JP4319676B2 - Wireless communication terminal and wireless communication method - Google Patents

Description

  The present invention relates to a wireless communication terminal and a wireless communication method.

Conventionally, a wireless communication terminal such as a mobile phone is connected to the Internet via an access point (AP) serving as a base station, and transmits / receives data such as VoIP (Voice over IP) communication with other wireless communication terminals. Do. When a wireless communication terminal moves from one point to another point, the terminal performs a so-called handover (Hand Over) in which the access point connected so far is switched to an access point with higher communication quality. Prior to this handover, the wireless communication terminal performs a so-called scan (search) that searches for an access point that can communicate with the terminal itself (see, for example, Patent Document 1).
JP 2004-180297 A

  The wireless communication terminal consumes power by performing the scan and the handover. When a wireless communication terminal moves frequently, scanning and handover associated with the movement are frequently performed, and the power consumed by the terminal increases.

  On the other hand, it is difficult to give a constant power supply to a wireless communication terminal such as a cellular phone, for example, to be supplied to a personal computer. In addition, wireless communication terminals tend to be downsized and are often limited by battery size, and there is a limit to the amount of power that can be secured.

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to provide a wireless communication terminal and a wireless communication method capable of reducing power consumption when the wireless communication terminal moves.

In order to solve the above-described problem, a wireless communication terminal of the present invention includes a communication quality measurement unit that measures communication quality in wireless communication between an access point and the terminal, and another access point that can communicate with the terminal. A scan execution unit that performs a scan for searching, and the scan execution unit scans at each first scan interval when the communication quality measured by the communication quality measurement unit is less than the first threshold. And when the communication quality measured by the communication quality measuring means is less than the second threshold lower than the first threshold, the scan is performed at each second scan interval shorter than the first scan interval, and the scan is executed. When the means searches for another access point communicable with its own terminal by scanning performed at each first scan interval, information for identifying the access point is stored. A storage means and a handover execution means for performing a handover when the communication quality measured by the communication quality measurement means is less than the second threshold, and the handover execution means is configured to store information in the storage means. In addition, the handover is performed to the access point specified by the information, and when the information is not stored in the storage unit, the scan execution unit performs the handover to the access point searched by the scan performed every second scan interval. It is characterized by that.

The wireless communication method of the present invention is a wireless communication method in a wireless communication terminal that performs wireless communication with an access point, and the communication quality measuring means measures the communication quality in wireless communication between the access point and the terminal itself. The communication quality measurement step and the scan execution means include a scan execution step that performs scanning to search for another access point that can communicate with the own terminal. In the scan execution step, the measurement is performed by the communication quality measurement step. When the communication quality is less than the first threshold, the scan execution means performs a scan at each first scan interval, and the second communication quality measured by the communication quality measurement step is lower than the first threshold. When the scan execution means falls below the threshold value, the scan execution means scans every second scan interval shorter than the first scan interval. There rows down at scan execution step, the performed scan every first scanning interval, when the other access point capable of communicating with the own terminal has been searched, the storage means, identifying the access point A storage step for storing information to be performed, and a handover execution step in which a handover execution unit performs a handover when the communication quality measured in the communication quality measurement step is less than a second threshold, When the information is stored in the storing step, the handover executing means performs a handover to the access point specified by the information, and when the information is not stored in the storing step, the handover executing means Search by scanning performed at every second scanning interval in the scanning execution step. And performing a handover to the access point.

  According to such a wireless communication terminal and wireless communication method of the present invention, when the communication quality between the access point and the own terminal becomes less than the first threshold, the scan execution means is set for each first scan interval. To scan. In addition, when the communication quality is less than a second threshold value that is lower than the first threshold value, the scan execution unit performs a scan every second scan interval that is shorter than the first scan interval.

  Thus, according to the present invention, the frequency of scanning can be adjusted according to the communication status between the access point and the terminal itself. That is, after the communication quality becomes less than the second threshold, frequent scanning is performed at every second scan interval, and an access point that can communicate with the own terminal can be searched quickly. In addition, until the communication quality becomes less than the second threshold, the number of scans can be reduced by performing the scan at each first scan interval, and power consumption is reduced by the reduced amount. Can be reduced. Therefore, it is possible to suppress unnecessary power consumption due to unnecessary scanning, such as preventing frequent scanning when the communication quality is good.

Further , according to these inventions, when another access point that can communicate with the own terminal is searched by a scan performed at each first scan interval, the access point is identified without being immediately executed. Store information to be used. Thus, by not performing the handover until the communication quality becomes less than the second threshold, it is possible to reduce the power consumption by the amount of the handover that has not been performed. Then, when the handover execution means executes handover due to the communication quality being less than the second threshold, if the information is stored, it is specified by the information without performing another scan. Handover to a certain access point. Therefore, power consumption can be reduced by the amount of scanning that has not been performed.

  In the wireless communication terminal, the communication quality measuring unit measures the communication quality based on the intensity of the radio wave received from the access point. The wireless communication terminal of the present invention is particularly useful when the intensity of radio waves received from an access point is used as a measure of communication quality.

  According to the present invention, power consumption can be reduced when a wireless communication terminal moves.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a wireless communication terminal and a wireless communication method according to the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  First, a configuration of a wireless communication system 1 as an embodiment including the wireless communication terminal of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a wireless communication system 1. As shown in FIG. 1, the wireless communication system 1 includes a mobile phone 10 (wireless communication terminal) and a plurality of access points 20a to 20d. Hereinafter, the plurality of access points 20a to 20d are collectively referred to as “access point 20”. The mobile phone 10 and the access point 20 are configured to be able to communicate with each other via the communication network 30. The communication network 30 is a wireless LAN for performing VoIP communication, for example.

  The mobile phone 10 in the present embodiment is a communication terminal used when performing VoIP communication, and may be any wireless communication terminal as long as the terminal is connected to the access point 20 by wireless communication. FIG. 2 is a hardware configuration diagram of the mobile phone 10. As shown in FIG. 2, the cellular phone 10 physically includes a CPU 41, a ROM 42 and a RAM 43 as main storage devices, an operation unit 44 such as operation buttons, a display 45 such as an LCD (Liquid Crystal Display), and other terminals. A wireless communication unit 46 that is a device that wirelessly transmits and receives data to and from the device, an auxiliary storage device 47 such as a memory device, and the like. A storage device such as the ROM 42 or the RAM 43 stores a profile of an access point that performs wireless communication with the terminal itself. The profile includes a group name for identifying a wireless LAN network such as ESSID (Extended Service Set IDentifier), setting information for connecting to the communication network 30, and the like. Each function of the cellular phone 10 to be described later is configured such that predetermined software is read on the hardware such as the CPU 41 and the RAM 43 shown in FIG. 2 to control the operation unit 44, the display 45, and the wireless communication unit 46 under the control of the CPU 41. This is realized by reading and writing data in the RAM 43 and the auxiliary storage device 47.

  Returning to FIG. 1, the functional configuration of the mobile phone 10 will be described. As shown in FIG. 1, the mobile phone 10 includes a communication quality measurement unit 110 (communication quality measurement unit), a scan execution unit 120 (scan execution unit), a handover execution unit 130 (handover execution unit), and a storage unit 140 (storage). Means).

  The communication quality measuring unit 110 measures communication quality in wireless communication between the access point 20 and the own terminal. Specifically, the communication quality measuring unit 110 receives a beacon signal periodically transmitted from an access point (hereinafter referred to as “peripheral AP”) installed in the vicinity of the own terminal, Measure the radio field intensity. The measured radio wave intensity is used as a scale representing communication quality. In addition to the access points (hereinafter referred to as “connected APs”) that are currently connected to the local AP and the wireless link to the peripheral AP, the access points (hereinafter referred to as “connected APs”) that are not currently connected to the local terminal and the wireless link. "Non-connected AP"). The communication quality measurement unit 110 outputs information indicating the communication quality with the connected AP to the scan execution unit 120 and the handover execution unit 130. In addition, the communication quality measuring unit 110 describes information specifying a non-connected AP (hereinafter referred to as “detected AP”) whose communication quality is higher than a predetermined threshold in a profile and stores the information in the storage device. As will be described later, the detection AP is an access point to be scanned, regardless of whether it is singular or plural.

  The scan execution unit 120 performs a scan in order to search for other access points that can communicate with the own terminal in addition to the connected AP. Specifically, the scan execution unit 120 determines whether or not a radio link can be connected in the future to the detected AP specified from the information described in the profile. The scan execution unit 120 selects an access point that is determined to be connectable to a wireless link in the future as an access point (hereinafter referred to as “target AP”) that is a candidate for handover described later. In the present embodiment, the above determination is made by comparing the radio wave intensity of a signal transmitted from the access point to be determined with a predetermined threshold (hereinafter referred to as “target threshold”). That is, the scan execution unit 120 selects an access point whose radio wave intensity is equal to or higher than the target threshold as the target AP. When there are a plurality of access points whose radio field intensity is equal to or higher than the target threshold, the scan execution unit 120 selects an access point having the highest radio field intensity as the target AP from among the plurality of access points.

  Also, the scan execution unit 120 receives information indicating the communication quality of the connected AP from the communication quality measurement unit 110, and adjusts the frequency of executing the above-described scan according to the communication quality. FIG. 3 is a diagram for explaining the function of the scan execution unit 120. In FIG. 3, the strength of the radio wave received from the connected AP becomes weaker as the movable mobile phone 10 moves away from the connected AP that has been connected. The scan execution unit 120 adjusts the number of scans according to the intensity of the radio wave. That is, when the intensity of the radio wave received from the connected AP is equal to or higher than the scan threshold (first threshold), the scan execution unit 120 does not perform scanning. This case corresponds to a case where it is not necessary to consider handing over to another access point because the communication quality with the connected AP is good.

  In addition, the scan execution unit 120 scans at the first scan interval when the strength of the radio wave received from the connected AP is less than the scan threshold and greater than or equal to the handover threshold (second threshold). Hereinafter, the “handover threshold” is also referred to as “HO threshold”. Further, the scan threshold corresponds to a radio wave intensity stronger than the HO threshold. The above case corresponds to the case where the communication quality with the connected AP is not good, and the search for a candidate access point is started in consideration of handing over to another access point. Hereinafter, such a situation is referred to as a scan phase.

  In addition, the scan execution unit 120 scans at the second scan interval when the intensity of the radio wave received from the connected AP is less than the HO threshold. This case corresponds to a case where it is preferable to execute handover to another access point because the communication quality with the connected AP has deteriorated. Hereinafter, such a situation is referred to as a HO phase. The second scan interval (for example, Y seconds) is preferably shorter than the first scan interval (for example, X seconds) (Y <X), that is, the HO phase is preferably scanned more frequently than the scan phase. This is because, since the communication quality in the HO phase is worse than the communication quality in the scan phase, for example, when the target AP is not yet determined, it is preferable to select the target AP as soon as possible. Note that when the intensity of the radio wave received from the connected AP further deteriorates and the so-called out-of-service state is entered, the scan execution unit 120 does not perform scanning.

  When the target AP is selected by the scan executed at the first scan interval, the scan execution unit 120 outputs information specifying the selected target AP to the storage unit 140, and the storage unit 140 stores the information. To do. Further, when the target AP is selected by the scan executed at the second scan interval, the scan execution unit 120 outputs information for specifying the selected target AP to the handover execution unit 130.

  The handover executing unit 130 performs handover when information indicating the communication quality with the connected AP is input from the communication quality measuring unit 110 and the communication quality becomes less than the HO threshold. When executing a handover, the handover execution unit 130 first refers to the storage unit 140 and confirms whether information for specifying the target AP is stored in the storage unit 140. When information for specifying the target AP is stored in the storage unit 140, the handover execution unit 130 performs handover to the target AP. In other words, in this case, the scan execution unit 120 does not scan every second scan interval prior to the handover. On the other hand, when the information specifying the target AP is not stored in the storage unit 140, the handover execution unit 130 receives the information specifying the target AP from the scan execution unit 120, and performs handover to the target AP. Do. That is, in this case, the scan is executed at every second scan interval by the scan execution unit 120 prior to the handover.

  Next, an operation (wireless communication method) performed by the wireless communication system 1 will be described with reference to FIG. FIG. 4 is a flowchart showing the operation of the wireless communication system 1.

  The communication quality measuring unit 110 receives beacon signals periodically transmitted from peripheral APs including connected APs and non-connected APs, and between each peripheral AP and its own terminal based on the radio wave intensity of the beacon signals. Is measured (step S101). In step S101, an unconnected AP whose communication quality is higher than a predetermined threshold is registered in the profile as a detected AP. The measurement of the communication quality in step S101 is always performed at regular intervals, for example.

  The handover execution unit 130 determines whether or not the communication quality with the connected AP measured in step S101 is less than the HO threshold (step S102).

  If it is determined in step S102 that the communication quality is not less than the HO threshold, the scan execution unit 120 determines whether the communication quality is less than the scan threshold (step S103). If it is determined in step S103 that the communication quality is not less than the scan threshold, the process flow proceeds to step S101. This case corresponds to the case where the communication quality with the connected AP is good in FIG. 3 described above.

  On the other hand, if it is determined in step S103 that the communication quality is less than the scan threshold, the scan execution unit 120 scans at the first scan interval. At this time, the detected AP registered in the profile in step S101 becomes an access point to be scanned (step S104).

  In step S104, when an access point whose radio wave intensity is equal to or higher than the target threshold is detected (step S105: YES), the access point is selected as the target AP. Then, information specifying the selected target AP is stored in the storage unit 140 (step S106). On the other hand, when an access point whose radio wave intensity is equal to or higher than the target threshold is not detected in step S104 (step S105: NO), the process proceeds to step S104.

  The situation in steps S104 to S106 corresponds to the scan phase in FIG. 3 described above.

  On the other hand, when it is determined in step S102 that the communication quality is less than the HO threshold, it is determined whether information for specifying the target AP is stored in the storage unit 140 (step S107).

  In step S107, when the information for specifying the target AP is not stored in the storage unit 140, the scan execution unit 120 scans at the second scan interval. Since the communication quality has deteriorated and the target AP has not yet been selected, it is preferable to frequently scan at a second scan interval that is shorter than the first scan interval.

  If an access point whose radio field intensity is equal to or higher than the target threshold is detected in step S108 (step S109: YES), the access point is selected as a target AP (step S110). Then, the handover execution unit 130 executes a handover to the target AP selected in Step S110 (Step S111). On the other hand, when an access point whose radio wave intensity is equal to or higher than the target threshold is not detected in step S108 (step S109: NO), the process proceeds to step S108.

  On the other hand, when information for specifying the target AP is stored in the storage unit 140 in step S107, the handover execution unit 130 executes handover to the target AP (step S111).

  The situation in step S107 to step S111 corresponds to the HO phase in FIG. 3 described above.

  Then, the effect | action and effect of the radio | wireless communications system 1 concerning this embodiment are demonstrated. According to the wireless communication system 1 of the present embodiment, when the communication quality between the connected AP and the own terminal is less than the scan threshold (however, greater than or equal to the HO threshold), the scan execution unit 120 performs the first scan interval. A scan is performed every (for example, X seconds). Further, when the communication quality is less than the HO threshold, the scan execution unit 120 scans at a second scan interval (for example, Y seconds) different from the first scan interval. Thus, according to the present embodiment, the frequency of scanning can be adjusted according to the communication status between the connected AP and the own terminal. Therefore, for example, it is possible to prevent unnecessary power consumption due to unnecessary scanning, such as preventing frequent scanning (for example, scanning every Y seconds) when communication quality is good (for example, scanning phase). it can.

  In addition, according to the present embodiment, when a target AP is searched by a scan performed at each first scan interval, information for specifying the target AP is stored in the storage unit 140 without performing a handover immediately. To do. In this way, by not performing the handover until the communication quality becomes less than the second threshold, it is possible to reduce the power consumption by the amount of the handover that has not been performed. Then, when the handover execution unit 130 executes handover due to the communication quality being less than the HO threshold, if the information is stored, it is specified by the information without performing another scan. Handover can be performed to the target AP. Therefore, power consumption can be reduced by the amount of scanning that has not been performed.

  According to the present embodiment, the second scan interval is shorter than the first scan interval. As a result, when the communication quality is less than the HO threshold and handover is executed, more frequent scanning is performed, and the target AP can be searched faster. Further, before the communication quality becomes less than the HO threshold, the number of scans can be reduced, and power consumption can be reduced by the reduced amount.

  Further, according to the present embodiment, the intensity of the radio wave received from the access point is used as a measure of communication quality. This is because the intensity of the received radio wave is optimal for representing the communication quality with the access point.

  As mentioned above, although preferred embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to the said embodiment.

  For example, in the above embodiment, the intensity of the received radio wave is directly measured. However, the present invention is not limited to this. For example, the intensity of the received radio wave is indirectly calculated by back-calculating the intensity of noise included in the received radio wave. It may be measured.

1 is a schematic configuration diagram of a wireless communication system 1. FIG. FIG. 2 is a hardware configuration diagram of the mobile phone 10. FIG. 5 is a diagram for explaining functions of a scan execution unit 120. 3 is a flowchart showing the operation of the wireless communication system 1;

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wireless communication system, 10 ... Mobile phone, 20, 20a, 20b, 20c, 20d ... Access point, 110 ... Communication quality measurement part, 120 ... Scan execution part, 130 ... Handover execution part, 140 ... Storage part, 30 ... Communication network.

Claims (3)

Communication quality measuring means for measuring communication quality in wireless communication between the access point and the own terminal;
Scanning execution means for performing scanning in order to search for another access point capable of communicating with the own terminal,
The scan execution means includes
When the communication quality measured by the communication quality measuring unit is less than a first threshold, the scan is performed at each first scan interval,
When said communication quality communication quality measuring means has measured is less than the first lower threshold value of the second threshold value, for each of the shorter than the first scanning interval second scan interval, row physician the scan ,
A storage unit that stores information for identifying the access point when the scan execution unit searches for another access point that can communicate with the terminal by a scan performed at each of the first scan intervals;
A handover execution unit for performing a handover when the communication quality measured by the communication quality measurement unit is less than the second threshold;
Further comprising
The handover execution means includes
When the information is stored in the storage means, a handover is performed to the access point specified by the information,
A radio communication terminal characterized in that, when the information is not stored in the storage means, the scan execution means performs a handover to an access point searched by a scan performed at each second scan interval . The communication quality measuring means, on the basis of the strength of the received radio wave from the access point, according to claim 1 Symbol placement of the wireless communication terminal and measuring the communication quality. A wireless communication method in a wireless communication terminal that performs wireless communication with an access point,
A communication quality measuring means for measuring a communication quality in wireless communication between the access point and the own terminal; and
A scan execution means comprising a scan execution step of performing a scan to search for another access point capable of communicating with the own terminal;
In the scan execution step,
When the communication quality the measured by the communication quality measuring step is less than the first threshold value, the scan execution unit, each first scan interval, it has row the scan,
When the communication quality measured in the communication quality measurement step is less than a second threshold value that is lower than the first threshold value, the scan execution unit is configured to make every second scan interval shorter than the first scan interval. To perform the scan,
In the scan execution step, when another access point communicable with the terminal is searched by scanning performed at each first scan interval, the storage means stores information for identifying the access point. A storage step for storing;
A handover execution step in which a handover execution means performs a handover when the communication quality measured in the communication quality measurement step is less than the second threshold;
Further comprising
In the handover execution step,
When the information is stored in the storing step, the handover execution means performs a handover to the access point specified by the information,
When the information is not stored in the storing step, the handover executing means performs a handover to an access point searched by a scan performed at the second scan interval in the scan executing step. A wireless communication method characterized by the above.

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