JP2001095028A - Mobile communication terminal - Google Patents

Abstract

(57) [Problem] To improve the communication quality by reducing the time required for searching for a base station, thereby shortening the connection time or switching time for the base station. SOLUTION: PHS terminals PS1 to PSn are provided with base station pre-search control means 51. In this means 51, non-operating periods such as an initial setting period immediately after power-on, a standby state period, and an idle slot period during communication. During the communication period,
The RSSI of the peripheral base station is detected and this search information is stored in the internal memory. At the time of calling or handover, a base station whose RSSI detection value is equal to or greater than a second threshold value is selected based on the search information of each peripheral base station stored in the internal memory. Is immediately determined as the connection destination or the handover destination, and the establishment control of the radio link channel is performed with this base station.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PHS (Person
al Handyphone System) and a mobile communication terminal used in a cellular mobile communication system.

[0002]

2. Description of the Related Art Generally, in a cellular mobile communication system, a large number of base stations are dispersedly arranged in a service area, cells are formed by these base stations, and a mobile communication terminal is connected to a base station of a cell in which the terminal exists. The wireless communication is enabled by connecting to the wireless LAN through a wireless channel. Also, when the mobile communication terminal device moves to another cell during communication, the communication can be continued by performing a handover.

[0003] In handover, for example, a mobile communication terminal device monitors the reception quality of a radio signal arriving from a communication destination base station during communication, and interrupts communication with the base station if the reception quality deteriorates below a predetermined level. I do. In this state, all the surrounding base stations are searched without fail, and the base station transmitting the radio wave with the highest received electric field strength is selected as the switching destination,
A link channel establishment request is transmitted to the selected base station. Then, the base station receiving the request allocates a link channel to the requesting mobile communication terminal device, and uses the allocated link channel to transmit a link between the mobile communication terminal device and the switching destination base station. The procedure is set so that a new wireless link is formed, and after that, a predetermined connection switching procedure is performed between the mobile communication terminal apparatus and the switching destination base station, and then the connection destination base station is switched.

[0004] However, this conventional handover procedure interrupts communication with the switching source base station,
An optimum base station is selected as a switching destination from all the surrounding base stations. Therefore, the communication is interrupted for a relatively long time during the handover period, and the communication quality is deteriorated.

[0005] For example, in the PHS, each base station repeatedly transmits a paging channel called PCH at a cycle of 1.2 seconds, and the PHS terminal searches the PCH transmission cycle in order to search for all the surrounding base stations without fail. A period corresponding to three times is set as the search period. Then, the received field strength of the PCH detected during the search period is averaged for each base station, and the base station having the largest average value is selected as the switching destination. For this reason, it takes 3.6 seconds or more to select the switching destination base station, during which time the PHS terminal user is forced to interrupt the communication.

[0006]

As described above, the conventional base station search procedure executed at the time of handover, for example, searches all the surrounding base stations without fail and receives the received base station in each of the searched base stations. A base station transmitting a radio wave having the highest electric field strength is selected as a connection destination. For this reason, a lot of time is required to select a connection-destination base station, which increases connection time and switching time, which is one of the causes of communication quality deterioration.

The present invention has been made in view of the above circumstances, and has as its object to shorten the time required for searching for a base station, thereby shortening the connection time or switching time for the base station, and thereby achieving communication. An object of the present invention is to provide a mobile communication terminal device capable of improving quality.

[0008]

In order to achieve the above object, a first aspect of the present invention is to select a base station suitable for communication from a plurality of distributed base stations and to establish a connection with the selected base station. In a mobile communication terminal device for establishing a wireless link, during non-communication periods, the reception qualities of the wireless signals arriving from the plurality of base stations are respectively detected and stored, and a wireless link is established with the base station. When it is necessary to determine whether there is any of the stored reception qualities of the base stations that satisfies a predetermined determination condition, the base station having a reception quality that satisfies the determination condition is determined. When there is, the base station is selected as a base station suitable for communication, and the process proceeds to a radio link establishment procedure.

The reception quality detecting means arrives from a plurality of base stations during at least one of an initialization period from when the power is turned on to a transition to a standby state and a period in a standby state. The reception quality of the radio signal is detected and stored.

Therefore, according to the present invention, the reception quality of each base station in the vicinity is detected and stored in advance during a non-communication period, and when establishing a wireless link, the base station is determined based on the stored search result. A station is selected and an immediate radio link establishment procedure is performed. That is, for example, when the connection or switching procedure of the base station is started, the base station search procedure is omitted and the radio link establishment procedure is immediately executed. For this reason, the connection time to the base station or the time required for handover is greatly reduced, thereby improving the communication quality.

Further, according to the present invention, in the base station selecting means, if there is no base station whose reception quality satisfies the judgment condition as a result of the judgment by the judging means, the reception quality is detected in advance by the reception quality detecting means. It is characterized in that a base station having the best reception quality is selected from the selected base stations, and the procedure shifts to a radio link establishment procedure.

In this way, even if no base station whose reception quality satisfies the determination condition is found, it is possible to select a base station having reception quality equivalent thereto and establish a radio link. Therefore, the call completion rate and the handover completion rate can be kept high.

Further, according to the present invention, when there is a base station whose reception quality satisfies the determination condition, the reception quality of a radio signal arriving from the base station is detected again by the base station selection means. It is also characterized by checking whether or not the above-mentioned criterion is satisfied, and selecting the relevant base station as a base station suitable for communication and shifting to a radio link forming procedure when it is confirmed that the satisfaction is satisfied. I have.

By doing so, it is again confirmed immediately before the execution of the wireless link establishment procedure whether or not the base station selected based on the search result of the base station in advance is suitable for communication. A radio link establishment procedure for the base station is executed. Therefore, if the reception quality obtained in the search for the base station in advance deteriorates thereafter, it is possible not to select this base station, thereby reducing connection and handover failures.

According to a second aspect of the present invention, a base station suitable for communication is selected from a plurality of distributed base stations and a radio link is established with the base station. In the mobile communication terminal device, when it is necessary to form a radio link with the base station, the mobile station sequentially receives the radio signals coming from the plurality of base stations, detects the reception quality thereof, and detects the detected reception. It is determined whether or not the quality satisfies a predetermined determination condition. When a base station whose reception quality satisfies the determination condition is found by this determination, a procedure for selecting the base station as a base station suitable for communication and establishing a radio link with this base station It is intended to shift to.

Therefore, according to the present invention, when a base station that satisfies the determination condition is detected in the base station search procedure, the radio link establishment procedure is immediately executed for this base station. For this reason, the time required for selecting a base station is reduced and the connection time is reduced as compared with the case where the reception quality is detected for all the surrounding base stations and the optimum base station is selected and the radio link establishment procedure is executed. Alternatively, the time required for handover can be reduced.

[0017]

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

(First Embodiment) FIG. 1 shows a first embodiment of a cellular mobile communication system according to the present invention.
It is a schematic structure figure of HS. That is, a plurality of base stations CS1 to CSm are distributed and arranged in the service area, and the radius of each of the base stations CS1 to CSm is 100 to 100 m.
Cells Z1 to Zm of 500 meters are formed. The base stations CS1 to CSm include an integrated service digital network (hereinafter abbreviated as ISDN) INW provided with a PHS connection device PM.
Connected to each other. The I 'interface is used as the connection interface.

PHS terminals PS1 to PSn as mobile stations
Are cells Z1-Z formed by the base stations CS1-CSm.
m, selectively connected to any of the base stations CS1 to CSm via a radio channel, and further connected to the base station CS1.
... CSm to the wired telephones TEL1 to TELk via the ISDN or this ISDN and an analog telephone network (PSTN) SNW. Also, the base station CS
1 to CSm, the PHS terminal PS
Direct communication between 1 to PSn is also possible.

Note that the base stations CS1 to CSm and the PHS
As a wireless access method between the terminals PS1 to PSn, time division multiple access (TDMA) is used.
le Access) system, and as a transmission system, a time division duplex (TDD) system is employed.

The PHS includes a control center CC having a database, a customer information management database, and the like. The control center CC includes the PHS
Information relating to the terminals PS1 to PSn and the base stations CS1 to CSm is collected via the ISDN and the packet network PNW, and service management and control such as authentication / charging and network management are performed based on this information.

By the way, the PHS terminals PS1 to PSn
Is configured as follows. FIG. 2 is a circuit block diagram showing the configuration.

The PHS terminals PS1 to PSn are connected to an antenna 1
, A modem unit 2 and a TDMA unit 3
A communication unit 4, a control unit 5A, an information storage unit 6, a data communication unit 7, an input unit 8 having a keypad, and a display unit 9 using a liquid crystal display (LCD). I have.

That is, the radio carrier signals arriving from the base stations CS1 to CSm are received by the antenna 11 and then input to the receiving unit 13 via the high frequency switch (SW) 12 of the radio unit 1. In the receiving unit 13, the received radio carrier signal is mixed with the local oscillation signal generated from the synthesizer 14 and down-converted into a received intermediate frequency signal. The local oscillation signal frequency generated from the synthesizer 14 is set to a value corresponding to the radio channel frequency to be used according to an instruction from the control unit 5A. Also, the radio unit 1 includes a reception field strength detection unit (RSS
I) 16 is provided. This reception electric field strength detection unit 16
Detects the reception electric field strength of a signal of a broadcast channel (BCCH) or a paging channel (PCH) periodically transmitted by a base station in communication or a peripheral base station, and determines the detected value, for example, to determine reception quality. Then, the control unit 5A is notified to perform the display.

The received intermediate frequency signal output from the receiving section 13 is input to the demodulating section 21 of the modem section 2. The demodulation section 21 performs digital demodulation of the received intermediate frequency signal, thereby reproducing a digital demodulated signal.

The TDMA decoding section 31 of the TDMA section 3
Separates the digital demodulated signal for each reception time slot. If the data of the separated slot is voice data, the voice data is input to the communication unit 4. On the other hand, if the data of the separated slot is packet data or control data, these data are input to the data communication unit 7.

The communication unit 4 has an ADPCM (Adaptive Diffe
rential Pulse Code Modulation) Transcoder 41
And PCM (Pulse Code Modulation) codec 42
, A speaker 43, and a microphone 44. The ADPCM transcoder 41 decodes the audio data output from the TDMA decoding unit 31. P
The CM codec 42 converts the digital audio signal output from the ADPCM transcoder 41 into an analog signal, and outputs this audio signal from the speaker 43.

The data communication section 7 receives the data supplied from the TDMA decoding section 31, and supplies the data to the control section 5A. If the received data is control data, the control unit 5A analyzes the control data and performs necessary control. On the other hand, if the received data is packet data that has arrived from, for example, a server on the Internet, the packet data is depacketized, stored in the information storage unit 6, and supplied to the display unit 9 for display.

On the other hand, the voice signal of the user input to the microphone 44 is PCM-coded by the PCM codec 42 and then compression-coded by the ADPCM transcoder 41. Then, the encoded audio data is TDM
It is input to the A encoding unit 32. The control data and packet data output from the control unit 5A are input to the TDMA encoding unit 32 via the data communication unit 7.

[0030] The TDMA encoding unit 32 uses the ADP.
The digital audio data of each channel output from the CM transcoder 41 and the control data and packet data output from the data communication unit 7 are inserted and multiplexed in the transmission time slot specified by the control unit 5A. The modulation section 22 digitally modulates the transmission intermediate frequency signal with the multiplexed digital transmission signal output from the TDMA encoding section 32, and inputs the modulated transmission intermediate frequency signal to the transmission section 15.

The transmitting section 15 mixes the modulated transmission intermediate frequency signal with the local oscillation signal generated from the synthesizer 14, upconverts the signal into a radio carrier frequency, and further amplifies the signal to a predetermined transmission power level. The wireless carrier signal output from the transmitting unit 15 is transmitted from the antenna 11 to the base station via the high frequency switch 12.

The control unit 5A includes, for example, a microcomputer as a main control unit. The control function according to the present invention includes a base station pre-search control unit 51,
And a handover / calling control means 52.

First, the base station pre-search control means 51
During at least one of an initial setting period immediately after power-on, a standby state period, and an idle slot period during communication, each of the peripheral base stations is periodically The received field strength of the broadcast channel (BCCH) or the paging channel (PCH) being transmitted is detected via the received field strength detection unit 16 and the detection result and the time slot are stored in the memory in the control unit 5A. I do.

The handover / calling control means 51 reads out the search information of the peripheral base station stored in the memory in the control section 5A at the time of calling and handover, and detects RSSI based on the search information. It is determined whether there is a base station whose value is equal to or higher than a predetermined determination level. If there is a base station that satisfies this condition, the base station is selected as a call destination or a handover destination base station, and a radio link is established based on the time slot information stored with the selected base station. After executing control for establishing a channel, a call control procedure or a handover control procedure is executed.

Next, the operation of the PHS terminals PS1 to PSn configured as described above will be described. PHS terminals PS1
The PSn performs a preliminary search control of the peripheral base station during the non-communication period. FIG. 3 is a flowchart showing the control procedure and control contents.

That is, the PHS terminals PS1 to PSn monitor their non-communication periods in step 3a.
Here, the non-communication period includes an initial setting period immediately after the power is turned on and a standby state period.

In the non-communication period, PHS terminals PS1-P
Sn proceeds to step 3b, where one neighboring base station is searched to receive its control channel, and step 3c
Broadcast channel (BCCH) or paging channel (P
CH) has been received. And BCC
If H or PCH can be received, it is determined in step 3d whether or not the identification information (for example, base station number) of the base station that is the transmission source of this BCCH or PCH is already stored in the memory in the control unit 5A. judge. If the result of this determination is that the identification information of the base station has already been stored, the process proceeds to step 3e, where the RSSI detection value stored in association with the identification information of the base station is newly detected. The updated RSSI detection value is used. On the other hand, if the identification information of the base station is not stored, the process proceeds to step 3f, where the identification information of the base station and its RSSI detection value are newly registered in the memory in the control unit 5A.

When the search for one peripheral base station has been completed, the PHS terminals PS1 to PSn proceed to step 3g and determine whether or not the non-communication period has ended.
If the non-communication period continues, the process returns to step 3b to repeat the above-described process of searching for the peripheral base station.

On the other hand, when the non-communication period ends, the PHS terminals PS1 to PSn proceed to step 3h, where the search information of the peripheral base station stored in the internal memory of the control unit 5A is replaced with the RSSI detection value. Sort in descending order.
Each piece of search information stored in the internal memory is added with a storage timing. And PHS
The terminals PS1 to PSn detect the storage time of each search information based on the storage timing at the time of the rearrangement, and automatically delete the search information whose storage time exceeds a predetermined time. In this way, a preliminary search process for the peripheral base station using the non-communication period is performed.

Now, in this state, for example, the PHS terminal P
In S3, it is assumed that the user needs to perform a call operation or perform a handover. Then, PHS terminal PS3 executes handover / call control as follows. FIG. 4 is a flowchart showing the control procedure and control contents.

On the other hand, during communication, the PHS terminal PS3
Is the RSSI of the base station CS1 of the communication partner in step 4a.
Value in step 4b.
It is determined whether or not it has dropped below the threshold value. Then, when it is detected that the RSSI detection value has dropped below the first threshold value, the mobile station transmits a communication channel (TCH) switching request for requesting handover to the base station CS1 in communication. When a TCH switching instruction is returned from the communicating base station CS1 in response to the TCH switching request, a process of selecting an appropriate base station as a switching destination is performed. Note that the first threshold value is, for example, R required for maintaining communication.
It is set corresponding to the minimum value of the SSI value.

When the process proceeds to the base station selection process, the PHS
In step 4c, the terminal PS3 reads, from the memory in the control unit 5A, the search information of the peripheral base station detected in advance by the base station pre-search control described above. This search information is read out in descending order of the RSSI detection value. The PHS terminal PS3 compares the RSSI detection value of the retrieved search information with the second threshold value in step 4d, and determines whether the value is equal to or greater than the second threshold value.
Note that the second threshold is set corresponding to an RSSI value sufficient to select a connection destination or a switching destination,
The value is higher than the first threshold.

According to the above determination, RS equal to or more than the second threshold value
When the base station having the SI detection value is found, the PHS terminal P
In step S3, this base station (for example, CS3) is immediately selected as a connection destination or a switching destination in step 4e, and subsequently, the process proceeds to step 4f, where the base station time slot information stored in the selected base station CS3 is stored. FIG. 5 based on
The wireless link channel establishment request is transmitted as shown in FIG.
On the other hand, if no base station having an RSSI detection value equal to or greater than the second threshold value is found by the above determination,
The S terminal PS3 proceeds to step 4f, selects a base station having the largest RSSI detection value based on the search information stored in the internal memory, and transmits a radio link channel establishment request to this base station.

By transmitting the wireless link channel establishment request, a control procedure for establishing a wireless link channel is executed between the PHS terminal PS3 and the base station CS3. The handover destination base station CS1
When the control unit 5A is connected via the wireless communication channel, the control unit 5A shifts from step 4h to step 4j, and thereafter executes the handover procedure or the calling procedure.

On the other hand, if the wireless link channel cannot be established with the base station CS13, the control unit 5A shifts from step 4h to step 4i, where it is stored in the internal memory. R based on search information
The base station with the next largest SSI detection value is selected, and a procedure for establishing a radio link channel with the selected base station is performed.

As described above, in the first embodiment, the RSSI of the peripheral base station is detected during the non-communication period such as the initial setting period immediately after the power is turned on or the standby state, and the search information is stored in the internal memory. Remember. At the time of calling or handover, the RSSI detection value is set to the second value based on the search information of each peripheral base station stored in the internal memory.
Is selected, the base station is immediately determined as a connection destination or a handover destination, and control of establishing a radio link channel with the base station is executed.

Therefore, according to the first embodiment, at the time when a call operation is performed or when the necessity of handover is detected, based on the search information of the neighboring base stations previously searched during the non-communication period. The connection destination or the handover destination base station is immediately selected, and the establishment control procedure of the radio link channel is executed. Therefore, as compared with a case where a search for a neighboring base station is started in response to a calling operation or a need for a handover is detected and an appropriate base station is selected, a time taken to establish a radio link channel is longer. The required time can be greatly reduced, thereby shortening the time from the calling operation to the transition to the communication state and the communication interruption time during the handover, thereby improving the communication quality.

Also, by searching for the surrounding base stations using the initial setting period and the standby period immediately after the power is turned on, the search result is always updated to the latest one. The search information of the base station whose time has passed is automatically deleted from the memory.
For this reason, there is little fear that a selection error of the base station will occur, whereby the call completion rate and the handover completion rate can be kept relatively high.

(Second Embodiment) A second embodiment according to the present invention
The embodiment of the present invention does not perform a search for all surrounding base stations in response to a call operation or a need for a handover, but does not perform a search for all the surrounding base stations. When a base station exceeding a predetermined threshold value can be detected, the subsequent base station search procedure is stopped and the procedure immediately shifts to a radio link channel establishment control procedure.

FIG. 6 shows a PH according to the second embodiment.
It is a circuit block diagram which shows the structure of S terminal. 2, the same parts as those in FIG. 2 are denoted by the same reference numerals, and detailed description is omitted.

The control unit 5B includes a base station shortage search control unit 53 and a handover /
And a calling control unit 54.

Among them, first, the base station shortened search control means 53
Initiates a search process for neighboring base stations in response to a calling operation or in response to the need for handover being detected,
Each time the RSSI of one base station is detected, its value is compared with a second threshold value, and when the RSSI detection value is equal to or greater than the second threshold value, the subsequent base station search procedure is stopped. Then, this base station is immediately selected as a connection destination or a handover destination base station. In addition, search information of the base station searched in the search processing is stored, and R
If a base station whose SSI detection value is equal to or larger than the second threshold value cannot be detected, the base station having the largest RSSI detection value is selected.

The handover / calling control means 54 executes the radio link channel establishment control procedure immediately when the connection destination or the handover destination base station is selected by the base station shortage search control means 53, and then the handover / Execute the calling control procedure.

Next, the operation of the PHS terminal configured as described above will be described. Now, suppose that a user performs a calling operation at the PHS terminal PS3, or the RSSI value from the base station in communication decreases, and a handover to another base station needs to be performed. Then PHS terminal PS3
Performs search control and handover / calling control of the base station as follows. FIG. 7 is a flowchart showing the control procedure and control contents.

That is, the PHS terminal PS3 executes step 7
After starting the timer operation in step a, one of the neighboring base stations is searched in step 7b and its control channel is received. In step 3c, a broadcast channel (BCCH) or a paging channel (PCH) is received. Determine whether or not. When the BCCH or PCH can be received, the received field strength (RSSI) is detected in step 7d,
It is determined in step 7e whether or not the detected value of the RSSI is equal to or larger than a second threshold value set in advance.

If the result of this determination is that the RSSI detection value is less than the second threshold value, the base station is not selected as a connection destination or a handover destination, and the routine proceeds to step 7g, where the timer It is determined whether or not the counted value of the time exceeds the set value. And if not, step 7
c, search for the next neighboring base station and
The SI value is detected and determined. Thereafter, similarly, only within the time period of the timer, the peripheral base stations are sequentially searched and the RSS
The detection and determination of the I value are repeated. The time counted by the timer is determined by the paging channel (PCH) transmitted by the base station.
Is set to a time corresponding to three times the transmission cycle of Also,
The search information on each peripheral base station obtained in the above search processing is stored in the memory in the control unit 5B.

Now, during the execution of the search processing, for example, the RSSI of the BCCH or PCH arriving from the base station CS3
Assume that the value is greater than or equal to the second threshold. Then PH
The S terminal PS3 immediately selects this base station CS3 as a connection destination or a handover destination in step 7f, and stops the subsequent base station search processing.

After clearing the count value of the timer in step 7j, a request for establishing a radio link channel is transmitted to the selected base station as shown in FIG. By transmitting the wireless link channel establishment request, a control procedure for establishing a wireless link channel is executed between the PHS terminal PS3 and the base station CS3. Then, when the connection with the handover destination base station CS13 is established via the wireless communication channel, the PHS terminal PS3 thereafter executes the calling procedure or the handover procedure.

On the other hand, it is assumed that the count value of the timer reaches the set value during the search processing of the peripheral base station. Then, the PHS terminal PS3 performs steps 7g to 7h.
Then, based on the search information of each peripheral base station obtained during the search processing period, the peripheral base station with the largest RSSI detection value is selected. Then, in step 7i, after receiving the BCCH or PCH of the selected base station and storing its RSSI value, the above-mentioned radio link channel establishment control and calling procedure or handover procedure are executed.

As described above, in the second embodiment, a base station whose RSSI detection value is equal to or larger than the second threshold is detected in the search processing of the peripheral base station activated by the calling operation or the handover instruction. At this point, the subsequent base station search processing is stopped, this base station is immediately selected as a connection destination or a handover destination, and the process shifts to radio link channel establishment control.

Therefore, the selection of the base station is required as compared with the case where the RSSI values are detected for all the surrounding base stations and the optimum base station is selected from the detected values and the procedure for establishing the radio link channel is executed. The time is shortened, and the time required for connection or handover can be shortened.

By the way, in order to detect the RSSI value in all the surrounding base stations without fail, the search processing period is set to a period corresponding to three times the PCH transmission cycle. The time required from the start of the station search processing procedure to the selection of a connection destination or a handover destination base station is, as shown in FIG.
And a time Ts required to receive the PCH of the selected base station, and a very long time is required to establish a radio link channel.

On the other hand, in the second embodiment described above,
The time required from the start of the base station search processing procedure to the selection of a connection destination or a handover destination base station is as follows:
The BCCH or PC of the selected base station as shown in FIG.
Only the time Ts required until H is received is obtained, and the time required for selection can be extremely reduced.

(Other Embodiments) In the first embodiment, the base stations whose RSSI values are equal to or larger than the second threshold value are among the base stations whose search information is obtained in advance by using the non-communication period. If there is, the base station is selected as a connection destination or a handover destination, and the control procedure for establishing a radio link channel is immediately executed with the base station. But,
Before shifting to the radio link channel establishment control, a process of checking whether or not the RSSI value of the selected base station is equal to or greater than a second threshold value is performed, and if the RSSI value is equal to or greater than the second threshold value. When it is confirmed that there is, a control procedure for establishing a radio link channel with this base station may be executed.

By doing so, the time required for shifting to the radio link channel establishment control procedure is slightly longer by the time required for confirming the RSSI value. , Thereby increasing the call completion rate and the handover completion rate.

In each of the above embodiments, the received field strength (RSSI value) of the BCCH or PCH from the neighboring base station is used.
Is detected as information indicating the reception quality, and the base station is selected based on the information. The frame error ratio (FER) of the signal received from the peripheral base station is detected as data indicating the reception quality. The base station may be selected based on this. Alternatively, both the RSSI value and the FER may be detected, the reception quality may be determined based on the detection results, and the base station may be selected based on the determination result.

Further, in each of the above embodiments, the PHS has been described as an example. However, a cellular mobile communication system which executes a process of selecting an appropriate base station as a connection destination or a handover destination from peripheral base stations at the time of calling or handover. Then, the present invention can be applied to other systems. In addition, the circuit configuration of the mobile communication terminal device, the control procedure and control content of handover and call, the procedure and content of the search and selection means of the peripheral base station, etc.,
Various modifications can be made without departing from the scope of the present invention.

[0068]

As described above in detail, in the first invention, the reception qualities of the radio signals arriving from the plurality of base stations are detected and stored during the non-communication period, and the reception qualities with the base stations are determined. If it is necessary to establish a wireless link between the base stations, it is determined whether or not there is any of the stored reception qualities of the base stations that satisfies a predetermined determination condition, and the determination condition is satisfied. When there is a base station having a reception quality that is high, the base station is selected as a base station suitable for communication, and the procedure shifts to a radio link establishment procedure.

Further, in the second invention, when it is necessary to form a radio link with the base station, radio signals coming from each of the surrounding base stations are sequentially received, and the reception quality is detected. It is determined whether or not the detected reception quality satisfies a predetermined determination condition. When a base station whose reception quality satisfies the determination condition is found by this determination, a procedure for selecting the base station as a base station suitable for communication and establishing a radio link with this base station To move to.

Therefore, according to these inventions, it is possible to shorten the time required for searching for a base station, thereby shortening the connection time or switching time to the base station and improving the communication quality. A communication terminal device can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a PHS as an embodiment of a cellular mobile communication system according to the present invention.

FIG. 2 is a circuit block diagram showing a configuration of a PHS terminal which is a first embodiment of the mobile communication terminal device according to the present invention.

FIG. 3 is a flowchart showing a procedure and control contents of base station advance search control in the PHS terminal shown in FIG. 2;

FIG. 4 is a flowchart showing procedures and control contents of handover / calling control in the PHS terminal shown in FIG. 2;

FIG. 5 is a sequence diagram for explaining a handover operation by the PHS terminal shown in FIG. 2;

FIG. 6 is a circuit block diagram showing a configuration of a PHS terminal which is a second embodiment of the mobile communication terminal device according to the present invention.

7 is a flowchart showing a procedure and control contents of base station shortening search control in the PHS terminal shown in FIG.

8 is a sequence diagram for explaining a handover operation by the PHS terminal shown in FIG.

FIG. 9 is a sequence diagram for explaining a handover operation by a conventional PHS terminal.

[Explanation of symbols]

 INW: Integrated Services Digital Network (ISDN) SNW: Subscribed Telephone Network (PSTN) PNW: Packet Network TEL1-TELk: Wired Telephone CC: Control Center CS1-CSm: Base Station PS1-PSn: PHS Terminal Z1-Zm: Cell 1 ... Radio unit 2 Modem unit 3 TDMA unit 4 Talk unit 5A, 5B Control unit 6 Information storage unit 7 Data communication unit 8 Input unit 9 Display unit 11 Antenna 12 High-frequency switch (SW) 13 Receiving unit 14 Synthesizer 15 Transmitting unit 16 Received field strength detecting unit (RSSI) 21 Demodulating unit 22 Modulating unit 31 TDMA decoding unit 32 TDMA encoding unit 41 ADPCM transcoder 42 PCM codec 43 Speaker 44 ... microphone 51 ... base station pre-search control means 52, 54 ... c Dooba / calling control means 53 ... base stations short retrieval control means

Claims (6)

[Claims] 1. A mobile communication terminal device which selects a base station suitable for communication from a plurality of base stations arranged in a distributed manner and establishes a radio link with the base station. Reception quality detection means for detecting and storing the reception quality of the radio signals arriving from the plurality of base stations, respectively, and when it becomes necessary to establish a radio link with the base station, the reception quality detection means There is a determining unit that determines whether the reception quality of a base station detected in advance satisfies a predetermined determination condition, and as a result of the determination by the determination unit, there is a base station whose reception quality satisfies the determination condition. And a base station selecting means for selecting the base station as a base station suitable for communication and shifting to a radio link establishment procedure. 2. The reception quality detection unit according to claim 1, wherein at least one of an initial setting period from power-on to a transition to a standby state and a period in a standby state,
2. The mobile communication terminal device according to claim 1, wherein the reception qualities of the radio signals arriving from the plurality of base stations are respectively detected and stored. 3. The base station selecting means, if the result of the determination by the determining means indicates that there is no base station whose reception quality satisfies the determination condition, the base station whose reception quality is detected in advance by the reception quality detecting means. 2. The mobile communication terminal device according to claim 1, wherein a base station having the best reception quality is selected from the stations and the procedure shifts to a radio link establishment procedure. 4. When there is a base station whose reception quality satisfies the determination condition, the base station selection means detects again the reception quality of a radio signal coming from the base station, and determines the reception quality. Confirming whether or not the standard is satisfied, and if satisfied, selecting the base station as a base station suitable for communication and moving to a radio link formation procedure. Item 2. The mobile communication terminal device according to Item 1. 5. A mobile communication terminal device for selecting a base station suitable for communication from a plurality of base stations arranged in a distributed manner and establishing a radio link with the base station. When it is necessary to form a wireless link, wireless signals arriving from the plurality of base stations are sequentially received and their reception quality is detected, and whether the detected reception quality satisfies a predetermined determination condition is determined. Determining a base station whose reception quality satisfies the determination condition by selecting the base station as a base station suitable for communication and wirelessly communicating with the base station. And a base station selecting means for shifting to a procedure for establishing a link. 6. The base station, wherein, if no base station whose reception quality satisfies the determination condition is found by the determination unit within a predetermined time, the base station detects the reception quality within the predetermined time. 6. The mobile communication terminal device according to claim 5, wherein a base station having the best reception quality is selected from the following, and the procedure shifts to a procedure for establishing a radio link with the base station.