System and method for high-speed Doppler compensation in a cellular environment

Abstract

The present invention discloses a method and apparatus for calculating and compensating for Doppler shift in a high-speed environment. When in a high-speed environment, the Doppler shift on the transmitted RF signal may become extremely large, which may make it difficult or even impossible for the receiving device to accurately decipher the signal. Therefore, the embodiments of the present disclosure describe how tracking reference signals can be transmitted from multiple transmission / reception points and processed by the UE. For example, the TRS transmitted from the TRP can be enhanced to allow TRS information from two different TRPs. Additionally or alternatively, a flag can be set within the TRS information to identify it as originating from the first TRP or the second TRP. In addition, the UE can calculate the Doppler shift information and report the information back to the base station in a report message such as an SRS message. In this way, the base station can pre-compensate for the Doppler shift.

Description

Technical Field

[0001] Various aspects may generally relate to the field of wireless communications. Summary of the Invention

[0002] Some embodiments include apparatus, methods, and computer program products for implementing Doppler compensation in a high-speed cellular communication environment, such as on a high-speed train. In such high-speed systems, it is typically required that the UE track tracking reference signals (TRS) from multiple transmission and reception points (TRPs), which is currently not allowed in the Third Generation Partnership Project (3GPP) specifications. Specifically, due to the rate of the user equipment (UE), these TRSs will each experience very different Doppler drifts. Therefore, in order to allow the UE to receive these signals and perform accurate Doppler measurements, the TRS can be modified. In one such embodiment, the CORESETPoolIndex variable within the TRS can be configured to notify whether the TRS is being received from the first TRP or the second TRP. In addition, the TRS is typically transmitted in two consecutive time slots. Therefore, in another embodiment, the network configures the first time slot to include the TRS from the first TRP and the second time slot to include the TRS from the second TRP. In any of these embodiments, the network requires a mechanism to notify the UE of the advanced channel estimation configuration. In an embodiment, as described above, this may be done via radio resource control (RRC), MAC-CE, or via configuration of the TRS.

[0003] In one embodiment, a user equipment is disclosed that includes a transceiver configured to transmit and receive signals between a first transmission-reception point (TRP) and a second TRP and one or more processors. The one or more processors are configured to: receive reference signals from a plurality of TRPs via the transceiver, each reference signal including an identifier; determine an originating TRP as one of the first TRP or the second TRP based on the identifier; calculate a Doppler shift associated with each of the first TRP and the second TRP based on the determination; coherently combine the plurality of reference signals based on the calculation; and transmit an uplink signal to at least one of the first TRP or the second TRP via the transceiver based on the combined plurality of reference signals.

[0004] In one embodiment, the identifier is the CORESETPoolIndex variable.

[0005] In one embodiment, a CORESETPoolIndex value of 0 identifies the first TRP as the originating TRP, and a CORESETPoolIndex value of 1 identifies the second TRP as the originating TRP.

[0006] In one embodiment, the absence of the CORESETPoolIndex variable in the received reference signal identifies the first TRP as the originating TRP.

[0007] In one embodiment, the reference signal is included within a corresponding tracking reference signal (TRS) transmitted from the TRP.

[0008] In one embodiment, the reference signal is triggered using downlink control information (DCI) received in a CORESET configured with a corresponding CORESETPoolIndex.

[0009] In one embodiment, the reference signal includes a first pair of TRS symbols in a first time slot associated with a first TRP, and a second pair of TRS symbols in a second time slot associated with a second TRP, wherein the first time slot and the second time slot are consecutive.

[0010] In one embodiment, a user equipment for reporting Doppler shift to a transmission-reception point (TRP) is disclosed, the user equipment comprising a transceiver configured to transmit and receive signals with a first TRP and a second TRP, and one or more processors. The one or more processors are configured to: receive a reference signal from at least one of the first TRP and the second TRP; estimate a Doppler shift associated with each of the first TRP and the second TRP based on the received reference signal; generate a report signal based on the estimated Doppler shift; and transmit the report signal to a gNB via the transceiver.

[0011] In one embodiment, the one or more processors are further configured to determine a reporting scheme based on the estimated Doppler shift.

[0012] In one embodiment, the report signal includes a signed difference value corresponding to the difference between the Doppler shift associated with the first TRP and the Doppler shift associated with the second TRP.

[0013] In one embodiment, the report signal includes a first Doppler shift associated with the first TRP and a second Doppler shift associated with the second TRP.

[0014] In one embodiment, the report signal includes an unsigned absolute value of a difference between a first Doppler shift associated with a first TRP and a second Doppler shift associated with a second TRP.

[0015] In one embodiment, the report signal includes: a first absolute Doppler shift associated with a first TRP, and a difference corresponding to the difference between the absolute first Doppler shift and an absolute second Doppler shift associated with a second TRP, together with the signs of the first Doppler shift and the second Doppler shift.

[0016] In one embodiment, the reporting signal is a channel state information (CSI) message, and wherein the Doppler shift information is encoded into a CSI report configured by CSI-ReportConfig.

[0017] In one embodiment, a transmission reception point (TRP) for compensating for Doppler shift in a high-speed environment is disclosed, the transmission reception point comprising a transceiver configured to communicate with a user equipment (UE) and one or more processors. The one or more processors are configured to: receive a notification from a backend regarding whether the TRP is a first TRP or a second TRP; generate a tracking reference signal based on the received notification; and transmit the tracking reference signal to the UE, wherein the tracking reference signal includes an identifier based on the received notification.

[0018] In one embodiment, the identifier is the value of a variable within the tracking reference signal.

[0019] In one embodiment, the variable is CORESETPoolIndex, and the one or more processors are further configured to: set the value of the variable to 0 in response to the received notification indicating that the TRP is the first TRP, and set the value of the variable to 1 in response to the received notification indicating that the TRP is the second TRP.

[0020] In one embodiment, the one or more processors are further configured to: receive a report signal from the UE, the report signal including Doppler shift information associated with the TRP; calculate precompensation based on the received Doppler shift information; and generate a signal transmission to the UE based on the calculated precompensation.

[0021] In one embodiment, precompensation increases the frequency of signal transmission in response to the Doppler shift information indicating a negative frequency shift, and wherein precompensation decreases the frequency of signal transmission in response to the Doppler shift information indicating a positive frequency shift.

[0022] In one embodiment, the one or more processors are further configured to receive a dual TRP flag from the backend, and in response to receiving the dual TRP flag, generating the tracking reference signal includes transmitting reference information in only one of the first time slot or the second time slot of the tracking reference signal based on the received notification.

[0023] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of authorized use should be clearly stated to users. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 An exemplary wireless communication environment according to one aspect of the present disclosure is shown;

[0025] Figure 2 illustrates an exemplary Doppler effect of a transmitted signal within a wireless communication environment according to one aspect of the present disclosure;

[0026] Figure 3 shows an exemplary tracking reference transmission signal according to one aspect of the present disclosure;

[0027] Figure 4 A flowchart illustrating an exemplary method for a UE to track TRSs from multiple TRPs according to one aspect of the present disclosure is shown;

[0028] Figure 5 A flowchart illustrating an exemplary method for compensating for Doppler shift in user equipment according to one aspect of the present disclosure is shown;

[0029] Figure 6 A flowchart illustrating an exemplary method for pre-compensating Doppler shift by a base station according to one aspect of the present disclosure is shown;

[0030] Figure 7 shows a block diagram representation of an exemplary general-purpose computer system capable of implementing certain aspects of the present disclosure;

[0031] Figure 8 A flowchart illustrating an exemplary method for pre-compensating Doppler shift through TRP according to one aspect of the present disclosure is shown;

[0032] Figure 9 A flowchart illustrating an exemplary method for pre-compensating Doppler shift by TRP according to one aspect of the present disclosure is shown; and

[0033] Figure 10 A block diagram of an example system of an electronic device implementing Doppler shift compensation according to aspects of the present disclosure is shown. DETAILED DESCRIPTION

[0034] The Tracking Reference Signal (TRS) plays a crucial role, especially at mmWave frequencies, to minimize time and frequency errors that may occur due to Doppler shift.

[0035] In high-speed systems, UEs are typically required to track TRSs from multiple transmission and reception points (TRPs). Specifically, due to the speed of the user equipment (UE), the UE must be able to quickly transition from one TRP to another, and sometimes communicate with both simultaneously.

[0036] Additionally, when the UE is traveling at a sufficiently high speed, there may be significant Doppler shift between the two TRSs. Doppler shift occurs when the transmitter of a signal moves relative to the receiver. This relative motion shifts the frequency of the signal, causing it to differ at the receiver from that at the transmitter. In other words, the frequency perceived by the receiver is different from the frequency originally transmitted by the transmitter. When the Doppler shift exceeds 1 kHz, performance degradation becomes more severe.

[0037] In high-speed systems, such as those on high-speed trains, UEs may travel at speeds exceeding 500 km / h. In high-frequency bands, such as approximately 5-6 GHz, this speed results in Doppler shifts of up to 2 kHz in signals received from a given TRP. This significantly degrades channel capabilities or makes accurate channel estimation by the UE extremely challenging. Therefore, a system is needed that can accurately estimate the channel even when moving at high speeds between two different TRPs.

[0038] Figure 1 An exemplary wireless communication environment 100 is shown according to an embodiment. Figure 1 As shown, environment 100 includes multiple TRPs 110, 112, and 114 located near a travel path of UE 102. Figure 1 In the example of FIG, UE 102 is located on a fast-moving vehicle, such as a high-speed train (HST) 105. Although the specific implementations described herein are with respect to a high-speed train, other high-speed environments are also contemplated. Therefore, all such high-speed environments will be collectively referred to as high-speed trains (HSTs) in this disclosure.

[0039] As UE 102 travels through environment 100, it will pass within the transmission range of various TRPs 110, 112, and 114. Within the range of a first TRP 110, UE 102 will receive a TRS 120 associated with the first TRP 110. Within the range of a second TRP 112, UE 102 will receive a TRS 130 associated with the second TRP 112. Finally, within the range of a third TRP 114, UE 102 will receive a TRS 140 associated with the third TRP 114.

[0040] When the UE travels between two consecutive TRPs, the UE 102 according to an embodiment of the present disclosure receives TRS from each of the nearby TRPs. Figure 1As shown, when the UE travels between the first TRP 110 and the second TRP 112, the UE 102 receives both TRS 120 and TRS 130 as TRS1 and TRS2, respectively. Similarly, when the UE 102 travels between the second TRP 112 and the TRP 114, the UE 102 receives both TRS 130 and TRS 140 as TRS2 and TRS1, respectively.

[0041] Figure 2 2 illustrates an exemplary Doppler effect on a transmitted signal within a wireless communication environment 200 according to an embodiment. Figure 2 In the example shown, HST 205 is traveling to the right and is located, for example, between TRP 110 and TRP 112. When traveling at a high rate of speed, signal transmission 220a from TRP 110 (located behind the train) will appear to be stretched toward the UE located on HST 205. Due to the Doppler shift caused by the UE's speed of movement, this will result in an apparent frequency lower than the frequency originally transmitted from TRP 110. Simultaneously, signal transmission 220b from TRP 112 (located in front of the train) will appear to be compressed toward the UE located on HST 205. Due to the Doppler shift caused by the UE's speed of movement, this will result in an apparent frequency higher than the frequency originally transmitted from TRP 112.

[0042] To address these issues, the network can be configured to pre-compensate for Doppler shift, provided the network knows the actual amount of Doppler shift occurring from each TRP. By pre-compensating for these shifts, the two signals (TRS from the first TRP and TRS from the second TRP) arrive at the UE without any additional shift and can therefore be coherently combined. This provides maximum channel capacity.

[0043] TRS Enhancement

[0044] In one embodiment, compensation for Doppler drift can be achieved by enhancing the TRS configuration. To do this, the UE should be able to track TRSs from two different TRPs. Therefore, in one embodiment, for any non-zero power (NZP) CSI-RS resource set (NZP-CSI-RS-ResourceSet) in which TRSs are configured, the variable CORESETPoolIndex can also be configured. When the variable is set to 0 (CORESETPoolIndex=0), or when the variable does not exist, the UE interprets it as meaning that the TRS is transmitted from the first TRP. Alternatively, when the variable is set to 1 (CORESETPoolIndex=1), the UE interprets it as meaning that the TRS is transmitted from the second TRP.

[0045] In another embodiment, downlink control information (DCI) may indicate to the UE which TRP is appropriate. For example, for DCI decoded in the CORESETPool associated with CORESETPoolIndex=0, the UE identifies the triggered aperiodic tracking reference signal (AP-TRS) and the corresponding periodic tracking reference signal (P-TRS) as transmitted from the first TRP. Alternatively, for DCI decoded in the CORESETPool associated with CORESETPoolIndex=1, the UE identifies the triggered AP-TRS and the corresponding P-TRS as transmitted from the second TRP.

[0046] Figure 3 An exemplary TRS transmission signal 300 is shown according to an exemplary embodiment. For ease of explanation, Figure 3 The transmission signal 300 shown includes two signal time slots 310 and 320. As is known, a typical TRS is transmitted across four OFDM symbols in two consecutive time slots 310 and 320. Traditionally, this would result in symbols 315a, 315b in the first time slot 310 and symbols 325a, 325b in the second time slot being dedicated to a single TRS. In other words, by setting trs-info, the NZP-CSI-RS-ResourceSet can be configured as a TRS with four periodic NZP CSI-RS resources in two consecutive time slots, with two periodic NZP CSI-RS in each time slot.

[0047] In one embodiment, when a separate information element (IE) is indicated, the IE is added to the non-zero power (NZP) CSI-RS-ResourceSet to enable HST TRS. In this scenario, the first two NZP CSI-RS resources transmitted in the first time slot correspond to TRS from the first TRP, and the second two NZP CSI-RS resources transmitted in the second time slot correspond to TRS from the second TRP, where this configuration is referred to herein as 2-TRS. If applicable, the TRS resources in the first time slot are quasi-co-located (QCL) with QCL type A and QCL type D. Similarly, the TRS resources in the second time slot are quasi-co-located (QCL) with QCL type A and QCL type D. As is known, QCL type A describes symbols transmitted with the same delay spread, and QCL type D describes symbols transmitted with the same spatial beam. It is worth noting that there is no QCL assumption between NZP CSI-RS resources transmitted in different time slots.

[0048] Because the two time slots are typically used to support a single TRS, replacing this scheme with supporting TRS from two TRPs may result in errors. Specifically, considering that only half the amount of information is provided, the UE may not be able to accurately estimate the Doppler. In other words, although the 2-TRS configuration may be sufficient for FR2 (frequency band from 24.25GHz to 52.6GHz), it may not be sufficient for FR1 (sub-6GHz frequency band). Therefore, in one embodiment, conditions are set for 2-TRS transmission to ensure that TRS is transmitted widely enough. Specifically, in the embodiment, subject to UE capabilities, the network can configure 2-TRS for FR2 at any time. However, when the configured TRS occupies at least 52 physical resource blocks (PRBs) in the frequency domain, the network can only configure 2-TRS for FR1.

[0049] It is worth noting that the above HST configuration consumes bandwidth and computing power unnecessarily and may result in poor overall performance when the UE is not experiencing HST conditions. Therefore, in an embodiment, a mechanism is provided for triggering or signaling the HST mode between the UE and the network. In one such embodiment, the HST mode may be configured via radio resource control (RRC) or medium access control control element (MAC-CE). In a preferred embodiment, the HST configuration is explicitly signaled in the RRC, for example in the PDSCH-Config. However, in an alternative embodiment, the HST may be implicitly signaled to the UE, such as by implicitly mapping the TRS to the TRP in a logical manner, such as via CORESETPoolIndex, as described above.

[0050] SRS detection enhancement

[0051] Sounding is the method by which the TRP determines the channel quality of the uplink path for a given UE. Sounding is currently performed via a Sounding Reference Signal (SRS) transmitted by the UE and configured by RRC. As discussed above, in the case of HST, if the TRP wants to pre-compensate for Doppler shift, the TRP needs to first estimate the Doppler shift. In one embodiment, a new SRS configuration is disclosed with the usage set to "HST". In this embodiment, the transmission of the SRS is frequency locked based on the TRS so that the TRP can determine on which frequency the UE is transmitting the SRS. This allows the TRP to accurately determine the Doppler shift.

[0052] This can also be achieved in other ways. For example, in one embodiment, the SRS is transmitted using the same beam used to receive the TRS. In another embodiment, the SRS is transmitted using power control based on the path loss estimated from the TRS. This allows the UE to estimate the phase change between the transmitted SRS and the SRS after the Doppler shift. In this embodiment, the TRS can be used by the UE to derive the uplink power control and the uplink frequency for transmitting the SRS, so that the TRP can estimate the absolute Doppler shift. Specifically, the SRS is transmitted using a frequency estimate from the TRS and / or the SRS is transmitted using power control based on the path loss estimated from the TRS.

[0053] In one embodiment, TRS can be used as a spatial relation reference signal for SRS transmission. When used in this manner, the SRS is transmitted using the frequency estimate from the TRS and using the same beam used for TRS reception.

[0054] In the above embodiment, the path loss reference signal and the spatial relationship reference signal should be configured consistently with each other. This ensures that the power calculation is accurate. However, this requires two different reference signals, one for which beam to transmit and the other for path loss estimation. Therefore, in one embodiment, if a TRS is configured as a path loss reference signal for an SRS, the same TRS should be configured for a spatial relationship reference signal for the same SRS. Similarly, when a TRS is configured for a spatial relationship reference signal for an SRS, the same TRS should be configured as a path loss reference signal for the same SRS.

[0055] Although the above concerns SRS, it is desirable to be able to distinguish which SRS corresponds to which TRP. This is because, as mentioned above, there are two TRPs and two TRSs. In one embodiment, this distinction is made based on aperiodic SRS (AP-SRS) triggered by DCI. In the DCI, AP-SRS is scheduled in a specific corset (configured with the corresponding CORESETPoolIndex). Therefore, by triggering DCI with different CORESETPoolIndexes, the UE can distinguish SRS as coming from the first TRP or from the second TRP. For example, when AP-SRS is triggered using DCI scheduled in a CORESET with CORESETPoolIndex=0, the NZP CSI-RS resources associated with CORESETPoolIndex=0 are used. At the same time, when AP-SRS is triggered using DCI scheduled in a CORESET with CORESETPoolIndex=1, the NZP CSI-RS associated with CORESETPoolIndex=1 is used.

[0056] It is worth noting that the conventional construction of SRS does not support Doppler shift estimation in the same way as TRS. Specifically, SRS requires two symbols in a timeslot with a minimum symbol distance between them to ensure optimal estimation quality. However, SRS currently does not allow this structure. Therefore, in one embodiment, the SRS configuration is modified to allow TRP Doppler shift estimation. This can be instantiated using the special tag "trs-info" in the SRS-ResourceSet. In this embodiment, up to four SRS resources can be configured in each SRS resource set. These four SRS resources are transmitted in two consecutive timeslots, with two SRS resources in each timeslot. For a given timeslot, the two SRS resources are N symbols apart, where N is 3, 4, or 5 symbols. Although the starting symbol of the first SRS resource in each timeslot can be flexibly indicated, the relative position of the SRS resources within a timeslot should be the same. This allows TRP to estimate Doppler shift based on SRS. To support this embodiment, modifications to the current 3gpp specifications may be required.

[0057] CSI Reporting Enhancements

[0058] As discussed above, there are two ways that the TRP can obtain Doppler shift. The first is for the TRP to estimate Doppler shift based on the SRS, as described above. In another embodiment, the UE estimates Doppler shift and reports this information to the TRP. In one such embodiment, this report is defined in a new CSI report, which is not currently supported in the 3GPP specification.

[0059] The CSI reporting framework consists of two main components: one for configuration and the other for triggering states associated with a specific configuration. The former includes one or more CSI-ReportConfig fields that define the configuration. In this embodiment, the TRS is configured as a CMR, namely resourcesForChannelMeasurement, which is configured in CSI-ResourceConfig. In CSI-ReportConfig, when the TRS is configured as a CMR, a new reportQuantity is introduced, referred to herein as "FrequencyShift". The UE then reports the frequency estimated on the configured TRS as a CMR within the ReportConfig field.

[0060] In another embodiment, multiple CSIs are configured so that the UE can report the frequency shift corresponding to both the first TRP and the second TRP in a single report. In one such embodiment, a single TRS is configured as a CMR but contains NZP CSI-RS resources from multiple TRPs. In an alternative embodiment, more than one TRS is configured as a CMR, each corresponding to a separate TRP.

[0061] We also consider how the UE reports these frequency shifts. In one embodiment, the UE reports only the difference between the two frequency shifts. In other words, the UE calculates the difference between the frequency shift from the first TRP and the frequency shift from the second TRP and reports this difference. In this embodiment, the difference is signed, allowing the network to determine which TRP has a positive versus negative Doppler shift.

[0062] In another embodiment, the UE reports the absolute value of the difference between the frequency shift from the first TRP and the frequency shift of the second TRP. Because the two TRPs are known to have opposite signs in their respective frequency shifts, the sign of the difference may not always be needed. Therefore, in one embodiment, to save bandwidth, the difference is reported as an unsigned absolute value.

[0063] In another embodiment, the UE reports the absolute value of the frequency shift of the first TRP and the difference in frequency shift for the second TRP. In other words, the UE reports (|TRP1 offset|, TRP1 offset-TRP2 offset).

[0064] As discussed above, frequency shift can be reported in the new reportQuantity. However, in one embodiment, frequency shift is reported in addition to the existing reportQuantity to allow better TRP pre-compensation and beamforming. In this embodiment, the UE reports the frequency shift along with the already defined CRI-RI-PMI-CQI reportQuantity. In this way, the UE informs the TRP of the frequency shift and relative phase for each TRP. The reported frequency shift allows the TRP to compensate for the frequency shift, and the reported phase allows the TRP to ensure coherent reception.

[0065] In another embodiment, the UE reports the frequency shift along with the already defined CRI-RI-LI-PMI-CQIreportQuantity. In one embodiment, the UE reports the quantized phase that the UE wants the TRP to apply, where the phase is the phase difference between the first TRP and the second TRP.

[0066] Figure 4 FIG. 4 is a flow chart illustrating an exemplary method 400 for a UE to track TRSs from two TRPs. Figure 4As shown, the UE receives TRSs from each of two different TRPs, each including a ResourceSet (410). For all NZP CSI-RS ResourceSets in which the TRSs are configured, the UE checks the value of the variable CORESETPoolIndex (420).

[0067] A CORESETPoolIndex value of 0 indicates that the TRS is from the first TRP, while a CORESETPoolIndex value of 1 indicates that the TRS is from the second TRP. Therefore, the UE determines the source of the TRP based on the value of the CORESETPoolIndex variable in the ResourceSet (430). Once the sources of the different TRSs are identified, the UE can perform Doppler compensation and then coherently combine the TRSs based on their origin and corresponding frequency shift (440).

[0068] Figure 5 A flow chart of an exemplary method 500 for compensating for Doppler shift in a UE is shown. Again, the UE receives a TRS having a ResourceSet defined therein from a TRP (510). Within the ResourceSet is a variable trs-info. The UE identifies whether the received TRS includes TRS information for two TRPs based on the value of the trs-info variable (520). In response to determining that the TRS is a 2-TRP TRS, the UE extracts first TRS information corresponding to the first TRP from the first time slot (530) and extracts second TRS information corresponding to the second TRP from the second time slot (540).

[0069] Using this information, the UE estimates the Doppler shift associated with each of the TRPs (550). The UE then compensates for these Doppler shifts imposed on signals received from the different TRPs (560).

[0070] Figure 6 1 shows a flow chart of an exemplary method 600 for pre-compensating Doppler shift according to an embodiment. Figure 6 As shown, the UE first calculates the Doppler shift associated with each of the multiple TRPs in any of the ways described above (610). The UE then generates a sounding reference signal (SRS) with a CSI-ReportConfig field (620).

[0071] The UE determines the transmission conditions or other parameters (630) and then fills the CSI-ReportConfig field accordingly in response to the determination. For example, based on the transmission conditions, the UE transmits the difference between the first TRP Doppler shift and the second TRP Doppler shift (632), the actual offset corresponding to each of the first TRP and the second TRP (634), or the actual offset of the first TRP and the difference between the offset and the offset of the second TRP (636). The UE then transmits the report to the TRP (640). The UE then receives a signal pre-compensated based on the reported offset from the TRP (650).

[0072] Figure 8 FIG. 1 is a flow chart illustrating an exemplary method for pre-compensating Doppler shift by TRP according to one aspect of the present disclosure. Figure 8 As shown, the TRP first receives a sounding reference signal (SRS) from the UE (810). In one embodiment, the transmission of the SRS by the UE is frequency locked based on the TRS so that the TRP can determine the frequency on which the UE is transmitting the SRS. This allows the TRP to accurately determine Doppler shift. In addition, in one embodiment, the SRS is transmitted by the UE using the same beam used to receive the TRS. In another embodiment, the SRS is transmitted by the UE using power control based on the path loss estimated from the TRS.

[0073] Based on the received SRS, the TRP estimates the Doppler shift of the signal transmitted to the UE (820). Sometime thereafter, the TRP prepares for signal transmission to the UE (830). Based on the previously calculated Doppler estimate, the TRP changes the frequency of the transmission (840) to pre-compensate for the expected Doppler shift that will occur during the transmission. The TRP then transmits the frequency-changed signal to the UE (850).

[0074] Figure 9 Flowchart showing an exemplary method for pre-compensating Doppler shift by TRP according to one aspect of the present disclosure. Figure 9 As shown, the TRP receives a notification from the backend identifying the TRP as one of the first TRP or the second TRP (910). Based on the received notification, the TRP generates a TRS signal for transmission to the UE (920). The TRP then transmits the TRS to the UE (930) along with an identifier or other identifying information to identify the TRP as the source of the TRS information. In response to the TRS, the TRP receives a Doppler report (940) from the UE, which includes Doppler measurements or other information sufficient for the TRP to estimate the Doppler shift. The TRP calculates frequency precompensation based on the information in the Doppler report (950) and then transmits the precompensated transmission signal to the UE (960).

[0075] Although the above method has been described in terms of one specific implementation, it should be understood that many of the steps may be performed in a different order or omitted depending on the specifics of the application.

[0076] Figure 10 A block diagram of an exemplary system of an electronic device 1000 that implements Doppler shift compensation according to some aspects of the present disclosure is shown. System 1000 can be any electronic device in the electronic devices of system 100 (e.g., TRP 110, UE 102). System 1000 includes a processor 1010, one or more transceivers 1020, a communication infrastructure 1040, a memory 1050, an operating system 1052, an application 1054, and one or more antennas 1060. The illustrated system is provided as an exemplary portion of system 1000, and system 1000 may include other circuits and subsystems. In addition, although the system of system 1000 is illustrated as separate components, aspects of the present disclosure may include any combination of these components, fewer components, or more components.

[0077] Memory 1050 may include random access memory (RAM) and / or cache memory, and may include control logic components (e.g., computer software) and / or data. Memory 1050 may include other storage devices or memories, such as, but not limited to, a hard drive and / or a removable storage device / unit. According to some examples, an operating system 1052 may be stored in memory 1050. Operating system 1052 may manage the transfer of data from memory 1050 and / or one or more application programs 1054 to processor 1010 and / or one or more transceivers 1020. In some examples, operating system 1052 maintains one or more network protocol stacks (e.g., an Internet protocol stack, a cellular protocol stack, etc.), which may include multiple logical layers. At the corresponding layer of the protocol stack, operating system 1052 includes control mechanisms and data structures to perform the functions associated with that layer.

[0078] According to some examples, applications 1054 may be stored in memory 1050. Applications 1054 may include applications used by wireless system 1000 and / or a user of wireless system 1000 (e.g., user applications). Applications in applications 1054 may include applications such as, but not limited to, Siri, TM , FaceTime TM , broadcast streaming, video streaming, remote control and / or other user applications.

[0079] The system 1000 may also include a communication infrastructure 1040. The communication infrastructure 1040 provides, for example, communication between the processor 1010, one or more transceivers 1020, and the memory 1050. In some implementations, the communication infrastructure 1040 may be a bus. The processor 1010, in conjunction with instructions stored in the memory 1050, executes operations that enable the system 1000 to implement the mechanism for Doppler shift compensation as described above.

[0080] One or more transceivers 1020 transmit and receive communication signals that support a mechanism for Doppler shift compensation. According to some aspects, one or more transceivers 1020 may be coupled to an antenna 1060. Antenna 1060 may include one or more antennas that may be the same or different types. One or more transceivers 1020 allow system 1000 to communicate with other devices that may be wired and / or wireless. In some examples, one or more transceivers 1020 may include circuits / devices such as a processor, a controller, a radio component, a socket, a plug, a buffer, etc. for connecting to a network and communicating on the network. According to some examples, one or more transceivers 1020 include one or more circuits for connecting to and communicating on a wired and / or wireless network.

[0081] According to some aspects of the present disclosure, the one or more transceivers 1020 may include a cellular subsystem, a WLAN subsystem, and / or a Bluetooth subsystem. TM The subsystems each include their own wireless transceiver and protocol, as will be understood by those skilled in the art based on the discussion provided herein. In some implementations, the one or more transceivers 1020 may include more or fewer systems for communicating with other devices.

[0082] In some examples, transceiver(s) 1020 may include one or more circuits, including a WLAN transceiver, to enable connection and communication via a WLAN network, such as, but not limited to, a network based on the standards described in IEEE 802.11.

[0083] Additionally or alternatively, the one or more transceivers 1020 may include one or more circuits (including Bluetooth TM transceiver) to implement Bluetooth-based TM Protocol, Bluetooth TM Low energy protocol, or Bluetooth TM For example, one or more transceivers 1020 may include Bluetooth TM transceiver.

[0084] Additionally, the one or more transceivers 1020 may include one or more circuits (including cellular transceivers) for connecting to and communicating on a cellular network. Cellular networks may include, but are not limited to, 3G / 4G / 5G networks, such as Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), etc. For example, the one or more transceivers 1020 may be configured to operate in accordance with one or more of Rel-15, Rel-16, Rel-17, or later versions of the 3GPP standards.

[0085] According to some aspects of the present disclosure, the processor 1010, alone or in combination with computer instructions stored in the memory 1050 and / or one or more transceivers 1020, implements the methods and mechanisms discussed in the present disclosure. For example, the processor 1010, alone or in combination with computer instructions stored in the memory 1050 and / or one or more transceivers 1020, implements a mechanism for Doppler shift compensation. According to some aspects of the present disclosure, the processor 1010, alone or in combination with computer instructions stored in the memory 1050 and / or one or more transceivers 1020, receives reference signals from multiple TRPs and determines their sources.

[0086] For example, one or more computer systems such as Figure 7 The computer system 700 shown is used to implement various aspects. The computer system 700 can be any known computer capable of performing the functions described herein, such as Figure 7 Device 710, 720, or Figure 2 200. Computer system 700 includes one or more processors (also known as central processing units or CPUs), such as processor 704. Processor 704 is connected to a communication infrastructure 706 (e.g., a bus). Computer system 700 also includes user input / output devices 703, such as a monitor, keyboard, pointing device, etc., that communicate with communication infrastructure 706 via user input / output interface 702. Computer system 700 also includes main memory or primary storage 708, such as random access memory (RAM). Main memory 708 may include one or more levels of cache. Main memory 708 has control logic components (e.g., computer software) and / or data stored therein.

[0087] The computer system 700 may also include one or more secondary storage devices or memories 710. The secondary storage 710 may include, for example, a hard disk drive 712 and / or a removable storage device or drive 714. The removable storage drive 714 may be a floppy disk drive, a tape drive, an optical disk drive, an optical storage device, a tape backup device, and / or any other storage device / drive.

[0088] The removable storage drive 714 can interact with a removable storage unit 718. The removable storage unit 718 includes a computer-usable or readable storage device having computer software (control logic) and / or data stored thereon. The removable storage unit 718 can be a floppy disk, a magnetic tape, a compact disk, a DVD, an optical storage disk, and / or any other computer data storage device. The removable storage drive 714 reads from and / or writes to the removable storage unit 718 in a well-known manner.

[0089] According to some aspects, the secondary memory 710 may include other devices, tools, or other means for allowing the computer system 700 to access computer programs and / or other instructions and / or data. Such devices, tools, or other means may include, for example, a removable storage unit 722 and an interface 720. Examples of the removable storage unit 722 and interface 720 may include a program cartridge and cartridge interface (such as found in video game devices), a removable memory chip (such as an EPROM or PROM) and an associated socket, a memory stick and USB port, a memory card and an associated memory card slot, and / or any other removable storage unit and associated interface.

[0090] The computer system 700 may also include a communication or network interface 724. The communication interface 724 enables the computer system 700 to communicate and interact with any combination of remote devices, remote networks, remote entities, and the like (individually and collectively referenced by reference numeral 728). For example, the communication interface 724 may allow the computer system 700 to communicate with the remote device 728 via a communication path 726, which may be wired and / or wireless and may include any combination of a LAN, a WAN, the Internet, and the like. Control logic components and / or data may be transferred to and from the computer system 700 via the communication path 726.

[0091] The operations in the foregoing aspects can be implemented in various configurations and architectures. Thus, some or all of the operations in the foregoing aspects may be performed in hardware, software, or in both hardware and software. In some aspects, a tangible, non-transient device or article includes a tangible, non-transient computer-usable or readable medium on which a control logic component (software) is stored, also referred to herein as a computer program product or program storage device. This includes, but is not limited to, a computer system 700, a main memory 708, an auxiliary memory 710, and removable storage units 718 and 722, as well as tangible articles embodying any combination of the foregoing. Such control logic components, when executed by one or more data processing devices (such as computer system 700), cause such data processing devices to operate as described herein.

[0092] Based on the teachings contained in this disclosure, it will be apparent to those skilled in the relevant art how to use Figure 7 The various aspects of the present disclosure may be made and used with data processing devices, computer systems, and / or computer architectures other than those shown. In particular, the various aspects may operate with software, hardware, and / or operating system implementations other than those described herein.

[0093] It should be understood that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary aspects of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the present disclosure and the appended claims in any way.

[0094] The present disclosure has been described above with the aid of functional building blocks, which illustrate the implementation of specified functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. As long as the specified functions and their relationships are properly performed, alternative boundaries may be defined.

[0095] The above description of specific aspects will fully demonstrate the general nature of the present disclosure, so that others can easily modify and / or adjust various applications of such specific aspects by applying knowledge within the technical scope of the art without undue experimentation, without departing from the general concept of the present disclosure. Therefore, based on the teachings and guidance presented herein, such adjustments and modifications are intended to be within the meaning and scope of equivalents of the aspects disclosed herein. It should be understood that the wording or terminology herein is for illustrative purposes only and not for limiting purposes, so the terms or wording of this specification will be interpreted by the skilled person in accordance with the teachings and guidance.

[0096] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary aspects, but should be defined only in accordance with the following claims and their equivalents.

[0097] Example

[0098] Embodiment 1 includes a user equipment having: a transceiver configured to transmit and receive signals between a first transmission-reception point (TRP) and a second TRP; and one or more processors configured to: receive reference signals from a plurality of TRPs via the transceiver, each reference signal including an identifier; determine an originating TRP as one of a first TRP or a second TRP based on the identifier; calculate a Doppler shift associated with each of the first TRP and the second TRP based on the determination; coherently combine the plurality of reference signals based on the calculation; and transmit an uplink signal to at least one of the first TRP or the second TRP via the transceiver based on the combined plurality of reference signals.

[0099] Embodiment 2 includes the user equipment of embodiment 1, wherein the identifier is a CORESETPoolIndex variable.

[0100] Embodiment 3 includes the user equipment of embodiment 2, wherein a CORESETPoolIndex value of 0 identifies the first TRP as an originating TRP, and wherein a CORESETPoolIndex value of 1 identifies the second TRP as an originating TRP.

[0101] Embodiment 4 includes the user equipment of embodiment 2, wherein the absence of a CORESETPoolIndex variable in the received reference signal identifies the first TRP as an originating TRP.

[0102] Embodiment 5 includes the user equipment of embodiment 1, wherein the reference signal is included in a corresponding tracking reference signal (TRS) transmitted from the TRP.

[0103] Embodiment 6 includes the user equipment of embodiment 1, wherein the reference signal is transmitted within downlink control information (DCI).

[0104] Embodiment 7 includes the user equipment of embodiment 1, wherein the reference signal comprises a first pair of TRS symbols in a first time slot associated with a first TRP, and a second pair of TRS symbols in a second time slot associated with a second TRP, wherein the first time slot and the second time slot are consecutive.

[0105] Embodiment 8 includes a user equipment for reporting Doppler shift to a TRP, the user equipment comprising: a transceiver configured to transmit and receive signals with a first transmission-reception point (TRP) and a second TRP; and one or more processors configured to: receive a reference signal from at least one of the first TRP and the second TRP; estimate the Doppler shift associated with each of the first TRP and the second TRP based on the received reference signal; generate a report signal based on the estimated Doppler shift; and transmit the report signal to the TRP via the transceiver.

[0106] Embodiment 9 includes the user equipment of embodiment 8, wherein the one or more processors are further configured to determine a reporting scheme based on the estimated Doppler shift.

[0107] Embodiment 10 includes the user equipment of embodiment 8, wherein the report signal comprises a signed difference value corresponding to a difference between a Doppler shift associated with the first TRP and a Doppler shift associated with the second TRP.

[0108] Embodiment 11 includes the user equipment of embodiment 8, wherein the reporting signal comprises a first Doppler shift associated with the first TRP and a second Doppler shift associated with the second TRP.

[0109] Embodiment 12 includes the user equipment of embodiment 8, wherein the report signal comprises an unsigned absolute value of a difference between a first Doppler shift associated with the first TRP and a second Doppler shift associated with the second TRP.

[0110] Embodiment 13 includes the user equipment of embodiment 8, wherein the report signal includes a first Doppler shift associated with the first TRP, and a difference corresponding to a difference between the first Doppler shift and a second Doppler shift associated with the second TRP.

[0111] Embodiment 14 includes the user equipment of embodiment 8, wherein the reporting signal is a CSI message, and wherein the Doppler shift information is encoded into a CSI-ReportConfig field of the CSI message.

[0112] Embodiment 15 includes a base station for compensating for Doppler drift in a high-speed environment, the base station comprising: a transceiver configured to communicate with a user equipment (UE); and one or more processors configured to: receive a notification from a back end regarding whether the base station is a first base station or a second base station; generate a tracking reference signal based on the received notification; and transmit the tracking reference signal to the UE, wherein the tracking reference signal includes an identifier based on the received notification.

[0113] Embodiment 16 includes the base station of embodiment 15, wherein the identifier is a value of a variable within a tracking reference signal.

[0114] Embodiment 17 includes the base station of embodiment 16, wherein the variable is CORESETPoolIndex, and wherein the one or more processors are further configured to: set the value of the variable to 0 in response to the received notification indicating that the base station is the first TRP; and set the value of the variable to 1 in response to the received notification indicating that the base station is the second TRP.

[0115] Embodiment 18 includes the base station of embodiment 15, wherein the one or more processors are further configured to: receive a report signal from a UE, the report signal including Doppler shift information associated with the base station; calculate precompensation based on the received Doppler shift information; and generate a signal transmission to the UE based on the calculated precompensation.

[0116] Embodiment 19 includes the base station of embodiment 18, wherein in response to the Doppler shift information indicating a negative frequency shift, precompensation increases the frequency of signal transmission, and wherein in response to the Doppler shift information indicating a positive frequency shift, precompensation decreases the frequency of signal transmission.

[0117] Embodiment 20 includes a base station according to claim 15, wherein the one or more processors are further configured to receive a dual TRP flag from a back end, and wherein in response to the dual TRP flag, generating the tracking reference signal includes transmitting reference information in only one of the first time slot or the second time slot of the tracking reference signal based on the received notification.

[0118] Embodiment 21 includes any of the above embodiments, wherein the user equipment is located on a high-speed train.

[0119] Embodiment 22 includes any of the above embodiments, wherein the UE identifies a triggered aperiodic tracking reference signal (AP-TRS) and a corresponding periodic tracking reference signal (P-TRS) transmitted from one of the first TRP or the second TRP based on information within the downlink control information (DCI).

[0120] Embodiment 23 includes embodiment 22, wherein in response to the CORESETPoolIndex value being 1, the UE identifies the AP-TRS and the P-TRS as originating from the first TRP.

[0121] Embodiment 24 includes embodiment 22, wherein in response to the CORESETPoolIndex value being 0, the UE identifies the AP-TRS and the P-TRS as originating from the second TRP.

[0122] Embodiment 25 includes any of the above embodiments, wherein an information element (IE) within a zero power (ZP) CSI-RS-ResourceSet enables HST TRS at the UE when indicated.

[0123] Example 26 includes example 25, wherein the HST TRS recognizes the 2-TRP TRS to be treated.

[0124] Embodiment 27 includes embodiment 26, wherein the TRS resources within the first time slot of the 2-TRP TRS and the TRS resources within the second time slot of the 2-TRP TRS are quasi-co-located.

[0125] Embodiment 28 includes embodiment 26, wherein the TRS resources in the first time slot and the second time slot are QCL type A and QCL type D.

[0126] Embodiment 29 includes embodiment 26, wherein the 2-TRP TRS is configured for FR1 only when the configured TRS occupies at least 52 physical resource blocks in the frequency domain.

[0127] Embodiment 30 includes any of the above embodiments, wherein the HST mode is configured via radio resource control (RRC).

[0128] Embodiment 31 includes any one of embodiments 1-29, wherein the HST mode is configured via a medium access control element (MAC-CE).

[0129] Embodiment 32 includes a method of operating a user equipment (UE), the method comprising: receiving a tracking reference signal (TRS) from a transmission receive point (TRP) using a transceiver; determining a frequency of the TRS; generating a sounding reference signal (SRS) having the frequency of the received TRS of the TRP; and transmitting the SRS to the TRP using the transceiver to enable the TRP to determine a Doppler shift associated with wireless communication between the TRP and the UE.

[0130] Embodiment 34 includes a method of operating a user equipment (UE), the method comprising: receiving a tracking reference signal (TRS) from a transmission receive point (TRP) using a transceiver; identifying a beam or beam direction from a plurality of beams or beam directions for receiving the TRS; generating a sounding reference signal (SRS); and transmitting the SRS to the TRP using the identified beam or beam direction using the transceiver, so that the TRP can determine a Doppler shift associated with wireless communication between the TRP and the UE.

[0131] Embodiment 35 includes a method of operating a user equipment (UE), the method comprising: receiving a tracking reference signal (TRS) from a transmission receive point (TRP) using a transceiver; estimating a path loss between the TRP and the TRS based on the TRS; generating a sounding reference signal (SRS) using power control of the SRS based on the path loss; and transmitting the SRS to the TRP using the transceiver to enable the TRP to determine a Doppler shift associated with wireless communication between the TRP and the UE.

[0132] Embodiment 36 includes any one of embodiments 33 to 35 implemented by one or more processors of a UE.

Claims

1. A user equipment comprising: a transceiver configured to transmit and receive signals between a first transmission-reception point (TRP) and a second TRP; and One or more processors configured to: receiving, via the transceiver, reference signals from a plurality of TRPs, each reference signal including an identifier; determining an originating TRP as one of the first TRP or the second TRP based on the identifier; calculating a Doppler shift associated with each of the first TRP and the second TRP based on the determining; coherently combining the plurality of reference signals based on the calculating; transmitting, via the transceiver, an uplink signal to at least one of the first TRP or the second TRP based on the combined plurality of reference signals; as well as A report signal is generated and transmitted based on the calculated Doppler shift, the report signal including an absolute first Doppler shift associated with the first TRP, and a difference corresponding to the difference between the absolute first Doppler shift and an absolute second Doppler shift associated with the second TRP, together with signs of the absolute first Doppler shift and the absolute second Doppler shift. 2 . The user equipment of claim 1 , wherein the identifier is a CORESETPoolIndex variable.

3. The user equipment of claim 2, wherein a CORESETPoolIndex value of 0 identifies the first TRP as the originating TRP, and The CORESETPoolIndex value of 1 identifies the second TRP as the originating TRP.

4. The user equipment of claim 2, wherein the absence of a CORESETPoolIndex variable in the received reference signal identifies the first TRP as the originating TRP.

5. The user equipment according to claim 1, wherein the reference signal is included in a corresponding tracking reference signal TRS transmitted from the TRP.

6. The user equipment according to claim 1, wherein the reference signals from the multiple TRPs are triggered using downlink control information (DCI) received in a CORESET configured with a corresponding CORESETPoolIndex.

7. A user equipment according to claim 1, wherein the reference signal includes a first pair of tracking reference signal (TRS) symbols in a first time slot associated with the first TRP, and a second pair of TRS symbols in a second time slot associated with the second TRP, wherein the first time slot and the second time slot are consecutive.

8. A user equipment for reporting Doppler shift to a transmission-reception point (TRP), the user equipment comprising: a transceiver configured to transmit and receive signals with the first TRP and the second TRP; and One or more processors configured to: receiving a reference signal from at least one of the first TRP and the second TRP; estimating a Doppler shift associated with each of the first TRP and the second TRP based on a received reference signal; generating a reporting signal based on the estimated Doppler shift; as well as transmitting, via the transceiver, the report signal to a gNB; wherein the report signal comprises an absolute first Doppler shift associated with the first TRP, and a difference corresponding to the difference between the absolute first Doppler shift and an absolute second Doppler shift associated with the second TRP, together with the signs of the absolute first Doppler shift and the absolute second Doppler shift.

9. The user equipment of claim 8, wherein the one or more processors are further configured to determine a reporting scheme based on the estimated Doppler shift.

10. The user equipment of claim 8, wherein the difference value is a signed difference value. The user equipment of claim 8 , wherein the report signal comprises an unsigned absolute value of the difference. 12 . The user equipment according to claim 8 , wherein the report signal is a channel state information (CSI) message, and wherein Doppler shift information is encoded into a field in the CSI message configured by CSI-ReportConfig.

13. A transmission reception point (TRP) for compensating for Doppler shift in a high-speed environment, the TRP comprising: a transceiver configured to communicate with user equipment UE; and One or more processors configured to: Receive notification from the backend about whether the TRP is the first TRP or the second TRP; receiving a dual TRP signature from the back end; generating a tracking reference signal based on the received notification, the generating comprising transmitting reference information in only one of a first time slot or a second time slot of the tracking reference signal based on the received notification; as well as transmitting the tracking reference signal to the UE, Wherein the tracking reference signal comprises an identifier based on the received notification.

14. The TRP of claim 13, wherein the identifier is a value of a variable within the tracking reference signal.

15. The TRP of claim 14, wherein the variable is CORESETPoolIndex, and wherein the one or more processors are further configured to: In response to the received notification indicating that the TRP is the first TRP, setting the value of the variable to 0; and In response to the received notification indicating that the TRP is the second TRP, the value of the variable is set to 1.

16. The TRP of claim 13, wherein the one or more processors are further configured to: receiving a report signal from the UE, the report signal including Doppler shift information associated with the TRP; calculating precompensation based on the received Doppler shift information; and A signal transmission to the UE is generated based on the calculated precompensation.

17. The TRP of claim 16, wherein in response to the Doppler shift information indicating a negative frequency shift, the pre-compensation increases the frequency of the signal transmission, and wherein in response to the Doppler shift information indicating a positive frequency shift, the pre-compensation decreases the frequency of the signal transmission.

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