KR20110071363A - Apparatus for processing handover of mobile communication system - Google Patents

Abstract

PURPOSE: An apparatus of processing handover of a mobile communication system is provided to create the tunnel establishment based on a user terminal standard instead of not a fixed bearer standards established in a user terminal in the source eNB. CONSTITUTION: A bit- map information generator(520) receives an external PDCP data packet and a SN state information forward message, in which the RB information is included, through the UL / DL packet forwarding tunnel from a source eNB. The bit- map information generator compartmentalizes the PDCP SDU by using the RB information in the external PDCP data packet. A bit- map information generator creates UL bit map information by the RB information. The bit- map information generator requests the UL data retransmission to a user terminal by using the UL bit map information.

Description

Handover processing device for mobile communication system {APPARATUS FOR PROCESSING HANDOVER OF MOBILE COMMUNICATION SYSTEM}

The present invention relates to a 3GPP LTE (Long Term Evolution, hereinafter called 'LTE') system, and more particularly, Packet Data Convergence Protocol (PDCP) for lossless handover between base stations. Bitmap information indicating whether a PDCP SDU (Service Data Unit, hereinafter referred to as SDU) is received in the layer is called a SN (Sequence Number, hereinafter referred to as 'SN') between the base station and the base station. .) A handover processing apparatus of a mobile communication system for transmitting status information.

The present invention is derived from a study conducted as part of the IT growth engine technology development project of the Ministry of Knowledge Economy [Task Management Number: 2006-S-003-04, Task name: Development of next generation mobile communication service platform].

E-UMTS (Evolved Universal Mobile Telecommunications System, hereinafter referred to as UMTS) system is a high-data-rate, low-latency, IP-based high-speed data transmission in the existing UMTS system LTE is an evolving system that is being standardized in 3GPP with the goal of packet-optimized system. Therefore, the E-UMTS system may be referred to as an LTE system.

The LTE system, which is a next-generation communication system, uses the X2-AP protocol when performing handover, wherein the X2-AP protocol transmits control signals such as context information of a terminal required for handover between eNBs as base stations. In charge of. That is, the handover method of the next-generation communication system is UL / DL (UpLoad / DownLoad, hereinafter, 'UL /) through a signaling path X2-AP from a source eNB (evolved NodeB, hereinafter referred to as' eNB') to a target eNB. The actual data is transmitted through the SN information of the DL 'and X2-UP, which is a data path. The target eNB receiving the lossless handover is performed through the in-sequence transmission of the DL data packet and the duplication detection and re-ordering function of the UL data packet.

However, in the conventional handover, even though the target eNB performs the duplicate detection and reordering function through the PDCP (Packet Data Convergence Protocol) Status Report with the terminal after the handover, the UL data packet for SN bitmap generation indicating whether reception is performed is generated by the source eNB and transmitted to the target eNB.

There may be a mismatch between the SN and UL bitmap information transmitted over X2-AP and the actual data sent from the source eNB to the target eNB via UDP / IP-based (Connectionless) X2-UP. have. That is, the actual data may be lost further between eNBs. In other words, the bitmap information and the information of the actual data packet may be different due to the loss between the eNBs. In this case, the target eNB uses the GTP-U (GPRS Tunneling Protocol for User plane, GTP-U) specification from the source eNB. , Called 'GTP-U.) New UL bitmap for transmitting PDCP Status Report to UE based on data after FMS (Fisrt Missing SN) received with PDCP through protocol The information must be reconstructed. This may result in overhead due to duplication of UL bitmap generation and overhead of additional control signals due to transmission of UL bitmap information between eNBs, which may ultimately reduce overall handover efficiency.

In addition, the conventional handover requires as many X2-UP GTP tunnels as the number of bearers configured in one UE for forwarding UL / DL data from the source eNB to the target eNB, and further, UL and DL data per bearer. An X2-UP GTP tunnel had to be created for forwarding packets. This reduces the complexity of the function module and the efficiency of the processing time.

The present invention is to solve the above problems, by generating the tunnel configuration by the user terminal criteria rather than the bearer criteria set in the user terminal in the source eNB, not only can efficiently use the tunnel resources, but also internal processing during handover processing The present invention provides a handover processing apparatus of a mobile communication system that can simplify the procedure.

The present invention generates bitmap information for UL data packets by exchanging PDCP status reports with actual user terminals in a target eNB in charge of duplication detection and rearrangement, thereby overwriting the size of additional control signals and bitmap generation. The present invention provides a handover processing apparatus of a mobile communication system capable of removing a head.

The object of the present invention is not limited to the above-mentioned object, and other objects which are not mentioned will be clearly understood by those skilled in the art from the following description.

An apparatus for processing handover in a mobile communication system according to an exemplary embodiment of the present invention is an apparatus for handing over a user terminal. A tunnel setting unit configured to establish a UL / DL packet forwarding tunnel with the target eNB, and RB information for identifying a bearer of the user terminal in each UL / DL data packet generated in a PDCP layer to use the configured packet forwarding tunnel A packet processing unit for forwarding the target eNB to the target eNB and transmitting an SN status information transmission message including the UL / DL count value to the eNB, and a tunnel setup unit of the source eNB receiving the handover request from the user terminal. External PDCP data packet including RB information from the source eNB via UL / DL packet forwarding tunnel The PDCP SDU is classified using the RB information in the external PDCP data packet as received through the X2-UP and the SN status information transmission message is received through the X2-AP, and generates UL bitmap information for each RB information. And a bitmap information generator for requesting UL data retransmission to the user terminal by using the generated UL bitmap information.

In the present invention, by generating the tunnel configuration at the source eNB based on the user terminal instead of the bearer criteria set in the user terminal, not only can the tunnel resource be efficiently used but also the internal procedure can be simplified during the handover process, thereby improving handover efficiency. It can be effected.

In addition, the present invention generates the bitmap information for the UL data packet in the target eNB that is responsible for the overlapping detection and rearrangement by receiving a status report with the actual user terminal, according to the overlap of the size of the additional control signal and bitmap generation The overhead can be eliminated, improving handover processing power.

Objects and effects of the present invention, and technical configurations for achieving them will become apparent with reference to the embodiments described below in detail with the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and may be changed according to the intentions or customs of the user, the operator, and the like.

The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The present embodiments are merely provided to complete the disclosure of the present invention and to fully inform the scope of the invention to those skilled in the art, and the present invention is defined by the scope of the claims. It will be. Therefore, the definition should be based on the contents throughout this specification.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

Before explaining the LTE system and the handover process of the next generation mobile communication system applied to the present invention will be described.

As shown in FIG. 1, an LTE system, which is a next generation mobile communication system, may be broadly classified into an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) and an Evolved Packet Core (EPC). The E-UTRAN is located at the end of a user equipment (UE), an eNB, and a network and is connected to an external network and is connected to an EPC. The EPC is a mobility management entity (MME: Mobility Management Entity, hereinafter referred to as 'MME') that manages the mobility of the UE, and a gateway (GW: GateWay) that is responsible for data traffic transmission between the external network and the E-UMTS. It is composed. The gateway is again composed of a Serving Gateway (S-GW) and a PDN Gateway (P-GW).

2a to 2b is an interface protocol base layer structure between each node from the terminal to the base station and the EPC in the E-UMTS network applied to the present invention. That is, FIG. 2A is a control plane stack for transmitting control signals, and FIG. 2B is a user plane stack for data transmission.

As shown in FIG. 2A to FIG. 2B, the radio interface protocol based on the 3GPP radio access network standard between the terminal and the base station is MAC (Medium), which is the L1 layer and the L2 layer, which are physical layers in both the control plane and the user plane. Access Control (hereinafter referred to as "MAC"), RLC (Radio Link Control, referred to as "RLC") and PDCP (Packet Data Convergence Protocol, hereinafter referred to as "PDCP") layer, L3 layer RRC (Radio Resource Control, hereinafter referred to as 'RRC') is defined only in the control plane.

The L1 layer and the MAC of the second layer are connected through a transport channel, and the MAC and the RLC are connected through a logical channel. The RLC layer supports reliable data transmission, and the PDCP layer reduces header size of IP packets containing relatively unnecessary control information in order to efficiently transmit IP packets in a low bandwidth wireless section. In addition, encryption of the data of the control plane Signal Radio Bearer (SRB) and the data of the user plane (DRB: Data Radio Bearer) is also performed. RRC, which is defined only in the control plane, is responsible for the control of logical channels, transport channels, and physical channels in connection with the setup and release of radio bearers (RBs).

3 is a protocol stack of a control plane and a user plane defined between eNBs applied to an embodiment of the present invention, and the SCTP / IP-based X2-AP protocol is used for context information of a terminal required for handover between eNBs. X2-UP protocol, which is responsible for transmitting control signals and uses UDP / IP-based GPRS Tunneling Protocol for User Plane (GTP-U) standards, forwards packets between eNBs through logical channels called tunnels for lossless handover. In charge of.

FIG. 4 is a signal flow diagram illustrating a process of UE performing handover between eNBs in LTE.

Referring to FIG. 4, when the UE measures signal strength and the like for each cell, and the measurement satisfies a criterion determined by the eNB, a measurement report message is sent to the source eNB through the allocated uplink (UL). Send (S400). The source eNB which receives this determines the handover to the target eNB by referring to the content of the message (S402).

Then, the source eNB loads the context information of the terminal to the target eNB and requests preparation for handover (S404).

The target eNB extracts and stores the context information of the corresponding UE in the received handover request message (S406), and then establishes a tunnel for packet forwarding between radio resources and the eNB, and wireless resources including new C-RNTI for the corresponding UE. The handover request response message is transmitted to the source eNB including the configuration information and the tunnel ID (TEID) for packet forwarding (S408).

After receiving the handover request response message, the source eNB transmits an RRC reset (Handover Command) command to the UE (S410), and then converts the UL / DL user data (PDCP SDU) into the GTP-U protocol format using the PDCP layer of the source eNB. In step S412, the mobile station transmits to the target eNB through the preset forwarding tunnel. In this case, the forwarding criterion of UL data is the PDCP sequence number (hereinafter, referred to as SN) among the data from the UE received from the RLC, is forwarded from the first non-contiguous data (PDCP SDU) to the target eNB. The DL data forwarding criterion transmits data (PDCP SDUs) that have not been acknowledged by the terminal among data transmitted by the PDCP to the target eNB.

In addition, the source eNB sends the SN status via X2-AP to UL / DL PDCP SN information (exactly including HFN and SN, called COUNT, and UL Bitmap for UL: 3GPP TS36.423 and 36.323) for lossless handover. A SN status transfer message is transmitted to the target eNB (S414).

Packets transmitted to the target eNB through this step are buffered and stored in the target eNB.

Upon receiving the RRC reset (handover) command, the UE resets radio resources with the target eNB, including timing synchronization (S416), and transmits an RRC Reset Complete (Handover Complete) message to the target eNB (S418).

Thereafter, the UE PDCP layer makes a request for retransmission through the PDCP Status Report to the target eNB for a request for retransmission of the DL packet for the SN that is not received at the PDCP level (S420). The UL transmits the packet from the unacknowledged SN of the source eNB before the handover to the target eNB at the PDCP level of the UE.

In addition, at this time, the PDCP of the target eNB buffers the UL / DL packet received from the source eNB through X2-UP and sets the PDCP SN information of the UL / DL packet to X2-AP. After the RRC is reset with the UE, the buffered DL data is started to be transmitted to the UE, and the UL data received from the UE is the same as the UL forwarding data, and then PDCP level is performed through SN Reordering and Duplication Detection. After sequencing packets, send them to GW. At this time, by transmitting the PDCP Status Report to the terminal for the UL packet retransmission request with the SN information transmitted through X2-AP, it requests the retransmission of the UL packet (S422, S424).

Thereafter, the target eNB requests path switching to the S-GW through the MME to change the eNB to which the UE belongs (S426), and after completing the path switch, that is, the S-GW which has changed the DL path transmits all packets to the source eNB. It transmits the End Marker packet in the sense (S428). In addition, a new packet is transmitted to the target eNB after the path switch of the S-GW (S430), and the target eNB receives the end marker from the source eNB after buffering it (S432) and transmits all the forwarding data through the new path. The received data is transmitted to the user terminal (S434).

After receiving the path switching response (S436), the target eNB transmits the context release request of the terminal to the source eNB (S438), and the source eNB releases the context information of the terminal (S440).

Based on the above, in the handover method of the next generation mobile communication system according to an embodiment of the present invention, the tunnel eNB generates the tunnel setting based on the user terminal instead of the bearer criteria set in the user terminal, thereby efficiently using the tunnel resource. In addition, a handover processing apparatus capable of simplifying an internal procedure in handover processing will be described.

In addition, according to an embodiment of the present invention, by generating a bitmap information on the UL data packet in the target eNB that exchanges the status report with the actual user terminal and is responsible for duplication detection and rearrangement, the size of the additional control signal and bitmap generation A handover processing apparatus capable of removing overhead due to duplication will be described.

FIG. 5 is a block diagram illustrating an apparatus for processing a packet during handover in a mobile communication system according to an exemplary embodiment of the present invention. FIG. 5 illustrates a tunnel setup unit 500, a packet processor 510, and a bitmap information generator 520. Include.

The packet processing apparatus according to an embodiment of the present invention may be implemented in an eNB of an LTE system.

The tunnel setting unit 500 transmits a handover request message according to the determination of handover through a measurement report of an arbitrary user terminal, and when a response message is received therein, an eNB which transmits a response message (e.g., base station to be handed over: A tunnel for UL / DL packet forwarding with the target eNB) is established. The response message received from the eNB to be handed over includes radio resource configuration information including new C-RNTI for any user terminal and a UL / DL tunnel ID (TEID) for packet forwarding.

As the response message is received, the source eNB transmits an RRC reset command to the user terminal and then transmits UL / DL user data, that is, PDCP SDU, to the target eNB which has transmitted the response message through the tunnel for forwarding using the PDCP layer. This may be processed by the packet processor 510.

In other words, the packet processing unit 510 targets the PDCP data packet including the RB information of each UL / DL data (packet) generated in the PDCP layer by using the packet forwarding tunnel set by the tunnel setting unit 500. Forward through X2-UP.

Meanwhile, the packet processing unit 510 of the eNB performs a packet forwarding and transmits an SN state information transmission message. Unlike the conventional art, the SN state information transmission message does not include UL bitmap information and only a UL / DL count value. Included.

The SN status information transmission message including the UL / DL count value is transmitted to the eNB to be handed over through the X2-AP.

The bitmap information generation unit 520 of the eNB includes an SN, that is, an PDCP data packet (external PDCP data packet) including an RB information from an arbitrary eNB through an established packet forwarding tunnel with an eNB, that is, an eNB measured and reported by a user terminal. As the status information transmission message is received, PDCP SDUs are classified using RB information in the external PDCP data packet, UL bitmap information is generated for each RB information, and UL data is retransmitted to the user terminal to be handed over using the PDB status. Request a report.

According to an embodiment of the present invention, by generating the bitmap information for the UL data in the target eNB responsible for the overlapping detection and rearrangement by exchanging status information with the user terminal and providing it to the user terminal, the additional control signal Other overhead can be eliminated for duplication of size and bitmap generation.

A handover process between eNBs having the above configuration will be described with reference to FIGS. 6 to 7.

6 is a flowchart illustrating a process of processing handover in a source eNB according to an embodiment of the present invention.

First, as shown in FIG. 6, the source eNB determines the handover through the measurement report from the user terminal, and then transmits a handover request message including the context information of the user terminal to the target eNB, and requests a handover from the target eNB. A response message is received in response to the message (S600). Here, the response message includes radio resource configuration information including new C-RNTI for the user terminal and UL / DL tunnel ID (TEID) for packet forwarding. The tunnel ID (TEID) is based on a bearer criterion set in the user terminal. Not based on user terminal.

Next, the tunnel setup unit 500 of the source eNB searches for the UL / DL tunnel ID (TEID) included in the response message (S602) and then uses the searched UL / DL tunnel ID (TEID) for the tunnel for packet forwarding. Is set (S604).

Thereafter, the packet processing unit 510 forwards the UL / DL data packet generated in the PDCP layer to the target eNB through the established tunnel (S606), in which case the UL / DL data packet (PDCP SDU) is forwarded based on the actual user terminal. The UL / DL data packet is forwarded to the target eNB by including RB information for bearer classification at the PDCP level.

Then, the packet processing unit 510 transmits the SN status information transmission message to the target eNB for lossless handover, and transmits the SN status information transmission message including only the count value of each UL / DL data packet to the target eNB ( S608).

According to an embodiment of the present invention, by creating a tunnel configuration in a source eNB, which is a source eNB, based on a user terminal instead of a bearer criterion set in a user terminal, not only can the tunnel resource be efficiently used but also the internal procedure is simplified in the handover process. You can.

7 is a flowchart illustrating a handover process in a target eNB according to an embodiment of the present invention.

As shown in FIG. 7, the target eNB receives the UL / DL data packet including the RB information forwarded through the tunnel established from the source eNB and stores the UL / DL data packet in a buffer (not shown), and from the source eNB through the established tunnel. The SN status information transmission message is received (S700).

Then, the bitmap information generation unit 520 of the target eNB distinguishes the UL / DL data for each RB from the received UL / DL data packet (S702).

Thereafter, the bitmap information generator 520 generates UL bitmap information using UL data for each RB (S704), and then uses a PDCP status report message including UL bitmap information for a UL data packet retransmission request. It transmits to the terminal (S706).

According to an embodiment of the present invention, by generating a bitmap information on the UL data packet in the target eNB that is in charge of the overlapping detection and rearrangement by receiving a status report with the actual user terminal, the size of the additional control signal and bitmap generation Overhead due to duplication can be eliminated.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. For example, those skilled in the art can change the material, size, etc. of each component according to the application field, or combine or replace the disclosed embodiments in a form that is not clearly disclosed in the embodiments of the present invention, but this also It does not depart from the scope of the invention. Therefore, the above-described embodiments are to be considered in all respects as illustrative and not restrictive, and such modified embodiments should be included in the technical spirit described in the claims of the present invention.

1 is a diagram illustrating an LTE network, which is a next generation mobile communication system applied to the present invention.

2a to 2b is an interface protocol basic layer structure between each node from the terminal to the eNB and the EPC in the E-UMTS network applied to the present invention,

3 is a protocol stack of a control plane and a user plane defined between eNBs applied to the present invention,

4 is a signal flow diagram illustrating a process of performing handover between eNBs by an eNB in LTE according to the present invention;

5 is a block diagram illustrating an apparatus for processing a packet during handover in a mobile communication system according to an embodiment of the present invention.

6 is a flowchart illustrating a process of processing a handover in a source eNB that is a source eNB according to an embodiment of the present invention.

7 is a flowchart illustrating a process of processing handover in a target eNB, which is a target eNB, according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

500: tunnel setting unit 510: packet processing unit

520: bitmap information generation unit

Claims (1)

An apparatus for handing over a user terminal, A tunnel setting unit configured to set up a UL / DL packet forwarding tunnel with the target eNB using the information in the response message as a response message is received from the handover target eNB; Including the RB information for distinguishing the bearer of the user terminal in each UL / DL data packet generated in the PDCP layer forwarding to the target eNB using the set packet forwarding tunnel, the SN state including the UL / DL count value A packet processor for transmitting an information transmission message to the target eNB, As the external PDCP data packet including the RB information and the SN state information transmission message are received from the source eNB through a UL / DL packet forwarding tunnel established by the tunnel setup unit of the source eNB receiving the handover request from the user terminal. A PDCP SDU is classified using RB information in an external PDCP data packet, UL bitmap information is generated for each RB information, and then a bitmap for requesting UL data retransmission to the user terminal using the generated UL bitmap information. Including an information generator Handover processing apparatus of a mobile communication system.

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