WO2013055338A1

WO2013055338A1 - Improved inter-rat measurements using timing offset

Info

Publication number: WO2013055338A1
Application number: PCT/US2011/056048
Authority: WO
Inventors: Ming Yang; Tom Chin; Qingxin Chen; Guangming Shi
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2011-10-13
Filing date: 2011-10-13
Publication date: 2013-04-18
Anticipated expiration: 2014-04-13

Abstract

A user equipment (UE) capable of communication with multiple radio access technologies (RATs) may receive offset timing information from a cell of a RAT. The offset timing information indicates the timing offset between a communication frame of one RAT relative to a communication frame of another RAT. The UE may use the timing offset information to more accurately identify desired portions of a signal of a non-connected RAT, thereby improving inter-RAT signal measurement and mobility.

Description

IMPROVED INTER-RAT MEASUREMENTS USING TIMING OFFSET

BACKGROUND

Field

[0001] Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to an improved method of signal measurement in TDD- LTE (Time Division Long Term Evolution) and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA)/Global System for Mobile Communications (GSM) networks.

Background

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

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

BRIEF DESCRIPTION OF THE DRAWINGS

[0004] FIGURE 1 is a block diagram conceptually illustrating an example of a telecommunications system.

[0005] FIGURE 2 is a block diagram conceptually illustrating an example of a frame structure in a telecommunications system.

[0006] FIGURE 3 is a block diagram conceptually illustrating an example of a node B in communication with a UE in a telecommunications system.

[0007] FIGURE 4 is a block diagram conceptually illustrating an example of a frame structure in a Long Term Evolution telecommunications system.

[0008] FIGURE 5 is a block diagram conceptually illustrating an example of a frame structure in a Time Division-Synchronous Code Division Multiple Access telecommunications system

[0009] FIGURE 6 is a block diagram conceptually illustrating frame alignment according to one aspect of the present disclosure.

[0010] FIGURE 7 is a diagram illustrating a call flow according to one aspect of the present disclosure.

[0011] FIGURE 8 is a diagram illustrating a call flow according to one aspect of the present disclosure.

[0012] FIGURE 9 is a functional block diagram illustrating example blocks executed to implement one aspect of the present disclosure.

[0013] FIGURE 10 is a block diagram illustrating components to implement one aspect of the present disclosure.

[0014] FIGURE 11 is a functional block diagram illustrating example blocks executed to implement one aspect of the present disclosure.

[0015] FIGURE 12 is a block diagram illustrating components to implement one aspect of the present disclosure.

SUMMARY [0016] A method of wireless communication is offered. The method includes receiving, from a serving base station of a first radio access technology, a relative timing offset between a frame of the serving base station and a frame of a base station of a second radio access technology. The method also includes measuring a signal of the base station of the second radio access technology using a timing of the serving base station and the relative timing offset.

[0017] A user equipment (UE) configured for wireless communication is offered. The

UE includes means for receiving, from a serving base station of a first radio access technology, a relative timing offset between a frame of the serving base station and a frame of a base station of a second radio access technology. The UE also includes means for measuring a signal of the base station of the second radio access technology using a timing of the serving base station and the relative timing offset.

[0018] A computer program product is offered. The computer program product includes a non-transitory computer-readable medium having program code recorded thereon. The program code includes program code to receive, from a serving base station of a first radio access technology, a relative timing offset between a frame of the serving base station and a frame of a base station of a second radio access technology. The program code also includes program code to measure a signal of the base station of the second radio access technology using a timing of the serving base station and the relative timing offset.

[0019] A user equipment (UE) configured for wireless communication is offered. The

UE includes a processor(s) and a memory coupled to the processor(s). The processor(s) is configured to receive, from a serving base station of a first radio access technology, a relative timing offset between a frame of the serving base station and a frame of a base station of a second radio access technology. The processor(s) is also configured to measure a signal of the base station of the second radio access technology using a timing of the serving base station and the relative timing offset.

[0020] A method of wireless communication is offered. The method includes acquiring timing information for a base station of a second radio access technology. The method also includes determining a relative timing offset between a frame of a base station of a first radio access technology and a frame of the base station of the second radio access technology. The method further includes sending the relative timing offset to a user equipment served by the base station of the first radio access technology. [0021] A base station for wireless communication is offered. The base station includes means for acquiring timing information for a base station of a second radio access technology. The base station also includes means for determining a relative timing offset between a frame of a base station of a first radio access technology and a frame of the base station of the second radio access technology. The base station further includes means for sending the relative timing offset to a user equipment served by the base station of the first radio access technology.

[0022] A computer program product is offered. The computer program product includes a non-transitory computer-readable medium having program code recorded thereon. The program code includes program code to acquire timing information for a base station of a second radio access technology. The program code also includes program code to determine a relative timing offset between a frame of a base station of a first radio access technology and a frame of the base station of the second radio access technology. The program code further includes program code to send the relative timing offset to a user equipment served by the base station of the first radio access technology.

[0023] A base station for wireless communication is offered. The base station includes a processor(s) and a memory coupled to the processor(s). The processor(s) is configured to acquire timing information for a base station of a second radio access technology. The processor(s) is also configured to determine a relative timing offset between a frame of a base station of a first radio access technology and a frame of the base station of the second radio access technology. The processor(s) is further configured to send the relative timing offset to a user equipment served by the base station of the first radio access technology.

[0024] This has outlined, rather broadly, the features and technical advantages of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described below. It should be appreciated by those skilled in the art that this disclosure may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the teachings of the disclosure as set forth in the appended claims. The novel features, which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages, will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

DETAILED DESCRIPTION

[0025] 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.

[0026] Turning now to FIGURE 1, a block diagram is shown illustrating an example of a telecommunications system 100. The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. By way of example and without limitation, the aspects of the present disclosure illustrated in FIGURE 1 are presented with reference to a UMTS system employing a TD-SCDMA standard. In this example, the UMTS system includes a (radio access network) RAN 102 (e.g., UTRAN) that provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The RAN 102 may be divided into a number of Radio Network Subsystems (RNSs) such as an RNS 107, each controlled by a Radio Network Controller (RNC) such as an RNC 106. For clarity, only the RNC 106 and the RNS 107 are shown; however, the RAN 102 may include any number of RNCs and RNSs in addition to the RNC 106 and RNS 107. The RNC 106 is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS 107. The RNC 106 may be interconnected to other RNCs (not shown) in the RAN 102 through various types of interfaces such as a direct physical connection, a virtual network, or the like, using any suitable transport network. [0027] 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.

[0028] 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.

[0029] In this example, the core network 104 supports circuit-switched services with a mobile switching center (MSC) 112 and a gateway MSC (GMSC) 1 14. 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 1 12 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 1 14 provides a gateway through the MSC 112 for the UE to access a circuit- switched network 116. The GMSC 1 14 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 1 14 queries the HLR to determine the UE's location and forwards the call to the particular MSC serving that location.

[0030] 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 1 10 with packet-based network connectivity. Data packets are transferred between the GGSN 120 and the UEs 1 10 through the SGSN 118, which performs primarily the same functions in the packet-based domain as the MSC 1 12 performs in the circuit-switched domain.

[0031] 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.

[0032] FIGURE 2 shows a frame structure 200 for a TD-SCDMA carrier. The TD-

SCDMA carrier, as illustrated, has a frame 202 that is 10 ms in length. The 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, TSl, 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. In the example illustrated, TS 1-TS3 are allocated for uplink and TS4-TS6 are allocated for downlink. A downlink pilot time slot (DwPTS) 206, a guard period (GP) 208, and an uplink pilot time slot (UpPTS) 210 (also known as the uplink pilot channel (UpPCH)) are located between TS0 and TS1. Each time slot, TS0-TS6, may allow data transmission multiplexed on a maximum of 16 code channels. Data transmission on a code channel includes two data portions 212 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. The chip rate in TD-SCDMA is 1.28 Mcps.

FIGURE 3 is a block diagram of a node B 310 in communication with a UE 350 in a RAN 300, where the RAN 300 may be the RAN 102 in FIGURE 1, the node B 310 may be the node B 108 in FIGURE 1, and the UE 350 may be the UE 1 10 in FIGURE 1. In the downlink communication, a transmit processor 320 may receive data from a data source 312 and control signals from a controller/processor 340. The transmit processor 320 provides various signal processing functions for the data and control signals, as well as reference signals (e.g., pilot signals). For example, the transmit processor 320 may provide cyclic redundancy check (CRC) codes for error detection, coding and interleaving to facilitate forward error correction (FEC), mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M- quadrature amplitude modulation (M-QAM), and the like), spreading with orthogonal variable spreading factors (OVSF), and multiplying with scrambling codes to produce a series of symbols. Channel estimates from a channel processor 344 may be used by a controller/processor 340 to determine the coding, modulation, spreading, and/or scrambling schemes for the transmit processor 320. These channel estimates may be derived from a reference signal transmitted by the UE 350 or from feedback contained in the midamble 214 (FIGURE 2) from the UE 350. The symbols generated by the transmit processor 320 are provided to a transmit frame processor 330 to create a frame structure. The transmit frame processor 330 creates this frame structure by multiplexing the symbols with a midamble 214 (FIGURE 2) from the controller/processor 340, resulting in a series of frames. The frames are then provided to a transmitter 332, which provides various signal conditioning functions including amplifying, filtering, and modulating the frames onto a carrier for downlink transmission over the wireless medium through smart antennas 334. The smart antennas 334 may be implemented with beam steering bidirectional adaptive antenna arrays or other similar beam technologies.

[0034] At the UE 350, a receiver 354 receives the downlink transmission through an antenna 352 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 354 is provided to a receive frame processor 360, which parses each frame, and provides the midamble 214 (FIGURE 2) to a channel processor 394 and the data, control, and reference signals to a receive processor 370. The receive processor 370 then performs the inverse of the processing performed by the transmit processor 320 in the node B 310. More specifically, the receive processor 370 descrambles and despreads the symbols, and then determines the most likely signal constellation points transmitted by the node B 310 based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor 394. The soft decisions are then decoded and deinterleaved to recover the data, control, and reference signals. The CRC codes are then checked to determine whether the frames were successfully decoded. The data carried by the successfully decoded frames will then be provided to a data sink 372, which represents applications running in the UE 350 and/or various user interfaces (e.g., display). Control signals carried by successfully decoded frames will be provided to a controller/processor 390. When frames are unsuccessfully decoded by the receiver processor 370, the controller/processor 390 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0035] In the uplink, data from a data source 378 and control signals from the controller/processor 390 are provided to a transmit processor 380. The data source 378 may represent applications running in the UE 350 and various user interfaces (e.g., keyboard). Similar to the functionality described in connection with the downlink transmission by the node B 310, the transmit processor 380 provides various signal processing functions including CRC codes, coding and interleaving to facilitate FEC, mapping to signal constellations, spreading with OVSFs, and scrambling to produce a series of symbols. Channel estimates, derived by the channel processor 394 from a reference signal transmitted by the node B 310 or from feedback contained in the midamble transmitted by the node B 310, may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor 380 will be provided to a transmit frame processor 382 to create a frame structure. The transmit frame processor 382 creates this frame structure by multiplexing the symbols with a midamble 214 (FIGURE 2) from the controller/processor 390, resulting in a series of frames. The frames are then provided to a transmitter 356, which provides various signal conditioning functions including amplification, filtering, and modulating the frames onto a carrier for uplink transmission over the wireless medium through the antenna 352.

[0036] The uplink transmission is processed at the node B 310 in a manner similar to that described in connection with the receiver function at the UE 350. A receiver 335 receives the uplink transmission through the antenna 334 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 335 is provided to a receive frame processor 336, which parses each frame, and provides the midamble 214 (FIGURE 2) to the channel processor 344 and the data, control, and reference signals to a receive processor 338. The receive processor 338 performs the inverse of the processing performed by the transmit processor 380 in the UE 350. The data and control signals carried by the successfully decoded frames may then be provided to a data sink 339 and the controller/processor, respectively. If some of the frames were unsuccessfully decoded by the receive processor, the controller/processor 340 may also use an acknowledgement (ACK) and/or negative acknowledgement ( ACK) protocol to support retransmission requests for those frames.

[0037] The controller/processors 340 and 390 may be used to direct the operation at the node B 310 and the UE 350, respectively. For example, the controller/processors 340 and 390 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories 342 and 392 may store data and software for the node B 310 and the UE 350, respectively. For example, the memory 392 of the UE 350 may store an inter- RAT timing offset module 391 which, when executed by the controller/processor 390, processes a timing offset between one radio access technology and another. As another example, the memory 342 of the node B 310 may store an inter-RAT timing offset calculation module 341 which, when executed by the controller/processor 340, calculates a timing offset between one radio access technology and another. 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.

[0038] Certain mobile equipment may be configured to allow for operation on multiple wireless communication networks. For example, a UE may be capable of operating either on a TD-SCDMA/GSM network or on a TDD-LTE (Time Division Duplexed - Long Term Evolution) network. Certain situations may direct the UE to communicate on one particular available network. For example, a multi-mode UE capable of communicating on either TD-SCDMA or on TDD-LTE may wish to connect to TDD- LTE for data service and to TD-SCDMA for voice service.

[0039] FIGURE 4 shows a frame structure for a TDD-LTE carrier. The TDD-LTE carrier, as illustrated, has a frame 402 that is 10 ms in length. Each radio frame has 307200 Ts, where T is the basic time unit of TDD-LTE. Each frame has two 5 ms half frames 404, and each of the half frames 404 includes five time subframes, giving each individual frame ten subframes, shown as subframes #0 through #9 (412-430). Each subframe can be either a downlink subframe (D), uplink subframe (U), or special subframe (S). Downlink subframes and uplink subframes can be divided into two slots, each of 0.5 ms. A special subframe may be divided into DwPTS (Downlink Pilot Timeslot), UpPTS (Uplink Pilot Timeslot), and gap period. Depending on configuration, the duration of DwPTS, UpPTS, and the gap period can vary.

[0040] As illustrated in FIGURE 4, subframe #1 414 and subframe #6 424 are special subframes each with a DwPTS 406, gap period 408, and UpPTS 410. Subframes #0, 3, 4, 5, 8, and 9 (412, 418, 420, 422, 428, and 430) are downlink subframes and subframes #2 and 7 (416 and 426) are uplink subframes. This uplink-downlink configuration corresponds to TDD-LTE frame configuration 2. Table 1 below shows the possible uplink-downlink configurations in TDD-LTE: Subframe number

Uplink-downlink Downlink-to-Uplink

configuration Switch-point periodicity 0 1 2 3 4 5 6 7 8 9

0 5 ms D s u u U D S U U U

1 5 ms D s u u D D S U U D

2 5 ms D s u D D D s U D D

3 10 ms D s u u U D D D D D

4 10 ms D s u u D D D D D D

5 10 ms D s u D D D D D D D

6 5 ms D s u u U D S U U D

TABLE 1

[0041] FIGURE 5 shows a frame structure 500 for a TD-SCDMA carrier. The TD-

SCDMA carrier, as illustrated, has a frame 502 that is 10 ms in length. The frame 502 has two 5 ms subframes 504, and each of the subframes 504 includes seven time slots, TS0 through TS6. The first time slot, TS0, is usually allocated for downlink communication, while the second time slot, TSl, is usually allocated for uplink communication. The remaining time slots, TS2 and TS3 are usually allocated for uplink communications whereas time slots TS4, TS5, and TS6, are usually allocated for downlink communications. A downlink pilot time slot (DwPTS) 506, a guard period (GP) 508, and an uplink pilot time slot (UpPTS) 510 (also known as the uplink pilot channel (UpPCH)) are located between time slots TS0 and TS l. The DwPTS 506 and guard period 508 are 96 chips long. The UpPTS 510 is 160 chips long. In between the DwPTS 506 and the guard period 508, there is a switching point 512, where communications switch between downlink communications to uplink communications. Between time slots TS3 and TS4 there is another switching point 514, where communications switch from uplink communications to downlink communications. Other uplink/downlink configurations for a TD-SCDMA frame are also possible.

[0042] TDD-LTE and TD-SCDMA networks may be deployed to share physical base stations and/or frequency bands. In such deployments the two radio access technologies (RATs) may align their respective uplink and downlink communications to avoid interference with the other RAT's downlink/uplink. TDD-LTE radio frame parameters and TD-SCDMA relative timing may be adjusted to allow co-existence between TD- SCDMA downlink/uplink with TDD-LTE uplink/downlink, thereby reducing interference between the two RATs.

[0043] Both TDD-LTE and TD-SCDMA feature a special timeslot featuring a downlink pilot timeslot, a gap period, and an uplink pilot timeslot. In TDD-LTE, the special timeslot is configurable, thus allowing the alignment of switching points between TDD- LTE and TD-SCDMA. As shown in Table 2 below, the length of the TDD-LTE downlink pilot timeslot (DwPTS), a gap period (GP), and an uplink pilot timeslot (UpPTS) may differ based on particular configurations. The lengths shown in Table 2 are listed in terms of number of orthogonal frequency division multiplexing (OFDM) symbols for normal cyclic prefix (CP). As shown below, the total length of the special subframe (DwPTS + GP + UpPTS) is 14 OFDM symbols (1 ms) for normal CP, but the length for each section of the special subframe may vary with the LTE configuration:

TABLE 2

[0044] The relative timing of TDD-LTE to TD-SCDMA may be adjusted to allow coexistence of the two technologies and reduction of interference when the two RATs are deployed on the same or adjacent frequencies. As shown in FIGURE 6, the TD- SCDMA frame 602 may be aligned with the TDD-LTE frame 604 using a relative timing offset 606 between the beginning of the two frames such that interference causing overlap between downlink on one RAT and uplink on the other RAT may be reduced.

[0045] Table 3 shows an example for configurations between TD-SCDMA (illustrated by number of downlink (DL) timeslots versus uplink (UL) timeslots) and TDD-LTE (illustrated by configuration number) for normal cyclic prefix arranged to reduce interference. The set of possible lengths of DwPTS/GP/UpPTS is selected to support coexistence deployments of TD-SCDMA and TDD-LTE, and also to provide an improved degree of guard-period flexibility.

[0046] In current deployments both TDD-LTE and TD-SCDMA are synchronized systems. A network deployment does not necessarily signal the relative timing offset between TDD-LTE and TD-SCDMA to any particular user equipment (UE).

[0047] When a UE is in TD-SCDMA mode and needs to perform LTE measurement, the UE executes an acquisition procedure (such as primary synchronization signal (PSS) and secondary synchronization signal (SSS) search to find the TDD-LTE frame boundary timing). The UE also captures either SF0 or SF5 to ensure the UE has captured the reference signal (RS) symbols to perform Reference Signal Received Power (RSRP) or Reference Signal Received Quality (RSRQ) measurements of neighbor TDD-LTE cells. The measurements are processed through numerous timing hypotheses, because the UE may not know which subframe is the appropriate downlink subframe to measure. For example, if the TDD-LTE UL-DL configuration is type 2, then only subframes 0, 3, 4, 5, 8, 9 can be measured. If the UE attempts to measure an uplink subframe or special subframe, there will be errors. This is less of a concern in frequency division duplexing (FDD) LTE systems because every subframe has a downlink cell-specific reference signal in FDD systems.

[0048] When a UE is in TDD-LTE mode and performs TD-SCDMA measurement, the

UE performs a complicated acquisition procedure. The procedure identifies the sub- frame boundary at time slot 0 to perform primary common control physical channel (PCCPCH) received signal code power (RSCP) measurements of the TD-SCDMA signal through numerous timing hypotheses. [0049] Generally, it takes a longer time for a UE to perform inter-RAT measurement when the UE is in idle mode because the UE has to awaken. Even when a UE is in connected mode, inter-RAT measurement/scheduling can be challenging.

[0050] Offered is a method to facilitate inter-RAT measurement between TDD-LTE and TD-SCDMA. When a UE is in TD-SCDMA idle mode, in addition to the frequency and cell ID of a neighbor TDD-LTE cell, the relative time offset between the TDD-LTE signal and the TD-SCDMA signal is indicated to the UE via a message on system information block (SIB) 19. When the UE is in TD-SCDMA dedicated channel (i.e., connected) mode, the relative time offset between the TDD-LTE signal and the TD-SCDMA signal is indicated to the UE via measurement control messages (MCM).

[0051] Relative timing offsets may be calculated by base stations using back channel network communications according to a variety of protocols for such communications. A common timing reference, such as global positioning system (GPS) time may be used by the different RATs to calculate and communicate a timing offset. Timing offset calculations may be updated by a base station to ensure the timing offset is accurate.

[0052] The UE can use the relative timing offset information to perform target TDD-

LTE measurements, as the UE can now more accurately determine when the UE should listen to the TDD-LTE signal to identify the signal portions the UE wishes to obtain for measurement. Specifically the UE can use the TD-SCDMA serving cell timing and timing offset relative to the neighbor TDD-LTE cell to identify TDD-LTE sub-frame 0 and 6 to perform RSRP measurements.

[0053] The UE can use this timing offset information to schedule inter-RAT measurement, avoid blind searches, and reduce time spent in inter-RAT measurement. The UE may thus increase standby time when the UE is in TD-SCDMA idle mode, and expedite TDD-LTE inter-RAT measurement to reduce the probability of call drops before handing over to TDD-LTE. The UE may also measure more reference signals and report to the network with more accurate RSRP/RSRQ measurement results. The UE may also make measurement results available more quickly.

[0054] FIGURE 7 illustrates the above measurements in a call flow diagram. A UE 702 may be in TD-SCDMA idle mode as shown in block 708. In that scenario, the TD- SCDMA cell 704 sends the UE 702 the relative timing offset in a SIB 11 message at time 710. The UE 702 may then perform inter-RAT (IRAT) measurements of the TDD- LTE signal using the timing offset information to locate the desired sections of the TDD-LTE signal to measure, as shown in block 712. Alternatively, the UE 702 may be in TD-SCDMA connected mode, as shown in block 714. In that scenario, the TD- SCDMA cell 704 sends the UE 702 the relative timing offset in a measurement control message (MCM) at time 716. The UE 702 may then perform inter-RAT (IRAT) measurements of the TDD-LTE signal using the timing offset information to locate the desired sections of the TDD-LTE signal to measure, as shown in block 718. If appropriate, the UE 702 may send the TD-SCDMA cell 704 a measurement report 720 indicating the results of the inter-RAT measurement performed by the UE 702. The TD-SCDMA cell 704 may then trigger handover based on the measurement report, as shown in block 722.

[0055] When the UE is TDD-LTE idle mode, the relative timing offset between the

TDD-LTE signal and the TD-SCDMA signal can be indicated to the UE via a message on SIB 6. When the UE is in dedicated channel (i.e., connected) mode, the relative timing offset between the TDD-LTE signal and the TD-SCDMA signal can be indicated to the UE via a physical channel reconfiguration radio resource control (RRC) message.

[0056] The UE can perform target TD-SCDMA measurements with the relative timing offset information, as the UE can now more accurately determine when the UE should listen to the TD-SCDMA signal to identify the signal portions the UE wishes to obtain for measurement. Specifically the UE can use the TDD-LTE service cell timing and timing offset relative to the neighbor TD-SCDMA cell to identify TD-SCDMA sub- frame and frame boundaries and time slot 0 to perform PCCPCH and RSCP measurements.

[0057] FIGURE 8 illustrates the above measurements in a call flow diagram. A UE 802 may be in TDD-LTE idle mode as shown in block 808. In that scenario, the TDD-LTE cell 806 sends the UE 802 the relative timing offset in a SIB 6 message at time 810. The UE 802 may then perform inter-RAT (IRAT) measurements of the TD-SCDMA signal using the timing offset information to locate the desired sections of the TD- SCDMA signal to measure, as shown in block 812. Alternatively, the UE 802 may be in TDD-LTE connected mode, as shown in block 814. In that scenario, the TDD-LTE cell 806 sends the UE 802 the relative timing offset in a physical channel reconfiguration message at time 816. The UE 802 may then perform inter-RAT (IRAT) measurements of the TD-SCDMA signal using the timing offset information to locate the desired sections of the TD-SCDMA signal to measure, as shown in block 818. If appropriate, the UE 802 may send the TDD-LTE cell 806 a measurement report at time 820, indicating the results of the inter-RAT measurement performed by the UE 802. The TDD-LTE cell 806 may then trigger handover based on the measurement report, as shown in block 822.

[0058] The proposed methods employing inter-RAT timing offset information enables enhanced efficiency of inter-RAT measurements to support mobility between synchronized RATs such as TDD-LTE and TD-SCDMA. The UE may use the timing offset information to schedule inter-RAT measurement and to avoid complicated initial acquisition procedures through numerous timing hypotheses. Use of the timing offset information allows a UE to reduce time spent in inter-RAT measurement, increase UE standby time, and improve inter-RAT mobility performance through a reduced number of potential call drops during mobility between RATs.

[0059] Although described in reference to two synchronous RATs, the above methods may also be employed between a synchronous RAT and an asynchronous RAT.

[0060] As shown in FIGURE 9 a UE may receive, from a serving base station of a first radio access technology (RAT), a relative timing offset between a frame of the serving base station and a frame of a base station of a second RAT, as shown in block 902. The UE may measure a signal of the base station of the second RAT using a timing of the serving base station and the relative timing offset, as shown in block 904.

[0061] FIGURE 10 shows a design of an apparatus 1000 for a UE, such as the UE 350 of FIGURE 3. The apparatus 1000 includes a module 1002 to receive, from a serving base station of a first RAT, a relative timing offset between a frame of the serving base station and a frame of a base station of a second RAT. The apparatus also includes a module 1004 to measure a signal of the base station of the second RAT using a timing of the serving base station and the relative timing offset. The modules in FIGURE 10 may be processors, electronics devices, hardware devices, electronics components, logical circuits, memories, software codes, firmware codes, etc., or any combination thereof.

[0062] In one configuration, the apparatus, for example the UE 350, for wireless communication includes means for receiving, from a serving base station of a first RAT, a relative timing offset between a frame of the serving base station and a frame of a base station of a second RAT. In one aspect, the aforementioned means may include the antenna 352, controller/processor 390, receiver 354, receive processor 370, and/or memory 392 configured to perform the functions recited by the aforementioned means. The apparatus also includes means for measuring a signal of the base station of the second RAT using a timing of the serving base station and the relative timing offset. In one aspect, the aforementioned means may include the antenna 352, controller/processor 390, receiver 354, receive frame processor 360, receive processor 370, memory 392, and/or inter-RAT timing offset module 391 configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a module or any apparatus configured to perform the functions recited by the aforementioned means.

[0063] As shown in FIGURE 11 a node B may acquire timing information for a base station of a first RAT, as shown in block 1 102. The node B may determine a relative timing offset between a frame of a base station of a first RAT and a frame of the base station of the second RAT, as shown in block 1104. The node B may send the relative timing offset to a UE served by the base station of the first RAT, as shown in block 1 106

[0064] FIGURE 12 shows a design of an apparatus 1200 for a node B, such as the node

B 310 of FIGURE 3. The apparatus 1200 includes a module 1202 to acquire timing information for a base station of a first RAT. The apparatus also includes a module 1204 to determine a relative timing offset between a frame of a base station of a first RAT and a frame of the base station of the second RAT. The apparatus 1200 also includes a module 1206 to send the relative timing offset to a UE served by the base station of the first RAT. The modules in FIGURE 12 may be processors, electronics devices, hardware devices, electronics components, logical circuits, memories, software codes, firmware codes, etc., or any combination thereof.

[0065] In one configuration, the apparatus, for example the node B 310, for wireless communication includes means for acquiring timing information for a base station of a second RAT. In one aspect, the aforementioned means may include the controller/processor 340, and/or scheduler/processor 346 configured to perform the functions recited by the aforementioned means. The node B also includes means for determining a relative timing offset between a frame of a base station of a first RAT and a frame of the base station of the second RAT. In one aspect, the aforementioned means may include the controller/processor 340, and/or scheduler/processor 346, and the inter- RAT timing offset calculation module 341 configured to perform the functions recited by the aforementioned means. The node B also includes means for sending the relative timing offset to a UE served by the base station of the first RAT. In one aspect, the aforementioned means may include the controller/processor 340, the transmitter 332, and/or the antenna 334 configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a module or any apparatus configured to perform the functions recited by the aforementioned means.

[0066] Several aspects of a telecommunications system has been presented with reference to TD-SCDMA and TDD-LTE systems. 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 FDD Long Term Evolution (LTE), 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.

[0067] 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.

[0068] 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).

[0069] 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.

[0070] 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.

[0071] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more." Unless specifically stated otherwise, the term "some" refers to one or more. A phrase referring to "at least one of a list of items refers to any combination of those items, including single members. As an example, "at least one of: a, b, or c" is intended to cover: a; b; c; a and b; a and c; b and c; and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112, sixth paragraph, unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the element is recited using the phrase "step for."

WHAT IS CLAIMED IS:

Claims

1. A method of wireless communication comprising:

receiving, from a serving base station of a first radio access technology, a relative timing offset between a frame of the serving base station and a frame of a base station of a second radio access technology; and

measuring a signal of the base station of the second radio access technology using a timing of the serving base station and the relative timing offset.

2. The method of claim 1 in which the receiving occurs when a user equipment is in connected mode with respect to the serving base station.

3. The method of claim 1 in which the receiving occurs when a user equipment is in idle mode with respect to the serving base station.

4. The method of claim 1 in which the measuring occurs when a user equipment is in connected mode with respect to the serving base station.

5. The method of claim 1 in which the measuring occurs when a user equipment is in idle mode with respect to the serving base station.

6. The method of claim 1 in which the first radio access technology comprises Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) and the second radio access technology comprises Time Division Duplex-Long Term Evolution (TDD-LTE).

7. The method of claim 1 in which the first radio access technology comprises Time Division Duplex-Long Term Evolution (TDD-LTE) and the second radio access technology comprises Time Division-Synchronous Code Division Multiple Access (TD-SCDMA).

8. The method of claim 1 in which at least one of the first radio access technology and the second radio access technology is a synchronous radio access technology.

9. The method of claim 1 in which at least one of the first radio access technology and the second radio access technology is an asynchronous radio access technology.

10. A user equipment (UE) configured for wireless communication, the UE comprising:

means for receiving, from a serving base station of a first radio access technology, a relative timing offset between a frame of the serving base station and a frame of a base station of a second radio access technology; and

means for measuring a signal of the base station of the second radio access technology using a timing of the serving base station and the relative timing offset.

1 1. A computer program product, comprising:

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

program code to receive, from a serving base station of a first radio access technology, a relative timing offset between a frame of the serving base station and a frame of a base station of a second radio access technology; and program code to measure a signal of the base station of the second radio access technology using a timing of the serving base station and the relative timing offset.

12. A user equipment (UE) configured for wireless communication, comprising: at least one processor; and

a memory coupled to the at least one processor, the at least one processor being configured:

to receive, from a serving base station of a first radio access technology, a relative timing offset between a frame of the serving base station and a frame of a base station of a second radio access technology; and to measure a signal of the base station of the second radio access technology using a timing of the serving base station and the relative timing offset.

13. The user equipment of claim 12 in which the at least one processor is configured to receive when a user equipment is in connected mode with respect to the serving base station.

14. The user equipment of claim 12 in which the at least one processor is configured to receive when a user equipment is in idle mode with respect to the serving base station.

15. The user equipment of claim 12 in which the at least one processor is configured to measure when a user equipment is in connected mode with respect to the serving base station.

16. The user equipment of claim 12 in which the at least one processor is configured to measure when a user equipment is in idle mode with respect to the serving base station.

17. The user equipment of claim 12 in which the first radio access technology comprises Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) and the second radio access technology comprises Time Division Duplex-Long Term Evolution (TDD-LTE).

18. The user equipment of claim 12 in which the first radio access technology comprises Time Division Duplex-Long Term Evolution (TDD-LTE) and the second radio access technology comprises Time Division-Synchronous Code Division Multiple Access (TD-SCDMA).

19. The user equipment of claim 12 in which at least one of the first radio access technology and the second radio access technology is a synchronous radio access technology.

20. The user equipment of claim 12 in which at least one of the first radio access technology and the second radio access technology is an asynchronous radio access technology.

21. A method of wireless communication comprising:

acquiring timing information for a base station of a second radio access technology;

determining a relative timing offset between a frame of a base station of a first radio access technology and a frame of the base station of the second radio access technology; and sending the relative timing offset to a user equipment served by the base station of the first radio access technology.

22. The method of claim 21 further comprising updating the timing information.

23. A base station for wireless communication comprising:

means for acquiring timing information for a base station of a second radio access technology;

means for determining a relative timing offset between a frame of a base station of a first radio access technology and a frame of the base station of the second radio access technology; and

means for sending the relative timing offset to a user equipment served by the base station of the first radio access technology.

24. The base station of claim 23 further comprising means for updating the timing information.

25. A computer program product, comprising:

program code to acquire timing information for a base station of a second radio access technology;

program code to determine a relative timing offset between a frame of a base station of a first radio access technology and a frame of the base station of the second radio access technology; and

program code to send the relative timing offset to a user equipment served by the base station of the first radio access technology.

26. The computer program product of claim 25 in which the program code further comprises program code to update the timing information.

27. A base station for wireless communication comprising: at least one processor; and

to acquire timing information for a base station of a second radio access technology;

to determine a relative timing offset between a frame of a base station of a first radio access technology and a frame of the base station of the second radio access technology; and

to send the relative timing offset to a user equipment served by the base station of the first radio access technology.

28. The base station of claim 27 in which the at least one processor is further configured to update the timing information.