Patent Description:
<CIT> relates to a base station and a terminal performing periodic and/or aperiodic beam training. The base station sends a reference signal through transmission beam sweeping, and the terminal performs full beam sweeping by examining all the transmission beams and reception beams to obtain optimal beam information for the beam pairs. The terminal sends the preferred beam information to the base station. The base station transmit data using the optimal beam information of the received preferred beam information. The terminal transmits the base station ACK/NACK corresponding to the data. The base station determines whether the link is broken or disconnected on the basis of NACK reception and the HARQ mode.

<CIT> observes that a receiving UE may not have accurate information about a channel from the receiving UE to the transmitting UE (unless channel reciprocity is ensured). For this reason, a Tx beam width for the ACK/NACK response may be different from the beam width used for the initial signal transmission. The receiving may transmit the ACK/NACK response on as omni-directional or broad a beam as possible. In an alternative, the receiving UE may repeatedly transmit the ACK/NACK response by beam cycling.

Advantageous embodiments are subject to the dependent claims.

In the following, each of the described methods, apparatuses, systems, examples and aspects, which does not fully correspond to the invention as defined in the appended claims, is thus not according to the invention and is, as well as the whole following description, present for illustration purposes only or to highlight specific aspects or features of the appended claims.

Each of the figures is provided for the purposes of illustration and description.

It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure.

Rather, these aspects are provided so that this disclosure will be thorough and complete, and the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. In addition, the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein.

Controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform one or more techniques associated with beam switching based at least in part on a NACK transmission, as described in more detail elsewhere herein. For example, controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform or direct operations of, for example, process <NUM> of <FIG>, process <NUM> of <FIG>, and/or other processes as described herein. Memories <NUM> and <NUM> may store data and program codes for base station <NUM> and UE <NUM>, respectively. In some aspects, memory <NUM> and/or memory <NUM> may include a non-transitory computer-readable medium storing one or more instructions (e.g., code and/or program code) for wireless communication. For example, the one or more instructions, when executed (e.g., directly, or after compiling, converting, and/or interpreting) by one or more processors of the base station <NUM> and/or the UE <NUM>, may cause the one or more processors, the UE <NUM>, and/or the base station <NUM> to perform or direct operations of, for example, process <NUM> of <FIG>, process <NUM> of <FIG>, and/or other processes as described herein. In some aspects, executing instructions may include running the instructions, converting the instructions, compiling the instructions, and/or interpreting the instructions, among other examples.

In some aspects, the UE includes means for transmitting a measurement report indicating a set of channel quality indicators for a set of candidate beams; means for determining that a downlink transmission from a base station is not received via one or more beams of the set of candidate beams; or means for transmitting a negative acknowledgement for the downlink transmission via one or more new beams of the set of candidate beams. The means for the UE to perform operations described herein may include, for example, one or more of antenna <NUM>, demodulator <NUM>, MIMO detector <NUM>, receive processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, modulator <NUM>, controller/processor <NUM>, or memory <NUM>.

In some aspects, the UE includes means for performing beam sweeping using the one or more new beams.

In some aspects, the UE includes means for performing the beam sweeping using the one or more new beams and the one or more beams.

In some aspects, the UE includes means for sequentially transmitting the negative acknowledgement for the downlink transmission via the one or more new beams and the one or more beams in an order that is based at least in part on the set of channel quality indicators.

In some aspects, the UE includes means for transmitting the negative acknowledgement for the downlink transmission via the one or more beams of the set of candidate beams; or means for receiving an indication of an interpretation, by the base station, of a hybrid automatic repeat request (HARQ) feedback occasion associated with the negative acknowledgement as an acknowledgement, wherein transmitting the negative acknowledgement for the downlink transmission via the one or more new beams is based at least in part on a mismatch between the interpretation by the base station and the negative acknowledgement.

In some aspects, the UE includes means for receiving radio resource control (RRC) reconfiguration, RRC connection setup, RRC reestablishment, RRC setup, or RRC resume signaling including an indication to monitor the set of candidate beams for one or more reference signals; means for configuring the UE to monitor the set of candidate beams for the one or more reference signals; or means for transmitting an indication that the UE is configured to monitor the set of candidate beams for the one or more reference signals.

In some aspects, the UE includes means for obtaining measurements of the one or more reference signals received over the set of candidate beams; or means for determining a ranking, based at least in part on the measurements of the one or more reference signals, of candidate beams of the set of candidate beams.

In some aspects, the UE includes means for selecting, for receiving the downlink transmission, the one or more beams based at least in part on the set of channel quality indicators.

In some aspects, the UE includes means for selecting a number of the one or more beams based at least in part on a configuration of the UE.

In some aspects, the UE includes means for selecting, for transmitting the negative acknowledgement for the downlink transmission, the one or more new beams based at least in part on the set of channel quality indicators.

In some aspects, the UE includes means for selecting a number of the one or more new beams based at least in part on a configuration of the UE.

In some aspects, the UE includes means for determining that a timing offset, between transmitting the measurement report and an occasion for transmitting the negative acknowledgement via the one or more new beams of the set of candidate beams, satisfies a timing threshold, wherein transmitting the negative acknowledgement via the one or more new beams of the set of candidate beams is based at least in part on determining that the timing offset satisfies the timing threshold.

In some aspects, the UE includes means for receiving a downlink control information message indicating that at least one of the one or more new beams is to be used for at least one additional downlink transmission.

In some aspects, the UE includes means for transmitting the negative acknowledgement for the downlink transmission via the one or more new beams without receiving, from a base station, an indication to transmit the negative acknowledgement for the downlink transmission via the one or more new beams after determining that the downlink transmission from the base station is not received via the one or more beams.

In some aspects, the base station includes means for receiving, from a UE, a measurement report indicating a set of channel quality indicators for a set of candidate beams; means for transmitting a downlink transmission to the UE via one or more beams of the set of candidate beams; or means for receiving, from the UE, a negative acknowledgement for the downlink transmission via one or more new beams of the set of candidate beams. The means for the base station to perform operations described herein may include, for example, one or more of transmit processor <NUM>, TX MIMO processor <NUM>, modulator <NUM>, antenna <NUM>, demodulator <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>, memory <NUM>, or scheduler <NUM>.

In some aspects, the base station includes means for monitoring the one or more new beams of the set of candidate beams for the negative acknowledgement for the downlink transmission.

In some aspects, the base station includes means for monitoring the one or more new beams of the set of candidate beams and the one or more beams for the negative acknowledgement for the downlink transmission.

In some aspects, the base station includes means for sequentially monitoring for the negative acknowledgement for the downlink transmission via the one or more new beams and the one or more beams in an order that is based at least in part on the set of channel quality indicators.

In some aspects, the base station includes means for selecting at least one of the one or more new beams of the set of candidate beams for at least one additional downlink transmission.

In some aspects, the base station includes means for selecting the at least one of the one or more new beams of the set of candidate beams for the at least one additional downlink transmission based at least in part on the set of channel quality indicators.

In some aspects, the base station includes means for transmitting a downlink control information message indicating that at least one of the one or more new beams is to be used for the at least one additional downlink transmission.

In some aspects, the base station includes means for determining that a timing offset, between receiving the measurement report and an occasion for receiving the negative acknowledgement via the one or more new beams of the set of candidate beams, satisfies a timing threshold, wherein transmitting the downlink control information message indicating that the at least one of the one or more new beams is to be used for the at least one additional downlink transmission is based at least in part on determining that the timing offset satisfies the timing threshold.

In some aspects, the base station includes means for selecting a number of the one or more new beams based at least in part on an indication provided to the UE.

In some aspects, the base station includes means for transmitting RRC reconfiguration signaling including an indication to monitor the set of candidate beams for one or more reference signals; or means for receiving an indication that the UE is configured to monitor the set of candidate beams for the one or more reference signals.

In some aspects, the base station includes means for selecting, for transmitting the downlink transmission, the one or more beams based at least in part on the set of channel quality indicators.

In some aspects, the base station includes means for selecting a number of the one or more beams based at least in part on an indication provided to the UE.

In some aspects, the base station includes means for receiving the negative acknowledgement for the downlink transmission via the one or more new beams without transmitting an indication to transmit the negative acknowledgement for the downlink transmission via the one or more new beams after transmitting the downlink transmission to the UE via the one or more beams of the set of candidate beams.

<FIG> is a diagram illustrating an example <NUM> of HARQ feedback, in accordance with the present disclosure. As shown in <FIG>, a base station and a UE may communicate downlink transmissions and HARQ feedback using one or more beams.

As shown in <FIG>, and in cycle <NUM>, the base station may transmit a downlink transmission, having a sequence number <NUM>, via a beam <NUM> and a beam <NUM>. The base station may transmit the downlink transmission using a physical downlink shared channel (PDSCH). The PDSCH may be scheduled using semi-persistent scheduling.

As further shown in cycle <NUM>, the UE may transmit an acknowledgement (ACK) to indicate that the UE received the downlink transmission having the sequence number <NUM>. The UE may transmit the ACK for sequence number <NUM> using a physical uplink control channel (PUCCH). The UE may transmit the ACK for sequence number <NUM> using one or more beams. When the PUCCH and the PDSCH have beam reciprocity, the UE may transmit the ACK for sequence number <NUM> using the beam <NUM> and/or the beam <NUM>. The base station may receive the ACK from the UE to indicate that the UE received the downlink transmission having the sequence number <NUM>.

As shown in cycle <NUM>, the base station may transmit a downlink transmission, having a sequence number <NUM>, via the beam <NUM> and the beam <NUM>. As further shown, the UE may not receive the downlink transmission having the sequence number <NUM> (e.g., based at least in part on blocking, interference, and/or the like).

The UE may monitor for an occasion associated with the downlink transmission having the sequence number <NUM> (e.g., based at least in part on scheduling from the base station). Based at least in part on the UE not receiving the downlink transmission having the sequence number <NUM>, the UE may transmit a NACK via the beam <NUM> and/or the beam <NUM>. As further shown, the base station may not receive the NACK (e.g., based at least in part on blocking, interference, and/or the like).

In some configurations, the base station may be configured to interpret an occasion for HARQ feedback, in which no HARQ feedback is received, as an ACK. In these configurations, the base station may interpret an occasion, associated with receiving the HARQ feedback associated with the NACK of cycle <NUM>, as an ACK instead of the intended NACK. This may be referenced as a NACK to ACK error or a mismatch of HARQ feedback.

As shown in cycle <NUM>, the base station may transmit a downlink transmission, having a sequence number <NUM>, via the beam <NUM> and the beam <NUM>, based at least in part on failing to receive the NACK of cycle <NUM> that was intended to indicate that the UE did not receive a previous transmission using the beam <NUM> and the beam <NUM>. As further shown, the UE may not receive the downlink transmission having the sequence number <NUM> (e.g., based at least in part on blocking, interference, and/or the like).

The UE may monitor for an occasion associated with the downlink transmission having the sequence number <NUM> (e.g., based at least in part on scheduling from the base station). Based at least in part on the UE not receiving the downlink transmission having the sequence number <NUM>, the UE may transmit a NACK via beam <NUM> and/or the beam <NUM>. As further shown, the base station may not receive the NACK (e.g., based at least in part on blocking, interference, and/or the like). Similar to cycle <NUM>, the base station may interpret the failure to receive the NACK as an ACK.

The base station may continue to transmit downlink transmissions using the beam <NUM> and the beam <NUM> because the base station is unaware that the UE is not receiving the downlink transmissions. Based at least in part on the UE transmitting the NACK using the beam <NUM> and/or the beam <NUM>, which may be blocked (e.g., by obstacles along paths associated with the beams), the UE may be unable to indicate to the base station that the downlink transmissions are not received by the UE. This may consume computing, communication, and network resources for unsuccessful attempts of communications between the base station and the UE.

As shown in <FIG>, and in cycle <NUM>, the base station may transmit a downlink transmission, having a sequence number <NUM>, via a beam <NUM> and a beam <NUM>. The base station may transmit the downlink transmission using a PDSCH. The PDSCH may be scheduled using semi-persistent scheduling.

As further shown in cycle <NUM>, the UE may transmit a NACK, via the beam <NUM> and/or the beam <NUM>, to indicate that the UE did not receive the downlink transmission having the sequence number <NUM>. As shown, the base station may not receive the NACK. The base station may retransmit the downlink transmission having the sequence number <NUM> using the beam <NUM> and/or the beam <NUM>. The base station may determine to retransmit the downlink transmission having the sequence number <NUM> based at least in part on interpreting an occasion, associated with receiving HARQ feedback for the transmission of the downlink transmission having the sequence number <NUM>, as a NACK. The base station may interpret the occasion as a NACK based at least in part on not receiving any HARQ feedback during the occasion and based at least in part on a configuration of the UE to transmit either an ACK or a NACK (e.g., the UE is not configured for discontinuous transmission of HARQ feedback). Additionally, or alternatively, the base station may determine to retransmit the downlink transmission having the sequence number <NUM> based at least in part on a scheduled retransmission that is independent from the NACK.

As further shown in cycle <NUM>, the UE does not have an occasion to transmit HARQ feedback associated with the retransmission of the downlink transmission associated with the sequence number <NUM>. The UE may not receive the downlink transmission based at least in part on interference, the beam <NUM> and/or the beam <NUM> being blocked, and/or the like. Alternatively, the UE may receive (e.g., receive and decode) the downlink transmission based at least in part on compiling the retransmission of beam <NUM> and/or the retransmission of beam <NUM>. In other words, even though the UE does not properly receive the downlink transmission via any single transmission, the UE may properly receive the downlink transmission using multiple transmissions.

As shown in cycle <NUM>, the base station may transmit a downlink transmission, having a sequence number <NUM>, via the beam <NUM> and the beam <NUM>. The UE may transmit a NACK, via the beam <NUM> and/or the beam <NUM>, to indicate that the UE did not receive the downlink transmission having the sequence number <NUM>. As in cycle <NUM>, the base station may not receive the NACK and may retransmit the downlink transmission having the sequence number <NUM> using the beam <NUM> and/or the beam <NUM>. As in cycle <NUM>, the UE does not have an occasion during cycle <NUM> to transmit HARQ feedback associated with the retransmission of the downlink transmission associated with the sequence number <NUM>.

Based at least in part on the UE not having an occasion to transmit the HARQ feedback during the cycles <NUM>, <NUM>, and <NUM>, the base station may be unaware of whether the UE received the downlink transmissions. Instead, the base station may make assumptions of reception or non-reception of the downlink transmissions, and an incorrect assumption may consume computing, communication, and/or network resources to detect and correct.

As described above, during some communications between a base station and a UE, the UE may be unable to provide HARQ feedback to the base station. For example, as in <FIG>, the UE may be unable to provide the HARQ feedback based at least in part on blocking of one or more beams used to transmit the HARQ feedback, which may also be used to receive a downlink transmission associated with the HARQ feedback. In some communication systems, the base station may be configured to interpret an occasion, during which no HARQ feedback is received, as an ACK, which may be incorrect if a NACK is transmitted by the UE and not received by the base station. In another example, as in <FIG>, the UE may not have an occasion to transmit the HARQ feedback based at least in part on a limited time budget of a cycle. Without receiving the HARQ feedback from the UE, the base station may make an assumption of whether the UE received the downlink transmission. If the assumption is incorrect (e.g., a mismatch occurs), the UE and/or the base station may consume computing, communication, and/or network resources to detect and/or correct the incorrect assumption.

In some aspects according to the invention, a base station (e.g., base station <NUM>) may transmit one or more reference signals via a set of candidate beams. A UE (e.g., UE <NUM>) may monitor for the one or more reference signals via the one or more candidate beams. The UE may obtain measurements of the one or more reference signals and generate a measurement report to identify a ranking of the set of candidate beams based at least in part on the measurements. The UE transmits the measurement report to the base station to identify a ranking of the set of candidate beams. The UE and the base station communicate via one or more beams of the set of candidate beams. The one or more beams may be selected based at least in part on the measurement report.

The UE is configured to, in response to not receiving a downlink transmission from the base station, transmit a NACK for the downlink transmission via one or more new beams of the set of candidate beams. In some aspects, the UE may select the one or more new beams for transmitting the NACK, and the base station may be configured to monitor the one or more new beams of the set of candidate beams for the NACK, based at least in part on the measurements of the one or more reference signals, the measurement report, and/or the ranking of the set of candidate beams. The UE and the base station continue communicating via the one or more new beams. In this way, the UE and the base station switch to at least one new beam for communications after a failed attempt to receive a downlink transmission via one or more current beams. In this way, the UE and the base station may conserve computing, communication, and/or network resources that may otherwise have been used to attempt to transmit and receive additional downlink transmissions using a beam through which the UE has failed to receive the downlink transmission.

<FIG> is a diagram illustrating an example <NUM> of beam switching based at least in part on a NACK transmission, in accordance with the claimed invention. As shown, a UE (e.g., UE <NUM>) and a base station (e.g., base station <NUM>) may communicate using one or more of RRC signaling, reference signals (RSs), measurement reports, downlink transmissions, HARQ feedback, downlink control information (DCI), and/or the like. In some aspects, the base station and the UE may be part of a wireless network (e.g., the wireless network <NUM>).

As shown in <FIG>, and by reference number <NUM>, the base station may transmit RRC signaling to the UE. The RRC signaling may include one or more indications of configurations for the UE. In some aspects, the RRC signaling may include one or more indications associated with scheduling downlink transmissions (e.g., semi-persistent scheduling). In some aspects, the RRC signaling may include an RRC reconfiguration message (RRCReconfiguration or RRCR), an RRC connection setup message, an RRC reestablishment message, an RRC setup message, or an RRC resume message with one or more information elements to configure a cell group (e.g., CellGroupConfig). The information element to configure the cell group may include a serving cell configuration (e.g., ServingCellConfiguration) with an information element to configure channel state information (CSI) measurements (e.g., CSI-MeasConfig). In some aspects, the RRC signaling may include an RRC setup (e.g., RRCSetup) message and/or an RRC resume (e.g., RRCResume) message to configure the UE to monitor CSI reference signals (CSI-RSs).

In some aspects, the RRC signaling may indicate that the UE is to monitor a set of candidate beams for one or more reference signals when performing reference signal (e.g., CSI-RS) measurements. In some aspects, the RRC signaling may indicate that the UE is to transmit a NACK, for a downlink transmission scheduled for one or more current beams, via one or more new beams of the set of candidate beams. In some aspects, the RRC signaling may indicate that the UE is to transmit a NACK, for a downlink transmission scheduled for one or more current beams, via one or more new beams of the set of candidate beams if a threshold number of downlink transmissions were not received via one or more current beams (e.g., a threshold number of consecutive downlink transmissions, a threshold portion of downlink transmission, a threshold number of downlink transmissions received over a period of time, and/or the like). In some aspects, the RRC signaling may indicate that the UE is to transmit a NACK, for a downlink transmission scheduled for one or more current beams, via one or more new beams of the set of candidate beams if an indication of an interpretation, by the base station, of HARQ feedback for a previous transmission is incorrect.

In some aspects, the RRC signaling may indicate a number of beams to monitor for downlink transmissions, a number of new beams to use to transmit the NACK, and/or the like. In some aspects, the RRC signaling may indicate a procedure for selecting one or more new beams to use to transmit the NACK. For example, the RRC signaling may indicate that the UE is to use a number of highest ranked beams from a most recent measurement report (e.g., including the one or more current beams or excluding the one or more current beams).

As shown by reference number <NUM>, the UE may configure the UE based at least in part on the RRC signaling. In some aspects, the UE may be configured to monitor one or more beams of a set of candidate beams for one or more downlink transmissions. For example, the UE may configure one or more components of the UE to monitor a bandwidth part using one or more antennas of the UE. In some aspects, the UE may be configured to transmit a NACK, for a downlink transmission scheduled for one or more current beams, via one or more new beams of the set of candidate beams. In some aspects, the UE may be configured to receive multiple downlink transmissions during multiple downlink transmission occasions scheduled via the RRC (e.g., based at least in part on semi-persistent scheduling).

As shown by reference number <NUM>, the UE may transmit an indication that configuration is complete. In some aspects, the UE may transmit the indication within an RRC reconfiguration complete (e.g., RRCReconfigurationComplete or RRCRC) message. Based at least in part on receiving the indication that configuration is complete, the base station may determine that the UE is configured to perform one or more processes for which the UE is configured (e.g., semi-persistent scheduling, monitoring the set of candidate beams for the one or more reference signals, transmitting a NACK via one or more new beams for a downlink transmission scheduled for one or more current beams, and/or the like).

As shown by reference number <NUM>, the base station may transmit one or more reference signals (e.g., CSI-RSs) via a set of candidate beams. In some aspects, the base station may transmit the one or more reference signals using beam sweeping.

As shown by reference number <NUM>, the UE may obtain a set of measurements of the one or more reference signals received over the set of candidate beams. In some aspects, the UE may identify a beam identification associated with a received reference signal based at least in part on a timing at which the UE receives the reference signal and an indication of times at which the base station is scheduled to transmit the one or more reference signals via the set of candidate beams.

As shown by reference number <NUM>, the UE transmits a measurement report to the base station. The measurement report may include the obtained set of measurements of the reference signals, such as RSRP, RSSI, RSRQ, and/or CQI, a ranking of the set of candidate beams (e.g., based at least in part on the obtained measurements), and/or the like.

As shown by reference number <NUM>, the UE may determine a ranking of the set of candidate beams based at least in part on the measurements of the reference signals. In some aspects, the ranking may be based at least in part on an order of highest to lowest signal quality (e.g., as indicated using RSRP, RSSI, RSRQ, CQI, and/or the like).

As shown by reference number <NUM>, the UE may determine the ranking of the candidate beams. In some aspects, the base station may determine the ranking of the candidate beams based at least in part on a ranking indicated within the measurement report, based at least in part on the measurements of the reference signals indicated in the measurement report, and/or the like. In some aspects, the base station and the UE may be configured to determine the ranking of the set of candidate beams based at least in part on a same procedure and/or metric so that the base station and the UE agree on the ranking.

In some aspects, the UE and the base station may be configured to automatically activate a number of the highest ranked candidate beams for communication between the UE and the base station. In some aspects, the number of highest ranked candidate beams may be based at least in part on the RRC signaling, a DCI message, and/or the like.

As shown by reference number <NUM>, the base station transmits a downlink transmission to the UE. In some aspects, the base station may transmit the downlink transmission using a subset of the activated highest ranked candidate beams. In some aspects, the base station may select one or more beams for transmitting the downlink transmission based at least in part on an indication provided to the UE. For example, the base station may select the one or more beams based at least in part on RRC signaling to the UE to indicate that the base station is configured to transmit downlink transmissions via one or more beams having a highest ranked CQI. In some aspects, the base station may select a number of the one or more beams based at least in part on an indication provided to the UE. For example, the base station may select two as the number of the one or more beams, based at least in part on RRC signaling indicating to the UE that the base station is configured to transmit downlink transmissions via two beams. In some aspects, the base station may transmit DCI (e.g., a transmission configuration indicator (TCI) state activating DCI) to indicate one or more beams of the activated highest ranked candidate beams through which the base station is configured to transmit the downlink transmission.

In some aspects, the base station may transmit the downlink transmission during a downlink transmission occasion that was previously scheduled (e.g., using RRC signaling). In some aspects, the UE may not receive the downlink transmission during the downlink transmission occasion.

As shown by reference number <NUM>, the UE transmits a NACK, via one or more new beams of the set of candidate beams, as HARQ feedback for the downlink transmission scheduled for the one or more beams of the set of candidate beams. In some aspects, the UE may transmit and the base station may receive the NACK via the one or more beams of the set of candidate beams (e.g., one or more current beams).

In some aspects, the UE may transmit the NACK via the one or more new beams of the set of candidate beams based at least in part on determining that a threshold number of downlink transmissions were not received via one or more current beams (e.g., a threshold number of consecutive downlink transmissions, a threshold portion of downlink transmission, a threshold number of downlink transmissions received over a period of time, and/or the like).

In some aspects, the UE may receive an indication of an interpretation, by the base station, of a HARQ feedback occasion associated with a previous NACK, as an ACK. The UE may transmit the NACK for the downlink transmission via the one or more new beams based at least in part on a mismatch between the interpretation by the base station and the previous NACK.

In some aspects, transmitting the NACK may include performing beam sweeping using the one or more new beams. In some aspects, the beam sweeping may include transmitting the NACK via the one or more new beams, the one or more current beams, or a combination of the one or more new beams and the one or more current beams. In some aspects, beam sweeping may be performed in an order that is based at least in part on the ranking of the set of beams, the set of measurements of the one or more reference signals received using the set of candidate beams, and/or the like.

In some aspects, the UE may select a number of the one or more new beams, to transmit the NACK, based at least in part on an indication from the base station (e.g., an indication within RRC signaling, DCI, and/or the like). In some aspects, the UE may select, for transmitting the NACK, the one or new beams based at least in part on the measurements of the set of reference signals, the measurement report, the ranking of the set of beams, and/or the like. In some aspects, the UE may transmit the NACK via the number of new beams without beam sweeping.

In some aspects, the UE may determine a timing offset between transmitting the measurement report and an occasion for the NACK feedback. In some aspects, the base station may determine to transmit the NACK via the one or more new beams based at least in part on the timing offset satisfying a threshold. In other words, the UE may transmit the NACK using an agreed beam sweeping pattern if a most recent measurement report was received at a time instant whose difference with a time instant for transmitting the NACK satisfies a threshold (e.g., is less than the threshold, is less than or equal to the threshold, and/or the like). This may avoid beam switching to the one or more new beams based at least in part on outdated, or invalid, information. This may conserve computing, communication, and/or network resources that may otherwise be consumed by beam switching to, and using for subsequent downlink transmissions, one or more new beams that are likely to fail for the subsequent downlink transmissions, but were ranked highly at the time of an outdated measurement report.

As shown by reference number <NUM>, the base station may monitor the one or more new beams for the NACK. In some aspects the base station may be configured to monitor the one or more current beams during every HARQ feedback occasion, during every HARQ feedback occasion after a threshold number of NACKs, during periodic HARQ feedback occasions (e.g., based at least in part on time intervals, after a particular number of HARQ feedback occasions), and/or the like. In some aspects, based at least in part on receiving the NACK associated with the downlink transmission, the base station may determine that the base station is to retransmit the downlink transmission via the one or more new beams.

As shown by reference number <NUM>, the base station may select at least one of the one or more new beams for at least one additional downlink transmission. In some aspects, the base station may select the at least one of the one or more new beams based at least in part on the measurement report, a set of measurements of the reference signals, such as RSRP, RSSI, RSRQ, and/or CQI, a ranking of the set of candidate beams (e.g., based at least in part on the obtained measurements), and/or the like.

As shown by reference number <NUM>, the base station transmits DCI to activate one or more new TCI states. The one or more new TCI states may be associated with the at least one of the one or more new beams. In some aspects, the base station may transmit the DCI within a DCI message to activate the at least one of one or more new beams for monitoring for a retransmission of the downlink transmission.

As shown by reference number <NUM>, the base station transmits an additional downlink transmission via the at least one of the one or more new beams. In some aspects, the base station may retransmit the downlink transmission via the at least one of the one or more new beams of the set of candidate beams. In some aspects, the base station may retransmit the downlink transmission via the at least one of the one or more new beams without transmitting an indication to activate the one or more new beams after the occasion for the NACK feedback. In some aspects, the base station may continue to transmit additional downlink transmissions using the at least one of the one or more new beams.

Based at least in part on beam switching to at least one new beam for communications after a failed attempt to receive a downlink transmission via one or more current beams, the UE and the base station may conserve computing, communication, and/or network resources that may otherwise have been used to attempt to transmit and receive additional downlink transmissions using the one or more current beams through which the UE has failed to receive the downlink transmission.

<FIG> is a diagram illustrating an example <NUM> of beam switching based at least in part on a NACK transmission, in accordance with theinvention. As shown, a UE (e.g., UE <NUM>) and a base station (e.g., base station <NUM>, such as a gNB) may communicate using one or more of RRC signaling, reference signals, measurement reports, downlink transmissions, HARQ feedback, DCI, and/or the like. In some aspects, the base station and the UE may be part of a wireless network (e.g., the wireless network <NUM>).

As shown in <FIG>, and in cycle <NUM>, the base station may transmit a downlink transmission, having a sequence number <NUM>, via a beam <NUM> and a beam <NUM>. The base station may transmit the downlink transmission using a PDSCH. The PDSCH may be scheduled using semi-persistent scheduling. The UE may receive the downlink transmission having the sequence number <NUM> and may determine to transmit an ACK or to not transmit HARQ feedback (e.g., based at least in part on the UE being configured for discontinuous transmission (DTX) of HARQ feedback). The base station may interpret the ACK, or not receiving any HARQ feedback in the case of discontinuous transmission, as an indication that the UE received the downlink transmission having the sequence number <NUM> from at least one of the beam <NUM> or the beam <NUM>, or from both of the beam <NUM> and the beam <NUM> (e.g., if the UE is configured to use a soft NACK). In some aspects, the downlink transmission having the sequence number <NUM> may expire at the end of cycle <NUM>.

As also shown in cycle <NUM>, the base station may transmit RRC signaling, such as an RRCR message, an RRC setup message, an RRC resume message, and/or the like. The RRC signaling may indicate that the UE is to be configured to monitor a set of candidate beams for one or more reference signals, to transmit a NACK via one or more new beams of the set of candidate beams, and/or the like. The UE may transmit an indication (e.g., an RRCRC message) that the UE has been configured based at least in part on the RRC signaling.

As further shown in cycle <NUM>, the base station may transmit one or more reference signals (e.g., CSI-RSs) via a set of candidate beams. The UE may monitor the set of candidate beams and obtain measurements of the reference signals. In some aspects, the UE may determine a ranking of the set of candidate beams based at least in part on the measurements. In some aspects, the UE may automatically activate a number of the highest ranked candidate beams for communication with the base station.

The UE transmits a measurement report (MR) to the base station. In some aspects, the base station may determine the ranking of the set of candidate beams based at least in part on the measurements, an indication of the ranking of the set of candidate beams within the measurement report, and/or the like. In this way, the base station and the UE may agree on a ranking of the set of candidate beams. In some aspects, the base station may automatically activate the number of highest ranked candidate beams for communication with the UE.

As shown in cycle <NUM>, the base station transmits a downlink transmission, having a sequence number <NUM>, via the beam <NUM> and the beam <NUM>. The downlink transmission may include DCI to indicate TCI state activation (e.g., if the UE is not configured to automatically activate the number of highest ranked candidate beams for communication with the base station). In some aspects, the downlink transmission may include an indication of an interpretation of HARQ feedback from a previous downlink transmission (e.g., the ACK of the downlink transmission having the sequence number <NUM> (zero)). The beam <NUM> and the beam <NUM> may be blocked and the UE may not receive the downlink transmission having the sequence number <NUM> during a scheduled occasion for receiving the downlink transmission.

The UE may transmit a NACK (e.g., using a PUCCH), using one or more new beams (e.g., beam <NUM> and/or beam <NUM>), to indicate that the UE did not receive the downlink transmission having the sequence number <NUM>. In some aspects, the UE does not receive the downlink transmission having the sequence number <NUM> based at least in part on interference (e.g., from one or more other cells), blocking, and/or the like. In some aspects, the base station may receive the NACK from the UE via the beam <NUM> and/or the beam <NUM>.

As also shown in cycle <NUM>, the base station retransmits the downlink transmission having the sequence number <NUM> via at least one of the one or more new beams (e.g., the beam <NUM> and the beam <NUM>) based at least in part on receiving the NACK via the at least one of the one or more new beams. In some aspects, the downlink transmission may include DCI to indicate a new TCI state activation (e.g., if the UE is not configured to automatically activate the one or more new beams through which the UE transmitted the NACK).

The UE may receive the retransmission of the downlink transmission having the sequence number <NUM> and may determine to transmit an ACK or to not transmit HARQ feedback. The base station may interpret the ACK, or not receiving any HARQ feedback if the UE is configured for discontinuous transmission of HARQ feedback, as an indication that the UE received the downlink transmission having the sequence number <NUM> from at least one of the beam <NUM> or the beam <NUM>, or from both of the beam <NUM> and the beam <NUM> (e.g., if the UE is configured to use a soft NACK).

The base station and the UE may communicate at least one additional message using the one or more new beams. For example, the base station may transmit a downlink transmission, having a sequence number <NUM>, via the beam <NUM> and the beam <NUM>. The UE may monitor the beam <NUM> and the beam <NUM> for the downlink transmission having the sequence number <NUM> and transmit HARQ feedback for the downlink transmission having the sequence number <NUM>.

<FIG> is a diagram illustrating an example <NUM> of beam switching based at least in part on a NACK transmission, in accordance with the invention. As shown, a UE (e.g., UE <NUM>) and a base station (e.g., base station <NUM>, such as a gNB) may communicate using one or more of RRC signaling, reference signals, measurement reports, downlink transmissions, HARQ feedback, DCI, and/or the like. In some aspects, the base station and the UE may be part of a wireless network (e.g., the wireless network <NUM>).

As shown in <FIG>, and in cycle <NUM>, the base station may transmit a downlink transmission, having a sequence number <NUM>, via a beam <NUM> and a beam <NUM>. The base station may transmit the downlink transmission using a PDSCH. The PDSCH may be scheduled using semi-persistent scheduling. The UE may receive the downlink transmission having the sequence number <NUM> and may determine to transmit an ACK or to not transmit HARQ feedback. The base station may interpret the ACK, or not receiving any HARQ feedback in the case of discontinuous transmission, as an indication that the UE received the downlink transmission having the sequence number <NUM> from at least one of the beam <NUM> or the beam <NUM>, or from both of the beam <NUM> and the beam <NUM> (e.g., if the UE is configured to use a soft NACK). In some aspects, the downlink transmission having the sequence number <NUM> may expire at the end of cycle <NUM>.

The UE transmits a measurement report to the base station. In some aspects, the base station may determine the ranking of the set of candidate beams based at least in part on the measurements, an indication of the ranking of the set of candidate beams within the measurement report, and/or the like. In this way, the base station and the UE may have a synchronized ranking of the set of candidate beams. In some aspects, the base station may automatically activate the number of highest ranked candidate beams for communication with the UE.

As also shown in cycle <NUM>, the UE may perform beam sweeping using one or more new beams (e.g., a beam <NUM> and a beam <NUM>) and/or the beam <NUM> and the beam <NUM>. The UE transmits the NACK for the downlink transmission having the sequence number <NUM> via the one or more new beams in an order (e.g., chronologically) based at least in part on the measurements of one or more reference signals received using the set of candidate beams, the ranking of the set of candidate beams, the measurement report, and/or the like. In some aspects, the UE may be configured to transmit the NACK via multiple beams simultaneously and the base station may simultaneously monitor multiple candidate beams for the NACK.

In some aspects, the base station retransmits the downlink transmission having the sequence number <NUM> using at least one of the one or more new beams. In some aspects, the base station transmits DCI to indicate TCI state activation (e.g., if the UE is not configured to automatically activate the number of highest ranked candidate beams for communication with the base station). In some aspects, the UE may transmit an ACK using the one or more new beams or may determine to not transmit HARQ feedback (e.g., based at least in part on the UE being configured for DTX of HARQ feedback).

The base station may interpret the ACK, or not receiving any HARQ feedback, as an indication that the UE received the downlink transmission having the sequence number <NUM> from at least one of the beam <NUM>, the beam <NUM>, or from both of the beam <NUM> and the beam <NUM> (e.g., if the UE is configured to use a soft NACK).

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a UE, in accordance with the invention. Process <NUM> is an example where the UE (e.g., UE <NUM> and/or the like) performs operations associated with beam switching based at least in part on a NACK transmission.

As shown in <FIG>, process <NUM> includes transmitting a measurement report indicating a set of CQI for a set of candidate beams (block <NUM>). For example, the UE (e.g., using controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, antenna <NUM>, and/or the like) may transmit a measurement report indicating a set of CQIs for a set of candidate beams, as described above.

As further shown in <FIG>, process <NUM> includes determining that a downlink transmission from a base station is not received via one or more beams of the set of candidate beams (block <NUM>). For example, the UE (e.g., using antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>, and/or the like) may determine that a downlink transmission from a base station is not received via one or more beams of the set of candidate beams, as described above.

As further shown in <FIG>, process <NUM> includes transmitting a NACK for the downlink transmission via one or more new beams of the set of candidate beams (block <NUM>). For example, the UE (e.g., using controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, antenna <NUM>, and/or the like) may transmit a NACK for the downlink transmission via one or more new beams of the set of candidate beams, as described above.

Further, process <NUM> includes receiving a DCI message indicating that at least one of the one or more new beams is to be used for at least one additional downlink transmission. The at least one additional downlink transmission includes a retransmission of the downlink transmission.

In an aspect, transmitting the NACK for the downlink transmission via the one or more new beams of the set of candidate beams includes performing beam sweeping using the one or more new beams.

In another aspect, alone or in combination with the preceding aspect, performing the beam sweeping includes performing the beam sweeping using the one or more new beams and the one or more beams.

In a further aspect, alone or in combination with one or more of the preceding aspects, performing the beam sweeping includes sequentially transmitting the NACK for the downlink transmission via the one or more new beams and the one or more beams in an order that is based at least in part on the set of CQIs.

In yet another aspect, alone or in combination with one or more of the preceding aspects, process <NUM> includes transmitting the NACK for the downlink transmission via the one or more beams of the set of candidate beams, and receiving an indication of an interpretation, by the base station, of a HARQ feedback occasion associated with the NACK as an acknowledgement, and transmitting the NACK for the downlink transmission via the one or more new beams is based at least in part on a mismatch between the interpretation by the base station and the NACK.

In an even further aspect, alone or in combination with one or more of the preceding aspects, process <NUM> includes receiving RRC reconfiguration, RRC connection setup, RRC reestablishment, RRC setup, or RRC resume signaling including an indication to monitor the set of candidate beams for one or more reference signals, configuring the UE to monitor the set of candidate beams for the one or more reference signals, and transmitting an indication that the UE is configured to monitor the set of candidate beams for the one or more reference signals.

In another aspect, alone or in combination with one or more of the preceding aspects, process <NUM> includes obtaining measurements of the one or more reference signals received over the set of candidate beams, and determining a ranking, based at least in part on the measurements of the one or more reference signals, of candidate beams of the set of candidate beams.

In a further aspect, alone or in combination with one or more of the preceding aspects, process <NUM> includes selecting, for receiving the downlink transmission, the one or more beams based at least in part on the set of CQIs.

In yet another aspect, alone or in combination with one or more of the preceding aspects, process <NUM> includes selecting a number of the one or more beams based at least in part on a configuration of the UE.

In an even further aspect, alone or in combination with one or more of the preceding aspects, process <NUM> includes selecting, for transmitting the NACK for the downlink transmission, the one or more new beams based at least in part on the set of CQIs.

In another tenth aspect, alone or in combination with one or more of the preceding aspects, process <NUM> includes selecting a number of the one or more new beams based at least in part on a configuration of the UE.

In a further aspect, alone or in combination with one or more of the preceding aspects, process <NUM> includes determining that a timing offset, between transmitting the measurement report and an occasion for transmitting the NACK via the one or more new beams of the set of candidate beams, satisfies a timing threshold, and transmitting the NACK via the one or more new beams of the set of candidate beams is based at least in part on determining that the timing offset satisfies the timing threshold.

In yet another aspect, alone or in combination with one or more of the preceding aspects, transmitting the NACK for the downlink transmission via the one or more new beams of the set of candidate beams includes transmitting the NACK for the downlink transmission via the one or more new beams without receiving, from a base station, an indication to transmit the NACK for the downlink transmission via the one or more new beams after determining that the downlink transmission from the base station is not received via the one or more beams.

<FIG> is a diagram illustrating an example process <NUM> performed, for example, by a base station, useful for understanding the invention. Example process <NUM> is an example where the base station (e.g., base station <NUM> and/or the like) performs operations associated with beam switching based at least in part on a NACK transmission.

As shown in <FIG>, in some aspects, process <NUM> may include receiving, from a UE, a measurement report indicating a set of CQIs for a set of candidate beams (block <NUM>). For example, the base station (e.g., using antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>, and/or the like) may receive, from a UE, a measurement report indicating a set of CQIs for a set of candidate beams, as described above.

As further shown in <FIG>, in some aspects, process <NUM> may include transmitting a downlink transmission to the UE via one or more beams of the set of candidate beams (block <NUM>). For example, the base station (e.g., using controller/processor <NUM>, transmit processor <NUM>, TX MIMO processor <NUM>, MOD <NUM>, antenna <NUM>, and/or the like) may transmit a downlink transmission to the UE via one or more beams of the set of candidate beams, as described above.

As further shown in <FIG>, in some aspects, process <NUM> may include receiving, from the UE, a NACK for the downlink transmission via one or more new beams of the set of candidate beams (block <NUM>). For example, the base station (e.g., using antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>, and/or the like) may receive, from the UE, a NACK for the downlink transmission via one or more new beams of the set of candidate beams, as described above.

In a first aspect, receiving the NACK for the downlink transmission via the one or more new beams of the set of candidate beams includes monitoring the one or more new beams of the set of candidate beams for the NACK for the downlink transmission.

In a second aspect, alone or in combination with the first aspect, receiving the NACK for the downlink transmission via the one or more new beams of the set of candidate beams includes monitoring the one or more new beams of the set of candidate beams and the one or more beams for the NACK for the downlink transmission.

In a third aspect, alone or in combination with one or more of the first and second aspects, monitoring the one or more new beams and the one or more beams includes sequentially monitoring for the NACK for the downlink transmission via the one or more new beams and the one or more beams in an order that is based at least in part on the set of CQIs.

In a fourth aspect, alone or in combination with one or more of the first through third aspects, process <NUM> includes selecting at least one of the one or more new beams of the set of candidate beams for at least one additional downlink transmission.

In a fifth aspect, alone or in combination with one or more of the first through fourth aspects, selecting the at least one of the one or more new beams of the set of candidate beams for the at least one additional downlink transmission includes selecting the at least one of the one or more new beams of the set of candidate beams for the at least one additional downlink transmission based at least in part on the set of CQIs.

In a sixth aspect, alone or in combination with one or more of the first through fifth aspects, process <NUM> includes transmitting a DCI message indicating that at least one of the one or more new beams is to be used for the at least one additional downlink transmission.

In a seventh aspect, alone or in combination with one or more of the first through sixth aspects, process <NUM> includes determining that a timing offset, between receiving the measurement report and an occasion for receiving the NACK via the one or more new beams of the set of candidate beams, satisfies a timing threshold, and transmitting the DCI message indicating that the at least one of the one or more new beams is to be used for the at least one additional downlink transmission is based at least in part on determining that the timing offset satisfies the timing threshold.

In an eighth aspect, alone or in combination with one or more of the first through seventh aspects, the at least one additional downlink transmission includes a retransmission of the downlink transmission.

In a ninth aspect, alone or in combination with one or more of the first through eighth aspects, process <NUM> includes selecting a number of the one or more new beams based at least in part on an indication provided to the UE.

In a tenth aspect, alone or in combination with one or more of the first through ninth aspects, process <NUM> includes transmitting RRC reconfiguration signaling including an indication to monitor the set of candidate beams for one or more reference signals, and receiving an indication that the UE is configured to monitor the set of candidate beams for the one or more reference signals.

In an eleventh aspect, alone or in combination with one or more of the first through tenth aspects, process <NUM> includes selecting, for transmitting the downlink transmission, the one or more beams based at least in part on the set of CQIs.

In a twelfth aspect, alone or in combination with one or more of the first through eleventh aspects, process <NUM> includes selecting a number of the one or more beams based at least in part on an indication provided to the UE.

In a thirteenth aspect, alone or in combination with one or more of the first through twelfth aspects, receiving the NACK for the downlink transmission via the one or more new beams of the set of candidate beams includes receiving the NACK for the downlink transmission via the one or more new beams without transmitting an indication to transmit the NACK for the downlink transmission via the one or more new beams after transmitting the downlink transmission to the UE via the one or more beams of the set of candidate beams.

Claim 1:
A user equipment, UE, (<NUM>) for wireless communication, comprising:
a memory (<NUM>); and
one or more processors (<NUM>), operatively coupled to the memory, configured to:
transmit a measurement report indicating a set of channel quality indicators for a set of candidate beams;
determine that an attempt to receive a downlink transmission from a base station via one or more beams of the set of candidate beams fails;
transmit a negative acknowledgement for the downlink transmission via one or more new beams of the set of candidate beams, wherein the one or more new beams are different from the one or more beams; and
receive a downlink control information message indicating that at least one of the one or more new beams is to be used for at least one additional downlink transmission,
wherein the at least one additional downlink transmission includes a retransmission of the downlink transmission.