JPH099330A - Channel changeover system between radio zones in mobile communication system - Google Patents

Abstract

PURPOSE: To reduce the traffic of control channels at inter-zone channel switching and to relieve the load for signal processing in a base station. CONSTITUTION: A base station 2-2 belonging to a radio zone 4-1 sends communication channel information used by an adjacent radio zone to a mobile station 3 with a communication channel information channel of a TDM slot. The mobile station 3 stores the channel information. When the mobile station 3 moves from a point A to a point B and a reception level of an outgoing communication channel Tch2 from the base station 2-2 is reduced, the mobile station 3 measures the reception level of the outgoing communication channel of an adjacent radio zone. The mobile station 3 receiving the measurement result selects the communication channel for a communication channel Tch1 of the base station 2-1 representing a highest reception level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base station which is controlled by a control station and is arranged in each of a plurality of radio zones, and freely moves through the radio zones and uses a communication channel to communicate with the base station. The present invention relates to a channel switching method between mobile stations in a mobile communication system that maintains a communication by switching the base station and the communication channel even if the mobile station moves in the wireless zone.

[0002]

2. Description of the Related Art In a conventional channel switching system between radio zones in a mobile communication system of this kind, for example, a cellular car telephone system, a mobile station communicating with one of base stations is connected to an adjacent radio zone. Of the control channel transmitted by the base station and the reception level of the communication channel during communication are constantly measured. When the reception electric field level of the communication channel during communication falls below a predetermined value, the mobile station
It determines that it is moving away from the wireless zone in which it is located, and switches the communication channel to a communication channel of an adjacent wireless zone that has a high control channel reception level and satisfies predetermined conditions. In this communication channel switching, the base station of the channel switching destination transmits and receives a control signal on the control channel to and from the mobile station in order to allocate a new communication channel. The communication with the base station before switching is started at the same time.

[0003]

In the conventional channel switching method between radio zones in a mobile communication system, when a large number of mobile stations move between a plurality of base stations, transmission / reception of a channel switching control signal is performed. Therefore, the traffic of the control channel and the wired control line between the base station and the mobile station and between the base station and the control station increases, and the load of signal processing at the base station accompanying the switching of the communication channel increases. There was a problem.

[0004]

A channel switching method between radio zones in a mobile communication system according to the present invention includes a base station arranged in each of a plurality of radio zones and controlled by a control station; Comprising a plurality of mobile stations that freely move and communicate with the base station using a communication channel, even if the mobile station moves in the wireless zone, by switching the base station and the communication channel. In the channel switching method between radio zones of the mobile communication system that maintains the communication, each of the base stations,
Communication channel information notifying means for notifying adjacent zone communication channel information that is information of the communication channel used in an adjacent wireless zone, wherein each of the mobile stations receives the adjacent zone communication received from the base station. Communication channel information storage means for storing channel information immediately after the start of the communication, communication quality detection means for detecting the quality of the communication channel from the base station during communication, and quality deterioration of the communication channel is detected. Then, reception level measuring means for measuring the downlink reception level of the adjacent zone communication channel,
Communication channel switching means for setting the communication channel to a communication channel of the own wireless zone or the adjacent wireless zone where the highest reception level is measured.

[0005] In a first embodiment of the channel switching method between radio zones in the mobile communication system, the base station always transmits the adjacent zone communication channel information on the communication channel being transmitted to the mobile station. Configuration can be taken.

In a second embodiment of the channel switching method between radio zones in the mobile communication system, the base station intermittently puts the adjacent zone communication channel information on the communication channel being transmitted to the mobile station. It can be configured to transmit.

In a third embodiment of the channel switching method between radio zones in the mobile communication system, each of the mobile stations is connected only to mobile stations in a group of the plurality of mobile stations grouped into a plurality of groups. A configuration may be adopted in which group communication is performed, and the communication channel, which is a predetermined TDM channel, is assigned to each group of the mobile stations.

In a fourth embodiment of the channel switching method between radio zones in the mobile communication system, each of the mobile stations can perform communication only in the limited radio zone.

[0009]

Next, the present invention will be described with reference to the drawings.

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

There are a plurality of mobile communication systems, here 5
The two wireless zones 4-1, 4-2, 4-3, 4-4 and 4-5 are service areas. Wireless zone 4-
Base stations 2 are provided at 1, 4-2, 4-3, 4-4 and 4-5.
-1, 2-2, 2-3, 2-4 and 2-5 are arranged, respectively, and the base stations 2-1 to 2-5 are connected to the control station 1 by a wired line and are supervised. The mobile station 3 moves freely in the wireless zones 4-1 to 4-5 and communicates with the base stations 2-1 to 2-5 which satisfy predetermined conditions using the communication channel Tch. This mobile communication system includes a plurality of mobile stations having the same function as the mobile station 3.

Now, the mobile station 3 is located at a point A substantially at the center of the radio zone 4-2, and this mobile station 3 is communicating with the base station 2-2 via the communication channel Tch2. Generally, the mobile station 3 often communicates with another base station and a mobile station via the base station 2-2. Next, the mobile station 3 passes through the peripheral point B of the wireless zone 4-2 to the wireless zone 4
When the mobile station 3 moves to a point C within the communication channel T-1, the communication channel Tch2 near the point B is changed to the communication channel T
Switch to ch1 and switch to base station 2 (base stations 2-1 to 2-
5 is maintained).

The above-described channel switching between radio zones in the mobile communication system will be described in more detail.

The base station 2-2 communicating with the mobile station 3 transmits information on communication channels used in the adjacent radio zones 4-1, 4-3, 4-4 and 4-5, that is, the adjacent base stations. Adjacent zone communication channel information, which is information on communication channels used by the stations 4-1, 4-3, 4-4 and 4-5, is broadcast to the mobile station 3 using the communication channel Tch2 during communication. .

The mobile station 3 stores the adjacent zone communication channel information received from the base station 2-2 in the communication channel information storage unit immediately after the start of communication. The mobile station 3 is also the base station 2
-2, the quality of the communication channel Tch2 transmitted, for example, the reception level is constantly detected by the communication quality detection unit. When the mobile station 3 moves to the point B and the communication quality detecting unit detects the quality deterioration of the communication channel Tch2, the built-in reception level measuring unit of the mobile station 3 stores the base station 2 in the adjacent wireless zone which has already been stored. All communication channels Tch1, Tch3, T used in -1, 2-3, 2-4 and 2-5
The downlink reception levels of ch4 and Tch5 are measured. The mobile station 3 measures the reception level of the communication channel Tch1 used by the base station 4-1 at the point B at the highest level.
The mobile station 3 controls the communication channel T by the communication channel switching unit.
The ch2 is switched to the communication channel Tch1 of the base station 4-1. Thereafter, the mobile station 3 moves to the point C in the wireless zone 4-1.
, The communication with the base station 2-1 is continued while maintaining the switched communication channel Tch1.

FIG. 2 is a signal configuration diagram of a communication channel Tch transmitted from the base station 2 to the mobile station 3 in the present embodiment, and shows two signal configuration examples (a) and (b). FIG. 3 is a signal configuration diagram of adjacent zone communication channel information included in the communication channel Tch. Communication channel T shown here
ch is one slot of the TDM system. The communication channel Tch needs to be identified by a combination of any of a plurality of radio channels (frequency channels) and any of a plurality of TDM slots.

Referring to FIG. 2A, the communication channel Tch includes a radio control channel (RCCH) for transmitting the overhead of the communication channel and a communication channel information channel (C) for transmitting the adjacent zone communication channel information.
CTCH) and an information channel (TC) for transmitting communication information.
H) and a low-speed associated control channel (SACCH) for transmitting control information associated with the information channel.
M channel. Using this communication channel Tch, the base station 2 can transmit the adjacent zone communication channel information every time the communication channel Tch is transmitted. The information channel transmits a voice signal, a data signal, a call control signal, and the like, and the low-speed associated control channel transmits a signal indicating the type of the information channel.

Referring to FIG. 2B, the communication channel Tch includes a radio control channel (RCCH) for transmitting overhead of the communication channel, an information channel (TCH) for transmitting communication information, and the information channel. A low-speed associated control channel (S
ACCH). The information channel (TCH) transmits a voice signal, a data signal, a call control signal, adjacent zone communication channel information, and the like, and the low-speed associated control channel transmits a signal indicating the type of the information channel. When using this communication channel Tch, the base station 2 transmits the adjacent zone communication channel information to the information channel TC.
H can be transmitted intermittently.

Referring to FIG. 3, adjacent zone communication channel information transmitted on the communication channel information channel (CCTCH) of FIG. 2A or the information channel (TCH) of FIG. It consists of the number n of wireless zones (adjacent wireless zones) adjacent to the wireless zone of the station 2, the code of the adjacent wireless zone, and communication channel information corresponding to each of the adjacent wireless zones. The communication channel information includes a frequency number having the same meaning as the wireless channel number and a slot number of the TDM channel. The communication channels Tch that can be used by the base station 2 are generally a plurality of channels based on a combination of a frequency number and a slot number.

Referring to FIG. 1 and FIG. 3, when the mobile station 3 is at the point A, the mobile station 3 receives the downlink communication channel Tch2 from the base station 2-2. Base station 2-
2 adjacent wireless zones are wireless zones 2-1, 2-3, 2-
4 and 2-5. Therefore, the base station 2-2 has the number of the adjacent radio zones 4, the codes of the base stations 2-1 to 2-3, 2-4 and 2-5, and the communication channel Tch used in these base stations, for example, Tch1. , Tch3, Tch4
And the adjacent zone communication channel information including the frequency number and the slot number respectively corresponding to Tch5 and Tch5 are transmitted on the communication channel Tch2.

FIG. 4 is a block diagram of the base station 2 used in this embodiment.

The base station 2 communicates with the control device 21 and its own I
D, a code of an adjacent wireless zone, information of a communication channel Tch used in the adjacent wireless zone (adjacent zone communication channel information, that is, a frequency number and a slot number), and the like. A hopping synthesizer 23 that can be changed and a transmitter 2
4, a receiver 25, an antenna duplexer 26, and an antenna 27. The adjacent zone communication channel information is collected from the adjacent wireless zone via the control station 1.
The memory 22 also stores a frequency number and a slot number used by the own station as the communication channel Tch. If the next TDM slot is a communication channel, the control device 21 specifies the frequency number to the hopping synthesizer 23 from the information in the memory 22 and includes the ID of the own station and the adjacent zone communication channel information to the transmitter 24. Of the communication channel Tch.

FIG. 5 is a block diagram of the mobile station 3 used in this embodiment.

The mobile station 3 includes a control device 31, a memory 32 for storing the adjacent zone communication channel information received from the base station 2 immediately after the start of communication, and a frequency for each communication channel Tch received by the control device 31. , A transmitter, a receiver, an antenna duplexer, an antenna 37, a reception level of a communication channel Tch received from the base station 2, a reception quality such as a signal error rate, and an adjacent radio zone. A quality measuring device 38 for measuring the reception level of the communication channel in use.

FIG. 6 is a flowchart showing the operation of the mobile station 3 according to this embodiment.

Referring to FIGS. 1, 5 and 6 together,
The mobile station 3 starts communication with the base station 2-2 using the communication channel Tch2 at the point A in the wireless zone 4-1. The mobile station 3 transmits the downlink communication channel Tch to the antenna 3
7. Received by the control device 31 via the antenna duplexer 36 and the receiver 35. Immediately after the start of communication, the memory 32
The adjacent zone communication channel information transmitted by the downlink communication channel Tch2 is received from the control device 31 and stored (step 1). When the mobile station 3 is in the wireless zone 4-2
When the communication ends while the user is inside (y in step 2),
The control device 31 terminates communication with the base station 2-2 (step 3).

During the continuation of the communication (n in Step 2), the quality measuring device 38 constantly measures the reception level of the downlink communication channel Tch2 (Step 4). If the reception level is equal to or higher than the predetermined level (n in Step 5), the mobile station 3 repeats the operation from Step 2 and
Causes the base station 2-2 to continue communication using the communication channel Tch. Here, when the mobile station 3 moves to the point B at the end of the wireless zone 4-2 closer to the wireless zone 4-1, the quality measuring device 38 detects the reception level deterioration of the downlink communication channel Tch2 and sends the control device 31 Notify (y in step 5).

When receiving the report of the detection of the deterioration of the reception level of the communication channel Tch2 during communication, the control device 31
2, the base stations 2-1 and 2- in the adjacent wireless zone stored in
The quality measuring device 38 measures the downlink reception levels of all the communication channels Tch1, Tch3, Tch4 and Tch5 used in 3, 2-4 and 2-5 (n in steps 6 and 7). When the measurement of the reception level of the downlink communication channel from the base stations in all the adjacent wireless zones is completed (y in step 7), the control device 31 sends the signal to the synthesizer 3
3 to control the communication channel Tch of the receiver 35.
Is set as the communication channel with the highest reception level among the downlink communication channels Tch1 to Tch5 from the base station 2-2 in the own wireless zone and the base station in the adjacent wireless zone. At the point B, the quality measurement device 38 measures the highest reception level of the communication channel Tch1 used by the base station 4-1. Therefore, the control device 31 switches the communication channel Tch2 received by the receiver 35 to the base station 4 -1 communication channel Tch
1 (step 8). Thereafter, the mobile station 3
Returning to the operation of step 2, the communication with the base station 2-1 is continued while maintaining the switched communication channel Tch1. This state continues even if the mobile station 3 moves to the point C in the wireless zone 4-1.

The channel switching method between radio zones in the mobile communication system according to the present invention described above with reference to the embodiments is particularly applied to a mobile communication system for group communication represented by a digital mobile communication system for public service and an MCA system. It is valid. In group communication, mobile stations in a service area are grouped into a plurality of groups, and the mobile stations perform one-to-N communication with N mobile stations in the group. In the case of such group communication, each of the base stations 2 determines in advance a communication channel Tch for each group of mobile stations, and this communication channel Tch
In many cases, communication can be performed without interruption by using a URL. When the communication channels used by each mobile station group are determined in advance in this way, the burden of selecting a communication channel on the mobile station 3 is reduced.

The channel switching method between radio zones in the mobile communication system according to the present invention may, of course, limit the range of the radio zone 4 with which the mobile station 3 can communicate, as in a conventional MCA system. . In this case,
A function of limiting the partner station that can communicate with the base station 2 or the mobile station 3 is provided.

[0031]

As described above, according to the present invention, each of a plurality of base stations broadcasts adjacent zone communication channel information which is information of the communication channel used in an adjacent wireless zone. A communication channel information storage means for storing information on the adjacent zone communication channel received from the base station immediately after the start of the communication, and Communication quality detection means for detecting the quality of the communication channel, reception level measurement means for measuring the downlink reception level of the adjacent zone communication channel when the quality deterioration of the communication channel is detected, Communication channel switching means for setting a communication channel of the own wireless zone or the adjacent wireless zone whose reception level has been measured. The mobile station can independently switch communication channels without any need to transmit and receive control signals for switching, can reduce the traffic of wireless and wired control lines when switching channels, and can reduce the load of signal processing at the base station. There is an effect that it can be reduced.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a signal configuration of a communication channel Tch transmitted from a base station 2 to a mobile station 3 according to the present embodiment.
(B) shows a second example.

FIG. 3 is a signal configuration diagram of adjacent zone communication channel information included in a communication channel Tch.

FIG. 4 is a block diagram of a base station 2 used in the present embodiment.

FIG. 5 is a block diagram of a mobile station 3 used in the present embodiment.

FIG. 6 is a flowchart illustrating an operation of the mobile station 3 according to the present embodiment.

[Explanation of symbols]

 Reference Signs List 1 control station 2-1 to 2-5 base station 3 mobile station 4-1 to 4-5 radio zone 21 control device 22 memory 23 hopping synthesizer 24 transmitter 25 receiver 26 antenna duplexer 27 antenna 31 control device 32 memory 33 Synthesizer 34 Transmitter 35 Receiver 36 Antenna duplexer 37 Antenna 38 Quality measuring device

Claims (5)

[Claims] 1. Communication between a base station arranged in each of a plurality of radio zones and controlled by a control station, and a base station that moves freely in the radio zones and uses a communication channel. A plurality of mobile stations, wherein the mobile station switches between the base station and the communication channel even if the mobile station moves in the wireless zone, and maintains the communication. Each of the stations comprises communication channel information notifying means for notifying adjacent zone communication channel information that is information of the communication channel used in an adjacent wireless zone, and each of the mobile stations is transmitted from the base station. Communication channel information storage means for storing the received information of the adjacent zone communication channel immediately after the start of the communication, and the communication from the base station during communication Communication quality detection means for detecting channel quality; reception level measurement means for measuring a downlink reception level of the adjacent zone communication channel when quality deterioration of the communication channel is detected; Communication channel switching means for setting a measured communication channel of the own wireless zone or the adjacent wireless zone. 2. The mobile communication system according to claim 1, wherein the base station always transmits the adjacent zone communication channel information on the communication channel being transmitted to the mobile station. Channel switching method. 3. The wireless communication system according to claim 1, wherein the base station transmits the adjacent zone communication channel information intermittently on the communication channel being transmitted to the mobile station. Channel switching method between zones. 4. Each of the mobile stations performs group communication only with mobile stations in a group of the plurality of mobile stations grouped into a plurality of groups, and each of the mobile stations has a predetermined group. 2. The system according to claim 1, wherein the communication channel is a TDM channel. 5. The system according to claim 1, wherein each of the mobile stations can communicate only in the limited wireless zone.