HK1171589B - Methods and apparatus for interference decrease/cancellation on downlink acquisition signals - Google Patents

Description

Method and apparatus for interference reduction/cancellation on downlink acquisition signals

Cross Reference to Related Applications

This application claims the benefit of U.S. provisional application serial No.61/234,595 entitled "interim cell related non-linear and non-linear information systems" filed on 8/17/2009, which is hereby expressly incorporated herein by reference in its entirety.

Technical Field

The present disclosure relates generally to communication systems, and more particularly to methods and apparatus for interference reduction or cancellation on a downlink acquisition signal.

Background

Wireless communication systems have been widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasting. Typical wireless communication systems may use multiple access techniques capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access techniques include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

These multiple access techniques have been adopted in various telecommunications standards to provide a common protocol that enables different wireless devices to communicate on a city-wide, country-wide, region-wide, or even global scale. An example of an emerging telecommunications standard is Long Term Evolution (LTE). LTE is an enhanced set of Universal Mobile Telecommunications System (UMTS) mobile standards promulgated by the third generation partnership project (3 GPP). The standard is designed to better support mobile broadband internet access by improving spectral efficiency, reducing costs, improving services, utilizing new spectrum, and better integrate with other open standards by using OFDMA on the Downlink (DL), SC-FDMA on the Uplink (UL), and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there is a need to further improve LTE technology. Preferably, these improvements should be applicable to other multiple access techniques and telecommunications standards using these techniques.

Disclosure of Invention

In one aspect of the invention, a method of wireless communication includes: estimating a channel from the received signal using one or more channel estimation schemes; removing component signals using the estimated channel from the received signal to generate a processed signal; residual signals in the processed signals are detected.

In another aspect of the present invention, an apparatus for wireless communication comprises: means for receiving a signal comprising components from a plurality of cells; means for estimating a channel from the received signal using one or more channel estimation schemes; means for removing a component signal using the estimated channel from the received signal to generate a processed signal; means for detecting a residual signal in the processed signal.

In yet another aspect of the invention, a computer program product includes a computer-readable medium including code for: estimating a channel from the received signal using one or more channel estimation schemes; removing component signals using the estimated channel from the received signal to generate a processed signal; residual signals in the processed signals are detected.

In yet another aspect of the present invention, an apparatus for wireless communication comprises at least one processor and a memory coupled to the at least one processor, wherein the at least one processor is configured to: estimating a channel from the received signal using one or more channel estimation schemes; removing component signals using the estimated channel from the received signal to generate a processed signal; and detecting a residual signal in the processed signal.

Drawings

FIG. 1 is a diagram depicting an example of a hardware implementation of an apparatus using a processing system;

FIG. 2 is a diagram depicting an example of a network architecture;

fig. 3 is a diagram depicting an example of an access network;

fig. 4 is a diagram depicting an example of a frame structure used in an access network;

fig. 5 shows an exemplary format for UL in LTE;

fig. 6 is a diagram depicting an example of a radio protocol architecture for the user plane and the control plane;

fig. 7 is a diagram depicting an example of an evolved node B and user equipment in an access network;

FIG. 8 is a block diagram example architecture of a wireless communication device;

fig. 9 is a block diagram depicting an exemplary architecture of a node B configured for interference reduction/cancellation in accordance with an aspect;

fig. 10 depicts an exemplary block diagram of an interference reduction system, according to an aspect;

fig. 11 is a block diagram of an example system that facilitates implementing interference cancellation in accordance with an aspect of the subject innovation;

FIG. 12 is another block diagram of an example system that facilitates implementing interference cancellation in accordance with an aspect of the subject innovation;

FIG. 13 is a flow diagram of an exemplary method of signal processing in accordance with the disclosed aspects;

FIG. 14 is a conceptual block diagram depicting the functionality of an exemplary apparatus;

FIG. 15 is a flow diagram of an exemplary method of signal processing in accordance with the disclosed aspects;

FIG. 16 is a conceptual block diagram depicting the functionality of an exemplary apparatus.

Detailed Description

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 various concepts. It will be apparent, however, to one 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.

Aspects of a communication system are now presented with reference to various apparatus and methods. These apparatus and methods are described in the following detailed description and are illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, and so forth (collectively, "elements"). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

For example, an element, or any portion of an element, or any combination of elements, may be implemented with a "processing system" that includes one or more processors. Examples of a processor include a microprocessor, microcontroller, Digital Signal Processor (DSP), Field Programmable Gate Array (FPGA), Programmable Logic Device (PLD), state machine, gated logic, discrete hardware circuitry, and other suitable hardware for performing the various functions described throughout this disclosure. One or more processors in the processing system may execute software. Software should be construed broadly to mean instructions, instruction sets, code segments, program code, programs, subroutines, software modules, 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 other terminology. The software may reside on a computer readable medium. The computer readable medium may be a non-transitory computer readable medium. By way of example, non-transitory computer-readable media include magnetic storage devices (e.g., hard disks, floppy disks, magnetic tape), optical disks (e.g., Compact Disks (CDs), Digital Versatile Disks (DVDs)), smart cards, flash memory devices (e.g., cards, sticks, key drives), Random Access Memories (RAMs), Read Only Memories (ROMs), programmable ROMs (proms), erasable proms (eproms), electrically erasable proms (eeproms), registers, removable disks, and any other suitable medium for storing software and/or instructions that may be accessed and read by a computer. By way of example, computer-readable media may also include carrier waves, transmission lines, and any other suitable media for transmitting software and/or instructions that can be accessed and read by a computer. The computer readable medium may be located in the processing system, may be located external to the processing system, or may be distributed among multiple entities including the processing system. The computer readable medium may be embodied in a computer program product. By way of example, a computer program product may include a computer-readable medium in a packaging material. Those of ordinary skill in the art will recognize how best to implement the described functionality presented throughout the present disclosure, depending on the particular application and the overall design constraints imposed on the overall system.

Fig. 1 is a conceptual diagram depicting an exemplary hardware implementation of an apparatus 100 using a processing system 114. In this example, the processing system 114 may be implemented with a bus architecture, represented generally by the bus 102. The bus 102 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 114 and the overall design constraints. The bus 102 links together various circuits including one or more processors, represented generally by the processor 104, and computer-readable media, represented generally by the computer-readable medium 106. In addition, the bus 102 also links various other circuits such as clock sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. Bus interface 108 provides an interface between bus 102 and transceiver 110. The transceiver 110 provides a means for communicating with various other apparatus over a transmission medium. Depending on the nature of the device, a user interface 112 (e.g., keypad, display, speaker, microphone, joystick, etc.) may also be provided.

The processor 104 is responsible for managing the bus 102 and for general processing, including the execution of software stored on the computer-readable medium 106. The software, when executed by the processor 104, causes the processing system 114 to perform the various functions described below for any particular apparatus. The computer-readable medium 106 may also be used for storing data that is generated when the processor 104 executes software.

Fig. 2 is a diagram depicting an LTE network architecture 200 using various apparatus 100 (see fig. 1). The LTE network architecture 200 may be referred to as an Evolved Packet System (EPS) 200. The EPS200 may include one or more User Equipments (UEs) 202, evolved UMTS terrestrial radio Access networks (E-UTRAN)204, Evolved Packet Core (EPC)210, Home Subscriber Server (HSS)220, and operator's IP services 222. The EPS may interconnect with other access networks, but for simplicity these entities/interfaces are not shown. As shown, the EPS provides packet switched services, however, as will be readily appreciated by those of ordinary skill in the art, the various concepts presented throughout the present invention may be extended to networks providing circuit switched services.

The E-UTRAN includes evolved node Bs (eNBs) 206 and other eNBs 208. eNB206 provides user plane and control plane protocol terminations toward UE 202. eNB206 may connect to other enbs 208 through an X2 interface (i.e., backhaul). eNB206 may also be referred to by those of ordinary skill in the art as a base station, a base station transceiver, a radio base station, a radio transceiver, a transceiver function, a Basic Service Set (BSS), an Extended Service Set (ESS), or some other suitable terminology. eNB206 provides an access point for UE202 to EPC 210. Examples of UEs 202 include a cellular phone, a smart phone, a Session Initiation Protocol (SIP) phone, a laptop, a Personal Digital Assistant (PDA), a satellite radio, a global positioning system, 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. A person of ordinary skill in the art may also refer to a UE202 as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

eNB206 connects to EPC210 through the S1 interface. The EPC210 includes a Mobility Management Entity (MME)212, other MMEs 214, a serving gateway 216, and a Packet Data Network (PDN) gateway 218. MME212 is a control node that handles signaling between UE202 and EPC 210. Generally, MME212 provides bearer and connection management. All user IP packets are transported through the serving gateway 216, where the serving gateway 216 is itself connected to the PDN gateway 218. The PDN gateway 218 provides ue ip address allocation as well as other functions. The PDN gateway 218 connects to the operator's IP service 222. The operator's IP services 222 include the internet, intranet, IP Multimedia Subsystem (IMS), and PS streaming service (PSs).

Fig. 3 is a diagram depicting an example of an access network in an LTE network architecture. In this example, the access network 300 is divided into a plurality of cellular regions (cells) 302. One or more low power class enbs 308, 312 may have cellular regions 310, 314, respectively, where the cellular regions 310, 314 overlap with one or more of the cells 302. The low power class enbs 308, 312 may be femto cells (e.g., home enbs (henbs)), pico cells, or micro cells. A higher power class or macro eNB304 is allocated to the cell 302 and is configured to provide an access point to the EPC210 for all UEs 306 in the cell 302. In this example of an access network 300, there is no centralized controller, but a centralized controller may be used in alternative configurations. The eNB304 is responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to the serving gateway 216 (see fig. 2).

The modulation and multiple access schemes used by the access network 300 may vary depending on the particular telecommunications standard being deployed. In LTE applications, OFDM is used on the DL and SC-FDMA is used on the UL to support Frequency Division Duplex (FDD) and Time Division Duplex (TDD). As will be readily appreciated by one of ordinary skill in the art from the following detailed description, the various concepts presented herein are well suited for use in LTE applications. However, these concepts can be readily extended to other telecommunications standards using other modulation and multiple access techniques. These concepts may be extended to evolution-data optimized (EV-DO) or Ultra Mobile Broadband (UMB), for example. EV-DO and UMB are air interface standards promulgated by the third generation partnership project 2(3GPP2) as part of the CDMA2000 family of standards, and are using CDMA to provide broadband internet access to mobile stations. These concepts may also be extended to Universal Terrestrial Radio Access (UTRA) using wideband CDMA (W-CDMA) and other variants of CDMA (e.g., TD-SCDMA); global system for mobile communications (GSM) using TDMA; and evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE802.11(Wi-Fi), IEEE802.16(WiMAX), IEEE802.20, and flash OFDM using OFDMA. UTRA, E-UTRA, UMTS, LTE, and GSM are described in documents from the 3GPP organization. CDMA2000 and UMB are described in documents from the 3GPP2 organization. The actual wireless communication standard and multiple access technique used depend on the particular application and the overall design constraints imposed on the system.

eNB304 may have multiple antennas supporting MIMO technology. The use of MIMO technology enables the eNB304 to use the spatial domain to support spatial multiplexing, beamforming, and transmit diversity.

Spatial multiplexing may be used to transmit different data streams simultaneously on the same frequency. The data stream may be sent to a single UE306 to increase the data rate or to multiple UEs 306 to increase the overall system capacity. This may be accomplished by spatially precoding each data stream and then transmitting each spatially precoded stream over the downlink via a different transmit antenna. The spatially precoded data streams carry data streams to the UE306 with different spatial characteristics, which enables each UE306 to recover one or more data streams destined for that UE 306. On the uplink, each UE306 transmits a spatially precoded data stream, which enables eNB304 to identify the source of each spatially precoded data stream.

When the channel conditions are good, spatial multiplexing is typically used. Beamforming may be used to focus the transmit energy in one or more directions when channel conditions are less favorable. This may be achieved by spatially precoding data transmitted via multiple antennas. To achieve good coverage at the edge of the cell, single stream beamforming transmission may be used in conjunction with transmit diversity.

In the detailed description that follows, various aspects of an access network will be described with reference to a MIMO system that supports OFDM on the downlink. OFDM is a spread spectrum technique that modulates data over multiple subcarriers in an OFDM symbol. The subcarriers are spaced apart at precise frequencies. This spacing provides "orthogonality" that enables the receiver to recover the data from the subcarriers. In the time domain, a guard interval (e.g., cyclic prefix) may be added to each OFDM symbol to prevent inter-OFDM symbol interference. The uplink may use SC-FDMA in the form of a DFT-spread OFDM signal to compensate for the higher peak-to-average power ratio (PARR).

Various frame structures may be used to support DL and UL transmissions. An example of a DL frame structure is now given with reference to fig. 4. However, as will be readily appreciated by one of ordinary skill in the art, the frame structure for any particular application may differ depending on any number of factors. In this example, one frame (10ms) is divided into 10 uniform-sized subframes. Each subframe includes two consecutive slots.

A resource grid may be used to represent two slots, each slot comprising a resource block. The resource grid is divided into a plurality of resource units. In LTE, one resource block includes 12 consecutive subcarriers in the frequency domain (for a normal cyclic prefix in each OFDM symbol), 7 consecutive OFDM symbols in the time domain, or 84 resource elements. Some of these resource elements include DL reference signals (DL-RS), as indicated by R402, 404. The DL-RS includes cell-specific RS (crs) (which is also sometimes referred to as general RS)402 and UE-specific RS (UE-RS) 404. The UE-RS404 is transmitted only on the resource blocks to which the corresponding Physical Downlink Shared Channel (PDSCH) is mapped. The number of bits carried by each resource unit depends on the modulation scheme. Thus, the more resource blocks a UE receives and the higher the modulation scheme order, the higher the data rate for that UE.

An example of a UL frame structure 500 is now given with reference to fig. 5. Fig. 5 shows an exemplary format for UL in LTE. The available resource blocks for the UL may be divided into a data part and a control part. The control section may be formed at both edges of the system bandwidth, the control section having a configurable size. The resource blocks in the control section may be allocated to the UE to transmit control information. The data part may include all resource blocks not included in the control part. The design in fig. 5 results in a data portion that includes contiguous subcarriers, which allows a single UE to be allocated all contiguous subcarriers in the data portion.

The UE may be allocated resource blocks 510a, 510b in the control section to transmit control information to the eNB. In addition, the UE may be assigned resource blocks 520a, 520b in the data section to transmit data to the eNB. The UE may transmit control information in a Physical Uplink Control Channel (PUCCH) on the resource blocks allocated in the control section. The UE may transmit only data or both data and control information in a Physical Uplink Shared Channel (PUSCH) on the resource blocks allocated in the data section. The UL transmission may span two slots of a subframe and may hop between frequencies, as shown in fig. 5.

As shown in fig. 5, initial system access may be performed using a set of resource blocks and UL synchronization is achieved in a Physical Random Access Channel (PRACH) 530. The PRACH530 carries a random sequence, which cannot carry any UL data/signaling. Each random access preamble occupies a bandwidth corresponding to six consecutive resource blocks. The starting frequency is specified by the network. That is, the transmission of the random access preamble is limited to certain time and frequency resources. For PRACH, there is no frequency hopping. The PRACH is carried in a single subframe (1ms), and the UE makes only a single PRACH attempt per frame (10 ms).

Under the heading "EvervedUniversal TerriesterRadioaccess (E-UTRA): PUCCH, PUSCH and PRACH in LTE are described in 3GGPTS36.211 of physical channels and modulation ", which is publicly available.

The wireless protocol architecture may take various forms depending on the particular application. An example for an LTE system is now given with reference to fig. 6. Fig. 6 is a conceptual diagram depicting an example of a radio protocol architecture for the user plane and the control plane.

Turning to fig. 6, the radio protocol architecture for the UE and eNB is shown with three layers: layer 1, layer 2 and layer 3. Layer 1 is the lowest layer that implements various physical layer signal processing functions. Layer 1 is referred to herein as physical layer 606. Above the physical layer 606 is a layer 2(L2 layer) 608, which is responsible for the link between the UE and the eNB on the physical layer 606.

In the user plane, the L2 layer 608 includes a Medium Access Control (MAC) sublayer 610, a Radio Link Control (RLC) sublayer 612, and a Packet Data Convergence Protocol (PDCP)614 sublayer, where these sublayers terminate at the eNB on the network side. Although not shown, the UE may have upper layers above the L2 layer 608, including a network layer (e.g., IP layer) that terminates at the PDN gateway 208 (see fig. 2) on the network side and an application layer that terminates at the other end of the connection (e.g., far end UE, server, etc.).

The PDCP sublayer 614 provides multiplexing between different radio bearers and logical channels. The PDCP sublayer 614 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and inter-eNB handover support for UEs. The RLC sublayer 612 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ). The MAC sublayer 610 provides multiplexing between logical channels and transport channels. The MAC sublayer 610 is also responsible for allocating various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer 610 is also responsible for HARQ operations.

In the control plane, the radio protocol architecture for the UE and eNB is substantially the same for the physical layer 606 and the L2 layer 608, except that there is no header compression function for the control plane. The control plane also includes a Radio Resource Control (RRC) sublayer 616 in layer 3. The RRC sublayer 616 is responsible for obtaining radio resources (i.e., radio bearers) and for configuring lower layers using RRC signaling between the eNB and the UE.

Fig. 7 is a block diagram of an eNB710 in an access network communicating with a UE 750. In the DL, upper layer packets from the core network are provided to the controller/processor 775. The controller/processor 775 performs the functions of the L2 layer previously described in connection with fig. 6. In the DL, the controller/processor 775 provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocation to the UE750 based on various priority metrics. The controller/processor 775 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE 750.

TX processor 716 performs various signal processing functions for the L1 layer (i.e., the physical layer). The signal processing functions include coding and interleaving to facilitate Forward Error Correction (FEC) at the UE750, and 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)). The coded and modulated symbols are then split into parallel streams. Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to generate a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to generate a plurality of spatial streams. Channel estimates from channel estimator 774 may be used to determine the coding and modulation schemes and to implement spatial processing. The channel estimates may be derived from reference signals and/or channel condition feedback transmitted by UE 750. Each spatial stream is then provided to a different antenna 720 via a separate transmitter 718 TX. Each transmitter 718TX modulates an RF carrier with a respective spatial stream for transmission.

At UE750, each receiver 754RX receives a signal through its respective antenna 752. Each receiver 754RX recovers information modulated onto an RF carrier and provides the information to a Receiver (RX) processor 756.

RX processor 756 performs various signal processing functions at the L1 layer. RX processor 756 performs spatial processing on the information to recover any spatial streams destined for UE 750. If multiple spatial streams are destined for UE750, RX processor 756 may combine them into a single OFDM symbol stream. The RX processor 756 then transforms the OFDM symbol stream from the time-domain to the frequency-domain using a Fast Fourier Transform (FFT). The frequency domain signal may comprise a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, as well as the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB 710. These soft decisions may be based on channel estimates computed by the channel estimator 758. These soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB710 on the physical channel. These data and control signals are then provided to a controller/processor 759.

The controller/processor 759 implements the L2 layer previously described in connection with fig. 6. In the UL, the controller/processor 759 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network. The upper layer packets are then provided to a data sink 762, where the data sink 762 represents all protocol layers above the L2 layer. In addition, various control signals may also be provided to the data sink 762 for L3 processing. The controller/processor 759 is also responsible for error detection using an Acknowledgement (ACK) and/or Negative Acknowledgement (NACK) protocol to support HARQ operations.

In the UL, a data source 767 is used to provide upper layer packets to the controller/processor 759. The data source 767 represents all protocol layers above the L2 layer (L2). Similar to the functionality described in connection with the DL transmission by the eNB710, the controller/processor 759 implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocations by the eNB 710. The controller/processor 759 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB 710.

The channel estimate derived by channel estimator 758 from a reference signal or feedback transmitted by eNB710 may be used by TX processor 768 to select the appropriate coding and modulation schemes and to facilitate spatial processing. The spatial streams generated by the TX processor 768 are provided to different antennas 752 via separate transmitters 754 TX. Each transmitter 754TX modulates an RF carrier with a respective spatial stream for transmission.

The eNB710 processes the UL transmissions in a manner similar to that described in connection with the receiver function at the UE 750. Each receiver 718RX receives a signal through its respective antenna 720. Each receiver 718RX recovers information modulated onto an RF carrier and provides the information to an RX processor 770. RX processor 770 implements the L1 layer.

The controller/processor 759 implements the L2 layer previously described in connection with fig. 6. In the UL, the controller/processor 759 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE 750. Upper layer packets from the controller/processor 775 may be provided to the core network. The controller/processor 759 is also responsible for error detection using ACK and/or NACK protocols to support HARQ operations.

The processing system 114 described in connection with fig. 1 may include an eNB 710. In particular, the processing system 114 may include the TX processor 716, the RX processor 770, and the controller/processor 775. The processing system 114 described in connection with fig. 1 may include the UE 750. In particular, the processing system 114 may include a TX processor 768, an RX processor 756, and a controller/processor 759.

Turning now to fig. 8, an exemplary Wireless Communication Device (WCD)800 is depicted. As depicted in fig. 8, WCD800 may include a receiver 802 that receives a signal from, for instance, a receive antenna (not shown), performs typical actions on (e.g., filters, amplifies, downconverts, etc.) the received signal, and digitizes the conditioned signal to obtain samples. Receiver 802 can comprise a demodulator 804 that can demodulate received symbols and provide them to a processor 806 for channel estimation. Processor 806 can be a processor dedicated to analyzing information received by receiver 802 and/or generating information for transmission by a transmitter 820, a processor that controls one or more components of WCD800, and/or a processor that both analyzes information received by receiver 802, generates information for transmission by transmitter 820, and controls one or more components of WCD 800.

WCD800 may also include memory 808, memory 808 operatively coupled to processor 806, memory 808 capable of storing data to be transmitted, received data, information related to available channels, data associated with analyzed signal and/or interference strength, information related to assigned channels, power, rate, etc., and any other suitable information for estimating a channel and transmitting over the channel. Additionally, memory 808 can store protocols and/or algorithms associated with estimating a channel and/or utilizing a channel (e.g., performance based, capacity based, etc.).

Further, the processor 806 may provide means for implementing the following functions: receiving a signal comprising components from a plurality of cells; estimating a channel from the received signal using one or more channel estimation schemes; removing component signals using the estimated channel from the received signal to generate a processed signal; residual signals in the processed signals are detected.

It will be appreciated that the memory 808 described herein can be either volatile memory or nonvolatile memory, or can include both volatile and nonvolatile memory. By way of example, 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 example, and not limitation, RAM may be available in a variety of forms such as Synchronous RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and Direct Rambus RAM (DRRAM). The memory 808 of the subject systems and methods can include, but is not limited to, these and any other suitable types of memory.

WCD800 may also include an interference reduction/cancellation (IDC) module 830 to facilitate interference reduction or cancellation for downlink acquisition signals by WCD 800. In one aspect, the IDC module 830 may include a channel estimation module 832, a processed signal generation module 834, and a residual signal detection module 836. In an aspect, channel estimation module 832 may be used to estimate a channel from a received signal using one or more channel estimation schemes. In an aspect, processed signal generation module 834 may be used to remove component signals from the received signal that use the estimated channel generated by channel estimation module 832 to generate a processed signal. In one aspect, the residual signal detection module 836 may be used to detect a residual signal in the processed signal.

In addition, WCD800 may also include a user interface 840. The user interface 840 may include: input device 842, for generating inputs to WCD 800; and output device 844 for generating information for use by a user of WCD 800. For example, input device 842 may include devices such as a key or keyboard, a mouse, a touch screen display, a microphone, and so forth. Further, for example, output devices 844 may include a display, an audio speaker, a haptic feedback device, a Personal Area Network (PAN) transceiver, and so forth. In the depicted aspect, the output device 844 may include: a display for presenting content in an image or video format; or an audio speaker for presenting content in an audio format.

Referring to fig. 9, an example system 900 can comprise an eNodeB902 having a receiver 910 and a transmitter 922, wherein the receiver 910 receives signals from one or more user devices 202 through a plurality of receive antennas 906 and the transmitter 922 transmits to the one or more user devices 202 through a plurality of transmit antennas. Receiver 910 can receive information from receive antennas 906 and is operatively associated with a demodulator that demodulates received information. The demodulated symbols are analyzed by a processor 914 that can be coupled to a memory 916, and the memory 916 can store information such as information related to mobile device performance measurements and location. Processor 914 can be a processor dedicated to analyzing information received by receiver 910 and/or generating information for transmission by a transmitter 922, a processor that controls one or more components of base station 902, and/or a processor that both analyzes information received by receiver 910, generates information for transmission by transmitter 922, and controls one or more components of base station 902. As described above, base station 902 can also include memory 916, the memory 916 operatively coupled to processor 914, the memory 916 storing various items of information such as information related to mobile device performance measurements and location. It will be appreciated that the data store (e.g., memories) described herein can be either volatile memory or nonvolatile memory, or can include both volatile and nonvolatile memory. By way of example, 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 example, and not limitation, RAM may be available in a variety of forms such as Synchronous RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM (SDRAM), Double Data Rate SDRAM (DDRSDRAM), Enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and Direct Rambus RAM (DRRAM). The memory 916 of the subject apparatus and methods is intended to comprise, without being limited to, these and any other suitable types of memory.

Processor 914 is also coupled to an interference reduction/cancellation (IDC) module 930 to facilitate interference reduction or cancellation for downlink acquisition signals by WCD 900. In an aspect, the IDC module 930 may include a channel estimation module 932, a processed signal generation module 934, and a residual signal detection module 936. In an aspect, channel estimation module 932 may be configured to estimate a channel from a received signal using one or more channel estimation schemes. In one aspect, the processed signal generation module 934 may be used to remove component signals from the received signal using the estimated channel generated by the channel estimation module 932 to generate a processed signal. In one aspect, the residual signal detection module 936 may be used to detect a residual signal in the processed signal.

Referring to fig. 10, a detailed block diagram of an interference reduction system 1000, such as MME212 depicted in fig. 2, is depicted. Interference reduction system 1000 may include at least one of any type of hardware, server, personal computer, microcomputer, mainframe computer, or any computing device (special purpose computing device or general purpose computing device). Further, the modules and applications described in this application that run on or are executed by the interference reduction system 1000 may execute entirely on a single network device, as shown in fig. 2, or in other aspects separate servers, databases, or computer devices may work in tandem to provide data in a usable format to a community and/or to provide a separate layer of control in the data flow between the communication device 202 and the modules and applications executed by the interference reduction system 1000.

The interference reduction system 1000 includes a computer platform 1002, the computer platform 1002 can transmit and receive data over wired and wireless networks, and can execute routines and applications. Computer platform 1002 includes memory 1004, which memory 1004 may include volatile and nonvolatile memory such as read only memory and/or random access memory (ROM and RAM), EPROM, EEPROM, flash cards, or any memory common to computer platforms. Further, memory 1004 may include one or more flash memory cells, or it may be any secondary or tertiary storage device, such as magnetic media, optical media, tape, or soft or hard disk. Further, computer platform 1002 also includes a processor 1030, which processor 1030 may be an application specific integrated chip ("ASIC"), or other chipset, logic circuit, or other data processing device. Processor 1030 can include various processing subsystems 1032 embodied in hardware, firmware, software, and combinations thereof, such subsystems 1032 enable the functionality of a media content distribution system and the operability of network devices on a wired network or a wireless network.

Further, the computer platform 1002 also includes a communication module 1050 embodied in hardware, firmware, software, and combinations thereof, the communication module 1050 enabling communication among the various components of the interference reduction system 1000, as well as between the interference reduction system 1000, the device 202, and the eNodeB 206. The communication module 1050 may include hardware, firmware, software, and/or combinations thereof necessary for establishing a wireless communication connection. According to the described aspects, the communication module 1050 may include hardware, firmware, and/or software necessary to facilitate wireless broadcast, multicast, and/or unicast communication of requested content items, control information, applications, and/or the like.

The memory 1004 of the interference reduction system 1000 includes an IDC module 1010, the IDC module 1010 operable to facilitate the system in achieving interference reduction or cancellation for downlink acquisition signals. In one aspect, the IDC module may include a channel estimation module 1012, a processed signal generation module 1014, and a residual signal detection module 1016. In an aspect, the channel estimation module 1012 may be configured to estimate a channel from a received signal using one or more channel estimation schemes. In an aspect, the processed signal generation module 1014 may be used to remove component signals from the received signal that use the estimated channel generated by the channel estimation module 1012 to generate a processed signal. In one aspect, the residual signal detection module 1016 may be used to detect a residual signal in the processed signal.

Fig. 11 depicts an example system 1100 that facilitates employing a base station and a user equipment to implement interference cancellation, reduction, or removal on an acquisition signal, where the cancellation or reduction is performed at the user equipment. System 1100 can include a number of disparate components, such as a base station 1102 (e.g., an access point, node B, eNodeB, eNB, or other suitable device) that communicates with user equipment 1104 (UE). For example, the user equipment may take the form of mobile stations, mobile devices, and any other suitable devices and/or any number of suitable devices discussed herein. Base station 1102 can transmit information to user device 1104 in a number of different manners, e.g., over forward link channels or downlink channels. Further, base station 1102 can receive information from user device 1104 over at least a reverse link channel or an uplink channel.

The system 1100 may operate according to a number of different arrangements. System 1100 can be a MIMO system, for example. Additionally, system 1100 may operate in an OFDMA wireless network. Examples of suitable OFDMA wireless networks include 8GPP, 8GPP2, 8GPP, and LTE, among others.

User equipment 1104 can include a signal acquisition component 1106, and signal acquisition component 1106 can facilitate acquisition of downlink signals from base station 1102, for instance. The terms "strong cell", "stronger cell" and "strongest cell" in this application indicate a cell with a strong signal, a stronger signal or a strongest signal, respectively. The terms "weak cell", "weaker cell" and "weakest cell" indicate a cell with weak, weaker, or weakest signals, respectively. In a homogeneous network, the user equipment 1104 can search for a serving cell, e.g., from a downlink acquisition signal, and select or use the cell with the strongest signal as the serving cell. On the other hand, in a heterogeneous network, the strongest cell may not be accessible to the user equipment 1104, and thus, the user equipment 1104 may need to search for a serving cell that is significantly weaker than the strongest cell. In these and other situations, detecting cells from Primary Synchronization Signals (PSS) and/or Secondary Synchronization Signals (SSS) may not be sufficiently reliable. False detected cells caused by this approach may result in reduced IC performance. Furthermore, even with the timing between cell signals off, the signals after interference cancellation may be too weak and/or susceptible to other cell data interference. A practical implementation may require a larger bandwidth. Furthermore, there are performance issues when cells have the same PSSID.

For example, signal acquisition component 1106 can include interference reduction component 1110, channel estimation component 1108, and processed signal generation component 1112. Each of interference reduction component 1110, channel estimation component 1108, and processed signal generation component 1112 may be used together, for example, to remove or reduce interference in a received signal, remove component signals using an estimated channel from the received signal, generate a processed signal, and generate or detect a residual signal in the processed signal. Once the processed signals and/or other signals are obtained, processed signal generation component 1112 generates the processed signals and/or other signals. The processed signal generation component 1112 may perform additional processing on the signals, such as filtering, scaling, or otherwise manipulating the signals.

The interference reduction component 1110 can cancel, remove, or reduce interference from other cells such that the user equipment 1104 can access a weaker serving cell. For example, the cancellation, removal, or reduction of signals from interfering cells by interference reduction component 1110 may be a function of the channel estimates provided by channel estimation component 1108 to interference reduction component 1110. Channel estimation, which may be useful in interference cancellation, reduction, or removal, among other things, is a process for characterizing the effect of a channel on a signal. Channel estimation may be particularly useful in reducing interference from residual signals of strong cells.

To perform channel estimation, channel estimation component 1108 may use various mechanisms/methods. For example, according to a variant, channel estimating component 1108 can estimate the channel using the detected PSS. This channel estimate may then be used to reconstruct the strong cell signal, which may then be used to cancel the strong cell signal. Using PSS for channel estimation may be advantageous, among other reasons, because PSS is generally readily available in the initial cell search when performing coherent SSS detection. However, PSS may have a Single Frequency Network (SFN) effect, especially when only three PSS are present in the system (since multiple enbs may share the same PSS).

In another variation, the channel estimation component 1108 may estimate the channel using the detected SSS. There may be a greater number of SSSs per system (e.g., in a particular system there may be one hundred sixty eight or more SSSs). Due to the large number of SSSs, the SFN effect is lower when the SSS is used to estimate the channel than when the PSS is used to estimate the channel. This is because the possibility of any two enbs sharing the same SSS is considered very unlikely compared to the possibility of any two enbs sharing the same PSS.

In another variation, channel estimation component 1108 may perform Reference Signal (RS) based channel estimation. In particular, user equipment 1104 can acquire a strong cell and obtain a channel estimate using RS symbols corresponding to the strong cell. In this variation, the RS symbol may be wideband, and it may include a plurality of subframes adjacent to each other. The combination of RS symbols among multiple subframes may depend on the presence of multimedia broadcast unicast single frequency network (MBSFN) or on blank subframes.

The MBSFN subframe may include a control region and a data region. In an aspect, data to be transmitted is not allocated to the data region, and thus, the data portion of the MBSFN subframe may appear as a blank subframe. Further, a blank subframe may refer to a subframe in which no transmission occurs. In this and other cases, the presence of MBSFN/blank subframes may be obtained or determined from a System Information Block (SIB). Using MBSFN subframes, RSs within the first two symbols in the control region may be combined to facilitate channel estimation. In addition, blank subframes may be skipped.

There is a difference in implementation of performing RS-based channel estimation between the single antenna system and the multiple antenna system. For example, in a single antenna system, an RS-based channel may be directly used. Alternatively, for a multiple transmit antenna system, the PSS/SSS may use precoding vector control (PVS) to allow the UE to determine the transmission phase and decode the transmission appropriately. In contrast, the RS-based approach does not use PVS. In particular, the precoding vector may be linked to a System Frame Number (SFN) or other quantity. Further, the RS-based channel estimate may be multiplied by a precoding vector to obtain a channel for the PSS/SSS.

According to yet another variation, channel estimating component 1108 may perform Physical Broadcast Channel (PBCH) assisted channel estimation. In this variation, user equipment 1104 may decode the PBCH of the strong cell and use the decoded PBCH to perform or enhance channel estimation. In addition, the decoded strong cell PBCH may also be used to reduce the likelihood of false alarms. The term "false alarm" refers to, among other things, a misidentification as to whether a detected cell is actually present.

There are differences between single antenna systems and multiple antenna systems in the implementation for performing Physical Broadcast Channel (PBCH) assisted channel estimation. For example, in a single antenna system, a physical channel signal estimated from PBCH may be directly applied to PSS/SSS. On the other hand, for a multi-antenna system, the physical channel estimated from the PBCH is multiplied by a precoding vector to obtain a channel applied to the PSS/SSS.

In addition, the signal capture component 1106 can further include a verification component 1114 to reduce false alarms. In a variation, verification component 1114 may reduce false alarms or perform verification based on Reference Signal Received Power (RSRP) measurements. This may be accomplished, for example, by comparing the RSRP to a plurality of quantities. For example, verification component 1114 may compare the RSRP to a threshold (e.g., an absolute or a predefined or specified threshold value). Verification component 1114 may compare the RSRP to a relative threshold generated from the strongest detected cell and/or to a threshold generated from an average of a plurality of detected cells. This variant is advantageous in case RSRP measurements are already needed, e.g. in release 8. Furthermore, this variant method improves reliability. However, RSRP measurement/thresholding may involve or even require time averaging. This may result in an increase in search time.

According to another variation, the verification component 1114 can reduce false alarms or perform verification based on PBCH decoding. For example, in this variation, the presence of a cell may be confirmed by performing a Cyclic Redundancy Check (CRC) on the residual signal. Since PBCH has a sixteen bit CRC, this CRC may give a reliable indication of the active cell. In addition, the detection time for CRC is shorter than RSRP measurement and averaging. Generally, user equipment 1104 may need to decode PBCHs of multiple or even all neighbor cells.

In yet another variation, verification component 1114 may combine RSRP measurement-based verification with PBCH decoding-based verification. For example, PBCH may be decoded only for those cells whose RSRP passes a certain threshold. This variant leads to, among other things, good reliability and reduced complexity/power consumption. Furthermore, RSRP does not require a long average length.

The scaling component 1116 of the signal acquisition component 1106 and the user device 1104 may perform signal scaling to improve the weak residual signals and/or increase their detectability. The residual signal obtained by eliminating or reducing strong interference may be relatively weak compared to the detection capability. Therefore, a larger bit width is required to process, use, or interpret the weak signal. Furthermore, when the system is not strictly synchronized, the presence of data from strong cells (which is not easily eliminated, reduced, or removed) may make it more difficult to interpret weak signals. In response, the scaling component 1116 may perform Automatic Gain Control (AGC) after cancellation. For example, AGC can be used to increase the residual signal strength (e.g., increase the signal strength after interference cancellation, removal, or reduction) so that the residual signal reaches a similar level as the received signal. Such scaling can be based on, for example, the estimated channel from channel estimation component 1108 and/or the energy difference between the received signal and the residual signal, among others.

Further, the UE1104 may also be configured to acquire signals and reduce interference when the strong and weak cells have the same PSS. In this case, errors in channel estimation may partially or effectively cancel the desired PSS. Careful planning may address situations where, for example, all femto enbs surrounding such a macro eNB use a different PSS than the macro eNB. Another option is to store information associated with the estimated channel and the detected time to allow the UE to distinguish between multiple similar estimated channels.

Fig. 12 depicts an example system 1200 that facilitates employing a base station and user equipment to implement interference cancellation, reduction, or removal on an acquisition signal, where the cancellation or reduction is performed at the base station. It should be understood that the components and functions shown and described below in the base stations 1102, 1204 may be present in the user equipment 1104, 1202 and vice versa.

System 1200 can include a number of disparate components, such as a base station 1204 (e.g., an access point, node B, eNodeB, eNB, or other suitable device) that can communicate with a user equipment 1202 (UE). For example, the user equipment may take the form of mobile stations, mobile devices, and any other suitable devices and/or any number of suitable devices discussed herein. Base station 1204 can transmit information to user device 1202 in a number of different manners, e.g., over forward link channels or downlink channels. Further, the base station 1204 can receive information from the user equipment 1202 over at least a reverse link channel or an uplink channel.

The system 1200 may operate according to a number of different arrangements. System 1100 can be a MIMO system, for example. Additionally, system 1200 may operate in an OFDMA wireless network. Examples of suitable OFDMA wireless networks include 8GPP, 8GPP2, 8GPP, and LTE, among others.

Base station 1204 can include a signal acquisition component 1206, which acquisition component 1206 can facilitate acquisition of downlink signals, for example. The terms "strong cell", "stronger cell" and "strongest cell" in this application indicate a cell with a strong signal, a stronger signal or a strongest signal, respectively. The terms "weak cell", "weaker cell" and "weakest cell" indicate a cell with weak, weaker, or weakest signals, respectively. In a homogeneous network, the base station 1204 may search for a serving cell, e.g., from a downlink acquisition signal, and select or use the cell with the strongest signal as the serving cell. On the other hand, in a heterogeneous network, the strongest cell may not be accessible to the base station 1204, and thus, the base station 1204 may need to search for a serving cell that is significantly weaker than the strongest cell. In these and other situations, detecting cells from PSS and/or SSS may not be sufficiently reliable. False detected cells caused by this approach may result in reduced IC performance. Furthermore, even where the timing between cell signals is off, the signals after interference cancellation may be too weak and/or susceptible to other cell data interference. Practical implementations require more bandwidth. Furthermore, there are performance issues when cells have the same PSSID.

For example, signal acquisition component 1206 can comprise interference reduction component 1210, channel estimation component 1208, and processed signal generation component 1212. Each of interference reduction component 1210, channel estimation component 1208, and processed signal generation component 1212 may be used together, for example, to remove or reduce interference in a received signal, to remove component signals using an estimated channel from the received signal to generate a processed signal, and to generate or detect a residual signal in the processed signal. Once the processed signals and/or other signals are obtained, the processed signal generation component 1212 generates the processed signals and/or other signals. The processed signal generation component 1212 may perform additional processing on the signals, such as filtering, scaling, or otherwise manipulating the signals.

Interference reducing component 1210 can eliminate, remove, or reduce strong interfering cells such that base station 1204 can access weaker serving cells. For example, the cancellation, removal, or reduction of signals from interfering cells by interference reducing component 1210 may be dependent on the channel estimates provided by channel estimating component 1208 to interference reducing component 1210 by channel estimation. Channel estimation, which is useful in interference cancellation, reduction, or removal, among other things, is a process for characterizing the effect of a channel on a signal. Channel estimation may be particularly useful when reducing interference from residual signals of strong cells.

To perform channel estimation, channel estimation component 1208 may use various mechanisms/methods. For example, according to a variation, channel estimation component 1208 may estimate the channel using the detected PSS. This channel estimate may then be used to reconstruct the strong cell signal to be cancelled. Using PSS for channel estimation may be advantageous, since PSS is typically readily available in the initial cell search, among other reasons, when performing coherent SSS detection. However, PSS may have a Single Frequency Network (SFN) effect, especially when only three PSS are present in the system.

In another variation, the channel estimating component 1208 may estimate the channel using the detected SSS. There may be a greater number of SSSs per system (e.g., in a particular system there may be one hundred sixty eight or more SSSs). Due to the large number of SSSs, the SFN effect is lower when the SSS is used to estimate the channel than when the PSS is used to estimate the channel.

In another variation, channel estimation component 1208 may perform Reference Signal (RS) based channel estimation. In particular, user equipment 1104 can acquire a strong cell and obtain a channel estimate using RS symbols corresponding to the strong cell. In this variation, the RS symbol may be wideband and it may include a plurality of subframes that are adjacent. The combination of RS symbols across multiple subframes may depend on MBSFN or on the presence of blank subframes.

There is a difference in implementation of performing RS-based channel estimation between the single antenna system and the multiple antenna system. For example, in a single antenna system, an RS-based channel may be directly used. Alternatively, for a multiple transmit antenna system, the PSS/SSS may use precoding vector control (PVS) to allow the UE to determine the transmission phase and decode the transmission appropriately. In contrast, the RS-based method does not use PVS. In particular, the precoding vector may be linked to a System Frame Number (SFN) or other quantity. Further, the RS-based channel estimate may be multiplied by a precoding vector to obtain a channel for the PSS/SSS.

According to yet another variation, channel estimating component 1208 may perform Physical Broadcast Channel (PBCH) assisted channel estimation. In this variation, the base station 1204 may decode the PBCH of the strong cell and perform or enhance channel estimation using the decoded strong cell PBCH. Further, the decoded strong cell PBCH may be used to reduce false alarms, where "reducing false alarms" means, among other things, identifying whether an apparently detected cell is actually present or detectable.

There is a difference in the implementation of performing Physical Broadcast Channel (PBCH) assisted channel estimation between single antenna systems and multiple antenna systems. For example, in a single antenna system, the physical channel experienced by the PBCH may be directly applied to the PSS/SSS. On the other hand, for a multi-antenna system, the physical channel experienced by the PBCH is multiplied by the precoding vector to obtain the channel applied to the PSS/SSS.

Additionally, the signal capture component 1206 can further include a verification component 1214 to reduce false alarms. In a variation, verification component 1214 can reduce false alarms or perform verification based on Reference Signal Received Power (RSRP) measurements. This may be accomplished, for example, by comparing the RSRP to a plurality of quantities. For example, verification component 1214 can compare the RSRP to a threshold (e.g., an absolute or predefined value or a specified threshold value). Verification component 1214 can compare the RSRP to a relative threshold generated from the strongest detected cell and/or to a threshold generated from an average of a plurality of detected cells. This variant is advantageous in case RSRP measurements are already needed, e.g. in release 8. Furthermore, this variant method improves reliability. However, RSRP measurement/thresholding may involve or even require time averaging. This may result in an increase in search time.

According to another variation, verification component 1214 can reduce false alarms or perform verification based upon PBCH decoding. For example, in this variation, the presence of a cell may be confirmed by performing a Cyclic Redundancy Check (CRC) on the residual signal. Since PBCH has a sixteen bit CRC, this CRC may give a reliable indication of the active cell. In addition, the detection time for CRC is shorter than RSRP measurement and averaging. In general, the user equipment 1204 may need to decode PBCHs of multiple or even all neighbor cells.

In yet another variation, verification component 1214 may combine RSRP measurement-based verification with PBCH decoding-based verification. For example, PBCH may be decoded only for those cells whose RSRP passes a certain threshold. This variant yields, among other things, good reliability and reduced complexity/power consumption. Furthermore, RSRP does not require a long average length.

Scaling component 1216 of signal acquisition component 1206 and user equipment 1204 may perform signal scaling to improve weak residual signals and/or increase their detectability. The residual signal obtained by eliminating or reducing strong interference may be relatively weak compared to the detection capability. Thus, a larger bit width may be required to process, use, or interpret the weak signal. Furthermore, when the system is not strictly synchronized, the presence of data from strong cells (which is not easily eliminated, reduced, or removed) can make it more difficult to interpret weak signals. In response, scaling component 1216 may perform Automatic Gain Control (AGC) after cancellation. For example, AGC can be used to increase the residual signal strength (e.g., increase the signal strength after interference cancellation, removal, or reduction) so that the residual signal reaches a similar level as the received signal. Such scaling may be based on, for example, an estimated channel from channel estimation component 1208 and/or an energy difference between the received signal and a residual signal, among others.

In addition, the base station 1204 may also be configured to acquire signals and reduce interference when the strong cell and the weak cell have the same PSS. In this case, an error in channel estimation may partially or effectively cancel the desired PSS. Careful planning may address this situation, e.g., where all femto enbs around a macro eNB use a different PSS than the macro eNB. Another option is to store information associated with the estimated channel and the detected timing (detecting) to enable discrimination between multiple similarly marked estimated channels.

13-16 depict various methods and apparatus in accordance with the claimed subject matter. While, for purposes of simplicity of explanation, the methodologies are shown and described as a series of acts, 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.

Referring to fig. 13, depicted is a system 1300 that can include a UE, a first eNB, and any suitable number of additional enbs or UEs. Further, in operation of system 1300, either the UE or the eNB may reduce or eliminate interference.

At reference numeral 1302, a UE or eNB can estimate a channel from a received signal using one or more channel estimation schemes. The received signal may include components from multiple cells. At reference numeral 1304, the UE or eNB may remove a component signal using the estimated channel from the received signal to generate a processed signal. At reference numeral 1306, the UE or eNB may detect a residual signal in the processed signal.

In an aspect, the UE or eNB may also detect a primary synchronization signal in the received signal and use the primary synchronization signal to generate a channel estimate.

In another aspect, the UE or eNB may also detect for a secondary synchronization signal in the received signal and use the secondary synchronization signal to generate a channel estimate.

In yet another aspect, the UE or eNB may also obtain a reference signal and use the reference signal to generate a channel estimate. The UE or eNB may also detect for signals from the first cell including reference signals with reference signal symbols and may use the reference signal symbols to obtain an estimated channel. The reference signal symbols may be included in a reference signal spanning multiple subframes. Furthermore, the reference signal symbols may also be included in reference signals in Multimedia Broadcast Single Frequency Network (MBSFN) subframes or blank subframes. In this aspect, the UE or eNB may also detect the reference symbols directly using a single antenna system, or detect the primary and secondary synchronization signals using precoding vector control, or directly detect the reference symbols in a multi-antenna system. In an aspect, the UE or eNB may also estimate a channel from the reference symbols and combine with at least one of the channel estimates from the primary or secondary synchronization signals in a single antenna system.

In another aspect, the UE or eNB may also estimate the channel from the reference symbols and combine with at least one of the channel estimates from the primary or secondary signals using precoding vector control in a multi-antenna system. The UE or eNB may also link the precoding vectors used in the primary and secondary synchronization signals with the cell ID and system frame number.

In one aspect, one of the one or more channel estimation schemes comprises: the method includes decoding a first cell physical broadcast channel and applying the decoded first cell physical broadcast channel to primary and secondary synchronization signals associated with the received signal. In this aspect, the UE or eNB may also multiply the physical broadcast channel with a precoding vector to obtain a channel applied to the primary and secondary synchronization signals. In addition, the UE or eNB may also link the precoding vectors used in the primary and secondary synchronization signals with the cell ID and system frame number.

In an aspect, the UE or eNB may also apply one or more false alarm reduction schemes. One of the one or more false alarm reduction schemes may include: the received power of the residual signal is compared to a threshold value. The threshold value may include at least one of: a defined threshold value, a threshold generated from the strongest detected cell, or a threshold generated from an average of a plurality of detected cells. In an aspect, the UE or eNB may also perform a cyclic redundancy check on the detected signal. In another aspect, the UE or eNB may also determine that the reference signal received power is above a threshold for a residual signal and decode the physical broadcast channel based on the residual signal.

In one aspect, automatic gain control may be performed on the residual signal. In this aspect, the UE or eNB may also apply a scaling factor to the residual signal based on at least one of the estimated channel or an energy difference between the received signal and the residual signal. Further, the UE or eNB may also determine that the residual signal and a signal associated with the estimated channel have similar (similar) transmitted primary synchronization signals and store information associated with the estimated channel and the detected timing, where the stored information may also include the detected primary synchronization signal.

Fig. 14 is a conceptual block diagram depicting the functionality of an exemplary apparatus 1400. Referring to fig. 14, a system 1400 may include a first UE, a first eNB, and any suitable number of additional enbs or UEs. Further, in operation of system 1400, a UE or eNB can reduce or eliminate interference.

Apparatus 1400 includes a module 1402, where module 1402 can estimate a channel from a received signal using one or more channel estimation schemes. Additionally, apparatus 1400 includes a module 1404 that module 1404 can remove the estimated channel from the received signal to generate a processed signal. The received signal may include components from multiple cells. The apparatus 1400 further includes a module 1406, and the module 1406 may detect a residual signal in the processed signal.

In one aspect, module 1402 may detect a primary synchronization signal in a received signal and use the primary synchronization signal to generate a channel estimate. In another aspect, module 1402 can detect for a secondary synchronization signal in a received signal and use the secondary synchronization signal to generate a channel estimate.

In another aspect, module 1402 can obtain a reference signal and use the reference signal to generate a channel estimate. In this regard, module 1402 may also detect a signal from a first cell, wherein the signal from the first cell includes reference signals having reference signal symbols, and may use the reference signal symbols to obtain an estimated channel. In this aspect, the reference signal symbols may be included in a reference signal spanning multiple subframes. In this aspect, the reference signal symbols may also be included in a reference signal in an MBSFN subframe or a blank subframe. In this regard, module 1402 may also detect the reference symbols directly using a single antenna system, or detect the primary and secondary synchronization signals using precoding vector control, or directly detect the reference symbols in a multi-antenna system.

In another aspect, module 1404 can decode a first cell physical broadcast channel and apply the decoded first cell physical broadcast channel to primary and secondary synchronization signals associated with the received signal. In this regard, module 1404 may also multiply the physical broadcast channel with a precoding vector to obtain a channel applied to the primary and secondary synchronization signals.

In one aspect, module 1406 can detect a residual signal in the processed signal. In another aspect, module 1406 can apply one or more false alarm reduction schemes. In this regard, the module 1406 may compare the received power of the reference signal to a threshold value. In this aspect, the threshold value may include at least one of: a defined threshold value, a threshold generated from the strongest detected cell, or a threshold generated from an average of a plurality of detected cells. In one aspect, the module 1406 can perform a cyclic redundancy check on the residual signal. In another aspect, the module 1406 can perform a cyclic redundancy check on the residual signal.

In one aspect, module 1406 can perform automatic gain control on the residual signal. In this regard, the module 1406 may apply a scaling factor to the residual signal based on at least one of the estimated channel or an energy difference between the received signal and the residual signal. In an aspect, it may be determined that the residual signal and a signal associated with the estimated channel have the same primary synchronization signal, and information associated with the estimated channel and the detected timing may be stored.

Referring to fig. 15, depicted is a system 1500 that can include a UE, a first eNB, and any suitable number of additional enbs or UEs. Further, in operation of system 1500, either the UE or the eNB can reduce or eliminate interference.

At reference numeral 1502, a UE or eNB may estimate a channel from a received one of the received signals using one or more channel estimation schemes. At reference numeral 1504, the UE or eNB may remove the estimated channel from the received signal to generate a processed signal. The received signal may include components from multiple cells. At reference numeral 1506, the UE or eNB may detect a residual signal in the processed signal. At reference numeral 1508, the UE or eNB may apply one or more false alarm reduction schemes. At reference numeral 1510, the UE or eNB may perform automatic gain control on the residual signal.

In an aspect, the UE or eNB may also detect a primary synchronization signal in the received signal and use the primary synchronization signal to generate a channel estimate. In another aspect, the UE or eNB may also detect for a secondary synchronization signal in the received signal and use the secondary synchronization signal to generate a channel estimate.

In another aspect, the UE or eNB may also obtain a reference signal and use the reference signal to generate a channel estimate. In this aspect, the UE or eNB detects signals from a first cell, where the signals from the first cell include reference signals having reference signal symbols, and uses the reference signal symbols to obtain an estimated channel. In this aspect, the reference signal symbols may be included in a reference signal spanning multiple subframes. In this aspect, the reference signal symbols may also be included in a reference signal in an MBSFN subframe or a blank subframe. In this aspect, the UE or eNB may also detect the reference symbols directly using a single antenna system, or detect the primary and secondary synchronization signals using precoding vector control, or directly detect the reference symbols in a multi-antenna system.

In another aspect, the UE or eNB may decode the first cell physical broadcast channel and apply the decoded first cell physical broadcast channel to primary and secondary synchronization signals associated with the received signal. In this regard, the UE or eNB may multiply the physical broadcast channel with a precoding vector to obtain a channel applied to the primary and secondary synchronization signals.

In an aspect, the UE or eNB may compare the received power of the reference signal to a threshold value. In this aspect, the threshold value may include at least one of: a specified threshold value, a threshold generated from the strongest detected cell, or a threshold generated from an average of a plurality of detected cells. In one aspect, one of the one or more false alarm reduction schemes may include: a cyclic redundancy check is performed on the residual signal. In another aspect, the UE or eNB may perform a cyclic redundancy check on the residual signal.

In an aspect, the UE or eNB may perform automatic gain control and apply a scaling factor to a residual signal based on at least one of an estimated channel or an energy difference between a received signal and the residual signal. In an aspect, it may be determined that the residual signal and a signal associated with the estimated channel have the same primary synchronization signal, and information associated with the estimated channel and the detected timing may be stored.

Fig. 16 is a conceptual block diagram depicting the functionality of an exemplary apparatus 1600. Referring to fig. 16, a system 1600 may include a first UE, a first eNB, and any suitable number of additional enbs or UEs. Further, in operation of system 1600, either the UE or the eNB may reduce or eliminate interference.

Apparatus 1600 includes a module 1602 that can estimate a channel from a received one of the received signals using one or more channel estimation schemes. Apparatus 1600 includes a module 1604 that may remove an estimated channel from a received signal to generate a processed signal. The received signal may include components from multiple cells. Apparatus 1600 includes a module 1606, and module 1606 may detect a residual signal in the processed signal. The apparatus 1600 includes a module 1608, which may apply one or more false alarm reduction schemes. The apparatus 1600 includes a module 1610, where the module 1610 may perform automatic gain control on the residual signal.

In an aspect, module 1602 can detect a primary synchronization signal in a received signal and use the primary synchronization signal to generate a channel estimate. In another aspect, module 1602 can detect a secondary synchronization signal in a received signal and use the secondary synchronization signal to generate a channel estimate.

In another aspect, module 1602 can obtain a reference signal and use the reference signal to generate a channel estimate. In this regard, module 1602 may also detect a signal from a first cell, where the signal from the first cell includes reference signals having reference signal symbols, and use the reference signal symbols to obtain an estimated channel. In this aspect, the reference signal symbols may be included in a reference signal spanning multiple subframes. In this aspect, the reference signal symbols may also be included in a reference signal in an MBSFN subframe or a blank subframe. In this regard, module 1602 can also detect the reference symbols directly using a single antenna system, or detect the primary and secondary synchronization signals using precoding vector control, or directly detect the reference symbols in a multi-antenna system.

In another aspect, module 1604 may decode a first cell physical broadcast channel and apply the decoded first cell physical broadcast channel to primary and secondary synchronization signals associated with the received signal. In this regard, module 1604 may also multiply the physical broadcast channel with a precoding vector to obtain a channel applied to the primary synchronization signal and the secondary synchronization signal.

In one aspect, module 1606 may detect a residual signal in the processed signal. In another aspect, module 1608 may apply one or more false alarm reduction schemes. In this regard, module 1608 may compare the received power of the reference signal to a threshold value. In this aspect, the threshold value may include at least one of: a defined threshold value, a threshold generated from the strongest detected cell, or a threshold generated from an average of a plurality of detected cells. In one aspect, module 1604 may perform a cyclic redundancy check on the residual signal. In another aspect, module 1604 may perform a cyclic redundancy check on the residual signal.

In one aspect, block 1610 may perform automatic gain control on the residual signal. In this regard, the module 1610 may apply a scaling factor to the residual signal based on at least one of an estimated channel or an energy difference between the received signal and the residual signal. In an aspect, it may be determined that the residual signal and a signal associated with the estimated channel have the same primary synchronization signal, and information associated with the estimated channel and the detected timing may be stored.

Referring to fig. 1-7, in one configuration, an apparatus 100 for wireless communication may comprise: means for estimating a channel from the received signal using one or more channel estimation schemes; means for removing component signals using the estimated channel from the received signal to generate a processed signal; means for detecting a residual signal in the processed signal. In one configuration, the means for estimating may further include: means for detecting a primary synchronization signal in the received signal; and means for generating a channel estimate using the primary synchronization signal. In one configuration, the means for estimating may further include: means for detecting a secondary synchronization signal in the received signal; and means for generating a channel estimate using the secondary synchronization signal. In another configuration, the means for estimating may further comprise: means for obtaining a reference signal; and means for generating a channel estimate using the reference signal.

In one configuration, the means for obtaining may further include: means for detecting a signal from a first cell, wherein the signal from the first cell comprises a reference signal having reference signal symbols; and means for obtaining an estimated channel using the reference signal symbols. In this configuration, the reference signal symbols may be included in a reference signal that spans multiple subframes. Alternatively, the reference signal symbols may be included in a reference signal in an MBSFN subframe or a blank subframe. In one configuration, the means for obtaining an estimated channel using reference signal symbols further comprises: means for estimating a channel from the reference symbols in a single antenna system; and means for combining with at least one of the channel estimates from the primary synchronization signal or the secondary synchronization signal. In another configuration, the means for obtaining the estimated channel using the reference signal symbols further comprises: means for estimating a channel from the reference symbols in a multi-antenna system; and means for combining with at least one of channel estimation from the primary signal or the secondary signal using precoding vector control. In this configuration, it may further include: means for linking a precoding vector used in the primary synchronization signal and the secondary synchronization signal with a cell ID and a system frame number.

In one configuration, apparatus 100 includes means for estimating a channel from a received signal using one or more channel estimation schemes, which may include means for decoding a first cell physical broadcast channel, and means for applying the decoded first cell physical broadcast channel to a primary synchronization signal and a secondary synchronization signal associated with the received signal. In this configuration, the means for applying may further include: means for multiplying the physical broadcast channel with a precoding vector to obtain a channel applied to a primary synchronization signal and a secondary synchronization signal. In this configuration, it may further include: means for linking a precoding vector used in the primary synchronization signal and the secondary synchronization signal with a cell ID and a system frame number. In one configuration, the apparatus 100 includes means for detecting, which may further include: means for applying one or more false alarm reduction schemes. In this configuration, the means for applying one of the one or more false alarm reduction schemes may comprise: means for comparing the received power of the residual signal to a threshold value. In this configuration, the threshold value may include at least one of: a defined threshold value, a threshold generated from the strongest detected cell, or a threshold generated from an average of a plurality of detected cells. In one configuration, the apparatus 100 includes means for applying one of the one or more false alarm reduction schemes, which may include: means for performing a cyclic redundancy check on the detected signal. In another configuration, the apparatus 100 includes means for applying one of the one or more false alarm reduction schemes, which may include: means for determining that a reference signal received power is above a threshold for a residual signal; and means for decoding a physical broadcast channel based on the residual signal.

In one configuration, the apparatus 100 comprises: means for performing automatic gain control on the residual signal. In this configuration, the means for performing automatic gain control may further include: means for applying a scaling factor to a residual signal based on at least one of the estimated channel or an energy difference between the received signal and the residual signal.

In one configuration, the apparatus 100 comprises: means for determining that the residual signal and a signal associated with the estimated channel have similar transmitted primary synchronization signals; and means for storing information associated with the estimated channel and the detected timing, wherein the stored information may further include the detected primary synchronization signal.

The aforementioned means is the processing system 114 configured to perform the functions described by the aforementioned means. As described supra, the processing system 114 includes the TX processor 716, the RX processor 770, and the controller/processor 775. As such, in one configuration, the aforementioned means may be the TX processor 716, the RX processor 770, and the controller/processor 775 configured to perform the functions described by the aforementioned means.

It is to be understood that the specific order or hierarchy of steps in the methods disclosed are merely illustrative of exemplary approaches. It should be understood that the specific order or hierarchy of steps in the processes may be rearranged according to design preferences. 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.

The above detailed description is provided to enable any person of ordinary skill 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 present invention is not limited to the aspects shown herein, but is to be accorded the full scope consistent with the claims so described, 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. The term "some" refers to one or more unless specifically stated otherwise. 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. Furthermore, nothing disclosed in this application is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. Furthermore, no element of any claim should be construed in accordance with clause 6 of U.S. patent Law 112, unless the element is explicitly recited in the language of a "functional module" or in a method claim, the element is recited in the language of a "functional step".

Claims (46)

1. A method of wireless communication, comprising:

estimating a channel from the received signal using one or more channel estimation schemes;

removing component signals using the estimated channel from the received signal to generate a processed signal; and

detecting a residual signal in the processed signal, the detecting comprising applying one or more false alarm reduction schemes, wherein one of the one or more false alarm reduction schemes comprises:

determining a threshold for a reference signal received power above the residual signal; and

in response to determining that the reference signal received power is above the threshold for the residual signal, decoding a physical broadcast channel based on the residual signal.

2. The method of claim 1, wherein the received signal comprises components from a plurality of cells.

3. The method of claim 1, wherein one of the one or more estimation schemes comprises:

detecting a primary synchronization signal in the received signal; and

generating a channel estimate using the primary synchronization signal.

4. The method of claim 1, wherein one of the one or more estimation schemes comprises:

obtaining a reference signal; and

generating a channel estimate using the reference signal.

5. The method of claim 4, wherein the obtaining further comprises:

detecting a signal from a first cell, wherein the signal from the first cell comprises the reference signal having reference signal symbols; and

obtaining an estimated channel using the reference signal symbols.

6. The method of claim 5, wherein the reference signal symbols are included in a reference signal spanning multiple subframes.

7. The method of claim 5, wherein the reference signal symbols are included in a reference signal in a Multimedia Broadcast Single Frequency Network (MBSFN) subframe or a blank subframe.

8. The method of claim 5, wherein obtaining the estimated channel using the reference signal symbols further comprises:

estimating the channel from the reference signal symbols in a single antenna system, an

Combined with at least one of the channel estimates from the primary or secondary synchronization signals.

9. The method of claim 5, wherein obtaining the estimated channel using the reference signal symbols further comprises:

estimating the channel from the reference signal symbols in a multi-antenna system, an

Precoding vector control is used to combine with at least one of channel estimation from the primary synchronization signal or the secondary synchronization signal.

10. The method of claim 9, further comprising:

linking precoding vectors used in the primary synchronization signal and the secondary synchronization signal with a cell ID and a system frame number.

11. The method of claim 1, wherein one of the one or more channel estimation schemes comprises:

decoding a first cell physical broadcast channel; and

the decoded first cell physical broadcast channel is applied to a primary synchronization signal and a secondary synchronization signal associated with the received signal.

12. The method of claim 11, wherein the applying further comprises:

multiplying the physical broadcast channel with a precoding vector to obtain a channel applied to the primary synchronization signal and the secondary synchronization signal.

13. The method of claim 11, further comprising:

linking precoding vectors used in the primary synchronization signal and the secondary synchronization signal with a cell ID and a system frame number.

14. The method of claim 1, wherein one of the one or more false alarm reduction schemes comprises: comparing the received power of the residual signal to a threshold value.

15. The method of claim 14, wherein the threshold value comprises at least one of:

a specified threshold value;

a threshold is generated according to the detected strongest cell; or

A threshold generated from an average of a plurality of detected cells.

16. The method of claim 1, wherein one of the one or more false alarm reduction schemes comprises: a cyclic redundancy check is performed on the detected signal.

17. The method of claim 1, further comprising:

performing automatic gain control on the residual signal.

18. The method of claim 17, wherein the automatic gain control further comprises applying a scaling factor to the residual signal based on at least one of:

an estimated channel; or

An energy difference between the received signal and the residual signal.

19. The method of claim 1, further comprising:

determining that the residual signal and a signal associated with the estimated channel have the same transmitted primary synchronization signal; and

storing information associated with the estimated channel and the detected timing, wherein the stored information further includes the detected primary synchronization signal.

20. An apparatus for wireless communication, comprising:

means for estimating a channel from the received signal using one or more channel estimation schemes;

means for removing a component signal using the estimated channel from the received signal to generate a processed signal; and

means for detecting a residual signal in the processed signal,

wherein the means for detecting comprises means for applying one or more false alarm reduction schemes,

wherein one of the one or more false alarm reduction schemes comprises:

determining a threshold for a reference signal received power above the residual signal; and

in response to determining that the reference signal received power is above the threshold for the residual signal, decoding a physical broadcast channel based on the residual signal.

21. The apparatus of claim 20, wherein the received signal comprises components from multiple cells.

22. The apparatus of claim 20, wherein one of the one or more estimation schemes comprises:

means for detecting a primary synchronization signal in the received signal; and

means for generating a channel estimate using the primary synchronization signal.

23. The apparatus of claim 20, wherein one of the one or more estimation schemes comprises:

means for obtaining a reference signal; and

means for generating a channel estimate using the reference signal.

24. The apparatus of claim 23, wherein the means for obtaining further comprises:

means for detecting a signal from a first cell, wherein the signal from the first cell comprises the reference signal having reference signal symbols; and

means for obtaining an estimated channel using the reference signal symbols.

25. The apparatus of claim 24, wherein the reference signal symbols are included in a reference signal spanning multiple subframes.

26. The apparatus of claim 24, wherein the reference signal symbols are included in a reference signal in a Multimedia Broadcast Single Frequency Network (MBSFN) subframe or a blank subframe.

27. The apparatus of claim 24, wherein the means for using the reference signal symbols to obtain the estimated channel further comprises:

means for estimating the channel from the reference signal symbols in a single antenna system, an

Means for combining with at least one of a channel estimate from a primary synchronization signal or a secondary synchronization signal.

28. The apparatus of claim 24, wherein the means for using the reference signal symbols to obtain the estimated channel further comprises:

means for estimating the channel from the reference signal symbols in a multi-antenna system, an

Means for combining with at least one of channel estimation from a primary synchronization signal or a secondary synchronization signal using precoding vector control.

29. The apparatus of claim 28, further comprising:

means for linking a precoding vector used in the primary synchronization signal and the secondary synchronization signal with a cell ID and a system frame number.

30. The apparatus of claim 20, wherein the means for estimating a channel from the received signal using one or more channel estimation schemes comprises:

means for decoding a first cell physical broadcast channel;

means for applying the decoded first cell physical broadcast channel to a primary synchronization signal and a secondary synchronization signal associated with the received signal.

31. The apparatus of claim 30, wherein the means for applying further comprises:

means for multiplying the physical broadcast channel with a precoding vector to obtain a channel applied to the primary synchronization signal and the secondary synchronization signal.

32. The apparatus of claim 30, further comprising:

means for linking a precoding vector used in the primary synchronization signal and the secondary synchronization signal with a cell ID and a system frame number.

33. The apparatus of claim 20, wherein the means for applying one of the one or more false alarm reduction schemes further comprises: means for comparing a received power of the residual signal to a threshold value.

34. The apparatus of claim 33, wherein the threshold value comprises at least one of:

a specified threshold value;

a threshold is generated according to the detected strongest cell; or

A threshold generated from an average of a plurality of detected cells.

35. The apparatus of claim 20, wherein the means for applying one of the one or more false alarm reduction schemes further comprises:

means for performing a cyclic redundancy check on the detected signal.

36. The apparatus of claim 20, wherein the means for applying one of the one or more false alarm reduction schemes further comprises:

means for determining that a reference signal received power is above the residual signal threshold; and

means for decoding a physical broadcast channel based on the residual signal.

37. The apparatus of claim 20, further comprising:

means for performing automatic gain control on the residual signal.

38. The apparatus of claim 37, wherein the means for performing automatic gain control further comprises: means for applying a scaling factor to the residual signal based on at least one of:

an estimated channel; or

An energy difference between the received signal and the residual signal.

39. The apparatus of claim 20, further comprising:

means for determining that the residual signal and a signal associated with the estimated channel have the same transmitted primary synchronization signal; and

means for storing information associated with the estimated channel and the detected timing, wherein the stored information further includes the detected primary synchronization signal.

40. An apparatus for wireless communication, comprising:

at least one processor; and

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

estimating a channel from the received signal using one or more channel estimation schemes;

removing component signals using the estimated channel from the received signal to generate a processed signal;

detecting a residual signal in the processed signal; and

one or more false alarm reduction schemes are applied,

wherein to apply one of the one or more false alarm reduction schemes, the at least one processor is further configured to:

determining a threshold for a reference signal received power above the residual signal; and

in response to determining that the reference signal received power is above the threshold for the residual signal, decoding a physical broadcast channel based on the residual signal.

41. The apparatus of claim 40, wherein the received signal comprises components from multiple cells.

42. The apparatus of claim 40, wherein to estimate a channel from the received signal using one or more channel estimation schemes, the at least one processor is further configured to:

detecting a primary synchronization signal in the received signal; and

generating a channel estimate using the primary synchronization signal.

43. The apparatus of claim 40, wherein to estimate a channel from the received signal using one or more channel estimation schemes, the at least one processor is further configured to:

decoding a first cell physical broadcast channel; and

the decoded first cell physical broadcast channel is applied to a primary synchronization signal and a secondary synchronization signal associated with the received signal.

44. The apparatus of claim 40, wherein to apply one of one or more false alarm reduction schemes, the at least one processor is further configured to:

comparing the received power of the residual signal to a threshold value.

45. The apparatus of claim 40, wherein the at least one processor is further configured to:

performing automatic gain control on the residual signal.

46. The apparatus of claim 40, wherein the at least one processor is further configured to:

determining that the residual signal and a signal associated with the estimated channel have the same transmitted primary synchronization signal; and

storing information associated with the estimated channel and the detected timing, wherein the stored information further includes the detected primary synchronization signal.