JPH0746644A - Mobile communication system - Google Patents

Abstract

PURPOSE:To prevent the interruption and disconnection of communication due to the changeover failure of a base station in a mobile object communication system for automatically switching the base station with which a mobile station performs communication to the other base station when the communication state of the mobile station and the base station is degraded. CONSTITUTION:When the mobile stations PS1-4 move during the communication with one of the base stations CS1-3 connected to a switchboard XS by wires K1-3 and are about to deviate from the communication areas E1-3 of the base station (communication base station) during the communication, the communication base station lets the mobile station report the reception level of radio waves received from the other base stations and informs the switchboard XS of the reported result. The switchboard XS judges whether or not the other base stations CS1-3 capable of the communication with the mobile stations PS1-4 are present based on the reported result and transmits voice data indicating that the changeover of the base station can not be performed and the communication is to be interrupted when the mobile station moves further through the communication base station to the mobile station when the other base station is not present. The users of the mobile stations PS1-4 are informed by the above mentioned procedure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system for automatically switching a base station with which a mobile station communicates to another base station when the communication condition between the mobile station and a predetermined base station deteriorates. .

[0002]

2. Description of the Related Art Due to the recent development of communication technology and the increasing demand for communication tools that support speedy acquisition of information and space movement, mobile communication systems such as car phones and mobile phones have been put to practical use. . Then, in such a mobile communication system, each mobile station such as a telephone sets a communication radio channel from the base station within the communication area of any one of the base stations connected to the predetermined communication network. By receiving the allocation, wireless communication with the base station becomes possible, and the base stations are connected to each other or to a predetermined communication network.

In this type of mobile communication system, when the mobile station moves and tends to deviate from the communication area of the base station in communication, the communication condition deteriorates and it becomes impossible to continue communication. It is necessary to automatically switch the base station with which the mobile station communicates according to the movement of the mobile station.

Therefore, conventionally, in this type of mobile communication system, for example, when a mobile station moves and the communication state with a base station (switching base station) currently in communication deteriorates,
First, the switching start means provided in the mobile station communicates with a base station (switch destination base station) in charge of a communication area other than the communication area of the switch source base station in which the mobile station is invading. A switching destination base station that transmits a request signal for requesting channel allocation receives a wireless signal (a wireless line such as a carrier frequency or a slot) or a wired resource (a wired line connecting a communication network and a base station). ) Determines whether or not a communication radio channel can be assigned to the mobile station, and if so, information (carrier frequency, communication protocol, etc.) on the communication radio channel can be assigned to the mobile station. And requests the communication network to switch the communication line from the switching source base station to its own station, and further, the switching source base station to the wireless channel for communication to the mobile station via the communication network. After instructing to cut, to initiate communication with the mobile station, procedures are automatically perform switching of the base station in such.

That is, the switching operation of the base station is started when the switching start means of the mobile station requests the allocation of the communication radio channel to another base station.

[0006]

However, in the above-mentioned conventional mobile communication system, it is preferable if the switching destination base station can allocate the communication radio channel to the mobile station as described above. However, if the allocation cannot be made, the switching destination base station transmits a refusal signal indicating that the communication radio channel cannot be allocated to the mobile station, and the mobile station receiving the refusal signal switches It is designed to give up communication with the destination base station and restart communication with the switching source base station.

Therefore, in the above conventional mobile communication system, when the switching destination base station cannot allocate the communication radio channel to the mobile station, that is, when the switching of the base station fails, the mobile station If communication is interrupted before resuming communication with the switching source base station, and if the mobile station is already outside the communication area of the switching source base station at that time, the mobile station There is a problem that communication cannot be resumed because the communication with the base station cannot be resumed. Then, such interruption or disconnection of communication could not be done by the intention of the user who uses the mobile station.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a mobile communication system capable of preventing interruption or disconnection of communication due to a switching failure of a base station.

[0009]

SUMMARY OF THE INVENTION That is, the present invention, which has been made to achieve the above-mentioned object, has a plurality of base stations connected to a communication network and each having a predetermined communication area, as shown in FIG. A mobile station capable of communicating with the base station by receiving a radio channel for communication from the base station within a communication area of a predetermined base station among the base stations; When the communication state with the predetermined base station deteriorates as the station moves, the other base station in charge of the communication area in which the mobile station is located becomes a new communication partner of the mobile station. In a mobile communication system comprising switching start means for requesting a station to allocate a communication radio channel and starting switching operation of a base station, the switching start means switches to the mobile station or the base station. Start operation Provided with a communication state detection means for detecting the deterioration of the communication state between the mobile station and the base station before,
When the mobile station detects that the communication state with the communication base station communicating with the mobile station has deteriorated by the communication state detecting means, the mobile station transmits at least each base station other than the communication base station. The reception level notifying means for measuring the reception level of the radio wave present and notifying the measurement result to the communication network via the communication base station, and the fact that the base station cannot be switched from the communication network via the communication base station. Means for notifying the user of the mobile station that the base station cannot be switched, and notifies the communication network from the mobile station via the communication base station. Upon receiving the measured result, the determination means for determining whether or not there is a base station capable of communicating with the mobile station other than the communication base station based on the measurement result, and a determination means other than the communication base station. Mobile station above When it is determined that there is no communicable base station, the mobile station is provided with a notification command means for issuing the notification command to the mobile station via the communication base station. There is.

[0010]

In the mobile communication system of the present invention configured as described above, first, the communication state detection means provided in the mobile station or the base station and the switching start means of the mobile station are provided in another base. Before requesting the station to allocate the radio channel for communication and starting the switching operation of the base station, the deterioration of the communication state between the mobile station and the base station is detected.

Then, when the communication state detecting means detects that the communication state with the communication base station communicating with the mobile station has deteriorated, the reception level notifying means provided in the mobile station at least the communication base station. Other than that, the reception level of the radio wave transmitted from each base station is measured, and the measurement result is notified to the communication network via the communication base station.

Then, the determination means provided in the communication network
Based on the measurement result, it is determined whether or not there is a base station capable of communicating with the mobile station other than the communication base station, and the notification command means also provided in the communication network is the mobile station other than the communication base station by the determining means. When it is determined that there is no communicable base station, a notification command indicating that the base station cannot be switched is issued to the mobile station via the communication base station.

The notifying means provided in the mobile station is
Upon receiving the notification command, the user of the mobile station is notified that the base station cannot be switched. That is, in the mobile communication system of the present invention, similarly to the conventional mobile communication system, when the mobile station moves and the communication state with the base station deteriorates, the base station that communicates with the mobile station is automatically determined. Before starting the switching operation, it is determined whether or not there is a base station that can communicate with the mobile station. If there is no base station that can communicate with the mobile station, the mobile station The user is notified that the base station cannot be switched.

Therefore, according to the mobile system of the present invention, it becomes possible for the user of the mobile station to recognize in advance that communication will not be possible if the user moves further, and switching of the base station fails. It is possible to prevent the interruption and disconnection of communication according to the intention of the user of the mobile station.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is a block diagram showing the configuration of a mobile communication system of an embodiment to which the present invention is applied.

As shown in FIG. 2, the mobile communication system according to the present embodiment is arranged on the premises of a business office or the like and the INS
An exchange XS that is connected to a public communication network such as a network and that connects extension telephones within a premises to each other and also connects extension telephones to a public communication network.
And a plurality (three in FIG. 2) of base stations CS1 to CS3 which are arranged at predetermined locations on the premises and are connected to the exchange XS by wires K1 to K3, respectively, and which are part of the communication network
And a plurality of (four in FIG. 2) cordless telephones as mobile stations, which are connected to a public communication network and are mutually connected by performing wireless communication between the base stations CS1 to CS3. , Simply called a telephone) PS1-PS
4 and.

In FIG. 2, the main purpose of C1 is to control incoming / outgoing calls, which is carried out in order to realize communication for actual communication between the base stations CS1 to CS3 and the telephones PS1 to PS4 as described later. Represents a control carrier commonly used by each communication device, and C2 represents a communication carrier individually assigned to each communication device and used for communication for an actual call. Also, E1 to E3
Represent communication areas of the base stations CS1 to CS3, respectively.

The mobile communication system of this embodiment is
Time Division Multiplex Acces (TDMA) in which frequencies are time-division multiplexed and a time slot is assigned to each telephone.
s) method, and TDD (Time Division Duty) that uses the same frequency in time division for downlink communication (communication from the base station to the telephone) and uplink communication (communication from the telephone to the base station).
piex) method, 4-channel multiplexing multi-carrier TDMA that can multiplex and use up to 4 lines per frequency.
A so-called PHP (Personal Handy P
Hone) is a digital cordless phone system called.

Next, as shown in FIG. 3, each of the telephone sets PS1 to PS4 includes a CPU 2, a ROM 4, a RAM 6, an operation key 8 including a power switch, a transmission switch, a dial button, and a communication logic circuit group for processing communication data. The analog audio signal from the gate array unit 10 and the microphone 12 is converted into a digital signal and output to the gate array unit 10, and the digital audio signal from the gate array unit 10 is converted into an analog signal and output to the speaker 14. Communication data from the voice processing circuit 16 and the gate array unit 10 is shifted by π / 4 QPSK at a radio frequency of 1.9 GHz band.
(Quadrature PhaseShift Keying) Modulation and demodulation of a reception signal from the antenna 18 and transmission of the signal from the antenna 18, and a radio unit 20 including a modulation / demodulation circuit for outputting to the gate array unit 10 and a signal received by the antenna 18. A reception level detector 22 for detecting the reception level of
It is configured as a well-known cordless telephone equipped with.

Here, the gate array unit 10 includes the CPU 2
Based on the communication timing instructed by the TDMA, various control data generated by the CPU 2 for the incoming and outgoing call control and the base station switching control, and the call voice data converted into a digital signal by the microphone 12 and the voice processing circuit 16 are transferred to the TDMA. It is converted into communication data for transmission and output to the wireless unit 20, and
Various kinds of control for outgoing / incoming call control and base station switching control transmitted from the received signals by the base stations CS1 to CS3 are taken out from the received voice signal demodulated by the radio unit 20 and output to the voice processing circuit 16. The data is taken out and output to the CPU 2. Then, the CPU 2, based on the command input from the operation key 8 and the control data for controlling the incoming and outgoing calls from the base stations CS1 to CS3, as described later, when the power switch of the operation key 8 is turned on, the telephone set concerned. Is registered in the switching center XS via any of the base stations, or a communication wireless channel (hereinafter, simply referred to as a communication channel used for a call with the base station before the actual communication for the call is started). , A radio channel), a process for establishing a link, etc.
When various incoming / outgoing call control processes for connecting to CS3 are executed and the telephone moves and the communication state with the base station in communication deteriorates, the base station switching control from the base station in communication is performed. Based on the control data, a base station switching control process or the like for switching a base station to be a communication partner is executed, and further, before the base station switching control process is executed, a wireless status report process described later, which is specific to the present invention. To execute.

As shown in FIG. 3, the base stations CS1 to CS3 are connected to a CPU 32, a ROM 34, a RAM 36, a gate array section 38 including a communication logic circuit group for processing communication data, and an exchange XS. The communication data generated by the ISDN interface unit 40 and the gate array unit 38 is modulated and transmitted from the antenna 42 exactly as in the case of the telephone sets PS1 to PS4, and the reception signal from the antenna 42 is demodulated to generate the gate array. Part 38
It is configured as a well-known transmitting / receiving station including a radio unit 44 including a modulation / demodulation circuit for outputting to.

Then, the base station CS configured as described above
In 1 to CS3, the gate array unit 38 includes the CPU 3
2 based on the communication timing instructed by the CPU 32
Various control data for outgoing / incoming call control and base station switching control, which have been generated in step S1, and communication data input from the exchange XS via the ISDN interface section 40 are converted into communication data for TDMA transmission, and the wireless section is converted. Output to 44,
The reception signal demodulated by the radio unit 44 is output to the exchange XS via the ISDN interface unit 40, and
Various control data for outgoing / incoming call control and base station switching control transmitted from the telephones PS1 to PS4 are extracted from the received signal and output to the CPU 32. And the CPU 32
Is based on control data for controlling incoming / outgoing calls from the telephone sets PS1 to PS4, a line use state at that time, incoming call request (call request) data input from the exchange XS via the ISDN interface section 40, and the like. PS1 to PS
Location registration with 4 and processing for link establishment, etc.
While performing various incoming and outgoing call control processing for connecting each of the telephones PS1 to PS4 to the exchange XS, and when the telephone in communication moves and the communication state with the telephone deteriorates, the telephone and the exchange XS are connected. Base station switching control processing for switching the base station with which the telephone communicates from the base station to another base station based on the control data for base station switching control Before executing the above, a communication state detecting process and a base station state reporting process, which will be described later and are unique to the present invention, are executed.

On the other hand, the exchange XS has a CPU 52 and a ROM.
54, the RAM 56, the base stations CS1 to CS4 and the ISDN interface unit 58 for connecting to the public communication network, the exchange processing unit 60 for performing the exchange process of the communication data sent from each of the base stations CS1 to CS4 and the public communication network, And CP
It is configured as a well-known exchange equipped with a talkie 62 for notifying a telephone of various messages preset by a command from U52 through an exchange processing unit 60, an ISDN interface unit 58 and a base station.

The exchange XS having the above-mentioned configuration
At 52, the CPU 52 controls the exchange processing unit 60 to connect the telephones PS1 to PS4 to each other or to the public communication network, and when the communication state between the telephone and the base station deteriorates, the base station switching control from the base station is performed. Based on the control data for use, the base station switching control for switching the base station with which the telephone communicates to another base station is executed, and further, before the base station switching control process is executed, a specific description will be made later on the present invention. Base station switchability determination processing is executed.

Here, the telephone set PS configured as described above
An outline of communication performed between the base stations 1 to PS4 and the base stations CS1 to CS3 will be described with reference to FIG. First, FIG.
As shown in (A), in the 4-channel TDMA / TDD system transmission used in the mobile communication system of the present embodiment, one frame on one frequency (hereinafter, TDM) is used.
A frame) is set to 5 ms, and each TD
The MA frame is divided into eight slots every 625 μs. The first 4 slots are assigned as the first to fourth slots for downlink communication from the base station to the telephone, and the last 4 slots are assigned as the first to fourth slots for uplink communication from the telephone to the base station. Each of the telephones PS1 to PS4 is adapted to perform its own transmission 2.5 ms after receiving the signal from the base station. That is, for example, when the base station transmits to the telephone in the second slot for downlink communication, the telephone sends back in the second slot for uplink communication, so that the telephone and the base station have the same frequency. Communication is performed using slots for uplink communication and downlink communication having the same number. The code length of each slot is 240 bits and the transmission rate is 384 kbps.

The telephones PS1 to PS4 and the base station C
The communication slots used for communication with S1 to CS3 are transmitted and received by a communication carrier that can be used exclusively by each telephone, and as shown in FIG. PR, unique word UW indicating the beginning of the slot, channel type CI, SACCH for transmitting control data for base station switching control, etc.
And a TCH for transmitting voice data and an error detection check bit CRC.

Next, the base stations CS1 to CS3 and the telephone PS
An outline of outgoing / incoming call control (location registration, link establishment, etc.) performed to realize communication for actual communication with 1 to PS4 will be described. In addition, normally, each base station CS
1 to CS3 constantly transmit information about their own station or notification information indicating the telephone number of a telephone that has called by a control carrier commonly used by each station,
Further, between the base station and the telephone, control data for controlling incoming and outgoing calls is exchanged using a control carrier.

First, in the mobile communication system of this embodiment, the power switches of the telephones PS1 to PS4 are turned on.
At this time, the switching center XS is registered in the switching center XS.
It is possible to recognize which base station the communication area is in and to promptly call the telephone from the exchange XS via the corresponding base station. Position registration is performed between the telephone and the base station when the power switch of the telephone is turned on in this way, and is generally executed in the following procedure.

When the user turns on the power switch of the telephone while the notification information is being transmitted from each of the base stations CS1 to CS3 as described above, first, the telephone notifies the notification from each of the base stations CS1 to CS3. Information is received, and a link establishment request for requesting radio channel allocation is transmitted to the base station having the highest reception level using the control carrier. The link establishment request is made up of data relating to the type of channel to be used, the type of communication protocol, and the like.

On the other hand, the base station which has received the link establishment request determines whether the wireless channel is vacant, the wired state with the exchange XS is vacant, and the type of channel or protocol requested by the telephone is the base station. It is determined whether or not it matches that of the station, and whether or not a wireless channel can be assigned to the telephone. And
When it is determined that the wireless channel can be allocated, the control carrier is also used to return information about the wireless channel such as the carrier number and slot number of the frequency (communication carrier) used for the call.

Then, the telephone recognizes that the wireless channel allocation permission has been obtained, and transmits a burst signal to the base station at the frequency and slot corresponding to the designated carrier number and slot number, and The base station also transmits burst signals at the same frequency and slot accordingly, thereby performing burst synchronization between them. After that, both parties checked each other's phone number and a predetermined ID code,
Also, various function settings are made to recognize each other's communication partners, and the exchange XS registers the position of the telephone and ends the position registration.

Here, each of the telephones PS1 to PS4 is
In addition to the above location registration, when the telephone number of the user is included in the notification information from the base station, that is, when a call is received from the base station, or the call button of the operation key 8 is pressed by the user. When the dial button is pressed and a dialing operation (an operation for making a call) is performed, a link establishment request is transmitted to the base station whose location is registered at that time. Then, the base station that has received the link establishment request judges whether or not the wireless channel can be allocated, just as in the case of the location registration. When it is judged that the wireless channel can be allocated, the base station performs communication. Returns information about the radio channel used.

That is, when each of the telephone sets PS1 to PS4 transmits a link establishment request to the base station and receives the information on the wireless channel returned from the base station,
The wireless channel used for the call is decided (link establishment),
After that, preparations for a call such as burst synchronization are made, and then actual communication is started. When the base station receives the link establishment request from the telephone and determines that the radio channel cannot be allocated, the base station transmits a link allocation refusal with data indicating the reason why the control carrier cannot allocate the radio channel. Then, when the telephone receives the link allocation refusal, it returns to the state of waiting for the user to perform the outgoing call operation again.

Next, after the telephone set receives a radio channel allocation from the base station and starts communication for a call, when the telephone set is about to move out of the communication area of the base station, it is automatically An outline of base station switching control for switching a base station with which a telephone communicates will be described.

This base station switching control is generally executed in the following procedure. First, the switching source base station communicating with the telephone constantly measures the reception level of the radio wave from the telephone,
When the reception level falls below a predetermined reference value, it is determined that the telephone has moved and the communication state has deteriorated, and the telephone is instructed to switch the base station.

Then, the telephone set transmits a link establishment request to another base station (switching destination base station) in charge of the communication area currently invading, and the switching destination base station which has received the link establishing request As in the case of location registration, it is determined whether or not a radio channel can be assigned to the telephone, and if the radio channel can be assigned, information regarding the radio channel is transmitted to the telephone and the exchange XS is notified. Request that the communication line be switched from the switching source base station to its own station, and further instruct the switching source base station to disconnect the communication wireless channel for the telephone, and at the same time, communicate with the telephone. Start.

By sequentially switching the base stations in this way, communication can be continued even when the mobile station moves. If it cannot be assigned, the switching destination base station transmits a link allocation refusal to the telephone, and the telephone receiving the same restarts communication with the switching source base station again.

Therefore, normally, in this type of mobile communication system, when the switching destination base station cannot allocate the communication radio channel to the telephone, that is, when the switching of the base station fails, the telephone is If communication is interrupted before resuming communication with the switching source base station, and if the telephone has already moved out of the communication area of the switching source base station at that time, the telephone is switched to the switching source base station. Therefore, the communication cannot be resumed and the communication is completely disconnected.

However, in the mobile communication system of the present embodiment, each base station CS1 to CS3 executes the communication state detecting process and the base station state reporting process before performing the above-mentioned base station switching control. , Telephones PS1 to PS4
Performs a wireless status report process, and the exchange XS performs a base station switchability determination process, thereby notifying the user of the telephone that communication will not be possible after further movement. It is possible to prevent interruption or disconnection of communication due to failure of station switching.

That is, first, the communication state detection processing performed by each of the base stations CS1 to CS3 is always executed at predetermined time intervals, and is executed as shown in FIG. As shown in FIG.
When the communication state detection process is started, first, in step (hereinafter, simply referred to as S) 110, the reception level of the radio wave from the currently communicating telephone is measured. Then, in subsequent S120, a process as communication state detecting means for determining whether or not the measured reception level is lower than a predetermined value is executed, and it is determined that the reception level is not lower than the predetermined value. If so, this process is terminated.

On the other hand, when it is determined in S120 that the reception level is lower than the predetermined value, it is determined that the communication state with the telephone has deteriorated, and the process proceeds to S130. Incidentally, S1
The predetermined value for the determination in 20 is set to be slightly larger than the reference value for determining whether or not the base station instructs the telephone to switch the base station in the above-described base station switching control, Thereby, each processing described below is executed prior to the above-mentioned base station switching control.

In S130, the telephone is inquired about the radio condition for measuring the reception level of the radio wave transmitted from the surrounding base stations and reporting the measurement result. This wireless status inquiry is transmitted to the telephone together with voice data by a predetermined bit in the SACCH in the communication slot shown in FIG. 4 (B).

Then, in the subsequent S140, it waits for the wireless status report in response to the wireless status inquiry to be returned from the telephone. Here, when the base station makes a wireless status inquiry, the telephone set receives the inquiry and executes the wireless status reporting process shown in FIG.

This radio status report processing is executed every time the telephone receives a radio status inquiry from the base station.
At S210, radio waves transmitted from all the base stations other than the base station with which the telephone is communicating are received and the reception level thereof is measured. Then, in subsequent S220, a process as a reception level notifying means for transmitting a radio condition report representing the measurement result to the base station in communication is executed, and the process is finished. This radio status report is also transmitted to the base station together with the voice data by a predetermined bit in the SACCH in the communication slot shown in FIG. 4 (B).

In this way, when the telephone transmits the radio condition report and the base station receives this report, the execution of the communication condition detection processing in the base station proceeds from S140 to S150. Then, in S150, the identification number of the base station whose reception level is equal to or higher than the predetermined value and the reception level are transmitted to the exchange XS based on the radio status report from the telephone, and the base station switching control is performed soon. Then, the base station switching prediction notification indicating that the switching operation is started by using these base stations as the switching destination base stations is transmitted to the exchange XS, and the communication state detecting process is ended.

Next, the base station switchability determination processing performed by the exchange XS will be described. This base station switchability determination processing is executed every time the exchange XS receives a base station switch predictive notification from the base station, and is executed as shown in FIG. When the base station switchability determination processing is started, first, S31
At 0, a process as a determination unit for determining whether or not there is a candidate for the switching destination base station based on the identification number of the base station and the reception level transmitted together with the base station switching prediction notification from the base station. Run. Then, when there is a candidate for the switching destination base station, the process proceeds to S320, and a base station state inquiry is made to report to the base station whether or not the telephone is in a state where radio channels can be allocated. .

Then, in step S330, it waits for a base station status report to be returned from the base station that has made the base station status inquiry. Here, when the exchange XS makes a base station status inquiry, the base station that has received the inquiry executes the base station status reporting process shown in FIG.

This base station status report processing is executed each time the base station receives a base station status inquiry from the exchange XS. First, in S410, the base station status report processing is currently used between the base station and each telephone. It is determined whether or not the number of wireless channels being used is equal to or more than a preset number M of channels that can be used simultaneously, and the number of currently used wireless channels is not equal to or more than the number M of channels that can be used simultaneously. When it is determined that S
Proceed to 420. Then, in S420, this time, it is determined whether or not the number of wireless channels currently used is equal to or more than the number of wires Y provided between the switching center XS and the wireless channel currently used. When it is determined that the number of lines is not equal to or greater than the number of wired lines Y, the process proceeds to S430.

In step S430, the wireless channel of the base station and the wired line to the exchange XS are currently vacant, and "vacant" indicating that the wireless channel can be assigned to the telephone is set to the base station. Set to status report and continue S4
At 40, the base station status report is transmitted to the exchange XS, and then the process ends.

On the other hand, if it is determined in S410 that the number of currently used wireless channels is equal to or more than the number M of channels that can be used simultaneously, or in S420, the number of currently used wireless channels. If it is determined that the number of wired lines is equal to or more than Y, the process proceeds to S450, and in S450, there is currently no available wireless channel of the base station or the wired line with the exchange XS, and the wireless communication to the telephone is performed. “Busy” indicating that the channel cannot be assigned is set in the base station status report, the process proceeds to S440, the base station status report is transmitted to the exchange XS, and then the process ends.

As described above, when the candidate for the switching destination base station transmits the base station status report and the exchange XS receives this report, the execution of the base station switching availability determination processing in the exchange XS proceeds from S330 to S340. In step S340, it is determined whether the base station status report indicates "vacant" or "busy".

When it is determined in S340 that the base station status report indicates "empty", it is determined that the base station communicating with the telephone can be switched to the base station by the base station switching control. , The base station switching availability determination processing ends. If it is determined in S340 that the base station status report indicates "busy", the process returns to S310, and based on the identification number of the base station received together with the base station switching prediction notification and the reception level thereof, the switching destination base station It is determined whether there is another candidate for the station, and the above processing is repeated.

When it is determined in S310 that there is no candidate for the switching destination base station, the process proceeds to S350, and the exchange processing unit 60 shown in FIG. 3 transfers the talk box 62 to the communication line connected to the telephone. , And transmits voice data to the base station that is communicating with the telephone from the toe 62, indicating that the communication will be interrupted or disconnected when the telephone moves further.
The processing as the notification instruction means is executed.

Then, the voice data is received by the telephone in communication on the TCH of the communication slot transmitted from the base station, and the speaker 14 as the notifying means.
From this, the user of the telephone is notified of a message (base station switching failure notice message) that communication will be interrupted or disconnected if the user moves further.

That is, in this base station switchability determination processing, if there is no candidate for the switch destination base station from the beginning,
Alternatively, if all the candidates for the switching destination base station cannot allocate the wireless channel to the telephone, it is determined that the switching of the base station fails and the user of the telephone is informed accordingly. I am doing it.

Here, in the mobile communication system of the present embodiment which executes each of the processes described above, as shown in FIG. 2, the telephone set PS3 communicating with the base station CS1 is connected to the base station C.
From the communication area E1 of S1 to the communication area E of the base station CS2
The flow of each signal will be described with reference to FIG. 9 by taking the case of moving to 2 as an example. In FIG. 9, the numbers in parentheses are
The step number of each processing described above is shown.

First, the base station CS1 measures the reception level with the telephone PS3, and when the reception level falls below a predetermined value, it makes a wireless state inquiry to the telephone PS3. Then, the telephone set PS3 measures the reception level of the radio waves transmitted from the surrounding base stations CS2 and CS3,
2, a radio condition report indicating the reception level from CS3 is transmitted to the base station CS1.

When the base station CS1 receives the radio status report from the telephone set PS3, the reception level from the base station CS3 is extremely small. In anticipation of switching to the base station CS2, the switching center XS transmits a base station switching prediction notification to that effect to the switching center XS.

Then, the switching center XS makes a base station status inquiry to the base station CS2, and when the base station CS2 receives the base station status inquiry, can the local station newly allocate a radio channel? It is judged whether or not it is returned, and a base station status report showing the judgment result is returned to the exchange XS. Then, if the base station status report is "busy" indicating that the wireless channel cannot be allocated, the switching center XS judges that the base station cannot be switched, and sets the torch 62 to the telephone PS.
3 is connected to the communication line being connected to the communication line 3 and the user of the telephone PS3 is notified from the speaker 14 of the telephone PS3 of a base station switching failure notice message indicating that the communication will be interrupted or disconnected if the user moves as it is.

As described above, according to the mobile communication system of the present embodiment, the users of the telephones PS1 to PS4 can recognize in advance that they will be unable to communicate if they move further. Depending on the intention of the user of the mobile station, it becomes possible to prevent the interruption or disconnection of the communication due to the failure of the switching of the base station.

In the mobile communication system of the above embodiment, the communication state detection processing executed by the base station
Although the deterioration of the communication state between the telephone and the base station is detected, the telephone itself may detect the deterioration of the communication state and may transmit the wireless state report to the base station.

In the mobile communication system of the above embodiment, the base stations CS1 to CS3 are connected to the switching center XS via the wires K1 to K3.
~ CS3 and the exchange XS, a predetermined control station may be interposed, and each of the base stations CS1 to CS3 may be connected to the control station by radio to connect to the exchange XS.

In the above embodiment, the case where the present invention is applied to a digital cordless telephone system that is being put to practical use has been described. Of course, the present invention can be applied to a communication channel between a mobile station and a base station. The present invention can also be applied to mobile communication systems that have already been put into practical use, such as analog cordless telephones and car telephones, which use different frequencies for each and every uplink / downlink communication.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of the present invention.

FIG. 2 is a block diagram showing a configuration of a mobile communication system according to an embodiment.

FIG. 3 is a block diagram showing configurations of a telephone set, a base station, and a switching center in the mobile communication system according to the embodiment.

FIG. 4 is an explanatory diagram illustrating an outline of communication in the mobile communication system according to the embodiment.

FIG. 5 is a flowchart showing a communication state detection process performed by a base station.

FIG. 6 is a flowchart showing a wireless status reporting process performed by the telephone.

FIG. 7 is a flowchart showing a base station switchability determination process performed by an exchange.

FIG. 8 is a flowchart showing a base station status reporting process performed by the base station.

FIG. 9 is an explanatory diagram illustrating signal flows in a telephone set, a base station, and a switching center.

[Explanation of symbols]

PS1, PS2, PS3, PS4 ... Telephone X
S ... Exchange station CS1, CS2, CS3 ... Base station
2, 32, 52 ... CPU 4, 34, 54 ... ROM 6, 36, 56 ... RAM 18, 42 ... Antenna 2
0,44 ... Wireless unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location 7304-5K H04Q 7/04 K (72) Inventor Takashi Oda 1-1, Showa-cho, Kariya city, Aichi prefecture Inside Nihon Denso Co., Ltd. (72) Inventor Katsuma Matsui 1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd.

Claims (1)

[Claims] 1. A plurality of base stations connected to a communication network and each having a predetermined communication area, and a radio channel for communication is allocated from the base station within a communication area of a predetermined base station among the base stations. Mobile station that can communicate with the base station by receiving the information, and the communication area in which the mobile station is located when the mobile station is provided and the communication state with the predetermined base station deteriorates as the mobile station moves. A switching start means for requesting the other base station to allocate a radio channel for communication so that the other base station in charge of becomes a new communication partner of the mobile station, and a switching operation of the base station. In the mobile communication system including the above, the mobile station or the base station is provided with communication state detection means for detecting deterioration of the communication state between the mobile station and the base station before the switching start means starts the switching operation. With When the mobile station detects that the communication state with the communication base station communicating with the mobile station has deteriorated by the communication state detecting means, at least each base station other than the communication base station sends the message. A reception level notifying means for measuring the reception level of the radio wave present and notifying the measurement result to the communication network via the communication base station, and the fact that the base station cannot be switched from the communication network via the communication base station. Means for notifying the user of the mobile station that the base station cannot be switched, and notifies the communication network from the mobile station via the communication base station. Upon receiving the measured result, the determining means determines whether or not there is a base station communicable with the mobile station other than the communication base station based on the measurement result, Transfer above When it is determined that communicatable base station is not a station, a mobile communication system, characterized in that, provided a notification command means for performing the notification command via the communication base station to the mobile station.