WO2013019288A1

WO2013019288A1 - Method for improving blind redirection performance

Info

Publication number: WO2013019288A1
Application number: PCT/US2012/032201
Authority: WO
Inventors: Ming Yang; Tom Chin; Guangming Shi
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2011-08-01
Filing date: 2012-04-04
Publication date: 2013-02-07
Anticipated expiration: 2014-02-01
Also published as: TW201320785A

Abstract

A method of wireless communication includes receiving an instruction from a serving radio access technology (RAT) to redirect to a target RAT. The instruction includes redirection information indicating a set of target RATs. Separate timer values may be received, from the serving RAT, for each of the target RATs, where the timer values indicate how long a UE should attempt to camp on each of the target RATs. A redirection priority level can also be received.

Description

METHOD FOR IMPROVING BLIND REDIRECTION PERFORMANCE

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit under 35 U.S.C. § 119(e) to United States Provisional Patent Application No. 61/513,878 entitled "METHOD FOR IMPROVING BLIND REDIRECTION PERFORMANCE," filed on August 01, 2011, the disclosure of which is expressly incorporated by reference herein in its entirety.

BACKGROUND

Field

[0002] Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to blind redirection in mobile devices capable of communication on multiple networks, particularly TDD-LTE networks and UMTS networks.

Background

[0003] 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 technology or 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 (3 GPP). 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.

[0004] 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

[0005] FIGURE 1 is a block diagram conceptually illustrating an example of a telecommunications system.

[0006] FIGURE 2 is a block diagram conceptually illustrating an example of a downlink frame structure in a telecommunications system.

[0007] FIGURE 3 is a block diagram conceptually illustrating an example frame structure in uplink communications.

[0008] FIGURE 4 is a diagram conceptually illustrating an example of a base station/eNodeB and a UE in a telecommunications system.

[0009] FIGURE 5 is a diagram illustrating a mixed network that includes coverage areas of a TD-SCDMA network and a TDD-LTE network.

[0010] FIGURE 6 is a call flow diagram illustrating redirection to a target RAT, where only one RAT is included in the redirection information.

[0011] FIGURE 7 is a call flow diagram illustrating redirection where multiple RATs are included in the redirection information.

[0012] FIGURES 8A-8D are block diagrams illustrating redirection to a target RAT where multiple RATs are included in the redirection information.

[0013] FIGURES 9 and 10 are block diagrams illustrating components for blind redirection according to one aspect of the present disclosure.

SUMMARY

[0014] In one aspect of the present disclosure, a method of wireless communication is disclosed. The method includes receiving an instruction from a serving radio access technology (RAT) to redirect to a target RAT. The instruction includes redirection information that indicates a set of target RATs. The method also includes receiving, from the serving RAT, a separate timer value for each of the target RATs. The timer values indicate how long a UE should attempt to camp on each of the target RATs.

[0015] Another aspect discloses a method that includes receiving an instruction to redirect to a target RAT (radio access technology) from a serving RAT where the instruction includes redirection information indicating a set of target RATs. A redirection priority level for each of the target RATs is received from the serving RAT.

[0016] Another aspect discloses a method that includes sending an instruction to a UE to redirect to another RAT (radio access technology). The instruction includes redirection information indicting a set of RATs. A separate timer value is sent to the UE for each of the RATs. The timer values indicate how long the UE should attempt to camp on each of the RATs.

[0017] Another aspect discloses a method that includes sending an instruction to a UE to redirect to another RAT (radio access technology). The instruction includes redirection information indicting a set of RATs. A redirection priority level is sent to the UE for each of the RATs.

[0018] In another aspect, an apparatus for wireless communication having a memory and at least one processor coupled to the memory is disclosed. The processor(s) is configured to receive an instruction, from a serving radio access technology (RAT) to redirect to a target RAT. The instruction includes redirection information indicating a set of target RATs. The processor(s) is also configured to receive, from the serving RAT, a separate timer value for each of the target RATs. The timer values indicate how long a UE should attempt to camp on each of the target RATs.

[0019] Another aspect discloses an apparatus having a memory and at least one processor coupled to the memory. The processor(s) is configured to receive an instruction from a serving radio access technology (RAT) to redirect to a target RAT. The instruction includes redirection information indicating a set of target RATs. The processor(s) is also configured to receive, from the serving RAT, a redirection priority level for each of the target RATs.

[0020] Another aspect discloses an apparatus having a memory and at least one processor coupled to the memory. The processor(s) is configured to send an instruction to a UE to redirect to another RAT (radio access technology). The instruction includes redirection information indicting a set of RATs. The processor(s) is also configured to send a separate timer value to the UE for each of the RATs. The timer values indicate how long the UE should attempt to camp on each of the RATs.

[0021] Another aspect discloses an apparatus having a memory and at least one processor coupled to the memory. The processor(s) is configured to send an instruction to a UE to redirect to another RAT (radio access technology). The instruction includes redirection information indicting a set of RATs. The processor(s) is also configured to send a redirection priority level to the UE for each of the RATs.

[0022] In another aspect, a computer program product for wireless communication in a wireless network having a non-transitory computer-readable medium is disclosed. The computer readable medium has non-transitory program code recorded thereon which, when executed by the processor(s), causes the processor(s) to perform operations of receiving an instruction from a serving radio access technology (RAT) to redirect to a target RAT. The instruction includes redirection information indicating a set of target RATs. The program code also causes the processor(s) to receive, from the serving RAT, a separate timer value for each of the target RATs. The timer values indicate how long a UE should attempt to camp on each of the target RATs.

[0023] Another aspect discloses a computer program product for wireless

communications in a wireless network having a non-transitory computer-readable medium. The computer readable medium has non-transitory program code recorded thereon which, when executed by the processor(s), causes the processor(s) to perform operations of sending an instruction to a UE to redirect to another RAT (radio access technology). The instruction includes redirection information indicting a set of RATs. A separate timer value is sent to the UE for each of the RATs. The timer values indicate how long the UE should attempt to camp on each of the RATs.

[0024] Another aspect discloses a computer program product for wireless

communications in a wireless network having a non-transitory computer-readable medium. The computer readable medium has non-transitory program code recorded thereon which, when executed by the processor(s), causes the processor(s) to perform operations of receiving an instruction from a serving radio access technology (RAT) to redirect to a target RAT. The instruction includes redirection information indicating a set of target RATs. The program code also causes the processor(s) to receive, from the serving RAT, a redirection priority level for each of the target RATs. [0025] Another aspect discloses a computer program product for wireless

communications in a wireless network having a non-transitory computer-readable medium. The computer readable medium has non-transitory program code recorded thereon which, when executed by the processor(s), causes the processor(s) to perform operations of sending an instruction to a UE to redirect to another RAT (radio access technology). The instruction includes redirection information indicting a set of RATs. The program code also causes the processor(s) to send a separate timer value to the UE for each of the RATs, the timer values indicating how long the UE should attempt to camp on each of the RATs.

[0026] Another aspect discloses a computer program product for wireless

communications in a wireless network having a non-transitory computer-readable medium. The computer readable medium has non-transitory program code recorded thereon which, when executed by the processor(s), causes the processor(s) to perform operations of sending an instruction to a UE to redirect to another RAT (radio access technology). The instruction includes redirection information indicting a set of RATs. The program code also causes the processor(s) to send a redirection priority level to the UE for each of the RATs.

[0027] In another aspect, an apparatus for wireless communication is disclosed and includes means for receiving an instruction from a serving radio access technology (RAT) to redirect to a target RAT. The instruction includes redirection information indicating a set of target RATs. The apparatus also includes means for receiving, from the serving RAT, a separate timer value for each of the target RATs. The timer values indicate how long a UE should attempt to camp on each of the target RATs.

[0028] Another aspect discloses an apparatus for wireless communication and includes means for receiving an instruction from a serving radio access technology (RAT) to redirect to a target RAT. The instruction includes redirection information indicating a set of target RATs. The apparatus also includes means for receiving, from the serving RAT, a redirection priority level for each of the target RATs.

[0029] Another aspect discloses an apparatus for wireless communication and includes means for sending an instruction to a UE to redirect to another RAT (radio access technology). The instruction includes redirection information indicting a set of RATs. The apparatus also includes means for sending a separate timer value to the UE for each of the RATs. The timer values indicate how long the UE should attempt to camp on each of the RATs.

[0030] Another aspect discloses an apparatus for wireless communication and includes means for sending an instruction to a UE to redirect to another RAT (radio access technology). The instruction includes redirection information indicting a set of RATs. The apparatus also includes means for sending a redirection priority level to the UE for each of the RATs.

[0031] 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

[0032] 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.

[0033] The wireless network 100 includes a number of base stations (e.g., evolved node Bs (eNodeBs)) 110 and other network entities. An eNodeB may be a station that communicates with the UEs and may also be referred to as a base station, a node B, an access point, and the like. Each eNodeB 110 may provide communication coverage for a particular geographic area. In 3GPP, the term "cell" can refer to this particular geographic coverage area of an eNodeB and/or an eNodeB subsystem serving the coverage area, depending on the context in which the term is used.

[0034] An eNodeB may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cell. A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions with the network provider. A pico cell would generally cover a relatively smaller geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A femto cell would also generally cover a relatively small geographic area (e.g., a home) and, in addition to unrestricted access, may also provide restricted access by UEs having an association with the femto cell (e.g., UEs in a closed subscriber group (CSG), UEs for users in the home, and the like). An eNodeB for a macro cell may be referred to as a macro eNodeB. An eNodeB for a pico cell may be referred to as a pico eNodeB. And, an eNodeB for a femto cell may be referred to as a femto eNodeB or a home eNodeB. In the example shown in FIGURE 1, the eNodeBs 110a, 110b and 110c are macro eNodeBs for the macro cells 102a, 102b and 102c, respectively. The eNodeB 1 lOx is a pico eNodeB for a pico cell 102x. And, the eNodeBs HOy and l lOz are femto eNodeBs for the femto cells 102y and 102z, respectively. An eNodeB may support one or multiple (e.g., two, three, four, and the like) cells.

[0035] The wireless network 100 may also include relay stations. A relay station is a station that receives a transmission of data and/or other information from an upstream station (e.g., an eNodeB, UE, etc.) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE or an eNodeB). A relay station may also be a UE that relays transmissions for other UEs. In the example shown in FIGURE 1, a relay station HOr may communicate with the eNodeB 110a and a UE 120r in order to facilitate communication between the eNodeB 110a and the UE 120r. A relay station may also be referred to as a relay eNodeB, a relay, etc.

[0036] The wireless network 100 may be a heterogeneous network that includes eNodeBs of different types, e.g., macro eNodeBs, pico eNodeBs, femto eNodeBs, relays, etc. These different types of eNodeBs may have different transmit power levels, different coverage areas, and different impact on interference in the wireless network 100. For example, macro eNodeBs may have a high transmit power level (e.g., 20 Watts) whereas pico eNodeBs, femto eNodeBs and relays may have a lower transmit power level (e.g., 1 Watt).

[0037] A network controller 130 may couple to a set of eNodeBs 110 and provide coordination and control for these eNodeBs 110. The network controller 130 may communicate with the eNodeBs 110 via a backhaul. The eNodeBs 110 may also communicate with one another, e.g., directly or indirectly via a wireless backhaul or a wireline backhaul.

[0038] The UEs 120 are dispersed throughout the wireless network 100, and each UE may be stationary or mobile. A UE may also be referred to as a terminal, a mobile station, a subscriber unit, a station, or the like. A UE may be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, or the like. A UE may be able to communicate with macro eNodeBs, pico eNodeBs, femto eNodeBs, relays, and the like. In FIGURE 1, a solid line with double arrows indicates desired transmissions between a UE and a serving eNodeB, which is an eNodeB designated to serve the UE on the downlink and/or uplink. A dashed line with double arrows indicates interfering transmissions between a UE and an eNodeB.

[0039] LTE utilizes orthogonal frequency division multiplexing (OFDM) on the downlink and single-carrier frequency division multiplexing (SC-FDM) on the uplink. OFDM and SC-FDM partition the system bandwidth into multiple (K) orthogonal subcarriers, which are also commonly referred to as tones, bins, or the like. Each subcarrier may be modulated with data. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDM. The spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system bandwidth.

[0040] FIGURE 2 shows a downlink FDD frame structure used in LTE. The transmission timeline for the downlink may be partitioned into units of radio frames. Each radio frame may have a predetermined duration (e.g., 10 milliseconds (ms)) and may be partitioned into 10 subframes with indices of 0 through 9. Each subframe may include two slots. Each radio frame may thus include 20 slots with indices of 0 through 19. Each slot may include L symbol periods, e.g., 7 symbol periods for a normal cyclic prefix (as shown in FIGURE 2) or 6 symbol periods for an extended cyclic prefix. The 2L symbol periods in each subframe may be assigned indices of 0 through 2L-1. The available time frequency resources may be partitioned into resource blocks. Each resource block may cover N subcarriers (e.g., 12 subcarriers) in one slot.

[0041] In LTE, an eNodeB may send a primary synchronization signal (PSC or PSS) and a secondary synchronization signal (SSC or SSS) for each cell in the eNodeB. For FDD mode of operation, the primary and secondary synchronization signals may be sent in symbol periods 6 and 5, respectively, in each of subframes 0 and 5 of each radio frame with the normal cyclic prefix, as shown in FIGURE 2. The synchronization signals may be used by UEs for cell detection and acquisition. For FDD mode of operation, the eNodeB may send a Physical Broadcast Channel (PBCH) in symbol periods 0 to 3 in slot 1 of subframe 0. The PBCH may carry certain system information.

[0042] The eNodeB may send a Physical Control Format Indicator Channel (PCFICH) in the first symbol period of each subframe, as seen in FIGURE 2. The PCFICH may convey the number of symbol periods (M) used for control channels, where M may be equal to 1, 2 or 3 and may change from subframe to subframe. M may also be equal to 4 for a small system bandwidth, e.g., with less than 10 resource blocks. In the example shown in FIGURE 2, M=3. The eNodeB may send a Physical HARQ Indicator Channel (PHICH) and a Physical Downlink Control Channel (PDCCH) in the first M symbol periods of each subframe. The PDCCH and PHICH are also included in the first three symbol periods in the example shown in FIGURE 2. The PHICH may carry

information to support hybrid automatic retransmission (HARQ). The PDCCH may carry information on uplink and downlink resource allocation for UEs and power control information for uplink channels. The eNodeB may send a Physical Downlink Shared Channel (PDSCH) in the remaining symbol periods of each subframe. The PDSCH may carry data for UEs scheduled for data transmission on the downlink.

[0043] The eNodeB may send the PSC, SSC and PBCH in the center 1.08 MHz of the system bandwidth used by the eNodeB. The eNodeB may send the PCFICH and PHICH across the entire system bandwidth in each symbol period in which these channels are sent. The eNodeB may send the PDCCH to groups of UEs in certain portions of the system bandwidth. The eNodeB may send the PDSCH to groups of UEs in specific portions of the system bandwidth. The eNodeB may send the PSC, SSC, PBCH, PCFICH and PHICH in a broadcast manner to all UEs, may send the PDCCH in a unicast manner to specific UEs, and may also send the PDSCH in a unicast manner to specific UEs.

[0044] A number of resource elements may be available in each symbol period. Each resource element may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value. For symbols that are used for control channels, the resource elements not used for a reference signal in each symbol period may be arranged into resource element groups (REGs). Each REG may include four resource elements in one symbol period.

[0045] A UE may be within the coverage of multiple eNodeBs. One of these eNodeBs may be selected to serve the UE. The serving eNodeB may be selected based on various criteria such as received power, path loss, signal-to-noise ratio (SNR), etc.

[0046] FIGURE 3 is a block diagram conceptually illustrating an exemplary FDD and TDD (non-special subframe only) subframe structure in uplink long term evolution (LTE) communications. The available resource blocks (RBs) for the uplink may be partitioned into a data section and a control section. The control section may be formed at the two edges of the system bandwidth and may have a configurable size. The resource blocks in the control section may be assigned to UEs for transmission of control information. The data section may include all resource blocks not included in the control section. The design in FIGURE 3 results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all of the contiguous subcarriers in the data section.

[0047] A UE may be assigned resource blocks in the control section to transmit control information to an eNodeB. The UE may also be assigned resource blocks in the data section to transmit data to the eNode B. The UE may transmit control information in a Physical Uplink Control Channel (PUCCH) on the assigned resource blocks in the control section. The UE may transmit only data or both data and control information in a Physical Uplink Shared Channel (PUSCH) on the assigned resource blocks in the data section. An uplink transmission may span both slots of a subframe and may hop across frequency as shown in FIGURE 3. According to one aspect, in relaxed single carrier operation, parallel channels may be transmitted on the UL resources. For example, a control and a data channel, parallel control channels, and parallel data channels may be transmitted by a UE. [0048] FIGURE 4 shows a block diagram of a design of a base station/eNodeB 110 and a UE 120, which may be one of the base stations/eNodeBs and one of the UEs in FIGURE 1. The base station 110 may be the macro eNodeB 110c in FIGURE 1, and the UE 120 may be the UE 120y. The base station 110 may also be a base station of some other type. The base station 110 may be equipped with antennas 434a through 434t, and the UE 120 may be equipped with antennas 452a through 452r.

[0049] At the base station 110, a transmit processor 420 may receive data from a data source 412 and control information from a controller/processor 440. The control information may be for the PBCH, PCFICH, PHICH, PDCCH, etc. The data may be for the PDSCH, etc. The processor 420 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The processor 420 may also generate reference symbols, e.g., for the PSS, SSS, and cell-specific reference signal. A transmit (TX) multiple-input multiple-output (MIMO) processor 430 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 432a through 432t. Each modulator 432 may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator 432 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 432a through 432t may be transmitted via the antennas 434a through 434t, respectively.

[0050] At the UE 120, the antennas 452a through 452r may receive the downlink signals from the base station 110 and may provide received signals to the demodulators (DEMODs) 454a through 454r, respectively. Each demodulator 454 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator 454 may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 456 may obtain received symbols from all the demodulators 454a through 454r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 458 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 120 to a data sink 460, and provide decoded control information to a controller/processor 480. [0051] On the uplink, at the UE 120, a transmit processor 464 may receive and process data (e.g., for the PUSCH) from a data source 462 and control information (e.g., for the PUCCH) from the controller/processor 480. The processor 464 may also generate reference symbols for a reference signal. The symbols from the transmit processor 464 may be precoded by a TX MIMO processor 466 if applicable, further processed by the modulators 454a through 454r (e.g., for SC-FDM, etc.), and transmitted to the base station 110. At the base station 110, the uplink signals from the UE 120 may be received by the antennas 434, processed by the demodulators 432, detected by a MIMO detector 436 if applicable, and further processed by a receive processor 438 to obtain decoded data and control information sent by the UE 120. The processor 438 may provide the decoded data to a data sink 439 and the decoded control information to the controller/processor 440. The base station 110 can send messages to other base stations, for example, over an X2 interface 441.

[0052] The controllers/processors 440 and 480 may direct the operation at the base station 110 and the UE 120, respectively. The processor 440 and/or other processors and modules at the base station 110 may perform or direct the execution of various processes for the techniques described herein. The processor 480 and/or other processors and modules at the UE 120 may also perform or direct the execution of the functional blocks illustrated in FIGURE 5 and/or other processes for the techniques described herein. The memories 442 and 482 may store data and program codes for the base station 110 and the UE 120, respectively. A scheduler 444 may schedule UEs for data transmission on the downlink and/or uplink.

[0053] FIGURE 5 is a diagram illustrating a mixed network 50 that includes coverage areas of a 2G/3G network 500 and a TDD-LTE network 501. The mixed network 50 includes areas where there is dual coverage between the 2G/3G network 500 and the TDD-LTE network 501 and other areas where there is only coverage of the individual networks. The base stations 502-505 operate node Bs for the 2G/3G network 500 and eNode Bs for the TDD-LTE network 501. For example, the base station 502 may operate a single node B for the 2G/3G network 500, while the base station 505 may operate a single eNode B for the TDD-LTE network 501. The base stations 503 and 504 may each operate one node B for the 2G/3G network 500 and an eNode B for the TDD-LTE network 501. UEs, such as the UE 507 within the coverage area of base station 503, may connect for communication through both or either of the 2G/3G network 500 and the TDD-LTE network 501, while UEs such as the UEs 506 and 508 within the coverage areas of the base stations 502 and 505, respectively, would only be able to connect for communication through either the 2G/3G network 500 (for the UE 506 through the base station 502) or the TDD-LTE network 501 (for the UE 508 through the base station 505).

[0054] In order for a UE, such as the UE 507, to connect to both the 2G/3G network 500 and the TDD-LTE network 501, the UE includes both hardware and software enabling it to establish communication with the protocols of both 2G/3G and TDD-LTE technologies.

[0055] Blind redirection may be used, for load balancing and for, circuit switched fall back (CSFB) from LTE to other radio access technologies (RATs), such as TD- SCDMA, UMTS FDD, UMTS TDD, and GSM. Generally, operators may have three or more RATs deployed. For example, the initial deployment of LTE is not expected to provide an IMS (IP multimedia subsystem) voice service. Therefore, the voice service will fall back to other RATs for circuit-switched voice. The 3GPP standards have supported procedures to allow the voice call to be set up when the UE is communicating with the TDD-LTE network, whether in idle or connected mode. Inter- RAT redirection may be blind or non-blind. Blind redirection occurs without knowledge of the radio conditions of the other technology. One advantage of blind redirection is that redirection may be executed quickly without additional measurements. However, because of the unknown coverage quality of the target cell, the redirection may fail.

[0056] In the current 3 GPP specification, redirection information includes only one target RAT. In case of failure when attempting to camp on the indicated RAT (i.e., not being able to camp on the indicated RAT within a fixed period of time), the UE will perform a full frequency scan to find an alternate RAT. It typically takes much longer for the UE to camp on other RATs that are not in the redirection information because of the time for a full frequency scan and acquisition procedures.

[0057] Referring to FIGURE 6, a call flow diagram illustrates processing with redirection information containing only one RAT. At time 610, the UE 602 is in the LTE idle mode or connected mode. In order to perform a particular function, for example to place a voice call, the UE 602, at time 612, sends an Extended Service Request so the UE can disconnect from the LTE network 606 (serving RAT). The LTE network 606 sends an RRC (radio resource control) connection release message at time 614. The RRC connection release message contains one target RAT in the redirection information. At time 616, the UE 602 tunes to the target RAT indicated in the RRC connection release message. Next, at time 618, the UE performs cell selection on the target RAT. An upbound timer expires at time 620 and then at 622 the UE fails to camp on the target RAT. Next, at time 624, the UE 602 performs a full frequency scan to search for other RATs. At time 626, the UE 602 receives broadcast information from the 2G/3G network 604, such as system information blocks (SIBs) from other RATs. Next, at 628, the UE connects to a different RAT with the information collected from the full frequency scan.

[0058] In one aspect of the present disclosure, blind redirection is configured to include multiple RATs in the redirection information from the LTE network. If the UE fails to find a suitable cell in one RAT, the UE can perform cell selection in a second RAT, third RAT, etc. based on the redirection information. The supplemental redirection information reduces the time for acquiring a cell by eliminating a full frequency scan for other RATs, which are not included in redirection information. Consequently, redirection performance is improved. The redirection information for each RAT may include a list of frequencies, cell IDs and broadcast system information, such as MIBs and/or SIBs (master information blocks and/or system information blocks).

[0059] In another configuration, the redirection priority level may be configured for each RAT within the redirection information. In other words, the different RATs may be given different priority levels. In one example, the UE first attempts to camp on the highest priority RAT, but if it fails, the UE may attempt to camp on a second priority level RAT. In an alternate configuration, one or more different RATs are given the same redirection priority level.

[0060] A separate timer may be configured for each RAT in the redirection information. This prevents a UE from spending too much time on one particular RAT. If, the UE does not camp on a first RAT with the time allocated for that RAT, the UE can quickly move to a second RAT. The network can properly set the timer value based on the number of frequencies and cells for the UE to perform cell selection for each RAT.

[0061] In one aspect, blind redirection performance is enhanced for multi RAT deployments, overcoming limitations in the current 3GPP specification. In an example, where the UE fails to camp on one RAT, the UE can identify another RAT without performing a blind full scan. The UE can identify another RAT, by identifying frequencies and cell IDs, and reading broadcast system information (e.g., MIB/SIBs, etc.) Once the UE has identified another RAT, the UE can quickly camp on the alternate RAT. The delay of circuit switched fallback from LTE to other RATs may be decreased. Additionally, the UE can spend less time on one RAT before moving to other RATs, because of the proposed individual timer values.

[0062] FIGURE 7 illustrates a call flow of a UE performing circuit switched fall back when multiple target RAT information is included in the redirection information. At time 710 the UE 702 is in LTE idle/connected mode. At time 712, the UE sends an extended service request to the LTE network 706 (serving RAT) to prepare for the fall back. At time 714, a RRC connection release message is received by the UE 702. Multiple target RATs are included in the redirection information received by the UE 702.

[0063] At time 716, the UE performs cell selection on the highest priority RAT and a timer for that highest priority RAT is started. At time 718, the timer expires and the UE 702 stops searching for the highest priority RAT. If the UE 702 fails to find a suitable cell before the timer stops, the UE can perform cell selection in a second RAT having a second priority (where the second priority is of lower priority than highest priority RAT). The second priority RAT, as well as its associated timer value, are provided in the redirection information. At time 720, the UE performs cell selection on the second priority RAT and a second timer is started. At time 722, the UE 702 connects to the second priority RAT 704 without performing a full frequency scan and without collection system information. Thus, the UE 702 quickly connects to the second priority RAT 704.

[0064] FIGURES 8A-8D are functional block diagram illustrating example blocks executed to implement aspects of the present disclosure. In FIGURE 8 A, at block 810, a user equipment (UE) receives an instruction from a serving radio access technology (RAT) to redirect to a target RAT. The instruction includes redirection information indicating multiple target RATs. Next, in block 812, the UE receives a separate timer value for each of the target RATs, where the timer values indicate the amount of time the UE should attempt to camp on each target RAT.

[0065] In FIGURE 8B, at block 820, a user equipment (UE) receives an instruction from a serving radio access technology (RAT) to redirect to a target RAT. The instruction includes redirection information indicating multiple target RATs. At block 822, the UE receives, from a serving RAT, a redirection priority level for each target RAT.

[0066] In FIGURE 8C, at block 830, a serving RAT sends an instruction to a UE to redirect to another RAT. The instruction includes redirection information to indicate a set of target RATs. At block 832, the serving RAT sends a separate timer value to the UE for each of the RATs. The timer values indicate how long the UE should attempt to camp on each of the target RATs.

[0067] In FIGURE 8D, at block 840, a serving RAT sends an instruction to a UE to redirect to another RAT. The instruction includes redirection information to indicate a set of target RATs. At block 842, the serving RAT sends a redirection priority level to the UE for each of the target RATs.

[0068] FIGURES 9 and 10 are diagrams illustrating examples of hardware

implementations for an apparatus 900 employing a blind redirection system 914. The blind redirection system 914 may be implemented with a bus architecture, represented generally by a bus 924. The bus 924 may include any number of interconnecting buses and bridges depending on the specific application of the blind redirection system 914 and the overall design constraints. The bus 924 links together various circuits including one or more processors and/or hardware modules, represented by a processor 926, an instruction receiving module 902, a timer value receiving module 904 and a redirection priority level receiving module 906, an instruction sending module 1002, a timer value sending module 1004, a redirection priority sending module 1006, and/or a computer- readable medium 928. The bus 924 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

[0069] The apparatus includes the blind redirection system 914 coupled to a transceiver 922. The transceiver 922 is coupled to one or more antennas 920. The transceiver 922 provides a means for communicating with various other apparatus over a transmission medium. The blind redirection system 914 includes the processor 926 coupled to the computer-readable medium 928. The processor 926 is responsible for general processing, including the execution of software stored on the computer-readable medium 928. The software, when executed by the processor 926, causes the blind redirection system 914 to perform the various functions described supra for any particular apparatus. The computer-readable medium 928 may also be used for storing data that is manipulated by the processor 926 when executing software.

[0070] If the apparatus 900 is a UE 120, the blind redirection system 914 includes the instruction receiving module 902 for receiving an instruction to redirect to a target RAT, the timer value receiving module 904 for receiving separate timer values for each target RAT and/or the redirection priority receiving module 906 for receiving redirection priority levels for each target RAT. The instruction receiving module 902, the timer value receiving module 904 and the redirection priority receiving module 906 may be software modules running in the processor 926, resident/stored in the computer readable medium 928, one or more hardware modules coupled to the processor 926, or some combination thereof. The blind redirection system 914 may be a component of the UE 120 and may include the memory 482 and/or the processor 480. In one configuration, the apparatus 900 for wireless communication includes means for receiving instructions, means for receiving separate timer values and/or means for receiving redirection priority levels. The means may be the instruction receiving module 902, timer value receiving module 904, redirection priority receiving module 906 and/or the blind redirection system 914 of the apparatus 900 configured to perform the functions recited by the receiving means. In another aspect, the aforementioned means may be any module or any apparatus configured to perform the functions recited by the aforementioned means.

[0071] Referring now to FIGURE 10, if the apparatus 900 is a base station 110, the blind redirection system 914 includes the instruction sending module 1002 for sending an instruction to redirect to a target RAT, the timer value sending module 1004 for sending separate timer values for each target RAT and/or the redirection priority sending module 1006 for sending redirection priority levels for each target RAT. The instruction sending module 1002, the timer value sending module 1004 and the redirection priority sending module 1006 may be software modules running in the processor 926, resident/stored in the computer readable medium 928, one or more hardware modules coupled to the processor 926, or some combination thereof. The blind redirection system 914 may be a component of the base station 110 and may include the memory 442 and/or the controller/processor 440. In one configuration, the apparatus 900 for wireless communication includes means for sending instructions, means for sending separate timer values and/or means for sending redirection priority levels. The means may be the instruction sending module 1002, timer value sending module 1004, redirection priority sending module 1006 and/or the blind redirection system 914 of the apparatus 900 configured to perform the functions recited by the receiving means. In another aspect, the aforementioned means may be any module or any apparatus configured to perform the functions recited by the aforementioned means.

[0072] Several aspects of a telecommunications system has been presented with reference to TD-SCDMA and TDD-LTE systems. It is noted, however, that other systems, such as FDD LTE systems are also contemplated. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards. By way of example, various aspects may be extended to other UMTS systems such as W-CDMA, High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), High Speed Packet Access Plus (HSPA+) and TD-CDMA. Various aspects may also be extended to systems employing Long Term Evolution (LTE) (in FDD, TDD, or both modes), LTE- Advanced (LTE-A) (in FDD, TDD, or both modes), CDMA2000, Evolution-Data Optimized (EV- DO), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth, and/or other suitable systems. The actual telecommunication standard, network architecture, and/or communication standard employed will depend on the specific application and the overall design constraints imposed on the system.

[0073] 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.

[0074] 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).

[0075] 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.

[0076] 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.

[0077] 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 or "at least" 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. "At least one of a, b, and c" has an identical meaning. "At least a, b, or c" also has the same meaning. 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."

[0078] WHAT IS CLAIMED IS:

Claims

1. A method of wireless communication, comprising:

receiving an instruction to redirect to a target RAT (radio access technology) from a serving RAT, the instruction including redirection information indicating a plurality of target RATs, and

receiving, from the serving RAT, a separate timer value for each of the target RATs, the timer values indicating how long a UE should attempt to camp on each of the target RATs.

2. The method of claim 1 , in which the redirection information comprises at least one of a cell ID, a frequency, and broadcast system information for each of the target RATs.

3. A method of wireless communication, comprising:

receiving, from the serving RAT, a redirection priority level for each of the plurality of target RATs.

4. The method of claim 3, in which the redirection priority level is the same for each of the plurality of target RATs.

5. The method of claim 3, in which the redirection priority level is different for each of the plurality of target RATs.

6. A method of wireless communication, comprising:

sending an instruction to a UE to redirect to another RAT (radio access technology), the instruction including redirection information indicting a plurality of RATs; and

sending a separate timer value to the UE for each of the plurality of RATs, the timer values indicating how long the UE should attempt to camp on each of the plurality of RATs.

7. The method of claim 6, in which the redirection information comprises at least one of a cell ID, a frequency, and broadcast system information for each of the plurality of RATs.

8. A method of wireless communication, comprising: sending an instruction to a UE to redirect to another RAT (radio access technology), the instruction including redirection information indicting a plurality of RATs; and

sending a redirection priority level to the UE for each of the plurality of RATs.

9. The method of claim 8, in which the redirection priority level is the same for each of the plurality of target RATs.

10. The method of claim 8, in which the redirection priority level is different for each of the plurality of target RATs.

11. An apparatus for wireless communication, comprising:

a memory; and

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

to receive an instruction to redirect to a target RAT (radio access technology) from a serving RAT, the instruction including redirection information indicating a plurality of target RATs, and

to receive, from the serving RAT, a separate timer value for each of the target RATs, the timer values indicating how long a UE should attempt to camp on each of the target RATs.

12. The apparatus of claim 11, in which the redirection information comprises at least a cell ID, a frequency, or broadcast system information for each of the target RATs.

13. An apparatus for wireless communication, comprising:

a memory; and

to receive, from the serving RAT, a redirection priority level for each of the plurality of target RATs.

14. The apparatus of claim 13, in which the redirection priority level is the same for each of the plurality of target RATs.

15. The apparatus of claim 13, in which the redirection priority level is different for each of the plurality of target RATs.

16. An apparatus for wireless communication, comprising:

a memory; and

to send an instruction to a UE to redirect to another RAT (radio access technology), the instruction including redirection information indicting a plurality of RATs; and

to send a separate timer value to the UE for each of the plurality of RATs, the timer values indicating how long the UE should attempt to camp on each of the plurality of RATs.

17. The apparatus of claim 16, in which the redirection information comprises at least a cell ID, a frequency, or broadcast system information for each of the plurality of RATs.

18. An apparatus for wireless communication, comprising:

a memory; and

to send a redirection priority level to the UE for each of the plurality of

RATs.

19. The apparatus of claim 18, in which the redirection priority level is the same for each of the plurality of target RATs.

20. The apparatus of claim 18, in which the redirection priority level is different for each of the plurality of target RATs.

21. A computer program product for wireless communication in a wireless network, comprising:

a non-transitory computer-readable medium having non-transitory program code recorded thereon, the program code comprising: program code to receive an instruction to redirect to a target RAT (radio access technology) from a serving RAT, the instruction including redirection information indicating a plurality of target RATs, and

program code to receive, from the serving RAT, a separate timer value for each of the target RATs, the timer values indicating how long a UE should attempt to camp on each of the target RATs.

22. A computer program product for wireless communication in a wireless network, comprising:

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

program code to receive an instruction to redirect to a target RAT (radio access technology) from a serving RAT, the instruction including redirection information indicating a plurality of target RATs, and

program code to receive, from the serving RAT, a redirection priority level for each of the plurality of target RATs.

23. A computer program product for wireless communication in a wireless network, comprising:

program code to send an instruction to a UE to redirect to another RAT (radio access technology), the instruction including redirection information indicting a plurality of RATs; and

program code to send a separate timer value to the UE for each of the plurality of RATs, the timer values indicating how long the UE should attempt to camp on each of the plurality of RATs.

24. A computer program product for wireless communication in a wireless network, comprising:

program code to send an instruction to a UE to redirect to another RAT (radio access technology), the instruction including redirection information indicting a plurality of RATs; and program code to send a redirection priority level to the UE for each of the plurality of RATs.

25. An apparatus for wireless communication, comprising:

means for receiving an instruction to redirect to a target RAT (radio access technology) from a serving RAT, the instruction including redirection information indicating a plurality of target RATs, and

means for receiving, from the serving RAT, a separate timer value for each of the target RATs, the timer values indicating how long a UE should attempt to camp on each of the target RATs.

26. An apparatus for wireless communication, comprising:

means for receiving, from the serving RAT, a redirection priority level for each of the plurality of target RATs.

27. An apparatus for wireless communication, comprising:

means for sending an instruction to a UE to redirect to another RAT (radio access technology), the instruction including redirection information indicting a plurality of RATs; and

means for sending a separate timer value to the UE for each of the plurality of RATs, the timer values indicating how long the UE should attempt to camp on each of the plurality of RATs.

28. An apparatus for wireless communication, comprising:

means for sending a redirection priority level to the UE for each of the plurality of RATs.