JP2001112038A - Mobile communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the user-friendliness of a terminal and the communication quality by reducing the time required for the connection to a wireless channel. SOLUTION: A base station retrieval control means 54 searches peripheral base stations to detect an effective base station as a connection destination and places priority on the detected base station on the basis of the reception level and number of times of reception for a prescribed search period and registers it to a priority table 63. Then a link channel setup request is sent to the base station, whether or not a link channel assignment is received is monitored, when not received, whether or not two effective base stations or over are registered is discriminated. When the two stations or over are registered, a connection request revision transmission means 52 changes the destination base station and transmits the line channel setup request. When only one valid base station is registered, a connection request re-transmission control means 51 repeats re-transmission of the link channel setup request to the same base station.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to, for example, PHS
(Personal Handyphone System) A cellular mobile communication system in which a plurality of base stations are installed in a service area and a mobile station is selectively connected to these base stations for communication. Mobile communication terminal.

[0002]

2. Description of the Related Art In PHS, when a mobile communication terminal originates a call,
When the mobile communication terminal moves during communication and communication with the base station becomes difficult, a connection procedure of a wireless channel is executed between the mobile communication terminal and the base station.

For example, a mobile communication terminal searches for nearby base stations to select a valid base station, and transmits a link channel establishment request to the selected base station. On the other hand, the base station allocates a link channel to the requesting mobile communication terminal to form a wireless link with the mobile communication terminal, and thereafter performs a predetermined connection procedure and thereafter starts or resumes wireless communication. I do.

[0004] When a link channel is not allocated from a base station after a certain period of time has passed with respect to transmission of a link channel establishment request, the mobile communication terminal issues a link channel establishment request to the same base station again. Transmit, thereby receiving a link channel assignment. This retransmission of the link channel establishment request is repeatedly performed at a predetermined time interval up to a specified number of times until a link channel is allocated from the base station.

[0005]

However, if the retransmission procedure of the link channel establishment request is repeated until the link channel is allocated as described above, until the link channel is established and the radio communication is started, or the radio communication is started. It will take a lot of time before it is resumed. This means that the connection waiting state continues for a long time for the user of the mobile communication terminal, and the usability of the terminal device is reduced. In particular, in the case of performing a so-called handover in which the connection-destination base station is switched during communication, the communication interruption time becomes long, and the communication quality is deteriorated. For example, since the communication interruption time is generally several seconds or more, some users may mistakenly think that the communication has been disconnected and perform the call termination operation, which is extremely undesirable.

[0006] In addition, the fact that the retransmission procedure of the link channel establishment request is repeated without receiving the link channel assignment may cause the radio environment between the requesting mobile communication terminal and the base station to be significantly degraded. High in nature. For this reason,
Even if a link channel is established and communication is started or restarted, the mobile communication terminal is forced to perform communication in a state where the communication quality is degraded.

The present invention has been made in view of the above circumstances, and has as its object to reduce the time required for connecting a wireless channel, thereby improving the usability and communication quality of a terminal device. To provide a communication terminal.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a mobile communication system in which a plurality of base stations distributed in a service area are selectively connected via a radio channel for communication. A terminal for selecting a valid base station as a wireless channel connection target, and transmitting a wireless channel connection request to a first base station among the base stations selected by the selection unit; In addition to connection request transmitting means for monitoring the return of a valid response to the request, the apparatus further comprises a connection request change transmitting means. If the connection request transmitting unit does not detect the return of a valid response, the connection request change transmitting unit differs from the first base station among the valid base stations selected by the selecting unit. It is configured to transmit a wireless channel connection request to a second base station.

Therefore, according to the present invention, when the response to the transmission of the wireless channel connection request is not returned from the first base station, the wireless environment between the mobile communication terminal and the first base station is reduced. Judging that it has deteriorated,
The retransmission procedure of the wireless channel connection request to the base station is not performed, and the wireless channel connection request is transmitted to another second base station. For this reason, the problem that the retransmission procedure of the wireless channel connection request is repeated for the base station in which the wireless environment is deteriorated is prevented, whereby the connection waiting time or the connection interruption time is reduced, and the usability and communication quality of the terminal device are reduced. improves. Further, even after the connection of the wireless channel, the inconvenience of being forced to communicate in a state where the wireless environment is degraded is reduced, so that the communication quality after the start of communication is maintained at a high level.

[0010] More specifically, the present invention further comprises determining means for determining whether or not the number of valid base stations selected by the selecting means is equal to or greater than a predetermined number. Is determined to be a predetermined number or more,
And, when the return of a valid response is not detected by the connection request transmitting unit, the connection request change transmitting unit
The first base station among the valid base stations selected by the selection means.
Is configured to transmit a wireless channel connection request to a second base station different from the second base station.

[0011] Also, a connection request retransmitting means is provided, and if the number of valid base stations is determined to be less than a predetermined number by the determining means, the wireless channel connection request is retransmitted to the first base station. The configuration is as follows.

By doing so, the base station of the connection request destination is changed only when there is a suitable base station as the transmission change destination of the wireless channel connection request, and otherwise, the base station of the connection request is transmitted to the same base station. A retransmission procedure is performed. Therefore,
There is no fear that the connection of the wireless channel will fail as a result of changing the transmission destination of the connection request, thereby maintaining high reliability.

Further, according to the present invention, when there are a plurality of valid base stations selected as connection targets, the selection means has a function of assigning a priority to these base stations. It is also characterized in that a second base station is selected from the base stations selected by the means in accordance with the above-mentioned priority and a connection request for a wireless channel is transmitted.

By doing so, the probability that a base station in a good wireless environment can be selected as a transmission change destination of a wireless channel connection request is increased, and thereby a stable connection control procedure can be executed.

The following two configurations can be considered as means for giving the priority. That is, in the first configuration, the selection means is provided with a counting means for counting the number of receptions of the signals transmitted by the respective base stations in the predetermined period for each base station, and for the effective base station selected as the connection target, The priority is assigned based on the counting result obtained by the counting means. With this configuration, it is possible to easily assign the priority to the selected effective base station.

In a second configuration, the selection means includes a reception level detection means for detecting a reception level of a signal arriving from each of the surrounding base stations, and a base station which determines the number of receptions of the signal arriving from each of the base stations in a predetermined period. Counting means for counting for each station, for the effective base station selected as a connection target, for the reception level detected by the reception level detection means,
The priority is assigned based on the counting result obtained by the counting means. With this configuration, the state of the wireless environment can be determined more accurately from the reception level and the number of receptions, and this can be reflected in the priority assignment.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a mobile communication system according to the present invention.
1 to CSn indicate base stations. These base stations CS
1 to CSn are geographically distributed in a service area covered by the system, and each form a wireless area called a cell.

The mobile communication terminals PS1 to PSm are connected to the nearest base station via a radio communication channel (traffic channel) in a cell formed by each of the base stations CS1 to CSn. As a radio access scheme between the base stations CS1 to CSn and the mobile communication terminals PS1 to PSm, for example, TDMA-TDD (Time Division Multiple
Tiple Access-Time Division Duplex) is used. The mobile communication terminals PS1 to PSm are connected to a portable information terminal PS1 and PS2 having a data communication function and a wireless access function, and a personal computer PC to the mobile phone PSi, in addition to the mobile phone Pm having only a call function. There are things.

Each of the base stations CS1 to CSn is connected to the public network INW via a wired line. Public network INW is an integrated services digital network (ISDN)
And an I 'interface network for accommodating each of the base stations CS1 to CSn in the ISDN. Public Network I
The NW is connected to a computer network, a corporate network, and the like, in addition to many subscriber wire terminal devices. For example, in the case of the Internet, the access server A of the Internet service provider is provided in the ISDN.
S is connected and connected to the Internet ITN via the access server AS. Internet ITN
Has many WWW (World-Wide Web) servers WS1 and W
Are connected, and by using the TCP / IP protocol, it is possible to access not only the subscriber wired terminals but also the mobile terminal devices PS1 to PSm.

The content server TS owned by the Internet service provider is connected to the access server AS. This content server TS
Are the subscriber wired terminals and the mobile terminal devices PS1 to PSm
Has the function of downloading various information in response to the request of

Further, the mobile data communication system of this embodiment includes a management control device MS. The management control device MS has, for example, a function as a mail server in addition to a system management function of performing authentication and accounting processing for each of the mobile terminal devices PS1 to PSm, and each of the base stations CS1 to CSn via the public network INW. Connected to.

The mobile communication terminals PS1 to PS
m is configured as follows. FIG. 2 is a circuit block diagram showing the configuration. The mobile communication terminals PS1 to PSm include a radio unit 1 having an antenna 11, a modem unit 2, a TDM
A section 3, communication section 4, control section 5, information storage section 6,
The system includes a data communication unit 7, an input unit 8 having a keypad, and a display unit 9 using a liquid crystal display (LCD).

That is, the radio carrier signals arriving from the base stations CS1 to CSn 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 a local oscillation signal generated from the frequency synthesizer 14 and down-converted into a received intermediate frequency signal. The frequency of the local oscillation signal generated from the frequency synthesizer 14 is set to a value corresponding to the radio channel frequency according to an instruction from the control unit 5.

The radio unit 1 includes a reception electric field strength detection unit 1
6 are provided. The reception field strength detection unit 16 detects the reception field strength (RSSI) of a radio carrier signal arriving from a base station in communication or a nearby base station, and the detected value is used, for example, to determine and display reception quality. Is notified to the control unit 5.

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 audio data, the audio data is transmitted to the interface unit 4.
To enter. 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
, A PCM codec 42, a speaker 43, and a microphone 44. The ADPCM transcoder 41 decodes the audio data output from the TDMA decoding unit 31. The PCM codec 42 uses the A
The digital audio signal output from the DPCM transcoder 41 is converted into an analog signal, and this audio signal is output from the speaker 43 as loudspeaker.

The data communication unit 7 receives the data supplied from the TDMA decoding unit 31 and supplies the data to the control unit 5. If the received data is control data, the control unit 5 analyzes the control data and performs necessary control.
On the other hand, if the received data is packet data arriving from a server or the like, 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 is further compression-coded by the ADPCM transcoder 41. The encoded audio data is TD
It is input to the MA encoding unit 32. The control data and packet data output from the control unit 5 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 voice data output from the CM transcoder 41 and the control data and packet data output from the data communication unit 7 are multiplexed by inserting them into the transmission time slots specified by the control unit 5. The modulation unit 22 digitally modulates the transmission intermediate frequency signal with the multiplexed digital communication signal output from the TDMA encoding unit 32, and inputs the modulated transmission intermediate frequency signal to the transmission unit 15.

The transmission section 15 mixes the modulated transmission intermediate frequency signal with the local oscillation signal generated from the frequency synthesizer 14, upconverts the mixed 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 information storage unit 6 includes a search table 61 used for base station search processing and a sorting table 6 in addition to a data storage unit for storing transmitted / received mail data and the like.
2 and a priority order table 63 are provided. The search table 61 stores the peripheral base stations detected by the base station search and the reception electric field strength (reception level) thereof.
The organizing table 62 is used to store the average reception level of each peripheral base station and the number of receptions within the search period obtained based on the search results stored in the search table 61. The priority order table 63 stores the priority order of each peripheral base station obtained based on the storage result of the organizing table 62.

The control unit 5 includes, for example, a microcomputer as a main control unit. The functions related to the present invention include connection request retransmission control means 51, connection request change transmission control means 52, connection procedure selection control Means 53;
A base station search control unit 54 is provided.

The base station search control means 54 searches the surrounding base stations for a predetermined reception period in accordance with the outgoing / incoming call and the handover, and searches the reception level of the search table 61.
To memorize. Then, the average reception level of each peripheral base station detected during the reception period is obtained, the number of receptions of the downlink control signal for each peripheral base station is counted, and the average reception level and the count value are stored in the organizing table 62. Remember.
Further, based on the average reception level and the count value stored in the organizing table 62, priority is given to each of the neighboring base stations, and the result is stored in the priority table 63.

If the connection request retransmission control means 51 cannot receive the link channel assignment from the transmission destination base station after transmitting the link channel establishment request, the connection request retransmission control means 51 transmits the link channel to the base station until it can receive the link channel assignment. A certain period of time (1.2
(Seconds).

The connection request change transmission means 52, after transmitting the link channel establishment request, if it cannot receive the link channel assignment from the base station of the transmission partner, and transmits the priority table created by the base station search control means 54. 6
According to 3, the base station with the next highest priority is selected and a link channel establishment request is transmitted. Until a link channel assignment can be received, different base stations are sequentially selected in accordance with the priority order and a link channel establishment request is transmitted.

The connection procedure selection control means 53 includes a priority table 6 created by the base station search control means 54.
3, the number of valid peripheral base stations as a connection destination is determined, and when there are two or more valid base stations, the connection request change transmission unit 52 is selected to execute the connection procedure. When only one peripheral base station is valid as a connection destination, the connection request retransmission control means 51 is selected to execute the connection procedure.

Next, the operation of the apparatus configured as described above will be described. Now, suppose that, as shown in FIG. 6, for example, while the mobile communication terminal PSi is performing wireless communication with the base station CSj, a deterioration in the reception level or a deterioration in the reception quality is detected in the mobile communication terminal PSi. Then, the mobile communication terminal PSi first executes search control of the peripheral base station by the base station search control means 54. FIG. 4 is a flowchart showing the control procedure and control contents.

That is, the mobile communication terminal PSi firstly, in step 4a, transmits each of the neighboring base stations CS on the control carrier.
The reception levels of the downlink signals arriving from 1 to CSn, that is, the reception electric field strength, are sequentially detected in time series in a preset search period. FIG. 3 shows an example of the detection result. Then, the detection result is stored in the search table 61 as shown in FIG.

Next, in step 4b, each of the neighboring base stations CS whose reception levels are stored in the search table 61
For each of 1 to CS4, the average value of the reception level is calculated, and the number of receptions of the downlink signal is counted. Then, the average value of the reception level and the number of receptions are shown in FIG.
As shown in (b), it is stored in the organizing table 62 in association with each of the peripheral base stations CS1 to CS4.

Further, in step 4c, each of the peripheral base stations CS1 to CS4 stored in the
Of the switching destination is determined based on the reception level average value and the number of times of reception, and priorities are assigned in order from the switching destination that is preferable. Then, the peripheral base stations CS1 to CS4 are rearranged according to the priority and stored in the priority table 63.

For example, first, priority is temporarily assigned to the neighboring base stations CS1 to CS4 in descending order of the reception level.
Next, the number of receptions is compared between base stations whose reception level differences are within a predetermined range, and the priority is changed so that the priority of a base station having a large number of receptions is increased. FIG. 5C shows an example of the configuration of the priority order table 63 determined in this way.

When the peripheral base station search is completed, the mobile communication terminal PSi next selects the first base station CS4 in the priority table 63, and the base station CS4 receives the first priority. A link channel establishment request is transmitted as shown in FIG. Then, in response to this request, the base station CS4 returns a link channel assignment, and if this signal is received by the mobile communication terminal PSi, the mobile communication terminal PSi thereafter executes a connection procedure defined by the standard, and Handover from CSj to base station CS4 is performed.

However, now, for example, the mobile communication terminal PSi
, The radio environment between the base station CS4 and the mobile communication terminal PSi is degraded, and the link channel assignment returned from the base station CS4 cannot be received by the requesting mobile communication terminal PSi.

Then, in the mobile communication terminal PSi, the connection procedure selection control means 53 determines whether or not, for example, two or more valid base stations are registered in the priority order table 63 as switching destinations. Since two or more stations are registered at this time, the connection request change transmitting unit 52 is activated, and the base station CS having the second highest priority is obtained from the priority table 63.
1 and transmits a link channel establishment request to the base station CS1 as shown in FIG. In response to this request, the base station CS1 monitors the return of the link channel assignment from the base station CS1, and if the link channel assignment is received, shifts to a connection procedure for handover. The base station of the third rank is selected and a link channel establishment request is transmitted. Thereafter, similarly, until the link channel assignment can be received, the mobile communication terminal PSi sequentially selects each of the peripheral base stations registered in the priority order table 63 according to its priority and repeats the transmission of the link channel establishment request.

That is, when two or more valid base stations are registered as switching destinations in the priority order table 63, the base station of the transmission destination is changed each time a link channel establishment request is transmitted.

On the other hand, it is assumed that only one valid base station is registered in the priority order table 63 as a switching destination. In this case, since the mobile communication terminal PSi cannot change the transmission destination of the link channel establishment request, it activates the connection request retransmission control means 51, and as shown in FIG.
Resend the link channel establishment request to. Thereafter, the retransmission procedure of the link channel establishment request is repeated as shown in FIG. 7 until the link channel assignment is returned from the base station CS4 and can be received by the mobile communication terminal PSi.

The above-described transmission control of the link channel establishment request is executed not only at the time of handover but also at the time of initial setting of the radio channel when the mobile communication terminal PSi performs a calling operation. FIG. 8 is a sequence diagram showing a transmission control procedure of a link channel establishment request executed at the time of wireless channel initialization upon transmission.

As described above, in this embodiment, when a new radio link needs to be set or switched, such as at the time of calling or handover, the base station search control means 54 searches for and connects to neighboring base stations. A valid base station is detected first, and a priority is assigned to the valid base station based on the reception level and the number of receptions in a fixed search period, and the priority is registered in the priority table 63. Then, a link channel establishment request is transmitted to the base station selected as the connection destination, and it is monitored whether or not the link channel assignment can be received from this base station. If the link channel assignment cannot be received,
It is determined whether or not two or more valid base stations are registered. If two or more base stations are registered, the connection request change transmitting unit 52 is activated, and the destination base station is transmitted until the link channel assignment can be received. And transmission of the link channel establishment request is repeated. On the other hand, if only one valid base station is registered, the connection request retransmission control means 5
1 is started to repeatedly transmit a link channel establishment request to the same base station.

Therefore, according to this embodiment, the problem that the retransmission procedure of the link channel establishment request is repeated for the base station whose radio environment is degraded is prevented, whereby the connection waiting time at the time of transmission and the connection at the time of handover are prevented. The interruption time is shortened, and the usability and communication quality of the mobile communication terminal are improved. Also, even after connecting to a wireless channel,
Communication is no longer forced in a state where the wireless environment is degraded, so that high communication quality after the start of communication can be maintained.

Further, the transmission destination of the link channel establishment request is changed only when two or more valid base stations are found as connection destinations, and when only one station is found, a link channel establishment request is sent to the same base station. Is performed. For this reason, compared to the case where the connection request change control procedure is always executed, the probability of failing the connection of the radio link is kept low, thereby reducing the probability of being busy and keeping the success rate of handover high. it can.

FIG. 9 shows the effect of using the connection request change transmission control procedure according to the present invention in comparison with the conventional case, ie, the case of using only the connection request retransmission control procedure. 5 shows the result of measuring the connection time at the time of handover and quantitatively analyzing this. FIG. 10 is a graph showing the results of the measurement and analysis shown in FIG. 9, wherein Q1, Q2, and Q3 indicate the method of the present invention, and N1, N2, and N3 indicate the conventional method. As is clear from the results of the measurement analysis, the time required for the connection is greatly reduced without affecting the success rate of the handover.

Further, in this embodiment, when assigning priorities to the neighboring base stations obtained by the search, based on the average reception level of each peripheral base station and the number of receptions obtained within a predetermined search period. Is determined as a switching destination, and priorities are assigned in order from the switching destination that is preferred. Therefore, more appropriate priorities can be easily assigned according to the actual state of the wireless environment.

That is, in general, in a cellular mobile communication system such as a PHS, even when the distance between a plurality of mobile communication terminals and a base station are equal and the reception levels are substantially equal, the state of the radio environment and the mobile Communication quality differs depending on the location of the communication terminal because shadowing and fading occur. In other words, there may be a case where the communication quality is high even if the reception level is low, and vice versa.

Therefore, as in this embodiment, if the priority order is determined in consideration of the number of receptions from each peripheral base station in a predetermined search period, the wireless environment between each base station and the mobile communication terminal can be determined. In consideration of the difference, the priority can be more appropriately and easily assigned.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the PHS has been described as an example, but a PDC (Personal Digital Cellu
lar) and GSM (Global System for Mobile Communicat)
The present invention can also be applied to mobile communication terminals used in other cellular mobile communication systems, such as ion communication.

In addition, the circuit configuration of the mobile communication terminal, the base station search control procedure and its contents, the procedures and control contents of the connection request change transmission control and the connection request retransmission control, and the validity in selecting the connection request change transmission control The number of base stations and the like can be variously modified and implemented without departing from the gist of the present invention.

[0058]

As described above in detail, according to the present invention, a selection means for selecting an effective base station as a connection target of a radio channel, and a first base station among the base stations selected by the selection means In addition to a connection request transmitting means for transmitting a wireless channel connection request and monitoring the return of a valid response to the connection request, a connection request change transmitting means is provided.
If the connection request transmitting unit does not detect the return of a valid response, the connection request change transmitting unit differs from the first base station among the valid base stations selected by the selecting unit. It is configured to transmit a wireless channel connection request to the second base station.

Therefore, according to the present invention, it is possible to prevent a problem that the retransmission procedure of the radio channel connection request is repeated for the base station whose radio environment is degraded, thereby shortening the connection waiting time or the connection interruption time, A mobile communication terminal capable of improving the usability of the terminal device and the communication quality can be provided.

[Brief description of the drawings]

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

FIG. 2 is a circuit block diagram showing a configuration of a mobile communication terminal of the system shown in FIG.

FIG. 3 is a diagram showing an example of a search result of a peripheral base station.

FIG. 4 is a flowchart showing a procedure and control contents of base station search control.

FIG. 5 is a diagram showing an example of a search table, an arrangement table, and a priority table used for selecting an effective base station in base station search control.

FIG. 6 is a sequence diagram showing an example of a connection request change transmission procedure performed at the time of handover.

FIG. 7 is a sequence diagram showing an example of a connection request retransmission procedure performed at the time of handover.

FIG. 8 is a sequence diagram showing an example of a connection request change transmission procedure performed at the time of calling.

FIG. 9 is a diagram showing the effects of the present invention in the form of a table in comparison with the conventional example.

FIG. 10 is a diagram showing the effect of the present invention in the form of a graph in comparison with the related art.

[Explanation of symbols]

CS1 to CSn: Base stations PS1 to PSm: Mobile communication terminals INW: Public network MS: Management control device ITN: Internet WS1, WS2, WS3: WWW server AS: Access server of Internet service provider TS: Content server 1. Wireless Unit 2 Modem unit 3 TDMA unit 4 Talk unit 5 Control unit 6 Information storage unit 7 Data communication unit 8 Input unit 9 Display unit 11 Antenna 12 High-frequency switch (SW) 13 Receiver unit 14 ... Synthesizer 15 ... Transmission unit 16 ... Reception electric field strength detection unit (RSSI detection unit) 21 ... Demodulation unit 22 ... Modulation unit 31 ... TDMA decoding unit 32 ... TDMA encoding unit 41 ... ADPCM transcoder 42 ... PCM codec 43 ... Speaker 44 ... Microphone 51: Connection request retransmission control means 52: Connection Request change transmission controller 53 ... connection procedure selection control means 54 ... base station search control section 61 ... search table 62 ... organized tables 63 ... priority table

Claims (6)

[Claims] 1. A mobile communication terminal selectively connected to a plurality of base stations distributed in a service area via a wireless channel to perform communication, and selects an effective base station as a connection target of the wireless channel. Connection request transmitting means for transmitting a wireless channel connection request to the first base station among the base stations selected by the selection means, and monitoring the return of a valid response to the connection request; When no valid response is returned by the connection request transmitting means, a radio channel is transmitted to a second base station different from the first base station among the valid base stations selected by the selecting means. And a connection request change transmission means for transmitting the connection request. 2. A mobile communication terminal, which is selectively connected to a plurality of base stations distributed in a service area via a wireless channel to perform communication, selects an effective base station as a connection target of the wireless channel. Selecting means, and a first base station among the valid base stations selected by the selecting means.
A connection request transmitting unit that transmits a wireless channel connection request to the base station and monitors the return of a valid response to the connection request; and the number of valid base stations selected by the selection unit is a predetermined number or more. Determining means for determining whether or not a valid base station is determined to be a predetermined number or more by the determining means, and when the return of a valid response is not detected by the connection request transmitting means, Connection request change transmission means for transmitting a wireless channel connection request to a second base station different from the first base station among the valid base stations selected by the selection means. Mobile communication terminal. 3. A connection request retransmitting means for retransmitting a wireless channel connection request to the first base station when the determining means determines that the number of valid base stations is less than a predetermined number. 3. The apparatus according to claim 2, further comprising:
The mobile communication terminal as described. 4. When there are a plurality of valid base stations selected as a connection target, said selection means has means for giving priority to these base stations based on the reception quality thereof. The request change transmitting means selects a second base station from the base stations selected by the selecting means according to the priority and transmits a wireless channel connection request. Mobile communication terminal. 5. The selecting means includes counting means for counting the number of receptions of a signal transmitted by each peripheral base station in a predetermined period for each base station, and for a valid base station selected as a connection target, The mobile communication terminal according to claim 4, wherein priorities are assigned based on counting results obtained by said counting means. 6. A receiving level detecting means for detecting a receiving level of a signal arriving from each of the peripheral base stations, and a receiving number of the signal arriving from each of the base stations in a predetermined period for each base station. Counting means for counting, based on the reception level detected by the reception level detection means and the counting result obtained by the counting means, for a valid base station selected as a connection target, 5. The mobile communication terminal according to claim 4, wherein