WO2015131311A1

WO2015131311A1 - Apparatus and methods for handover in td-scdma

Info

Publication number: WO2015131311A1
Application number: PCT/CN2014/072797
Authority: WO
Inventors: Yong Xie; Yizhen Yang; Weijin RAO; Xuqiang ZHANG; Xiaoyu Li; Chao JIN
Original assignee: Qualcomm Incorporated
Priority date: 2014-03-03
Filing date: 2014-03-03
Publication date: 2015-09-11

Abstract

Apparatus and methods for handover in wireless communication include attempting, by a user equipment (UE), to perform a hard handover procedure from a first cell to a second cell, where the hard handover procedure is configured for the UE by a network; determining, by the UE, that the hard handover procedure has failed; and in response to determining that the hard handover procedure has failed, attempting, by the UE, to perform a baton handover procedure from the first cell to the second cell. In some aspects, the UE may attempt to perform the baton handover procedure without first reporting to the network that the hard handover procedure has failed. The hard handover procedure may be determined as failed when the UE determines that a Fast Physical Access Channel (FPACH) is not received from the network in response to a transmission of a SYNC_UL code from the UE to the network.

Description

APPARATUS AND METHODS FOR HANDOVER IN TD-SCDMA

BACKGROUND

[0001] Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to apparatus and methods for handover in Time Division-Synchronous Code Division Multiple Access (TD- SCDMA).

[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, in some countries like China, TD-SCDMA is being considered as the underlying air interface in the UTRAN architecture with existing GSM infrastructure as the core network. The UMTS also supports enhanced 3G data communications protocols, such as High Speed Downlink Packet Data (HSDPA), which provides higher data transfer speeds and capacity to associated UMTS networks.

[0003] Conventionally, in TD-SCDMA, a failure in hard handover may result in dropped calls at some locations. Accordingly, improved apparatus and methods for handover in TD-SCDMA may be desired.

SUMMARY

[0004] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0005] In one aspect, a method of handover in wireless communication is provided that includes attempting, by a user equipment (UE), to perform a hard handover procedure from a first cell to a second cell, where the hard handover procedure is configured for the UE by a network; determining, by the UE, that the hard handover procedure has failed; and in response to determining that the hard handover procedure has failed, attempting, by the UE, to perform a baton handover procedure from the first cell to the second cell.

[0006] In another aspect, an apparatus for handover in wireless communication is provided that includes a processing system configured to attempt, by a UE, to perform a hard handover procedure from a first cell to a second cell, where the hard handover procedure is configured for the UE by a network; determine, by the UE, that the hard handover procedure has failed; and in response to determining that the hard handover procedure has failed, attempt, by the UE, to perform a baton handover procedure from the first cell to the second cell.

[0007] In a further aspect, a computer program product for handover in wireless communication in provided that includes a non-transitory computer-readable medium including code for attempting, by a UE, to perform a hard handover procedure from a first cell to a second cell, where the hard handover procedure is configured for the UE by a network; code for determining, by the UE, that the hard handover procedure has failed; and code for, in response to determining that the hard handover procedure has failed, attempting, by the UE, to perform a baton handover procedure from the first cell to the second cell.

[0008] To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The disclosed aspects will hereinafter be described in conjunction with the appended drawings, provided to illustrate and not to limit the disclosed aspects, wherein like designations denote like elements, and in which:

[0010] FIG. 1 is a diagram illustrating an example of a wireless communications system according to some present aspects;

[0011] FIGs. 2-4 are flow charts of example methods of wireless communications in aspects of the wireless communications system of FIG. 1;

[0012] FIG. 5 is a diagram of a hardware implementation for an apparatus employing a processing system, including aspects of the wireless communications system of FIG. 1;

[0013] FIG. 6 is a diagram illustrating an example of a telecommunications system, including aspects of the wireless communications system of FIG. 1;

[0014] FIG. 7 is a diagram illustrating an example of a frame structure in a telecommunications system, in aspects of the wireless communications system of FIG. 1; and

[0015] FIG. 8 is a diagram illustrating an example of a Node B in communication with a UE in a telecommunications system, including aspects of the wireless communications system of FIG. 1.

DETAILED DESCRIPTION

[0016] 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.

[0017] Some present aspects improve the handover success rate in Time Division - Synchronous Code Division Multiple Access (TD-SCDMA). In some aspects, when a network configures a hard handover for a user equipment (UE), the UE may first attempt a conventional hard handover procedure. In these aspects, if the hard handover procedure fails (e.g., subsequent to transmitting a SYNC-UL code to the network, the SYNC-UL code is not received or not properly received by the network or the network receives the SYNC-UL code but is busy and cannot respond, and therefore the UE does not receive any Fast Physical Access Channel (FPACH) from the network in response), instead of reporting a hard handover failure to the network, the UE may attempt a baton handover directly and without intervention from the network. Accordingly, the success rate when handing over the UE from, for example, a first cell to a second cell, may be improved.

[0018] Referring to FIG. 1, a wireless communications system 100 is illustrated with aspects configured to improve the handover success rate in a TD-SCDMA network 112. Wireless communications system 100 includes user equipment (UE) 102 that is communicating with first base station 104 in first cell 108 of TD-SCDMA network 112 and that is moving from first cell 108 to second cell 110 of TD-SCDMA network 112. Accordingly, TD-SCDMA network 112 may configure a handover for UE 102 from first base station 104 in first cell 108 to second base station 106 in second cell 110.

[0019] Conventionally, when configuring a handover of UE 102, TD-SCDMA network 112 controls the usage of a baton handover or a hard handover. For example, TD-SCDMA network 112 may first configure a hard handover for UE 102, and if the hard handover fails, TD-SCDMA network 112 may configure a baton handover for UE 102. Conventionally, in a hard handover, UE 102 sends a SYNC_UL code to TD- SCDMA network 112 (e.g., via base station 104) and receives a Fast Physical Access Channel (FPACH) in response from TD-SCDMA network 112 (e.g., via base station 104) when the SYNC_UL code is received and properly decoded by TD-SCDMA network 112. Upon receiving the FPACH, UE 102 uses the timing and power information in FPACH to determine uplink Dedicated Physical Channel (DPCH) transmission for communicating with second base station 106 in second cell 110.

[0020] In a baton handover, however, UE 102 does not send a SYNC_UL code to the network. Instead, the UE 102 determines the timing information required for handover from first cell 108 to second cell 110 by performing measurements, and then starts communicating with second base station 106 on DPCH without having to first wait for an FPACH from TD-SCDMA network 112. That is, in a baton handover, UE 102 does not send a SYNCJJL code to TD-SCDMA network 112 and does not receive an FPACH in response, therefore, in a baton handover, UE 102 does not have to wait for receiving an FPACH from TD-SCDMA network 112.

[0021] Conventionally, in TD-SCDMA network 112, a hard handover procedure configured for UE 102 may fail, resulting in a call drop. For example, a hard handover procedure may fail if uplink interference levels in an Uplink Pilot Time Slot (UPPTS) are so high that TD-SCDMA network 112 cannot receive a SYNCJJL code from UE 102, or if TD-SCDMA network 112 is busy and cannot reply to a transmission of a SYNC_UL code from UE 102, and consequently UE 102 does not receive FPACH from TD-SCDMA network 112.

[0022] In some aspects, failure of a hard handover procedure configured for UE 102 may depend on a location of UE 102. However, a baton handover procedure that takes place at that same location where the hard handover procedure failure occurs may result in a successful handover of UE 102. Accordingly, in some present aspects, if TD-SCDMA network 112 configures a hard handover for UE 102, UE 102 first attempts a hard handover procedure. If the hard handover procedure fails (e.g., in response to transmitting a SYNCJJL code to TD-SCDMA network 112, UE 102 does not receive any FPACH from TD-SCDMA network 112), instead of reporting the hard handover failure to TD-SCDMA network 112, UE 102 attempts a baton handover directly (e.g., without intervention from TD-SCDMA network 112). Accordingly, the handover success rate for UE 102 may be increased.

[0023] For example, in some aspects, UE 102 may include handover component 114 that manages a handover of UE 102 from cell 108 to cell 110 when TD-SCDMA network 112 configures such handover. For example, handover component 114 may include hard handover component 116 that first attempts a hard handover procedure if TD-SCDMA network 112 configures a hard handover for UE 102. For example, hard handover component 116 may configure UE 102 to transmit a SYNC_UL code to TD-SCDMA network 112 in order to obtain a FPACH from TD-SCDMA network 112 in response. In some aspects, however, in response to transmitting the SYNCJJL code, UE 102 may not receive any FPACH from TD-SCDMA network 112. For example, handover component 114 may include hard handover failure determination component 118 that determines a failed hard handover procedure when in response to transmitting the SYNCJJL code, UE 102 does not receive any FPACH from TD-SCDMA network 112. For example, hard handover failure determination component 118 may indicate a failed hard handover procedure when, in response to transmitting the SYNC_UL code, UE 102 does not receive any FPACH from TD- SCDMA network 112 after a certain time has passed since the transmission of the SYNC_UL code, where the amount of such certain time may be configured by the network.

[0024] In some aspects, in response to determining a failed hard handover procedure, instead of reporting the hard handover failure to TD-SCDMA network 112, handover component 114 may attempt a baton handover directly and without intervention from TD-SCDMA network 112. For example, handover component 114 may include baton handover component 120 that, when hard handover failure determination component 118 indicates a failed hard handover procedure, attempts a baton handover directly and without intervention from TD-SCDMA network 112. Accordingly, the hand over success rate for UE 102 may be increased. For example, in some aspects, the hand over success rate for UE 102 may be increased when failure of a hard handover procedure configured for UE 102 depends on the location of UE 102, and a baton handover procedure that takes place at that same location where the hard handover procedure failure occurs may result in a successful handover of UE 102. In some aspects, optionally, if the baton handover fails, UE 102 may act as if a normal/conventional hard handover failure has occurred, and report a hard handover failure to TD-SCDMA network 112.

[0025] FIGs. 2-4 describe methods 200, 300, and 400, respectively, in aspects of the wireless communications system of FIG. 1. For example, methods 200, 300, and 400 may be performed by UE 102 executing handover component 114 (FIG. 1) as described herein.

[0026] Referring now to FIG. 2, at block 202, method 200 includes attempting, by a UE, to perform a hard handover procedure from a first cell to a second cell, where the hard handover procedure is configured for the UE by a network. For example, in some aspects, hard handover component 116 in handover component 114 of UE 102 may attempt to perform a hard handover procedure from first cell 108 to second cell 110, where the hard handover procedure is configured for UE 102 by TD-SCDMA network 112.

[0027] At block 204, method 200 includes determining, by the UE, that the hard handover procedure has failed. For example, hard handover failure determination component 118 in handover component 114 of UE 102 may determine that the hard handover procedure attempted by hard handover component 116 has failed.

[0028] At block 206, method 200 includes, in response to determining that the hard handover procedure has failed, attempting, by the UE, to perform a baton handover procedure from the first cell to the second cell. For example, in response to the determination of hard handover failure determination component 118 that the hard handover procedure attempted has failed, baton handover component 120 in handover component 114 of UE 102 may attempt to perform a baton handover procedure from first cell 108 to second cell 110. In some aspects, the baton handover procedure is not configured for UE 102 by TD-SCDMA network 112 (e.g., when TD-SCDMA network 112 configures a hard handover for UE 102, it does not configure a baton handover as a fallback). In some aspects, in response to determining that the hard handover procedure has failed and prior to attempting to perform the baton handover procedure, UE 102 does not report to TD-SCDMA network 112 that the hard handover procedure has failed. In other words, the UE may attempt to perform the baton handover procedure without first reporting to the network that the hard handover procedure has failed. In some aspects, UE 102 performs timing measurements in the baton handover procedure and performs a Dedicated Physical Channel (DPCH) transmission for communicating with second cell 110 based on the timing measurements in the baton handover procedure.

[0029] Referring to FIG. 3, method 300 includes further, and optional, aspects related to block 202 of method 200 of FIG. 2 to perform the hard handover procedure.

[0030] At optional block 302, method 500 includes transmitting, by the UE, a SYNCJJL code to the network. For example, UE 102 may transmit a SYNCJJL code to TD-SCDMA network 112 as part of the hard handover procedure.

[0031] Referring to FIG. 4, method 400 includes further, and optional, aspects related to block 204 of method 200 of FIG. 2 to determine that the hard handover procedure has failed.

[0032] At optional block 402, method 400 includes determining, by the UE, that an FPACH is not received from the network in response to the transmission of a SYNC_UL code to the network. For example, hard handover failure determination component 118 may determine that an FPACH is not received from TD-SCDMA network 112 in response to the SYNC_UL code transmitted by UE 102. [0033] Referring to FIG. 5, an example of a hardware implementation for an apparatus 500 employing a processing system 514 is shown. In an aspect, apparatus 500 may be UE 102 of FIG. 1, including handover component 114, and may be configured to perform any functions described herein with reference to UE 102 and/or handover component 114.

[0034] In this example, the processing system 514 may be implemented with a bus architecture, represented generally by the bus 502. The bus 502 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 514 and the overall design constraints. The bus 502 links together various circuits including one or more processors, represented generally by the processor 504, one or more communications components, such as, for example, handover component 114 of FIG. 1, and computer-readable media, represented generally by the computer-readable medium 506. The bus 502 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. A bus interface 508 provides an interface between the bus 502 and a transceiver 510. The transceiver 510 provides a means for communicating with various other apparatus over a transmission medium. Depending upon the nature of the apparatus, a user interface 512 (e.g., keypad, display, speaker, microphone, joystick) may also be provided.

[0035] The processor 504 is responsible for managing the bus 502 and general processing, including the execution of software stored on the computer-readable medium 506. The software, when executed by the processor 504, causes the processing system 514 to perform the various functions described herein for any particular apparatus.

[0036] The computer-readable medium 506 may also be used for storing data that is manipulated by the processor 504 when executing software, such as, for example, software modules represented by handover component 114. In one example, the software modules (e.g., any algorithms or functions that may be executed by processor 504 to perform the described functionality) and/or data used therewith (e.g., inputs, parameters, variables, and/or the like) may be retrieved from computer- readable medium 506. The modules may be software modules running in the processor 504, resident and/or stored in the computer-readable medium 506, one or more hardware modules coupled to the processor 504, or some combination thereof.

[0037] Turning now to FIG. 6, a block diagram is shown illustrating an example of a telecommunications system 600. Telecommunications system 600 includes UEs 610 which may be examples of UE 102 of FIG. 1 and which may include and execute handover component 114 to perform any functions described herein. 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 FIG. 6 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 602 (e.g., UTRAN) that provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The RAN 602 may be divided into a number of Radio Network Subsystems (RNSs) such as an RNS 607, each controlled by a Radio Network Controller (RNC) such as an RNC 606. For clarity, only the RNC 606 and the RNS 607 are shown; however, the RAN 602 may include any number of RNCs and RNSs in addition to the RNC 606 and RNS 607. The RNC 606 is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS 607. The RNC 606 may be interconnected to other RNCs (not shown) in the RAN 602 through various types of interfaces such as a direct physical connection, a virtual network, or the like, using any suitable transport network.

[0038] The geographic region covered by the RNS 607 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 608 are shown; however, the RNS 607 may include any number of wireless Node Bs. The Node Bs 608 provide wireless access points to a core network 604 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 610, which may be the same as or similar to UE 102 of FIG. 1, are shown in communication with the Node Bs 608, which may be the same as or similar to base stations 104 and 106 of FIG. 1. 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.

[0039] The core network 604, 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.

[0040] In this example, the core network 604 supports circuit-switched services with a mobile switching center (MSC) 612 and a gateway MSC (GMSC) 614. One or more RNCs, such as the RNC 606, may be connected to the MSC 612. The MSC 612 is an apparatus that controls call setup, call routing, and UE mobility functions. The MSC 612 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 612. The GMSC 614 provides a gateway through the MSC 612 for the UE to access a circuit- switched network 616. The GMSC 614 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 614 queries the HLR to determine the UE' s location and forwards the call to the particular MSC serving that location. [0041] The core network 604 also supports packet-data services with a serving GPRS support node (SGSN) 618 and a gateway GPRS support node (GGSN) 620. 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 620 provides a connection for the RAN 602 to a packet-based network 622. The packet-based network 622 may be the Internet, a private data network, or some other suitable packet-based network. The primary function of the GGSN 620 is to provide the UEs 610 with packet-based network connectivity. Data packets are transferred between the GGSN 620 and the UEs 610 through the SGSN 618, which performs primarily the same functions in the packet- based domain as the MSC 612 performs in the circuit-switched domain.

[0042] 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 UMTSAV-CDMA systems. TDD uses the same carrier frequency for both the uplink (UL) and downlink (DL) between a Node B 608 and a UE 610, but divides uplink and downlink transmissions into different time slots in the carrier.

[0043] FIG. 7 shows a frame structure 700 for a TD-SCDMA carrier, which may be used for communications between base stations 104, 106 of FIG. 1, and UE 102, also of FIG. 1. The TD-SCDMA carrier, as illustrated, has a frame 702 that is 10 milliseconds (ms) in duration. The frame 702 has two 5 ms subframes 704, and each of the subframes 704 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) 706, a guard period (GP) 708, and an uplink pilot time slot (UpPTS) 710 (also known as the uplink pilot channel (UpPCH)) are located between TS0 and TS1. In some present aspects, the SYNCJJL code may be transmitted through the UpPTS 710 of FIG. 7. In some present aspects, FPACH may be received in TSO of FIG. 7. 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 712 separated by a midamble 714 and followed by a guard period (GP) 716. The midamble 714 may be used for features, such as channel estimation, while the GP 716 may be used to avoid inter-burst interference.

[0044] FIG. 8 is a block diagram of a Node B 810 in communication with a UE 850 in a RAN 800. In an aspect, Node B 810 may be an example of base station 104 or base station 106 of FIG. 1, and UE 850 may be an example of UE 102 of FIG. 1 and may include and execute handover component 114 of FIG. 1 to perform any functions described herein.

[0045] In the downlink communication, a transmit processor 820 may receive data from a data source 812 and control signals from a controller/processor 840. The transmit processor 820 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 820 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 844 may be used by a controller/processor 840 to determine the coding, modulation, spreading, and/or scrambling schemes for the transmit processor 820. These channel estimates may be derived from a reference signal transmitted by the UE 850 or from feedback contained in the midamble 714 (FIG. 7) from the UE 850. The symbols generated by the transmit processor 820 are provided to a transmit frame processor 830 to create a frame structure. The transmit frame processor 830 creates this frame structure by multiplexing the symbols with a midamble 714 (FIG. 7) from the controller/processor 840, resulting in a series of frames. The frames are then provided to a transmitter 832, 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 834. The smart antennas 834 may be implemented with beam steering bidirectional adaptive antenna arrays or other similar beam technologies.

[0046] At the UE 850, a receiver 854 receives the downlink transmission through an antenna 852 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 854 is provided to a receive frame processor 860, which parses each frame, and provides the midamble 714 (FIG. 7) to a channel processor 894 and the data, control, and reference signals to a receive processor 870. The receive processor 870 then performs the inverse of the processing performed by the transmit processor 820 in the Node B 810. More specifically, the receive processor 870 descrambles and despreads the symbols, and then determines the most likely signal constellation points transmitted by the Node B 810 based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor 894. 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 872, which represents applications running in the UE 850 and/or various user interfaces (e.g., display). Control signals carried by successfully decoded frames will be provided to a controller/processor 890. When frames are unsuccessfully decoded by the receiver processor 870, the controller/processor 890 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0047] In the uplink, data from a data source 878 and control signals from the controller/processor 890 are provided to a transmit processor 880. The data source 878 may represent applications running in the UE 850 and various user interfaces (e.g., keyboard). Similar to the functionality described in connection with the downlink transmission by the Node B 810, the transmit processor 880 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 894 from a reference signal transmitted by the Node B 810 or from feedback contained in the midamble transmitted by the Node B 810, may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor 880 will be provided to a transmit frame processor 882 to create a frame structure. The transmit frame processor 882 creates this frame structure by multiplexing the symbols with a midamble 714 (FIG. 7) from the controller/processor 890, resulting in a series of frames. The frames are then provided to a transmitter 856, 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 852.

[0048] The uplink transmission is processed at the Node B 810 in a manner similar to that described in connection with the receiver function at the UE 850. A receiver 835 receives the uplink transmission through the antenna 834 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 835 is provided to a receive frame processor 836, which parses each frame, and provides the midamble 714 (FIG. 7) to the channel processor 844 and the data, control, and reference signals to a receive processor 838. The receive processor 838 performs the inverse of the processing performed by the transmit processor 880 in the UE 850. The data and control signals carried by the successfully decoded frames may then be provided to a data sink 839 and the controller/processor, respectively. If some of the frames were unsuccessfully decoded by the receive processor, the controller/processor 840 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0049] The controller/processors 840 and 890 may be used to direct the operation at the Node B 810 and the UE 850, respectively. For example, the controller/processors 840 and 890 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories 842 and 892 may store data and software for the Node B 810 and the UE 850, respectively. A scheduler/processor 846 at the Node B 810 may be used to allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs.

[0050] Several aspects of a telecommunications system has been presented with reference to a TD-SCDMA system. 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.

[0051] 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.

[0052] 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 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).

[0053] 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.

[0054] 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.

[0055] 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, or 35 U.S.C. § 112(f), whichever is appropriate, 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."

[0056] WHAT IS CLAIMED IS:

Claims

1. A method of handover in wireless communication, comprising:

attempting, by a user equipment (UE), to perform a hard handover procedure from a first cell to a second cell, wherein the hard handover procedure is configured for the UE by a network;

determining, by the UE, that the hard handover procedure has failed; and in response to determining that the hard handover procedure has failed, attempting, by the UE, to perform a baton handover procedure from the first cell to the second cell.

2. The method of claim 1, wherein the network is a Time Division- Synchronous Code Division Multiple Access (TD-SCDMA) network.

3. The method of claim 1, wherein the UE attempts to perform the baton handover procedure without first reporting to the network that the hard handover procedure has failed.

4. The method of claim 1, wherein the UE performs timing measurements in the baton handover procedure.

5. The method of claim 4, wherein the UE performs a Dedicated Physical Channel (DPCH) transmission for communicating with the second cell based on the timing measurements in the baton handover procedure.

6. The method of claim 1, wherein the attempting to perform the hard handover procedure comprises:

transmitting, by the UE, a SYNC_UL code to the network.

7. The method of claim 6, wherein the determining that the hard handover procedure has failed comprises:

determining, by the UE, that a Fast Physical Access Channel (FPACH) is not received from the network in response to the transmission of the SYNC_UL code.

8. An apparatus for handover in wireless communication, comprising: a processing system configured to:

attempt, by a user equipment (UE), to perform a hard handover procedure from a first cell to a second cell, wherein the hard handover procedure is configured for the UE by a network;

determine, by the UE, that the hard handover procedure has failed; and

in response to determining that the hard handover procedure has failed, attempt, by the UE, to perform a baton handover procedure from the first cell to the second cell.

9. The apparatus of claim 8, wherein the network is a Time Division- Synchronous Code Division Multiple Access (TD-SCDMA) network.

10. The apparatus of claim 8, wherein the UE attempts to perform the baton handover procedure without first reporting to the network that the hard handover procedure has failed.

11. The apparatus of claim 8, wherein the UE performs timing measurements in the baton handover procedure.

12. The apparatus of claim 11, wherein the UE performs a Dedicated Physical Channel (DPCH) transmission for communicating with the second cell based on the timing measurements in the baton handover procedure.

13. The apparatus of claim 8, wherein the processor is configured to attempt to perform the hard handover procedure by:

transmitting, by the UE, a SYNC-UL code to the network.

14. The apparatus of claim 13, wherein the processor is configured to determine that the hard handover procedure has failed by: determining, by the UE, that a Fast Physical Access Channel (FPACH) is not received from the network in response to the SYNC-UL code.

15. A computer program product for handover in wireless communication, comprising:

a non-transitory computer-readable medium comprising:

code for attempting, by a user equipment (UE), to perform a hard handover procedure from a first cell to a second cell, wherein the hard handover procedure is configured for the UE by a network;

code for determining, by the UE, that the hard handover procedure has failed; and

code for, in response to determining that the hard handover procedure has failed, attempting, by the UE, to perform a baton handover procedure from the first cell to the second cell.

16. The computer program product of claim 15, wherein the network is a Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) network.

17. The computer program product of claim 15, wherein the UE attempts to perform the baton handover procedure without first reporting to the network that the hard handover procedure has failed.

18. The computer program product of claim 15,

wherein the UE performs timing measurements in the baton handover procedure, and

wherein the UE performs a Dedicated Physical Channel (DPCH) transmission for communicating with the second cell based on the timing measurements in the baton handover procedure.

19. The computer program product of claim 15, wherein the code for attempting to perform the hard handover procedure comprises:

code for transmitting, by the UE, a SYNC-UL code to the network.

20. The computer program product of claim 19, wherein the code for determining that the hard handover procedure has failed comprises:

code for determining, by the UE, that a Fast Physical Access Channel (FPACH) is not received from the network in response to the SYNC-UL code.