JPH1065600A - Mobile communication equipment and radio line switch control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To synchronize a base station at the destination to move at the time of hand-over during speaking by providing a function for receiving a carrier for control transmitted from any base station excepting for the base station at the destination of speaking and measuring its carrier strength while transmission/reception is not performed by a carrier for communication and a function for switching a reception frequency, receiving the control signal transmitted from any base station excepting for the base station at the destination of speaking by the carrier for control and establishing synchronism corresponding to that control signal. SOLUTION: A communication control part 2 at PHS terminal equipment 1 performs timing control for synchronizing the transmission/reception slot of the terminal equipment 1 with the control signal outputted from a modem 3 and converted to a base band or the frequency control of a radio part 4 based on the output of a carrier detection part 4d for receiving the control signal transmitted from the peripheral base station. Besides, the function for receiving an incoming calling signal or a speaking signal transmitted from the base station and the function for transmitting the speaking signal to the base station or the like are provided as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication device used in a mobile communication system using both a time division multiple access system and a time division duplex system, and a radio line switching control method for the mobile communication device.

[0002]

2. Description of the Related Art As a mobile communication system using a time division multiple access system and a time division duplex system, a personal handy phone system (PHS) is known.

[0003] First, the configuration of the PHS will be described.

[0004] The PHS is composed of a public base station, which is a radio station installed by a telecommunications carrier on the street or the like for the public, and a mobile communication device, which is a radio station used by each PHS subscriber. When a telephone, a connection device, a private branch exchange, or the like having a function as a base unit for the mobile communication device is installed as a self-contained base station between the public base station and the mobile communication device in a home or an office. There is also.

A public base station controls a wireless communication line of a mobile communication device served by the public base station, and establishes a connection with a mobile communication device or a fixed telephone set served by another public base station via a wired public line network. belongs to.

[0006] On the other hand, a mobile communication device is a wireless communication device configured to be mounted on a vehicle or portable so as to communicate with a public base station (hereinafter, simply referred to as a base station) or a self-owned base station. . Although the above mobile communication device includes a mobile communication device for performing data communication by connecting to a facsimile communication or a personal computer or the like,
Generally, it is a wireless communication device for making a voice call, and particularly refers to a small and lightweight wireless telephone (hereinafter referred to as a terminal) having excellent portability.

Next, the wireless connection system of the PHS will be described.

[0008] In a time division multiple access system (hereinafter, referred to as a TDMA (time division multiple access) system) used for the PHS, a carrier (carrier wave) of the same frequency is transmitted by transmitting and receiving four channels in sequence at a shifted timing. ), And the four-channel multiplexed TD
It is called MA.

In the time division duplex method used for PHS together with TDMA, an up-call (a call from a terminal to a base station) and a down-call (a call from a base station to a terminal) have the same frequency. This is a transmission method performed alternately by using the communication carrier.

[0010] For transmission and reception between the base station and the terminal, a control carrier for exchanging control signals related to incoming / outgoing calls and TDMA timing control, and a communication carrier for exchanging speech signals such as voice. And have been used. The communication carrier and the control carrier used by one base station have different frequencies from each other, and these frequencies are selected from frequencies not used by peripheral base stations at the start of communication.

One base station of the PHS can simultaneously control up to four terminals based on a four-channel multiplexing TDMA system. That is, as shown in FIG. 6, control signals and communication signals exchanged between the base station and the terminal by the TDMA method are transmitted and received only within a fixed time called a slot allocated to each channel.

In FIG. 6, Tx indicates transmission and Rx
Indicates reception, respectively.

More specifically, the base station includes four transmission slots from channel CH1 to channel CH4, which are used by four terminals from terminal 1 to terminal 4, respectively. , And four reception slots from channel CH4 to four channels are collectively transmitted and received.

Note that a continuous slot on the time axis, such as a slot transmitted from the base station, is called a burst. In the 4-channel multiplexing TDMA system, a basic cycle in which slots for 4 channels are transmitted and received is called a frame.

In a TDMA communication system,
If a terminal performs transmission / reception at a timing other than the slot allocated to the channel used by its own device, it will collide with slots on other channels on the time axis, causing interference, or making it possible for the device to receive data normally. Will be gone. For this reason, the terminal performs control to match the transmission / reception timing of the slot allocated to the channel used by the terminal with the transmission / reception timing of the slot in the base station.
The control for matching the transmission / reception timings in the TDMA system in slot units is called slot synchronization.

Slot synchronization (hereinafter simply referred to as synchronization) in a terminal device is performed by a base station for continuous time transmission by a control carrier having a frequency different from a communication carrier used for transmitting and receiving a speech signal such as voice. This is performed by receiving a TDMA timing control signal (hereinafter, simply referred to as a control signal).

Next, the configuration of the PHS radio zone will be described.

A service area in which a PHS call can be made is called a microcell with a radius of about 100 to several hundred meters centered on a base station in order to accommodate a large number of wireless lines by effectively using a limited frequency. It is divided into wireless zones (hereinafter simply referred to as cells), and one base station is arranged in each cell.

A plurality of frequencies are repeatedly assigned to base stations in the service area so that base stations using the same frequency are not adjacent to each other for effective use of frequencies and avoidance of interference between cells. In addition, the carrier transmission power of the base station and the terminal is suppressed to the minimum level required for communication within a cell in order to minimize interference between cells and between channels. 500mW
Hereinafter, in a terminal device, it is as weak as 10 mW or less.

As described above, the PHS is configured such that radio communication between a terminal and a base station is limited to within a cell. Therefore, when the user of the terminal moves by walking or the like during a call and comes out of the cell covered by the called base station, that is, when the carrier strength is reduced beyond the effective reach of the carrier. , The call cannot be continued.

Therefore, in the PHS, at least one of the base station and the terminal has a means for detecting that the terminal in communication has moved to a different cell. When the user of the terminal performs a call while moving over a plurality of cells, control is performed to automatically switch the wireless line to continue the call. Such control is called handover. Note that the handover is also performed when the communication state between the terminal and the base station is deteriorated due to the obstacle behind an obstacle such as a building.

For this reason, the conventional PHS terminal also includes a carrier detection unit for measuring the reception strength of the carrier transmitted from the called base station and monitoring the call state. That is, the terminal determines that the terminal has shifted to another cell when the reception strength of the carrier transmitted from the called base station of the terminal becomes equal to or less than a predetermined constant value.

The terminal which has determined that the terminal has shifted to another cell by the above means or the like, switches the reception frequency and sequentially receives the carriers transmitted from the peripheral base station,
A base station having an empty channel and in which the best communication state can be expected is selected as a transfer destination of the wireless line. This process is called carrier sense. Then, based on the result of the carrier sense, the terminal switches the radio line to the destination base station and performs control to continue the call.

[0024] Since the PHS terminal uses the TDMA system, a speech signal exchanged with a base station is intermittently transmitted and received using a slot on a communication carrier. Accordingly, there is a vacant time (hereinafter, referred to as a vacant slot) on the communication carrier used by each terminal between the transmission slot and the reception slot during which no transmission / reception of a call signal is performed. Therefore, the terminal receives a control signal transmitted by a control carrier from a peripheral base station other than the callee base station during a call using the empty slot on the communication carrier, and transmits the control signal to the terminal. You should be able to synchronize.

However, in the conventional PHS, a transmission slot and a reception slot of 625 μs each are accommodated in four channels in a frame of 5 ms, so that there are only 1875 μs of empty slots in each channel.

On the other hand, switching of the reception frequency in the terminal is generally performed by a frequency synthesizer in the radio unit, and the switching requires several hundred μs. For this reason, conventionally, the terminal uses the empty slots of the above three slots to increase the reception frequency from the frequency of the communication carrier used for transmitting and receiving the communication signal with the called base station. Switching to the frequency of a control carrier transmitted from another base station, receiving a control signal transmitted using the control carrier, establishing synchronization with the control signal, It was virtually impossible to switch to the frequency of the communication carrier transmitted from the base station.

Of course, the frequency switching time is apparently shortened by means such as providing a plurality of frequency synthesizers in the radio section and sharing the frequencies assigned to them, and utilizing the above three empty slots. It is possible to switch the reception frequency. However, since the PHS is intended to provide a small, lightweight, and inexpensive PHS by simply configuring a terminal, the above-described means of providing a plurality of frequency synthesizers is not appropriate.

For this reason, when performing handover in the conventional PHS, the terminal interrupts the call,
Switching the reception frequency, performing carrier sense of the peripheral base station, selecting the destination base station, receiving the control signal transmitted by the destination base station on the control carrier, performing synchronization with the control signal, After that, switch the wireless line,
Further, a radio line switching control method is employed in which the reception frequency is switched to the frequency of the communication carrier of the destination base station and the call is resumed.

[0029]

As described above, in the conventional terminal and the PHS using the conventional radio line switching control method for the terminal, during a telephone call, a control is performed from a base station other than the called base station. Since the control signal transmitted by the carrier could not be received, the call had to be interrupted when performing the handover.

Since the interruption time of the call due to the handover can be as long as about 6 seconds, the conventional terminal is
Normally, a user is informed that a call is interrupted due to handover by a method such as ringing a specific display sound from a ringer unit or the like. However, the user may feel uncomfortable because the call is suddenly interrupted, or may be anxious that the call may be interrupted because the call may be interrupted for about 6 seconds. There was a practical problem of doing so. For this reason, the conventional PHS has been required to reduce the interruption time of the call due to the handover.

The breakdown of the time required for the handover in the conventional PHS is as follows. The terminal performs a carrier sense, selects a destination base station of a radio line, and newly establishes synchronization with the destination base station. This requires about 4 seconds, and about 2 seconds is required to establish a new wireless channel between the terminal and the destination base station. For this reason, in order to reduce the interruption time of the call due to the handover, if the terminal can complete the synchronization with the destination base station during the call in advance, if the terminal can complete the call due to the above handover, It was believed that the interruption time could be reduced to about 2 seconds.

The present invention has been proposed in view of such a situation in the conventional PHS, and has an empty space on the communication carrier caused by the half-rate operation in which the TDMA frame period is operated twice as long as the conventional PHS. An object of the present invention is to provide a terminal that can synchronize with a destination base station at the time of handover during a call using a slot.

Further, the present invention provides a PHS operated at a half rate, using a terminal having a function capable of performing synchronization with a transfer destination base station at the time of a handover during a call. It is an object of the present invention to provide a handover control method for switching a wireless channel after performing synchronization with a destination base station during a call.

[0034]

A mobile communication apparatus according to the present invention, which has achieved the above-mentioned object, uses a control carrier and a communication carrier having different frequencies from each other, so that uplink communication and downlink communication have the same frequency. A mobile communication device used in a time division multiple access mobile communication system sharing a carrier for communication, and a communication control unit, based on the control of the communication control unit, when transmission and reception by the communication carrier is not performed,
Receives a control carrier transmitted from a base station other than the called base station, a carrier detection unit having a function of measuring the carrier strength, based on the control of the communication control unit,
It has a function of receiving a control signal transmitted by a control carrier from a base station other than the called base station by switching the reception frequency during a time when transmission and reception by the communication carrier are not performed, and establishing a synchronization with the control signal. And a wireless unit.

According to the mobile communication apparatus of the present invention configured as described above, in any of the standby state and the call state, the control transmitted from the peripheral base station using the control carrier is used. A signal can be received and synchronization can be established in advance with the control signal.

[0036] Further, in the radio channel switching control method for a mobile communication device according to the present invention, a control carrier and a communication carrier having different frequencies from each other are used, and an uplink call and a downlink call share a communication carrier of the same frequency. A wireless channel switching control method for a mobile communication device used in a time-division multiple access mobile communication system, wherein a control carrier is used from a base station other than the called base station during a time when transmission and reception by a communication carrier are not performed. A mobile communication device having a function of receiving a control signal to be transmitted and establishing synchronization with a base station other than the called base station can be used during a time when transmission / reception by a communication carrier is not performed. Receiving the control carrier transmitted from the base station, measuring the carrier strength thereof, selecting the base station to which the wireless channel is switched based on the measurement result, and Receiving a control signal transmitted from the base station of the line switching destination, after the synchronization for the control signal, a radio channel switching control method for a mobile communication device, characterized in that for switching the radio channel.

Then, the above-mentioned radio line switching control method is
By applying the present invention to handover control in the PHS, it is possible to reduce the interruption time of a call due to the handover.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, as a specific embodiment to which the present invention is applied, a terminal used for a PHS operated at a half rate will be described with reference to FIG.

The terminal 1 includes a communication control unit 2, a modem 3 connected to the communication control unit 2, a radio unit 4 connected to the modem 3, and an antenna 5 connected to the radio unit 4.

The radio section 4 includes a transmitting section 4a, a receiving section 4b, a frequency synthesizer 4c, and a carrier detecting section 4.
d and a duplexer 4e. The transmitting unit 4a and the receiving unit 4b are connected to the modem 3. The frequency synthesizer 4 c is controlled by the communication control unit 2,
a and the receiving unit 4b. Carrier detector 4
d is connected to the receiving unit 4b and supplies an output to the communication control unit 2. The duplexer 4e is connected to the antenna 5, the transmitting unit 4a, and the receiving unit 4b.

Further, the communication control unit 2 is connected with the audio codec unit 7 and the man-machine interface control unit 12. A speaker 9 is connected to the audio codec unit 7 via a speaker amplifier 8. The audio codec unit 7 has a microphone 11 via a microphone amplifier 10.
Is connected. A ringer unit 13 and an operation unit 14 are connected to the man-machine interface control unit 12 connected to the communication control unit 2.

Note that the terminal device 1 is also configured such that when a user performs non-voice communication such as facsimile communication or data communication, the data communication signal does not pass through the voice codec unit 7. .

Next, main functions and operations of the terminal 1 will be described with reference to FIG.

The communication control unit 2, the modem 3, the radio unit 4, and the antenna 5 are mainly used when communicating with a base station (not shown).

The above-mentioned terminal 1 responds to the control signal transmitted from the base station received by the antenna 5 by the radio section 4.
To perform processing such as amplification, and further perform processing such as demodulation by the modem 3 to convert it to a baseband signal.

The communication control unit 2 controls the communication of the terminal 1. For example, the communication control unit 2 synchronizes a transmission / reception slot of the terminal 1 with a baseband-converted control signal output from the modem 3. Radio unit 4 based on an output of a carrier detection unit 4d, which will be described later, in order to perform timing control such as the
The control related to the handover such as the frequency control of the above is performed. The communication control unit 2 also has a function of receiving an incoming signal and a call signal transmitted from the base station, a function of transmitting a call signal to the base station, and the like.

The modem 3 connected to the communication control unit 2
Performs a process of appropriately modulating the speech signal digitized by the audio codec unit 7 for wireless transmission and demodulating a received digital speech signal into a baseband signal.

The radio section 4 connected to the modem 3 transmits and receives carriers under the control of the communication control section 2.

More specifically, the transmitting unit 4 a
A high frequency output of the transmission frequency supplied from the frequency synthesizer 4c controlled by the control unit is mixed with a speech signal supplied from the modem 3 to generate a transmission signal, and the transmission signal is amplified. To the antenna 5 via the antenna.

On the other hand, the receiving section 4b amplifies the high frequency received signal supplied from the antenna 5 via the duplexer 4e,
The signal is mixed with a high-frequency signal supplied from the frequency synthesizer 4c controlled by the communication control unit 2 to perform frequency conversion to an intermediate frequency or a baseband.

The frequency synthesizer 4 c generates a high-frequency output under the control of the communication control unit 2. Generally, a voltage control oscillator (VCO) is used for the oscillation unit, and the oscillation frequency is controlled by a control voltage from the communication control unit.

The carrier detection section 4d detects a carrier component from the intermediate frequency or baseband reception signal generated by frequency conversion or the like in the reception section 4b, measures its intensity, and outputs it to the communication control section 2.

The duplexer 4e is for sharing the antenna 5 for transmitting and receiving, and performs impedance matching between the antenna 5 and the transmitting unit 4a and between the antenna 5 and the receiving unit 4b. It also serves to block the transmission signal output from the unit 4a from flowing into the receiving unit 4b.

The antenna 5 connected to the radio unit 4 is for transmitting and receiving a call signal and a control signal between the terminal 1 and the base station.

The audio codec 7, the speaker amplifier 8, the speaker 9, the microphone amplifier 10, and the microphone 11
Is mainly used when making a call with the terminal 1.

The audio codec unit 7 includes a microphone amplifier 10
, Converts an analog call signal such as voice input from the microphone 11 into a digital call signal, performs compression suitable for digital wireless communication on the digital call signal, or transmits the digital call signal through the communication control unit 2 from the modem 3. The output digital call signal is expanded, decoded into a baseband analog call signal, and transmitted to the speaker amplifier 8.

More specifically, the voice codec unit 7 converts an analog speech signal such as voice into a digital signal suitable for digital wireless communication by high-efficiency voice coding.

The speaker amplifier 8 includes the audio codec 7
Performs processing such as amplification on the call signal output from
The processed call signal is sent to the speaker 9. Then, the speaker 9 outputs the speech signal, which has been subjected to the processing such as amplification by the speaker amplifier 8, as voice.

The microphone 11 converts the voice and the like of the user of the terminal 1 into an analog call signal, and sends the analog call signal to the microphone amplifier 10. The microphone amplifier 10 is connected to the microphone 11
Performs processing such as amplification on the call signal input from
The processed call signal is sent to the voice codec unit 7.

In the terminal 1, the man-machine interface control unit 12, the ringer unit 13, and the operation unit 1
Reference numeral 4 denotes a portion related to the man-machine interface of the terminal 1.

More specifically, the man-machine interface control section 12 controls the man-machine interface of the terminal 1, and controls the operation of the ringer section 13 and the operation section 14, and the like.

The ringer unit 13 is controlled by the man-machine interface control unit 12, and emits an incoming notification sound when the terminal 1 receives an incoming signal from a base station, for example.

The operation unit 14 serves as an interface for the user, and includes a display device using liquid crystal or the like, dial keys, and the like. The operation unit 1
Reference numeral 4 also includes, in addition to dial keys, dedicated switches and keys used for starting and ending a call, switching modes for ancillary functions, and the like. And this operation unit 14
Is used, for example, when a user inputs a telephone number of a called party to make a call from the terminal 1.

Next, as a specific embodiment to which the present invention is applied, a PHS operated at a half rate is controlled by a base station other than the called base station during a period when transmission / reception by a communication carrier is not performed. A radio line switching control method using a terminal having a function of receiving a control signal transmitted by a carrier for establishing synchronization with a base station other than the called base station will be described.

First, control signals and communication signals transmitted and received between the base station and the terminal will be described.

As described above, the PHS uses two types of carriers, a control carrier and a communication carrier, for transmission and reception between a base station and a terminal. The control carrier is a carrier to which only a common use channel shared by a plurality of communications can be assigned, and that the base station can perform regular intermittent transmission. On the other hand, the communication carrier is a carrier to which an individual channel used for an individual call is allocated in order for the PHS user to make a call.

The function channels obtained by classifying the channels by paying attention to the functions of signals transmitted and received by the control carrier and the communication carrier will be described below.

The function channel is a control channel CCH (control channel) which is a generic name of channels for transmitting and receiving control signals.
l channel) and an information channel TCH (traffic channel) used for transmitting and receiving information such as voice.

The control channel CCH includes a common channel used by PHS users for common channel setting control and the like, and a channel individually occupied by each PHS user after establishing a radio link. Are performed.

The common channel is a broadcast channel that is a point-to-multipoint downlink one-way channel (for example, transmission from one base station to a plurality of terminals) that can be transmitted on a control carrier. BCCH (broa
dcast control channel) and paging channel PCH
(Paging channel) and a point-to-point bidirectional channel (for example, transmission / reception between one base station and one terminal) that can be transmitted on the control carrier, and an individual cell channel SCCH ( signaling
control channel) and a common control channel CCC
H (common control channel).

Next, the configuration of a control slot for transmitting and receiving a control signal and a configuration of a control slot and a communication slot for transmitting and receiving a call signal will be described with reference to FIG.
How to use the function channel will be described.

FIG. 2A shows a channel SCC for an individual cell.
3 shows a configuration of a control slot including H. That is, the control slot including the individual cell channel SCCH includes a 4-bit transient response ramp time R provided to guarantee the rise time of the burst and a 2-bit start symbol SS provided to indicate the start of the burst. And a 62-bit preamble PR provided for reproducing a timing signal from a received signal to establish bit synchronization between the base station and the terminal, and a 32-bit unique word UW provided for burst word synchronization. , A 4-bit channel identification CI provided to indicate the slot usage status, and a 42-bit calling identification code H
1, a 28-bit destination identification code H2, a 34-bit control data I, and a 16-bit parity CRC for error detection.
And a guard bit GB of 16 bits, for a total of 240 bits, and have a length of 625 μs. The guard bit is used to provide a time margin for preventing the base station from colliding with the reception slot of each channel due to a difference in radio wave propagation time between the base station and each terminal or an error in slot synchronization. It is.

Here, the individual cell channel SCCH is
This is a bidirectional channel for transferring information necessary for call connection between the base station and the terminal, and the control data I portion of the control slot shown in FIG.
CH.

FIG. 2B shows the configuration of a control slot including a broadcast channel BCCH or a paging channel PCH. That is, the control slot including the broadcast channel BCCH or the paging channel PCH has a 4-bit transient response ramp time R and a 2-bit start symbol SS similarly to the individual cell channel SCCH described above.
, A 62-bit preamble PR, a 32-bit unique word UW, a 4-bit channel identification CI,
42-bit source identification code H1, 62-bit control data I, 16-bit error detection parity CRC,
It consists of a total of 240 bits including 6 guard bits GB, and has a length of 625 μs.

Here, the broadcast channel BCCH is a downlink one-way channel for broadcasting control information from the base station to the terminals, and the paging channel PCH is the same information from the base station to a plurality of terminals. Is a one-way downlink channel that transmits all channels simultaneously. Then, the part of the control data I of the control slot shown in FIG.
H or paging channel PCH.

FIG. 2C shows the configuration of a communication slot including an information channel. That is, the communication slot including the information channel is the same as the individual cell channel S described above.
Like the CCH, the broadcast channel BCCH and the paging channel PCH, a 4-bit transient response ramp time R
, A 2-bit start symbol SS, a 6-bit preamble PR, and a 16-bit unique word UW
, 4-bit channel identification CI, 16-bit low-speed associated channel SA, and 160-bit user information TCH
, A 16-bit error detection parity CRC, and a 16-bit guard bit GB, for a total of 240 bits, and have a length of 625 μs.

Here, the information channel is a bidirectional channel for transferring user information such as voice data between the base station and the terminal, and the user information TCH of the communication slot shown in FIG. Is an information channel.

Then, the base station is notified of, for example, an incoming call from a wired public line network to which the base station is connected to a terminal whose position is registered in a wireless zone that covers a plurality of cells called a paging area. Then, using the paging channel PCH of the control slot, the incoming signal is notified to the terminal.

Next, a description will be given of a procedure in which a base station and a terminal perform communication using a slot including the above-mentioned function channel.

The radio link between the base station and the terminal is established through three states called a link channel establishment phase, a service channel establishment phase, and a communication phase.

The link channel establishment phase is a state in which information transfer is being performed on a control carrier in order to establish a wireless channel called a link channel on a communication carrier, and is a state characteristic of wireless communication. The function channels used in this phase are collectively called a logical control channel LCCH (logical control channel).

The service channel establishment phase is a state in which a link channel has already been established on a communication carrier and a wireless channel called a service channel for transmitting voice or the like has been established.

The communication phase is a state in which a radio link is established and transmission of voice and the like is performed. When the service is started from the base station to the terminal, the communication channel shifts from the service channel establishment phase to the communication phase. I do. Note that the function channels used in this communication phase are collectively referred to as a service channel SCH (service channel).

Next, the timing of transmitting and receiving a slot having the above-described configuration will be described with reference to FIG. 3 for the case of the conventional full rate and the case of the half rate to which the present invention is applied. FIG. 3 shows transmission / reception of a communication slot performed on a communication carrier for only one channel. In FIG. 3, Tx indicates transmission,
Rx represents reception, respectively.

FIG. 3A shows the transmission / reception timing of the conventional communication slot at the full rate. In this case, the number of empty slots in which transmission / reception of a communication slot is not performed during one frame (5 ms) is 1/3 of the number of slots.
It is as short as 875 μs. Therefore, as described above, the terminal switches the reception frequency during the empty slot, receives the control signal transmitted by the control carrier of the destination base station, and establishes synchronization with the control signal. I couldn't do it.

FIG. 3B shows the transmission / reception timing of the communication slot at the half rate to which the present invention is applied. Even if the half rate is set, the slot is 625 μs, which is the same as the full rate. Therefore, the time T of an empty slot in which transmission / reception of a communication slot is not performed during one frame (10 ms) is 2.5 ms × 3−625 μs = 6875 μ.
s. Therefore, the terminal can switch the receiving frequency at this time T and receive the control signal transmitted from the destination base station by the control carrier.

In order for the terminal to synchronize with the control signal of the destination base station, specifically, a broadcast channel BCCH or a paging channel PCH transmitted from the base station is used.
CH needs to be received.

The BCCH, PCH, SCCH and optionally used user-defined packet channel USC transmitted on the logical control channel LCCH from the base station.
The minimum cycle composed of a CH (user specific packet channel) is called a superframe. As shown in FIG. 4, the superframe is intermittently transmitted from the base station at intervals of 100 ms and a period of 1.2 s in the PHS.

In the transmission / reception timing of the half rate, the time T during which the terminal can receive the super frame transmitted from the destination base station during one frame is set.
As shown in FIG. 3B, from the 10 ms frame, the TCH reception time for one slot on the communication carrier and the reception frequency of the terminal are changed from the communication carrier frequency of the called base station to the transfer destination base station. A time excluding two slots to be considered as a spare time for switching to the control carrier frequency of the station and for switching again from the control carrier frequency of the destination base station to the communication carrier frequency of the destination base station. It is.

Therefore, at the time T described above,
The probability of receiving the superframe transmitted from the destination base station while continuing the call is as follows: {10− (2.5 + 0.625 × 3)} / 10 =
0.5625.

At this time, in order to establish slot synchronization with the destination base station, the terminal must transmit the broadcast channel BCCH which is always transmitted first in the superframe having the configuration shown in FIG. , Or the paging channel PCH, and does not need to receive the entire superframe.

Next, the sequence of the handover control method to which the radio line switching control method according to the present invention is applied is shown in FIG.
This will be described with reference to FIG. In addition, the sequence of FIG.
FIG. 9 shows a procedure in a case where a terminal detects a decrease in the intensity of carrier reception transmitted from a called base station and activates handover control from the terminal side.

First, the configuration of an interface related to PHS control will be described. The interface related to PHS control has a three-layer hierarchical structure called layer 1, layer 2, and layer 3.

Layer 1 is also called a physical layer and has a PHS
This is an interface related to the basic interface structure and functions limited to always-on operation, and specifically defines functions such as transmission and reception of control signals.

Layer 2 is an interface related to a function limited between the points of the PHS, and specifically defines a call connection procedure. Therefore, in the link channel establishment phase described above,
Layer 2 does not exist.

[0096] Layers 1 and 2 in the above PHS interface are ISDN (integrated).
services digital network) in the same manner as layer 1 and layer 2.

Layer 3 is an interface relating to functions specific to the PHS, and specifically defines functions such as terminal location registration and handover.

[0098] The terminal according to the present invention can monitor the carrier strength of the peripheral base station using the empty slot on the call carrier generated by the half-rate operation in both the call state and the standby state. Be composed. Therefore, in the following, description will be given on the assumption that the terminal always selects in advance a transfer destination base station when performing a handover due to, for example, a decrease in the strength of the carrier transmitted from the callee base station. .

When the carrier detection unit of the terminal detects that the strength of the carrier transmitted from the called base station has decreased, the terminal detects the layer 3 from the layer 3 in the terminal as shown in step ST1. An individual cell channel SCCH transmission request is made. Then, the call between the terminal and the base station is interrupted after step ST1.

Next, in the terminal, as shown in step ST2, layer 1 transmits a link channel establishment request to the transfer destination base station at the time of handover based on the SCCH transmission request from layer 3.

Next, the handover destination base station receiving the link channel establishment request from the terminal transmits the link channel assignment to the terminal as shown in step ST3.

Next, the terminal which has received the link channel assignment from the destination base station at the time of handover transmits a synchronization burst to the destination base station at the time of handover as shown in step ST4.

Next, the handover destination base station receiving the synchronization burst transmitted from the terminal transmits a synchronization burst to the terminal as shown in step ST5.

According to the above-described procedure, frame synchronization of the link channel is performed, the link channel and the service channel are sequentially established, the radio line is switched to the transfer destination base station at the time of handover, the call is restored, and the handover is performed. Complete.

According to the above radio line switching control method of the present invention, when the terminal activates the handover control, immediately after detecting the decrease in the strength of the carrier transmitted from the called base station, Since the SCCH transmission request can be made, it takes about 2 seconds to establish the radio line shown in FIG.
Handover is completed in seconds. Therefore, call interruption time due to handover is reduced to about 2 seconds,
The discomfort and discomfort of the user are considerably reduced.

The present invention is not limited to the above-described example, and it is possible to arbitrarily change the configuration of the terminal, the procedure in the wireless line switching control method of the terminal, and the like without departing from the gist of the present invention. Needless to say,

In particular, the application of the present invention is not limited to a PHS operated at a half rate, but is premised on a PHS having a slot interval of 20 ms (four times the full-rate slot interval) or longer. Is also good. Note that TDMA in which the slot interval is four times the full rate is called a quarter rate. In this case, the vacant slot of the communication slot is longer than in the case of the half rate, so that it is easy to synchronize with two or more peripheral base stations during a call.

The present invention is applied not only to handover control performed between different base stations, but also to channel switching control for switching a radio line to a radio channel of a different frequency in the same base station for the purpose of avoiding interference or the like. Of course, it is also effective.

[0109]

As is apparent from the above description, PHS
In the above, the use of the terminal of the present invention allows the terminal to preliminarily synchronize with the destination base station at the time of a handover during a call, so that the call interruption time due to the handover is reduced. Can be shortened, and PHS
The practicality of is improved.

Further, in the PHS, by using the radio line switching control method of the present invention, it is possible to reduce the interruption time of the call due to the handover, and the practicability of the PHS is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a terminal according to the present invention.

FIG. 2 is a diagram showing a configuration of a control slot and a communication slot.

FIG. 3 is a diagram illustrating slot transmission / reception timing of the PHS terminal of the present invention. (A) is a diagram showing slot transmission / reception timing in the case of the conventional full rate.
(B) is a diagram showing slot transmission / reception timing in the case of a half rate applied to the present invention.

FIG. 4 is a diagram illustrating a configuration of a superframe.

FIG. 5 is a diagram showing a sequence of a handover control method according to the present invention.

FIG. 6 is a diagram illustrating transmission / reception timing of 4-channel multiplex TDMA.

[Explanation of symbols]

1 terminal, 2 communication control unit, 3 modem, 4
Radio section, 4a transmitting section, 4b receiving section, 4c frequency synthesizer, 4d carrier detecting section, 4e duplexer, 5 antenna, 7 voice codec section, 8
Speaker amplifier, 9 speaker, 10 microphone amplifier, 11 microphone, 12 man-machine interface control unit, 13 ringer unit, 14 operation unit

Claims (6)

[Claims] 1. A mobile communication apparatus for use in a time division multiple access mobile communication system in which a control carrier and a communication carrier having different frequencies from each other are used, and an uplink call and a downlink call share a communication carrier of the same frequency. In the communication control unit, based on the control of the communication control unit, during a time when transmission and reception by the communication carrier is not performed, receiving a control carrier transmitted from a base station other than the called base station, A carrier detection unit having a function of measuring the strength; and a control unit that switches a reception frequency and controls from a base station other than the called base station during a time when transmission / reception is not performed by a communication carrier based on control of the communication control unit. A radio unit having a function of receiving a control signal transmitted by the carrier for use and establishing synchronization with the control signal. Mobile communication device. 2. The radio unit is configured to switch the oscillation frequency of an oscillator under the control of a communication control unit to perform transmission and reception by a control carrier and a communication carrier having different frequencies. The mobile communication device according to claim 1. 3. The mobile communication device according to claim 1, wherein the mobile communication device is a personal handyphone system operated at a half rate. 4. A mobile communication system for use in a time-division multiple access mobile communication system, wherein a control carrier and a communication carrier having different frequencies from each other are used, and an uplink call and a downlink call share a communication carrier of the same frequency. In the wireless line switching control method of the device, a control signal transmitted by a control carrier from a base station other than the callee base station is received during a time when transmission / reception by the communication carrier is not performed, and A mobile communication device having a function of establishing synchronization with a base station receives a control carrier transmitted from a base station other than the called base station at a time when transmission / reception by a communication carrier is not performed, and Measuring the strength, selecting a base station of a wireless channel switching destination based on the measurement result, receiving a control signal transmitted from the base station of the wireless channel switching destination, A radio line switching control method for a mobile communication device, wherein a radio line is switched after synchronization with the control signal. 5. The mobile communication device according to claim 4, wherein transmission and reception by the control carrier and the communication carrier having different frequencies are performed by switching an oscillation frequency of an oscillator provided in the mobile communication device. Switching control method. 6. The method according to claim 4, wherein the mobile communication device is a mobile communication device of a personal handyphone system operated at a half rate.