Abstract:
To support very high QAM rates, a user equipment (UE) needs extremely good signal-to-noise ratio (SNR). Using a receiver configuration that improves SNR comes at the expense of higher power consumption. However, consuming higher power to support very high QAM rates when poor channel conditions are present is a waste of power. By correlating the modulation and coding scheme used by the UE with the UE channel quality estimate, the UE can modify the receiver configuration to improve SNR only when channel conditions support very high QAM rates.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of U.S. Provisional Application Ser. No. 61/884,869, entitled “DYNAMIC SNR ADJUSTMENT IN A RECEIVER SUPPORTING 256QAM” and filed on Sep. 30, 2013, which is expressly incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates generally to communication systems, and more particularly, to determining an opportunistic time to change a user equipment (UE) mode of operation from a low signal-to-noise ratio (SNR)-low current mode to a high SNR-high current mode. 
     2. Background 
     Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies 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 technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards 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 exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies. 
     SUMMARY 
     In an aspect of the disclosure, a method, a computer program product, and an apparatus are provided. The apparatus determines to change a mode of operation from a first signal-to-noise ratio (SNR) mode to an increased SNR mode, sends channel quality information (CQI) to a base station indicating an ability to receive data at the increased SNR, and receives the data from the base station according to a higher order modulation and coding scheme (MCS) corresponding to the increased SNR when the base station is capable of providing the data at the higher order MCS. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating an example of a network architecture. 
         FIG. 2  is a diagram illustrating an example of an access network. 
         FIG. 3  is a diagram illustrating an example of a DL frame structure in LTE. 
         FIG. 4  is a diagram illustrating an example of an UL frame structure in LTE. 
         FIG. 5  is a diagram illustrating an example of a radio protocol architecture for the user and control planes. 
         FIG. 6  is a diagram illustrating an example of an evolved Node B and user equipment in an access network. 
         FIG. 7  is a diagram illustrating a range expanded cellular region in a heterogeneous network. 
         FIG. 8A  is a diagram illustrating a relationship between RF power at an antenna port and SNR (or carrier-to-noise ratio (C/N)) for different orders of modulation and coding schemes (MCSs). 
         FIG. 8B  is a diagram illustrating an example of a gain lineup for a UE. 
         FIG. 9  is a diagram illustrating communication between a UE and base station for determining a modulation and coding scheme. 
         FIG. 10  is a diagram illustrating timeslots for receiving data. 
         FIG. 11  is a flow chart of a method of wireless communication. 
         FIG. 12  is a conceptual data flow diagram illustrating the data flow between different modules/means/components in an exemplary apparatus. 
         FIG. 13  is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system. 
     
    
    
     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. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts. 
     Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “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. 
     By way of 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 processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. 
     Accordingly, in one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise a random-access memory (RAM), a read-only memory (ROM), an electrically erasable programmable ROM (EEPROM), compact disk ROM (CD-ROM) or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes CD, laser disc, optical disc, digital versatile disc (DVD), and floppy disk where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. 
       FIG. 1  is a diagram illustrating an LTE network architecture  100 . The LTE network architecture  100  may be referred to as an Evolved Packet System (EPS)  100 . The EPS  100  may include one or more user equipment (UE)  102 , an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)  104 , an Evolved Packet Core (EPC)  110 , a Home Subscriber Server (HSS)  120 , and an Operator&#39;s Internet Protocol (IP) Services  122 . The EPS can interconnect with other access networks, but for simplicity those entities/interfaces are not shown. As shown, the EPS provides packet-switched services, however, as those skilled in the art will readily appreciate, the various concepts presented throughout this disclosure may be extended to networks providing circuit-switched services. 
     The E-UTRAN includes the evolved Node B (eNB)  106  and other eNBs  108 . The eNB  106  provides user and control planes protocol terminations toward the UE  102 . The eNB  106  may be connected to the other eNBs  108  via a backhaul (e.g., an X2 interface). The eNB  106  may also be referred to as a base station, a Node B, an access point, a base transceiver station, 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. The eNB  106  provides an access point to the EPC  110  for a UE  102 . Examples of UEs  102  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, a tablet, or any other similar functioning device. The UE  102  may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. 
     The eNB  106  is connected to the EPC  110 . The EPC  110  may include a Mobility Management Entity (MME)  112 , other MMEs  114 , a Serving Gateway  116 , a Multimedia Broadcast Multicast Service (MBMS) Gateway  124 , a Broadcast Multicast Service Center (BM-SC)  126 , and a Packet Data Network (PDN) Gateway  118 . The MME  112  is the control node that processes the signaling between the UE  102  and the EPC  110 . Generally, the MME  112  provides bearer and connection management. All user IP packets are transferred through the Serving Gateway  116 , which itself is connected to the PDN Gateway  118 . The PDN Gateway  118  provides UE IP address allocation as well as other functions. The PDN Gateway  118  is connected to the Operator&#39;s IP Services  122 . The Operator&#39;s IP Services  122  may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), and a PS Streaming Service (PSS). The BM-SC  126  may provide functions for MBMS user service provisioning and delivery. The BM-SC  126  may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a PLMN, and may be used to schedule and deliver MBMS transmissions. The MBMS Gateway  124  may be used to distribute MBMS traffic to the eNBs (e.g.,  106 ,  108 ) belonging to a Multicast Broadcast Single Frequency Network (MBSFN) area broadcasting a particular service, and may be responsible for session management (start/stop) and for collecting eMBMS related charging information. 
       FIG. 2  is a diagram illustrating an example of an access network  200  in an LTE network architecture. In this example, the access network  200  is divided into a number of cellular regions (cells)  202 . One or more lower power class eNBs  208  may have cellular regions  210  that overlap with one or more of the cells  202 . The lower power class eNB  208  may be a femto cell (e.g., home eNB (HeNB)), pico cell, micro cell, or remote radio head (RRH). The macro eNBs  204  are each assigned to a respective cell  202  and are configured to provide an access point to the EPC  110  for all the UEs  206  in the cells  202 . There is no centralized controller in this example of an access network  200 , but a centralized controller may be used in alternative configurations. The eNBs  204  are responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to the serving gateway  116 . An eNB may support one or multiple (e.g., three) cells (also referred to as a sector). The term “cell” can refer to the smallest coverage area of an eNB and/or an eNB subsystem serving are particular coverage area. Further, the terms “eNB,” “base station,” and “cell” may be used interchangeably herein. 
     The modulation and multiple access scheme employed by the access network  200  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 both frequency division duplex (FDD) and time division duplex (TDD). As those skilled in the art will readily appreciate from the detailed description to follow, the various concepts presented herein are well suited for LTE applications. However, these concepts may be readily extended to other telecommunication standards employing other modulation and multiple access techniques. By way of example, these concepts may be extended to Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interface standards promulgated by the 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations. These concepts may also be extended to Universal Terrestrial Radio Access (UTRA) employing Wideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA; Global System for Mobile Communications (GSM) employing TDMA; and Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Flash-OFDM employing 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 the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system. 
     The eNBs  204  may have multiple antennas supporting MIMO technology. The use of MIMO technology enables the eNBs  204  to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing may be used to transmit different streams of data simultaneously on the same frequency. The data streams may be transmitted to a single UE  206  to increase the data rate or to multiple UEs  206  to increase the overall system capacity. This is achieved by spatially precoding each data stream (i.e., applying a scaling of an amplitude and a phase) and then transmitting each spatially precoded stream through multiple transmit antennas on the DL. The spatially precoded data streams arrive at the UE(s)  206  with different spatial signatures, which enables each of the UE(s)  206  to recover the one or more data streams destined for that UE  206 . On the UL, each UE  206  transmits a spatially precoded data stream, which enables the eNB  204  to identify the source of each spatially precoded data stream. 
     Spatial multiplexing is generally used when channel conditions are good. When channel conditions are less favorable, beamforming may be used to focus the transmission energy in one or more directions. This may be achieved by spatially precoding the data for transmission through multiple antennas. To achieve good coverage at the edges of the cell, a single stream beamforming transmission may be used in combination with transmit diversity. 
     In the detailed description that follows, various aspects of an access network will be described with reference to a MIMO system supporting OFDM on the DL. OFDM is a spread-spectrum technique that modulates data over a number of subcarriers within an OFDM symbol. The subcarriers are spaced apart at precise frequencies. The spacing provides “orthogonality” that enables a 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 combat inter-OFDM-symbol interference. The UL may use SC-FDMA in the form of a DFT-spread OFDM signal to compensate for high peak-to-average power ratio (PAPR). 
       FIG. 3  is a diagram  300  illustrating an example of a DL frame structure in LTE. A frame (10 ms) may be divided into 10 equally sized subframes. Each subframe may include two consecutive time slots. A resource grid may be used to represent two time slots, each time slot including a resource block. The resource grid is divided into multiple resource elements. In LTE, a resource block contains 12 consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, 7 consecutive OFDM symbols in the time domain, or 84 resource elements. For an extended cyclic prefix, a resource block contains 6 consecutive OFDM symbols in the time domain and has 72 resource elements. Some of the resource elements, indicated as R  302 ,  304 , include DL reference signals (DL-RS). The DL-RS include Cell-specific RS (CRS) (also sometimes called common RS)  302  and UE-specific RS (UE-RS)  304 . UE-RS  304  are transmitted only on the resource blocks upon which the corresponding physical DL shared channel (PDSCH) is mapped. The number of bits carried by each resource element depends on the modulation scheme. Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate for the UE. 
       FIG. 4  is a diagram  400  illustrating an example of an UL frame structure in LTE. The available resource blocks for the UL may be partitioned into a data section and a control section. The control section may be formed at the two edges of the system bandwidth and may have a configurable size. The resource blocks in the control section may be assigned to UEs for transmission of control information. The data section may include all resource blocks not included in the control section. The UL frame structure results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all of the contiguous subcarriers in the data section. 
     A UE may be assigned resource blocks  410   a ,  410   b  in the control section to transmit control information to an eNB. The UE may also be assigned resource blocks  420   a ,  420   b  in the data section to transmit data to the eNB. The UE may transmit control information in a physical UL control channel (PUCCH) on the assigned resource blocks in the control section. The UE may transmit only data or both data and control information in a physical UL shared channel (PUSCH) on the assigned resource blocks in the data section. A UL transmission may span both slots of a subframe and may hop across frequency. 
     A set of resource blocks may be used to perform initial system access and achieve UL synchronization in a physical random access channel (PRACH)  430 . The PRACH  430  carries a random sequence and 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 restricted to certain time and frequency resources. There is no frequency hopping for the PRACH. The PRACH attempt is carried in a single subframe (1 ms) or in a sequence of few contiguous subframes and a UE can make only a single PRACH attempt per frame (10 ms). 
       FIG. 5  is a diagram  500  illustrating an example of a radio protocol architecture for the user and control planes in LTE. The radio protocol architecture for the UE and the eNB is shown with three layers: Layer 1, Layer 2, and Layer 3. Layer 1 (L1 layer) is the lowest layer and implements various physical layer signal processing functions. The L1 layer will be referred to herein as the physical layer  506 . Layer 2 (L2 layer)  508  is above the physical layer  506  and is responsible for the link between the UE and eNB over the physical layer  506 . 
     In the user plane, the L2 layer  508  includes a media access control (MAC) sublayer  510 , a radio link control (RLC) sublayer  512 , and a packet data convergence protocol (PDCP)  514  sublayer, which are terminated at the eNB on the network side. Although not shown, the UE may have several upper layers above the L2 layer  508  including a network layer (e.g., IP layer) that is terminated at the PDN gateway  118  on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc.). 
     The PDCP sublayer  514  provides multiplexing between different radio bearers and logical channels. The PDCP sublayer  514  also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between eNBs. The RLC sublayer  512  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  510  provides multiplexing between logical and transport channels. The MAC sublayer  510  is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer  510  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  506  and the L2 layer  508  with the exception that there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC) sublayer  516  in Layer 3 (L3 layer). The RRC sublayer  516  is responsible for obtaining radio resources (e.g., radio bearers) and for configuring the lower layers using RRC signaling between the eNB and the UE. 
       FIG. 6  is a block diagram of an eNB  610  in communication with a UE  650  in an access network. In the DL, upper layer packets from the core network are provided to a controller/processor  675 . The controller/processor  675  implements the functionality of the L2 layer. In the DL, the controller/processor  675  provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE  650  based on various priority metrics. The controller/processor  675  is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE  650 . 
     The transmit (TX) processor  616  implements various signal processing functions for the L1 layer (i.e., physical layer). The signal processing functions include coding and interleaving to facilitate forward error correction (FEC) at the UE  650  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 produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator  674  may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE  650 . Each spatial stream may then be provided to a different antenna  620  via a separate transmitter  618 TX. Each transmitter  618 TX may modulate an RF carrier with a respective spatial stream for transmission. 
     At the UE  650 , each receiver  654 RX receives a signal through its respective antenna  652 . Each receiver  654 RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor  656 . The RX processor  656  implements various signal processing functions of the L1 layer. The RX processor  656  may perform spatial processing on the information to recover any spatial streams destined for the UE  650 . If multiple spatial streams are destined for the UE  650 , they may be combined by the RX processor  656  into a single OFDM symbol stream. The RX processor  656  then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB  610 . These soft decisions may be based on channel estimates computed by the channel estimator  658 . The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB  610  on the physical channel. The data and control signals are then provided to the controller/processor  659 . 
     The controller/processor  659  implements the L2 layer. The controller/processor can be associated with a memory  660  that stores program codes and data. The memory  660  may be referred to as a computer-readable medium. In the UL, the controller/processor  659  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  662 , which represents all the protocol layers above the L2 layer. Various control signals may also be provided to the data sink  662  for L3 processing. The controller/processor  659  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  667  is used to provide upper layer packets to the controller/processor  659 . The data source  667  represents all protocol layers above the L2 layer. Similar to the functionality described in connection with the DL transmission by the eNB  610 , the controller/processor  659  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  610 . The controller/processor  659  is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB  610 . 
     Channel estimates derived by a channel estimator  658  from a reference signal or feedback transmitted by the eNB  610  may be used by the TX processor  668  to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor  668  may be provided to different antenna  652  via separate transmitters  654 TX. Each transmitter  654 TX may modulate an RF carrier with a respective spatial stream for transmission. 
     The UL transmission is processed at the eNB  610  in a manner similar to that described in connection with the receiver function at the UE  650 . Each receiver  618 RX receives a signal through its respective antenna  620 . Each receiver  618 RX recovers information modulated onto an RF carrier and provides the information to a RX processor  670 . The RX processor  670  may implement the L1 layer. 
     The controller/processor  675  implements the L2 layer. The controller/processor  675  can be associated with a memory  676  that stores program codes and data. The memory  676  may be referred to as a computer-readable medium. In the UL, the control/processor  675  provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE  650 . Upper layer packets from the controller/processor  675  may be provided to the core network. The controller/processor  675  is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations. 
       FIG. 7  is a diagram  700  illustrating a range expanded cellular region in a heterogeneous network. A lower power class eNB such as the RRH  710   b  may have a range expanded cellular region  703  that is expanded from the cellular region  702  through enhanced inter-cell interference coordination between the RRH  710   b  and the macro eNB  710   a  and through interference cancelation performed by the UE  720 . In enhanced inter-cell interference coordination, the RRH  710   b  receives information from the macro eNB  710   a  regarding an interference condition of the UE  720 . The information allows the RRH  710   b  to serve the UE  720  in the range expanded cellular region  703  and to accept a handoff of the UE  720  from the macro eNB  710   a  as the UE  720  enters the range expanded cellular region  703 . 
     In an aspect, the present disclosure is related to 256-quadrature amplitude modulation (QAM). A signal-to-noise ratio (SNR) requirement for supporting 256-QAM may be extremely high and may require a UE to consume a large amount of current. Accordingly, the present disclosure provides a method that facilitates the UE to opportunistically determine when to toggle between a low SNR-low current mode and a high SNR-high current mode. 
       FIG. 8A  is a diagram  800  illustrating a relationship between RF power at an antenna port and SNR (or carrier-to-noise ratio (C/N)) for different orders of modulation and coding schemes (MCSs). For particular MCSs (e.g., QPSK, 16-QAM, and 64-QAM), the SNR (C/N) may decrease over certain RF power values (“C/N dip”  802 ). To receive data at higher order MCSs (e.g., 16-QAM or 64-QAM) at a radio receiver, a higher SNR (C/N) is desired. A default UE SNR is sufficient to support 64-QAM. However, such default UE SNR is not sufficient to support 256-QAM. Compared to 64-QAM, to see a measurable throughput gain using 256-QAM, a significant change in receiver configuration is needed at the expense of higher power consumption. As shown in  FIG. 8A , the C/N dip  802  may be eliminated by changing a gain state to support 256-QAM. 
       FIG. 8B  is a diagram  850  illustrating an example of a gain lineup for a UE. For example, when the UE is near a base station, the UE may receive a signal at a high strength. Therefore, the UE may not require high gain output at a low noise amplifier (LNA), and the UE may operate at a low gain LNA, low current state. If the UE is at a cell edge, the UE may receive a very weak signal. Hence, the UE may consume a large amount of current to amplify the signal before digitizing the signal at an analog-to-digital converter (ADC). Hence, the UE consumes more current when the UE is at the cell edge. 
     Different gain states are needed depending on the received signal power at the UE. When a gain state is changed, a noise figure (NF) changes. For example, if 40 dB SNR is desired, a low NF may not be achieved simultaneously. Thus, the UE is forced to operate the LNA at a state that produces a low NF. However, gain may need to be lowered. For example, if the LNA is operated at a high gain mode, too many signals may be received, thus compressing the ADC. Accordingly, what is needed is for the UE to operate at a low gain and low NF at the same time. This may be accomplished by consuming more current, operating the LNA at a high gain state, and cutting the gain at a base band amplifier (BB) located after a mixer (see  FIG. 8B ). In this way, an overall NF and an overall gain are lowered. 
     Referring to  FIG. 8B , at an initial gain state G0, an overall gain output is 50 dB. At gain state G1, the UE may be near the base station, and therefore, 50 dB gain is unnecessary. For example, 25 dB gain may be sufficient. At 25 dB overall gain, LNA gain is −5 dB, BB gain is 30 dB, and NF is 20 dB (higher than NF at gain state G0). Notably, 20 dB NF may be sufficient for 64-QAM but is too high for 256-QAM. At gain state G1 (256-QAM), the UE achieves an overall gain of 25 dB by operating the LNA at 15 dB gain but reducing the BB gain to 10 dB. This allows an NF of 4 dB, which is sufficient for receiving data at 256-QAM. 
       FIG. 9  is a diagram  900  illustrating communication between a UE  902  and a base station (or eNB)  904  for determining a modulation and coding scheme.  FIG. 10  is a diagram  1000  illustrating timeslots for receiving data. 
     In an example, a UE  902  desiring to download a data file (e.g., movie file) may be unaware of a file size. A base station buffer  906  holding the data file along with other data for other UEs is aware of the file size. The base station buffer  906  desirably wishes to send the data file as soon as possible but cannot because of limited bandwidth. Accordingly, the base station  904  schedules to send the data on timeslots (see  FIG. 10 ). 
     An amount of data the base station  904  can deliver to the UE  902  may depend on the SNR (C/N) of the UE  902  at any given time in a network. Each UE  902  in the network may have a different SNR (C/N) at any given time. The base station  904  knows the amount of data (e.g., transport block size) to schedule for the UE  902  per timeslot based on the UE&#39;s channel quality information (CQI) feedback  908 . The CQI feedback  908  may include an estimate of the SNR (C/N) measured by the UE  902 . In each timeslot, the base station  904  may assign a bandwidth and MCS  910  associated with the data to be sent to the UE  902 . 
     In an aspect, each time the UE  902  decodes a timeslot, the UE  902  determines the SNR (C/N) at that given time. The UE  902  may feed the SNR (C/N)  908  back to the base station  904 . Based on the feedback, the base station  904  decides how much data (the transport block size) to send to the UE and what MCS to apply to the data. 
     Each timeslot, the amount of data that is received by the UE  902  according to different MCSs may change. The data amount may be a function of what the UE  902  is willing to accept or how much data other UEs in the network are receiving. 
     In an aspect of the disclosure, the amount of data received by the UE (gain state) may not be a function of received power but a function of the MCS used at the time. Referring to  FIG. 10 , if the UE receives data at an initial MCS (e.g., QPSK or 64-QAM) for n number of slots  1002 , then there is a high probability that the UE will be receiving data at the initial MCS for the next several slots. Accordingly, the UE may indicate to the base station that the UE is capable of receiving at a higher SNR (C/N), e.g., approximately 40 dB, which prompts the base station to schedule the data at the higher order MCS (e.g., 256-QAM)  1004 . This allows the UE to receive the data in a lesser number of timeslots. For example, at a next CQI feedback opportunity, the UE may change a gain state and operate at a high current mode to maximize SNR. The UE may then send CQI feedback (SNR (C/N) feedback) indicating that the UE is capable of receiving data at the higher SNR (C/N), and begin receiving the data at the higher order MCS ( 1004 ). Alternatively, if the UE does not receive any data, or continues to receive data at the initial MCS (e.g., QPSK or 64-QAM) after sending the CQI feedback indicating the higher SNR (C/N), then the UE may determine that the base station is not capable of providing data at the higher order MCS and revert back to a low SNR mode, low current mode. 
     In an aspect, the UE may shift to a high SNR mode (high current mode) by moving a gain state from G1 to G1 (256-QAM), as shown in  FIG. 8B . This allows for a low noise figure (NF) simultaneously with a low gain, and is achieved by a fixed high-gain low noise amplifier (LNA) state and a post-mixer adjustable-gain base band amplifier state. Referring to  FIG. 8A , the UE may further shift to the high SNR mode (high current mode) by increasing a voltage-controlled oscillator (VCO)/phase-locked loop (PLL) current, invoking real-time residual side band (RSB) calibration, and/or bypassing front-end lossy components (e.g., filters). 
       FIG. 11  is a flow chart  1100  of a method of wireless communication. The method may be performed by a UE. At step  1102 , the UE determines to change a mode of operation from a first signal-to-noise ratio (SNR) mode to an increased SNR mode. 
     In an aspect, the UE may determine to change the mode of operation by first obtaining a downlink SNR measurement and thereafter changing the mode of operation to the increased SNR mode based on the downlink SNR measurement. In another aspect, the UE may determine to change the mode of operation by first receiving signaling from a base station indicating the UE to use at least one CQI value corresponding to a higher order modulation and coding scheme (MCS) and thereafter changing the mode of operation to the increased SNR mode based on the received signaling. 
     In a further aspect, the UE may determine to change the mode of operation by first receiving data from the base station according to a first MCS while operating at the first SNR mode. Thereafter, if the UE continues to receive the data according to the first MCS for a number of consecutive timeslots, the UE may determine that there is a high likelihood that additional data exists in a base station buffer waiting to be scheduled for transmission. Accordingly, the UE changes the mode of operation to the increased SNR mode to receive the additional data at the higher order MCS. In an example, the first MCS may be 64-quadrature amplitude modulation (QAM) while the higher order MCS may be 256-QAM. In another example, the first MCS may be quadrature phase-shift keying (QPSK) while the higher order MCS may be 16-QAM or 64-QAM. 
     In an aspect, the UE may change the mode of operation to the increased SNR mode by: 1) moving a gain state such that a low noise figure (NF) and a low gain are achieved simultaneously by a fixed high-gain low noise amplifier (LNA) state and a post-mixer adjustable-gain base band amplifier state; 2) increasing a voltage-controlled oscillator (VCO)/phase-locked loop (PLL) current; 3) invoking real-time residual side band (RSB) calibration; and/or 4) bypassing front-end lossy components (e.g., filters). In a further aspect, the UE may receive signaling from the base station via multi-carrier downlink signaling in a network configuration where base station downlink signals are: 1) co-located or not co-located; and/or 2) time-aligned or not time-aligned. 
     At step  1104 , the UE sends channel quality information (CQI) to the base station indicating an ability to receive data at the increased SNR. At step  1106 , the UE receives the data from the base station according to the higher order MCS corresponding to the increased SNR when the base station is capable of providing the data at the higher order MCS. At step  1108 , the UE may determine that the base station has completed providing the data at the higher order MCS. Accordingly, the UE may proceed to step  1114  and revert the mode of operation back to the first SNR mode. 
     Alternatively, at step  1110 , the UE may continue to receive the data according to the first MCS, or fail to receive any data, after sending the CQI indicating the ability to receive the data at the increased SNR. As such, at step  1112 , the UE may determine that the base station is not capable of providing the data at the higher order MCS. Thereafter, at step  1114 , the UE may revert the mode of operation back to the first SNR mode. 
       FIG. 12  is a conceptual data flow diagram  1200  illustrating the data flow between different modules/means/components in an exemplary apparatus  1202 . The apparatus may be a UE. The apparatus includes a receiving module  1204 , an SNR mode processing module  1206 , a CQI processing module  1208 , a data processing module  1210 , and a transmission module  1212 . 
     The SNR mode processing module  1206  determines to change a mode of operation from a first signal-to-noise ratio (SNR) mode to an increased SNR mode. In an aspect, the SNR mode processing module  1206  may determine to change the mode of operation by first obtaining a downlink SNR measurement (via the receiving module  1204 ) and thereafter changing the mode of operation to the increased SNR mode based on the downlink SNR measurement. 
     In another aspect, the SNR mode processing module  1206  may determine to change the mode of operation when informed by the CQI processing module  1208  of the reception of signaling from a base station  1250  indicating the use of at least one CQI value corresponding to a higher order modulation and coding scheme (MCS). Thereafter, the SNR mode processing module  1206  may change the mode of operation to the increased SNR mode based on the received signaling. 
     In a further aspect, the SNR mode processing module  1206  may determine to change the mode of operation based on data received from the base station  1250 . Here, the data processing module  1210  may first receive the data from the base station  1250  according to a first MCS while operating at the first SNR mode. Thereafter, if the data processing module  1210  continues to receive the data according to the first MCS for a number of consecutive timeslots, the SNR mode processing module  1206  may determine that there is a high likelihood that additional data exists in a base station buffer waiting to be scheduled for transmission. Accordingly, the SNR mode processing module  1206  changes the mode of operation to the increased SNR mode to receive the additional data at the higher order MCS. In an example, the first MCS may be 64-quadrature amplitude modulation (QAM) while the higher order MCS may be 256-QAM. In another example, the first MCS may be quadrature phase-shift keying (QPSK) while the higher order MCS may be 16-QAM or 64-QAM. 
     In an aspect, the SNR mode processing module  1206  may change the mode of operation to the increased SNR mode by: 1) moving a gain state such that a low noise figure (NF) and a low gain are achieved simultaneously by a fixed high-gain low noise amplifier (LNA) state and a post-mixer adjustable-gain base band amplifier state; 2) increasing a voltage-controlled oscillator (VCO)/phase-locked loop (PLL) current; 3) invoking real-time residual side band (RSB) calibration; and/or 4) bypassing front-end lossy components (e.g., filters). In a further aspect, the receiving module  1204  may receive signaling from the base station  1250  via multi-carrier downlink signaling in a network configuration where base station downlink signals are: 1) co-located or not co-located; and/or 2) time-aligned or not time-aligned. 
     The CQI processing module  1208  sends (via the transmission module  1212 ) channel quality information (CQI) to the base station  1250  indicating an ability of the apparatus  1202  to receive data at the increased SNR. The data processing module  1210  receives the data from the base station  1250  according to the higher order MCS corresponding to the increased SNR when the base station  1250  is capable of providing the data at the higher order MCS. The data processing module  1210  may determine that the base station  1250  has completed providing the data at the higher order MCS. Accordingly, the SNR mode processing module  1206  may revert the mode of operation back to the first SNR mode. 
     Alternatively, the data processing module  1210  may continue to receive the data according to the first MCS, or fail to receive any data, after the CQI processing module  1208  sends the CQI indicating the ability to receive the data at the increased SNR. As such, the SNR mode processing module  1206  may determine that the base station  1250  is not capable of providing the data at the higher order MCS. Thereafter, the SNR mode processing module  1206  may revert the mode of operation back to the first SNR mode. 
     The apparatus may include additional modules that perform each of the steps of the algorithm in the aforementioned flow chart of  FIG. 11 . As such, each step in the aforementioned flow chart of  FIG. 11  may be performed by a module and the apparatus may include one or more of those modules. The modules may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof. 
       FIG. 13  is a diagram  1300  illustrating an example of a hardware implementation for an apparatus  1202 ′ employing a processing system  1314 . The processing system  1314  may be implemented with a bus architecture, represented generally by the bus  1324 . The bus  1324  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  1314  and the overall design constraints. The bus  1324  links together various circuits including one or more processors and/or hardware modules, represented by the processor  1304 , the modules  1204 ,  1206 ,  1208 ,  1210 ,  1212 , and the computer-readable medium/memory  1306 . The bus  1324  may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. 
     The processing system  1314  may be coupled to a transceiver  1310 . The transceiver  1310  is coupled to one or more antennas  1320 . The transceiver  1310  provides a means for communicating with various other apparatus over a transmission medium. The transceiver  1310  receives a signal from the one or more antennas  1320 , extracts information from the received signal, and provides the extracted information to the processing system  1314 , specifically the receiving module  1204 . In addition, the transceiver  1310  receives information from the processing system  1314 , specifically the transmission module  1212 , and based on the received information, generates a signal to be applied to the one or more antennas  1320 . The processing system  1314  includes a processor  1304  coupled to a computer-readable medium/memory  1306 . The processor  1304  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory  1306 . The software, when executed by the processor  1304 , causes the processing system  1314  to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory  1306  may also be used for storing data that is manipulated by the processor  1304  when executing software. The processing system further includes at least one of the modules  1204 ,  1206 ,  1208 ,  1210 , and  1212 . The modules may be software modules running in the processor  1304 , resident/stored in the computer readable medium/memory  1306 , one or more hardware modules coupled to the processor  1304 , or some combination thereof. The processing system  1314  may be a component of the UE  650  and may include the memory  660  and/or at least one of the TX processor  668 , the RX processor  656 , and the controller/processor  659 . 
     In one configuration, the apparatus  1202 / 1202 ′ for wireless communication includes means for determining to change a mode of operation from a first signal-to-noise ratio (SNR) mode to an increased SNR mode, means for sending channel quality information (CQI) to a base station indicating an ability to receive data at the increased SNR, means for receiving the data from the base station according to a higher order modulation and coding scheme (MCS) corresponding to the increased SNR when the base station is capable of providing the data at the higher order MCS, means for continuing to receive the data according to the first MCS, or failing to receive any data, after sending the CQI indicating the ability to receive the data at the increased SNR, means for determining that the base station is not capable of providing the data at the higher order MCS, and means for reverting the mode of operation back to the first SNR mode. 
     The aforementioned means may be one or more of the aforementioned modules of the apparatus  1202  and/or the processing system  1314  of the apparatus  1202 ′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system  1314  may include the TX Processor  668 , the RX Processor  656 , and the controller/processor  659 . As such, in one configuration, the aforementioned means may be the TX Processor  668 , the RX Processor  656 , and the controller/processor  659  configured to perform the functions recited by the aforementioned means. 
     It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. Further, some steps may be combined or omitted. 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 previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.” Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C,” “at least one of A, B, and C,” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C,” “at least one of A, B, and C,” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.”