GB2359701A

GB2359701A - System for preventing cell overloading and a method of call processing

Info

Publication number: GB2359701A
Application number: GB0023210A
Authority: GB
Inventors: Won Cheon Lee
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 1999-09-21
Filing date: 2000-09-21
Publication date: 2001-08-29
Anticipated expiration: 2020-09-21
Also published as: GB0023210D0; GB2359701B

Abstract

A system for preventing overloading of a cell determines a cell to be in an overloaded state if a number of available resources is below a threshold. A dedicated overload managing workstation 306 then selects at least one adjacent cell within a zone and transfers cell information to a radio network controller 302a-p. The radio network controller receives current resource availability for the selected cell and classifies cells in order from greatest to smallest available resources if more than one adjacent cell has been selected. A list of cell identities are prepared for adjacent cells having available resources above a second threshold, and at least one mobile station communicating in the overloading cell is transferred to an adjacent cell in the list. In a further embodiment, a method for processing a call comprises the step of constructing a bearer capability table at a radio network controller using a program loading data at a time of initialization.

Description

2359701 METHOD AND APPARATUS FOR EFFICIENTLY PROCESSING A CALL IN A MOBILE

COMMUNICATION SYSTEM

Field of the Invention

The present method relates to a mobile communication system, and more particularly, to a method and apparatus for efficiently processing a call in a mobile communication system of the next generation.

Background of the Related Art

A mobile communication system of the next generation, such as the IMT2000, allows users to transmit multimedia information, such as text, video and audio data; and allows international roaming by which a user can receive communication services throughout the world using one mobile station.

Particularly, an object of the IMT-2000 system is to provide a higher level mobile communication service in addition to communication services provided by communication systems such as CT-2, CT-3, PHS, PCS, satellite communication systems, pager systems, and stationary networks. The IMT-2000 system can generally provide a communication with a quality equal to or better than a stationary network, at a data transmission rate up to 2Mbps, and uses an intelligent network for quick implementation of additional services. Thus, the IMT-2000 system is constantly being developed to provide multimedia services at any place or time to anyone, without limitation. Moreover, the IMT-2000 accommodates various networks other than personal mobile stations such as the PS7IN and ISDN.

1 FIG. 1 shows a next generation mobile communication system in the related art including mobile stations 1 00a - 1 00n; base stations 101 a 101 n which make radio connection to the mobile stations 1 00a - 1 00n to connect originating or destination calls; radio network controllers (RNC) 102a - 102p which controls the base stations 10 1 a - 10 1 n; Base Station Manager (BSM) 103a - 103p which analyzes and stores traffic occurring at each base stations 10 1 a - 10 1 n; a mobile switching center (MSC) 104 which processes originating or destination calls from/to the mobile stations 1 00a - 1 00n; a Home Location Register (HLR) 105 which registers and manages positional information of the mobile stations 1 00a - 1 0On.

In the above system, the base stations 10 1 a - 10 1 n and the radio network controllers 102a - 102p are collectively called a Radio Access Network (RAN), and the MSC 104 and the HLR 105 are collectively called a Core Network (CN). Accordingly, as a mobile station 1 00a - 1 00n moves, the mobile station may connect to a plurality of other RANs and the CN may connect to other communication networks, such as the PSTN, the Internet, and packet data network. Thus, a next generation mobile communication system is provided with a plurality of RNCs 102a - 102p connected to one MSC 104, and a plurality of base stations 101 a - 101 n connected respectively to RNCs 102a - 102p.

Here, each of the base stations may be called a cell and each cell has limited traffic load or resources. A load of each cell can be determined by a signaling and traffic load for transmitting information to a mobile station to process calls such as originating call, destination call, handoffs, and location register; and a resource load.

2 If an overload occurs at a RNC and base stations or cells belonging to the RNC, all mobile stations within a service region of the cell cannot be serviced. Therefore, one method for preventing an overload of a cell is by managing a base station or a cell resource within a region in which user services are not limited. That is, users within a cell with a heavy load are transferred to other cells to prevent an overload of one cell. However, a transfer requires a location register which creates an additional load. Another method to prevent an overload in the cell limits calls when the load of a cell reaches a predetermined threshold. However, limiting services to prevent an overload results in a poor quality of service to users.

Moreover, a RNC must provide lu, lur, and lub interfaces for transmission of signaling messages, as shown in FIG. 2, using the CN, other RNCs, a base station, and ATM as a back bone. Also, the RNC must provide an Access Link Control Application Part (ALCAP) protocol for a data transport bearer. Here, the Iu interface is a Radio Access Network Application Part (RANAP) for processing messages and protocol stacks to transmit signaling messages between a RNC and a CN, without loss; the lur interface is a Radio Network Subsystem Application Part (RNSAP) for processing messages and protocol stacks to transmit signaling messages between RNCs, without loss; and the lub interface is a Node B Application Part (NBAP) for processing messages and protocol stacks to transmit signaling messages between a RNC and base stations managed by the RNC, without loss.

Furthermore, a RNC must provide a process for connecting a Radio Resource Control (RRC) to connect a signaling bearer with a mobile station. Namely, the RNC must establish several signaling paths to allow a mobile station to receive or transmit the RRC message.

3 This is called a RRC connection process in a DS type.

The RRC connection process requires a radio link setup process between a RNC and a base station, and requires a bearer capacity information setup which indicates a bearer capability. FIG. 3 shows a flow chart of a procedure for processing a call in a mobile communication system in the related art, and more particularly, a process for a setup of a RRC connection when a mobile station originates a call. As shown in FIG. 3, there are two radio access bearer (RAB) setup during a process for a RRC connection.

Referring to FIG. 3A and 313, when a mobile station requests the RNC for RRC connection (S200), the RNC orders a base station to setup a radio link (S201) and the base station transmits a radio link setup response (S202). Accordingly, a RRC connection is established between the mobile station and the RNC (S203). A call control message processing procedure is then made between the mobile station and the RNC (S204 - S212).

Particularly, the mobile station directly transmits mobile station capacity information and a CM service request message to the RNC (S204, S205), and the RNC transmits an initial mobile station message requesting for the CM service to the CN (S206). The CN then transmits a CM service accept message to the RNC (S207), and the RNC directly transmits the CM service reception message to the mobile station (S208). Thereafter, the mobile station directly transmits a setup message to the RNC (S209), and the RNC transmits the setup message to the CN (S21 0). In response, the CN transmits a call proceeding message to the RNC (S21 1), and the RNC directly forwards the call proceeding message to the mobile station (S212).

4 Upon completion of the above procedure for processing a call control message, the CN transmits a RAB assignment request message to the RNC (S213). The RNC then transmits a radio link reconfiguration response message to the base station (S214) and the base station transmits the radio link reconfiguration response message back to the RNC (S215). Upon receiving the radio link reconfiguration response message, the RNC completes the RAB setup with the mobile station and transmits a RAB assignment response message to the CN (S216 - S218).

However, the above method for processing a call requires two RB setup processes, i.

during a setup of the RRC connection and during a reception of the RAB assignment request message from the CN. These two RB setup processes causes an increase of the load for internal processing of signaling in the RNC each time one call is processed.

SummM of the Invention

The present invention addresses these and other problems and disadvantages of the related art.

It would be desirable 4o provide a more efficient next generation mobile communication system.

It would also be desirable Ao provide a device and method for preventing an overload of a cell in a mobile communication system.

It would also be desirable to -provide a more efficient method for processing a call in a mobile communication system.

e.

It would also be desirable - to prevent an overload of a cell by reducing the load of a cell during a processing of a call in a mobile communication system.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.

To achieve the objects and in accordance with the purposes of the invention, as embodied and broadly described herein, a device for preventing an overload of a cell in a mobile communication system includes a plurality of mobile stations; a plurality of base stations, each making a radio connection with the mobile stations to connect originating or destination calls; radio network controllers for controlling the base stations; base station managers connected to the radio network controllers for analyzing and storing average resource occupation number for each base station or cell per weekday and time zone; a mobile switching center for managing originating or destination calls of the mobile stations; and a dedicated overload managing workstation for selecting a cell of the least traffic from information on cell ID search within a zone by using the zone information of the cells in an overload alarm state and on traffic analysis of the cells, and providing the selected cell to radio network controller when an overload occurs in base station and cell.

A method for preventing an overload of a cell in a mobile communication system includes (1) determining an occasion when a number of available resources in the cell is 6 1 1 below a predetermined value as an overload alarm state, (2) searching the cell in an overload alarm state for cell IDs in a zone by using zone information of the cell in the overload alarm state, (3) selecting the cell of the least traffic by using information on average resource occupation numbers for the searched cell IDs, (4) searching information on the available resource numbers for the selected cells, and preparing cell ID information in a descending order of the available resource numbers, and (5) informing the cell ID information to the cell, or base station and the mobile stations in the overload alarm state,, so that mobile stations can access other cells within the same zone according to the cell ID information.

In another embodiment of the present invention to prevent an overload in a cell is a method for processing a call in a mobile communication system including (1) a radio network controller forming a bearer capability table using a program loading data at the time of initialization, (2) a mobile station transmitting a bearer capability information including data information to the radio network controller when making an originating call, and requesting a radio link connection, (3) the radio network controller establishing a radio access bearer accommodating a bearer capability requested by the mobile station at a base station, using the bearer capability information and the bearer capability table, and (4) the radio network controller completing the radio access bearer assignment requested by the core network using the established radio access bearer, when a core network requests for a radio access bearer assignment.

In (1), a base station manager manages base stations which transmit the program loading data for identifying the bearer capability to the radio network controller, and the 1 7 bearer capability table is formed according to respective bearer capability parameters by the program loading data. Also, in (3), the radio network controller broadcasts system information to the mobile stations for sharing the bearer capability information.

Brief Description of the Drawing

ETbodments cE the itlm will now be des=bed, ty;uy cE e> cnl-y, -oath referenoe to the foll3.mDM draAurxjs Jin WUch like r&eiTree nureraLs refer to like elts YkE=n:

FIG. 1 is a block diagram showing a portion of a next generation mobile communication system in the related art; FIG. 2 shows a method for interfacing between systems in a next generation mobile communication system of FIG. I; FIG. 3A and 313 are a flow chart showing a procedure for processing a call in a mobil communication system of FIG. I; FIG. 4 shows a next generation mobile communication system in accordance with the present invention; FIG. 5 shows an interface between an MSC and RNCs; FIG. 6A and 613 are a flow chart of a method for preventing an overload of a cell in a mobile communication system in accordance with the present invention; and FIG. 7A and 713 are a flow chart showing a another method for preventing an overload of a cell in a mobile communication system in accordance with the present invention.

8 Detailed Description of the Invention

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. FIG. 4 is a next generation mobile communication system in accordance with the present invention.

Referring to FIG. 4, a mobile communication system in accordance with the present invention includes mobile stations 3 00a - 3 00n; base stations 3 0 1 a - 3 0 1 n for making radio connection with the mobile stations 300a - 300n to connect originating or destination calls; RNCs 302a - 302p which controls the base stations 301a - 301n; BSMs 303a - 303p which analyzes and stores traffic occurring at each base stations 301 a - 30 In; a MSC 304 which processes originating or destination calls from/to the mobile stations 300a - 300n; a HLR 305 which registers and manages positional information of the mobile stations 300a - 300n; and a dedicated overload managing workstation 306 for preventing anoverload of a cell.

The dedicated overload managing workstation 306 has information on geographical map as well as information on each cell and adjacent cells of each cells. Here, the adjacent cells mean cells within a same zone with respect to zones managed by location registration.

A dedicated overload managing workstation 306 is connected to each RNCs 302a - 302p which is connected to the MSC 304 by TCP/IP, and the dedicated overload managing workstation 306 is connected to each of the BSMs 303a 303p. Also, the dedicated overload managing workstation 306 is separately implemented, in addition to the BSMs 303a - 303p, to share the load of the BSMs during an overloaded state or when the system has a heavy load. Accordingly, the information stored in the dedicated overload managing -workstation 9 306 contains zone information on cells and adjacent cells within a same zone. The zone information is transferred to and updated at the dedicated overload managing workstation 306 when a reorganization of cells is required, such as during an addition, change, and removal of cells.

The lur interfaces for exchange of signaling messages between the RNCs 302a - 302p and lu interfaces for interconnection points between the MSC and RNCs are shown in FIG. 5.

As described above, the lu interface is an interface defined in a protocol for data transmission and/or reception between the MSC and the RNCs, and the lur is an interface defined in a protocol for data transmission and/or reception between RNCs.

Referring to FIG. 5, a signaling message is exchanged between adjacent RNCs by the lur interface, in which the signaling message is information on a handoff call connection between RNCs. Also, a signaling message is exchanged between each RNC and the MSC by the lu interface, in which the signaling message is information on originating calls, destination calls, and location registrations.

Each BSM 303a periodically collects and stores information on each cell traffic in each of the base stations at fixed intervals by weekday and by time zone, and obtains an average resource occupation number. That is, the BSM collects information on traffic of each base stations at fixed intervals. The BSM then analyzes and stores traffic for each base station by weekday and by time zone to calculate and store an average occupation number for each base stations for each weekday and each time zone. Thus, the stored information can be provided to the dedicated overload managing workstation 306, when requested.

A method for preventing an overload of a cell in an IMT,2000 system in accordance with the present invention will next be explained with reference!the flow chart in FIG. 6A and 6B.

As a method for detecting whether an overload is possible such that an overload can be prevented, an overload alarming factor may used or a number of available resources may simply be used. That is, a determination is made whether the number of available resources in a cell is below a predetermined threshold value (S401), and if the number drops below the threshold value, a cell is determined to be in an overload alarm state. Here, the threshold value is provided from a RNC through system information when a cell or base station restarts.

When the RNC is informed of an overload alarm state (S402), the RNC informs the dedicated overload managing workstation 306 of the overload alarm state through TCP/IP (S403). Upon receiving the overload alarm state message, the dedicated overload managing workstation 306 searches for cell IDs within a zone of the cell in the overload alarm state, using the zone information (S404). The dedicated overload managing workstation 306 then requests a BSM for information on the average resource occupation number of the searched cell IDs by the weekday and the time of cell in the overload alann state (S405). When the dedicated overload managing workstation 306 receives the requested traffic analysis information from the BSM, at least one cell with a low or least traffic is selected (S406), and information on the selected cell(s) is transferred to the RNC (S407).

As explained above, the BSM periodically collects and stores information on the cell traffic, and analyzes and stores an average occupation number for each base station based 11 upon each weekday and time zone.

Accordingly, upon receiving the information of the selected cell(s) from the dedicated overload managing workstation 306, the RNC transmits inquiries to other base stations to obtain a currently available resource number for cell(s) in the information of the selected cell(s). For this, a determination is made whether the cells are connected to their own RNCs (S408). If a cell is connected to its own RNC, the inquiry may be made through the Itib interface. Otherwise, if a cell is not connected to its own RNC, the inquiry is made through the Iur interface.

Namely, as a RNC is connected to a plurality of base stations and each of the base stations manages a plurality of cells, a cell selected by the dedicated overload managing workstation 306 may be connected to a base station or RNC in which the cell belongs, or to other RNC by a handoff. Therefore, if a cell is connected to a RNC in which the cell belongs, the available resource information may be obtained through the lub interface (S409), and if a cell is connected to a RNC other than the RNC in which the cell belongs, the available resource information is obtained through the lur interface (S41 0).

Thus, the RNC receives available resource information of cells through the lub and lur interfaces, classifies cells in an order from the greatest to smallest number of the available resources, and prepares a cell 11) information of cells having a number of resources equal to or greater than a predetermined threshold value (S41 1). Thereafter, the cell ID Information transferred to the base station or to a cell in the overload alarm state, and to mobile stations (S412).

is 12 As a result, mobile station(s) will attempt to access other cells according to the cell ID information, and the mobile station(s) which does move to other cells does not require a location registration because the cells belong to the same zone. An overload alarm state is lifted when the base station informs both the RNC and the mobile stations that there is no possibility of overload when the number of resources of the cell increases above the threshold value. Moreover, services such as originating calls and destination calls, may be provided as before, while a possibility of an overload in a cell is reduced, thereby allowing a more efficient mobile communication system To further increase the efficiently of a mobile communication system, the present invention also suggests a method for processing a call which reduced a load caused by repetitive assignment of a RAB Generally, the bearer capability, information is contained and transmitted during a setup of the RRC connection to reduce signaling messages between a RNC and a base station or between a RNC and a mobile station when informing the CN of the RAB assignment.

Namely, during the setup of RRC connection, the present invention uses an advanced RRC connection request message which includes a bearer capability information. Thus, the RRC connection request message, including the bearer capability information is transmitted from a mobile station. Also, during the setup of the RRC connection, the RRC broadcasts a system information to mobile stations such that the bearer capability information can be shared between the mobile stations and the RNC. Finally, the RNC of the present invention prepares a bearer capability table according to the bearer capability parameters to extract 13 information, such as data rate, upon reception of the RRC connection request message.

The system to implement the present method for precessing a call in a mobile communication system is identical to the system shown in FIG. 1, except the length of the RRC connection request is increased in the channel radio protocol between a mobile station and the base station. The length is increased because a RRC connection request message generated by the mobile station and the base station does not contain the bearer capability information. Thus, the radio message is modified to transmit the bearer capability information. At this time, a system information is broadcasted such that the bearer capability information, which is distinguished by the additionally assigned bits, can smoothly be interpreted by the RNC and the mobile station.

To share the bearer capability information between the mobile station and the RNC, the bearer capability information is represented as 8 Kbps speech: 0, 64 Kbps data: 1, 384 Kbps moving picture: 2, 2 Mbps: 3. Such representation is determined at the RNC. To accomplish this, the BSM stores a Programmable Loading Data (PLD) and transmits the PLD to the RNC when the RNC operates to construct a data base regarding the bearer capability.

At this time also, the bearer capability information is broadcasted through a system information message to the mobile stations. As a result, when a particular bearer capability information is requested between the mobile station and the RNC, the same variable is available.

So far, the construction of the bearer capability table has been explained. The present method for processing a call in a mobile communication system will next be explained with 14 reference to FIG. 7A and 7B.

Referring to FIG. 7A and 713, a mobile station requests the RNC for RRC connection (S500) by transmitting an advanced RRC connection request. The advanced RRC connection request message has a parameter which allows an identification of the bearer capability information parameters of the RRC connection request message in the related art. The RNC then prepares and maintains the bearer capability table according to the bearer capability parameters using the PLI) received from the BSM, and uses the bearer capability table during a setup or re-confirmation of the radio link with the base station.

Accordingly, the RNC orders a base station to setup a radio link using the bearer capability parameters extracted from the advanced RRC connection request message and the bearer capability table (S501). That is, the RNC sets up the radio bearer which can accommodate an appropriate bearer capability during the setup of a radio link with the base station. Thereafter, the base station transmits a radio link setup response (S502) and a RRC connection is established between the mobile station and the RNC (S503). Upon completion of the RRC connection setup, a call control message processing procedure is then made between the mobile station and the RNC (S504 - S512) by the same method as explained with reference to S204 - S212 of FIGs. 4A and 4B.

i Namely, the mobile station directly transmits mobile station capacity information and a CM service request message to the RNC (S504, S505), and the RNC transmits an initial mobile station message requesting for the CM service to the CN (S506). The CN then transmits a CM service accept message to the RNC (S507), and the RNC directly transmits the CM service accept message to the mobile station (S508). Thereafter, the mobile station directly transmits a setup message to the RNC (S509), and the RNC transmits the setup message to the CN (S51 0). In response, the CN transmits a call proceeding message to the RNC (S51 1), and the RNC directly transmits the call proceeding message to the mobile station (S512).

Upon completion of the above procedure for processing a call control message, the CN transmits a RAB assignment request (S413) and the RNC transmits a RAB assignment response message to the CN (S415). In contrast to the method in the related art, a RRC link reconfirmation processing procedure is not required upon receiving the RAB assignment request message from the CN because informing of the RAB assignment required for providing the call service to the mobile station is already done in the RRC connection setup process.

Furthermore, since the method for processing a call in a mobile communication system is applicable to a destination call, loads in processing an originating or destination call of the RNC can significantly be reduced. Moreover, as the signaling procedure includes control primitive such as a lower Radio Link Control (RLC), Medium Access Control (MAC), and Layer 1 (LI), a substantial load reduction results.

As explained above, the present invention allows a more efficient mobile communication by preventing an overload of a cell in a mobile communication system and by reducing the load during a call processing in a mobile communication system.

Particularly, a device and method for preventing overloading of a cell in a mobile 16 communication system senses an overload state of a cell or a base station before an overload state occurs, thereby preventing a cell overload. Also, by providing a separate dedicated overload managing workstation, an overload control load of the base station manager or the RNC can be reduced when an overall system load becomes larger. Moreover, an overload of a cell can be avoided without creating any additional load, such as location registration, of the mobile stations served in the cell or base station in which an overload may occur.

Finally, since the method for processing a call in a next generation mobile communication system of DS-MAP type of the present invention can reduce a load for RAB assignment for an effective processing of originating or destination call at the RNC, a Busy Hour Call Attempt of the RNC can be improved.

The foregoing embodiments are merely exemplary and are not to be construed as limiting the present invention. The present teachings can be readily applied to other types of apparatuses. The description of the present invention is intended, to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art.

i 1 1 7

Claims

What is claimed is

1. A device for preventing a cell overload in a mobile communication system comprising:

a plurality of mobile stations; a plurality of base stations which makes radio connection with the plurality of mobile stations to connect originating or destination calls; a RNC which controls the plurality of base stations; a BSM which is connected to the RNC, wherein the BSM obtains and stores average traffic load information of each of the plurality of base stations; a MSC which processes originating or destination calls from/to the plurality of mobile stations; and a dedicated overload managing workstation which selects at least one adjacent cell in a zone of a cell in an overload alann state and transfers information the selected cell to the RNC, wherein an adjacent cell with a traffic load equal to or below a first predetermined threshold is selected based upon the average traffic load information from the BSM; wherein the RNC receives a current resource availability information on the selected adjacent cell and classifies cells in an order from the greatest to smallest number of the available resources if more than one adjacent cell has been selected, and prepares cell ID information of adjacent cells having a number of available resources equal to or greater than a second predetermined threshold value; and wherein at least one mobile station is transferred from the cell in the overload alar:m state to an adjacent cell in the cell ID information.

18 1

2. A device of claim 1, wherein the BSM periodically collects and stores cell traffic load of each base stations at fixed intervals based upon weekday and time zone, and stores an average number of occupation for each of the base stations for each weekday and time zone as the average traffic load information.

3. A device of claim 2, wherein the dedicated overload managing workstation selects an adjacent cell with a traffic load equal to or below the first predetermined threshold during the weekday and time of the cell in the overload alarm state.

4. A device of claim 1, wherein the dedicated overload managing workstation stores zone information including information on geographical map, information on each cell and information on cells adjacent to each cells.

1

5. A device of claim 4, wherein the zone information is updated when a reorganization of cells is required.

6. A device of claim 4, wherein the dedicated overload managing workstation searches for cells within a zone of the cell in the overload alarm state using the zone information and obtains the average traffic load information of the searched cells from the BSM to select said at least one adjacent cell.

19

7. A device of claim 1, wherein the RNC obtains the current available resource information through an lub interface if the selected adjacent cell is connected to the RNC, and if the selected adjacent cell is connected to a different RNC, the current available resource information is obtained through an lur and Iub interface.

8. system, comprising:

A method for preventing an overload of a cell in a mobile communication (a) determining a cell to be in an overload alarm state, if a number of available resources in a cell is below a first predetermined threshold value; (b) searching for adjacent cells within a zone of the cell in the overload alarm state, using a zone information; (c) selecting at least one cell with an average traffic load equal to or lower than a second predetermined threshold value, using a stored average traffic load information of the searched adjacent cells; (d) receiving a current resource availability information on the selected cell and classifying the selected cells in an order from the greatest to the smallest number of the available resources if more than one cell has been selected, and preparing a cell ID information of the selected cells having a number of available resources equal to or greater than a third predetermined threshold value; (e) transmitting the cell ID information to base stations and mobile stations within the zone of the cell in the overload alarm state; and h (f) executing handoffs of mobile stations to other cells within the same zone of the cell in the overload alarm state, according to the cell ID information.

9. A method of claim 8, wherein the first predetermined threshold value is provided from a RNC through a system information when a cell or base station restarts.

10. A method of claim 8, wherein in (c), the average traffic load information is obtained and stored for each weekday and time zone.

11. A method of claim 8, wherein in (c), selecting a cell with an average traffic load equal to or below the second predetermined threshold during a weekday and time of the cell in the overload alarm state.

12. A method of claim 8, wherein in (d) obtaining the current available resource information through an lub interface if a selected cell is connected to a RNC to which the selected cell belongs, and otherwise, obtaining the current available resource information through an lur and Iub interface.

13. A method for processing a call in a mobile communic: ation system comprising:

(a) constructing a bearer capability table at a RNC using aprogram loading data at a time of initialization; 21 i (b) transmitting from a mobile station a bearer capability information to the RNC at a time of making an originating call and requesting for a radio link connection; (c) establishing, at the RNC, a radio bearer accommodating a bearer capability requested by the mobile station at a base station using the bearer capability information and the bearer capability table; and (d) completing, at the RNC, a radio bearer assignment requested by a core network using the set radio bearer, when the core network requests for the radio bearer assignment.

14. A method of claim 13, wherein (a) includes; transmitting to the RNC a programmable loading data for identifying the bearer capability, and forming the bearer capability table according to corresponding bearer capability parameters based upon the program loading data.

15. A method of claim 13, wherein (c) includes broadcasting from the RNC system information to mobile stations to share the bearer capability information.

16. A device for preventing cell overload in a mobile corrminication system substantially as herein described, with reference to figures 4 to 7B of the accaTpanying drawings.

17. A method for preventing overload of a cell in a mobile camunication system substantially as herein described, with reference to figures 4 to 7B of the acccrrpanying drawings. 22