JPH07121143B2 - Channel switching method during communication in mobile communication - Google Patents

Description

The present invention relates to a communication channel switching method in high-speed and reliable mobile communication.

[Conventional technology]

In mobile communication, effective use of frequency is the biggest problem, and for this reason, a so-called cell type mobile communication system is generally used. This is to improve the frequency utilization efficiency by covering a service area with a plurality of base stations and repeatedly using the same frequency between base stations that are separated by a certain distance. The area covered by one base station is called a cell, and the smaller the cell radius is, the more the frequency can be repeated at a closer distance, so that the frequency utilization efficiency is improved.

However, on the other hand, there is a greater chance that the mobile station leaves the area of the base station in communication and moves to the area of the adjacent base station. At this time, since the reception level at the base station during communication decreases, in order to continue communication, it is necessary to switch the partner base station with which the mobile device communicates to the transfer destination base station. This is called in-communication channel switching because it is necessary to switch the frequency of the mobile device to an empty channel of the transfer destination base station together with switching of the wired transmission path to the base station.

FIG. 7 is a system configuration diagram for explaining a conventional technique, in which 1 is a central control station, 2-5 are base stations, 6-9 are cells,
Reference numeral 10 is a mobile station, and 11 to 14 are transmission lines between the base station and the central control station. Each base station is further connected to a fixed telephone network (not shown) via the central control station 1.

It is now assumed that the mobile device is in cell 8 and is communicating with base station 4. The control operation of channel switching during communication when the mobile device moves into the area of the cell 7 will be described below.

Since the distance between the base station 4 and the mobile device 10 becomes equal to or larger than the cell radius, the reception level of the base station 4 drops below the specified value. Upon detecting this, the base station 4 requests the central control station 1 to switch the communication channel of the mobile device 10 via the transmission line 13.

The central control station 1 instructs the base stations 2, 3 and 5 around the base station 4 to monitor the radio waves from the mobile unit 10 via the transmission lines 11, 12 and 14.

The base stations 2, 3, and 5 receive the use channel of the mobile device instructed to monitor and measure the reception level thereof. The measurement result is reported to the central control station 1.

The central control station 1 identifies the base station received at the highest level among the reports from the base stations 2, 3 and 5. In this case, the base station 3 becomes the maximum level receiving station.

The central control station instructs the base station 3 to notify the idle communication channel number (#N).

Based on the instruction, the base station 3 sends an idle communication channel number #
Report N to central control station 1.

The central control station 1 instructs the base station 4 to send a switching instruction signal to the mobile station 10 from the base station 4 to the communication channel #N. At the same time, the base station 3 is instructed to turn on the transceiver of the communication channel #N, and the wired communication path to the base station is switched from the base station 4 to the communication channel #N of the base station 3.
Switch to the line corresponding to.

The base station 4 sends a switching signal to the communication channel #N to the mobile device 10.

The mobile device 10 switches to the instructed communication channel.
As a result, the mobile device can establish a communication channel with the base station 3.

[Problems to be Solved by the Invention]

As described above, according to the conventional channel switching method, it is necessary to switch between the central control station and the base station until the switching of the channel during communication is actually completed after the base station 4 detects the decrease in the reception level. There is a drawback that it takes a lot of time because it requires a signal transmission / reception and control associated therewith.

For this reason, when the cell radius is small, it may happen that the in-communication channel switching is not completed yet, but the cell moves to the adjacent cell area, and the in-communication channel switching may fail. Therefore, in order to avoid this, there is a constraint that the cell radius cannot be reduced to a certain value or less, and this has been a limit for improving the frequency utilization rate.

The present invention has been made in view of such conventional problems, and an object thereof is to provide a communication channel switching method capable of switching communication channels in a short time.

[Means for Solving the Problems]

According to the invention, the above mentioned objects are achieved by means of the patent claims.

That is, the invention of claim 1 comprises at least a central control station, a plurality of base stations, and a mobile device, and when the mobile device transfers the area of the base station during communication, the channel of the mobile device is transferred to the transfer destination base. In a mobile communication system that continues communication by switching to an idle communication channel of a station, a loop transmission line that connects the central control station and the plurality of base stations in a loop is provided, and each base station has its own identification code, A signal including the communication channel number communicating with the mobile device and the reception quality information of the channel is transmitted to the loop transmission line, and each base station receives the signal transmitted from the upper station on the loop transmission line. At the same time, it is relayed to a lower station on the loop transmission line, and a base station that is predetermined corresponding to the transmission source base station of the signal transmits the communication channel indicated by the communication channel number in the signal. After receiving and monitoring the quality, if the reception quality is better than the reception quality displayed in the reception quality information in the signal, it is determined that the mobile device has moved to its own area and the channel switching during communication is performed. In the above system, the base station that determines that the mobile station has moved to its own station is the identification code of the own station and the idle communication channel number. Is transmitted to the loop transmission line, and the base station communicating with the mobile unit instructs the mobile unit to switch to this idle communication channel based on this signal.

[Work]

The present invention installs a transmission line that penetrates in a loop between the central control station and each base station, and each base station identifies the identification code of its own station, the number of the communication channel communicating with the mobile station, and the communication channel The reception quality information is sent to the loop transmission line, the other base stations receive and relay this signal, and the base station determined in advance corresponding to the source base station of the signal transmits the communication channel in this signal. The communication channel indicated by the signal is received from time to time and its communication quality (for example, reception level, S / N ratio, etc.)
The mobile station determines that the mobile unit has moved to its own area when it is received in a state in which the reception quality displayed in the reception quality information in the signal is better than the reception quality at the signal transmission source base station. Is the most important feature.

Further, in the invention of claim 2, in the base station (hereinafter, referred to as a transfer destination base station) in which it is determined that the mobile device has moved to the area of the own station, the identification code of the own station, the free communication channel of the own station, The number is sent to the loop transmission line, and the base station communicating with the mobile device (hereinafter referred to as the transfer source base station) receives this and instructs the mobile device to switch to this communication channel.

In the conventional technique, each time a request for channel switching during communication is generated, the central control station instructs the peripheral base stations to measure the reception level of the communication channel, and reports the result.
Based on this, the central control station identifies the transfer destination base station, inquires of the transfer destination base station about the free communication channel number, and notifies the transfer source base station of the result, whereas in the present invention, , Each base station voluntarily monitors the communication channels of other base stations regardless of instructions from the central control station, determines whether the mobile device has moved to the area of its own station, and moves to its own station. Since the transfer-destination base station determined to have performed the transmission of the idle communication channel number, the transfer-source base station can immediately use this information to specify a new channel to the mobile device.

〔Example〕

FIG. 1 is a diagram for explaining an embodiment of the present invention,
Reference numeral 19 denotes a loop transmission line which returns to the central control station via the central control station 1 and the base stations 2-5. FIG. 2 shows a configuration example of a signal flowing through the loop transmission line, where 20 is a signal type, 21 is a base station identification number, 22 is a channel number, and 23 is reception level information 23. FIG. 3 shows a configuration example of the base station device.
Is an antenna, 25 is a transmitter / receiver (one or more channels can be transmitted / received), 26 is a control circuit, 27 is a transmission line with a central control station, 28 is a part of a loop transmission line, and transmission from a higher station The reference numeral 29 represents a transmission path to the lower station.

1 for each base station depending on the traffic in its cell area
One or more communication channels are assigned. The control circuit 26 controls the channel in which the base station is communicating with the mobile station,
Signal format 20 and base station identification number 2 in the format of Fig. 2
1, the communication channel number 22 and the reception level information 23 are generated and transmitted to the transmission path 29 to the lower station.

On the other hand, the transmission line 28 receives the same signal as that sent by the upper station on the loop transmission line. The base station receives this and relays it to the transmission path 29. The base stations that are adjacent to or close to the signal transmission source base station and that have a relationship that causes channel switching during communication with the signal transmission source base station correspond to each of the transmission source base stations. The control circuit 26 of each base station stores which base station the own station is in this relationship with.

When a base station receives a signal on a loop transmission line, and the source base station that sent this signal is a base station that has the above-mentioned relationship with itself, the base station always changes the communication channel indicated by the signal. Receive and measure the reception level. When this reception level is higher than the reception level information displayed by the signal, the base station determines that the mobile device has moved to its own area.

Next, the base station that determines that it is the transfer destination base station,
The local station identification code, the free communication channel number of the local station, the migration source base station identification code (read from the signal transmitted from the migration source base station), and the communication channel number whose level has been measured are transmitted. If there is no available communication channel in the local station, these signals will not be transmitted.

FIG. 4 is a diagram showing an example of a signal configuration, where 30 is a signal type, 31 is an identification code of its own station, 32 is a free communication channel number,
Reference numeral 33 is a source base station identification code, and 34 is a communication channel number.

FIG. 5 shows a second example of the signal configuration, and the signal transmitted by the transfer destination base station is added after the signal from the transfer source base station when relaying the signal. That is, as shown in FIG. 5, 20 to 23 transmitted from the source base station
To the loop transmission line 29,
Add ~ 34. In this case, the signal type 30 of 30 to 34 and the transfer source base station identification code 33 can of course be omitted.

FIG. 6 is a diagram for explaining the third example of the signal configuration, in which the base station communicating with the mobile device has a signal type of 20, a local station identification code of 21,
And the signals 35, 22, and 36 described below are sent out on the loop transmission line. Reference numeral 35 is the identification number of the base station whose level has been measured, and in this case, the identification code of the transmission source base station of this signal. 22 is a communication channel number as in FIG. 36 is a measurement level.

The other base stations that received this signal relay it to the next base station through the loop transmission line, but the base station that measured the communication channel specified in 22 has the reception level measured by itself. , If the received level is lower than the level represented by 36 in the signal transmitted on the loop transmission line, the signal on the loop transmission line is relayed as it is. If the reception level measured at the local station is higher than the reception level represented by 36 in the signal transmitted on the loop transmission line, 35 is changed to the local station identification code and 36 is the reception level measured at the local station. To be sent on the loop transmission line.

In this way, when a signal related to the channel is returned to the original transmission source base station after making one round in the loop transmission line, the base station determines the transition destination base station and the empty channel available in the base station from this signal. It detects and sends a channel switching signal during communication to the mobile station to switch to this channel.

The base station does not allocate the channel sent to the loop transmission line as an empty channel to other communication until the central control station gives an instruction as to whether or not the channel is designated as a channel switching destination.

Now, it is assumed that the mobile station 10 currently communicating with the base station 4 changes its cell area and needs to switch the channel during communication. At this time, the base station 4 creates the above signal and sends it to the loop transmission line. It is assumed that the base station 3 receives the channel at the highest reception level, notifies the idle channel information (communication channel #N), and the base station 4 detects this. The control operation after this will be described below.

The base station 4 notifies the central control station 1 that the base station 3 is the transfer source base station.

The central control station 1 has become the switching destination base station for switching the channel during communication with the base station 3, and the switching destination base station of the channel has been assigned to another base station for the other base stations. To notify. In addition, the wired transmission line destined for the base station is connected to both the transmission lines for the base station 4 and the base station 3.

The base station 4 sends an in-communication channel switching signal to the mobile device 10 so as to switch to the communication channel #N.

The base station 3 turns on the #N transceiver and
The central control station 1 is notified that the mobile station 10 has switched from the base station 4 to the communicating channel on the #N channel.

Based on the signal from the base station 3, the central control station 1 sends the wired transmission line from the line for the base station 4 to the #N for the base station 3.
Connect only to the line corresponding to the channel. By the above, the channel switching during communication is completed.

In the case of the signaling system shown in FIG. 6, a base station sends empty channel information to the write loop transmission line in response to the signal sent from the base station, but a lower station sends the channel to a higher reception level. When receiving and rewriting with free channel information of the own station, the base station that first wrote the free channel information cannot know that. However,
This problem can be solved by the central control station notifying each base station of whether it has been adopted as the transfer destination base station.

In the above description, the case where the central control station is an independent station from the base station has been described, but the present invention can be applied to the case where any one of the base stations functions as the central control station.

Further, in the above description, the method of comparing the magnitude of the reception level is described, but the number of detection errors in the received signal is not limited to the reception level, and in the case of digital with error correction coding,
The degree of opening of the eye pattern, the S / N ratio of the received signal in the case of an analog signal, and the combination thereof may be used as long as they generally represent the reception quality.

〔The invention's effect〕

As described above, according to the method of the present invention, each base station adds reception level information to the number of the communication channel that the base station is receiving and sends it to the above loop transmission line, and the other base stations at any time. Since this channel is received, its level is monitored, and when it is received at a level higher than the reception level, the idle channel information can be immediately sent to the loop transmission line to cause the mobile device to switch the channel during communication. There is an advantage that the channel switching during communication can be completed in a short time.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention, FIG. 2 is a diagram showing an example of a signal configuration flowing through a loop transmission line, FIG. 3 is a diagram showing an example of a configuration of a base station device, and FIG. 5 and 6 are diagrams showing examples of signal configurations, and FIG. 7 is a diagram showing examples of conventional system configurations. 1 ... Central control station, 2-5 ... Base station, 6-9 ... Cell, 10 ... Mobile station, 15-19 ... Loop transmission line, 20 ... Signal type, 21 ... Base station identification number , 22 …… communication channel number, 23 …… reception level information, 24 …… antenna, 25 …… transceiver, 26 …… control circuit, 27 …… transmission path to central control station, 28 …… upper station Transmission line from 29, lower station, 30 ...
… Signal type, 31 …… base station identification code, 32 …… free communication channel number, 33 …… base station identification code, 34 …… communication channel number, 35 …… base station identification code, 36 …… measurement level.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-59-146233 (JP, A) JP-A-1-248838 (JP, A) JP-A-61-1126 (JP, A)

Claims (2)

[Claims] 1. At least a central control station, a plurality of base stations,
Central control in a mobile communication system that is composed of a mobile device and continues the communication by switching the channel of the mobile device to an empty communication channel of the transfer destination base station when the mobile device moves the area of the base station during communication. A loop transmission line that connects the station and the plurality of base stations in a loop is provided, and each base station uses the identification code of its own station, the number of the communication channel communicating with the mobile station, and the reception quality information of the channel. To the loop transmission line, each base station receives the signal transmitted from the upper station on the loop transmission line, relays this signal to the lower station on the loop transmission line, and the base station from which the signal is transmitted. In the base station predetermined corresponding to the station, the communication channel indicated by the communication channel number in the signal is received at any time to monitor its quality, and the reception quality is the reception quality information in the signal. A communication channel switching method in mobile communication, characterized in that, when the received quality is better than the displayed reception quality, the mobile device determines that it has moved to its own area and switches the communication channel. 2. A base station, which has determined that the mobile unit has moved to its own area, sends a signal including its own identification code and an idle communication channel number to the loop transmission line to communicate with the mobile unit. 2. The communication channel switching method in mobile communication according to claim 1, wherein the base station instructs the mobile device to switch to this idle communication channel based on this signal.