KR20070107560A - Data transmitting method in mobile communication system - Google Patents

Abstract

A data transmitting method in a mobile telecommunication system is provided to enable a base station indicate a gateway to perform recording operations of a data unit when the data unit upwardly transmitted by wireless UE(User Equipment) may be transmitted to the gateway through plural base station due to handover or the like, thereby improving a transfer rate of the data unit by solving a problem that a previous base station unnecessarily delays time for sequential transmission of the data unit. If handover of UE(User Equipment) is generated, a base station transmits information, for indicating reordering performance of a data unit, to a gateway(S30). The gateway receives the data unit, transmitted by the UE, from at least one or more base stations according to the information and performs reordering. The data unit is an SDU(Service Data Unit). The information is transmitted through a signaling message defined between an RLC(Radio Link Control) layer of the base station and a PDCP(Packet Data Convergence Protocol) layer of the gateway.

Description

Data transmission method in mobile communication system {DATA TRANSMITTING METHOD IN MOBILE COMMUNICATION SYSTEM}

1 is a network structure of the conventional E-UMTS mobile communication system to which the present invention is applied.

2 is a control plane structure of a radio interface protocol between a terminal and a UTRAN based on the 3GPP radio access network standard;

3 is a user plane structure of a radio interface protocol between a UE and a UTRAN based on the 3GPP radio access network standard;

4 is a diagram illustrating a handover process of changing a wireless network node to which a conventional terminal is connected in an E-UTRAN;

5 is a diagram illustrating a network structure model for explaining a data transmission method of a mobile communication system according to the present invention;

6 is a diagram illustrating an example in which an RLC of a base station receives a data unit transmitted upward by a terminal and transmits the received data unit to a gateway;

7 is an E-UTRAN protocol structure for transmitting an uplink data unit,

8 is a diagram illustrating a rearrangement instruction by a base station when transmitting an uplink data unit;

9 is a diagram illustrating a rearrangement instruction by a base station when transmitting a downlink data unit;

10 is an E-UTRAN protocol structure for transmitting downlink data units.

The present invention relates to an Evolved Universal Mobile Telecommunications System (E-UMTS) system, and more particularly, to a data transmission method of a mobile communication system that can increase data transmission efficiency when a radio terminal is handed over.

1 is a network structure of an Evolved Universal Mobile Telecommunications System (E-UMTS), which is a mobile communication system to which the present invention and the present invention are applied.

The E-UMTS system is an evolution from the existing UMTS system and is currently undergoing basic standardization work in 3GPP. The E-UMTS system may be referred to as a Long Term Evolution (LTE) system.

As shown in FIG. 1, an E-UMTS network is largely divided into an E-UTRAN and an Evolved Packet Core (EPC). E-UTRAN is also referred to as an Access Gateway (AG, MME / UPE) connected to an external network by being located at a terminal (User Equipment (hereinafter abbreviated as UE)), a base station (hereinafter referred to as eNB or eNode B), and an end of a network. Available). The AG may be divided into a part for processing user traffic and a part for processing control traffic. At this time, the AG for processing new user traffic and the AG for controlling traffic may communicate with each other using the new interface.

One or more cells may exist in one eNode B (eNB), and an interface for transmitting user traffic or control traffic may be used between the eNode Bs.

The EPC may be configured as a node for user registration of AG and other UEs. In addition, an interface for distinguishing an E-UTRAN and an EPC may be used in the UMTS of FIG. 1. An S1 interface may be connected between the eNodeB and the AG. The eNodeBs are connected to each other through an X2 interface, and have a meshed network structure in which X2 interfaces always exist between adjacent eNodeBs.

Layers of the radio interface protocol between the terminal and the network are based on the lower three layers of the Open System Interconnection (OSI) reference model, which is widely known in communication systems. (Second layer) and L3 (third layer). Among them, the physical layer belonging to the first layer provides an information transfer service using a physical channel, and the radio resource control (RRC) layer located in the third layer includes a terminal and a terminal. It controls radio resources between manganeses. To this end, the RRC layer exchanges RRC messages between the terminal and the network. The RRC layer may be distributed in network nodes such as an eNode B and an AG, or may be located only in the eNode B or an AG.

FIG. 2 illustrates a control plane structure of a radio interface protocol between a terminal and a UTRAN (UMTS Terrestrial Radio Access Network) based on the 3GPP radio access network standard.

The wireless interface protocol of FIG. 2 consists of a physical layer, a data link layer, and a network layer horizontally, and a user plane for transmitting data information vertically. And Control Plane for Signaling. The protocol layers of FIG. 2 are divided into L1 (first layer), L2 (second layer), and L3 (third layer) based on the lower three layers of the Open System Interconnection (OSI) reference model, which is well known in communication systems. Can be distinguished. Hereinafter, each layer of the control plane of the wireless protocol of FIG. 2 and the user plane of the wireless protocol of FIG. 3 will be described.

The physical layer, which is the first layer, provides an information transmission service to a higher layer by using a physical channel. The physical layer is connected to the upper medium access control layer through a transport channel, and data between the medium access control layer and the physical layer moves through the transport channel. Then, data is moved between different physical layers, that is, between physical layers of a transmitting side and a receiving side through physical channels.

Medium access control (MAC) of the second layer provides a service to a radio link control layer, which is a higher layer, through a logical channel. The radio link control (RLC) layer of the second layer supports reliable data transmission. The function of the RLC layer may be implemented as a functional block inside the MAC. In this case, the RLC layer may not exist. The PDCP layer of the second layer uses a header compression function to reduce unnecessary control information so that data transmitted using an IP packet such as IPv4 or IPv6 can be efficiently transmitted in a relatively low bandwidth wireless section. Perform.

The radio resource control (RRC) layer located at the top of the third layer is defined only in the control plane, and the configuration, re-configuration, and release of radio bearers (RBs) are performed. It is responsible for controlling logical channels, transport channels and physical channels. In this case, RB means a service provided by the second layer for data transmission between the terminal and the UTRAN.

A downlink transmission channel for transmitting data from a network to a UE includes a BCH (Broadcast Channel) for transmitting system information and a downlink shared channel (SCH) for transmitting user traffic or control messages. Traffic or control messages of a downlink multicast or broadcast service may be transmitted through a downlink SCH or may be transmitted through a separate downlink multicast channel (MCH). Meanwhile, the uplink transmission channel for transmitting data from the terminal to the network includes a random access channel (RAC) for transmitting an initial control message and an uplink shared channel (SCH) for transmitting user traffic or control messages.

4 illustrates a handover process of changing a wireless network node to which a terminal is connected in an E-UTRAN.

The source eNodeB exchanges area restriction information with the access gateway AG (hereinafter abbreviated as gateway) (or MME / UPE) (S10). In this case, the region restriction information is included in the UE context.

The source eNodeB transmits a radio environment measurement condition to a UE (hereinafter abbreviated to a terminal) (S11), and the terminal transmits a radio base station after measuring the radio environment according to the measurement condition (S12). . The source base station determines a handover to a neighbor base station (or cell) based on the measurement information received from the terminal and transmits a HO request message to the target base station (Target eNodeB) (S13, S14). .

The target base station determines whether to accept the handover request (HO Request) message in consideration of its own radio and radio resources (S15). If it is determined to accept the handover, the target base station transmits a handover response (HO Response) message to the source base station (S16), the source base station transmits a handover command (HO command) to the terminal (S17).

Upon receiving the handover command, the UE performs signaling for accessing the layer 1 and 2 levels with the target base station (S18). The L1 / L2 signaling includes a synchronization process. When the Layer 1 and 2 connection is terminated, the terminal transmits a handover complete message to the target base station (S19), and the target base station transmits a handover complete message to the gateway AG (or MME / UPE). S20).

The gateway receiving the handover complete message responds by transmitting a HO complete ACK message to the target base station (S21), and the target base station transmits a resource release message to the source base station (S22). ). Accordingly, the source base station receiving the resource release message releases all resources related to the handover, and the terminal updates the location (S23 and S24).

In general, when a terminal and a base station transmit and receive data units, the terminal or base station is responsible for reordering for sequential transmission of the data units.

However, when the terminal moves to a new base station (in case of handover) while the terminal is transmitting an uplink data unit to a specific base station, the previous base station receives a data unit that has not been received (the data unit already received by the new base station). In order to receive, data units that have been sequentially received for a predetermined time period are not transmitted to the upper layer (gateway). The reason is that the old base station cannot know that the new base station has received a data unit that it did not receive.

Therefore, the previous base station delays the transmission time because the new base station waits for the data unit already received for the sequential transmission of the data units, and also because the previous base station does not transmit the sequentially received data units to the upper buffer for a predetermined time. Will be used unnecessarily.

For this reason, when the data unit transmitted by the conventional wireless terminal is transmitted to the gateway through various base stations due to handover, the transmission efficiency of the data unit is inferior.

Accordingly, an object of the present invention is to provide a data transmission method of a mobile communication system that can increase uplink data transmission efficiency when a terminal performs handover.

In order to achieve the above object, in the data transmission method of the mobile communication system according to the present invention, when the handover of the terminal occurs, the base station transmits the information instructing the rearrangement of the data unit to the gateway, the gateway is Receive and rearrange data units transmitted by the terminal from at least one base station according to the corresponding information.

Preferably, the data unit is an RLC SDU (Service data unit).

Preferably, the information is transmitted through a signaling message defined between the RLC layer of the base station and the PDCP layer of the gateway.

Preferably, the signaling message is a rearrangement indication message.

Preferably, the rearrangement indication message is a one-way message or a bidirectional message requiring a response.

Preferably, the information may be included in one of the data unit generated in the RLC, one bit, and the header field of the RLC.

Preferably, the base station is a source base station or a destination base station.

Preferably, the base station transmits the data unit received before the handover occurs to the gateway regardless of the sequence number.

Preferably, the rearrangement of the data unit is performed in the PDCP layer of the gateway or a lower layer of the PDCP, and the data unit transmitted by the terminal is stored in the rearrangement buffer of the gateway.

The present invention is implemented in a mobile communication system such as E-UMTS. However, the present invention can also be applied to communication systems operating according to other standards. Hereinafter, preferred embodiments of the present invention will be described in detail.

The present invention proposes a method for causing a gateway (AG or AGW) to perform reordering of data units transmitted from the wireless terminal through a base station when the wireless terminal performs handover.

That is, when a data unit transmitted upward by a wireless terminal is transmitted to a higher level (= gateway) through a base station due to a handover or the like, the base station transmits from the received data unit to the gateway regardless of the sequence number. The gateway rearranges the received data units according to sequence numbers.

Specifically, the source base station (formerly base station) sends a rearrangement indication message requesting the gateway to perform the rearrangement function. Preferably, the rearrangement indication message is transmitted when it is determined that the terminal is in the handover process, and may be transmitted from a source base station or a target base station.

The data unit represents a data block to be transmitted to a higher level in a specific protocol or node. The data unit may be an SDU service data unit (SDU) in the RLC. The base station may instruct the gateway to perform rearrangement using one bit or may include the RLC in the header field of the RLC.

The base station no longer considers the sequence number of the data unit after allowing the gateway to assume the rearrangement function. In other words, it does not perform a rearrangement function. Therefore, when a specific data unit transmitted upward by the terminal is completely received by the base station, the base station directly transmits the data to the gateway regardless of the order (sequence number) of the data units.

For example, if an RLC of a base station receives a PDU from a lower layer and completely receives an SDU of a specific sequence number, the RLC may directly transmit to an upper layer, that is, a gateway, regardless of whether the SDUs are sequentially received. . At this time, the SDU transmitted to the gateway is received by the PDCP corresponding to the upper layer of the RLC.

The gateway receives the data unit transmitted by the base station. At this time, the data units may not be sequentially received. In addition, the gateway may receive data units transmitted upward by a specific terminal from several base stations as well as one base station. The gateway stores the received data units in a rearrangement buffer in order to sequentially transmit the data units. After receiving the specific data unit that has not been received and the sequential reception is completed, the gateway transmits the data unit to the upper layer.

For example, the RLC of the base station sends the SDU to the gateway, and the PDCP of the gateway receives the SDU. In this case, the received SDU may not have a sequential sequence number. In addition, the RLC SDU transmitted by one UE may be transmitted to the gateway through several base stations. The PDCP layer of the gateway or a lower layer of PDCP may receive the RLC SDU and store it in the rearrangement buffer for sequential processing. When a specific RLC SDU is received and sequential reception is performed, the PDCP layer transmits SDUs corresponding to the SDU sequence number of which a corresponding sequence is completed (no gap due to an SDU not received in the middle) to a higher layer. .

5 shows a method of transmitting an uplink data unit according to the present invention.

Referring to FIG. 5, in a handover situation, when a terminal transmits a data unit upward, the source base station and the target base station do not perform a rearrangement function of the data unit, but may be in charge of the gateway. That is, the gateway receives and rearranges the uplink data unit transmitted by the terminal from the source base station and the target base station. The data unit is stored in the rearrangement buffer (elliptical portion of the AG) of the gateway. The reorder buffer may be located in the PDCP of the gateway or may be included in a functional block of a lower layer of the PDCP.

6 illustrates an example in which the RLC of the base station receives a data unit (e.g., SDU) transmitted upward by the terminal and transmits the data unit (e.g., SDU) to the gateway.

In the E-UTRAN, the RLC is located at the base station and located above the MAC. The RLC may obtain an SDU from the received PDUs. In FIG. 6, S denotes an SDU, P denotes a PDU, sNB denotes a source base station, and tNB denotes a target base station.

In general, the RLC may not sequentially receive PDUs, and the order of completely received SDUs may not be sequentially. In FIG. 6, S60, S61, S64, and S65 are completely received because the PDU constituting the SDU is received, but S62 and S63 are not completely received because the PDU constituting the SDU is not received.

Therefore, if the handover is not in progress, the terminal will continue to attempt to retransmit to the source base station (sNB) to transmit the PDU, the gateway receives the PDU through the source base station to obtain the SDU. On the other hand, if the handover is in progress, the terminal may transmit the PDU to the target base station (tNB) rather than the base station. Therefore, in the state where the handover is in progress, the target base station may configure the SDU by receiving the PDU that the source base station has not yet received.

That is, in FIG. 6, the target base station tNB may configure S62 and S63 by receiving PDUs capable of configuring S62 and S63. At this time, the source base station can not know that the destination base station has received the S62, S63. Accordingly, the source base station may perform unnecessary operations such as requesting retransmission to the terminal for receiving S62 and S63 or waiting for reception for a specific time for sequential transmission of the SDU.

For this reason, when the handover of the terminal is in progress, it is more efficient to perform the rearrangement function through the gateway that can receive the SDU from several base stations, rather than performing the rearrangement function at the base station.

Therefore, when the source base station confirms that S60, S61, S63, and S64 have been completely received, the source base station transmits to the gateway, which is the upper layer. When the SDU is completely received, the destination base station may transmit to the gateway, the higher layer, or may sequentially transmit to the gateway after rearranging.

7 is an E-UTRAN protocol structure for transmitting an uplink data unit.

In FIG. 7, PDCP, RLC, MAC, PHY, PDCP, etc. mean an air interface protocol. Unlike the RLC and PDCP of the UE, in the E-UTRAN, the RLC and the PDCP are located at base stations (eNodeB) and gateways (AG), which are different network nodes. Depending on whether or not the RLC SDU is received, it affects PDU retransmission, application layer, etc. in PDCP. In other words, the signaling message defined in the S1 interface may be newly defined between the RLC layer of the base station and the PDCP layer of the gateway for information transmission and control. In this case, the newly defined signaling message may be used for the purpose of indicating a reordering function of the gateway. In E-UTRAN, it corresponds to S1, but in an existing network, it may be considered as an NBAP message defined in an Iub interface. In addition, the rearrangement indication information may be included in a field of header information for a data unit (SDU) or a transport or frame protocol generated through an RLC and transmitted or specified to minimize signaling amount. Bits can also be allocated for transmission.

Hereinafter, a method of transmitting uplink data during handover in a mobile communication system according to the present invention will be described.

The base station receives the measurement information from the terminal to determine that the terminal needs a handover. When the terminal determines the handover, as shown in FIG. 8, the base station transmits a reordering indication message to the gateway so that the rearrangement process for the data unit can be performed at the gateway (S30).

Preferably, the rearrangement indication message may be a one-way message or a bidirectional message requiring a response (S31). The rearrangement indication message may be a signaling message defined between the base station and the gateway. In addition, the request for performing the rearrangement function of the gateway may be included as a specific information field in a data unit or other signaling message.

For example, the RLC of the base station does not operate the rearrangement function when the handover is prepared, and requires the rearrangement process to be performed by the gateway through a signaling message. Alternatively, the base station may indicate (set) whether or not the rearrangement function is operated in a specific field such as RLC or MAC, and may inform that the gateway should perform the rearrangement process without undergoing the rearrangement process.

Alternatively, the base station may allow the gateway to take care of the rearrangement process for the data unit while maintaining its rearrangement process. In this case, the rearrangement function between the base station and the terminal may be maintained to maintain the robustness of transmission between the base station and the terminal once more.

Accordingly, the gateway reorders the uplink data units according to the rearrangement indication message transmitted from the base station and transmits the upstream data units to the upper layer.

As shown in FIG. 9, the base station may perform the rearrangement indication message not only when the uplink data unit is transmitted but also when the downlink data unit is transmitted (S40). In this case, the rearrangement indication message may be a one-way message or a bidirectional message requiring a response (S41).

The rearrangement instruction message means an indication of how the terminal performs the rearrangement function. The base station may generate a rearrangement indication message and instruct to perform the rearrangement function in the PDCP layer of the terminal. In this case, the PDCP layer of the terminal performs the rearrangement process by the PDCP sequence (sequence) number. When the rearrangement process of the PDCP layer is performed, the rearrangement function in the RLC layer may not be performed. However, it is possible to continue the rearrangement of the RLC layer for robust downlink data unit transmission.

Preferably, the rearrangement instruction message may include information on whether the rearrangement function of the RLC layer should be continuously used or stopped. The rearrangement instruction message may be a message generated by the RRC of the base station. When generating the RLC SDU generated when the downlink data unit is transmitted, information on the rearrangement function operation in PDCP and RLC is included and transmitted. May be

10 is an E-UTRAN protocol structure for transmitting a downlink data unit.

As shown in FIG. 10, the RLC layer and the PDCP layer of the terminal may perform a rearrangement function at the same time, or may perform the rearrangement function only in the RLC layer or the PDCP layer. The terminal performs the rearrangement process in the PDCP layer when the rearrangement indication message includes a rearrangement function request in the PDCP layer.

The base station may send a rearrangement indication message when it is determined that the terminal is in the handover process. Through the rearrangement function of the PDCP layer during the handover period, the terminal may receive the downlink data unit in the order of creation and transmission in the gateway. When the handover is completed, the rearrangement process in the PDCP layer may not be necessary anymore, so the base station transmits a handover complete message or a message requesting completion of the rearrangement function to the terminal, and the terminal receives the corresponding message. Terminate the rearrangement function in the PDCP layer.

The rearrangement function in the PDCP layer may be performed in a newly defined layer between the PDCP layer and the RLC layer. In this case, the layer performing the rearrangement function may be located below the PDCP layer and above the RLC layer. In the case of uplink data unit transmission, the uplink data unit may be located under the PDCP layer located in the gateway to perform a rearrangement function.

As described above, in the present invention, when a data unit transmitted upward by a wireless terminal can be transmitted to a gateway through several base stations due to a handover, etc., the base station instructs the gateway to perform a rearrangement operation of the data units. In addition, the previous base station solves the problem of unnecessarily delaying time for sequential transmission of the data unit, thereby increasing the transmission efficiency of the data unit.

In addition, although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary and will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. . Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (10)

In a data transmission method in which a data unit transmitted upward by a wireless terminal is delivered to a gateway through various base stations due to handover, When a handover of the terminal occurs, the base station transmits information instructing the rearrangement of the data units to the gateway, and the gateway receives and rearranges the data units transmitted by the terminal from at least one base station according to the corresponding information. Uplink data transmission method of a mobile communication system characterized in that. The method of claim 1, wherein the data unit Upstream data transmission method of a mobile communication system, characterized in that the service data unit (SDU). The method of claim 1, wherein the information is The uplink data transmission method of the mobile communication system, characterized in that transmitted through a signaling message defined between the RLC layer of the base station and the PDCP layer of the gateway. The method of claim 1, wherein the signaling message is Uplink data transmission method of a mobile communication system, characterized in that the rearrangement indication message. The method of claim 4, wherein the rearrangement indication message Uplink data transmission method of a mobile communication system, characterized in that the one-way message or a bidirectional message requiring a response. The method of claim 1, wherein the information is The uplink data transmission method of the mobile communication system, characterized in that the data unit generated in the RLC, one bit, may be included in one of the header field of the RLC. The method of claim 1, wherein the base station Upstream data transmission method of a mobile communication system, characterized in that the source base station or the target base station. The method of claim 1, wherein the base station The uplink data transmission method of the mobile communication system, wherein the data unit received before the handover occurs is transmitted to the gateway regardless of the sequence number. The method of claim 1, wherein the rearrangement of the data unit is Uplink data transmission method of a mobile communication system, characterized in that performed in the PDCP layer of the gateway or a lower layer of PDCP. According to claim 1, wherein the data unit transmitted by the terminal Upstream data transmission method of a mobile communication system, characterized in that stored in the rearrangement buffer of the gateway.

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