Patent Description:
<NUM>/NR is part of a continuous mobile broadband evolution promulgated by Third Generation Partnership Project (3GPP) to meet new requirements associated with latency, reliability, security, scalability (e.g., with Internet of Things (IoT)), and other requirements. Some aspects of <NUM>/NR may be based on the <NUM> Long Term Evolution (LTE) standard. There exists a need for further improvements in <NUM>/NR technology.

Radio Link Monitoring (RLM) may be an important procedure to track radio link conditions. The RLM procedure may indicate whether the air link is in-sync or out-of-sync. For monitoring active link performances, a User Equipment (UE) needs to perform measurements of a set of reference signals for RLM and beam recovery. The measurements may include deriving a metric similar to Signal to Interference plus Noise Ratio (SINR) for a reference signal. There are a number of challenges associated with radio link monitoring in multi-beam wireless communication systems, e.g., mmW communication, sub-<NUM> wireless communication, or other multi-beam operation.

<CIT> discloses handling Channel State Information, CSI, measurements when operating in a wireless network in a dynamic Time Division Duplex, TDD, scenario where a network node serving the wireless device can switch between different up-link-downlink configurations comprising flexible subframes which can be uplink or downlink. When the wireless device determines that a link direction of at least one of the flexible subframes is ambiguous, the wireless device indicates to the serving network node that the wireless device has not made a valid CSI measurement due to the ambiguous link direction. Then, the network node re-uses a CSI measurement from a CSI report previously received from the wireless device, e.g. for link adaptation.

Preferred embodiments of the invention are stipulated in the dependent claims. While several embodiments and/or examples have been disclosed in the description, the subject matter for which protection is sought is limited to those examples and/or embodiments which are encompassed by the scope of the appended claims. Embodiments and/or examples that do not fall under the scope of the claims are useful for understanding the invention.

There are a number of challenges associated with radio link monitoring in multi-beam wireless communication systems. In order to perform RLM, the UE needs to measure the quality of a reference signal. However, there might not be a direct reference signal that is always transmitted, e.g., such as CRS, which can be monitored in relation to New Radio-Physical Downlink Control Channel (NR-PDCCH). Additionally, the transmission of downlink (DL) and/or uplink (UL) communication with the UE may be sporadic. Therefore, the UE may not have a persistent observation of DL control channel performance. A UE might not know whether a base station is transmitting a DL control channel transmission, e.g., Physical Downlink Control Channel (PDCCH) or NR-PDCCH, and therefore, faces difficulties in deriving PDCCH reliability.

While a base station could transmit PDCCH or Demodulation Reference Signal (DMRS) for PDCCH periodically to improve monitoring PDCCH reliability for RLM, this increased PDCCH requirement would cause unnecessary overhead and increased use of wireless resources. For example, in multi-beam operation, a reference signal transmitted by a base station in a particular beam can only be received by a small subset of users. Therefore, the base station would be required to transmit a periodic PDCCH, or other reference signals, for each of multiple beam directions.

The present application provides a solution that enables a UE in multi-beam operation to perform RLM while reducing the burden of reference signal transmission at the base station by enabling conditional reference signal transmission and/or conditional RLM and beam recovery.

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided for multi-beam operation at a base station. The apparatus determines whether a transmission is received at a UE within a time window and determines whether to transmit a reference signal, based on whether the transmission is received at the UE within the time window. The base station may determine that the transmission is received at the UE upon receiving at least one of a control channel, a data channel, a sounding reference signal, and an acknowledgement from the UE having a signal quality that meets a threshold within the time window. Upon determining that the transmission was received at the UE, the apparatus may skip transmission of the reference signal or modify at least one of a time, a frequency, a power, or a reference signal offset for the reference signal.

In another aspect of the disclosure, a method according to claim <NUM>, a user equipment according to claim <NUM> and a computer-program, according to claim <NUM>, comprising instructions for performing a method according to any of claims <NUM> to <NUM>, when executed by a processor, are provided.

A network that includes both small cell and macro cells may be known as a heterogeneous network. The base stations <NUM> / UEs <NUM> may use spectrum up to Y MHz (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL).

D2D communication may be through a variety of wireless D2D communications systems, such as for example, FlashLinQ, WiMedia, Bluetooth, ZigBee, Wi-Fi based on the IEEE <NUM> standard, LTE, or <NUM>/NR.

When communicating in an unlicensd frequency Spectrum the STAs <NUM> / AP <NUM> may perform a clear channel assessment (CCA) prior to communicating in order to determine whether the channel is available.

When operating in an unlicensed frequency spectrum, the small cell <NUM>' may employ <NUM>/NR and use the same <NUM> unlicensed frequency spectrum as used by the Wi-Fi AP <NUM>. The small cell <NUM>', employing <NUM>/NR in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network.

The IP Services <NUM> may include the Internet an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service, and/or other IP services.

The base station may also be referred to as a gNB, Node B, evolved Node B (eNB), an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), or some other suitable terminology. The base station <NUM> provides an access point to the EPC <NUM> for a UE <NUM>. Examples of UEs <NUM> include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, a vehicle, an electric meter, a gas pump, a toaster, or any other similar functioning device. Some of the UEs <NUM> may be referred to as IoT devices (e.g., parking meter, gas pump, toaster, vehicles, etc.).

Referring again to <FIG>, in certain aspects, the base station <NUM> may comprise a reference signal component <NUM> configured for conditional reference signal transmission, as described in connection with any of <FIG> and <FIG>, including skipping transmission of reference signals when certain conditions are met. Similarly, the UE <NUM> may comprise a reference signal measurement component <NUM> configured to perform conditional reference signal measurement, as described in connection with any of <FIG>, including skipping measurement of a reference signal when certain conditions are met.

<FIG>is a diagram <NUM> illustrating an example of a DL frame structure. <FIG> is a diagram <NUM> illustrating an example of channels within the DL frame structure. <FIG> is a diagram <NUM> illustrating an example of an UL frame structure. <FIG> is a diagram <NUM> illustrating an example of channels within the UL frame structure. A frame (<NUM>) may be divided into <NUM> 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)). For a normal cyclic prefix, an RB may contain <NUM> consecutive subcarriers in the frequency domain and <NUM> consecutive symbols (for DL, OFDM symbols; for UL, SC-FDMA symbols) in the time domain, for a total of <NUM> REs. For an extended cyclic prefix, an RB may contain <NUM> consecutive subcarriers in the frequency domain and <NUM> consecutive symbols in the time domain, for a total of <NUM> REs.

As illustrated in <FIG>, 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> illustrates CRS for antenna ports <NUM>, <NUM>, <NUM>, and <NUM> (indicated as R<NUM>, R<NUM>, R<NUM>, and R<NUM>, respectively), UE-RS for antenna port <NUM> (indicated as R<NUM>), and CSI-RS for antenna port <NUM> (indicated as R).

<FIG> illustrates an example of various channels within a DL subframe of a frame. The physical control format indicator channel (PCFICH) is within symbol <NUM> of slot <NUM>, and carries a control format indicator (CFI) that indicates whether the PDCCH occupies <NUM>, <NUM>, or <NUM> symbols (<FIG> illustrates a PDCCH that occupies <NUM> 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 <NUM>, <NUM>, or <NUM> RB pairs (<FIG> shows two RB pairs, each subset including one RB pair). The physical hybrid automatic repeat request (ARQ) (HARQ) indicator channel (PHICH) is also within symbol <NUM> of slot <NUM> 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 <NUM> of slot <NUM> within subframes <NUM> and <NUM> of a frame. The PSCH carries a primary synchronization signal (PSS) that is used by a UE <NUM> to determine subframe/symbol timing and a physical layer identity. The secondary synchronization channel (SSCH) may be within symbol <NUM> of slot <NUM> within subframes <NUM> and <NUM> 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 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).

As illustrated in <FIG>, 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.

<FIG> illustrates an example of various channels within an UL subframe of a frame. A physical random access channel (PRACH) may be within one or more subframes within a frame based on the PRACH configuration. The PRACH may include six consecutive RB pairs within a subframe. The PRACH allows the UE to perform initial system access and achieve UL synchronization. A physical uplink control channel (PUCCH) may be located on edges of the UL system bandwidth.

<FIG> is a diagram <NUM> illustrating a base station <NUM> in communication with a UE <NUM>. Referring to <FIG>, the base station <NUM> may transmit a beamformed signal to the UE <NUM> in one or more of the directions 402a, 402b, 402c, 402d, 402e, 402f, <NUM>, <NUM>. The UE <NUM> may receive the beamformed signal from the base station <NUM> in one or more receive directions 404a, 404b, 404c, 404d. The UE <NUM> may also transmit a beamformed signal to the base station <NUM> in one or more of the directions 404a-404d. The base station <NUM> may receive the beamformed signal from the UE <NUM> in one or more of the receive directions 402a-<NUM>.

Radio Link Monitoring (RLM) may be an important procedure to track radio link conditions. The RLM procedure may indicate whether the air link is in-sync or out-of-sync. For monitoring active link performances, a UE may perform measurements of a set of reference signals for RLM and beam recovery. The measurements may include deriving a metric similar to Signal to Interference plus Noise Ratio (SINR) for a reference signal. The reference signal may comprise any of CSI-RS, Demodulation Reference Signal (DMRS) for NR-PDCCH in common search space (C-SS), DMRS for New Radio-Physical Broadcast Channel (NR-PBCH), New Radio-Secondary Synchronization Signal (NR-SSS), other reference signals for time and/or frequency tracking, etc. The UE may monitor the reference signal(s) and determine the signal quality, e.g., Reference Signal Received Power (RSRP) for the reference signal. The measurement may correspond to the UE's ability to decode a transmission, e.g., a DL control transmission from the base station.

Thresholds may be defined in tracking the radio link conditions, the threshold(s) may correspond to a block error rate that indicates an in-sync condition and/or an out-of-sync condition of the radio link.

An RLM procedure may comprise two types of indications, e.g., "out-of-sync" indicating that the radio link condition is poor and "in-sync" indicating that the radio link condition is acceptable and the UE is likely to receive a transmission transmitted on the radio link. An Out-of-Sync condition may be declared when a block error rate for the radio link falls below a threshold over a specified time interval, e.g., a <NUM> time interval. An in-sync condition may be declared when a block error rate for the radio link is better than a threshold over a second, specified time interval, e.g., over <NUM> time interval. The thresholds and time intervals for the in-sync and out-of-sync determinations may be the same or may be different.

If the UE receives a number n of consecutive out-of-sync measurements over a period of time, the UE may declare a radio link failure (RLF).

Based on input from RLM or beam recovery when an RLF is detected, a UE may take appropriate actions to recover the connection. Radio link failure may be based on in-sync or out-of-sync indications as an input from lower layers. The radio link quality may be associated with the reliability of a DL control channel. For example, in <NUM>/NR, the radio link quality may be associated with <NUM>/NR-PDCCH. In LTE, radio link quality may also relate to DL control channel performance, e.g., PDCCH.

There are a number of challenges associated with radio link monitoring in multi-beam wireless communication systems, e.g., as described in connection with <FIG>. Examples of such multi-beam communication may include mmW communication, sub-<NUM> wireless communication, etc..

In order to perform RLM, the UE needs to measure the quality of a reference signal. However, there might not be a direct reference signal that is always transmitted, e.g., such as CRS, which can be monitored in relation to NR-PDCCH. As there might not be a direct reference signal that is consistently transmitted, it may be difficult for a UE to perform the needed measurements.

Additionally, the transmission of DL and/or UL communication with the UE may be sporadic. Therefore, the UE may not have a persistent observation of DL control channel performance. A UE might not know whether a base station is transmitting a DL control channel transmission, e.g., PDCCH or NR-PDCCH. Therefore, the UE faces difficulties in deriving PDCCH reliability. Acknowledgements (Acks) may be sent on a DL for Semi-Persistent Scheduling (SPS) uplink traffic and may be pre-configured to occur at fixed time intervals. Acks for other UL transmissions such as SRS, beam-failure indication or SR may also be acquired by the UE. In this example, even if the definite time of an Ack transmission is not known, when no Ack is received in a time window, the UE knows that there was a missed PDCCH carrying the Ack. While a base station could transmit PDCCH or DMRS for PDCCH periodically just for the purpose of monitoring PDCCH reliability for RLM, this increased PDCCH requirement causes unnecessary overhead and use of wireless resources. For example, in multi-beam operation, a reference signal transmitted by a base station in a particular beam can only be received by a small subset of users. If the base station is required to transmit a periodic PDCCH, or other reference signal, transmission for RLM, the base station would be required to make the periodic transmissions for each of multiple beam directions. The transmissions in multiple beam directions increases the overhead burden and use of wireless resources.

The present application provides a solution that enables a UE in multi-beam operation to perform RLM, beam recovery and beam management in a manner that reduces the burden of reference signal transmission at the base station by enabling conditional reference signal transmission and/or conditional RLM and beam recovery. A reference signal transmission and measurement for RLM or beam recovery may be skipped or modified when certain conditions are met. For example, a base station may skip, or otherwise modify, a RS transmission over a period when data/control/RS is received from the UE within a window of time. The reception of the data/control/RS from the UE may indicate to the base station that the UE received the previous reference signal transmission from the base station. A UE may skip a measurement of a reference signal when the UE has received control/data/RS from the base station within a window of time.

<FIG> illustrates an example of multi-beam wireless communication <NUM> between a UE <NUM> and a base station <NUM>. UE <NUM> may correspond to UE <NUM>, <NUM>, <NUM>, <NUM>, the apparatus <NUM>, <NUM>', and base station <NUM> may correspond to base station <NUM>, <NUM>, <NUM>, <NUM>, the apparatus <NUM>, <NUM>'. As illustrated in <FIG>, the base station <NUM> may skip or modify a reference signal transmission when certain conditions are met and/or the UE <NUM> may skip measuring a reference signal when certain conditions are met.

The base station <NUM> may provide reference signal configuration information <NUM> to UE <NUM> for monitoring one or more beam pair links. For example, the base station <NUM> may notify UE <NUM> to monitor one or more reference signals. The reference signals may include, e.g., any of CSI-RS, DMRS for NR-PDCCH in C-SS, DMRS for NR-PBCH in user search space (U-SS), NR-SSS, and a reference signal for time/frequency tracking. The reference signals may comprise periodic, aperiodic or semi-persistent transmissions. The reference signal configuration information <NUM> indicated by the base station <NUM> may specify any of a number of antenna ports, a reference signal configuration in time and frequency, and/or a sub-frame configuration. A subset of reference signal configurations may be reserved by the base station for RLM.

The base station <NUM> may transmit reference signals, e.g., <NUM>, <NUM> to UE <NUM>. The base station may skip or modify reference signal transmissions when certain conditions are met. For example, when the base station <NUM> has received a transmission <NUM>, e.g., a data transmission, a control transmission, or a reference signal transmission, from the UE <NUM> within a time window <NUM>, and the received transmission has an SNR or signal quality above a threshold, the base station may skip or modify <NUM> a transmission of a reference signal. The skipped reference signal may be, e.g., for RLM, beam recovery, beam management, etc. The data/control/RS transmission <NUM> received from the UE <NUM> may comprise any of PUCCH, PUSCH, SRS, DMRS, ACK/NACK, etc. The receipt of PUCCH, PUSCH, DMRS, SRS, or ACK/NACK from the UE may indicate to the base station that the UE received a previous reference signal transmission.

<FIG> illustrates an example <NUM> having n as a current point in time, e.g., a current symbol. The base station may use a time window <NUM> to determine whether a data/control/reference signal transmission has been received from a UE within the period from n to n - time window <NUM>, e.g., within the time window from the current point n. For example, n may represent a symbol, e.g., a current symbol. In <FIG>, a data transmission, a control transmission, or a reference signal transmission <NUM> was received from the UE within the time window, e.g., between n and n - time window. If the signal quality of the received transmission <NUM> meets a threshold, the base station may determine to skip or modify a reference signal transmission during a period extending from the current symbol, e.g., n, to n + time window. Thus, the base station may transmit a modified RS <NUM> in the period from n to n + time window based on the receipt of data/control/RS <NUM> from the UE. <FIG> illustrate a similar time window that may be used by a UE. The time windows may be configured differently by the base station.

If the base station <NUM> has not received a data/control/reference signal transmission from the UE <NUM> within the time window <NUM>, e.g., n - time window, then the base station may transmit the reference signal <NUM>, e.g., for RLM, beam recovery, beam management, in the current symbol or over the next period <NUM>, e.g., n + time window. <FIG> illustrates an example <NUM> I which no data transmission, control transmission, or reference signal transmission was received from the UE within the time window <NUM>, e.g., between n and n - time window. In this example, the condition is not met, and the base station transmits the reference signal <NUM> within the period between the current point n and n + time window.

The transmission received from the UE, e.g., <NUM>, may need to satisfy a signal quality threshold for the base station to skip or modify the reference signal transmission. For example, if the network has received a data/control/reference signal transmission from the UE within a time window, but the network determines that the SNR or signal quality of the received data/control/reference signal transmission is below a threshold, the base station may transmit the reference signal in the current symbol or over the next period n + time window, n being the current point in time. The reference signal may be transmitted for RLM, beam recovery, beam management, etc. Thus, the base station may determine not to skip or modify the reference signal transmission even though a transmission was received from the UE within the time window, when the received transmission has a signal quality or SNR below a threshold. <FIG> illustrates an example <NUM> where the base station receives a transmission <NUM> from the UE having a signal quality below the threshold. In this example, the base station transmits the RS <NUM>, similar to <FIG>.

When a condition is met, e.g., the base station has received a data/control/RS transmission from the UE that meets a signal quality threshold within the time window, the base station may skip a reference signal transmission during a certain period. For example, the base station may skip transmission of the reference signal during a period of time from the current point in time corresponding to the time window, e.g., n + time window.

In a second example, the base station may still transmit the reference signal, but may modify the reference signal transmission, e.g., as illustrated in <FIG>. For example, the base station may modify the timing of the reference signal, a frequency of the reference signal, and/or a transmission power for the reference signal. The base station may modify the reference signal for a subset of users.

In a third example, the base station may schedule other UEs instead of transmitting the reference signal transmission. For example, a different UE may be scheduled for data transmission instead of transmitting the reference signal.

When the base station determines to skip the reference signal transmission, e.g., as in the first and third examples, the base station may indicate <NUM> to the UE <NUM> that the reference signal is skipped, e.g., as illustrated in the example of <FIG>. The indication may be comprised in PDCCH or PDSCH, for example. Without such an indication, the UE may expect the reference signal transmission and may interpret the absence of the reference signal as a measurement of poor signal quality.

Similar to the conditional transmission of a reference signal performed by the base station, the UE may perform conditional measurement of a reference signal. For example, as illustrated in <FIG>, when the UE has received a transmission, e.g., a data transmission, a control transmission, or a reference signal transmission <NUM>, having an SNR or signal quality above a threshold within a time window <NUM>, the UE may skip <NUM> measurement of a reference signal. The skipped reference signal may be, e.g., for RLM, beam recovery, beam management, etc. The data/control/RS transmission received from the base station may comprise any of PDCCH, PDSCH, RS, etc..

The base station may provide or otherwise indicate a time window <NUM> to UE <NUM>. The size of the time window may be indicated to the UE in terms of slots, symbols, SFN, etc. The time window for the UE, e.g., as described in connection with <FIG>, may be the same or may be different than the time window used by the base station, e.g., as described in connection with <FIG>. As illustrated in <FIG>, the base station may also indicate a reference signal based offset <NUM> and/or a signal quality threshold <NUM> to the UE <NUM>. Although the time window <NUM>, the reference signal based offset <NUM>, and the signal quality threshold <NUM> are illustrated as three separate transmissions, this information may also be indicated to the UE <NUM> in a single transmission from the base station <NUM>.

<FIG> illustrates an example <NUM> having n as a current point in time, e.g., a current symbol. The UE may use a time window to determine whether a data/control/reference signal transmission has been received from a base station within the period from n to point <NUM>, e.g., n - time window, e.g., within the time window <NUM> from the current point n. For example, n may represent a symbol, e.g., a current symbol. In <FIG>, a data transmission, a control transmission, or a reference signal transmission <NUM> has been received from the base station within the time window <NUM>, e.g., between n and n - time window. If the signal quality of the received transmission meets a threshold, the UE may determine to skip or measurement of a reference signal during a period following n, e.g., during a period in time extending from the current symbol to point <NUM>, e.g., n to n + time window. The threshold may be based on the signal quality threshold <NUM> signaled to the UE <NUM> from the base station <NUM>.

When a condition is met, e.g., when the UE has received a data/control/RS transmission from the base station within a prior time window that meets a signal quality threshold, the UE may go to sleep or remain in sleep during a subsequent time window, in a first example. For example, the UE need not wake up during the period n to n + time window to perform RS measurements.

In a second example, the UE may use a reference signal based offset to map a signal quality from one reference signal to another reference signal, e.g., to the skipped reference signal. The reference signals may be different types. Therefore, the UE may derive a signal quality or performance metric for a first type of reference signal using a measured signal quality for a different type of reference signal based on the reference signal based offset. For example, if the skipped reference signal comprises a CSI-RS, the UE may use the reference signal based offset to map a signal quality from a measured DMRS to infer the quality of the hypothetical CSI-RS that was skipped. The reference signal based offset may be the one signaled to the UE, e.g., at <NUM>.

In a third example, the UE may send an in-sync or out-of-sync indication to higher layers based on the reference signal measurements during the prior time period, e.g., the period from n to n - time window. The measurements might be measurements for other reference signals than those typically used for RLM. Therefore, the in-sync or out-of-sync indications may also be based on the reference signal based offset as applied to the different reference signals, as described in connection with the second example.

In a fourth example, the UE may indicate <NUM> to the base station, e.g., via PUCCH or PUSCH, that the reference signal measurement will be skipped over a time window.

If the UE <NUM> has not received a data/control/reference signal transmission from the base station <NUM> within the time window, e.g., between n to n - time window, then the UE may perform a measurement of the reference signal, e.g., for RLM, beam recovery, beam management, in the current symbol or over the next period n + time window. <FIG> illustrates an example <NUM> in which no data transmission, control transmission, or reference signal transmission has been received during time period <NUM>. Therefore, the condition is not met, and the UE measures the reference signal within the subsequent time period, e.g., during the time between the current point n and n + time window.

<FIG> illustrates an example <NUM> where the UE receives a transmission <NUM> from the base station, but the transmission <NUM> has a signal quality that does not meet the threshold. In this example, the UE measures the reference signal during the subsequent time period following n, e.g., during the period n to n + time window, similar to <FIG>.

If the UE performs reference signal measurements and determines that the signal quality of reference signal has changed significantly, or is DTX, then the UE may determine not to use the measurement for an in-sync/out-of-sync indication. A significant change in the measured signal quality may indicate that the base station has skipped the RS transmission during this period, because consecutive reference signal transmissions should have similar signal qualities. By refraining from using the measurement for in-sync/out-of-sync indications, the UE avoids using an inaccurate measurement for the in-sync/out-of-sync indication. The UE may determine whether a change in reference signal measurements is significant by comparing the difference between the measurements to a change threshold. The change threshold may be configurable by the network. The change threshold may depend on time and/or frequency differences between the measurements. In one example for mmW communication, two reference signal measurements approximately <NUM> apart should have a signal quality measurement within about <NUM> dB of each other. Therefore, the change threshold may be approximately <NUM> dB, which would indicate a significant change between the two reference signal measurements.

<FIG> is a flowchart <NUM> of a method of wireless communication. The method is performed by a UE (e.g., UE <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, the apparatus <NUM>, <NUM>') communicating with a base station (e.g., the base station <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, the apparatus <NUM>, <NUM>') using multi-beam wireless communication. Optional aspects of <FIG> are illustrated with a dashed line.

At <NUM>, the UE determines whether a transmission is received from the base station within a time window, e.g., within a time window prior to the current time. <FIG> illustrate an example time window <NUM> prior to a current symbol n and extending to n-time window. A transmission received from the base station may comprise at least one of a data transmission, a control transmission, and/or a reference signal transmission. In one example, the transmission may be any measurable transmission from the base station. The transmission may comprise data, control, or a reference signal. A reference signal may comprise a reference signal associated with a beam link pair. The UE may receive a notification from the base station to monitor one or more reference signals and may receive a reference signal configuration for monitoring, e.g., as described in connection with <NUM> in <FIG>. The UE may receive, e.g., at <NUM>, an indication from the base station for at least one of the time window, a reference signal based offset to the user equipment, and a signal quality threshold, e.g., as described in connection with <NUM>, <NUM>, <NUM> in <FIG>. Therefore, the time window that the UE uses in <NUM> may be based on the indication received from the base station at <NUM>.

The UE determines at <NUM> whether a signal quality of the transmission received from the base station meets a threshold.

When the transmission is not received from the base station within the time window or when the signal quality of the transmission does not meet the threshold, the user equipment may measure a reference signal at <NUM>, e.g. as described in connection with <FIG>. The UE may refrain from measuring the reference signal during a period following the determination. As described in connection with <FIG>, the UE may skip measurement of the reference signal during a subsequent time window, e.g., during a time period from n to n + time window.

At <NUM>, the UE skips measurement of the reference signal, when the transmission is received from the base station within the time window and meets the signal quality threshold, e.g., as described in connection with <FIG>.

As illustrated in <FIG>, skipping measurement of the reference signal at <NUM> may include entering a sleep mode or remaining in a sleep mode <NUM>.

The UE further maps a signal quality from a different reference signal to the reference signal based on a reference signal based offset at <NUM>. The two reference signals may be different type of reference signals. At <NUM>, UE may transmit an in-synchronization indication or an out-of-synchronization indication based on a measurement within the time window.

At <NUM>, the UE may transmit an indication to the base station of the skipped measurement of the reference signal, e.g., as described in connection with indication <NUM> in <FIG>. The indication may be transmitted in PUCCH or PUSCH.

As illustrated at <NUM>, the UE may perform a measurement of a prior reference signal from a base station. At <NUM>, the UE may determine whether a difference between a first signal quality of the reference signal and a second signal quality of the prior reference signal meets a change threshold. At <NUM>, the UE may transmit an in-synchronization indication or an out-of-synchronization indication based on the reference signal when the difference is within the change threshold. At <NUM>, the UE may refrain from transmitting the in-synchronization indication or the out-of-synchronization indication based on the reference signal when the difference is outside the change threshold. This enables the UE to address situations in which the base station might refrain from transmitting the RS.

<FIG> is a conceptual data flow diagram <NUM> illustrating the data flow between different means/components in an exemplary apparatus <NUM>. The apparatus may be UE (e.g., UE <NUM>, <NUM>, <NUM>, <NUM>) communicating with base station <NUM> (e.g., base station <NUM>, <NUM>, <NUM>, <NUM>) using multi-beam operation. The apparatus includes a reception component <NUM> that receives DL communication from base station <NUM> and a transmission component <NUM> that transmits UL communication to base station <NUM>.

The apparatus includes an RS component <NUM> that performs measurements of reference signals, a transmission detection component <NUM> that determines whether a transmission is received from the base station within a time window, a signal quality component <NUM> that determines whether the received transmission has a signal quality that meets a threshold. When a transmission is detected within the time window that meets the signal quality threshold, an indication may be provided to the RS measurement component <NUM> to skip measurement of a second reference signal. The apparatus may also include an IS/OOS component <NUM> configured to determine whether to transmit an IS/OOS indication using a reference signal measurement based on whether a difference between a first signal quality of the first reference signal and a second signal quality of the second reference signal meets a change threshold.

<FIG> is a diagram <NUM> illustrating an example of a hardware implementation for an apparatus <NUM>' employing a processing system <NUM>. The processing system <NUM> may be implemented with a bus architecture, represented generally by the bus <NUM>. The bus <NUM> may include any number of interconnecting buses and bridges depending on the specific application of the processing system <NUM> and the overall design constraints. The bus <NUM> links together various circuits including one or more processors and/or hardware components, represented by the processor <NUM>, the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and the computer-readable medium / memory <NUM>. The bus <NUM> may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system <NUM> may be coupled to a transceiver <NUM>. The transceiver <NUM> is coupled to one or more antennas <NUM>. The transceiver <NUM> provides a means for communicating with various other apparatus over a transmission medium. The transceiver <NUM> receives a signal from the one or more antennas <NUM>, extracts information from the received signal, and provides the extracted information to the processing system <NUM>, specifically the reception component <NUM>. In addition, the transceiver <NUM> receives information from the processing system <NUM>, specifically the transmission component <NUM>, and based on the received information, generates a signal to be applied to the one or more antennas <NUM>. The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium / memory <NUM>. The processor <NUM> is responsible for general processing, including the execution of software stored on the computer-readable medium / memory <NUM>. The software, when executed by the processor <NUM>, causes the processing system <NUM> to perform the various functions described supra for any particular apparatus. The computer-readable medium / memory <NUM> may also be used for storing data that is manipulated by the processor <NUM> when executing software. The processing system <NUM> further includes at least one of the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The components may be software components running in the processor <NUM>, resident/stored in the computer readable medium / memory <NUM>, one or more hardware components coupled to the processor <NUM>, or some combination thereof. The processing system <NUM> may be a component of the UE <NUM> and may include the memory <NUM> and/or at least one of the TX processor <NUM>, the RX processor <NUM>, and the controller/processor <NUM>.

In one configuration, the apparatus <NUM>/<NUM>' for wireless communication includes means for performing a measurement of a first reference signal from a base station; means for determining whether a transmission is received from the base station within a time window; means for skipping measurement of a second reference signal, when the transmission is received from the base station within the time window; means for entering a sleep mode or remaining in a sleep mode; means for mapping a signal quality from the first reference signal to the second reference signal based on a reference signal based offset; means for measuring the reference signal; means for transmitting an in-synchronization indication or an out-of-synchronization indication based on a measurement within the time window; means for transmitting an indication to the base station of the skipped measurement of the second reference signal; means for determining whether a difference between a first signal quality of the first reference signal and a second signal quality of the second reference signal meets a change threshold; means for transmitting an in-synchronization indication or an out-of-synchronization indication based on the second reference signal when the difference is within the change threshold; means for refraining from transmitting the in-synchronization indication or the out-of-synchronization indication based on the second reference signal when the difference is outside the change threshold; and means for receiving an indication from the base station for at least one of the time window, a reference signal based offset to the user equipment, and a signal quality threshold.

<FIG> is a flowchart <NUM> of a method of wireless communication. The method may be performed by a base station (e.g., the base station <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, the apparatus <NUM>, <NUM>') using multi-beam wireless communication to communicate with a UE (e.g., UE <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, the apparatus <NUM>, <NUM>'). The method can be used in conjunction with the method according to <FIG>. Optional aspects are illustrated with a dashed line.

At <NUM>, the base station configures a UE to monitor one or more reference signals associated with a beam pair link. For example, the base station may notify the UE to monitor one or more reference signals, e.g., for RLM, beam recovery, or beam management. The base station may indicate an RS configuration that indicates a number of antenna ports, an RS signal configuration in time and frequency, a sub-frame configuration, etc., as described in connection with <NUM> in <FIG>.

The base station may indicate a time window to the user equipment at <NUM>, e.g., as described in connection with <NUM> in <FIG> and <NUM> in <FIG>. The time window may be indicated for a unit based on at least one of a slot, a symbol, or a SFN. The UE may indicate a reference signal based offset to the user equipment at <NUM>, e.g., as described in connection with <NUM> in <FIG>. The UE may indicate a threshold for a signal quality to the user equipment at <NUM>, e.g., as described in connection with <NUM> in <FIG>.

At <NUM>, the base station transmits a first signal in a transmission to the UE. The signal may comprise any measurable transmission, e.g., a reference signal transmission, a data transmission, or a control transmission. At <NUM>, the base station determines whether the transmission is received at a user equipment within a time window. The determination may be based on whether the base station receives a transmission from the UE within the time window, e.g., a control transmission, a data transmission, a reference signal transmission, etc. For example, when the base station receives PUCCH, PUSCH, SRS, or ACK/NACK from the UE within the time window, the base station may determine that the UE received the transmission from the base station.

At <NUM>, the base station determines whether to transmit a reference signal based on whether the transmission is received at the user equipment within the time window. <FIG> illustrate examples of a time window <NUM> and possible results of the determination by the base station.

Upon determining that the transmission was received at the user equipment, the base station may skip transmission of the reference signal at <NUM> or may modify the reference signal at <NUM>. <FIG> illustrates an example in which the base station skips or modifies transmission of the reference signal over a period of time following the determination. In <FIG>, the base station determines to skip/modify the reference signal during a period n to n + time period. For example, the base station may modify at least one of a time, a frequency, a power, or a reference signal offset for the reference signal during this period following the determination. Once the period ends, the base station may need to make further determinations regarding whether a transmission has been received by the UE in order to determine whether to transmit an RS during a later period in time.

Upon determining that the transmission was received at the user equipment, the base station may schedule a different user equipment, at <NUM>, in place of transmitting the reference signal.

Upon determining that the transmission was received at the user equipment, the base station may indicate, at <NUM>, to the user equipment that the reference signal is skipped.

When the base station determines that the transmission is not received at a user equipment within a time window, the base station transmits the reference signal at <NUM>. <FIG> illustrate examples in which the base station may determine to transmit the reference signal.

<FIG> is a conceptual data flow diagram <NUM> illustrating the data flow between different means/components in an exemplary apparatus <NUM>. The apparatus may be a base station (e.g., the base station <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) communicating with UE <NUM> using multi-beam operation. The apparatus includes a reception component <NUM> that receives UL communication from UE <NUM> and a transmission component <NUM> that transmits DL communication, including reference signals, to UE <NUM>. The apparatus includes a reference signal configuration component <NUM> configured to configure a UE to monitor one or more reference signals associated with a beam pair link, and which may indicate any of a timing window, a reference signal based offset, or a signal quality threshold to the UE. The apparatus includes a reference signal component <NUM> configured to transmit a first reference signal in a transmission to the UE and a transmission determination component <NUM> configured to determine whether the transmission is received at a user equipment within a time window. For example, the transmission determination component <NUM> may determine whether a first signal transmission was received by the UE based upon receiving at least one of a control channel, a data channel, a sounding reference signal, and an acknowledgement from the user equipment having a signal quality that meets a threshold within the time window.

The apparatus may include a RS determination component <NUM> configured to determine whether to transmit a reference signal, based on whether the transmission is received at the user equipment within the time window. The RS determination component <NUM> may determine to skip and/or modify the RS transmission, as described in connection with <FIG>.

As such, each block in the aforementioned flowcharts of <FIG> and <FIG>. may be performed by a component and the apparatus may include one or more of those components.

The processing system <NUM> may be coupled to a transceiver <NUM>. The transceiver <NUM> is coupled to one or more antennas <NUM>. The transceiver <NUM> provides a means for communicating with various other apparatus over a transmission medium. The transceiver <NUM> receives a signal from the one or more antennas <NUM>, extracts information from the received signal, and provides the extracted information to the processing system <NUM>, specifically the reception component <NUM>. In addition, the transceiver <NUM> receives information from the processing system <NUM>, specifically the transmission component <NUM>, and based on the received information, generates a signal to be applied to the one or more antennas <NUM>. The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium / memory <NUM>. The processor <NUM> is responsible for general processing, including the execution of software stored on the computer-readable medium / memory <NUM>. The software, when executed by the processor <NUM>, causes the processing system <NUM> to perform the various functions described supra for any particular apparatus. The computer-readable medium / memory <NUM> may also be used for storing data that is manipulated by the processor <NUM> when executing software. The processing system <NUM> further includes at least one of the components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The components may be software components running in the processor <NUM>, resident/stored in the computer readable medium / memory <NUM>, one or more hardware components coupled to the processor <NUM>, or some combination thereof. The processing system <NUM> may be a component of the base station <NUM> and may include the memory <NUM> and/or at least one of the TX processor <NUM>, the RX processor <NUM>, and the controller/processor <NUM>.

In one configuration, the apparatus <NUM>/<NUM>' for wireless communication includes means for configuring a UE to monitor one or more reference signals associated with a beam pair link; means for means for transmitting a first signal in a transmission to the UE; means for determining whether the transmission is received at a user equipment within a time window; means for determining whether to transmit a reference signal, based on whether the transmission is received at the user equipment within the time window; means for skipping transmission of the reference signal; means for modifying at least one of a time, a frequency, a power, or a reference signal offset for the reference signal; means for scheduling a different user equipment in place of transmitting the reference signal; means for indicating to the user equipment that the reference signal is skipped; means for indicating the time window to the user equipment, wherein the time window is indicated for a unit based on at least one of a slot, a symbol, or a SFN; and means for indicating a reference signal based offset to the user equipment; and means for indicating a threshold for a signal quality to the user equipment.

Claim 1:
A method of wireless communication at a user equipment, comprising:
determining (<NUM>) whether a transmission is received from a base station within a time window from a current point in time, wherein the user equipment determines (<NUM>) that the transmission is received from the base station when a signal quality of the transmission from the base station meets a threshold;
skipping (<NUM>) measurement of a reference signal, when the transmission is determined to be received from the base station within the time window and when the transmission has a signal quality above the threshold; and
mapping (<NUM>) a signal quality from a second reference signal to the reference signal based on a reference signal based offset; and
transmitting (<NUM>) an indication to the base station of a skipped measurement of the reference signal.