WO2015123883A1

WO2015123883A1 - Radio link control entity re-establishment

Info

Publication number: WO2015123883A1
Application number: PCT/CN2014/072454
Authority: WO
Inventors: Xuepan GUAN; Huan Xu; Tim Tynghuei Liou
Original assignee: Qualcomm Incorporated
Priority date: 2014-02-24
Filing date: 2014-02-24
Publication date: 2015-08-27

Abstract

In wireless communications a method includes determining whether an acknowledgement is received for a transmitted data unit during a re-establishment procedure for a radio link. The method also includes storing the data unit when the acknowledgement is not received for the transmitted data unit. The method further includes re-transmitting at least a portion of the unacknowledged data unit at a lower layer during the re-establishment procedure.

Description

RADIO LINK CONTROL ENTITY RE-ESTABLISHMENT

BACKGROUND

Field

[0001] Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to re-establishment of a radio link control entity.

Background

[0002] Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the Universal Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). For example, China is pursuing TD- SCDMA as the underlying air interface in the UTRAN architecture with its existing GSM infrastructure as the core network. The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks. HSPA is a collection of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), that extends and improves the performance of existing wideband protocols.

[0003] As the demand for mobile broadband access continues to increase, research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications. SUMMARY

[0004] According to one aspect of the present disclosure, a method for wireless communication includes determining whether an acknowledgement is received for a transmitted data unit during a re-establishment procedure for a radio link. The method may also include storing the data unit when the acknowledgement is not received for the transmitted data unit. The method may also include re-transmitting at least a portion of the unacknowledged data unit at a lower layer during the re-establishment procedure.

[0005] According to another aspect of the present disclosure, an apparatus for wireless communication includes means for determining whether an acknowledgement is received for a transmitted data unit during a re-establishment procedure for a radio link. The apparatus may also include means for storing the data unit when the acknowledgement is not received for the transmitted data unit. The apparatus may also include means for retransmitting at least a portion of the unacknowledged data unit at a lower layer during the re-establishment procedure.

[0006] According to one aspect of the present disclosure, a computer program product for wireless communication in a wireless network includes a computer readable medium having non-transitory program code recorded thereon. The program code includes program code to determine whether an acknowledgement is received for a transmitted data unit during a re-establishment procedure for a radio link. The program code also includes program code to store the data unit when the acknowledgement is not received for the transmitted data unit. The program code also includes program code to re-transmit at least a portion of the unacknowledged data unit at a lower layer during the re-establishment procedure.

[0007] According to one aspect of the present disclosure, an apparatus for wireless communication includes a memory and a processor(s) coupled to the memory. The processor(s) is configured to determine whether an acknowledgement is received for a transmitted data unit during a re-establishment procedure for a radio link. The processor(s) is further configured to store the data unit when the acknowledgement is not received for the transmitted data unit. The processor(s) is further configure to re-transmit at least a portion of the unacknowledged data unit at a lower layer during the re-establishment procedure.

[0008] This has outlined, rather broadly, the features and technical advantages of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described below. It should be appreciated by those skilled in the art that this disclosure may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the teachings of the disclosure as set forth in the appended claims. The novel features, which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages, will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The features, nature, and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout.

[0010] FIGURE 1 is a block diagram conceptually illustrating an example of a telecommunications system.

[0011] FIGURE 2 is a block diagram conceptually illustrating an example of a frame structure in a telecommunications system.

[0012] FIGURE 3 is a block diagram conceptually illustrating an example of a node B in communication with a UE in a telecommunications system.

[0013] FIGURE 4 is a conceptual diagram illustrating an example of a radio protocol architecture for the user and control plane.

[0014] FIGURE 5 illustrates an example of network coverage areas.

[0015] FIGURE 6 shows an example of a wireless communication method according to one aspect of the present disclosure. [0016] FIGURE 7 is a diagram illustrating a processing system according to one aspect of the present disclosure.

[0017] FIGURE 8 is a diagram illustrating an RLC re-establish operation according to the prior art.

[0018] FIGURE 9 is a diagram illustrating an RLC re-establish operation according to one aspect of the present disclosure.

DETAILED DESCRIPTION

[0019] The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0020] Turning now to FIGURE 1 , a block diagram is shown illustrating an example of a telecommunications system 100. The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. By way of example and without limitation, the aspects of the present disclosure illustrated in FIGURE 1 are presented with reference to a UMTS system employing a TD-SCDMA standard. In this example, the UMTS system includes a (radio access network) RAN 102 (e.g., UTRAN) that provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The RAN 102 may be divided into a number of Radio Network Subsystems (RNSs) such as an RNS 107, each controlled by a Radio Network Controller (RNC) such as an RNC 106. For clarity, only the RNC 106 and the RNS 107 are shown; however, the RAN 102 may include any number of RNCs and RNSs in addition to the RNC 106 and RNS 107. The RNC 106 is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS 107. The RNC 106 may be interconnected to other RNCs (not shown) in the RAN 102 through various types of interfaces such as a direct physical connection, a virtual network, or the like, using any suitable transport network.

[0021] The geographic region covered by the RNS 107 may be divided into a number of cells, with a radio transceiver apparatus serving each cell. A radio transceiver apparatus is commonly referred to as a node B in UMTS applications, but may also be referred to by those skilled in the art as a base station (BS), a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), or some other suitable terminology. For clarity, two node Bs 108 are shown; however, the RNS 107 may include any number of wireless node Bs. The node Bs 108 provide wireless access points to a core network 104 for any number of mobile apparatuses. Examples of a mobile apparatus include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a notebook, a netbook, a smartbook, a personal digital assistant (PDA), a satellite radio, a global positioning system (GPS) device, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, or any other similar functioning device. The mobile apparatus is commonly referred to as user equipment (UE) in UMTS applications, but may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a wireless terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology. For illustrative purposes, three UEs 110 are shown in communication with the node Bs 108. The downlink (DL), also called the forward link, refers to the communication link from a node B to a UE, and the uplink (UL), also called the reverse link, refers to the communication link from a UE to a node B.

[0022] The core network 104, as shown, includes a GSM core network. However, as those skilled in the art will recognize, the various concepts presented throughout this disclosure may be implemented in a RAN, or other suitable access network, to provide UEs with access to types of core networks other than GSM networks. [0023] In this example, the core network 104 supports circuit-switched services with a mobile switching center (MSC) 112 and a gateway MSC (GMSC) 114. One or more RNCs, such as the RNC 106, may be connected to the MSC 112. The MSC 112 is an apparatus that controls call setup, call routing, and UE mobility functions. The MSC 112 also includes a visitor location register (VLR) (not shown) that contains subscriber-related information for the duration that a UE is in the coverage area of the MSC 112. The GMSC 114 provides a gateway through the MSC 112 for the UE to access a circuit-switched network 116. The GMSC 114 includes a home location register (HLR) (not shown) containing subscriber data, such as the data reflecting the details of the services to which a particular user has subscribed. The HLR is also associated with an authentication center (AuC) that contains subscriber-specific authentication data. When a call is received for a particular UE, the GMSC 114 queries the HLR to determine the UE's location and forwards the call to the particular MSC serving that location.

[0024] The core network 104 also supports packet-data services with a serving GPRS support node (SGSN) 118 and a gateway GPRS support node (GGSN) 120. GPRS, which stands for General Packet Radio Service, is designed to provide packet-data services at speeds higher than those available with standard GSM circuit-switched data services. The GGSN 120 provides a connection for the RAN 102 to a packet-based network 122. The packet-based network 122 may be the Internet, a private data network, or some other suitable packet-based network. The primary function of the GGSN 120 is to provide the UEs 110 with packet-based network connectivity. Data packets are transferred between the GGSN 120 and the UEs 110 through the SGSN 118, which performs primarily the same functions in the packet-based domain as the MSC 112 performs in the circuit-switched domain.

[0025] The UMTS air interface is a spread spectrum Direct-Sequence Code Division Multiple Access (DS-CDMA) system. The spread spectrum DS-CDMA spreads user data over a much wider bandwidth through multiplication by a sequence of pseudorandom bits called chips. The TD-SCDMA standard is based on such direct sequence spread spectrum technology and additionally calls for a time division duplexing (TDD), rather than a frequency division duplexing (FDD) as used in many FDD mode UMTS/W-CDMA systems. TDD uses the same carrier frequency for both the uplink (UL) and downlink (DL) between a node B 108 and a UE 110, but divides uplink and downlink transmissions into different time slots in the carrier.

[0026] In a conventional RAN, the service area may be divided into a plurality of routing areas (RAs). Here, each RA is identified by a corresponding routing area identity (RAI). The RA corresponding to a particular RAI is generally defined by the network operator, and includes one or more cells defining a paging area for incoming packet- switched calls. A location area (LA) is a group of one or more RAs, and defines a paging area for incoming circuit-switched calls. The LA is identified by a corresponding location area identity (LAI).

[0027] The RAI is made up of the LAI and a routing area code (RAC). The LAI includes a mobile country code (MCC), a mobile network code (MNC), and a location area code (LAC). With this information, page messages for a particular UE may be routed to the corresponding RNS so that the UE can receive the incoming page.

[0028] FIGURE 2 shows a frame structure 200 for a TD-SCDMA carrier. The TD- SCDMA carrier, as illustrated, has a frame 202 that is 10 ms in length. The chip rate in TD-SCDMA is 1.28 Mcps. The frame 202 has two 5 ms subframes 204, and each of the subframes 204 includes seven time slots, TS0 through TS6. The first time slot, TS0, is usually allocated for downlink communication, while the second time slot, TS1, is usually allocated for uplink communication. The remaining time slots, TS2 through TS6, may be used for either uplink or downlink, which allows for greater flexibility during times of higher data transmission times in either the uplink or downlink directions. A downlink pilot time slot (DwPTS) 206, a guard period (GP) 208, and an uplink pilot time slot (UpPTS) 210 (also known as the uplink pilot channel (UpPCH)) are located between TS0 and TS1. Each time slot, TS0-TS6, may allow data transmission multiplexed on a maximum of 16 code channels. Data transmission on a code channel includes two data portions 212 (each with a length of 352 chips) separated by a midamble 214 (with a length of 144 chips) and followed by a guard period (GP) 216 (with a length of 16 chips). The midamble 214 may be used for features, such as channel estimation, while the guard period 216 may be used to avoid inter-burst interference. Also transmitted in the data portion is some Layer 1 control information, including Synchronization Shift (SS) bits 218. Synchronization Shift bits 218 only appear in the second part of the data portion. The Synchronization Shift bits 218 immediately following the midamble can indicate three cases: decrease shift, increase shift, or do nothing in the upload transmit timing. The positions of the SS bits 218 are not generally used during uplink communications.

[0029] FIGURE 3 is a block diagram of a node B 310 in communication with a UE 350 in a RAN 300, where the RAN 300 may be the RAN 102 in FIGURE 1, the node B 310 may be the node B 108 in FIGURE 1, and the UE 350 may be the UE 110 in FIGURE 1. In the downlink communication, a transmit processor 320 may receive data from a data source 312 and control signals from a controller/processor 340. The transmit processor 320 provides various signal processing functions for the data and control signals, as well as reference signals (e.g., pilot signals). For example, the transmit processor 320 may provide cyclic redundancy check (CRC) codes for error detection, coding and interleaving to facilitate forward error correction (FEC), mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM), and the like), spreading with orthogonal variable spreading factors (OVSF), and multiplying with scrambling codes to produce a series of symbols. Channel estimates from a channel processor 344 may be used by a controller/processor 340 to determine the coding, modulation, spreading, and/or scrambling schemes for the transmit processor 320. These channel estimates may be derived from a reference signal transmitted by the UE 350 or from feedback contained in the midamble 214 (FIGURE 2) from the UE 350. The symbols generated by the transmit processor 320 are provided to a transmit frame processor 330 to create a frame structure. The transmit frame processor 330 creates this frame structure by multiplexing the symbols with a midamble 214 (FIGURE 2) from the controller/processor 340, resulting in a series of frames. The frames are then provided to a transmitter 332, which provides various signal conditioning functions including amplifying, filtering, and modulating the frames onto a carrier for downlink transmission over the wireless medium through smart antennas 334. The smart antennas 334 may be implemented with beam steering bidirectional adaptive antenna arrays or other similar beam technologies.

[0030] At the UE 350, a receiver 354 receives the downlink transmission through an antenna 352 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 354 is provided to a receive frame processor 360, which parses each frame, and provides the midamble 214 (FIGURE 2) to a channel processor 394 and the data, control, and reference signals to a receive processor 370. The receive processor 370 then performs the inverse of the processing performed by the transmit processor 320 in the node B 310. More specifically, the receive processor 370 descrambles and despreads the symbols, and then determines the most likely signal constellation points transmitted by the node B 310 based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor 394. The soft decisions are then decoded and deinterleaved to recover the data, control, and reference signals. The CRC codes are then checked to determine whether the frames were successfully decoded. The data carried by the successfully decoded frames will then be provided to a data sink 372, which represents applications running in the UE 350 and/or various user interfaces (e.g., display). Control signals carried by successfully decoded frames will be provided to a controller/processor 390. When frames are unsuccessfully decoded by the receiver processor 370, the controller/processor 390 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0031] In the uplink, data from a data source 378 and control signals from the controller/processor 390 are provided to a transmit processor 380. The data source 378 may represent applications running in the UE 350 and various user interfaces (e.g., keyboard). Similar to the functionality described in connection with the downlink transmission by the node B 310, the transmit processor 380 provides various signal processing functions including CRC codes, coding and interleaving to facilitate FEC, mapping to signal constellations, spreading with OVSFs, and scrambling to produce a series of symbols. Channel estimates, derived by the channel processor 394 from a reference signal transmitted by the node B 310 or from feedback contained in the midamble transmitted by the node B 310, may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor 380 will be provided to a transmit frame processor 382 to create a frame structure. The transmit frame processor 382 creates this frame structure by multiplexing the symbols with a midamble 214 (FIGURE 2) from the controller/processor 390, resulting in a series of frames. The frames are then provided to a transmitter 356, which provides various signal conditioning functions including amplification, filtering, and modulating the frames onto a carrier for uplink transmission over the wireless medium through the antenna 352.

[0032] The uplink transmission is processed at the node B 310 in a manner similar to that described in connection with the receiver function at the UE 350. A receiver 335 receives the uplink transmission through the antenna 334 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 335 is provided to a receive frame processor 336, which parses each frame, and provides the midamble 214 (FIGURE 2) to the channel processor 344 and the data, control, and reference signals to a receive processor 338. The receive processor 338 performs the inverse of the processing performed by the transmit processor 380 in the UE 350. The data and control signals carried by the successfully decoded frames may then be provided to a data sink 339 and the controller/processor, respectively. If some of the frames were unsuccessfully decoded by the receive processor, the controller/processor 340 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0033] The controller/processors 340 and 390 may be used to direct the operation at the node B 310 and the UE 350, respectively. For example, the controller/processors 340 and 390 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories 342 and 392 may store data and software for the node B 310 and the UE 350, respectively. For example, the memory 392 of the UE 350 may store a radio link control re-establishment module 391 which, when executed by the controller/processor 390, configures the UE 350 to re-establish a radio link control entity. A scheduler/processor 346 at the node B 310 may be used to allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs.

[0034] In a wireless telecommunication system, the communication protocol architecture may take on various forms depending on the particular application. For example, in a 3GPP UMTS system, the signaling protocol stack is divided into a Non- Access Stratum (NAS) and an Access Stratum (AS). The NAS provides the upper layers, for signaling between the UE 110 and the core network 104 (referring to FIGURE 1), and may include circuit switched and packet switched protocols. The AS provides the lower layers, for signaling between the UTRAN and the UE, and may include a user plane and a control plane. Here, the user plane or data plane carries user traffic, while the control plane carries control information (i.e., signaling).

[0035] Turning to FIGURE 4, the AS is shown with three layers: Layer 1, Layer 2, and Layer 3. Layer 1 is the lowest layer and implements various physical layer signal processing functions. Layer 1 will be referred to herein as the physical layer 406. The data link layer, called Layer 2 408, is above the physical layer 406 and is responsible for the link between the UE and Node B over the physical layer 406.

[0036] At Layer 3, the RRC layer 416 handles the control plane signaling between the UE and the Node B. RRC layer 416 includes a number of functional entities for routing higher layer messages, handling broadcasting and paging functions, establishing and configuring radio bearers, etc.

[0037] In the illustrated air interface, the L2 layer 408 is split into sublayers. In the control plane, the L2 layer 408 includes two sublayers: a medium access control (MAC) sublayer 410 and a radio link control (RLC) sublayer 412. In the user plane, the L2 layer 408 additionally includes a packet data convergence protocol (PDCP) sublayer 414. Although not shown, the UE may have several upper layers above the L2 layer 408 including a network layer (e.g., IP layer) that is terminated at a PDN gateway on the network side and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc.).

[0038] The PDCP sublayer 414 provides multiplexing between different radio bearers and logical channels. The PDCP sublayer 414 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between Node Bs.

[0039] The RLC sublayer 412 generally supports an acknowledged mode (AM) (where an acknowledgment and retransmission process may be used for error correction), an unacknowledged mode (UM), and a transparent mode for data transfers, and provides segmentation and reassembly of upper layer data packets and reordering of data packets to compensate for out-of-order reception due to a hybrid automatic repeat request (HARQ) at the MAC layer. In the acknowledged mode, RLC peer entities such as an RNC and a UE may exchange various RLC protocol data units (PDUs) including RLC Data PDUs, RLC Status PDUs, and RLC Reset PDUs, among others. In the present disclosure, the term "packet" may refer to any RLC PDU exchanged between RLC peer entities.

[0040] The MAC sublayer 410 provides multiplexing between logical and transport channels. The MAC sublayer 410 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer 410 is also responsible for HARQ operations.

[0041] Some base stations in a network may cover only a portion of a geographical area. FIGURE 5 illustrates coverage of a network, such as a TD-SCDMA network, as represented by individual base stations. A geographical area 500 may include multiple TD- SCDMA base stations, illustrated by towers 502a, 502b, and 502c, each serving their own respective geographic locations, illustrated by geographic cells 504a, 504b, and 504c, respectively. A user equipment (UE) 506 may move from one cell, such as cell 504a, to another cell, such as a cell 504b. The movement of the UE 506 may specify a handover or a cell reselection. The different base stations may be coordinated through a single radio network controller (RNC) or through different RNCs. If the base stations are controlled by different RNCs, they may be considered to be on different subsystems.

RADIO LINK CONTROL ENTITY RE-ESTABLISHMENT

[0042] Third generation (3G) communications networks (e.g., wideband code division multiple access (WCDMA) and time division synchronous code division multiple access (TD-SCDMA)) carry many traffic types from real-time circuit switched communication to internet protocol based packet switched communication. When the network changes a configuration of a radio link control (RLC) acknowledged mode (AM) entitya re- establishment procedure may be implemented at a user equipment (UE) based on a communications specification. For example, the UE performs re-establishment of the RLC AM entity for all active signaling radio bearers (SRBs, available for transmission of radio resource control (RRC) messages) as well as for user radio bearers (RBs, such as the RB for packet-switched data service) during a source radio network subsystem(SRNS) relocation pending state. The UE also perform re-establishment of the RLC AM entity when the network includes a re-establishment indicator in a RRC message. The RLC AM entity can be implemented as a transmitter or a receiver based on an implemented procedure or application. For example, the RLC AM entity includes a transmitting side and a receiving side, where the transmitting side transmits RLC protocol data units (PDUs) and the receiving side receives RLC PDUs.

[0043] According to some specifications (e,g., 3 GPP 25.322), when the re-establish procedure is implemented, some pending service data units (SDUs)that have not being acknowledged (i.e., no ACK received) by the network are dropped or discarded. Discarding these SDUs may be consequential to some signaling radio bearers. For example, some important signaling messages (e.g., lg/2a report) and/or transport control protocol (TCP) data may be dropped when the SDUs are discarded because the UE is unable to deliver the signaling messages (e.g., SRB messages) or the TCP data to the network. Further, discarding the SDUs may result in dropped calls or service interruptions. Furthermore, discarding SDUs associated with user applications, for example, may cause re-transmission of the SDUs at a higher layer. For example, in some instances, if these service data units are submitted to a lower layer (e.g., radio link control layer), the UE drops or discards the service data units during the re-establishment procedure regardless of whether an ACK is received for the service data units. Discarding the service data unit at the lower layer causes re-transmission of the service data unit at the higher layer (e.g., TCP layer).However, re-transmitting the SDUs at the higher layer increases the delay for the user application.

[0044] Aspects of the present disclosure allow re-transmission of service data units (that would otherwise have been discarded) during the re-establish procedure at a lower layer, such as the radio link control layer. For example, instead of discarding the unacknowledged SDUs during the re-establishment procedure, the UE stores the SDUs and re-transmits the SDUs when the RLC entity is re-established. By saving these SDUs and performing the re-transmission of the SDUs at the lower layer, aspects of the present disclosure preserve ongoing calls and improve performance of packet switched data calls. In this aspect, the higher layer is prevented from re-transmitting the unacknowledged SDUs during the re-establishment procedure to reduce communication delay. This follows because processing the unacknowledged SDUs at the higher layer consumes more time than processing PDUs at a lower layer. For example, the time to detect a discarded SDU and to initialize and re-transmit the SDU is longer. [0045] In some instances, the unacknowledged signaling messages during the re- establishment procedure may or may not be received by the network. As a result, a radio resource controller (RRC) of the UE may re-transmit a same signaling message with a same RRC message sequence number as the previously transmitted unacknowledged signaling message. Some specifications allow for protocol checks (e.g., internet protocol IP checks) for live networks to determine whether a signaling message was received by the network. For example, the network checks the RRC message sequence number to determine whether a same RRC message sequence number is received more than once. When the UE re-transmits the signaling message having a RRC message sequence number to the network, the network checks whether the RRC message sequence number matches an RRC message sequence number of a previous message. For example, the RRC message sequences match when the network receives the signaling message twice. In this case, the network discards the duplicate signaling message. Otherwise, if the network receives the re-transmitted message for the first time, the network operates normally, as if the signaling message was never lost. This tolerance feature when duplicate signaling messages are transmitted by the UE to the network may be applied to acknowledged mode user radio bearer, TCP and user datagram protocol.

[0046] FIGURE 6 shows an example of a wireless communication method 600 that may be used by the controller/processor 390 of the UE 110/350 to re-establish a radio link control entity. A UE determines whether an acknowledgement is received for a transmitted data unit during a re-establishment procedure for a radio link, as shown in block 602. The UE also stores the data unit when the acknowledgement is not received for the transmitted data unit, as shown in block 604. The UE also re-transmits at least a portion of the unacknowledged data unit at a lower layer during the re-establishment procedure, as shown in block 606.

[0047] FIGURE 7 is a diagram illustrating an example of a hardware implementation for an apparatus 700 employing a processing system 714. The processing system 714 may be implemented with a bus architecture, represented generally by the bus 724. The bus 724 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 714 and the overall design constraints. The bus 724 links together various circuits including one or more processors and/or hardware modules, represented by the processor 722 the modules 702, 704, 706 and the non-transitory computer-readable medium 726. The bus 724 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

[0048] The apparatus includes a processing system 714 coupled to a transceiver 730. The transceiver 730 is coupled to one or more antennas 720. The transceiver 730 enables communicating with various other apparatus over a transmission medium. The processing system 714 includes a processor 722 coupled to a non-transitory computer-readable medium 726. The processor 722 is responsible for general processing, including the execution of software stored on the computer-readable medium 726. The software, when executed by the processor 722, causes the processing system 714 to perform the various functions described for any particular apparatus. The computer-readable medium 726 may also be used for storing data that is manipulated by the processor 722 when executing software.

[0049] The processing system 714 includes a determining module 702 for determining whether an acknowledgement is received for a transmitted data unit during a re- establishment procedure for a radio link. The processing system 714 includes a storing module 704 for storing the data unit when the acknowledgement is not received for the transmitted data unit. The processing system 714 includes a transmitting module 706 for re-transmitting at least a portion of the unacknowledged data unit at a lower layer during the re-establishment procedure. The modules may be software modules running in the processor 722, resident/stored in the computer readable medium 726, one or more hardware modules coupled to the processor 722, or some combination thereof. The processing system 614 may be a component of the UE 110 and may include the memory 392, and/or the controller/processor 390.

[0050] In one configuration, an apparatus such as a UE 110/350 is configured for wireless communication including means for determining. In one aspect, the determining means may be the channel processor 394, the receive processor 370, the controller/processor 390, processor 722, the memory 392, radio link control re- establishment module 391, determining module 702and/or the processing system 714 configured to perform the determining means. [0051] The UE is also configured to include means for storing. In one aspect, the storing means may be the memory 392, the computer readable medium 726, the radio link control re-establishment module 391, the storing module 704, and/or the processing system 714 configured to perform the storing means. In one aspect the means functions recited by the aforementioned means. In another aspect, the aforementioned means may be a module or any apparatus configured to perform the functions recited by the aforementioned means.

[0052] The UE is also configured to include means for re-transmitting. In one aspect, the re-transmitting means may be the antenna 720/352, the transmitter 356, the transmit frame processor 382, the transmit processor 380, controller/processor 390, the radio link control re-establishment module 391, the transmitting module 706, transceiver 730, and/or the processing system 714 configured to perform the re-transmitting means. In one aspect the means functions recited by the aforementioned means. In another aspect, the aforementioned means may be a module or any apparatus configured to perform the functions recited by the aforementioned means.

[0053] Further operation details explaining current operation in various networks compared to prior operation may be found in FIGURES 8 and 9. FIGURE 8 is a diagram illustrating an RLC re-establish operation according to the prior art. FIGURE 9 is a diagram illustrating an RLC re-establish operation according to one aspect of the present disclosure.

[0054] Several aspects of a telecommunications system has been presented with reference to 3GPP in general, and to TD-SCDMA in particular. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards. By way of example, various aspects may be extended to other UMTS systems such as W-CDMA, High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), High Speed Packet Access Plus (HSPA+) and TD-CDMA. Various aspects may also be extended to systems employing Long Term Evolution (LTE) (in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD, or both modes), CDMA2000, Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system.

[0055] Several processors have been described in connection with various apparatuses and methods. These processors may be implemented using electronic hardware, computer software, or any combination thereof. Whether such processors are implemented as hardware or software will depend upon the particular application and overall design constraints imposed on the system. By way of example, a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented with a microprocessor, microcontroller, digital signal processor (DSP), a field-programmable gate array (FPGA), a programmable logic device (PLD), a state machine, gated logic, discrete hardware circuits, and other suitable processing components configured to perform the various functions described throughout this disclosure. The functionality of a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented with software being executed by a microprocessor, microcontroller, DSP, or other suitable platform.

[0056] Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. The software may reside on a non-transitory computer-readable medium. A computer-readable medium may include, by way of example, memory such as a magnetic storage device (e.g., hard disk, floppy disk, magnetic strip), an optical disk (e.g., compact disc (CD), digital versatile disc (DVD)), a smart card, a flash memory device (e.g., card, stick, key drive), random access memory (RAM), read only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), a register, or a removable disk. Although memory is shown separate from the processors in the various aspects presented throughout this disclosure, the memory may be internal to the processors (e.g., cache or register).

[0057] Computer-readable media may be embodied in a computer-program product. By way of example, a computer-program product may include a computer-readable medium in packaging materials. Those skilled in the art will recognize how best to implement the described functionality presented throughout this disclosure depending on the particular application and the overall design constraints imposed on the overall system.

[0058] It is to be understood that the specific order or hierarchy of steps in the methods disclosed is an illustration of exemplary processes. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the methods may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented unless specifically recited therein.

[0059] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more." Unless specifically stated otherwise, the term "some" refers to one or more. A phrase referring to "at least one of a list of items refers to any combination of those items, including single members. As an example, "at least one of: a, b, or c" is intended to cover: a; b; c; a and b; a and c; b and c; and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the element is recited using the phrase "step for."

WHAT IS CLAIMED IS:

Claims

1. A method of wireless communication, comprising:

determining whether an acknowledgement is received for a transmitted data unit during a re-establishment procedure for a radio link; and

storing the data unit when the acknowledgement is not received for the transmitted data unit; and

re-transmitting at least a portion of the unacknowledged data unit at a lower layer during the re-establishment procedure.

2. The method of claim 1, in which the lower layer comprises a radio link control layer.

3. The method of claim 1, in which the data unit comprises a service data unit.

4. The method of claim 1, in which the portion of the unacknowledged data unit comprises a protocol data unit.

5. The method of claim 1, further comprising, preventing re-transmission of the unacknowledged data unit at a higher layer during the re-establishment procedure.

6. An apparatus for wireless communication, comprising:

means for determining whether an acknowledgement is received for a transmitted data unit during a re-establishment procedure for a radio link; and

means for storing the data unit when the acknowledgement is not received for the transmitted data unit; and

means for re-transmitting at least a portion of the unacknowledged data unit at a lower layer during the re-establishment procedure.

7. The apparatus of claim 6, in which the lower layer comprises a radio link control layer.

8. The apparatus of claim 6, in which the data unit comprises a service data unit.

9. The apparatus of claim 6, in which the portion of the unacknowledged data unit comprises a protocol data unit.

10. The apparatus of claim 6, further comprising, preventing re-transmission of the unacknowledged data unit at a higher layer during the re-establishment procedure.

11. An apparatus for wireless communication, comprising:

a memory; and

at least one processor coupled to the memory and configured:

to determine whether an acknowledgement is received for a transmitted data unit during a re-establishment procedure for a radio link; and

to store the data unit when the acknowledgement is not received for the transmitted data unit; and

to re-transmit at least a portion of the unacknowledged data unit at a lower layer during the re-establishment procedure.

12. The apparatus of claim 11, in which the lower layer comprises a radio link control layer.

13. The apparatus of claim 11 , in which the data unit comprises a service data unit.

14. The apparatus of claim 11, in which the portion of the unacknowledged data unit comprises a protocol data unit.

15. The apparatus of claim 11, in which the at least one processor is further configured to prevent re-transmission of the unacknowledged data unit at a higher layer during the re- establishment procedure.

16. A computer program product for wireless communication, comprising:

a non-transitory computer-readable medium having program code recorded thereon, the program code comprising:

program code to determine whether an acknowledgement is received for a transmitted data unit during a re-establishment procedure for a radio link; and

program code to store the data unit when the acknowledgement is not received for the transmitted data unit; and

program code to re-transmit at least a portion of the unacknowledged data unit at a lower layer during the re-establishment procedure.

17. The computer program product of claim 16, in which the lower layer comprises a radio link control layer.

18. The computer program product of claim 16, in which the data unit comprises a service data unit.

19. The computer program product of claim 16, in which the portion of the unacknowledged data unit comprises a protocol data unit.

20. The computer program product of claim 16, in which the program code further comprises program code to prevent re-transmission of the unacknowledged data unit at a higher layer during the re-establishment procedure.