WO2008025253A1

WO2008025253A1 - Method and system for transferring data in switching procedure

Info

Publication number: WO2008025253A1
Application number: PCT/CN2007/002545
Authority: WO
Inventors: Fei Shao; Xiaoxiao Zheng
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2006-08-22
Filing date: 2007-08-22
Publication date: 2008-03-06
Also published as: CN101132609A; CN101132609B

Abstract

A method and a system for transferring data in switching procedure have the purpose to resolve the problem of that the time delay is too high caused by the downlink data transfer in switching procedure at present. The method involves: A. a source eNodeB transfers service data unit SDU to a target eNodeB; B. the target eNodeB transfers the received SDU to user side and imparts the ending point of the transferred data; C. RLC of the user side transmits the received SDU to PDCP layer of the user side; D. The PDCP layer collates the SDU before the ending point of the transferred data by PDCP number and transmits to the higher layer. The method could reduce the time delay caused by the downlink data transfer.

Description

Method and system for forwarding data in handover process

The present invention relates to the field of communications, and in particular, to a method and system for forwarding data during handover. Background technique

In the early 1990s, WCDMA research began. From the beginning of 1998 to the present, the technical specifications of WCDMA systems have gone through the stages of Release 99, Release 4, Release 5, Release 6, and currently on Release 7 Standardization work has begun to be implemented. At the same time, longer-term research on LTE (Long Term Evolution) has begun to become a new hotspot in standardization.

In the Release 99 system, the downlink transmission uses a dedicated channel, and its maximum rate can reach 384 kbps. Starting from Release 4, the MSC (Kobile Service Switch Center) is split into MSC Server and MGW (Multi-media Gate Way), thus controlling and Separation of services. The concept of IMS (IP Multi-media Subsystem) was introduced in Release 5, which is based on the IP transport layer and introduces HSDPA (High Speed Downlink Packet Access) in the radio access technology. 14.4Mbps. HSUPA (High Speed Uplink Packet Access) technology was introduced in Release 6, which enables the uplink rate to reach 5.76Mbps. The above standards have been relatively stable. The Release 7 protocol discussed at present is based on Release 6. Small changes, improve system performance. LTE will be completely new from system framework to physical layer, aiming to provide users with higher speed and better performance service. Currently UTRAN in LTE is called E-UTRAN.

Referring to FIG. 1, it is an E-UTRAN system architecture diagram, which includes an access gateway aGW (access gateway), and a plurality of base stations eNodeBs in communication therewith.

The aGW is in a core network, and a core network may include multiple aGWs. The aGW is responsible for paging initiation, LTE-IDLE state management, user plane encryption, and packet data convergence protocol PDCP (Packet). Data Convergence Protocol ), System Architecture Evolution (SAE), bearer control, security and integrity protection of non-access stratum NAS (Non Access Stratum) signaling.

The eNodeB is located in the access network and is connected to the aGW, and is responsible for scheduling and transmission of paging information, scheduling and transmission of broadcast information, allocation of uplink and downlink resources, radio bearer control, radio management control, and connection mobility in the LTE-AC state. Sexual control.

Currently, the E-UTRAN protocol stack architecture diagram is shown in Figure 2.

Prior Art 1: Based on the above E-UTRAN protocol stack architecture, the data forwarding process during handover in the E-UTRAN system is shown in FIG. 3. After receiving the handover preparation confirmation, the source eNodeB starts to forward data to the target eNodeB, where the data is the RLC (Radio Link Control) radio link control layer service data unit SDU, that is, the protocol data unit PDU of the PDCP layer. During the handover, the RLC layer is reset, and the data sent from the aGW to the target eNodeB and the data forwarded by the source eNodeB are stored in the target eNodeB, and after the target eNodeB and the user terminal synchronize, and communication is established, the transmission starts. The data is given to the user terminal. The data forwarded by the source eNodeB to the target eNodeB may be interleaved to the target eNodeB, so the data forwarded by the source eNodeB received by the target eNodeB may be out of order. of.

The RLC layer of the target eNodeB obtains the RLC PDUs after reordering the out-of-order data in the receiving order, but it is obvious that the RLC PDUs obtained after renumbering are still out of order. The target eNodeB forwards the RLC PDU to the user terminal after renumbering, and then the user terminal submits it to the PDCP layer. Obviously, the continuity of the service cannot be guaranteed.

Prior Art 2: Currently, the handover process of LTE across different eNodeBs, as shown in FIG. 4, includes the following steps:

1. The principle of the UE triggering status report is issued by the protocol or system message, and so on.

2. The source eNodeB makes a handover decision according to the measurement report reported by the UE and the RRM information. In order for the target eNodeB to prepare for handover, the source eNodeB will send the relevant information to the target eNodeB in the handover request message. 3. The target eNodeB layer is ready for handover at layer two, and feeds back the new C-RNTI and possibly other parameters such as access parameters, SIB, etc. to the source eNodeB. Upon receipt of the acknowledgment of the HO preparation, the source eNodeB begins forwarding the data packet to the target eNodeB.

4. The UE will receive a HANDOVER COMMAND message containing the new C-RNTI and the possible start time, target e NB SIB and other mandatory parameters. This RRC information will be transmitted in RLC AM mode, which means that UE RLC will confirm this information to ensure its reliability.

5. When the start time in the HO COMMAND expires, the UE will perform a synchronization process with the target eNodeB to start its uplink synchronization.

6. The network performs uplink resource allocation and timing advance. These resources are used by the UE to send a handover confirmation 'HANDOVER CONFIRM' message to the target eNodeB, and the handover process of the UE ends. The "HO CONFIRM" message sent by the UE is transmitted in the RLC acknowledge mode, and the network side confirmation is required to ensure that reliability.

7a. The target eNodeB notifies the source eNodeB to successfully switch, so that the source eNodeB will delete the data that has been forwarded in the cache. If there is still data in the source eNodeB cache or the UPE continues to send data to the source eNodeB, the source eNodeB will continue to forward the data to the target eNodeB.

7b. In order for the UPE to directly forward the data packet to the correct target eNodeB, the UE location information change is updated in the mobility management entity/data plane entity MME/UPE.

When LTE switches across different eNodeBs, the first processing scheme for user data is as follows:

1) After the source eNodeB sends a handover command to the UE (HO COMMAND), all SDUs are started from the first RLC buffer in the source eNodeB that is not correctly acknowledged by the UE (ie, the smallest numbered PDU or SDU). ) forwarded to the target eNodeB.

2) The target eNodeB reconstructs the corresponding RLC entity, caches the forwarded data packet, and performs data plane transmission after receiving the information synchronized by the UE. Therefore, the RLC control context (such as information such as SN) is not required to be exchanged between the source eNodeB and the target eNodeB. The target eNodeB re-numbers the forwarded data or reads the high-level number of each packet, and then sends the data to the user side.

3) After the aGW performs the path switch, the high-level data packet will be sent from the aGW to the target eNodeB. The problem that will arise at this time is the first new packet sent from the aGW. (after path switching) The time to reach the target eNodeB may be earlier than the time when the last packet forwarded by the source eNodeB arrives at the target eNodeB. In this way, the packet arrives out of order on the target eNodeB side. In order to solve this problem, in the eNodeB, a certain reordering (or not) may be performed according to the higher layer number (PDCP number).

The inventor found in the process of the invention that the problem with this scheme is that forwarding the data packet from the first one that is not correctly acknowledged by the UE means that some data that is discontinuous but has been correctly received by the UE will be re-forwarded, which wastes the air interface. Resources also increase switching latency (from a high-level perspective). At the same time, this large amount of data forwarding will cause the data sent from the upper layer of the aGW to arrive at the target eNodeB later. If such out-of-order is reordered on the target eNodeB, it will bring a relatively large delay.

When LTE is switched across different eNodeBs, the second processing scheme for user data is as follows:

1) After the source eNodeB sends a handover command to the UE (HO COMMAND), the SDUs in the RLC buffer of the source eNodeB that are not correctly acknowledged by the UE (these SDUs may be discontinuous, selective) are forwarded to the target eNodeB.

2) The target eNodeB reconstructs the corresponding RLC entity, caches the forwarded packets, performs data plane transmission after receiving the information of the UE synchronization, re-numbers the forwarded data packets, or reads the number of each packet upper layer and then sends the data packet. .

3) There are also problems with out of order here. That is, after the aGW performs the path switch, the high-level data packet will be sent from the aGW to the target eNodeB. At this time, the first data packet sent from the aGW (after path switching) will be forwarded than by the source eNodeB. The last packet arrives at the target eNodeB early, causing the target eNodeB to receive out-of-order reception of the data packet.

The inventor found in the process of the invention that the scheme for performing selective retransmission is optimized compared to the first scheme for user data, and no air interface resources are wasted. However, the problem of out-of-order data forwarding and transmission path conversion cannot be solved, and reordering at the target eNodeB brings about a large delay. Summary of the invention

Embodiments of the present invention provide a method and system for forwarding data during a handover process, in which In the process, reduce the delay caused by downlink data forwarding.

The method of the embodiment of the present invention includes the following steps: A. The source eNodeB forwards the service data unit SDU to the target eNodeB; B. The target eNodeB forwards the received SDU to the user side, and informs the end point of the forwarded data; C. The RLC delivers the received SDU to the user-side PDCP layer. D. The user-side PDCP layer sorts the SDUs before the end point of the forwarding data by the PDCP number and submits them to the upper layer.

The system of the embodiment of the present invention includes: a delivery unit, which is located at the user side RLC layer, and is used for submitting an SDU to the PDCP layer; and a sorting unit, which is located at the PDCP layer, and is used to send the data to the delivery unit before the end point of the data is forwarded by the PDCP number. The SDUs are sorted; a data end point notification unit is located, which is located at the target eNodeB for notifying the forwarding data end point.

The embodiment of the present invention does not perform the out-of-order reordering at the RLC layer, but the source eNodeB sequentially delivers the forwarded SDU to the PDCP layer of the user side through the target eNodeB and the user-side RLC, and the target eNodeB goes to the user side. The end point of the forwarding data is notified; the PDCP layer sorts the SDUs before the end point of the forwarding data by the PDCP number and submits them to the upper layer. Since the PDCP layer on the user side performs reordering, it can support that the target eNodeB does not need reordering, thereby reducing the delay caused by downlink data forwarding. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a structural diagram of an existing E-UTRAN system;

2 is a structural diagram of an existing E-UTRAN protocol stack;

3 is a flow chart of data forwarding when switching in an existing E-UTRAN system;

4 is a flow chart of handover of existing LTE across different eNodeBs;

FIG. 5 is a flowchart of steps of a method according to an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a system according to an embodiment of the present invention. detailed description

In order to reduce the delay caused by the downlink data forwarding, the embodiment of the present invention provides A method for forwarding data in a handover process, as shown in FIG. 5, includes the following main steps: S1. The source eNodeB forwards the SDU to the target eNodeB.

When switching, the source eNodeB forwards the SDU that has not been correctly acknowledged by the user or the SDU that is not correctly confirmed by the user to the target eNodeB in the order of reception (ie, in order) or in an out-of-order manner, and can inform the end point of the forwarded data. .

In the process of forwarding the SDU to the target eNodeB, the source eNodeB identifies the last SDU forwarded by the transport network (ie, adds a label to the last SDU forwarded to indicate the end point of the out-of-order reception, and transmits it through the FP); or A timer is set on the target eNodeB side. If an SDU is not received within the time limit, the target eNodeB determines that the forwarding data node arrives.

S2. The target eNodeB forwards the received SDU to the user side and informs the end point of the forwarded data.

In this step, the target eNodeB sends the data in an orderly manner according to the SDU number, and may also be sent out of order. Based on the SDU, the target eNodeB informs the user side of the manner of forwarding the data end point in one of the following manners: Mode 01: The target eNodeB is forwarding the data SDU. Find the data packet with the highest serial number, add an identifier to the data packet, or notify the user side by displaying signaling, indicating that the data packet is the end point of forwarding data.

Mode 02: The target eNodeB adds an identifier to the first data packet sent by the core network, or notifies the user side by displaying signaling, indicating that the data packet is the end point of forwarding data.

Mode 03: The target eNodeB indicates all forwarding data (for example, an identifier may be added to the forwarding data), or the user side is notified by displaying signaling to identify any unindicated data as core network data.

Mode 04: After sending all the forwarding data, the target eNodeB adds an identifier to each of the transmitted data, or notifies the user side by displaying signaling, indicating that any identified data is core network data, and receiving the corresponding data. The identification of the data is stopped after the confirmation of the identified data.

Alternatively, the target eNodeB divides the received SDU into PDUs, and performs RLC numbers on the PDUs according to the forwarding order or in an out-of-order manner. Based on the split PDUs, the target eNodeB informs the user side of the manner of forwarding the data end points in one of the following manners: Manner 11: The target eNodeB adds an indication bit in the header of the last PDU of the last SDU to be forwarded, or identifies the last PDU of the last SDU to be forwarded by displaying signaling.

Mode 12: (as a variant of mode 1) The target eNodeB adds an indication bit in the header of the last PDU of each SDU forwarded; or, by means of signaling, identifies the last PDU of each SDU forwarded. That is, not only the last PDU of the last SDU that needs to be forwarded is identified, but also the last PDU of each of its previous SDUs is identified.

Manipulation 13: After the eNB sends the last PDU of the SDU to be forwarded, the target eNodeB adds an indication bit in the header of the last PDU of the first SDU transmitted from the aGW; or transmits the indication from the aGW by displaying the signaling manner. The last PDU of the first SDU coming.

Mode 14: (as a variant of mode 3) after the PDUs of the last SDU that need to be forwarded are sent, the target eNodeB adds an indication bit to the header of the last PDU of each SDU transmitted from the aGW; or, by displaying The signaling mode identifies the last PDU of each SDU transmitted from the aGW. When the target eNodeB receives a response message that any of the identified PDUs are correctly received, the operation of adding the indication is stopped.

S3. The user side RLC submits the received SDU to the user side PDCP layer.

User side RLC performs an orderly delivery function, or

The function of the user side RLC to deliver the data to the PDCP layer in an out-of-order manner is triggered when the first SDU sent by the target eNodeB is received after the start of the handover.

In this step, the manner in which the user side submits the SDU to the PDCP layer is one of the following modes: Mode 20: When detecting the complete SDU, the user-side RLC determines whether the order is received, and if yes, submits to the PDCP, otherwise the buffer is In the RLC reordering buffer, until the order is received, or the RLC timer expires, when the window moves, the received SDU is delivered to the PDCP layer.

Mode 21 (corresponding mode 11 to mode 14 and corresponding mode 01 to mode 04): When the user side RLC detects that there is a complete SDU in the local cache, it immediately submits it to the PDCP layer (indiscriminate delivery).

Mode 22 (corresponding to mode 11): The user side RLC caches the PDUs sent by the target eNodeB, and sorts according to the PDU number. After the user side RLC correctly receives the identified PDU, the cached PDU The SDU check is performed, and then the SDU corresponding to the number of the identified PDU is numbered and delivered to the PDCP layer.

Mode 23 (corresponding to the method 12): The user-side RLC caches the PDUs sent by the target eNodeB and sorts them according to the PDU number. After the user-side RLC receives the unidentified PDUs, the number in the cache is smaller than the number of the unidentified PDUs. The PDU is SDU-calibrated, and then the SDU corresponding to the number of the unidentified PDU is numbered and submitted to the PDCP layer.

Method 24 (corresponding to mode 13 and mode 14):

The user-side RLC caches the PDUs sent by the target eNodeB and sorts them according to the PDU number. After receiving the identified PDUs, the user-side RLC performs SDU check on the PDUs whose number is smaller than the number of the identified PDUs, and then numbers them. The SDU corresponding to the number of the identified PDU is delivered to the PDCP layer.

In this step, the manner in which the user side informs the PDCP layer to forward the end point of the data is in the following manner 31 (corresponding to the above manner 21 + mode 11): when the user side RLC sets the number corresponding to the SDU corresponding to the number of the identified PDU When submitting to the PDCP layer or ending the RLC ordering, the PDCP layer is notified to end the out-of-order reception, and the subsequently received SDUs are sequentially delivered.

Mode 32 (corresponding to the foregoing mode 21+mode 12): when the user-side RLC submits the SDU corresponding to the identified PDU to the PDCP layer or ends the RLC sorting, the PDCP layer is notified to the out-of-order reception, and the subsequent received is sequentially delivered. SDU.

Mode 33: (corresponding to the above-mentioned mode 21+ mode 13; mode 21+mode 14): When the user-side RLC submits the SDUs whose number is smaller than the number of the identified PDUs to the PDCP layer or ends the RLC sorting, the PDCP layer is notified of the out-of-order The reception ends, and the subsequently received SDUs are submitted in order.

Mode 34 (corresponding to the foregoing mode 22, mode 23, and mode 24): After the user-side RLC delivers the corrected SDU to the PDCP layer, it notifies the PDCP layer to forward the data, and sequentially delivers the subsequently received SDU.

Further, based on the manner in which the user side submits the SDU to the PDCP layer, and the forwarding data end point corresponding thereto, the user side RLC may also record that the complete and delivered PDCP layer is received. The number of the PDU is based on the number of the recorded PDU and the end point of the forwarding data to check whether the SDU corresponding to the PDU received before the end point of the forwarding data is an out-of-order SDU, thereby avoiding the SUD of the subsequent sequence before the last out-of-order The SDU arrives at the user side, causing the sequential SUD to be mistaken for the out-of-order SDU, which is then submitted to the PDCP layer for misordering (also in step S4).

S4. The PDCP layer on the user side sorts the SDUs before the end point of the forwarding data by the PDCP number and submits them to the upper layer.

The PDCP layer triggers the sorting function when the user side performs the RLC reset, sorts the received SDUs by the PDCP SDU sequence number, and delivers the data to the upper layer when the SDU is received in an orderly manner, otherwise the data is cached in the rearrangement buffer. Until the end of the forwarding data sent by the user side is received, the sorting function is ended and the sorted SDUs are submitted to the upper layer;

Further, the user-side PDCP layer may determine the ordered reception of the forwarding data according to the forwarding data end point sent by the target eNodeB;

In this step, the manner in which the user-side PDCP layer determines that the forwarding data is received in an order is in the following manner 41 (corresponding to the above 01): When the RLC delivers the received SDU to the PDCP in an orderly manner, the highest sequence number is received on the PDCP layer of the user side. When forwarding data, stop the PDCP reordering function, and deliver the ordered data to the upper layer; or set a timer, and judge whether the data smaller than the serial number is received within the timer range, and if so, Stop the PDCP reordering function and deliver the ordered data to the upper layer; otherwise, until the timer expires, stop the PDCP reordering function and deliver the received data to the upper layer.

Mode 42 (corresponding to the above 02): The RLC delivers the received SDU to the PDCP in an orderly manner, and when the user-side PDCP layer receives the first data packet from the core network, stops the PDCP re-discharging function and receives the ordered order. The data is submitted to the upper layer; or a timer is set, and it is judged whether the data smaller than the serial number is received within the timer range, and if so, the PDCP reordering function is stopped, and the orderly received data is delivered to the upper layer. Otherwise, until the timer expires, the PDCP reordering function is stopped, and the received data is delivered to the upper layer.

Mode 43 (corresponding to the above 03): Receive any unspecified data packet at the user side PDCP layer Stop the PDCP reordering function and deliver the received data to the upper layer;

Method 44 (corresponding to the above 04): When the PDCP layer of the user side receives any identified data packet, stop the PDCP reordering function, and deliver the received data to the upper layer;

Or

The PDCP layer extracts the received PDCP number of each PDU, and reorders the SDUs by the PDCP number until the end of the forwarding data sent by the user side, ends the sorting, and delivers the sorted SDUs to a higher layer. The SDU is then submitted to the higher layers in the order of reception.

Further, the PDCP layer may also record the mapping relationship between the PDCP number of the received PDU and the RLC number, and according to the mapping relationship and the forwarding data end point check, whether the SDU corresponding to the PDU received before the end of the forwarding data is an out-of-order SDU .

The following is specifically described by eight examples.

Embodiment 1: Combination of the above mode 11, mode 21 and mode 31.

L11. After the source eNodeB receives the handover confirmation of the target eNodeB or the source eNodeB sends a handover command to the user side, the source eNodeB, according to the reception order, will not correctly confirm the SDU by the user side or from the first one that is not correctly confirmed by the user. The SDU is forwarded to the target eNodeB. At the same time, the last SDU forwarded is identified by the transmission network. Alternatively, a timer is set on the target eNodeB side. If an SDU is not received within the timeout period, the target eNodeB determines to forward the data node accordingly.

L12. The target eNodeB generates a corresponding RLC entity to buffer the received SDU. After receiving the handover confirmation or synchronization information of the user side, the transmission of the user plane data is started. In the process of forwarding the SDU, the target eNodeB re-executes the RLC number of the PDU in the order of the arrival of the SDU data packet (ie, splits the SDU into several PDUs and sequentially numbers the PDUs), or reads The PDCP number in the SDU is sent to the user side in the order of reception.

In this step, the received SDUs are not sorted by the PDCP number on the target eNodeB side.

L13. The target eNodeB adds an indication bit in the header of the last PDU of the last SDU to be forwarded in the process of sending the SDU to the user side, or identifies the last SDU to be forwarded by displaying the signaling manner. The last PDU to inform the user to forward W 200

The end point of the data.

L14. After the user side receives the handover command message (can be connected to step L11), the operation of resetting the RLC entity is started, including: notifying the upper layer (PDCP layer) to generate (activate) the PDCP sorting unit, and starting out-of-order sequencing; detecting Whether the RLC receives the complete SDU in the buffer; deletes the incomplete SDU segment; initializes the parameters such as the user side timer and the state variable.

L15. When the first SDU sent by the target eNodeB is received, the reset RLC entity triggers the RLC receive buffer reassembly delivery function, and immediately reports the complete SDU, and immediately submits to the PDCP layer, regardless of The order of the PDU number. The user side starts to deliver the SDUs received from the target eNodeB in the out-of-order manner to the PDCP layer.

L16. When the user-side RLC submits the SDUs whose number is less than or equal to the number of the identified PDUs to the PDCP layer or ends the RLC ordering, notify the PDCP layer to end the out-of-order reception, and submit the subsequently received SDUs in order; After receiving the identified PDU, the user side performs the SDU in the RLC receiving buffer with the PDU number corresponding to the PDU number corresponding to the identified PDU number N, and must wait until the PDU with the PDU number less than or equal to N is successfully received or deleted. The complete SDU corresponding to the N PDU can be reassembled to the PDCP layer. The PDU is deleted according to a set reordering mechanism, controlled by a window or a chronograph.

The L17 and PDCP layers are reordered according to the received PDCP number of the SDU.

L18. When each PDU whose TDU number is less than or equal to N is delivered to the PDCP layer or reaches the maximum number of retransmissions or moves out of the receiving window, the user-side RLC entity notifies the PDCP entity, and the PDCP sends the sorted SDU to a higher layer, and hangs Start its sorting function.

Embodiment 2: A combination of the above mode 12, mode 21 and mode 32.

L21 and L22 are the same as L11 and L12.

L23. The target eNodeB adds an indication bit in the header of the last PDU of each SDU forwarded during the process of sending the SDU to the user side; or, by displaying the signaling mode, the last PDU of each SDU that is forwarded.

L24 is the same as L14.

L25 is the same as L15. L26. When the user-side RLC submits the SDU corresponding to the identified PDU to the PDCP layer or ends the RLC ordering, it notifies the PDCP layer that the out-of-order reception ends, and sequentially delivers the subsequently received SDU; that is, correctly receives the unidentified PDU. After that, the user side delivers the SDUs corresponding to the unrecognized PDU number N in the RLC receiving buffer, and must wait until the PDU whose PDU number is less than N is successfully received or deleted, and the PDU is greater than or equal to N. The corresponding complete SDU can be reassembled to the PDCP layer. The PDU is deleted according to a set reordering mechanism, controlled by a window or a chronograph.

L27 is the same as L17.

L28. When each PDU whose PDU number is less than N is delivered to the PDCP layer or reaches the maximum number of retransmissions or moves out of the receiving window, the user-side RLC entity notifies the PDCP entity, and the PDCP sends the sorted SDU to a higher layer, suspending Its sorting function.

Embodiment 3: A combination of the above mode 11, mode 22 and mode 34.

L31 to L34 are the same as L11 to L14.

L35, the user side RLC caches the PDUs sent by the target eNodeB, and sorts according to the PDU number. After the user side RLC correctly receives the identified PDU, performs SDU check on the buffered PDU (that is, the number is less than or equal to the number of the identified PDU). The corresponding SDUs are delivered to the PDCP layer. The SDUs corresponding to the PDUs with the number greater than N are delivered in order.

L36. After the user-side RLC delivers the verified SDU to the PDCP layer, it notifies the PDCP layer to forward the data, and sequentially delivers the subsequently received SDU.

L37. The PDCP layer reorders according to the received PDCP number of the SDU.

L38 is the same as L18.

Embodiment 4: A combination of the above modes 13, mode 21 and mode 33.

L41 and L42 are the same as L11 and L12.

L43. In the process of sending the SDU to the user side, the target eNodeB adds an indication bit in the header of the last PDU of the first SDU transmitted from the aGW after issuing the last PDU of the SDU to be forwarded, or Display signaling mode identification from the aGW transmission The last PDU of an SDU to inform the user side of the end point of forwarding data.

L44 and L45 are the same as L14 and L15.

L46. When the user-side RLC submits the SDUs whose number is smaller than the number of the identified PDUs to the PDCP layer or ends the RLC ordering, it notifies the PDCP layer that the out-of-order reception ends, and sequentially delivers the SDUs that are subsequently received.

The L47 and PDCP layers are reordered according to the received PDCP number of the SDU.

After receiving the notification from the user-side RLC entity, the L48 and PDCP layers send the sorted SDU to a higher layer and suspend its sorting function.

Embodiment 5: Combination of the above method 14, mode 21 and mode 33.

L51 and L52 are the same as L11 and L12.

L53. The target eNodeB adds an indication bit in the header of the last PDU of each SDU transmitted from the aGW after transmitting the SDU to the user side, after issuing the last PDU of the SDU to be forwarded; or The signaling mode is displayed to identify the last PDU of each SDU transmitted from the aGW. When the target eNodeB receives a response message that any of the identified PDUs are correctly received, the operation of adding the indication is stopped.

L54 and L55 are the same as L14 and L15.

L56. When the user-side RLC submits the SDUs whose number is smaller than the number of the identified PDUs to the PDCP layer or ends the RLC ordering, notify the PDCP layer that the out-of-order reception ends, and sequentially delivers the subsequently received SDUs; After the identified PDU, a correctly received response message is returned to the target eNodeB.

L57 and L58 are the same as L47 and L48.

Embodiment 6: A combination of the above modes 13, mode 24 and mode 34.

L61 to L63 are the same as L41 to L43.

L64, the user side RLC caches the PDUs sent by the target eNodeB, and sorts according to the PDU number. After receiving the identified PDUs, the user side RLC performs SDU check on the PDUs whose number is smaller than the number of the identified PDUs. The SDUs whose numbers are smaller than the number of the identified PDUs are delivered to the PDCP layer. L65. After the user-side RLC delivers the verified SDU to the PDCP layer, it notifies the PDCP layer to forward the data, and sequentially delivers the subsequently received SDU.

L67 and L68 are the same as L37 and L38.

Embodiment 7: The combination of the foregoing mode 11, mode 21 and mode 31; and the PDCP layer records and verifies the out-of-order SDU according to the mapping relationship.

L71 to L74 are the same as L11 to L14.

L75 is the same as L15; and the PDCP layer records the mapping relationship between the PDCP number of the received PDU and the RLC number.

L76 is the same as L16.

The L77 and the PDCP layer firstly determine whether the SDU corresponding to the PDU received before the data end point is an out-of-order SDU according to the mapping relationship and the forwarding data end point. After that, the PDCP layer reorders according to the PDCP number of the received PDU.

L78 is the same as L18.

Embodiment 8: A combination of the foregoing mode 11, mode 21 and mode 31; and the user side RLC record receives the RLC number of the complete PDU that has been delivered to the PDCP layer, and verifies the out-of-order SDU.

L81 to L874 are the same as U1 to L14.

L85 is the same as L15; and the user side RLC records the RLC number of the PDU that received the complete and delivered PDCP layer.

L86, which is the same as L16; and after the user-side RLC entity correctly receives the identified PDU sent by the target eNodeB, according to the recorded PDU number and the forwarding data end point check, the PDU received before the end point of the forwarding data is verified. Whether the corresponding SDU is an out-of-order SDU. If an SDU corresponding to the number N of the identified PDU has been reassembled and delivered to the PDCP layer, the SDU is deemed to have been successfully received, and if necessary, the corresponding timing is further updated. The window or window boundary, while notifying the PDCP layer that the SDU is not an out-of-order SDU.

The L87 and PDCP layers are reordered according to the received PDCP number of the SDU.

L88 is the same as L18.

Embodiment 9: a combination of the above mode 01, mode 21 and mode 41; W

L91. After the source eNodeB receives the handover confirmation of the target eNodeB or the source eNodeB sends a handover command to the user side, the source eNodeB forwards the SDU that is not correctly confirmed by the user side or from the first SDU that is not correctly confirmed by the user to the target eNodeB. . At the same time, the last SDU of the forwarding is identified by the transmission network. Alternatively, a timer is set on the target eNodeB side. If an SDU is not received within the time limit, the target eNodeB determines that the forwarding data node arrives.

L92. The target eNodeB buffers the received SDU. After receiving the handover confirmation or synchronization information on the user side, the transmission of the user plane data is started.

L93. In the process of transmitting the SDU to the user side, the target eNodeB adds an indication bit to the data of the highest sequence number in the forwarding data, or identifies the data by displaying signaling manner to notify the user side to forward the data end point.

L94. After receiving the handover command message, the user side starts to perform the operation of resetting the RLC entity, including: notifying the upper layer (PDCP layer) to generate (activate) the PDCP sorting unit, starting the sorting; detecting whether the complete SDU exists in the RLC receiving buffer. ; Delete incomplete SDU segments; initialize parameters such as user side timers and state variables.

The L95 and RLC layers perform the out-of-order delivery function, and as long as the complete SDU is detected in the RLC buffer, it is delivered to the PDCP layer.

The L96.PDCP layer performs reordering according to the received PDCP number of the SDU. When the user side PDCP rearrangement entity receives the data of the highest sequence number, the timer is started, and the timer is determined to be smaller than the sequence number. Whether the data is received completely, if yes, stop the PDCP reordering function, and deliver the received data to the upper layer; otherwise, until the timer expires, stop the PDCP reordering function and deliver the received data to the upper layer.

Embodiment 10: a combination of the above modes 02, 21 and 42;

L101 is the same as L91.

L102 is the same as L92.

L103. The target eNodeB sends an SDU to the user side, and adds an indication bit to the first data from the core network in the forwarding data, or identifies the data by displaying signaling manner to notify the user side to forward the data end point. L104 is the same as L94.

The L105.RLC layer performs the out-of-order delivery function, and as long as the complete SDU is detected in the RLC buffer, it is delivered to the PDCP layer.

L106. The PDCP layer performs reordering according to the PDCP number of the received SDU. When the user-side PDCP rearrangement entity receives the first data from the core network, the timer is started, and the data is determined within the timer range. Whether all the previous data is received, if yes, stop the PDCP reordering function, and deliver the received data to the upper layer; otherwise, until the timer expires, stop the PDCP reordering function and deliver the received data to the upper layer.

Embodiment 11: Combination of the above modes 03, 20 and 43;

L111 is the same as L91.

L112 is the same as L92.

L113. The target eNodeB sends the SDU in sequence to the user side, and adds an indication bit to all the forwarding data in the forwarding data, or identifies the data by displaying signaling, indicating that the data is forwarding data.

L114 is the same as L94.

The L115 and RLC layers perform an ordered delivery function, and the SDU is delivered to the PDCP layer only when the RLC detects the ordered SDUs.

L116, the PDCP layer on the user side reorders according to the PDCP number of the received SDU. When the user side PDCP rearrangement entity receives any unidentified data, the PDCP reordering function is stopped, and the received data is delivered to High level.

Embodiment 12: a combination of the above modes 04, 20 and 44;

L121 is the same as L91.

L122 is the same as L92.

L123. The target eNodeB sends an SDU to the user side, and after sending all the forwarding data, adds an indication bit to each subsequent data, or identifies the data by displaying signaling, indicating that the data is core network data, and After receiving the confirmation of any core network data, the identification of the core network data is stopped. L124 is the same as L94.

L125 is the same as L95.

L126, the PDCP layer on the user side reorders according to the PDCP number of the received SDU. When the user side PDCP rearrangement entity receives data of any core network, the PDCP reordering function is stopped, and the received data is delivered to High level.

The embodiment of the present invention further provides a system for forwarding data during a handover process. Referring to FIG. 6, the method includes a sorting unit, and a delivery unit and a forwarding data end point notification unit connected to the sorting unit. The first trigger unit and the second trigger unit are connected to the sorting unit.

The delivery unit is located at the user side RLC layer and is used to deliver the SDU to the user side PDCP layer. The sorting unit is located at the user side PDCP layer, and is configured to perform 4 out-of-order SDUs sent by the submitting unit before the end point of the forwarding data by the PDCP sequence number.

The first trigger unit is located at the user side PDCP layer, and is used to trigger the sorting unit to start sorting when the RLC reset is performed on the user side.

The second triggering unit is located at the user side PDCP layer, and is configured to: after receiving the SDU data of the identification end point, determine that the data before the identification data is ordered by the sorting unit, and stop the sorting unit. Sorting function.

The forwarding data end point notification unit is located in the target eNodeB for notifying the forwarding data end point.

In summary, the method in the embodiment of the present invention does not perform out-of-order reordering in the RLC layer, but in the handover, the source eNodeB sequentially passes the target eNodeB and the user-side RLC, and the SDU that is not correctly confirmed by the user or from the first The SDUs that are not correctly acknowledged by the user are delivered to the PDCP layer on the user side, and the target eNodeB informs the user side of the end point of the forwarding data. The PDCP layer sorts the SDUs before the end point of the forwarding data by PDCP number and submits them to the upper layer. .

The embodiment of the invention further provides a system for forwarding data during a handover process.

The reordering of the PDCP layer on the user side in the embodiment of the present invention can support that the target eNodeB does not need to be reordered, thereby reducing the delay caused by downlink data forwarding.

The PDCP layer reordering on the user side according to the embodiment of the present invention is compared to the existing user side RLC. The reliability of the sequential delivery scheme is more strictly guaranteed, reducing the complexity of higher layer processing.

In the embodiment of the present invention, when the PDCP layer is sorted on the user side, the user-side RLC may not perform the RLC numbering of the PDU, that is, the out-of-order delivery may be supported, thereby reducing the processing delay caused by the unnecessary two-layer sequencing on the user side. . The spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of the inventions

Claims

Rights request

A method for forwarding data during a handover process, comprising the steps of:

A. The source base station forwards the service data unit SDU to the target base station;

B. The target base station forwards the received SDU to the user side, and informs the end point of the forwarded data;

C. The user side RLC submits the received SDU to the user side PDCP layer;

D. The PDCP layer on the user side sorts the SDUs before the end point of the forwarding data by PDCP number and submits them to the upper layer.

2. The method according to claim 1, wherein in step A, the source base station sequentially forwards the SDU, and the SDU is an SDU that is not correctly confirmed by the user, or is the first SDU that is not correctly confirmed by the user. And all SDUs after the SDU.

The method according to claim 1, wherein in step B, the target base station sequentially forwards the received SDU to the user side.

The method according to claim 1, wherein the target base station sets the end point of the forwarding data in the step B: setting a timer on the target base station side, and after the timer expires, the target eNB stops receiving and forwarding. Data, and set the end point of the forwarding data in the received data.

The method according to claim 1, wherein the method in which the target base station sets the end point of forwarding data in step B is: the source base station identifies the last SDU through the transmission network, and the target base station receives the identified forwarding. After the data is stopped, the received data is stopped, and the end point of the forwarding data is set in the received data.

6. The method according to claim 1, wherein the function of sorting by the FDCP layer in step D is triggered when the user side performs RLC reset.

The method according to any one of claims 1 to 6, wherein in step D, after receiving the SDU data of the identification end point, the PDCP layer of the user side determines that the data before the identification data has been sorted. When ordered, the PDCP sorting function is stopped.

8. The method according to claim 7, wherein in step B, the manner of informing the end point of forwarding data is: The SDU that identifies the highest sequence number in the forwarding data is the end point of the forwarding data.

The method according to claim 8, wherein in step D, it is determined that the data before the identification data is sorted and the order is:

The RLC delivers the received SDU to the PDCP in an orderly manner, and after receiving the identification data, the user-side PDCP layer determines that the data before the identification data is sorted and is ordered; or

A timer is started, and when the timer expires or the data before the identification data has been received within the timing, the data before the identification data is determined to be ordered.

10. The method according to claim 7, wherein in step B, the manner of informing the end point of the forwarding data is:

Notifying the user side of the sequence number of the first data packet received by the target base station from the core network, to identify the data packet of the sequence number as the end point of the forwarding data; or

The user is informed of the previous sequence number of the sequence number of the first data packet received by the target base station from the core network, to identify the data packet of the sequence number as the end point of the forwarding data.

The method according to claim 10, wherein in step D, it is determined that the data before the identification data is sorted and has been ordered:

The RLC delivers the received SDU to the PDCP in an orderly manner, and after receiving the data of the serial number, the user-side PDCP determines that the data before the identification data is sorted and is already ordered; or

A timer is started, and when the timer expires or the data before the data of the serial number has been received within the time limit, the teaching before the identification data is determined: the order is sorted.

12. The method according to claim 7, wherein in step B, the manner of informing the end point of the forwarding data is:

The target base station indicates all the forwarded data to identify the non-forwarded data as the end point of the forwarded data.

The method according to claim 12, wherein in step D, the data before the identification data is sorted is ordered: the user side PDCP layer receives any unindicated data. Then, it is determined that the data before the identification data is sorted and then ordered.

14. The method according to claim 7, wherein in step B, the notification is forwarded The way the data ends up is:

After all the forwarded data has been sent, each data that is subsequently sent is identified.

The method according to claim 14, wherein in step D, the data before the identification data is sorted is ordered: the user side PDCP layer receives any one of the identified data. Then, it is determined that the data before the identification data is sorted and is already ordered.

The method according to claim 14, wherein in step B, after receiving the confirmation of any pair of identification data, the target base station stops identifying the transmitted data.

17. A system for forwarding data during a handover process, comprising:

a delivery unit, which is located at the user-side RLC layer, for delivering the SDU to the user-side PDCP layer, and a sorting unit, which is located at the user-side PDCP layer, for sorting the SDUs sent by the delivery unit before the end point of the forwarding data by the PDCP number;

The forwarding data end point notification unit is located at the target base station for notifying the forwarding data end point.

The system of claim 17, wherein the system further comprises: a first triggering unit, located at a user-side PDCP layer, for triggering the sorting unit to start sorting when the user side performs an RLC reset;

a second triggering unit, which is located at the user side PDCP layer, and is configured to: after receiving the SDU data of the identification end point, determine that the data before the identification data is ordered by the sorting unit, and stop the sorting function of the sorting unit .