Method of early time domain channel properties (TDCP) feedback via 4-step random access channel (RACH) procedure

Abstract

A method, system and apparatus for early time domain channel properties, TDCP, feedback via a 4-step random access channel, RACH, procedure are disclosed. According to one aspect, a method in a user equipment, UE, configured to communicate with a network node includes receiving assistance information from the network node to assist the UE to acquire time domain channel properties, TDCP, receiving a triggering signal from the network node in a message 2 of a 4-step random access procedure, performing TDCP measurements based at least in part on the received assistance information, and responsive to the triggering signal, transmitting to the network node a TDCP report in a message 3 of the 4-step random access procedure.

Description

[0001]METHOD OF EARLY TIME DOMAIN CHANNEL PROPERTIES (TDCP) FEEDBACK VIA 4-STEP RANDOM ACCESS CHANNEL (RACH) PROCEDURE TECHNICAL FIELD The present disclosure relates to wireless communications, and in particular, to methods of early time domain channel properties (TDCP) feedback via a 4-step random access channel (RACH) procedure. BACKGROUND The Third Generation Partnership Project (3GPP) has developed and is developing standards for Fourth Generation (4G) (also referred to as Long Term Evolution (LTE)) and Fifth Generation (5G) (also referred to as New Radio (NR)) wireless communication systems. Such systems provide, among other features, broadband communication between network nodes, such as base stations, and mobile user equipment (UE) or wireless devices (WD), as well as communication between network nodes and between UEs. The 3GPP is also developing standards for Sixth Generation (6G) wireless communication networks. Synchronization Signal Block (SSB) In NR, a UE acquires time and frequency synchronization with a cell based on two synchronization signals (SS), i.e., a primary synchronization signal (PSS) and a secondary synchronization signal (SSS). The PSS and SSS are also used by the UE to detect the physical layer Cell ID of the cell. PSS, SSS and a Physical Broadcast Channel (PBCH) are transmitted together in consecutive symbols and form a SS / PBCH block or SSB. In the time domain, an SS / PBCH block has 4 orthogonal frequency division multiplexed (OFDM) symbols, numbered in increasing order from 0 to 3 within the SS / PBCH block. In the frequency domain, an SS / PBCH block consists of 240 contiguous subcarriers with the subcarriers numbered in increasing order from 0 to 239 within the SS / PBCH block. This is illustrated in FIG. 1. More details of SS / PBCH block may be found in 3GPP Technical Standard (TS) 38.211. An SS / PBCH block is transmitted periodically with a possible period of 5ms, 10ms, 20ms, 40ms, 80ms, or 160ms. One or multiple SS / PBCH block(s), each with a synchronization signal block (SSB) index, may be transmitted in a serving cell. The one or multiple SS / PBCH block(s) within a 5ms time window form an SSB burst set. The default SS burst set periodicity value for initial cell selection is 20ms. The maximum number of SS-blocks within an SS burst set depends on frequency ranges and is 4 for up to 3GHz and 8 between 3GHz to 6GHz. More details of possible time locations of an SS / PBCH block may be found in 3GPP TS 38.213. Channel State Information Reference Signals (CSI-RS) For CSI measurement and feedback, CSI-RS are defined. A CSI-RS is transmitted on each antenna port and is used by a UE to measure downlink channels between each of the transmit antenna ports and each of its receive antenna ports. The transmit antenna ports are also referred to as CSI-RS ports. The supported number of antenna ports in NR are {1, 2, 4, 8, 12, 16, 24, 32}. By measuring the received CSI-RS, a UE may estimate the channel that the CSI-RS is traversing, including the radio propagation channel and antenna gains. The CSI-RS for the above purpose is also referred to as Non-Zero Power (NZP) CSI-RS. CSI-RS may be configured to be transmitted in certain REs in a slot and certain slots. FIG. 2 is an example of CSI-RS REs for 12 antenna ports, where 1 RE per RB per port is shown. In addition, an interference measurement resource (IMR) is also defined in NR for a UE to measure interference. An IMR resource contains 4 REs, either 4 adjacent REs in frequency in the same OFDM symbol or 2 by 2 adjacent REs in both time and frequency in a slot. By measuring both the channel based on non-zero power (NZP) CSI-RS and the interference based on an IMR, a UE may estimate the effective channel and noise plus interference to determine the CSI, i.e., rank, precoding matrix, and the channel quality. Furthermore, a UE in NR may be configured to measure interference based on one or multiple NZP CSI-RS resource. TRS Due to oscillator imperfections, transmission and reception may not be synchronized in time and / or frequency, which may cause inter-symbol interference and intra-symbol interference. In NR, a tracking reference signal (TRS) was introduced that may be used by the UE for fine time / frequency synchronization. In the NR 3GPP specifications, a TRS may be configured when a CSI report setting is not configured or when the higher layer parameter ‘reportQuantity’ in the CSI- ReportConfig information element (IE), associated with all the report settings linked with the CSI-RS resource set containing the TRS(s) is set to ‘none’. This means that CSI reporting based on measurements on TRS is not supported in NR. TRS may be configured, for example, via ‘trs-Info’ in the NZP-CSI-RS- ResourceSet IE of 3GPP TS 38.331 V17.5.0, which is associated with a CSI-RS resource set, for which the UE may assume that the antenna port with the same port index of the configured NZP CSI-RS resources in the said resource set is the same. From a 3GPP specifications perspective, TRS is specified as a special kind of NZP CSI-RS where the corresponding NZP CSI-RS resource set containing the TRS(s) has a higher layer parameter ‘trs-info’ set to true. TRS is not really a CSI-RS, rather it is a resource set consisting of multiple periodic NZP CSI-RSs. More specifically, a TRS has four one-port, density-3 CSI-RSs located within two consecutive slots. The CSI-RS within the said resource set, may be configured with a periodicity of 10, 20, 40, or 80 ms. Note that the exact set of REs used for the TRS CSI-RS may vary. There is always a four-symbol time-domain separation between the two CSI-RS within a slot. FIG. 3 is an example of a periodic TRS, where TRS locations within two consecutive slots are shown. The TRS in the two slots are also referred to a TRS burst. NR also supports aperiodic TRS. CSI framework in NR In NR, a UE may be configured with multiple CSI reporting settings and multiple CSI-RS resource settings. Each resource setting may contain multiple resource sets, and each resource set may contain up to 8 CSI-RS resources. For each CSI reporting setting, a UE feeds back a CSI report. Each CSI reporting setting may contain at least the following information: • A CSI-RS resource set for channel measurement; • An IMR resource set for interference measurement; • Optionally, a CSI-RS resource set for interference measurement; • Time-domain behavior, i.e. periodic, semi-persistent, or aperiodic reporting; • Frequency granularity, i.e. wideband or subband; • CSI parameters to be reported such as rank indicator (RI), precoder matrix indicator (PMI), channel quality indicator (CQI), and CSI-RS resource indicator (CRI) in case of multiple CSI-RS resources in a resource set; • Codebook types, i.e. Type I or II, and codebook subset restriction; • Measurement restriction; and • Subband size. One out of two possible subband sizes is indicated, the value range depends on the bandwidth of the bandwidth part (BWP). One CQI / PMI (if configured for subband reporting) is fed back per subband). In NR, CSI-AperiodicTriggerState is configured in order to trigger aperiodic CSI reports. The CSI-AperiodicTriggerList IE is defined in 3GPP TS 38.331 V17.2.0 as follows: There is list of trigger states which may include up to 128 of CSI- AperiodicTriggerStates. Each trigger state may include up to 16 CSI- AssociatedReportConfigInfo. Each CSI-AssociatedReportConfigInfo contains a reportconfig id which associates it to a CSI-Reportconfig. The UE may have up to 48 different reportconfigs configured. Each Reportconfig includes codebookConfig as a field. Rel-18 TRS based TDCP reporting It has been considered that TRS based TDCP (time domain channel properties) reporting will be supported in NR Technical Release 18 (3GPP Rel-18). There are several use cases for the network node to know the TDCP (time domain channel properties) based on TRS measurements. One use case for TDCP reporting is to enable the network node to select a transmission scheme that is more robust to channel ageing when the channel varies fast. For instance, based on the TRS-based TDCP reported by the UE to the network node, the network node may need to decide whether the precoder for the UE should be based on CSI obtained from uplink measurements or from CSI feedback obtained from the UE. Another example is that the network node may need to decide whether the precoder to schedule the UE should be based on Type I CSI feedback (as specified in 3GPP TS 38.214) obtained from the UE or Type II CSI feedback (as specified in 3GPP TS 38.214) obtained from the UE. FIGS. 4 and 5 show examples of mean user throughput for a particular scheme relative to the mean throughput for feedback-based single user-multiple input multiple output (SU-MIMO) precoding (the baseline). The throughput is calculated for a traffic load corresponding to 70% resource utilization for the baseline case at each UE speed. Results for both SU-MIMO and multi-user (MU)-MIMO are shown in FIGS. 4 and 5. The scenario is UMa with 500 m inter-site distance. The carrier frequency is 2 GHz and the subcarrier spacing is 15 kHz. The CSI periodicity is 20 ms for both feedback and reciprocity-based CSI. The results show that reciprocity-based precoding has better performance at 3 km / h for both SU-MIMO and MU-MIMO. However, at UE speeds around 10 km / h the feedback-based precoding has better performance. Hence, the feedback-based precoding is more robust to rapidly varying channels. A speed of 10 km / h corresponds to a channel coherence time which is longer than two slots. These results show that it may be beneficial to select a precoding scheme based on some parameter that is related to the UE speed. It should be noted that it is not the UE speed per se that is the fundamental parameter in this context. Rather, it is how fast the channel varies which depends on the UE speed and on the angle between the UE velocity vector and the propagation paths seen from the UE. Therefore, selection of a precoding scheme based on some TDCP such as coherence time or autocorrelation is a more suitable parameter. UE measurement and reporting of time domain correlation based on TRS samples across different time lags is an efficient way to report TDCP based on TRS. In order to define the time domain correlation measurement across TRS samples, let ^^^^^, ^ = 0,1, … , ^ − 1 be the received frequency domain TRS samples after matched filtering and after removing the reference signal sequence. Index ^ denotes the different OFDM symbols carrying the TRSs used for the correlation estimation. Note that the TRSs used for the correlation estimation may be located in the same or different slots. The starting point in time of the OFDM symbol ^ is given by ^^(to be precise ^^denotes the start of the non-CP part of the OFDM symbol). Index n denote TRS sample index (assumed to be proportional to subcarrier index). Let ^^^^^, ^ = 1 … ^, ^ = 1,2 be the ^-indices of ^ symbol pairs to use for the estimation of the correlation for a delay ^ = ^^^^^^− It is assumed that the ^ symbol pairs are separated by the same distance in time. In one example, a low-complexity estimate of the normalized time domain correlation for a delay ^ is calculated in the frequency domain as: In another example, the inverse discrete Fourier transform (DFT) is calculated for each OFDM symbol ^: / ^^0^= 122^^^^^^^^The estimate of the normalized correlation for time delay ^ is calculated as: where the sum over time samples is over sets Γ^^^defined to suppress noise, e.g., by using a noise threshold such as, for example: where A^^^I^are noise estimates. Note that at low speeds, the change in the channel is small and the change in correlation at different delays within a TRS burst (i.e., within two slots) is quite small. Within a TRS burst, correlation may be measured for delays of 4 symbols, 10 symbols, 14 symbols, and 18 symbols, as shown in the examples of FIGS. 6 and 7. As the change in correlation at different delays within a TRS burst is quite small for low velocities, intra TRS burst measurements are not enough to distinguish between different velocities in the low velocity region. Therefore, measuring and reporting correlation for time delays corresponding to multiple TRS bursts will also be supported in 3GPP Rel-18. See FIG. 8. TDCP reporting supported in 3GPP (NR) Rel-18 is performed after radio resource control (RRC) configuration when the UE is in RRC connected mode. Random access procedures in LTE and NR The random-access procedures in LTE and NR are similar. In the existing random- access design, random-access procedures serve multiple purposes such as initial access when establishing a radio link, scheduling request, etc. Among others, an objective of the random-access procedures is to achieve uplink synchronization, which is for maintaining the uplink orthogonality in LTE and NR. To preserve the orthogonality of uplink signals from different UEs in an OFDM access (OFDMA) based system, the time of arrival of each UE’s signal needs to be within the cyclic prefix (CP) of the OFDM signal at the network node. In the rest of this document, steps 2, 3, and 4 shown in FIG. 9 will be referred to as message 2, message 3, and message 4, respectively. LTE and NR random access may be either contention-based or contention-free. The contention-based random access procedure has four steps, as illustrated in FIG. 9: 1) Message 1: the UE transmits a random access preamble; 2) Message 2: the network node (e.g., gNB / eNB) transmits a random access response that contains timing advance (TA) command and the scheduling of uplink resource for the UE to use in the third step. Note that random access response is a PDCCH / PDSCH transmission wherein the PDCCH is transmitted in the common search space; 3) Message 3: the UE transmits its identity to the network using the scheduled resources; and 4) Message 4: the network node transmits a contention-resolution message to resolve any contention due to multiple UEs transmitting the same random-access preamble in the first step. For contention-free random access, the UE uses reserved preambles assigned by the network node (e.g., gNB / eNB). In this case, contention resolution is not needed and therefore, only Steps 1 and 2 are required. In NR, message 3 is scheduled by random access response (RAR) uplink grant. The contents of an RAR uplink grant are shown in Table 1 below. It should be noted that in 3GPP (NR) Rel-15, the CSI request bit in an RAR uplink grant is reserved. Table 1: Random Access Response Grant Content field size (from Table 8.2-1 of 3GPP TS 38.213 V17.6.0) The ‘PUSCH time resource allocation’ field in an RAR grant is used to indicate the timing offset and the start / length of resources allocated for message 3. This four-bit field is used to indicate one of the rows in Table 2, which provides a time offset value K2 (note that K2is given in slots), the start symbol S and the length of the allocated resources L. The value j used to define K2depends on subcarrier spacing (SCS) of the physical uplink shared channel (PUSCH) (denoted as µPUSCH) and is given in Table 3. Table 2: Default Physical Uplink Shared Channel (PUSCH) time domain resource allocation A for normal cyclic prefix (CP) (from Table 6.1.2.1.1-2 of 3GPP TS 38.214, V17.6.0) Table 3: Definition of value j (from Table 6.1.2.1.1-4 of 3GPP TS 38.214 V17.6.0) The timing offset for message 3 relative to message 2 is depicted in the example of FIG. 10. For a physical downlink shared channel (PDSCH) with a RAR message ending in slot n, the UE transmits the message 3 PUSCH in slot n+ K2+ Δ, where Δ is given in Table 4. SSBs and SS Burst Set In NR, NR-PSS (NR - Primary Synchronization Signal), NR-SSS (NR - Secondary Synchronization Signal) and NR-PBCH (NR - Physical Broadcast Channel) are transmitted within an SS block (An SS block may also be referred to as SS / PBCH block or SSB). An SSB spans 4 OFDM symbols with: • the NR-PSS being transmitted in 127 subcarriers in the 1stOFDM symbol of the SSB; • the NR-SSS being transmitted in 127 subcarriers in the 3rdOFDM symbol of the SSB; and • the NR-PBCH is transmitted in 240 subcarriers in the 2ndand 4thOFDM symbols of the SSB, and in 96 subcarriers in the 3rdOFDM symbol of the SSB. It should be noted that the narrow band physical broadcast channel (NB-PBCH) consumes 576 REs which also contain the PBCH demodulation reference signals (DMRS) which are used for demodulation of NR-PBCH. An SS burst set consists of one or multiple SSBs. The default periodicity of an SS burst set is 20ms, and the transmission of SSBs within an SS burst set is confined to a 5ms window regardless of the periodicity of SS burst set. The maximum number L of SSBs within SS burst set for different frequency ranges are defined as follows: • For frequency range up to 3 GHz, L is 4; • For frequency range from 3 GHz to 6 GHz, L is 8; and • For frequency range from 6 GHz to 52.6 GHz, L is 64 QCL Several signals may be transmitted from the same network node antenna from different antenna ports. These signals may have the same large-scale properties, for instance in terms of Doppler shift / spread, average delay spread, or average delay. These antenna ports are then said to be quasi co-located (QCL). The network may then signal to the UE that two antenna ports are QCL. If the UE knows that two antenna ports are QCL with respect to a certain parameter (e.g., Doppler spread), the UE may estimate that parameter based on one of the antenna ports and use that estimate when receiving the other antenna port. Typically, the first antenna port is represented by a measurement reference signal (known as source RS) such as CSI-RS (Channel State Information RS) and the second antenna port is a demodulation reference signal (DMRS) (known as target RS). This is useful for demodulation since the UE may know beforehand the properties of the channel when doing channel estimation with DMRS. Information about what assumptions may be made regarding QCL is signaled to the UE from the network. In NR, four types of QCL relations between a transmitted source RS and transmitted target RS were defined: • Type A: {Doppler shift, Doppler spread, average delay, delay spread}; • Type B: {Doppler shift, Doppler spread}; • Type C: {average delay, Doppler shift}; and • Type D: {Spatial Rx parameter}. QCL type D was introduced to facilitate beam management with analog beamforming and is known as spatial QCL. There is currently no strict definition of spatial QCL, but the understanding is that if two transmitted antenna ports are spatially QCL, the UE may use the same Rx beam to receive them. Since 3GPP Rel-18 TDCP reporting is performed after RRC configuration when the UE is in RRC connected mode, decisions made based on TDCP reports at the network side (e.g., configuring UE for reciprocity-based CSI versus configuring UE for feedback- based CSI) may only be performed after the network receives a TDCP report which occurs after the UE moves to RRC connected mode and after RRC configuration. This means that the network may first RRC configure the UE with TDCP reporting after the UE is in RRC connected mode, then receive the configured TDCP report from the UE, and thereafter do other configurations (e.g., for reciprocity-based CSI vs. feedback-based CSI) based on the TDCP feedback. This will result in large delays as the configurations that depend on the TDCP feedback may only be performed after receiving the TDCP report. Hence, how to reduce TDCP acquisition delay is an open problem to be solved. SUMMARY Some embodiments advantageously provide methods, systems, and apparatuses for early time domain channel properties (TDCP) feedback via a 4-step random access channel (RACH) procedure. Methods for acquiring a TDCP report early during a 4 step RACH procedure are disclosed herein. Some embodiments include one or more of the following: • determining how the UE receives information on RS(s) to be used for TDCP measurement and reporting via a system information block (SIB); • triggering an aperiodic TDCP report request in message 2 of a 4-step RACH procedure, and / or • providing a TDCP report as part of message 3 of a 4-step RACH procedure. In some embodiments, the network may get an early TDCP report as part of message 3 of 4-step RACH procedure. The early TDCP report may be used by the network node to appropriately configure the UE with an RRC parameter configurations when the UE moves to RRC connected state. This reduces the configuration delays associated with the 3GPP Rel-18 based TDCP reporting solutions where the TDCP reporting is only available after the UE has received RRC configuration once the UE has moved to RRC connected state. According to one aspect, a network node configured to communicate with a UE is provided. The network node is configured to transmit information to the UE to assist the UE to acquire time domain channel properties, TDCP. The network node is also configured to configure the UE by a triggering signal in a message 2 of a 4-step random access procedure, the triggering signal causing the UE to transmit a TDCP report. The network node is also configured to receive the TDCP report in a message 3 of the 4-step random access procedure. According to this aspect, in some embodiments, the network node is configured to receive from the UE a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission. In some embodiments, the network node is configured to transmit to the UE at least one tracking reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource relative to a previously received signal. In some embodiments, the network node is configured to indicate at least one aperiodic tracking reference signal to be used for TDCP measurements by the UE. In some embodiments, the at least one aperiodic tracking reference signal to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure. In some embodiments, the at least one aperiodic tracking reference signal is received in a same slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered. In some embodiments, the at least one aperiodic tracking reference signal is received in a slot after a slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received. In some embodiments, the TDCP report is an aperiodic TDCP report. In some embodiments, the transmitted information includes a correlation value of a correlation of samples of a tracking reference signal, TRS. In some embodiments, the method includes transmitting to the UE at least one periodic reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource. According to another aspect, a method implemented in a network node configured to communicate with a user equipment, UE, is provided. The method includes transmitting information to the UE to assist the UE to acquire time domain channel properties, TDCP. The method also includes configuring the UE by a triggering signal in a message 2 of a 4- step random access procedure, the triggering signal causing the UE to transmit a TDCP report. The method includes receiving the TDCP report in a message 3 of the 4-step random access procedure. According to this aspect, in some embodiments, the method includes receiving from the UE a TDCP report in a message 3 of the 4-step random access procedure. In some embodiments, the method includes receiving from the UE a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission. In some embodiments, the method includes transmitting to the UE at least one tracking reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource relative to a previously received signal. In some embodiments, the method includes indicating at least one aperiodic tracking reference signal to be used for TDCP measurements by the UE. In some embodiments, the at least one aperiodic tracking reference signal to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure. In some embodiments, the method includes receiving the at least one aperiodic tracking reference signal in a same slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered. In some embodiments, the method includes receiving the at least one aperiodic tracking reference signal in a slot after a slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received. In some embodiments, the TDCP report is an aperiodic TDCP report. In some embodiments, the transmitted information includes a correlation value of a correlation of samples of a tracking reference signal, TRS. In some embodiments, the method includes transmitting to the UE at least one periodic reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource. According to yet another aspect, a user equipment, UE, configured to communicate with a network node is provided. The UE is configured to receive assistance information from the network node to assist the UE to acquire time domain channel properties, TDCP. The UE is configured to receive a triggering signal from the network node on message 2 of a 4-step random access procedure. The UE is also configured to perform TDCP measurements based at least in part on the received assistance information. The UE is also configured to, responsive to the triggering signal, transmit to the network node a TDCP report in a message 3 of the 4-step random access procedure. According to this aspect, in some embodiments, the UE is configured to transmit to the network node a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission. In some embodiments, the UE is configured to receive from the network node at least one tracking reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource relative to a previously received signal. In some embodiments, the UE is configured to receive an indication of at least one aperiodic tracking reference signal to be used for TDCP measurements by the UE. In some embodiments, the at least one aperiodic tracking reference signal to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure. In some embodiments, the at least one aperiodic tracking reference signal is transmitted in a second slot corresponding to a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered. In some embodiments, the at least one aperiodic tracking reference signal is transmitted in a second slot after a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4- step random access procedure is received. In some embodiments, the UE is configured to receive from the network node at least one periodic reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource. In some embodiments, the TDCP report is an aperiodic TDCP report. In some embodiments, the received assistance information includes a correlation value of a correlation of samples of a tracking reference signal, TRS. According to another aspect, a method implemented in a user equipment, UE, configured to communicate with a network node is provided. The method includes receiving assistance information from the network node to assist the UE to acquire time domain channel properties, TDCP. The method includes receiving a triggering signal from the network node on message 2 of a 4-step random access procedure. The method also includes performing TDCP measurements based at least in part on the at least one correlation delay value. The method also includes, responsive to the triggering signal, transmitting to the network node a TDCP report in a message 3 of the 4-step random access procedure. According to this aspect, in some embodiments, the method includes transmitting to the network node a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission. In some embodiments, the method includes receiving from the network node at least one tracking reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource relative to a previously received signal. In some embodiments, the method includes receiving an indication of at least one aperiodic tracking reference signal to be used for TDCP measurements by the UE. In some embodiments, the at least one aperiodic tracking reference signal to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure. In some embodiments, the at least one aperiodic tracking reference signal is transmitted in a second slot corresponding to a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered. In some embodiments, the at least one aperiodic tracking reference signal is transmitted in a second slot after a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4- step random access procedure is received. In some embodiments, the method includes receiving from the network node at least one periodic reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource. In some embodiments, the TDCP report is an aperiodic TDCP report. In some embodiments, the received assistance information includes a correlation value of a correlation of samples of a tracking reference signal, TRS. BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: FIG. 1 illustrates a time-frequency structure of a synchronization signal / physical broadcast (SS / PBCH) block; FIG. 2 is an example of resource element (RE) allocation for a 12 port channel state information reference signal in New Radio (NR); FIG. 3 is an example of periodic tracking reference signaling (TRS); FIG. 4 is a graph of relative mean user input versus user equipment (UE) speed for reciprocity based channel state information (CSI) and feedback based CSI for 16 network node antenna ports; FIG. 5 is a graph of relative mean user input versus UE speed for reciprocity based channel state information (CSI) and feedback based CSI for 32 network node antenna ports; FIG. 6 is a graph of elative mean user input versus UE speed for Type II CSI for 16 network node antenna ports; FIG. 7 is a graph of elative mean user input versus UE speed for Type II CSI for 32 network node antenna ports; FIG. 8 illustrates delays for which the correlation may be estimated based on intra TRS burst measurements using a TRS signal; FIG. 9 illustrates a contention based random access procedure; FIG. 10 illustrates a timing offset of message 3; FIG. 11 is a schematic diagram of an example network architecture illustrating a communication system according to principles disclosed herein; FIG. 12 is an example of a user equipment and network node configured for early time domain channel properties (TDCP) feedback via a 4-step random access channel (RACH) procedure; FIG. 13 is a flowchart of an example process in a network node for methods of early time domain channel properties (TDCP) feedback via a 4-step random access channel (RACH) procedure. FIG. 14 is a flowchart of an example process in a network node for methods of early time domain channel properties (TDCP) feedback via a 4-step random access channel (RACH) procedure; FIG. 15 is a flowchart of one example process for acquiring an early TDCP report via of 4 step random access channel (RACH) procedure; FIG. 16 is an example of triggering TDCP by a downlink control information (DCI) scheduling a random access response; and FIG. 17 is an example of using message 2 to trigger aperiodic reference signals to be used for TDCP measurement. DETAILED DESCRIPTION Before describing in detail example embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to methods of early time domain channel properties (TDCP) feedback via a 4-step random access channel (RACH) procedure. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Like numbers refer to like elements throughout the description. As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and / or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication. In some embodiments described herein, the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and / or wireless connections. The term “network node” used herein may be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi- standard radio (MSR) radio node such as MSR BS, multi-cell / multicast coordination entity (MCE), integrated access and backhaul (IAB) node, relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rdparty node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term “radio node” used herein may be used to also denote a wireless device (WD) or user equipment (UE). In some embodiments, the non-limiting terms wireless device (WD) or a user equipment (UE) are used interchangeably. The UE herein may be any type of wireless device capable of communicating with a network node or another UE over radio signals, such as a wireless device (WD). The UE may also be a radio communication device, target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine communication (M2M), low-cost and / or low-complexity UE, a sensor equipped with UE, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (IoT) device, or a Narrowband IoT (NB-IOT) device, etc. Also, in some embodiments the generic term “radio network node” is used. It may be any kind of a radio network node which may comprise any of base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, Multi-cell / multicast Coordination Entity (MCE), IAB node, relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH). Note that although terminology from one particular wireless system, such as, for example, 3GPP LTE and / or New Radio (NR), may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system. Other wireless systems, including without limitation Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from exploiting the ideas covered within this disclosure. Note further, that functions described herein as being performed by a wireless device or a network node may be distributed over a plurality of wireless devices and / or network nodes. In other words, it is contemplated that the functions of the network node and wireless device described herein are not limited to performance by a single physical device and, in fact, may be distributed among several physical devices. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Some embodiments provide methods of early time domain channel properties (TDCP) feedback via a 4-step random access channel (RACH) procedure. Returning now to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in FIG. 11 a schematic diagram of a communication system 10, according to an embodiment, such as a 3GPP-type cellular network that may support standards such as LTE and / or NR (5G), which comprises an access network 12, such as a radio access network, and a core network 14. The access network 12 comprises a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes 16), such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas 18). Each network node 16a, 16b, 16c is connectable to the core network 14 over a wired or wireless connection 20. A first user equipment (UE) 22a located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16a. A second UE 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16b. While a plurality of UEs 22a, 22b (collectively referred to as wireless devices 22) are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding network node 16. Note that although only two UEs 22 and three network nodes 16 are shown for convenience, the communication system may include many more UEs 22 and network nodes 16. Also, it is contemplated that a UE 22 can be in simultaneous communication and / or configured to separately communicate with more than one network node 16 and more than one type of network node 16. For example, a UE 22 can have dual connectivity with a network node 16 that supports LTE and the same or a different network node 16 that supports NR. As an example, UE 22 can be in communication with an eNB for LTE / E-UTRAN and a gNB for NR / NG-RAN. A network node 16 is configured to include a RACH unit 32 which may be configured to configure the UE by a triggering signal in a message 2 of a 4-step random access procedure, the triggering signal causing the UE to transmit a TDCP report. A wireless device 22 is configured to include a TDCP unit 34 which may be configured to, responsive to the triggering signal, perform TDCP measurements based at least in part on received assistance information. Example implementations, in accordance with an embodiment, of the UE 22 and network node 16 discussed in the preceding paragraphs will now be described with reference to FIG. 12. The communication system 10 includes a network node 16 provided in a communication system 10 and including hardware 28 enabling it to communicate with the UE 22. The hardware 28 may include a radio interface 30 for setting up and maintaining at least a wireless connection 32 with a UE 22 located in a coverage area 18 served by the network node 16. The radio interface 30 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 30 includes an array of antennas 34 to radiate and receive signal(s) carrying electromagnetic waves. In the embodiment shown, the hardware 28 of the network node 16 further includes processing circuitry 36. The processing circuitry 36 may include a processor 38 and a memory 40. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 36 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 38 may be configured to access (e.g., write to and / or read from) the memory 40, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory). Thus, the network node 16 further has software 42 stored internally in, for example, memory 40, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the network node 16 via an external connection. The software 42 may be executable by the processing circuitry 36. The processing circuitry 36 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by network node 16. Processor 38 corresponds to one or more processors 38 for performing network node 16 functions described herein. The memory 40 is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 42 may include instructions that, when executed by the processor 38 and / or processing circuitry 36, causes the processor 38 and / or processing circuitry 36 to perform the processes described herein with respect to network node 16. For example, processing circuitry 68 of the network node 16 may include a RACH unit 32 which may be configured to configure the UE by a triggering signal in a message 2 of a 4-step random access procedure, the triggering signal causing the UE to transmit an aperiodic TDCP report. The communication system 10 further includes the UE 22 already referred to. The UE 22 may have hardware 44 that may include a radio interface 46 configured to set up and maintain a wireless connection 32 with a network node 16 serving a coverage area 18 in which the UE 22 is currently located. The radio interface 46 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 46 includes an array of antennas 48 to radiate and receive signal(s) carrying electromagnetic waves. The hardware 44 of the UE 22 further includes processing circuitry 50. The processing circuitry 50 may include a processor 52 and memory 54. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 50 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 52 may be configured to access (e.g., write to and / or read from) memory 54, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory). Thus, the UE 22 may further comprise software 56, which is stored in, for example, memory 54 at the UE 22, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the UE 22. The software 56 may be executable by the processing circuitry 50. The software 56 may include a client application 58. The client application 58 may be operable to provide a service to a human or non-human user via the UE 22. The processing circuitry 50 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by UE 22. The processor 52 corresponds to one or more processors 52 for performing UE 22 functions described herein. The UE 22 includes memory 54 that is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 56 and / or the client application 58 may include instructions that, when executed by the processor 52 and / or processing circuitry 50, causes the processor 52 and / or processing circuitry 50 to perform the processes described herein with respect to UE 22. For example, the processing circuitry 50 of the UE 22 may include a TDCP unit 34 which may be configured to, responsive to the triggering signal, perform TDCP measurements based at least in part on received assistance information. In some embodiments, the inner workings of the network node 16 and UE 22 may be as shown in FIG. 12 and independently, the surrounding network topology may be that of FIG. 11. The wireless connection 32 between the UE 22 and the network node 16 is in accordance with the teachings of the embodiments described throughout this disclosure. More precisely, the teachings of some of these embodiments may improve the data rate, latency, and / or power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime, etc. In some embodiments, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. Although FIGS. 11 and 12 show various “units” such as RACH unit 24 and TDCP unit 26 as being within a respective processor, it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry. FIG. 13 is a flowchart of an example process in a network node 16 for methods of early time domain channel properties (TDCP) feedback via a 4-step random access channel (RACH) procedure. One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 68 (including the RACH unit 32), processor 70, radio interface 62 and / or communication interface 60. Network node 16 such as via processing circuitry 68 and / or processor 70 and / or radio interface 62 and / or communication interface 60 is configured to transmit information to the UE to assist the UE to acquire time domain channel properties, TDCP (Block S10). The process includes configuring the UE 22 by a triggering signal in a message 2 of a 4-step random access procedure (Block S12). The process also includes receiving the TDCP report in a message 3 of the 4-step random access procedure (Block S14). In some embodiments, the method includes receiving from the UE 22 a TDCP report in a message 3 of the 4-step random access procedure. In some embodiments, the method includes receiving from the UE 22 a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission. In some embodiments, the method includes transmitting to the UE 22 at least one tracking reference signal to be used for TDCP measurements by the UE 22 in a pre-defined time-frequency resource relative to a previously received signal. In some embodiments, the method includes indicating at least one aperiodic tracking reference signal to be used for TDCP measurements by the UE 22. In some embodiments, the at least one aperiodic tracking reference signal to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure. In some embodiments, the method includes receiving the at least one aperiodic tracking reference signal in a same slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered. In some embodiments, the method includes receiving the at least one aperiodic tracking reference signal in a slot after a slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received. In some embodiments, the TDCP report is an aperiodic TDCP report. In some embodiments, the transmitted information includes a correlation value of a correlation of samples of a tracking reference signal, TRS. In some embodiments, the method includes transmitting to the UE at least one periodic reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource. FIG. 14 is a flowchart of an example process in a wireless device 22 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of wireless device 22 such as by one or more of processing circuitry 84 (including the TDCP unit 34), processor 86, radio interface 82 and / or communication interface 60. Wireless device 22 such as via processing circuitry 84 and / or processor 86 and / or radio interface 82 is configured to receiving assistance information from the network node 16 to assist the UE 22 to acquire time domain channel properties, TDCP (Block S16). The process also includes receiving a triggering signal from the network node 16 on message 2 of a 4-step random access procedure (Block S18). The process also includes performing TDCP measurements based at least in part on the received assistance information (Block S20). The process also includes, responsive to the triggering signal (Block S22), transmitting to the network node a TDCP report in a message 3 of the 4-step random access procedure. In some embodiments, the method includes transmitting to the network node 16 a TDCP report in a message 3 of the 4-step random access procedure. In some embodiments, the method includes transmitting to the network node 16 a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission. In some embodiments, the method includes receiving from the network node at least one tracking reference signal to be used for TDCP measurements by the UE 22 in a pre-defined time-frequency resource relative to a previously received signal. In some embodiments, the method includes receiving an indication of at least one aperiodic tracking reference signal to be used for TDCP measurements by the UE 22. In some embodiments, the at least one aperiodic tracking reference signal to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure. In some embodiments, the at least one aperiodic tracking reference signal is transmitted in a second slot corresponding to a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered. In some embodiments, the at least one aperiodic tracking reference signal is transmitted in a second slot after a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received. In some embodiments, the method includes receiving from the network node at least one periodic reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource. In some embodiments, the TDCP report is an aperiodic TDCP report. In some embodiments, the received assistance information includes a correlation value of a correlation of samples of a tracking reference signal, TRS. Having described the general process flow of arrangements of the disclosure and having provided examples of hardware and software arrangements for implementing the processes and functions of the disclosure, the sections below provide details and examples of arrangements for methods of early time domain channel properties (TDCP) feedback via a 4-step random access channel (RACH) procedure. Some embodiments may be summarized as shown in FIG.15. Further details of each step in the flow-chart are disclosed herein. Note that the order of the second and the third steps in FIG. 15 may be reversed in some embodiments, i.e., the UE 22 may measure TDCP based on a periodic downlink (DL) RS before being triggered for a TDCP report. Some embodiments acquire early TDCP according to principles disclosed herein. Although the embodiments may be written in terms of NR terminology, the embodiments are non-limiting and are equally applicable for future wireless standards such as 6G and beyond. During initial access the UE 22 searches for and finds a cell via an associated SSB from which it acquires the physical cell Identity (PCI) of the cell and some information of the cell in the associated master information block (MIB). Second, the UE 22 receives SIB1, and acquires remaining system information (RMSI) containing information on how to access the cell. Step 1: In some embodiments, the UE 22 receives information related to one or more reference signal (RS) resource(s) to be used for acquiring the early TDCP. In some embodiments, the information received by the UE 22 may be received via a system information block (SIB): • In some embodiments, the information received by the UE 22 may be the time and frequency resource allocation of the one or more RS resource(s), the correlation delay between two RS resources or samples of one RS resource to be used for TDCP measurement, and / or a scrambling sequence, etc. In some embodiments, the information the UE 22 receives may cause the UE 22 to perform early time domain channel property (TDCP) measurements and reporting for a single correlation delay (i.e., only a single correlation delay value indicated in the information received by the UE 22). In some embodiments, the information received by the UE 22 may cause the UE 22 to perform early TDCP measurements and reporting for more than one correlation delay (i.e., more than one correlation delay value indicated in the information received by the UE 22). In some embodiments, the information received by the UE 22 may cause the UE 22 to perform early TDCP measurements and then report information indicating whether the UE 22 is experiencing rapid channel variations. The type of RS in this embodiment may be any one of SSB, DM-RS associated with SSB, DMRS associated with PDCCH, DM-RS associated with PDSCH, CSI-RS, or TRS. In some embodiments, these RSs are available to the UE 22 before the UE 22 enters RRC connected mode. In some embodiments, these RSs are configured for TDCP measure if UE 22 is in idle state; and / or • In some embodiments, the information may be configured to use the existing CSI framework in NR and hence, the UE 22 may receive a default CSI reporting setting(s) and an associated CSI resource setting(s) from the network node 16 via SIB (e.g., SIB1) to be used for the purpose of acquiring early TDCP. The RS type of the RS resources may be indicated as part of the associated CSI resource setting(s) and may be one of SSB, DM- RS, CSI-RS or TRS. Note that in some embodiments of the first alternative above, the RSs used to measure TDCP may be configured as a standalone RSs, i.e., outside the normal CSI framework defined in NR. The CSI-RS sequence may for instance be initialized by a function of the PCI value. In the second alternative, an existing CSI framework is reused and hence more flexibility is obtained at the expense of larger SIB overhead. Step 2: In some embodiments, the UE 22 receives a trigger for TDCP measurement and reporting via message 2 (e.g., normalized correlation amplitude and / or phase for indicated correlation delay(s), or information indicating whether the UE 22 is experiencing rapid channel variations): • In some embodiments, a trigger from the network node 16 indicates to the UE 22 one or more aperiodic RS(s) to be used for TDCP measurement using message 2 of the 4-step random access procedure. In this case, the trigger may be triggered by the CSI request field in a message 2 or RAR in Msg2 physical downlink shared channel (PDSCH). The aperiodic RS(s) may be a CSI-RS, TRS or DM-RS associated with physical downlink control channel (PDCCH) and / or PDSCH. The aperiodic RS(s) may either be received in the same slot in which PDCCH for message 2 is triggered or in a slot after the slot in which PDCCH for message 2 is received; • In some embodiments, the RS(s) to be used for TDCP measurement is not aperiodically triggered; instead the RS(s) is transmitted in a pre-defined time / frequency position (physical resource), relative to one of the earlier received channels / signals (i.e. SSB, SIB1). Hence, in some embodiments, the UE 22 directly measures TDCP on the RS(s) after acquiring SIB information without the need to receive a trigger. In some embodiments, the RS(s) is continually or continuingly transmitted by the network, in association to with, for example, an SIB: o In some embodiments, when SSB is used for TDCP measurement, the SSB is selected by the UE 22 among multiple SSBs each with a SSB index. The selected SSB may be one of the multiple SSBs with the strongest received signal power or the one based on which the UE 22 derives the corresponding physical random access channel (PRACH). The TDCP may be measured within a SS / PBCH block (i.e., correlations between different symbols within a SS / PBCH block) or between SSB blocks (i.e., correlations between different SS / PBCH blocks with a same SSB index at different time locations) or both within a SS / PBCH block and between SS / PBCH blocks with a same SSB index. Step 3: In some embodiments, the UE 22 performs TDCP measurement on the RS(s) that the UE 22 received in Step 1. Upon completing the TDCP measurements on the RS(s), the UE 22 computes an aperiodic TDCP report according to either the information received by the UE 22 in Step 1 or the default CSI report setting received by the UE 22 in Step 1. Step 4: In some embodiments, the UE 22 sends the aperiodic TDCP report as part of message 3 or alternatively as a separate PUSCH transmission scheduled by a PDCCH. Note that although the autocorrelation based TDCP reporting is specifically mentioned in the disclosure, the UE 22 may also be configured to report other type of information (e.g., other TDCP quantities, or an implicit identifier such as UE 22 moving speed or an explicit identifier such as a number of bits for indicating the severity of channel variation (e.g., according to a pre-defined table)), that indicates the channel variation experienced by the UE 22. Example Embodiment 1: Detailed signaling of RS(s) and TDCP In some embodiments, an aperiodic TDCP report is triggered via message 2. In NR, message 2 (also known as random access response or RAR message) is scheduled by a DCI with format 1_0 which has its CRC scrambled by random access radio network temporary identifier (RA-RNTI). Note that a DCI with format 1_0 and scrambled by RA- RNTI has 16 reserved bits. An example is shown in FIG. 16, where TDCP is measured by the UE 22 based on a periodic DL RS such as a SSB and TDCP is reported after receiving a request or trigger carried in a DCI that schedules a RACH response message carried by a PDSCH. In some, embodiments, the aperiodic TDCP report may be triggered and message 2 may also optionally trigger aperiodic RS(s) which are to be used for TDCP measurements. In some embodiments, the TDCP may be triggered by a DCI other than the one scheduling the PDSCH for a RACH response message, e.g., a uplink DCI (i.e., DCI format 0_0). In some embodiments, information on a default CSI reporting setting and RS resource(s) (e.g., CSI resource setting(s)) are indicated to the UE 22 from the network node 16 via a SIB (e.g., SIB1). Information included in the default CSI reporting setting may include one or more of: • RS resource(s) for TDCP measurement; • the number of correlation delay value(s) for which TDCP quantities shall be evaluated / estimated; • the one or more correlation delay value(s) each of which corresponds to one TDCP measurement (i.e., a first TDCP measurement corresponding to a first correlation delay value ^^, a second TDCP measurement corresponding to a second correlation delay value ^^, etc.); • information identifying whether the UE 22 is allowed to report TDCP quantities for a subset of configured RS resources; and / or • the TDCP quantities to evaluate and report (e.g., whether to report only normalized correlation amplitude, only normalized correlation phase, or both normalized correlation amplitude and phase), etc. Similarly, information regarding RS(s) to be used for TDCP measurement may include one or more of: • the time and frequency location(s) (e.g., slots, symbols, resource elements, slot / symbol offset between 2 RS resources to be measured, subcarrier spacing, frequency offset to the point A etc.) of the one or more RS resource(s); • the correlation delay between two RS resources or different samples of one RS resource to be used for TDCP measurement; • scrambling sequence; and / or • (optionally) power ratio between RSs or between RSs and data, etc. In some embodiments, a set of default CSI reporting settings for TDCP reporting and corresponding CSI resource setting(s) for TDCP measurement may be predefined in 3GPP specifications. In some embodiments, the “CSI request” field in DCI Format 1_0 scrambled with RA-RNTI is used to trigger an aperiodic TDCP report. In some embodiments, the “CSI request” bit in an RAR uplink grant is used to jointly trigger a default CSI reporting setting for TDCP reporting and CSI resource setting(s) for TDCP measurement indicated to the UE 22 from network node 16 via SIB (e.g., SIB1). In some embodiments, the “CSI request” bit in RAR uplink grant is used to trigger a default CSI reporting setting for TDCP reporting indicated to the UE 22 from network node 16 via SIB (e.g., SIB1). In some embodiments, when the aperiodic CSI report is to be carried on message 3 where the PUSCH may carry early data and where PUSCH resource allocation may be limited, it may be beneficial to limit the TDCP report to a wideband report. That is, the normalized correlation amplitude and correlation phase may be wideband measurements spanning the bandwidth of the RS(s) used for TDCP measurement. In some embodiments, when the resources for message 3 are limited, the UE 22 reports TDCP for only one of the correlation delay values among the multiple correlation delays configured in the default CSI reporting setting. Furthermore, the UE 22 may down- select the correlation delay for which to report TDCP based on the amplitude of the normalized correlation estimated at each of the delays. In a specific example, the UE 22 selects the correlation delay for which the amplitude of the normalized correlation is farthest from 1. In some embodiments, the TDCP report may be multiplexed with message 3 data in the physical layer, where a power offset between the TDCP and message 3 data may be applied. The power offset may be either pre-specified or signaled in a SIB (e.g., SIB1). In another embodiment, the TDCP report may be included in a MAC CE as part of a MAC PDU carrying the message 3. In some embodiments, a TDCP report may be triggered after message 3, i.e., with a UL grant, e.g., DCI 0-0, may be used to request a TDCP feedback. The TDCP request may be implicitly indicated by using one or more existing field in the DCI. For example, a TDCP request may be indicated when 28≤IMCS≤ 31 , the “New data indicator” is set to 0, and / or the “Redundancy version” is set to 0. A default modulation and coding scheme (MCS) may be used for the corresponding PUSCH. A default reference signal may be used for CSI measurement such as a CSI-RS, a TRS, SSB, or DMRS. Thus, the “CSI request” field may be used to trigger a TDCP report, in some embodiments. A dedicated field specific to the TDCP request (e.g., a “TDCP request” field) may be used instead of the “CSI request” field. In some embodiments, a UE 22 may indicate whether TDCP is reported or not reported to the network when a TDCP is triggered and / or requested. In some scenarios, a UE 22 may not be capable of performing TDCP measurement and reporting or there may not be enough time for the UE 22 to complete the TDCP measurement and report for the given amount of time from the DCI triggering the TDCP to the scheduled PUSCH transmission. Example Embodiment 2: Aperiodic triggering of early triggered RS(s). In addition to triggering the aperiodic TDCP report, DCI for scheduling message 2 may also optionally trigger aperiodic RS(s) which are to be used for TDCP measurements, in some embodiments. An example is shown in FIG. 17, where an aperiodic RS transmitted in two-time locations separated by a delay ^ is triggered and the TDCP is reported in message 3. The configuration of the aperiodic RS may be signaled in a SIB. In some embodiments, aperiodic RS(s) and a TDCP measurement request may be triggered by the DCI scheduling MSG2 and a separate uplink DCI (e.g., DCI format 0_0) may be used later to trigger a TDCP report in another PUSCH scheduled by the DCI. Some embodiments provide the UE 22 with additional time when the UE 22 is to measure TDCP and the existing MSG3 timing is maintained. Some embodiments may include one or more of the following: Embodiment A1. A network node configured to communicate with a user equipment (UE), the network node configured to, and / or comprising a radio interface and / or comprising processing circuitry configured to: transmit information to the UE to assist the UE to acquire time domain channel properties, TDCP, the information including at least one correlation delay value; and configure the UE by a triggering signal in a message 2 of a 4-step random access procedure, the triggering signal causing the UE to transmit a TDCP report. Embodiment A2. The network node of Embodiment A1, wherein the network node, radio interface and / or processing circuitry are configured to receive from the UE a TDCP report in a message 3 of the 4-step random access procedure. Embodiment A3. The network node of any of Embodiments A1 and A2, wherein the network node, radio interface and / or processing circuitry are configured to receive from the UE a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission. Embodiment A4. The network node of any of Embodiments A1-A3, wherein the network node, radio interface and / or processing circuitry are configured to transmit to the UE at least one reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource relative to a previously received signal. Embodiment A5. The network node of any of Embodiments A1-A3, wherein the network node, radio interface and / or processing circuitry are configured to indicate at least one aperiodic reference signal to be used for TDCP measurements by the UE. Embodiment A6. The network node of Embodiment A5, wherein the at least one aperiodic reference signal to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure. Embodiment A7. The network node of any of Embodiments A5 and A6, wherein the at least one aperiodic reference signal is received in a same slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered. Embodiment A8. The network node of any of Embodiments A5 and A6, wherein the at least one aperiodic reference signal is received in a slot after a slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received. Embodiment A9. The network node of any of Embodiments A1 – A8, wherein the TDCP report is an aperiodic TDCP report. Embodiment B1. A method implemented in a network node configured to communicate with a wireless device, UE, the method comprising: transmitting information to the UE to assist the UE to acquire time domain channel properties, TDCP, the information including at least one correlation delay value; and configuring the UE by a triggering signal in a message 2 of a 4-step random access procedure, the triggering signal causing the UE to transmit a TDCP report. Embodiment B2. The method of Embodiment B1, further comprising receiving from the UE a TDCP report in a message 3 of the 4-step random access procedure. Embodiment B3. The method of any of Embodiments B1 and B2, further comprising receiving from the UE a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission. Embodiment B4. The method of any of Embodiments B1-B3, further comprising transmitting to the UE at least one reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource relative to a previously received signal. Embodiment B5. The method of any of Embodiments B1-B3, further comprising indicating at least one aperiodic reference signal to be used for TDCP measurements by the UE. Embodiment B6. The method of Embodiment B5, wherein the at least one aperiodic reference signal to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure. Embodiment B7. The method of any of Embodiments B5 and B6, further comprising receiving the at least one aperiodic reference signal in a same slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered. Embodiment B8. The method of any of Embodiments B5 and B6, further comprising receiving the at least one aperiodic reference signal in a slot after a slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received. Embodiment B9. The method of any of Embodiments B1-B8, wherein the TDCP report is an aperiodic TDCP report. Embodiment C1. A user equipment (UE) configured to communicate with a network node, the UE configured to, and / or comprising a radio interface and / or processing circuitry configured to: receive assistance information from the network node to assist the UE to acquire time domain channel properties, TDCP, the assistance information including at least one correlation delay value; receive a triggering signal from the network node on message 2 of a 4-step random access procedure, the triggering signal causing the UE to transmit a TDCP report; and responsive to the triggering signal, perform TDCP measurements based at least in part on the at least one correlation delay value. Embodiment C2. The UE of Embodiment C1, wherein the UE, radio interface and / or processing circuitry are configured to transmit to the network node a TDCP report in a message 3 of the 4-step random access procedure. Embodiment C3. The UE of any of Embodiments C1 and C2, wherein the UE, radio interface and / or processing circuitry are configured to transmit to the network node a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission. Embodiment C4. The UE of any of Embodiments C1-C3, wherein the UE, radio interface and / or processing circuitry are configured to receive from the network node at least one reference signal to be used for TDCP measurements by the UE in a pre- defined time-frequency resource relative to a previously received signal. Embodiment C5. The UE of any of Embodiments C1-C3, wherein the UE, radio interface and / or processing circuitry are configured to receive an indication of at least one aperiodic reference signal to be used for TDCP measurements by the UE. Embodiment C6. The UE of Embodiment C5, wherein the at least one aperiodic reference signal to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure. Embodiment C7. The UE of any of Embodiments C5 and C6, wherein the at least one aperiodic reference signal is transmitted in a second slot corresponding to a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered. Embodiment C8. The UE of any of Embodiments C5 and C6, wherein the at least one aperiodic reference signal is transmitted in a second slot after a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received. Embodiment C9. The UE of any of Embodiments C1 – C8, wherein the TDCP report is an aperiodic TDCP report. Embodiment D1. A method implemented in a wireless device, UE, configured to communicate with a network node, the method comprising: receiving assistance information from the network node to assist the UE to acquire time domain channel properties, TDCP, the assistance information including at least one correlation delay value; receiving a triggering signal from the network node on message 2 of a 4-step random access procedure, the triggering signal causing the UE to transmit a TDCP report; and responsive to the triggering signal, performing TDCP measurements based at least in part on the at least one correlation delay value. Embodiment D2. The method of Embodiment D1, further comprising transmitting to the network node a TDCP report in a message 3 of the 4-step random access procedure. Embodiment D3. The method of any of Embodiments D1 and D2, further comprising transmitting to the network node a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission. Embodiment D4. The method of any of Embodiments D1-D3, further comprising receiving from the network node at least one reference signal to be used for TDCP measurements by the UE in a pre-defined time-frequency resource relative to a previously received signal. Embodiment D5. The method of any of Embodiments D1-D3, further comprising receiving an indication of at least one aperiodic reference signal to be used for TDCP measurements by the UE. Embodiment D6. The method of Embodiment D5, wherein the at least one aperiodic reference signal to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure. Embodiment D7. The method of any of Embodiments D5 and D6, wherein the at least one aperiodic reference signal is transmitted in a second slot corresponding to a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4- step random access procedure is triggered. Embodiment D8. The method of any of Embodiments D5 and D6, wherein the at least one aperiodic reference signal is transmitted in a second slot after a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received. Embodiment D9. The method of any of Embodiments D1-D8, wherein the TDCP report is an aperiodic TDCP report. As will be appreciated by one of skill in the art, the concepts described herein may be embodied as a method, data processing system, computer program product and / or computer storage media storing an executable computer program. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Any process, step, action and / or functionality described herein may be performed by, and / or associated to, a corresponding module, which may be implemented in software and / or firmware and / or hardware. Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that may be executed by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD-ROMs, electronic storage devices, optical storage devices, or magnetic storage devices. Some embodiments are described herein with reference to flowchart illustrations and / or block diagrams of methods, systems and computer program products. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. These computer program instructions may also be stored in a computer readable memory or storage medium that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function / act specified in the flowchart and / or block diagram block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. It is to be understood that the functions / acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality / acts involved. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows. Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Python, Java® or C++. However, the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the “C” programming language. The program code may execute entirely on the user’s computer, partly on the user’s computer, as a stand-alone software package, partly on the user’s computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, all embodiments may be combined in any way and / or combination, and the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination. It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope of the following claims.

Claims

What is claimed is:

1. A method implemented in a user equipment, UE (22), configured to communicate with a network node (16), the method comprising: receiving (S16) assistance information from the network node (16) to assist the UE (22) to acquire time domain channel properties, TDCP; receiving (S17) a triggering signal from the network node (16) in a message 2 of a 4-step random access procedure; performing (S20) TDCP measurements based at least in part on the received assistance information; and responsive to the triggering signal (S22), transmitting to the network node (16) a TDCP report in a message 3 of the 4-step random access procedure.

2. The method of Claim 1, further comprising transmitting to the network node (16) a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission.

3. The method of any of Claims 1 and 2, further comprising receiving from the network node (16) at least one tracking reference signal, TRS, to be used for TDCP measurements by the UE (22) in a pre-defined time-frequency resource relative to a previously received signal.

4. The method of any of Claims 1-3, further comprising receiving an indication of at least one aperiodic tracking reference signal, TRS, to be used for TDCP measurements by the UE (22).

5. The method of Claim 4, wherein the at least one aperiodic TRS to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure.

6. The method of any of Claims 4 and 5, wherein the at least one aperiodic TRS is transmitted in a second slot corresponding to a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered.

7. The method of any of Claims 4 and 5, wherein the at least one aperiodic TRS is transmitted in a second slot after a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received.

8. The method of any of Claims 1 and 2, further comprising receiving from the network node (16) at least one periodic reference signal to be used for TDCP measurements by the UE (22) in a pre-defined time-frequency resource.

9. The method of any of Claims 1-8, wherein the TDCP report is an aperiodic TDCP report.

10. The method of any of Claims 1-9, wherein the received assistance information includes a correlation value of a correlation of samples of a tracking reference signal, TRS.

11. A user equipment, UE (22), configured to communicate with a network node (16), the UE (22) configured to: receive assistance information from the network node (16) to assist the UE (22) to acquire time domain channel properties, TDCP; receive a triggering signal from the network node (16) on message 2 of a 4-step random access procedure; perform TDCP measurements based at least in part on the received assistance information; and responsive to the triggering signal, transmit to the network node (16) a TDCP report in a message 3 of the 4-step random access procedure.

12. The UE (22) of Claim 11, wherein the UE (22) is configured to transmit to the network node (16) a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission.

13. The UE (22) of any of Claims 11 and 12, wherein the UE (22) is configured to receive from the network node (16) at least one tracking reference signal, TRS, to be used for TDCP measurements by the UE (22) in a pre-defined time-frequency resourcerelative to a previously received signal.

14. The UE (22) of any of Claims 11-13, wherein the UE (22) is configured to receive an indication of at least one aperiodic TRS to be used for TDCP measurements by the UE (22).

15. The UE (22) of Claim 14, wherein the at least one aperiodic TRS to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure.

16. The UE (22) of any of Claims 14 and 15, wherein the at least one aperiodic TRS is transmitted in a second slot corresponding to a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered.

17. The UE (22) of any of Claims 14 and 15, wherein the at least one aperiodic TRS is transmitted in a second slot after a first slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received.

18. The UE (22) of any of Claims 11 and 12, further comprising receiving from the network node (16) at least one periodic reference signal to be used for TDCP measurements by the UE (22) in a pre-defined time-frequency resource.

19. The UE (22) of any of Claims 11-18, wherein the TDCP report is an aperiodic TDCP report.

20. The UE (22) of any of Claims 11-19, wherein the received assistance information includes a correlation value of a correlation of samples of a tracking reference signal, TRS.

21. A method implemented in a network node (16) configured to communicate with a user equipment, UE (22), the method comprising: transmitting (S10) information to the UE (22) to assist the UE (22) to acquire time domain channel properties, TDCP;configuring (S12) the UE (22) by a triggering signal in a message 2 of a 4-step random access procedure, the triggering signal causing the UE (22) to transmit a TDCP report; and receiving (S14) the TDCP report in a message 3 of the 4-step random access procedure.

22. The method of Claim 21, further comprising receiving from the UE (22) a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission.

23. The method of any of Claims 21 and 22, further comprising transmitting to the UE (22) at least one tracking reference signal, TRS, to be used for TDCP measurements by the UE (22) in a pre-defined time-frequency resource relative to a previously received signal.

24. The method of any of Claims 21-23, further comprising indicating at least one aperiodic tracking reference signal, TRS, to be used for TDCP measurements by the UE (22).

25. The method of Claim 24, wherein the at least one aperiodic TRS to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure.

26. The method of any of Claims 24 and 25, further comprising receiving the at least one aperiodic TRS in a same slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is triggered.

27. The method of any of Claims 24 and 25, further comprising receiving the at least one aperiodic TRS in a slot after a slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received.

28. The method of any of Claims 21-27, wherein the TDCP report is an aperiodic TDCP report.

29. The method of any of Claims 21-28, wherein the transmitted informationincludes a correlation value of a correlation of samples of a tracking reference signal, TRS.

30. The method of any of Claims 21-29, further comprising transmitting to the UE (22) at least one periodic reference signal to be used for TDCP measurements by the UE (22) in a pre-defined time-frequency resource.

31. A network node (16) configured to communicate with a user equipment, UE (22), the network node (16) configured to: transmit information to the UE (22) to assist the UE (22) to acquire time domain channel properties, TDCP; configure the UE (22) by a triggering signal in a message 2 of a 4-step random access procedure, the triggering signal causing the UE (22) to transmit a TDCP report; and receive the TDCP report in a message 3 of the 4-step random access procedure.

32. The network node (16) of Claim 31, wherein the network node (16) is configured to receive from the UE (22) a TDCP report in a scheduled physical uplink shared channel, PUSCH, transmission.

33. The network node (16) of any of Claims 31 and 32, wherein the network node (16) is configured to transmit to the UE (22) at least one tracking reference signal, TRS, to be used for TDCP measurements by the UE (22) in a pre-defined time-frequency resource relative to a previously received signal.

34. The network node (16) of any of Claims 31-33, wherein the network node (16) is configured to indicate at least one aperiodic tracking reference signal, TRS, to be used for TDCP measurements by the UE (22).

35. The network node (16) of Claim 34, wherein the at least one aperiodic TRS to be used for TDCP measurements is indicated in a message 2 of the 4-step random access procedure.

36. The network node (16) of any of Claims 34 and 35, wherein the at least one aperiodic TRS is received in a same slot in which a physical downlink control channel,PDCCH, for message 2 of the 4-step random access procedure is triggered.

37. The network node (16) of any of Claims 34 and 35, wherein the at least one aperiodic TRS is received in a slot after a slot in which a physical downlink control channel, PDCCH, for message 2 of the 4-step random access procedure is received.

38. The network node (16) of any of Claims 31-37, wherein the TDCP report is an aperiodic TDCP report.

39. The network node (16) of any of Claims 31-38, wherein the transmitted information includes a correlation value of a correlation of samples of a tracking reference signal, TRS.

40. The network node of any of Claims 31-39, wherein the network node is configured to transmit to the UE (22) at least one periodic reference signal to be used for TDCP measurements by the UE (22) in a pre-defined time-frequency resource.

Images