# Patent

## Title
Alternate transmission scheme for high speed packet access (HSPA)

## Abstract

Post-hard handover processing in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network may be improved to allow operation of High Speed Packet Access (HSPA) in hard handover. For example, uplink synchronization may be completed concurrent with HSPA to quickly resume HSPA operation in hard handovers. User Equipment (UE) may receive downlink data while completing uplink synchronization. In another example, a unique SYNC_UL code may be assigned to a UE for hard handover. The unique SYNC_UL code allows Node Bs of the TD-SCDMA network to know which UE is performing hard handover. When a Node B is receiving the unique SYNC_UL, the Node B may begin to allocate UL data grants. After receiving UL data from the UE, the Node B may resume High Speed Downlink Packet Access (HSDPA).

## Background
CROSS REFERENCE TO RELATED APPLICATION
This application claims the benefit of U.S. provisional patent application No. 61/348,140 filed May 25, 2010, in the names of CHIN et al., the disclosure of which is expressly incorporated by reference in its entirety.


BACKGROUND
1. Field
Aspects of the present disclosure relate, in general, to wireless communication systems, and more particularly, to facilitating high performance during High Speed Packet Access (HSPA) in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network.
2. Background
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 Downlink Packet Data (HSDPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
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
In one aspect of the disclosure, a method for performing a handover in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network includes performing uplink synchronization with a target Node B (NB) of the TD-SCDMA network. The method also includes receiving an uplink grant and high speed downlink data from the target NB before completion of the uplink synchronization.
In another aspect, a computer program product for communicating in a wireless network includes a computer-readable medium having code to perform uplink synchronization with a target Node B (NB) of the TD-SCDMA network. The medium also includes code to receive an uplink grant and high speed downlink data from the target NB before completion of the uplink synchronization.
In yet another aspect, an apparatus for communicating in a wireless network includes a processor and a memory coupled to the processor. The processor is configured to perform uplink synchronization with a target Node B (NB) of the TD-SCDMA network. The processor is also configured to receive an uplink grant and high speed downlink data from the target NB before completion of the uplink synchronization.
In a further aspect, an apparatus for communicating in a wireless network includes means for performing uplink synchronization with a target Node B (NB) of the TD-SCDMA network. The apparatus also includes means for receiving an uplink grant and high speed downlink data from the target NB before completion of the uplink synchronization.
In one aspect, a method for performing a handover in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network includes receiving an uplink synchronization code associated with a User Equipment (UE) from a source Node B (NB) of the TD-SCDMA network. The method also includes transmitting the uplink synchronization code to a target NB of the TD-SCDMA network.
In another aspect, a computer program product for communicating in a wireless network includes a computer-readable medium having code to receive an uplink synchronization code associated with a User Equipment (UE) from a source Node B (NB) of the TD-SCDMA network. The medium also includes code to transmit the uplink synchronization code to a target NB of the TD-SCDMA network.
In yet another aspect, an apparatus for communicating in a wireless network includes a processor and a memory coupled to the processor. The processor is configured to receive an uplink synchronization code associated with a User Equipment (UE) from a source Node B (NB) of the TD-SCDMA network. The processor is also configured to transmit the uplink synchronization code to a target NB of the TD-SCDMA network.
In a further aspect, an apparatus for communicating in a wireless network includes means for receiving an uplink synchronization code associated with a User Equipment (UE) from a source Node B (NB) of the TD-SCDMA network. The apparatus also includes means for transmitting the uplink synchronization code to a target NB of the TD-SCDMA network.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating an example of a telecommunications system.
FIG. 2 is a block diagram conceptually illustrating an example of a frame structure in a telecommunications system.
FIG. 3 is a block diagram of a Node B in communication with a user equipment in a radio access network.
FIG. 4 is a block diagram illustrating carrier frequencies in a multi-carrier TD-SCDMA communication system.
FIG. 5 is a call flow showing a hard handover in a TD-SCDMA network according to one aspect.
FIG. 6 is a call flow showing a hard handover with concurrent UL synchronization in a TD-SCDMA network according to one aspect.
FIG. 7 is a call flow showing hard handover with a unique SYNC_UL code in a TD-SCDMA network according to one aspect.
FIG. 8 is a flow chart illustrating hard handover in a TD-SCDMA network according to one aspect.
FIG. 9 is a flow chart illustrating hard handover in a TD-SCDMA network according to one aspect.



DETAILED DESCRIPTION
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.
Turning now to FIG. 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 FIG. 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.
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.
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.
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.
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.
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.
FIG. 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 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 (also known as the Downlink Pilot Channel (DwPCH)), 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 separated by a midamble 214 and followed by a Guard Period (GP) 216. The midamble 214 may be used for features, such as channel estimation, while the GP 216 may be used to avoid inter-burst interference.
FIG. 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 FIG. 1, the Node B 310 may be the Node B 108 in FIG. 1, and the UE 350 may be the UE 110 in FIG. 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 (FIG. 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 (FIG. 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.
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 (FIG. 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.
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, pointing device, track wheel, and the like). 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 (FIG. 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.
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 smart antennas 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 (FIG. 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 340, respectively. If some of the frames were unsuccessfully decoded by the receive processor 338, the controller/processor 340 may also use an Acknowledgement (ACK) and/or Negative Acknowledgement (NACK) protocol to support retransmission requests for those frames.
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 342 of the Node B 310 includes a handover module 343, which, when executed by the controller/processor 340, the handover module 343 configures the Node B to perform handover procedures from the aspect of scheduling and transmission of system messages to the UE 350 for implementing a handover from a source cell to a target cell. 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 not only for handovers, but for regular communications as well.
In order to provide more capacity, the TD-SCDMA system may allow multiple carrier signals or frequencies. Assuming that N is the total number of carriers, the carrier frequencies may be represented by the set {F(i), i=0, 1, . . . , N−1}, where the carrier frequency, F(0), is the primary carrier frequency and the rest are secondary carrier frequencies. For example, a cell can have three carrier signals whereby the data can be transmitted on some code channels of a time slot on one of the three carrier signal frequencies.
FIG. 4 is a block diagram illustrating carrier frequencies 40 in a multi-carrier TD-SCDMA communication system. The multiple carrier frequencies include a primary carrier frequency 400 (F(0)), and two secondary carrier frequencies 401 and 402 (F(1) and F(2)). In such multi-carrier systems, the system overhead may be transmitted on the first time slot (TS0) of the primary carrier frequency 400, including the Primary Common Control Physical Channel (P-CCPCH), the Secondary Common Control Physical Channel (S-CCPCH), the Pilot Indicator Channel (PICH), and the like. The traffic channels may then be carried on the remaining time slots (TS1-TS6) of the primary carrier frequency 400 and on the secondary carrier frequencies 401 and 402. Therefore, in such configurations, a UE will receive system information and monitor the paging messages on the primary carrier frequency 400 while transmitting and receiving data on either one or all of the primary carrier frequency 400 and the secondary carrier frequencies 401 and 402.
High Speed Downlink Packet Access (HSDPA) protocols in a TD-SCDMA network operate on several channels including a High-Speed Shared Control Channel (HS-SCCH), a High-Speed Physical Downlink Shared Channel (HS-PDSCH), and a High-Speed Shared Information Channel (HS-SICH). The HS-SCCH indicates a Modulation and Coding Scheme (MCS), channelization codes, and time slot resource information for data busts on the HS-PDSCH. The HS-PDSCH is a downlink channel for the UE to receive data. The HS-SICH is an uplink channel for the UE to send Channel Quality Indicator (CQI) reports and HARQ ACK/NACK for HS-PDSCH transmission.
High Speed Uplink Packet Access protocols in a TD-SCDMA network operate on several channels including an Enhanced Dedicated Channel (E-DCH) Physical Uplink Channel (E-PUCH), an Enhanced Dedicated Channel (E-DCH) Absolute Grant Channel (E-AGCH), and an E-DCH Hybrid ARQ Acknowledgement Indicator Channel (E-HICH). The E-PUCH is an uplink channel for the UE to send data. The E-AGCH is a downlink channel for indicating the uplink absolute grant control information. The E-HICH is a downlink channel for sending HARQ ACK/NACK.
Hard handovers occur in TD-SCDMA networks when a UE changes both downlink (DL) and uplink (UL) channels from a source cell (or Node B) to a target cell (or Node B) simultaneously. In hard handovers, the UE performs UL synchronization procedures on the Uplink Pilot Channel (UpPCH) by sending a SYNC_UL code to the target cell and receiving the timing adjustment on the Fast Physical Access Channel (FPACH) from the target cell. The TD-SCDMA network signals from the source cell (or Node B or RNC) the SYNC_UL code resources and FPACH information for use by the UE before hard handover to a target cell. Additionally, the TD-SCDMA network may specify an activation time to the UE during which the hard handover occurs.
FIG. 5 is a call flow showing a hard handover in a TD-SCDMA network according to one aspect. At time 510 a source cell 504 sends to the UE 502 the HS-SCCH and E-AGCH. Then, at time 512 the source cell 504 sends to the UE 502 a HS-PDSCH. At time 514, the UE 502 sends to the source cell 504 an E-PUCH. Then, at time 516 the UE 502 sends to the source cell 504 a HS-SICH. At time 518 the source cell 504 sends to the UE 502 an E-HICH. Then, at time 520, the source cell 504 sends to the UE 502 a measurement control message. At time 522, the UE 502 returns a measurement report to the source cell 504.
At time 524 the source cell 504 sends to the UE 502 a physical channel reconfiguration message. At time 526 the UE 502 sends a SYNC_UL code to a target cell 506. The target cell 506 responds at time 528 to the UE 502 with an FPACH acknowledgement. At time 530 the reconfiguration of the UE 502 for the target cell 506 is complete and data on HSDPA and HSUPA channels resumes.
Standards currently do not clearly define how the HSPA channels should resume or whether or not the HSPA communications should resume after completing UL synchronization procedure, i.e. receiving the ACK on FPACH. Moreover, SYNC_UL codes may be shared by multiple UEs such that the target cell can not determine when a UE has completed uplink synchronization and hard handover to the target cell. Thus, there is a need for new post hard handover procedures.
According to one aspect, HSPA reconfiguration occurs concurrently with UL synchronization. Thus, HSPA may quickly resume operation after a hard handover. Concurrent UL synchronization at a target Node B includes allocating the UL data grant on the E-AGCH allowing the UE to send UL data and a physical channel reconfiguration complete message. The target Node B also allocates DL data transmission on the HS-SCCH if DL data is pending for transmission to the UE.
Concurrent UL synchronization occurs on a UE while monitoring the HS-SCCH/HS-PDSCH and the E-AGCH after acquiring a DL of a target Node B. If DL data is pending, the UE receives data on the HS-PDSCH. According to one aspect, the data Acknowledgement (ACK) is sent after receiving the FPACH acknowledgement. If an UL data grant on the E-AGCH is pending, the UE transmits UL data or messages after the UL synchronization completes.
FIG. 6 is a call flow showing a hard handover with concurrent UL synchronization in a TD-SCDMA network according to one aspect. At time 610 a UE 602 enters an activation time for hard handover from a source cell (not shown) to a target cell 604. Then at time 612 the target cell 604 transmits the HS-SCCH and the E-AGCH to the UE 602. The E-AGCH may be a code corresponding to the UE. According to one aspect, the E-AGCH is scrambled with a code having a one-to-one correspondence with the media access control (MAC) address of the UE 602. At time 612, the target cell 604 performs UL synchronization procedures concurrently with HSDPA and HSUPA transmission; and the UE 602 performs the UL synchronization procedure concurrently with monitoring the HS-SCCH, the HS-PDSCH, and the E-AGCH.
At time 614 the UE 602 transmits the SYNC_UL code to the target cell 604 and at time 616 receives DL data on the HS-PDSCH. According to one aspect, the UE 602 transmits the SYNC_UL code in a different subframe than the target cell 604 sends the DL data on the HS-PDSCH. At time 618 the target cell 604 transmits an acknowledgement on the FPACH to the UE 602. The FPACH ACK signals the UE 602 to resume transmission of the HS-SICH, the E-PUCH, and the E-HICH.
At time 620, the UE 602 transmits a physical channel reconfiguration complete message to the target cell 604 over the E-PUCH and transmits uplink data. At time 622 the target cell 604 transmits a HARQ ACK on the E-HICH to the UE 602 and the UE 602 responds with a HARQ ACK on the HS-SICH at time 624.
According to another aspect, a source Node B allocates a unique SYNC_UL code to a specific UE for hard handover. The UL synchronization uses the unique SYNC_UL code followed by HSUPA and HSDPA transmissions. When the target Node B receives the SYNC_UL code, the target Node B knows the specific UE is performing a hard handover. When a reconfiguration complete message is sent to the target Node B, the target Node B knows the handover is complete.
During hard handover a UE performs UL synchronization after acquiring a DL of a target NB. Then, after receiving an acknowledgement on the FPACH, the UE begins monitoring the HS-SCCH and the E-AGCH.
During hard handover a target NB allocates UL data grants on the E-AGCH for the UE to send UL data and a physical channel reconfiguration complete message while receiving the SYNC _UL code and sending an acknowledgement on the FPACH. According to one aspect, a small amount of UL data grants occur periodically in each subframe. After receiving UL data from the UE, the NB resumes HSDPA if DL data is pending by allocating DL data to the UE on the HS-SCCH.
FIG. 7 is a call flow showing hard handover with a unique SYNC_UL code in a TD-SCDMA network according to one aspect. At time 710 during an activation time a UE 702 performs hard handover to a target cell 704. At time 712 the UE 702 transmits a unique SYNC_UL code to the target cell 704 and the target cell 704 responds with an acknowledgement on the FPACH at time 714. After sending the FPACH ACK, the target cell 714 resumes HSUPA operation. After receiving the FPACH ACK at time 714, the UE 702 resumes HSDPA and HSUPA operation. Then, at time 716 the target cell 704 transmits the E-AGCH to the UE 702 and the UE 702 sends a reconfiguration complete message on the E-PUCH along with pending UL data at time 718. According to one aspect, the E-AGCH is scrambled with a code having a one-to-one correspondence with the MAC address of the UE 702. The target cell 704 resumes HSDPA operation after receiving the first UL data at time 718.
At time 720 the target cell 704 sends a HARQ acknowledgement on the E-HICH and at time 722 transmits the HS-SCCH. At time 724 the target cell 704 transmits pending DL data on the HS-PDSCH to the UE 702. Then, the UE 702 transmits a HARQ acknowledgement on the HS-SICH at time 726.
Performing post-hard handover processing according to the aspects above allows HSPA operations to continue in the hard handover with reduced latency.
FIG. 8 is a flow chart illustrating hard handover in a TD-SCDMA network according to one aspect. At block 802 a UE performs uplink synchronization with a target Node B (NB) of the wireless network. At block 804 a UE receives an uplink grant and high speed downlink data from the target NB before completion of the uplink synchronization.
FIG. 9 is a flow chart illustrating hard handover in a TD-SCDMA network according to one aspect. At block 902 a UE receives a unique uplink synchronization from a source Node B (NB) of the wireless network. At block 904 the UE transmits the uplink synchronization code to a target NB of the wireless network.
Several aspects of a telecommunications system has been presented with reference to TD-SCDMA. 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, Global System for Mobile Communications (GSM), 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.
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.
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).
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.
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.
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.”

## Claims

1. A method for performing a handover in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network, comprising:
receiving an uplink synchronization code unique to a user equipment (UE) from a source Node B (NB) of the TD-SCDMA network;
performing uplink synchronization with a target Node B (NB) of the TD-SCDMA network after changing both downlink and uplink channels from the source NB to the target NB to stop high speed data communication including high speed downlink data from the source NB and high speed uplink data to the source NB at an activation time specified by the TD-SCDMA network and communicated to the UE, the activation time indicating a time during which handover of the high speed data communication with the target NB occurs;
receiving a data uplink grant assigning network resources for resuming sending uplink data and receiving high speed downlink data from the target NB before completion of the uplink synchronization, the data uplink grant allocated to the UE based at least in part on the uplink synchronization code unique to the UE, the uplink data sent to the target NB and the high speed downlink data from the target NB associated with the high speed data communication handed over from the source NB.

2. The method of claim 1, further comprising transmitting a message to the target NB after completion of the uplink synchronization, wherein the message indicates completion of the handover.

3. A computer program product for performing a handover in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network, comprising:
a non-transitory computer-readable medium comprising:
code to receive an uplink synchronization code unique to a user equipment (UE) from a source Node B (NB) of the TD-SCDMA network;
code to perform uplink synchronization with a target Node B (NB) of the TD-SCDMA network after changing both downlink and uplink channels from the source NB to the target NB to stop high speed data communication including high speed downlink data from the source NB and high speed uplink data to the source NB at an activation time specified by the TD-SCDMA network and communicated to the UE, the activation time indicating a time during which handover of the high speed data communication with the target NB occurs; and
code to receive a data uplink grant assigning network resources for resuming sending uplink data and to receive high speed downlink data from the target NB before completion of the uplink synchronization, the data uplink grant allocated to the UE based at least in part on the uplink synchronization code unique to the UE, the uplink data sent to the target NB and the high speed downlink data from the target NB associated with the high speed data communication handed over from the source NB.

4. The computer program product of claim 3, wherein the medium further comprises code to transmit a message to the target NB after completion of the uplink synchronization indicating completion of the handover.

5. An apparatus for performing a handover in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network, comprising:
at least one processor; and
a memory coupled to the at least one processor, wherein the at least one processor is configured:
to receive an uplink synchronization code unique to a user equipment (UE) from a source Node B (NB) of the TD-SCDMA network;
to perform uplink synchronization with a target Node B (NB) of the TD-SCDMA network after changing both downlink and uplink channels from the source NB to the target NB to stop high speed data communication including high speed downlink data from the source NB and high speed uplink data to the source NB at an activation time specified by the TD-SCDMA network and communicated to the UE, the activation time indicating a time during which handover of the high speed data communication with the target NB occurs; and
to receive a data uplink grant assigning network resources for resuming sending uplink data and to receive high speed downlink data from the target NB before completion of the uplink synchronization, the data uplink grant allocated to the UE based at least in part on the uplink synchronization code unique to the UE, the uplink data sent to the target NB and the high speed downlink data from the target NB associated with the high speed data communication handed over from the source NB.

6. The apparatus of claim 5, wherein the at least one processor is further configured to transmit a message to the target NB after completion of the uplink synchronization indicating completion of the handover.

7. An apparatus for performing a handover in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network, comprising:
means for receiving an uplink synchronization code unique to a user equipment (UE) from a source Node B (NB) of the TD-SCDMA network;
means for performing uplink synchronization with a target Node B (NB) of the TD-SCDMA network after changing both downlink and uplink channels from the source NB to the target NB to stop high speed data communication including high speed downlink data from the source NB and high speed uplink data to the source NB at an activation time specified by the TD-SCDMA network and communicated to the UE, the activation time indicating a time during which handover of the high speed data communication with the target NB occurs; and
means for receiving a data uplink grant assigning network resources for resuming sending uplink data and for receiving high speed downlink data from the target NB before completion of the uplink synchronization, the data uplink grant allocated to the UE based at least in part on the uplink synchronization code unique to the UE, the uplink data sent to the target NB and the high speed downlink data from the target NB associated with the high speed data communication handed over from the source NB.

8. The apparatus of claim 7, further comprising means for transmitting a message to the target NB after completion of the uplink synchronization, wherein the message indicates completion of the handover.

9. A method for performing a handover in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network, comprising:
receiving an uplink synchronization code unique to a User Equipment (UE) from a source Node B (NB) of the TD-SCDMA network;
changing both downlink and uplink channels from the source NB to a target NB to stop high speed data communication including high speed downlink data from the source NB and high speed uplink data to the source NB at an activation time specified by the TD-SCDMA network and communicated to the UE, the activation time indicating a time during which handover of the high speed data communication with the target NB occurs;
transmitting the uplink synchronization code to the target NB of the TD-SCDMA network after the activation time in accordance with an uplink synchronization;
receiving a data uplink grant assigning network resources for resuming sending uplink data and receiving high speed downlink data from the target NB before completion of the uplink synchronization, the data uplink grant allocated to the UE based at least in part on the uplink synchronization code unique to the UE; and
resuming high speed data communication including sending uplink data and receiving high speed downlink data from the target NB before completion of the uplink synchronization, the high speed data communication with the target NB associated with the high speed data communication handed over from the source NB.

10. The method of claim 9, further comprising:
receiving a synchronization acknowledgement; and
transmitting a message to the target NB, the message indicating completion of the handover.

11. The method of claim 9, wherein the uplink synchronization code comprises one of a set of synchronization codes for the handover.

12. A computer program product for performing a handover in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network, comprising:
a non-transitory computer-readable medium comprising:
code to receive an uplink synchronization code unique to a User Equipment (UE) from a source Node B (NB) of the TD-SCDMA network;
code to change both downlink and uplink channels from the source NB to a target NB to stop high speed data communication including high speed downlink data from the source NB and high speed uplink data to the source NB at an activation time specified by the TD-SCDMA network and communicated to the UE, the activation time indicating a time during which handover of the high speed data communication to the target NB occurs;
code to transmit the uplink synchronization code to the target NB of the TD-SCDMA network after the activation time in accordance with an uplink synchronization;
code to receive a data uplink grant assigning network resources for resuming sending uplink data and receiving high speed downlink data from the target NB before completion of the uplink synchronization, the data uplink grant allocated to the UE based at least in part on the uplink synchronization code unique to the UE; and
code to resume high speed data communication including sending uplink data and receiving high speed downlink data from the target NB before completion of the uplink synchronization, the high speed data communication with the target NB associated with the high speed data communication handed over from the source NB.

13. The computer program product of claim 12, wherein the medium further comprises:
code to receive a synchronization acknowledgement; and
code to transmit a message to the target NB, the message indicating completion of the handover.

14. The computer program product of claim 12, wherein the uplink synchronization code comprises one of a set of synchronization codes for the handover.

15. An apparatus for performing a handover in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network, the apparatus comprising:
at least one processor; and a memory coupled to the at least one processor, wherein the at least one processor is configured:
to receive an uplink synchronization code unique to a User Equipment (UE) from a source Node B (NB) of the TD-SCDMA network;
to change both downlink and uplink channels from the source NB to a target NB to stop high speed data communication including high speed downlink data from the source NB and high speed uplink data to the source NB at an activation time specified by the TD-SCDMA network and communicated to the UE, the activation time indicating a time during which handover of the high speed data communication to the target NB occurs;
to transmit the uplink synchronization code to the target NB of the TD-SCDMA network after the activation time in accordance with an uplink synchronization;
to receive a data uplink grant assigning network resources for resuming sending uplink data and receiving high speed downlink data from the target NB before completion of the uplink synchronization, the data uplink grant allocated to the UE based at least in part on the uplink synchronization code unique to the UE; and
to resume high speed data communication including sending uplink data and receiving high speed downlink data from the target NB before completion of the uplink synchronization, the high speed data communication with the target NB associated with the high speed data communication handed over from the source NB.

16. The apparatus of claim 15, wherein the at least one processor is further configured:
to receive a synchronization acknowledgement; and
to transmit a message to the target NB, the message indicating completion of the handover.

17. The apparatus of claim 15, wherein the uplink synchronization code is unique to the UE for the handover.

18. An apparatus for performing a handover in a Time Division—Synchronous Code Division Multiple Access (TD-SCDMA) network, comprising:
means for receiving an uplink synchronization code unique to a User Equipment (UE) from a source Node B (NB) of the TD-SCDMA network;
means for changing both downlink and uplink channels from the source NB to a target NB to stop high speed data communication including high speed downlink data from the source NB and high speed uplink data to the source NB at an activation time specified by the TD-SCDMA network and communicated to the UE, the activation time indicating a time during which handover of the high speed data communication to the target NB occurs;
means for transmitting the uplink synchronization code to the target NB of the TD-SCDMA network after the activation time in accordance with an uplink synchronization;
means for receiving a data uplink grant assigning network resources for resuming sending uplink data and receiving high speed downlink data from the target NB before completion of the uplink synchronization, the data uplink grant allocated to the UE based at least in part on the uplink synchronization code unique to the UE; and
means for resuming high speed data communication including sending uplink data and receiving high speed downlink data from the target NB before completion of the uplink synchronization, the high speed data communication with the target NB associated with the high speed data communication handed over from the source NB.

19. The apparatus of claim 18, further comprising:
means for receiving a synchronization acknowledgement; and
means for transmitting a message to the target NB, the message indicating completion of the handover.

20. The apparatus of claim 18, wherein the uplink synchronization code is unique to the UE for the handover.