Patent Description:
These systems may be capable of supporting communication with multiple users by sharing available system resources. A wireless multiple-access communications system may include a number of base stations (BSs), each simultaneously supporting communications for multiple communication devices, which may be otherwise known as user equipment (UE). BSs may have numerous transmission and reception points (TRPs, also known as remote radio heads (RRHs)) connected to them (e.g., via fiber), spaced at various points distant from the BS to expand the coverage area outside the range of the BS itself.

<NPL>, relates to a summary of an email discussion for Rel. <NUM> enhancement for NR MIMO.

<NPL>, relates to a contribution that provides justification of the proposed new SI of NR enhancement for high speed train scenario.

<NPL>, relates to an analysis on DMRS based transmission for Rel-<NUM> LTE UE HST.

Some TRPs may be located along the path of a high-speed train to enable communication between the BS and UEs located on the train during transit. The TRPs may operate using a single (common) frequency when communicating with a UE, making the existence of multiple TRPs transparent to the UE. As the UE moves at high velocity along the railway, the UE may receive signals from multiple TRPs at once and perform channel state estimation and provide channel state information (CSI) reports based on reference signals from multiple TRPs.

However, problems arise when transmitting and receiving reference signals in the context of a rapidly-moving UE. As the UE moves rapidly toward a TRP, the UE may perceive reference signals originating at the TRP at a higher frequency than expected because of the Doppler effect. Similarly, as the UE moves rapidly away from a TRP, the UE may perceive reference signals originating at the TRP at a lower frequency than expected because of the Doppler effect. If the Doppler shift becomes too great, i.e., greater than the pull-in range at the UE, the UE may be unable to acquire the reference signals transmitted from the TRP. Thus, there is a need to provide techniques for mitigating the effect of a large Doppler shift in a high-speed train single frequency network to enable a UE to effectively receive reference signals from TRPs in the network.

The following summarizes some aspects of the present disclosure to provide a basic understanding of the discussed technology. This summary is not an extensive overview of all contemplated features of the disclosure and is intended neither to identify key or critical elements of all aspects of the disclosure nor to delineate the scope of any or all aspects of the disclosure. Its sole purpose is to present some concepts of one or more aspects of the disclosure in summary form as a prelude to the more detailed description that is presented later.

This disclosure relates generally to wireless communications systems, also referred to as wireless communications networks. In various embodiments, the techniques and apparatus may be used for wireless communication networks such as code division multiple access (CDMA) networks, time division multiple access (TDMA) networks, frequency division multiple access (FDMA) networks, orthogonal FDMA (OFDMA) networks, single-carrier FDMA (SC-FDMA) networks, LTE networks, Global System for Mobile Communications (GSM) networks, <NUM>th Generation (<NUM>) or new radio (NR) networks, as well as other communications networks. As described herein, the terms "networks" and "systems" may be used interchangeably.

An OFDMA network may implement a radio technology such as evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers (IEEE) <NUM>, IEEE <NUM>, IEEE <NUM>, flash-OFDM and the like. UTRA, E-UTRA, and GSM are part of universal mobile telecommunication system (UMTS). 3GPP long term evolution (LTE) is a 3GPP project which was aimed at improving the UMTS mobile phone standard.

In particular, <NUM> networks contemplate diverse deployments, diverse spectrum, and diverse services and devices that may be implemented using an OFDM-based unified, air interface. In order to achieve these goals, further enhancements to LTE and LTE-A are considered in addition to development of the new radio technology for <NUM> NR networks. The <NUM> NR will be capable of scaling to provide coverage (<NUM>) to a massive Internet of things (IoTs) with an ultra-high density (e.g., ~<NUM> nodes/km<NUM>), ultra-low complexity (e.g., ~<NUM> of bits/sec), ultra-low energy (e.g., -<NUM>+ years of battery life), and deep coverage with the capability to reach challenging locations; (<NUM>) including mission-critical control with strong security to safeguard sensitive personal, financial, or classified information, ultra-high reliability (e.g., -<NUM>% reliability), ultra-low latency (e.g., ~ <NUM>), and users with wide ranges of mobility or lack thereof; and (<NUM>) with enhanced mobile broadband including extreme high capacity (e.g., ~ <NUM> Tbps/km<NUM>), extreme data rates (e.g., multi-Gbps rate, <NUM>+ Mbps user experienced rates), and deep awareness with advanced discovery and optimizations.

The <NUM> NR may be implemented to use optimized OFDM-based waveforms with scalable numerology and transmission time interval (TTI); having a common, flexible framework to efficiently multiplex services and features with a dynamic, low-latency time division duplex (TDD)/frequency division duplex (FDD) design; and with advanced wireless technologies, such as massive multiple input, multiple output (MIMO), robust millimeter wave (mmWave) transmissions, advanced channel coding, and device-centric mobility. Scalability of the numerology in <NUM> NR, with scaling of subcarrier spacing, may efficiently address operating diverse services across diverse spectrum and diverse deployments. For example, in various outdoor and macro coverage deployments of less than <NUM> FDD/TDD implementations, subcarrier spacing may occur with <NUM>, for example over <NUM>, <NUM>, <NUM>, and the like bandwidth (BW). For other various outdoor and small cell coverage deployments of TDD greater than <NUM>, subcarrier spacing may occur with <NUM> over <NUM>/<NUM> BW. For other various indoor wideband implementations, using a TDD over the unlicensed portion of the <NUM> band, the subcarrier spacing may occur with <NUM> over a <NUM> BW. Finally, for various deployments transmitting with mmWave components at a TDD of <NUM>, subcarrier spacing may occur with <NUM> over a <NUM> BW.

The present disclosure describes mechanisms to better communicate reference signals in a high-speed train (HST) single frequency network (SFN) so that the effective Doppler spread of the reference signals are within the pull-in range of receiving user equipment (UEs). In an HST SFN, a number of transmission and reception points (TRPs) are distributed along the path of an HST. The TRPs are connected to one or more base stations (BSs) through, for example, a fiber connection, and expand the coverage area of the BS(s). As the train moves along the track, a UE on the train may transition its connection from a TRP it is moving away from, to another TRP it is moving towards. A UE may be connected to multiple TRPs at once. For example, each TRP may use the same frequency for downlink communication to a UE so that the UE is only aware of a single TRP or BS, regardless of how many TRPs the UE is connected to.

Each TRP may transmit a reference signal, e.g., a tracking reference signal (TRS), which each TRP may have received from one or more BS(s). The TRS (which may also be a CSI-RS with TRS information) may indicate to the UE the Quasi-Colocation (QCL) type, which may indicate, for example, Doppler shift, Doppler spread, average delay, and/or delay spread. Each TRS may be associated with a Transmission Configuration Indicator (TCI) state, from which the UE may derive time, frequency, and/or spatial properties of a signal for use in demodulating data (e.g., on the physical downlink shared channel) quasi-colocated with the reference signal. For example, a given BS may control multiple TRPs along the path of the track. The BS may determine a TRS with a first TCI for a first TRP and a second TRS with a second TCI for a second TRP. The BS may derive a third TRS (e.g., from the first and second TRSs) with a third TCI state, with each TRP transmitting the third TRS on the SFN. The existence of the two distinct TRPs may remain invisible to the UE when using SFN, since both TRPs transmit the TRS on the same time/frequency resources.

A channel in an HST SFN may possess different characteristics than a channel used for communication between a BS (or TRP) and a UE which is stationary or moving slower than an HST. An HST SFN channel undergoes a higher Doppler shift and is highly direction (i.e., line-of-sight dominant), with low frequency selectivity. An HST SFN channel may also have a narrow Doppler spread (e.g., a maximum of about <NUM> at <NUM> for a UE travelling at <NUM>/h). Existing TRS schemes in Frequency Range <NUM> (which includes millimeter wave frequencies) may have a pull-in range of about ±<NUM>. Because the effective Doppler spread in an HST SFN channel may be too large in relation to the pull-in range possible at the UE, existing TRS schemes may not allow a UE to acquire TRSs from TRPs in the HST SFN without prohibitive search overhead at the UE. According the aspects of the present disclosure, however, a BS may apply frequency pre-compensation to the transmission of the TRSs on a per-beam or per-panel basis (or also, possibly, on a per-TRP basis) to allow effective use of existing TRS structures in an HST SFN.

In some embodiments, a BS may determine a first frequency pre-compensation value for a first TRP in an HST SFN to apply when transmitting the TRS to a UE. The BS may also determine a second frequency pre-compensation value for a second TRP to apply when transmitting the TRS to the UE. The first and second pre-compensation values may be the same, or may be different from each other. For example, if the UE is travelling away from the first TRP and toward the second TRP, the pre-compensation value for the first TRP may be positive (i.e., the first TRP would increase the frequency at which the TRS is transmitted), and the pre-compensation value for the second TRP may be negative (i.e., the second TRP would decrease the frequency at which the TRS is transmitted). Each TRP may apply its respective pre-compensation value on a per-beam or per-panel basis (or, alternatively, per-TRP basis). For example, different beams originating at a TRP may employ different pre-compensation values, and beams originating from different panels on the same TRP may employ different pre-compensation values. The pre-compensation values may be arbitrary under the current operating conditions, or selected from a set of candidate values.

In some embodiments, the BS may indicate the first and/or second pre-compensation value to the UE, for example, in a downlink control information (DCI) message or a radio resource control (RRC) signal through the first and/or second TRPs. The indication may be in the form of an index into a look-up table pre-configured on the UE. The UE may use the pre-compensation value(s) to inform its search for the TRS. For example, the UE may narrow the range of the tracking loop used to acquire the TRS based on the pre-compensation value(s). The UE may then acquire the TRS and perform channel estimation based on the narrowed tracking loop range.

In some embodiments, the pre-compensation value(s) may be based on the current properties of the SFN (e.g., on properties of the UE or the TRPs) and/or updated based on changes to the SFN. For example, the pre-compensation value(s) may be based on the position and velocity of the UE, which may be reported by the UE (e.g., based on GPS) or determined by the BS. The pre-compensation values may also be based on, for example, the beams and/or panels used by the first and/or second TRPs to transmit the TRS. The pre-compensation value(s) may be updated any time the SFN undergoes a change, and the new values may be applied to the TRS by the respective TRPs and indicated to the UE.

In some embodiments, the BS may additionally or alternatively determine frequency pre-compensation values and apply them to other types of signals (e.g., synchronization signals, signals carrying system information, and/or synchronization signal blocks) as described herein with respect to reference signals. For example, primary synchronization and/or secondary synchronization signals may also be frequency pre-compensated on a per-beam, per-panel, or per-TRP basis to enable meaningful reception by the UE (as discussed with respect to the other embodiments herein). Moreover, the coarse-level pre-adjustment may be conveyed as system information.

Aspects of the present application provide several benefits. For example, embodiments of the present disclosure allow a UE to better acquire a TRS in an HST SFN by reducing the effective Doppler spread of the TRS. Narrowing the effective Doppler spread of the TRS (hence narrowing the UE's tracking loop) also reduces the search and processing overhead involved in locating the TRS.

<FIG> illustrates a wireless communication network <NUM> according to some embodiments of the present disclosure. The network <NUM> may be a <NUM> network. The network <NUM> includes a number of base stations (BSs) <NUM> (individually labeled as 105a, 105b, 105c, 105d, 105e, and 105f) and other network entities. A BS <NUM> may be a station that communicates with UEs <NUM> and may also be referred to as an evolved node B (eNB), a next generation eNB (gNB), an access point, and the like. Each BS <NUM> may provide communication coverage for a particular geographic area. In 3GPP, the term "cell" may refer to this particular geographic coverage area of a BS <NUM> and/or a BS subsystem serving the coverage area, depending on the context in which the term is used.

The UEs <NUM> are dispersed throughout the wireless network <NUM>, and each UE <NUM> may be stationary or mobile. A UE <NUM> may also be referred to as a terminal, a mobile station, a subscriber unit, a station, or the like. A UE <NUM> may be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a wireless local loop (WLL) station, or the like. In one aspect, a UE <NUM> may be a device that includes a Universal Integrated Circuit Card (UICC). In another aspect, a UE may be a device that does not include a UICC. In some aspects, the UEs <NUM> that do not include UICCs may also be referred to as IoT devices or internet of everything (IoE) devices. The UEs 115a-115d are examples of mobile smart phone-type devices accessing network <NUM>. A UE <NUM> may also be a machine specifically configured for connected communication, including machine type communication (MTC), enhanced MTC (eMTC), narrowband IoT (NB-IoT) and the like. The UEs 115e-<NUM> are examples of various machines configured for communication that access the network <NUM>. A UE <NUM> may be able to communicate with any type of the BSs, whether macro BS, small cell, or the like, as well as in some embodiments with any type of other UE <NUM>. In <FIG>, a lightning bolt (e.g., communication links) indicates wireless transmissions between a UE <NUM> and a serving BS <NUM>, which is a BS designated to serve the UE <NUM> on the downlink and/or uplink, or desired transmission between BSs, and backhaul transmissions between BSs, or sidelink transmissions between UEs (or via UEs serving as relays to BSs).

The BSs <NUM> may also communicate with a core network. The core network may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. At least some of the BSs <NUM> (e.g., which may be an example of a gNB or an access node controller (ANC)) may interface with the core network through backhaul links (e.g., NG-C, NG-U, etc.) and may perform radio configuration and scheduling for communication with the UEs <NUM>. In various examples, the BSs <NUM> may communicate, either directly or indirectly (e.g., through core network), with each other over backhaul links (e.g., X1, X2, etc.), which may be wired or wireless communication links.

The network <NUM> may also support mission critical communications with ultra-reliable and redundant links for mission critical devices, such as the UE 115e, which may be a drone. Redundant communication links with the UE 115e may include links from the macro BSs 105d and 105e, as well as links from the small cell BS 105f. Other machine type devices, such as the UE 115f (e.g., a thermometer), the UE <NUM> (e.g., smart meter), and UE <NUM> (e.g., wearable device) may communicate through the network <NUM> either directly with BSs, such as the small cell BS 105f, and the macro BS 105e, or in multi-hop configurations by communicating with another user device which relays its information to the network, such as the UE 115f communicating temperature measurement information to the smart meter, the UE <NUM>, which is then reported to the network through the small cell BS 105f. The network <NUM> may also provide additional network efficiency through dynamic, low-latency TDD/FDD communications, such as in a vehicle-to-vehicle (V2V) communication. The network <NUM> may also further provide additional network efficiency through other device-to-device communication such as via PC5 links or other sidelinks, including according to embodiments of the present disclosure.

In some implementations, the network <NUM> utilizes OFDM-based waveforms for communications. An OFDM-based system may partition the system BW into multiple (K) orthogonal subcarriers, which are also commonly referred to as subcarriers, tones, bins, or the like. Each subcarrier may be modulated with data. In some instances, the subcarrier spacing between adjacent subcarriers may be fixed, and the total number of subcarriers (K) may be dependent on the system BW. The system BW may also be partitioned into subbands. In other instances, the subcarrier spacing and/or the duration of TTIs may be scalable.

In an embodiment, the BSs <NUM> may assign or schedule transmission resources (e.g., in the form of time-frequency resource blocks (RB)) for downlink (DL) and uplink (UL) transmissions in the network <NUM>. DL refers to the transmission direction from a BS <NUM> to a UE <NUM>, whereas UL refers to the transmission direction from a UE <NUM> to a BS <NUM>. The communication may be in the form of radio frames. A radio frame may be divided into a plurality of subframes or slots, for example, about <NUM>. Each slot may be further divided into mini-slots. In a FDD mode, simultaneous UL and DL transmissions may occur in different frequency bands. For example, each subframe includes a UL subframe in a UL frequency band and a DL subframe in a DL frequency band. In a TDD mode, UL and DL transmissions occur at different time periods using the same frequency band. For example, a subset of the subframes (e.g., DL subframes) in a radio frame may be used for DL transmissions and another subset of the subframes (e.g., UL subframes) in the radio frame may be used for UL transmissions.

The DL subframes and the UL subframes may be further divided into several regions. For example, each DL or UL subframe may have pre-defined regions for transmissions of reference signals, control information, and data. Reference signals are predetermined signals that facilitate the communications between the BSs <NUM> and the UEs <NUM>. For example, a reference signal may have a particular pilot pattern or structure, where pilot tones may span across an operational BW or frequency band, each positioned at a pre-defined time and a pre-defined frequency. For example, a BS <NUM> may transmit cell specific reference signals (CRSs) and/or channel state information - reference signals (CSI-RSs) to enable a UE <NUM> to estimate a DL channel. Similarly, a UE <NUM> may transmit sounding reference signals (SRSs) to enable a BS <NUM> to estimate a UL channel. Control information may include resource assignments and protocol controls. Data may include protocol data and/or operational data. In some embodiments, the BSs <NUM> and the UEs <NUM> may communicate using self-contained subframes. A self-contained subframe may include a portion for DL communication and a portion for UL communication. A self-contained subframe may be DL-centric or UL-centric. A DL-centric subframe may include a longer duration for DL communication than for UL communication. A UL-centric subframe may include a longer duration for UL communication than for UL communication.

In an embodiment, the network <NUM> may be an NR network deployed over a licensed spectrum. The BSs <NUM> may transmit synchronization signals (e.g., including a primary synchronization signal (PSS) and a secondary synchronization signal (SSS)) in the network <NUM> to facilitate synchronization. The BSs <NUM> may broadcast system information associated with the network <NUM> (e.g., including a master information block (MIB), remaining system information (RMSI), and other system information (OSI)) to facilitate initial network access. In some instances, the BSs <NUM> may broadcast the PSS, the SSS, and/or the MIB in the form of synchronization signal block (SSBs) over a physical broadcast channel (PBCH) and may broadcast the RMSI and/or the OSI over a physical downlink shared channel (PDSCH). The BS <NUM> may determine and apply beam-specific and/or panel-specific frequency pre-compensation to the SSB (e.g., to the signals in the SSB) when transmitting the SSB through a TRP as described in detail herein with respect to reference signals according to embodiments of the present disclosure.

In an embodiment, a UE <NUM> attempting to access the network <NUM> may perform an initial cell search by detecting a PSS from a BS <NUM>. The PSS may enable synchronization of period timing and may indicate a physical layer identity value. The UE <NUM> may then receive a SSS. The SSS may enable radio frame synchronization, and may provide a cell identity value, which may be combined with the physical layer identity value to identify the cell. The PSS and the SSS may be located in a central portion of a carrier or any suitable frequencies within the carrier.

After receiving the PSS and SSS, the UE <NUM> may receive a MIB. The MIB may include system information for initial network access and scheduling information for RMSI and/or OSI. After decoding the MIB, the UE <NUM> may receive RMSI and/or OSI. The RMSI and/or OSI may include radio resource control (RRC) information related to random access channel (RACH) procedures, paging, control resource set (CORESET) for physical downlink control channel (PDCCH) monitoring, physical uplink control channel (PUCCH), physical uplink shared channel (PUSCH), power control, and SRS.

After obtaining the MIB, the RMSI and/or the OSI, the UE <NUM> may perform a random access procedure to establish a connection with the BS <NUM>. In a four-step random access procedure, the UE <NUM> may transmit a random access preamble and the BS <NUM> may respond with a random access response. The random access response (RAR) may include a detected random access preamble identifier (ID) corresponding to the random access preamble, timing advance (TA) information, a UL grant, a temporary cell-radio network temporary identifier (C-RNTI), and/or a backoff indicator. Upon receiving the random access response, the UE <NUM> may transmit a connection request to the BS <NUM> and the BS <NUM> may respond with a connection response. The connection response may indicate a contention resolution. In some examples, the random access preamble, the RAR, the connection request, and the connection response may be referred to as a message <NUM> (MSG <NUM>), a message <NUM> (MSG <NUM>), a message <NUM> (MSG <NUM>), and a message <NUM> (MSG <NUM>), respectively. In other examples, the random access procedure may be a two-step random access procedure, where the UE <NUM> may transmit a random access preamble and a connection request in a single transmission and the BS <NUM> may respond by transmitting a random access response and a connection response in a single transmission. The combined random access preamble and connection request in the two-step random access procedure may be referred to as a message A (msgA). The combined random access response and connection response in the two-step random access procedure may be referred to as a message B (msgB).

After establishing a connection, the UE <NUM> and the BS <NUM> can enter an operational state, where operational data may be exchanged. For example, the BS <NUM> may schedule the UE <NUM> for UL and/or DL communications. The BS <NUM> may transmit UL and/or DL scheduling grants to the UE <NUM> via a PDCCH. The BS <NUM> may transmit a DL communication signal to the UE <NUM> via a PDSCH according to a DL scheduling grant. The UE <NUM> may transmit a UL communication signal to the BS <NUM> via a PUSCH and/or PUCCH according to a UL scheduling grant. Further, the UE <NUM> may transmit a UL communication signal to the BS <NUM> according to a configured grant scheme.

A configured grant transmission is an unscheduled transmission, performed on the channel without a UL grant. A configured grant UL transmission may also be referred to as a grantless, grant-free, or autonomous transmission. In some examples, the UE <NUM> may transmit a UL resource via a configured grant. Additionally, configured-UL data may also be referred to as grantless UL data, grant-free UL data, unscheduled UL data, or autonomous UL (AUL) data. Additionally, a configured grant may also be referred to as a grant-free grant, unscheduled grant, or autonomous grant. The resources and other parameters used by the UE for a configured grant transmission may be provided by the BS in one or more of a RRC configuration or an activation DCI, without an explicit grant for each UE transmission. Moreover, the UE may utilize a configured grant transmission in one or more sidelink communications with one or more other UEs (either for D2D communication or the other UE operating as an L2 or L3 relay to a BS).

The coverage range of a BS <NUM> can be extended by connecting one or more TRPs <NUM> (as illustrated in <FIG>) via, for example, a fiber connection. A TRP <NUM> may itself be a BS <NUM>. Alternatively, a TRP <NUM> may include transmit functionality under the control of a remote BS <NUM>, e.g. the TRP <NUM> may be an example of a remote radio head (RRH). A BS <NUM> may communicate through one or more TRPs <NUM> with a UE <NUM>. The BS <NUM> may transmit data intended for the UE <NUM> to the TRP <NUM>, which in turn may transit the data to the UE <NUM>. Similarly, the UE <NUM> may transmit a signal intended for a BS <NUM> to a TRP <NUM>, which may then transmit the signal to the BS <NUM>.

<FIG> illustrates aspects of an HST SFN <NUM> according to embodiments of the present disclosure. For simplicity, a single BS <NUM> (or baseband unit), two TRPs <NUM>, and one UE <NUM> are illustrated, but any fewer or more than two TRPs <NUM> and more than one UE <NUM> are possible according to aspects of the present disclosure. BS <NUM> may rely upon one or more of the TRPs <NUM> to communicate with the UE <NUM>. In other examples, one or more of TRPs <NUM> may be examples of BSs <NUM> in <FIG> (under control of one or more BBUs).

A UE <NUM> traveling on a high-speed train (or at high speed generally) may quickly move out of the coverage range of a single BS <NUM>. To provide connectivity to UE <NUM>, a number of TRPs <NUM> may be connected via links <NUM> (e.g., fiber) to the BS <NUM> and placed at various points along the path of a railway. For example, TRP 205a is illustrated as connected to BS <NUM> via link 204a and TRP 205b is connected to BS <NUM> via link 204b. As the UE <NUM> moves along the railway it may transition between one or more TRPs <NUM>. As illustrated, UE <NUM> may be in range of and communicating with TRPs 205a and 205b. Each TRP <NUM> may transmit a reference signal (e.g., a TRS) to UE <NUM>. According to embodiments of the present disclosure, TRP 205a may transmit TRS 206a using a beam 208a and TRP 205b may transmit TRS 206b using a beam 208b. While TRS 206a and TRS 206b may be transmitted using distinct TCI states <NUM> and <NUM>, according to embodiments of the present disclosure, BS <NUM> may derive a single TRS appropriate for transmission from both TRSs <NUM> using TCI state <NUM> with joint QCL data so that UE <NUM> is unaware it is receiving the TRSs <NUM> (i.e., the same TRS) from two different TRPs <NUM>. As UE <NUM> moves away from TRP 205a and toward TRP 205b, the doppler effect may cause UE <NUM> to perceive TRS 206a as being transmitted on a lower frequency than it is actually transmitted on, and TRS 206b as being transmitted at a higher frequency than it is actually transmitted on. This may cause enough frequency shift that it falls outside the pull-in range of the UE <NUM>'s tracking loop.

For example, turning now to <FIG> and <FIG>, <FIG> illustrates a Doppler power spectral density (PSD) model <NUM> for a signal (e.g., a TRS) transmitted from a single source (e.g., from a single TRP <NUM>, originating at a BS <NUM>, or from multiple TRPs <NUM> in an SFN) and received by a UE <NUM> according to aspects of the present disclosure. The X-axis <NUM> represents the frequency shift from the carrier, and the Y-axis <NUM> represents the Doppler PSD. Fc represents the central (expected) frequency, and Fd represents the maximum Doppler shift. Point <NUM> is the PSD at the central frequency (Fc), while point <NUM> illustrates the PSD when the frequency is shifted downward by Fd, and point <NUM> illustrates the PSD when the frequency is shifted upward by Fd. The Doppler PSD model <NUM> is based on Clarke's model, which assumes rich scattering around the UE's antenna upon reception. This may be applicable in scenarios where the UE <NUM> is receiving signals in one or more sub-<NUM> bands, and therefore lower Doppler shift (e.g., due to the lower carrier frequency) with corresponding better pull-in range for the UE <NUM>'s tracking loop.

By contrast, <FIG> illustrates the Doppler PSD in an HST SFN for a signal (e.g., a TRS) transmitted by two TRPs <NUM> (and originating at a BS <NUM>) and received by a UE <NUM> where there is a larger Doppler shift (e.g., due to higher velocity and/or higher carrier frequency e.g. in the mmW bands). Due to the high directionality of the beams (line-of-sight dominant) and low frequency selectivity, the Doppler spread is narrower. Instead, it is Doppler shift dominant. As a result of these characteristics, as illustrated there are effectively two copies of the PSD curve, one centered at point <NUM> corresponding to the receding TRP <NUM> (the TRP the UE is moving away from), and one centered at point <NUM> corresponding to the TRP <NUM> the UE is moving toward. Due to the high frequency and high speed, the Doppler spread is greater than what is seen in <FIG>. The larger Doppler spread in the HST SFN scenario of <FIG> makes it difficult for the UE <NUM> to receive the TRS using existing TRS structures, without incurring significant search and processing overhead, and possibly renders the UE <NUM> unable to recover the TRS if the Doppler shift pushes the copies outside the pull-in range of the UE <NUM>'s tracking loop. According to embodiments of the present disclosure, the TRP(s) <NUM> may apply one or more frequency pre-compensation values before transmitting the TRSs so that they are within the pull-in range of the UE <NUM>.

<FIG> is a block diagram of an exemplary UE <NUM> according to embodiments of the present disclosure. The UE <NUM> may be a UE <NUM> as discussed above in <FIG>. As shown, the UE <NUM> may include a processor <NUM>, a memory <NUM>, a frequency compensation module <NUM>, a transceiver <NUM> including a modem subsystem <NUM> and a radio frequency (RF) unit <NUM>, and one or more antennas <NUM>. These elements may be in direct or indirect communication with each other, for example via one or more buses.

The memory <NUM> may include a cache memory (e.g., a cache memory of the processor <NUM>), random access memory (RAM), magnetoresistive RAM (MRAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, solid state memory device, hard disk drives, other forms of volatile and non-volatile memory, or a combination of different types of memory. In an embodiment, the memory <NUM> includes a non-transitory computer-readable medium. The memory <NUM> may store, or have recorded thereon, instructions <NUM>. The instructions <NUM> may include instructions that, when executed by the processor <NUM>, cause the processor <NUM> to perform the operations described herein with reference to the UEs <NUM> in connection with embodiments of the present disclosure, for example, aspects of <FIG> and <FIG>. Instructions <NUM> may also be referred to as program code. The program code may be for causing a wireless communication device (or specific component(s) of the wireless communication device) to perform these operations, for example by causing one or more processors (such as processor <NUM>) to control or command the wireless communication device (or specific component(s) of the wireless communication device) to do so. The terms "instructions" and "code" should be interpreted broadly to include any type of computer-readable statement(s). For example, the terms "instructions" and "code" may refer to one or more programs, routines, sub-routines, functions, procedures, etc. "Instructions" and "code" may include a single computer-readable statement or many computer-readable statements.

The frequency compensation module <NUM> may be implemented via hardware, software, or combinations thereof. For example, frequency compensation module <NUM> may be implemented as a processor, circuit, and/or instructions <NUM> stored in the memory <NUM> and executed by the processor <NUM>. In some examples, the frequency compensation module <NUM> can be integrated within the modem subsystem <NUM>. For example, the frequency compensation module <NUM> can be implemented by a combination of software components (e.g., executed by a DSP or a general processor) and hardware components (e.g., logic gates and circuitry) within the modem subsystem <NUM>.

The frequency compensation module <NUM> may be used for various aspects of the present disclosure, for example, aspects of <FIG> and <FIG>. The frequency compensation module <NUM> is configured to communicate with other components of the UE <NUM> to recover a TRS originating at a BS <NUM> and transmitted by one or more TRPs <NUM> in an HST SFN. The TRS may have a frequency pre-compensation value applied by one or more of the TRPs <NUM>. For example, considering only two TRPs <NUM> (though any number of TRPs <NUM> are possible), the first TRP <NUM> may apply a first pre-compensation value to the TRS, and the second TRP <NUM> may apply a second pre-compensation value to the TRS (each before transmission). The pre-compensation values may be the same, or different from each other. For example, if the UE <NUM> is travelling away from the first TRP <NUM> and toward the second TRP <NUM>, the frequency compensation module <NUM> may recover the TRS from the first TRP <NUM> after the first TRP <NUM> applied a positive pre-compensation value (i.e., at an increased frequency), and it may recover the TRS from the second TRP <NUM> after the second TRP <NUM> applied a negative pre-compensation value (i.e., at a decreased frequency). The TRS may also or alternatively be transmitted on different beams or from different panels on the TRPs <NUM>, with the TRS originating at each beam or panel having a different frequency pre-compensation value applied.

According to embodiments of the present disclosure, the frequency compensation module <NUM> may be able to recover the TRS because the pre-compensation values shift the TRSs to a range around the carrier frequency that is within the tracking loop capability of the UE <NUM>. In some examples, the frequency compensation module <NUM> may have further stored the one or more pre-compensation values that the TRPs <NUM> will apply (e.g., received at a prior time via RRC and/or DCI signaling). In such examples, the frequency compensation module <NUM> may use as the initial value for the frequency tracking loop the compensated frequency per the corresponding beam/pane/TRP. The frequency compensation module <NUM> may, in some examples, use an index signaled from the TRP(s) <NUM> that identifies what entry to access within a look-up table that stores a plurality of pre-compensation values for the UE <NUM> to apply over time.

According to embodiments of the present disclosure, the BS may additionally or alternatively determine frequency pre-compensation values and apply them to other types of signals (e.g., to synchronization signals and signals carrying system information, or to SSBs) as described herein within to reference signals. For example, primary synchronization and/or secondary synchronization signals may also be frequency pre-compensated on a per-beam, per-panel, or per-TRP <NUM> basis to enable meaningful reception by the UE <NUM> (as discussed with respect to the other embodiments herein). Moreover, the coarse-level pre-adjustment may be conveyed as system information. The frequency compensation module <NUM> would process such signals and information in similar manner as described above with respect to the reference signal examples.

As shown, the transceiver <NUM> may include the modem subsystem <NUM> and the RF unit <NUM>. The transceiver <NUM> can be configured to communicate bi-directionally with other devices, such as the BSs <NUM>. The modem subsystem <NUM> may be configured to modulate and/or encode the data from the memory <NUM>, and/or the frequency compensation module <NUM> according to a modulation and coding scheme (MCS) (e.g., a low-density parity check (LDPC) coding scheme, a turbo coding scheme, a convolutional coding scheme, a digital beamforming scheme, etc.). The RF unit <NUM> may be configured to process (e.g., perform analog to digital conversion or digital to analog conversion, etc.) modulated/encoded data (e.g., UL data bursts, RRC messages, configured grant transmissions, ACK/NACKs for DL data bursts) from the modem subsystem <NUM> (on outbound transmissions) or of transmissions originating from another source such as a UE <NUM> or a BS <NUM>. The RF unit <NUM> may be further configured to perform analog beamforming in conjunction with the digital beamforming. Although shown as integrated together in transceiver <NUM>, the modem subsystem <NUM> and the RF unit <NUM> may be separate devices that are coupled together at the UE <NUM> to enable the UE <NUM> to communicate with other devices.

The RF unit <NUM> may provide the modulated and/or processed data (e.g., data packets or, more generally, data messages that may contain one or more data packets and other information) to the antennas <NUM> for transmission to one or more other devices. The antennas <NUM> may further receive data messages transmitted from other devices. The antennas <NUM> may provide the received data messages for processing and/or demodulation at the transceiver <NUM>. The transceiver <NUM> may provide the demodulated and decoded data (e.g., system information message(s), RACH message(s) (e.g., DL/UL scheduling grants, DL data bursts, RRC messages, ACK/NACK requests, reference signals such as TRSs, etc.) to the frequency compensation module <NUM> for processing. The antennas <NUM> may include multiple antennas of similar or different designs in order to sustain multiple transmission links. The RF unit <NUM> may configure the antennas <NUM>.

In an embodiment, the UE <NUM> can include multiple transceivers <NUM> implementing different RATs (e.g., NR and LTE). In an embodiment, the UE <NUM> can include a single transceiver <NUM> implementing multiple RATs (e.g., NR and LTE). In an embodiment, the transceiver <NUM> can include various components, where different combinations of components can implement different RATs.

<FIG> is a block diagram of an exemplary BS <NUM> according to embodiments of the present disclosure. The BS <NUM> may be a BS <NUM> as discussed above in <FIG>. As shown, the BS <NUM> may include a processor <NUM>, a memory <NUM>, a frequency compensation module <NUM>, a transceiver <NUM> including a modem subsystem <NUM> and a RF unit <NUM>, and one or more antennas <NUM>. These elements may be in direct or indirect communication with each other, for example via one or more buses.

The instructions <NUM> may include instructions that, when executed by the processor <NUM>, cause the processor <NUM> to perform operations described herein, for example, aspects of <FIG> and <FIG>.

The frequency compensation module <NUM> may be implemented via hardware, software, or combinations thereof. For example, the frequency compensation module <NUM> may be implemented as a processor, circuit, and/or instructions <NUM> stored in the memory <NUM> and executed by the processor <NUM>. In some examples, the frequency compensation module <NUM> can be integrated within the modem subsystem <NUM>. For example, the frequency compensation module <NUM> can be implemented by a combination of software components (e.g., executed by a DSP or a general processor) and hardware components (e.g., logic gates and circuitry) within the modem subsystem <NUM>.

The frequency compensation module <NUM> may be used for various aspects of the present disclosure, for example, aspects of <FIG> and <FIG>. The frequency compensation module <NUM> may be configured to communicate with other components of the BS <NUM> to help determine a TRS for transmission to a UE <NUM> from one or more TRPs <NUM>, and to help determine a frequency pre-compensation value for the TRPs <NUM> to apply when transmitting the TRS to the UE <NUM>. For example, the frequency compensation module <NUM> may be configured to determine a first frequency pre-compensation value for a first TRP in an HST SFN to apply to a TRS when transmitting the TRS to a UE. The frequency compensation module <NUM> may also be configured to determine a second frequency pre-compensation value for a second TRP to apply to the TRS when transmitting the TRS to the UE. The first and second pre-compensation values may be the same, or may be different from each other. For example, if the UE is travelling away from the first TRP <NUM> and toward the second TRP <NUM>, the pre-compensation value for the first TRP <NUM> may be positive (i.e., the first TRP <NUM> would increase the frequency at which the TRS is transmitted), and the pre-compensation value for the second TRP <NUM> may be negative (i.e., the second TRP <NUM> would decrease the frequency at which the TRS is transmitted). Each TRP <NUM> may apply its respective pre-compensation value as determined by the frequency compensation module <NUM> on a per-beam or per-panel basis (or, alternatively, on a per-TRP basis). For example, different beams originating at a TRP <NUM> may employ different pre-compensation values (e.g., even if from the same panel), and beams originating from different panels on the same TRP <NUM> may employ different pre-compensation values (i.e., multiple beams from the same panel apply the same pre-compensation value, but different from beams from other panels).

The frequency compensation module <NUM> may select pre-compensation values arbitrarily or select the pre-compensation values from a set of candidate values. In another example, the frequency compensation module <NUM> may be configured to determine the pre-compensation value(s) based on the current properties of the SFN (e.g., on properties of the UE <NUM> or the TRPs <NUM>) and/or update the pre-compensation value(s) based on changes to the SFN. For example, the pre-compensation value(s) may be based on the position and velocity of the UE <NUM>, which may be reported by the UE <NUM> (e.g., based on GPS) or determined (or estimated) by the BS <NUM>. Or, the BS <NUM> may be in communication with an HST itself in the SFN to obtain current or future velocity information (and/or related position information). The frequency compensation module <NUM> may also determine the pre-compensation values based on, for example, the beam directions used by the first and/or second TRPs to transmit the TRS. The frequency compensation module <NUM> may update the pre-compensation value(s) any time the SFN undergoes a change, and the new values may be applied to the TRS by the respective TRPs <NUM>.

In some embodiments, the frequency compensation module <NUM> may be configured to indicate the first and/or second pre-compensation value to the UE <NUM> (e.g., in a downlink control information (DCI) or radio resource control (RRC) message) through the first and/or second TRPs <NUM>. The indication may be in the form of an index into a look-up table pre-configured on the UE <NUM>, for example. Further, in embodiments where the frequency compensation module <NUM> updates one or more of the pre-compensation values (e.g., based on a change in the SFN, detected or predicted/estimated), the frequency compensation module <NUM> may cause the values to be indicated to the UE <NUM> (e.g., in a DCI message or an RRC message if for a longer time horizon, either with the value itself being signaled or an index or other identifier that the UE <NUM> may use to locate the value).

In some embodiments, the UE may additionally or alternatively receive other types of signals (e.g., synchronization signals and signals carrying system information, and/or SSBs) with frequency pre-compensation applied as described herein with respect to reference signals. The UE may also receive indications of the frequency pre-compensation applied to the other types of signals. For example, primary synchronization and/or secondary synchronization signals may also be frequency pre-compensated on a per-beam, per-panel, or per-TRP <NUM> basis to enable meaningful reception by the UE <NUM> (as discussed with respect to the other embodiments herein). Moreover, the coarse-level pre-adjustment may be conveyed as system information. The frequency compensation module <NUM> would perform similar operations to achieve this in similar manner as described above with respect to the reference signal examples. As shown, the transceiver <NUM> may include the modem subsystem <NUM> and the RF unit <NUM>. The transceiver <NUM> can be configured to communicate bi-directionally with other devices, such as the UEs <NUM> and/or <NUM> and/or another core network element. The modem subsystem <NUM> may be configured to modulate and/or encode data according to a MCS (e.g., a LDPC coding scheme, a turbo coding scheme, a convolutional coding scheme, a digital beamforming scheme, etc.). The RF unit <NUM> may be configured to process (e.g., perform analog to digital conversion or digital to analog conversion, etc.) modulated/encoded data (e.g., RRC messages, TRSs, etc.) from the modem subsystem <NUM> (on outbound transmissions) or of transmissions originating from another source, such as a UE <NUM> or <NUM>. The RF unit <NUM> may be further configured to perform analog beamforming in conjunction with the digital beamforming. Although shown as integrated together in transceiver <NUM>, the modem subsystem <NUM> and/or the RF unit <NUM> may be separate devices that are coupled together at the BS <NUM> to enable the BS <NUM> to communicate with other devices.

The RF unit <NUM> may provide the modulated and/or processed data, (e.g., data packets or, more generally, data messages that may contain one or more data packets and other information) to the antennas <NUM> for transmission to one or more other devices. The antennas <NUM> may further receive data messages transmitted from other devices and provide the received data messages for processing and/or demodulation at the transceiver <NUM>. The transceiver <NUM> may provide the demodulated and decoded data (e.g., RRC messages, UL data, information about a UE <NUM>'s position and velocity, etc.) to the frequency compensation module <NUM> for processing. The antennas <NUM> may include multiple antennas of similar or different designs in order to sustain multiple transmission links.

In an embodiment, the BS <NUM> can include multiple transceivers <NUM> implementing different RATs (e.g., NR and LTE). In an embodiment, the BS <NUM> can include a single transceiver <NUM> implementing multiple RATs (e.g., NR and LTE). In an embodiment, the transceiver <NUM> can include various components, where different combinations of components can implement different RATs.

<FIG> illustrates a flow diagram of a wireless communication method <NUM> according to some embodiments of the present disclosure. Aspects of the method <NUM> can be executed by a wireless communication device, such as a BS <NUM>/<NUM>, utilizing one or more components, such as the processor <NUM>, the memory <NUM>, the frequency compensation module <NUM>, the transceiver <NUM>, the modem <NUM>, the one or more antennas <NUM>, and various combinations thereof. The BS <NUM> may be communicating with a UE <NUM> on an HST travelling within the range of two or more TRPs <NUM> on an SFN. For simplicity, the method is illustrated with reference to two TRPs <NUM>, though a greater number of TRPs <NUM> may be possible. As illustrated, the method <NUM> includes a number of enumerated steps, but embodiments of the method <NUM> may include additional steps before, during, after, and in between the enumerated steps. Further, in some embodiments, one or more of the enumerated steps may be omitted or performed in a different order.

At block <NUM>, the BS <NUM> determines a first frequency pre-compensation value to apply to a reference signal (e.g., a TRS or a CSI-RS with TRS information) to be transmitted by a first TRP <NUM> to a UE <NUM>. The first frequency pre-compensation value may be based on properties (and/or estimates of those properties) of the SFN, for example, the current position and/or velocity of the UE <NUM>, or the beam(s) and/or panel(s) to be used by the first TRP <NUM> to transmit the TRS. The first frequency pre-compensation value may be positive (e.g., if the UE <NUM> is moving away from the first TRP) or negative (e.g., if the UE <NUM> is moving toward the first TRP). The first frequency pre-compensation value may be chosen arbitrarily, selected from a set (e.g., a predefined set) of candidate values, or from a calculation or derivation.

At block <NUM>, the BS <NUM> determines a second frequency pre-compensation value to apply to the reference signal to be transmitted by a second TRP <NUM> to the UE <NUM>. The second frequency pre-compensation value may be based on properties (and/or estimates of those properties) of the SFN, for example, the current position and/or velocity of the UE <NUM>, or the beam(s) and/or panel(s) to be used by the second TRP <NUM> to transmit the second TRS. The first frequency pre-compensation value may be positive (e.g., if the UE <NUM> is moving away from the second TRP) or negative (e.g., if the UE <NUM> is moving toward the second TRP), and may be the same or different than the first frequency pre-compensation value. The second frequency pre-compensation value may be chosen arbitrarily, selected from a set of candidate values, or from a calculation or derivation.

At block <NUM>, the BS <NUM> transmits (e.g., in a DCI or RRC message) an indication of the first frequency pre-compensation value to the UE <NUM> (e.g., via the first TRP <NUM>). The value may be a raw value, or an index into look-up table configured at the UE <NUM>.

At block <NUM>, the BS <NUM> transmits (e.g., in a DCI or RRC message) an indication of the second frequency pre-compensation value to the UE <NUM> (e.g., via the second TRP <NUM>). The value may be a raw value, or an index into look-up table configured at the UE <NUM>. Further, the first and second pre-compensation values may be transmitted via the TRPs <NUM> at approximately the same time as each other, as part of the same message, or one after the other. Further, in some embodiments the first and second pre-compensation values may be transmitted via respective TRPs <NUM>, while in other embodiments the values may be transmitted from one of the multiple TRPs <NUM>.

At block <NUM>, the BS <NUM> applies the first frequency pre-compensation value to the reference signal (or directs the first TRP <NUM> to apply the value). The first frequency pre-compensation value may increase or decrease the frequency of the reference signal depending, respectively, on whether the UE <NUM> is moving away from or toward the first TRP <NUM>.

At block <NUM>, the BS <NUM> directs the first TRP <NUM> to transmit the reference signal (with the first frequency pre-compensation value applied) to the UE <NUM>.

At block <NUM>, the BS <NUM> applies the second frequency pre-compensation value to the reference signal (or directs the second TRP <NUM> to apply the value). The second frequency pre-compensation value may increase or decrease the frequency of the reference signal depending, respectively, on whether the UE <NUM> is moving away from or toward the second TRP <NUM>. The BS <NUM> may apply the first frequency pre-compensation value to the first reference and the second frequency pre-compensation value to the second reference signal at or near the same time as each other, or sequentially.

At block <NUM>, the BS <NUM> directs the second TRP <NUM> to transmit the reference signal (with the second frequency pre-compensation value applied) to the UE <NUM>. Further, the BS <NUM> may direct the first and second TRPs <NUM> to transmit their respective (pre-compensated) reference signals to the UE at approximately the same time.

At decision block <NUM>, the BS <NUM> determines whether any characteristics of the SFN have changed. For example, the UE <NUM> may be in a different position, travelling in a different direction, or travelling at a different speed (either actually measured, reported, or estimated). Alternatively, one of the TRPs <NUM> may have adjusted the beam(s) and/or panel(s) used to transmit their respective TRSs to the UE <NUM>. If no change to the SFN is detected, the method proceeds to block <NUM>, where the BS <NUM> maintains the existing pre-compensation values. Alternately, if a change in the SFN is detected, the method returns to block <NUM>, and the BS <NUM> repeats at least some aspects of the method <NUM>. For example, the BS <NUM> may repeat the entire method <NUM>, or it may only perform parts of the method <NUM> related to one of the two TRPs <NUM>.

According to embodiments of the present disclosure, the BS <NUM> may additionally or alternatively perform aspects of the method <NUM> in relation to other types of signals. For example, the BS <NUM> may determine frequency pre-compensation values and apply them to synchronization signals and signals carrying system information, or to SSBs. For example, primary synchronization and/or secondary synchronization signals may also be frequency pre-compensated on a per-beam, per-panel, or per-TRP basis to enable meaningful reception (as discussed with respect to the other embodiments herein). Moreover, the coarse-level pre-adjustment may be conveyed as system information.

<FIG> illustrates a flow diagram of a wireless communication method <NUM> according to some embodiments of the present disclosure. Aspects of the method <NUM> can be executed by a wireless communication device, such as a UE <NUM>/<NUM>, utilizing one or more components, such as the processor <NUM>, the memory <NUM>, the frequency compensation module <NUM>, the transceiver <NUM>, the modem <NUM>, the one or more antennas <NUM>, and various combinations thereof. The UE <NUM> may be on an HST travelling within the range of two or more TRPs <NUM> on an SFN. For simplicity, the method is illustrated with reference to two TRPs <NUM>, though a greater number of TRPs <NUM> may be possible. As illustrated, the method <NUM> includes a number of enumerated steps, but embodiments of the method <NUM> may include additional steps before, during, after, and in between the enumerated steps. Further, in some embodiments, one or more of the enumerated steps may be omitted or performed in a different order.

At block <NUM>, a UE <NUM> receives an indication of a first frequency pre-compensation value from a TRP <NUM> (e.g., a first TRP <NUM>), originating at a BS <NUM>. The first frequency pre-compensation value may be an arbitrary value, or in index into a lookup table of frequency pre-compensation values configured on the UE <NUM>, and/or from a calculation or derivation.

At block <NUM>, the UE <NUM> receives an indication of a second frequency pre-compensation value originating from a TRP <NUM> (e.g., a second TRP <NUM>), originating at a BS <NUM>. The indication of the second frequency pre-compensation value may be received from the same TRP <NUM> as the first frequency pre-compensation value (e.g., as sequential messages or as part of a common message) or from a different TRP <NUM>. The second frequency pre-compensation value may be an arbitrary value, or in index into a lookup table of frequency pre-compensation values configured on the UE <NUM>, and/or from a calculation or derivation. Thus, the first and second frequency pre-compensation values may be transmitted at the same time as each other or at different times, for use in configuring at least a frequency tracking loop aspect of the UE <NUM>.

At block <NUM>, the UE <NUM> narrows the range of the tracking loop used to acquire the TRS based on the first pre-compensation value and the second pre-compensation value (received at blocks <NUM> and <NUM> as discussed above). For example, the <NUM> UE may adjust the frequency range it uses to search for the TRS from the first TRP <NUM> and the second TRP <NUM> (as the TRS is received as part of the SFN, and thus the UE <NUM> does not know which TRP <NUM> sent the TRS).

At block <NUM>, the UE <NUM> receives a reference signal (e.g., a TRS) modified by the first frequency pre-compensation value. The frequency of the reference signal may have been adjusted upward (e.g., if the UE <NUM> is moving away from the first TRP <NUM>) or downward (e.g., if the UE <NUM> is moving toward the first TRP <NUM>).

At block <NUM>, the UE <NUM> receives the reference signal (e.g., a TRS) modified by the second frequency pre-compensation value. The frequency of the reference signal may have been adjusted upward (e.g., if the UE <NUM> is moving away from the second TRP <NUM>) or downward (e.g., if the UE <NUM> is moving toward the second TRP <NUM>). The UE <NUM> may receive the first and second reference signals (e.g., which have the same identifier and are sent on the same time/frequency resources as part of the SFN) at the same time, such that the actions of blocks <NUM> and <NUM> occur at approximately the same time.

At block <NUM>, the UE <NUM> performs channel estimation based on the TRS received at blocks <NUM> and <NUM>. The UE <NUM> may determine a channel state based on the TRS and/or determine parameters for further communication with the BS <NUM>.

At decision block <NUM>, if there is a change in the SFN due to, for example, a change in the UE <NUM>'s position or velocity, the UE <NUM> may report the change to the BS <NUM> and return to block <NUM> to repeat aspects method <NUM> based on the new SFN characteristics. As another example, if a different aspect of the SFN changes, for example, the beam characteristics used by either or both TRPs <NUM> to transmit the reference signal, the method <NUM> may return to block <NUM> to repeat aspects of method <NUM>. Some or all aspects of the method <NUM> may be repeated. For example, if only characteristics of one of the TRPs <NUM> change, only aspects of the method related to that TRP <NUM> may be repeated. Alternately, if no change to the SFN occurs, the method progresses to block <NUM> where the UE will maintain the range of the tracking loop for TRSs.

In some embodiments, the UE <NUM> may additionally or alternatively perform aspects of the method <NUM> in relation to other types of signals. For example, the UE <NUM> may receive synchronization signals and signals carrying system information, and/or SSBs, with frequency pre-compensation applied. The UE <NUM> may also receive indications of the frequency pre-compensation values applied to other types of signals. For example, primary synchronization and/or secondary synchronization signals may also be frequency pre-compensated on a per-beam, per-panel, or per-TRP basis to enable meaningful reception by the UE <NUM> (as discussed with respect to the other embodiments herein). Moreover, the coarse-level pre-adjustment may be conveyed as system information.

Also, as used herein, including in the claims, "or" as used in a list of items (for example, a list of items prefaced by a phrase such as "at least one of' or "one or more of') indicates an inclusive list such that, for example, a list of [at least one of A, B, or C] means A or B or C or AB or AC or BC or ABC (i.e., A and B and C).

Claim 1:
A method (<NUM>) of wireless communications, the method (<NUM>) comprising:
determining (<NUM>), by a base station, a frequency pre-compensation value for a transmission and reception point, TRP, on a single frequency network, SFN;
indicating (<NUM>), by the base station to a user equipment, UE, the frequency pre-compensation value via the TRP; and
applying (<NUM>), by the base station, the frequency pre-compensation value to a signal for transmission by the TRP to the UE.