GB2404310A

GB2404310A - Managing radio resources in a mobile communication system

Info

Publication number: GB2404310A
Application number: GB0412561A
Authority: GB
Inventors: Takeshi Yamoto; Hirofumi Shiotsuki; Takahiro Sakamoto
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2003-06-05
Filing date: 2004-06-04
Publication date: 2005-01-26
Anticipated expiration: 2024-06-04
Also published as: GB0412561D0; GB2404310B; JP2004363979A; JP4167545B2

Abstract

A mobile communication system includes a plurality of base stations 13-16, a mobile terminal 11 and a base station controller (BSC) 12 controlling the radio resource of the base stations 13-16. The BSC 12 receives from each of the base stations 13-16 a signal 22-25 indicative of how much of the radio resource is used by each of the base stations 13-16 and data indicative of the quality of the radio channels 18-21 of the mobile terminal 11 in a macro diversity condition. When the amount of radio resource used exceeds a first threshold, the BSC 12 keeps a first number of radio channels 18-21 alive and releases the rest of the radio channels 18-21. The first number of radio channels 18-21 kept alive is a minimum number of channels 18-21 that the mobile terminal 11 is allowed to have and these are selected for having higher radio quality than the radio channels 18-21 that are released.

Description

MOBILE COMMUNICATION SYSTEM

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The invention relates to a mobile communication system, and more particularly to a CDMA (Code Division Multiple Access) type mobile communication system carrying out handover in predetermined cases.

DESCRIPTION OF THE RELATED ART

In a mobile communication system for providing communication service to a plurality of mobile terminals, including a plurality of base stations each having a service area inherent thereto, a plurality of mobile terminals each making radio-signal communication with a base station located closest to the mobile terminal among the plurality of base stations, and a base station controller controlling the plurality of base stations, each of the base stations can have limited radio-resource such as radio-channels.

In such a mobile communication system, if each of the base stations uses almost all of the assigned radio-resource, it might be impossible to provide radio-channel to a mobile terminal entering a service area thereof, in which case, a call in the mobile terminal might be stopped or the mobile terminal cannot make a call in the service area.

In order to avoid such a problem, Japanese Patent Application Publication No. 2001-333007 has suggested a mobile communication system for effectively making use of radio-resource, including a mobile terminal and a base station.

In the suggested mobile communication system, if radio step-out occurs in a certain period of time or some accidents occur in the mobile terminal or the base station, the mobile terminal and the base station are monitored thereafter in a certain period of time for controlling connections, based on signals transmitted as a result of the monitoring. Thus, the mobile terminal and the base station release unnecessary connections to thereby effectively make use of radio-resource.

However, radio-channels are released in the suggested mobile communication system only when radio step-out and/or some accidents occur, it would be impossible to ensure radio-resource for a mobile terminal, if radio-channels are tight.

Furthermore, it is not possible in the suggested mobile communication system to ensure radio-resource for a mobile terminal without disconnecting a call.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems in the conventional mobile communication system, it is an object of the present invention to provide a mobile communication system which is capable of effectively making use of radio-resource, even when the radio-resource is tight.

It is also an object of the present invention to provide a mobile communication system which is capable of ensuring radio-resource for a mobile terminal without disconnecting a call.

It is further an object of the present invention to provide a base station controller which is capable of doing the same as mentioned above.

It is further an object of the present invention to provide a method of controlling radio-resource in a mobile communication system which method is capable of doing the same as mentioned above.

It is further an object of the present invention to provide a program for causing a computer to carry out a method of controlling radio-resource in a mobile communication system which program is capable of doing the same as mentioned above.

Hereinbelow are described a mobile communication system, a base station controller, a method of controlling radio-resource in a mobile communication system, and a program for causing a computer to carry out the method all in accordance with the present invention through the use of reference numerals used in later-described embodiments. The reference numerals are indicated only for the purpose of clearly showing correspondence between claims and the embodiments. It should be noted that the reference numerals are not allowed to interpret claims of the present application.

The present invention provides a mobile communication system including a plurality of base stations (13-16) each having a service (A1-A4) area inherent thereto, a mobile terminal (11) making radio-signal communication with a base station located closest to the mobile terminal (11) among the plurality of base stations (13-16), and a base station controller (12) controlling radio-resource of the plurality of base stations (13-16) and receiving from each of the plurality of base stations (13-16) a signal indicative of how much degree each of the plurality of base stations (13-16) uses radio-resource, wherein each of the plurality of base stations (13-16) adds radio-quality data to data received from the mobile terminal (11), and transmits the resultant data to the base station controller (12) , the base station controller (12), when the degree becomes over a first threshold, keeps a first number of radio-channels alive among a plurality of radio-channels of the mobile terminal (12) in a macro-diversity condition, and releases the rest of radio-channels, the first number is defined as a minimum number in a predetermined range of numbers of radio- channels which the mobile terminal (12) is allowed to have, and the first number of radio-channels are determined by the base station controller (12) as having higher radio- quality than radio-quality of radio-channels to be released, based on the radio-quality data received from the plurality of base stations (13-16).

The base station controller is designed to have a function of monitoring radio-quality of up-channel data transmitted to the base stations from the mobile terminal which is in a macro-diversity condition, through radio-channels. When the degree by which each of the plurality of base stations uses radio-resource becomes over a first threshold, the base station controller keeps the predetermined first number of radio-channels alive among a plurality of radio-channels of the mobile terminal which is in a macro-diversity condition, and releases the rest of radio-channels. Thus, even radio-channel which is available is released, if radio-quality thereof is judged degraded. In addition, the first number defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal is allowed to have is determined for each of mobile terminals. The first number of radio-channels is not released.

It is preferable that the base station controller (12) stores the radioquality data (33), and averages variance in the radio-quality data (33) in a predetermined period of time for administrating quality of each of radio-channels.

It is preferable that when the mobile terminal (11) makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, the base station controller (12) rejects establishment of new radio-channel, and that the base station controller (12) allows the mobile terminal (11) to have (P+1) radio-channels only at handover, and releases radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.

It is preferable that the base station controller (12), when the degree becomes below a second threshold, periodically repeats increasing the predetermined range of number by one until the degree becomes over the second threshold or the predetermined range of numbers reaches a predetermined maximum number.

When the degree becomes below a second threshold, the predetermined range of number is increased one by one. Thus, the mobile terminal which is in a macro-diversity condition could have radio-channels having high radioquality, ensuring high communication quality.

It is preferable that the radio-quality data (33) is comprised of at least one of first data (QE) indicative of quality of communication to be made through the radio-channels, and results (CRCT) of comparison made through the use of predetermined codes (CRC).

The present invention further provides a mobile communication system including a plurality of base stations each having a service area inherent thereto, a mobile terminal making radio-signal communication with a base station located closest to the mobile terminal among the plurality of base stations, and a base station controller controlling radio-resource of the plurality of base stations and receiving from each of the plurality of base stations a signal indicative of how much degree each of the plurality of base stations uses radio-resource, wherein the mobile terminal in a macro-diversity condition calculates radio-quality, based on sensitivity of radio-signals received through a plurality of radio-channels, and, 16 on receipt of a request to inform the base station controller of radiochannel(s) which may be released, selects radio-channel(s) having sufficient radio-quality, based on the radio-quality, and informs the base station controller of the selected radio-channel(s), each of the plurality of base stations checks whether radio-resource is in short, and, if radio-resource is in short, so informs the base station controller, the base station controller, when the degree becomes below a predetermined threshold, transmits a request to the mobile terminal located in a service area of the base station using radio-resource in excess of the predetermined threshold, to inform the base station controller of radio-channel(s) which may be released, and, keeps a first number of radio-channels alive among the plurality of radio-channels of the mobile terminal and releases the rest of radio-channels, based on a response received from the mobile terminal, the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal is allowed to have, and the first number of radio-channels are determined by the base station controller as having higher radio-quality than the same of radio-channels to be released.

The mobile terminal in a macro-diversity condition has a function of calculating radio-quality, based on sensitivity of down-channel radiosignals received from the base stations through a plurality of radiochannels. The base station controller, when the degree becomes below a predetermined threshold, transmits a request to the mobile terminal located in a service area of the base station using radio-resource in excess of the predetermined threshold, to inform the base station controller of radio-channel(s) which may be released. On receipt of the request, the mobile terminal selects radio-channel(s) having sufficient radio-quality, based on the radio-quality, and informs the base station controller of the selected radio-channel(s). Then, the base station controller keeps the first number of radio-channels alive among the plurality of radio-channels of the mobile terminal, and releases the rest of radio-channels, based on a response received from the mobile terminal. Thus, even radio-channel which is available is released, if radio-quality thereof is judged degraded. In addition, the first number defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal is allowed to have is determined for each of mobile terminals. The first number of radio-channels is not released.

The present invention provided a base station controller (12) in a mobile communication system including a plurality of base stations (13-16) each having a service area (A1-A4) inherent thereto, and a mobile terminal (11) making radio-signal communication with a base station located closest to the mobile terminal (11) among the plurality of base stations (13-16), wherein the base station controller (12) controls radio-resource of the plurality of base stations (13-16) and receives from each of the plurality of base stations (13-16) both a signal indicative of how much degree each of the plurality of base stations (13-16) uses radio-resource, and radio-quality data (33), the base station controller (12), when the degree becomes over a first threshold, keeps a first number of radio-channels alive among a plurality of radio- channels of the mobile terminal (11) in a macro-diversity condition, and releases the rest of radio-channels, the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal (11) is allowed to have, and the first number of radio-channels are determined by the base station controller (12) as having higher radio- quality than radio-quality (33) of radio-channels to be released, based on the radio-quality data (33) received from the plurality of base stations (13-16).

It is preferable that when the mobile terminal (11) makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, the base station controller (12) rejects establishment of new radio-channel, and wherein the base station controller (12) allows the mobile terminal (11) to have (P+1) radio- channels only at handover, and releases radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.

It is preferable that base station controller (12), when the degree becomes below a second threshold, periodically repeats increasing the predetermined range of number by one until the degree becomes over the second threshold or the predetermined range of numbers reaches a predetermined maximum number.

The present invention further provides a base station controller (12) including a plurality of base stations (13-16) each having a service area (A1-A4) inherent thereto, and a mobile terminal (11) making radio-signal communication with a base station located closest to the mobile terminal (11) among the plurality of base stations (13-16), wherein the base station controller (12) controls radio-resource of the plurality of base stations (13-16) and receives from each of the plurality of base stations (13-16) a signal indicative of how much degree each of the plurality of base stations (13-16) uses radio-resource, the base station controller (12) receives a signal from each of the plurality of base stations (13-16) which signal indicates that radio-resource is in short, the base station controller (12), when the degree becomes below a predetermined threshold, transmits a request to the mobile terminal (11) located in a service area (A1-A4) of the base station using radio-resource in excess of the predetermined threshold, to inform the base station controller (12) of radio-channel(s) which may be released, the base station controller (12) receives a response from the mobile terminal (11) which response indicates radio- channel(s) having sufficient radio-quality, based on the radio-quality (33) calculated by the mobile terminal (11), based on sensitivity of radio-signals received through a plurality of radio-channels in a macro- diversity condition, the base station controller (12) keeps a first number of radio-channels alive among the plurality of radio-channels of the mobile terminal (11) and releases the rest of radio-channels, based on a response received from the mobile terminal (11), the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal (11) is allowed to have, and the first number of radio-channels are determined by the base station controller (12) as having higher radioquality than the same of radio-channels to be released.

The present invention provides a method of controlling radio-resource in a mobile communication system including a plurality of base stations (1316) each having a service area (A1-A4) inherent thereto, a mobile terminal (11) making radio-signal communication with a base station located closest to the mobile terminal (11) among the plurality of base stations (13-16), and a base station controller (12) controlling radio- resource of the plurality of base stations (13-16) and receiving from each of the plurality of base stations (13-16) a signal indicative of how much degree each of the plurality of base stations (13-16) uses 6 radio-resource, the method including each of the plurality of base stations (13-16) adding radio-quality data (33) to data received from the mobile terminal (11), and transmitting the resultant data to the base station controller (12), and the base station controller (12), when the degree becomes over a first threshold, keeping a first number of radio- channels alive among a plurality of radio-channels of the mobile terminal (11) in a macro-diversity condition, and releasing the rest of radio- channels, wherein the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal (11) is allowed to have, and the first number of radio-channels are determined by the base station controller (12) as having higher radio- quality than radio-quality of radio-channels to be released, based on the radio-quality data (33) received from the plurality of base stations (13- 16).

The method may further include the base station controller (12) storing the radio-quality data (33), and averages variance in the radio-quality data (33) in a predetermined period of time for administrating quality of each of radio-channels.

The method may further include, when the mobile terminal (11) makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, the base station controller (12) rejecting establishment of new radio-channel, and the base station controller (12) allowing the mobile terminal (11) to have (P+1) radiochannels only at handover, and releasing radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.

The method may further include the base station controller (12), when the degree becomes below a second threshold, periodically repeating increasing the predetermined range of number by one until the degree becomes over the second threshold or the predetermined range of numbers reaches a predetermined maximum number.

The present invention provides a method of controlling radio-resource in a mobile communication system including a plurality of base stations (1316) each having a service area (A1-A4) inherent thereto, a mobile terminal (11) making radio-signal communication with a base station located closest to the mobile terminal (11) among the plurality of base stations (13-16), and a base station controller (12) controlling radio- resource of the plurality of base stations (13-16) and receiving from each of the plurality of base stations (13-16) a signal indicative of how much degree each of the plurality of base stations (13-16) uses radio-resource, the method including the mobile terminal (11) calculating radio-quality, based on sensitivity of radio- signals received through a plurality of radio-channels in a macro- diversity condition, and, on receipt of a request to inform the base station controller (12) of radio-channel(s) which may be released, selecting radio-channel(s) having sufficient radio-quality, based on the radio-quality, and informing the base station controller (12) of the selected radio-channel(s), each of the plurality of base stations (13-16) checking whether radio-resource is in short, and, if radio-resource is in short, so informing the base station controller (12), and the base station controller (12), when the degree becomes below a predetermined threshold, transmitting a request to the mobile terminal (11) located in a service area (A1-A4) of the base station using radio-resource in excess of the predetermined threshold, to inform the base station controller (12) of radio-channel(s) which may be released, and, keeping a first number of radio-channels alive among the plurality of radio-channels of the mobile terminal (11) and releasing the rest of radio-channels, based on a response received from the mobile terminal (11), the first number is defined as a minimum number in a predetermined range of numbers of radio- channels which the mobile terminal (11) is allowed to have, and the first number of radio-channels are determined by the base station controller (12) as having higher radio-quality than the same of radio-channels to be released.

The method may further include when the mobile terminal (11) makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, the base station controller (12) rejecting establishment of new radio-channel, and the base station controller (12) allowing the mobile terminal (11) to have (P+1) radio- channels only at handover, and releasing radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.

The present invention further provides a program for causing a computer to carry out a method of controlling radio-resource in a mobile communication system including a plurality of base stations (13-16) each having a service area (A1-A4) inherent thereto, a mobile terminal (11) making radio-signal communication with a base station located closest to the mobile terminal (11) among the plurality of base stations (13-16), and a base station controller (12) controlling radio-resource of the plurality of base stations (13-16) and receiving from each of the plurality of base stations (13-16) a signal indicative of how much degree each of the plurality of base stations (13-16) uses radio-resource, wherein steps executed by said computer in accordance with said program includes receiving from each of the plurality of base stations (13-16) both a signal indicative of how much degree each of the plurality of base stations (13-16) uses radio-resource, and radio-quality data (33), and when the degree becomes over a first threshold, keeping a first number of radio- channels alive among a plurality of radio-channels of the mobile terminal (11) in a macro-diversity condition, and releasing the rest of radio- channels, wherein the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal (11) is allowed to have, and the first number of radio-channels are determined by the base station controller (12) as having higher radio-quality than radio-quality of radio-channels to be released, based on the radio-quality data (33) received from the plurality of base stations (13-16).

It is preferable that the steps further include storing the radio-quality data (33), and averages variance in the radio-quality data (33) in a predetermined period of time for administrating quality of each of radiochannels.

It is preferable that the steps further include, when the mobile terminal (11) makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, rejecting establishment of new radio-channel, and wherein the base station controller (12) allows the mobile terminal (11) to have (P+1) radio-channels only at hangover, and releasing radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.

It is preferable that the steps further include, when the degree becomes below a second threshold, periodically repeating increasing the predetermined range of number by one until the degree becomes over the second threshold or the predetermined range of numbers reaches a predetermined maximum number.

The present invention provides a program for causing a computer to carry out a method of controlling radio-resource in a mobile communication system including a plurality of base stations (13-16) each having a service area (A1-A4) inherent thereto, a mobile terminal (11) making radio-signal communication with a base station located closest to the mobile terminal (11) among the plurality of base stations (13-16), and a base station controller (12) controlling radio-resource of the plurality of base stations (13-16) and receiving from each of the plurality of base stations (13-16) a signal indicative of how much degree each of the plurality of base stations (13-16) uses radio-resource, wherein steps executed by said computer in accordance with said program includes receiving from each of the plurality of base stations (13-16) a signal indicative of how much degree each of the plurality of base stations (1316) uses radio-resource, receiving a signal from each of the plurality of base stations (13-16) which signal indicates that radio-resource is in short, when the degree becomes below a predetermined threshold, transmitting a request to the mobile terminal (11) located in a service area (A1-A4) of the base station using radio-resource in excess of the predetermined threshold, to inform the base station controller (12) of radio-channel(s) which may be released, receiving a response from the mobile terminal (11) which response indicates radio-channel(s) having sufficient radio-quality, based on the radio-quality calculated by the mobile terminal (11), based on sensitivity of radio-signals received through a plurality of radio- channels in a macro-diversity condition, and keeping a first number of radio-channels alive among the plurality of radio-channels of the mobile terminal (11) and releasing the rest of radio-channels, based on a response received from the mobile terminal (11), wherein the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal (11) is allowed to have, and the first number of radio-channels are determined by the base station controller (12) as having higher radio-quality than the same of radio- channels to be released.

It is preferable that the steps further include, when the mobile terminal (11) makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, rejecting establishment of new radio-channel, and wherein the base station controller (12) allows the mobile terminal (11) to have (P+1) radio-channels only at handover, and releasing radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of a mobile communication system in accordance with the first embodiment of the present invention.

FIG. 1B is a block diagram of the base station controller in the mobile 6 communication system in accordance with the first embodiment.

FIG. 2 shows a relation between thresholds and steps to be carried out by the base station controller when radio-resource is in short.

FIG. 3 shows a relation between calculation of radio-quality and storage of radio-quality data.

FIG. 4 shows an example of simulation of radio-quality calculation.

FIG. 5 is a block diagram of a mobile communication system in accordance with the second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments in accordance with the present invention will be explained hereinbelow with reference to drawings.

[First Embodiment] FIG. 1A is a block diagram of a mobile communication system in accordance with the first embodiment of the present invention.

The illustrated mobile communication system is a CDMA type mobile communication system, and is comprised of first to fourth base stations 13, 14, 15 and 16 each having a service area A1, A2, AS and A4 inherent thereto, a mobile terminal 11 making radio-signal communication with a base station located closest thereto among the first to fourth of base stations 13 to 16, and a base station controller 12 controlling the first to fourth base stations 13 to 16. The mobile terminal 11 is located within the service areas A1 and A3.

FIG. 1B is a block diagram of the base station controller 12.

As illustrated in FIG. 1B, the base station controller 12 is comprised of a central processing unit 12A, a first memory 12B, and a second memory 12C.

Each of the first and second memories 12B and 12C is comprised of a semiconductor memory such as a read only memory (ROM), a random access memory (RAM) or an IC memory card, or a storage device such as a flexible disc, a hard disc or an optic magnetic disc.

The first memory 12B stores therein a program for driving the central processing unit 12A. The second memory 12C stores therein various data and parameters. The central processing unit 12A reads the program out of the first memory 12B, and executes the program. Thus, the central processing unit 12A operates in accordance with the program stored in the first memory 12B.

Further, as illustrated in FIG. 1A, the base station controller l 2 includes a diversity handover controller 17.

The mobile terminal 11 makes radio-signal communication with the first base station 13 through first radio-channel 18, the second base station 14 through second radio-channel 19, the third base station 15 through the third radio-channel 20, and the fourth base station 16 through fourth radio-channel 21.

Each of the first to fourth base stations 13 to 16 makes communication with the diversity handover controller 17 through first to fourth Iub channels 22 to 25, respectively.

Each of the first to fourth base stations 13 to 16 makes communication with the mobile terminal 11 through the first to fourth radio-channels 18 to 21, respectively, and transmits a signal indicative of how much degree it uses radio-resource, to the base station controller 12 through the first to fourth Iub channels 22 to 25, respectively.

The diversity handover controller 17 is designed to have functions of receiving up-channel data transmitted from the first to fourth base stations 13 to 16 which up-channel data was transmitted from the mobile terminal 11 to the first to fourth base stations 13 to 16 through the first to fourth radio-channels 18 to 21, selecting data having highest quality, copying down-channel data to distribute the copied data to the first to fourth base stations 13 to 16, and monitoring radio-quality of up-channel data transmitted from the first to fourth base stations 13 to 16 which up- channel data was transmitted from the mobile terminal 11 to the first to fourth base stations 13 to 16 through the first to fourth radio-channels 18 to 21, for each of the radio-channels 18 to 21.

The base station controller 12 administrates radio-resource, and identifies and releases quality-degraded radio-channel, if necessary, based on the degree of using radio-resource, transmitted from the first to fourth base stations 13 to 16, and radio-quality data received from the diversity handover controller 17.

Hereinbelow is explained an operation of the mobile communication system in accordance with the first embodiment, with reference to FIGs. 1A, 2, 3 and 4.

With reference to FIG. 1A, it is assumed that the mobile terminal 11 is in communication with the first to fourth base stations 13 to 16 through the first to fourth radio-channels 18 to 21, that is, the mobile terminal 11 is in a macro-diversity condition where the mobile terminal 11 has four multi-paths. It is also assumed that a maximum number of radio- channels which the mobile terminal 11 is allowed to have is six (6), and a minimum number of radio-channels which the mobile terminal 11 is allowed to have is two (2).

Each of the first to fourth base stations 13 to 16 converts data received from the mobile terminal 11, into frame data, and then, adds QE (Quality Estimate) data and CRCI (CRC indicator) to the frame data. Herein, QE data indicates communication quality in radio-channel, and CRCI indicates comparison results expressed with CRC codes. Then, each of the first to fourth base stations 13 to 16 transmits the frame data along with QE data and CRCI to the diversity handover controller 17 through the first to fourth tub channels 22 to 25, respectively.

On receipt of the frame data along with QE data and CRCI transmitted from the first to fourth base stations 13 to 16 through the first to fourth tub channels 22 to 25, the diversity handover controller 17 selects frame data having highest communication quality, and transmits the selected frame data to an upper-grade network. The diversity handover controller 17 concurrently monitors radio-quality of the first to fourth radio- channels 18 to 21.

FIG. 3 shows radio-quality data 33 of each of the first to fourth radiochannels 18 to 21.

The diversity handover controller 17 monitors radio-quality of the first to fourth radio-channels 18 to 21, based on the radio-quality data 33 illustrated in FIG. 3. The radio-quality data 33 is comprised of the above-mentioned QE data and CRCI. The diversity handover controller 17 may judge radio-quality of the first to fourth radio-channels 18 to 21, based on QE data, CRCI or a combination of them. Hereinbelow, it is assumed that the diversity handover controller 17 judges radio-quality of the first to fourth radio-channels 18 to 21, based only on QE data.

As illustrated in FIG. 3, the mobile terminal 11 transmits up-channel radio-data 31 to the first to fourth base stations 13 to 16. The first to fourth base stations 13 to 16 convert the received radio-data 31 to frame data 32 and add the radio-quality data 33 to the frame data 32, and then, transmit the frame data 32 along with the radio-quality data 33 to the diversity handover controller 17.

If radio-channel quality is degraded, each of the first to fourth base stations 13 to 16 receiving the radio-data 31 through the qualitydegraded radio-channel makes the radio-quality data 33 to which the degradation of the radio-channel is reflected.

Each time the diversity handover controller 17 receives the radio-quality data 33 added to the frame data 32, the diversity handover controller 17 stores the received radio-quality data 33. The diversity handover controller 17 can store therein any number of past radio-quality data 33. The diversity handover controller 17 averages variance of the received radio-quality data 33 for administrating radio-quality of each of the first to fourth radio-channels 18 to 21.

Radio-channel quality can be calculated in any ways. For instance, radiochannel quality may be calculated based on QE data. FIG. 4 shows results 6 of calculating radio-channel quality, based on QE.

In FIG. 4, radio-quality data I corresponding to the radio-quality data 33 shown in FIG. 3 indicates QE data, and radio-quality II indicates data calculated by the diversity handover controller 17. In FIG. 4, an axis of ordinates indicates QE, and an axis of abscissa indicates the number of a received frame. Better radio-quality has smaller QE.

In FIG. 4, n-th radio-quality MAQn is calculated in accordance with the equation (A) wherein QEn indicates radio-quality data I of an n-th received frame, m indicates a number of radio-quality data II stored in the diversity handover controller 17, and MAQ (Managemented Air Quality) indicates 16 calculated radio-quality II. m

QEnt MAQp MAQn = m+ 1 (A) By using the radio-quality MAQn calculated in accordance with the equation (A), it is possible to ensure redundancy for significant variance in the radio-quality data I in a frame, and hence, it is also possible to prevent wrong judgment because of instantaneous variance in the radio-quality data. Based on the radio-quality MAQn calculated in accordance with the equation (A), the diversity handover controller 17 can monitor quality of all of the first to fourth radiochannels 18 to 21.

Hereinbelow is explained a process of releasing radio-channel(s) when radio-resource is in short in the mobile communication system in accordance with the first embodiment.

As mentioned earlier, the first to fourth base stations 13 to 16 informs the base station controller 12 of a degree to which the base station uses radio-resource.

The base station controller 12 judges that radio-resource becomes tight, if the degree to which each of the first to fourth base stations 13 to 16 uses radio-resource exceeds a predetermined threshold. Then, the base station controller 12 reads radio-quality data of the first to fourth radio-channels 18 to 21 out of the diversity handover controller 17. The mobile terminal 11 is now in a macro-diversity condition, that is, uses four radio-channels 18 to 21. Hence, the base station controller 12 keeps two radio-channels alive, and releases the rest of the radio-channels one by one. Specifically, the base station controller 12 keeps alive radio-channels having best and second best radio-quality, and releases radio-channels having worst and second worst radio-quality. For instance, if the first radio-channel 18 through which the mobile terminal 11 and the first base station 13 make communication with other and the third radio-channel 20 through which the mobile terminal 11 and the third base station 15 make communication with other keep good radio-quality, and the second radio- channel 19 through which the mobile terminal 11 and the second base station 14 make communication with other and the fourth radio-channel 21 through which the mobile terminal 11 and the fourth base station 16 make communication with other have degraded radio-quality, the base station controller 12 releases the second and fourth radio-channels 19 and 21.

Even when the mobile terminal 11 has two radio-channels, if one of the radio-channels has radio-quality equal to or smaller than a predetermined threshold, the base station controller 12 may release the radio-channel.

When handover is to be carried out while the mobile terminal 11 is allowed to have a limited number of radio-channels, the mobile terminal 11 is allowed to have (P+1) radio-channels at maximum only while handover is being carried out, where P indicates a maximum number of radio- channels which the mobile terminal 11 is allowed to have. Since a maximum number of radio-channels which the mobile terminal 11 is allowed to have is set equal to two (2) as mentioned earlier, (P+1) is equal to three (3). After handover has been completely carried out, the base station controller 12 releases radio-channel having worst radio-quality.

If the base station controller 12 confirms that radio-channels are available by a number greater than the predetermined threshold, based on the degree of using radio-resource, transmitted from the first to fourth base stations 13 to 16, the base station controller 12 ceases limitation in a number of radio-channels which the mobile terminal 11 is allowed to have while the mobile terminal 11 is in a macro-diversity condition.

A process of releasing radio-channel(s) when radio-resource is in short is explained in detail hereinbelow with reference to FIG. 2.

With reference to FIG. 2, the mobile terminal 11 is in a macro-diversity condition, that is, the mobile terminal 11 establishes radio-channels with two or more base stations (specifically, four base stations 13 to 16) , and the base station controller 12 monitors radio-quality of the first to fourth radio-channels 18 to 21 and the degree of using radio-resource in the first to fourth base stations 13 to 16, as in-use radio-resource 111.

It is assumed that a first threshold 112 is used for judging whether a number of available radio-channels is tight, a second threshold 113 indicates that there is a sufficient number of available radio-channels, A indicates a minimum number of radio-channels which the mobile terminal 11 is allowed to have, determined by the base station controller 12, and B indicates a maximum number of radio-channels which the mobile terminal 11 is allowed to have.

If the in-use radio-resource 111 becomes over the first threshold 112, the base station 12 reduces a number of radio-channels which the mobile terminal 11 is allowed to have, by one. Specifically, the base station 12 releases radio-channel having worst radio-quality among the first to fourth radio-channels 18 to 21 established by the mobile terminal 11 in a macro-diversity condition.

Thereafter, if the in-use radio-resource 111 is not below the first threshold 112 in a predetermined period of time, the base station controller 12 reduces a number of radio-channels which the mobile terminal 11 is allowed to have, further by one. Specifically, the base station 12 releases radio-channel having worst radio-quality among the radio-channels established by the mobile terminal 11 at that time. The base station 12 repeats reducing a number of radio-channels which the mobile terminal 11 is allowed to have, one by one, until the in-use radio- resource 111 becomes below the first threshold 112 or the mobile terminal 11 comes to have A radio-channels.

When soft handover is to be carried out while the mobile terminal 11 is allowed to have a limited number of radio-channels, after the soft handover has been completely carried out, if the in-use radio-resource is over the first threshold 112, that is, a number of used radio-channels is over A, the base station 12 repeats reducing a number of radio-channels which the mobile terminal 11 is allowed to have, one by one, until the in-use radio-resource 111 becomes below the first threshold 112 or the mobile terminal 11 comes to have A radio-channels.

If the mobile terminal 11 makes an attempt to establish radio-channel in excess of a limited number of radio-channels which the mobile terminal 11 is allowed to have, the base station controller 12 rejects establishment of new radio-channel.

However, when handover is to be carried out while the mobile terminal 11 is allowed to have a limited number of radio-channels, the mobile terminal 11 is allowed to have (P+1) radio-channels at maximum only while handover is being carried out, where P indicates a maximum number of radio-channels which the mobile terminal 11 is allowed to have. After handover has been completely carried out, the base station controller 12 releases radio-channel having worst radio-quality.

When the in-use radio-resource 111 becomes below the second threshold 113, the base station controller 12 does no longer reduce a number of radiochannels of the mobile terminal 11, and increases a number of radiochannels which the mobile terminal 11 is allowed to have, by one.

Thereafter, when the in-use radio-resource 111 is not over the second threshold 113 for a predetermined period of time, the base station controller 12 increases a number of radio-channels which the mobile terminal 11 is allowed to have, further by one.

The base station 12 repeats increasing a number of radio-channels which the mobile terminal 11 is allowed to have, one by one, until the in-use radio-resource 111 becomes over the second threshold 113 or the mobile terminal 11 comes to have B radio-channels wherein B indicates a maximum number of radio-channels which the mobile terminal 11 is allowed to have, as mentioned earlier.

The mobile terminal 11 in a macro-diversity condition in a CDMA mobile communication system can have radio-quality sufficient for making radiocommunication, if the mobile terminal 11 has at least one radio-channel.

Accordingly, by causing the mobile terminal 11 to have a limited number of radio-channels, it would be possible to distribute radio-resource with flexibility, but without reduction in radio-quality, ensuring avoiding tightness of radio-resource.

In accordance with the first embodiment, the diversity handover controller 17 continuously monitors radio-quality of the first to fourth radio-channels 18 to 21, based on the radio-quality data 33 received from the first to fourth base stations 13 to 16 through the first to fourth Iub channels 22 to 25.

The diversity handover controller 17 releases radio-channel(s) judged to have degraded radio-quality, even if step-out does not occur therein, for ensuring sufficient radio-resource. Thus, the diversity handover controller 17 can have many candidates of radio-channels to be released, and hence, can readily provide radio-resource when the in-use radioresource 111 becomes over the first threshold 112, indicating that the radio-resource becomes tight.

In the first embodiment, since a minimum number of radio-channels which the mobile terminal 11 is allowed to have, that is, the number B is already determined, even if all of radio-channels are judged to have poor radio-quality, the predetermined minimum number of radio-channels are kept alive. Thus, it is possible to concurrently ensure radio-resource and avoid interrupting a call.

The mobile communication system in accordance with the first embodiment limits a number of radio-channels which the mobile terminal 11 is allowed to have while the mobile terminal 11 is in a macro-diversity condition, in accordance with the in-use radio-resource. Thus, it is possible to effectively distribute radio-resource with radio-quality being kept at a certain level, ensuring radio-resource is effectively used.

[Second Embodiment] FIG. 5 is a block diagram of a mobile communication system in accordance with the second embodiment of the present invention.

Parts or elements that correspond to those of the mobile communication system illustrated in FIG. 1 have been provided with the same reference numerals, and operate in the same manner as the corresponding parts or elements in the first embodiment, unless explicitly explained hereinbelow.

A mobile terminal 41 in the second embodiment is designed to include a radio-signal receiver 56 which receives down-channel radio-signals through the first to fourth radio-channels 18 to 21, calculates radio- quality, based on sensitivity of the received radio-signals, and stores the calculated radio-quality.

The first to fourth base stations 13 to 16 check whether radio-resource is in short or not, and, if radio-resource is in short, each of the first to fourth base stations 13 to 16 transmits a signal indicative of shortage of radio-resource, to the base station controller 12.

It is assumed that a maximum number of radio-channels which the mobile terminal 41 is allowed to have is six (6), and a minimum number of radiochannels which the mobile terminal 41 is allowed to have is two (2).

The mobile terminal 41 moves along edges of the service areas A1 to A4.

It is assumed that the mobile terminal 41 is now located within the service areas A1 and AS of the first and third base stations 13 and 15, as illustrated in FIG. 5.

The base station controller 42 assigns radio-channel to the first and third base stations 13 and 15 both covering the service areas A1 and As in which the mobile terminal 41 is now located, and the second and fourth base stations 14 and 16 both covering the service areas A2 and A4 in which the mobile terminal 41 was located. Namely, the base station controller 12 assigns totally four radio-channels to the base stations 13 to 16.

It is assumed that radio-channel is good, if it has radio-quality lower than a predetermined threshold, and radio-channel is poor, if it has radio-quality greater than the predetermined threshold. It is also assumed that the first radio-channel 18 has best radio-quality, the third radio-quality 20 has good radio-quality, the second radio-channel 19 has poor radio-quality, and the fourth radio-channel 21 has poorest radioquality.

The mobile terminal 41 calculates radio-quality in the radio-signal receiver 56 each time receiving down-channel radio-signal data, and stores the calculation results.

The base station controller 12 judges that radio-resource is in short, if radio-resource informed from the first to fourth base stations 13 to 16 is below the predetermined threshold, and then, transmits a request to the mobile terminal 41 located in a service area(s) of a base station(s) which has radio-resource lower than the predetermined threshold, to let the base station 12 know radio-channel(s) which may be released.

On receipt of the request, the mobile terminal 41 selects two radiochannels having good radio-quality, based on the radio-quality having been calculated by and stored in the radio-signal receiver 56, and then, informs the base station 12 of the selected two radio-channels.

The base station 12 selects radio-channels to be released in accordance with the information received from the mobile terminal 41, and releases the selected radio-channels one by one.

Specifically, when a certain base station which is in a condition of shortage of radio-resource, among the first to fourth base stations 13 to 16, informs the base station 12 of shortage of radio-resource, the base station 12 keeps the first and third radio-channels 18 and 20 alive, and releases the second and fourth radio-channels 19 and 21.

Whereas the base station 12 in the above-mentioned first embodiment judges whether radio-channel(s) is(are) to be released, based on radio- quality of up-channel radio-signals, the base station 12 in the second embodiment judges whether radio-channel(s) is(are) to be released, based on radio-quality of down-channel radio-signals. The mobile communication system in accordance with the second embodiment limits a number of radiochannels which the mobile terminal 41 is allowed to have while the mobile terminal 41 is in a macro-diversity condition, in accordance with the inuse radio-resource, similarly to the first embodiment. Hence, regardless of the above-mentioned structural difference, the second embodiment makes it possible to effectively distribute radio-resource with radio-quality being kept at a certain level, ensuring radio-resource is effectively used.

In the above-mentioned first and second embodiments, the mobile communication system is designed to separately include the base station controller 12 and the diversity handover controller 17. However, it is not always necessary for the mobile communication system to have the two controllers 12 and 17, but the mobile communication system may be designed to have a single controller having the functions to be carried out by both the base station controller 12 and the diversity handover controller 17.

The advantages obtained by the aforementioned present invention will be described hereinbelow.

In accordance with the present invention, radio-quality is continuously monitored as to whether it is degraded or not. If radio-channel(s) is(are) judged to have degraded radio-quality, the radio-channel(s) is(are) released for ensuring sufficient radio-resource, even if step-out does not occur therein,. Thus, it is possible to have many candidates of radiochannels to be released, and hence, also possible to readily provide radio-resource when the in-use radio-resource becomes over a threshold indicating that the radio-resource becomes tight.

In addition, the present invention makes it possible to relax concentration of radio-resource to a particular mobile terminal when radio-resource becomes tight, by limiting a number of radio-channels which the mobile terminal is allowed to have while the mobile terminal is in a macro-diversity condition. As a result, radio-resource can be assigned to other mobile terminal(s), ensuring it possible to receive a greater number of calls.

Since a mobile terminal is allowed to have at least a minimum number of radio-channels having good radio-quality, even if radio-channel(s) of the mobile terminal is(are) released, it would be possible to keep radioquality at a certain level.

In CDMA communication, since power transmitted through certain radiochannel interferes with power transmitted through adjacent radio-channel, radio-quality in the adjacent radio-channel is degraded. In order to have a necessary gain, increased power is transmitted through the radiochannel having degraded radio-quality. In turn, the increased power interferes with power transmitted through adjacent radio-channel. Thus, an increase in power transmitted through certain radio-channel causes an increase in power transmitted through adjacent radio-channel(s). As a result, radio-resource soon becomes tight. Since the present invention reduces a number of available radio-channels when radio-resource becomes tight, it would be possible to relax such an increase in power.

Claims

CLAIMS: 1. A mobile communication system comprising: a plurality of base

stations each having a service area inherent thereto; a mobile terminal making radio-signal communication with a base station located closest to the mobile terminal among the plurality of base stations; and a base station controller controlling radio-resource of the plurality of base stations and receiving from each of the plurality of base stations a signal indicative of how much degree each of the plurality of base stations uses radio-resource, wherein each of the plurality of base stations adds radio- quality data to data received from the mobile terminal, and transmits the resultant data to the base station controller, the base station controller, when the degree becomes over a first threshold, keeps a first number of radio-channels alive among a plurality of radio-channels of the mobile terminal in a macro-diversity condition, and releases the rest of radio-channels, the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal is allowed to have, and the first number of radio-channels are determined by the base station controller as having higher radio-quality than radio-quality of radio-channels to be released, based on the radio- quality data received from the plurality of base stations.
2. The mobile communication system as set forth in claim 1, wherein the base station controller stores the radio-quality data, and averages variance in the radio-quality data in a predetermined period of time for administrating quality of each of radio-channels.
3. The mobile communication system as set forth in claim 1, wherein when the mobile terminal makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, the base station controller rejects establishment of new radio-channel, and wherein the base station controller allows the mobile terminal to have (P+ 1) radio-channels only at handover, and releases radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.
4. The mobile communication system as set forth in claim, wherein the base station controller, when the degree becomes below a second threshold, periodically repeats increasing the predetermined range of number by one until the degree becomes over the second threshold or the predetermined range of numbers reaches a predetermined maximum number.
5. The mobile communication system as set forth in any one of claims 1 to 4, wherein the radio-quality data is comprised of at least one of first data indicative of quality of communication to be made through the radiochannels, and results of comparison made through the use of predetermined codes.
6. A mobile communication system comprising: a plurality of base stations each having a service area inherent thereto; a mobile terminal making radio-signal communication with a base station located closest to the mobile terminal among the plurality of base stations; and a base station controller controlling radio-resource of the plurality of base stations and receiving from each of the plurality of base stations a signal indicative of how much degree each of the plurality of base stations uses radio-resource, wherein the mobile terminal in a macro-diversity condition calculates radio-quality, based on sensitivity of radio-signals received through a plurality of radio-channels, and, on receipt of a request to inform the base station controller of radio-channel(s) which may be released, selects radio-channel(s) having sufficient radio-quality, based on the radio-quality, and informs the base station controller of the selected radio-channel(s), each of the plurality of base stations checks whether radio-resource is in short, and, if radio-resource is in short, so informs the base station controller, the base station controller, when the degree becomes below a predetermined threshold, transmits a request to the mobile terminal located in a service area of the base station using radio-resource in excess of the predetermined threshold, to inform the base station controller of radio-channel(s) which may be released, and, keeps a first number of radio-channels alive among the plurality of radio-channels of the mobile terminal and releases the rest of radio-channels, based on a response received from the mobile terminal, the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal is allowed to have, and the first number of radio-channels are determined by the base station controller as having higher radio-quality than the same of radio-channels to be released.
7. The mobile communication system as set forth in claim 6, wherein when the mobile terminal makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, the base station controller rejects establishment of new radio-channel, and wherein the base station controller allows the mobile terminal to have (P+ 1) radio-channels only at handover, and releases radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.
8. A base station controller in a mobile communication system including a plurality of base stations each having a service area inherent thereto, and a mobile terminal making radio-signal communication with a base station located closest to the mobile terminal among the plurality of base stations, wherein the base station controller controls radio- resource of the plurality of base stations and receives from each of the plurality of base stations both a signal indicative of how much degree each of the plurality of base stations uses radio-resource, and radio- quality data, the base station controller, when the degree becomes over a first threshold, keeps a first number of radio-channels alive among a plurality of radio-channels of the mobile terminal in a macro-diversity condition, and releases the rest of radio-channels, the first number is defined as a minimum number in a predetermined range of numbers of radio- channels which the mobile terminal is allowed to have, and the first number of radio-channels are determined by the base station controller as having higher radio-quality than radio-quality of radio-channels to be released, based on the radio-quality data received from the plurality of base stations.
9. The base station controller as set forth in claim 8, wherein the base station controller stores the radio-quality data, and averages variance in the radio-quality data in a predetermined period of time for administrating quality of each of radio-channels.
10. The base station controller as set forth in claim 8, wherein when the mobile terminal makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, the base station controller rejects establishment of new radio-channel, and wherein the base station controller allows the mobile terminal to have (P+ 1) radio-channels only at handover, and releases radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.
11. The base station controller as set forth in claim 8, wherein the base station controller, when the degree becomes below a second threshold, periodically repeats increasing the predetermined range of number by one until the degree becomes over the second threshold or the predetermined range of numbers reaches a predetermined maximum number.
12. The base station controller as set forth in any one of claims 8 to 11, wherein the radio-quality data is comprised of at least one of first data indicative of quality of communication to be made through the radiochannels, and results of comparison made through the use of predetermined codes.
13. A base station controller including a plurality of base stations each having a service area inherent thereto, and a mobile terminal making radio-signal communication with a base station located closest to the mobile terminal among the plurality of base stations, wherein the base station controller controls radio-resource of the plurality of base stations and receives from each of the plurality of base stations a signal indicative of how much degree each of the plurality of base stations uses radio-resource, the base station controller receives a signal from each of the plurality of base stations which signal indicates that radio-resource is in short, the base station controller, when the degree becomes below a predetermined threshold, transmits a request to the mobile terminal located in a service area of the base station using radio-resource in excess of the predetermined threshold, to inform the base station controller of radio-channel(s) which may be released, the base station controller receives a response from the mobile terminal which response indicates radio-channel(s) having sufficient radio-quality, based on the radio-quality calculated by the mobile terminal, based on sensitivity of radio-signals received through a plurality of radio- channels in a macro-diversity condition, the base station controller keeps a first number of radio-channels alive among the plurality of radio- channels of the mobile terminal and releases the rest of radio-channels, based on a response received from the mobile terminal, the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal is allowed to have, and the first number of radio-channels are determined by the base station controller as having higher radio-quality than the same of radio-channels to be released.
14. The base station controller as set forth in claim 13, wherein when the mobile terminal makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, the base station controller rejects establishment of new radio-channel, and wherein the base station controller allows the mobile terminal to have (P+ 1) radio-channels only at handover, and releases radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.
15. A method of controlling radio-resource in a mobile communication system including a plurality of base stations each having a service area inherent thereto, a mobile terminal making radio-signal communication with a base station located closest to the mobile terminal among the plurality of base stations, and a base station controller controlling radio-resource of the plurality of base stations and receiving from each of the plurality of base stations a signal indicative of how much degree each of the plurality of base stations uses radio-resource, the method comprising: each of the plurality of base stations adding radio-quality data to data received from the mobile terminal, and transmitting the resultant data to the base station controller; and the base station controller, when the degree becomes over a first threshold, keeping a first number of radio-channels alive among a plurality of radio-channels of the mobile terminal in a macro-diversity condition, and releasing the rest of radio-channels, wherein the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal is allowed to have, and the first number of radio- channels are determined by the base station controller as having higher radio-quality than radio-quality of radio-channels to be released, based on the radio-quality data received from the plurality of base stations.
16. The method as set forth in claim 15, further comprising the base station controller storing the radio-quality data, and averages variance in the radio-quality data in a predetermined period of time for administrating quality of each of radio-channels.
17. The method as set forth in claim 15, further comprising, when the mobile terminal makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, the base station controller rejecting establishment of new radio-channel, and the base station controller allowing the mobile terminal to have (P+1) radiochannels only at handover, and releasing radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.
18. The method as set forth in claim 15, further comprising the base station controller, when the degree becomes below a second threshold, periodically repeating increasing the predetermined range of number by one until the degree becomes over the second threshold or the predetermined range of numbers reaches a predetermined maximum number.
19. A method of controlling radio-resource in a mobile communication system including a plurality of base stations each having a service area inherent thereto, a mobile terminal making radio-signal communication with a base station located closest to the mobile terminal among the plurality of base stations, and a base station controller controlling radio-resource of the plurality of base stations and receiving from each of the plurality of base stations a signal indicative of how much degree each of the plurality of base stations uses radio-resource, the method comprising: the mobile terminal calculating radio-quality, based on sensitivity of radio-signals received through a plurality of radio- channels in a macro-diversity condition, and, on receipt of a request to inform the base station controller of radio-channel(s) which may be released, selecting radio-channel(s) having sufficient radio-quality, based on the radio-quality, and informing the base station controller of the selected radio-channel(s); each of the plurality of base stations checking whether radio-resource is in short, and, if radio-resource is in short, so informing the base station controller; and the base station controller, when the degree becomes below a predetermined threshold, transmitting a request to the mobile terminal located in a service area of the base station using radio-resource in excess of the predetermined threshold, to inform the base station controller of radio-channel(s) which may be released, and, keeping a first number of radio-channels alive among the plurality of radio-channels of the mobile terminal and releasing the rest of radio-channels, based on a response received from the mobile terminal, the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal is allowed to have, and the first number of radio-channels are determined by the base station controller as having higher radio-quality than the same of radio-channels to be released.
20. The method as set forth in claim 19, further comprising when the mobile terminal makes attempt to newly establish radio-channel in excess of said predetermined range of numbers of radio-channels, the base station controller rejecting establishment of new radio-channel, and the base station controller allowing the mobile terminal to have (P+1) radiochannels only at handover, and releasing radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.
21. A program for causing a computer to carry out a method of controlling radio-resource in a mobile communication system including a plurality of base stations each having a service area inherent thereto, a mobile terminal making radio-signal communication with a base station located closest to the mobile terminal among the plurality of base stations, and a base station controller controlling radio-resource of the plurality of base stations and receiving from each of the plurality of base stations a signal indicative of how much degree each of the plurality of base stations uses radio-resource, wherein steps executed by said computer in accordance with said program includes: receiving from each of the plurality of base stations both a signal indicative 6 of how much degree each of the plurality of base stations uses radio- resource, and radio-quality data, and when the degree becomes over a first threshold, keeping a first number of radio-channels alive among a plurality of radio-channels of the mobile terminal in a macro-diversity condition, and releasing the rest of radio-channels, wherein the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal is allowed to have, and the first number of radio-channels are determined by the base station controller as having higher radio-quality than radio-quality of radio- channels to be released, based on the radio-quality data received from the plurality of base stations.
22. The program as set forth in claim 21, wherein the steps further include storing the radio-quality data, and averages variance in the radio-quality data in a predetermined period of time for administrating quality of each of radio-channels.
23. The program as set forth in claim 21, wherein the steps further include, when the mobile terminal makes attempt to newly establish radiochannel in excess of said predetermined range of numbers of radiochannels, rejecting establishment of new radio-channel, and wherein the base station controller allows the mobile terminal to have (P+1) radiochannels only at handover, and releasing radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.
24. The program as set forth in claim 21, wherein the steps further include, when the degree becomes below a second threshold, periodically repeating increasing the predetermined range of number by one until the degree becomes over the second threshold or the predetermined range of numbers reaches a predetermined maximum number.
25. A program for causing a computer to carry out a method of controlling radio-resource in a mobile communication system including a plurality of base stations each having a service area inherent thereto, a mobile terminal making radio-signal communication with a base station located closest to the mobile terminal among the plurality of base stations, and a base station controller controlling radio-resource of the plurality of base stations and receiving from each of the plurality of base stations a signal indicative of how much degree each of the plurality of base stations uses radio-resource, wherein steps executed by said computer in accordance with said program includes: receiving from each of the plurality of base stations a signal indicative of how much degree each of the plurality of base stations uses radio-resource, receiving a signal from each of the plurality of base stations which signal indicates that radio-resource is in short, when the degree becomes below a predetermined threshold, transmitting a request to the mobile terminal located in a service area of the base station using radio-resource in excess of the predetermined threshold, to inform the base station controller of radiochannel(s) which may be released, receiving a response from the mobile terminal which response indicates radio-channel(s) having sufficient radio-quality, based on the radio-quality calculated by the mobile terminal, based on sensitivity of radio-signals received through a plurality of radio-channels in a macro-diversity condition, and keeping a first number of radio-channels alive among the plurality of radiochannels of the mobile terminal and releasing the rest of radio-channels, based on a response received from the mobile terminal, wherein the first number is defined as a minimum number in a predetermined range of numbers of radio-channels which the mobile terminal is allowed to have, and the first number of radio-channels are determined by the base station controller as having higher radio-quality than the same of radio-channels to be released.
26. The program as set forth in claim 25, wherein the steps further include, when the mobile terminal makes attempt to newly establish radiochannel in excess of said predetermined range of numbers of radiochannels, rejecting establishment of new radio-channel, and wherein the base station controller allows the mobile terminal to have (P+1) radiochannels only at handover, and releasing radio-channel having poorest radio-quality after establishment of radio-channel at handover, where P indicates the predetermined range of numbers.
27. A mobile communication system substantially described herein with reference to Figures 1A, 1B, 2, 3, 4 and 5 of the accompanying drawings.
28. A base station substantially described herein with reference to Figures 1A, 1B, 2, 3, 4 and 5 of the accompanying drawings.
29. A method of controlling radio-resource in a mobile communication system, substantially described herein with reference to Figures 1A, 1B, 2, 3, 4 and 5 of the accompanying drawings.
30. A program for causing a computer to carry out a method of controlling radio-resource in a mobile communication system, substantially described herein with reference to Figures 1A, 1B, 2, 3, 4 and 5 of the accompanying drawings.