Patent Publication Number: US-11032823-B2

Title: Informing base station regarding user equipment&#39;s reception of beam change instruction

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. application Ser. No. 15/400,446, entitled “INFORMING BASE STATION REGARDING USER EQUIPMENT&#39;S RECEPTION OF BEAM CHANGE INSTRUCTION” and filed on Jan. 6, 2017, which claims the benefit of U.S. Provisional Application Ser. No. 62/348,829, entitled “INFORMING BASE STATION REGARDING USER EQUIPMENT&#39;S RECEPTION OF BEAM CHANGE INSTRUCTION” and filed on Jun. 10, 2016, the entire contents of both of which are expressly incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     Field 
     The present disclosure relates generally to communication systems, and more particularly, to a beam change in wireless communication between a user equipment and a base station. 
     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. 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 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). LTE is designed to support mobile broadband access through improved spectral efficiency, lowered costs, and improved services using OFDMA on the downlink, SC-FDMA on the uplink, 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. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies. 
     SUMMARY 
     The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later. 
     With a beam-forming technique, a base station may select one of beams pointing to different directions to communicate the selected beam. After selection of the beam, an optimal beam may change, and thus the base station may determine to change from a current beam to another beam. In a process of beam change, the base station transmits a beam change instruction to a user equipment to confirm a change from a current beam to another beam. However, an indication about a user equipment (UE) successfully detecting the beam change instruction may be interfered by a process involving a CRC. 
     In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a base station. The base station determines to change from a first beam to a second beam. The base station generates a beam change instruction to indicate the determination to change from the first beam to the second beam. The base station transmits, to a UE, the beam change instruction in a downlink control information (DCI). The base station determines whether or not the beam change instruction is detected by the UE. 
     In an aspect, the apparatus may be a base station. The base station includes means for determining to change from a first beam to a second beam. The base station includes means for generating a beam change instruction to indicate the determination to change from the first beam to the second beam. The base station includes means for transmitting, to a UE, the beam change instruction in a DCI. The base station includes means for determining whether or not the beam change instruction is detected by the UE. 
     In an aspect, the apparatus may be a base station including a memory and at least one processor coupled to the memory. The at least one processor is configured to: determine to change from a first beam to a second beam, generate a beam change instruction to indicate the determination to change from the first beam to the second beam, transmit, to a UE, the beam change instruction in a DCI, and determine whether or not the beam change instruction is detected by the UE. 
     In an aspect, a computer-readable medium storing computer executable code for a base station includes code to: determine to change from a first beam to a second beam, generate a beam change instruction to indicate the determination to change from the first beam to the second beam, transmit, to a UE, the beam change instruction in a DCI, and determine whether or not the beam change instruction is detected by the UE. 
     In another aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a base station. The base station transmits a beam change instruction in a DCI using a first beam. The base station receives a first sample signal using the first beam. The base station receives a second sample signal using a second beam indicated by the beam change instruction. The base station selects one of the first beam and the second beam based on the first sample signal and the second sample signal. 
     In an aspect, the apparatus may be a base station. The base station includes means for transmitting a beam change instruction in a DCI using a first beam. The base station includes means for receiving a first sample signal using the first beam. The base station includes means for receiving a second sample signal using a second beam indicated by the beam change instruction. The base station includes means for selecting one of the first beam and the second beam based on the first sample signal and the second sample signal. 
     In an aspect, the apparatus may be a base station including a memory and at least one processor coupled to the memory. The at least one processor is configured to: transmit a beam change instruction in a DCI using a first beam, receive a first sample signal using the first beam, receive a second sample signal using a second beam indicated by the beam change instruction, and select one of the first beam and the second beam based on the first sample signal and the second sample signal. 
     In an aspect, a computer-readable medium storing computer executable code for a base station includes code to: transmit a beam change instruction in a DCI using a first beam, receive a first sample signal using the first beam, receive a second sample signal using a second beam indicated by the beam change instruction, and select one of the first beam and the second beam based on the first sample signal and the second sample signal. 
     In another aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE. The UE receives a DCI from a base station. The UE determines whether a beam change instruction is detected in the DCI. The UE indicates via an uplink transmission which is associated with the DCI whether the beam change instruction is detected, the uplink transmission including at least one of a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH). The UE transmits the uplink transmission to the base station. 
     In an aspect, the apparatus may be a UE. The UE includes means for receiving a DCI from a base station. The UE includes means for determining whether a beam change instruction is detected in the DCI. The UE includes means for indicating via an uplink transmission which is associated with the DCI whether the beam change instruction is detected, the uplink transmission including at least one of a PUCCH or a PUSCH. The UE includes means for transmitting the uplink transmission to the base station. 
     In an aspect, the apparatus may be a UE including a memory and at least one processor coupled to the memory. The at least one processor is configured to: receive a DCI from a base station, determine whether a beam change instruction is detected in the DCI, indicate via an uplink transmission which is associated with the DCI whether the beam change instruction is detected, the uplink transmission including at least one of a PUCCH or a PUSCH, and transmit the uplink transmission to the base station. 
     In an aspect, a computer-readable medium storing computer executable code for a UE includes code to: receive a DCI from a base station, determine whether a beam change instruction is detected in the DCI, indicate via an uplink transmission which is associated with the DCI whether the beam change instruction is detected, the uplink transmission including at least one of a PUCCH or a PUSCH, and transmit the uplink transmission to the base station. 
     To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating an example of a wireless communications system and an access network. 
         FIGS. 2A, 2B, 2C, and 2D  are diagrams illustrating LTE examples of a DL frame structure, DL channels within the DL frame structure, an UL frame structure, and UL channels within the UL frame structure, respectively. 
         FIG. 3  is a diagram illustrating an example of an evolved Node B (eNB) and user equipment (UE) in an access network. 
         FIGS. 4A and 4B  are diagrams illustrating an example of the transmission of beamformed signals between a base station and a UE. 
         FIG. 5A through 5D  illustrate diagrams of a wireless communications system. 
         FIGS. 6A and 6B  are example diagrams illustrating communication between a user equipment and a base station for a beam change. 
         FIGS. 7A-7D  are example diagrams illustrating the first, second, third, and fourth aspects of the disclosure. 
         FIGS. 8A-8C  are example diagrams illustrating the fifth, sixth, and seventh aspects of the disclosure. 
         FIG. 9  is a flowchart of a method of wireless communication, according to an aspect of the disclosure. 
         FIG. 10  is a flowchart of a method of wireless communication, according to an aspect of the disclosure. 
         FIG. 11  is a conceptual data flow diagram illustrating the data flow between different means/components in an exemplary apparatus. 
         FIG. 12  is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system. 
         FIG. 13  is a flowchart of a method of wireless communication, according to an aspect of the disclosure. 
         FIG. 14  is a conceptual data flow diagram illustrating the data flow between different means/components in an exemplary apparatus. 
         FIG. 15  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, components, circuits, 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 as a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, systems on a chip (SoC), baseband processors, 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 components, 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 example embodiments, the functions described may be implemented in hardware, software, 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), optical disk storage, magnetic disk storage, other magnetic storage devices, combinations of the aforementioned types of computer-readable media, or any other medium that can be used to store computer executable code in the form of instructions or data structures that can be accessed by a computer. 
       FIG. 1  is a diagram illustrating an example of a wireless communications system and an access network  100 . The wireless communications system (also referred to as a wireless wide area network (WWAN)) includes base stations  102 , UEs  104 , and an Evolved Packet Core (EPC)  160 . The base stations  102  may include macro cells (high power cellular base station) and/or small cells (low power cellular base station). The macro cells include eNBs. The small cells include femtocells, picocells, and microcells. 
     The base stations  102  (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) interface with the EPC  160  through backhaul links  132  (e.g., S 1  interface). In addition to other functions, the base stations  102  may perform one or more of the following functions: transfer of user data, radio channel ciphering and deciphering, integrity protection, header compression, mobility control functions (e.g., handover, dual connectivity), inter-cell interference coordination, connection setup and release, load balancing, distribution for non-access stratum (NAS) messages, NAS node selection, synchronization, radio access network (RAN) sharing, multimedia broadcast multicast service (MBMS), subscriber and equipment trace, RAN information management (RIM), paging, positioning, and delivery of warning messages. The base stations  102  may communicate directly or indirectly (e.g., through the EPC  160 ) with each other over backhaul links  134  (e.g., X2 interface). The backhaul links  134  may be wired or wireless. 
     The base stations  102  may wirelessly communicate with the UEs  104 . Each of the base stations  102  may provide communication coverage for a respective geographic coverage area  110 . There may be overlapping geographic coverage areas  110 . For example, the small cell  102 ′ may have a coverage area  110 ′ that overlaps the coverage area  110  of one or more macro base stations  102 . A network that includes both small cell and macro cells may be known as a heterogeneous network. A heterogeneous network may also include Home Evolved Node Bs (eNBs) (HeNBs), which may provide service to a restricted group known as a closed subscriber group (CSG). The communication links  120  between the base stations  102  and the UEs  104  may include uplink (UL) (also referred to as reverse link) transmissions from a UE  104  to a base station  102  and/or downlink (DL) (also referred to as forward link) transmissions from a base station  102  to a UE  104 . The communication links  120  may use MIMO antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The communication links may be through one or more carriers. The base stations  102 /UEs  104  may use spectrum up to Y MHz (e.g., 5, 10, 15, 20 MHz) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction. The carriers may or may not be adjacent to each other. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL). The component carriers may include a primary component carrier and one or more secondary component carriers. A primary component carrier may be referred to as a primary cell (PCell) and a secondary component carrier may be referred to as a secondary cell (SCell). 
     The wireless communications system may further include a Wi-Fi access point (AP)  150  in communication with Wi-Fi stations (STAs)  152  via communication links  154  in a 5 GHz unlicensed frequency spectrum. When communicating in an unlicensed frequency spectrum, the STAs  152 /AP  150  may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available. 
     The small cell  102 ′ may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell  102 ′ may employ LTE and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP  150 . The small cell  102 ′, employing LTE in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. LTE in an unlicensed spectrum may be referred to as LTE-unlicensed (LTE-U), licensed assisted access (LAA), or MuLTEfire. 
     The millimeter wave (mmW) base station  180  may operate in mmW frequencies and/or near mmW frequencies in communication with the UE  182 . Extremely high frequency (EHF) is part of the RF in the electromagnetic spectrum. EHF has a range of 30 GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters. Radio waves in the band may be referred to as a millimeter wave. Near mmW may extend down to a frequency of 3 GHz with a wavelength of 100 millimeters. The super high frequency (SHF) band extends between 3 GHz and 30 GHz, also referred to as centimeter wave. Communications using the mmW/near mmW radio frequency band has extremely high path loss and a short range. The mmW base station  180  may utilize beamforming  184  with the UE  182  to compensate for the extremely high path loss and short range. 
     The EPC  160  may include a Mobility Management Entity (MME)  162 , other MMES  164 , a Serving Gateway  166 , a Multimedia Broadcast Multicast Service (MBMS) Gateway  168 , a Broadcast Multicast Service Center (BM-SC)  170 , and a Packet Data Network (PDN) Gateway  172 . The MME  162  may be in communication with a Home Subscriber Server (HSS)  174 . The MME  162  is the control node that processes the signaling between the UEs  104  and the EPC  160 . Generally, the MME  162  provides bearer and connection management. All user Internet protocol (IP) packets are transferred through the Serving Gateway  166 , which itself is connected to the PDN Gateway  172 . The PDN Gateway  172  provides UE IP address allocation as well as other functions. The PDN Gateway  172  and the BM-SC  170  are connected to the IP Services  176 . The IP Services  176  may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service (PSS), and/or other IP services. The BM-SC  170  may provide functions for MBMS user service provisioning and delivery. The BM-SC  170  may serve as an entry point for content provider MBMS transmission, may be used to authorize and initiate MBMS Bearer Services within a public land mobile network (PLMN), and may be used to schedule MBMS transmissions. The MBMS Gateway  168  may be used to distribute MBMS traffic to the base stations  102  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. 
     The base station may also be referred to as a Node B, evolved Node B (eNB), 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 base station  102  provides an access point to the EPC  160  for a UE  104 . Examples of UEs  104  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, a smart device, a wearable device, or any other similar functioning device. The UE  104  may also be referred to as a station, 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. 
     Referring again to  FIG. 1 , in certain aspects, the UE  104 /eNB  102  may be configured to enable the eNB  102  to more reliably determine whether the UE  104  has detected a beam change instruction from the eNB  102  ( 198 ). 
       FIG. 2A  is a diagram  200  illustrating an example of a DL frame structure in LTE.  FIG. 2B  is a diagram  230  illustrating an example of channels within the DL frame structure in LTE.  FIG. 2C  is a diagram  250  illustrating an example of an UL frame structure in LTE.  FIG. 2D  is a diagram  280  illustrating an example of channels within the UL frame structure in LTE. Other wireless communication technologies may have a different frame structure and/or different channels. 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 the two time slots, each time slot including one or more time concurrent resource blocks (RBs) (also referred to as physical RBs (PRBs)). The resource grid is divided into multiple resource elements (REs). In LTE, for a normal cyclic prefix, an RB contains 12 consecutive subcarriers in the frequency domain and 7 consecutive symbols (for DL, OFDM symbols; for UL, SC-FDMA symbols) in the time domain, for a total of 84 REs. For an extended cyclic prefix, an RB contains 12 consecutive subcarriers in the frequency domain and 6 consecutive symbols in the time domain, for a total of 72 REs. The number of bits carried by each RE depends on the modulation scheme. 
     As illustrated in  FIG. 2A , some of the REs carry DL reference (pilot) signals (DL-RS) for channel estimation at the UE. The DL-RS may include cell-specific reference signals (CRS) (also sometimes called common RS), UE-specific reference signals (UE-RS), and channel state information reference signals (CSI-RS).  FIG. 2A  illustrates CRS for antenna ports 0, 1, 2, and 3 (indicated as R 0 , R 1 , R 2 , and R 3 , respectively), UE-RS for antenna port 5 (indicated as R 5 ), and CSI-RS for antenna port 15 (indicated as R).  FIG. 2B  illustrates an example of various channels within a DL subframe of a frame. The physical control format indicator channel (PCFICH) is within symbol 0 of slot 0, and carries a control format indicator (CFI) that indicates whether the physical downlink control channel (PDCCH) occupies 1, 2, or 3 symbols ( FIG. 2B  illustrates a PDCCH that occupies 3 symbols). The PDCCH carries downlink control information (DCI) within one or more control channel elements (CCEs), each CCE including nine RE groups (REGs), each REG including four consecutive REs in an OFDM symbol. A UE may be configured with a UE-specific enhanced PDCCH (ePDCCH) that also carries DCI. The ePDCCH may have 2, 4, or 8 RB pairs ( FIG. 2B  shows two RB pairs, each subset including one RB pair). The physical hybrid automatic repeat request (ARQ) (HARQ) indicator channel (PHICH) is also within symbol 0 of slot 0 and carries the HARQ indicator (HI) that indicates HARQ acknowledgement (ACK)/negative ACK (HACK) feedback based on the physical uplink shared channel (PUSCH). The primary synchronization channel (PSCH) is within symbol 6 of slot 0 within subframes 0 and 5 of a frame, and carries a primary synchronization signal (PSS) that is used by a UE to determine subframe timing and a physical layer identity. The secondary synchronization channel (SSCH) is within symbol 5 of slot 0 within subframes 0 and 5 of a frame, and carries a secondary synchronization signal (SSS) that is used by a UE to determine a physical layer cell identity group number. Based on the physical layer identity and the physical layer cell identity group number, the UE can determine a physical cell identifier (PCI). Based on the PCI, the UE can determine the locations of the aforementioned DL-RS. The physical broadcast channel (PBCH) is within symbols 0, 1, 2, 3 of slot 1 of subframe 0 of a frame, and carries a master information block (MIB). The MIB provides a number of RBs in the DL system bandwidth, a PHICH configuration, and a system frame number (SFN). The physical downlink shared channel (PDSCH) carries user data, broadcast system information not transmitted through the PBCH such as system information blocks (SIBs), and paging messages. 
     As illustrated in  FIG. 2C , some of the REs carry demodulation reference signals (DM-RS) for channel estimation at the eNB. The UE may additionally transmit sounding reference signals (SRS) in the last symbol of a subframe. The SRS may have a comb structure, and a UE may transmit SRS on one of the combs. The SRS may be used by an eNB for channel quality estimation to enable frequency-dependent scheduling on the UL.  FIG. 2D  illustrates an example of various channels within an UL subframe of a frame. A physical random access channel (PRACH) may be within one or more subframes within a frame based on the PRACH configuration. The PRACH may include six consecutive RB pairs within a subframe. The PRACH allows the UE to perform initial system access and achieve UL synchronization. A physical uplink control channel (PUCCH) may be located on edges of the UL system bandwidth. The PUCCH carries uplink control information (UCI), such as scheduling requests, a channel quality indicator (CQI), a precoding matrix indicator (PMI), a rank indicator (RI), and HARQ ACK/NACK feedback. The PUSCH carries data, and may additionally be used to carry a buffer status report (BSR), a power headroom report (PHR), and/or UCI. 
       FIG. 3  is a block diagram of an eNB  310  in communication with a UE  350  in an access network. In the DL, IP packets from the EPC  160  may be provided to a controller/processor  375 . The controller/processor  375  implements layer 3 and layer 2 functionality. Layer 3 includes a radio resource control (RRC) layer, and layer 2 includes a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The controller/processor  375  provides RRC layer functionality associated with broadcasting of system information (e.g., MIB, SIBs), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functionality associated with header compression/decompression, security (ciphering, deciphering, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with the transfer of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization. 
     The transmit (TX) processor  316  and the receive (RX) processor  370  implement layer 1 functionality associated with various signal processing functions. Layer 1, which includes a physical (PHY) layer, may include error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, interleaving, rate matching, mapping onto physical channels, modulation/demodulation of physical channels, and MIMO antenna processing. The TX processor  316  handles 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 may then be split into parallel streams. Each stream may then be 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  374  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  350 . Each spatial stream may then be provided to a different antenna  320  via a separate transmitter  318 TX. Each transmitter  318 TX may modulate an RF carrier with a respective spatial stream for transmission. 
     At the UE  350 , each receiver  354 RX receives a signal through its respective antenna  352 . Each receiver  354 RX recovers information modulated onto an RF carrier and provides the information to the receive (RX) processor  356 . The TX processor  368  and the RX processor  356  implement layer 1 functionality associated with various signal processing functions. The RX processor  356  may perform spatial processing on the information to recover any spatial streams destined for the UE  350 . If multiple spatial streams are destined for the UE  350 , they may be combined by the RX processor  356  into a single OFDM symbol stream. The RX processor  356  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  310 . These soft decisions may be based on channel estimates computed by the channel estimator  358 . The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB  310  on the physical channel. The data and control signals are then provided to the controller/processor  359 , which implements layer 3 and layer 2 functionality. 
     The controller/processor  359  can be associated with a memory  360  that stores program codes and data. The memory  360  may be referred to as a computer-readable medium. In the UL, the controller/processor  359  provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, and control signal processing to recover IP packets from the EPC  160 . The controller/processor  359  is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations. 
     Similar to the functionality described in connection with the DL transmission by the eNB  310 , the controller/processor  359  provides RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting; PDCP layer functionality associated with header compression/decompression, and security (ciphering, deciphering, integrity protection, integrity verification); RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demultiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization. 
     Channel estimates derived by a channel estimator  358  from a reference signal or feedback transmitted by the eNB  310  may be used by the TX processor  368  to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor  368  may be provided to different antenna  352  via separate transmitters  354 TX. Each transmitter  354 TX may modulate an RF carrier with a respective spatial stream for transmission. 
     The UL transmission is processed at the eNB  310  in a manner similar to that described in connection with the receiver function at the UE  350 . Each receiver  318 RX receives a signal through its respective antenna  320 . Each receiver  318 RX recovers information modulated onto an RF carrier and provides the information to a RX processor  370 . 
     The controller/processor  375  can be associated with a memory  376  that stores program codes and data. The memory  376  may be referred to as a computer-readable medium. In the UL, the controller/processor  375  provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover IP packets from the UE  350 . IP packets from the controller/processor  375  may be provided to the EPC  160 . The controller/processor  375  is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations. 
     Wireless communication systems employing narrow bandwidths and high frequency carriers are being developed and deployed. An mmW system may be utilized for wireless communication at a high transmission rate. In mmW systems, because the carrier frequency is high (e.g., 28 GHz), path loss may be high. For example, the carrier frequency for mmW communication may be 10 times higher than a carrier frequency for other types of wireless communication. As a result, the mmW system may experience a path loss that is approximately 20 dB higher than other types of wireless communication systems employing lower frequency carriers. To mitigate the path loss in mmW systems, a base station may perform transmissions in a directional manner, where the transmissions are beam-formed to steer the transmissions of the beams in different directions. 
     Using a higher carrier frequency for wireless communication results in a shorter wavelength which may allow a higher number of antennas to be implemented within a given antenna array length than can be implemented when a lower carrier frequency is used. Therefore, the mmW system (using a high carrier frequency) may use a higher number of antennas in a base station and/or a UE. For example, the BS may have 128 or 256 antennas and the UE may have 8, 16 or 24 antennas. With the higher number of antennas, a beam-forming technique may be used to digitally change the direction of the beam by applying different phases to the different antennas. Because beam-forming in a mmW system provides a narrower beam for increased gain, the base station may transmit the narrower beam in multiple directions when transmitting a synchronization signal to provide coverage over a wider area using multiple narrower beams. 
     One challenge in using beam-forming for a mmW system arises from the directional nature of a beam-formed beam. Due to the directional nature of the beam-formed beam, the base station should point the beam directly at the UE such that the direction of the beam aligns with the location of the UE to provide more antenna receive gain at the UE. If the direction of the beam is not properly aligned, the antenna gain at the UE may be decreased (e.g., resulting in low SNR, higher block error rates, etc.). Further, when the UE enters the coverage area of the mmW system and receives transmitted data from the base station over the mmW, the base station should be able to determine the best beam(s) (e.g., beam(s) with the highest signal strength, highest SNR, lowest error rate, etc.) for mmW communication with the particular UE. Thus, the base station may transmit beam reference signals (BRSs) in multiple directions (or all directions) so that the UE may identify the best beam of the one or more beams received from the base station based on measurements of the BRSs. In the mmW communication, the base station may also transmit a primary synchronization signal (PSS), a secondary synchronization signal (SSS), an extended synchronization signal (ESS), and PBCH signals for synchronization and for broadcasting system information. In the mmW communication, such signals may be transmitted directionally via multiple beams to enable the UE to receive such synchronization and system information at various locations within the coverage area of the base station. 
     If there are multiple antenna ports (multiple sets of antennas) in the base station, the base station may transmit multiple beams per symbol. For example, the base station may sweep in one set of multiple directions using multiple antenna ports in a cell specific manner in a first symbol of a synchronization sub-frame. The base station may then sweep in another set of multiple directions using the multiple antenna ports in a cell specific manner in another symbol of the synchronization sub-frame. Each antenna port may include a set of antennas. For example, an antenna port including a set of antennas (e.g., 64 antennas) may transmit one beam, and several antenna ports may each transmit a beam, each beam in a different direction. Thus, if there are four antenna ports, the four antenna ports may sweep through four directions (e.g., transmit four beams in four different directions). 
       FIGS. 4A and 4B  are diagrams illustrating an example of the transmission of beamformed signals between a base station (BS) and a UE. The BS may be embodied as a BS in a mmW system (mmW BS). Referring to  FIG. 4A , diagram  400  illustrates a BS  404  of a mmW system transmitting beamformed signals  406  (e.g., beam reference signals) in different transmit directions (e.g., directions A, B, C, and D). In an example, the BS  404  may sweep through the transmit directions according to a sequence A-B-C-D. In another example, the BS  404  may sweep through the transmit directions according to the sequence B-D-A-C. Although four transmit directions and two transmit sequences are described with respect to  FIG. 4A , any number of different transmit directions and transmit sequences are contemplated. 
     After transmitting the signals, the BS  404  may switch to a receive mode. In the receive mode, the BS  404  may sweep through different receive directions in a sequence or pattern corresponding (or mapping) to a sequence or pattern in which the BS  404  previously transmitted the synchronization/discovery signals in the different transmit directions. For example, if the BS  404  previously transmitted the synchronization/discovery signals in transmit directions according to the sequence A-B-C-D, then the BS  404  may sweep through receive directions according to the sequence A-B-C-D in an attempt to receive an association signal from a UE  402 . In another example, if the BS  404  previously transmitted the synchronization/discovery signals in transmit directions according to the sequence B-D-A-C, then the BS  404  may sweep through receive directions according to the sequence B-D-A-C in an attempt to receive the association signal from the UE  402 . 
     A propagation delay on each beamformed signal allows a UE  402  to perform a receive (RX) sweep. The UE  402  in a receive mode may sweep through different receive directions in an attempt to detect a synchronization/discovery signal via the beam formed signal  406  (see  FIG. 4B ). One or more of the synchronization/discovery signals  406  may be detected by the UE  402 . When a strong synchronization/discovery signal  406  is detected, the UE  402  may determine an optimal transmit direction of the BS  404  and an optimal receive direction of the UE  402  corresponding to the strong synchronization/discovery signal. For example, the UE  402  may determine preliminary antenna weights/directions of the strong synchronization/discovery signal  406 , and may further determine a time and/or resource where the BS  404  is expected to optimally receive a beamformed signal (e.g., with high signal strength). Thereafter, the UE  402  may attempt to associate with the BS  404  via a beamformed signal. 
     The BS  404  may sweep through a plurality of directions using a plurality of ports in a cell-specific manner in a first symbol of a synchronization subframe. For example, the BS  404  may sweep through different transmit directions (e.g., directions A, B, C, and D) using four ports in a cell-specific manner in a first symbol of a synchronization subframe. In an aspect, the different transmit directions (e.g., directions A, B, C, and D) may be considered “coarse” beam directions. In an aspect, a beam reference signal (BRS) may be transmitted in different transmit directions (e.g., directions A, B, C, and D). 
     In an aspect, the BS  404  may sweep the four different transmit directions (e.g., directions A, B, C, and D) in a cell-specific manner using four ports in a second symbol of a synchronization subframe. A synchronization beam may occur in a second symbol of the synchronization subframe. 
     Referring to diagram  420  of  FIG. 4B , the UE  402  may listen for beamformed discovery signals in different receive directions (e.g., directions E, F, G, and H). In an example, the UE  402  may sweep through the receive directions according to a sequence E-F-G-H. In another example, the UE  402  may sweep through the receive directions according to the sequence F-H-E-J. Although four receive directions and two receive sequences are described with respect to  FIG. 4B , any number of different receive directions and receive sequences are contemplated. 
     The UE  402  may attempt the association with the BS  404  by transmitting beamformed signals  426  (e.g., association signals or another indication of a best “coarse” beam or a best “fine” beam) in the different transmit directions (e.g., directions E, F, G, and H). In an aspect, the UE  402  may transmit an association signal  426  by transmitting along the optimal receive direction of the UE  402  at the time/resource where the BS  404  is expected to optimally receive the association signal. The BS  404  in the receive mode may sweep through different receive directions and detect the association signal  426  from the UE  402  during one or more timeslots corresponding to a receive direction. When a strong association signal  426  is detected, the BS  404  may determine an optimal transmit direction of the UE  402  and an optimal receive direction of the BS  404  corresponding to the strong association signal. For example, the BS  404  may determine preliminary antenna weights/directions of the strong association signal  426 , and may further determine a time and/or resource where the UE  402  is expected to optimally receive a beamformed signal. Any of the processes discussed above with respect to  FIGS. 4A and 4B  may be refined or repeated over time such that the UE  402  and BS  404  eventually learn the most optimal transmit and receive directions for establishing a link with each other. Such refinement and repetition may be referred to as beam training. 
     In an aspect, the BS  404  may choose a sequence or pattern for transmitting the synchronization/discovery signals according to a number of beamforming directions. The BS  404  may then transmit the signals for an amount of time long enough for the UE  402  to sweep through a number of beamforming directions in an attempt to detect a synchronization/discovery signal. For example, a BS beamforming direction may be denoted by n, where n is an integer from  0  to N, N being a maximum number of transmit directions. Moreover, a UE beamforming direction may be denoted by k, where k is an integer from  0  to K, K being a maximum number of receive directions. When the UE  402  detects a synchronization/discovery signal from the BS  404 , the UE  402  may discover that the strongest synchronization/discovery signal is received when the UE  402  beamforming direction is k=2 and the BS  404  beamforming direction is n=3. Accordingly, the UE  402  may use the same antenna weights/directions for responding (transmitting a beamformed signal) to the BS  404  in a corresponding response timeslot. That is, the UE  402  may send a signal to the BS  404  using UE  402  beamforming direction k=2 during a timeslot when the BS  404  is expected to perform a receive sweep at BS  404  beamforming direction n=3. 
     Path loss may be relatively high in mmW systems. Transmission may be directional to mitigate path loss. A base station may transmit one or more beam reference signals by sweeping in multiple directions so that a user equipment (UE) may identify a best “coarse” beam. Further, the base station may transmit a beam refinement request signal so that the UE may track “fine” beams. If a “coarse” beam identified by the UE changes, the UE may need to inform the base station so that the base station may perform beam training for one or more new “fine” beams for the UE. 
     In various aspects, a base station may transmit a beam reference signal (BRS) by sweeping in all directions that so a user equipment (UE) may determine the index or identifier (ID) of a best “coarse” beam. The base station may further transmit a beam refinement request signal so that the UE may track “fine” beams. The UE may signal a best “fine” beam to the base station. The base station and the UE may have to continuously update and/or recover beams to sustain a communication link. 
     In  FIG. 4A  and  FIG. 4B , the base station  404  and the UE  402  may sweep through four directions using four ports in a cell-specific manner in the first symbol of the synchronization subframe. The four directions may be considered “coarse” beam directions. In an aspect, a BRS may be included in a first symbol. In an aspect, the base station  404  and the UE  402  may sweep through four different directions in a cell-specific manner using four ports in the second symbol of the synchronization subframe. Note that while beams are shown adjacent, beams transmitted during a same symbol may not be adjacent. 
       FIGS. 5A through 5G  are diagrams illustrating an example of the transmission of beamformed signals between a base station (BS) and a UE. The BS  504  may be a BS in a mmW system (mmW BS). While some beams are illustrates as adjacent to one another, such an arrangement may be different in different aspects (e.g., beams transmitted during a same symbol may not be adjacent to one another). 
     In an aspect, a beam set may contain eight different beams. For example,  FIG. 5A  illustrates eight beams  521 ,  522 ,  523 ,  524 ,  525 ,  526 ,  527 ,  528  for eight directions. In aspects, the BS  504  may be configured to beamform at least one of the beams  521 ,  522 ,  523 ,  524 ,  525 ,  526 ,  527 ,  528  for transmission toward the UE  502 . 
     In an aspect, a BS may transmit a first tracking signal (e.g., a BRS) in a plurality of directions during a synchronization subframe. In one aspect, the transmission may be cell-specific. Referring to  FIG. 5B , the BS  504  may transmit beams  521 ,  523 ,  525 ,  527  in four directions. In an aspect, the beams  521 ,  523 ,  525 ,  527  transmitted in the four directions may be odd-indexed beams  521 ,  523 ,  525 ,  527  for the four directions out of a possible eight for the beam set. For example, the BS  504  may be capable of transmitting beams  521 ,  523 ,  525 ,  527  in directions adjacent to other beams  522 ,  524 ,  526 ,  528  that the BS  504  is configured to transmit. In an aspect, the configuration in which the BS  504  transmits odd-indexed beams  521 ,  523 ,  525 ,  527  for the four directions may be considered a “coarse” beam set. 
     In  FIG. 5C , the UE  502  may determine a beam index that is strongest or preferable. For example, the UE  502  may determine that the beam  525  carrying a BRS is strongest or optimal (e.g., with a highest signal strength). The UE  502  may transmit an indication  560  of the beam index of beam  525  to the BS  504 . In an aspect, the indication  560  may include a request to transmit a second tracking signal (e.g., a beam refinement reference signal (BRRS)). The BRRS may be UE-specific. 
     In  FIG. 5D , the BS  504  may transmit a second tracking signal (e.g., a BRRS) based on the index included in the indication  560 . For example, the UE  502  may indicate that a first beam  525  is strongest or optimal and, in response, the BS  504  may transmit a plurality of beams  524 ,  525 ,  526  to the UE  502  based on the indicated beam index. In an aspect, the beams  524 ,  525 ,  526  transmitted based on the indicated beam index may be considered a “fine” beam set. In an aspect, a BRRS may be transmitted in each of the beams  524 ,  525 ,  526  of the fine beam set. In an aspect, the beams  524 ,  525 ,  526  of the fine beam set may be adjacent. 
     Based on one or more BRRSs received in the beams  524 ,  525 ,  526  of the fine beam set, the UE  502  may transmit a second indication  565  to the BS  504  to indicate a best “fine” beam (e.g., the beam that provides the highest SNR, lowest error rate, etc.). In an aspect, the second indication  565  may use 2 bits to indicate the selected beam. For example, the UE  502  may transmit an indication  565  that indicates the selected beam  525 . The BS  504  may then communicate with the UE  502  using the selected beam  525 . 
     After selection of a transmit beam to transmit from a base station, the best transmit beam from a base station to a UE may change over time. The best transmit beam may be a beam that provides the highest signal strength, the highest SNR, and/or the lowest error rate. The base station may transmit a BRS in multiple directions (or all directions) periodically. Based on the reception of the BRS, if the UE determines that another transmit beam in a certain direction used to transmit the BRS is better than the current transmit beam, then the UE may determine to change the transmit beam of the base station from the current beam to another transmit beam. To change to another transmit beam, the UE may utilize the beam selection process, as discussed above, involving beam refinement based on a “coarse” beam set. 
     When the UE determines to change a beam of the base station from a current beam to a second beam, the UE informs the base station about the determination to change to the second beam. The current beam and the second beam may be transmit beams of the base station or receive beams of the base station. In response, the base station sends a beam change instruction to the UE (e.g., via a PDCCH) to indicate whether the base station will change the current beam to the second beam. In an aspect, when the UE informs the base station about the change, the base station may determine not to change the current beam to the second beam if the change from the current beam to the second beam is not appropriate (e.g., if the second beam interferes with a neighboring base station). When the base station determines that the change from the current beam to the second beam is appropriate (e.g., does not interfere with a neighboring base station), the base station sends a beam change instruction to the UE (e.g., via a PDCCH) to indicate that the base station will change the beam. In an aspect, a portion (e.g., a certain number of bits) of DCI included in the PDCCH is used to convey the beam change instruction to indicate whether the base station will change from the current beam to the second beam. If the UE receives the beam change instruction indicating that the base station will change from the current beam to the second beam, the UE may change the beam of the UE to a corresponding receive beam that corresponds to the second beam. 
     The base station should confirm that the UE has received the beam change instruction. If the base station cannot determine that the UE has received the beam change instruction, the base station may not change the current beam of the base station. At least one of several approaches may be utilized for the base station to determine whether or not the UE received the beam change instruction. For example, the base station may send the beam change instruction in a DCI for a downlink grant or a DCI for an uplink grant, and the UE may respond by transmitting an ACK (to indicate that the UE received the beam change instruction) or a NACK (to indicate that the UE did not receive the beam change instruction). When the base station receives an ACK, the base station may confirm that the UE received the beam change instruction. Bits may be reserved in the PDCCH for a DCI for a downlink grant and/or a DCI for an uplink grant. A downlink transmission and/or an uplink transmission may take place at the (n+k)th subframe and a beam change may occur at the (n+k′)th subframe, where k′&gt;k. That is, the UE may receive the beam change instruction included in at least one of a DCI for a downlink grant or a DCI for an uplink grant at the n-th subframe, and then transmit an ACK if the UE received the beam change instruction at the (n+k)th subframe, such that the base station may change the beam at the (n+k′)th subframe, where k′ is greater than k. 
     A base station may transmit a DCI to the UE in the PDCCH and may also transmit a PDSCH to the UE within one HARQ process. If the base station transmits the DCI to indicate to the UE that the base station may change a transmit beam of the base station for the UE, the base station should be informed whether the UE has successfully decoded the DCI to detect the beam change instruction, regardless of whether a CRC for a corresponding PDSCH passes or fails. In an aspect, if the UE is able to decode the DCI from the PDCCH and to detect the beam change instruction in the DCI, the UE should indicate to the base station that the beam change instruction is successfully detected. When the base station receives the indication that the beam change instruction is successfully detected at the UE, the base station may change the beam of the base station to another beam. As discussed above, the base station may change the beam at the (n+k′)th subframe, whereas the DCI is received in the n-th subframe and the corresponding PDSCH is received in (n+k)th subframe, where k′ is greater than k. 
     If the DCI is for an uplink grant, the base station may detect a PUSCH to determine whether the UE has decoded the DCI or not. If the UE does not decode the DCI for the uplink grant, the UE does not transmit a PUSCH. Thus, if the base station does not detect a PUSCH from the UE, the base station may determine that the UE has not decoded the DCI for the uplink grant. Bits/portions in the DCI are generally reserved to convey a beam change instruction. Hence, UE&#39;s transmission of the PUSCH indicates that the UE has detected the beam change instruction by the successfully decoding the DCI. The base station can utilize at least one of several ways to determine whether the UE has tried to transmit a PUSCH. For example, the base station may measure the energy of the DMRS of the PUSCH and/or may try to decode the DMRS indicating that the beam change request is successfully detected. For example, if the energy of the DMRS is greater than an energy threshold, the base station may determine that the UE has successfully decoded the DCI for an uplink grant to detect the beam change instruction. On the other hand, if the energy of the DMRS is less than or equal to the energy threshold, the base station may determine that the UE has not successfully decoded the DCI. In another example, if the base station can decode a DMRS, the base station may determine that the UE has successfully decoded the DCI for an uplink grant to detect the beam change instruction. On the other hand, if the base station cannot decode DMRS, the base station may determine that the UE has not successfully decoded the DCI. In another example, the base station may use the energy of the traffic of a PUSCH to determine if the UE has successfully decoded the DCI for an uplink grant to detect the beam change instruction. If the energy of the received samples of the uplink traffic (e.g., PUSCH traffic) is greater than an energy threshold, the base station may determine that the UE has successfully decoded the DCI for an uplink grant to detect the beam change instruction. On the other hand, if the energy of the received samples of the uplink traffic (e.g., PUSCH traffic) is less than or equal to the energy threshold, the base station may determine that the UE has not successfully decoded the DCI. 
     In a case with the DCI for a downlink grant, because a PUCCH may contain an ACK/NACK response for another HARQ process unrelated to the beam change request, the UE may not correctly indicate whether the beam change request is successfully detected when transmitting the ACK/NACK response in the PUCCH. A NACK may be a default response when the DCI is not decoded. When a base station transmits a DCI for a downlink grant via a PDCCH, the UE attempts to decode the PDCCH to recover the DCI that includes a beam change instruction. The UE may determine based on the DCI that when the UE receives a PDSCH at (n+k)th subframe, the beam change may occur at (n+k′)th subframe, where k′ is greater than k. If the UE receives the PDSCH at the (n+k)th subframe but cannot decode the PDSCH, then a cyclic redundancy check (CRC) for the PDSCH fails. In such a scenario, because the UE cannot decode the PDSCH, the UE sends a NACK on the PUCCH to the base station. Thus, even in a case where the UE has successfully decoded PDCCH, the UE may still send a NACK on the PUCCH to the base station if the UE cannot decode the PDSCH. In such a situation, due to the UE sending a NACK to the base station, the base station may mistakenly determine that the UE has not successfully decoded the DCI even when the UE successfully decoded the DCI to obtain the beam change instruction. In another example, the UE may send a combined ACK/NACK response for multiple HARQ processes. The UE may decode a PDCCH, which conveys a beam change instruction in the DCI, and may also decode a PDSCH corresponding with the PDCCH successfully. However, the UE may not decode a PDCCH or a PDSCH of another HARQ process successfully. If the UE sends a combined ACK/NACK response for the two different PDSCH transmissions, the UE sends a NACK to the base station even if the UE successfully decoded the beam change instruction of the PDCCH. The base station may mistakenly determine that the UE has not successfully decoded the DCI even though the UE successfully decoded the DCI to obtain the beam change instruction. In summary, if the UE decodes the DCI to successfully detect the beam change instruction but the CRC for the PDSCH fails, the UE may transmit a NACK on the PUCCH due to the CRC failure. In this case, the UE is informed based on the beam change instruction that a beam change should occur, but the base station may determine incorrectly that the UE has not detected the beam change instruction from the DCI based on the NACK. Therefore, an approach to address the above-identified issues is desired. 
       FIGS. 6A and 6B  are example diagrams illustrating communication between a user equipment and a base station for a beam change.  FIG. 6A  is an example diagram  600  illustrating communication between a UE and a base station for a beam change when a DCI for a downlink grant is used. The example diagram  600  involves communication between a UE  602  and a base station  604 . At  610 , the UE  602  indicates to the base station  604  that the UE  602  has determined to change the current beam of the base station  604  to another beam (e.g., upon determining that there is a better beam that provides a higher SNR than the current beam). At  612 , the base station  604  generates a beam change instruction to indicate whether the base station  604  will perform beam change from the current beam to another beam, and includes the beam change instruction in a DCI for a downlink grant. At  614 , the base station transmits a PDDCH including the DCI and also transmits a PDSCH. At  622 , the UE successfully decodes the DCI to detect the beam change instruction. At  624 , the UE performs a CRC for the PDSCH. At  630 , the UE transmits an ACK/NACK response based on whether nor not the UE successfully decoded the DCI to detect the beam change instruction via a PUCCH. At  642 , based on the ACK/NACK, the base station  604  determines whether to change the current beam to another beam. As discussed above, in a case where the DCI is for a DL grant, even if the UE  602  successfully decodes the DCI (e.g., at  622 ) to detect the beam change instruction, the UE  602  may still send a NACK via the PUCCH if the CRC for the PDSCH fails (e.g., at  624 ). 
       FIG. 6B  is an example diagram  650  illustrating communication between a UE and a base station for a beam change when a DCI for an uplink grant is used. The example diagram  650  involves communication between a UE  602  and a base station  604 . At  660 , the UE  602  indicates to the base station  604  that the UE  602  has determined to change the current beam of the base station  604  to another beam (e.g., upon determining that there is a better beam than the current beam). At  662 , the base station  604  generates a beam change instruction to indicate whether the base station  604  will perform beam change from the current beam to another beam, and includes the beam change instruction in a DCI for an uplink grant. At  664 , the base station transmits a PDCCH including the DCI. At  672 , the UE successfully decodes the DCI to detect the beam change instruction. At  680 , the UE transmits a PUSCH if the UE successfully decoded the DCI to detect the beam change instruction. At  642 , based on the PUSCH, the base station  604  determines whether to change the current beam to another beam. The example diagram  650  does not exhibit the same problem as the example diagram  600 , where the UE  602  of the example diagram  600  may still send a NACK even if the UE  602  successfully decodes the DCI as long as the CRC for the PDSCH fails. 
     According to an aspect of the disclosure, when the base station generates a beam change instruction to indicate that the base station will change from the current beam to another beam, the base station transmits the beam change instruction in DCI to the UE. The beam associated with the beam change instruction may be a transmit beam of the base station or a receive beam of the base station. When the UE receives DCI from the base station, the UE decodes the DCI to attempt to detect a beam change instruction in the DCI. Subsequently, the UE may indicate to the base station whether the UE has detected the beam change instruction, such that the base station may determine whether the UE has detected the beam change instruction based on the indication. If the base station determines that the beam change instruction is detected by the UE, the base station may change from the current beam to another beam. Several approaches may be utilized to implement the features according to the aspect of the disclosure, as discussed infra. 
     According to a first aspect of the disclosure, the base station may utilize a DCI for an uplink grant, to communicate a beam change instruction. Thus, for example, the base station may utilize a DCI for an uplink grant when a DCI is used to communicate a beam change instruction to the UE.  FIG. 7A  is an example diagram  700  illustrating the first aspect of the disclosure. After the base station  704  determines to change the beam, the base station  704  transmits at  712  a PDCCH with a DCI for an uplink grant. The UE  702  attempts to decode the DCI to detect the beam change instruction at  714 . The UE  702  transmits at  716  an indication to indicate whether the beam change instruction is detected via a PUSCH. At  718 , based on the indication from the UE  702 , the base station  704  determines whether to change the beam (e.g., by decoding the indication). In one example, as discussed above, the base station may measure the energy of the DMRS of the PUSCH to determine whether the DCI for uplink is successfully decoded to detect the beam change request. As discussed above, if the energy of the DMRS is greater than an energy threshold, the base station may determine that the UE has successfully decoded the DCI for uplink grant to detect the beam change instruction. In another example, the base station may attempt to decode the DMRS of the PUSCH, where the DMRS indicates that the beam change instruction is detected by the UE. Because the base station relies on at least one of the energy of the DMRS for such determination, decoding of the DMRS, or an energy of the uplink traffic, the ACK/NACK response for the CRC for the PDSCH does not interfere with the base station determining whether the DCI for uplink is successfully decoded to detect the beam change request. 
     According to a second aspect of the disclosure, the base station may use a semi-persistent scheduling (SPS) type DCI such that an ACK is expected based on successful decoding of the SPS type DCI. In a case where one ACK/NACK response is used for both a PDSCH and the SPS type DCI decoding, if the UE does not successfully receive a PDSCH, the UE may send a NACK to the base station regardless of whether the SPS type DCI is successfully decoded. In the second aspect of the disclosure, a response to the SPS type DCI is not associated with a response to the PDSCH. Thus, in the second aspect, although the UE may transmit an ACK/NACK response in response to the PDSCH, the UE transmits a separate ACK/NACK response for decoding of the SPS type DCI, where the separate ACK/NACK response is different from the ACK/NACK response in response to the PDSCH. For example, the UE transmits an ACK/NACK response in response to the PDSCH, and also transmits a separate ACK/NACK response in response to the SPS type DCI. The SPS type DCI has a different bit pattern than other types of DCI. For example, when the UE decodes the PDDCH and detects a different bit pattern indicating the SPS type DCI, the UE becomes aware that the UE should transmit a separate ACK/NACK response for the PDDCH carrying the SPS type DCI, independent from the PDSCH.  FIG. 7B  is an example diagram  730  illustrating the second aspect of the disclosure. After the base station  704  determines to change the beam, the base station  704  transmits at  732  a PDCCH with a SPS type DCI, and may transmit a PDSCH. The UE  702  attempts to decode the SPS type DCI to detect the beam change instruction at  734 . The UE  702  transmits at  736  an indication (e.g., a separate ACK/NACK) to indicate whether the beam change instruction is detected to the base station  704  via a PUCCH, where the indication is a separate indication for the PDDCH carrying the SPS type DCI. At  738 , based on the indication from the UE  702 , the base station  704  determines whether to change the beam. Because a distinct SPS type DCI is utilized, for which a separate ACK/NACK response is transmitted, the ACK/NACK response for the CRC for the PDSCH does not interfere with the separate ACK/NACK response for the successful detection of the beam change instruction. 
     According to a third aspect of the disclosure, when the base station uses a DCI for a downlink grant to convey a beam change instruction, the UE may utilize a distinct scrambling code to scramble the PUCCH transmitted to the base station when the DCI is decoded and the beam switching command is detected from the DCI, where the distinct scrambling code is different from a scrambling code used to scramble the PUCCH when the DCI is not decoded to detect the beam switching command.  FIG. 7C  is an example diagram  750  illustrating the third aspect of the disclosure. After the base station  704  determines to change the beam, the base station  704  transmits at  752  a PDCCH with a DCI, and may transmit a PDSCH. The UE  702  attempts to decode the DCI to detect the beam change instruction at  754 . At  756 , if the UE  702  successfully decodes the DCI to detect the beam change instruction, the UE scrambles the PUCCH with a distinct scrambling code to indicate that the beam change instruction is detected. The UE  702  transmits at  758  the scrambled PUCCH. At  760 , based on the PUCCH scrambled with the distinct scrambling code received from the UE  702 , the base station  704  determines that the beam change instruction is detected and determines to change the beam. Because the distinct scrambling code is used when the beam switching command is detected, the PUCCH scrambled with the distinct scrambling code indicates to the base station that the beam switching command is detected. Thus, the base station may determine that the beam switching command is detected based on receiving the PUCCH scrambled with the distinct scrambling code, even if the UE concurrently sends a NACK for the corresponding PDSCH transmission. Thus, by detecting the PUCCH scrambled with the distinct scrambling code, the base station may determine that the beam switching command is detected. 
     According to a fourth aspect of the disclosure, the UE may include a distinct DMRS sequence in the PUCCH transmitted to the base station when a DCI is decoded and the beam switching command is detected from the DCI. The distinct DMRS sequence is different from a DMRS sequence used by the UE to transmit the PUCCH if the beam change instruction is not detected in the DCI. Thus, by detecting the distinct DMRS sequence in the PUCCH, the base station may determine that the beam switching command is detected.  FIG. 7D  is an example diagram  750  illustrating the fourth aspect of the disclosure. After the base station  704  determines to change the beam, the base station  704  transmits at  772  a PDCCH with a DCI, and may transmit a PDSCH. The UE  702  attempts to decode the DCI to detect the beam change instruction at  774 . At  776 , if the UE  702  successfully decodes the DCI to detect the beam change instruction, the UE includes a distinct DMRS sequence in the PUCCH to indicate that the beam change instruction is detected. The UE  702  transmits at  778  the PUCCH with the distinct DMRS sequence. At  780 , based on the distinct DMRS sequence in the PUCCH received from the UE  702 , the base station  704  determines that the beam change instruction is detected and determines to change the beam. Because the third and fourth aspects provide a specific indication that the beam switching command is detected, the ACK/NACK response for the CRC for the PDSCH does not interfere with this indication. 
     According to a fifth aspect of the disclosure, the UE may send a tri-state indicator (e.g., a tri-state ACK) to provide one of three indications. In an aspect, the tri-state indicator may be sent via a PUCCH (e.g., via bits in the PUCCH for the tri-state indicator). The first indication indicates that the DCI has been successfully decoded and the CRC for a PDSCH has failed. The second indication indicates that the DCI has been successfully decoded and the CRC for the PDSCH has passed. The third indication indicates that the DCI has not been successfully decoded.  FIG. 8A  is an example diagram  800  illustrating the fifth aspect of the disclosure. After the base station  804  determines to change the beam, the base station  804  transmits at  812  a PDCCH with a DCI, and transmits a PDSCH. At  814 , the UE  802  attempts to decode the DCI to detect the beam change instruction, and performs a CRC for the PDSCH. At  816 , the UE  802  generates a tri-state indicator including one of the three indications discussed above. The UE  802  transmits at  818  the tri-state indication. At  820 , based on the tri-state indication, the base station  804  determines whether to change the beam. For example, the base station  804  may determine to change the beam when the tri-state indication provides the first indication or the second indication because the first indication and the second indication indicate that the DCI has been successfully decoded to detect the beam change instruction. Because the tri-state indicator in the fifth aspect provides a specific indication for CRC pass/fail and successful decoding of the DCI, the ACK/NACK response for the CRC for the PDSCH does not interfere with the tri-state indicator. 
     According to a sixth aspect of the disclosure, the UE adds a portion (e.g., a bit) in a PUCCH to separately indicate an ACK/NACK response for successful decoding of the DCI (and detection of the beam change instruction), separate from the ACK/NACK response for the PDSCH.  FIG. 8B  is an example diagram  830  illustrating the sixth aspect of the disclosure. After the base station  804  determines to change the beam, the base station  804  transmits at  832  a PDCCH with a DCI, and may transmit a PDSCH. At  834 , the UE  802  attempts to decode the DCI to detect the beam change instruction. At  836 , the UE  802  includes a bit in a PUCCH to separately indicate an ACK/NACK response for successful decoding of the DCI and detection of the beam change instruction. The UE  802  transmits at  838  the PUCCH with the bit. At  840 , based on the bit included in the PUCCH, the base station  704  determines whether to change the beam. Because this aspect of the disclosure utilizes a separate portion to indicate an ACK/NACK response for the DCI, the ACK/NACK response for the CRC for the PDSCH does not interfere with the ACK/NACK response for the successful detection of the beam change instruction 
     According to a seventh aspect of the disclosure, after transmitting a DCI including a beam change instruction, the base station receives two or more sample signals using two or more different beams, respectively. The base station may also multiply the same samples of antenna elements with two different beam weights to receive two different samples. At least one of the two or more different beams is indicated by the beam change instruction. The current beam may also be indicated in the beam change instruction. The base station receives the sample signals in a subframe specified in the DCI. Based on the received sample signals, the base determines conditions (e.g., beamwidths) for each of the sample signals, and selects a beam corresponding to a sample signal with the best condition (e.g., narrowest beamwidth).  FIG. 8C  is an example diagram  850  illustrating the sixth aspect of the disclosure. After the base station  804  determines to change the beam, the base station  804  transmits at  852  a PDCCH with a DCI, and may transmit a PDSCH. At  854 , the UE  802  decodes the DCI to detect the beam change instruction. At  856 , the base station  804  receives a first sample signal using a current beam. At  858 , the base station  804  receives a second sample signal using a second beam indicated by the beam change instruction. At  860 , the base station  804  selects one of the current beam and the second beam based on the first sample signal and the second sample signal. 
       FIG. 9  is a flowchart  900  of a method of wireless communication, according to an aspect of the disclosure. The method may be performed by a base station (e.g., the base station  704 , the base station  804 , the apparatus  1202 / 1202 ′). At  902 , the base station determines to change from a first beam to a second beam. For example, as discussed supra, the base station may determine to change from a current beam to a second beam when the UE indicates to the base station to change the beam of the base station. In an aspect, the first beam and the second beam may be transmit beams or receive beams. At  904 , the base station generates a beam change instruction to indicate the determination to change from the first beam to the second beam. At  906 , the base station transmits, to a UE, the beam change instruction in a DCI. For example, as discussed supra, when the base station generates a beam change instruction to indicate that the base station will change from the current beam to another beam, the base station transmits the beam change instruction in DCI to the UE. For example, as discussed supra, the beam associated with the beam change instruction may be a transmit beam of the base station or a receive beam of the base station. In an aspect, the base station may transmit the beam change instruction by transmitting a PDCCH including the DCI that is for uplink grant or downlink grant or is communicated via SPS. As illustrated in  FIGS. 7A-7D , the base station  704  may transmit DCI for UL grant or DCI for DL grant, or may transmit SPS DCI, via a PDCCH. At  908 , the base station determines whether or not the beam change instruction is detected by the UE. For example, as discussed supra, the base station may determine whether the UE has detected the beam change instruction based on the indication from the UE. 
     In an aspect the DCI is an SPS DCI. In an aspect, the SPS DCI is independent from a PDSCH. In an aspect, the SPS DCI has a different bit pattern than other DCIs. The SPS type DCI has a different bit pattern than other types of DCI. In an aspect, the base station determines whether or not the beam change instruction is detected by receiving from the UE, an ACK indicating that the SPS DCI is received by the UE or a NACK indicating that the SPS DCI is not received by the UE. For example, as discussed supra, when the UE decodes the PDDCH and detects a different bit pattern indicating the SPS type DCI, the UE becomes aware that the UE should transmit a separate ACK/NACK response for the PDDCH carrying the SPS type DCI, independent from the PDSCH. For example, as illustrated in  FIG. 7B , the UE  702  transmits at  736  an indication (e.g., a separate ACK/NACK) to indicate whether the beam change instruction is detected to the base station  704  via a PUCCH, where the indication is a separate indication for the PDDCH carrying the SPS type DCI. For example, as illustrated in  FIG. 7B , at  738 , based on the indication from the UE  702 , the base station  704  determines whether to change the beam. 
     In an aspect, the DCI is for DL grant. In an aspect, base station determines whether or not the beam change instruction is detected by receiving an indication that the beam change instruction is detected, where the determining whether or not the beam change instruction is detected is based on the indication. In such an aspect, the indication is received via a physical uplink control channel (PUCCH), the PUCCH being associated with the DCI for the DL grant. For example, as illustrated in  FIGS. 7B-7D  and  FIG. 8B , the UE  702  may transmit, to the base station  704 , a PUCCH with an indication that the beam change instruction is detected. In one aspect, the indication may include the PUCCH scrambled with a beam change scrambling code indicating that the beam change instruction is detected by the UE. In such an aspect, the beam change scrambling code is different from a scrambling code used by the UE to transmit a PUCCH if the beam change instruction is not detected in the DCI. For example, as illustrated in  FIG. 7C , at  756 , if the UE  702  successfully decodes the DCI to detect the beam change instruction, the UE scrambles the PUCCH with a distinct scrambling code to indicate that the beam change instruction is detected, and the UE  702  transmits at  758  the scrambled PUCCH. For example, as illustrated in  FIG. 7C , at  760 , based on the PUCCH scrambled with the distinct scrambling code received from the UE  702 , the base station  704  determines that the beam change instruction is detected and determines to change the beam. 
     In another aspect, the indication may include the PUCCH including a beam change DMRS sequence indicating that the beam change instruction is detected by the UE. In such an aspect, the beam change DMRS sequence is different from a DMRS sequence used by the UE to transmit a PUCCH if the beam change instruction is not detected in the DCI. For example, as illustrated in  FIG. 7D , at  776 , if the UE  702  successfully decodes the DCI to detect the beam change instruction, the UE includes a distinct DMRS sequence in the PUCCH to indicate that the beam change instruction is detected, and the UE  702  transmits at  778  the PUCCH with the distinct DMRS sequence. For example, as illustrated in  FIG. 7D , at  780 , based on the distinct DMRS sequence in the PUCCH received from the UE  702 , the base station  704  determines that the beam change instruction is detected and determines to change the beam. 
     In another aspect, the indication includes a tri-state indicator indicating one of: successful decoding of the DCI and failure of a CRC for a PDSCH when the DCI is successfully decoded and the CRC for the PDSCH fails, successful decoding of the DCI and a pass of the CRC for the PDSCH when the DCI is successfully decoded and the CRC for the PDSCH passes, and unsuccessful decoding of the DCI when the DCI is not successfully decoded. As illustrated in  FIG. 8A , at  816 , the UE  802  generates a tri-state indicator including one of the three indications, where the three indications may include the first indication that the DCI has been successfully decoded and the CRC for a PDSCH has failed, the second indication that the DCI has been successfully decoded and the CRC for the PDSCH has passed, and the third indication that the DCI has not been successfully decoded, and the UE  802  transmits at  818  the tri-state indication. 
     In another aspect, the indication includes a DCI bit included in the PUCCH to indicate whether the DCI is successfully decoded. For example, as illustrated in  FIG. 8B , at  836 , the UE  802  includes a bit in a PUCCH to separately indicate an ACK/NACK response for successful decoding of the DCI and detection of the beam change instruction, and the UE  802  transmits at  838  the PUCCH with the bit. For example, as illustrated in  FIG. 8B , at  840 , based on the bit included in the PUCCH, the base station  704  determines whether to change the beam. 
     In one aspect, the DCI is transmitted for UL grant. In an aspect, the base station determines whether or not the beam change instruction is detected further by receiving an uplink transmission indicating that the UE has detected the beam change instruction, and decoding the uplink transmission to determine whether or not the beam change instruction is detected. For example, as illustrated in  FIG. 7A , the UE  702  transmits at  716  an indication to indicate whether the beam change instruction is detected via a PUSCH, and at  718 , based on the indication from the UE  702 , the base station  704  determines whether to change the beam (e.g., by decoding the indication). In an aspect, the base station determines whether or not the beam change instruction is detected by the UE further by receiving an uplink transmission indicating that the UE has detected the beam change instruction, and detecting an energy of the uplink transmission to determine whether or not the beam change instruction is detected. In such an aspect, the base station determines that the beam change instruction is detected if the detected energy of the uplink transmission is greater than an energy threshold. For example, as discussed supra, as discussed supra, if the energy of the DMRS is greater than an energy threshold, the base station may determine that the UE has successfully decoded the DCI for uplink grant to detect the beam change instruction. In another aspect, the base station determines whether or not the beam change instruction is detected by the UE further by receiving an uplink transmission indicating that the UE has detected the beam change instruction, and decoding a DMRS included in the uplink transmission, the DMRS indicating that the beam change instruction is detected. For example, as discussed supra, the base station may attempt to decode the DMRS of the PUSCH, where the DMRS indicates that the beam change instruction is detected by the UE. 
     At  910 , the base station may change from the first beam to the second beam upon determining that the beam change instruction is detected by the UE. For example, as discussed supra, if the base station determines that the beam change instruction is detected by the UE, the base station may change from the current beam to another beam. 
       FIG. 10  is a flowchart  1000  of a method of wireless communication, according to an aspect of the disclosure. The method may be performed by a base station (e.g., the base station  704 , the base station  804 , the apparatus  1202 / 1202 ′). At  1002 , the base station transmits a beam change instruction in a DCI using a first beam. At  1004 , the base station receives a first sample signal using the first beam. At  1006 , the base station receives a second sample signal using a second beam indicated by the beam change instruction. At  1008 , the base station selects one of the first beam and the second beam based on the first sample signal and the second sample signal. In an aspect, the first sample signal and the second sample signal are received in a subframe specified to the UE in the DCI. For example, as illustrated in  FIG. 8C , at  856 , the base station  804  receives a first sample signal using a current beam, and at  858 , the base station  804  receives a second sample signal using a second beam indicated by the beam change instruction. For example, as illustrated in  FIG. 8C , at  860 , the base station  804  selects one of the current beam and the second beam based on the first sample signal and the second sample signal. 
       FIG. 11  is a conceptual data flow diagram  1100  illustrating the data flow between different means/components in an exemplary apparatus  1102 . The apparatus may be a base station. The apparatus includes a reception component  1104 , a transmission component  1106 , a beam management component  1108 , a beam change instruction component  1110 , and a sample acquisition component  1112 . 
     The beam management component  1108  determines to change from a first beam to a second beam, and may signal the determination to change to the beam change instruction component  1110 , at  1162 . The beam change instruction component  1110  generates a beam change instruction to indicate the determination to change from the first beam to the second beam. The beam change instruction component  1110  transmits via a transmission component  1106 , to a UE (e.g., the UE  1140 ), the beam change instruction in a DCI, at  1164  and  1162 . 
     In an aspect, the DCI is an SPS DCI. In an aspect, the SPS DCI is independent from a physical downlink shared channel (PDSCH). In an aspect, the SPS DCI has a different bit pattern than other DCIs. In an aspect, the beam change instruction component  1110  determines whether or not the beam change instruction is detected by receiving from the UE, an ACK indicating that the SPS DCI is received by the UE  1040  or a NACK indicating that the SPS DCI is not received by the UE  1040 . 
     In an aspect, the DCI is for DL grant. The beam change instruction component  1110  determines whether or not the beam change instruction is detected by receiving, via the reception component  1104 , an indication that the beam change instruction is detected, from the UE  1140 , at  1168  and  1170 , where the determining whether or not the beam change instruction is detected is based on the indication. In an aspect, the indication is received via a PUCCH, the PUCCH being associated with the DCI for the DL grant. In one aspect, the indication may include the PUCCH scrambled with a beam change scrambling code indicating that the beam change instruction is detected by the UE. In such an aspect, the beam change scrambling code is different from a scrambling code used by the UE to transmit a PUCCH if the beam change instruction is not detected in the DCI. In another aspect, the indication may include the PUCCH including a beam change DMRS sequence indicating that the beam change instruction is detected by the UE. In such an aspect, the beam change DMRS sequence is different from a DMRS sequence used by the UE to transmit a PUCCH if the beam change instruction is not detected in the DCI. In another aspect, the indication includes a tri-state indicator indicating one of: successful decoding of the DCI and failure of a cyclic redundancy check (CRC) for a PDSCH when the DCI is successfully decoded and the CRC for the PDSCH fails, successful decoding of the DCI and a pass of the CRC for the PDSCH when the DCI is successfully decoded and the CRC for the PDSCH passes, and unsuccessful decoding of the DCI when the DCI is not successfully decoded. In another aspect, the indication includes a DCI bit included in the PUCCH to indicate whether the DCI is successfully decoded. 
     The beam change instruction component  1110  determines whether or not the beam change instruction is detected by the UE  1140 , and may signal the determination to the beam management component  1108 , at  1172 . The beam management component  1108  may change from the first beam to the second beam upon determining that the beam change instruction is detected by the UE. 
     In an aspect, the DCI may be for UL grant. In an aspect, the beam change instruction component  1110  determines whether or not the beam change instruction is detected by the UE  1040  further by receiving, via the reception component  1104 , an uplink transmission indicating that the UE has detected the beam change instruction, and decoding the uplink transmission to determine whether or not the beam change instruction is detected. In another aspect, the beam change instruction component  1110  determines whether or not the beam change instruction is detected further by receiving, via the reception component  1104 , an uplink transmission indicating that the UE has detected the beam change instruction, and detecting an energy of the uplink transmission to determine whether or not the beam change instruction is detected. In such an aspect, the beam change instruction component  1110  determines that the beam change instruction is detected if the detected energy of the uplink transmission is greater than an energy threshold. In another aspect, the beam change instruction component  1110  determines whether or not the beam change instruction is detected further by receiving, via the reception component  1104 , an uplink transmission indicating that the UE has detected the beam change instruction, and decoding a DMRS included in the uplink transmission, the DMRS indicating that the beam change instruction is detected. 
     In an aspect, the beam change instruction component  1110  transmits, via the transmission component  1106 , the beam change instruction by transmitting a PDCCH including the DCI that is for uplink grant or downlink grant or is communicated via SPS. 
     Following is another approach according to an aspect of the disclosure. The beam change instruction component  1110  transmits, via the transmission component  1106 , a beam change instruction in a DCI using a first beam (e.g., to the UE  1140 ), at  1164  and  1166 . The sample acquisition component  1112  receives, via the reception component  1104 , a first sample signal using the first beam, at  1168  and  1174 . The sample acquisition component  1112  receives, via the reception component  1104 , a second sample signal using a second beam indicated by the beam change instruction, at  1174 . The sample acquisition component  1112  may be forwarded information about the first and second sample singles to the beam management component  1108 , at  1176 . The beam management component  1108  selects one of the first beam and the second beam based on the first sample signal and the second sample signal. In an aspect, the first sample signal and the second sample signal are received in a subframe specified to the UE in the DCI. 
     The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowcharts of  FIGS. 9 and 10 . As such, each block in the aforementioned flowcharts of  FIGS. 9 and 10  may be performed by a component and the apparatus may include one or more of those components. The components 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. 12  is a diagram  1200  illustrating an example of a hardware implementation for an apparatus  1102 ′ employing a processing system  1214 . The processing system  1214  may be implemented with a bus architecture, represented generally by the bus  1224 . The bus  1224  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  1214  and the overall design constraints. The bus  1224  links together various circuits including one or more processors and/or hardware components, represented by the processor  1204 , the components  1104 ,  1106 ,  1108 ,  1110 ,  1112 , and the computer-readable medium/memory  1206 . The bus  1224  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  1214  may be coupled to a transceiver  1210 . The transceiver  1210  is coupled to one or more antennas  1220 . The transceiver  1210  provides a means for communicating with various other apparatus over a transmission medium. The transceiver  1210  receives a signal from the one or more antennas  1220 , extracts information from the received signal, and provides the extracted information to the processing system  1214 , specifically the reception component  1104 . In addition, the transceiver  1210  receives information from the processing system  1214 , specifically the transmission component  1106 , and based on the received information, generates a signal to be applied to the one or more antennas  1220 . The processing system  1214  includes a processor  1204  coupled to a computer-readable medium/memory  1206 . The processor  1204  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory  1206 . The software, when executed by the processor  1204 , causes the processing system  1214  to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory  1206  may also be used for storing data that is manipulated by the processor  1204  when executing software. The processing system  1214  further includes at least one of the components  1104 ,  1106 ,  1108 ,  1110 ,  1112 . The components may be software components running in the processor  1204 , resident/stored in the computer readable medium/memory  1206 , one or more hardware components coupled to the processor  1204 , or some combination thereof. The processing system  1214  may be a component of the eNB  310  and may include the memory  376  and/or at least one of the TX processor  316 , the RX processor  370 , and the controller/processor  375 . 
     In one configuration, the apparatus  1102 / 1102 ′ for wireless communication includes means for determining to change from a first beam to a second beam, means for generating a beam change instruction to indicate the determination to change from the first beam to the second beam, means for transmitting, to a UE, the beam change instruction in a DCI, and means for determining whether or not the beam change instruction is detected by the UE. In an aspect, the apparatus  1102 / 1102 ′ may further include means for changing from the first beam to the second beam upon determining that the beam change instruction is detected by the UE. 
     In an aspect, the means for determining whether or not the beam change instruction is detected is configured to receive an uplink transmission indicating that the UE has detected the beam change instruction. In one aspect, the means for determining whether or not the beam change instruction is detected is further configured to receive an uplink transmission indicating that the UE has detected the beam change instruction, and decode the uplink transmission to determine whether or not the beam change instruction is detected. In another aspect, the means for determining whether or not the beam change instruction is detected is further configured to receive an uplink transmission indicating that the UE has detected the beam change instruction, and detect an energy of the uplink transmission to determine whether or not the beam change instruction is detected. In an aspect, the means for determining whether or not the beam change instruction is configured to determine that the beam change instruction is detected if the detected energy of the uplink transmission is greater than an energy threshold. In another aspect, the means for determining whether or not the beam change instruction is detected is further configured to receive an uplink transmission indicating that the UE has detected the beam change instruction, and decode a DMRS included in the uplink transmission, the DMRS indicating that the beam change instruction is detected. 
     In an aspect, the means for determining whether or not the beam change instruction is detected is configured to receive from the UE, an ACK indicating that the SPS DCI is received by the UE or a NACK indicating that the SPS DCI is not received by the UE. In an aspect, the means for transmitting the beam change instruction is configured to transmit a PDCCH including the DCI that is for uplink grant or downlink grant or is communicated via SPS. 
     In an aspect, the means for determining whether or not the beam change instruction is detected may be configured to receive an indication that the beam change instruction is detected, where the determining whether or not the beam change instruction is detected is based on the indication. 
     In another configuration, the apparatus  1102 / 1102 ′ for wireless communication includes means for transmitting a beam change instruction in a DCI using a first beam, means for receiving a first sample signal using the first beam, means for receiving a second sample signal using a second beam indicated by the beam change instruction, and means for selecting one of the first beam and the second beam based on the first sample signal and the second sample signal. 
     The aforementioned means may be one or more of the aforementioned components of the apparatus  1102  and/or the processing system  1214  of the apparatus  1102 ′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system  1214  may include the TX Processor  316 , the RX Processor  370 , and the controller/processor  375 . As such, in one configuration, the aforementioned means may be the TX Processor  316 , the RX Processor  370 , and the controller/processor  375  configured to perform the functions recited by the aforementioned means. 
       FIG. 13  is a flowchart  1300  of a method of wireless communication. The method may be performed by a UE (e.g., the UE  702 , the UE  802 , the apparatus  1402 / 1402 ′). At  1302 , the UE receives a DCI from a base station. At  1304 , the UE determines whether a beam change instruction is detected in the DCI. At  1306 , the UE indicates via an uplink transmission which is associated with the DCI whether the beam change instruction is detected, the uplink transmission including at least one of a PUCCH or a PUSCH. In an aspect, the PUCCH may include an ACK to indicate successful decoding of the DCI or a NACK to indicate unsuccessful decoding of the DCI. At  1308 , the UE transmits the uplink transmission to the base station. For example, as discussed supra, when the base station generates a beam change instruction to indicate that the base station will change from the current beam to another beam, the base station transmits the beam change instruction in DCI to the UE. For example, as discussed supra, when the UE receives DCI from the base station, the UE decodes the DCI to attempt to detect a beam change instruction in the DCI. Subsequently, for example, as discussed supra, the UE may indicate to the base station whether the UE has detected the beam change instruction, such that the base station may determine whether the UE has detected the beam change instruction based on the indication. For example,  FIGS. 7A-7D  illustrate that a PUCCH or a PUSCH may be used to indicate whether the beam change instruction is detected by the UE. 
     In an aspect, the UE may receive the DCI by receiving at least one of a DCI for uplink grant including the beam change instruction, a DCI for downlink grant including the beam change instruction, or a SPS DCI including the beam change instruction. In such an aspect, the UE may transmit the uplink transmission by transmitting an ACK indicating that the beam change instruction is detected or a NACK indicating that the beam change instruction is not detected when the SPS DCI grant is received. In such an aspect, the receiving at least one of the DCI for uplink grant, the DCI for downlink grant, or the SPS DCI includes receiving a PDCCH including at least one of the DCI for uplink grant, the DCI for downlink grant, or the SPS DCI. In such an aspect, the SPS DCI is independent from a PDSCH. For example, as illustrated in  FIG. 7A , the UE  702  attempts to decode the DCI for an uplink grant to detect the beam change instruction at  714 , and the UE  702  transmits at  716  an indication to indicate whether the beam change instruction is detected via a PUSCH, and at  718 , based on the indication from the UE  702 . For example, as illustrated in  FIG. 7B , the  702  attempts to decode the SPS type DCI to detect the beam change instruction at  734 , and the UE  702  transmits at  736  an indication (e.g., a separate ACK/NACK) to indicate whether the beam change instruction is detected to the base station  704  via a PUCCH, where the indication is a separate indication for the PDDCH carrying the SPS type DCI. 
     In an aspect, the UE indicates via the uplink transmission that the beam change instruction is detected by scrambling the PUCCH with a beam change scrambling code indicating that the beam change instruction is detected. In such an aspect, the beam change scrambling code is different from a scrambling sequence used by the UE to transmit a PUCCH if the beam change instruction is not detected in the DCI. For example, as illustrated in  FIG. 7C , at  756 , if the UE  702  successfully decodes the DCI to detect the beam change instruction, the UE scrambles the PUCCH with a distinct scrambling code to indicate that the beam change instruction is detected, and the UE  702  transmits at  758  the scrambled PUCCH. For example, as discussed supra, because the distinct scrambling code is used when the beam switching command is detected, the PUCCH scrambled with the distinct scrambling code indicates to the base station that the beam switching command is detected. 
     In an aspect, the UE indicates via the uplink transmission that the beam change instruction is detected by including a beam change DMRS sequence in the PUCCH indicating that the beam change instruction is detected. In such an aspect, the beam change DMRS sequence is different from a DMRS sequence used by the UE to transmit a PUCCH if the beam change instruction is not detected in the DCI. For example, as illustrated in  FIG. 7D , at  776 , if the UE  702  successfully decodes the DCI to detect the beam change instruction, the UE includes a distinct DMRS sequence in the PUCCH to indicate that the beam change instruction is detected, and the UE  702  transmits at  778  the PUCCH with the distinct DMRS sequence. For example, as discussed supra, the distinct DMRS sequence is different from a DMRS sequence used by the UE to transmit the PUCCH if the beam change instruction is not detected in the DCI. 
     In an aspect, the UE indicates via the uplink transmission that the beam change instruction is detected by including a tri-state indicator in the PUCCH to indicate one of: successful decoding of the DCI and failure of a CRC for a PDSCH when the DCI is successfully decoded and the CRC for the PDSCH fails, successful decoding of the DCI and a pass of the CRC for the PDSCH when the DCI is successfully decoded and the CRC for the PDSCH passes, and unsuccessful decoding of the DCI when the DCI is not successfully decoded. As illustrated in  FIG. 8A , At  816 , the UE  802  generates a tri-state indicator including one of the three indications, where the three indications may include the first indication that the DCI has been successfully decoded and the CRC for a PDSCH has failed, the second indication that the DCI has been successfully decoded and the CRC for the PDSCH has passed, and the third indication that the DCI has not been successfully decoded, and the UE  802  transmits at  818  the tri-state indication. 
     In an aspect, the UE indicates via the uplink transmission that the beam change instruction is detected by including a DCI bit in the PUCCH to indicate whether the DCI is successfully decoded. For example, as illustrated in  FIG. 8B , at  836 , the UE  802  includes a bit in a PUCCH to separately indicate an ACK/NACK response for successful decoding of the DCI and detection of the beam change instruction, and the UE  802  transmits at  838  the PUCCH with the bit. 
       FIG. 14  is a conceptual data flow diagram  1400  illustrating the data flow between different means/components in an exemplary apparatus  1402 . The apparatus may be a UE. The apparatus includes a reception component  1404 , a transmission component  1406 , and a DCI processing component  1408 , an indication management component  1410 , and a UL management component  1412 . 
     The DCI processing component  1408  receives, via the reception component  1404 , a DCI from a base station (e.g., base station  1450 ), at  1462  and  1464 . The DCI processing component  1408  determines whether a beam change instruction is detected in the DCI, and may signal the determination result to the indication management component  1414 , at  1466 . The indication management component  1414  indicates via an uplink transmission which is associated with the DCI whether the beam change instruction is detected, the uplink transmission including at least one of a PUCCH or a PUSCH, and may communicate the PUCCH to the UL management component  1412  at  1468 . In an aspect, the UL management component  1412  may transmit, via the transmission component  1406 , the uplink transmission to the base station, at  1470  and  1472 . In an aspect, the PUCCH includes an ACK to indicate successful decoding of the DCI or a NACK to indicate unsuccessful decoding of the DCI. 
     In an aspect, the DCI processing component  1408  may receive the DCI by receiving at least one of a DCI for uplink grant including the beam change instruction, a DCI for downlink grant including the beam change instruction, or a SPS DCI including the beam change instruction. In such an aspect, at  1310 , the indication management component  1414  and the UL management component  1412  may transmit the uplink transmission by transmitting, via the transmission component  1470 , an ACK indicating that the beam change instruction is detected or a NACK indicating that the beam change instruction is not detected when the SPS DCI grant is received. In such an aspect, the receiving at least one of the DCI for uplink grant, the DCI for downlink grant, or the SPS DCI includes receiving a PDCCH including at least one of the DCI for uplink grant, the DCI for downlink grant, or the SPS DCI. In such an aspect, the SPS DCI is independent from a PDSCH. 
     In an aspect, the indication management component  1414  indicates via the uplink transmission that the beam change instruction is detected by scrambling the PUCCH with a beam change scrambling code indicating that the beam change instruction is detected. In such an aspect, the beam change scrambling code is different from a scrambling sequence used by the UE to transmit a PUCCH if the beam change instruction is not detected in the DCI. 
     In an aspect, the indication management component  1414  indicates via the uplink transmission that the beam change instruction is detected by including a beam change DMRS sequence in the PUCCH indicating that the beam change instruction is detected. In such an aspect, the beam change DMRS sequence is different from a DMRS sequence used by the UE to transmit a PUCCH if the beam change instruction is not detected in the DCI. 
     In an aspect, the indication management component  1414  indicates via the uplink transmission that the beam change instruction is detected by including a tri-state indicator in the PUCCH to indicate one of: successful decoding of the DCI and failure of a CRC for a PDSCH when the DCI is successfully decoded and the CRC for the PDSCH fails, successful decoding of the DCI and a pass of the CRC for the PDSCH when the DCI is successfully decoded and the CRC for the PDSCH passes, and unsuccessful decoding of the DCI when the DCI is not successfully decoded. 
     In an aspect, the indication management component  1414  indicates via the uplink transmission that the beam change instruction is detected by including a DCI bit in the PUCCH to indicate whether the DCI is successfully decoded. 
     The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowcharts of  FIG. 13 . As such, each block in the aforementioned flowcharts of  FIG. 13  may be performed by a component and the apparatus may include one or more of those components. The components 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. 15  is a diagram  1500  illustrating an example of a hardware implementation for an apparatus  1402 ′ employing a processing system  1514 . The processing system  1514  may be implemented with a bus architecture, represented generally by the bus  1524 . The bus  1524  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  1514  and the overall design constraints. The bus  1524  links together various circuits including one or more processors and/or hardware components, represented by the processor  1504 , the components  1404 ,  1406 ,  1408 ,  1410 ,  1412 , and the computer-readable medium/memory  1506 . The bus  1524  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  1514  may be coupled to a transceiver  1510 . The transceiver  1510  is coupled to one or more antennas  1520 . The transceiver  1510  provides a means for communicating with various other apparatus over a transmission medium. The transceiver  1510  receives a signal from the one or more antennas  1520 , extracts information from the received signal, and provides the extracted information to the processing system  1514 , specifically the reception component  1404 . In addition, the transceiver  1510  receives information from the processing system  1514 , specifically the transmission component  1406 , and based on the received information, generates a signal to be applied to the one or more antennas  1520 . The processing system  1514  includes a processor  1504  coupled to a computer-readable medium/memory  1506 . The processor  1504  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory  1506 . The software, when executed by the processor  1504 , causes the processing system  1514  to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory  1506  may also be used for storing data that is manipulated by the processor  1504  when executing software. The processing system  1514  further includes at least one of the components  1404 ,  1406 ,  1408 ,  1410 ,  1412 . The components may be software components running in the processor  1504 , resident/stored in the computer readable medium/memory  1506 , one or more hardware components coupled to the processor  1504 , or some combination thereof. The processing system  1514  may be a component of the UE  350  and may include the memory  360  and/or at least one of the TX processor  368 , the RX processor  356 , and the controller/processor  359 . 
     In one configuration, the apparatus  1402 / 1402 ′ for wireless communication includes means for receiving a DCI from a base station, means for determining whether a beam change instruction is detected in the DCI, and means for indicating via an uplink transmission which is associated with the DCI whether the beam change instruction is detected, the uplink transmission including at least one of a PUCCH or a PUSCH, and means for transmitting the uplink transmission to the base station. 
     In an aspect, the means for indicating via the uplink transmission is configured to scramble the PUCCH with a beam change scrambling code indicating that the beam change instruction is detected. In an aspect, the means for indicating via the uplink transmission is configured to include a beam change DMRS sequence in the PUCCH indicating that the beam change instruction is detected. In an aspect, the means for indicating via the uplink transmission is configured to include a tri-state indicator in the PUCCH to indicate one of: successful decoding of the DCI and failure of a CRC for a PDSCH when the DCI is successfully decoded and the CRC for the PDSCH fails, successful decoding of the DCI and a pass of the CRC for the PDSCH when the DCI is successfully decoded and the CRC for the PDSCH passes, and unsuccessful decoding of the DCI when the DCI is not successfully decoded. In an aspect, the means for indicating in the PUCCH is configured to include a DCI bit in the PUCCH to indicate whether the DCI is successfully decoded. 
     In an aspect, the means for receiving the DCI comprises means for receiving at least one of a DCI for uplink grant including the beam change instruction, a DCI for downlink grant including the beam change instruction, or a SPS DCI including the beam change instruction. In such an aspect, the means for transmitting the uplink transmission may be configured to transmit an ACK indicating that the beam change instruction is detected or a NACK indicating that the beam change instruction is not detected when the SPS DCI grant is received. In such an aspect, the means for receiving at least one of the DCI for uplink grant, the DCI for downlink grant, or the SPS DCI is configured to receive a PDCCH including at least one of the DCI for uplink grant, the DCI for downlink grant, or the SPS DCI. 
     The aforementioned means may be one or more of the aforementioned components of the apparatus  1402  and/or the processing system  1514  of the apparatus  1402 ′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system  1514  may include the TX Processor  368 , the RX Processor  356 , and the controller/processor  359 . As such, in one configuration, the aforementioned means may be the TX Processor  368 , the RX Processor  356 , and the controller/processor  359  configured to perform the functions recited by the aforementioned means. 
     It is understood that the specific order or hierarchy of blocks in the processes/flowcharts disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes/flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks 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,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more 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,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more 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. The words “module,” “mechanism,” “element,” “device,” and the like may not be a substitute for the word “means.” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.”