

  FIG. 3 is a flowchart for explaining a handover method in radio base station 100-1 shown in FIG.

  FIG. 4 is a diagram illustrating a state when the wireless terminal 200 exists in the cell 300-2 (before moving to the cell 300-1).

  FIG. 5 shows an example of the magnitude of power used for a frequency band that can be used by the radio base station 100-1 when the radio terminal 200 exists in the cell 300-2 (before moving to the cell 300-1). FIG. A predetermined frequency band is set in advance between the broken line and the broken line shown in FIG.

  As shown in FIG. 4, when the radio terminal 200 exists in the cell 300-2 (before moving to the cell 300-1), as shown in FIG.

  Thereafter, when the movement detection unit 101 detects that the wireless terminal has moved from the cell 300-2 to the cell 300-1 (step S1), the handover execution unit 102 sets a specific frequency set in advance. A handover process is executed using the bandwidth (step S2). This handover process has been described above. Then, wireless communication is performed between the wireless base station 100-1 and the wireless terminal 200 using the specific frequency band.

  FIG. 6 is a diagram illustrating the position of the wireless terminal 200 when the processes of steps S1 and S2 are performed.

  FIG. 7 is a diagram illustrating an example of the amount of power used for the frequency band when the process of step S2 is performed.

  As shown in FIG. 6, when the radio terminal 200 moves from the cell 300-2 to the cell 300-1, radio communication is performed using the specific frequency band. Therefore, as shown in FIG. Electric power increases. At this time, as shown in FIG. 6, radio terminal 200 is present in an area (a hatched portion in FIG. 6) at a predetermined distance from the boundary in cell 300-1.

  The scanning unit 103 scans all frequency bands that can be used for wireless communication in the cell 300-1 that is covered by the wireless base station 100-1. As described above, the entire frequency band refers to all the frequency bands that can be used in wireless communication, with restrictions on business services removed.

  Subsequently, a frequency band used by a wireless terminal other than the wireless terminal 200 existing in the cell 300-1 is detected by the scanning unit 103 by this scanning (step S3). That is, the frequency band used by the wireless terminals existing around the wireless terminal 200 is detected.

  Then, the selection unit 104 selects a frequency band used for radio communication between the radio base station 100-1 and the radio terminal 200 from frequency bands other than the frequency band detected by the scan unit 103 among all frequency bands. (Step S4).

  Then, the selection unit 104 switches the frequency band used for wireless communication between the wireless base station 100-1 and the wireless terminal 200 from the specific frequency band to the selected frequency band. Then, wireless communication is performed between the wireless base station 100-1 and the wireless terminal 200 using the switched frequency band.

  FIG. 8 is a diagram illustrating a state after the wireless terminal 200 has moved into the cell 300-1.

  FIG. 9 is a diagram illustrating an example of the amount of power used for the frequency band after switching from the specific frequency band to the selected frequency band.

  As shown in FIG. 8, when the radio terminal 200 is switched from the specific frequency band to the selected frequency band and moves into the cell 300-1, the selected frequency band (free frequency band) is switched. As shown, the power in the selected frequency band (free frequency band) increases.

  The processing performed by each component provided in the above-described radio base stations 100-1 to 100-2 may be performed by a logic circuit produced according to the purpose. Further, the program describing the processing contents is recorded on a recording medium readable by the radio base stations 100-1 to 100-2, and the program recorded on the recording medium is stored in the radio base stations 100-1 to 100-2. It may be read and executed. The recording media readable by the radio base stations 100-1 to 100-2 include transferable recording media such as a floppy (registered trademark) disk, a magneto-optical disk, a DVD, and a CD, as well as the radio base station 100-1. ˜100-2 indicates a memory such as ROM and RAM, HDD, and the like. The program recorded on the recording medium is read by a CPU (not shown) provided in the radio base stations 100-1 to 100-2, and the same processing as described above is performed under the control of the CPU. Here, the CPU operates as a computer that executes a program read from a recording medium on which the program is recorded.

100-1 to 100-2 Radio base station 101 Movement detection unit 102 Handover execution unit 103 Scan unit 104 Selection unit 105 Radio interface unit 106 Host device interface unit 200 Radio terminal 300-1 to 300-2 Cell

Claims (6)

A wireless base station that performs wireless communication with a wireless terminal,
A movement detection unit for detecting that the wireless terminal has moved into a cell covered by the wireless base station;
When the movement detection unit detects that the wireless terminal has moved into a cell covered by the wireless base station, a handover process is performed using a predetermined specific frequency band, and the specific frequency band is A handover execution unit for performing wireless communication with the wireless terminal using,
When the movement detection unit detects that the wireless terminal has moved into a cell covered by the wireless base station, all the frequency bands that can be used for the wireless communication within the cell covered by the wireless base station A scan unit that scans and detects a frequency band used by a wireless terminal other than the wireless terminal present in the cell;
A frequency band used for wireless communication with the wireless terminal is selected from frequency bands other than the frequency band detected by the scan unit among the entire frequency bands, and the frequency band used for the wireless communication is specified. A radio base station comprising: a selection unit that switches from a frequency band to the selected frequency band. In the radio base station according to claim 1,
The scan unit detects the frequency band using cognitive radio communication technology,
The radio base station, wherein the selection unit selects the frequency band using the cognitive radio communication technology. A handover method executed by a wireless terminal moving between a plurality of cells respectively covered by a plurality of wireless base stations,
Detecting movement of the wireless terminal between the cells;
When detecting movement between the cells of the wireless terminal, a step of performing a handover process using a preset specific frequency band;
Performing wireless communication between the wireless terminal and a wireless base station covering a cell in which the wireless terminal exists using the specific frequency band after performing the handover process;
When the movement of the wireless terminal between the cells is detected, the entire frequency band that can be used for wireless communication is scanned in the cell in which the wireless terminal exists, and the wireless terminal other than the wireless terminal existing in the cell A scanning step to detect the frequency band being used;
A selection step of selecting a frequency band used for radio communication between the radio terminal and a radio base station covering the cell from frequency bands other than the detected frequency band out of the total frequency bands;
And a step of switching a frequency band used for the wireless communication from the specific frequency band to the selected frequency band after selecting the frequency band. The handover method according to claim 3, wherein
The scanning step detects the frequency band using cognitive radio communication technology,
In the handover method, the selection step includes selecting the frequency band using the cognitive radio communication technology. To a wireless base station that performs wireless communication with wireless terminals,
A procedure for detecting that the wireless terminal has moved into a cell covered by the wireless base station;
When it is detected that the wireless terminal has moved into a cell covered by the wireless base station, a handover process is performed using a preset specific frequency band, and the wireless terminal is connected to the wireless terminal using the specific frequency band. Procedure for wireless communication between
When it is detected that the wireless terminal has moved into the cell covered by the wireless base station, the entire frequency band that can be used for the wireless communication is scanned in the cell covered by the wireless base station. A scanning procedure for detecting a frequency band used by a wireless terminal other than the wireless terminal existing in
A selection procedure for selecting a frequency band to be used for wireless communication with the wireless terminal from a frequency band other than the detected frequency band among the total frequency bands;
A program for executing a procedure of switching a frequency band used for the wireless communication from the specific frequency band to the selected frequency band after selecting the frequency band. The program according to claim 5,
The scanning procedure detects the frequency band using cognitive radio communication technology,
The selection procedure includes selecting the frequency band using the cognitive radio communication technology.

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