WO2014059665A1

WO2014059665A1 - Adaptive Receive Diversity (ARD) processes in a TD-SCDMA network

Info

Publication number: WO2014059665A1
Application number: PCT/CN2012/083215
Authority: WO
Inventors: Wanlun Zhao; Insung Kang; Qiang Shen; Jinghu Chen; Jilei Hou
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2012-10-19
Filing date: 2012-10-19
Publication date: 2014-04-24
Anticipated expiration: 2015-04-19

Abstract

A method for wireless communication includes activating at least a first antenna and a second antenna. The method also includes determining whether to turn off either the first antenna or the second antenna. The method also includes turning off either the first antenna or the second antenna.

Description

Adaptive Receive Diversity (ARD) processes in a TD-SCDMA network

BACKGROUND

Field

[0001] Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to Adaptive Receive Diversity (ARD) processes in a TD-SCDMA network.

Background

[0002] Wireless communication networks are widely deployed to provide various

communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the Universal Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System

(UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). For example, China is pursuing TD-SCDMA as the underlying air interface in the UTRAN architecture with its existing GSM infrastructure as the core network. The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks. HSPA is a collection of two mobile telephony protocols, High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), that extends and improves the performance of existing wideband protocols.

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

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0007] FIGURES 4 and 5 are block diagrams illustrating finite state machines for a system with an adaptive receive diversity process according to aspects of the present disclosure.

DETAILED DESCRIPTION

[0008] 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.

[0009] Turning now to FIGURE 1 , a block diagram is shown illustrating an example of a telecommunications system 100. The various concepts presented throughout this disclosure may be implemented across a broad variety of telecommunication systems, network architectures, and communication standards. By way of example and without limitation, the aspects of the present disclosure illustrated in FIGURE 1 are presented with reference to a UMTS system employing a TD-SCDMA standard. In this example, the UMTS system includes a (radio access network) RAN 102 (e.g., UTRAN) that provides various wireless services including telephony, video, data, messaging, broadcasts, and/or other services. The RAN 102 may be divided into a number of Radio Network Subsystems (RNSs) such as an RNS 107, each controlled by a Radio Network Controller (RNC) such as an RNC 106. For clarity, only the RNC 106 and the RNS 107 are shown; however, the RAN 102 may include any number of RNCs and RNSs in addition to the RNC 106 and RNS 107. The RNC 106 is an apparatus responsible for, among other things, assigning, reconfiguring and releasing radio resources within the RNS 107. The RNC 106 may be interconnected to other RNCs (not shown) in the RAN 102 through various types of interfaces such as a direct physical connection, a virtual network, or the like, using any suitable transport network.

[0010] 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 R S 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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] FIGURE 2 shows a frame structure 200 for a TD-SCDMA carrier. The TD-SCDMA carrier, as illustrated, has a frame 202 that is 10 ms in length. The chip rate in TD-SCDMA is 1.28 Mcps. 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, TS 1 , 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 (each with a length of 352 chips) separated by a midamble 214 (with a length of 144 chips) and followed by a guard period (GP) 216 (with a length of 16 chips). The midamble 214 may be used for features, such as channel estimation, while the guard period 216 may be used to avoid inter-burst interference. Also transmitted in the data portion is some Layer 1 control information, including

Synchronization Shift (SS) bits 218. Synchronization Shift bits 218 only appear in the second part of the data portion. The Synchronization Shift bits 218 immediately following the midamble can indicate three cases: decrease shift, increase shift, or do nothing in the upload transmit timing. The positions of the SS bits 218 are not generally used during uplink communications .

[0016] FIGURE 3 is a block diagram of a node B 310 in communication with a UE 350 in a RAN 300, where the RAN 300 may be the RAN 102 in FIGURE 1 , the node B 310 may be the node B 108 in FIGURE 1, and the UE 350 may be the UE 110 in FIGURE 1. In the downlink communication, a transmit processor 320 may receive data from a data source 312 and control signals from a controller/processor 340. The transmit processor 320 provides various signal processing functions for the data and control signals, as well as reference signals (e.g., pilot signals). For example, the transmit processor 320 may provide cyclic redundancy check (CRC) codes for error detection, coding and interleaving to facilitate forward error correction (FEC), mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M- phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM), and the like), spreading with orthogonal variable spreading factors (OVSF), and multiplying with scrambling codes to produce a series of symbols. Channel estimates from a channel processor 344 may be used by a controller/processor 340 to determine the coding, modulation, spreading, and/or scrambling schemes for the transmit processor 320. These channel estimates may be derived from a reference signal transmitted by the UE 350 or from feedback contained in the midamble 214 (FIGURE 2) from the UE 350. The symbols generated by the transmit processor 320 are provided to a transmit frame processor 330 to create a frame structure. The transmit frame processor 330 creates this frame structure by multiplexing the symbols with a midamble 214 (FIGURE 2) from the controller/processor 340, resulting in a series of frames. The frames are then provided to a transmitter 332, which provides various signal conditioning functions including amplifying, filtering, and modulating the frames onto a carrier for downlink transmission over the wireless medium through smart antennas 334. The smart antennas 334 may be implemented with beam steering bidirectional adaptive antenna arrays or other similar beam technologies.

[0017] At the UE 350, a receiver 354 receives the downlink transmission through an antenna 352 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 354 is provided to a receive frame processor 360, which parses each frame, and provides the midamble 214 (FIGURE 2) to a channel processor 394 and the data, control, and reference signals to a receive processor 370. The receive processor 370 then performs the inverse of the processing performed by the transmit processor 320 in the node B 310. More specifically, the receive processor 370 descrambles and despreads the symbols, and then determines the most likely signal constellation points transmitted by the node B 310 based on the modulation scheme. These soft decisions may be based on channel estimates computed by the channel processor 394. The soft decisions are then decoded and deinterleaved to recover the data, control, and reference signals. The CRC codes are then checked to determine whether the frames were successfully decoded. The data carried by the successfully decoded frames will then be provided to a data sink 372, which represents applications running in the UE 350 and/or various user interfaces (e.g., display). Control signals carried by successfully decoded frames will be provided to a

controller/processor 390. When frames are unsuccessfully decoded by the receiver processor 370, the controller/processor 390 may also use an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0018] In the uplink, data from a data source 378 and control signals from the

controller/processor 390 are provided to a transmit processor 380. The data source 378 may represent applications running in the UE 350 and various user interfaces (e.g., keyboard). Similar to the functionality described in connection with the downlink transmission by the node B 310, the transmit processor 380 provides various signal processing functions including CRC codes, coding and interleaving to facilitate FEC, mapping to signal constellations, spreading with OVSFs, and scrambling to produce a series of symbols.

Channel estimates, derived by the channel processor 394 from a reference signal transmitted by the node B 310 or from feedback contained in the midamble transmitted by the node B 310, may be used to select the appropriate coding, modulation, spreading, and/or scrambling schemes. The symbols produced by the transmit processor 380 will be provided to a transmit frame processor 382 to create a frame structure. The transmit frame processor 382 creates this frame structure by multiplexing the symbols with a midamble 214 (FIGURE 2) from the controller/processor 390, resulting in a series of frames. The frames are then provided to a transmitter 356, which provides various signal conditioning functions including amplification, filtering, and modulating the frames onto a carrier for uplink transmission over the wireless medium through the antenna 352.

[0019] The uplink transmission is processed at the node B 310 in a manner similar to that described in connection with the receiver function at the UE 350. A receiver 335 receives the uplink transmission through the antenna 334 and processes the transmission to recover the information modulated onto the carrier. The information recovered by the receiver 335 is provided to a receive frame processor 336, which parses each frame, and provides the midamble 214 (FIGURE 2) to the channel processor 344 and the data, control, and reference signals to a receive processor 338. The receive processor 338 performs the inverse of the processing performed by the transmit processor 380 in the UE 350. The data and control signals carried by the successfully decoded frames may then be provided to a data sink 339 and the controller/processor, respectively. If some of the frames were unsuccessfully decoded by the receive processor, the controller/processor 340 may also use an

acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support retransmission requests for those frames.

[0020] The controller/processors 340 and 390 may be used to direct the operation at the node B 310 and the UE 350, respectively. For example, the controller/processors 340 and 390 may provide various functions including timing, peripheral interfaces, voltage regulation, power management, and other control functions. The computer readable media of memories 342 and 392 may store data and software for the node B 310 and the UE 350, respectively. For example, the memory 392 of the UE 350 may store an adaptive resource diversity module 391 which, when executed by the controller/processor 390, configures the UE 350 for executing an adaptive resource diversity process. 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.

Adaptive Receive Diversity (ARD) Process

[0021] Adaptive Receive Diversity (ARD) processes perform various functions. In some cases, the ARD process may detect long term antenna imbalance and turn off the weaker antenna if the imbalance is greater than an imbalance threshold (ThIB). Turning off the weaker antenna may improve power saving and may also improve performance. In some aspects, the ARD process may determine interference and thermo limited scenarios. In other cases, the ARD process may detect high antenna correlations and turn off one antenna if the correlation is greater than a correlation threshold (ThHC). The correlation may be based on an estimate of long term antenna correlation.

[0022] In other cases, the ARD process may switch between two spatial combining linear multi-user detection (SC-LMUD) modes. In some aspects, one mode may be a baseline mode (e.g., minimum mean squared error (MMSE) with covariance perturbation).

Furthermore, another mode may be a pilot weighted combine (PWC) mode. The different modes may be selected to improve performance.

[0023] FIGURE 4 is a the finite state machine with receive dynamic power management (RxDPM)/RDDS (receive diversity dynamic switching). RxDPM may be used for high speed data transmissions and RDDS may be used for voice communication. For data traffic, if there is active traffic, then it is desirable to activate both antennas. As shown in FIGURE 4, from the initial state, the device may initiate an RD_OFF state in which only one antenna is active. Alternatively, the device may initiate the Run ARD state for enabling both antennas and executing the ARD process based on the aspects of the present disclosure. The

Run_ARD state may also be initiated from the RD_OFF state. Furthermore, a RD TRANS (receive diversity transmit state may be initiated from the Run ARD state.

[0024] In one aspect, the imbalance detection may be executed only for thermo limited scenarios. In some cases, for each slot, the instantaneous power is computed in dBm for one antenna, such as RxO. The instantaneous power is computed based on serving shift power (Pserv), e.g., channel power, and a noise variance (Pnoise). The instantaneous power may be computed periodically, such as, for example, every 40ms.

[0025] Still, the instantaneous power may be unreliable, thus, according to an aspect, IIR filtering is performed to average the computed antenna powers with certain time constants. In one aspect, the IIR filtering is performed based on equations 1 and 2:

[0026] P_s serv (1)

[0027] P (2)

[0028] The receive power is then compared to the filtered (e.g., averaged) powers. That is, if the filtered serving shift power ( P_serv ) is less than a threshold (ThServ) and the filtered noise power ( P_mise )is less than a threshold (ThNoise), then thermo noise scenario for the receive power(Rx0_Power_t) is true and the imbalance detection may be performed. In one aspect, the receive power is then compared to the filtered (e.g., averaged) powers based on equation 3: [0029] bool RxO_Power_t = ( P_serv < ThServ) & ( P_noise < ThNoise) (3)

[0030] After determining a thermo noise scenario, the antenna imbalance may be determined. In some cases, the instantaneous signal to noise ratio (SNR) is computed in each time slot for each antenna (rxO and rxl). The instantaneous signal to noise ratio may be computed based on e uations 4 and 5.

[0032] SNR_nl = ^ (5)

[0033] In equations 4 and 5 P_{s nQ} and P_{s ral} are the serving shift power (Pserv) for each antenna at a specific time slot. Furthermore, N_{s n0} and N_s are the noise variance (Pnoise) for each antenna at a specific time slot.

[0034] In one aspect, the averaged SNR is computed based on the instantaneous SNR. For each antenna, the averaged SNR is SNRrxo and

[0035] Long term imbalance determines if the averaged SNR for a first antenna ( SNRrxi ) is less than a product of a threshold imbalance (Thta ) and the averaged SNR of a second antenna ( SNR_rxo ). In one aspect, the imbalance is calculated for both antennas based on equations 6 and 7

[0036] bool AntennaJmbalanceJ = SNR„i < Th ^■ SNR

[0037] bool AntennaJmbalanceJ =

(7)

[0038] If the long term imbalance is true, then the weaker antenna is turned off.

[0039] It should be noted that the constant threshold (TI B) used for all scenarios should be conservative. It is desirable to have the threshold imbalance (This) as an adaptive threshold.

An adaptive threshold (Thm) is calculated based on the following:

[0040] Th_IB = T_1MB . f (8)

[0041] In equation 8, Thre may be a constant maximum imbalance threshold and is an IIR filtered Walsh factor and is calculated based on the following equation:

[0042] / = min( ⁷°-^CT° , 1) (9)

" ' -' max.nrO [0043] In equation 9, I_{0 rx0} is the total received power of an antenna and P_{max rx0} is the maximum shift power from interfering cells. The IIR filtered Walsh factor is calculated as follows:

[0044] / = /? . / + (! _ ?) . / (10)

[0045] In equation 10, β is a filtering constant. In some aspects, the Walsh factor is measured for one antenna.

[0046] In some cases, the instantaneous correlation is estimated based on the following equations:

[0049] In equations 1 1 and 12, T^, is an inner product, _T is an offset, _r and h₀ , are channel vectors that may be 128 bits in length. Furthermore, i is the index of the cell, p is the normalized inner product, and I_{0 ra0} is the total received power. After determining the normalized inner product, an averaged antenna correlation ( p ) is computed

[0050] In one aspect, the antenna correlation is determined based on whether the averaged antenna correlation ( p ) is greater than a threshold (Thnc)- The antenna correlation may be determined as follows:

[0051] bool Correlation_t = p > Th_HC (13)

[0052] In some cases, it is desired to improve (spatial combining-linear multi user detection (SC-LMUD) robustness. With highly structured interference, the pilot weighted combining (PWC) mode may outperform MMSE (minimum mean squared error) with covariance perturbations and may be more robust under high antenna correlations. The adaptive mode selection logic is as follows, if an IIR filtered Walsh factor ( / ) is greater than a threshold Th_fyp , then enter PWC mode. ( / < 7%^ ), otherwise, enter the baseline mode. Th^ is the threshold for Walsh loading from interfering cells.

[0053] In one aspect, the adaptive receive diversity process may be based on the following:

[0054] bool ARD_PJ}_Off = ((Rx0_Power_t & Antenna_Imbalance_t) | CorrelationJ ) (14) [0055] In equation 14, the ARD RD OFF state is true if the power (RxO_Power_t) is low and the antennas are imbalanced (Antenna_Imbalance_t), or, if the antennas are correlated (Correlation^).

[0056] Furthermore, the PWC mode may be set, based on the following:

[0057] bool P WC_Mode = f < Th^ ( 15)

[0058] In equation 15, the PWC_Mode is true if the an IIR filtered Walsh factor ( ) is greater than a threshold Th^ . The threshold is a Walsh loading threshold from interfering cells.

[0059] PWC_Mode and ARD RD OFF are specified for the finite state machine for an adaptive resource diversity process shown in FIGURE 5. As shown in FIGURE 5, from the initial RD_OFF state in which only one antenna is active, a timer (timerARD) controls the time for staying in the RD OFF mode. Once the timer expires (!timerARD), a baseline mode (RxD_On Baseline) or PWC mode (RxD On PWC) may be selected. The baseline mode or PWC mode is selected based on the value of the PWC Mode. That is, if PWC_Mode is true, the PWC mode is selected, if P WC Mode is false, the baseline mode is selected. In the baseline mode and PWC mode, both antennas are active. The system may switch between the baseline mode and PWC mode. Furthermore, when the ARD RD OFF condition is true, one antenna is turned off and the state moves to the RD OFF state, additionally, a timer is set to a specific value (TARD)-

[0060] The timer TARD m y be adaptively set based on a number of samples that are available. Furthermore, if an IIR filter is used for instantaneous SINR or correlation averaging, the filter coefficients may be adaptively set based on the number of samples. Moreover, the same filtering may be used across all antennas.

[0061] 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.

[0062] 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.

[0063] 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).

[0064] 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. [0065] 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.

[0066] 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 for wireless communication, the method comprising:

activating at least a first antenna and a second antenna;

determining whether to turn off either the first antenna or the second antenna; and turning off either the first antenna or the second antenna.

2. The method of claim 1, in which the determining comprises:

detecting a thermo noise limited scenario based when an average serving shift power of the first antenna is less than a shift power threshold and an averaged noise variance of the first antenna is less than a noise threshold; and

determining an antenna imbalance when the thermo limited scenario is likely

3. The method of claim 2, in which determining the antenna imbalance comprises:

determining whether a receive signal to noise ratio (SNR) of the first antenna is less than a receive SNR of the second antenna, and

determining whether the receive SNR of the second antenna is less than the receive SNR of the second antenna, and

in which the turning off comprises turning off an antenna that has a receiver power that is less than another antenna.

4. The method of claim 1, in which the determining comprises determining whether an averaged correlation of the first and second antennas is greater than a correlation threshold.

5. The method of claim 1, further comprising:

selecting a pilot weighted combine mode for executing an linear multiuser detector (LMUD) process when an IIR filtered Walsh factor is greater than a threshold; and

selecting a baseline combine mode when for executing the LUMD process when the IIR filtered Walsh factor is less than the threshold.

6. An apparatus for wireless communication, comprising:

a memory; and

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

to activate at least a first antenna and a second antenna;

to determine whether to turn off either the first antenna or the second antenna; and

to turn off either the first antenna or the second antenna.

7. The apparatus of claim 6, in which the at least one processor is further configured:

to detect a thermo noise limited scenario based when an average serving shift power of the first antenna is less than a shift power threshold and an averaged noise variance of the first antenna is less than a noise threshold; and

to determine an antenna imbalance when the thermo limited scenario is likely

8. The apparatus of claim 7, in which the at least one processor is configured to determining the antenna imbalance by:

9. The apparatus of claim 6, in which the at least one processor is configured to determine by determining whether an averaged correlation of the first and second antennas is greater than a correlation threshold.

10. The apparatus of claim 6, in which the at least one processor is further configured: to select a pilot weighted combine mode for executing an linear multiuser detector (LMUD) process when an IIR filtered Walsh factor is greater than a threshold; and

to select a baseline combine mode when for executing the LUMD process when the IIR filtered Walsh factor is less than the threshold.

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

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

program code to activate at least a first antenna and a second antenna;

program code to determine whether to turn off either the first antenna or the second antenna; and

program code to turn off either the first antenna or the second antenna.

12. An apparatus for wireless communication, comprising:

activating at least a first antenna and a second antenna;

determining whether to turn off either the first antenna or the second antenna; and

turning off either the first antenna or the second antenna.