Patent Publication Number: US-10327154-B2

Title: Beam switching

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 62/396,082, entitled “FAST BEAM RECOVERY” and filed on Sep. 16, 2016, the benefit of U.S. Provisional Application Ser. No. 62/401,814, entitled “BEAM SWITCH MESSAGE” and filed on Sep. 29, 2016, the benefit of U.S. Provisional Application Ser. No. 62/504,412, entitled “BEAM SWITCHING AND RECOVERY” and filed on May 10, 2017, and the benefit of U.S. Provisional Application Ser. No. 62/504,428, entitled “BEAM SWITCHING WITH RESET STATES” and filed on May 10, 2017, each of which is expressly incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     Field 
     The present disclosure relates generally to communication systems, and more particularly, to apparatuses and methods for beam switching in wireless communication. 
     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 5G New Radio (NR). 5G NR is part of a continuous mobile broadband evolution promulgated by Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with Internet of Things (IoT)), and other requirements. Some aspects of 5G NR may be based on the 4G Long Term Evolution (LTE) standard. There exists a need for further improvements in 5G NR technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies. 
     For example, some wireless communications may utilize different beam pairs from different antenna subarrays at a base station and at a user equipment (UE). The wireless communication may include transmitting and receiving control and data signals. An efficient scheme for the base station and/or the UE to switch beam pairs for wireless communication may improve the overall performance of the wireless communications. 
     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. 
     Beamforming can be used to create a narrow beam pattern between, for example, a base station (e.g., gNB) and a user equipment (e.g., a cell phone) that may enhance link budget and/or signal-to-noise ratio (SNR). Beamforming can offer several benefits, particularly for technologies that can suffer from high path loss, such as millimeter wave (mmW) communication. New techniques such as hybrid beamforming (analog and digital), which are not present in 3G and 4G systems, may be used to further enhance some benefits. In single-beam implementations, beamforming can be used to create a single beam. In multi-beam implementations, multiple beams can be created and used to cover a wider area. 
     In multi-beam wireless communication (or simply, multi-beam communication), devices communicating via a beam pair may switch to a different beam pair for various reasons. For example, a base station and a UE communicating via a first beam pair may switch to a second beam pair because the UE is moving out of the coverage area of the first beam pair and into the coverage area of the second beam pair. The condition and environment may change such that communication via a different beam pair between the base station and the UE would be more advantageous. However, to be effective, beam switching requires a coordinated effort between the base station and the UE. In some situations, the beam switching may not be so easily confirmed or synchronized. 
     Apparatuses and methods for beam switching are presented below. The ideas described below may, for example, increase the efficiency of beam switching in various implementations by providing an enhanced form of messaging, may allow faster beam recovery when devices fail to switch beams properly, etc. 
     In various embodiments, a first device can transmit a beam switch message (BSM) to a second device via a first beam set. The BSM can include a command to switch from communication via the first beam set to communication via a second beam set at a switch time. The first device can receive a response message from the second device via the first beam set. The response message can indicate that the second device received the BSM. The first device can send, to the second device, a communication via the second beam set after the switch time if the response message is received. The communication can be, for example, data, control information, or reference signals. 
     In some cases, the BSM can further include a command to switch from communication via the second beam set to communication via a third beam set at a second switch time, and the first device can send, to the second device, a communication via the third beam set after the second switch time if the response message is received. 
     The response message can include, for example, a reference signal strength indicator (RSSI), reference signal received power (RSRP), reference signal received quality (RSRQ), an SNR, a signal to interference plus noise ratio (SINR), an acknowledgment (ACK), or a measurement report. 
     In various embodiments, a first device can monitor for a BSM from a second device via a first beam set. The BSM can include a command to switch from communication via the first beam set to communication via a second beam set at a switch time. The first device can send a response message to the second device when the BSM is received and can switch from communication via the first beam set to communication via the second beam set at the switch time. 
     In various embodiments, a first device can transmit a beam switch message to a second device via a first beam set. The beam switch message can include a command to switch from communication via the first beam set to communication via a second beam set at a switch time. The first device can monitor for a response message from the second device. The response message can indicate the second device received the beam switch message. The first device can determine whether the response message was received from the second device. The first device can switch to communication via the second beam set at the switch time whether or not the response message was received. For example, switching beam sets whether or not a response message was received may avoid a time-consuming recovery process, particularly if the second device received the beam switch message and switched beam sets. 
     In various embodiments, a first device can transmit a beam switch message to a second device via a first beam set and can switch to communication via the second beam set at the switch time without monitoring prior to the switch time for a response message indicating the second device received the beam switch message. The first device can determine after the switch time if the second device is communicating via the second beam set. In this way, for example, signaling may be reduced because a response process need not be performed. This approach may work well, particularly when the possibility of delivery failure of the beam switch message is low. 
     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 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 a base station and UE in an access network. 
         FIG. 4  is a diagram illustrating a base station in communication with a UE. 
         FIG. 5  includes diagrams of communications between a base station and a UE via multiple beams. 
         FIG. 6  illustrates an example of single-switch beam switch messages according to various embodiments. 
         FIG. 7  illustrates an example of multiple-switch BSMs according to various embodiments. 
         FIG. 8  illustrates an example situation of signal error in multi-beam wireless communication. 
         FIG. 9  illustrates another example situation of signal error in multi-beam wireless communication. 
         FIGS. 10A-C  illustrate an example implementation of a method of wireless communication in accordance with various embodiments. 
         FIGS. 11A-C  illustrates an example implementation of a method of wireless communication in accordance with various embodiments. 
         FIG. 12A-B  illustrate an example implementation of a method of wireless communication in accordance with various embodiments. 
         FIGS. 13A-B  illustrate another example implementation of a method of wireless communication in accordance with various embodiments. 
         FIG. 14  illustrates an example implementation of a method of wireless communication in accordance with various embodiments. 
         FIG. 15  illustrates an implementation of  FIG. 14  in a situation that a response to a BSM is lost. 
         FIG. 16  illustrates an implementation of  FIG. 14  in a situation that a BSM is lost. 
         FIG. 17  illustrates another example implementation of a method of wireless communication in accordance with various embodiments. 
         FIG. 18  illustrates an example implementation of a method of wireless communication in accordance with various embodiments. 
         FIG. 19  illustrates an example implementation of a method of wireless communication in accordance with various embodiments. 
         FIG. 20  is a flowchart illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. 
         FIG. 21  is a flowchart illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. 
         FIG. 22  is a flowchart illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. 
         FIG. 23  is a flowchart illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. 
         FIG. 24  is a flowchart illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. 
         FIG. 25  is a flowchart illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. 
         FIG. 26  is a conceptual data flow diagram illustrating the data flow between different means/components in an exemplary apparatus. 
         FIG. 27  is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system. 
         FIG. 28  is a conceptual data flow diagram illustrating the data flow between different means/components in an exemplary apparatus. 
         FIG. 29  is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system. 
         FIG. 30  is a conceptual data flow diagram illustrating the data flow between different means/components in an exemplary apparatus. 
         FIG. 31  is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system. 
         FIG. 32  is a conceptual data flow diagram illustrating the data flow between different means/components in an exemplary apparatus. 
         FIG. 33  is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system. 
         FIG. 34  is a conceptual data flow diagram illustrating the data flow between different means/components in an exemplary apparatus. 
         FIG. 35  is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system. 
         FIG. 36  is a conceptual data flow diagram illustrating the data flow between different means/components in an exemplary apparatus. 
         FIG. 37  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 base stations. 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., S1 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 multiple-input and multiple-output (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, 100 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 NR and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP  150 . The small cell  102 ′, employing NR in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. 
     The gNodeB (gNB)  180  may operate in millimeter wave (mmW) frequencies and/or near mmW frequencies in communication with the UE  104 . When the gNB  180  operates in mmW or near mmW frequencies, the gNB  180  may be referred to as an mmW base station. 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  104  to compensate for the extremely high path loss and short range. The base station  180  may wirelessly communicate with UE  182  via multiple beams (not shown). The multiple beams of base station  180  may provide communication coverage for the geographic coverage area of base station  180 , such that the geographic coverage area may include multiple beams emanating from base station  180 . Communication link  184  between base station  180  and UE  182  can be established via a beam set (for example, a beam pair) and may include UL (also referred to as reverse link) transmissions from the UE to the base station and/or DL (also referred to as forward link) transmissions from the base station to the UE. Communication link  184  may be established by beamforming based on, for example, MIMO antenna technology, and may also include spatial multiplexing, and/or transmit diversity. 
     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 gNB, 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, a vehicle, an electric meter, a gas pump, a toaster, or any other similar functioning device. Some of the UEs  104  may be referred to as IoT devices (e.g., parking meter, gas pump, toaster, vehicles, etc.). 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, UE  182  and/or base station  180  may be configured to perform beam recovery by, for example, sending a BSM, determining whether a response is received, and communicating via a target beam when a response to the BSM is unreceived, and performing a beam switch reset by, for example, sending a first BSM, selecting a reset state, and sending a second BSM indicating the reset state ( 198 ). 
       FIG. 2A  is a diagram  200  illustrating an example of a DL frame structure.  FIG. 2B  is a diagram  230  illustrating an example of channels within the DL frame structure.  FIG. 2C  is a diagram  250  illustrating an example of an UL frame structure.  FIG. 2D  is a diagram  280  illustrating an example of channels within the UL frame structure. Other wireless communication technologies may have a different frame structure and/or different channels. 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). 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.  2 A 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 ACK/negative ACK (NACK) feedback based on the physical uplink shared channel (PUSCH). The primary synchronization channel (PSCH) may be within symbol  6  of slot  0  within subframes  0  and  5  of a frame. The PSCH carries a primary synchronization signal (PSS) that is used by a UE to determine subframe/symbol timing and a physical layer identity. The secondary synchronization channel (SSCH) may be within symbol  5  of slot  0  within subframes  0  and  5  of a frame. The SSCH carries a secondary synchronization signal (SSS) that is used by a UE to determine a physical layer cell identity group number and radio frame timing. 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), which carries a master information block (MIB), may be logically grouped with the PSCH and SSCH to form a synchronization signal (SS) block. 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 base station. 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 a base station 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 a base station  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 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 base station  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 base station  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 base station  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 base station  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 base station  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. 
     Base station  310  may wirelessly communicate with UE  350  via multiple beams (not shown). For example, TX processor  316  of base station  310  may control antennas  320  to form a beam directed at UE  350 , and RX processor  356  of UE  350  may control antennas  352  to receive communication via a beam directed at base station  310 . In other words, a communication link between base station  310  and UE  350  can be established via a beam set (for example, a beam pair), which may include UL transmissions from the UE to the base station and/or DL transmissions from the base station to the UE. 
       FIG. 4  is a diagram  400  illustrating multi-beam communication in which a base station  402  is in communication with a UE  404 . Referring to  FIG. 4 , when the UE  404  turns on, the UE  404  searches for a nearby NR network. The UE  404  discovers the base station  402 , which belongs to an NR network. The base station  402  transmits an SS block including the PSS, SSS, and the PBCH (including the MIB) periodically in different transmit directions  402   a - 402   h . The UE  404  receives a transmission in transmit direction  402   e , including the PSS, SSS, and PBCH. Based on the received SS block, the UE  404  synchronizes to the NR network and camps on a cell associated with the base station  402 . 
       FIG. 5  includes diagrams of communications between a base station and a UE via multiple beams. In some examples, diagrams  560  and  561  depict mmW communications between base station  562  and UE  566 . The diagram  560  depicts the case where base station  562  (e.g., an example of a base station) transmits to UE  566  via at least one of beam sets  510  and  512 , which may be referred to simply as beams  510  and  512 . The beams  510 / 512  may carry the DL/UL signals discussed in the previous sections. The diagram  561  depicts the case where UE  566  transmits to base station  562  via at least one of beams  520  and  522 . The beams  520 / 522  may carry the DL/UL signals discussed in the previous sections. For example, beam  510  of first beam pair  550  and beam  512  of second beam pair  552  carry the DL signals. The beam  520  of first beam pair  550  and beam  522  of second beam  552  carry the UL signals. 
     Each of beams  510 ,  512 ,  520 , and  522  may include more than one beam. In this regard, a beam set may include one or more beams. For example, beam  510  may include a beam  510 _C to carry control signals and channels and a beam  510 _D to carry data signals and channels. In some examples, the beams may be associated. For example, in one case, base station  562  and UE  566  may communicate via beam  510  and beam  520 . That is, base station  562  may transmit to UE  566  via beam  510  and receive from UE  566  via beam  520 . The beams  510  and  520  are thus associated and may be referred to as a beam pair. For example, beam  510  and associated beam  520  may be referred to as first beam pair  550 , and beam  512  and associated beam  522  may be referred to as second beam pair  552 . 
     The base station (e.g., a gNB)  562  and UE  566  may communicate over active beam pairs (e.g., first beam pair  550  and or second beam pair  552 ). Active beam pairs may be base station  562  and UE  566  beam pairs that carry data and control channels such as PDSCH, PDCCH, PUSCH, and PUCCH. In one aspect, base station  562  may monitor active beam pairs using reported measurements of signals (e.g., reported by UE  566  by the beams from the base station (e.g., the base station can monitor the beams from the UE by measuring such beams directly)) such as measurement reference signal (MRS), CSI-RS, primary synchronization signal and Secondary synchronization signal (SYNC). To do so, base station  562  may send a measurement request, for example, a beam state information request to UE  566 . UE  566  may, in response, measure the measurement signals and send a report that contains beam identifications and beam quality for each beam measured. Base station  562  may then signal a beam switch to the UE. The beam switch signal (e.g., message) may contain the target beam identifier (e.g., identify the target beam pair) and/or time to switch base station  562  and UE  566  beam pairs. The time may be indicated in terms of, for example, subframes, slots, or mini-slots (e.g., specifying a subframe, slot, or mini-slot identifier or an offset). In some examples, base station  562  may signal to switch the beam pairs without explicit beam identifiers. For example, the beam switch may be based on an agreement prior to the transmission of the signal to switch the beam pairs. At such a time, both base station  562  and UE  566  can switch beam pairs (e.g., switch from a source first beam pair  550  to target second beam pair  552 ). 
     UE  566  may transmit to base station  562  a response message for the beam switch. In some examples, UE  566  may signal the beam switch, and base station  562  may transmit the response message as described above. Where the embodiment provided relates to base station  562  initiating the beam switch (and UE  566  confirms the beam switch), it is understood the example likewise applies to the example in which UE  566  initiates the beam switch (and base station  562  confirms the beam switch). 
       FIG. 6  illustrates an example of single-switch beam switch messages according to various embodiments. In  FIG. 6 , a base station  601  is communicating with a UE  603  via a first beam set  605  at subframe  0 . The base station  601  and UE  603  may be, for example, base station  562  and UE  566 , respectively, in  FIG. 5  above. At subframe  1 , base station  601  transmits a BSM  607  to UE  603  via first beam set  605 . The BSM  607  includes an instruction for UE  603  to switch from communication via first beam set  605  to communication via a second beam set  609  at a switch time  611 . The BSM  607  is an example of a single-switch BSM because BSM  607  instructs UE  603  to perform only one beam switch. In this example, base station  601  expects to receive a response message, e.g., an ACK, from the UE at an expected ACK time  613 , and therefore, the base station is monitoring for the response message. In various embodiments of the current example and other examples presented herein, a response message may be any indication that a BSM or other signal has been received. For example, a response message may be an ACK, a Received Signal Strength Indicator (RSSI), a SNR, a measurement report, etc., that is in response to a BSM or other signal. Monitoring for a response message may be done actively or passively. For example, a base station may take active measures to monitor, such as tuning to a particular frequency or channel on which the response message is expected. On the other hand, a base station may monitor passively by, for example, merely expecting to receive a response message in the normal course of operation. 
     UE  603  receives BSM  607  and transmits an ACK  615  for base station  601  to receive at expected ACK time  613 . The base station  601  receives ACK  615  at expected ACK time  613 , and as a result, base station  601  knows that UE  603  will perform the beam switch. At switch time  611 , base station  601  and UE  603  perform a beam switch  617  from first beam set  605  to second beam set  609 . 
     At subframe  9 , base station  601  may decide to switch beams again and can transmit a BSM  619  to UE  603  via second beam set  609 . The BSM  619  includes an instruction for UE  603  to switch from communication via second beam set  609  to communication via a third beam set  621  at a switch time  623 . BSM  619  is another example of a single-switch BSM because BSM  619  instructs UE  603  to perform only one beam switch. The base station  601  monitors for an ACK at expected ACK time  625 . UE  603  receives BSM  619  and transmits an ACK  627  for base station  601  to receive at expected ACK time  625 . The base station  601  receives ACK  627  at expected ACK time  625 , and as a result, base station  601  knows that UE  603  will perform the beam switch. At switch time  623 , base station  601  and UE  603  perform a beam switch  629  from second beam set  609  to third beam set  621 . Thus, in the example of  FIG. 6 , BSM  607  and BSM  619  are examples of single-switch BSMs. 
       FIG. 7  illustrates an example of multiple-switch BSMs according to various embodiments. In  FIG. 7 , a base station  701  is communicating with a UE  703  via a first beam set  705  at subframe  0 . At subframe  1 , base station  701  transmits a BSM  707  to UE  703  via first beam set  705 . The BSM  707  includes an instruction for UE  703  to switch from communication via first beam set  705  to communication via a second beam set  709  at a first switch time  711 , and to switch from communication via second beam set  709  to communication via a third beam set  721  at a second switch time  723 . The BSM  707  is an example of a multiple-switch BSM because BSM  707  instructs UE  703  to perform multiple beam switches. In this example, base station  701  expects to receive a response message, e.g., an ACK, from the UE at an expected ACK time  713 , and therefore, the base station is monitoring for the response message. 
     UE  703  receives BSM  707  and transmits an ACK  715  for base station  701  to receive at expected ACK time  713 . The base station  701  receives ACK  715  at expected ACK time  713 , and as a result, base station  701  knows that UE  703  will perform the beam switches. At first switch time  711 , base station  701  and UE  703  perform a beam switch  717  from first beam set  705  to second beam set  709 . At second switch time  723 , base station  701  and UE  703  perform a beam switch  729  from second beam set  709  to third beam set  721 . Thus, BSM  707  is an example of a multiple-switch BSM because BSM  707  includes instructions to perform multiple beam switches. 
     In various embodiments, multiple-switch BSMs may be useful. For example, as a comparison of  FIGS. 6 and 7  shows, using a multiple-switch BSM to signal multiple beam switches can reduce the amount of signaling by eliminating the need for additional BSMs and ACKs for each beam switch after the first beam switch. Also, by reducing the number of BSMs and ACKs required for multiple beam switches, a multi-switch BSM can reduce the number of instances in which signal failure can occur. Therefore, systems that use multi-switch BSMs may be less susceptible to the effects of signal failure. 
     Multiple-switch BSMs can be used, for example, when multiple beam switches can be determined prior to transmission of a BSM. For example, in communication systems in which a UE moves through the coverage areas of multiple beam sets in a predictable way, a base station may be able to predict at one time the multiple beam switches will be necessary to stay in communication with the UE. For example, a base station may serve a rail line on which trains travel at a known speed through multiple beam sets of the base station. The base station may know, for example, when a UE traveling on a southbound train reaches the coverage area of the base station, the UE will establish a connection with a first beam set of the base station. The base station may also know that it takes the southbound train a first amount of time to pass through the first beam set and reach a second beam set, and a second amount of time to pass through the second beam set and reach a third beam set, and so on. Therefore, when the base station determines a new UE has established a connection via the first beam set, the base station may predict that a first beam switch from the first beam set to the second beam set should occur after the first amount of time and that a second beam switch from the second beam set to the third beam set should occur after the second amount of time after the first beam switch. Thus, the base station may send a multi-switch BSM to each southbound UEs, for example, immediately after the connection with the first beam set is established. In this way, for example, the base station may be able to reduce significantly the number of BSMs and corresponding ACKs, along with the potential signal errors associated with the multiple BSMs and ACKs. 
     However, regardless of whether single-switch or multi-switch BSMs are used, signal error can occur. In some examples, a base station does not receive an expected response message from the UE in a timely fashion. 
       FIG. 8  illustrates an example situation of signal error in multi-beam wireless communication. In this example, a base station  801  and a UE  803  are communicating via a first beam set  805 , and base station  801  transmits a BSM  807  instructing UE  803  to switch beams at a switch time  809 . However, UE  803  does not receive BSM  807 . Because UE  803  does not receive BSM  807 , UE  803  does not transmit an ACK, and base station  801  does not receive an ACK at an expected ACK time  811 . The base station  801  does not know whether UE  803  will switch beams at switch time  809  because the base station  801  does not know whether the UE  803  failed to receive the BSM  807  or the UE  803  received the BSM  807  and sent an ACK that was not received by the base station  801 . In this case, UE  803  will not switch beam sets at switch time  809 , but will continue communicating via first beam set  805 . 
       FIG. 9  illustrates another example situation of signal error in multi-beam wireless communication. In this example, a base station  901  and a UE  903  are communicating via a first beam set  905 , and base station  901  transmits a BSM  907  instructing UE  903  to switch beams to a second beam set  908  at a switch time  909 . In this example, UE  903  receives BSM  907  and transmits an ACK  910 . However, base station  901  does not receive ACK  910  at an expected ACK time  911 . As in the example of  FIG. 8 , base station  901  does not know whether UE  903  will switch beams at switch time  909  because the base station  901  does not know whether the UE  903  failed to receive the BSM  907  or the UE  903  received the BSM  907  and sent an ACK that was not received by the base station  901 . In this case, UE  903  does perform a beam switch  913  to switch to communication via second beam set  908  at switch time  909 . 
     Both scenarios described with respect to  FIGS. 8 and 9  result in the base station not receiving the response message (e.g., an ACK from the UE), and hence the base station may not know if the UE will switch to the target beam set. If the base station switches to the target beam set at the switch time, but the UE does not switch, beam misalignment may result (e.g., the transmitting apparatus and the receiving apparatus communicating via different beam pairs). Likewise, if the UE switches to the target beam set at the switch time, but the base station does not switch, beam misalignment may result. 
     It is noted that some implementations of various embodiments described herein may help avoid or help mitigate the affects of beam misalignment due to, for example, signaling errors such as BSM or ACK delivery failure as described above. In particular,  FIGS. 11 and 12  illustrate example beam switch methods that may be implemented before a switch time.  FIGS. 14-18  illustrate example beam switch methods that may be implemented after a switch time.  FIG. 19  illustrates an example beam switch method that may be implemented to avoid BSM and ACK signaling errors altogether. 
     Turning first to  FIGS. 10-13 , these figures describe various examples of systems and methods in which a beam switch message can indicate a beam reset state, which may provide advantages to beam switching in multi-beam systems.  FIG. 10  illustrates two reset states in which a BSM can either indicate to continue execution of a previous beam switch instruction or can indicate to disregard the previous beam switch instruction.  FIGS. 11 and 12  illustrate two example ways in which a BSM indicating a reset state may help avoid a time-consuming beam recovery procedure and mitigate instances of beam misalignment.  FIG. 13  illustrates an example use of beam reset states in a multiple-switch BSM, such as described above with respect to  FIG. 7 . 
       FIGS. 10A-C  illustrate an example implementation of a method of wireless communication in accordance with various embodiments.  FIG. 10A  shows the state of communication between a base station  1001  and a UE  1003  at a first time.  FIG. 10B  shows the state of communication between base station  1001  and UE  1003  at a later time in the case that a first reset state is selected.  FIG. 10C  shows the state of communication between base station  1001  and UE  1003  at the later time in the case that a second reset state is selected. Turning first to  FIG. 10A , base station  1001  can transmit a BSM  1005  including a first instruction for switching beams to UE  1003 , which can establish a planned beam switch  1007 . For example, base station  1001  and UE  1003  may be communicating via a first beam set, and BSM  1005  instructs UE  1003  to switch to a second beam set. The UE  1003  receives BSM  1005  and transmits an ACK  1009 , and base station receives ACK  1009 . 
     The base station  1001  decides to transmit a second BSM to UE  1003 , and the base station  1001  selects a reset state to be indicated by the second BSM.  FIG. 10B  and  FIG. 10C  illustrate communication resulting from selection of, respectively, a first reset state and a second reset state. 
       FIG. 10B  illustrates communication based on a first reset state, in which UE  1003  disregards the first instruction sent in BSM  1005 . The base station  1001  transmits a BSM  1011  to UE  1003 . BSM  1011  includes a second instruction for switching beams, which can establish a new beam switch  1013 , and indicates the selected reset state in which UE  1003  disregards the first instruction. The UE  1003  receives BSM  1011  and transmits an ACK  1015 , and base station receives ACK  1015 . In this example, UE  1003  has not completed execution of the first instruction because UE  1003  has not executed planned beam switch  1007 . Therefore, UE  1003  disregards planned beam switch  1007 , which is represented as disregarded beam switch  1017  in  FIG. 10 , and executes only new beam switch  1013 . 
     On the other hand,  FIG. 10C  illustrates communication based on a second reset state, in which UE  1003  maintains execution of the first instruction sent in BSM  1005 , thus, UE  1003  augments the first instruction with a second instruction. The base station  1001  transmits a BSM  1019  to UE  1003 . BSM  1019  includes a second instruction for switching beams, which can establish an added beam switch  1021 , and indicates the selected reset state in which UE  1003  maintains execution of the first instruction. The UE  1003  receives BSM  1019  and transmits an ACK  1023 , and base station receives ACK  1023 . In this example, UE  1003  has not completed execution of the first instruction because UE  1003  has not executed planned beam switch  1007 . UE  1003  maintains execution of the first instruction by executing planned beam switch  1007 , and augments the first instruction with the second instruction by also executing added beam switch  1021 . 
     In various embodiments, the second BSM can indicate which of the reset states was selected by setting a bit to 0 or 1, such as a flag. For example, a bit set to 0 may indicate maintaining execution of the first instruction, and the bit set to 1 may indicate disregarding the first instruction. In various embodiments, the second BSM may indicate one of the selected states by not providing an indicator. In other words, the second BSM may indicate one of the selected states by excluding information that one of the reset states was selected. For example, if no indicator is provided, the UE may default to one of the reset states, such as defaulting to disregarding the first instruction. In some examples, the reset state field may operate similarly to the new data indicator or NDI bit for HARQ operation. In some examples, the reset state information may be an empty field (e.g., the reset state indicates a null flag or no reset state information is provided in the beam switch message). 
       FIGS. 11 and 12  will now be discussed. These figures illustrate various embodiments that may be implemented before a switch time to help avoid potential beam misalignment due to signal errors such as described above, thus helping to avoid potentially time-consuming beam recovery procedures. 
       FIGS. 11A-C  illustrates an example implementation of a method of wireless communication in accordance with various embodiments.  FIG. 11A  shows the state of communication between a base station  1101  and a UE  1103  at a first time,  FIG. 11B  shows the state of communication between base station  1101  and UE  1103  at a second time later than the first time, and  FIG. 11C  shows the state of communication between base station  1101  and UE  1103  at a third time later than the second time. Turning first to  FIG. 11A , base station  1101  can transmit a BSM  1105  to UE  1103 . For example, base station  1101  and UE  1103  may be communicating via a first beam set, and BSM  1105  instructs UE  1103  to switch to a second beam set. Thus, BSM  1105  establishes a planned beam switch  1107 . In this example, base station  1101  expects a response message from UE  1103  at an expected ACK time  1109 . The UE  1103  receives BSM  1105  and transmits an ACK  1111 . However, base station  1101  does not receive ACK  1111 , and therefore, the base station does not know whether UE  1103  will perform planned beam switch  1107 . 
     Turning to  FIG. 11B , because insufficient time exists between expected ACK time  1109  and planned beam switch  1107 , base station  1101  transmits a BSM  1113  to UE  1103  that establishes a new beam switch  1115  at a later time than planned beam switch  1107 . The UE  1103  receives BSM  1113 , and because the default behavior of UE  1103  is to cancel execution of any instructions in previous BSMs if the UE receives a new BSM, planned beam switch  1107  becomes disregarded beam switch  1117 . The base station  1101  monitors for a response message at an expected ACK time  1119 . UE  1103  transmits an ACK  1121 . However, base station  1101  does not receive ACK  1121 , and therefore, the base station does not know whether UE  1103  will perform new beam switch  1115 . However, because BSM  1113  instructed UE  1103  to delay the beam switch, base station  1101  is able to transmit another BSM and potentially receive a response message before new beam switch  1115 . 
     Turning to  FIG. 11C , because insufficient time again exists before the beam switch (i.e., new beam switch  1115 ), base station  1101  transmits a BSM  1123  to UE  1103  that establishes a new beam switch  1125  at a later time than new beam switch  1115 . The UE  1103  receives BSM  1123 , and new beam switch  1115  becomes disregarded beam switch  1127 . The base station  1101  monitors for a response message at an expected ACK time  1129 . UE  1103  transmits an ACK  1131 . This time, base station  1101  receives ACK  1131 , and both base station  1101  and UE  1103  can switch beams according to new beam switch  1125 . Thus, by delaying the planned beam switch, a base station and a UE may continue communication on a source beam set until a response is received. In contrast, if base station  1101  had not delayed the planned beam switch, a time-consuming beam recovery process may have been initiated at the time of planned beam switch  1107 , for example. 
       FIG. 12A-B  illustrate an example wireless communication via multiple beams according to various embodiments. In particular,  FIG. 12A  shows the state of communication between a base station  1201  and a UE  1203  at a first time, and  FIG. 12B  shows the state of communication between base station  1201  and UE  1203  at a later time. Turning first to  FIG. 12A , base station  1201  can transmit a BSM  1205  to UE  1203 . For example, base station  1201  and UE  1203  may be communicating via a first beam set, and BSM  1205  instructs UE  1203  to switch to a second beam set. Thus, BSM  1205  establishes a planned beam switch  1207 . In this example, base station  1201  expects a response message from UE  1203  at an expected ACK time  1209 . However base station  1201  does not receive a response message, and therefore, the base station does not know whether UE  1203  will perform planned beam switch  1207 . 
     Turning to  FIG. 12B , because sufficient time exists between expected ACK time  1209  and planned beam switch  1207 , base station  1201  transmits another BSM  1211  to UE  1203 . BSM  1211  establishes a new beam switch  1213 . In this example, new beam switch  1213  is the same as planned beam switch  1207 , i.e., the same target beam set and the same switch time. The base station  1201  monitors for a response message at an expected ACK time  1215 . In this example, UE  1203  receives BSM  1205  and transmits an ACK  1217 , which is received by base station  1201 . In this example, the default behavior of UE  1203  is to cancel execution of any instructions in previous BSMs if the UE receives a new BSM. In this case, base station  1201  and UE  1203  can both switch to the target beam set and continue communicating. This approach can work well if there is sufficient time between the first BSM and the planned beam switch because the base station and UE can continue communication via the source beam set. However, in some cases, the base station might not have sufficient time before a planned beam switch to communicate effectively with the UE. 
       FIGS. 13A-B  illustrate another example implementation of a method of wireless communication in accordance with various embodiments. In particular,  FIGS. 13A-B  illustrate an example use of reset states in an implementation with multiple-switch BSMs.  FIG. 13A  shows the state of communication between a base station  1301  and a UE  1303  at a first time, and  FIG. 13B  shows the state of communication between base station  1301  and UE  1303  at later time in the case that a first reset state is selected. Turning first to  FIG. 13A , base station  1301  can transmit a BSM  1305  including a first instruction for switching beams to UE  1303 . In this case, the first instruction includes multiple beam switches, such as BSM  707  described above with respect to  FIG. 7 . BSM  1305  establishes two planned beam switches, i.e., planned beam switch  1307  and planned beam switch  1308 . For example, base station  1301  and UE  1303  may be communicating via a first beam set, and BSM  1305  instructs UE  1303  to switch to a second beam set for planned beam switch  1307  and to switch to a third beam set for planned beam switch  1308 . The UE  1303  receives BSM  1305  and transmits an ACK  1309 , and base station receives ACK  1309 . 
     The base station  1301  decides to transmit a second BSM to UE  1303 , and the base station  1301  selects a reset state to be indicated by the second BSM.  FIG. 13B  illustrates the communication resulting from selection of a reset state in which UE  1303  maintains execution of the first instruction. Unlike the example of  FIG. 10C , base station  1301  transmits the second BSM after UE  1303  has started execution of the first instruction for beam switching. However, the second BSM is transmitted before UE  1303  completes execution of the first instruction. 
       FIG. 13B  illustrates communication based on a first reset state, in which UE  1303  maintains execution of the first instruction sent in BSM  1305 . The base station  1301  transmits a BSM  1311  to UE  1303  after planned beam switch  1307  has been completed. The completion of planned beam switch  1307  is illustrated in  FIG. 13B  by completed beam switch  1312 . BSM  1311  includes a second instruction for switching beams, which can establish an added beam switch  1313 , and indicates the selected reset state in which UE  1303  maintains execution of the first instruction. In this case, UE  1303  has not completed execution of the first instruction because the UE has not completed planned beam switch  1308 . The UE  1303  receives BSM  1305  and transmits an ACK  1315 , and base station receives ACK  1315 . In this example, UE  1303  has not completed execution of the first instruction because UE  1303  has not executed planned beam switch  1308 . Therefore, UE  1303  augments planned beam switch  1308  with added beam switch  1313 . 
     In various embodiments, the BSM  1311  could indicate a reset state in which UE  1303  disregards the first instruction, similar to the example of  FIG. 10B . In this case, even though completed beam switch  1312  has already been executed, UE  1303  can disregard planned beam switch  1308 . In other words, UE  1303  can disregard the unexecuted portion of the first instruction. 
     Now turning to  FIGS. 14-18 , these figures illustrate example beam switch methods that may be implemented after a switch time to recover from potential beam misalignment due to signal errors such as described above. 
       FIG. 14  illustrates an example implementation of a method of wireless communication in accordance with various embodiments. Initially, a base station  1401  and a UE  1403  can be communicating via a first beam set  1405  using, for example, mmW communications. The base station  1401  and UE  1403  may, for example, correspond to base station  562  and UE  566  in  FIG. 5  above, and base station  1401  may transmit various DL signals and channels to UE  1403  via first beam set  1405 , such as beam or beams  510 . UE  1403  may transmit various UL signals and channels to base station  1401  via first beam set  1405 , such as beam or beams  520  (which are associated with beam or beams  510  in first beam pair  550 , e.g., first beam set  1405 ). 
     The base station  1401  can transmit a BSM  1407  including an instruction to switch to communication via a second beam set  1409  at a switch time  1411 . The BSM  1407  may include information of a beam identifier for second beam set  1409 , also referred to as the target beam, which could be, e.g., second beam pair  552 . In some examples, BSM  1407  may not include a beam identifier. In some examples, BSM  1407  may be transmitted as part of a MAC or RRC message. The base station  1401  may expect a response message, e.g., an ACK, from UE  1403  at an expected ACK time  1413  and, therefore, may be monitoring for a response indicating receipt of BSM  1407 . UE  1403  may include the target beam (second beam set) identifiers in the UL transmission to echo back the target beam identifiers. In one aspect, UE  1403  may generate a sequence from the target beam identifiers, and include the sequence in the UL transmission. The base station  1401  may determine and confirm the target beam pair from the sequence in the UL transmission. In some examples, both the source beam pair (first beam set) and the target beam pair may be of sufficient quality for communication, the mechanism may help base station  1401  to determine which of the source beam pair and the target beam pair to use. 
     However, in this example, when the base station determines whether a response message was received, base station  1401  determines that no ACK was received, i.e., the response message is unreceived. Therefore, the beam set on which UE  1403  will be communicating after the switch time is unknown to base station  1401 , and this situation is represented in  FIG. 14  by an unknown beam set  1414  on which UE  1403  is communicating after switch time  1411 . Even though base station  1401  does not know whether UE  1403  will switch beams, base station  1401  performs a beam switch  1415  to second beam set  1409  at switch time  1411 . 
     The base station  1401  can then transmit a signal  1417  to UE  1403  via second beam set  1409  after performing beam switch  1415 . In various embodiments, signal  1417  can be, for example, a request for a response that UE  1403  is communicating via second beam set  1409 . In various embodiments, signal  1417  can be, for example, merely the continuation of normal communications between base station  1401  and UE  1403  (e.g., control and data signals). In this regard, base station  1401  may monitor for an ACK in response to signal  1417 , may monitor for normal communication in response to signal  1417 , etc. In some embodiments, base station might not transmit a signal, such a signal  1417 , after switching beams, but may simply switch beams and then await communication from UE  1403  via the second beam set. 
     In the example of  FIG. 14 , base station  1401  monitors for an ACK to signal  1417 . If UE  1403  had received BSM  1407  and had switched to communication via second beam set  1409 , then UE  1403  can send an ACK  1419  to base station  1401 . In this case, base station  1401  can receive ACK  1419  and can continue communication with UE  1403  via second beam set  1409 . In other words, the unknown beam set  1414  is now known to be second beam set  1409 , and the remaining beam switches, signals, and potential ACKS shown in  FIG. 14  can be disregarded. 
     However, if UE  1403  did not receive BSM  1407  and did not switch to second beam set  1409 , UE  1403  would not have switched to the second beam set and, therefore, would not receive signal  1417  from base station  1401 . In this case, UE  1403  would not transmit ACK  1419 . Because ACK  1419  may or may not be transmitted, ACK  1419  is shown as a dashed arrow. This dashed arrow representation will be used herein for other signals that may or may not be transmitted. 
     If base station  1401  does not receive ACK  1419 , base station  1401  can perform a beam switch  1421  to switch communication back to first beam set  1405 . In other words, if UE  1403  is not communicating via second beam set  1409  after switch time  1411 , base station  1401  can assume that UE  1403  did not receive BSM  1407  and is, therefore, still communicating via first beam set  1405 . After beam switch  1421 , base station  1401  can transmit a signal  1423  to UE  1403  via first beam set  1405  and monitor for an ACK. UE  1403  may or may not transmit an ACK  1425 . If base station  1401  receives ACK  1425 , base station  1401  and UE  1403  can continue communication, as described above, on first beam set  1405  (i.e., the unknown beam set  1414  is now know to be first beam set  1405 ). However, if base station  1401  does not receive ACK  1425 , base station  1401  can repeat the switching back and forth between the first and second beam sets, e.g., by performing a beam switch  1427 , transmitting a signal  1429 , and monitoring for an ACK  1431 . 
     It should be noted that in some embodiments, base station  1401  might not transmit signal  1423  after switching back to first beam set  1405 , because the probability can be high that UE  1403  did not switch beams and is, therefore, communicating on the first beam set. Thus, it may be more efficient for base station  1401  to simply continue normal communications when switching back to the first beam set after determining that UE  1403  did not switch beams. 
       FIGS. 15 and 16  illustrate the example shown in  FIG. 14  in two different signaling error situations. 
       FIG. 15  illustrates an implementation of  FIG. 14  in a situation that a response to a BSM is lost. Initially, a base station  1501  and a UE  1503  can be communicating via a first beam set  1505  using, for example, mmW communications. The base station  1501  can transmit a BSM  1507  including an instruction to switch to communication via a second beam set  1509  at a switch time  1511 . The base station  1501  may expect a response message, e.g., an ACK, from UE  1503  at an expected ACK time  1513  and, therefore, may be monitoring for a response indicating receipt of BSM  1507 . In this example, UE  1503  receives BSM  1507  and transmits a response message, e.g., ACK  1525 . The UE  1503  prepares to switch to communication via second beam set  1509  at switch time  1511 . 
     However, in this example, ACK  1525  is lost, e.g., is not received by base station  1501 . Therefore, base station  1501  determines that no ACK was received, i.e., the response message is unreceived. Therefore, the beam set on which UE  1503  will be communicating after the switch time is unknown to base station  1501 . Even though base station  1501  does not know whether UE  1503  will switch beams, base station  1501  performs a beam switch  1515  to second beam set  1509  at switch time  1511 . 
     The base station  1501  can then transmit a signal  1517  to UE  1503  via second beam set  1509  after performing beam switch  1515 . In this example, signal  1517  can be a request for a response that UE  1503  is communicating via second beam set  1509 . Base station  1501  can monitor for an ACK to signal  1517 . As described above with respect to  FIG. 14 , if the base station does not receive an ACK to the signal sent on the second beam set, the base station can switch back to communication via the first beam set and attempt to communicate with the UE. In the example of  FIG. 15 , base station  1501  remains on second beam set  1509  for a time period  1518  during which an ACK should be received from UE  1503 . In other words, base station  1501  can set time period  1518  as an amount of time to remain on second beam set  1509  in order to determine if UE  1503  is communicating via the second beam set. In this case, time period  1518  can be am amount of time required for an ACK to be received from UE  1503 . In various embodiments, time period  1518  can be set in other ways. For example, the base station may send multiple ACK requests and set the time period to begin at the time of sending the first ACK request and to end at a time after an ACK to the last ACK request is expected to be received. In various embodiments, the base station might not send an ACK request, but may simply attempt normal communication via the second beam set, and may set the time period based on, e.g., a confidence determination that normal communication would be established within a particular time period if the UE is communicating via the second beam set. For example, the time period may be set based on a SNR of the environment, e.g., a shorter time period may set in a high-SNR environment and a longer time period may be set in a low-SNR environment. 
     In this example, because UE  1503  received BSM  1507  and switched to communication via second beam set  1509 , then UE  1503  receives signal  1517  and sends an ACK  1519  to base station  1501 . In this case, base station  1501  can receive ACK  1519  and can continue communication with UE  1503  via second beam set  1509 . 
       FIG. 16  illustrates an implementation of  FIG. 14  in a situation that a BSM is lost. Initially, a base station  1601  and a UE  1603  can be communicating via a first beam set  1605  using, for example, mmW communications. The base station  1601  can transmit a BSM  1607  including an instruction to switch to communication via a second beam set  1609  at a switch time  1611 . The base station  1601  may expect a response message, e.g., an ACK, from UE  1603  at an expected ACK time  1613  and, therefore, may be monitoring for a response indicating receipt of BSM  1607 . In this example, BSM  1607  is lost, e.g., not received by UE  1603 . Therefore, UE  1603  does not transmit a response message and does not prepare to switch to communication via second beam set  1609  at switch time  1611 . Instead, UE  1603  continues to communicate via first beam set  1605  after switch time  1611 . 
     Base station  1601  determines that no ACK was received, i.e., the response message is unreceived. Therefore, the beam set on which UE  1603  will be communicating after the switch time is unknown to base station  1601 . Even though base station  1601  does not know whether UE  1603  will switch beams, base station  1601  performs a beam switch  1615  to second beam set  1609  at switch time  1611 . 
     Base station  1601  can then transmit a signal  1617  to UE  1603  via second beam set  1609  after performing beam switch  1615 . In this example, signal  1617  can be a request for a response that UE  1603  is communicating via second beam set  1609 . Base station  1601  can monitor for an ACK to signal  1617  and can remain on second beam set  1609  for a time period  1618  during which an ACK should be received from UE  1603 . For example, base station  1601  can set time period  1618  as described above for time period  1518  of  FIG. 15 . 
     In this example, because UE  1603  did not receive BSM  1607  and did not switch to communication via second beam set  1609 , UE  1603  does not send an ACK to base station  1601 . In this case, base station  1601  can wait until time period  1618  ends and then can perform a beam switch  1621  to switch back to communication via first beam set  1605 . Base station  1601  can then transmit a signal  1623  to UE  1603  via first beam set  1605  after performing beam switch  1621 . In this example, signal  1623  can be a request for a response that UE  1603  is communicating via first beam set  1605 . Base station  1601  can monitor for an ACK to signal  1623  and can remain on first beam set  1605  for a time period  1624  during which an ACK should be received from UE  1603 . For example, base station  1601  can set time period  1624  as described above for time period  1518  of  FIG. 15 . In this example, UE  1603  receives signal  1623  and sends an ACK  1625  to base station  1601 . In this case, base station  1601  can receive ACK  1525  and can continue communication with UE  1603  via first beam set  1505 . 
     Accordingly,  FIGS. 14-16  illustrate examples of beam switch methods that may be implemented after a switch time to recover from potential beam misalignment, including switching to a target beam set when a response to a BSM is unreceived and communicating via the target beam set for a time period during which communication is expected to be established. 
       FIG. 17  illustrates another example implementation of a method of wireless communication in accordance with various embodiments. A base station  1701  and a UE  1703  can be communicating via a first beam set  1705  using, for example, mmW communications. The base station  1701  and UE  1703  may, for example, correspond to base station  562  and UE  566  in  FIG. 5  above, and base station  1701  may transmit various DL signals and channels to UE  1703  via first beam set  1705 , such as beam or beams  510 . UE  1703  may transmit various UL signals and channels to base station  1701  via first beam set  1705 , such as beam or beams  520  (which are associated with beam or beams  510  in first beam pair  550 , e.g., first beam set  1705 ). 
     The base station  1701  can transmit a BSM  1707  including an instruction to switch to communication via a second beam set  1709  at a switch time  1711 . The BSM  1707  may include information of a beam identifier for second beam set  1709 , also referred to as the target beam, which could be, e.g., second beam pair  552 . In some examples, BSM  1707  may not include a beam identifier. In some examples, BSM  1707  may be transmitted as part of a MAC or RRC message. The base station  1701  may expect a response message, e.g., an ACK, from UE  1703  at an expected ACK time  1713  and, therefore, may be monitoring for a response indicating receipt of BSM  1707 . UE  1703  may include the target beam (second beam set) identifiers in the UL transmission to echo back the target beam identifiers. In one aspect, UE  1703  may generate a sequence from the target beam identifiers, and include the sequence in the UL transmission. The base station  1701  may determine and confirm the target beam pair from the sequence in the UL transmission. In some examples, both the source beam pair (first beam set) and the target beam pair may be of sufficient quality for communication, the mechanism may help base station  1701  to determine which of the source beam pair and the target beam pair to use. 
     However, in this example, when the base station determines whether a response message was received, base station  1701  determines that no ACK was received, i.e., the response message is unreceived. Therefore, the beam set on which UE  1703  will be communicating after the switch time is unknown to base station  1701 , and this situation is represented in  FIG. 17  by an unknown beam set  1714  on which UE  1703  is communicating after switch time  1711 . Even though base station  1701  does not know whether UE  1703  will switch beams, base station  1701  performs a beam switch  1715  to second beam set  1709  at switch time  1711 . 
     The base station  1701  can then transmit a signal  1717  to UE  1703  via second beam set  1709  after performing beam switch  1715 . In various embodiments, signal  1717  can be, for example, a request for a response that UE  1703  is communicating via second beam set  1709 . 
     However, unlike the example of  FIG. 14  above, base station  1701  does not continuously maintain communication via second beam set  1709  to monitor for an ACK in response to signal  1717 . Instead, base station  1701  performs a beam switch  1719  to switch to first beam set  1705 , transmits a signal  1721  to UE  1703  via first beam set  1705 , and performs a beam switch  1723  to switch back to second beam set  1709  before an expected ACK time for receiving a possible ACK  1725  to signal  1717 . In other words, in this example there is enough time in between transmission of signal  1717  and the expected ACK time of ACK  1725  in response to signal  1717 , that base station  1701  can switch to the first beam set, send another signal, and switch back to the second beam set to monitor for ACK  1725 . In this way, for example, base station  1701  may recover from beam misalignment more quickly. More specifically, by transmitting signal  1721  on the first beam set during the time the base station is waiting for ACK  1725 , a response to signal  1721  can be received sooner (because the base station does not have to wait to determine if ACK  1725  was received before switching to first beam set  1705  and transmitting signal  1721 ). Thus, base station  1701  can determine sooner if UE  1703  did not switch beams. 
     After base station  1701  switches back to second beam set  1709  at beam switch  1723 , base station  1701  monitors for ACK  1725 . If base station  1701  receives ACK  1725 , communication with UE  1703  can continue via second beam set  1709 . In other words, unknown beam set  1714  can become second beam set  1709 , and the remaining beam switches, signals, and potential ACKS shown in  FIG. 17  can be disregarded. 
     If base station  1701  does not receive ACK  1725 , base station  1701  can perform a beam switch  1727  to switch to communication via first beam set  1705  and monitor for an ACK  1729  in response to signal  1721 . If base station  1701  receives ACK  1729 , communication with UE  1703  can continue via first beam set  1705 . In other words, unknown beam set  1714  can become first beam set  1705 , and the remaining beam switches, signals, and potential ACKS shown in  FIG. 17  can be disregarded. If base station  1701  does not receive ACK  1729 , base station can continue switching back and forth between the first and second beam sets with beam switches  1731 ,  1733 ,  1735 , and  1737 , sending signals  1739  and  1741 , and monitoring for potential ACKs  1743  and  1745  as shown in  FIG. 17 . Of course, base station  1701  might change the recovery method, for example, after a time period, after a number of failed attempts, etc. For example, after 6 failed attempts at receiving an ACK, base station  1701  may switch to using a method similar to the one described with respect to  FIG. 14  above, or may switch to another recovery method. 
     It should be noted that in some embodiments, base station  1701  might not transmit signal  1721  after switching back to first beam set  1705 , because the probability can be high that UE  1703  did not switch beams and is, therefore, communicating on the first beam set. Thus, it may be more efficient for base station  1701  to simply continue normal communications when switching back to the first beam set after determining that UE  1703  did not switch beams. 
     Accordingly,  FIG. 17  illustrates an example beam switch method that may be implemented after a switch time to recover from potential beam misalignment, including performing multiple switches between a target beam set and a source beam set in the event that a response to a BSM is unreceived, where some of the beam switches are performed between a time of sending a signal and an expected time of response to the signal. 
       FIG. 18  illustrates an example implementation of a method of wireless communication in accordance with various embodiments. Initially, a base station  1801  and a UE  1803  can be communicating via a first beam set  1805  using, for example, mmW communications. The base station  1801  and UE  1803  may, for example, correspond to base station  562  and UE  566  in  FIG. 5  above, and base station  1801  may transmit various DL signals and channels to UE  1803  via first beam set  1805 , such as beam or beams  510 . UE  1803  may transmit various UL signals and channels to base station  1801  via first beam set  1805 , such as beam or beams  520  (which are associated with beam or beams  510  in first beam pair  550 , e.g., first beam set  1805 ). 
     The base station  1801  can transmit a BSM  1807  including an instruction to switch to communication via a second beam set  1809  at a switch time  1811 . The BSM  1807  may include information of a beam identifier for second beam set  1809 , also referred to as the target beam, which could be, e.g., second beam pair  552 . In some examples, BSM  1807  may not include a beam identifier. In some examples, BSM  1807  may be transmitted as part of a MAC or RRC message. The base station  1801  may expect a response message, e.g., an ACK, from UE  1803  at an expected ACK time  1813  and, therefore, may be monitoring for a response indicating receipt of BSM  1807 . UE  1803  may include the target beam (second beam set) identifiers in the UL transmission to echo back the target beam identifiers. In one aspect, UE  1803  may generate a sequence from the target beam identifiers, and include the sequence in the UL transmission. The base station  1801  may determine and confirm the target beam pair from the sequence in the UL transmission. In some examples, both the source beam pair (first beam set) and the target beam pair may be of sufficient quality for communication, the mechanism may help base station  1801  to determine which of the source beam pair and the target beam pair to use. 
     However, in this example, when the base station determines whether a response message was received, base station  1801  determines that no ACK was received, i.e., the response message is unreceived. Therefore, the beam set on which UE  1803  will be communicating after the switch time is unknown to base station  1801 , and this situation is represented in  FIG. 18  by an unknown beam set  1814  on which UE  1803  is communicating after switch time  1811 . The base station  1801  can determine whether to switch to second beam set  1809  at switch time  1811 . In this example, base station  1801  determines not to switch to second beam set  1809  at switch time  1811 . Therefore, at switch time  1811 , base station  1801  continues communication via first beam set  1805 . The base station  1801  can send a signal  1817  via first beam set  1805 . In this example, signal  1817  can be a request for a response that UE  1803  is communicating via first beam set  1805 . In this case, base station  1801  may be expecting to receive a response message, and can monitor for an ACK. In various embodiments, signal  1817  can be normal communication (e.g., data signals, control signals, etc.) with UE  1803 , and base station  1801  can simply determine if UE  1803  is communicating via first beam set  1805  based on receiving communications from UE  1803  via the first beam set. In some embodiments, base station might not transmit a signal, such a signal  1817 , after switch time  1811 , but may await communication from UE  1803  via the first beam set. 
     In the example of  FIG. 18 , base station  1801  monitors for an ACK to signal  1817 . If UE  1803  had not received BSM  1807  and had not switched beams, then UE  1803  can send an ACK  1819  to base station  1801  via first beam set  1805 . In this case, base station  1801  can receive ACK  1819  and can continue communication with UE  1803  via first beam set  1805 . In other words, the unknown beam set  1814  is now known to be first beam set  1805 , and the remaining beam switches, signals, and potential ACKs shown in  FIG. 18  can be disregarded. 
     However, if UE  1803  did receive BSM  1807  and switched to second beam set  1809  at switch time  1811 , UE  1803  would not have received signal  1817  from base station  1801 . In this case, UE  1803  would not transmit ACK  1819 . Because ACK  1819  may or may not be transmitted, ACK  1819  is shown as a dashed arrow. 
     If base station  1801  does not receive ACK  1819 , base station  1801  can perform a beam switch  1821  to switch communication to second beam set  1809 . In other words, if UE  1803  is not communicating via first beam set  1805  after switch time  1811 , base station  1801  can assume that UE  1803  received BSM  1807  and is, therefore, communicating via second beam set  1809 . After beam switch  1821 , base station  1801  can transmit a signal  1823  to UE  1803  via second beam set  1809  and monitor for an ACK. UE  1803  may or may not transmit an ACK  1825 . If base station  1801  receives ACK  1825 , base station  1801  and UE  1803  can continue communication, as described above, on second beam set  1809  (i.e., the unknown beam set  1814  is now know to be second beam set  1809 ). However, if base station  1801  does not receive ACK  1825 , base station  1801  can repeat the switching back and forth between the first and second beam sets, e.g., by performing a beam switch  1827 , transmitting a signal  1829 , and monitoring for an ACK  1831 . 
     It should be noted that in some embodiments, base station  1801  might not transmit signal  1823  after switching to second beam set  1809 , because the probability can be high that UE  1803  switched beams and is, therefore, communicating on the second beam set. Thus, it may be more efficient for base station  1801  to simply continue normal communications when switching to the second beam set after determining that UE  1803  is not communicating on first beam set  1805 . 
     Accordingly,  FIG. 18  illustrates an example beam switch method that may be implemented after a switch time to recover from potential beam misalignment, including sending a BSM to switch from a source beam set to a target beam set at a switch time, determining that a response to the BSM is unreceived, and determining whether to perform a beam switch to the target beam set at the switch time or to maintain communication via the source beam set at the switch time. 
     Now turning to  FIG. 19 , this figure illustrates an example beam switch method that may be implemented to avoid signaling errors such as described above. In various embodiments, for example, a method according to  FIG. 19  can use a fast beam recovery procedure in place of a conventional ACK procedure. 
       FIG. 19  illustrates an example implementation of a method of wireless communication in accordance with various embodiments. Initially, a base station  1901  and a UE  1903  can be communicating via a first beam set  1905  using, for example, mmW communications. The base station  1901  and UE  1903  may, for example, correspond to base station  562  and UE  566  in  FIG. 5  above, and base station  1901  may transmit various DL signals and channels to UE  1903  via first beam set  1905 , such as beam or beams  510 . UE  1903  may transmit various UL signals and channels to base station  1901  via first beam set  1905 , such as beam or beams  520  (which are associated with beam or beams  510  in first beam pair  550 , e.g., first beam set  1905 ). 
     The base station  1901  can transmit a BSM  1907  including an instruction to switch to communication via a second beam set  1909  at a switch time  1911 . The BSM  1907  may include information of a beam identifier for second beam set  1909 , also referred to as the target beam, which could be, e.g., second beam pair  552 . In some examples, BSM  1907  may not include a beam identifier. In some examples, BSM  1907  may be transmitted as part of a MAC or RRC message. The base station  1901  does not expect a response message and does not monitor for a response message, and this is represented in  FIG. 19  by a period of time labeled no expected ACK  1913 , which is the time period between the sending of BSM  1907  and switch time  1911 . Because base station  1901  does not monitor for a response, base station  1901  does not know whether UE  1903  received BSM  1907 . Therefore, the beam set on which UE  1903  will be communicating after the switch time is unknown to base station  1901 , and this situation is represented in  FIG. 19  by an unknown beam set  1914  on which UE  1903  is communicating after switch time  1911 . The base station  1901  performs a beam switch  1915  to second beam set  1909  at switch time  1911 . 
     The base station  1901  can then transmit a signal  1917  to UE  1903  via second beam set  1909  after performing beam switch  1915 . In various embodiments, signal  1917  can be, for example, a request for a response that UE  1903  is communicating via second beam set  1909 . In various embodiments, signal  1917  can be, for example, merely the continuation of normal communications between base station  1901  and UE  1903  (e.g., control and data signals). In this regard, base station  1901  may monitor for an ACK in response to signal  1917 , may monitor for normal communication in response to signal  1917 , etc. In some embodiments, base station might not transmit a signal, such a signal  1917 , after switching beams, but may simply switch beams and then await communication from UE  1903  via the second beam set. 
     In the example of  FIG. 19 , base station  1901  monitors for an ACK to signal  1917 . If UE  1903  had received BSM  1907  and had switched to communication via second beam set  1909 , then UE  1903  can send an ACK  1919  to base station  1901 . In this case, base station  1901  can receive ACK  1919  and can continue communication with UE  1903  via second beam set  1909 . In other words, the unknown beam set  1914  is now known to be second beam set  1909 , and the remaining beam switches, signals, and potential ACKS shown in  FIG. 19  can be disregarded. 
     However, if UE  1903  did not receive BSM  1907  and did not switch to second beam set  1909 , UE  1903  would not have switched to the second beam set and, therefore, would not receive signal  1917  from base station  1901 . In this case, UE  1903  would not transmit ACK  1919 . Because ACK  1919  may or may not be transmitted, ACK  1919  is shown as a dashed arrow. 
     If base station  1901  does not receive ACK  1919 , base station  1901  can perform a beam switch  1921  to switch communication back to first beam set  1905 . In other words, if UE  1903  is not communicating via second beam set  1909  after switch time  1911 , base station  1901  can assume that UE  1903  did not receive BSM  1907  and is, therefore, still communicating via first beam set  1905 . After beam switch  1921 , base station  1901  can transmit a signal  1923  to UE  1903  via first beam set  1905  and monitor for an ACK. UE  1903  may or may not transmit an ACK  1925 . If base station  1901  receives ACK  1925 , base station  1901  and UE  1903  can continue communication, as described above, on first beam set  1905  (i.e., the unknown beam set  1914  is now know to be first beam set  1905 ). However, if base station  1901  does not receive ACK  1925 , base station  1901  can repeat the switching back and forth between the first and second beam sets, e.g., by performing a beam switch  1927 , transmitting a signal  1929 , and monitoring for an ACK  1931 . 
     It should be noted that in some embodiments, base station  1901  might not transmit signal  1923  after switching back to first beam set  1905 , because the probability can be high that UE  1903  did not switch beams and is, therefore, communicating on the first beam set. Thus, it may be more efficient for base station  1901  to simply continue normal communications when switching back to the first beam set after determining that UE  1903  did not switch beams. Furthermore, although the process performed after beam switch  1915  in  FIG. 19  is similar to the process performed with respect to the example of  FIG. 14 , it should be understood that any of the forgoing methods of beam recovery after a planned beam switch could be implemented in the example of  FIG. 19 . For example, in some embodiments, after beam switch  1915 , base station  1901  could perform a recovery process similar to the example of  FIG. 17  to quickly switch between beam sets. In some embodiments, base station  1901  could determine a likelihood of delivery failure of BSM  1907  and determine if beam switch  1915  should be performed or if base station  1901  should continue to communicate via first beam set  1905 , similar to the approach of  FIG. 18 . Other forms of beam recovery could be implemented, and various combinations could be implemented, in the example of  FIG. 19 . 
       FIG. 20  is a flowchart  2000  illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. A first device can transmit ( 2001 ) a BSM to a second device via a first beam set (such as a source beam set, also referred to simply as a source beam), the BSM including a command to switch from communication via the first beam set to communication via a second beam set (such as a target beam set, also referred to simply as a target beam) at a switch time. Referring to  FIG. 6 , for example, base station  601  can send BSM  607  to UE  603  via first beam set  605 . The first device can receive ( 2002 ) a response message from the second device via the first beam set, the response message indicating that the second device received the BSM. For example, the first device can monitor for an acknowledgement message via the source beam and can determine whether an acknowledgement message is received. For example, base station  601  can monitor for ACK  615  at expected ACK time  613 . The first device can send ( 2003 ), to the second device, a communication via the second beam set after the switch time if the response message is received. 
       FIG. 21  is a flowchart  2100  illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. A first device can monitor ( 2101 ) for a BSM from a second device via a first beam set, the BSM including a command to switch from communication via the first beam set to communication via a second beam set at a switch time. Referring to  FIG. 6 , for example, UE  603  can monitor for BSM  607  to from base station  601  via first beam set  605 . The first device can send ( 2102 ) send a response message to the second device when the BSM is received. For example, UE  603  can send ACK  615  at expected ACK time  613 . The first device can switch ( 2103 ) switch from communication via the first beam set to communication via the second beam set at the switch time. For example, UE  603  can perform beam switch  617 . 
       FIG. 22  is a flowchart  2200  illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. A first device can transmit ( 2201 ) a first BSM to a second device. The first BSM can include a first instruction for switching beams. Referring to  FIG. 11A , for example, base station  1101  can transmit BSM  1105  to UE  1103 , and the BSM can instruct the UE to execute planned beam switch  1107  at a particular switch time. The first device can monitor ( 2202 ) for an ACK from the second device, the ACK acknowledging receipt of the BSM. For example, base station  1101  monitors for an ACK at expected ACK time  1109 . The first device can determine ( 2203 ) if an ACK is received. If an ACK is received, the first device can switch beams ( 2204 ) in accordance with the BSM that the ACK is in response to, which in this case is the first BSM. 
     However, if the first device determines at  2203  that an ACK was not received, the first device can select a reset state from a plurality of reset states including a first state for the second device to disregard the first instruction and a second state for the second device to maintain execution of the first instruction. For example, the first device can select ( 2205 ) a reset state of 1, which can indicate that the second device should disregard the beam switch instruction of the first BSM. The first device can also advance ( 2206 ) the switch time to a later time, which can allow the beam switch to occur after the first device receives an ACK from the second device, for example. The first device can transmit a second BSM to the second device before the second device completes execution of the first instruction. The second BSM can include a second instruction for switching beams and can indicate which of the reset states is selected. For example, the first device can transmit ( 2207 ) the second BSM indicating a reset state of 1 and indicating the advanced switch time. Referring to  FIG. 11B , for example, base station  1101  can transmit BSM  1113 , which indicates to disregard planned beam switch  1107  and to execute new beam switch  1115  at the later time shown in the figure. Base station  1101  can transmit BSM  1113  before the time that planned beam switch  1107  is scheduled to be executed, which is shown as subframe  9  in  FIG. 11A . Therefore, BSM  1113  is transmitted before UE  1103  completes execution of the first instruction, i.e., the beam switch instruction in BSM  1105 . 
     The first device can again monitor ( 2208 ) for an ACK and determine ( 2209 ) whether an ACK is received. If an ACK to the second BSM is received, the first device can switch beams ( 2204 ) in accordance with the BSM that the ACK is in response to, which in this case is the second BSM. However, if the first device determines at  2209  that an ACK was not received, the first device can determine ( 2210 ) whether a maximum number of attempts at beam recovery have been performed. In other words, the first device might limit the number of attempts of sending BSMs with reset of 1 and advanced switch time. For example, the first device might try sending a maximum of 10 such BSMs. If the first device determines at  2210  that the maximum number of attempts has been tried, the first device can attempt ( 2211 ) an alternative recovery procedure. However, if the first device determines at  2210  that the maximum number of attempts has not been tried, the process can proceed to  2205  to repeat selecting ( 2205 ) the reset state of 1, advancing ( 2206 ) the switch time, transmitting ( 2207 ) the BSM, monitoring ( 2208 ) for an ACK, and determining ( 2209 ) whether an ACK is received. For example, as shown in  FIGS. 11B-C , base station  1101  can transmit BSM  1123  after failing to receive an ACK from UE  1103  at expected ACK time  1119 . 
       FIG. 23  is a flowchart  2300  illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. A first device can receive ( 2301 ) a first BSM from a second device and can send ( 2302 ) an acknowledgement message. The first BSM can include a first instruction for switching beams. Referring to  FIG. 10A , for example, UE  1003  can receive BSM  1005  from base station  1001  and can send ACK  1009  to base station  1001 . The first device can receive ( 2303 ) a second BSM from the second device, the second BSM including a second instruction for switching beams and indicating a reset state associated with the first BSM. Referring to  FIGS. 10B-C , for example, UE  1003  can receive a second BSM, i.e., BSM  1011  (indicating a first reset state, which is to disregard the beam switch instruction of BSM  1005 ) or BSM  1019  (indicating a second reset state, which is to maintain execution of the beam switch instruction of BSM  1005 ). The first device can send ( 2304 ) an acknowledgement message. In  FIGS. 10B-C , for example, UE  1003  can send ACK  1015  or ACK  1023 . 
     The first device can determine whether to disregard the first instruction or to maintain execution of the first instruction based on the indicated reset state. For example, the first device can determine ( 2305 ) which selected reset state the second BSM indicates. In  FIG. 10B , for example, UE  1003  determines that BSM  1011  indicates the first reset state, e.g., reset state=1. On the other hand, in  FIG. 10C , UE  1003  determines that BSM  1019  indicates the second reset state, e.g., reset state=0. If the indicated reset state is 1, for example, the first device can disregard ( 2306 ) the beam switch instruction of the first BSM and can switch beams according to the beam switch instruction of the second BSM. In  FIG. 10B , for example, UE  1003  disregards planned beam switch  1007  (i.e., disregarded beam switch  1017 ) and executes only new beam switch  1013 . On the other hand, if the indicated reset state is 0, for example, the first device can switch beams ( 2307 ) according to the instructions of the first and second BSMs. In  FIG. 10C , for example, UE  1003  executes both planned beam switch  1007  and added beam switch  1021 . 
       FIG. 24  is a flowchart  2400  illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. A first device can transmit ( 2401 ) a BSM to a second device via a first beam set (such as a source beam set, also referred to simply as a source beam), the BSM including a command to switch from communication via the first beam set to communication via a second beam set (such as a target beam set, also referred to simply as a target beam) at a switch time. Referring to  FIG. 14 , for example, base station  1401  can send BSM  1407  to UE  1403  via first beam set  1405 . The first device can determine whether a response message is received from the second device via the first beam set, the response message indicating that the second device received the BSM. For example, the first device can monitor ( 2402 ) for an acknowledgement message via the source beam and can determine ( 2403 ) whether an acknowledgement message is received. For example, base station  1401  can monitor for a ACK at expected ACK time  1413 . If a response message, such as an ACK, is received the first device can switch ( 2404 ) beams to the target beam at the switch time and can continue ( 2405 ) to communicate with the second device. 
     If a response message is unreceived, the first device can still switch ( 2406 ) beams to the target beam at the switch time. For example, base station  1401  can execute beam switch  1415  at switch time  1411  to switch to communication via second beam set  1409 . The first device can then send, to the second device, a communication via the target beam after the switch time. For example, the first device can send ( 2407 ) an ACK request to the second device via the target beam. In  FIG. 14 , for example, base station  1401  can send signal  1417  via second beam set  1409 . The first device can monitor ( 2408 ) for an ACK via the target beam and, if an ACK is received can continue ( 2405 ) communications with the second device via the target beam. On the other hand, if an ACK is not received via the target beam, the first device can determine ( 2409 ) whether a maximum number of attempts at beam recovery have been performed. In other words, the first device might limit the number of attempts of switching beams and sending ACK requests. For example, the first device might try switching beams a maximum of 10 times. If the first device determines at  2409  that the maximum number of attempts has been tried, the first device can attempt ( 2410 ) an alternative recovery procedure. However, if the first device determines at  2409  that the maximum number of attempts has not been tried, the first device can switch beams ( 2411 ) to the source beam and can send ( 2412 ) an ACK request via the source beam, and the process can proceed to  2402  to monitor for an ACK. For example, base station  1401  can execute beam switch  1421  to switch back to first beam set  1405  and can send signal  1423  via the first beam set. In this way, for example, the first device can simply proceed with the planned beam switch even though an ACK to the BSM is unreceived, which may potentially avoid time-consuming beam recovery procedures. 
       FIG. 25  is a flowchart  2500  illustrating an example method of wireless communication via multiple beams in accordance with various embodiments. A first device can monitor ( 2501 ) for a BSM from a second device via a first beam set, the BSM including a command to switch from communication via the first beam set to communication via a second beam set at a switch time. The first device can send ( 2502 ) a response message to the second device when the BSM is received and can monitor ( 2503 ) for a second communication from the second device via the first beam set when the BSM is unreceived. The second communication via the first beam set can be monitored at a second time subsequent to a first time in which a first communication is sent to the first device via the second beam set. Referring to  FIGS. 15 and 16 , for example, UE  1503  and UE  1603  can monitor for BSMs.  FIG. 15  illustrates when BSM  1507  is received, UE  1503  can send a response message, i.e., ACK  1525 . On the other hand,  FIG. 16  illustrates when BSM  1607  is unreceived, UE  1603  can monitor for a second communication, i.e., signal  1623 , at a time subsequent to the time a first communication, i.e., signal  1617 , is sent via second beam set  1609 . 
       FIG. 26  is a conceptual data flow diagram  2600  illustrating the data flow between different means/components in an exemplary apparatus  2602 . The apparatus may be a base station, for example. The apparatus includes a receiver  2604  that receives signals, a controller  2606  that controls various functions of apparatus  2602 , a response monitor  2608  that monitors for a response, and a transmitter  2610  that transmits signals. For example, UL/DL signals can be received from and transmitted to an apparatus  2650  via first and second beam pairs. Apparatus  2650  can be a UE, for example. Response monitor  2608  can, for example, determine whether a response message is received from apparatus  2650  via a first beam set, the response message indicating that apparatus  2650  received a BSM sent by apparatus  2602 . Transmitter  2610  can, for example, send to apparatus  2650 , a communication via a second beam set after a switch time when the response message is received. 
     The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowchart of  FIG. 20 . As such, each block in the aforementioned flowchart of  FIG. 20  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. 27  is a diagram  2700  illustrating an example of a hardware implementation for an apparatus  2602 ′ employing a processing system  2714 . The processing system  2714  may be implemented with a bus architecture, represented generally by the bus  2724 . The bus  2724  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  2714  and the overall design constraints. The bus  2724  links together various circuits including one or more processors and/or hardware components, represented by the processor  2704 , the components  2604 ,  2606 ,  2608 ,  2610 , and the computer-readable medium/memory  2706 . The bus  2724  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  2714  may be coupled to a transceiver  2710 . The transceiver  2710  is coupled to one or more antennas  2720 . The transceiver  2710  provides a means for communicating with various other apparatus over a transmission medium. The transceiver  2710  receives a signal from the one or more antennas  2720 , extracts information from the received signal, and provides the extracted information to the processing system  2714 , specifically the receiver  2604 . In addition, the transceiver  2710  receives information from the processing system  2714 , specifically the transmitter  2610 , and based on the received information, generates a signal to be applied to the one or more antennas  2720 . The processing system  2714  includes a processor  2704  coupled to a computer-readable medium/memory  2706 . The processor  2704  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory  2706 . The software, when executed by the processor  2704 , causes the processing system  2714  to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory  2706  may also be used for storing data that is manipulated by the processor  2704  when executing software. The processing system  2714  further includes at least one of the components  2604 ,  2606 ,  2608 ,  2610 . The components may be software components running in the processor  2704 , resident/stored in the computer readable medium/memory  2706 , one or more hardware components coupled to the processor  2704 , or some combination thereof. The processing system  2714  may be a component of the base station  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  2602 / 2602 ′ for wireless communication includes means for transmitting a BSM to a second device via a first beam set, the BSM including a command to switch from communication via the first beam set to communication via a second beam set at a switch time, means for receiving a response message from the second device via the first beam set, the response message indicating that the second device received the BSM, and means for sending, to the second device, a communication via the second beam set after the switch time if the response message is received. The aforementioned means may be one or more of the aforementioned components of the apparatus  2602  and/or the processing system  2714  of the apparatus  2602 ′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system  2714  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. 28  is a conceptual data flow diagram  2800  illustrating the data flow between different means/components in an exemplary apparatus  2802 . The apparatus may be a UE, for example. The apparatus includes a receiver  2804  that receives signals, a controller  2806  that controls various functions of apparatus  2802 , a response monitor  2808  that monitors for a response, and a transmitter  2810  that transmits signals. For example, UL/DL signals can be received from and transmitted to an apparatus  2850  via first and second beam pairs. Apparatus  2850  can be a base station, for example. Response monitor  2808  can, for example, monitor for a BSM from apparatus  2850  via a first beam set, the BSM including a command to switch from communication via the first beam set to communication via a second beam set at a switch time, can send a response message to apparatus  2850  via the first beam set when the BSM is received, and can switch from communication via the first beam set to communication via the second beam set at the switch time. 
     The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowchart of  FIG. 21 . As such, each block in the aforementioned flowchart of  FIG. 21  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. 29  is a diagram  2900  illustrating an example of a hardware implementation for an apparatus  2802 ′ employing a processing system  2914 . The processing system  2914  may be implemented with a bus architecture, represented generally by the bus  2924 . The bus  2924  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  2914  and the overall design constraints. The bus  2924  links together various circuits including one or more processors and/or hardware components, represented by the processor  2904 , the components  2804 ,  2806 ,  2808 ,  2810 , and the computer-readable medium/memory  2906 . The bus  2924  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  2914  may be coupled to a transceiver  2910 . The transceiver  2910  is coupled to one or more antennas  2920 . The transceiver  2910  provides a means for communicating with various other apparatus over a transmission medium. The transceiver  2910  receives a signal from the one or more antennas  2920 , extracts information from the received signal, and provides the extracted information to the processing system  2914 , specifically the receiver  2804 . In addition, the transceiver  2910  receives information from the processing system  2914 , specifically the transmitter  2810 , and based on the received information, generates a signal to be applied to the one or more antennas  2920 . The processing system  2914  includes a processor  2904  coupled to a computer-readable medium/memory  2906 . The processor  2904  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory  2906 . The software, when executed by the processor  2904 , causes the processing system  2914  to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory  2906  may also be used for storing data that is manipulated by the processor  2904  when executing software. The processing system  2914  further includes at least one of the components  2804 ,  2806 ,  2808 ,  2810 . The components may be software components running in the processor  2904 , resident/stored in the computer readable medium/memory  2906 , one or more hardware components coupled to the processor  2904 , or some combination thereof. The processing system  2914  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 , 
     In one configuration, the apparatus  2802 / 2802 ′ for wireless communication includes means for monitoring for a BSM from a second device via a first beam set, the BSM including a command to switch from communication via the first beam set to communication via a second beam set at a switch time, means for sending a response message to the second device when the BSM is received, and means for switching from communication via the first beam set to communication via the second beam set at the switch time. The aforementioned means may be one or more of the aforementioned components of the apparatus  2802  and/or the processing system  2914  of the apparatus  2802 ′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system  2914  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. 
       FIG. 30  is a conceptual data flow diagram  3000  illustrating the data flow between different means/components in an exemplary apparatus  3002 . The apparatus may be a base station, for example. The apparatus includes a receiver  3004  that receives signals, a controller  3006  that controls various functions of apparatus  3002 , a reset state selector  3008  that selects a reset state, and a transmitter  3010  that transmits signals. For example, UL/DL signals can be received from and transmitted to an apparatus  3050  via first and second beam pairs. Apparatus  3050  can be a UE, for example. Reset state selector  3008  can, for example, select a reset state from a plurality of reset states including a first state indicating to disregard a first beam switch instruction and a second state to maintain execution of the first instruction. 
     The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowchart of  FIG. 22 . As such, each block in the aforementioned flowchart of  FIG. 22  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. 31  is a diagram  3100  illustrating an example of a hardware implementation for an apparatus  3002 ′ employing a processing system  3114 . The processing system  3114  may be implemented with a bus architecture, represented generally by the bus  3124 . The bus  3124  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  3114  and the overall design constraints. The bus  3124  links together various circuits including one or more processors and/or hardware components, represented by the processor  3104 , the components  3004 ,  3006 ,  3008 ,  3010 , and the computer-readable medium/memory  3106 . The bus  3124  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  3114  may be coupled to a transceiver  3110 . The transceiver  3110  is coupled to one or more antennas  3120 . The transceiver  3110  provides a means for communicating with various other apparatus over a transmission medium. The transceiver  3110  receives a signal from the one or more antennas  3120 , extracts information from the received signal, and provides the extracted information to the processing system  3114 , specifically the receiver  3004 . In addition, the transceiver  3110  receives information from the processing system  3114 , specifically the transmitter  3010 , and based on the received information, generates a signal to be applied to the one or more antennas  3120 . The processing system  3114  includes a processor  3104  coupled to a computer-readable medium/memory  3106 . The processor  3104  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory  3106 . The software, when executed by the processor  3104 , causes the processing system  3114  to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory  3106  may also be used for storing data that is manipulated by the processor  3104  when executing software. The processing system  3114  further includes at least one of the components  3004 ,  3006 ,  3008 ,  3010 . The components may be software components running in the processor  3104 , resident/stored in the computer readable medium/memory  3106 , one or more hardware components coupled to the processor  3104 , or some combination thereof. The processing system  3114  may be a component of the base station  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  3002 / 3002 ′ for wireless communication includes means for transmitting a first BSM to a second device, the first BSM including a first instruction for switching beams, means for selecting a reset state from a plurality of reset states including a first state for the second device to disregard the first instruction and a second state for the second device to maintain execution of the first instruction, and means for transmitting a second BSM to the second device before the second device completes execution of the first instruction, the second BSM including a second instruction for switching beams and indicating which of the reset states is selected. The aforementioned means may be one or more of the aforementioned components of the apparatus  3002  and/or the processing system  3114  of the apparatus  3002 ′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system  3114  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. 32  is a conceptual data flow diagram  3200  illustrating the data flow between different means/components in an exemplary apparatus  3202 . The apparatus may be a UE, for example. The apparatus includes a receiver  3204  that receives signals, a controller  3206  that controls various functions of apparatus  3202 , a reset state determiner  3208  that determines a reset state, and a transmitter  3210  that transmits signals. For example, UL/DL signals can be received from and transmitted to an apparatus  3250  via first and second beam pairs. Apparatus  3250  can be a base station, for example. Reset state determiner  3208  can, for example, determine whether to disregard a first beam switch instruction or to maintain execution of the first beam switch instruction based on an indicated reset state of a BSM. 
     The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowchart of  FIG. 23 . As such, each block in the aforementioned flowchart of  FIG. 23  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. 33  is a diagram  3300  illustrating an example of a hardware implementation for an apparatus  3202 ′ employing a processing system  3314 . The processing system  3314  may be implemented with a bus architecture, represented generally by the bus  3324 . The bus  3324  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  3314  and the overall design constraints. The bus  3324  links together various circuits including one or more processors and/or hardware components, represented by the processor  3304 , the components  3204 ,  3206 ,  3208 ,  3210 , and the computer-readable medium/memory  3306 . The bus  3324  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  3314  may be coupled to a transceiver  3310 . The transceiver  3310  is coupled to one or more antennas  3320 . The transceiver  3310  provides a means for communicating with various other apparatus over a transmission medium. The transceiver  3310  receives a signal from the one or more antennas  3320 , extracts information from the received signal, and provides the extracted information to the processing system  3314 , specifically the receiver  3204 . In addition, the transceiver  3310  receives information from the processing system  3314 , specifically the transmitter  3210 , and based on the received information, generates a signal to be applied to the one or more antennas  3320 . The processing system  3314  includes a processor  3304  coupled to a computer-readable medium/memory  3306 . The processor  3304  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory  3306 . The software, when executed by the processor  3304 , causes the processing system  3314  to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory  3306  may also be used for storing data that is manipulated by the processor  3304  when executing software. The processing system  3314  further includes at least one of the components  3204 ,  3206 ,  3208 ,  3210 . The components may be software components running in the processor  3304 , resident/stored in the computer readable medium/memory  3306 , one or more hardware components coupled to the processor  3304 , or some combination thereof. The processing system  3314  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  3202 / 3202 ′ for wireless communication includes means for receiving a second BSM from a second device, the second BSM including a second instruction for switching beams and indicating a reset state associated with a first BSM including a first instruction for switching beams, and means for determining whether to disregard the first instruction or to maintain execution of the first instruction based on the indicated reset state. The aforementioned means may be one or more of the aforementioned components of the apparatus  3202  and/or the processing system  3314  of the apparatus  3202 ′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system  3314  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. 
       FIG. 34  is a conceptual data flow diagram  3400  illustrating the data flow between different means/components in an exemplary apparatus  3402 . The apparatus may be a base station, for example. The apparatus includes a receiver  3404  that receives signals, a controller  3406  that controls various functions of apparatus  3402 , a response monitor  3408  that monitors for a response, and a transmitter  3410  that transmits signals. For example, UL/DL signals can be received from and transmitted to an apparatus  3450  via first and second beam pairs. Apparatus  3450  can be a UE, for example. Response monitor  3408  can, for example, determine whether a response message is received from apparatus  3450  via a first beam set, the response message indicating that apparatus  3450  received a BSM sent by apparatus  3402 . Transmitter  3410  can, for example, send to apparatus  3450 , a communication via a second beam set after a switch time when the response message is unreceived. 
     The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowchart of  FIG. 24 . As such, each block in the aforementioned flowchart of  FIG. 24  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. 35  is a diagram  3500  illustrating an example of a hardware implementation for an apparatus  3402 ′ employing a processing system  3514 . The processing system  3514  may be implemented with a bus architecture, represented generally by the bus  3524 . The bus  3524  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  3514  and the overall design constraints. The bus  3524  links together various circuits including one or more processors and/or hardware components, represented by the processor  3504 , the components  3404 ,  3406 ,  3408 ,  3410 , and the computer-readable medium/memory  3506 . The bus  3524  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  3514  may be coupled to a transceiver  3510 . The transceiver  3510  is coupled to one or more antennas  3520 . The transceiver  3510  provides a means for communicating with various other apparatus over a transmission medium. The transceiver  3510  receives a signal from the one or more antennas  3520 , extracts information from the received signal, and provides the extracted information to the processing system  3514 , specifically the receiver  3404 . In addition, the transceiver  3510  receives information from the processing system  3514 , specifically the transmitter  3410 , and based on the received information, generates a signal to be applied to the one or more antennas  3520 . The processing system  3514  includes a processor  3504  coupled to a computer-readable medium/memory  3506 . The processor  3504  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory  3506 . The software, when executed by the processor  3504 , causes the processing system  3514  to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory  3506  may also be used for storing data that is manipulated by the processor  3504  when executing software. The processing system  3514  further includes at least one of the components  3404 ,  3406 ,  3408 ,  3410 . The components may be software components running in the processor  3504 , resident/stored in the computer readable medium/memory  3506 , one or more hardware components coupled to the processor  3504 , or some combination thereof. The processing system  3514  may be a component of the base station  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  3402 / 3402 ′ for wireless communication includes means for transmitting a BSM to a second device via a first beam set, the BSM including a command to switch from communication via the first beam set to communication via a second beam set at a switch time, means for determining whether a response message is received from the second device via the first beam set, the response message indicating that the second device received the BSM, and means for sending, to the second device, a communication via the second beam set after the switch time when the response message is unreceived. The aforementioned means may be one or more of the aforementioned components of the apparatus  3402  and/or the processing system  3514  of the apparatus  3402 ′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system  3514  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. 36  is a conceptual data flow diagram  3600  illustrating the data flow between different means/components in an exemplary apparatus  3602 . The apparatus may be a UE, for example. The apparatus includes a receiver  3604  that receives signals, a controller  3606  that controls various functions of apparatus  3602 , a response monitor  3608  that monitors for a response, and a transmitter  3610  that transmits signals. For example, UL/DL signals can be received from and transmitted to an apparatus  3650  via first and second beam pairs. Apparatus  3650  can be a base station, for example. Response monitor  3608  can, for example, monitor for a BSM from apparatus  3650  via a first beam set, the BSM including a command to switch from communication via the first beam set to communication via a second beam set at a switch time, and can monitor for a second communication from apparatus  3650  via the first beam set when the BSM is unreceived, the second communication via the first beam set being monitored at a second time subsequent to a first time in which a first communication is sent to apparatus  3602  via the second beam set. 
     The apparatus may include additional components that perform each of the blocks of the algorithm in the aforementioned flowchart of  FIG. 25 . As such, each block in the aforementioned flowchart of  FIG. 25  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. 37  is a diagram  3700  illustrating an example of a hardware implementation for an apparatus  3602 ′ employing a processing system  3714 . The processing system  3714  may be implemented with a bus architecture, represented generally by the bus  3724 . The bus  3724  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  3714  and the overall design constraints. The bus  3724  links together various circuits including one or more processors and/or hardware components, represented by the processor  3704 , the components  3604 ,  3606 ,  3608 ,  3610 , and the computer-readable medium/memory  3706 . The bus  3724  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  3714  may be coupled to a transceiver  3710 . The transceiver  3710  is coupled to one or more antennas  3720 . The transceiver  3710  provides a means for communicating with various other apparatus over a transmission medium. The transceiver  3710  receives a signal from the one or more antennas  3720 , extracts information from the received signal, and provides the extracted information to the processing system  3714 , specifically the receiver  3604 . In addition, the transceiver  3710  receives information from the processing system  3714 , specifically the transmitter  3610 , and based on the received information, generates a signal to be applied to the one or more antennas  3720 . The processing system  3714  includes a processor  3704  coupled to a computer-readable medium/memory  3706 . The processor  3704  is responsible for general processing, including the execution of software stored on the computer-readable medium/memory  3706 . The software, when executed by the processor  3704 , causes the processing system  3714  to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory  3706  may also be used for storing data that is manipulated by the processor  3704  when executing software. The processing system  3714  further includes at least one of the components  3604 ,  3606 ,  3608 ,  3610 . The components may be software components running in the processor  3704 , resident/stored in the computer readable medium/memory  3706 , one or more hardware components coupled to the processor  3704 , or some combination thereof. The processing system  3714  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 , 
     In one configuration, the apparatus  3602 / 3602 ′ for wireless communication includes means for monitoring for a BSM from a second device via a first beam set, the BSM including a command to switch from communication via the first beam set to communication via a second beam set at a switch time, means for sending a response message to the second device when the BSM is received, and monitoring for a second communication from the second device via the first beam set when the BSM is unreceived, the second communication via the first beam set being monitored at a second time subsequent to a first time in which a first communication is sent to the first device via the second beam set. The aforementioned means may be one or more of the aforementioned components of the apparatus  3602  and/or the processing system  3714  of the apparatus  3602 ′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system  3714  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.”