KR20190067024A - Method for transmitting data packet in handover procedure of a mobile communication system - Google Patents

Abstract

The present invention relates to a method for transmitting a data packet in a handover procedure of a mobile communication system, which is capable of minimizing waste of wireless resources. According to one embodiment of the present invention, the method comprises: a step in which a relay node selects a target node based on a measurement report received from a terminal, and determines to execute handover to the target node; a step in which the relay node calculates a flushing time required for transmitting all data packets of a transmission queue to the terminal, and calculates the amount of data packets to be directly transmitted to the terminal of the transmission queue based on a maximum delay time, which is a maximum time capable of holding connection between the relay node and the terminal from when determining to execute the handover, and the flushing time; a step in which the relay node requests a donor base station to stop transmission of the data packet to the relay node, and transmits state information of the transmission queue including the calculated amount of the data packets to a content server through the donor base station; and a step in which the relay node receives a handover request reply message from the target node and then, directly transmits the data packet of the transmission queue corresponding to the calculated amount of the data packets to the terminal.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for transmitting a data packet in a handover procedure of a mobile communication system,

The present invention relates to a method of transmitting a data packet in a handover procedure of a mobile communication system, and more particularly, to a method of transmitting a data packet stored in a transmission queue of a relay node to a mobile station in a handover procedure of a mobile communication system including a relay node To a data packet transmission method capable of minimizing the waste of radio resources due to data packet transmission.

BACKGROUND ART [0002] Relay technology in a mobile communication system is widely used as a cooperative communication technology in which a relay node located between a base station and a user equipment relays bilateral communication. Conventionally, the relay technology merely performs a function of amplifying and forwarding a communication signal. However, at present, it is difficult to decode-and-forward a communication signal or reconstruct a communication signal reconfiguration-and-forward).

Meanwhile, a mobile communication system provides a handover technology for automatically switching a channel so that a user can transmit and receive data seamlessly on the move. The handover procedure is started based on a value representative of the channel quality, such as the signal-to-noise ratio (SNR) of the base station signal. That is, when the mobile station receives a signal of another base station that is stronger than the signal of the source base station, the handover procedure starts with the target base station as the target base station.

Such a handover procedure includes forwarding a data packet stored in a transmission queue of a source base station to a target base station. However, if the handover procedure of a mobile communication system including a relay node serving as a source base station is performed in the same manner, wireless resources are wasted in the process of transmitting a data packet.

In order to solve such a problem, in the handover procedure of the mobile communication system including the relay node, all or part of the data packets stored in the transmission queue of the relay node are directly transmitted from the relay node to the mobile station, And to provide a data packet transmission method capable of minimizing waste of data packets.

According to an aspect of the present invention, there is provided a method of transmitting a data packet in a handover procedure of a mobile communication system, the relay node selecting a target node based on a measurement report received from the terminal, Determining to execute; Wherein the relay node calculates a flushing time which is a time required for transmitting all the data packets of the transmission queue to the terminal and calculates a flushing time which is the maximum time required for maintaining the connection between the relay node and the terminal Calculating the amount of data packets of the transmission queue that can be directly transmitted to the terminal based on the maximum delay time in the time and the flushing time; The relay node requests the donor base station to stop transmitting the data packet to the relay node and transmits the status information of the transmission queue including the amount of the calculated data packet to the content server through the donor base station step; And a step in which the relay node directly transmits a data packet of the transmission queue corresponding to the calculated amount of the data packet to the terminal immediately after receiving the handover request response message from the target node A method of transmitting a data packet is provided.

According to another aspect of the present invention, there is provided a method of transmitting a data packet in a handover procedure of a mobile communication system, the relay node selecting a target node based on a measurement report received from the terminal, Determining to execute; Wherein the relay node calculates a flushing time which is a time required for transmitting all the data packets of the transmission queue to the terminal and calculates a flushing time which is the maximum time required for maintaining the connection between the relay node and the terminal Calculating the amount of data packets of the transmission queue that can be directly transmitted to the terminal based on the maximum delay time in the time and the flushing time; The relay node requests the donor base station to stop transmitting the data packet to the relay node and transmits the status information of the transmission queue including the amount of the calculated data packet to the content server through the donor base station step; And directly transmitting a data packet of the transmission queue corresponding to the calculated amount of the data packet to the terminal immediately after the relay node transmits a handover request message to the target node, A method of transmitting a data packet is provided.

The data packet transmission method in the handover procedure according to the present embodiment is effective in minimizing the waste of radio resources by directly or indirectly transmitting all or a part of the data packets stored in the transmission queue by the relay node.

In the method of transmitting a data packet in the handover procedure according to the present embodiment, the relay node transmits the status information of the transmission queue to the content server through the donor base station, thereby minimizing the overhead of signal exchange necessary for the handover execution .

1 is a diagram schematically showing a configuration of a mobile communication system including a relay node.
2 is a diagram illustrating a handover procedure according to the related art.
3 is a diagram illustrating a handover procedure according to an aspect of the present embodiment.
4 is a diagram illustrating a data packet transmission process in a handover procedure according to an embodiment of the present invention.
5 is a diagram illustrating a handover procedure according to another aspect of the present embodiment.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals even though they are shown in different drawings. In the following description of the embodiments 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.

In describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. Throughout the specification, when an element is referred to as being "comprising" or "comprising", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise . In addition, '... The term "module" refers to a unit that processes at least one function or operation, which may be implemented in hardware, software, or a combination of hardware and software.

In this embodiment, the mobile communication service is a service for providing voice, image, data, or the like, and may be provided based on various mobile communication standards and mobile communication technologies. For example, the mobile communication service according to the present embodiment includes a Wideband Code Division Multiple Access (WCDMA) mobile communication service and a CDMA2000 mobile communication service according to the 3G mobile communication standard, a High Speed Downlink Packet (HSDPA) Access) mobile communication service, LTE (Long Term Evolution) mobile communication service, LTE-A (LTE Advanced) mobile communication service according to 4G mobile communication standard, and mobile communication service provided in 5G mobile communication. It should be noted, however, that this is merely an example, and is not intended to limit the embodiments of the present invention.

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

1 is a diagram schematically showing a configuration of a mobile communication system including a relay node.

Referring to FIG. 1, a mobile communication system 100 including a relay node is a system for providing various mobile communication services such as voice call and data packet, and includes a content server 110, a base station 130, (150) and a terminal (170).

The content server 110 may be implemented as a database server that stores and manages a plurality of data packets in order to provide a terminal 170 with a content providing service such as video and audio.

The base station 130 is a fixed station used for communicating with a plurality of terminals and may be expressed in various terms such as a Node B, an evolved Node B (eNB), a base station (BS), or an access point (AP) At least one cell serving as a mobile communication service providing region may exist in one base station 130.

The relay node 150 is a fixed station or a mobile station used for relaying communication between the base station 130 and the terminal 170 and may be expressed in various terms such as an RN (Relay Node) or an RS (Relay Station) . The relay node 150 is installed between the base station 130 and the terminal 170 and relays transmission and reception signals to improve the data throughput of the base station 130 or to cover the service shadow area by expanding the cell area. can do.

The relay node 150 may operate in a full duplex manner in which transmission and reception bands are separated or in a half duplex manner in which transmission and reception time periods are separated.

The relay node 150 may classify the relay node 150 into a transparent relay node and a non-transparent relay node depending on whether the terminal 170 can recognize the existence of the relay node 150. [ Transparent relay node means that the terminal 170 can recognize whether it is communicating with the network through the relay node 150 and the opaque relay node means that the terminal 170 communicates with the network through the relay node 150 Or if it can not be recognized.

The transparent relay node amplifies only the data channel and relays it to the terminal 170 in order to improve data throughput. The link between the transparent relay node and the terminal 170 is directly controlled by the base station 130, which is referred to as a centralized control scheme.

The opaque relay node relays both the control channel and the data channel to the terminal 170 in order to expand the cell area of the base station 130. [ The link between the opaque relay node and the terminal 170 is directly controlled by the opaque relay node 130, which is referred to as a distributed control scheme.

The terminal 170 is a device having a wireless communication function such as a smart phone, a notebook computer, etc., and can be expressed in various terms such as a user equipment (UE), a mobile equipment (ME)

The content server 110 and the base station 130 can be connected to an IP-based wired network for bidirectional communication. The network element between the content server 110 and the base station 130 includes an access gateway (System Architecture Evolution Access gateway) for performing a gateway function for interconnection, routing and forwarding of data packets, And a Mobility Management Entity (MME) that performs management, authentication, and NAS (Non-Access Stratum) signaling control.

The base station 130 and the relay node 150 may be connected to each other via a wireless backhaul link to perform bi-directional communication.

The base station 130 and the terminal 170 or the relay node 150 and the terminal 170 may be connected via a wireless access link and bidirectionally communicate with each other.

The downlink refers to a communication channel from the base station 130 to the relay node 150 or from the base station 130 to the terminal 170 and the uplink refers to the communication channel from the relay node 150 to the base station 130, Or a communication channel from the terminal 170 to the base station 130. [

The mobile communication system 100 transmits the data packet to the base station 130 through the wireless backhaul downlink from the content server 110 to the base station 130 via the wired network, To the relay node 150, and from the relay node 150 to the terminal 170 via the wireless access downlink, respectively.

Hereinafter, the present embodiment will be described on the premise of a mobile communication system including an opaque relay node. It should be noted, however, that this is merely for convenience of description and does not limit the present embodiment.

2 is a diagram schematically showing a handover procedure according to the prior art.

Referring to FIG. 2, in step 1, the UE transmits a measurement report message to a currently connected relay node (hereinafter referred to as a serving relay node).

(1) Reference Signal Receive Power (RSRP), Received Signal Strength Indicator (RSSI), and the like, which measure the signal strength of the serving cell and the neighboring cell or the signal strength with respect to the total received power, , RRM (Radio Resource Monitoring) measurement such as Reference Signal Received Quality (RSRQ), and the like, and (2) RLM (Radio Link Monitoring) measurement.

The UE transmits a measurement report message to the serving relay node when the RSRP or RSRQ value of the neighboring cell is equal to or greater than a predetermined threshold, or periodically. At this time, the serving relay node may determine that the measurement report message received from the UE is an initial message triggering the handover execution.

In step 2, the serving relay node determines to perform the handover of the UE based on the measurement report message and the radio resource management (RRM) information received from the UE, and selects the target node. Here, the target node may be a base station (or relay node) of a neighboring cell that transmits a stronger signal to the terminal than the serving relay node (i.e., has better channel quality than the serving relay node).

In step 3, the serving relay node transmits a handover request message to the target node through the donor base station. The handover request message includes information necessary for the target node to prepare for handover. For example, the handover request message includes context data such as a bearer to be set by the target node, a target cell ID, a signaling context reference of a terminal X2 in a relay node, a terminal EPC signaling context reference, an RRC context including a C- . ≪ / RTI >

In step 4, the target node receives the handover request message and determines whether to accept the handover request in consideration of the available radio resource status of the target node. That is, if the target node has radio resources for connection with the terminal, the target node can accept the handover request.

In step 5, if the target node has accepted the handover request of the terminal, the target node transmits a Handover Request Acknowledgment message to the donor base station through the donor base station. The handover request response message may include a part of handover command information to be transmitted to the terminal, for example, a new C-RNTI, a dedicated RACH preamble, and the like in the form of a transparent container.

In step 6, the serving relay node transmits state information of the transmission queue to the donor base station, including the number of all data packets that have been accumulated in the current transmission queue in response to the request of the donor base station.

In step 7, the donor base station transmits the status information of the transmission queue received from the serving relay node to the content server.

In step 8, the content server transmits all the data packets accumulated in the transmission queue to the target node based on the status information of the transmission queue received from the donor base station.

In step 9, the serving relay node transmits a handover command to the terminal. The handover command is transmitted through an RRC Connection Reconfiguration message.

In step 10, the UE performs synchronization for connection with the target node in response to the handover command, and accesses the target node through a random access channel (RACH). If the terminal successfully accesses the target node, in step 11, the terminal transmits a handover complete message to the target node, and the handover procedure is completed.

A method of transmitting a data packet in a handover procedure according to the related art is summarized as follows.

(1) The data packet stored in the transmission queue of the serving relay node is a data packet transmitted from the content server through the donor base station using the wireless backhaul link.

(2) When the handover of the UE is determined and the serving relay node receives the handover request response message from the target node (i.e., the target base station or the target relay node), the serving relay node notifies the donor base station of the status of the transmission queue And transmits information. The donor base station transmits the status information of the transmission queue received from the serving relay node to the content server again.

(3) The content server transmits all the data packets accumulated in the transmission queue to the target node based on the status information of the transmission queue received from the donor base station.

However, there are some problems in the data packet transmission method in the handover procedure according to the related art.

First, the consumed radio resources (i.e., wireless backhaul links) are wasted in the process of transmitting data packets to the serving relay node.

Second, since the content server must receive the status information of the transmission queue of the serving relay node from the donor base station in order to transmit the data packet accumulated in the transmission queue to the target node, the overhead of signal exchange increases.

The embodiments of the present invention have been made to solve the above problems,

First, the serving relay node transmits the data packet of the transmission queue directly to the terminal, thereby minimizing the waste of radio resources and preventing inefficiency of transmitting the already queued data packet to the target node again.

Second, if the handover is determined, the serving relay node transmits the status information of the transmission queue to the donor base station even if there is no separate request, thereby minimizing the overhead of signal exchange for transmitting the data packet of the transmission queue to the target node . In addition, the donor base station can grasp the data packet to be transmitted to the target node in advance, thereby improving the efficiency of transmission.

Hereinafter, a data packet transmission method in a handover procedure according to the present embodiment will be described in detail with reference to the accompanying drawings.

3 is a diagram illustrating a handover procedure according to an aspect of the present embodiment.

Referring to FIG. 3, in step 1, the UE transmits a measurement report message to a currently connected relay node (hereinafter referred to as a serving relay node).

In step 2, the serving relay node determines to perform the handover of the UE based on the measurement report message and the radio resource management (RRM) information received from the UE, and selects the target node. Here, the target node may be a base station (or relay node) of a neighboring cell that transmits a stronger signal to the terminal than the serving relay node (i.e., has better channel quality than the serving relay node).

In step 3, the serving relay node generates the status information of the transmission queue including the number of all data packets accumulated in the current transmission queue, the number of data packets that can be directly transmitted to the UE before the handover is performed, and the like. The concrete contents and the creation process are as follows.

Set maximum handover delay time

)을 설정한다. 최대 핸드오버 지연시간(

)이란 단말이 서빙 릴레이 노드에서 타겟 노드로의 핸드오버를 실행하지 않고 서빙 릴레이 노드와의 연결을 유지할 수 있는 최대 허용시간을 말한다.The serving relay node transmits the maximum handover delay time (

). Maximum handover delay time (

Refers to a maximum allowable time at which a UE can maintain a connection with a serving relay node without performing a handover from a serving relay node to a target node.

)은 단말로 전송될 데이터 패킷의 중요도에 따라 다양하게 가변될 수 있다. 여기서, 데이터 패킷의 중요도는, 예컨대 H.264/AVC(Advanced Video Coding) 표준에 따른 멀티미디어 데이터 패킷의 경우, NAL(Network Abstraction Layer) 헤더의 Priority 필드 등을 기초로 식별될 수 있다.Maximum handover delay time (

May vary in various ways depending on the importance of data packets to be transmitted to the terminal. Here, the importance of the data packet can be identified based on, for example, a Priority field of a Network Abstraction Layer (NAL) header in the case of a multimedia data packet conforming to the H.264 / AVC (Advanced Video Coding) standard.

)은 미리 설정된 시스템 파라미터일 수 있다.Alternatively, the maximum handover delay time (

) May be a predetermined system parameter.

Flushing time calculation

The serving relay node calculates the time required to empty all data packets stored in the transmission queue (hereinafter, flushing time). Here, the flushing time can be calculated by the following equation (1).

는 플러싱 시간,

은 서빙 릴레이 노드의 전송 큐에 저장된 데이터의 총량,

은 프레임(frame)당 단말로 전송되는 데이터의 평균량,

는 프레임의 지속시간(duration)을 의미한다.here,

Flushing time,

The total amount of data stored in the transmission queue of the serving relay node,

The average amount of data transmitted to the terminal per frame,

Means the duration of the frame.

Calculating the Transmittable Capacity of the Serving Relay Node

)을 최대 핸드오버 지연시간(

)과 비교하여, 핸드오버 실행 전에 단말로 직접 전송할 수 있는 데이터의 양(이하, 전송 가능량)을 산출한다.Next, the serving relay node transmits the flushing time (

) To the maximum handover delay time (

), And calculates the amount of data that can be directly transmitted to the terminal (hereinafter referred to as " transmittable amount ") before the handover is executed.

)이 최대 핸드오버 지연시간(

) 이하인 경우, 전송 가능량은 서빙 릴레이 노드의 전송 큐에 저장된 데이터의 총량이 된다. 즉, 서빙 릴레이 노드는 플러싱 시간 동안 전송 큐에 저장된 모든 데이터 패킷을 단말로 직접 전송할 수 있다.As a result of the comparison,

) Is the maximum handover delay time (

), The transmittable amount is the total amount of data stored in the transmission queue of the serving relay node. That is, the serving relay node can directly transmit all the data packets stored in the transmission queue to the terminal during the flushing time.

)을 초과하는 경우, 전송 가능량은 하기 수학식 2의 계산에 의해 산출될 수 있다.Conversely, if the comparison result indicates that the flushing time is the maximum handover delay time (

), The transferable amount can be calculated by the following equation (2).

는 전송 가능량,

은 최대 핸드오버 지연시간,

는 프레임의 지속시간(duration),

은 프레임(frame)당 단말로 전송되는 데이터의 평균량을 의미한다.here,

Lt; RTI ID = 0.0 >

The maximum handover delay time,

Is the duration of the frame,

Means an average amount of data transmitted to a terminal per frame.

In step 4, the serving relay node transmits a data packet transmission discontinuation request message including status information of the transmission queue to the donor base station. Here, the data packet transmission stop request message refers to a message requesting to stop transmitting the data packet addressed to the terminal to the serving relay node.

In step 5, the donor base station stops transmission of data packets to the serving relay node via the backhaul link in response to the data packet transmission stop request message.

As the donor base station stops transmitting data packets to the serving relay node, the generation of late data packets is prevented. Here, the rate data packet is a data packet transmitted to the serving relay node after the handover decision, and is a data packet that can not be transmitted to the terminal and must be transmitted to the target node. This prevents waste of wireless backhaul link resources consumed when transmitting data packets from the donor base station to the serving relay node.

In step 6, the donor base station transmits the status information of the transmission queue included in the data packet transmission stop request message to the content server.

In step 7, the content server transmits to the target node the remaining data packets excluding the data packets to be directly transmitted to the terminal by the serving relay node, based on the status information of the transmission queue received from the donor base station.

In step 8, the serving relay node transmits a handover request message to the target node through the donor base station. The handover request message includes information necessary for the target node to prepare for handover.

In step 9, the target node determines whether to accept the handover request based on the available radio resource status in response to the handover request message. That is, if the target node has radio resources for connection with the terminal, the target node can accept the handover request.

When the target node accepts the handover request of the terminal, in step 10, the target node transmits a Handover Request Acknowledgment message to the donor base station through the donor base station.

)에 해당하는 개수의 데이터 패킷을 전송 큐로부터 단말로 직접 전송할 수 있다. In step 11, the serving relay node transmits the handover request response message

) Can be directly transmitted from the transmission queue to the mobile station.

)에 해당하는 개수의 데이터 패킷을 전송 큐로부터 단말로 직접 전송할 수 있다.Specifically, the serving relay nodes sequentially transmit (in a first-in first-out (FIFO) manner) the transmittable amount

) Can be directly transmitted from the transmission queue to the mobile station.

)에 해당하는 개수의 데이터 패킷을 전송 큐로부터 단말로 직접 전송할 수 있다. 여기서, 데이터 패킷의 중요도는, 예컨대 H.264/AVC(Advanced Video Coding) 표준에 따른 멀티미디어 데이터 패킷의 경우, NAL(Network Abstraction Layer) 헤더의 Priority 필드 등을 기초로 식별될 수 있다.Alternatively, the serving relay node may selectively transmit the transmittable amount (< RTI ID = 0.0 >

) Can be directly transmitted from the transmission queue to the mobile station. Here, the importance of the data packet can be identified based on, for example, a Priority field of a Network Abstraction Layer (NAL) header in the case of a multimedia data packet conforming to the H.264 / AVC (Advanced Video Coding) standard.

According to an aspect of the embodiment, in order to prevent deterioration of the channel condition of the UE, the serving relay node may increase the transmission power temporarily while transmitting the data packet directly to the UE.

)에 따른 데이터 패킷을 전송 큐로부터 단말로 모두 전송하는 시점이, 단말의 핸드오버 실행(Handover Execution) 시점이 될 수 있다.If the Serving Relay Node is unable to transmit

May be a handover execution time point of the terminal. In this case, the data packet is transmitted from the transmission queue to the terminal.

In step 12, the serving relay node transmits a handover command to the terminal. The handover command is transmitted through an RRC Connection Reconfiguration message.

In step 13, the MS receiving the RRC reconnection message performs synchronization for connection with the target node and accesses the target node through a random access channel (RACH). If the UE successfully accesses the target node, in step 14, the UE transmits a handover complete message to the target node, and the handover procedure is completed.

The data packet transmission method in the handover procedure according to one aspect of the present invention is as follows.

(1) The data packet stored in the transmission queue of the serving relay node is a data packet transmitted from the content server through the donor base station using the wireless backhaul link.

(2) When the handover execution of the UE is determined, the serving relay node generates the status information of the transmission queue. The UE transmits a data packet transmission stop request message including status information of the transmission queue to the donor base station.

(3) The donor base station transmits the status information of the transmission queue included in the data packet transmission stop request message to the content server.

(4) Based on the status information of the received transmission queue, the content server transmits to the target node the remaining data packets excluding the data packet to be directly transmitted to the terminal by the serving relay node.

(5) The serving relay node transmits all or a part of the data packets stored in the transmission queue until the handover is executed based on the status information of the transmission queue, in particular, the available transmission capacity.

As described above, according to the data packet transmission method in the handover procedure according to the present embodiment, two problems of the prior art described above with reference to FIG. 2 can be solved.

First, the serving relay node directly transmits all or a part of the data packets stored in the transmission queue, thereby minimizing the waste of radio resources generated in the data packet transmission process.

Second, even if the serving relay node does not have a separate request, it can transmit the status information of the transmission queue to the donor base station, thereby minimizing the overhead of signal exchange for transmitting the data packet of the transmission queue to the target node.

4 is a diagram illustrating a data packet transmission process in a handover procedure according to an embodiment of the present invention.

Referring to FIG. 4, in operation S410, the serving relay node determines to perform handover of the UE based on the measurement report message and the RRM information received from the UE, .

In step S420, the serving relay node sets a maximum handover delay time, which is the maximum allowed time in which the UE can maintain the connection with the serving relay node without performing the handover from the serving relay node to the target node.

In step S430, the serving relay node calculates a time required to empty all the data packets stored in the transmission queue (hereinafter, flushing time). Here, the specific method of calculating the flushing time is as described above with reference to FIG.

In step S440, the serving relay node compares the flushing time with the maximum handover delay time, and calculates the amount of data that the serving relay node can directly transmit to the terminal before the handover is executed (hereinafter referred to as a transmittable amount).

As a result of the comparison in step S440, if the flushing time is equal to or less than the maximum handover delay time (Yes), the transferable amount is the total amount of data stored in the transmission queue of the serving relay node, and proceeds to step S450.

In step S450, the serving relay node may transmit all the data packets stored in the transmission queue to the terminal directly during the flushing time.

On the contrary, if the flushing time exceeds the maximum handover delay time as a result of the comparison in step S440, the maximum available handover delay time, the duration of the frame, and the average amount of data transmitted to the terminal per frame . ≪ / RTI > Here, a concrete method of calculating the transferable amount is as described above with reference to FIG. 3, and the process proceeds to step S460.

In step S460, the serving relay node transmits the status information of the transmission queue including the transferable amount calculated in step S440 to the content server through the donor base station. The content server transmits to the target node the remaining data packets of the transmission queue excluding the data packets directly transmitted to the terminal by the serving relay node, based on the status information of the transmission queue received from the donor base station.

In step S470, the serving relay node may directly transmit the data packet corresponding to the transmittable amount calculated in step S440 from the transmit queue to the mobile station during the maximum handover delay time. At this time, the data packets directly transmitted from the transmission queue to the mobile station can be selected sequentially according to the queued order (i.e., in a first-in first-out (FIFO) manner) or according to the importance of the data packet.

According to an aspect of the embodiment, in order to prevent deterioration of the channel condition of the UE, the serving relay node may increase the transmission power temporarily while transmitting the data packet directly to the UE.

A time point at which the serving relay node transmits all the transmittable amount to the mobile station may be a handover execution time of the mobile station.

5 is a diagram illustrating a handover procedure according to another aspect of the present embodiment.

The handover procedure of FIG. 5 differs from the handover procedure of FIG. 3 and the point at which the relay node transmits the data packet of the transmission queue to the terminal. Hereinafter, descriptions overlapping with those in FIG. 3 will be omitted or briefly described.

Referring to FIG. 5, in step 1, the UE transmits a measurement report message to a currently connected relay node (hereinafter referred to as a serving relay node).

In step 2, the serving relay node determines to perform handover of the UE based on the measurement report message and the radio resource management information received from the UE, and selects the target node.

In step 3, the serving relay node sets the maximum handover delay time and calculates the time required to clear all the data packets stored in the transmission queue (hereinafter, flushing time). Then, the serving relay node calculates the transmittable amount to the terminal based on the comparison result of the maximum handover delay time and the flushing time. Each concrete production and calculation method is as described above with reference to Fig.

Through this process, the serving relay node generates the status information of the transmission queue including the number of data packets that can be directly transmitted to the UE before the handover is executed.

In step 4, the serving relay node transmits a data packet transmission discontinuation request message including status information of the transmission queue to the donor base station.

In step 5, the donor base station stops transmission of data packets to the serving relay node via the backhaul link in response to the data packet transmission stop request message.

In step 6, the donor base station transmits the status information of the transmission queue included in the data packet transmission stop request message to the content server.

In step 7, the content server transmits to the target node the remaining data packets excluding the data packets to be directly transmitted to the terminal by the serving relay node, based on the status information of the transmission queue received from the donor base station.

In step 8, the serving relay node transmits a handover request message to the target node through the donor base station.

In step 9, the serving relay node may directly transmit a number of data packets corresponding to the transmittable amount calculated in step 3 from the transmission queue to the mobile station immediately after transmitting the handover request message.

)에 해당하는 개수의 데이터 패킷을 전송 큐로부터 단말로 직접 전송할 수 있다.Specifically, the serving relay nodes sequentially transmit (in a first-in first-out (FIFO) manner) the transmittable amount

) Can be directly transmitted from the transmission queue to the mobile station.

)에 해당하는 개수의 데이터 패킷을 전송 큐로부터 단말로 직접 전송할 수 있다. 여기서, 데이터 패킷의 중요도는, 예컨대 H.264/AVC(Advanced Video Coding) 표준에 따른 멀티미디어 데이터 패킷의 경우, NAL(Network Abstraction Layer) 헤더의 Priority 필드 등을 기초로 식별될 수 있다.Alternatively, the serving relay node may selectively transmit the transmittable amount (< RTI ID = 0.0 >

) Can be directly transmitted from the transmission queue to the mobile station. Here, the importance of the data packet can be identified based on, for example, a Priority field of a Network Abstraction Layer (NAL) header in the case of a multimedia data packet conforming to the H.264 / AVC (Advanced Video Coding) standard.

According to an aspect of the embodiment, in order to prevent deterioration of the channel condition of the UE, the serving relay node may increase the transmission power temporarily while transmitting the data packet directly to the UE.

The time point at which the serving relay node transmits the data packet according to the available transmission amount from the transmission queue to the mobile station may be the handover execution time of the mobile station.

In step 10, the target node determines whether to accept the handover request based on the available radio resource status in response to the handover request message. That is, if the target node has radio resources for connection with the terminal, the target node can accept the handover request.

When the target node accepts the handover request of the terminal, in step 11, the target node transmits a handover request acknowledgment message to the donor base station through the donor base station.

In step 12, the serving relay node transmits a handover command to the terminal. The handover command is transmitted through an RRC Connection Reconfiguration message.

In step 13, the MS receiving the RRC reconnection message performs synchronization for connection with the target node and accesses the target node through a random access channel (RACH). If the UE successfully accesses the target node, in step 14, the UE transmits a handover complete message to the target node, and the handover procedure is completed.

2 to 5, it is described that a plurality of processes are sequentially performed, but this is merely an illustration of the technical idea of this embodiment. In other words, it will be understood by those skilled in the art that changes may be made to the procedures described in FIGS. 2 through 5 without departing from the essential characteristics of the present embodiment, It is to be understood that the invention is not limited to the above-described embodiments.

2 to 5 can be implemented as computer-readable codes on a computer-readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. That is, a computer-readable recording medium includes a magnetic storage medium (e.g., ROM, floppy disk, hard disk, etc.), an optical reading medium (e.g., CD ROM, And the like). The computer-readable recording medium may also be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner.

The foregoing description is merely illustrative of the technical idea of the present embodiment, and various modifications and changes may be made to those skilled in the art without departing from the essential characteristics of the embodiments. Therefore, the present embodiments are to be construed as illustrative rather than restrictive, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

110: Content server 130: Base station
150: relay node 170: terminal

Claims (9)

A method of transmitting a data packet in a handover procedure of a mobile communication system,
The relay node selecting a target node based on a measurement report received from the terminal and determining to perform the handover to the target node;
Wherein the relay node calculates a flushing time which is a time required for transmitting all the data packets of the transmission queue to the terminal and calculates a flushing time which is the maximum time required for maintaining the connection between the relay node and the terminal Calculating the amount of data packets of the transmission queue that can be directly transmitted to the terminal based on the maximum delay time in the time and the flushing time;
The relay node requests the donor base station to stop transmitting the data packet to the relay node and transmits the status information of the transmission queue including the amount of the calculated data packet to the content server through the donor base station step; And
The relay node directly transmitting the data packet of the transmission queue corresponding to the calculated amount of the data packet directly to the terminal immediately after receiving the handover request response message from the target node
A method of transmitting a data packet in a handover procedure. The method according to claim 1,
Further comprising the step of the content server transmitting to the target node a remaining data packet excluding data packets directly transmitted from the relay node to the terminal in the transmission queue
A method of transmitting a data packet in a handover procedure. The method according to claim 1,
The target node comprises:
A base station or a relay node of a neighboring cell, which is different from the serving cell to which the UE belongs
A method of transmitting a data packet in a handover procedure. The method according to claim 1,
The flushing time,
The total amount of data packets in the transmission queue, the average amount of data packets transmitted to the terminal per frame, and the duration of the frame
A method of transmitting a data packet in a handover procedure. The method according to claim 1,
The data packet of the transmission queue corresponding to the calculated amount of the data packet,
It is selected according to first-in first-out (FIFO) method.
A method of transmitting a data packet in a handover procedure. The method according to claim 1,
The data packet of the transmission queue corresponding to the calculated amount of the data packet,
Depending on the importance of the data packet,
A method of transmitting a data packet in a handover procedure. The method according to claim 1,
In the step of directly transmitting the data packet of the transmission queue to the terminal,
The relay node temporarily increases the transmission power
A method of transmitting a data packet in a handover procedure. 3. The method according to claim 1 or 2,
Further comprising the step of performing a handover by disconnecting the relay node from the relay node and accessing the target node at the time the transmission of the data packet from the relay node to the terminal is completed
A method of transmitting a data packet in a handover procedure. A method of transmitting a data packet in a handover procedure of a mobile communication system,
The relay node selecting a target node based on a measurement report received from the terminal and determining to perform the handover to the target node;
Wherein the relay node calculates a flushing time which is a time required for transmitting all the data packets of the transmission queue to the terminal and calculates a flushing time which is the maximum time required for maintaining the connection between the relay node and the terminal Calculating the amount of data packets of the transmission queue that can be directly transmitted to the terminal based on the maximum delay time in the time and the flushing time;
The relay node requests the donor base station to stop transmitting the data packet to the relay node and transmits the status information of the transmission queue including the amount of the calculated data packet to the content server through the donor base station step; And
Directly transmitting the data packet of the transmission queue corresponding to the calculated amount of the data packet to the terminal immediately after the relay node transmits the handover request message to the target node
A method of transmitting a data packet in a handover procedure.

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