JPH06339177A - Channel changeover system in busy state - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a channel switching method during a call in a mobile communication system, and an object thereof is to reduce the time required for channel switching during a call. A plurality of radio base stations are provided, each including a switching center that performs call processing of mobile stations located in a plurality of adjacent radio zones, and a plurality of radio base stations that form each radio zone and serve as a radio interface of a radio channel. Between the station and the exchange, a plurality of wireless base stations are individually connected via inter-station transmission lines,
A plurality of modulation / demodulation means for modulating / demodulating information transmitted / received to / from a mobile station via a wireless channel, and a switching center connected via a communication link, and these communication links and a plurality of modulation / demodulation means are variably connected. Channel switching control during a call is performed via the switching means and the modulation / demodulation means, and a communication path between the mobile station and an empty wireless channel of the transfer destination wireless zone is set via the switching means based on the control procedure. A centralized base station including a control means for controlling the operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication system in which a service area is composed of a plurality of wireless zones, and for a mobile station to which the wireless zone has been transferred during a call, the wireless channel for the call is transferred to the wireless zone of the transfer destination. The present invention relates to an in-call channel switching method for switching to a channel and continuing a call.

[0002]

2. Description of the Related Art In a mobile communication system, a high-quality call service with less interference is provided to a large number of mobile stations distributed over a wide geographical area, and the frequency is reused to improve the economy. Therefore, the service area is divided into a plurality of wireless zones and formed, and the channel is switched to the mobile station that has moved to the wireless zone during the call to continue the call.

FIG. 5 is a diagram showing a configuration example of a conventional channel switching system during a call. In the figure, the switching center 51 connected to the public telephone network includes wired communication lines 52 _{1 to} 53 _N.
And are connected to the base wireless stations 53 _{1 to} 53 _N respectively. Each of the base wireless stations 53 _{1 to} 53 _N has a wireless zone 5
4 _{1 to} 54 _N are formed, and mobile terminals (here, only the mobile terminal 55 located in the wireless zone 54 ₁ is located for simplicity) are located in these wireless zones.

In the wireless base station 53 ₁ , the wired communication line 52
₁ is connected to the terminal terminal of the line terminator 56 ₁ and its output is connected to the transmission input of the duplexer (D) 59 ₁ via the modulator (MOD) 57 ₁ and the transmission amplifier 58 ₁ . The antenna terminal of the transmission / reception separator 59 ₁ is connected to the antenna 60 _1, and the reception output of the transmission / reception separator 59 _{1 is} passed through the reception amplifier 61 ₁ and the demodulator (DEM) 62 ₁ to the line terminator 56 ₁
Connected to the input of. In addition, the wireless base stations 53 _{2 to} 53 _N
Since the configuration is the same as that of the wireless base station 53 ₁ , the corresponding individual constituent elements are shown here with the same reference numbers having subscripts “ ₂ ” to “ _N ”. The description is omitted.

In the call channel switching system having such a configuration, the mobile terminal 55 monitors the magnitude relationship between the received electric field level of the call channel captured during a call and a predetermined threshold value, and as a result of the monitoring, On the basis of recognizing that the transmission quality of the corresponding speech channel has deteriorated, it is determined that the mobile station has moved out of the wireless zone 54 ₁ . The mobile terminal 55 that makes such a determination sends a control signal requesting “control of reconnection” to the radio base station 53 ₁ (FIG. 6).
).

In the radio base station 53 ₁ , the antenna 60 ₁ ,
After receiving such a control signal through the transmission / reception separator 59 ₁ and the reception amplifier 61 ₁ , and further demodulating it through the demodulator 62 ₁ , the line terminator 56 ₁ and the wired communication line 5
2 through ₁ to the exchange 51 (FIG. 6),
Temporarily suspend the call. Upon recognizing such a control signal, the switching center 51 suspends the corresponding channel on the wired communication line 52 ₁ and waits (FIG. 6).

[0007] On the other hand, the mobile terminal 55 determines whether the received electric field level is high or low with respect to a specific wireless channel (for example, a control wireless channel) in a wireless zone corresponding to a wireless channel during a call and a wireless zone adjacent to the wireless zone. The wireless zone of the transfer destination (here, the wireless zone 54 ₂ is used for simplicity) is determined based on the determination criteria, and a specific wireless channel of the wireless zone (for example, a control wireless channel).
A line connection request including the identification information of its own station is transmitted to
).

A radio base station 5 forming a radio zone 54 _2.
When receiving such a line connection request, 3 ₂ allocates a vacant wireless channel for communication in the corresponding wireless zone, establishes the wireless channel for communication with the mobile terminal 55, and and adding identification information of a radio channel to the line connection request (in this case, a wired communication line 52 ₂ corresponding to the radio base station 53 ₂₎ wire communication line and sends to the exchange 51 through a (FIG. 6). In addition, the mobile terminal 55
In this way, the call channel established is waited for and the call continues.

The exchange 51 requests such a line connection request.
When receiving, the identification of the wireless channel for communication included in the request
Wired communication line that extracts different information and corresponds to the identification information
52 ₂Establish the channel above and
The wired communication line that the mobile terminal 55 used earlier for the call
52₁Call path required to use in place of the above channel
Switch. Further, the switching center 51 is
Line communication line 52₁Open the upper channel. According to
The mobile terminal 55 is connected to the wireless zone 54₁Adjacent during a call
Wireless zone 54₂To continue the call even after moving to
You can

[0010]

By the way, in such a conventional channel switching method during a call, the switching center 51 performing call processing for all calls is required for channel switching during a call in parallel with the call processing. Since the processing of switching the communication path and other processing were performed, the time required to complete the switching of the communication channel may become long.

Further, in this case, the corresponding mobile terminal moves to another wireless zone within the above-mentioned time, so that the communication quality in the new communication channel after the completion of the channel switching during communication is improved. When the mobile terminal is deteriorated or the moving speed of the mobile terminal is high, a predetermined call quality cannot be ensured, so that the call may be forcibly interrupted.

Further, in the mobile communication system adopting the method of setting the radius of the radio zone to be small like the micro cell method, the probability that the call is forcibly interrupted frequently occurs during the call as described above. It becomes larger in response to a request for channel switching during a call, and the processing amount of the switching center 51 increases in response to the request.

An object of the present invention is to provide a call channel switching system capable of shortening the time required for channel switching during a call.

[0014]

SUMMARY OF THE INVENTION The present invention relates to a mobile station located in any one of a plurality of wireless zones adjacent to each other in a geographically fixed relationship, and a switching center for performing call processing of a generated call,
A plurality of radio base stations that individually form a plurality of radio zones and take a radio interface of radio channels assigned to the radio zones; and a plurality of radio base stations between the plurality of radio base stations and the switching center. A plurality of modulation / demodulation means that are individually connected to the base station via an inter-station transmission line and that modulate and demodulate information transmitted and received facing the mobile station via a wireless channel, and a plurality of communications individually corresponding to the wireless base station. It is connected to the switching center via a link, and switching means for performing variable connection between these communication links and a plurality of modulation / demodulation means, and control of channel switching during a call via the modulation / demodulation means, and the control procedure is On the basis of the above, the centralized base station including the mobile station and the control means for setting the communication path between the mobile station and the idle radio channel in the wireless zone of the transfer destination of the mobile station via the switching means is provided. And butterflies.

[0015]

In the in-call channel switching system according to the present invention, the control means controls the in-call channel switching control opposite to the in-call mobile station connected via the modulation / demodulation means, the inter-station transmission path and the radio base station. Then, based on the control procedure, the connection between the modulation / demodulation means and the communication link is variably set through the switching means, and the call path is updated and set according to the shift of the mobile station during the call.

That is, while maintaining the speech path set by the exchange at the time of starting the speech of the above-mentioned mobile station, between the communication link connected to the speech path and the modulation / demodulation means corresponding to the radio channel for speech. By changing the connection, the communication path is switched according to the transition of the mobile station, so the wireless channel allocation that was conventionally distributed to the wireless base stations that individually form multiple adjacent wireless zones The centralized base station collectively performs the processing and the processing for switching the communication path that has been performed by the exchange.

Therefore, these processes are smoothly carried out by distributing the load to each centralized base station stationed in each service area, and the processing amount of the exchange station is reduced so that the time required for channel switching during a call is reduced. Shortened.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram showing an embodiment of the present invention.

In the figure, parts having the same functions and configurations as those shown in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted here. In the present embodiment, the characteristic configuration of the present invention is that the conventional radio base stations 53 _{1 to} 53
Instead of _N , the transmission amplifiers 58 _K of these radio base stations,
Receiver amplifier 61 _K , transmitter / receiver separator 59 _K , antenna 60 _K
(K = 1 to 3) to have been provided with a radio base station 10 ₁ to 10 ₃ configured to separate respectively, between full-duplex stations between and these radio base station wired communication line 52 _{1-52 3} Transmission line 11 ₁
~ 11 ₃ and the centralized base station 12 are connected.

In the toll base station 12, the conventional radio base station 5
Line terminators 56 _{1 to} 5 separated from 3 _{1 to} 53 ₃
6 _3, modulator 57 _{1-57 3,} in conjunction with the demodulator 62 _{1-62 3,} the line terminal 56 ₁ to 56 ₃ and the modulator 57 _1-5
7 ₃ and a transmission switching device 13 forming a matrix switching circuit, and a reception switching device forming a matrix switching circuit between the demodulators 62 _{1 to} 62 ₃ and the line terminators 56 _{1 to} 56 ₃ . 14, control inputs of the reception switcher and the transmission switcher 12, and demodulators 62 _{1 to} 62 _1.
Switching controller 15 connected to ₃ field level output
Composed of.

[0021] As to the correspondence relationship between the present embodiment and the components shown in claim 1, wired communication line 52 _{1-52 3}
Corresponds to a communication link, line terminator 56 _{1-56 3,} transmits the switching device 13 and the receiving switching unit 14 corresponds to the switching means, the modulator 57 _{1-57 3} and demodulator 62
_{1-62 3} corresponds to modulation and demodulation means, the switching controller 15
Corresponds to the control means, and the mobile terminal 55 corresponds to the mobile station, but the radio base stations 10 ₁ to 10 ₃ and the inter-station transmission paths 11 ₁ to 1
1 ₃ and the toll base station 12 respectively correspond to components having the same name.

The operation of this embodiment will be described below. In the present embodiment, as described above, the conventional radio base stations 53 _{1 to} 53 are used.
₃ but is separated into a radio base station 10 ₁ to 10 ₃ and the centralized base station 12, the reception wave to be applied to the demodulator 62 _{1-62 3} and the modulated wave output from the modulator 57 _{1-57 3} A signal is transmitted / received via the inter-station transmission paths 11 _{1 to} 11 ₃ and is set by the switching controller 15 to the transmission switching device 1
A radio base station similar to the conventional example is formed according to the positions of the contacts 3 and the reception switcher 14.

The switching controller 15 individually acquires the presence / absence, allocation destination, and belonging of the wireless channels that can be used for a call in the wireless zone formed by the centralized base station 12 via the wireless base stations 10 ₁ to 10 _3. A channel management table in which wireless zones are registered and a zone management table in which adjacent wireless zones of individual wireless zones are registered are provided. Further, the switching controller 15 constantly refers to the above-mentioned channel management table to capture the reception electric field level of each wireless channel already used for a call through the demodulators 62 _{1 to} 62 ₃ and monitor it.

On the other hand, for example, the mobile terminal 55 located in the wireless zone 54 ₁ and communicating with the exchange 51 via the wired communication line 52 ₁ via the preset communication path is connected to any of the adjacent radios. Switching to zone 1
5 detects such a transition when the received electric field level of the corresponding radio channel continuously decreases over a certain time (FIG. 2). Furthermore, the switching controller 15
Recognizes the wireless zone to which the corresponding wireless channel belongs from the above-mentioned channel management table and refers to the zone management table based on the wireless zone to acquire the adjacent wireless zones 54 ₂ , ...

The switching controller 15 measures the reception electric field level of each of the adjacent radio zones thus acquired through the demodulators 62 _{1 to} 62 _3, and the adjacent radio zone in which the maximum reception electric field level is obtained. (Here, for the sake of simplicity, the wireless zone 54 ₂ is used) as the transfer destination wireless zone (FIG. 2).

Further, the switching controller 15 refers to the channel management table on the basis of the wireless zone of the transfer destination thus obtained and the wireless channel used for the call at this time, and the wireless communication of the transfer destination is performed. Test if the same radio channel is available in the zone.

As a result of such a test, if the same wireless channel can be used in the wireless zone of the transfer destination, the switching controller 15 registers in the channel management table that the wireless channel is to be captured, and , For the corresponding wireless channel, a modulator 57 ₂ and a demodulator 62 ₂ corresponding to the transfer destination wireless zone 54 ₂ and a line terminator 56 ₁ corresponding to the wireless zone 54 ₁ before the transfer (when the call starts). The two are connected via a transmission switch 13 and a reception switch 14 (FIG. 2).

Furthermore, for the radio channel that has been subjected to the call before migration, it is opened through the radio base station 10 _1, transmission and reception of the modulated wave is canceled between the centralized base station 12 and the wireless base station (Fig. 2). Furthermore, for the radio channel to be used for the migrated call is established via the radio base station 10 _2, transmission and reception of the modulated wave is initiated between a centralized base station 12 and the wireless base station (FIG. 2)
So the call continues.

If the switching controller 15 recognizes that the same wireless channel cannot be used in the transfer destination wireless zone as a result of the above-mentioned test, it first selects an empty wireless channel in the transfer destination wireless zone. Then, the fact that the wireless channel is captured is registered in the channel management table. further,
The switching controller 15 sends a channel switching request including the identification information of the wireless channel thus selected to the wireless base station 10 ₁ corresponding to the wireless zone before the transition (FIG. 3A).

The radio base station 10 ₁ sends the channel switching request to the mobile terminal 55 (FIG. 3B), and the mobile terminal releases the radio channel with which it is talking. Therefore,
The transmission / reception of the modulated wave in the radio channel before the transition is stopped between the radio base station 10 ₁ and the toll base station 12 (FIG. 3).
C).

Upon receiving the above-mentioned channel switching request, the mobile terminal 55 switches to the wireless channel indicated by the identification information included in the request and stands by. Such migration destination radio channel is established via the radio base station 10 ₂ between the centralized base station 12 and the wireless base station starts transmission and reception of the modulated wave, it is possible to continue the call (Fig. 3
).

In FIG. 3, the processing performed by the toll base station 12 in the same manner as the procedure shown in FIG. 2 is indicated by the same circle number (-), and the description thereof is omitted here. As described above, in this embodiment, the centralized base station is placed in the service area formed by a plurality of adjacent wireless zones, and in each individual centralized base station, conventionally, a wireless base station that individually forms a plurality of adjacent wireless zones is provided. Wireless channel allocation processing that has been performed in a distributed manner, the call path switching processing that has been performed collectively in the switching center 51, and the mobile terminal 55.
The process of selecting the transfer destination wireless zone, which has been performed by the above, is collectively performed.

Therefore, the above-mentioned processes are smoothly performed, the load is distributed for each service area, the processing amount of the exchange 51 is reduced, and the time required for switching the communication channel is shortened. In addition, since the probability that the corresponding mobile terminal moves quickly during the call channel switching and moves to another wireless zone is reduced, the deterioration of the call quality of the new call channel after the completion of the call channel switching. And the probability that the call is forcibly interrupted because a predetermined call quality cannot be secured in the call channel.

In this embodiment, a single centralized radio base station 12 is provided, but the present invention is not limited to such a configuration, and for example, a plurality of non-overlapping service areas each have a plurality of radio zones. In a mobile communication system formed by, a centralized radio base station is provided for each service area, and the same can be applied.

Further, in the present embodiment, the present invention is applied to the digital cordless system, but the present invention is not limited to such a system, and the toll base station 12 (switch controller 15) uses the busy channel. If it is possible to reliably acquire the wireless zone of the transfer destination and the wireless channel vacant in the wireless zone based on a predetermined switching procedure, for example, it can be similarly applied to the current analog car telephone system. Is.

Further, in this embodiment, the switching controller 1
5 selects the wireless zone of the transfer destination of the mobile terminal 55 and the wireless channel vacant in the wireless zone, the invention is not limited to such a method, and the mobile terminal 55 determines the transfer destination zone, for example. When the present invention is applied to a mobile communication system that switches channels during a call by doing so, as shown by the dotted line in FIG. 4, transmission is performed in correspondence with the transfer destination zone and wireless channel indicated by the line connection request. It suffices to switch between the switch 13 and the reception switch 14. Note that the processes shown in FIGS. 4A to 4C correspond to the processes with the same circle numbers shown in FIG. 6, and among these processes,
The processing indicated by ,, and is performed by the centralized base station 12 in place of the switching center 51, and therefore its description is omitted here.

Further, in this embodiment, the wired communication line 52 ₁
To 52 ₃ and has metallic link is used as the inter-station transmission path 11 ₁ to 11 _3, the present invention is not limited to such a wired communication line and inter-station transmission line, for example,
A wireless multiple link or an optical transmission line may be adopted.

[0038]

As described above, according to the present invention, the communication link connected to the communication path and the wireless channel for communication are maintained while maintaining the communication path set by the mobile switching center at the start of the communication of the mobile station. The connection between channels is variably set and the call path is switched according to the transition of the mobile station, and the wireless channel allocation that was conventionally distributed to the wireless base stations that individually form multiple adjacent wireless zones is performed. The centralized base station collectively performs the processing and the switching processing of the communication path which has been performed in the exchange.

In other words, the processing related to channel switching during a call is smoothly performed by distributing the load to each centralized base station located in each service area, and the processing amount of the switching center is reduced. The time required for channel switching is shortened.

Therefore, in the mobile communication system to which the present invention is applied, a mobile station in a call moves to the outer periphery or the outside of the radio zone of the switching destination during the switching of the channel during the call, and a sufficient call quality cannot be obtained. Or, the probability that the call is forcibly interrupted is reduced and the service quality is improved.

[Brief description of drawings]

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

FIG. 2 is a diagram (1) explaining the operation of the present embodiment.

FIG. 3 is a diagram (2) explaining the operation of the present embodiment.

FIG. 4 is a diagram showing another method of obtaining a switching destination of a call radio channel.

FIG. 5 is a diagram showing a configuration example of a conventional in-call channel switching system.

FIG. 6 is a diagram illustrating an operation of a conventional example.

[Explanation of symbols]

 10, 53 Radio base station 11 Inter-station transmission line 12 Centralized base station 13 Transmission switcher 14 Reception switcher 15 Switching controller 51 Switching station 52 Wired communication line 54 Radio zone 55 Mobile terminal 56 Line terminator 57 Modulator (MOD) 58 transmission amplifier 59 transmission / reception separator (D) 60 antenna 61 reception amplifier 62 demodulator (DEM)

Claims (1)

[Claims] 1. A mobile station located in any of a plurality of wireless zones adjacent to each other in a geographically fixed relationship, and a switching center that performs call processing of a generated call, and the plurality of wireless zones are individually formed. , A plurality of radio base stations that take a radio interface of radio channels assigned to the radio zone, and between the plurality of radio base stations and the switching center, the plurality of radio base stations are individually stationed. Via a plurality of communication links that are connected via inter-channel transmission lines and that modulate and demodulate information transmitted and received facing the mobile station via the wireless channel, and via a plurality of communication links individually corresponding to the wireless base stations. Switching means connected to the switching center for variable connection between these communication links and the plurality of modulation / demodulation means, and control of channel switching during communication via the modulation / demodulation means, A centralized base station including control means for setting a communication path between the mobile station and an empty radio channel in a wireless zone to which the mobile station is transferred, through the switching means, based on the control procedure. A channel switching method during a call characterized by the following.