JP2010219997A - Wireless mobile station device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a wireless mobile station device in a mobile communication system to select an optimal wireless base station to make speech or data communication. <P>SOLUTION: In a wireless mobile station device, a first threshold and a second threshold smaller than the first threshold, of reception level, are stored. When a reception level (selected station reception level) of a reception signal from a base station being connected is detected, in a first case where the selected station reception level is higher than the first threshold, a state of connection with the base station being connected is maintained. In a second case where the selected station reception level is lower than or equal to the second threshold, a base station search is performed to select as a connection station a base station having a maximum signal reception level among reception signals from the other base stations. In a third case where the selected station reception level is lower than or equal to the first threshold and higher than the second threshold, a base station search is performed when a state of the third case is continued beyond a predetermined time. If there is a base station having a reception signal level higher than the first threshold among reception signals from the other base stations, the station is selected as a connection base station. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to, for example, a base station selection processing technique when performing handover in a radio mobile station apparatus in a mobile radio communication system.

The operation of the conventional radio mobile station apparatus will be described.
When the wireless mobile station device moves between areas of a plurality of wireless base stations during communication, the communication with the wireless base station in the old area is switched to the communication with the wireless base station in the new connection area, A handover process for continuing communication such as a call or data communication is performed.
When performing this handover process, selection of a radio base station for a new connection destination area has been performed as follows. In other words, when the received signal level of the radio wave received from the currently connected radio base station falls below a predetermined threshold, the received signal of the radio wave received from another radio base station other than the currently connected radio base station The level is detected, and the connection processing is performed by selecting the radio base station having the maximum received signal level detected. At this time, if the predetermined threshold is set higher, the channel quality is improved, but a base station search for searching for another connectable radio base station is frequently performed. Since the power consumption increases when the base station search is frequently performed, the predetermined threshold is set to a received signal level such as “communication is possible but the line quality is not good”.

  As described above, when the reception signal level of the radio wave from the wireless base station connected so far is below a predetermined threshold (reception signal level where communication is possible but the line quality is not good), The level of the received signal from the base station was checked, and the radio base station with the maximum received signal level was selected and connected, so there was another radio base station with a higher received signal level than the connected radio base station. However, the radio base station cannot be switched unless the received signal level of the radio wave from the connected radio base station falls below the predetermined threshold (the received signal level where communication is possible but the line quality is not good). However, it is not always possible to select a radio base station having an appropriate reception signal level.

  In addition, in order to select a radio base station having the maximum received signal level, a selected base station connected to a plurality of radio mobile station apparatuses may be biased toward a specific base station having a large received signal level. Since the selected base station is not changed until the level is equal to or lower than a predetermined threshold (received signal level where communication is possible but channel quality is not good), the bias of the selected base station is likely to continue.

  Also, if the received signal level of the radio wave from the connected wireless base station is not less than the predetermined threshold (received signal level where communication is possible but the line quality is not good), the base station switching selection process is not performed. At the time of base station switching, the received signal level, that is, the line quality may deteriorate considerably.

  Also, if the received signal level of a radio wave from a certain radio base station momentarily exceeds a predetermined threshold due to fading, etc., if that radio base station is selected, handover will fail as a result. I had a problem.

  In Patent Literature 1, when the radio wave state from a radio base station deteriorates during communication, the received signal level of radio waves from other radio base stations is detected, and the detection level is set in the radio communication device in advance. If the threshold is greater than 1, a handover request is made to the radio base station. If the detection level is less than the first threshold, the state is set to be smaller than the first threshold when the state continues for a predetermined period. It is described that a handover request is made to a radio base station having a detection level larger than the set second threshold.

JP 2008-283332 A

However, in the base station selection process of the conventional radio mobile station apparatus as described above, it is determined whether the received signal level of the radio wave from the connected radio base station is a level for switching the radio base station. Since there is only one type of threshold, it is necessary to set the threshold to a received signal level such as “communication is possible but line quality is not good”. As a result, an appropriate radio base station having a received signal level is always selected. There is a problem that it is not always possible, or that the channel quality is considerably deteriorated at the time of base station switching, or that the selected base station tends to be biased.
The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a radio mobile station apparatus capable of selecting a suitable radio base station and performing a call or data communication. To do.

In order to achieve the above object, in the present invention, the radio mobile station apparatus has the following configuration. That is,
A radio mobile station apparatus in a mobile radio communication system,
A wireless transmission / reception unit that transmits and receives signals wirelessly communicated between the base station device and the wireless mobile station device;
A reception level detection unit for detecting a reception level based on a reception signal received by the wireless transmission / reception unit;
A storage unit that stores a first threshold of the reception level and a second threshold smaller than the first threshold;
A reception level comparison unit that compares the reception level detected by the reception level detection unit with the first threshold value and the second threshold value stored in the storage unit;
A base station search unit that performs a base station search so as to receive a received signal from another base station other than the connected base station;
A base station selection unit that selects a base station to be connected based on a reception level of a received signal received from another base station by the base station search;
When the reception level detection unit detects a selection station reception level that is a reception level of a reception signal from a connected base station, the reception level comparison unit stores the selection station reception level and the storage unit stores Compare the threshold of 1 and the second threshold,
In the first case where the selected station reception level is greater than the first threshold, maintain the connection state with the connected base station,
In the second case where the reception level of the selected station is less than or equal to the second threshold, the base station search unit performs a base station search so as to receive a received signal from another base station, and the base station selection unit , Select the base station with the highest reception level as the connected base station from the received signals from other base stations,
In the third case where the selected station reception level is less than or equal to the first threshold and greater than the second threshold, the state of the third case continues for more than a predetermined time, A base station search unit performs a base station search so as to receive a reception signal from another base station, and the base station selection unit receives a reception level greater than the first threshold among the reception signals from the other base station. When there is a base station, the wireless mobile station apparatus selects the base station as a connection base station.

  The reception level from the above-mentioned radio base station is measured by, for example, measuring the received signal strength indicator (RSSI: Received Signal Strength Indicator) of the radio wave from the radio base station, or setting this as the reception level. Instead of measuring the signal strength, it is possible to measure an error rate such as a bit error rate or a frame error rate of data during communication, and set a reception level based on the error rate.

According to the present invention, the radio mobile station apparatus stores the first threshold value of the reception level and the second threshold value smaller than the first threshold value, and receives the received signal from the connected base station. If the selected station reception level, which is a level, is less than or equal to the second threshold value, a base station search is performed, the base station with the maximum reception level is selected as a connected base station, and the selected station reception level is the first level If it is less than or equal to a threshold and greater than the second threshold, when the state continues beyond a predetermined time, a base station search is performed and a base station with a reception level greater than the first threshold is found. If so, this is selected as a connection base station, so that the base station can be switched before the line quality deteriorates, and a radio base station with a more appropriate reception signal level is selected. Can also be selected groups The bias of the ground station can be suppressed.
When the selected station reception level is equal to or lower than the first threshold and greater than the second threshold, a base station search is performed when the state continues for a predetermined time. Therefore, power consumption can be reduced. That is, predetermined communication quality can be ensured while suppressing frequent searches of base stations that consume a large amount of power, and power consumption and communication quality can be balanced.

  In the present invention, when the base station search is performed in the third case where the selected station reception level is equal to or less than the first threshold and greater than the second threshold, the reception level is the first level. Although a base station larger than the threshold is selected as a connection base station, a base station larger than the selected station reception level may be selected as a connection base station. In this way, it is possible to switch to a base station with better channel quality than the currently connected base station.

  In the present invention, when a base station search is performed in the second case where the reception level of the selected station is equal to or less than the second threshold, the base station having the maximum reception level is selected as a connection base station. However, it is also possible to select a base station larger than the selected station reception level as the connected base station. In this way, it is possible to switch to a base station with better channel quality than the currently connected base station.

In the present invention, when the selected station reception level is less than or equal to the first threshold and greater than the second threshold, the state continues for a predetermined time. The base station search is performed, but the base station search may be performed without waiting for a predetermined time. In this way, power consumption increases for base station search, but base station switching can be performed before line quality deteriorates, and a radio base station with a more appropriate received signal level is selected. It has the effect that it can be made.
The continuation exceeding the predetermined time may be determined by a timer, or may be determined by counting the number of detections of the selected station reception level using a counter or the like.

It is a figure which shows the structural example of the mobile radio | wireless communications system which concerns on this invention. It is a figure which shows the structural example of the radio | wireless mobile station apparatus which concerns on this invention. It is explanatory drawing which shows an example of the connection sequence at the time of the handover which concerns on this invention. It is a flowchart figure which shows the example of a radio base station selection process at the time of the handover in the radio | wireless mobile station apparatus which concerns on this invention.

  An embodiment for carrying out the present invention will be described with reference to FIG. 1, taking a communication system using PHS as an example of a radio mobile station apparatus. FIG. 1 is a diagram showing a configuration example of a mobile radio communication system according to the present invention. As shown in FIG. 1, a mobile radio communication system using PHS is used in factories, offices, etc., and includes a plurality of radio mobile station devices (PHS terminals) 7-1 to 7-2, Radio base stations 3-1 to 3-2, a line control device 5, and a control table 6 are provided. Of course, the radio mobile station device 7 and the radio base station 3 may each include three or more.

The PHS terminals 7-1 to 7-2 are carried by the user to perform telephone calls and data communication.
The wireless base stations 3-1 to 3-2 are repeaters between the PHS terminals 7-1 to 7-2 and the line control device 5, and perform wireless communication with the PHS terminals 7-1 to 7-2. It is. Each of the wireless base stations 3-1 to 3-2 stores a unique wireless base station ID.
In addition, cells having a radius of 100 to 500 meters are formed as the communication areas 4-1 to 4-2 of the radio base stations 3-1 to 3-2.

  The line control device 5 controls telephone calls and data communication in the system, and is connected to the radio base stations 3-1 to 3-2 by approach lines 2-1 to 2-2, respectively. The line control device 5 stores a unique system ID. In a communication system in which a plurality of line control devices 5 exist, management for each system can be performed with this unique ID. The line control device 5 can be connected to a fixed telephone (not shown) by wire. In this case, the line control apparatus 5 performs a call between the fixed telephones or between the fixed telephone and the PHS terminal 7.

  In the communication system, the PHS terminals 7-1 to 7-2 make handover requests to the radio base stations 3-1 to 3-2, and the communication of the plurality of radio base stations 3-1 to 3-2. Calls and data communications are continued while moving in areas 4-1 to 4-2.

Next, a configuration example of the radio mobile station apparatus according to the present invention will be described. FIG. 2 is a diagram illustrating a configuration example of a radio mobile station apparatus according to the present invention.
The radio mobile station apparatus 7 of this example is a mobile station in a mobile communication system, and includes an antenna 21, a SW 22, a receiving unit 23, a transmitting unit 24, a receiving unit 25, a transmitting unit 26, and an operating unit. 27, a display unit 28, a storage unit 29, a timer 30, and a control unit 31.

SW22 is a high frequency switch for switching between transmission and reception.
The receiving unit 23 receives radio waves from the base station 3 via the antenna 21 and the SW 22 and outputs a received signal to the control unit 31.
The transmission unit 24 performs predetermined processing on the audio signal and data signal transmitted from the control unit 31, and transmits the signal to the radio base station via radio waves via the SW 22 and the antenna 21. The receiving unit 23 and the transmitting unit 24 are collectively referred to as a wireless transmitting / receiving unit.

The receiver 25 is composed of a speaker or the like, and converts an input electrical signal into a voice signal and outputs the voice signal.
The transmitter 26 is composed of a microphone or the like, and converts an input voice signal into an electric signal and outputs it.

The operation unit 27 includes dial keys including “0” to “9”, “*”, and “#”, a cross key for controlling operations, and the like for a user to input a telephone number and operation control instructions. is there.
The display unit 28 is composed of a liquid crystal display or the like, displays received data, and displays data according to the operation of the operation unit 27.

The storage unit 29 stores received data, data input from the operation unit 27, radio frequencies of a plurality of usable base stations, and the like. In addition, the storage unit 29 stores a reception level detection value detected by a reception level detection unit 33 (to be described later) and a base station ID of a radio base station that has transmitted the radio wave of the reception level detection value in association with each other. This reception level detection value and base station ID are used when a handover request is made.
The storage unit 29 stores a first threshold value, a second threshold value, and the like used for the radio base station selection process at the time of handover. For example, the second threshold value can be a threshold value used for location registration and handover, and the first threshold value can be a threshold value dedicated to handover. Since the threshold used for location registration needs to be smaller than the threshold dedicated to handover, the first threshold is set to a value larger than the second threshold. In the case of the present embodiment, the second threshold is set to a received signal level such as “communication is possible but line quality is not good”, which is about the same as the conventional example, but is not limited to this. .

  The control unit 31 includes a main control unit 32, a reception level detection unit 33, a reception level comparison unit 34, a base station search unit 35, a base station selection unit 36, and a timer control unit 37 as functions. The hardware configuration includes a CPU and a memory in which various operation programs are stored. The control unit 31 operates according to the processing program stored in the memory of the control unit 31 and controls each unit other than the control unit 31. For example, the control unit 31 performs a radio base station selection process, a handover process, etc. at the time of handover Is.

The reception level detection unit 33 detects the reception level of the reception signal based on the radio wave reception signal received by the reception unit 23. The reception level detection unit 33 may be provided in the reception unit 23 so that the detection result is sent to the control unit 31.
The reception level comparison unit 34 compares the reception level detection value detected and output by the reception level detection unit 33 with the first threshold value and the second threshold value preset in the storage unit 29. is there.

The base station search unit 35 is used for searching for a connectable base station device 3 (base station search), and the reception frequency of the wireless mobile station device 7 is stored in the storage unit 29. Control is performed so as to switch to a plurality of possible base station radio frequencies one after another and receive a signal of the set frequency from the base station apparatus 3.
Specifically, the reception frequency of the radio mobile station apparatus 7 is set to a first frequency among a plurality of usable base station radio frequencies stored in the storage unit 29, and the frequency of the set frequency is set. Control is performed so that the signal is received from the base station apparatus 3. The reception level of the received signal received is detected by the reception level detection unit 33 and is stored in the storage unit 29 in association with the base station ID of the radio base station 3.
Next, the base station search unit 35 sets the reception frequency of the radio mobile station device 7 to another usable base station radio frequency stored in the storage unit 29, and the signal of the set frequency is set to the base station Control to receive from the device 3. The reception level of the received reception signal is detected by the reception level detection unit 33 and is stored in the storage unit 29 in association with the base station ID of the radio base station 3 as described above.

  The base station selection unit 36 selects a base station to be connected based on the reception level of a received signal from another base station obtained by the base station search. In the present embodiment, the base station selection unit 36, when the selection station reception level, which is the reception level of the reception signal from the connected base station, is larger than the first threshold, In the second case where the selected station reception level is less than or equal to the second threshold value, the reception level of the received signals from other base stations obtained by the base station search is In the third case where the largest base station is selected as the connection base station, and the reception level of the selected station is equal to or lower than the first threshold value and greater than the second threshold value, the state in the third case If there is a base station whose reception level is higher than the first threshold among the received signals from other base stations obtained by the base station search when the time exceeds a predetermined time, this is used as a connection base station Operate to select.

The timer control unit 37 can set a desired measurement time in the timer 30, can start measurement of the timer 30, and can reset the measurement value of the timer 30.
The main control unit 32 controls the call processing of the radio mobile station apparatus 7, and also includes the SW 22, the reception unit 23, the transmission unit 24, the reception unit 25, the transmission unit 26, the operation unit 27, the display unit 28, and the reception level detection unit. 33, a reception level comparison unit 34, a base station search unit 35, a base station selection unit 36, a timer control unit 37, and the like.

Next, a handover sequence of the communication system using the radio mobile station apparatus 7 will be described with reference to FIG. FIG. 3 is a diagram for explaining an example of a connection sequence at the time of handover of this communication system using the radio mobile station apparatus 7.
In FIG. 3, a PHS terminal 7 as a radio mobile station apparatus 7 is connected to another PHS terminal or a fixed telephone (in FIG. 3, a call is made to a fixed telephone) via the radio base station 3-1 and the line control apparatus 5. When a radio wave deterioration from the radio base station 3-1, that is, a decrease in reception level is detected during a call, the process proceeds to a radio base station selection process.

  In this radio base station selection process, first, a radio base station 3 that can communicate with other than the radio base station 3-1 that is performing communication is searched for. For example, in the case of FIG. Radio waves are received from the radio base stations 3-2 and 3-3 other than the radio base station 3-1. Then, the reception level of the radio waves received from the radio base stations 3-2 and 3-3 is detected, and processing for selecting an appropriate radio base station 3 based on the detected reception level is performed. The radio base station selection process will be described in detail later.

  When the above-described radio base station selection process is performed, the PHS terminal 7 next proceeds to a handover request process for the selected radio base station 3. In this handover request process, the PHS terminal 7 issues a handover request to the selected radio base station 3 (radio base station 3-2 in FIG. 3) (S31). Upon receiving the handover request, the radio base station 3-2 transmits the request to the line control device 5 (S32). When receiving the handover request, the line control device 5 performs an authentication calculation process using a random number or the like, and outputs a call setting acceptance (S33) and an authentication request (S34) addressed to the PHS terminal 7 to the radio base station 3-2. To do.

  Upon receiving the call setting acceptance (S33) and the authentication request (S34), the wireless base station 3-2 transmits the call setting acceptance (S35) and the authentication request (S36) to the PHS terminal 7. When the PHS terminal 7 receives the call setting acceptance (S35) and the authentication request (S36) from the line control device 5 via the radio base station 3-2, the PHS terminal 7 performs an authentication calculation process using a random number or the like, and the calculation result Is sent to the radio base station 3-2 (S37).

  When the line control apparatus 5 receives the authentication response (S38) received via the radio base station 3-2, the line control apparatus 5 collates the authentication calculation result. If the authentication calculation result is OK, the line control apparatus 5 thereafter receives the response from the PHS terminal 7. The call is continued through the radio base station 3-2. In this way, in the PHS terminal 7, the handover process is performed by the radio base station selection process and the handover request process, and the call and data communication are continued.

Next, the radio base station selection processing operation at the time of handover in the radio mobile station apparatus 7 of the present invention will be described using the flowchart of FIG. FIG. 4 is a flowchart showing an example of radio base station selection processing at the time of handover in the radio mobile station apparatus according to the present invention.
A first threshold value of the reception level and a second threshold value smaller than the first threshold value are stored in advance in the storage unit 29 of the wireless mobile station device 7 (step S1 not shown).
Thereafter, at a predetermined timing, the reception unit 23 receives a reception signal from the selection station 3 which is the currently selected radio base station (selection station), and based on the reception signal from the selection station 3, The reception level detection unit 33 detects the reception level (step S2 in FIG. 4). Next, the reception level comparison unit 34 compares the detected reception level of the received signal from the selected station 3 (selected station reception level) with the first threshold value stored in the storage unit 29 (FIG. 4). Step S3).

As a result of comparison, in the first case where the selected station reception level is higher than the first threshold (No in step S3 in FIG. 4), the timer controller 37 resets the measured value of the timer 30 (FIG. 4). In step S4), the process returns to step S2 in FIG. 4 while maintaining the connection state with the selected station 3.
In the second case where the selected station reception level is equal to or lower than the first threshold (Yes in step S3 in FIG. 4) and equal to or lower than the second threshold (Yes in step S5 in FIG. 4), the base station The station search unit 35 receives a reception signal from a base station other than the selected station 3, and the reception level detection unit 33 checks the reception level of the reception signal (step S6 in FIG. 4). The base station selection unit 36 Thus, the base station having the maximum reception level among the received signals from other base stations is selected as the connection base station (step S7 in FIG. 4).

In the third case where the selected station reception level is equal to or lower than the first threshold value and larger than the second threshold value (No in step S5 in FIG. 4), the measured value of the timer 30 is determined by the timer control unit 37. It is determined whether or not it is zero (step S8 in FIG. 4). If the measured value of the timer 30 is zero (Yes in step S8 in FIG. 4), the timer control unit 37 starts measuring the timer 30 (step S9 in FIG. 4), and the connection state with the selected station 3 The process returns to step S2 in FIG.
When the measured value of the timer 30 is not zero (No in step S8 in FIG. 4), the timer control unit 37 determines whether or not the measured value of the timer 30 is larger than a predetermined value X (FIG. 4). Step S10). That is, it is determined whether or not the state in which the selected station reception level is equal to or lower than the first threshold and greater than the second threshold continues for a predetermined time (time corresponding to X). To do. When the measured value of the timer 30 is equal to or smaller than the predetermined value X (No in step S10 in FIG. 4), the process returns to step S2 in FIG. 4 while maintaining the connection state with the selected station 3.

When the measured value of the timer 30 is larger than the predetermined value X (Yes in step S10 in FIG. 4), the base station search unit 35 receives a reception signal from a base station other than the selected station 3, The reception level detection unit 33 checks the reception level of the reception signal (step S11 in FIG. 4), and the reception level comparison unit 34 determines that the reception level is higher than the first threshold in the reception signals from other base stations. It is determined whether there is a large base station (step S12 in FIG. 4).
If there is a base station whose reception level is higher than the first threshold in the received signals from other base stations other than the selected station 3 (Yes in step S12 in FIG. 4), the base station is selected as the base station. The unit 36 selects the connection base station (step S13 in FIG. 4). If there is no base station whose reception level is higher than the first threshold in the received signals from other base stations other than the selected station 3 (No in step S12 in FIG. 4), the connection state with the selected station 3 is set. Returning to step S2 of FIG.

  In the flowchart of FIG. 4, first, in step S3, the selected station reception level is compared with the first threshold value, and then in step S5, the selected station reception level is compared with the second threshold value. However, the order may be reversed, and the comparison between the reception level of the selected station and the second threshold value may be performed before the comparison with the first threshold value. That is, a comparison is first made between the reception level of the selected station and the second threshold value. When the reception level is equal to or lower than the second threshold value, a base station search is performed to connect the base station with the maximum reception level to the connected base station. (Corresponding to step S7 in FIG. 4), if the reception level is greater than the second threshold value, the selected station reception level is compared with the first threshold value. When the selected station reception level is equal to or lower than the first threshold, the measurement value of the timer 30 is greater than a predetermined value X, and the reception level is the first level in the received signal from another base station. If there is a base station larger than the threshold value of 1, the base station is selected as a connected base station by the base station selector 36 (corresponding to step S13 in FIG. 4).

Note that the present invention is not only a wireless mobile station apparatus that executes the processing according to the present invention, but also a method and system for executing the processing according to the present invention, or a program for realizing the method and system according to the present invention. Or a recording medium for recording the program. The present invention may be configured such that the CPU performs control by executing a control program stored in a memory, or may be configured as a hardware circuit.
The wireless mobile station apparatus of the present invention is not limited to the above-described PHS, and may be, for example, a wireless communication terminal connected to a DTE (Data Terminal Equipment) such as a vending machine, or a disaster prevention radio. Various wireless communication devices in a private wireless communication system such as a system or a business wireless system, or a public wireless communication system may be used.

  1 .... control station 2 .... approach line 3 .... wireless base station 4 .... communication area 5 .... line control device 6 .... control board 7 .... wireless mobile station device 21 ... antenna , 22 ..High frequency switch (SW), 23 ..Reception unit, 24 ..Transmission unit, 25 ..Reception unit, 26 ..Transmission unit, 27 ..Operation unit, 28 .. Display unit, 29. Storage unit 30..Timer 31..Control unit 32..Main control unit 33..Reception level detection unit 34..Reception level comparison unit 35..Base station search unit 36..Base station Selection unit, 37..Timer control unit.

Claims (1)

A radio mobile station apparatus in a mobile radio communication system,
A wireless transmission / reception unit that transmits and receives signals wirelessly communicated between the base station device and the wireless mobile station device;
A reception level detection unit for detecting a reception level based on a reception signal received by the wireless transmission / reception unit;
A storage unit that stores a first threshold of the reception level and a second threshold smaller than the first threshold;
A reception level comparison unit that compares the reception level detected by the reception level detection unit with the first threshold value and the second threshold value stored in the storage unit;
A base station search unit that performs a base station search so as to receive a received signal from another base station other than the connected base station;
A base station selection unit that selects a base station to be connected based on a reception level of a received signal received from another base station by the base station search;
When the reception level detection unit detects a selection station reception level that is a reception level of a reception signal from a connected base station, the reception level comparison unit stores the selection station reception level and the storage unit stores Compare the threshold of 1 and the second threshold,
In the first case where the selected station reception level is greater than the first threshold, maintain the connection state with the connected base station,
In the second case where the reception level of the selected station is less than or equal to the second threshold, the base station search unit performs a base station search so as to receive a received signal from another base station, and the base station selection unit , Select the base station with the highest reception level as the connected base station from the received signals from other base stations,
In the third case where the selected station reception level is less than or equal to the first threshold and greater than the second threshold, the state of the third case continues for more than a predetermined time, A base station search unit performs a base station search so as to receive a reception signal from another base station, and the base station selection unit receives a reception level greater than the first threshold among the reception signals from the other base station. When there is a base station, the wireless mobile station apparatus selects the base station as a connection base station.

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