WO2014078996A1

WO2014078996A1 - Method and apparatus for improved gap detection

Info

Publication number: WO2014078996A1
Application number: PCT/CN2012/084959
Authority: WO
Inventors: Jinghu Chen; Insung Kang; Wanlun Zhao; Qiang Shen; Jilei Hou; Dario FERTONANI
Original assignee: Qualcomm Incorporated
Priority date: 2012-11-21
Filing date: 2012-11-21
Publication date: 2014-05-30

Abstract

An apparatus and method of optimizing resources on a FTPICH is offered. The apparatus and method includes receiving a signal with an energy pattern from a network entity at a UE and summing the energy pattern of the signal at predetermined sample lengths. The apparatus and method also includes matching the summed energy pattern at the predetermined sample lengths to a HLHL energy pattern and determining that the summed energy pattern matches the HLHL energy pattern. In addition, the apparatus and method includes detecting a gap in the received signal based on determining that the summed energy pattern matches the HLHL energy pattern.

Description

METHOD AND APPARATUS FOR IMPROVED GAP DETECTION

BACKGROUND

Field

[0001] Aspects of the present disclosure relate, in general, to wireless communication systems, and more particularly, for improved gap detection in a wireless network, particularly in a Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) network cell search.

Background

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

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

SUMMARY

[0004] A method for improved gap detection in a wireless network, particularly in a TD-

SCDMA network cell search is offered. The method includes receiving a signal with an energy pattern from a network entity at a UE and summing the energy pattern of the signal at predetermined sample lengths.

[0005] The method includes matching the summed energy pattern at the predetermined sample lengths to a high-low-high-low (HLHL) energy pattern and determining that the summed energy pattern matches the HLHL energy pattern. Last, the method includes detecting a gap in the received signal based on determining that the summed energy pattern matches the HLHL energy pattern.

[0006] An apparatus of optimizing resources on a FTPICH is offered. The apparatus includes receiving a signal with an energy pattern from a network entity at a UE and summing the energy pattern of the signal at predetermined sample lengths. The apparatus also includes matching the summed energy pattern at the predetermined sample lengths to a HLHL energy pattern and determining that the summed energy pattern matches the HLHL energy pattern. In addition, the apparatus includes detecting a gap in the received signal based on determining that the summed energy pattern matches the HLHL energy pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a block diagram illustrating an example of a telecommunications system.

[0008] FIG. 2 is a block diagram conceptually illustrating an example of a frame structure in a telecommunications system.

[0009] FIG. 3 is a block diagram of a Node B in communication with a user equipment in a radio access network.

[0010] FIG. 4 is a diagram illustrating signal sample times according to one aspect of the present disclosure.

[0011] FIG. 5 is a schematic graph illustrating the accumulated energy over time according to one aspect of the present disclosure.

[0012] FIG. 6 is a schematic graph illustrating the shifted accumulated energy over time according to another aspect of the present disclosure.

[0013] FIG. 7 is a flow diagram illustrating example blocks that are executed to implement one aspect of the present disclosure.

DETAILED DESCRIPTION

[0014] 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.

[0015] Turning now to FIG. 1, a block diagram is shown illustrating an example of a telecommunications system 100. The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. By way of example and without limitation, the aspects of the present disclosure illustrated in FIG. 1 are presented with reference to a UMTS system employing a TD-SCDMA standard. In this example, the UMTS system includes a (Radio Access Network) RAN 102 (e.g., UTRAN) that provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The RAN 102 may be divided into a number of Radio Network Subsystems (RNSs), such as an RNS 107, each controlled by a Radio Network Controller (RNC), such as an RNC 106. For clarity, only the RNC 106 and the RNS 107 are shown; however, the RAN 102 may include any number of RNCs and RNSs in addition to the RNC 106 and RNS 107. The RNC 106 is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS 107. The RNC 106 may be interconnected to other RNCs (not shown) in the RAN 102 through various types of interfaces, such as a direct physical connection, a virtual network, or the like, using any suitable transport network.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] The core network 104 also supports packet-data services with a Serving GPRS

Support Node (SGSN) 1 18 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.

[0020] 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.

[0021] FIG. 2 shows a frame structure 200 for a TD-SCDMA carrier. The TD-SCDMA carrier, as illustrated, has a frame 202 that is 10 ms in length. The frame 202 has two 5 ms subframes 204, and each of the subframes 204 includes seven time slots, TSO through TS6. The first time slot, TSO, is usually allocated for downlink communication, while the second time slot, TS1, is usually allocated for uplink communication. The remaining time slots, TS2 through TS6, may be used for either uplink or downlink, which allows for greater flexibility during times of higher data transmission times in either the uplink or downlink directions. A Downlink Pilot Time Slot (DwPTS) 206 (also known as the Downlink Pilot Channel (DwPCH)), a guard period (GP) 208, and an Uplink Pilot Time Slot (UpPTS) 210 (also known as the uplink pilot channel (UpPCH)) are located between TSO and TS1. The Downlink Pilot Time Slot 206 is 96 chips (75 μβ) in length. The guard period 208 is 96 chips (75 μβ) in length. The Uplink Pilot Time Slot 210 is 160 chips (125 μβ) in length. The Downlink Pilot Time Slot 206 includes a guard period 218 and a synchronization downlink (SYNC-DL) sequence 220. The guard period 218 is 32 chips (25 μβ) in length. The SYNC- DL sequence 220 is 64 chips (50 μβ) in length. Each time slot, TS0-TS6, may allow data transmission multiplexed on a maximum of 16 code channels. Each time slot TS0-TS6 is 675 μβ in length. 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. [0022] FIG. 3 is a block diagram of a Node B 310 in communication with a UE 350 in a

RAN 300, where the RAN 300 may be the RAN 102 in FIG. 1, the Node B 310 may be the Node B 108 in FIG. 1, and the UE 350 may be the UE 110 in FIG. 1. In the downlink communication, a transmit processor 320 may receive data from a data source 312 and control signals from a controller/processor 340. The transmit processor 320 provides various signal processing functions for the data and control signals, as well as reference signals (e.g., pilot signals). For example, the transmit processor 320 may provide Cyclic Redundancy Check (CRC) codes for error detection, coding and interleaving to facilitate Forward Error Correction (FEC), mapping to signal constellations based on various modulation schemes (e.g., Binary Phase-Shift Keying (BPSK), Quadrature Phase-Shift Keying (QPSK), M-Phase- Shift Keying (M-PSK), M-Quadrature Amplitude Modulation (M-QAM), and the like), spreading with Orthogonal Variable Spreading Factors (OVSF), and multiplying with scrambling codes to produce a series of symbols. Channel estimates from a channel processor 344 may be used by a controller/processor 340 to determine the coding, modulation, spreading, and/or scrambling schemes for the transmit processor 320. These channel estimates may be derived from a reference signal transmitted by the UE 350 or from feedback contained in the midamble 214 (FIG. 2) from the UE 350. The symbols generated by the transmit processor 320 are provided to a transmit frame processor 330 to create a frame structure. The transmit frame processor 330 creates this frame structure by multiplexing the symbols with a midamble 214 (FIG. 2) from the controller/processor 340, resulting in a series of frames. The frames are then provided to a transmitter 332, which provides various signal conditioning functions including amplifying, filtering, and modulating the frames onto a carrier for downlink transmission over the wireless medium through smart antennas 334. The smart antennas 334 may be implemented with beam steering bidirectional adaptive antenna arrays or other similar beam technologies.

[0023] At the UE 350, a receiver 354 receives the downlink transmission through an antenna

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

[0024] In the uplink, data from a data source 378 and control signals from the controller/processor 390 are provided to a transmit processor 380. The data source 378 may represent applications running in the UE 350 and various user interfaces (e.g., keyboard, pointing device, track wheel, and the like). Similar to the functionality described in connection with the downlink transmission by the Node B 310, the transmit processor 380 provides various signal processing functions including CRC codes, coding and interleaving to facilitate FEC, mapping to signal constellations, spreading with OVSFs, and scrambling to produce a series of symbols. Channel estimates, derived by the channel processor 394 from a reference signal transmitted by the Node B 310 or from feedback contained in the midamble transmitted by the Node B 310, may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor 380 will be provided to a transmit frame processor 382 to create a frame structure. The transmit frame processor 382 creates this frame structure by multiplexing the symbols with a midamble 214 (FIG. 2) from the controller/processor 390, resulting in a series of frames. The frames are then provided to a transmitter 356, which provides various signal conditioning functions including amplification, filtering, and modulating the frames onto a carrier for uplink transmission over the wireless medium through the antenna 352.

[0025] The uplink transmission is processed at the Node B 310 in a manner similar to that described in connection with the receiver function at the UE 350. A receiver 335 receives the uplink transmission through the smart antennas 334 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 335 is provided to a receive frame processor 336, which parses each frame, and provides the midamble 214 (FIG. 2) to the channel processor 344 and the data, control, and reference signals to a receive processor 338. The receive processor 338 performs the inverse of the processing performed by the transmit processor 380 in the UE 350. The data and control signals carried by the successfully decoded frames may then be provided to a data sink 339 and the controller/processor 340, respectively. If some of the frames were unsuccessfully decoded by the receive processor 338, the controller/processor 340 may also use an Acknowledgement (ACK) and/or Negative Acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0026] The controller/processors 340 and 390 may be used to direct the operation at the Node

B 310 and the UE 350, respectively. For example, the controller/processors 340 and 390 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories 342 and 392 may store data and software for the Node B 310 and the UE 350, respectively. For example, the memory 342 of the Node B 310 includes a handover module 343, which, when executed by the controller/processor 340, the handover module 343 configures the Node B to perform handover procedures from the aspect of scheduling and transmission of system messages to the UE 350 for implementing a handover from a source cell to a target cell. A scheduler/processor 346 at the Node B 310 may be used to allocate resources to the UEs and schedule downlink and/or uplink transmissions for the UEs not only for handovers, but for regular communications as well.

[0027] There are a number of situations when a user equipment may attempt to acquire a signal, including during power-on, wake up, etc. When a user equipment attempts to locate a signal in a TD-SCDMA network on a certain frequency band, the user equipment does not know whether any cell is actually transmitting on that band, nor any timing associated with such transmissions. In TD-SCDMA, to help during this acquisition stage, each base station transmits the same pilot signal at every subframe (i.e., every 6400 chips = 5 milliseconds (ms)). Different base stations may use different pilot signals in the downlink pilot time slot. Each pilot signal identifies the base station from which it was sent. These signals are known as synchronization downlink (SYNC-DL) sequences. There are 32 different SYNC-DL sequences, each is 64-chips (50 microseconds (μβ)) long.

[0028] Typically, correlation-based algorithms are used in the acquisition stage. Such correlation-based algorithms involve computing a correlation between each SYNC-DL sequence possibly transmitted, and each 64-chip window of received samples possibly aligned to the SYNC-DL sequence. Because no timing reference is yet available at this stage, all 64-chip windows in an interval of 5 ms (i.e., the repetition period for the pilot signal) are equally likely. Each subframe 204, as shown in FIG. 2, is 6,400 chips in length. This results in the testing of 6,400 potential windows (5 ms * 1.28 Mcps) if the target granularity for timing acquisition is one chip, or 12,800 windows (5 ms * 2.56 Mcps) if the target granularity is half a chip. The evaluation of so many correlations results in a significant expenditure of time and power consumption and may bottleneck the processing during the acquisition stage.

[0029] In one aspect of the present disclosure, a method is proposed which allows a rough timing acquisition without the typical correlation computations. The proposed method may reduce the SYNC-DL acquisition time by a factor on the order of 100.

[0030] As part of TD-SCDMA communications, a first time slot in a subframe, called time slot zero (TSO), and the SYNC-DL field are transmitted with similar power and are separated by a silent guard period of 48 chips, 16 chips at the end of TSO and 32 chips as part of a guard (or gap) period 218 at the beginning of the Downlink Pilot Time Slot (DwPTS) 206. The SYNC-DL field and the following time slot, time slot one (TS1) are also separated by a guard (or gap) period. This sequence of TSO, guard (or gap), SYNC-DL field, guard (or gap), makes up a power pattern characterized by high-low-high- low (HLHL). The first low zone has a duration of 48 chips and the second high zone has a duration of 64 chips. This particular HLHL power pattern is unique in the TD-SCDMA subframe. Because TD- SCDMA communications are synchronous, the pattern is preserved even in the presence of interfering cells.

[0031] Referring to Fig. 1, in one aspect of the present apparatus and method, a wireless communication system 10 is configured to include wireless communications between network 12 and UE 14. The wireless communications system may be configured to support communications between a number of users. Fig. 1 illustrates a manner in which network 12 communicates with UE 14. The wireless communication system 10 can be configured for downlink message transmission or uplink message transmission, as represented by the up/down arrows between network 12 and UE 14. Note, communication between the UE 12 and network 12 may occur on a primary carrier 16 and a secondary carrier 18.

[0032] In an aspect, within the UE 14 resides a call processing component 40. The call processing component 40 may be configured, among other things, to include a receiving component 42 capable of receiving a signal with an energy pattern from a network entity at a UE. The call processing component 40 is also configured to include a summing component 43 for summing the energy pattern of the signal at predetermined sample lengths.

[0033] Still further, the call processing component 40 may also be configured to include a matching component 44 capable of matching the summed energy pattern at the predetermined sample lengths to a HLHL energy pattern. [0034] The determining component 45 that resides in the call processing component 40 is configured to determine that the summed energy pattern matches the HLHL energy pattern while the detecting component 46 detects a gap in the received signal based on determining that the summed energy pattern matches the HLHL energy pattern.

[0035] Note, the gap in the received signal includes a gap between a first time slot of a subframe and a downlink pilot time slot in the subframe. Additionally, the gap in transmission is a gap between a downlink pilot time slot in a subframe and a next time slot in the subframe.

[0036] Fig. 5 is a diagram illustrating signal sample times according to one aspect of the present disclosure. Gap detection with constant A does not fully take advantage of the sample energy in estimating the 4 average energies in the gap, denoted as Qo, Qi, Q₂, and Q₃ (or the slope of the energy accumulation function).

[0037] For each hypothesis k (k=0 to 6399), to estimate the 4 average energies as Qo, Qi, Q₂, and Q₃, the following two vectors A and D are defined as:

[0038] D[4] : the offset of the starting point in sample energy summation for Q0 to Q3, and

[0039] A[4] : length of chips in energy summation

[0040] In gap detection with a constant A, D and A do not match the energy pattern exactly.

For instance, when D = [-64, 0, 48, 112] and A = [16, 16, 16, 16]. However, in the improved design, D=[-96, 0, 48, 112] and A=[96, 48, 64, 96].

[0041] In other words, aspects of this method and apparatus perform gap detection that is utilized to identify the HLHL energy pattern between TS0 and DwPTS, as illustrated in Fig. 5.

As stated above, the HLHL energy pattern is unique in the TD-SCDMA sub-frame and there are 6400 hypotheses of the gap position, corresponding to 6400 chips in every sub-frame.

For each hypothesis, four average energy values are estimated, corresponding to the four periods of HLHL. The average energy for each period is denoted as Qo, Qi, Q₂, and Q₃ for H,

L, H and L, respectively.

[0042] Note, when the hypothesis matches the gap position, Q₀ and Q₂ are supposed to be higher than Qi and Q₃ such as in ideal cases where the noise is not significant. Based on Qo, Qi, Q₂, and Q₃, a metric of perceivability, denoted as M, is computed for each hypothesis.

[0043] Generally, the method proposed for gap detection, the estimates of Qo, Qi, Q₂, and Q₃ are based on the same length of samples. Indeed, Qi may be calculated as:

[00441 & = f -S&^f2fc_i + ¾> [0045] For each hypothesis of gap position, denoted as k, the gap detector accumulates sample energies over 4 segments of samples with equal length, i.e., where are receive samples. The starting point of each segment is ¾— ¾ ^~ ¾ , ¾ = ¾ , ¾ = & - ½ and

¾ = ¾ +½. Each segment is represented in Fig. 4 as k + D[0J, k, k +D[2], and k + D[3J, respectively. Also note that the length of samples is a constant A for all the 4 segments and the division by A can be omitted since A is a constant.

[0046] After ¾ (i = 0 to 3) are estimated, the perceivability of the HLHL pattern is derived by:

[0047] ** ^' *nwi¾.*&3

[0048] To improve gap detection, aspects of this invention includes takings sample of different length to estimate fe%f¾ and ¾ The length of samples should match that of the gaps. More specifically, to estimate ¾ (i = 0 to 3), not only is the starting point for sample energy accumulation specified, but the length of samples, denoted as ^i, is also specified as follows:

[0049] ¾ - ^^=^ + ^

[0050] Specifically, the sample length of may be represented as -¾ = 48, s = St and i½ = ¾ to match the length the gaps. The selection of ^ s is need not be strict, so ^ s may be represented as ⁼ Please note that for both &i and ^ss, the value can be adjusted by several chips to account the energy leakage during the transition step. The value of and ^s;, may also be adjusted for the ease of computation.

[0051] Consequently, two benefits are derived from following the above procedure. First, if the noise is present, the longer length of samples results in a more accurate estimation.

Second, by matching the length to the gap, the ambiguity is reduced in computing the average energy with hypotheses since the true gap position taken into account.

[0052] Aspects of this method and apparatus also include an approach to improve the perceivability of the HLHL energy pattern. Indeed, the perceivability ) of the HLHL pattern can be measured by the three difference in average energy between H->L, L->H, and

H->L transitions, i.e., where:

[0054] *

[0055] Other methods for the derivation of M are also possible, where:

[0056] · ' ¾*¾

[0059] Fig. 6 is a schematic graph illustrating the accumulated energy over time according to one aspect of the present disclosure. Fig. 6 involves aspects of this method and apparatus that involves interpreting accumulated energy in another fashion. First, a function of accumulated energy may be defined and denoted as ¾«¾ . Note, the function is expected to be monotonically increasing and piece-wise linear, as shown in Fig. 6. However, due to the presence of noise and the variation of signal power, the lines in Fig. 6 would not be straight.

The slope of the^■¾«« curve corresponds to the average energy

[0060] For example, the following angles in Fig. 6 are defined as

» £ €_S 2 ^a^¾ = C _ Also the slopes of lines AB, BC, CD and DE are denoted as ¾.'%f ¾ and *¾. respectively.

[0061] As a result, the summation of A chip samples f, in ⁱ A^^s=^^{' '} , is used as an ap roximation of slopes and ¾ However, to better estimate ¾s and ¾ in v^*

, aspects of this invention includes summing over different length of chips to match the duration of gaps, and then normalize the sums occurs.

—■— sad—

[0062] The ratios of & reflect how large the angles &¾: and ¾ are, respectively.

Indeed, the large the ratio, the smaller the angle is, and the more perceivable the HLHL pattern

becomes. Therefore, s taken as the metric to measure the perceivability of the gap energy pattern.

[0063] An estimate of the gap position may be obtained by finding an index k that maximizes

M_k. An estimate of the position of the target gap may be expressed as:

where S is a positive integer parameter. The estimate of the gap position is obtained by finding the index that achieves the highest value of M_k, evaluating one gap detection metric every S. S = 8 is recommended in one aspect of the present disclosure. Larger values may cause performance degradation in the presence of large channel delay spreads (above 20 chips) while smaller values may provide no noticeable performance improvement. Values other than S=8 are also considered to be within the scope of the present disclosure, however.

[0064] Gap detection may be declared successful if the most desirable metric M_k is above a certain threshold THQAP- In other words, gap detection is successful if M_K > 7¾GAP- The value of 7¾GAP regulates the tradeoff between misses and false alarms. A recommended value is 2.5 (i.e., 4 dB), although other values are also contemplated . If the most desirable metric M_k is not greater than the threshold, then gap detection failure may be declared.

[0065] If gap detection is successful, timing synchronization may be achieved with an uncertainty roughly equal to the silence gap duration (nominally 48 chips). Thus, the window size to test correlations against the SYNC-DL sequences is reduced to 48 chips from the benchmark value of 6,400. Even adding a margin to the nominal gap duration of 48 chips, the reduction of the search time is reduced by a factor on the order of 100.

[0066] Fig. 7 is a schematic graph illustrating the shifted accumulated energy over time according to another aspect of the present disclosure. Fig. 6 involves aspects of this method and apparatus that improve upon the implementation design. In particular, a sliding window, denoted as W in Fig. 7, is maintained with size L = D3 - DO + A3. The sliding window is used to store the accumulated sample energy.

[0067] For each hypothesis k, W is updated by popping out the oldest accumulated energy, and appending a new accumulated energy (step 1). Afterwards, the four Δ values of Fig. 6 are calculated (step 2):

[0068] AO = WfAOJ - W[0]

[0069] Al = W[D1-D0 + A1J - W[D1-D0]

[0070] A2 = W[D2-D0 + A2J - W[D2-D0]

[0071] A3 = W[D3-D0 + A3] - W[D3-D0]

[0072] The four Δ values are then normalized to obtain $s and & (step 3). Last, based on the ¾>%< ^;¾ and the new gap detection metric M is computed for the sliding window (step 4), where Mjnax and gap position (kjiaf) is then updated with the current M. Note, the above steps 2-4 may be done once every S>1 hypotheses.

[0073] The teachings above are illustrated for gap patterns found in TD-SCDMA communications, however the different equations and variables, such as the metric M_k, the power profile Qt, the number of power profiles, the spacing between the power profiles, etc. may be configured to determine different power/gap pattern including those in networks other than TD-SCDMA. For example, while the above describes seeking to identify a HLHL (high-low-high-low) power pattern, the above techniques may be used to identify a HHLL power pattern, a HHL power pattern, etc.

[0074] Fig. 8 is a flow diagram, in operation, illustrating an exemplary method 50 for executing the call processing component 40 (Fig. 1) for improved gap detection in a wireless network. For example, in an aspect, UE 10 (Fig. 1) is configured to receive an energy pattern, sum the received energy pattern at predetermined sample lengths via receiving component 42 and summing component 43. Additionally, the UE 10 matches the summed energy pattern at the predetermined sample lengths to a HLHL energy pattern via matching component 44. Last, determining that the summed energy pattern matches the HLHL energy pattern and detecting a gap in the received signal occurs via determining component 45 and detecting component 46.

[0075] Specifically, method 50 includes receiving a signal with an energy pattern (Block 52).

For example, the call processing component 40 (Fig. 1) may execute receiving a signal with an energy pattern from a network entity at a UE via the receiving component 42.

[0076] Afterwards, method 50 includes summing the energy pattern of the signal (Block 53).

For example, the call processing component 40 (Fig. 1) may execute summing the energy pattern of the signal at predetermined sample lengths via the summing component 43.

[0077] Method 50 includes matching the summed energy (Block 54). For example, the call processing component 40 (Fig. 1) may execute matching the summed energy pattern at the predetermined sample lengths to a HLHL energy pattern via the matching component 44.

[0078] Moreover, method 50 includes determining that the summed energy pattern matches the HLHL energy pattern (Block 55). For example, the call processing component 40 (Fig. 1) may execute determining that the summed energy pattern matches the HLHL energy pattern via the determining component 44.

[0079] Last, method 50 includes detecting a gap in the received signal (Block 56). For example, the call processing component 40 (Fig. 1) may execute detecting a gap in the received signal based on determining that the summed energy pattern matches the HLHL energy pattern via the detecting component 44.

[0080] In one configuration, the apparatus, for example the UE 350, for wireless communication includes means for determining a set of received powers spanning different portions of a frame and means for detecting a gap in transmission from the determined set of received powers. In one aspect, the aforementioned means may be the antenna 352, receiver 354, receive frame processor 360, receive processor 370, and/or controller/processor 390 configured to perform the functions recited by the aforementioned means. In another aspect, the aforementioned means may be a module or any apparatus configured to perform the functions recited by the aforementioned means.

[0081] Several aspects of a telecommunications system has been presented with reference to

TD-SCDMA systems. As those skilled in the art will readily appreciate, various aspects described throughout this disclosure may be extended to other telecommunication systems, network architectures and communication standards. By way of example, various aspects may be extended to other UMTS systems such as W-CDMA, High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), High Speed Packet Access Plus (HSPA+) and TD-CDMA. Various aspects may also be extended to systems employing 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.

[0082] 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.

[0083] 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).

[0084] 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.

[0085] 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.

[0086] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more." Unless specifically stated otherwise, the term "some" refers to one or more. A phrase referring to "at least one of a list of items refers to any combination of those items, including single members. As an example, "at least one of: a, b, or c" is intended to cover: a; b; c; a and b; a and c; b and c; and a, b and c. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112, sixth paragraph, unless the element is expressly recited using the phrase "means for" or, in the case of a method claim, the element is recited using the phrase "step for."

Claims

CLAIMS What is claimed is:

1. A method of wireless communication, comprising:

receiving a signal with an energy pattern from a network entity at a user equipment

(UE);

summing the energy pattern of the signal at predetermined sample lengths;

matching the summed energy pattern at the predetermined sample lengths to a high- low-high-low (HLHL) energy pattern;

determining that the summed energy pattern matches the HLHL energy pattern; detecting a gap in the received signal based on determining that the summed energy pattern matches the HLHL energy pattern.

2. The method of claim 1, wherein the HLHL energy pattern represents an average energy pattern for certain gaps segments of a Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) signal.

3. The method of claim 1, wherein the gap in the received signal comprises a gap between a first time slot of a subframe and a downlink pilot time slot in the subframe.

4. The method of claim 3, wherein the gap in transmission is a gap between a downlink pilot time slot in a subframe and a next time slot in the subframe.

5. An apparatus for wireless communication, comprising:

a memory; and

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

receive a signal with an energy pattern from a network entity at a UE;

sum the energy pattern of the signal at predetermined sample lengths; match the summed energy pattern at the predetermined sample lengths to a HLHL energy pattern;

determine that the summed energy pattern matches the HLHL energy pattern;

detect a gap in the received signal based on determining that the summed energy pattern matches the HLHL energy pattern.

6. The apparatus of claim 5, wherein the HLHL energy pattern represents an average energy pattern for certain gaps segments of a Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) signal.

7. The apparatus of claim 5, wherein the gap in the received signal comprises a gap between a first time slot of a subframe and a downlink pilot time slot in the subframe.

8. The apparatus of claim 7, wherein the gap in transmission is a gap between a downlink pilot time slot in a subframe and a next time slot in the subframe.

9. A computer program product for detecting frame timing in a wireless communication network, the computer program product comprising:

receiving a signal with an energy pattern from a network entity at a UE;

summing the energy pattern of the signal at predetermined sample lengths;

matching the summed energy pattern at the predetermined sample lengths to a HLHL energy pattern;

10. An apparatus for wireless communication comprising:

means for receiving a signal with an energy pattern from a network entity at a UE; means for summing the energy pattern of the signal at predetermined sample lengths; means for matching the summed energy pattern at the predetermined sample lengths to a HLHL energy pattern; means for determining that the summed energy pattern matches the HLHL energy pattern;

means for detecting a gap in the received signal based on determining that the summed energy pattern matches the HLHL energy pattern.