Methods for frequency offset tracking in NR mmwave for efficient beam management

Methods and systems for tracking frequency offset in NR are provided. A user equipment (UE) can compute the frequency offset comprising of crystal frequency drift and Doppler shift. Drift in frequencies generated by crystal oscillators in the UE and a base station are detected and nullified. Doppler shift of a serving beam is estimated using either data collected by sensors in the UE or reference signals received from the base station. Values of Doppler shift for a plurality of beams are estimated using the Doppler shift of the serving beam and sensor data, wherein the serving beam and the plurality of beams correspond to a same transmitter beam or different transmitter beams, wherein the type of QCL of the beams is either A, B, or C.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a U.S. National Stage application under 35 U.S.C. § 371 of an International application number PCT/KR2020/001954, filed on Feb. 12, 2020, which is based on and claims priority of an Indian provisional application number 201941005531, filed on Feb. 12, 2019, and an Indian patent application number 201941005531, filed on Oct. 3, 2019, in the Indian Intellectual Property Office, the disclosure of each of which is incorporated by reference herein in its entirety.

BACKGROUND

The disclosure relates to 5th Generation (5G) communication networks. More particularly, the disclosure relates to methods and systems for tracking frequency offset in new radio (NR) for efficient beam management.

2. Description of Related Art

Currently, communication devices are configured to estimate parameters, such as coarse frequency offset and Doppler shift, that can cause variations in frequency of a signal, transmitted from a source device (such as a base station), at a receiver device (such as a user equipment (UE)). The frequency offset can be caused due to variations in frequencies generated by crystal oscillators of the source device and the receiver device. The Doppler shift specifies the variations in the frequency of the transmitted signal at the receiver device, caused due to movement of the source/receiver device with respect to the receiver/source device. The Doppler shift causing the variation in the frequency is based on a velocity of the movement of the source/receiver device with respect to the receiver/source device. The communication devices in a wireless communication system can periodically estimate the variations in frequencies of the crystal oscillators of the source device and Doppler shift as part of signal transmission and reception.

FIG.1illustrates multiple copies of a wireless signal, transmitted by a source device, being received by a received device according to the related art.

Referring toFIG.1, the different copies of the signals arrive at the receiver, from the source through different paths (101and102). The different paths may have different channel qualities, which is likely to vary with respect to time. If the receiver is in motion with respect to the source, the frequency of the wireless signal at the receiver is likely to be shifted by a value with respect to the source. The shift of the frequency is a function of velocity of the receiver/source with respect to the source/receiver. If the receiver/source is moving with a velocity ‘v’ with respect to the source/receiver, the frequency shift will be f*v/c, wherein ‘c’ is the speed of light with frequency of the signal transmitted from the source being ‘f’. The receiver can be configured to negate the frequency shift.

FIG.2illustrates an architecture of a wireless receiver that can be configured to estimate and eliminate channel effects and frequency offset, comprising of Doppler shift according to the related art.

Referring toFIG.2, the architecture of a wireless receiver includes frontend108-0-108-(Mr-1), CP removal110-0-110-(Mr-1), FFT112-0-112-(Mr-1),106, channel estimator module114, demodulation120-0-120-(U-1), decoder122-0-122-(U-1), and an equalizer116. The wireless receiver comprises of carrier frequency offset (CFO) or Doppler estimation and correction module118-0-118-(U-1), which can estimate and eliminate the channel effects and the frequency offsets that are likely to cause signal distortion. The estimations can be performed using reference signals, which are periodically transmitted by a base station (source device)104-0-104-(Mr-1). The wireless receiver allows simultaneous reception from multiple users in single carrier-frequency division multiplexing Access (SC-FDMA) and orthogonal frequency division multiplexing (OFDM) systems.

FIG.3illustrates periodic transmission of reference signals by a gNB according to the related art.

In NR, a UE can perform an estimation of frequency offset using the reference signals that are periodically or semi-persistently transmitted by the base station. In an example, the base station can send demodulation reference signals (DMRS), primary/secondary synchronization signals (PSS/SSS), and physical broadcast channel (PBCH) according to the related art.

Referring toFIG.3, the PSS, SSS, DMRS, and PBCH, are periodically transmitted by a next generation node B (gNB) (base station) periodically in a synchronization signal block (SSB). The base station can configure the UE to utilize the reference signals to perform channel state information and reference signal received power/received signal strength indicator (RSRP/RSSI) computations. In addition to SSBs, the base station may also transmit channel state information-reference signals (CSI-RS) that can be used for performing CSI measurements. In NR, as reference signals and SSB transmissions can be received from the same or different transmission reception points (TRPs) (beams), the gNB indicates type of quasi co-Location (QCL) relation between two reference signals by configuring transmission configuration indication (TCI) state information. The QCL types are, viz., type A (Doppler shift, Doppler spread, average delay, delay spread), type B (Doppler shift, Doppler spread), type C (Doppler shift, average delay) and type D (Spatial Rx parameter).

The reference signals are received, as configured in a UE specific radio resource control (RRC) message or as indicated in a broadcast message. The UE can receive time and frequency mapping along with periodicity of transmission of the reference signals in the RRC message. During measurements, the UE may appropriately combine reference signals depending on the type of QCL. Further, DMRS which is transmitted as part of downlink transmissions can also be used, when applicable. Similarly, for uplink measurements, the gNB may request the UE to transmit a sounding reference signal (SRS) for link adaptation and beam selection. The DMRS is transmitted with data and control channels for channel estimation.

FIG.4is a sequence diagram depicting beam switching by a UE according to the related art.

Referring toFIG.4, at operation405, the UE can receive initial synchronization signals and system information from the gNB. In operation410, the gNB can send reference signals, such as SSB and DMRS according to the related art.

at operation415, the UE can estimate frequency offset and Doppler shift using the reference signals. At operation420, the UE can receive/transmit a physical random access channel (PRACH) from/to the gNB. In operation425, the UE can receive a physical downlink control channel (PDCCH), which is followed by a physical downlink shared channel (PDSCH) in operation430. As depicted in operation425and in operation435ofFIG.4, the PDCCH and PDSCH messages are received by the UE in different beams. The PDSCH is received in a different beam because the UE had performed a beam switch. In operation440, the UE can estimate the frequency offset and Doppler shift using the reference signals. In operation445, the UE can receive at least one of CSI-RS or tracking reference signal (TRS) from the gNB. In operation450, the UE can switch to a new beam for transmission/reception from an existing beam if the new beam is best for communication. In operation455, the UE can receive CSI-RS/TRS from the gNB. Once the beam switching is performed, in operation460, the UE re-estimates the frequency offset and Doppler shift using the reference signals. The UE estimating the frequency offset and Doppler shift on a per beam pair configuration basis, can incur an additional cost in terms of delay and computation whenever there is a transmitter or receiver beam switch.

FIG.5illustrates a UE performing a beam switching due to motion with respect to a gNB according to the related art.

In beamforming systems, the source device and the receiver device can communicate information using a plurality of beams according to the related art.

Referring toFIG.5, the UE can communicate with the gNB using any of the five beams, viz., B0, B1, B2, B3, and B4. At a particular instant, the UE can select at least one of the beams which is optimal (in terms of bit error rate (BER), signal to noise ratio (SNR), latency, and so on) for communication. Consider that at time T0, the UE, at location L2, determines that B1is the optimal beam, based on the direction of transmission/reception of data to/from the gNB. Each of the beams can be characterized by a beam angle ‘0’, which specifies a direction along which the beamforming gain is highest for a received or transmitted signal. The beam angle can be at the center of the beam. The angle between the beam directions can be θ12, θ23, and so on. Hence, during signal reception, the UE can determine the optimal beam and utilize the optimal beam for setting up communication with the gNB. Once the optimal beam has been selected, CFO/Doppler estimation, channel estimation, and so on, can be performed by the UE for signal reception specific to the selected optimal beam.

The optimal beam to be used for communication may change over time, due to factors, such as motion of the UE, environmental factors, appearance of obstacles, and so on. As depicted inFIG.5, at time T1, B2is the optimal beam at location L2; and at time T2, B3is the optimal beam at location L3. Hence, the UE may need to determine the optimal beam periodically and switch to the optimal beam prior to communicating with the gNB. After each beam switching operation, the UE needs to perform CFO/Doppler estimation, channel estimation, and so on, for successful signal reception. The estimations, performed at every instance of beam switch, can degrade latency and increase computational cost particularly if the UE is in motion with a high velocity.

FIG.6illustrates an architecture of a beamforming system in a communication device that is configured to perform CFO/Doppler estimation and channel estimation according to the related art.

Referring toFIG.6, the device performs CFO/Doppler estimation and channel estimation for each of the beams that are available to the UE for establishing communication with the gNB. When the device performs a beam switch, the CFO/Doppler and channel estimation modules perform the estimations, which can be utilized by the demodulators during equalization. However, performing the estimation every beam switch increases computational overhead, which is particularly high for the cases, such as high mobility, wherein beam switching is performed frequently.

FIG.7is a 2-Dimensional (2D) beam layout of a UE according to the related art.

Referring toFIG.7, the UE can communicate using 7 beams. The beam angles specifying the directions with maximum gain for each of the 7 beams are 01-07. The directions are fixed and the UE can switch to any of the beams or utilize at least one of the beams, if the UE determines that the beams are optimal. The angular shift in the direction of communication can be computed while performing the beam switching. Although a 2D beam layout is illustrated, the same can be extended to a 3D beam layout, wherein beam angle ‘θ’ can be represented by a pair of points using the polar coordinate system, indicating the azimuth and zenith angles of the beam.

SUMMARY

In New Radio (NR) 5th Generation (5G) systems, which utilize millimeter (mm) waves for communication, estimations of the Doppler shift and variations in frequencies of crystal oscillators are performed by the UE (acting as the receiver device) using reference signals transmitted by the base station (acting as the source device), on a per beam basis. This can result in a higher computational overhead, particularly in the scenarios, wherein the UE is in motion with respect to the base station, as the UE frequently performs beam switching.

Aspects of the disclosure are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the disclosure is to provide methods and systems for tracking frequency offset by a user equipment (UE) comprising of crystal frequency drift and Doppler shift in 5thGeneration (5G) communication systems.

Another aspect of the disclosure is to minimize frequency of computation of the frequency offset, by the UE, using reference signals transmitted by a base station by computing Doppler shift for a plurality of UE beams based on sensor data and estimated Doppler shift of a serving beam, wherein the Doppler shift of the serving beam is determined based on at least one of the reference signals and the sensor data.

Another aspect of the disclosure is to determine Doppler shift for the plurality of UE beams based on sensor data and estimated Doppler shift of the serving beam, wherein the serving beam and the plurality of UE beams correspond to same or different transmitter beams.

Another aspect of the disclosure is to determine velocity of the UE based on values of Doppler shift of a plurality of beams determined using the reference signals and sensor data.

Another aspect of the disclosure is to provide methods and systems for tracking frequency offset by a UE comprising of crystal frequency drift and Doppler shift in 5G communication systems.

Another aspect of the disclosure is to provide methods and systems for minimizing frequency of computation of the frequency offset, by the UE, using reference signals transmitted by a base station by computing Doppler shift for a plurality of UE beams based on sensor data and estimated Doppler shift of a serving beam, wherein the Doppler shift of the serving beam is determined based on at least one of the reference signals and the sensor data.

Another aspect of the disclosure is to provide methods and systems for determining Doppler shift for the plurality of UE beams based on sensor data and estimated Doppler shift of the serving beam, wherein the serving beam and the plurality of UE beams correspond to same or different transmitter beams.

Another aspect of the disclosure is to provide methods and systems for determining velocity of the UE based on values of Doppler shift of a plurality of beams determined using the reference signals and sensor data.

In accordance with an aspect of the disclosure, methods and systems for tracking frequency offset by a UE comprising of crystal frequency drift and Doppler shift in 5G communication systems are provided. The methods and systems include detecting and nullifying drift in frequencies generated by crystal oscillators in a UE and a base station. The embodiments include estimating Doppler shift of a serving beam through data collected by at least one sensor present in the UE and at least one reference signal received from the base station. The embodiments include estimating values of Doppler shift of a plurality of beams using the estimated Doppler shift of the serving beam and sensor data, wherein type of QCL of the serving beam and the plurality of beams are either of type A, B, or C, wherein the serving beam and the plurality of beams correspond to a same transmitter beam or different transmitter beams with QCL of type A, B, or C.

DETAILED DESCRIPTION

Embodiments herein disclose methods and systems for tracking frequency offset comprising of crystal frequency drift and Doppler shift in 5th Generation (5G) communication systems. The embodiments include detecting and nullifying drift in frequencies generated by crystal oscillators in a user equipment (UE) and a base station. The embodiments include estimating Doppler shift of a serving beam through data collected by at least one sensor present in the UE and at least one reference signal received from the base station. The embodiments include estimating values of Doppler shift of a plurality of beams using the estimated Doppler shift of the serving beam and sensor data, wherein type of quasi co-location (QCL) of the serving beam and the plurality of beams are either of type A, B, or C, wherein the serving beam and the plurality of beams correspond to a same transmitter beam or different transmitter beams with QCL of type A, B, or C.

Referring now to the drawings, and more particularly toFIGS.8A through16, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.

FIGS.8A and8Billustrate various units of a system configured to track frequency offset according to various embodiments the disclosure.

Referring toFIG.8A, a system800comprises at least one UE801and a base station802. The base station802can be an eNB or a gNB. If the UE801acts as a receiver device, the base station802can act as the source device. On the other hand, if the base station802acts as the receiver device and the UE801can act as the source device. The system800is configured to track frequency offset caused by variations in frequencies generated by crystal oscillators in the UE801and the base station802.

It can be noted that the system can comprise of the UE801and a second UE (instead of the base station802), wherein either of the UEs can act as the source or the destination device.

The communication device803, as depicted inFIG.8B, can act as the source device or the receiver device. Therefore, components of the communication device803can be present in both the UE801and the base station802. The components of the communication device803can include a plurality of antenna panels804a-n, RF interfaces805a-n, time-frequency converters806a-n, a sensor panel807, a memory808, CFO/Doppler estimators809a-n, channel estimators810a-n, demodulators811a-n, and decoders812a-n. The communication device803includes at least one crystal oscillator (not shown) for generating frequencies. In an embodiment of the disclosure, the antenna panels804a-ncan use one crystal oscillator for generating frequencies. In another embodiment of the disclosure, each of the antenna panel (804a-n) can use individual crystal oscillators to generate frequencies.

The UE801can communicate with the base station802through at least one of a plurality of beams. Each of the beams can be characterized by a beam angle ‘0’, which specifies a direction along which the beamforming gain is highest for a received or transmitted signal. For the sake of illustration, 3 beams generated by each antenna panel804a-nhave been depicted.

Consider that at time instant T1, the UE801is using a beam B1generated by the antenna panel804afor communicating with the base station802. The beam B1can be referred to as serving beam, as B1is being used by the UE800for communicating with the base station802. Consider Omi is an angle between a unit vector along the direction of motion of the UE801and the serving beam B1.

The UE801can determine that B1is the serving beam and the angle θm1based on data obtained from the sensor panel807of the UE801. In an embodiment of the disclosure, the velocity of motion of the UE801can be based on data obtained from the sensor panel807. If the velocity of motion of the UE801is ‘v’, the Doppler estimate caused by motion of the UE801is given by Equation 1:

wherein ‘c’ is the velocity of light and fc is the centre frequency or frequency of operation of the base station802.

If ΔFOis the frequency offset caused due to differences in frequencies generated by crystal oscillators of the UE801and the base station802, the total frequency offset estimate is given by Equation 2:
DT1=ΔFO+Db1Equation 2

The UE801can determine Doppler shift estimate for any other beam based on the value of Db1. Consider that the UE801attempts to estimate the Doppler shift for a beam B2. It can be noted that B2can be a beam that generated either by the antenna panel804aor any of the other antenna panels804b-804n. Consider θ12as the angle between the B1and B2, and θm2as the angle between the unit vector along the direction of motion of the UE801and the serving beam B2, wherein θm2=θm1+θ12. The UE801can determine the angle between the beams B1and B2using the sensor panel807.

Consider (for simplicity) that the velocity of motion of the UE801remains constant, i.e., ‘v’, the Doppler estimate caused by motion of the UE801is given by Equation 3:

The total frequency offset estimate is given by: DT2=ΔFO+Db2. Based on the comparison of Db1and Db2, the following relation can be defined by Equation 4:

Consider that DTI is determined at time T1. The ΔFOcan be initially high (prior to or just after UE801registration/attach procedure). The ΔFOcan be estimated during initial cell search and operating crystal frequency at the UE801can be synchronized with the crystal frequency of the base station802. Once the registration/attach procedure is completed, the value of ΔFOmay not be significant. This is because ΔFOis characterized by the crystal clock drift, which can be periodically estimated and corrected. Hence, if the total frequency offset DT2is determined at time T2, it can be assumed that ΔFOis 0 at time T2. Therefore, Db2can be equal to DT2.

In an example, consider that the UE801performs a beam switching at time T2, wherein B2becomes the serving beam (from B1) at time T2after the beam switching procedure. The UE801can perform the beam switching after determining that the beam B2is optimal for communicating with the base station802. The UE801can determine the optimality of a beam based on angle of arrival of signals from the base station802. The UE801can determine the Doppler shift for the beam B2based on the Doppler shift for the beam B1.

The UE801can initially determine ΔFO, Db1, and Db2, which can be characterized by velocity of motion of the UE801and an angle of arrival of signals from the base station802to the UE801, using reference signals transmitted by the base station802. The impact of the Doppler shift can be less pronounced if the channel is slow varying. However, if the UE801is in motion, the impact of Doppler shift can be significant. The Doppler shift can degrade accuracy of channel estimation. Therefore, the UE801can utilize the reference signals for frequency offset tracking.

Once the UE801determines the frequency offset (ΔFOand DT) using reference signals, the UE801can utilize sensor data, collected by the sensor panel807, to estimate values of Doppler shift. When the UE801performs beam switching (for example: B1to B2), the current value of Doppler shift (DB2) can be determined based on the previous value of Doppler shift (DB1). The UE801can store the estimated values of Doppler shift in the memory808. The UE801can retrieve the previous values of Doppler shift from the memory808when estimating the current Doppler shift.

The UE801can perform frequency offset tracking by computing the Doppler shift, when the serving beam is B2(due to beam switching), based on the previously computed Doppler shift when the serving beam was B1. The UE801can, however, periodically determine the frequency offset (Once the UE801determines the frequency offset (ΔFOand DT) based on the reference signals for ensuring accuracy of ΔFOand Doppler shift estimation, and channel estimation.

The UE801, with information of previous active beam and relative direction of previous beam and current (serving) beam, can derive Doppler estimates when the current beam is used for communicating with the base station802. This allows the UE801to avoid independent computation of frequency offset using the reference signals transmitted by the base station802.

FIGS.8A and8Billustrate various units of the system800, but it is to be understood that other embodiments are not limited thereon. In other embodiments of the disclosure, the system800may include less or more number of units. Further, the labels or names of the units are used only for illustrative purpose and does not limit the scope of the invention. One or more units can be combined together to perform same or substantially similar function in the system800.

FIG.9is a flowchart900depicting a method for estimating Doppler shift for a beam using data collected by sensors according to an embodiment of the disclosure.

Referring toFIG.9, at operation901, the method includes determining whether there is frequency offset caused by variations in frequencies generated by crystal oscillators in a source device and a receiver device. This can be achieved by performing reference signal based estimation with a predetermined periodicity using a timer or alternatively, by estimating the Doppler shift upon reception of reference signals and applying correction if the estimated shift is beyond a predetermined threshold. The frequency offset can be characterized by the drift in clocks of the crystals in the source and receiver devices. The crystal clock drift can be periodically estimated and corrected. The variations can be removed by synchronizing the clocks of the crystals of the source and receiver devices.

If the variations in frequencies generated by crystal oscillators are present, the method includes, at operation902, performing time and frequency tracking (determining frequency offset) using reference signals. Consider that the UE801is acting as the receiver device and the base station802is acting as the source device. The base station802can send the reference signals to the UE801. The UE801can determine a frequency offset comprising of Doppler shift for a serving beam and variations in frequencies of crystal oscillators using the reference signals. The serving beam is the beam used by the UE801for communicating with the base station802. At operation903, the method includes nullifying the effects of frequency offset caused due to Doppler shift and variations in the crystal frequencies.

Once the variations in frequencies generated by crystal oscillators are nullified, the method includes, at operation904, obtaining data from the sensor panel807. The data comprises of an angle between a unit vector along a direction of motion of the receiver/source device with respect to the source/receiver device and the serving beam, and velocity of motion of the receiver/source device. If the UE801is considered as the receiver device and the base station is considered as the source device, the sensor panel807in the UE801can determine the angle between the unit vector along the direction of motion of the UE801and the serving beam. The sensor panel can also determine the velocity of motion of the UE801with respect to the base station802. As the base station802is considered to be fixed, the velocity refers to the velocity of movement of the UE801.

At operation905, the method includes estimating the Doppler shift for the serving beam based on the data obtained from the sensor panel807, i.e., angle between a unit vector along the direction of motion and the serving beam. The estimated value of Doppler shift can be stored in a memory808of the source/receiver device. The estimated value of Doppler shift can be used for estimating values of Doppler shift of all the other beams. Consider that the UE801performs beam switching after determining that a current serving beam (current serving beam is the beam which is determined as optimal after beam switching). The UE801may not utilize the reference signals broadcasted by the UE801to estimate the Doppler shift each time beam switching is performed (which can be performed frequently, if the UE801is in motion). This can minimize computational overhead.

If the source/receiver device includes multiple antenna panels, which are driven by a plurality of crystals, then an estimated value of Doppler shift corresponding to a beam generated by an antenna panel cannot be used for estimating a value of Doppler shift corresponding to a beam generated by another antenna panel. If the multiple antenna panels are driven by a single crystal source then an estimated value of Doppler shift corresponding to a beam generated by an antenna panel can be used for estimating a value of Doppler shift corresponding to a beam generated by another antenna panel.

The various actions in the flowchart900may be performed in the order presented, in a different order, or simultaneously. Further, in some embodiments of the disclosure, some actions listed inFIG.9may be omitted.

FIG.10is a flowchart1000depicting a method for estimating a velocity of a UE801using reference signals and sensor data, according to an embodiment of the disclosure.

Referring toFIG.10, at operation1001, the method includes estimating a first frequency offset comprising of a first Doppler shift and drift in frequencies generated by the crystals in the UE801and the base station802. The first frequency offset can correspond to a first beam, acting as a serving beam. The embodiments include determining the first frequency offset using reference signals received from the base station802.

The first frequency offset can be expressed as: D1=ΔFO+Db1, wherein ΔFOrepresents the drift in frequencies generated by the crystals in the UE801and the base station802, and Db1represents the first Doppler shift.

At operation1002, the method includes determining an angle between a unit vector along the direction of motion of the UE801and the first beam, acting as the serving beam. The angle can be represented as θm1. The angle θm1can be determined using sensor data obtained from the sensor panel807in the UE801.

At operation1003, the method includes performing a beam switching. The UE801can switch to a second beam on determining that the second beam is optimal for communicating with the base station802. The optimality can be based on gain of signals received from the base station802. The UE801can switch to the second beam from the first beam on determining that the gain of the signals received from the base station802is likely to be highest, if the second beam is used for communicating with the base station802, as compared to the first beam or any other beams. It is assumed that the direction of motion of the UE801is unchanged prior to and after beam switching.

At operation1004, the method includes estimating a second frequency offset comprising of a second Doppler shift and drift in frequencies generated by the crystals in the UE801and the base station802. The second frequency offset, corresponding to the second beam, can act as a serving beam after beam switching. The second frequency offset can be determined using the reference signals received from the base station802.

The second frequency offset can be expressed as: D2=ΔFO+Db2, wherein ΔFOrepresents the drift in frequencies generated by the crystals in the UE801and the base station802, and Db2represents the second Doppler shift. It can be assumed that the value of ΔFOis small as the drift in the crystal frequencies is frequently estimated and compensated.

At operation1005, the method includes determining an angle between the unit vector along the direction of motion of the UE801and the second beam, acting as the serving beam. The angle can be represented as θm2. The angle θm2can be determined using sensor data obtained from the sensor panel807in the UE801. The UE801can determine an angle between the first beam and the second beam using sensor data obtained from the sensor panel807. The angle between the first beam and the second beam can be represented as012. The angle θm2can be expressed as: θm2=θm1+θ12. The angle θm2is dependent on the beam angles (direction along which gain of a particular beam is maximum) of the first beam and the second beam. Thus, θm2can be derived based on 0 ml.

At operation1006, the method includes determining the velocity of the UE801based on the values of the first Doppler shift, the second Doppler shift, the angle between the unit vector and the first beam, the angle between the unit vector and the second beam, and the angle between the first beam and the second beam. The velocity of motion of the UE801, ‘v’ can be derived by Equation 5 through Equation 8:

The various actions in the flowchart1000may be performed in the order presented, in a different order, or simultaneously. Further, in some embodiments of the disclosure, some actions listed inFIG.10may be omitted.

FIG.11is a flowchart1100depicting a method for estimating Doppler shift of multiple receiver device beams using reference signals and sensor data, according to an embodiment of the disclosure. Consider that the UE801acts as the receiver device and the base station802acts as the source device. The base station802communicates with the UE801using a single beam and the UE801can communicate with the base station802using a plurality of beams.

Referring toFIG.11, at operation1101, the method includes determining whether there is a frequency offset caused by variations in frequencies generated by crystal oscillators in the UE801and the base station802. If it is determined that the variations in the frequencies generated by crystal oscillators are present, the method includes, at operation1102, estimating the variations using the reference signals received from the base station802. At operation1103, the method includes nullifying the frequency offset caused by the variations in the frequencies generated by crystal oscillators of the UE801and the base station802.

Once it is determined that the crystal oscillators in the UE801and the base station802have been synchronized by nullifying drifts in the crystal clocks causing the variations in the frequencies generated by the UE801and the base station802, the method includes, at operation1104, determining whether Doppler shift for the serving beam, or any of the plurality of beams at the UE801, has been estimated. If it is determined that the Doppler shift of at least one of the beams at the UE801have not been estimated, the method includes, at operation1105, estimating the Doppler shift of the serving beam using the reference signals.

At operation1106, the method includes estimating the values of Doppler shift of each of the plurality of beams based on the value of Doppler shift of the serving beam. Once the value of Doppler shift corresponding to the serving beam has been estimated, the UE801can determine the values of the Doppler shifts corresponding to each of the plurality of the beams based on sensor data (velocity of motion of the UE, angles between the serving beam and each of the plurality of beams, and angle between the unit vector in the direction of motion of the UE801and the serving beam) and the estimated value of the Doppler shift corresponding to the serving beam.

The various actions in the flowchart1100may be performed in the order presented, in a different order, or simultaneously. Further, in some embodiments of the disclosure, some actions listed inFIG.11may be omitted.

FIG.12is a flowchart1200depicting a method for estimating Doppler shift of multiple receiver device beams using reference signals and sensor data, according to an embodiment of the disclosure. Consider that the UE801acts as the receiver device and the base station802acts as the source device. The base station802communicates with the UE801using a plurality of transmitter beams and the UE801can communicate with the base station802using a plurality of receiver beams.

Referring toFIG.12, at operation1201, the method includes determining whether there is a frequency offset caused by variations in frequencies generated by crystal oscillators in the UE801and the base station802. If it is determined that there are variations in the frequencies generated by crystal oscillators, the method includes, at operation1202, estimating the variations using the reference signals received from the base station802. At operation1203, the method includes nullifying the frequency offset caused by the variations in the frequencies generated by crystal oscillators of the UE801and the base station802.

Once it is determined that the crystal oscillators in the UE801and the base station802have been synchronized by nullifying drifts in the crystal clocks causing the variations in the frequencies generated by the UE801and the base station802, the method includes, at operation1204, determining whether value of Doppler shift of one of the plurality of receiver beams, corresponding to a current transmitter beam, has been estimated. If the values of Doppler shift of none of the plurality of receiver beams have been estimated, the method includes, at operation1205, determining whether value of Doppler shift of one of a plurality of receiver beams, corresponding to a previous transmitter beam has been estimated.

If it is determined that the value of Doppler shift of one of the receiver beams corresponding to the previous transmitter beam have been estimated, the method includes, at operation1208, estimating the values of Doppler shift of each of the plurality of receiver beams corresponding to the previous transmitter beam based on the value of Doppler shift of the one of the receiving beams corresponding to the previous transmitter beam and the sensor data. However, prior to the estimation (at operation1208), it needs to be ensured that the type of QCL of the previous transmitter beam and the type of QCL of the current transmitter beam is either of the type A, B, or C. This is because, the value of Doppler shift of the plurality of receiver beams corresponding to the previous transmitter beam cannot be used for estimating the value of Doppler shift of a receiver beam corresponding to the current transmitter if the types of QCL of the previous transmitter beam and the current transmitter beam is not one of the types A, B, or C. At operation1209, the method includes estimating the values of Doppler shift of each of the receiver beams corresponding to the current transmitter beam based on the estimated values of Doppler shift of the receiver beams corresponding to the previous transmitter beam and the sensor data.

If it is determined that the value of Doppler shift of one of the receiver beams corresponding to the previous transmitter beam has not been estimated, the method includes, at operation1206, estimating value of Doppler shift of the serving beam (serving beam corresponds to the current transmitter beam) using reference signals received from the base station802.

At operation1207, the method includes estimating the values of Doppler shift of each of the plurality of receiver beams corresponding to the current transmitter beam based on the estimated value of Doppler shift of the serving beam. Once the value of Doppler shift corresponding to the serving beam has been estimated, the values of the Doppler shifts corresponding to each of the plurality of the receiver beams corresponding to the current transmitter beam can be estimated based on the sensor data and the estimated value of the Doppler shift corresponding to the serving beam.

If it is determined (at operation1204) that the value of Doppler shift of one of the plurality of receiver beams corresponding to the current transmitter beam has been estimated, the Doppler shift of each of the plurality of receiver beams corresponding to the current transmitter beams can be estimated (operation1207) based on the estimated value of Doppler shift of one of the plurality of receiver beams corresponding to the current transmitter beam. However, it is to be noted that the types of QCL of the current transmitter beam and the previous transmitter beam are either of type A, B, or C.

The various actions in the flowchart1200may be performed in the order presented, in a different order, or simultaneously. Further, in some embodiments of the disclosure, some actions listed inFIG.12may be omitted.

FIG.13is a sequence diagram depicting estimation of Doppler shift of a serving beam in an event of beam switching by a UE according to an embodiment of the disclosure. Consider that the base station802is a gNB.

Referring toFIG.13, at operation1305, The UE801can receive initial synchronization signals and system information from the gNB802. Thereafter, in operation1310, the gNB802can send reference signals, such as synchronization signal block (SSB) and demodulation reference signal (DMRS). In operation1315, The UE801can estimate the total frequency offset, comprising of drifts in frequencies generated by the crystal oscillators in the UE801and the gNB802, and the Doppler shift; using the reference signals. The UE801can also estimate the Doppler shift of the serving beam based on the sensor data. In operation1320, the UE can receive/transmit a physical random access channel (PRACH) from/to the gNB. In operation1325, the UE can receive a physical downlink control channel (PDCCH), which is followed by a physical downlink shared channel (PDSCH). As depicted in operation1325and in operation1330ofFIG.13, the PDCCH and PDSCH messages are received by the UE in different beams. The PDSCH is received in a different beam because the UE had performed a beam switch. In operation1335, the UE can receive at least one of DMRS, PT-RS, CSI-RS or TRS. In operation1340, the UE can estimate the carrier frequency offset (CFO) and Doppler shift based on a previously active beam. In operation1345, the UE can receive at least one of CSI-RS or TRS from the gNB. In operation1350, the UE can switch default Rx beam. In operation1355, the UE can receive at least one of CSI-RS or TRS from the gNB. In operation1360, the UE re-estimates the UE can estimate the carrier frequency offset (CFO) and Doppler shift based on a previously active beam.

The UE801receives a physical downlink control channel (PDCCH), which is followed by a physical downlink shared channel (PDSCH). As depicted inFIG.13, the PDCCH and PDSCH messages are received by the UE801in different beams. The PDSCH is received in a different beam because the UE801had performed a beam switch, which is performed either because the best receiver beam is updated based on reference signal based measurements or because the transmitter beam for PDSCH is different, as indicated by PDCCH. Once the beam switching is performed, the current beam is considered as the serving beam. The UE801can estimate the Doppler shift corresponding to the current beam (serving beam) based on the value of Doppler shift of the previous beam (previous serving beam), which was estimated based on the reference signals.

FIG.14is a sequence diagram depicting estimation of Doppler shift of a serving beam in an event of beam switching by a UE for performing measurement of signals of neighboring cells according to an embodiment of the disclosure.

Referring toFIG.14, the UE801can perform measurements of signals received from the neighboring gNB (cell) for target cell selection during a handover procedure, or when the UE801attempts to connect to a neighboring cell to receive some service. Consider that the UE801acts as a receiver device. The UE801can perform a receiver beam sweep, wherein the UE801can perform measurement of the signals received from the neighboring gNB using all the beams. Initially, the UE801can perform the measurements using a first beam. Thereafter, the UE801can perform beam switching and perform signal measurement using a second beam. Similarly, the UE801perform measurement of the signals received from the neighboring gNB using all the beams available to the UE801. During each beam switch, the UE801can estimate the Doppler shift for a beam using the value of Doppler shift estimated for a previous beam. The UE801can similarly measure the signals received from other neighboring gNBs to enable faster switching.

FIG.15is a sequence diagram depicting estimation of Doppler shift of a plurality of beams, receiving independent physical downlink control channel (PDCCH) messages based on an estimated Doppler shift of one of the plurality of beams according to an embodiment of the disclosure.

The UE801can utilize multiple beams to communicate with the gNB802. The UE801can receive individual PDCCH messages through each of the beams.

Referring toFIG.15, the UE801can receive three independent PDCCH messages, along with resource configurations and periodicity configurations using three beams, viz., B1, B2, and B3beam. The PDCCH messages can be received with same or different periodicities in each of the different beams. The UE801can estimate the Doppler shift of one of the beams, say B1, using reference signals. If the QCL of the beams B1, B2, and B3, are of type A, B, or C, the UE801can utilize the estimate of Doppler shift of beam B1and sensor data to estimate the Doppler shift of the beam B2and B3, wherein the sensor data can include velocity of the UE801, and an angle between the unit vector along the direction of motion of the UE801and the direction of the beams.

The gNB802can initially send a first PDCCH message and the UE801can receive the first PDCCH message using the beam B1. The UE801can estimate the Doppler shift for the beam B1using the reference signals. Thereafter, the gNB802can send a second PDCCH message and a third PDCCH message. Once reception of the second and third PDCCH messages is initiated, the UE801can estimate the values of Doppler shift for the beams B2and B3using the estimated Doppler shift for the beam B1.

FIG.16is a sequence diagram depicting estimation of Doppler shift of a plurality of beams, receiving random access response (RAR) messages from a gNB802, based on an estimated Doppler shift of one of the plurality of beams, according to embodiments as disclosed herein.

Referring toFIG.16, once the UE801registers with the gNB802and is granted access to resources, the UE801(in CONNECTED state) can trigger random access. The UE801can perform physical random access channel (PRACH) preamble transmissions (msg-1) multiple times within a RAR window corresponding to the first transmission. Once the RAR response is received using the serving beam, the UE801can estimate Doppler shift using reference signals for the serving beam and decode the RAR response. Thereafter, the UE801can monitor for msg-2 or RAR receptions along different beams. In such scenarios, the UE801can estimate the values of Doppler shift for the different beams based on the Doppler shift estimated for the previous serving beam and sensor data. Further, when msg-1 transmission is attempted using different transmit beams, which may be indicated by the TCI-State configurations, the Doppler shift estimation during first RAR reception needs to be performed using the reference signals. For subsequent RAR receptions, the Doppler estimate can be derived based on the previous estimate of Doppler shift (estimated during reception of the first RAR) and sensor data.

FIG.17is a block diagram illustrating an electronic device (for example, one or more UEs)1601in a network environment according to various embodiments.

Referring toFIG.17, an electronic device1701in a network environment1700may communicate with an electronic device1702via a first network1798(e.g., a short-range wireless communication network), or an electronic device1704or a server1708via a second network1799(e.g., a long-range wireless communication network). According to an embodiment of the disclosure, the electronic device1701may communicate with the electronic device1704via the server1708. According to an embodiment of the disclosure, the electronic device1701may include a processor1720, memory1730, an input device1750, a sound output device1755, a display device1760, an audio module1770, a sensor module1776, an interface1777, a haptic module1779, a camera module1780, a power management module1788, a battery1789, a communication module1790, a subscriber identification module (SIM)1796, or an antenna module1797. In some embodiments of the disclosure, at least one (e.g., the display device1760or the camera module1780) of the components may be omitted from the electronic device1601, or one or more other components may be added in the electronic device1601. In some embodiments of the disclosure, some of the components may be implemented as single integrated circuitry. For example, the sensor module1776(e.g., a fingerprint sensor, an iris sensor, or an illuminance sensor) may be implemented as embedded in the display device1760(e.g., a display).

The processor1720may execute, for example, software (e.g., a program1740) to control at least one other component (e.g., a hardware or software component) of the electronic device1701coupled with the processor1720, and may perform various data processing or computation. According to one embodiment of the disclosure, as at least part of the data processing or computation, the processor1720may load a command or data received from another component (e.g., the sensor module1776or the communication module1790) in volatile memory1732, process the command or the data stored in the volatile memory1632, and store resulting data in non-volatile memory1734(e.g., an internal memory1736or an external memory1738). According to an embodiment of the disclosure, the processor1720may include a main processor1721(e.g., a central processing unit (CPU) or an application processor (AP)), and an auxiliary processor1723(e.g., a graphics processing unit (GPU), an image signal processor (ISP), a sensor hub processor, or a communication processor (CP)) that is operable independently from, or in conjunction with, the main processor1721. Additionally or alternatively, the auxiliary processor1723may be adapted to consume less power than the main processor1721, or to be specific to a specified function. The auxiliary processor1723may be implemented as separate from, or as part of the main processor1721.

The auxiliary processor1723may control at least some of functions or states related to at least one component (e.g., the display device1760, the sensor module1776, or the communication module1790) among the components of the electronic device1701, instead of the main processor1721while the main processor1721is in an inactive (e.g., sleep) state, or together with the main processor1721while the main processor1721is in an active state (e.g., executing an application). According to an embodiment of the disclosure, the auxiliary processor1723(e.g., an image signal processor or a communication processor) may be implemented as part of another component (e.g., the camera module1780or the communication module1790) functionally related to the auxiliary processor1723.

The memory1730may store various data used by at least one component (e.g., the processor1720or the sensor module1776) of the electronic device1701. The various data may include, for example, software (e.g., the program1740) and input data or output data for a command related thereto. The memory1730may include the volatile memory1732or the non-volatile memory1634.

The program1740may be stored in the memory1730as software, and may include, for example, an operating system (OS)1742, middleware1744, or an application1746.

The input device1750may receive a command or data to be used by other component (e.g., the processor1720) of the electronic device1701, from the outside (e.g., a user) of the electronic device1601. The input device1750may include, for example, a microphone, a mouse, a keyboard, or a digital pen (e.g., a stylus pen).

The sound output device1755may output sound signals to the outside of the electronic device1701. The sound output device1755may include, for example, a speaker or a receiver. The speaker may be used for general purposes, such as playing multimedia or playing record, and the receiver may be used for an incoming calls. According to an embodiment of the disclosure, the receiver may be implemented as separate from, or as part of the speaker.

The display device1760may visually provide information to the outside (e.g., a user) of the electronic device1701. The display device1760may include, for example, a display, a hologram device, or a projector and control circuitry to control a corresponding one of the display, hologram device, and projector. According to an embodiment of the disclosure, the display device1760may include touch circuitry adapted to detect a touch, or sensor circuitry (e.g., a pressure sensor) adapted to measure the intensity of force incurred by the touch.

The audio module1770may convert a sound into an electrical signal and vice versa. According to an embodiment of the disclosure, the audio module1770may obtain the sound via the input device1750, or output the sound via the sound output device1755or a headphone of an external electronic device (e.g., an electronic device1702) directly (e.g., wiredly) or wirelessly coupled with the electronic device1701.

The interface1777may support one or more specified protocols to be used for the electronic device1701to be coupled with the external electronic device (e.g., the electronic device1702) directly (e.g., wiredly) or wirelessly. According to an embodiment of the disclosure, the interface1777may include, for example, a high definition multimedia interface (HDMI), a universal serial bus (USB) interface, a secure digital (SD) card interface, or an audio interface.

A connecting terminal1778may include a connector via which the electronic device1701may be physically connected with the external electronic device (e.g., the electronic device1702). According to an embodiment of the disclosure, the connecting terminal1778may include, for example, a HDMI connector, a USB connector, a SD card connector, or an audio connector (e.g., a headphone connector).

The camera module1780may capture a still image or moving images. According to an embodiment of the disclosure, the camera module1780may include one or more lenses, image sensors, image signal processors, or flashes.

The power management module1788may manage power supplied to the electronic device1701. According to one embodiment of the disclosure, the power management module1788may be implemented as at least part of, for example, a power management integrated circuit (PMIC).

The battery1789may supply power to at least one component of the electronic device1701. According to an embodiment of the disclosure, the battery1789may include, for example, a primary cell which is not rechargeable, a secondary cell which is rechargeable, or a fuel cell.

The communication module1790may support establishing a direct (e.g., wired) communication channel or a wireless communication channel between the electronic device1701and the external electronic device (e.g., the electronic device1702, the electronic device1704, or the server1708) and performing communication via the established communication channel. The communication module1790may include one or more communication processors that are operable independently from the processor1720(e.g., the application processor (AP)) and supports a direct (e.g., wired) communication or a wireless communication. According to an embodiment of the disclosure, the communication module1790may include a wireless communication module1792(e.g., a cellular communication module, a short-range wireless communication module, or a global navigation satellite system (GNSS) communication module) or a wired communication module1794(e.g., a local area network (LAN) communication module or a power line communication (PLC) module). A corresponding one of these communication modules may communicate with the external electronic device via the first network1798(e.g., a short-range communication network, such as Bluetooth™, wireless-fidelity (Wi-Fi) direct, or infrared data association (IrDA)) or the second network1799(e.g., a long-range communication network, such as a cellular network, the Internet, or a computer network (e.g., LAN or wide area network (WAN)). These various types of communication modules may be implemented as a single component (e.g., a single chip), or may be implemented as multi components (e.g., multi chips) separate from each other. The wireless communication module1792may identify and authenticate the electronic device1701in a communication network, such as the first network1798or the second network1799, using subscriber information (e.g., international mobile subscriber identity (IMSI)) stored in the subscriber identification module1796.

The antenna module1797may transmit or receive a signal or power to or from the outside (e.g., the external electronic device) of the electronic device1701. According to an embodiment of the disclosure, the antenna module1797may include an antenna including a radiating element including a conductive material or a conductive pattern formed in or on a substrate (e.g., a PCB). According to an embodiment of the disclosure, the antenna module1797may include a plurality of antennas. In such a case, at least one antenna appropriate for a communication scheme used in the communication network, such as the first network498or the second network1799, may be selected, for example, by the communication module1790(e.g., the wireless communication module1792) from the plurality of antennas. The signal or the power may then be transmitted or received between the communication module1790and the external electronic device via the selected at least one antenna. According to an embodiment of the disclosure, another component (e.g., a radio frequency integrated circuit (RFIC)) other than the radiating element may be additionally formed as part of the antenna module1797.

According to an embodiment of the disclosure, commands or data may be transmitted or received between the electronic device1701and the external electronic device1704via the server1708coupled with the second network1799. Each of the electronic devices1702and1704may be a device of a same type as, or a different type, from the electronic device1701. According to an embodiment of the disclosure, all or some of operations to be executed at the electronic device1701may be executed at one or more of the external electronic devices1702,1704, or1708. For example, if the electronic device401should perform a function or a service automatically, or in response to a request from a user or another device, the electronic device1701, instead of, or in addition to, executing the function or the service, may request the one or more external electronic devices to perform at least part of the function or the service. The one or more external electronic devices receiving the request may perform the at least part of the function or the service requested, or an additional function or an additional service related to the request, and transfer an outcome of the performing to the electronic device401. The electronic device1701may provide the outcome, with or without further processing of the outcome, as at least part of a reply to the request. To that end, a cloud computing, distributed computing, or client-server computing technology may be used, for example.