KR20130044506A - Method for handover between pico cells - Google Patents

Abstract

PURPOSE: A handover method between small base stations is provided to reduce an unnecessary network load during a handover between pico base stations. CONSTITUTION: A PeNB-GW(Pico eNB(evolved Node B)-GateWay)(205) receives a path switching request message from a target pico eNB(203). The PeNB-GW generates a response message to the path switching request message using security context information of a terminal(232). The PeNB-GW transmits the generated response message to the target pico eNB(237). The security context information of the terminal is obtained from the initial context request message received from an MME(Mobility Management Entity)(207). [Reference numerals] (232) Generate a response message using prestored security context information of a terminal

Description

Handover method between small base stations {METHOD FOR HANDOVER BETWEEN PICO CELLS}

The present invention relates to handover in a mobile communication system. More particularly, the present invention relates to handover between pico cells in a mobile communication system.

Recently, interest in picocells has been increasing in the cellular mobile communication system in order to increase coverage and improve data throughput of existing macrocells. The pico cell refers to a small cell installed in an office or a house in a building to assist a macro cell and support a terminal in a surrounding area. The pico cell may also be called a femtocell or a microcell. Meanwhile, hereinafter, "cell" may be used as the same meaning as "base station", and the macro cell or macro base station may be abbreviated as "cell" or "base station".

Meanwhile, in the current LTE-Advanced standard, a method for improving system performance using the pico cell has been actively discussed.

1 is a view for explaining the configuration of a Long Term Evolution (LTE) system including a macro cell and a pico cell.

The LTE system includes MME / S-GWs 111 and 112 as core networks and eNBs 121, 123, 125, 141, 143, 145 and 147 as base stations. Meanwhile, the eNBs may be classified into macro eNBs 121, 123 and 125, which are macro base stations, PeNB (Pico eNB) 141 and 143, which are pico base stations, and HeNB (Home eNB) 145 and 147, which are home base stations. have. However, since the home base station performs only the same function as the pico base station, the home base station is included in the pico base station in a broad sense.

Meanwhile, the macro eNBs 121, 123, and 125 directly interwork with the MME / S-GWs 111 and 112 through an S1 interface, but the PeNB / HeNBs 141, 143, 145, and 147 are core networks. That is, in order to minimize the influence of the MME / S-GWs 111 and 112, the interworking with the MME / S-GWs 111 and 112 is performed through a pico gateway (Pico GW or PeNB GW, HeNB GW) 130.

The pico GW 130 is located between the PeNB / HeNBs 141, 143, 145, 147 and the MME / S-GWs 111, 112 and the MME / S for the PeNB / HeNBs 141, 143, 145, 147. -GW (111, 112) and the MME / S-GW (111, 112) should work as PeNB / HeNB (141, 143, 145, 147). Pico GW 130 interworks with PeNB / HeNBs 141, 143, 145, 147 and MME / S-GWs 111, 112 via S1 interface and PeNB / HeNBs 141, 143, 145, 147 Provides aggregation and distribution capabilities for

In the LTE system, an X2 interface for interworking between eNBs is defined. That is, the macro eNBs 121, 123, and 125 may exchange cell and neighbor information through the X2 interface and support X2 handover to minimize the load on the core network and ensure mobility of the UE. PeNB / HeNB 141, 143, 145, 147 must interwork with pico GW 130 for the X2 interface with macro eNBs 121, 123, 125. In addition, interworking with the pico GW 130 for the X2 interface between the PeNB / HeNBs (141, 143, 145, 147).

Meanwhile, there are three ways to provide handover between PeNB / HeNBs 141, 143, 145, and 147. The first scheme is an X2 handover using an X2 interface via the Pico GW 130, and the second scheme is a direct X2 handover using a direct X2 interface between PeNB / HeNBs 141, 143, 145, and 147. The third method is S1 handover using the S1 interface through the pico GW (130). Normally the first approach, X2 handover via Pico GW 130, is preferred to minimize handover latency.

However, in the case of X2 handover between PeNB / HeNBs 141, 143, 145, and 147 through the existing Pico GW 130, when the handover is completed, the target PeNB / HeNB is the MME / S-GW 111, 112. Send a S1 PATH SWITCH REQUEST message to inform the handover that the handover is complete, request to switch the downlink data path to the target PeNB / HeNB, and receive an acknowledgment (ACK). . At this time, since the entity functioning as an eNB in the MME / S-GW (111, 112) position is the pico GW 130, the source PeNB / HeNB and the target PeNB / HeNB are the same network in the MME / S-GW (111, 112) position. Becomes an entity

In the above case, the PATH SWITCH REQUEST / ACK message transmitted and received by the target PeNB / HeNB with the MME / S-GWs 111 and 112 becomes an unnecessary message transmission / reception procedure, thereby causing a network load. May increase and load increases of the pico GW 130 and the MME / S-GWs 111 and 112 may occur.

Therefore, there is a need for a handover scheme that can reduce unnecessary network load when performing handover between PeNB / HeNBs 141, 143, 145, 147.

The present invention provides a handover method between pico base stations for reducing unnecessary network load during handover between pico base stations.

The present invention provides a handover method for reducing handover delay time during handover between pico base stations.

The present invention provides a method in which the MME does not process a handover message during handover between pico base stations.

According to an embodiment of the present invention, a handover method of a pico gateway (GW) interworking with the pico base stations during handover between the pico base stations may include: receiving a path switching request message from a target pico base station; And generating a response message in the path switching request message by using security context information of one terminal, and transmitting the generated response message to the target pico base station.

According to an embodiment of the present disclosure, a handover method of a target pico base station during handover between pico base stations linked to a pico gateway (GW) may include: transmitting a path switching request message to the pico gateway; And receiving a response message from the pico gateway in response to the path switching request message generated by the pico gateway using security context information of the terminal.

According to the present invention, when a handover occurs between pico base stations, there is an advantage of reducing the network load by transmitting and receiving a message with the MME.

1 is a diagram illustrating a network configuration of a Long Term Evolution (LTE) system including a macro cell and a pico cell;
2 is a diagram illustrating a handover procedure between pico base stations according to an embodiment of the present invention;
3 is a diagram illustrating a process of acquiring a security context by a pico GW through a registration procedure of a terminal according to an embodiment of the present invention;
4 is a diagram illustrating a process of obtaining a security context by a pico GW through a context change according to an embodiment of the present invention;
5 is a diagram illustrating a process of acquiring a security context by a pico GW through an S1 handover procedure according to an embodiment of the present invention;
FIG. 6 is a diagram illustrating an operation of a pico GW for a pico base station handover scheme according to an embodiment of the present invention. FIG.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be noted that the same elements among the drawings are denoted by the same reference numerals whenever possible. Also, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

Prior to the description of the present invention, the main concepts of the present invention will be explained.

The present invention proposes an efficient handover scheme when handover between PeNB / HeNB occurs through a pico GW in an LTE system.

In the present invention, if a handover occurs between PeNB / HeNBs, the MME / S-GW is not informed of the fact that a handover occurs between PeNB / HeNBs. It reduces the load on the network to optimize the system and reduces the handover load of the MME / S-GW. Hereinafter, the handover scheme proposed by the present invention may be referred to as "hiding handover". In addition, PeNB / HeNB may hereinafter be referred to as a “pico cell” or “pico base station”.

In the present invention, in order to notify the MME / S-GW of the handover occurrence between the pico base stations, the pico GW processes the final handover message (for example, S1 PATH SWITCH REQUEST / ACK) to improve the handover processing time. In short, it supports faster X2 handover.

Meanwhile, in order to process the final handover message in the pico GW, the pico GW must have security context information about the terminal in advance. To this end, in the present invention, the pico GW receives and stores the security context information of the terminal from the MME / S-GW through (1) the terminal registration procedure, (2) context change procedure, and (3) S1 handover procedure. Upon over, the stored security context information is used to allow the pico GW to process the final handover message.

2 is a diagram illustrating a pico base station handover procedure according to an embodiment of the present invention.

When a handover situation between pico base stations occurs, in step 211, the source pico base station 201 transmits an X2 handover request (X2 HO REQUEST) message to the pico GW 205 to trigger an X2 handover. In step 215, the pico GW 205 transmits the X2 handover request message to the target pico base station 203, and receives the response (ACK), the pico GW 205 in step 219 is the source pico base station 201 X2 handover response message (X2 HO REQUEST ACK) for the X2 handover request is transmitted.

Upon receiving the X2 handover response message, the source pico base station 201 sends a handover command (HO COMMAND) message to instruct a terminal (not shown) to perform a handover to the target pico base station 203 in step 221. In step 223 and 224, an SN STATUS TRANSFER message is transmitted to the target pico base station 203 via the pico GW 205. In operation 225, the source pico base station 201 forwards the data to the pico GW 205. In step 229, the handover is completed.

In step 231, the target pico base station 203 transmits a PATH SWITCH REQUEST message to the pico GW 205 to inform that the handover is complete. The Pico GW 205 generates an S1 PATH SWITCH REQUEST ACK for the path switching request message using the security context information stored for the UE in step 232, and in step 237. The S1 path switching response message is transmitted to the target pico base station 203.

In step 239, the target pico base station 203 transmits an X2 UE context release request message to the source pico base station 201 via the pico GW 205 to inform that the handover is completed. The base station 201 allows the resource used for communication with the terminal to be released.

Although the MME 207 is shown in the description of the present invention of FIG. 2 above, it is not involved in the handover procedure of the present invention. This is because the target pico base station 203 does not notify the handover fact to the MME 207 through the pico GW 205 in the present invention as described above. That is, although the target pico base station 203 transmits a S1 PATH SWITCH REQUEST message to the MME 207 through the pico GW 205, the present invention transmits the path switching request message to the pico GW 205. ), The pico GW 205 responds (S1 PATH SWITCH REQUEST ACK). As such, the present invention does not notify the MME 207 of the handover occurrence.

Hereinafter, as described in step 232 of FIG. 2, the pico GW 205 describes a procedure of acquiring security context information about a corresponding terminal required to generate a response message for a path switching request. FIG. 3 is a procedure for acquiring a security context through (1) a registration procedure of a terminal, FIG. 4 is a procedure for acquiring a security context through (2) a context change procedure, and FIG. 5 is a procedure for (3) an S1 handover procedure. This is a procedure for obtaining security context information.

3 is a diagram illustrating a process of obtaining a security context by the pico GW through the registration procedure of the terminal according to an embodiment of the present invention.

In order to receive a network service, the UE needs to undergo a network registration process, which is called a network attachment. 4 illustrates the network attach procedure.

When the terminal (not shown) accesses the source pico base station 201, the source pico base station 201 transmits an S1 initial UE message to the pico GW 205 in step 301. In step 303, the Pico GW 203 transmits an S1 Initial UE Message to the MME 207. In steps 305 and 307, the MME 207 transmits a NAS message to the source pico base station 201 through the pico GW 205 for authentication of the terminal. Subsequently, if authentication of the terminal is successful, in step 309, the MME 207 may display an S1 Initial Context Setup Request message including path information for providing a traffic service to the terminal. To send). The S1 initial context setup request message includes security context information for the corresponding terminal as well as the route information. In step 311, the pico GW 205 stores the security context information to provide a "hiding" handover proposed by the present invention. Thereafter, the pico GW 205 transmits the initial context setup request message to the source pico base station 201 in step 313, receives a response thereto and transmits the response to the MME 207 in step 315.

4 is a diagram illustrating a process of obtaining a security context by a pico GW through a context change according to an embodiment of the present invention.

After the network attachment process described in FIG. 3 is completed in order for the terminal to receive the network service, it may be necessary to partially modify the context information of the terminal in some cases. In this case, the MME 207 transmits an S1 UE context modification request message including the security context information of the terminal to the pico GW 205 in step 401. In step 403, the Pico GW 205 stores the security context information to provide a "hiding" handover proposed by the present invention. The pico GW 205 transmits the S1 UE context change request message to the source pico base station 201 in step 405, receives the response in step 407, and forwards the response to the MME 207 in step 409.

FIG. 5 is a diagram illustrating a process in which a pico GW acquires a security context through an S1 handover procedure according to an embodiment of the present invention.

When an S1 handover situation occurs, in step 501 and 503, the source pico base station 201 transmits an S1 handover request (S1 HO REQUIRED) message to the MME 207 through the pico GW (205). In step 503, the MME 207 transmits an S1 handover request (HO REQUEST) message to the pico GW 205. The S1 handover request (HO REQUEST) message includes a security context for the terminal. In step 507, the pico GW 205 stores the security context information to provide a "hiding" handover proposed in the present invention. In steps 509 and 511, the pico GW 205 transmits an S1 handover request message to the target pico base station 203, receives the response, and transmits the response to the MME 207 in step 513.

In steps 515 and 517, the MME 207 transmits an S1 handover command message to the source pico base station 201 through the pico GW 205. The source pico base station 201 transmits an S1 ENB STATUS TRANSFER to the MME 207 in steps 519 and 521, and the MME 207 sends an S1 MME status transfer message (steps 523 and 525). S1 MME STATUS TRANSFER) is transmitted to the target pico base station 203. The target pico base station 203 transmits an S1 handover notification (HO NOTIFY) message to the MME 207 via the pico GW 205 in steps 527 and 529. Thereafter, the resources of the source pico base station are released through steps 531 and 533.

FIG. 6 is a diagram illustrating an operation of a pico GW for a pico base station handover scheme according to an embodiment of the present invention.

In step 601, the pico GW acquires and stores security context information of the corresponding terminal through a predetermined procedure. The predetermined procedure may be a registration procedure of the terminal described in FIGS. 3 to 5, a context information change procedure after the registration procedure, and an S1 handover procedure.

In step 603, the S1 path switching request message is received from the target pico base station in the handover procedure. In step 605, a response message for the S1 path switching request is transmitted to the target pico base station by using the security context information of the corresponding terminal obtained in step 601.

As described above, in the present invention, when performing X2 handover between pico base stations through the pico GW, the MME does not notify the handover. According to the configuration of the present invention, when the handover between the pico base station occurs, the network load by the message transmission and reception with the MME can be reduced. In addition, it is possible to reduce the handover load of the MME 으로써 system by hiding the handover situation between pico base stations to the MME handling the call for a large number of subscribers. In addition, the handover processing time may be shortened by processing the last handover related message processed by the MME when the handover between the pico base stations occurs in the pico GW.

Claims (8)

In the handover method of the pico gateway (GW) interworking with the pico base stations when the handover between the pico base stations,
Receiving a path switching request message from a target pico base station;
Generating a response message in the path switching request message by using the security context information of the terminal acquired in advance;
And transmitting the generated response message to the target pico base station.
The method of claim 1, wherein the security context information of the terminal,
Method of handover of the pico gateway, characterized in that obtained from the initial context request message received from the MME during the registration procedure of the terminal.
The security context procedure of claim 1, wherein
The handover method of the pico gateway, characterized in that obtained from the initial context change request message received from the MME during the context change procedure after the registration procedure of the terminal.
The security context procedure of claim 1, wherein
A method of handover of a pico gateway, characterized in that obtained from the S1 handover request message received from the MME of the S1 handover procedure of the terminal.
In the handover method of the target pico base station at the time of handover between pico base stations linked with the pico gateway (GW),
Transmitting a path switching request message to the pico gateway;
And receiving a response message from the pico gateway in response to the path switching request message generated by the pico gateway using previously obtained security context information of the terminal.
The method of claim 5, wherein the security context information of the terminal,
The handover method of the target pico base station, characterized in that the Pico gateway is obtained from the initial context request message received from the MME during the registration procedure of the terminal.
The method of claim 5, wherein the security context procedure of the terminal,
The handover method of the target pico base station, characterized in that obtained from the initial context change request message received by the pico gateway from the MME during the context change procedure after the registration procedure of the terminal.
The method of claim 5, wherein the security context procedure of the terminal,
The handover method of the target pico base station, characterized in that the Pico gateway is obtained from the S1 handover request message received from the MME during the S1 handover procedure of the terminal.

Images