JP2590692B2 - Method and system for switching channels during a call in mobile communication - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and system for switching channels during a call in mobile communication, and more particularly to a time division multiple access (Time Division Multiple Access).
e Access (TDMA)) The present invention relates to a method and system for switching channels during a call in mobile communication.

[0002]

2. Description of the Related Art Conventionally, this type of channel switching method during a call is based on a radio wave condition with a base station which handles the current call when a mobile phone, a car phone, or the like (hereinafter referred to as a mobile station) moves. Is deteriorated, the communication quality is degraded, and when there is another base station having a better radio condition than this base station, it is used to switch the busy channel to another base station having a better radio condition. ing.

[0003] As a first conventional example, a diagram showing a summary of control of a channel switching method during a call indicated in the second edition of the second generation cordless telephone system standard (RCR STD-28) issued by the Radio System Development Center. Referring to FIG.
When the communication quality with the base station 1a deteriorates, the mobile station establishes a link channel with the switching destination base station 2b, generates a call with the switching destination base station 2b, and switches the busy channel. I was

A second conventional example is disclosed in Japanese Patent Application Laid-Open No. 2-34 / 1990.
As disclosed in Japanese Patent Application Laid-Open No. 044, for example, in this method, a mobile station transmits and receives data to and from both a pre-switch base station and a target base station in order to prevent instantaneous interruption of a call when switching a busy channel. A channel switching unit comprising: two transmission / reception signal processing circuits connected to the control circuit; and a phase adjuster that matches information signals from the reception signal processing circuits among the transmission / reception signal processing circuits and inputs the information signals to the transmission / reception control circuit. In this case, both of the two transmission / reception signal processing circuits are started in parallel for a predetermined time, and then one of them is disconnected.

Further, as a third conventional example, Japanese Patent Application Laid-Open No. Sho 64-4
As exemplified in Japanese Patent No. 1529, switching control of a busy channel is performed by allocating the same frequency to all wireless zones,
One time slot in a TDMA frame is fixedly assigned to each wireless zone so as not to overlap with an adjacent wireless zone, and the busy channel is switched only by switching the time slot. In addition, channel switching between the mobile station and the mobile switching center has been performed by the mobile switching station transmitting a channel switching timing signal to the base station and the mobile station.

[0006]

In the first conventional example, since the link control of the communication channel is performed only between the mobile station and one base station during the communication, the communication between the mobile station and one base station is not performed. Since the link channel with the switching source base station is cut off when the link channel is established, there is a problem that the call is momentarily interrupted until the connection of the call with the switching destination base station is completed.

In the second conventional example, although the problem of instantaneous call interruption can be solved, two transceivers and a phase adjuster are provided for this purpose, so that the size and cost of the mobile station can be reduced. Hindered.

In the third conventional example, a plurality of frequencies are allocated to the radio zone when the traffic of the mobile communication network increases, but the same frequency as the source zone is not available in the destination zone. It is specified in this publication that instantaneous interruption occurs in some cases. Further, although the channel switching is performed by the channel switching timing signal from the mobile switching center, it is difficult to generate the channel switching timing signal by accurately considering the propagation delay between the mobile switching center, the base station, and the mobile station. Therefore, there is a possibility that instantaneous interruption may occur due to a difference in timing of channel switching between the mobile switching center and the mobile station.

An object of the present invention is to provide a method for switching a busy channel in mobile communication, which is capable of switching a busy channel to a destination base station without instantaneously interrupting a call when the mobile station moves to a different radio zone. And to provide a system.

[0010]

According to the present invention, there is provided a method for switching a channel during a call in mobile communication, comprising: a mobile station scattered and moving within a wireless zone; a mobile station connected to the mobile station via a wireless line; The communication quality between the base station and the base station that covers a predetermined wireless zone by performing transmission and reception switches the busy channel so that the mobile station has a predetermined value when the mobile station shifts to the wireless zone. In the method of switching a busy channel in a mobile communication in which a call is continued through a mobile switching center connecting the mobile stations, when the mobile station shifts between wireless zones during a call, a first base located in a wireless zone before the movement is performed. Between the mobile station and both the station and a second base station located in the moved radio zone
Simultaneous communication is performed using different time slots in a DMA frame, and an uplink voice signal from the mobile station is broadcasted to the mobile switching center through the first and second base stations, and the uplink voice signal is received. The mobile switching center broadcasts a downlink voice signal from a communication partner of the mobile station to a time slot corresponding to simultaneous communication with the first and second base stations, and in accordance with an instruction from the mobile switching center. The mobile station selects a downlink audio signal passing through the second base station, and then selects an uplink audio signal passing through the second base station.

A channel switching system during a call in mobile communication according to the present invention includes a mobile station scattered and moving within a wireless zone, and a TDM connected to the mobile station via a wireless line.
Before the mobile station moves , transmitting and receiving signals using the A communication method
Of a first base station and a mobile station covering a wireless zone of
A second base station that covers the wireless zone after the movement, and a base station and a fixed network switch that switch the busy channel so that the communication quality becomes a predetermined value when the mobile station shifts the wireless zone. In a channel switching system during a call in mobile communication comprising a mobile switching station to be connected, the mobile station transmits an uplink voice signal input from a transmitter of the mobile station to one of the first and second base stations or a transmission selector for selectively outputting to both one of the first contact
And a receiver for selecting which of the two downlink voice signals input from the second base station to output to the receiver of the mobile station, a call control signal and a voice included in a plurality of time slots of a TDMA frame. A time division multiplexing circuit for transmitting and receiving signals, the transmission selecting unit, and the time division multiplexing circuit.
Path, and the reception selector and the time division multiplexing circuit.
And receive call control signals and audio signals to and from the road in accordance with the control information from the mobile switching center, the output destination is the first and second groups of the uplink voice signal against the transmission selector
And indication of the one of Chikyoku, the indication of either outputs one of the against the receiving selection unit <br/> two downlink voice signal, against the time division multiplexing circuit call control signals and voice with indication of the time slot for transmitting and receiving signals, a first call control unit that performs the instructions of frequency transceiver to the transmitter and receiver, said mobile switching center, the first and
A second call control unit for transmitting and receiving a call control signal through a second base station, controlling a speech path switch in the mobile switching center based on the signal, and transmitting the control information to the first call control unit. , The first call control unit,
When a mobile station transitions between wireless zones during a call,
TD between both the first and second base stations and the mobile station
Simultaneous use of different time slots in MA frame
Communicate, the first uplink speech signal from the mobile station
And broadcast to the mobile switching center through a second base station
Then, the second call control unit receives the uplink voice signal
The downlink audio signal from the communication partner of the mobile station is transmitted to the first
And a time slot for simultaneous communication with the second base station.
And the first call control unit performs the mobile switching.
Downstream audio through the second base station according to the instructions of the station
After selecting a signal, the uplink voice through the second base station
Select a signal.

[0012]

Next, the present invention will be described with reference to the drawings. A mobile communication system includes mobile stations scattered in a wireless zone, a plurality of base stations connected to the mobile station via a wireless line and transmitting and receiving digital signals using a TDMA communication method, and a base station and a fixed network. And a mobile switching center that connects the switching center.

FIG. 1 is a block diagram showing a mobile station to which a method of switching a busy channel according to an embodiment of the present invention is applied. In this embodiment, a signal in the direction of the mobile switching center → the base station → the mobile station is called “down”, and a signal in the direction of the mobile station → the base station → the mobile switching center is called “up”. Referring to FIG. 1, a mobile station 1 includes a transmitter 11, a transmitter circuit 12 that converts an upstream analog voice signal from the transmitter 11 into a digital signal, and outputs a signal.
8, a receiver circuit 19 that converts a downstream digital audio signal into an analog signal and outputs it to a receiver 18, a first call controller A15 and a second call controller B110 that control a call,
A transmission selection unit 13 for selecting which of the call control units A15 and B110 to transmit an upstream voice signal according to instructions from these call control units; and a call control unit A15 and B110.
And a call control unit A1 for selecting which of the downstream audio signals input from the receiver is to be output to the reception circuit 19.
5, a time-division multiplexing circuit 16 for transmitting and receiving signals to and from a time slot designated by B110, a transmitter 17 for transmitting a signal at a frequency designated for each time slot, and a signal having a different frequency for each time slot 111, a duplexer 112, and an antenna 1
13 is provided.

The call control units A15 and B110 make outgoing calls,
A call control signal such as an incoming call, a disconnection, a channel change during a call, etc., and a voice signal are transmitted between the transmission selector 13 and the time division multiplexing circuit 16
Between the receiver selection unit 14 and the time division multiplexing circuit 16
And received between, and instructs the output and the output stop of the uplink speech signals against the transmission selector 13, and instructs the output and the output stopping against downstream audio signal to the receiver selecting section 14, against the division multiplexer 16 time A time slot for transmission / reception is specified, and a frequency is specified for the transmitter 17 and the receiver 111. Normally, one of the call control units A15 and B110 is in use and the other is in standby, and both are in use only when the channel is switched during a call. When both the call controllers A15 and B110 instruct the output of the uplink voice signal, the transmission selector 13 outputs the signal to both call controllers. When receiving a down voice signal from both of the call control units A15 and B110, the reception selection unit 14 receives the down voice signal from the call control unit, which is instructed later, by the reception circuit 19.
Output to

FIG. 2 is a block diagram of a mobile switching center to which the method of switching a busy channel according to one embodiment of the present invention is applied. Referring to FIG. 2, mobile switching center 2 includes a call control unit 21 for controlling a call, a base station interface unit 22 for connecting to a base station through base station communication lines C1, C2 to Cm, and a switching center communication line L1, A switching center interface unit 23 for connecting to a fixed network switching center through L2 to Ln;
And The call control unit 21 transmits and receives a call control signal to and from the base station interface unit 22 and the exchange interface unit 23, and controls the time division switch 24 based on the transmitted and received signals. The time division switch 24 interconnects the respective channels in the base station interface unit 22 and the exchange interface unit 23 under the control of the call control unit 21 and outputs an input from one channel to one channel or , Output to multiple channels.
The base station communication lines C1, C2 to Cm include base station a251,
Base stations b252 to 25m are connected, and transmit control signals and voice signals between these m base stations and mobile switching center 2. A fixed network switching center is connected to the switching center communication lines L1, L2 to Ln, and transmits control signals and voice signals to and from the fixed network switching center.

FIG. 3 is a sequence diagram showing a channel switching operation during a call according to an embodiment of the present invention.
FIG. 4 is a diagram showing an audio path when the sequence operation of FIG. 3 is performed. Referring to FIG. 6 exemplifying the use state of the time slots when the sequence operation of FIG. 3 is performed, there are four time slots each for up and down per unit time.
Channel bidirectional communication is enabled. This time slot is used for communication of both control signals and audio signals. Note that the same numbers in parentheses in FIGS. 3, 4, 5, and 6 indicate the same timing.

Next, referring to FIGS. 1 to 6, the base station a2
51, the operation when the mobile station 1 in communication with the other party connected to the fixed network via the mobile switching center 2 and the switching center communication line L1 moves and switches the channel from the base station a 251 to the base station b 252 explain.

In the state (1) of FIG. 3, the mobile station 1 is connected via the base station a 251 and the mobile switching center 2 to the exchange connecting line L1.
You are in a call with a party connected to. First, the internal operation of the mobile station 1 at this time will be described.

The voice of the user of the mobile station 1 is input to a transmitter 11, and a voice signal is transmitted through a transmitter circuit 12 to a transmitter selector 13.
Is input to The transmission selecting unit 13 determines which of the call control unit A15 and the call control unit B110 outputs this signal. This call is controlled by the call control unit A15, and the call control unit B110 is on standby. At this time, a voice signal is output to the call control unit A15 according to the instruction of the call control unit A15. The voice signal input to the call control unit A15 is output to the time division multiplexing circuit 16, and is output at the timing of the time slot T1 in which the link channel has already been established by the time division multiplexing circuit 16, and the transmitter 17 And the antenna 11 through the duplexer 112
3 is output.

On the other hand, a signal from the base station a 251 is input to the time division multiplexing circuit 16 via the antenna 113, the duplexer 112 and the receiver 111. Time division multiplexing circuit 1
6, the signal received at the timing of the time slot R1 in which the link channel is already established is transmitted to the call control unit A1.
5 is output. The call control unit A15 performs call processing when the input signal is a call control signal, and outputs the signal to the reception selection unit 14 when the signal is a voice signal. At this time, the receiver selection unit 1
In No. 4, it is instructed to output the signal received from the call control unit A15, and this signal is output to the receiver 18 via the receiver circuit 19. Further, the call control unit A15 measures the reception level of the received signal and notifies the call control unit B110. On the other hand, the standby call control unit B110 receives radio waves from other base stations at the timing of the time slots R2, R3, and R4, and determines the reception level and the base station a25.
The comparison with the reception level of the radio wave from No. 1 is performed.

Next, the internal operation of the mobile switching center 2 will be described. The base station a 251 is connected to the mobile switching center 2 via a base station communication line C1. The audio signal between the mobile station 1 and the mobile station 1 is connected to the time division switch 24 via the path of the base station a 251 → the base station communication line C 1 → the base station interface unit 22. The time-division switch 24 connects this voice signal to the exchange on the fixed network via the route of the exchange interface 23 to the exchange connecting line L1. This connection is made in response to an instruction from the call control unit 21 which has received control data from the mobile station 1 in the case of a call from the mobile station 1, and is established in the fixed network in the case of an incoming call to the mobile station 1. This is performed according to an instruction of the call control unit 21 that has received the control data from the exchange. Referring to (1) of FIG. 4 and (1) of FIG. 6, the path of the audio signal at this time uses the time slots T1 and R1, and both the upstream and downstream signals pass through the base station a251.

Next, when the mobile station 1 moves, the call control unit B110 deteriorates the radio wave condition with the base station a 251 to deteriorate the communication quality, and deters the radio wave condition with the base station b 252. Is changed from the standby state to the busy state, the time division multiplexing circuit 16 is instructed to use the time slots T3 and R3, and the link channel with the base station b252 is detected. ((2) in FIG. 3, (2) in FIG. 4, and (2) in FIG. 6). In this case, the frequency does not need to match the frequency used for communication with the base station a251. In this embodiment,
Although the case where the time slots T3 and R3 are used is illustrated, any time slot other than the time slot used with the base station a251 may be used. If the mobile station 1 and the base station b 252 have the current base station a 2
If only the same time slot as the time slot used between the base station a 251 and the base station a 251 is vacant and a different time slot is vacant between the base station a 251 and the base station a 251, The subsequent processing can be continued by changing the time slot between.

Next, the call control unit B 110
3 is also instructed to output an uplink audio signal to the call control unit B110, and the uplink audio signal is transmitted not only to the time slot T1 but also to the time slot T3 ((3) in FIG. 4 and FIG. 6 (3)), a channel switching request signal is transmitted to the base station b252. The base station b252 transmits this signal to the mobile switching center 2 ((3) in FIG. 3). The base station interface unit 22 of the mobile switching center 2 transmits the received channel switching request signal to the call control unit 21. The upstream voice signal transmitted by the time slot T3 at this time is input to the time division switch 24 via the base station b252 → the base station communication line C2 → the base station interface unit 22, but at this time, the call control unit 21 Does not output the upstream audio signal from the time division switch 24 anywhere.

Upon receiving the channel switching request signal, the call control unit 21 instructs the time division switch 24 to output the downlink voice signal from the exchange connecting line L1 not only to the base station a251 but also to the base station b252. , And transmits a channel switching acceptance signal to the mobile station 1. The time-division switch 24 also outputs a downstream audio signal to the base station b 252 based on this instruction ((4) in FIG. 3 and (4) in FIG. 4). At this stage, the downlink voice signal via the base station b252 is received by the receiver 111 of the mobile station 1, extracted by the time division multiplexing circuit 16 at the timing of the time slot R3, and
The signal is sent to the receiver selector 14 via 0, but the receiver selector 14 selects the signal from the call controller A15 as the downstream voice signal and does not output it to the receiver 18.

Next, the call control unit B110 of the mobile station 1 that has received the channel switching acceptance signal instructs the reception selection unit 14 to output a voice signal from the call control unit B110, and the reception selection unit 14 , A voice signal from the call control unit B110 instead of the voice signal from the call control unit A15,
The audio signal transmitted through the base station b 252 is output to the receiving circuit 19. This voice signal is converted into an analog signal by the receiver circuit 19 and output from the receiver 18. At this stage, the downstream voice signal between the mobile station 1 and the mobile switching center 2 is transmitted / received via the base station b252, and the upstream voice signal is transmitted / received via the base station a251. Then, the call control unit B110 transmits an uplink channel switching request signal to the mobile switching center 2 via the base station b252. ((5) in FIG. 3, (5) in FIG. 4, and (5) in FIG. 6).

The call control unit 21 of the mobile switching center 2 receiving the upstream channel switching request signal instructs the time division switch 24 to output an upstream voice signal via the base station connecting line C2 to the switching center connecting line L1. Then, an uplink channel switching completion signal is transmitted to the mobile station 1 through the base station b252. The time division switch 24 outputs an uplink audio signal to the base station b 252 based on this instruction. At this stage, both the upstream and downstream voice signals between the mobile station 1 and the mobile switching center 2 are transmitted to the base station b.
It is transmitted and received via 252 ((6) in FIG. 3 and (6) in FIG. 5).

The call control unit B110 of the mobile station 1 that has received the uplink channel switching completion signal transmits this uplink channel switching completion signal to the call control unit A15, and the call control unit A15 that has received this signal transmits a release request signal. It is transmitted to the mobile switching center 2 via the base station a251 ((7) in FIG. 3 and (7) in FIG. 5).

Upon receiving the release request signal, the call control unit 21
Instructs the time division switch 24 to stop outputting downlink audio signals from the exchange connecting line L1 to the base station a251, transmits a release completion signal to the mobile station 1 through the base station a251, and passes through the base station a251. The call to and from the mobile station 1 is released. The time division switch 24 stops the output of the downlink audio signal to the base station b 251 based on this instruction ((8) in FIG. 3 and (8) in FIG. 5).

Upon receiving the release completion signal, the call control unit A15 of the mobile station 1 releases the link channel with the base station a251 and enters a standby state ((9) in FIG. 3, (9) in FIG. 5 and FIG. 6 (9)).

According to the above procedure, the mobile station 1 can switch the busy channel from the base station a 251 to the base station b 252 without interrupting the call.

In the present embodiment, the state of radio waves between the mobile station 1 and a plurality of base stations is compared in the mobile station 1, and the operation of switching the busy channel is started by a request from the mobile station 1. However, a plurality of base stations receive transmission radio waves from the mobile station 1 to measure the reception level, transmit the reception level to the mobile switching center 2, and the mobile switching station 2 compares these reception levels. The operation of switching the channel during a call may be started. In this embodiment, the mobile station 1
Although a call between the mobile station and the other party connected to the exchange of the fixed network is illustrated, a call between mobile stations may be used.

[0032]

As described above, according to the present invention, since the mobile station uses two time slots and simultaneously communicates with two base stations, the call is instantaneously interrupted using one transceiver. Channel switching can be performed during a call without any need.

Further, if the time slot is different between the switching source zone and the switching destination zone, it is possible to switch the channel during a call without interruption even if the frequency is different, or to set the time within the switching source zone. By changing the slot, collision of the time slot with the switching destination zone can be avoided, so that there is an effect that the degree of freedom of frequency and wireless zone allocation in wireless zone design is increased.

Further, since a channel is formed between the mobile switching center and the mobile station on the path from the two base stations at the same time, the channel switching timing between the mobile switching center and the mobile station is shifted. Instantaneous interruption can be resolved.

[Brief description of the drawings]

FIG. 1 is a block diagram of a mobile station to which a busy channel switching method according to an embodiment of the present invention is applied.

FIG. 2 is a block diagram of a mobile switching center to which a method for switching a busy channel according to an embodiment of the present invention is applied.

FIG. 3 is a sequence diagram showing a channel switching operation according to one embodiment of the present invention.

FIG. 4 is a diagram showing an audio path when the sequence operation of FIG. 3 is performed.

FIG. 5 is a diagram showing an audio path when the sequence operation of FIG. 3 is performed.

FIG. 6 is a diagram showing a use state of a time slot when the sequence operation of FIG. 3 is performed.

FIG. 7 is a sequence diagram showing a conventional channel switching operation during a call.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mobile station 2 mobile switching center 11 transmitter 12 transmitter circuit 13 transmitter selector 14 receiver selector 15 call controller A 16 time division multiplexing circuit 17 transmitter 18 receiver 19 receiver circuit 21 call controller 22 base station Interface unit 23 Switching center interface unit 24 Time division switch 110 Call control unit B 111 Receiver 112 Demultiplexer 113 Antenna 251 Base station a 252 Base station b 25m Base station m C1, C2 to Cm Base station connection line L1, L2 Ln exchange office connection line

Claims (2)

(57) [Claims] A mobile station scattered and moving within a wireless zone, and a base station connected to the mobile station via a wireless line and transmitting and receiving signals using a TDMA communication method and covering a predetermined wireless zone. During a call in mobile communication, the communication channel is switched so that the communication quality becomes a predetermined value when the mobile station shifts to the wireless zone, and the call is continued through a mobile switching center connecting the base station and a fixed network exchange. In the channel switching method, when the mobile station shifts between wireless zones during a call, both the first base station located in the wireless zone before the movement and the second base station located in the wireless zone after the movement And the mobile station perform simultaneous communication using different time slots in a TDMA frame, and transmit an uplink voice signal from the mobile station through the first and second base stations. A time corresponding to simultaneous communication with the first and second base stations at which the mobile switching center broadcasts the mobile station and receives the upstream voice signal. Broadcast output to a slot, and in accordance with the instruction of the mobile switching center, the mobile station selects a downlink audio signal passing through the second base station, and then outputs an uplink audio signal passing through the second base station. A method of switching a channel during a call in mobile communication, characterized by selecting. 2. Mobile stations scattered and moving within a wireless zone.
And TDMA communication with this mobile station via a wireless line
To send and receive signals usingRadio before moving of mobile station
After movement of the first base station and mobile station covering the zone
Second covering the wireless zone ofA base station and the mobile station
Communication quality has reached a predetermined value when
Switch between active callsbase stationExchange of fixed net
Mobile communication with a mobile switching center that connects
In the communication channel switching system, the mobile station,From this mobile station ’s transmitter The input upstream audio signalSaid
Of the first and second base stationsEither one or both
A transmission selection unit for selectively outputting toFrom the first and second base stations Two descending inputs
Which of the audio signalsFor mobile station handsetWhether to output
A receiver selection unit to be selected, and a call included in a plurality of time slots of a TDMA frame.
Time division multiplexing circuit for transmitting and receiving control signals and audio signals
When,Between the transmission selector and the time division multiplexing circuit, and
Between the receiving selector and the time division multiplexing circuit Call control
Transmitting and receiving signals and voice signals, from the mobile switching center.
According to the control information, the transmission selecting sectionAgainstUpstream voice signal
Issue destinationIs any of the first and second base stations.
OrAnd the receiver selection sectionAgainstTwo downstream audio signals
Of which signal to output and the time division multiplexing
CircuitAgainstCall control signal and voice signal transmission / reception
Imslot instruction and transmission / reception to transmitter and receiver
And a first call control unit for instructing the frequency to be transmitted, wherein the mobile switching center,Through the first and second base stations Transmission and reception of call control signals
And on the basis of this signalIn the mobile switching centerCall path switch
And the first call control unit controls the
A second call control unit for transmitting information., The first call control unit is configured to control a wireless zone during a call by the mobile station.
When transitioning between stations, both the first and second base stations
In the TDMA frame between the mobile station and the mobile station.
Perform simultaneous communication using time slots
Through the first and second base stations.
Broadcast to the mobile switching center, The second call control unit receives the uplink voice signal and
The downlink audio signal from the communication partner of the mobile station is transmitted to the first and
To a time slot corresponding to simultaneous communication with the second base station
Broadcast output, The first call control unit responds to an instruction from the mobile switching center.
Selected the downlink audio signal passed through the second base station.
Thereafter, an uplink audio signal passing through the second base station is selected.
 Channel switching during communication in mobile communication
system.