KR100728850B1 - A method of search cell at hand over between the RNCs for WCDMA mobile communication system - Google Patents

Abstract

The present invention relates to a handoff between RNCs in an asynchronous mobile communication system. In the case of a handover request failure of a mobile communication terminal requested by an SRNC, neighboring cell information is provided in a response message to request handover to a neighboring cell having a lot of available resources. This is a cell search method for handover of control period of asynchronous mobile communication system which reduces processing time between RNCs and implements handover smoothly. The present invention has the effect of maintaining the optimal RRM (Radio Resource Management) because the radio resource management belongs to the RNC (DRNC) that has a large number of available resources, and can find the exact target cell (Target Cell), Increasing the utilization of resources has the effect of improving the operational efficiency of the WCDMA mobile communication system. In addition, the present invention takes less time according to the handover procedure and does not need to operate an unnecessary compressed mode.

Handover, SRNC, DRNC, Radio Link Setup / Radio Link Addition Failed messages.

Description

A method of search cell at hand over between the RNCs for WCDMA mobile communication system}

1 is a schematic configuration diagram of a conventional WCDMA asynchronous mobile communication system,

2 is a schematic flowchart of handover between RNCs;

3 is a schematic structural diagram of an asynchronous mobile communication system of the present invention;

4 is a flowchart of cell search operation during control period handover of the asynchronous mobile communication system of the present invention;

5 is an example of a radio link addition failure message,

6 is an example of a radio link setup failure message;

7 shows an example of a neighbor cell information message.

<Description of Major Symbols in Drawing>

60: mobile communication terminal 62, 70, 72: base station (BS, node ratio)

64: SRNC 68: DRNC

The present invention relates to a handoff between RNCs (Radio Network Controllers) in an asynchronous mobile communication system. Even when a handover request of a mobile communication terminal requested by a SRNC (SRNC) fails, neighboring cell information is added to a DRNC (Drift RNC). The present invention relates to a cell search method for handover of a control period of an asynchronous mobile communication system which reduces the processing time between RNCs and smoothly implements handover by requesting a handover to a neighboring cell with more available resources.

In general, the handover (handover) is to automatically switch the call channel to the call channel of the other radio zone when the mobile subscriber moves to another radio zone to continue the call. If the mobile communication terminal talking from a specific base station moves away from the base station, the signal strength is weakened. Therefore, in order to receive continuous service, the mobile terminal requests handoff to an adjacent base station receiving strong radio waves. The mobile communication system connects the call channel to the neighboring base station. Hand off may be described as being divided into softer handoff, soft handoff, and hard handoff.

Softer handoff is a handoff that occurs when moving between sectors within the same base station service area. When a mobile terminal moves from one sector in the base station to another to another sector, the mobile terminal can maintain the call in the new sector without interruption of the call. A sector is an area divided into service areas.

Soft handoff is a handoff that occurs when moving between adjacent base stations using the same frequency. When the mobile terminal in the call moves from the current service area to another adjacent service area, the call is maintained so that the call can be continued in the new service area without interruption of the call. Hard handoff is a handoff that occurs when moving between base stations using different frequencies or when moving between base stations belonging to different exchanges. Hard handoff is sometimes interrupted because a call channel must be allocated in a new service area after the communication channel is temporarily disconnected.

A handover between RNCs in a conventional WCDMA asynchronous mobile communication system will be described with reference to the drawings.

1 is a schematic configuration diagram of a WCDMA asynchronous mobile communication system, and FIG. 2 is a schematic flowchart of handover between RNCs.

1 illustrates a core network including a UTRAN consisting of a mobile communication terminal 20 node ratio and an RNC, an exchanger, SGSN, GGSN, and the like, for connecting a call or for connecting to the Internet or an intranet.

The UTRAN, which communicates with the mobile communication terminal 20 via the Uu interface, includes a plurality of Node-Bs and an RNC.

The RNC controls the node ratio and when the user selects the packet service such as the Internet or intranet as the mobile communication terminal 20, the RNC connects to the SGSN and the Iu interface, and the user selects the circuit service. The city connects with the MSC so that it can talk with other public networks (PLMN, PSDN) or the receiver's mobile terminal.

The UTRAN of FIG. 1 shows a Serving RNC (SRNC) and a Drift RNC (DRNC). The SRNC serves as an access point to a core network, processes a transmission channel, determines a handover, and controls power. 20) is a controller that is initially connected to the mobile communication network by the SRNC, and grasps the mobile information of the mobile communication terminal 20 and the like.

When the mobile communication terminal 20 moves and needs handover, the mobile station 20 makes a request using the RNSAP from the SRNC to the adjacent DRNC.

On the other hand, RNSAP is a signaling protocol defined between SRNC and DRNC.

The RNSAP defines procedures for supporting mobility of a terminal, procedures related to establishing and releasing radio links, and procedures related to measurement.

In addition, RNSAP has various procedures related to the establishment, addition, and release of radio links during handover.

Radio Link Setup is a procedure for instructing the SRNC to newly set up one or multiple radio links with the DRNC.

After deciding to add a radio link, the SRNC sends a Radio Link Setup Request message to the DRNC to establish a radio link to the DRNC.

The DRNC responds with a Radio Link Setup Response message after allocating resources because there is a spare resource for the radio link.

Radio Link Addition Message (Radio Link Addition Message) is a procedure to set up additional radio link to DRNC while radio link is established between a specific terminal and DRNC. SRNC sends radio link addition request message to DRNC. do.

After establishing a corresponding radio link, the DRNC transmits a radio link addition response message to the SRNC.

The Radio Link Addition Failure Message is used when one or more radio links are no longer available. The DRNC sends a Radio Link Failure Indication Message containing the relevant radio link and information to the SRNC.

FIG. 2 is a schematic flowchart of searching for a cell during handover between conventional RNCs.

A request is made using the above-described RNSAP protocol from an SRNC necessary for handover between a conventional controller (RNC) to an adjacent DRNC.

The SRNC requests a handover using a Radio Link Setup Request Message / Radio Link Addition Message (S50).

The DRNC transmits information of a neighbor cell capable of neighboring handovers to the SRNC in a Radio Link Setup Response Message / Radio Link Addition Response Message.

When the SRNC makes a handover request to an adjacent DRNC using the received neighbor cell information, the SRNC determines whether resource allocation for handover of the mobile communication terminal is possible, and if the mobile terminal cannot accept the mobile communication terminal, A link setup / addition failure message is transmitted to the SRNC (S52).

In this case, the SRNC has a problem with another cell search capable of new handover.

The SRNC performs handover processing by searching for an appropriate RNC by performing IUR common measurement between controllers for different cell search, thus causing a lot of load on the corresponding mobile communication system (S54 to S56).

The present invention is to solve the above problems. Neighbor cell information and failure cause information are attached to the radio link addition failure message and radio link setup failure message and provided to the SRNC requesting handover, and are available based on the neighbor cell information even when the mobile terminal fails the headover request. It is an object of the present invention to provide a cell search method for handover of a control period of an asynchronous mobile communication system for smoothly handling handover between RNCs by requesting handover to a neighboring cell having a large amount of resources.

In addition, the present invention can significantly reduce the load for the search of the cell with a lot of available resources when the handover failure of the mobile communication terminal in the SRNC, if it is determined that handover is impossible in the DRNC, having different frequencies within the same coverage The radio link addition failure information and the cause of the failure (Fail cause) information of the neighboring cells in the cell can be added to the Radio Link Addition Failure message and transmitted to the SRNC to inform and retry the radio link. To provide a cell search method for handover of control period of asynchronous mobile communication system that adds neighbor cell information and cause of failure to Radio Link Setup Failure so that SRNC can retry the handover request immediately. The purpose.

In addition, the present invention, if the failure cause (Fail Cause) items added to the Radio Link Addition Failure message (Radio Link Addition Failure) and Radio Link Setup Failure message (Radio Link Setup Failure) is set to Change Cell, It is an object of the present invention to provide a cell search method for handover of a control period of an asynchronous mobile communication system in which the SRNC is informed to retry a handover to another cell, thereby reducing the load and improving the speed of the controller system in case of a handover failure.

The cell search method in the control period handover of the asynchronous mobile communication system of the present invention for achieving the above object is to the DRNC for one cell due to the weak electric field strength of the mobile communication terminal from the SRNC connected to the mobile communication terminal; Step 1 in which the DRNC determines that setup for handover for the corresponding cell is impossible by the radio link setup request / radio link addition request message, and the DRNC identifies radio resources of other cells in the region, Step 2 of identifying neighboring cell information for this much remaining cell, step 3 of DRNC attaches the neighbor cell information to the radio link setup failure / radio link addition failure message sent to the SRNC, SRNC is the message Radio link setup request / radio link addition request message to the other cell with high radio resources Retransmission, and the DRNC includes allocating radio resources for handover of the mobile communication terminal requested by the SRNC, adding the mobile communication terminal to the other cell, and transmitting a response message to the SRNC. Characterized in that.

In addition, in the step 3, the radio link setup failure / radio link addition failure message may include setting the neighbor cell information and the cause of failure as a change cell and transmitting it to the SRNC.

In addition, the radio link setup failure message and the radio link addition failure message may be provided to the SRNC with a failure cause item indicating a neighbor cell information item and failure cause information separately.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a schematic configuration of an asynchronous mobile communication system of the present invention, FIG. 4 is a flowchart of cell search operation during a control period handover of the asynchronous mobile communication system of the present invention, and FIG. 5 is a radio link addition failure message. 6 is an example of a radio link setup failure message, and FIG. 7 is an example of a neighbor cell information message.

 3 shows a mobile communication terminal 60, a plurality of base stations 62, 70, 72, a controller (RNC) 64, 68, and a switch 66, and typically three base stations (node ratios). Indicates that FA (Frequency Alignment) is provided. The base station is typically provided with three sectors to process the mobile communication terminal.

The base stations 62, 70, and 72 are typically composed of three sectors and multi frequency alignment (FA).

The sector of the base station is composed of alpha, beta, and gamma, and covers the wireless section with a radius of 10-20 km from the base station's position according to the type. Perform service by communicating proper data with terminal.

In the three sectors of the base station, an overhead channel for transmitting / receiving data to make the mobile terminal and the mobile communication system aware of each other and traffic for transmitting / receiving actual voice data or service data ) Channel.

In the case of a voice call, one traffic channel is allocated to each mobile communication terminal to make a voice call, and the capacity of a traffic channel that can be used for a sector of a base station is limited. On the other hand, when a mobile subscriber moves, a handover for continuously providing a call or other service is necessary.

The present invention can receive information of another cell (base station) having a large amount of available resources even when handover fails in SRNC, and immediately re-request to the corresponding cell, thereby reducing the load on SRNC, handling handoffs easily, and resources of a mobile communication system. Increase the utilization of

The base station 70 of FIG. 3 indicates that 1FA has no available resources, and 3FA has the most available resources.

4 is a flowchart of a cell search operation during a control period handover of an asynchronous mobile communication system. When the SRNC 64 determines that a handover is necessary because the electric field strength of a specific channel of the mobile communication terminal 60 is weak, a radio link setup request is required. A radio link add request request (RNSAP) is transmitted to the 1FA of the DRNC 68 (S80).

If the DRNC 68 determines that setup for handover for the cell is impossible after receiving the above-described message, the DRNC 68 examines the radio resources of other FA cells within the coverage of the DRNC 68, and checks available resources. The information on this much remaining cell is shown in the UMTS neighbor list of FIG. 7 in the Radio Link Setup / Addition Failure messages 90 and 94 as shown in FIGS. 5 and 6. And Fail Cause (99) items are sent to the change cell (S82).

The DRNC 68 identifies other handoverable cells, and the neighbor cell information item and the failure cause item in the radio link setup failure / addition failure message shown in Figs. Neighbor cell information is attached, and the cause of failure is set as a change cell and transmitted to the SRNC 64.

In addition, by providing a neighbor cell information 98 as shown in FIG. Handover is possible.

When the SRNC 64 determines that there are available resources in the 3FA, the SRNC 64 uses the DRNC 68 to request a radio link setup request / radio link addition request message for handover of the mobile communication terminal to the 3FA. / Addition Request) is retransmitted (S84).

The DRNC 68 adds a radio resource for handover of the mobile communication terminal 60 requested by the SRNC 64 and adds the corresponding mobile communication terminal 60 to 3FA, and a radio link setup response message (Radio Link Setup Response message). Message) / Radio Link Add Response Response message (Radio Link Addition Response Message) is transmitted to SRNC 64 (S86).

The mobile communication terminal 60 is handed over to 3FA having a lot of available resources to continue using the mobile communication service (S88).

5 shows an example of a radio link addition failure message 90 of the present invention, in which a radio resource is added to a DRNC by adding a neighbor cell information item 92 and a fail cause item. Information on neighboring cells with a margin is transmitted to the SRNC in response.

The neighbor cell information is provided in the form as shown in FIG. 7.

6 illustrates an example of a radio link setup failure message 94. As shown in FIG. 5, a neighbor cell information item and a cause of failure are added to the neighboring area where a radio resource is available in the DRNC. The information of the cell is transmitted to the SRNC in response.

FIG. 7 illustrates an example of a neighbor cell information message 98. The radio link addition failure message 90 of FIG. 5 and the radio link setup failure message of FIG. This message is attached to the neighbor cell information.

The DRNC identifies cell information capable of handover due to a marginal radio resource, and sets up the radio link addition failure message 90 and the radio link addition failure message 90 described above in the form of neighbor cell information message as shown in FIG. Send to SRNC with attachment to Radio Link Setup Failure.

Therefore, in the present invention, since the SRNC requests a handover of the mobile communication terminal and in case of failure, the SRNC can receive the neighboring cell information capable of handover in the above-described manner and retry immediately, the SRNC communicates with other RNCs and has a high radio resource. No cell needs to be found, which reduces the load on the system, increases the utilization of radio resources, and speeds up handover processing.

The present invention described above has an effect of maintaining optimal RRM (Radio Resource Management) because radio resource management is performed by the associated RNC (DRNC) having a large number of available resources, and can find an accurate target cell. Therefore, it is effective to increase the operational efficiency of the WCDMA mobile communication system by increasing the utilization of radio resources.

In addition, the present invention takes less time according to the handover procedure and does not need to operate an unnecessary compressed mode.

Claims (3)

The SRNC accessed by the mobile communication terminal has a weak electric field strength, so a DRNC requests a radio link setup request / radio link add request message to a DRNC for handover to the cell. Determining that setup is impossible; Identifying, by the DRNC, radio resources of other cells in the region and determining neighboring cell information for cells in which many resources are available; Transmitting, by the DRNC, the neighbor cell information to the SRNC by attaching a radio link setup failure / radio link addition failure message; The SRNC receives and recognizes the message and retransmits a radio link setup request / radio link addition request message to the other cell having a lot of radio resources; The DRNC includes five steps of allocating a radio resource for handover of the mobile communication terminal requested by the SRNC, adding the mobile communication terminal to the other cell, and transmitting a response message to the SRNC. Cell search method during control period handover of asynchronous mobile communication system. The method of claim 1, In the step 3, the radio link setup failure / radio link addition failure message includes setting a change cell to the neighbor cell information and the cause of failure and transmitting the changed cell to the SRNC. Cell search method when over. The method according to claim 1 or 2, The radio link setup failure message and the radio link addition failure message may include a neighbor cause information item and a failure cause item for informing failure cause information and provide the information to the SRNC. Cell search method during a control period handover of a mobile station.

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