WO2012155447A1

WO2012155447A1 - Data back-transmission method and base station in the cross-base station handover process

Info

Publication number: WO2012155447A1
Application number: PCT/CN2011/080928
Authority: WO
Inventors: 李宾
Original assignee: 中兴通讯股份有限公司
Priority date: 2011-05-16
Filing date: 2011-10-18
Publication date: 2012-11-22
Also published as: CN102791008B; CN102791008A

Abstract

The invention provides a data back-transmission method and base station in the cross-base station handover process, and the method comprises the following steps that: a source base station evolved Node B(eNB) transmits a handover command to a User Equipment(UE), and back-transmits the downlink data stream from a core network(S302); after suspending the uplink data stream in the UE, the source eNB back-transmits the uplink data stream from the UE according to the current service bearing mode(S304). With the invention, the accuracy and effectiveness of the system are increased, and the utilization of air interface resources is improved.

Description

The present invention relates to the field of communications, and in particular, to a method and a base station for back-transferring data during handover between base stations. BACKGROUND OF THE INVENTION User equipment (User Equipment, UE for short) is a key technical problem in data transmission during handover. In order to realize the lossless transmission of data and save the radio resources of the air interface, the data that has not been sent by the source side base station needs to be forwarded to the target side base station for processing in the process of cross-base station handover, and the operation is called data forwarding or data forwarding. Before the start of the handover, between the source-side base station (ie, evolved Node B (eB)) and the target-side eNB, the user plane establishes two GTP UU tunnels: one for uplink data forwarding, one for Used for data forwarding on the downlink. For the uplink data stream, when the handover occurs, the Packet Data Convergence Protocol (PDCP) layer of the source eNB will successfully receive the ordered uplink PDCP service data unit (Service Data Unit, referred to as The SDU is sent to the Serving Gateway (S-GW); and the received out-of-order PDCP SDU is forwarded to the target side base station, and the uplink PDCP SDU is delivered to the serving gateway in sequence by the target side base station PDCP layer. The reordering feature is done. For the downlink data stream, when the handover occurs, the source-side base station forwards the following types of packets to the target-side base station: (1) The PDCP layer does not send a successful PDCP Protocol Data Unit (PDU) The corresponding SDU carries the PDCP serial number (SN). The unsuccessful transmission is an acknowledgment message that the UE is not received under the radio link control (Radio Link Control, RLC for short) layer, or the Acknowledged Mode (AM). (2) The PDCP layer has been processed, but the SDU corresponding to the transmitted PDCP PDU is received in the future when the handover occurs, and the PDCP sequence number is carried. (3) The downlink original data from the S1 interface of the core network and the PDUs that are transmitted in the future by the GPRS Tunneling Protocol for User Plane (GTPU) layer, that is, The packet is not processed by the PDCP layer and does not carry the PDCP serial number. FIG. 1 is a flowchart of switching data during a cross-base station handover process according to the related art. As shown in FIG. 1, the process includes the following steps: Step S101: The UE sends a measurement report (Measure Report) to the source eNB. Step S102: After receiving the measurement report, the source eNB sends a handover request (Handover Request) message. Step S103: The target eNB sends a handover request acknowledgement to the source eNB. Acknowledge (abbreviated as ACK) message; Step S104, the source eNB sends a handover command (HO Command) to the UE; Step S105, the source eNB performs user plane data back-transmission; Step S106, the source eNB sends the SN status transmission to the target eNB (Status Transfer a message, the random access is completed; in step S107, the UE sends a handover confirmation (HO Confirm) message to the target eNB; in step S108, the target eNB sends a path switch request to the mobility management entity (Mobile Management Entity, MME for short) (PathSwitch Request) The message is: Step S109, the MME returns a path switch request acknowledgement message to the target eNB; Step S110, the target eNB sends a Release Resource message to the source eNB. 2 is a schematic diagram of the interaction between the source side eNB and the UE when the data is switched according to the related art. As shown in FIG. 2, the source side eNB sends a handover command (Handover Command) to the UE and simultaneously performs uplink and downlink reverse transmission of the service data. Since the UE interrupts the uplink data stream after receiving the handover command, and the handover command has a delay in the transmission (for example, HARQ retransmission, RLC retransmission, etc.), the actual time of the UE re-establishment is later than the eNB user plane, that is, There may also be data sent from the UE after the source side eNB is reestablished. This will lead to the following problems: 1) If the unacknowledged mode (UM for UM) bears, it will inevitably cause uplink data loss; 2) If it is an Acknowledged mode (AM) bearer, it will cause an uplink report. The text is retransmitted after the UE handover is completed, and the air interface bandwidth is wasted. SUMMARY OF THE INVENTION The present invention provides a back-propagation scheme for data in a handover process between base stations to at least solve the above-mentioned related art, since uplink data packets are lost or switched after being switched after the source eNB is re-established. The problem of transmitting the upstream message. In order to achieve the above object, an embodiment of the present invention provides a back-propagation method for data in a handover process between base stations. The method for back-transmitting data in a cross-base station handover process according to the present invention includes the following steps: the source eNB sends a handover command to the UE, and performs a reverse transmission on the downlink data stream from the core network; the source eNB interrupts its uplink in the UE. After the data stream, the uplink data stream from the UE is back-transmitted according to the current service bearer mode. Preferably, the source eNB sends a handover command to the UE, and back-transmission of the downlink data stream from the core network includes: the control plane of the source eNB notifies the user of the source eNB to send a handover command to the UE; the control plane notification source of the source eNB The user of the eNB forwards the downlink data stream to the target eNB. Preferably, after the source eNB reverse-transmits the downlink data stream from the core network, the method further includes: the source eNB starts a local preset timer, and continues to receive the uplink data stream from the UE; the source eNB is in the UE. After the uplink data stream is interrupted, the uplink data stream from the UE is back-transmitted according to the current service bearer mode. The source eNB uplinks the UE according to the current service bearer mode after the timer expires. The data stream is back-transferred. Preferably, the timing duration of the timer is less than the random access delay. Preferably, the source eNB backhauls the uplink data stream from the UE according to the current service bearer mode, including: the source eNB re-establishes its user plane RLC layer, and delivers the RLC SDU to the PDCP layer; according to the current service bearer mode PDCP The layer reverses the RLC SDU. Preferably, the backhauling of the RLC SDU by the PDCP layer according to the current service bearer mode includes: when the service bearer mode is UM, the PDCP layer performs uplink back-transmission on the discontinuous RLC SDU, and sequentially delivers to the core network; Or, in the case that the service bearer mode is AM, the PDCP layer performs uplink back-transmission on the discontinuous RLC SDU, and constructs the receiving state information corresponding to the packet to be sent to the target e B for synchronizing the context of the UE. In order to achieve the above object, an embodiment of the present invention further provides an eNB. The e B according to the present invention includes: a sending module, configured to send a handover command to the UE, and backhaul the downlink data stream from the core network; and an uplink data back-transmission module, configured to interrupt the uplink of the UE After the data stream, the uplink data stream from the UE is back-transmitted according to the current service bearer mode. Preferably, the sending module is further configured to notify the user to send a handover command to the UE through the control plane, and notify the user to forward the downlink data stream to the target eNB through the control plane. Preferably, the uplink data back-transmission module includes: an RLC layer processing unit, configured to re-establish a user plane RLC layer, and deliver an RLC SDU to the PDCP layer; and a PDCP layer processing unit, configured to perform a PDCP layer-to-RLC SDU according to a current service bearer mode. Reverse the pass. Preferably, the PDCP layer processing unit is further configured to: when the service bearer mode is UM, the PDCP layer performs uplink back-transmission on the discontinuous RLC SDU, and sequentially delivers to the core network; and/or, the service bearer mode is AM. In the case of the PDCP layer, the PDCP layer performs uplink back-transmission on the discontinuous RLC SDU, and constructs the receiving state information corresponding to the packet to be sent to the target e B for synchronizing the context of the UE. With the present invention, the source eNB performs the uplink back-propagation according to the current service bearer mode after the UE interrupts its uplink data flow, and solves the problem in the related art that the UE can still receive the UE after the source eNB is re-established. The data causes the loss of the uplink data packet or the retransmission of the uplink packet after the handover, which increases the accuracy and effectiveness of the system and improves the utilization of the air interface resource. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set to illustrate,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, In the drawings: FIG. 1 is a flowchart of handover data during handover between base stations according to the related art; FIG. 2 is a schematic diagram of interaction between a source side eNB and a UE when handover data according to the related art; FIG. 3 is a diagram according to the present invention; FIG. 4 is a structural block diagram of a base station according to an embodiment of the present invention; FIG. 5 is a structural block diagram of a base station according to a preferred embodiment of the present invention; FIG. 6 is a block diagram of a base station according to a preferred embodiment of the present invention; FIG. 7 is a flowchart of data processing during AM bearer according to Embodiment 2 of the present invention; FIG. 8 is a UM according to Embodiment 3 of the present invention; Flow chart of data processing during bearer. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. According to an embodiment of the present invention, a reverse transmission method of data during handover between base stations is provided. FIG. 3 is a flowchart of a method for back-transmitting data in a process of handover between base stations according to an embodiment of the present invention. As shown in FIG. 3, the method includes the following steps: Step S302: A source eNB sends a handover command to a UE, and sends a handover command to the UE. The downlink data stream of the network is back-transferred; in step S304, after the UE interrupts its uplink data stream, the source eNB reverse-transmits the uplink data stream from the UE according to the current service bearer mode. Through the above steps, the source eNB is configured to perform uplink back-propagation according to the current service bearer mode after the UE interrupts its uplink data flow, and solves the problem in the related art that the UE can still receive the UE after the source eNB is re-established. The data causes the loss of the uplink data packet or the retransmission of the uplink packet after the handover, which increases the accuracy and effectiveness of the system and improves the utilization of the air interface resource. For example, in the implementation process, in step S304, the source eNB may perform uplink back-transmission after receiving the notification message that the UE interrupts its uplink data flow. Preferably, in step S302, the control plane of the source eNB notifies the user of the source eNB to send a handover command to the UE; the control plane of the source eNB notifies the user of the source eNB to forward the downlink data stream to the target eNB. This method is highly operable. Preferably, in step S302, the source eNB may perform a backhaul of the downlink data stream from the core network, start a local preset timer, and continue to receive the uplink data stream from the UE; in step S304, The source eNB may backhaul the uplink data stream from the UE according to the current service bearer mode after the timer expires. The method is simple to implement and has high operability. Preferably, the timing duration of the timer is less than a random access delay. This method is simple and practical, and can improve the compatibility of the system. Preferably, the source eNB backhauls the uplink data stream from the UE according to the current service bearer mode, including: the source eNB re-establishes its user plane RLC layer, and delivers the RLC SDU to the PDCP layer; according to the current service bearer mode PDCP The layer reverses the RLC SDU. The method is simple and practical, and has high operability. Preferably, in step S304, the PDCP layer performs backhauling on the RLC SDU according to the current service bearer mode. In the case that the service bearer mode is UM, the PDCP layer performs uplink back propagation on the discontinuous RLC SDU, and sequentially delivers And the core network; and/or, in the case that the service bearer mode is AM, the PDCP layer performs uplink back-transmission on the discontinuous RLC SDU, and constructs the receiving state information corresponding to the packet to be sent to the target e B, where Synchronize the context of the UE. This approach can increase the flexibility and adaptability of the system. Corresponding to the above method, an embodiment of the present invention further provides an e B. 4 is a structural block diagram of a base station according to an embodiment of the present invention. As shown in FIG. 4, the eNB 40 includes: a sending module 42 configured to send a handover command to the UE, and reverse the downlink data flow from the core network. The uplink data back-transmission module 44 is coupled to the transmitting module 42 and configured to perform back-transmission of the uplink data stream from the UE according to the current service bearer mode after the UE interrupts its uplink data stream. The eNB 40 uses the uplink data back-transmission module 44 to perform uplink back-propagation according to the current service bearer mode after the UE interrupts its uplink data flow, and solves the related art in the related art because the source eNB can still be reconstructed. The problem of receiving the data from the UE, causing the uplink data packet to be lost or retransmitting the uplink message after the handover, increases the accuracy and effectiveness of the system, and improves the utilization of the air interface resource. Preferably, the sending module 42 is further configured to notify the user to send a handover command to the UE through the control plane, and notify the user to forward the downlink data stream to the target eNB through the control plane. 5 is a structural block diagram of a base station according to a preferred embodiment of the present invention. As shown in FIG. 5, the uplink data back-transmission module 44 includes: an RLC layer processing unit 442, configured to re-establish a user plane RLC layer, and deliver RLC to the PDCP layer. The SDU; the PDCP layer processing unit 444 is coupled to the RLC layer processing unit 442, and configured to perform backhaul on the RLC SDU according to the current service bearer mode PDCP layer. Preferably, the PDCP layer processing unit 444 is further configured to: when the service bearer mode is UM, the PDCP layer performs uplink back-transmission on the discontinuous RLC SDU, and sequentially delivers to the core network; and/or, in the service bearer mode, In the case of the AM, the PDCP layer performs uplink back-transmission on the discontinuous RLC SDU, and constructs the reception status information corresponding to the packet to be sent to the target e B for synchronizing the context of the UE. The implementation process of the above embodiment will be described in detail below in conjunction with the preferred embodiments and the accompanying drawings. Embodiment 1 This embodiment provides a back propagation scheme of user plane data of an eNB when a UE performs handover between eNBs in a Long Term Evolution (LTE) system, and adjusts an eNB re-establishment timing to enable an eNB and a UE side. The uplink data processing of the handover is synchronized to ensure that the UE receives the handover command (Handover Command). The previously transmitted data packet is received and processed by the source side of the eNB, thereby reducing the waste of uplink packet loss and air interface resources, and improving the user switching experience. FIG. 6 is a schematic diagram of the interaction between the source side eNB and the UE when the data is switched according to the first embodiment of the present invention. As shown in FIG. 6, the method for processing the handover data in this embodiment includes the following steps: Step S602, the control plane sends Handling the command (Handover Command) and notifying the user to send to the UE; Step S604, the control plane notifies the user plane to start the handover process, that is, the user plane starts downlink data forwarding, starts the re-establishment timer, and waits for the UE to perform handover. And interrupting the uplink data stream; step S604, the UE side handover starts, and the uplink data stream is interrupted; Step S608, after the re-establishment timer expires, the user processes the uplink received data, that is, the eNB side starts uplink back-transmission (at this time, The UE upstream data stream has been interrupted). In the implementation process, if it is a UM mode service, it is sent to the core network; if it is an AM mode service, the uplink data forwarding is started. It should be noted that the re-establishment timer mentioned in step S604 and step S608 in this embodiment may adjust the eNB re-establishment timing to synchronize the uplink data processing of the eNB and the UE side handover. If the value of the timer is too short, the problem of switching packet loss or air interface retransmission cannot be solved. If it is too long, the uplink data forwarding and PDCP-SN status information may reach the target side too late. Preferably, during implementation, this value may take less than the time of the random access delay. Embodiment 2 In this embodiment, it is assumed that the current service bearer is in the RLC AM mode, and the uplink and downlink service data flows are forwarded to the target side base station during handover. FIG. 7 is a flowchart of data processing during AM bearer according to Embodiment 2 of the present invention. As shown in FIG. 7, the data processing method includes the following steps: Step S701: The control plane notifies a user to send a handover command (Handover Command) to the UE. Step S702, the control plane notifies the user plane to start downlink data back-transmission, but does not perform uplink data back-transmission at this time, but starts a re-establishment timer; Step S703, after the timer expires, the user plane RLC layer is re-established to PDCP. The layer delivers the RLC SDU. Step S704: The PDCP layer starts the uplink retransmission of the received discontinuous packet, and constructs the receiving state information of the uplink packet. In the implementation process, the receiving status information may be sent to the target side eNB through the x2 port signaling for synchronizing the Ue context. Embodiment 3 In this embodiment, it is assumed that the current service bearer is in the RLC UM mode, and the downlink service data flow is forwarded to the target side base station during handover. FIG. 8 is a flowchart of data processing during UM bearer according to Embodiment 3 of the present invention. As shown in FIG. 8, the data processing method includes the following steps: Step S801: The control plane notifies the user to send a handover command (Handover Command) to the UE. Step S802, the control plane notifies the user plane to start downlink data back-transmission, and starts a re-establishment timer; Step S803, after the timer expires, the user plane RLC layer is re-established, and the RLC SDU is delivered to the PDCP layer; Step S804, the PDCP layer will The received discontinuous messages are processed (δΡ, uplink back-propagation) and delivered to the core network in turn. For example, the PDCP layer sends the received discontinuous packet to the target side base station, and is reordered by the PDCP layer of the target side base station, and then delivered to the serving gateway in the core network in order. In summary, the method for the reverse transmission of the user plane data in the handover process provided by the embodiment is to adjust the eNB side re-establishment timing when the e B starts to send the handover command, so that the uplink data processing of the eNB and the UE side handover is synchronized. Thereby reducing the waste of uplink packet loss and air interface resources, and improving the user switching experience. Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general-purpose computing device, which can be concentrated on a single computing device or distributed over a network composed of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device so that they may be stored in the storage device by the computing device, or they may be separately fabricated into individual integrated circuit modules, or Multiple modules or steps are made into a single integrated circuit module. Thus, the invention is not limited to any specific combination of hardware and software. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

Claim

A method for backhauling data during handover between base stations, comprising the following steps:

The source base station eNB sends a handover command to the user equipment UE, and backhauls the downlink data stream from the core network;

After the UE interrupts its uplink data stream, the source eNB backhauls the uplink data stream from the UE according to the current service bearer mode.

2. The method of claim 1, wherein the source eNB sends the handover command to the UE, and backhauling a downlink data stream from the core network includes:

The control plane of the source eNB notifies the user of the source eNB to send the handover command to the UE;

The control plane of the source eNB notifies the user of the source eNB to forward the downlink data stream to the target eNB.

3. The method according to claim 1, wherein

After the source eNB reverses the downlink data stream from the core network, the method further includes: the source eNB starting a local preset timer, and continuing to receive an uplink data stream from the UE; After the UE interrupts its uplink data stream, the eNB performs backhauling the uplink data stream from the UE according to the current service bearer mode, including: after the timer expires, the source eNB according to the The current traffic bearer mode reverses the uplink data stream from the UE.

4. The method of claim 3, wherein the timer has a timing duration that is less than a random access delay.

The method according to any one of claims 1 to 4, wherein the source eNB backhauls an uplink data stream from the UE according to a current service bearer mode, including:

The source eNB re-establishes its user plane radio link control RLC layer, and delivers the RLC service data unit SDU to the packet data convergence protocol PDCP layer;

The PDCP layer performs backhaul on the RLC SDU according to the current service bearer mode. The method according to claim 5, wherein the backhauling the RLC SDU by the PDCP layer according to the current service bearer mode includes:

In the case that the service bearer mode is the unacknowledged mode UM, the PDCP layer performs uplink back-transmission on the discontinuous RLC SDUs and sequentially delivers them to the core network; and/or,

When the service bearer mode is the acknowledgment mode AM, the PDCP layer performs uplink back propagation on the discontinuous RLC SDU, and constructs the receiving state information corresponding to the packet to be sent to the target e B, A context for synchronizing the UE. A base station e B, comprising:

a sending module, configured to send a handover command to the user equipment UE, and perform backhaul on the downlink data stream from the core network;

The uplink data back-transmission module is configured to perform back-propagation of the uplink data stream from the UE according to the current service bearer mode after the UE interrupts its uplink data stream. The base station according to claim 7, wherein the sending module is further configured to notify a user to send the handover command to the UE by using a control plane, and notify a user to forward the downlink data flow to a target eNB by using a control plane. . The base station according to claim 7 or 8, wherein the uplink data back-transmission module comprises:

The RLC layer processing unit is configured to re-establish the user plane RLC layer, and deliver the RLC service data unit SDU to the packet data convergence protocol PDCP layer;

The PDCP layer processing unit is configured to perform back-transmission of the RLC SDU according to the PDCP layer according to the current service bearer mode. The base station according to claim 9, wherein the PDCP layer processing unit is further configured to: when the service bearer mode is the unacknowledged mode UM, the PDCP layer performs uplink reverse on the discontinuous RLC SDUs And transmitting to the core network in turn; and/or, in the case that the service bearer mode is the acknowledgment mode AM, the PDCP layer performs uplink back-transmission on the discontinuous RLC SDU, and constructs the packet with the packet Corresponding reception status information is sent to the target e B for synchronizing the context of the UE.