KR20040029722A - Method of soft handoff in universal mobile telecommunications system - Google Patents

Abstract

PURPOSE: A soft handover method in UMTS(Universal Mobile Telecommunications Systems) is provided to update an active set by a mobile station while performing a soft handover process, and to confirm whether a physical channel is perfectly set, then to transmit a soft handover complete message to a UTRAN, thereby more stably carrying out the soft handover process. CONSTITUTION: If a mobile station receives an active set update message from a UTRAN(12), the mobile station analyzes the active set update message(14). The mobile station additionally deletes a wireless link of an active set according to wireless link delete/add information of the active set update message(16). The mobile station starts setting a physical channel(18), and decides whether synchronization is carried out on the physical channel(20). If so, the mobile station generates an active set update complete message, transmits the message to the UTRAN(22), and informs that a soft handover process is completed.

Description

Soft handover method in general mobile communication system {METHOD OF SOFT HANDOFF IN UNIVERSAL MOBILE TELECOMMUNICATIONS SYSTEM}

The present invention relates to universal mobile telecommunications systems (hereinafter referred to as " UMTS "), and more particularly to a method of making soft handover in UMTS.

UMTS uses a cell structure to support many users with limited radio frequency resources. In other words, all the serviceable areas are allocated to a small area called a cell, and radio frequency resources are allocated to each cell to support more users. Here, the cell refers to an area where a service is provided by a specific base station.

Accordingly, when a mobile terminal located in a specific cell moves to another cell in UMTS, service must be continuously performed even in a cell moved through hand-over. In other words, the handover is moved from the base station (hereinafter, referred to as "source base station") area (hereinafter referred to as "cell") where the mobile terminal is serving to another base station (hereinafter referred to as "target base station"). When moving, it means converting a call path into a moved cell in order to keep a call. To this end, the mobile station measures received signal strengths from adjacent cells and transmits them to base stations to determine whether the handover is possible, and the base stations determine handovers according to the received signal strengths.

The handover may be divided into a soft handover and a hard handover. The soft handover is performed in such a manner that when the handover is required, the mobile station establishes a new channel with the target base station while the channel with the source base station is established, and disconnects any one channel at a predetermined time point.

1 is a diagram conceptually illustrating the soft handover performed in UMTS. Referring to FIG. 1, it can be seen that the mobile terminal 114 located in Cell 1 serviced from the source base station 110 is moving to the handover region. Typically, the mobile terminal 114 simultaneously receives the received signal from the target base station 112 corresponding to the received signal from the source base station 110 and another adjacent base station. In addition, the mobile terminal 114 transmits the measured values of the strengths of the two received signals to each of the base stations 110 and 112, and receives them through the base stations 110 and 112 (RNC: Radio Network Controller (RNC) ( 120 determines whether a handover is required and performs a handover.

In other words, when the mobile terminal 114 enters a soft handover region of the base station 110 and the base station 112, the mobile terminal 114 is a radio link with the base stations 110 and 112. ). In this case, a set of cells in which a radio link is established with the mobile station 114 is called an active set. The mobile terminal 114 periodically checks channel states with the active set cells and transmits a measurement message to the base stations 110 and 112. The base stations 110 and 112 transmit the received measurement message to the wireless network controller 120, and the wireless network controller 120 sends an active set update message to the mobile terminal 114 to perform soft handover. send. The mobile terminal 114 deletes and adds a radio link of a related cell that is currently configured according to the received active set update message. In addition, the mobile terminal 114 performs a physical layer synchronization process. By performing the synchronization process, the mobile station 114 can determine an uplink Dedicated Physical Control Channel / Dedicated Physical Data Channel (DPCCH) transmission time point for a call with a new cell. The mobile station 114 processes the remaining link connection of the active set update message, and transmits an active set update complete message to the base station (notifying the successful termination of the procedure through an uplink uplink dedicated control channel (DCCH) channel). 110, 112).

However, in the conventional soft handover process as described above, the mobile terminal 114 receives the active set update message and performs the physical layer synchronization process. send. This means that even if the physical layer synchronization performed to transmit consecutive uplink DPCCH / DPDCH with a new cell actually fails, i.e., even if the soft handover fails substantially, the base station recognizes that the soft handover is successful. Cause problems.

As a result, an error occurs at the time of transmission of data to be transmitted in the uplink, which may cause loss of data, and even a call may be disconnected.

Accordingly, an object of the present invention is to provide a soft handover processing method with high stability.

In order to achieve the above object, the present invention is a general mobile communication system, a process for configuring and transmitting an active set update message by analyzing a measurement message received from a mobile terminal by a UMTS Terrestrial Radio Access Network (UTRAN); A terminal deleting / adding a radio link according to the active set update message, and synchronizing a physical channel with respect to the added radio link within a predetermined time to determine whether the physical channel is normally established; When the physical channel is set within a predetermined time, the process of generating an active set update complete message and transmitting it to the UTRAN.

1 conceptually illustrates a soft handover in a general purpose mobile communication system;

2 is an operation flowchart of a mobile terminal according to the present invention;

3 is a diagram illustrating a protocol stack structure of a mobile terminal and a UTRAN to which the present invention is applied.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. And a detailed description of known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

In general, UMTS is a plurality of radio network subsystems (Radio Network) consisting of a core network (not shown), a plurality of base stations (110, 112) and a radio network controller 120, as shown in FIG. Subsystems) and the mobile terminal 114. The base stations 110 and 112 are in charge of a wireless interface with the mobile terminal, and the wireless network controller 120 controls the connected base stations 110 and 112, manages information of each mobile terminal, and is responsible for data transmission with the core network. . In addition, the core network, the radio network controller 120, and the base stations 110 and 112 are referred to as a UTRAN (UMTS Terrestrial Radio Access Network) 120.

In the UMTS, the soft handover according to the present invention is performed by the mobile terminal 114 and the UTRAN 120 transmitting and receiving a message for performing the soft handover. When the mobile terminal 114 enters a soft handover region, the mobile terminal 114 connects the UTRAN 120 with a plurality of radio links to establish an active set and periodically checks channel states with the active set cells. The measurement message is transmitted to the UTRAN 120. The UTRAN 120 analyzes the measurement message and transmits an active set update message to the mobile station 114 when it is determined that soft handover is required. In addition, the UTRAN 120 recognizes that the soft handover is successful when the active set update completion message is received from the mobile station 114 within a predetermined time. The mobile terminal 114 deletes and adds a radio link of a related cell that is currently configured according to the received active set update message. The mobile terminal 114 checks whether the physical layer synchronization process is performed within a predetermined time. If the synchronization process of the physical layer is achieved within a predetermined time, the mobile terminal 114 transmits an active set update completion message to the UTRAN 120 to indicate that the soft handover was successful. If the synchronization process of the physical layer is not performed within the predetermined time, the mobile terminal 114 does not transmit an active set update completion message to the UTRAN 120, thereby notifying that the soft handover has failed.

The detailed operation of the wireless terminal 114 and the wireless terminal protocol stack for soft handover as described above will be described with reference to FIGS. 2 and 3. 2 is an operation flowchart of a mobile terminal according to the present invention, and FIG. 3 is a diagram illustrating a protocol stack structure of a mobile terminal and a UTRAN to which the present invention is applied.

First, referring to FIG. 2, the mobile terminal 114 receives an active set update message indicating soft handover from the UTRAN 100.

Referring to FIG. 2, when the mobile terminal 114 receives the active set update message from the UTRAN 100 in step 12, the mobile terminal 114 proceeds to step 14. In step 14, the mobile terminal 114 analyzes the active set update message and proceeds to step 16. In step 16, the mobile terminal 114 further deletes the radio link of the active set according to the radio link deletion / addition information of the active set update message and proceeds to step 18. In step 18, the mobile terminal 114 starts the channel setting and proceeds to step 20. In step 20, the mobile terminal 114 determines whether the physical channel is synchronized within a predetermined time. The mobile terminal 114 proceeds to step 22 when the physical channel is synchronized within the predetermined time, and proceeds to step 24 when the physical channel is not synchronized within the predetermined time. In step 22, the mobile terminal 114 generates an active set update completion message and transmits it to the UTRAN 100, thereby informing that the soft handover is completed and ending the soft handover. Meanwhile, in step 24, the mobile terminal 114 does not generate an active set update completion message, thereby informing the UTRAN 100 that the soft handover has failed and terminates the soft handover.

The operation of the mobile terminal 114 according to the soft handover according to the protocol stack of the mobile terminal 114 has been described in detail below.

Referring to FIG. 3, the mobile terminal 114 and the UTRAN 120 access radio resource control (RRC) layers 200 and 300, radio link control (RLC) layers 202 and 302, and media access, respectively. It consists of a Media Access Control (MAC) layer 204 and 304 and a physical layer 206 and 306. The radio resource control layer (200, 300) is a call control layer (CC: Call Control) responsible for call setup and release, mobility management layer (MM: Mobility Management) responsible for authentication and registration of service users, radio resource allocation and management It is in charge of controlling the overall soft handover process in accordance with the present invention. The radio link control layer (202, 302) is responsible for a reliable data transmission function, the medium access control layer (204.304) is responsible for the function of efficiently providing a plurality of services at the same time, the physical layer (206, 306) is a practical radio It is in charge of the transmission.

The radio resource control layer 300 of the UTRAN 100 receives the measurement message from the mobile terminal 114 and analyzes the measurement message. When it is determined that soft handover is necessary, the radio resource control layer 300 generates an active set update message through the physical layer 306. Transmit to mobile terminal 114. The active set update message is a message for controlling a radio link connection state between the mobile station 114 and the UTRAN 100, and includes radio link addition information, radio link removal information, and radio. Combined radio link addition and removal information.

The physical layer 206 of the mobile terminal 114 transmits the received active set update message to the radio resource control layer 200 through the medium access control layer 204 and the radio link control layer 202. The radio resource control layer 200 analyzes the received active set update message and transmits radio link addition and removal information to the physical layer 206. The physical layer 206 first adds the radio links indicated in the radio link addition information, and then removes the link included in the radio link removal information. If the active set managed by the mobile terminal 114 is saturated, then the radio link to be removed is first removed, and then a new radio link is added. The physical layer 206 then starts physical channel synchronization for the new radio link and informs the radio resource control layer 200 of this. The radio resource control layer 200 checks whether a signal indicating completion of synchronization is received from the physical layer 206 within a predetermined time after the synchronization of the physical layer 206 is started. When the synchronization completion signal is received within the predetermined time, the radio resource control layer 200 determines that the physical channel is successfully set, generates an active set update completion message and transmits it to the UTRAN 100.

On the other hand, the radio resource control layer 200 determines that the configuration of the physical channel has failed, if the signal indicating the completion of the synchronization is not received from the physical layer 206 within a predetermined time after the synchronization start of the physical layer 206, the active set Do not generate an update complete message.

The predetermined time, which is a criterion for determining the successful establishment of a physical channel, is determined by system information received from the UTRAN 100, and the active set update completion message is a message indicating that soft handover has been successfully performed.

As described above, the present invention can safely perform soft handover by transmitting a soft handover complete message to the UTRAN 100 after the physical channel is completely configured.

In the above description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be defined by the described embodiments, but should be determined by the equivalent of claims and claims.

As described above, the present invention can perform soft handover with high stability by checking whether the physical channel is completely set after the active set update and transmitting a soft handover complete message to the UTRAN when performing the soft handover. have.

Claims (4)

The soft handover method of the universal mobile communication system UTRAN (UMTS Terrestrial Radio Access Network) analyzes the measurement message received from the mobile terminal to configure and transmit an active set update message, The mobile terminal deleting / adding a wireless link according to the active set update message, and determining whether the physical channel is normally established by synchronizing a physical channel with respect to the added wireless link within a predetermined time; And generating, by the mobile terminal, an active set update completion message and transmitting it to the UTRAN when the physical channel is set within a predetermined time. The method of claim 1, further comprising the mobile terminal not generating the act set update completion message if the physical channel is not set within a predetermined time. The soft handover method of the universal mobile communication system Deleting / adding a radio link according to an active set update message received from a UMTS Terrestrial Radio Access Network (UTRAN) and determining whether the radio channel is normally established by synchronizing the physical channel with respect to the added radio link within a predetermined time. Process, And if the physical channel is set within a predetermined time, generating an active set update completion message and transmitting it to the UTRAN. 4. The method of claim 3, further comprising: not generating the active set update completion message if the physical channel is not set within a predetermined time.