JP2010239573A - Mobile communication terminal, and handover control program and method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile communication terminal that allows a handover parameter to be set according to the size of a cover area of a base station, in a mobile terminal having a handover function. <P>SOLUTION: In the mobile communication terminal having a handover function, a handover parameter is set on the basis of the value of transmission power of a base station to be used (step 302). When the transmission power of the base station to be used is high, a large value is set to a handover interval, thereby reducing power to be consumed by a cellular phone for handover determination. When the transmit power of the base station to be used is low, on the other hand, a small value is set to the handover interval, thereby quickly responding to deviation of the cellular phone from a cover area. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a mobile communication terminal that performs handover between different base stations, a handover control program for the mobile communication terminal, and a handover control method for the mobile communication terminal.

In recent years, along with the spread of wireless communication lines, portable mobile communication terminals having a wireless communication function have been spread. A mobile phone, which is an example of a mobile communication terminal having a wireless communication function,
It has a voice communication function and a data communication function by telephone, and is used for various purposes such as voice calls, transmission / reception of e-mails, and browsing of websites. As mobile phones have become smaller and lighter in recent years, opportunities for communication while mobile phones are moving are increasing.

A cellular phone uses a wireless communication method generally called a cellular communication method. In the cellular communication system, each base station transmits / receives a radio signal to / from a mobile phone within a specific range centered on the base station (hereinafter simply referred to as a cell). By arranging a large number of base stations, cells are spread, and the mobile phone communicates while moving between cells.

Here, consider a process in which a mobile phone moves from one cell to another cell, disconnects communication with the currently used base station, and newly starts communication with the base station with the destination. It is a so-called handover technique that enables switching of communication between base stations. In mobile phones with a handover function, not only radio signals transmitted from the currently communicating base station, but also periodic periodic searches for radio signals transmitted from other base stations around the terminal itself is doing. The mobile phone evaluates the quality of the searched radio signal, and if the signal quality of another base station exceeds the signal quality of the currently communicating base station, it communicates with the base station with good signal quality. Change to. Generally, the quality of radio signals received by mobile phones is
The worse the distance between the base station and the mobile phone becomes. Therefore, by handing over the mobile phone as it moves and switching the wireless communication line to a base station with good signal quality, the mobile phone maintains communication with the base station even when moving between cells. can do.

As described above, the quality of the radio signal greatly depends on the distance between the base station and the mobile phone, and generally the quality improves as the mobile phone comes closer to the base station. Therefore, as a technique for evaluating the quality of a radio signal, a mobile phone uses GPS (GloBal Position)
Ning System). GPS and mobile phone location information
Use to get. If there is a base station in a close positional relationship with the base station that is currently communicating, it is determined that the close base station can perform communication using a radio signal with a higher quality, and the close base station An invention for performing a handover to is disclosed (for example, Patent Document 1)
See).

In addition, the mobile phone searches for a radio signal transmitted by a neighboring base station, and evaluates the signal quality of the searched radio signal. The evaluation of the signal quality by the mobile phone (hereinafter simply referred to as handover determination) is performed at a fixed time interval (hereinafter simply referred to as handover period). When another base station that can obtain a radio signal having a higher signal quality than that of the currently communicating base station is found, a handover is performed to another base station. When performing this handover determination, the mobile phone compares the signal quality including the offset value. An invention has been disclosed that prevents a situation in which handover is unnecessarily repeated when a variation in signal quality is severe by performing a comparison including an offset value (see, for example, Patent Document 2).

JP 2002-199428 A JP 2006-310773 A

By the way, even if the mobile phone is located indoors, in the shadow of a building, or in a crowded place such as a station and it is difficult to receive a radio signal transmitted from a distant base station, I want to perform stable radio communication There is an increasing demand. In order to solve such a demand, a technique for interpolating a wireless communication service by placing a base station with low transmission power in a place where transmission and reception of wireless signals is difficult locally has been put into practical use. A cell provided by such a base station with low transmission power is generally called a femto cell.

Here, when a mobile phone that communicates while moving performs communication within the femtocell, the coverage area is a small range because the femtocell has low transmission power. Therefore, when a mobile phone in a femto cell moves, the mobile phone in a large coverage area (hereinafter simply referred to as a macro cell) moves away from the coverage area and performs handover. It is thought that the frequency of performing it will increase. However, although the frequency of handover is high, the handover cycle is set at a constant time interval, so there is a possibility that the handover cannot be performed at an appropriate time.

On the other hand, when a mobile phone that communicates while moving communicates within the macro cell, the macro cell is less likely to deviate from the cover area due to the size of the cover area even when the mobile phone moves. Therefore, the frequency with which the mobile phone performs handover is reduced. However, although the frequency of handover is low, the handover cycle is set at a constant time interval, so there is a possibility that the power consumption of the mobile phone may increase due to useless handover determination.

The present invention has been made to solve the above problems, and sets parameters of a mobile communication terminal used for handover determination based on a value of a transmission power signal broadcast from a base station.
An object of the present invention is to provide a mobile communication terminal that can control handover frequency by changing parameters and contribute to reduction of power consumption and improvement of communication stability of the mobile communication terminal.

In order to achieve the above object, a mobile communication terminal of the present invention includes a communication unit that establishes a wireless communication line with a first base station and performs communication, and a wireless signal transmitted from the first base station. And a control unit that acquires transmission power information of the base station and sets a determination time interval for performing handover determination according to the transmission power information.

In addition, the mobile communication terminal handover control program of the present invention includes a communication function for establishing communication with a base station to perform communication, and transmission power information of the base station from a radio signal transmitted from the base station. And a handover parameter setting function for setting a handover time interval for acquiring and determining handover according to the transmission power information.

Further, the handover control method for a mobile communication terminal of the present invention is a handover control method for a mobile communication terminal having a communication means for establishing a radio communication line with a base station and performing communication, and transmitted from the base station The transmission power information of the base station is acquired from a radio signal, and a handover time interval for performing handover determination is set according to the transmission power information.

ADVANTAGE OF THE INVENTION According to this invention, the mobile communication terminal which can contribute to the power consumption reduction of a mobile communication terminal and the improvement of communication stability can be provided.

The block diagram which shows the internal structure of the mobile communication terminal concerning embodiment of this invention. The conceptual diagram of the radio | wireless communication network which connects the base station A in this embodiment, the base station B, and a mobile telephone. The flowchart of the process which performs the handover determination in each embodiment. The figure which shows the hysteresis characteristic of the evaluation value when the mobile telephone in each embodiment is close to the base station A. The figure which shows the hysteresis characteristic of the evaluation value when the mobile telephone in each embodiment is close to the base station B. 5 is a flowchart of processing for setting a handover parameter according to the first embodiment of the present invention. 10 is a flowchart of processing for setting a handover parameter according to the second embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Configuration of mobile phone communication unit)
FIG. 1 is a block diagram showing an internal structure of a mobile phone, which is an example of a mobile communication terminal according to this embodiment.

Radio signals transmitted from base stations A (71) and B (71), which will be described later, are received by the antenna 21, and then input to the receiving circuit (RX) 23 via the antenna duplexer (DUP) 22. The receiving circuit 23 mixes the received radio signal and the local transmission signal output from the frequency synthesizer (SYN) 24, and converts the frequency into an intermediate frequency signal (down-conversion).
To do. The receiving circuit 23 demodulates the down-converted intermediate frequency signal and outputs it as a received baseband signal.

The reception baseband signal output from the reception circuit 23 is a CDMA (Code Div.
(Sion Multiple Access) signal processing unit 26. The CDMA signal processing unit 26 includes a Rake receiver (not shown). In this Rake receiver, each of a plurality of paths included in the received baseband signal is despread with a spreading code (that is, the same spreading code as the spread code of the spread received signal). Then, the signal of each path subjected to the despreading process is subjected to coherent Rake synthesis after rotating the phase. The data sequence after Rake combining is subjected to deinterleaving and channel decoding (error correction decoding), and then binary data determination is performed. Through these processes, the CDMA signal processing unit 26 generates received packet data or audio data of a predetermined transmission format.

The received packet data and audio data are input from the CDMA signal processing unit 26 to the compression / decompression processing unit 27. The CDMA signal processing unit 26 is a DSP (Digital Sign).
al Processor). The audio data processed by the compression / decompression processing unit 27 is subjected to PCM decoding processing by the PCM codec 28 and converted into an audio signal. The converted audio signal is amplified to an appropriate level by the reception amplifier 29 and then output as audio from the speaker 8.

On the other hand, the audio signal input to the microphone 7 of the cellular phone is amplified to an appropriate level by the transmission amplifier 30 and then PCM encoded by the PCM codec 28. This P
The CM-encoded digital audio signal is input to the compression / decompression processing unit 27. A data signal such as a mail generated by the control unit 31 is also input to the compression / decompression processing unit 27.

The CDMA signal processing unit 26 performs spread spectrum processing on the transmission packet data output from the compression / decompression processing unit 27 to generate a spread signal. This spread spectrum process is performed using a spread code assigned to the transmission channel. The spread signal generated by the CDMA signal processing unit 26 is output to the transmission circuit (TX) 25. The transmission circuit 25 modulates the spread signal using a digital modulation method such as a QPSK (Quadrature Phase Shift Keying) method. Further, the transmission circuit 25 synthesizes the spread signal and the local transmission signal generated from the frequency synthesizer 24, and performs frequency conversion (up-conversion) into a radio signal. Then, the transmission circuit 25 amplifies the radio signal that has been up-converted so as to satisfy the transmission power level instructed by the control unit 31. The amplified radio signal is supplied to the antenna 21 via the antenna duplexer 22, and the radio signal is transmitted from the antenna 21 to base stations A (71) and B (72) described later.

The control unit 31 includes an electronic circuit such as a CPU (Central Processing Unit). The CPU executes processing according to a program stored in a ROM or RAM described later. Further, the CPU processes signals supplied from each circuit unit described above, generates various control signals, and supplies them to each circuit unit. Through these processes, CP
U controls the mobile phone 1 in an integrated manner. The storage unit 32 is, for example, a flash memory element that is an electrically rewritable or erasable nonvolatile memory, an HDD (Hard Disc Dr.
ive), ROM (Read Only Memory), and RAM (Random)
Access Memory). The storage unit 32 includes the C of the control unit 31.
In addition to various application programs and data groups executed by the PU, a handover parameter table is provided for storing various parameters used for handover determination.

(Handover processing)
Next, the handover process will be described. Here, the cellular phone 70 is connected to the cell A (81).
From the base station A (71) of the cell A (81) to the base station B (72) of the cell B (82) will be described.

FIG. 2 shows that the mobile phone 70 in the cell A (81) that is a range in which the base station A (71) provides a radio signal is transferred to the cell B (range in which the base station B (72) provides a radio signal. 82) shows a conceptual diagram of the network when moving to 82).

For example, it is assumed that the mobile phone 70 is located in the cell A (81) in FIG. Then, the cellular phone 70 leaves the cell A (81) and enters the cell B (82). The cellular phone 70 cannot receive a radio signal maintaining signal quality necessary for communication from the base station A (71) of the cell A (81). Therefore, the mobile phone 70 cannot continue the wireless communication.
Therefore, when the mobile phone 70 detects that the quality of the radio signal received from the base station A (71) has deteriorated, the base station B (72) of the cell B (82) that can receive a radio signal of better quality.
And a handover request is transmitted to establish a wireless communication line. Base station A (71)
In accordance with the handover request from the mobile phone 70, the connection with the mobile phone 70 is disconnected. On the other hand, the base station B (72) establishes a wireless communication line with the mobile phone 70 in accordance with the handover request. Since the process in which the mobile phone 70 transmits a handover request and switches the base station to be used is a known technique, it is omitted in this specification.

(Handover decision)
Next, handover determination performed when the mobile phone 70 determines whether or not to transmit a handover request will be described. In particular, handover determination performed using the signal-to-noise ratio of a radio signal transmitted from the base station will be described.

In general, the signal-to-noise ratio of a radio signal transmitted from a base station deteriorates as the mobile terminal 70 moves away from the base station. The handover determination of the mobile phone 70 is performed, for example, by comparing the signal-to-noise ratio values received from the base station A (71) and the base station B (72) around the mobile phone 70. FIG. 3 is a diagram illustrating a flowchart of handover determination.
A procedure for handover determination will be described below.

First, when the mobile phone 70 starts handover determination (step 200), the mobile phone 70 indicates the signal-to-noise ratio of the radio signal received from the base station in use (in the case of FIG. 2, it indicates the base station A (71)). Is measured (step 201). Further, the cellular phone 70 calculates the evaluation value of the used base station A (71) from the evaluation value calculation method described later using the value of the signal-to-noise ratio measured by the used base station A (71) (step 202). . Furthermore, the cellular phone 70 measures the signal-to-noise ratio of the radio signal received from the adjacent base station (in the case of FIG. 2, indicates the base station B (72)) (step 203). Furthermore, the mobile phone 70 is connected to the adjacent base station B (
The evaluation value of the adjacent base station B (72) is calculated using the measured signal-to-noise ratio value of (72) (step 204). In FIG. 2, the adjacent base station of the mobile phone 70 is the base station B (72).
However, since there are a plurality of adjacent base stations, the signal-to-noise ratio is measured for all adjacent base stations (step 205 and step 206).

Then, the cellular phone 70, which calculates the evaluation values of all adjacent base stations, compares the evaluation value of the used base station with the best evaluation value among the adjacent base stations (step 207). As a result of comparison,
When the evaluation value of the used base station A (71) exceeds (No in Step 207), the mobile phone 70 ends the handover determination (Step 209). On the other hand, when the evaluation value of the adjacent base station B (72) exceeds (Yes in Step 207), the mobile phone 70 transmits a handover request to the adjacent base station B (72) that has obtained the best evaluation value ( Step 208), the handover determination is terminated (Step 209).

(Calculation of base station evaluation value)
It has been stated that the determination as to whether the mobile phone 70 issues a handover request is made by comparing the evaluation values calculated based on the value of the signal-to-noise ratio. However, the value of the signal-to-noise ratio varies greatly due to changes in the surrounding environment of the mobile phone 70. For this reason, in order to ignore instantaneous fluctuations in the signal-to-noise ratio and perform a handover decision using a more useful evaluation value, it is necessary to use an averaged value obtained by measuring the signal-to-noise ratio multiple times. is there. Therefore, a method for calculating an evaluation value using a value obtained by averaging the signal-to-noise ratio of a radio signal received by the mobile phone 70 in terms of time will be described.

Equation 1 shows a mathematical formula for calculating the evaluation value.

In Equation 1, curr_SN represents a measured signal-to-noise ratio value, filter_length represents a filter time constant, a represents a filter weight, and total_SN represents an averaged signal-to-noise ratio value. EVA1 is the evaluation value of the base station used, EVA2 is the evaluation value of the adjacent base station, o
ffset indicates an offset value, and Hyst indicates a hysteresis value. The value of total_SN is updated each time the handover determination is performed and the signal-to-noise ratio of the received signal is measured.
Evaluation values EVA1 and EVA2 are calculated based on the value of tal_SN.

By changing the filter time constant filter_length and the filter weight a in Equation 1, it is possible to change the degree of reflecting a temporary change in the signal-to-noise ratio in the evaluation value. For example, when the communication time of the used base station is sufficiently long, it can be determined that the sudden movement of the mobile phone 70 to the adjacent base station does not occur. In this case, the filter time constant filter_length
If the signal weight is changed to a large value or the filter weight a is set to a small value, even if the signal-to-noise ratio changes due to the temporarily generated noise or the like, the evaluation value may change greatly. Can be prevented.

In this embodiment, the evaluation value is calculated using the value of the signal-to-noise ratio, but in addition to the signal-to-noise ratio, “reception power”, “radio signal error rate”, or “wireless at the base station” The “number of available lines” may be used for calculating the evaluation value. When calculating the evaluation value including the error rate of the received radio signal, the lower the error rate, the higher the evaluation value is calculated. Further, when calculating the evaluation value including the number of free wireless lines in the base station, the higher the number of free lines, the higher the evaluation value is calculated. Alternatively, the evaluation value may be increased or decreased based on various information transmitted from the base station.

(Hysteresis characteristics for handover decision)
As shown in Equation 1, the evaluation value (EVA1) of the used base station is equal to the evaluation value (EVA) of the adjacent base station.
Unlike A2), a value obtained by adding the offset value offset and the hysteresis value Hyst to the received power value is used. That is, the offset value offset and the hysteresis value Hyst
Has a role of biasing the evaluation value and changing the evaluation value. As a result, the evaluation value when moving between the base station in use and the adjacent base station transitions with hysteresis characteristics. In general, a different offset value offset is used for each base station. on the other hand,
As the hysteresis value Hyst, a different value is used for each type of wireless communication system used by the mobile phone 70.

For example, in FIG. 4, when the mobile phone 70 is located at a position 90 closer to the base station A (71) than the base station B (72), and the mobile phone 70 performs communication using the base station A (71) as a base station to be used. Comparison of evaluation values will be described.

When the mobile phone 70 is at the position 90, the evaluation value of the base station A (71) is the base station A (71).
The offset value offset and the hysteresis value Hyst are added to the value of the signal-to-noise ratio of the radio signal received from (1). The lower side of FIG. 4 shows the transition of the evaluation value. On the other hand, the evaluation value of the base station B (72) is calculated only from the value of the signal-to-noise ratio of the radio signal received from the base station B (72). Therefore, when the mobile phone 70 is at the position 90, the evaluation value of the base station A (71) exceeds the evaluation value of the base station B (72), so that the handover is not performed. On the other hand, when the mobile phone 70 moves close to the base station B (72) and is at the position 91, since the evaluation value of the base station B (72) exceeds, the mobile phone 70 has the base station B (72).
).

Next, consider a case where the mobile phone 70 handed over to the base station B (72) moves again near the base station A (71) as shown in FIG. When the mobile phone 70 is at a position 94 close to the base station B (72), the evaluation value of the base station B (72) is the value of the signal-to-noise ratio of the radio signal received from the base station B (72). , Offset value offset and hysteresis value Hyst
Calculated by adding. The lower side of FIG. 5 shows the transition of the evaluation value. On the other hand, the evaluation value of the base station A (71) is calculated from the signal-to-noise ratio value of the radio signal received from the base station A (71). Accordingly, when the position of the mobile phone 70 is at the position 94, the base station B (72
) Exceeds the evaluation value of the base station A (71), the handover is not performed. On the other hand, when the mobile phone 70 moves near the base station A (71) and is at the position 95 in the figure,
Since the evaluation value of the base station A (71) exceeds, the mobile phone 70 performs a handover to the base station A (71).

As described above, the mobile phone 70 sets the offset value offs to the value of the signal-to-noise ratio of the base station used.
By using the value obtained by adding et and the hysteresis value Hyst as an evaluation value, handover determination can be performed with hysteresis characteristics. As a result, even when the mobile phone 70 is located at a boundary where the signal-to-noise ratio values of the used base station and the adjacent base station are equal, it is possible to prevent a situation where the handover is repeated. Further, even when the signal-to-noise ratio of the base station in use is temporarily deteriorated due to a change in the usage environment of the mobile phone 70, it is possible to prevent a situation where the handover to the adjacent base station is inadvertently performed.

(First embodiment)
FIG. 6 is a flowchart of processing for setting a handover parameter based on the transmission power value of the used base station. In general, handover parameters are set when the base station used by the mobile phone 70 is switched by handover. The value set as the handover parameter is a handover interval HOt that specifies a time interval for handover determination.
im, and the offset value offset for calculating the evaluation value described above, hysteresis value Hyst, filter time constant filter_length, and the like. Hereinafter, the flow of processing for setting a handover parameter will be described. The storage unit 32
In the handover parameter table, the value of the handover parameter is set in advance corresponding to the value of transmission power and the value of continuous use time.

First, the cellular phone 70 starts setting handover parameters (step 300).
. First, the mobile phone 70 acquires the value of the transmission power of the base station from the information that the base station in use informs the terminals in the cover area (step 301). Next, the mobile phone 70 reads the value of the handover parameter from the handover parameter table stored in the storage unit 32 based on the magnitude of the transmission power value (step 302), sets it as a new handover parameter, and performs processing Is finished (step 303).

Here, a configuration example of the handover parameter table will be described. For example, the values set as the handover parameters are the handover interval HOtime, the offset value of
Let fset and the filter time constant filter_length. Further, the size of the base station is classified into, for example, three levels of large, medium and small according to the transmission power.

The handover parameter table stores three types of different handover parameters depending on the size of the base station. For example, when the transmission power of the base station is large, corresponding values, HOtime “L”, offset “L”, and filter_length “L” (“L” means “Large”) are set. On the other hand, when the transmission power of the base station is small, HOt
image "S", offset "S", filter_length "S"("S" is small
l means).

Here, an example has been described in which the handover parameter table is configured by classifying the base station size into three and setting corresponding handover parameters. However, the number of base stations to be classified may be a number larger than “3”, and a method of calculating a handover parameter according to the transmission power of the base station may be used regardless of the handover parameter table. Further, although the case where the mobile phone 70 holds the handover parameter table has been described, the base station may hold the handover parameter, and the mobile phone 70 may perform the handover determination using the handover parameter transmitted from the base station. .

When the value of the transmission power of the base station is large, the coverage area of the used base station is large. When the coverage area of the base station in use is large, it is considered that it is not necessary to frequently perform handover determination because the frequency of departure from the coverage area is low even when the mobile phone 70 moves. Therefore, when the value of the acquired transmission power is a large value, the mobile phone 70
Set a large value for the handover interval. That is, by reducing the frequency of handover determination, the frequency with which the mobile phone 70 measures the signal-to-noise ratio of a base station in the vicinity is also reduced.
Thereby, the power consumption of the mobile phone 70 can be reduced.

On the other hand, when the value of the transmission power of the base station is small, the coverage area of the used base station is small. When the coverage area of the base station in use is small, the mobile phone 70 moves frequently to deviate from the cover area. Therefore, it is necessary to frequently perform handover determination to cope with the deviation of the cover area. Therefore, when the acquired transmission power value is a small value, the mobile phone 70 sets a small value for the handover interval. That is, by increasing the frequency of handover determination, the mobile phone 70 performs handover in response to a deviation from the cover area. Thereby, the stability of communication of the mobile phone 70 can be improved.

Further, the handover parameter of the storage unit 32 set according to the value of the transmission power is not limited to the handover interval. For example, offset value offset or hysteresis value H
yst may be set according to the value of transmission power. When setting the offset value offset, a large offset value offset is set when the value of the transmission power of the base station is large. By setting a large value for the offset value offset, a high evaluation value can be obtained at the time of handover determination. This prevents a situation in which the mobile phone 70 is handed over due to a temporary change in radio wave environment, and a base station with a stable communication environment can be used for a long time. Even when the hysteresis value Hyst is set, the same effect of the invention can be obtained by setting a large hysteresis value Hyst when the value of the transmission power is large.

Further, the filter time constant filter_length may be set according to the value of the transmission power. When the filter time constant filter_length is set, for example, when the value of the transmission power of the base station is small, a small value is set for the filter time constant filter_length. When the coverage area of the base station in use is small, it is considered that the case where the connection is cut off increases when the reception quality of the radio signal deteriorates due to the fluctuation of the radio wave environment of the mobile phone 70. Therefore, by setting a small value to the filter time constant “flt_length”, the cellular phone 7
A handover request can be transmitted in response to a change in radio wave environment of zero.

(Second Embodiment)
In the first embodiment, the case has been described in which the handover parameter in the storage unit 32 is set based only on the value of the transmission power of the base station. However, when the mobile phone 70 does not move from the vicinity of the base station, it is considered that the frequency of deviating from the coverage area of the base station is low even when the transmission power of the base station is relatively small. In this case, set a large value for the handover interval,
Reduce the frequency of handover decisions. That is, power consumption of the mobile phone 70 can be reduced by reducing the frequency of measuring the signal-to-noise ratio of base stations in the vicinity of the mobile phone 70.

FIG. 7 is a flowchart of processing for setting a handover parameter in the storage unit 32 in accordance with the usage time of the used base station. Hereinafter, the flow of processing for setting a handover parameter will be described.

First, the cellular phone 70 starts setting handover parameters (step 400).
. First, the cellular phone 70 acquires “information on the time during which the used base station is continuously used” from the used base station (step 401). The continuous use time of the used base station is stored in the storage unit 32.
It may be stored in the base station, or it may be broadcast from the used base station. Further, the example in which the information on the continuous use time is acquired during the setting of the handover parameter has been described. Then, the value of the continuous use time may be read from the storage unit 32 when performing the handover parameter setting process.

Next, when the mobile phone 70 acquires the value of the continuous use time of the base station, the mobile phone 70 acquires the “value of the transmission power of the used base station” (step 402). Next, the cellular phone 70 reads the value of the handover parameter from the handover parameter table stored in the storage unit 32 based on the value of the continuous use time and the value of the transmission power of the base station (Step 403). Is set as a simple handover parameter, and the process is terminated (step 404).

As described above, when the continuous use time of the base station of the mobile phone 70 is long, the frequency of handover may be low because the mobile phone 70 is not moving. Therefore, when the continuous use time is a long value, the mobile phone 70 sets a large value for the handover interval. Thereby, when the mobile phone 70 is not moving, the power consumption of the mobile phone 70 can be reduced. Alternatively, when the continuous use time of the mobile phone 70 is a long value,
A large value is set to the offset value offset or the hysteresis value Hyst. Thereby, when the mobile phone 70 is not moving, it is possible to prevent a situation in which handover is performed due to a temporary change in the communication environment of the mobile phone 70.

With the above processing, when the mobile phone 70 performs the handover determination, the handover parameter value is set based on the transmission power value of the base station or the continuous use time value of the used base station. For example, when the mobile phone 70 is in a large cell or when the mobile phone 70 is not moving, a large value is set for the handover interval. Thereby, the power consumption of the mobile phone 70 can be reduced by reducing the frequency of handover determination. On the other hand, when the mobile phone 70 is in a small cell or when the mobile phone 70 moves frequently, a small value is set for the handover interval. Thereby, it is possible to perform handover in response to a deviation of the cover area of the mobile phone 70 quickly.

In the embodiment described here, a mobile phone has been described as an example of the mobile communication terminal. However, the scope of the present invention is not limited to this. For example, PDA (
(Personal Digital Assistant) and small information processing equipment. The present invention is not limited to the above-described embodiment, and the constituent elements may be modified and embodied as long as they do not depart from the gist of the invention. Various inventions may be formed by proper combinations of a plurality of constituent elements disclosed in the above embodiments. For example, some components may be excluded from all the components shown in each embodiment.

21 Antenna 31 Control Unit 32 Storage Unit 70 Mobile Phone 71 Base Station A
72 Base station B
81 cell A
82 cell B

Claims (8)

A communication means for establishing communication with a base station in use and communicating;
A control unit configured to acquire transmission power information of the base station from a radio signal transmitted from the use base station, and to set a determination time interval for performing handover determination according to the acquired transmission power information. Mobile communication terminal. A communication means for establishing communication with a base station in use and communicating;
Obtaining the transmission power information of the base station from the radio signal transmitted from the use base station, and the continuous use time value at which the communication means establishes the radio communication line with the use base station,
A mobile communication terminal comprising: a control unit that sets a determination time interval for performing handover determination according to the acquired transmission power information and the continuous use time. The controller is
When performing the handover determination,
Measure the received signal quality of the used base station for the used base station,
Based on the transmission power information and the received signal quality of the base station used, a first evaluation value is set,
Measuring the received signal quality of an adjacent base station for an adjacent base station with which the communication means has not established a wireless communication line;
A second evaluation value is set based on the received signal quality of the adjacent base station,
The mobile communication terminal according to claim 1 or 2, wherein a handover request is transmitted when the second evaluation value exceeds the first evaluation value. The controller is
The mobile communication terminal according to claim 3, wherein the first evaluation value is set based on the transmission power information, the received signal quality of the used base station, and the continuous use time. The controller is
The transmission power information, the received signal quality of the used base station, and the used base station are transmitted,
The mobile communication terminal according to claim 3 or 4, wherein the first evaluation value is set based on evaluation value bias information. A communication means for communicating with a base station in use via a wireless communication line;
Obtaining the transmission power information of the base station from the radio signal transmitted from the use base station, setting the evaluation value based on the quality of the radio signal received by the communication means and the transmission power information, the evaluation A mobile communication terminal comprising: a control unit that performs handover determination based on a value. A function of acquiring transmission power information of the base station from a radio signal transmitted from the base station in use;
A handover control program for a mobile communication terminal, comprising a function for setting a handover time interval for performing handover determination according to the transmission power information. A handover control method for a mobile communication terminal having a communication means for establishing and communicating with a base station in use, comprising:
Obtain the transmission power information of the base station from the radio signal transmitted from the use base station,
A handover control method for a mobile communication terminal, wherein a handover time interval for performing handover determination is set according to the transmission power information.

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