JP2008148136A - Radio communication terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption and to prolong the service life of a battery by preventing an unnecessary scan operation from being performed in a situation where it is hopeless that a connectable base station can be detected. <P>SOLUTION: In the situation where a connectable access point can not be detected, if an access point detected by scan is not different from that of the last scan and the variation of a received signal strength from the detected access point is within an allowable range x, it is judged that a present terminal STA1 is stopped. Only the access point of the highest received signal strength is set as a tracking target and in subsequent scan intervals, only scan to a radio channel of the only one access point set as the tracking target is performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless communication terminal including a communication interface for connecting to a wireless LAN (Local Area Network).

  In recent years, with the widespread use of wireless LAN, various wireless communication terminals equipped with a wireless LAN communication interface have appeared. For example, a notebook personal computer with a built-in wireless LAN communication interface, a dual-mode mobile phone with a wireless LAN communication interface in addition to a mobile phone communication interface, a PDA (Personal Digital Assistant), etc. That is it. If this type of wireless communication terminal is used, large-capacity data communication can be performed in an area where a wireless LAN is provided, such as a business district or a shopping street in an urban area.

  By the way, when this type of wireless communication terminal uses a wireless LAN, it is necessary to scan a wireless LAN access point to detect a communicable access point and make a connection request to the detected access point. is there. Therefore, a conventional general wireless communication terminal periodically scans all wireless channels used by the access point in preparation for generation of a communication request.

On the other hand, as another scanning method, a method is proposed in which active scanning and passive scanning are selectively used according to the situation of the wireless communication terminal (see, for example, Patent Document 1). In the active scan, a search probe packet is transmitted from a wireless communication terminal to an access point, and the access point detects a communicable access point by responding to the probe packet. On the other hand, the passive scan is to detect an access point capable of communication by receiving broadcast information periodically transmitted by the access point for a certain period. In the above proposal, the scan method is adaptively switched to the active scan or the passive scan with reference to the received signal quality of the radio signal transmitted from the access point.
JP 2005-012539 A

  However, in the conventional general scanning method described above, the access point is scanned regularly and always in the same procedure without particularly considering the situation of the wireless communication terminal. For this reason, for example, even when the wireless communication terminal is stationary at a position where connection permission cannot be obtained from any of the nearby access points, there is no possibility of detecting a connectable access point. Instead, scanning for all wireless channels is repeated. For this reason, the power consumption of the wireless communication terminal increases and the battery life is shortened, that is, the standby time and continuous communication time of the wireless communication terminal are shortened.

  On the other hand, in the proposal described in Japanese Patent Laid-Open No. 2005-012539, the active scan and the passive scan are used appropriately, so that an effect of reducing power consumption can be expected as compared with the above general scanning method. However, even in this proposal, even when it is unlikely that the wireless communication terminal can detect a connectable access point, scanning for all wireless channels is executed by active scanning or passive scanning. For this reason, the power consumption of the wireless communication terminal is still large, leading to a short battery life.

  The present invention has been made paying attention to the above circumstances, and its purpose is to prevent unnecessary scanning operations from being performed when it is unlikely that a connectable base station can be detected. It is an object of the present invention to provide a wireless communication terminal that can reduce power consumption and extend battery life.

In order to achieve the above object, one aspect of the present invention is that a plurality of base stations are used in a service area in which a plurality of base stations are distributed, and a plurality of radio channels used by the base stations are scanned periodically. In a wireless communication terminal with a function to detect a connectable base station based on the result,
In association with the identification information of the plurality of base stations, information indicating the radio channel used by the base station, information indicating whether or not the base station can be connected, and whether or not the base station is to be tracked for communication quality Storage means for storing tracking information indicating whether or not there is, first determination means for determining the presence or absence of a connectable base station based on information indicating whether or not connection is possible, stored in the storage means, and the storage Based on the radio channel information and tracking information stored in the means, the radio channel used by the base station whose communication quality is to be tracked is periodically scanned to determine the communication quality for each base station. Detection means for detecting, a second determination for calculating the time variation of the detected communication quality, and determining whether the calculated time variation of the communication quality is within a preset allowable range Means and When it is determined by the first determination means that there is no connectable base station and the second determination means determines that the amount of time variation in communication quality is within an allowable range, the storage means Means for selecting a smaller number of base stations than the number of base stations from among the base stations in which identification information is stored, and changing the tracking information so that only the selected base stations are subject to tracking of communication quality. Is.

  Therefore, in a situation where a connectable base station cannot be detected, if it is determined that the time variation amount of the communication quality of the base station is within an allowable range, that is, if it is determined that the terminal is stationary, The base stations whose communication quality is to be tracked are limited to a small number of base stations, and scanning is performed only on the radio channels of the limited base stations. For this reason, the number of radio channels to be scanned is greatly reduced, thereby greatly reducing the power consumption consumed for scanning and extending the battery life.

  In other words, according to the present invention, when there is no possibility that a connectable base station can be detected, unnecessary scanning operation is not performed, thereby reducing power consumption and extending battery life. An enabled wireless communication terminal can be provided.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of a radio communication terminal according to the present invention. This wireless communication terminal is a dedicated terminal for a wireless local area network (LAN), and includes a wireless unit 1 having an antenna 11, a control module 2, and an input / output interface 3. The wireless unit 1 performs wireless signal transmission / reception operations related to search, authentication, connection, and data communication of wireless LAN access points based on the IEEE 802.11 standard under the control of the control unit.

  The control unit 2 includes a main control module 21, an access point scan control module 22, an access point connection control module 23, an access point tracking control module 24, and a scan result acquisition control module 25 as control functions according to the present invention. And a memory module 26 and a scan interval timer 27.

  The memory module 26 uses a hard disk or a NAND flash memory as a storage medium, and stores an application program for realizing the functions of the control modules 21 to 25 and an access point management table 261. The access point management table 261 is used to store information representing access point scan results. The information indicating the scan result includes an access point name, a radio channel number used by the access point, a received signal strength of a radio signal transmitted from the access point, a determination result of connection possibility, a tracking target, The access point management table 261 is provided with fields for storing these information elements.

  The scan interval timer 27 has a function of notifying the main control module 21 and the access point scan control module 22 of a timeout signal every time a preset scan interval elapses. The start and stop of the time measuring operation in the scan interval timer 27 is controlled by the main control module 21 in accordance with the operation state of the wireless communication terminal, for example, the communication state, the connection state, and the out-of-service state. The scan interval time is also variably set by the main control module 21.

  The access point scan control module 22 includes a communication quality comparison unit 221, a scan channel selection unit 222, and a scan method selection unit 223. The communication quality comparison unit 221 determines the received signal level when the access point is detected, the current received signal level, and the current received signal level for the access point that has tracking “present” in the information stored in the access point management table 261. Are compared, and it is determined whether or not the comparison result is within a preset allowable range. The received signal level at the present time is detected by the access point tracking control module 24.

  The scan channel selection unit 222 refers to the tracking presence / absence field of the access point management table 261 and searches for an access point with tracking “present”. The access channel with tracking “present” is used as a radio channel to be scanned with reference to the channel number used. On the other hand, when an access point with tracking “present” cannot be searched, all available radio channels are set as scan targets. Further, when the access point is not registered in the access point management table 261, that is, when there is no detected access point, a usable radio channel number is generated.

  The scanning method selection unit 223 selects a wireless channel number to be scanned from wireless channels that can be used by its own wireless communication terminal. The selection of the radio channel number to be scanned is performed based on the comparison result of the communication quality comparison unit 221 and the selection result of the scan channel selection unit 223.

  The access point connection control module 23 executes control procedures necessary for connection, such as authentication and connection request for the access point detected by the access point scan control module 22, and determines whether connection is possible and whether there is tracking. The result is stored in the access point management table 261. The access point tracking control module 24 executes a control procedure for tracking with the access point according to the instruction of the access point connection control module 23.

  The scan result acquisition control module 25 generates information representing an access point scan result in accordance with the instruction from the access point scan control module 22 and stores this information in the access point management table 261. As described above, the information indicating the scan result includes the access point name, the radio channel number used by the access point, the received signal strength of the radio signal transmitted from the access point, and the determination as to whether or not connection is possible. It consists of a result and a determination result as to whether or not to be a tracking target.

  The main control module 21 controls the overall operation of the wireless communication terminal. The functions of the control modules 22 to 25 including the main control module 21 are realized by causing a CPU (Central Processing Unit) to execute an application program stored in the memory module 26.

The input / output interface unit 3 is provided with an input device 31 and a display device 32. The input device 31 includes, for example, a keyboard and a group of function keys, and is used for a user to input various commands and sentences. The display device 32 includes, for example, a liquid crystal display, and is used to display input information from the input device 31, pictogram information indicating the operation state of the terminal, and transmission / reception data.
In addition, although not shown, the wireless communication terminal includes a power supply unit that uses a battery as a power supply, and the wireless unit 1 and the control unit 2 operate by an operation power output generated by the power supply unit.

Next, the operation of the wireless communication terminal configured as described above will be described. 2 to 5 are flowcharts showing the control procedure and control contents of the control unit 2.
When the power is turned on, the control unit 2 of the wireless communication terminal STA1 first initializes the access point management table 261 in step S21 and initializes the channel number variable N to be scanned. Next, the control unit 2 searches the access point monitoring table 261 in step S22, and determines whether or not there is one tracking target access point in step S23 based on the search result. If the access point to be tracked is not stored in the access point management table 261 as immediately after the power is turned on, the control unit 2 executes the scanning process as follows for all available radio channels.

  That is, first, the Nth usable channel number Ch is selected in step S29, and the scanning process is performed in step S30 on the radio channel represented by this channel number Ch. In step S31, the access point ID and received signal level (received signal strength) detected by the scanning process are stored in the access point management table 261 together with the selected channel number. At the same time, in step S32, the tracking determination result of the detected access point is set to “present”.

When the scan process for one channel and the scan result storage process are completed, the control unit 2 increments the channel number N (N = N + 1) in step S33, and then performs the scan process for all available radio channels. It is determined in step S34 whether or not the processing has been completed. If there is still a radio channel that has not been scanned, the process returns to step S29, and the scan process and the scan result storage process are executed for the radio channel corresponding to the channel number N after the increment.
Thereafter, similarly, scan processing is executed for all usable radio channels, and information representing the scan results is sequentially stored in the access point management table 261.

  When the scan process is completed for all the available radio channels, the control unit 2 proceeds to step S35 shown in FIG. 3 and determines whether or not a new access point is detected by the scan process. If a new access point is detected as a result of this determination, connection processing for the detected new access point is started in step S36, and it is determined in step S37 whether or not the connection has failed. For example, it is assumed that the new access point is an access point other than a private network, or an access point operated by a non-subscribed wireless LAN operator. In this case, since the connection is rejected by the access point, the control unit 2 sets information indicating whether or not the access point can be connected to “No”, and then sets the tracking targets of all detected access points to “ Set to “Yes”.

The control unit 2 clears the scan counter to “0” in step S39, and then executes the scan interval timing process as follows. FIG. 4 is a flowchart showing the procedure and processing contents of this timing process.
That is, the control unit 2 sets a time measurement in the scan interval timer 27 and starts a time measurement operation, and monitors the expiration of the time measurement of the scan interval timer 27 in step S46. When the time measured by the scan interval timer 27 expires, the process returns to step S22 shown in FIG. 2, and the control operation in the next scan interval is started.

  In the next scan interval, the control unit 2 searches the access point management table 261 in step S22, and determines whether there is one tracking target access point in step S23 based on the result. If the access point to be tracked is stored in the access point management table 261 and there is only one, the process proceeds to step S24 to select a channel number for searching for the access point to be tracked. Scan processing is executed in step S25 for the radio channel corresponding to the selected channel number. In step S26, the name and received signal level (received signal strength) of the access point detected by the scan process are stored in the access point management table 261 together with the selected channel number.

  When the scanning process for the tracking-target access point is completed, the control unit 2 determines whether or not a new access point is detected in step S35 of FIG. And when a new access point is not detected, it transfers to step S40. In this step S40, with reference to the information stored in the access point management table 261, for the access point with tracking “present”, the received signal level when the access point is detected and the current received signal Compare the level. Then, it is determined in step S41 whether or not the fluctuation difference is within a preset allowable range. If the fluctuation difference exceeds the allowable range, it is determined that the wireless communication terminal is moving, and step S38 is performed. Migrate to Then, the tracking target of all detected access points is set to “present” in step S38, and the scan counter is cleared to “0” in step S39. Then, the process proceeds to the scan interval timing process shown in FIG. .

  On the other hand, it is assumed that the variation difference is within the allowable range as a result of the determination in step S41. In this case, the control unit 2 determines that the wireless communication terminal is at a low speed even if it is stationary or moving, and proceeds to step S42. Then, after the scan counter is incremented (+1) in step S42, it is determined in step S43 whether or not the value of the scan counter has reached “2”. If the value of the scan counter has not reached “2” as a result of this determination, the scan interval timing process shown in FIG. 4 is shifted to.

  On the other hand, when the value of the scan counter reaches “2”, the control unit 2 proceeds to step S44, and the received signal strength among the access points stored in the access point management table 261 is high. Only the highest access point is set as “present” as a tracking target, and all other access points are excluded from the tracking target. Then, the process proceeds to the scan interval timing process shown in FIG. Therefore, in the next scan interval, the control unit 2 executes the radio channel scan process for only the access point with the highest received signal strength set to “present” as the tracking target in steps S22 to S26 of FIG. To do.

  On the other hand, when a new access point is detected in step S35, the control unit 2 tries to connect to the new access point in step S36. In step S37, it is determined whether or not the connection has failed. If the connection fails, information indicating that the connection has been rejected is stored in the access point management table 261. Then, the process proceeds to step S38, where information indicating whether or not all detected access points stored in the access point management table 261 are tracking targets is set to “present”, and further, in step S39. After clearing the scan counter to “0”, the process proceeds to the scan interval timing process shown in FIG.

  On the other hand, it is assumed that the connection to the new access point is successful as a result of the above connection processing. In this case, the control unit 2 proceeds from step S37 to step S47 in FIG. 5 and executes control for monitoring the connection state as follows. That is, the control unit 2 performs processing for maintaining the connection state in step S47 while monitoring the received signal strength from the new access point that has been successfully connected in step S48. When the received signal strength from the connected access point falls below the reference value, the process proceeds to step S49, and information indicating whether or not all detected access points are tracking targets is set to “present”. To do. Then, the process shifts to a scan interval timing process shown in FIG. Therefore, in the next scan interval, the control unit 2 executes the scan process for all the radio channels for the access point in which the information indicating whether or not the tracking target is set to “present” in steps S22 to S26 of FIG. .

  Next, a specific example of an access point scan operation realized by the above control procedure and control content will be described. Here, for example, as shown in FIG. 6 and FIG. 7, in the service area where the wireless communication areas Z1 to Z4 are formed by the access points AP1 to AP4, the wireless communication terminal STA1 moves along the route R1 to the position P1. An example will be described in which the robot stops and then moves along the route R2 to reach the position P2. The wireless communication terminal STA1 will be described assuming that connection permission is not given from the access points AP1 to AP3 but connection permission is given from the access point AP4.

(1) Section from outside service area to position P0
When the wireless communication terminal STA1 is moving along the path R1 after power-on, the wireless communication terminal STA1 performs the scans for all the wireless channels Ch1 to Ch13 that can be used by the terminal at steps S29 to S34 at every scan interval. A scan is performed. As a result of the scan, when an access point whose received signal strength is equal to or higher than the threshold value is detected, the name of the detected access point and the received signal strength are stored in the access point management table 261 together with the radio channel number. . If a new access point is detected, connection to the new access point is attempted in step S36 and step S37 in the next scan interval. When the connection is rejected from the access point, information to that effect is stored in the access point management table 261. At the same time, “Yes” is stored in step S38 to set the access point as a tracking target.

  For example, when the wireless communication terminal STA1 reaches the position P0 in FIG. 6, the access points AP1 to AP3 are detected. Then, the name and received signal strength are stored in the access point management table 261 together with the radio channel number, for example, as shown in FIG. Further, whether or not connection is possible is determined for each of the access points AP1 to AP3, and the result is stored in the access point management table 261. For example, in this case, since none of the access points AP1 to AP3 permits the wireless communication terminal STA1 as a connection target, the access point management table 261 stores “x” indicating that connection is not possible as shown in FIG. At the same time, “Yes” (“◯”) is stored in the access point management table 261 as shown in FIG. 8 so that all detected access points AP1 to AP3 are to be tracked.

  Further, during the movement of the section, the received signal strength (received signal level) from the access points AP1 to AP3 in the wireless communication terminal STA1 varies as shown in FIG. 12, for example. At this time, the radio communication terminal STA1 compares the reception signal level detected last time in step S40 and step S41 with the reception signal level newly detected this time for each scan interval, and the fluctuation difference is set in a preset allowable range. It is determined whether or not it is within. If the fluctuation difference exceeds the allowable range, it is determined that the wireless communication terminal STA1 is moving, and the detected access points AP1 to AP3 stored in the access point management table 261 are shown in FIG. As shown, the tracking target is maintained as “present”.

  That is, when the wireless communication terminal STA1 is moving at a predetermined speed or more, the wireless communication terminal STA1 periodically sets each of the access points AP0 to AP3 in which the tracking target = “present” as illustrated in FIG. All wireless channel scans such as the scan at position P0 are repeated.

(2) Section from position P0 to position P1 and stationary state at position P1
When the wireless communication terminal STA1 reaches the position P0 and then decelerates and moves to the position P1, the distance in this section is short. In this section, the received signal strengths from the access points AP1 to AP3 are all as shown in FIG. The fluctuation amount is within the allowable range x. In this case, in the wireless communication terminal STA1, the value of the scan counter is incremented in step S42 and set to = 1, but since it has not reached 2, in the scan interval immediately after reaching the position P1, FIG. As shown in FIG. 4, all the access points AP1 to AP3 to be tracked are selected and scanning for all the radio channels is performed.

  However, when the wireless communication terminal STA1 is in a stationary state at the position P1, the access points detected by the scan remain unchanged from AP1 to AP3, and the fluctuation amount of the received signal strength from the detected access points AP1 to AP3 is Both are within the allowable range x. Therefore, the value of the scan counter is incremented to = 2. As a result, the information indicating the tracking target in the access point management table 261 is set to “present” (“◯”) as the tracking target for only the access point AP3 having the highest received signal strength as shown in FIG. All other access points AP1 and AP2 are excluded ("x") from the tracking target.

  Therefore, in the next and subsequent scan intervals, the wireless communication terminal STA1 selects only the access point AP3 in which the tracking target = “present” is set in steps S24 to S26. As a result, for example, FIG. As shown in b), only scanning for the wireless channel Ch11 is performed. Therefore, the power consumption of the radio communication terminal STA1 in the stationary state is reduced as compared with the conventional method that always scans all radio channels.

(3) Section from position P1 to position P2
The wireless communication terminal STA1 moves from the position P1 to the position P2 via the position P1.5 and the position P1.8. First, when moving to the position P1.5, the received signal strength detected by the scan of the wireless channel Ch11 of the access point AP3 performed at this time fluctuates from the received signal strength detected by the previous scan, and the fluctuation amount is allowable. Exceeding range x. Therefore, the wireless communication terminal STA1 determines that the terminal has resumed movement, and changes the information indicating the tracking targets of all access points AP1 to AP3 stored in the access point management table 261 to “present” in step S38. To do. Therefore, in the next scan interval, for example, all the access points AP1 to AP3 to be tracked are selected again, and the scan for all the radio channels is performed, as in the scan at the position P1.8 in FIG.

  As a result of the scan, when a new access point AP4 is detected as shown in FIG. 7, the wireless communication terminal STA1 attempts to connect to the new access point AP4 in step S36. Then, when the access point AP4 permits the connection, the connection state with the access point AP4 is maintained in step S47, and this state is continued as shown in FIG. 11C even after moving to the position P2. The

  Note that the management information in the access point management table 261 in the state of moving to the position P2 and standing still is set as shown in FIG. That is, the tracking state of the connected access point AP4 is set to “present”. In this state, the wireless communication terminal STA1 receives the beacon signal periodically transmitted by the access point AP4, measures the communication quality, and determines whether to execute a scan process for roaming or handover based on the measurement result Determine whether.

  As described above, in this embodiment, in a situation where a connectable access point cannot be detected, the access point detected by the scan is the same as in the previous scan, and the received signal strength from the detected access point is If both of the fluctuation amounts are within the allowable range x, it is determined that the wireless communication terminal STA1 is stationary. Only the access point with the highest received signal strength is set as a tracking target, and only the wireless channel of the only access point set as the tracking target is scanned in the subsequent scan interval.

Therefore, in a situation where a connectable access point cannot be detected and it is determined that the terminal is stationary, only one radio channel is scanned, and no other radio channel is scanned. . Therefore, the number of radio channels to be scanned is greatly reduced, thereby greatly reducing power consumption consumed for scanning and extending battery life.
Also, the access point with the highest received signal strength is selected even in the stationary state, and the scan for that one radio channel is maintained. For this reason, even when the wireless communication terminal STA1 resumes moving, this can be detected stably and reliably.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the access point with the highest received signal strength detected in the immediately preceding scan when it is determined that the state is stationary is selected, and the tracking state is set to “present” only for the selected access point. did. However, it is not always necessary to select an access point having the highest received signal strength, and an arbitrary access point may be selected from access points having a received signal strength equal to or higher than a threshold value.

  In the embodiment, scanning is performed for one radio channel at every scan interval in a state determined to be stationary. However, the present invention is not limited to this. When the length of the stationary state is measured and this length continues for a length corresponding to the predetermined number of scan intervals, a plurality of predetermined scans are performed thereafter. You may make it perform the scan with respect to the said one wireless channel once for every interval. In this way, it is possible to further reduce the number of scans in a state where the wireless communication terminal is stably stationary, thereby further reducing power consumption consumed for scanning.

  Furthermore, in the above-described embodiment, the wireless communication terminal used in the wireless LAN has been described as an example. However, the present invention can be applied to any system as long as the wireless system performs scanning in the same manner as the wireless LAN. In addition, the type and configuration of the wireless communication terminal, the scan control procedure and control contents of the base station, and the like can be variously modified without departing from the scope of the present invention.

  In short, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

It is a block diagram which shows one Embodiment of the radio | wireless communication terminal concerning this invention. The flowchart which shows the search control procedure in the radio | wireless communication terminal shown in FIG. 1, and the first half part of the content. 3 is a flowchart showing a search control procedure in the wireless communication terminal shown in FIG. 1 and the latter half of the control content. 3 is a flowchart showing a scan interval control routine in the wireless communication terminal shown in FIG. 1. 3 is a flowchart showing a control routine during connection in the wireless communication terminal shown in FIG. 1. It is a figure which shows the first half part of the movement path | route of the radio | wireless communication terminal shown in FIG. It is a figure which shows the second half part of the movement path | route of the radio | wireless communication terminal shown in FIG. It is a figure which shows the 1st state of the access point management table provided in the radio | wireless communication terminal shown in FIG. It is a figure which shows the 2nd state of the access point management table provided in the radio | wireless communication terminal shown in FIG. It is a figure which shows the 3rd state of the access point management table provided in the radio | wireless communication terminal shown in FIG. It is a figure which shows the transition of the scanning operation | movement by the radio | wireless communication terminal shown in FIG. It is a figure which shows the change of the received signal level accompanying the movement of the radio | wireless communication terminal shown in FIG.

Explanation of symbols

  AP1-AP4 ... access point, Z1-Z3 ... wireless communication area of access point, STA1 ... wireless communication terminal, R1, R2 ... movement path of wireless communication terminal, P0, P1, P1.5, P1.8, P2 ... wireless Movement path of communication terminal: 1 ... wireless unit, 2 ... control unit, 3 ... input / output interface unit, 11 ... antenna, 21 ... main control module, 22 ... access point scan control module, 23 ... access point connection control module, 24 ... Access point tracking control module, 25 ... Scan result acquisition control module, 26 ... Memory module, 31 ... Input device, 32 ... Display device, 221 ... Communication quality comparison unit, 222 ... Scan channel selection unit, 223 ... Scan method selection unit .

Claims (4)

A function of detecting a base station that can be connected based on a result of periodically scanning a plurality of radio channels used by a plurality of base stations in a service area in which a plurality of base stations are distributed. In the provided wireless communication terminal,
Corresponding to the identification information of the plurality of base stations, information indicating the radio channel used by the base station, information indicating whether or not the base station can be connected, and whether the base station is to be tracked for communication quality Storage means for storing tracking information indicating whether or not,
First determination means for determining the presence / absence of a connectable base station based on information indicating whether or not connection is possible stored in the storage means;
Based on the wireless channel information and tracking information stored in the storage means, the wireless channel used by the base station whose communication quality is to be tracked is periodically scanned to perform communication for each base station. Detection means for detecting quality;
A second determination unit configured to calculate a time variation amount of the detected communication quality and determine whether the calculated time variation amount of the communication quality is within a preset allowable range;
When it is determined by the first determination means that there is no connectable base station, and when the second determination means determines that the time variation of communication quality is within an allowable range, the storage means Means for selecting a base station having a smaller number than the number of base stations from among the base stations in which the identification information is stored, and changing the tracking information so that only the selected base station is a target for tracking communication quality. A wireless communication terminal characterized by the above.   The means for changing the tracking information selects a base station having the best communication quality from among the base stations whose identification information is stored in the storage means, and only the selected base station is a target for tracking the communication quality. The wireless communication terminal according to claim 1, wherein the tracking information is changed accordingly. After the tracking information is changed, the time variation amount is calculated based on the communication quality of the selected base station detected by the detecting means, and the time variation amount of the calculated communication quality falls within the allowable range. A third determination means for determining whether or not it has exceeded,
When it is determined by the third determination means that the calculated time variation of the communication quality exceeds the allowable range, the communication quality is tracked for all base stations whose identification information is stored in the storage means. The wireless communication terminal according to claim 1, further comprising means for re-changing the tracking information to restore the target. After the change of the tracking information, the time fluctuation amount is calculated based on the communication quality of the selected base station detected by the detecting means, and the time fluctuation amount of the calculated communication quality is preset. Fourth determination means for determining whether or not it is within the allowable range over a plurality of detection cycles;
Means for extending the detection period by the detection means when the determination means of 4 determines that the time fluctuation amount of the communication quality of the selected base station is within the allowable range over the plurality of detection periods. The wireless communication terminal according to claim 1, further comprising:

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