WO2014094430A1

WO2014094430A1 - Method and apparatus for improving frequency scanning using frequency pruning in a td-scdma system

Info

Publication number: WO2014094430A1
Application number: PCT/CN2013/080325
Authority: WO
Inventors: Shiau-He Tsai; Qingxin Chen; Jie Mao; Insung Kang
Original assignee: Qualcomm Incorporated
Priority date: 2012-12-17
Filing date: 2013-07-29
Publication date: 2014-06-26
Also published as: WO2014094210A1

Abstract

A method, an apparatus, and a computer program product for communication are provided in connection with improving frequency scanning during cell acquisition in a TD-SCDMA based network. In one example, a communications device is equipped to obtain power values for a plurality of frequency bands, generate a candidate list of frequencies by comparing the obtained power values for the plurality of frequency band with a first power threshold, and prune the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold.

Description

METHOD AND APPARATUS FOR IMPROVING FREQUENCY SCANNING USING FREQUENCY PRUNING IN A TD-SCDMA SYSTEM

Claim of Priority under 35 U.S.C. §119

[0001] The present Application for Patent claims priority to Patent Cooperation Treaty

(PCT) International Application No. PCT/CN2012/086774 entitled "METHOD AND APPARATUS FOR IMPROVING FREQUENCY SCANNING USING FREQUENCY PRUNING IN A TD-SCDMA SYSTEM" filed December 17, 2012, and assigned to the assignee hereof and hereby expressly incorporated by reference herein.

BACKGROUND

Field

[0002] Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to improving frequency scanning through use of frequency pruning in a Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) based network.

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 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 TD-SCDMA. For example, China is pursuing TD-SCDMA as the underlying air interface in the UTRAN architecture with its existing GSM infrastructure as the core network. The UMTS also supports enhanced 3G data communications protocols, such as High Speed Downlink Packet Data (HSDPA), which provides higher data transfer speeds and capacity to associated UMTS networks. [0004] Currently, in TD-SCDMA based networks, when a user equipment (UE) performs a cell acquisition process, for example to find other TD-SCDMA networks (a home public land mobile network (PLMN) search), during UE power on, etc., the UE may scan the full TD-SCDMA frequency band to find the frequencies in which a cell may be transmitting. During the scanning procedure, UE may measure the receive power in each frequency band and attempt to synchronize with a pilot channel and/or a broadcast channel of a cell in that frequency band to obtain network/cell status and identifying information from the cell. Based on this information, the UE may decide if it can camp on the cell and/or if the cell is a cell that the UE is attempting to locate. The bandwidth of a TD-SCDMA frequency is 1.6MHz, and different carriers may not overlap. Where a UE receives more than one receive power result at different frequencies within a frequency band, one of the power results does not coincide with a cell (e.g., is a fake frequency result). Any attempt to acquire the fake frequencies based on the fake results wastes time and UE power.

[0005] Accordingly, methods and apparatuses are needed to improve frequency scanning during cell acquisition in a TD-SCDMA based network.

SUMMARY

[0006] The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

[0007] In accordance with one or more aspects and corresponding disclosure thereof, various aspects are described in connection with improving frequency scanning during cell acquisition in a TD-SCDMA based network. In one example, a communications device is equipped to obtain power values for a plurality of frequency bands, generate a candidate list of frequencies by comparing the obtained power values for the plurality of frequency band with a first power threshold, prune the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold.

[0008] According to related aspects, a method for improving frequency scanning during cell acquisition in a TD-SCDMA based network is provided. The method can include obtaining power values for a plurality of frequency bands. Further, the method can include generating a candidate list of frequencies by comparing the obtained power values for the plurality of frequency band with a first power threshold. Moreover, the method may include pruning the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold.

[0009] Another aspect relates to a communications apparatus enabled to improve frequency scanning during cell acquisition in a TD-SCDMA based network. The communications apparatus can include means for obtaining power values for a plurality of frequency bands. Further, the communications apparatus can include means for generating a candidate list of frequencies by comparing the obtained power values for the plurality of frequency band with a first power threshold. Moreover, the communications apparatus can include means for pruning the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold.

[0010] Another aspect relates to a communications apparatus. The apparatus can include a processing system configured to obtain power values for a plurality of frequency bands. Further, the processing system may be configured to generate a candidate list of frequencies by comparing the obtained power values for the plurality of frequency band with a first power threshold. Moreover, the processing system may further be configured to prune the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold.

[0011] Still another aspect relates to a computer program product, which can have a computer-readable medium including code for obtaining power values for a plurality of frequency bands. Further, the computer-readable medium may include code for generating a candidate list of frequencies by comparing the obtained power values for the plurality of frequency band with a first power threshold. Moreover, the computer- readable medium can include code for pruning the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold.

[0012] To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a block diagram conceptually illustrating an example of a wireless communications networks.

[0014] FIG. 2 is a block diagram conceptually illustrating an example of a frame structure in a wireless communications networks.

[0015] FIG. 3 depicts an example TD-SCDMA based system with multiple user equipments (UEs) communicating with a node-B, as time progresses according to an aspect.

[0016] FIG. 4 is a block diagram conceptually illustrating an example of a Node B in communication with a UE in a wireless communications networks.

[0017] FIG. 5 a block diagram conceptually illustrating an example wireless communications network, according to an aspect.

[0018] FIG. 6 is a flow chart of an example wireless communication method, according to an aspect.

[0019] FIG. 7 is a block diagram of an example UE configured to perform a frequency scan, according to an aspect.

[0020] FIG. 8 illustrates a block diagram of an example a communications device for performing a frequency scan, according to an aspect.

DETAILED DESCRIPTION

[0021] 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. [0022] Turning now to FIG. 1, a block diagram is shown illustrating an example of a wireless communications networks 100. The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. By way of example and without limitation, the aspects of the present disclosure illustrated in FIG. 1 are presented with reference to a UMTS system employing a TD-SCDMA standard. In this example, the UMTS system includes a (radio access network) RAN 102 (e.g., UTRAN) that provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The RAN 102 may be divided into a number of Radio Network Subsystems (RNSs) such as an RNS 107, each controlled by a Radio Network Controller (RNC) such as an RNC 106. For clarity, only the RNC 106 and the RNS 107 are shown; however, the RAN 102 may include any number of RNCs and RNSs in addition to the RNC 106 and RNS 107. The RNC 106 is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS 107. The RNC 106 may be interconnected to other RNCs (not shown) in the RAN 102 through various types of interfaces such as a direct physical connection, a virtual network, or the like, using any suitable transport network.

[0023] 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.

[0024] 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.

[0025] In this example, the core network 104 supports circuit- switched services with a mobile switching center (MSC) 112 and a gateway MSC (GMSC) 114. One or more RNCs, such as the RNC 106, may be connected to the MSC 112. The MSC 112 is an apparatus that controls call setup, call routing, and UE mobility functions. The MSC 112 also includes a visitor location register (VLR) (not shown) that contains subscriber- related information for the duration that a UE is in the coverage area of the MSC 112. The GMSC 114 provides a gateway through the MSC 112 for the UE to access a circuit- switched network 116. The GMSC 114 includes a home location register (HLR) (not shown) containing subscriber data, such as the data reflecting the details of the services to which a particular user has subscribed. The HLR is also associated with an authentication center (AuC) that contains subscriber-specific authentication data. When a call is received for a particular UE, the GMSC 114 queries the HLR to determine the UE's location and forwards the call to the particular MSC serving that location.

[0026] The core network 104 also supports packet-data services with a serving GPRS support node (SGSN) 118 and a gateway GPRS support node (GGSN) 120. GPRS, which stands for General Packet Radio Service, is designed to provide packet-data services at speeds higher than those available with standard GSM circuit- switched data services. The GGSN 120 provides a connection for the RAN 102 to a packet-based network 122. The packet-based network 122 may be the Internet, a private data network, or some other suitable packet-based network. The primary function of the GGSN 120 is to provide the UEs 110 with packet-based network connectivity. Data packets are transferred between the GGSN 120 and the UEs 110 through the SGSN 118, which performs primarily the same functions in the packet-based domain as the MSC 112 performs in the circuit- switched domain.

[0027] 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.

[0028] FIG. 2 illustrates a frame structure 200 for a TD-SCDMA carrier. The TD-

SCDMA carrier, as illustrated, has a frame 202 that is 10 ms in length. The frame 202 has two 5 ms subframes 204, and each of the subframes 204 includes seven time slots, TS0 through TS6. The first time slot, TS0, is usually allocated for downlink communication, while the second time slot, TS1, is usually allocated for uplink communication. The remaining time slots, TS2 through TS6, may be used for either uplink or downlink, which allows for greater flexibility during times of higher data transmission times in either the uplink or downlink directions. A downlink pilot time slot (DwPTS) 206, 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.

[0029] Additionally, in an aspect where a wireless communications network supports multiple carriers, such as in an N-frequency TD-SCDMA supported network, the frame structure 200 may be used for each carrier 220 where carriers are defined within different frequencies 218. In one aspect, each carrier 220 may be allocated a 1.6 MHz frequency 218 band.

[0030] Turning now to FIG. 3, an example TD-SCDMA based system 300 with multiple UEs (304, 306, 308) communicating with a node-B 302, as time progresses, is illustrated. Generally, in TD-SCDMA systems, multiple UEs may share a common bandwidth in communication with a node-B 302. Additionally, one aspect in TD- SCDMA systems, as compared to CDMA and WCDMA systems, is UL synchronization. That it, in TD-SCDMA systems, different UEs (304, 306, 308) may synchronize on the uplink (UL) such that all UE (304, 306, 308) transmitted signals arrives at the Node B (NB) at approximately the same time. For example, in the depicted aspect, various UEs (304, 306, 308) are located at various distances from the serving node-B 302. Accordingly, in order for the UL transmission to reach the node-B 302 at approximately the same time, each UE may originate transmissions at different times. For example, UE 308 may be farthest from node-B 302 and may perform an UL transmission 314 before closer UEs. Additionally, UE 306 may be closer to node-B 302 than UE 308 and may perform an UL transmission 312 after UE 308. Similarly, UE 304 may be closer to node-B 302 than UE 306 and may perform an UL transmission 310 after UEs 306 and 308. The timing of the UL transmissions (310, 312, 314) may be such that the signals arrive at the node-B at approximately the same time.

FIG. 4 is a block diagram of a Node B 410 in communication with a UE 450 in a

RAN 400, where the RAN 400 may be the RAN 102 in FIG. 1, the Node B 410 may be the Node B 108 in FIG. 1, and the UE 450 may be the UE 110 in FIG. 1. In the downlink communication, a transmit processor 420 may receive data from a data source 412 and control signals from a controller/processor 440. The transmit processor 420 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 420 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 444 may be used by a controller/processor 440 to determine the coding, modulation, spreading, and/or scrambling schemes for the transmit processor 420. These channel estimates may be derived from a reference signal transmitted by the UE 450 or from feedback contained in the midamble 214 (FIG. 2) from the UE 450. The symbols generated by the transmit processor 420 are provided to a transmit frame processor 430 to create a frame structure. The transmit frame processor 430 creates this frame structure by multiplexing the symbols with a midamble 214 (FIG. 2) from the controller/processor 440, resulting in a series of frames. The frames are then provided to a transmitter 432, 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 434. The smart antennas 434 may be implemented with beam steering bidirectional adaptive antenna arrays or other similar beam technologies.

[0032] At the UE 450, a receiver 454 receives the downlink transmission through an antenna 452 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 454 is provided to a receive frame processor 460, which parses each frame, and provides the midamble 214 (FIG. 2) to a channel processor 494 and the data, control, and reference signals to a receive processor 470. The receive processor 470 then performs the inverse of the processing performed by the transmit processor 420 in the Node B 410. More specifically, the receive processor 470 descrambles and despreads the symbols, and then determines the most likely signal constellation points transmitted by the Node B 410 based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor 494. 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 472, which represents applications running in the UE 450 and/or various user interfaces (e.g., display). Control signals carried by successfully decoded frames will be provided to a controller/processor 490. When frames are unsuccessfully decoded by the receiver processor 470, the controller/processor 490 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0033] In the uplink, data from a data source 478 and control signals from the controller/processor 490 are provided to a transmit processor 480. The data source 478 may represent applications running in the UE 450 and various user interfaces (e.g., keyboard). Similar to the functionality described in connection with the downlink transmission by the Node B 410, the transmit processor 480 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 494 from a reference signal transmitted by the Node B 410 or from feedback contained in the midamble transmitted by the Node B 410, may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor 480 will be provided to a transmit frame processor 482 to create a frame structure. The transmit frame processor 482 creates this frame structure by multiplexing the symbols with a midamble 214 (FIG. 2) from the controller/processor 490, resulting in a series of frames. The frames are then provided to a transmitter 456, 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 452.

[0034] The uplink transmission is processed at the Node B 410 in a manner similar to that described in connection with the receiver function at the UE 450. A receiver 435 receives the uplink transmission through the antenna 434 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 435 is provided to a receive frame processor 436, which parses each frame, and provides the midamble 214 (FIG. 2) to the channel processor 444 and the data, control, and reference signals to a receive processor 438. The receive processor 438 performs the inverse of the processing performed by the transmit processor 480 in the UE 450. The data and control signals carried by the successfully decoded frames may then be provided to a data sink 439 and the controller/processor, respectively. If some of the frames were unsuccessfully decoded by the receive processor, the controller/processor 440 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0035] The controller/processors 440 and 490 may be used to direct the operation at the

Node B 410 and the UE 450, respectively. For example, the controller/processors 440 and 490 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories 442 and 492 may store data and software for the Node B 410 and the UE 450, respectively. A scheduler/processor 446 at the Node B 410 may be used to allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs.

[0036] FIG. 5 illustrates a wireless communications system 500. System 500 may include multiple cells (506, 507, 510), which in cell (506, 507, 510) including one or more node-Bs (504, 505, 508). Further, system 500 may provide a UE 502 with support from various radio access technologies (RATs), e.g., TD-SCDMA, LTE, etc.). A UE 502 initiated within system 500 may attempt to acquire a cell for support as part of a cell acquisition process. Signals 512 from one or more of the node-Bs (504, 505, 508) may be transmitted using one or more frequencies bands.

[0037] In a TD-SCDMA based network, during a frequency scan, to find the central frequency of the 1.6MHz band, UE 502 may measure in smaller frequency bins and return receive power results of each bin of the different central frequencies within a bandwidth range (e.g.,1.4MHz). UE 502 may make use of the TD-SCDMA frequency bandwidth information to modify measured values. In an aspect, UE 502 may detect there is a "real" cell in a TD-SCDMA frequency band with the central frequency (f). As there can be only one cell in each frequency band in TD-SCDMA, other frequency measurements within a frequency range (e.g., +1.4MHz) may be "fake" frequency measurements. UE 502 may remove the "fake" frequencies so as to avoid potentially attempting to acquire (synchronize, decode broadcast channel, etc.) those frequencies. The removal of "fake" frequencies (e.g., pruning the frequencies bins) may save UE 502 time and power during frequency scanning. In an aspect, UE 502 may determine frequency bins associated with a real cell based on prior communications with the cell (e.g., UE 502 has previously decoded the broadcast channel of the cell successfully). In another aspect, UE 502 may use the receive power of a frequency bin that is higher than a threshold. In another aspect, UE 502 may use the receive power of a frequency bin that is higher than other receive power results within the 1.6MHz by a threshold. In an aspect, the receive power measurement may be a received signal code power (RSCP). In another aspect, the receive power measurement may be a Received Signal Strength Indicator (RSSI) value.

[0038] FIG. 6 illustrates various methodologies in accordance with various aspects of the presented subject matter. While, for purposes of simplicity of explanation, the methodologies are shown and described as a series of acts or sequence steps, it is to be understood and appreciated that the claimed subject matter is not limited by the order of acts, as some acts may occur in different orders and/or concurrently with other acts from that shown and described herein. For example, those skilled in the art will understand and appreciate that a methodology could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a methodology in accordance with the claimed subject matter. Additionally, it should be further appreciated that the methodologies disclosed hereinafter and throughout this specification are capable of being stored on an article of manufacture to facilitate transporting and transferring such methodologies to computers.

The term article of manufacture, as used herein, is intended to encompass a computer program accessible from any computer-readable device, carrier, or media.

[0039] FIG. 6 is a functional block diagram 600 illustrating example blocks executed in conducting wireless communication according to one aspect of the present disclosure.

[0040] In block 602, a UE may obtain measurements for a plurality of frequency bands in a TD-SCDMA based network. In an aspect, the UE may measure RSCP. In another aspect, the UE may measure RSSI.

[0041] In block 604, the UE may generate a candidate frequency list of frequencies by comparing the measurements for the plurality of frequency bands with a first power threshold. In an aspect, measurements within each band may be allocated into bins associated with different portions of the frequency band.

[0042] In an optional aspect, at block 606, the UE may initiate a frequency list with all

NULL values. In another aspect, a previously initiated frequency list may be reset to all

NULL values.

[0043] At block 608, the UE may remove measurements from frequency bins around a central frequency bin for each frequency band in the candidate frequency list. For example, power values of all frequencies may be sorted in descending order. Then, the frequency associated with the greatest power value may be selected and frequencies within +1.4MHz around the selected frequency may be removed (e.g., pruned). Thereafter, another frequency may be selected which is associated with the next greatest power value in newly pruned frequency list and frequencies +1.4MHz around the newly selected frequency may be pruned. This process may continue until pruned frequency list is empty. In an aspect, the central frequency bin may be selected based on a highest RSCP value, a highest RSSI value, etc. In such an aspect, measurement values may be removed from bins within a frequency range of 1.4 MHz around the central frequency bin. In another aspect, the removal of the measurement values from non-central bins may be performed for each frequency band in which a value (e.g., RSCP, RSSI, etc.) above a second power threshold is detected.

[0044] In an optional aspect, at block 610, the UE may populate the frequency list with the frequencies obtained from pruning the candidate frequency list.

[0045] In an optional aspect, at block 612, the UE may use the frequency list as part of a cell acquisition process. [0046] FIG. 7 illustrates a user equipment (UE) 700 (e.g. a client device, wireless communications device (WCD) etc.) that provides an effective process for balancing loads and reducing call blocking in a TD-SCDMA network. UE 700 comprises receiver 702 that receives one or more signal from, for instance, one or more receive antennas (not shown), performs typical actions on (e.g., filters, amplifies, downconverts, etc.) the received signal, and digitizes the conditioned signal to obtain samples. Receiver 702 can further comprise an oscillator that can provide a carrier frequency for demodulation of the received signal and a demodulator that can demodulate received symbols and provide them to processor 706 for channel estimation. In one aspect, UE 700 may further comprise secondary receiver 704 and may receive additional channels of information.

[0047] Processor 706 can be a processor dedicated to analyzing information received by receiver 702 and/or generating information for transmission by one or more transmitters 720 (for ease of illustration, only one transmitter is shown), a processor that controls one or more components of UE 700, and/or a processor that both analyzes information received by receiver 702 and/or secondary receiver 704, generates information for transmission by transmitter 720 for transmission on one or more transmitting antennas (not shown), and controls one or more components of UE 700. In one aspect of UE 700, processor 706 may include at least one processor and memory, wherein the memory may be within the at least one processor 706. By way of example and not limitation, the memory could include on-board cache or general purpose register.

[0048] UE 700 can additionally comprise memory 708 that is operatively coupled to processor 706 and that can store data to be transmitted, received data, information related to available channels, data associated with analyzed signal and/or interference strength, information related to an assigned channel, power, rate, or the like, and any other suitable information for estimating a channel and communicating via the channel. Memory 708 can additionally store protocols and/or algorithms associated with estimating and/or utilizing a channel (e.g., performance based, capacity based, etc.). In an aspect, memory 708 may include a candidate frequency list 710. Candidate frequency list 710 may include one or more frequencies associated with power values for the plurality of frequency band. In an optional aspect, memory 708 may also include frequency list 712. In an aspect, the frequency list 712 may include modified frequency values associated with the candidate frequency list. [0049] In aspect, cell acquisition module 750, and/or processor 706, coupled to memory

708, may provide means for obtaining power values for a plurality of frequency bands, means for generating a candidate list of frequencies by comparing the obtained power values for the plurality of frequency band with a first power threshold, and means for pruning the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold.

[0050] It will be appreciated that the data store (e.g., memory 708) described herein can be either volatile memory or nonvolatile memory, or can include both volatile and nonvolatile memory. By way of illustration, and not limitation, nonvolatile memory can include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable PROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM), which acts as external cache memory. By way of illustration and not limitation, RAM is available in many forms such as synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM). Memory 708 of the subject systems and methods is intended to comprise, without being limited to, these and any other suitable types of memory.

[0051] UE 700 further include cell acquisition module 750 that assists the UE 700 with cell access in a network. In one aspect, cell acquisition module 750 further includes candidate frequency processing module 752. In an aspect, candidate frequency processing module 752 may organize the power values that are above a first power threshold 754 into a plurality of bins within each frequency band, determine that a power value in a central bin corresponds to a received power value from a cell, and remove the power values from one or more bins within a frequency range of the central bin associated with power values greater than a second power threshold 756. In an aspect, candidate frequency processing module 752 may store the modified frequency values from the candidate frequency list 710 in a frequency list 712.

[0052] Additionally, client device 700 may include user interface 740. User interface

740 may include input mechanisms 742 for generating inputs into UE 700, and output mechanisms 744 for generating information for consumption by the user of wireless device 700. For example, input mechanisms 742 may include a mechanism such as a key or keyboard, a mouse, a touch- screen display, a microphone, etc. Further, for example, output mechanisms 744 may include a display, an audio speaker, a haptic feedback mechanism, a Personal Area Network (PAN) transceiver etc. In the illustrated aspects, output mechanisms 744 may include a display operable to present content that is in image or video format or an audio speaker to present content that is in an audio format.

[0053] FIG. 8 depicts a block diagram of an example communication system 800 operable to facilitate improved frequency scanning during cell acquisition in a TD- SCDMA based network. For example, communication system 800 can reside at least partially within a communications device (e.g., communications device 700). It is to be appreciated that system 800 is represented as including functional blocks, which can be functional blocks that represent functions implemented by a processor, software, or combination thereof (e.g., firmware). System 800 includes a logical grouping 802 of electrical components that can act in conjunction.

[0054] For instance, logical grouping 802 can include an electrical component that may provide means for obtaining power values for a plurality of frequency bands 804. For example, the means for obtaining can include receiver 702, cell acquisition module 750, and/or processor 706 of communications device 700. In an aspect, the means for obtaining 804 (e.g., cell acquisition module 750) may be further configured to initiate the frequency list with NULL values. In an aspect, the power values may be RSCP values. In another aspect, the power values may be RSSI values. In another aspect, each frequency band of the plurality of frequency bands may be 1.6MHz.

[0055] Further, logical grouping 802 can include an electrical component that may provide means for generating a candidate list of frequencies by comparing the obtained power values for the plurality of frequency bands with a first power threshold 806. For example, the means for generating 806 can include candidate frequency processing module 752, and/or processor 706 of communications device 700. In an aspect, the means for generating 806 may be configured to organize the power values into frequency bins.

[0056] Further, logical grouping 802 can include an electrical component that may provide means for pruning the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold 808. For example, the means for pruning 808 can include candidate frequency processing module 752, and/or processor 706 of communications device 700. In an aspect, the means for pruning 808 may be configured to sort the obtained power values in a descending order, select a first frequency associated with a greater power value, and remove frequencies within the frequency range of the selected first frequency. In such an aspect, the frequency range may be +1.4MHz. Further, in such an aspect, the means for pruning 808 may be further configured to populate a frequency list with the selected first frequency. Still further, in such an aspect, the means for pruning 808 may be configured to sort remaining power values in descending order, select a second frequency associated a greatest remaining power value, and remove frequencies within the frequency range of the selected second frequency. In another aspect, the means for pruning 808 may be further configured to remove removing the power values from frequency bins within the frequency range of the selected first frequency.

[0057] In an optional aspect, logical grouping 802 can include an electrical component that may provide means for populating a frequency list with frequencies from the pruned candidate list 810. For example, the means for populating 810 can include cell acquisition module 750, frequency list 712 in memory 708, and/or processor 706.

[0058] In another optional aspect, logical grouping 802 can include an electrical component that may provide means for using the frequency list in a cell acquisition process 812. For example, the means for using 812 can include cell acquisition module 750, frequency list 712 in memory 708, and/or processor 706.

[0059] Additionally, system 800 can include a memory 814 that retains instructions for executing functions associated with the electrical components 804, 806, 808, 810, and 812, and stores data used or obtained by the electrical components 804, 806, 808, 810, 812, etc. In an aspect, memory 814 can include memory 708 and/or can be included in memory 708. While shown as being external to memory 814, it is to be understood that one or more of the electrical components 804, 806, 808, 810, and 812 may exist within memory 814. In one example, electrical components 804, 804, 806, 808, 810, and 812 can include at least one processor, or each electrical component 804, 804, 806, 808, 810, and 812 can be a corresponding module of at least one processor. Moreover, in an additional or alternative example, electrical components 804, 806, 808, 810, and 812 may be a computer program product including a computer readable medium, where each electrical component 804, 806, 808, 810, and 812 may be corresponding code.

[0060] Several aspects of a telecommunications system has been presented with reference to a TD-SCDMA system. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards. By way of example, various aspects may be extended to other UMTS systems such as W- CDMA, High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), High Speed Packet Access Plus (HSPA+) and TD-CDMA. Various aspects may also be extended to systems employing Long Term Evolution (LTE) (in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD, or both modes), CDMA2000, Evolution-Data Optimized (EV-DO), Ultra Mobile Broadband (UMB), IEEE 702.11 (Wi-Fi), IEEE 702.16 (WiMAX), IEEE 702.20, 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.

[0061] 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.

[0062] 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).

[0063] 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.

[0064] 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.

[0065] 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:

obtaining power values for a plurality of frequency bands;

generating a candidate list of frequencies by comparing the obtained power values for the plurality of frequency bands with a first power threshold; and

pruning the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold.

2. The method of claim 1, further comprising:

populating a frequency list with frequencies from the pruned candidate list; and using the frequency list in a cell acquisition process.

3. The method of claim 2, wherein the obtaining further comprises initiating the frequency list with NULL values.

4. The method of claim 1, wherein the power values comprise Received Signal Code Power (RSCP) values.

5. The method of claim 1, wherein the power values comprise Received Signal Strength Indicator (RSSI) values.

6. The method of claim 1, wherein the pruning comprises:

sorting the obtained power values in a descending order;

selecting a first frequency associated with a greater power value; and

removing frequencies within the frequency range of the selected first frequency.

7. The method of claim 6, wherein the frequency range comprises +1.4MHz.

8. The method of claim 6, wherein the pruning comprises populating the frequency list with the selected first frequency.

9. The method of claim 6, wherein the pruning comprises: sorting remaining power values in descending order;

selecting a second frequency associated with a greatest remaining power value; and

removing frequencies within the frequency range of the selected second frequency.

10. The method of claim 6, wherein the generating further comprises organizing the power values into frequency bins.

11. The method of claim 10, wherein the removing further comprises removing the power values from the frequency bins within the frequency range of the selected first frequency.

12. The method of claim 1, wherein each frequency band of the plurality of frequency bands is 1.6MHz.

13. The method of claim 1, wherein the plurality of frequencies bands are used in a multi-frequency Time Division Synchronous Code Division Multiple Access (TD- SCDMA) based network.

14. An apparatus for wireless communication, comprising:

means for obtaining power values for a plurality of frequency bands;

means for generating a candidate list of frequencies by comparing the obtained power values for the plurality of frequency bands with a first power value; and

means for pruning the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold.

15. A computer program product, comprising:

a computer-readable medium comprising code for:

obtaining power values for a plurality of frequency bands; generating a candidate list of frequencies by comparing the obtained power values for the plurality of frequency band with a first power threshold; and pruning the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold.

16. An apparatus for wireless communication, comprising:

a processing system configured to:

obtain power values for a plurality of frequency bands;

generate a candidate list of frequencies based on comparing the obtained power values for the plurality of frequency band with a first power threshold; and

prune the candidate list of frequencies by removing one or more frequencies in the candidate list within a frequency range of a frequency associated with a power value greater than a second power threshold.

17. The apparatus of claim 16, wherein the processing system is further configured to:

populate a frequency list with frequencies from the pruned candidate list; and use the frequency list in a cell acquisition process.

18. The apparatus of claim 17, wherein the processing system is further configured to initiate the frequency list with NULL values.

19. The apparatus of claim 16, wherein the power values comprise received signal code power (RSCP) values.

20. The method of claim 16, wherein the power values comprise Received Signal Strength Indicator (RSSI) values.

21. The apparatus of claim 16, wherein the processing system is further configured to:

sort the obtained power values in a descending order;

select a first frequency associated with a greater power value; and

remove frequencies within the frequency range of the selected first frequency.

22. The apparatus of claim 21, wherein the frequency range comprises +1.4MHz.

23. The apparatus of claim 21, wherein the processing system is further configured to populate the frequency list with the selected first frequency.

24. The apparatus of claim 21, wherein the processing system is further configured to:

sort remaining power values in descending order;

select a second frequency associated with a greatest remaining power value; and remove frequencies within the frequency range of the selected second frequency.

25. The apparatus of claim 21, wherein the processing system is further configured to organize the power values into frequency bins.

26. The apparatus of claim 25, wherein the processing system is further configured to remove the power values from the frequency bins within the frequency range of the selected first frequency.

27. The apparatus of claim 16, wherein each frequency band of the plurality of frequency bands is 1.6MHz.

28. The apparatus of claim 16, wherein the plurality of frequencies bands are used in a multi-frequency Time Division Synchronous Code Division Multiple Access (TD- SCDMA) based network.