JPH0568284A - Radio channel control system in mobile communication - Google Patents

Abstract

PURPOSE:To prevent interrupt of a busy radio channel by enabling the execution of the changeover of a busy channel even when no idle communication channel is in existence in a destination base station. CONSTITUTION:When a 1st mobile set 10 is going to move to the area of an adjacent base station 3 and communication channels allocated to the 2nd base station 3 are all busy, one of communication channels allocated to the 2nd base station 3 is replaced with the idle communication channel of a surrounding 3rd base station 15 and the communication channel of the 2nd base station 3 being idle is used for the 1st mobile set as its communication channel.

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 which is intended to prevent deterioration of communication quality due to deterioration of reception level and interference deterioration and disconnection of wireless channel during communication, especially when there is no free communication channel in a transfer destination base station. Wireless channel control system in.

[0002]

2. Description of the Related Art In mobile communication, effective use of frequency is the most important issue, and therefore a so-called cell type mobile communication system is generally used. This is to improve the frequency utilization efficiency by covering the service area with a plurality of base stations and repeatedly using the same frequency between base stations separated by a certain distance. The area covered by one base station is called a cell, and the smaller the cell radius, 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 in communication decreases, in order to continue communication, it is necessary to switch the partner base station with which the mobile station communicates to the transfer destination base station. Since it is necessary to switch the frequency of the mobile device to the idle channel of the transfer destination base station together with the switching of the wired transmission path to the base station, this is called communication channel switching.

FIG. 5 is a system configuration diagram for explaining a conventional technique. 1 is a central control station, 2-5 are base stations, and 6-
Reference numeral 9 is a cell, 10 is a mobile device, and 11 to 14 are transmission lines between a base station and a central control station. Each base station is also a central control station 1
And is connected to a fixed telephone network (not shown). It is now assumed that the mobile device 10 is in the cell 8 and is communicating with the 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 unit 10 becomes equal to or larger than the cell radius, the reception level of the base station 4 drops below a 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 station 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.

When the maximum level is higher than the reception level at the base station 4 by a certain value or more, the central control station decides to make the base station 3 switch the mobile station 10 to the base station 3 during communication. To notify the free communication channel number (#N). The constant value is usually selected to be 0 or a value of several dB. If the maximum level is not higher than the reception level at the base station 4 by a certain value or more, the central control station 1 judges that there is no suitable base station for switching the channel of the mobile station 10 during communication, and performs communication. Cancel the middle channel switching. Hereinafter, only the case of performing channel switching during communication will be described.

Based on the instruction, the base station 3 reports the free communication channel number #N to the central control station 1.

The central control station 1 instructs the base station 4 to send the mobile station 10 a switching instruction signal 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 unit 10.

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

[0013]

As is apparent from the above description, channel switching during communication is limited to the case where there is an empty communication channel in the transfer destination base station. If there is no free communication channel, the channel cannot be switched to the transfer destination, and as a result, the distance between the base station in communication and the mobile device is gradually increased and the communication quality is deteriorated. The deterioration of the communication quality causes not only the deterioration of the reception level itself but also the deterioration of the quality due to the increase of interference because the base station is approaching the same frequency. In the end, communication became impossible, and the wireless channel was disconnected even during communication, which was extremely inconvenient in terms of service. Normally, a wireless channel is arranged in each base station so that the call loss rate is within several percent. Therefore, when a request to use a new channel is made at a certain base station, the probability that there is no available communication channel is the above-mentioned several percent. In the case of a call from a mobile device or an incoming call to a mobile device, even if the connection cannot be established with a probability of several%, the purpose of communication can be achieved to some extent by redialing after a few minutes. However, it is extremely inconvenient for the user to disconnect a call once connected during communication, and it is desirable to make the value considerably smaller than the above-mentioned several%.

The present invention has been made in view of the above,
The purpose is to provide a wireless channel control method in mobile communication that enables switching of channels during communication and prevents disconnection of wireless channels during communication even if there is no available communication channel in the transfer destination base station. To do.

[0015]

In order to achieve the above object, a radio channel control system in mobile communication according to the present invention has a plurality of base stations arranged in a service area, and a first mobile station in communication performs communication. When the area of the partner's first base station moves to the area of the adjacent second base station, channel switching is performed for the first mobile device to one of the idle communication channels of the second base station. A radio channel control method in mobile communication for continuing communication with a second base station, whereby when all communication channels assigned to the second base station are in use, the second base station Of the communication channels allocated to the mobile station and the third base station, which is a peripheral base station of the second base station, communicating with the communication channel under the condition that the reception quality is equal to or higher than a predetermined value. Communication channel to meet Selected, the third call of the channel
In the above, the communication channel is switched to the free communication channel of the base station, and the communication channel of the second base station which becomes empty as a result is switched to the communication channel of the first mobile station.

[0016]

According to the radio channel control system for mobile communication of the present invention, when the first mobile station attempts to move to the area of the adjacent second base station, the communication channel assigned to the second base station is changed. If all are in use, then one of the communication channels assigned to the second base station may
The in-communication channel is switched to the idle communication channel of the base station, and the in-communication channel of the first mobile device is switched to the idle communication channel of the second base station.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram for explaining a system configuration example in the present invention. Reference numeral 15 is a base station, 16 is a cell, 17 is a transmission line between the base station 15 and a central control station, and 18 is a mobile unit. is there. The other numbers are the same as those in FIG. Figure 2
FIG. 4 is a diagram illustrating control operations of a base station and a mobile device according to the first embodiment. Base station 4 and first communication channel f1
It is assumed that the mobile device 10 that is in communication has moved from cell 8 to cell 7. At this time, the reception level of f1 in the base station 4 decreases, so the base station 4 detects this and requests the central control station 1 to switch the f1 channel during communication. The central control station instructs the base stations 2, 3 and 5 covering the cells around the cell 8 to receive the radio wave of the f1 channel from the mobile device 10 and measure the reception level. The base stations 2, 3 and 5 measure the reception level based on the instruction and report the reception level to the central control station 1. The central control station 1 selects the base station reporting the maximum level from these reporting levels. In this case, since the mobile device 10 has moved toward the base station 3, the report from the base station 3 should be the maximum. As in the case of the prior art, this maximum level is the base station 4
In the case where the reception level is not higher than the reception level by a certain value or more, the channel switching during communication is stopped, but hereinafter, the case where the reception level at the base station 4 is higher by a certain value or more will be described.

The central control station 1 commands the base station 3 to report one free communication channel number. Base station 3
If there is a vacant communication channel, the normal communication channel switching is completed (shown as A in FIG. 2). If the base station 3 has no available communication channel, the fact is reported to the central control station 1. Upon receiving this report, the central control station 1 instructs the base station 3 to switch the forced channel. Receiving this instruction, the base station 3 selects one channel having the lowest reception level from all the communication channels used by itself and reports it to the central control station 1. This channel is, for example, f
2 and is used by the mobile device 18. The central control station 1 has cells 6, 8, 9, 1 which are peripheral cells of the cell 7.
Instruct the base stations 2, 4, 5 and 15 covering 6 to measure the level of the f2 channel. Upon receiving the measurement result report from each base station, the central control station 1 selects the highest level base station among the report results. If the number of base stations is 15, the base station 15 is instructed to report an available communication channel. The base station 15 reports the channel number to the central control station if there is a free communication channel, and reports that there is no free communication channel. When there is no available communication channel, the central control station 1 may instruct the base station 3 to reselect a channel other than f2 and perform forced channel switching (shown as B in the figure). When it is reported that there is an available communication channel f3, the central control station 1
Instructs the mobile unit 18 via the base station 3 to f3 to switch the channel during communication. Based on this, the mobile device 18 switches to f3 and starts communication with the base station 15. After that, the central control station 1 instructs the mobile device 10 via the base station 4 to switch to the channel f2 during communication. Based on this, the mobile device 10 switches to f2 and starts communication with the base station 3.

In the second embodiment, when the base station 3 selects the f2 channel in the above-described first embodiment, the reception level of the communication channel of its own station is not the lowest and the reception level is constant. Select any channel that is less than or equal to the value.

The third embodiment is a case where the mobile station auxiliary channel switching is adopted. In this case, the channel between the base station and the mobile station is TDMA with a multiplexing number of 3 or more.
Has been adopted. FIG. 3 is a diagram for explaining a transmission / reception operation of a mobile device in 3-channel TDMA.
0, 21 are mobile station transmission time slots, 22, 23, 2
Reference numeral 4 is a mobile station reception time slot, and 25, 26 and 27 are time slots for measuring the reception level of radio waves transmitted from peripheral base stations. Since it is a three-channel multiplex TDMA, the mobile device basically repeats transmission, reception and idle alternately. The base station informs the mobile device of the number of the radio channel transmitted by the peripheral base station one by one, and the mobile device reports the transmitted channel of the peripheral base station 25, 26. , 27 time slots are sequentially received and the reception level is measured. At the same time, the reception level of the base station of the communication partner is also measured at 22, 23 and 24.
The mobile station reports the measurement results of these reception levels to the base station at any time.

FIG. 4 is a diagram for explaining the control operation of the base station and the mobile device. When it is reported that the reception level of the peripheral station is higher than the reception level of the radio wave of the own station by a certain value or more, it is determined that the mobile device has moved to the higher base station, and the channel switching during operation is started. .. That is, the central control station 1 instructs the base station 3 that has determined that the mobile device 10 has moved to, to report an available communication channel. If there is a free communication channel, the base station 3 performs a normal channel switching operation and completes the channel switching during communication (shown as A in the figure). If there is no available communication channel, the base station 3 reports to that effect to the central control station 1, and the central control station 1 instructs the base station 3 to perform forced channel switching. The instructed base station 3 mutually compares the peripheral base station reception levels in all communication channels of its own station reported by each mobile device, and the peripheral reception level is the maximum or the peripheral reception level is a certain value or more. Select one. By this selection, the number of the f2 channel and the transfer-destination base station to which the call of the channel is to be switched are specified. The base station 3 reports to the central control station the transfer destination base station (assuming this is 15) of the mobile station using the channel numbers f2 and f2. The central control station instructs the base station 15 to report an idle communication channel. The following operation is the same as in the case of FIG.

In the fourth embodiment, when it is necessary to switch channels during communication and there is no available communication channel in the transfer destination base station, the reception level of the first mobile station in the first base station is The present invention is applied only to those having a certain value or less.

In the above description, the case where the reception level is used as a criterion for determining whether or not to switch channels during communication has been described. However, not only the reception level but also the analog S type, the reception S / N and the detector are used. It may be output out-of-band noise or the like, and in the case of a digital system, it may be a measure corresponding to the reception quality such as the number of detection errors during error correction code decoding and the degree of opening of the eye pattern.

[0025]

As described above, according to the present invention,
When it is necessary to switch the channel during communication to the call being communicated and there is no available communication channel at the transfer destination base station, it is fixed even if the channel is switched to the peripheral base station of the call being communicated at the transfer destination base station. It is a drawback of the prior art because it is possible to forcibly switch the channel for which the communication quality is obtained and switch the first call to the communication channel of the transfer destination base station that has become idle. Although there is a transition from the cell to the adjacent cell but there is no free communication channel at the transition destination, it is not possible to switch the channel during communication, so the reception level drops significantly, interference increases, and communication disconnection occurs. This can be prevented, and communication can be continued with good quality.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a mobile communication system for explaining a radio channel control method in mobile communication according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a control operation of a base station and a mobile device according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a transmission / reception operation of a mobile device according to a third embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a control operation of a base station and a mobile device according to a third embodiment of the present invention.

FIG. 5 is a system configuration diagram illustrating channel switching during communication in a conventional mobile communication system.

[Explanation of symbols]

 1 Central Control Station 2-5, 15 Base Station 6-9, 16 Cell 11-14, 17 Transmission Line

Claims (1)

[Claims] 1. A plurality of base stations are arranged in a service area, and a first mobile station in communication is moved from an area of a first base station which is a communication partner to an area of an adjacent second base station. In the case of a radio channel control method in mobile communication, in which the communication with the second base station is continued by switching the channel of the first mobile station to one of the idle communication channels of the second base station. If all communication channels assigned to the second base station are in use, the second
Of the communication channels allocated to the base station of the second base station, the reception quality between the mobile station communicating with the communication channel and the third base station which is a peripheral base station of the second base station is equal to or more than a predetermined value. A communication channel satisfying a certain condition is selected, a call of the channel is switched to an idle communication channel of a third base station during communication, and the communication channel of the second base station which becomes idle as a result of the first communication is switched to the first communication channel. Radio channel control method in mobile communication, characterized in that the mobile device of the above is switched during communication.