Methods and apparatus related to beam refinement

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE configured to receive a plurality of beams through a plurality of different receive beam directions, each of the beams including broadcast information on a PBCH. The apparatus may be further configured to determine, for each of a subset of the received beams, a log likelihood ratio (LLR) for coded bits of the broadcast information. The apparatus may be further configured to decode the broadcast information associated with each of the subset of the received beams, and determine a refined receive beam direction based on the determined LLRs and based on whether the broadcast information associated with each of the subset of the received beams fails to decode or is successfully decoded.

BACKGROUND

Technical Field

The present disclosure relates generally to communication systems, and more particularly, to methods and apparatus related to beam refinement during initial cell search, e.g., using physical broadcast channel (PBCH) decoding.

Introduction

SUMMARY

Various aspects described herein are directed to methods and apparatus for beam refinement to determine a refined receive beam direction, e.g., during an initial cell search procedure. The initial cell search procedure may be performed by a user equipment (UE) to acquire synchronization and establish a connection to a base station. Performing the cell search procedure may allow the UE to detect cell timing and a cell identifier (ID) through a primary synchronization signal (PSS)/secondary synchronization signal (SSS) that may be received by the UE during the initial cell search, as well as to decode the master information block (MIB) carried in the physical broadcast channel (PBCH). In an aspect, a beam refinement process may be used to determine the refined receive beam direction. The beam refinement process may be based on PBCH decoding, e.g., decoding of broadcast information on a PBCH received by a device via a plurality of beams.

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE configured to receive a plurality of beams through a plurality of different receive beam directions, each of the beams including broadcast information on a PBCH. The apparatus may be further configured to determine, for each of a subset of the received beams, log likelihood ratios (LLRs) for coded bits of the broadcast information. The apparatus may be further configured to decode the broadcast information associated with each of the subset of the received beams, and determine a refined receive beam direction based on the determined LLRs and based on whether the broadcast information associated with each of the subset of the received beams fails to decode or is successfully decoded.

DETAILED DESCRIPTION

Referring again toFIG. 1, in certain aspects, the UE104, may be configured to receive a plurality of beams through a plurality of different receive beam directions, each of the beams including broadcast information on a PBCH, and perform a beam refinement process to determine a refined receive beam direction based on PBCH decoding (198). For example, the UE104may determine, for each of a subset of the received beams, LLRs for coded bits of the broadcast information, and decode the broadcast information associated with each received beam of the subset of the received beams (198). The UE104may then determine a refined receive beam direction based on the determined LLRs and based on whether the broadcast information associated with each received beam of the subset of the received beams fails to decode or is successfully decoded (198).

FIG. 2Ais a diagram200illustrating an example of a DL frame structure.FIG. 2Bis a diagram230illustrating an example of channels within the DL frame structure.FIG. 2Cis a diagram250illustrating an example of an UL frame structure.FIG. 2Dis a diagram280illustrating 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 may contain 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 may contain 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 inFIG. 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. 2Aillustrates CRS for antenna ports 0, 1, 2, and 3 (indicated as R0, R1, R2, and R3, respectively), UE-RS for antenna port 5 (indicated as R5), and CSI-RS for antenna port 15 (indicated as R).

FIG. 2Billustrates 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. 2Billustrates 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. 2Bshows two RB pairs, each subset including one RB pair). The physical hybrid automatic repeat request (ARQ) (HARQ) indicator channel (PHICH) is also within symbol 0 of slot 0 and carries the HARQ indicator (HI) that indicates HARQ acknowledgement (ACK)/negative ACK (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 UE104to 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 inFIG. 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. 2Dillustrates 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.

Cellular systems typically employ periodic or frequent transmission of broadcast information, such as the PBCH in LTE and other systems. Via the PBCH, the base station may broadcast a number of parameters needed for initial access of the cell such as, for example, downlink system bandwidth, the Physical Hybrid ARQ Indicator Channel structure, and the most significant bits of the System Frame Number. The parameters may be carried in a MIB.

FIG. 4is a diagram400illustrating a base station402(e.g., a gNB) in communication with a UE404. The base station402and the UE404may be a part of a mmW communication system. Referring toFIG. 4, the base station402may transmit a beamformed signal to the UE404in one or more of the directions402a,402b,402c,402d,402e,402f,402g,402h. The UE404may receive the beamformed signal from the base station402in one or more receive directions404a,404b,404c,404d. The UE404may also transmit a beamformed signal to the base station402in one or more of the directions404a-404d. The base station402may receive the beamformed signal from the UE404in one or more of the receive directions402a-402h. The base station402/UE404may perform beam training to determine the best receive and transmit directions for each of the base station402/UE404. The transmit and receive directions for the base station402may or may not be the same. The transmit and receive directions for the UE404may or may not be the same.

To acquire synchronization and establish a connection to a base station (e.g., a gNB), a UE (e.g., a 5G NR-UE that supports 5G NR) may perform a so-called initial cell search. The purpose of cell search may include detection of cell timing and a cell identifier (ID) by the UE through a primary synchronization signal (PSS)/secondary synchronization signal (SSS), as well as decoding the MIB carried in the PBCH. The acquired information during the cell search may allow the UE to initiate the random access procedure referred to as the random access channel (RACH) procedure to inform the network about the UE's desire to connect and/or gain access to the network.

In a millimeter wave (mmW) 5G NR system (e.g., with operating frequency >6 GHz), a mmW base station (e.g., a gNB such as base station180) may transmit the PSS/SSS and the PBCH through beam sweeping, e.g., with a plurality of beams being transmitted in different directions in a time division multiplexed (TDM) fashion. A UE (e.g., such as UE104) attempting to acquire system synchronization information and establish a connection may attempt to scan/receive in all of the UE's receive directions, for example, in 4 directions/orientations. The UE may receive a plurality of beams and perform the initial cell search on more than a single received (RX) beam. For example, in some configurations, the UE may perform initial cell search on all the UE's RX beams, e.g., 4 relatively wide (90°) RX beams in 4 directions. The RX beam where the strongest cell has been detected, may be used as the RX beam to continue to update measurements of the detected cell. Utilizing reciprocity, the same steering direction may be used as the direction of a transmit (TX) beam for the RACH procedure. For example, for initiating the RACH procedure, the UE may then use this direction for sending beamformed signals/messages (e.g., RACH preambles) to the mmW base station.

To refine the RX beam (e.g., to determine a refined/finer receive beam direction) at the UE, the UE may perform measurements of the detected cell by repeating the measurements for various refined RX beams (e.g., for various finer RX beam directions). However, the above approach of RX beam refinement may add latency and significantly increase power consumption due to increased RF open time (e.g., time for which RF elements need to stay on), e.g., because of having to perform the measurements for various refined (finer) beam directions. The added latency is owing to the fact that typically a mmW UE may not be able to listen on more than one RX beam (corresponding to one finer direction) at a time due to RF limitations. Thus, the UE may listen and perform measurements on one refined RX beam at a time. If measurements for multiple receive beam directions are performed for beam direction refinement (e.g., to find the best refined RX beam direction) then such measurements may be performed in different time intervals which may add to the latency. With regard to the increased power consumption, the power consumption is dominated by the on time for RF elements in mmW devices, e.g., with relatively more power consumption caused by the operation of RF elements (e.g., receive and/or transmit chains/circuitry) due to longer on time. Thus, in view of the above, it should be appreciated that improved methods and apparatus for determining a refined receive beam direction are desired.

Various features and aspects described herein relate to methods and apparatus for determining a refined receive beam direction based on decoding of broadcast information communicated via a plurality of beams which may be received by a UE during an initial cell search. The broadcast information may include, e.g., master information block (MIB) carried by the PBCH. Thus, as discussed infra, in accordance with certain aspects of the disclosure, beam refinement may be performed based on PBCH decoding. Various aspects and features of the methods described herein may reduce and/or overcome the various shortcomings (e.g., latency and power higher consumption) discussed above associated with some other beam refinement approaches. Thus, various aspects and features of the methods described herein may reduce beam refinement delays and power consumption associated with a beam refine process.

In an aspect, a UE may receive a plurality of beams (e.g., corresponding to different receive directions) from a cell, e.g., gNB serving the cell, during the initial cell search performed by the UE. Each of the received beams from the given cell may include synchronization information (e.g., PSS and SSS) and broadcast information, e.g., MIB carried in the PBCH. Each received beam from the same cell may carry the same broadcast information.

FIG. 5is a diagram500illustrating a UE502(e.g., a mmW UE) receiving 4 beams510,512,514and516, e.g., 4 relatively wide (90°) beams corresponding to 4 different receive directions, during an initial cell search performed by the UE502. The UE502may be any one of the UEs104,350,404. While in the illustrated example, the number of received beams is 4, the number of received beams during the initial cell search may be less or more. The UE may then proceed to perform PBCH decoding on at least some of the received beams, e.g., on a subset of the received beams. The subset of the received beams may be determined/selected based on a reliability metric determined from the processing in prior stages, for example, the processing of received PSS and SSS via the received beams. For example, a subset of received beams to be decoded may be selected based on power measurements on the PSS/SSS signals on the received beams, e.g., by selecting the received beams having strong PSS/SSS (and thus higher probability of cell detection) as the subset of the received beams for decoding and further processing. For the purposes of discussion ofFIGS. 5-6, consider that the UE502may attempt to decode PBCH on all 4 received beams510,512,514and516.

FIG. 6is a diagram600illustrating an example of processing associated with a PBCH decoding based beam refinement method. The processing is discussed with the reference to UE502and the plurality of beams illustrated inFIG. 5. In the illustration, the 4 received beams are shown on the left side of line604and indicated by arrow602while the corresponding processing of each of the 4 received beams510,512,514and516is illustrated to the right of line604. The processing of each of the 4 received beams510,512,514and516may include various stages including PSS processing, SSS processing, LLR computation for coded broadcast information (e.g., PBCH), decoding and cyclic redundancy check (CRC) as illustrated in the diagram600. In one configuration, for a detected cell (which may be determined by cell timing and cell ID obtained via the received PSS and SSS), the UE502may determine/compute log-likelihood ratios (LLRs) for the coded bits of the broadcast information (also referred to as PBCH coded bits) for each of the 4 received beams510,512,514and516individually. That is, for each received beam corresponding to the given detected cell, the UE502may determine LLRs of the coded bits of the broadcast information included in the RX beam (as illustrated by614,624,634, and644). While in the particular example being discussed, the UE502may perform PBCH decoding on each of the 4 received beams as shown, in some other configurations, the UE502decide to perform PBCH decoding and further processing related to beam refinement on a subset of the received beams. The LLR is a reliability metric used in communication systems and may be determined, e.g., by a receiving UE, for each received bit stream on a per bit basis. For a given bit of a bit stream in a received beam, a strongly positive value of an LLR may imply that the bit is most likely 0 whereas a negative value may imply that the bit is most likely 1.

As illustrated, for the first received beam510, the UE502may process the PSS received via beam510in the PSS processing stage610and process the SSS received via beam510in the SSS processing stage612. The cell timing and a cell ID corresponding to the detected call may be determined through the received PSS and SSS. The UE502may generate LLRs corresponding to the coded bits of the broadcast information (PBCH coded bits) associated with the first received beam510in the PBCH LLR computation stage614. Next, based on the determined LLRs corresponding to the coded bits of the broadcast information communicated in the first received beam510, the UE502may perform PBCH decoding at616and perform a CRC to determine whether the decoding at616is successful. Similarly, for the RX beams512,514, and516, the UE502may process the PSS received via beams512,514, and516in the corresponding PSS processing stages620,630, and640, and process the SSS received via beams512,514, and516in the corresponding SSS processing stages622,632, and642respectively. The UE502may generate LLRs corresponding to the coded broadcast information (PBCH coded bits) associated with the beams512,514, and516in the PBCH LLR computation stages624,634, and644respectively. Based on the determined LLRs corresponding to the PBCH coded bits communicated in the beams512,514, and516, the UE502may individually decode coded broadcast information associated with each of the beams at corresponding decoding stages626,636, and646, respectively. Furthermore, each PBCH decoding626,636, and646may be followed by a corresponding CRC pass/fail determination as shown in the diagram600. The PBCH decoding for the multiple received beams may be performed asynchronously in parallel (e.g., concurrently using multiple parallel decoders) or sequentially in any order.

In an aspect, depending on the result of PBCH decoding (at616,626,636,646) on each of the beams510,512,514and516, beam refinement may be performed in a number of different ways in accordance with the methods described herein. For example, in one configuration, if PBCH decoding fails (e.g., the CRC fails) for all of the received beams510,512,514and516, the UE502may combine the generated LLRs for the coded bits of the broadcast information associated with at least two adjacent received beams (e.g.,510and512;512and514;514and516; and/or516and510) and attempt to decode PBCH payload based on the combined LLRs (e.g., a set of combined LLRs also referred to as combined set of LLRs). For example, with reference toFIG. 6, if PBCH decoding fails for all of the 4 received beams (e.g., as determined based on CRC failure), the LLRs for the broadcast information associated with beams510and512which are adjacent (e.g., in a directional sense, as the beam510corresponding to the north receive direction is directionally adjacent to the beam512corresponding to the east receive direction) are combined as shown in diagram600at625. In the example discussed with respect toFIG. 6, the PBCH payload and the encoded bits are assumed to remain constant for the 4 received beam observation windows, that is, the coded bits of the broadcast information remain the same in all 4 received beams. In such a case, the LLR combining includes summing the LLRs of the coded broadcast information bits (also sometimes referred to as PBCH LLRs) from adjacent received beams. The UE502may then perform PBCH decoding at627based on the combined LLRs (e.g., output of625in case of received beams510and512) followed by a CRC to determine if the decoding at627is successful. If PBCH decoding (based on the combined LLRs) is successful (e.g., if the CRC passes), then in accordance with one aspect the UE502may conclude that the receive beam resulting from a combination of the two adjacent beams may be taken as the refined receive beam (or at least a refined receive beam candidate if other adjacent beam pairs are to be checked) for subsequent processing. That is, a receive beam direction resulting from a combination of the two adjacent receive beam directions (corresponding to beams510and512) may be taken as the refined receive beam direction. For example, in the case of combination of the two adjacent receive beam directions, a direction corresponding to a midpoint between the two adjacent receive beam directions may be considered to correspond to the refined receive beam direction. The subsequent processing may include further processing associated with the initial cell search procedure and/or uplink RACH procedure. If PBCH decoding at627based on the combined LLRs is unsuccessful (e.g., if the CRC fails), then the UE502may conclude that the refined received beam (and thus a refined receive direction) may not be determined based on the combination of the two adjacent received beams510and512.

In some configurations, prior to deciding on the refined receive beam direction, the UE502may perform similar checks for the other directionally adjacent beam pairs, e.g.,512and514;514and516; and516and510(but not510and514or512and516since the beams are not adjacent in these cases and are rather in opposite directions). For example, the LLRs for the PBCH coded bits corresponding to beams512and514(which are directionally adjacent) may be combined at635and the UE502may then perform PBCH decoding at637based on the combined LLRs (e.g., output of635) followed by a CRC to determine if the decoding at637is successful. If PBCH decoding based on the combined LLRs at637is successful (e.g., if the CRC passes), then the UE502may conclude that a beam direction resulting from a combination of the two adjacent beam directions (corresponding to beams512and514) may be taken as another refined receive beam direction candidate for subsequent processing (e.g., in addition to the refined beam candidate from the combination of RX beams510and512discussed above) otherwise if the PBCH decoding at637fails then the direction corresponding a beam resulting from the combination of the adjacent received beams512and514is not considered a candidate. Similarly, for the adjacent beam pair514and516, the LLRs for the PBCH coded bits associated with the adjacent beams514and516may be combined at645, and the UE502may perform PBCH decoding at647based on the combined LLRs (e.g., output of645) followed by a CRC. If the CRC indicates a pass, then the UE502may conclude that a beam direction resulting from a combination of the two adjacent beam directions (corresponding to beams514and516) may be taken as another refined receive beam direction candidate. However, if the CRC indicates a failure (decoding at647fails) then the beam direction resulting from the combination may not be considered a refined receive beam direction candidate.

For the last adjacent beam pair516and510, the LLRs for the coded bits of the broadcast information associated with beams516and510may be combined at655, and the UE502may then perform PBCH decoding at657based on the combined LLRs (e.g., output of655) followed by a CRC. If the CRC indicates a pass, then the UE502may conclude that a beam direction resulting from a combination of the two adjacent beam directions (corresponding to beams516and510) may be taken as another refined beam candidate for subsequent processing and not if the CRC indicates a failure (e.g., if decoding at657fails).

In the case where there may be multiple refined beam candidates (e.g., with more than one successful PBCH decoding based on combined LLRs from corresponding adjacent beams), the UE502may consider a post decoding reliability metric (e.g., determined by a channel decoder performing the PBCH decodings) for each of the PBCH decodings (627,637,647, and657) and may select the refined beam direction candidate that corresponds to the corresponding PBCH decoding with the largest post decoding reliability metric. For example, assuming largest reliability metric corresponds to the decoding based on the combined LLRs for the coded broadcast information bits associated with adjacent beams512(east receive direction) and514(south receive direction), the beam652resulting from the combination of the beams512and514may be taken as the refined receive beam (i.e., the south east receive direction may be considered the refined/best receive beam direction).

In another aspect, if PBCH decoding succeeds on one received beam (e.g., one of the 4 received beams510,512,514, and516), but fails on the other received beams, the UE502may combine the LLR for the broadcast information associated with the beam for which decoding has been successful and LLR for the broadcast information associated with an adjacent beam and attempt to decode the broadcast information (PBCH payload) based on the combined LLRs in the manner discussed above. For example, with reference toFIG. 6, if PBCH decoding (at626) succeeds for the beam512and fails for the other 3 received beams, then the UE502may combine the LLRs for the PBCH associated with beams512and510(which are directionally adjacent) at625. The UE502may then perform PBCH decoding at627based on the combined LLRs (e.g., output of625) followed by a CRC to determine if the decoding at627is successful. If PBCH decoding (based on the combined LLRs) is successful (CRC passes), then the UE502may take a receive beam direction resulting from a combination of the two adjacent receive beam directions (corresponding to512and510) as one refined beam direction candidate. Because the UE502is aware that with the beam512, one more adjacent beam pair may be formed, e.g., with the beams512and514, the UE502may perform similar processing for the adjacent beams512and514. That is, the UE502may combine the LLRs for the PBCH associated with beams512and514at635, and may perform PBCH decoding at637based on the combined LLRs (e.g., output of635) followed by a CRC to determine if the decoding at637is successful. If PBCH decoding at637(based on the combined LLRs) is also successful (CRC passes), then a receive beam direction resulting from a combination of the two adjacent receive beam directions (corresponding to beams512and514) may also be considered as another refined receive beam direction candidate. Again, because there are more than one refined receive beam direction candidate (e.g., beam direction corresponding to beam512for which PBCH decoding succeeded, beam direction resulting from the combination of the adjacent receive beam directions corresponding to adjacent beams512and510for which the combined LLRs based PBCH decoding succeeded, and beam direction resulting from the combination of the adjacent receive beam directions corresponding to beams512and514for which the combined LLRs based PBCH decoding succeeded), the UE502may consider post decoding reliability metric for each of the corresponding PBCH decodings (626,627, and637) and may select the refined receive beam direction candidate that corresponds to the decoding with the highest post decoding reliability metric. For example, assuming that the post decoding reliability metric for the combined LLRs based PBCH decoding at637is highest, the UE502may take the receive beam direction corresponding to beam652resulting from the combination of the adjacent beams512and514as the best receive beam direction and use RX beam520for subsequent processing.

In yet another aspect, if PBCH decoding succeeds on more than one received beams, and at least 2 of the succeeding received beams are adjacent, the UE502may combine the LLRs for the PBCH associated with the two adjacent beams and perform PBCH decoding based on the combined LLRs in a similar manner as discussed above. Again, the UE502may subsequently analyze decoding results, and based on the post decoding reliability metrics provided by the channel decoder, the UE502may select the best receive beam direction. For example, if the largest metric is obtained for the combined LLRs based PBCH decoding, then the UE502may select the receive beam direction resulting from the combination of the two adjacent receive beam directions (corresponding to the two adjacent receive beams for which PBCH decoding succeeded), otherwise, the UE502may select the beam direction corresponding to the original beam with largest metric.

While the above examples discussed with respect toFIGS. 5-6, describe the beam refinement methods considering 4 received beams to facilitate an understanding of the concepts, the techniques and concepts described supra may be generalized to multiple (e.g., fewer or more) beams. For example, the UE502may receive N received beams and decode PBCH on a subset R (|R|≤N) of the N received beams (where “| |” denotes cardinality/number of elements of a set), and may attempt to decode PBCH on all pairs of a beam subset P of R (|P|≤|R|), e.g., with PBCH decoding on each beam pair being based on combined LLRs as discussed above in detail with respect toFIG. 6. Furthermore, in various configurations, each beam pair being considered for PBCH decoding may include beams which are adjacent to each other, e.g., directionally adjacent. In an aspect, the selection of the subset R and P may, e.g., be based on reliability metrics obtained from the prior processing stages (e.g., based on PSS/SSS). With regard to combining PBCH LLRs (e.g., the LLRs for the PBCH of directionally adjacent received beams), if the PBCH payload and the encoded bits are assumed to remain constant for the different N received beam observation windows, LLR combining may include summing the LLRs of all N included received beams. However, if the encoded bits change (e.g., due to time-dependent scrambling), LLR combining may first need to compensate for the difference on the encoded bits (e.g., by de-scrambling) followed by the summation of the LLRs corresponding to the individual RX beams. If the PBCH payload bits change, various techniques of using decoding of multiple hypothesis of combined LLRs may be used. While current wireless communication standards (e.g., 3GPP specifications) have not finalized PBCH payload definition and exact PBCH payload encoding, depending on a final agreement one or more of the methods described above may be used. The examples discussed above with respect toFIG. 6assume N=4, |R|=4 and |P|=4, as well as constant PBCH payload and encoded bits.

As discussed above, the UE502may use the refined beam (e.g., best beam/direction) for subsequent measurements during the initial cell search as well as use the determined refined receive beam direction as the best transmit beam direction (assuming channel reciprocity), e.g., to perform processing/signaling related UL RACH procedure. That is, the UE502may use the refined beam direction as the best transmit direction for transmission during UL RACH, e.g., for initiating the RACH procedure, the UE502may use the determined refined receive beam direction as the best transmit direction for sending UL RACH signals, e.g., RACH preambles, to the mmW base station. With the above discussed approach, the success probability of UL RACH may significantly increase due to the refined beam selection. Furthermore, the additional complexity of the beam refinement process (e.g., with the additional PBCH decoding) discussed above may be lower compared to scanning with finer beam resolution as in some other beam refinement techniques.

FIG. 7, which comprises a combination ofFIGS. 7A and 7B, is a flowchart700of a method of wireless communication. The method of flowchart700may be performed by an apparatus (e.g., the UE104,350,404,502, apparatus802/802′). The first part of the flowchart700is illustrated inFIG. 7Aand the second part of the flowchart700is illustrated inFIG. 7B. Blocks shown as dashed boxes are optional and may or may not be performed in certain embodiments. Reference toFIGS. 5-6may be made to facilitate the discussion of flowchart700. At702, the apparatus (e.g., UE502) may receive a plurality of beams through a plurality of different receive beam directions, each of the beams including broadcast information on a PBCH. For example, referring toFIG. 5example, the UE502may receive a plurality of beams510,512,514, and516, each corresponding to a different receive directions and each communicating broadcast information associated with a PBCH. The plurality of beams may be received, e.g., during an initial cell search performed by the UE502.

At704, the apparatus may determine, for each of a subset of the received beams, log likelihood ratios (LLRs) for coded bits of the broadcast information. While multiple beams may be received, the apparatus may decide to pursue a subset of the total number of received beams for further processing and decoding as not all of the received beams may produce desired decoding results. For example, the UE502may select a subset of the received beams based on, for example, the processing of received PSS and SSS in the received beams, e.g., based on power measurements on the PSS/SSS signals on the received beams. In one configuration, the UE502may select the subset of received beams with strong power measurements for PSS/SSS for further decoding and/or further processing. For simplifying the discussion, consider that the UE502may select a subset of 2 received beams (e.g., beams512and514may be selected as having strongest cell measurements) and attempt to decode the broadcast information on the 2 received beams. In some configurations, the UE502may first determine LLRs for the coded bits of the broadcast information associated with the subset of the received beams. In the above example (with the subset including 2 received beams), the UE502may generate a first set of LLRs corresponding to the coded bits of the broadcast information associated with a first beam (e.g., as illustrated at624for beam512inFIG. 6) of the subset and a second set of LLRs corresponding to the coded bits of the broadcast information associated with a second beam (e.g., as illustrated at634for beam514inFIG. 6) of the subset. Thus, the first set of LLRs may include LLRs for the coded bits of the broadcast information associated with the beam512and the second set of LLRs may include LLRs for the coded bits of the broadcast information associated with the beam512.

At706, the apparatus may attempt to decode the broadcast information associated with each of the subset of the received beams. The decoding may be performed by the apparatus sequentially or concurrently. In various configurations, each of the broadcast information decodings may be performed based on the corresponding LLR values. For example, with reference toFIG. 6, the apparatus may decode (626) the broadcast information associated with the first beam based on the first set of LLRs (e.g., output from624) and the broadcast information associated with the second beam may be decoded (636) based on the second set of LLRs (e.g., output from634).

Next at708, in one configuration, the apparatus may determine whether the broadcast information associated with each received beam of the subset of the received beams failed decoding. For example, the apparatus may determine whether the decodings at706are successful, e.g., based on whether the CRC checks performed after the decodings are successful. If at708it is determined that broadcast information associated with each of the beams of the subset of received beams failed decoding, that is, the decoding of the PBCH for each of the beams in the subset of received beams failed (e.g., CRC fails for each decoding), the operation proceeds to710.

At710, the apparatus may generate a combined set of LLRs by combining the LLRs for the broadcast information associated with two adjacent receive beam directions. For example, with reference toFIG. 6, the subset of beams for which decoding is performed may include 2 beams, e.g.,512and514, that are directionally adjacent. If individual decoding for the broadcast information in each of the beams512and514fails, then in accordance with an aspect the UE502may generate a combined set of LLRs by combining the first set of LLRs (e.g., for the coded bits of the broadcast information associated with the beam512) and the second set of LLRs (e.g., for the coded bits of the broadcast information associated with the beam514). In the cases where the subset of received beams may have a number of additional beams, e.g., 4 beams, the UE502may determine a combined set of LLRs for each pair of adjacent beams as discussed in detail with respect toFIG. 6. As discussed earlier, the phrase adjacent beams refers to beams that are directionally adjacent, e.g., having adjacent receive beam directions.

At712, the apparatus may decode the broadcast information based on the combined set of LLRs. For example, with reference toFIG. 6, the UE502may decode (at637) the coded bits of the broadcast information based on the combined LLRs (e.g., output from the LLR combining stage635). For the purposes of discussion, it is assumed that the broadcast information remains the same in each of the beams of the subset and the broadcast information of either of the beams512or514may be decoded based on the combined set of LLRs. Because the decoding is performed based on the combined set of LLRs, the probability of successfully decoding the broadcast information at712may be higher as compared to the chances of successful decoding at706.

At714, the apparatus may perform beam refinement to determine a refined receive beam direction based on the determined LLRs and based on whether the broadcast information associated with each beam of the subset of the received beams fails to decode or successfully decodes. In the above case where broadcast information associated with each received beam of the subset of the received beams failed individual decoding, the beam refinement operation at714may include the operation illustrated with respect to box715where the refined receive beam direction is determined based on the two adjacent receive beam directions (e.g., beam directions corresponding to the two adjacent beams of the subset) when the broadcast information decoded based on the combined LLRs successfully decodes. Assuming that the broadcast information based on the combined LLRs is successfully decoded at712, the apparatus may select, as the refined receive beam direction, a direction resulting from the combination of the two adjacent beam directions. For example, with reference toFIG. 6, if the decoding (at626and636) of the individual beams512and514fails but the decoding (at637) based on the combined LLRs is successful, then the UE502may determine that the receive beam direction resulting from the combination of the individual receive beams directions corresponding to beams512and514may be taken as the refined receive beam direction. For example, as illustrated inFIG. 6, if the beam512is associated with the east receive direction and beam514is associated with the south receive direction, then in the above discussed case, at715the UE may determine that the south east direction is the refined receive beam direction. In an aspect, having determined the refined receive beam direction, at716the apparatus may use the determined receive beam direction for performing further measurements and/or in subsequent operations, e.g., related to the initial cell search procedure and/or related to the RACH procedure.

Returning to the operation at708, if at708it is determined that broadcast information associated with each of the received beams of the subset of received beams did not fail decoding (that is, the broadcast information decoding did not fail for all beams of the subset of beams, e.g., CRC succeeds for at least one or more of the beams), the operation proceeds to718. At718, the apparatus may determine whether broadcast information associated with each of at least two beams of the subset with adjacent receive beam directions is successfully decoded. In other words, the apparatus may determine if PBCH decoding succeeds for more than one beam, e.g., for two or more adjacent beams of the subset of the received beams. If at718it is determined that the broadcast information associated with each of at least two beams with adjacent receive beam directions is successfully decoded, the operation proceeds to720via connecting node A719.

For the purposes of discussion, consider that the broadcast information associated with two beams with adjacent receive beam directions (e.g., beams512and514) is successfully decoded. With the above consideration, in accordance with an aspect of one configuration, at720the apparatus may generate a combined set of LLRs by combining the LLRs for the broadcast information associated with the two beams with adjacent receive beam directions. For example, with reference toFIG. 6, if the individual decoding for the broadcast information in each of the beams512and514succeeds (e.g., determined by a successful CRC following each of the decoding626and636), the UE502may generate a combined set of LLRs by combining the first set of LLRs (e.g., for the coded bits of the broadcast information associated with the beam512) and the second set of LLRs (e.g., for the coded bits of the broadcast information associated with the beam514). In the cases where the subset may have a number of additional beams, e.g., 4 beams, in an aspect the UE502may determine a combined set of LLRs for each pair of adjacent beams for which PBCH decoding succeeded as discussed in detail with respect toFIG. 6.

At722, the apparatus may decode the broadcast information based on the combined set of LLRs. For example, with reference toFIG. 6, the UE502may decode (at637) the coded bits of the broadcast information based on the combined LLRs (e.g., output from the LLR combining stage635). The UE502may then determine whether the decoding based on the combined LLRs is successful. At724the apparatus may determine a post decoding reliability metric for each of the decoded broadcast information associated with each of the at least two adjacent receive beam directions (corresponding to the beams512and514in the example) and for the broadcast information decoded based on the combined LLRs. That is, the apparatus may determine a reliability metric corresponding to each of the PBCH decodings performed by the apparatus. For example, with reference toFIG. 6, considering decoding of the broadcast information associated with the adjacent beams512and514at626and636, and the decoding based on the combined LLRs at637, the UE502may determine a post decoding reliability metric for each of the decodings at626,636and637. Each post decoding reliability metric may provide an indication/measure of how accurate the corresponding decoding of the broadcast information is, e.g., with a post decoding reliability metric having the largest value being the most accurate/reliable.

At726, the apparatus may determine a refined receive beam direction based on the determined LLRs and based on whether the broadcast information associated with each of the subset of the received beams fails to decode or is successfully decoded. In the case being discussed where broadcast information associated with each of the at least two beams of the subset with adjacent receive beam directions is successfully decoded, the beam refinement operation at726may include determining the refined receive beam direction based on the determined reliability metrics. In some configurations, the beam refinement operation at726may include the performing one of the operations illustrated in boxes728or730. In one configuration, at728the apparatus may determine the refined receive beam direction to be one of the receive beam directions of the at least two adjacent receive beam directions when the reliability metric for the decoded broadcast information associated with the one of the receive beam directions is a largest of the determined reliability metrics. For example, with reference toFIG. 6, continuing with the example case with two adjacent beams512and514and where the individual decodings at626and636as well as the decoding based on the combined LLRs at637are successful, the UE508may consider three corresponding post reliability metrics. When the post decoding reliability metric for the decoded broadcast information associated with the receive beam direction corresponding to the beam512is the largest of the three determined reliability metrics, the UE508may select the receive beam direction corresponding to the beam512, e.g., east direction, as the refined beam direction. Similarly, when the post decoding reliability metric for the decoded broadcast information associated with the receive beam direction corresponding to the beam514is the largest of the three determined reliability metrics, the UE508may select the receive beam direction corresponding to the beam512, e.g., south direction, as the refined beam direction.

In one configuration, at730the refined receive beam direction may be determined to be a combination of the receive beam directions of the two adjacent receive beam directions when the reliability metric for the broadcast information decoded based on the combined set of LLRs is a largest of the determined reliability metrics. For example, with reference toFIG. 6, if the individual decodings at626and636, as well as the decoding based on the combined LLRs at637are successful, then the UE502may determine that the receive beam direction resulting from the combination of the receive beams directions corresponding to beams512and514may be taken as the refined receive beam direction. For example, when the post decoding reliability metric for the decoding (at637) based on the combined LLRs is the largest, the UE502may select the south east direction as the refined receive beam direction. Having determined the refined receive beam direction, at732the apparatus may use the determined receive beam direction for performing further measurements and/or in subsequent operations, e.g., related to the initial cell search procedure and/or related to the RACH procedure.

Returning to the operation at718, if at718it is determined that broadcast information associated with each of at least two beams of the subset with adjacent receive beam directions is not successfully decoded (e.g., PBCH decoding did not succeed for two or more adjacent beams), the operation proceeds to734. Having determined that that broadcast information decoding did not succeed for at least two adjacent beams of the subset of received beams, at734the apparatus may determine that the broadcast information associated with one received beam, e.g., a first beam, of the subset of received beams is successfully decoded.

Having determined at734that that broadcast information decoding for a first beam of the subset of received beams is successfully decoded, next at736the apparatus may determine that the broadcast information associated with a second beam of the subset of the received beams, that is directionally adjacent to the first beam, fails to decode. Operation proceeds from736to738via connecting node B737.

For the purposes of discussion, consider that the subset includes first and second beams (e.g., beams512and514) with adjacent receive beam directions, and the broadcast information associated with the first beam (e.g., beam512) is successfully decoded while the decoding fails for the broadcast information associated with the second beam (e.g., beam514). At738, the apparatus may generate a combined set of LLRs by combining the LLRs for the broadcast information associated with the first beam and the second beam. For example, with reference toFIG. 6, in the above discussed case, the UE502may generate (at635) a combined set of LLRs by combining the first set of LLRs (e.g., for the coded bits of the broadcast information associated with the beam512) and the second set of LLRs (e.g., for the coded bits of the broadcast information associated with the beam514) as illustrated inFIG. 6.

At740, the apparatus may decode the broadcast information based on the combined set of LLRs. For example, with reference toFIG. 6, the UE502may decode (at637) the coded bits of the broadcast information based on the combined LLRs (e.g., output from the LLR combining stage635). The UE502may then determine whether the decoding based on the combined LLRs is successful, e.g., by performing a CRC following the decoding based on the combined LLRs. At742the apparatus may determine a post decoding reliability metric corresponding to the successful decodings. For the purposes of discussion, further assuming that the PBCH decoding based on the combined LLRs is successful and because the PBCH decoding for the first beam is already determined to be successful, the apparatus may determine a post decoding reliability for decoded broadcast information associated with the first beam and for the broadcast information decoded based on the combined LLRs. For example, with reference toFIG. 6, considering decoding of the broadcast information associated with the first beam512at626and the decoding based on the combined LLRs at637, the UE502may determine a post decoding reliability metric for each of the decodings at626and637.

At744, the apparatus may determine a refined receive beam direction based on the determined LLRs and based on whether the broadcast information associated with each of the subset of the received beams fails to decode or is successfully decoded. In the example case being discussed where broadcast information associated with one beam (e.g., first beam512) of the subset is successfully decoded while the decoding fails for a directionally adjacent beam (e.g., second beam514) of the subset, and where the broadcast information decoding based on the combined LLRs is successful, the beam refinement operation at744may include determining the refined receive beam direction based on the reliability metrics determined at742. In some configurations, the beam refinement operation at744may include the performing one of the operations illustrated in boxes746or748, e.g., depending on the post decoding reliability metrics.

In one configuration, at746the apparatus may determine the refined receive beam direction to be a receive beam direction of the first beam (e.g., east) when the reliability metric for the decoded broadcast information associated with the first beam is a largest of the determined reliability metrics. For example, with reference toFIG. 6, when the post decoding reliability metric for the decoded broadcast information associated with the receive beam direction corresponding to the beam512is the largest of the determined reliability metrics, the UE508may select the receive beam direction corresponding to the beam512, e.g., east direction, as the refined beam direction. In one configuration, at748the refined receive beam direction may be determined to be a combination of the receive beam directions of the first beam and the second beam directions (e.g., receive directions of the first and second beams) when the reliability metric for the broadcast information decoded based on the combined set of LLRs is a largest of the determined reliability metrics. For example, with reference toFIG. 6, when the post decoding reliability metric for the decoding (at637) based on the combined set of LLRs is the largest, the UE502may select the south east direction (which is a combination of the receive beam directions of the beams512and514) as the refined receive beam direction. Having determined the refined receive beam direction, at750the apparatus may use the determined receive beam direction for performing further measurements and/or in subsequent operations, e.g., related to the initial cell search procedure and/or related to the RACH procedure.

While various aspects of an exemplary method are discussed with regard to flowchart700, other variations are possible. Additionally, some of the features discussed above may be desirable in some configurations but may not necessarily be needed.

FIG. 8is a conceptual data flow diagram800illustrating the data flow between different means/components in an exemplary apparatus802. The apparatus802may be used as any of the UEs, e.g., UE104/404/502. The apparatus802may include a reception component804, an LLR determination component806, an LLR combining component808, a decoding component (including one or more decoders)810, a determination component812, a refined beam direction determination component814, a control component816, and a transmission component818.

The reception component804may be configured to receive and process signals and/or information from other devices such as the base station850. The reception component804may be configured to receive a plurality of beams through a plurality of different receive beam directions, each of the beams including broadcast information on a PBCH. The received signals and/or information communicated via the plurality of beams may also include PSS, SSS and/or other signals as discussed in detail with respect to one or more preceding figures.

The LLR determination component806may be configured to determine, for each received beam of a subset of the received beams, LLRs for coded bits of the broadcast information. For each beam of the subset of received beams, the LLRs for the coded bits of the broadcast information may be determined on a per bit basis, e.g., using the coded bit stream of the broadcast information for which the LLRs are being generated. Thus the LLR for multiple coded bits of broadcast information associated with a given beam may include determined LLR values corresponding to the multiple coded bits. For example, the LLR determination component806may be configured to determine a first set of LLRs for the coded bits of the broadcast information (e.g., including LLRs for multiple coded bits) associated with a first received beam of the subset of received beams and second set of LLRs for coded bits of the broadcast information associated with a second received beam of the subset of received beams. In some configurations, the LLR determination component806may include multiple LLR determination components, e.g., for concurrently determining LLRs for coded broadcast information from multiple different received beams of the subset of received beams. The determined LLRs (e.g., first and second set of LLRs) may be provided as input to the decoding component810and the LLR combining component808in some configurations.

The LLR combining component808may be configured to generate a combined set of LLRs in accordance with various aspects of the disclosure, e.g., by combining the LLRs for the broadcast information associated with two directionally adjacent receive beams (e.g., two beams with adjacent receive beam directions such as beam510and512, or512and514inFIG. 5). For example, with reference toFIG. 6, a combined set of LLRs may be generated at635by combining the LLRs for the broadcast information associated with the two directionally adjacent receive beams512and514. In some configurations, the LLR combining component808may be further configured to provide the combined set of LLRs as an input to the decoding component810.

The decoding component810may include one or more decoders and may be configured to decode the broadcast information associated with each received beam of the subset of received beams as discussed in detail with respect toFIG. 6and the flowchart ofFIG. 7. In some configurations the decoding component810may be configured to decode the broadcast information associated with each received beam of the subset of received beams based on the corresponding LLRs provided by the LLR determination component806. For example, with reference toFIG. 6, assuming the subset of received beams being decoded includes at least a first and second beam512and514, the decoding component810may decode (e.g., at626) the broadcast information associated with beam512based on generated LLRs (e.g., first set of LLRs) for the broadcast information associated with the first beam512and may decode (e.g., at636) the broadcast information associated with beam514based on generated LLRs (e.g., second set of LLRs) for the broadcast information associated with the second beam514. In some configurations, the decoding component810may be configured to decode the broadcast information based on a combined set of LLRs provided by the LLR combining component808as discussed in detail with respect to respect toFIG. 6and the flowchart ofFIG. 7.

In some configurations, the decoding component810alone or in collaboration with the control component816may perform cyclic redundancy check of each decoding performed by the decoding component810to check whether the decoding succeeded or failed. In some configurations, the decoding component810may provide the result of decoding to the determination component812. The determination component812may be configured to determine whether the broadcast information associated with each received beam of the subset of received beams failed to decode or successfully decoded, e.g., based on decoding results for one or more decodings received from the decoding component810. Thus, based on the decoding results, in some configurations, the determination component812may determine that the broadcast information associated with each received beam of the subset of received beams failed to decode. In one configuration, the determination component812may determine that the broadcast information associated with each of at least two received beams with adjacent receive beam directions of the subset of received beams is successfully decoded. In one configuration, the determination component812may determine that the broadcast information associated with one beam (e.g., a first beam) of the subset of the received beams is successfully decoded while broadcast information associated with a second received beam of the subset of received beams, which is directionally adjacent the first beam, failed to decode.

In some configurations, the decoding component810may include a reliability metric component811configured to determine a reliability metric for each decoding or alternatively for each successful decoding performed by the decoding component810. For example, in one configuration the subset of received beams may include at least two adjacent beams for which the broadcast information successfully decodes and decoding of the broadcast information based on a combined set of LLRs (generated by combining the LLRs for the coded bits of the broadcast information associated with the at least two adjacent beams) also succeeds. In this case, the reliability metric component811may determine a post decoding reliability metric for each of the decoded broadcast information associated with each of the at least two adjacent receive beam directions and for the broadcast information decoded based on the combined set of LLRs. In another example, the broadcast information associated with a first beam of the subset of received beams may be successfully decoded while broadcast information associated with a second beam of the subset of received beams, which is directionally adjacent the first beam, may fail decoding. Furthermore, in the example, a decoding of the broadcast information based on a combined set of LLRs (generated by combining the LLRs for the broadcast information associated with the first beam and the second beam) may also be successful. In such an example case, the reliability metric component811may determine a post decoding reliability metric for decoded broadcast information associated with the first beam and for the broadcast information decoded based on a combined LLRs. As discussed supra in detail with respect toFIGS. 6-7, in some configurations, a refined receive beam direction may be determined based on the determined post decoding reliability metrics.

The refined beam direction determination component814may be configured to determine a refined receive beam direction based on the determined LLRs and based on whether the broadcast information associated with each received beam of the subset of received beams fails to decode or is successfully decoded. As discussed in detail with respect toFIGS. 6-7, depending on the given case and based on the result of PBCH decoding for each received beam of the subset of received beams, the refined beam direction determination component814may determine the refined receive beam direction in a variety of ways. For example, the refined beam direction determination component814may perform beam refinement to determine the refined beam direction in the manner discussed with respect to the operations at714and715, or in the manner discussed with respect to the operations at726,728and730, or in the manner discussed with respect to the operations at744,746and748. For example, in configuration, the refined beam direction determination component814may be configured to determine the refined receive beam direction based on the two adjacent receive beam directions when the broadcast information based on the combined set of LLRs is successfully decoded.

In one configuration, the refined beam direction determination component814may be configured to determine the refined receive beam direction based on determined reliability metrics (determined by the reliability metric component811). For example, in one configuration, where the broadcast information associated with each of at least two beams with adjacent receive beam directions of the subset of the received beams is successfully decoded, the refined beam direction determination component814may be configured to determine the refined receive beam direction to be one of the receive beam directions of the at least two adjacent receive beam directions when a reliability metric for the decoded broadcast information associated with the one of the receive beam directions is a largest of the determined reliability metrics. In one configuration, the refined beam direction determination component814may be configured to determine the refined receive beam direction to be a combination of the receive beam directions of the two adjacent receive beam directions when the reliability metric for the broadcast information decoded based on the combined set of LLRs is a largest of the determined reliability metrics.

In one configuration, the refined beam direction determination component814may be configured to determine the refined receive beam direction to be a receive beam direction of a first beam when the reliability metric for the decoded broadcast information associated with the first beam is a largest of the determined reliability metrics. In one configuration, the refined beam direction determination component814may be configured to determine the refined receive beam direction to be a combination of receive beam directions of the first beam and a second beam when the reliability metric for the broadcast information decoded based on the combined set of LLRs is a largest of the determined reliability metrics.

The control component816may be configured to provide transmission/reception timing information to the transmission and reception components818and804, respectively, to control transmission and reception of data and/or control information. The control component816may be further configured to control one or more other components of the apparatus802to implement various functions and/or perform operation in accordance with the method of flowchart700. In some configurations, the control component816may be further configured to control the apparatus802and/or one or more component therein to use the determined receive beam direction (determined by component814) for performing further measurements and/or in subsequent operations, e.g., related to the initial cell search procedure and/or related to the RACH procedure.

The transmission component818may be configured to transmit information, e.g., ACKs, NAKs, beacons, user data and/or control signals, to the base station850and/or other UEs.

FIG. 9is a diagram900illustrating an example of a hardware implementation for an apparatus802′ employing a processing system914. The processing system914may be implemented with a bus architecture, represented generally by the bus924. The bus924may include any number of interconnecting buses and bridges depending on the specific application of the processing system914and the overall design constraints. The bus924links together various circuits including one or more processors and/or hardware components, represented by the processor904, the components804,806,808,810,811,812,814,816,818, and the computer-readable medium/memory906. The bus924may 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 system914may be coupled to a transceiver910. The transceiver910may include individual transmitter and receiver circuits in some configurations. The transceiver910may be coupled to one or more antennas920. The transceiver910provides a means for communicating with various other apparatus over a transmission medium. The transceiver910receives a signal from the one or more antennas920, extracts information from the received signal, and provides the extracted information to the processing system914, specifically the reception component804. In addition, the transceiver910receives information from the processing system914, specifically the transmission component818, and based on the received information, generates a signal to be applied to the one or more antennas920. The processing system914includes a processor904coupled to a computer-readable medium/memory906. The processor904is responsible for general processing, including the execution of software stored on the computer-readable medium/memory906. The software, when executed by the processor904, causes the processing system914to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory906may also be used for storing data that is manipulated by the processor904when executing software. The processing system914further includes at least one of the components804,806,808,810,811,812,814,816, and818. The components may be software components running in the processor904, resident/stored in the computer-readable medium/memory906, one or more hardware components coupled to the processor904, or some combination thereof.

In one configuration, the apparatus802/802′ for wireless communication includes means for receiving a plurality of beams through a plurality of different receive beam directions, each of the beams including broadcast information on a PBCH. The apparatus802/802′ may further include means for determining, for each of a subset of the received beams, LLRs for coded bits of the broadcast information. The apparatus802/802′ may further include means for decoding the broadcast information associated with each of the subset of the received beams, and means for determining a refined receive beam direction based on the determined LLRs and based on whether the broadcast information associated with each of the subset of the received beams fails to decode or is successfully decoded. In some configurations, the apparatus802/802′ may further include means for determining that the broadcast information associated with each of the subset of the received beams failed to decode. In some configurations, the apparatus802/802′ may further include means for generating a combined set of LLRs by combining the LLRs for the broadcast information associated with two adjacent receive beam directions. In some such configurations, the means for decoding may be further configured to decode the broadcast information based on the combined set of LLRs. In some configurations, the means for determining the refined receive beam direction is configured to determine the refined receive beam direction based on the two adjacent receive beam directions when the broadcast information based on the combined set of LLRs is successfully decoded.

In some configurations, the apparatus802/802′ may include means for determining that the broadcast information associated with each of at least two beams with adjacent receive beam directions of the subset of the received beams is successfully decoded. In some configurations, the apparatus802/802′ may further include means for generating a combined set of LLRs by combining the LLRs for the broadcast information associated with the at least two adjacent receive beam directions. In some such configurations, the means for decoding is further configured to decode the broadcast information based on the combined set of LLRs. In some configurations, the apparatus802/802′ may further include means for determining a reliability metric for each of the decoded broadcast information associated with each of the at least two adjacent receive beam directions and for the broadcast information decoded based on the combined set of LLRs. In some such configurations, the means for determining the refined receive beam direction is configured to determine the refined receive beam direction based on the determined reliability metrics. In some configurations, the refined receive beam direction is determined to be one of the receive beam directions of the at least two adjacent receive beam directions when the reliability metric for the decoded broadcast information associated with the one of the receive beam directions is a largest of the determined reliability metrics. In some configurations, the refined receive beam direction is determined to be a combination of the receive beam directions of the two adjacent receive beam directions when the reliability metric for the broadcast information decoded based on the combined set of LLRs is a largest of the determined reliability metrics.

In some configurations, the apparatus802/802′ may further include means for determining that the broadcast information associated with a first beam of the subset of the received beams is successfully decoded. In some such configurations, the apparatus802/802′ may further include means for determining that the broadcast information associated with a second beam of the subset of the received beams fails to decode, the first and second beams being directionally adjacent. In some such configurations, the apparatus802/802′ may further include means for generating a combined set of LLRs by combining the LLRs for the broadcast information associated with the first beam and the second beam. In some such configurations, the means for decoding is further configured to decode the broadcast information based on the combined set of LLRs. In some configurations, the apparatus802/802′ may further include means for determining a reliability metric for decoded broadcast information associated with the first beam and for the broadcast information decoded based on the combined set of LLRs. In some such configurations, the means for determining the refined receive beam direction is configured to determine the refined receive beam direction based on the determined reliability metrics. In some such configurations, the refined receive beam direction is determined to be a receive beam direction of the first beam when the reliability metric for the decoded broadcast information associated with the first beam is a largest of the determined reliability metrics. In some configurations, the refined receive beam direction is determined to be a combination of the receive beam directions of the first beam and the second beam when the reliability metric for the broadcast information decoded based on the combined LLRs is a largest of the determined reliability metrics.

The aforementioned means may be one or more of the aforementioned components of the apparatus802and/or the processing system914of the apparatus802′ configured to perform the functions recited by the aforementioned means. In some embodiments the processing system914may include the TX Processor368, the RX Processor356, and the controller/processor359. As such, in one configuration, the aforementioned means may be the TX Processor368, the RX Processor356, and the controller/processor359configured to perform the functions recited by the aforementioned means.