KR20020091880A - Method for hand off in mobile communication system - Google Patents

Abstract

According to an embodiment of the present invention, a method for processing handoff in a mobile communication system includes: when a mobile station performs a hard handoff from a first RNC to a third RNC, requesting addition of a leg for handoff to the MSC server by the first RNC And requesting termination of the MSC server by the MGW and the second RNC, requesting the MGW to terminate a call procedure to the third RNC, and negotiating between the MGW and the second RNC through the negotiation. Establishing a new leg for the mobile station; performing rate control by the second RNC and the third RNC through negotiation; and when the terminating addition is completed, the MSC server establishes a connection with the first RNC. Requesting termination by the MGW, requesting the MGW to resume the interrupted call procedure to the third RNC, negotiating with the first RNC to perform the termination, and after the termination removal, remind DONGKUK this comprises the step of performing the first communication with 3RNC.

Description

Handoff method in mobile communication system {METHOD FOR HAND OFF IN MOBILE COMMUNICATION SYSTEM}

The present invention relates to a handoff method in a mobile communication system, and more particularly, to a method for processing hard handoff in an asynchronous mobile communication system.

IMT2000 (International Mobile Telecommunication 2000), one of the mobile communication systems, was reviewed by ITU-R (formerly CCIR) as Future Public Land Mobile Communication Systems (FPLMTS) since mid-1890, and ICG-FPLMTS (Intersector Coordination Group) in February 1997. -FPLMTS) agreed to the official name "IMT-2000" at the meeting. Since then, ITU-T and ITU-R have promoted single standardization of ITM-2000 in cooperation with each other, but by introducing the concept of IMT-2000 family at 1998 ITU-T conference, IMT-2000 international single standardization is not possible. The 3GPP DS-WCDMA (UMTS: Universal Mobile Telecommunication System) method in Europe and the 3Gpp2 MC-WCDMA (cdma2000) method in North America are compatible and standardized.

Meanwhile, in the mobile communication system, there are two handoff methods for maintaining communication when the mobile station moves out of the cell that is currently being served during the communication to another cell. One is a soft handoff that allocates a channel from a base station targeted for handoff during communication and communicates using a plurality of channels together with a channel received from a currently serving base station, and then cuts a channel whose channel quality falls below a certain reference value. hand off), and second is a hard hand off during communication, which first disconnects a channel received from a currently served base station and attempts to access a neighboring base station. The hard handoff has a problem that the call is instantly disconnected by switching. Therefore, there is a need for a seamless call maintenance method during hard handoff.

Accordingly, an object of the present invention is to provide a method for performing hard handoff without disconnection in a mobile communication system.

Another object of the present invention is to provide a method for performing hard handoff without call break using a call mixer in a UMTS system.

In order to achieve the above objects, a mobile switching center (MSC) server performing a call processing function, a media gateway (MGW) performing a call mixer function for handoff, and a first RNC corresponding to a handoff source Radio network controller), a second RNC in which a new leg is set up for handoff, and a third RNC corresponding to a handoff target, wherein the mobile station hardly moves from the first RNC to the third RNC. In the case of handoff, the first RNC requests the MSC server to add a leg for handoff, the MSC server requests the MGW and the second RNC to add the termination, and the MGW Requesting that the third RNC stop the call procedure, and the MGW and the second RNC negotiate to establish a new leg for the mobile station, and the second RNC and the third RNC communicate with each other; Performing rate control; and, when the terminating addition is completed, the MSC server requests terminating removal to the first RNC and the MGW, and the MGW sends the interrupted call pro to the third RNC. Requesting the resumption of a procedure, negotiating with the first RNC to perform termination, and after the termination, the mobile station performs communication with the third RNC.

1 is a diagram illustrating a configuration of a UMTS system according to an embodiment of the present invention.

2A and 2B illustrate a hard handoff procedure in a UMTS system according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, the present invention describes a method of seamlessly maintaining a call by using a call mixer method when switching a call by hard handoff in an asynchronous mobile communication system (UMTS system). The call mixing method according to the prior art is a function of supporting a conference call such as a three-way call and a six-way call as an additional function of the call processor. The present invention applies the conference call method to a media gateway during handoff so that a call of a mobile station can be handed off to another base station (RNC) without disconnection.

1 is a block diagram of a UMTS system according to an embodiment of the present invention. 1 illustrates a configuration of a handoff situation.

As shown, a mobile switching center (MSC) is separated into an MSC server 100 and a media gateway (MGW) 400. The MSC server 100 performs a function for call processing in a circuit switched domain. The MSC server 100 includes a first RANAP instance 110, a second RANAP instance new 120, and an instance bi CC 130. The media gateway (MGW) 400 performs a function as a media gateway. The media gateway 400 includes a T1 instance 410, a T3 instance 420, and a T2 instance 430. The first RNC 200 and the second RNC 300 perform functions such as inter-cell handoff processing and call control. Here, the first RNC 200 includes a third RANAP instance 210 and a first IUUP instance (Iu UP term. A) 220, and the second RNC 300 includes a fourth RANAP instance 310 and a second IUUP instance (Iu UP term.b). In this case, a predetermined protocol for exchanging information between the MSC server 100 and the MGW400 should be defined. For example, the Mc interface is used. The instances 110 to 130 of the MSC server 100 are connected to the corresponding instances 410 to 430 through the Mc, respectively. Meanwhile, the MSC server 100 and the RNCs 200 and 300 are connected to the Iu interface, and the MGW400 and the RNCs are also connected to the Iu interface.

Looking at the handoff processing operation based on the above configuration is as follows.

First, after the new Iu interface is set up, that is, after the Iu interface is set up on the second RNC300 side, the original TrFO relationship AB and the target TrFO relationship A'B exist in parallel until the previous link is released. Here, the instance 420 in the MGW400 initializes with the second RNC 300. The T2 instance 430 hides the initialization performed in the instance 420 to the handoff target RNC-B. The T2 instance 430 sends a 'SUSPEND' frame to the partner TrFO to prevent the A side handoff procedure from performing an interaction such as rate control on the B side. After relocation, the TrFO partner is informed of 'RESUME' to proceed to the normal mode. If the option to remove the call mixer after call setup is set, the entire call mixer needs to be inserted before performing the hard handoff. Initialization data needs to be used within the media gateway 400. After handoff, the call mixer is removed again and the media gateway 400 again acts as a pure ALL2 switch.

2A and 2B illustrate a handoff processing procedure according to an embodiment of the present invention. A case where the mobile handoffs from the first RNC200 to the third RNC (RNC-B) will be described. Here, a new leg is set to the second RNC300 during handoff for call matching (or trilateral call) according to the present invention. After the call mixing is completed, the previous termination set to the first RNC is removed. Then, the second RNC300 completes the handoff of the call of the mobile station to the third RNC.

Referring to FIG. 2A, first, in step 301, the first RNC 200 transmits a 'Relocation Requested' message to the MSC server 100 requesting Iu interface setting to the second RNC 300. In operation 203, the MSC server 100 transmits an 'Add.Req' message to the media gateway 400 to insert a new terminal for user data between the media gateway and the RNC. At this time, the protocol between the MSC server 100 and the media gateway 400 uses H.248 of the ITU-T. In step 205, the media gateway 400 transmits a 'SUSPEND' message to the RNC-B, which is a handoff target, to stop any UP call procedures (eg, rate control).

In step 207, the media gateway 100 transmits an 'Add.Reply' message to the MSC server 100 to allow relocation resource allocation. In operation 209, the MSC server 100 transmits a 'Relocation Request' message requesting relocation to the second RNC300. That is, the MSC server 100 starts to allocate an Iu leg to the second RNC 300. Then, in step 211, the second RNC300 transmits an 'ERQ' message to the media gateway 400 to perform AAL2 link establishment between the second RNC300 and the media gateway 400. In step 213, the media gateway 400 transmits an 'ECF' message in response to the ERQ message.

In step 215, the second RNC 300 transmits an 'INT' message to the media gateway 400 to perform initialization. That is, the IuUP instance 320 of the second RNC 300 performs initialization. In step 217, the media gateway 300 (T3 instance 420) initializes the IuUP instance 320 of the second RNC 300 with stored RFCI mappings corresponding to a previous A-B TrFO connection. That is, an 'INT' message is transmitted to the second RNC 300. Here, after performing relocation, the open point becomes an initial value for frame numbering. Upon receiving the INT message, the second RNC 300 transmits an 'INT ACK' message to the media gateway 400 in response to step 219. After successfully performing Q.2360 setup and IuUP initialization, the second RNC 300 recognizes that resource allocation has been successfully performed. In operation 221, the second RNC 300 transmits a 'Relocation Request Ack' message to the MSC server 100 in response to the relocation request message.

Then, the MSC server 100 transmits a 'ModifyReq' message to the media gateway 400 in step 233. The media gateway 400 receiving the ModiftReq message performs a call mixer according to the present invention. In step 225, the message 'ModifyReply' is transmitted to the MSC server 100 in response. Then, the MSC server 100 transmits a 'Relocation command' message to command the relocation to the first RNC200 in step 227. That is, the MSC server 100 triggers a relocation execution. Referring to FIG. Continue to explain.

In operation 229, the second RNC 300 transmits a 'Relocation Detect' message to the MSC server 100. In operation 231, the second RNC 300 and the opposite RNC-B directly perform rate control. After performing the rate control, the second RNC 300 transmits a 'Relocation Complete' message indicating completion of relocation to the MSC server 100 in step 233. Then, in order to release the previous Iu interface, the MSC server 100 transmits a 'Subtract Req' message to the media gateway 400 in step 235 and transmits an 'Iu Release Command' message to the first RNC 200 in step 237. In response to receiving the 'Subtract Req' message, the media gateway 400 transmits a 'RESUME' message to the counterpart RNC-B requesting to resume call procedures in step 239.

Thereafter, in step 241, Q.2630 between the first RNC 200 and the media gateway 400 is released. In operation 248, the first RNC 200 transmits an 'Iu Release Complete' message indicating release of an Iu interface to the MSC server 100. In step 245, the media gateway 400 transmits a 'Subtract Reply message' to the MSC server 100 in response to the 'Subtract Req' message. Thereafter, in step 247, a TrFO is performed between the second RNC 300 and the counterpart RNC-B. Thereafter, the mobile station communicates with the third RNC.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

As described above, the present invention can prevent a momentary call disconnection that occurs during hard handoff. In addition, it has the effect of maintaining user traffic without noise.

Claims (1)

Mobile switching center (MSC) server performing call processing function, media gateway (MGW) performing call mixer (call mixer) function for handoff, first radio network controller (RNC) corresponding to handoff source, handoff A handoff processing method in a mobile communication system comprising a second RNC in which a new leg is set and a third RNC corresponding to a handoff target, When the mobile station performs a hard handoff from the first RNC to the third RNC, requesting the first RNC to add a leg for handoff to the MSC server; Requesting the MSC server to add an end to the MGW and the second RNC; Requesting that the MGW stop the call procedure from the third RNC; Establishing a new leg for the mobile station through negotiation between the MGW and the second RNC and performing rate control through negotiation with the second RNC and the third RNC; When the termination addition is completed, requesting termination removal from the MSC server to the first RNC and the MGW; The MGW requesting the third RNC to resume the interrupted call procedure and negotiating with the first RNC to perform termination; After the termination is removed, the mobile station communicating with the third RNC.