Device and method for joint channel and phase noise estimation

Abstract

The present disclosure relates to a network device and a terminal device. The disclosure proposes a network device that is configured to: determine one or more first resources for at least one first reference signal based on one or more second resources of at least one second reference signal, wherein the at least one first reference signal is for channel phase de-noising, and the at least one second reference signal is for channel estimation; and providing resource configuration information to the terminal device, wherein the resource configuration information indicates the one or more first resources for transmitting or receiving the at least one first reference signal. This disclosure further proposes a terminal device configured to receive the resource configuration information from the network device.

Description

[0001] DEVICE AND METHOD FOR JOINT CHANNEL AND PHASE NOISE ESTIMATION

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to communication networks, and particularly to reference signal transmission in wireless communication networks. Communications and sensing in wireless communication networks are subject to phase noise. The disclosure proposes a network device, a terminal device, and corresponding methods for channel and phase noise estimation in wireless communication networks.

[0004] BACKGROUND

[0005] Communications and sensing in high-frequency bands, for instance, mmWave and sub-THz frequencies, which may be used in future wireless communications networks, are subject to phase noise. Random jitter in the local oscillator of wireless communication devices causes phase noise in the carrier signal generated by those oscillators. This phase noise is a physical quantity that changes randomly in time but its average intensity is proportional to the carrier frequency, meaning that the impact of phase noise cannot be ignored in wireless communication systems operating in high-frequency bands. In wireless systems based on orthogonal frequency division multiplexing (OFDM), the randomness of phase noise manifests itself in common phase errors (CPE) and inter-carrier interference (ICI). Estimating and compensating for this random phase noise is further complicated by the fact that many deployment scenarios of future wireless systems will involve high mobility.

[0006] In current wireless communication systems, sounding reference signal (SRS) is used to enable the estimation of channel state information (CSI) for the uplink link from user terminals to the network device. Channel state information reference signal (CSI-RS) is used to enable the estimation of CSI for the downlink link from the network device to user terminals. Phase tracking reference signal (PT-RS) is used to estimate the phase noise or at least its CPE affecting OFDM symbols with data based on a channel state that is assumed known, e.g., in the case of low-mobility CPE is estimated based on the channel state obtained from the latest demodulation reference signal (DM-RS) pilot symbol and is relative to the phase noise corrupting that symbol. When using PT-RS patterns having enough guard sub-carriers, the dominant ICI components of the phase noise realization in the symbol carrying the PT-RS can be estimated in addition to the CPE. However, the channel state estimate in high- mobility scenarios will itself be corrupted by multiple instances of phase noise, due to interpolating between multiple pilots in multiple symbols, each of which affected by a different insgtance of the random phase noise process, or from basis expansion model (BEM) estimation based on these symbols leading to imprecise phase noise estimates.

[0007] Therefore, an advanced solution is desired, which can de-noise, i.e., attenuate the effect of phase noise affecting the channel estimation or sensing reference signals.

[0008] SUMMARY

[0009] In view of the above-discussed challenges, this disclosure aims to propose a design of a new reference signal for joint channel and phase noise estimation. One objective is to enable channel estimation reference signal de-noising and precise channel and phase noise estimation. Another objective is to translate the resulting precise channel and phase noise estimation to allow high modulation and coding schemes (MCS) to be used even in high-mobility high-frequency scenarios. Another objective is to translate the resulting precise channel and phase noise estimation to obtain precise target range and velocity estimates in sensing applications.

[0010] These and other objectives are achieved by the solution of the present disclosure as provided in the enclosed independent claims. Advantageous implementations are further defined in the dependent claims.

[0011] A first aspect of the disclosure provides a network device, which is configured to determine one or more first resources for at least one first reference signal based on one or more second resources of at least one second reference signal, wherein the at least one first reference signal is for channel phase de-noising, and the at least one second reference signal is for channel estimation; and provide resource configuration information to a terminal device, wherein the resource configuration information indicates the one or more first resources for transmitting or receiving the at least one first reference signal.

[0012] This disclosure proposes a network device that allocates resource(s) for a new reference signal, namely the at least one first reference signal, for joint channel and phase noise estimation. Such a new reference signal is needed to de-noise, i.e., to attenuate the effect of phase noise affecting, the channel estimation or sensing reference signals. It may also be called a channel de-noising reference signal (CD-RS) in this disclosure. Notably, additional measurements can be obtained based on this new CD-RS, it thus enables the de-noising effect by providing the receiver with additional measurements for the same antenna port as the reference signal to be de-noised. It should be understood that the resources for transmitting / receiving the CD-RS are related to the resources for transmitting / receiving the to-be-denoised channel estimation or sensing reference signals.

[0013] The effect of the multiplicative noise (phase noise in this case) on the precision of the estimation decreases with the number of measurements provided that these measurements are carried out in different time instances. In a sense, getting a large number of measurements affected by different instances of the multiplicative noise attenuates the effect of that noise on the outcome of the estimation, so as to de-noise the channel state.

[0014] In an implementation form of the first aspect, the resource configuration information indicates a first set of symbols occupied by the one or more first resources, a first set of subcarriers occupied by the one or more first resources, and at least one first antenna port for transmitting the at least one first reference signal.

[0015] Possibly, the occupied subcarriers may be indicated using subcarrier indexes.

[0016] In an implementation form of the first aspect, the network device is configured to determine the first set of symbols based on a second set of symbols occupied by the one or more second resources, wherein the first set of symbols and the second set of symbols do not overlap.

[0017] In particular, the at least one first reference signal, which is for channel phase de-noising, and the at least one second reference signal, which is for channel estimation, are transmitted in different OFDM symbols.

[0018] In an implementation form of the first aspect, the network device is configured to determine the first set of subcarriers based on a second set of subcarriers occupied by the one or more second resources, wherein the first set of subcarriers is a subset of the second set of subcarriers. That is, the at least one first reference signal for channel phase de-noising is supposed to be transmitted on a subset of the subcarriers occupied by the at least one second reference signal for channel estimation, but in different OFDM symbols than the ones occupied by it.

[0019] In an implementation form of the first aspect, the network device is configured to determine the at least one first antenna port based on one or more antenna ports for transmitting the at least one second reference signal, wherein the at least one first antenna port is one of the one or more antenna ports for transmitting the at least one second reference signal.

[0020] Notably, the at least one first reference signal and the at least one second reference signal transmit using the same antenna port. When the to-be-denoised reference signal, i.e., the at least one second reference signal, has multiple ports, the at least one first reference signal may be transmitted using one or more of these ports.

[0021] In an implementation form of the first aspect, the network device is configured to determine whether to enable antenna port hopping for the at least one first reference signal; and if antenna port hopping is enabled, determine at least one second antenna port for transmitting the at least one first reference signal based on the one or more antenna ports for transmitting the at least one second reference signal, wherein the at least one second antenna port and the at least one first antenna port are associated with different transmission periods, and the at least one second antenna port is one of the one or more antenna ports for transmitting the at least one second reference signal.

[0022] Optionally, port hopping may be enabled for the CD-RS. In this case, the CD-RS may be associated with different ports in different transmission periods, e.g., slots.

[0023] In an implementation form of the first aspect, the network device is configured to determine a first subset resource associated with the at least one first antenna port, wherein the first subset resource occupies a first subset of symbols from the first set of symbols and a first subset of subcarriers from the first set of subcarriers, and / or determine a second subset resource associated with the at least one second antenna port, wherein the second subset resource occupies a second subset of symbols from the first set of symbols and a second subset of subcarriers from the first set of subcarriers. In case the antenna port hopping is enabled, the network device configures for each antenna port the time-frequency resources for transmitting the CD-RS.

[0024] In an implementation form of the first aspect, the network device is configured to provide a port hopping indication to the terminal device, if it is determined to enable antenna port hopping for the at least one first reference signal, wherein the port hopping indication indicates at least one first antenna port with its associated transmission periods and its associated first subset resource, and the at least one second antenna port with its associated transmission periods and its associated second subset resource.

[0025] If it is determined port hopping is required for CD-RS, the network device sends a signal to the terminal device indicating the hopping pattern to be adopted.

[0026] In an implementation form of the first aspect, the network device is configured to determine a time-domain density of the at least one first reference signal based on a phase noise level and / or a modulation and coding scheme.

[0027] Optionally, the CD-RS may be configured with different time-frequency patterns. For instance, different time-domain density may be determined for CD-RS based on how much de-noising is needed. It may be understood that the larger the number of additional measurements (higher time-domain density), the better the de-noising effect can be achieved (but the higher the overhead).

[0028] In an implementation form of the first aspect, the network device is configured to determine the first set of symbols further based on the time-domain density of the at least one first reference signal.

[0029] In an implementation form of the first aspect, the network device is configured to determine a frequency-domain density of the at least one first reference signal based on one or more of the following conditions: a bandwidth scheduled for the at least one first reference signal, a subcarrier spacing, a frequency selectivity of a channel for the at least one second reference signal, and a frequency-domain density of the one or more second resources. For instance, the CD-RS may be configured with a larger frequency domain density, possibly to accommodate de-nosing a DM-RS port channel that has a higher frequency selectivity.

[0030] In an implementation form of the first aspect, the network device is configured to determine the first set of subcarriers further based on the frequency-domain density of the at least one first reference signal.

[0031] In an implementation form of the first aspect, the network device is configured to send the at least one first reference signal and the at least one second reference signal to the terminal device, based on the one or more first resources and the one or more second resources.

[0032] Possibly, the resource configuration information further indicates the one or more second resources for transmitting or receiving the at least one second reference signal.

[0033] In an implementation form of the first aspect, the network device is configured to receive the at least one first reference signal and the at least one second reference signal from the terminal device, based on the one or more first resources and the one or more second resources; and perform channel estimation based on the received at least one first reference signal and the received at least one second reference signal to obtain a phase de-noised channel estimate.

[0034] In this example, the terminal device sends the at least one first reference signal and the at least one second reference signal based on the resource configuration information provided by the network device. The network device then obtains the measurements based on the received reference signals.

[0035] In an implementation form of the first aspect, the network device is configured to receive the at least one first reference signal and the at least one second reference signal from the terminal device, further based on the port hopping indication.

[0036] When antenna port hopping is enabled, the network device receives the at least one first reference signal based on the at least one first antenna port with its associated transmission periods and its associated first subset resource, and the at least one second antenna port with its associated transmission periods and its associated second subset resource. In an implementation form of the first aspect, the network device is configured to determine the first set of symbols and the first set of subcarriers further based on one or more third resources for transmitting or receiving at least one third reference signal, wherein the at least one third reference signal is for phase noise estimation based on a channel estimate.

[0037] Optionally, this disclosure also proposes to make use of a third reference signal, e.g., PT-RS, in order to achieve a good phase noise estimate.

[0038] In an implementation form of the first aspect, the network device is configured to send the at least one first reference signal, the at least one second reference signal, and at least one third reference signal to the terminal device, based on the one or more first resources, the one or more second resources and the one or more third resources.

[0039] Possibly, the resource configuration information further indicates the one or more third resources for transmitting or receiving the at least one third reference signal.

[0040] In an implementation form of the first aspect, the network device is configured to send the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal to the terminal device, further based on the port hopping indication.

[0041] In an implementation form of the first aspect, the network device is configured to receive the at least one first reference signal, the at least one second reference signal, and at least one third reference signal from the terminal device, based on the one or more first resources, the one or more second resources and the one or more third resources; and perform channel estimation or joint channel and phase noise estimation based on the received at least one first reference signal, the received at least one second reference signal, and the received at least one third reference signal.

[0042] In this example, the terminal device sends the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal, based on the resource configuration information provided by the network device. The network device then obtains the measurements based on the received reference signals. In an implementation form of the first aspect, the network device is configured to receive the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal from the terminal device, further based on the port hopping indication.

[0043] In an implementation form of the first aspect, to perform the channel estimation, the network device is configured to: estimate a channel based on measurements associated with the at least one first reference signal and the at least one second reference signal, to obtain a first phase denoised channel estimate; and estimate a phase noise realization based on measurements associated with the at least one third reference signal and the first channel estimate; and optionally further de-noise the channel phase based on the estimated phase noise realization to obtain a channel estimation result.

[0044] This channel estimation procedure may be named as “joint channel and phase noise estimation”. It may be considered as a two-step procedure consisting of first estimating the channel of the reference signal port having a CD-RS associated with it based on the channel estimation reference signal in conjunction with the associated CD-RS, followed by estimating the phase noise realization based on PT-RS (or some combination or reference signals) based on the thus obtained channel estimate. Optionally, the obtained phase noise estimate can be used to denoise those other ports of the original reference signal.

[0045] In an implementation form of the first aspect, the at least one third reference signal is a phase tracking reference signal.

[0046] In an implementation form of the first aspect, the at least one second reference signal comprises one of the following: a DM-RS, a CSI-RS, and an SRS.

[0047] In an implementation form of the first aspect, the network device is configured to receive a request from the terminal device, wherein the request indicates that the one or more first resources are to be assigned for the at least one first reference signal.

[0048] Possibly, the transmission procedure may be started with the terminal device requesting CD- RS resources for phase denoising. A second aspect of the disclosure provides a terminal device, which is configured to receive resource configuration information from a network device, wherein the resource configuration information indicates one or more first resources for transmitting or receiving at least one first reference signal, wherein the at least one first reference signal is for channel phase de-noising.

[0049] This disclosure further proposes a terminal device for assisting the joint channel and phase noise estimation. The terminal device may be the transmitter of the new reference signal, i.e., the at least one first reference signal, or the receiver of the new reference signal.

[0050] In an implementation form of the second aspect, the resource configuration information indicates a first set of symbols occupied by the one or more first resources, a first set of subcarriers occupied by the one or more first resources, and at least one first antenna port for transmitting the at least one first reference signal.

[0051] In an implementation form of the second aspect, the terminal device is configured to receive a port hopping indication from the network device, wherein the port hopping indication indicates the at least one first antenna port with its associated transmission periods and its associated first subset resource, and at least one second antenna port for transmitting the at least one first reference signal with its associated transmission periods and its associated second subset resource, wherein the at least one second antenna port and the at least one first antenna port are associated with different transmission periods, wherein the first subset resource occupies a first subset of symbols from the first set of symbols and a first subset of subcarriers from the first set of subcarriers, and the second subset resource occupies a second subset of symbols from the first set of symbols and a second subset of subcarriers from the first set of subcarriers.

[0052] If it is determined port hopping is required for CD-RS, the network device sends a signal to the terminal device indicating the hopping pattern to be adopted.

[0053] In an implementation form of the second aspect, the terminal device is configured to send the at least one first reference signal and at least one second reference signal to the network device, based on the one or more first resources and one or more second resources, wherein the one or more second resources are for transmitting or receiving the at least one second reference signal, wherein the at least one second reference signal is for channel estimation. The terminal device may be the transmitter of the CD-RS, i.e., it sends the CD-RS on determined time and frequency domain positions and uses the same antenna port as the reference signal port with which the CD-RS is associated during the current transmission interval.

[0054] In an implementation form of the second aspect, the terminal device is configured to send the at least one first reference signal and the at least one second reference signal to the terminal device, further based on the port hopping indication.

[0055] In an implementation form of the second aspect, the terminal device is configured to receive the at least one first reference signal and the at least one second reference signal from the network device, based on the one or more first resources and one or more second resources, wherein the one or more second resources are for transmitting or receiving the at least one second reference signal, wherein the at least one second reference signal is for channel estimation; and perform channel estimation based on the received at least one first reference signal and the received at least one second reference signal to obtain a phase de-noised channel estimate.

[0056] If the terminal device receives the CD-RS on determined time and frequency domain positions, it also performs channel estimation or joint channel and phase noise estimation based on the measurements associated with the CD-RS and with the reference signal ports with which the CD-RS is associated.

[0057] In an implementation form of the second aspect, the terminal device is configured to receive the at least one first reference signal and the at least one second reference signal from the terminal device, further based on the port hopping indication.

[0058] In an implementation form of the second aspect, the terminal device is configured to send the at least one first reference signal, the at least one second reference signal, and at least one third reference signal to the network device, based on the one or more first resources, the one or more second resources and one or more third resources, wherein the one or more third resources are for transmitting or receiving the at least one third reference signal, wherein the at least one third reference signal is for phase noise estimation based on a channel estimate. Optionally, this disclosure also proposes to make use of a third reference signal, e.g., PT-RS, in order to achieve a good phase noise estimate.

[0059] In an implementation form of the second aspect, the terminal device is configured to send the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal to the terminal device, further based on the port hopping indication.

[0060] In an implementation form of the second aspect, the terminal device is configured to receive the at least one first reference signal, the at least one second reference signal, and at least one third reference signal from the network device, based on the one or more first resources, the one or more second resources, and one or more third resources, wherein the one or more third resources are for transmitting or receiving the at least one third reference signal, wherein the at least one third reference signal is for phase noise estimation based on a channel estimate; and perform channel estimation or joint channel and phase noise estimation based on the received at least one first reference signal, the received at least one second reference signal, and the received at least one third reference signal.

[0061] In an implementation form of the second aspect, the terminal device is configured to receive the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal from the terminal device, further based on the port hopping indication.

[0062] In an implementation form of the second aspect, to perform the channel estimation, the terminal device is configured to: estimate a channel based on measurements associated with the at least one first reference signal and the at least one second reference signal, to obtain a first phase denoised channel estimate; and estimate a phase noise realization based on measurements associated with the at least one third reference signal and the first channel estimate; and optionally further de-noise the channel phase based on the estimated phase noise realization to obtain a channel estimation result.

[0063] In an implementation form of the second aspect, the at least one third reference signal is a phase tracking reference signal.

[0064] In an implementation form of the second aspect, the at least one second reference signal comprises one of the following: a DM-RS, a CSI-RS, and an SRS. In an implementation form of the second aspect, the terminal device is configured to send a request to the network device, wherein the request indicates that the one or more first resources are to be assigned for the at least one first reference signal.

[0065] Optionally, the terminal device may send a signal to the network device requesting the assignment of a CD-RS and the indexes of the reference signal ports with which the CD-RS is requested to be associated.

[0066] A third aspect of the disclosure provides a method performed by a network device, the method comprises: determining one or more first resources for at least one first reference signal based on one or more second resources of at least one second reference signal, wherein the at least one first reference signal is for channel phase de-noising, and the at least one second reference signal is for channel estimation; and providing resource configuration information to a terminal device, wherein the resource configuration information indicates the one or more first resources for transmitting or receiving the at least one first reference signal.

[0067] Implementation forms of the method of the third aspect may correspond to the implementation forms of the network device of the first aspect described above. The method of the third aspect and its implementation forms achieve the same advantages and effects as described above for the network device of the first aspect and its implementation forms.

[0068] A fourth aspect of the disclosure provides a method performed by a terminal device, the method comprises receiving resource configuration information from a network device, wherein the resource configuration information indicates one or more first resources for transmitting or receiving at least one first reference signal, wherein the at least one first reference signal is for channel phase de-noising.

[0069] Implementation forms of the method of the fourth aspect may correspond to the implementation forms of the terminal device of the second aspect described above. The method of the fourth aspect and its implementation forms achieve the same advantages and effects as described above for the terminal device of the second aspect and its implementation forms.

[0070] A fifth aspect of the disclosure provides a computer program product comprising a program code for carrying out, when implemented on a processor, the method according to the third aspect and any implementation forms of the third aspect, or the fourth aspect and any implementation forms of the fourth aspect.

[0071] A sixth aspect of the disclosure provides a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out, the method according to the third aspect and any implementation forms of the third aspect, or the fourth aspect and any implementation forms of the fourth aspect.

[0072] It has to be noted that all devices, elements, units, and means described in the present application could be implemented in software or hardware elements or any kind of combination thereof. All steps that are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity that performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements or any kind of combination thereof.

[0073] BRIEF DESCRIPTION OF DRAWINGS

[0074] The above-described aspects and implementation forms of the present disclosure will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which:

[0075] FIG. 1 shows a network device according to an embodiment of this disclosure;

[0076] FIG. 2 shows a time-frequency resource in one transmission slot according to an embodiment of this disclosure;

[0077] FIG. 3 shows an illustration of de-noising a sub-carrier of a reference signal with two time resources, here two OFDM symbols, using CD-RS with four time resources according to an embodiment of this disclosure and Ist-order linear regression; FIG. 4 shows a terminal device according to an embodiment of this disclosure;

[0078] FIG. 5 shows a wireless communication system according to an embodiment of this disclosure;

[0079] FIG. 6 shows two time-frequency patterns within a transmission slot of a CD-RS associated with a DM-RS port according to an embodiment of this disclosure;

[0080] FIG. 7 shows a time-frequency pattern of a CD-RS associated with one DM-RS port out of multiple DM-RS ports according to an embodiment of this disclosure;

[0081] FIG. 8 shows a schematic flowchart of a reference signal transmission method according to an embodiment of this disclosure;

[0082] FIG. 9 shows a schematic flowchart of a reference signal transmission method according to an embodiment of this disclosure;

[0083] FIG. 10 shows a time-frequency pattern of a CD-RS associated with one CSI-RS port out of four possible CSI-RS ports in two slots (not necessarily consecutive) according to an embodiment of this disclosure;

[0084] FIG. 11 shows a time-frequency pattern of a CD-RS associated with one CSI-RS port out of the four possible CSI-RS ports of FIG. 10 (but different from the port with which CSI-RS is associated in FIG. 10) in two slots (not necessarily consecutive) according to an embodiment of this disclosure;

[0085] FIG. 12 shows a schematic flowchart of a reference signal transmission method according to an embodiment of this disclosure;

[0086] FIG. 13 shows a time-frequency pattern of a CD-RS associated with one SRS port according to an embodiment of this disclosure;

[0087] FIG. 14 shows a schematic flowchart of a reference signal transmission method according to an embodiment of this disclosure; FIG. 15 shows a method according to an embodiment of this disclosure; and

[0088] FIG. 16 shows a method according to an embodiment of this disclosure

[0089] DETAILED DESCRIPTION OF EMBODIMENTS

[0090] Illustrative embodiments of a network device, a terminal device, and corresponding methods are described in the following with reference to the figures. Although this description provides a detailed example of possible implementations, it should be noted that the details are intended to be exemplary and in no way limit the scope of the application.

[0091] Moreover, an embodiment or example may refer to other embodiments or examples. For example, any description including but not limited to terminology, element, process, explanation, and / or technical advantage mentioned in one embodiment or example may also apply to the other embodiments or examples.

[0092] For ease of understanding of this application, conventional reference signals are first introduced here.

[0093] As previously mentioned, SRS is used in current wireless communications systems to enable the estimation of CSI for the uplink link from user terminals to the network device. This estimated CSI is then used by the network for scheduling purposes, i.e., the assignment of different users to different resources of the physical uplink shared channels (PUSCH). In the case of terminals equipped with multiple antennas, this CSI can be fed back to the users in a quantized form to help them determine the multiple input multiple output (MIMO) precoding to be applied to those antennas. The time-frequency resources of one SRS port assigned to one user can span multiple time instances, i.e., multiple OFDM symbols in the same slot. For instance, one SRS signal can be repeated on multiple subsequent OFDM signals to get coverage gain for cell edge users. Otherwise, the SRS signal could be divided in a frequency-hopping manner among several OFDM symbols (not necessarily adjacent to each other) to get diversity gain. Moreover, multiple SRS resources in multiple slots can be used to estimate the timevarying channel of the uplink from the terminal in mobility scenarios, using for example interpolation or BEM methods, or to get at least an estimate of the Doppler frequency shifts associated with that link in those scenarios. In all these cases, the SRS resources occupying different time instances will be subject to different instances of phase noise, itself random and time-varying. This results in the degradation of the quality of the CSI estimate or the Doppler shifts estimates obtained from the SRS in the presence of phase noise.

[0094] CSI-RS is used in current wireless communications systems to enable the estimation of CSI for the downlink link from the network device to user terminals. This CSI estimate can then be fed back in a quantized form to the network so that it can be used, for instance, to determine the MIMO precoding to be used by the network device when transmitting to the terminal device on the physical downlink shared channel (PDSCH) scheduled for that device. As for SRS, one CSI-RS signal can span multiple OFDM symbols in time within the same slot according to predefined time-frequency patterns. Also, multiple CSI-RS resources in multiple slots can be used to estimate (using for example interpolation or BEM methods) the time-varying channel of the downlink from the network device to the terminals in mobility scenarios or to get at least an estimate of the Doppler frequency shifts associated with that link in those scenarios. Again, the reference signal resources occupying different time instances will be subject to different instances of phase noise, itself random and time-varying resulting in degradation of the quality of the CSI estimate or the Doppler shifts estimates obtained from them in the presence of phase noise.

[0095] One of the projected requirements for future wireless communications systems is support for sensing as a service. It consists of providing to user devices either network sensing or network- supported / coordinated sensing thanks to integrated sensing and communications (ISAC) methods. One of the most practical ways to achieve that is to use channel estimation reference signals, either existing ones such as SRS and CSI-RS, or new dedicated ones for sensing purposes. Indeed, channel estimation gives the possibility to identify the delay and Doppler components associated with the propagation medium. This is relevant for sensing and radar applications since the delay-Doppler representation of the wireless channel associated with the round-trip propagation from the wireless transmitter to the targets in its vicinity and back to the transmitter translates into range-velocity information about those targets. In the presence of phase noise, and as is the case for channel estimation, different phase noise instances affecting different time instances of the sensing reference signals will result in errors in range and velocity estimation. FIG. 1 shows a network device 100 according to an embodiment of the disclosure.

[0096] The network device 100 may comprise processing circuitry (not shown) configured to perform, conduct, or initiate the various operations of the network device 100 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field- programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors. The network device 100 may further comprise memory circuitry, which stores one or more instruction(s) that can be executed by the processor or by the processing circuitry, in particular under the control of the software. For instance, the memory circuitry may comprise a non- transitory storage medium storing executable software code which, when executed by the processor or the processing circuitry, causes the various operations of the network device 100 to be performed. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to one or more processors. The non-transitory memory may carry executable program code which, when executed by one or more processors, causes the network device 100 to perform, conduct, or initiate the operations or methods described herein.

[0097] The network device 100 is configured to determine one or more first resources 101 for at least one first reference signal based on one or more second resources of at least one second reference signal. In particular, the at least one first reference signal is for channel phase de-noising, and the at least one second reference signal is for channel estimation. The network device 100 is further configured to provide resource configuration information 102 to a terminal device 110, wherein the resource configuration information 102 indicates the one or more first resources 101 for transmitting or receiving the at least one first reference signal.

[0098] The goal of the present disclosure is to address the above-mentioned challenges by designing a new reference signal, namely the at least one first reference signal, for joint channel and phase noise estimation. Such a new reference signal is needed to de-noise, i.e., to attenuate the effect of phase noise affecting, the channel estimation or sensing reference signals.

[0099] It may be understood that the at least one second reference signal comprises, but is not limited to, one of the following: a DM-RS, a CSI-RS, and an SRS. This new reference signal is proposed to:

[0100] 1. Enable channel estimation reference signal de-noising and precise channel and phase noise estimation so that a) high modulation and coding schemes (MCS) can be used even in high- mobility high-frequency scenarios, b) precise MIMO CSI can be obtained for better MIMO precoding performance and c) precise target range and velocity estimates can be obtained in sensing applications;

[0101] 2. Be compatible with low-complexity joint channel and phase noise estimation methods e.g., alternate optimization; and

[0102] 3. Without incurring excessive overhead increases.

[0103] Consider a port of a reference signal, e.g., DM-RS, SRS, or CSI-RS, with multiple resources in multiple OFDM symbols, either in the same slot or in multiple slots, used to estimate the wireless channel that is time-varying (due to user mobility) across these different symbols, which at the same time being subject to different instances of phase noise, itself random and time-varying. Estimating the time-varying channel based on the different instances of the reference signal in that case requires, when for instance using interpolation or BEM methods, to somehow attenuate the effect of phase noise on each of the individual instances of the reference signal by estimating this effect. That is, to “de-noise” these instances. This is needed to get good CSI based on DM-RS, SRS, or CSI-RS, to get a good range and velocity estimate if the reference signal is intended to be used for sensing, but also to get a good phase noise estimate based on PT-RS in the OFDM symbols carrying data based on the “de-noised” DM- RS CSI.

[0104] The solution proposed in this disclosure to achieve de-noising is to provide the receiver with additional measurements for the same port as the reference signal to be de-noised on a subset of the subcarriers occupied by that reference signal port but in different OFDM symbols than the ones occupied by it.

[0105] Possibly, the resource configuration information 102 indicates a first set of symbols occupied by the one or more first resources 101, a first set of subcarriers occupied by the one or more first resources 101, and at least one first antenna port for transmitting the at least one first reference signal. According to an embodiment of this disclosure, the network device 100 is further configured to determine the first set of symbols based on a second set of symbols occupied by the one or more second resources, wherein the first set of symbols and the second set of symbols do not overlap. That is, the at least one first reference signal, which is for channel phase de-noising, and the at least one second reference signal, which is for channel estimation, are transmitted in different OFDM symbols.

[0106] According to an embodiment of this disclosure, the network device 100 is further configured to determine the first set of subcarriers based on a second set of subcarriers occupied by the one or more second resources, wherein the first set of subcarriers is a subset of the second set of subcarriers. That is, the at least one first reference signal for channel phase de-noising is supposed to be transmitted in a subset of the subcarriers occupied by the at least one second reference signal for channel estimation.

[0107] According to an embodiment of this disclosure, the network device 100 is further configured to determine the at least one first antenna port based on one or more antenna ports for transmitting the at least one second reference signal, wherein the at least one first antenna port is one of the one or more antenna ports for transmitting the at least one second reference signal. Notably, the at least one first reference signal and the at least one second reference signal transmit using the same antenna port. When the to-be de-noised reference signal, i.e., the at least one second reference signal, has multiple ports, the at least one first reference signal may be transmitted using one or more of these ports.

[0108] This disclosure enables obtaining these additional measurements thanks to the proposed new reference signal, namely the at least one first reference signal. It may also be called a channel de-noising reference signal (CD-RS) in this disclosure. The problem of time-varying channel estimation under phase noise can be written, when using either interpolation or BEM methods, as an estimation problem subject to both multiplicative and additive noise (as opposed to only additive noise in the absence of phase noise), e.g., least-squares estimation under multiplicative additive noise. The effect of the multiplicative noise (phase noise in this case) on the precision of the estimation decreases with the number of measurements provided that these measurements are carried out in different time instances characterized by different, preferably statistically independent or little correlated, instances of the multiplicative noise. In a sense, getting a large number of measurements affected by different instances of the multiplicative noise attenuates the effect of that noise on the outcome of the estimation i.e., de-noise the channel state. With the additional measurements provided by the new proposed reference signal, CD-RS, this sought de-noising effect can be achieved.

[0109] According to an embodiment of this disclosure, the network device 100 may be further configured to determine whether to enable antenna port hopping for the at least one first reference signal. If antenna port hopping is enabled, the network device 100 is further configured to determine at least one second antenna port for transmitting the at least one first reference signal based on the one or more antenna ports for transmitting the at least one second reference signal. Notably, the at least one second antenna port and the at least one first antenna port are associated with different transmission periods, and the at least one second antenna port is also one of the one or more antenna ports for transmitting the at least one second reference signal.

[0110] Possibly, the network device 100 is further configured to determine a first subset resource associated with the at least one first antenna port, wherein the first subset resource occupies a first subset of symbols from the first set of symbols and a first subset of subcarriers from the first set of subcarriers. Possibly, the network device 100 is further configured to determine a second subset resource associated with the at least one second antenna port, wherein the second subset resource occupies a second subset of symbols from the first set of symbols and a second subset of subcarriers from the first set of subcarriers.

[0111] Optionally, the network device 100 is further configured to provide a port hopping indication to the terminal device 110, if it is determined to enable antenna port hopping for the at least one first reference signal, wherein the port hopping indication indicates at least one first antenna port with its associated transmission periods and its associated first subset resource, and the at least one second antenna port with its associated transmission periods and its associated second subset resource.

[0112] According to an embodiment of this disclosure, the network device 100 may be further configured to send the at least one first reference signal and the at least one second reference signal to the terminal device 110, based on the one or more first resources 101 and the one or more second resources. In this case, the network device 100 is the transmitter of the reference signals.

[0113] Optionally, when antenna port hopping is enabled, the network device 100 is configured to send the at least one first reference signal and the at least one second reference signal to the terminal device 110, further based on the port hopping indication. In particular, the network device 100 sends the at least one first reference signal based on the at least one first antenna port with its associated transmission periods and its associated first subset resource, and the at least one second antenna port with its associated transmission periods and its associated second subset resource.

[0114] Notably, the network device 100 may be configured to determine the first set of symbols and the the first set of subcarriers further based on one or more third resources for transmitting or receiving at least one third reference signal. The at least one third reference signal is for phase noise estimation based on a channel estimate. In particular, the at least one third reference signal is a PT-RS.

[0115] Optionally, the network device 100 may be further configured to send the at least one first reference signal, the at least one second reference signal, and at least one third reference signal to the terminal device 110, based on the one or more first resources 101, the one or more second resources and the one or more third resources.

[0116] Optionally, when antenna port hopping is enabled, the network device 100 is configured to send the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal to the terminal device 110, further based on the port hopping indication.

[0117] According to another embodiment of this disclosure, the network device 100 may be further configured to receive the at least one first reference signal and the at least one second reference signal from the terminal device 110, based on the one or more first resources 101 and the one or more second resources. Accordingly, the network device 100 is further configured to perform channel estimation based on the received at least one first reference signal and the received at least one second reference signal to obtain a phase de-noised channel estimate.

[0118] In this case, the network device 100 is the receiver of the reference signals. It may be understood that when antenna port hopping is enabled, the network device 100 is further configured to receive the at least one first reference signal and the at least one second reference signal from the terminal device 110, further based on the port hopping indication.

[0119] According to an embodiment of the disclosure, the network device 100 is further configured to receive the at least one first reference signal, the at least one second reference signal, and at least one third reference signal from the terminal device 110, based on the one or more first resources 101, the one or more second resources and the one or more third resources; and perform channel estimation or joint channel and phase noise estimation based on the received at least one first reference signal, the received at least one second reference signal, and the received at least one third reference signal.

[0120] Notably, the resource configuration information may further indicate the one or more third resources for transmitting or receiving at least one third reference signal.

[0121] When antenna port hopping is enabled, the network device 100 is further configured to receive the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal from the terminal device 110, further based on the port hopping indication.

[0122] Further, to perform the channel estimation, the network device 100 is configured to estimate a channel based on measurements associated with the at least one first reference signal and the at least one second reference signal, to obtain a first phase de-noised channel estimate; and estimate a phase noise realization based on measurements associated with the at least one third reference signal and the first channel estimate. Optionally, the network device 100 may be configured to further de-noise the channel phase based on the estimated phase noise realization to obtain a channel estimation result.

[0123] Notably, the network device 100 may be configured to receive a request from the terminal device 110, wherein the request indicates that the one or more first resources 101 are to be assigned for the at least one first reference signal. FIG. 2 shows a time-frequency resource in one transmission slot of the CD-RS according to an embodiment of this disclosure. Notably, the CD-RS is the at least one first reference signal discussed in the previous embodiments.

[0124] It can be seen that the frequency domain density of the CD-RS is lower than that of the channel estimation reference signal with which it is associated. In particular, this new reference signal is configured with resources that 1) occupy in time different symbols than the original reference signal, 2) occupy in frequency subcarriers that are also subcarriers of the original reference signal (actually a subset of them) and 3) is transmitted using the same port as the original reference signal port i.e., the same antenna elements and the same MIMO precoding or beamforming (if any).

[0125] FIG. 3 shows an illustration of de-noising a sub-carrier of a reference signal with two time resources using CD-RS and Ist-order linear regression. FIG. 3(a) shows two pilot measurements affected by phase noise and the noisy and erroneous channel estimates obtained based on them for the symbols in between. FIG. 3(b) shows the two pilot measurements complemented with four CD-RS measurements and the result of Ist-order linear regression channel estimation based on them.

[0126] In this embodiment, the channel estimation reference signal as shown in FIG. 3 provides Nt,dmrs=2 measurements per subcarrier per slot. With the disclosed reference signal, some of the subcarriers of the original reference signal will get Nt dmrs+ Nt cdrs= 6 measurements per slot.

[0127] If channel estimation is done in the presence of phase noise only based on the original reference signal without CD-RS, then the estimated channel state at the position of the resource elements of the reference signal will be in error i.e., noisy (as illustrated by dark ‘X’ signs in FIG. 3(a)) due to the different phase noise instances affecting the two different time instances of these resources. If channel estimation for the data symbols between the reference signal symbols is done using interpolation based on these noisy reference signal estimates the result will suffer from errors (as illustrated by the relatively large gap between the solid line and the dashed line in FIG. 3(a)). Based on this disclosure, if channel estimation for both the reference signal symbols and the data-carrying symbols is done jointly based on the measurements from both the original reference signal and the new CD-RS resource elements (using, for instance, least-squares first- order linear regression or other regression methods), then the effect of phase noise is attenuated for both the estimated channel state of the original reference signal symbols and the data- carrying symbols (as illustrated by the position of the new grey ‘X’ signs and the smaller gap between the solid and the dashed lines in FIG. 3(b)).

[0128] In this embodiment, it is assumed that linear regression is used as the de-noising method. But CD-RS is in no way limited to only linear regression. For instance, a similar de-noising effect can be obtained with CD-RS when channel estimation is done using higher-order regression methods or using BEM.

[0129] To obtain these new measurements and their de-noising effect, it does not require that the new reference signal be transmitted with the same frequency domain density of the original reference signal as that would be a waste of resources. However, to get the sought de-noising effect, the frequency domain density of the new reference signal should be large enough in relation to the frequency selectivity of the channel of the port of the original reference signal with which the new reference signal is associated. For instance, this frequency domain density of the new reference signal could be made related in an increasing way to the maximum delay shift of the channel of that port (since the larger that shift the more the frequency selectivity).

[0130] According to an embodiment of this disclosure, the network device 100 may be configured to determine a frequency-domain density of the at least one first reference signal based on one or more of the following conditions: a bandwidth scheduled for the at least one first reference signal, a subcarrier spacing, a frequency selectivity of a channel for the at least one second reference signal, and a frequency-domain density of the one or more second resources.

[0131] Optionally, the network device 100 may be further configured to determine the first set of subcarriers further based on the frequency-domain density of the at least one first reference signal. As for the time domain density of the new reference signal CD-RS, i.e., the value of Nt cdrsin the above formula, this value should be determined based on how much de-noising is needed, i.e. by what factor the power of the phase noise affecting the port of the original reference signal needs to be reduced. As can be understood from the above discussion of estimation in the presence of both multiplicative and additive noise, the larger the number of additional measurements the better the de-noising (but the higher the overhead). This target de-noising factor, and the ensuing time domain density, might be determined by the network device 100 and communicated to the terminal device 110 based on, but not limited to:

[0132] 1. A target channel estimation performance e.g., in terms of relative mean squared error (RMSE).

[0133] 2. The modulation and coding scheme (MCS) to be used for the data to be detected based on the CSI obtained from the de-noised channel estimation reference signal and its associated PT-RS resources.

[0134] 3. The signal-to-noise-ratio (SNR) or signal-to-interference-plus-noise ratio (SINR) of the wireless link (the lower the SNR the larger the required density, assuming the other factors remain constant).

[0135] 4. The maximum Doppler shift associated with the wireless link (more frequency CD-RS might be needed the higher the mobility).

[0136] According to an embodiment of this disclosure, the network device 100 may be configured to determine a time-domain density of the at least one first reference signal based on a phase noise level and / or a modulation and coding scheme.

[0137] Optionally, the network device 100 may be further configured to determine the first set of symbols further based on the time-domain density of the at least one first reference signal.

[0138] That was concerning the time and the frequency domain density of the resources of the new reference signal, CD-RS. As for the relative location of the resources in the time-frequency resource grid, this can be chosen by the network device 100 and communicated to the terminal device 110 based on multiple factors including but not limited to:

[0139] 1. The available resources not occupied by other reference signals in the frame: the resources of the CD-RS should not collide with other reference signals. 2. The cell ID: the relative position of the pattern of the resources of CD-RS inside the frame can be made cell-dependent.

[0140] When the reference signal to be de-noised has multiple ports i.e., different instances of the reference signal are assigned orthogonal resources and transmitted using different antenna ports, and when these antenna ports share the same local oscillator, then the phase noise process affecting all these ports is the same and de-noising one of the ports of the reference signal is sufficient to de-noise the other ports. Indeed, the de-noised reference signal port can be used in the estimation of the phase noise realization affecting the transmission interval to which that port belongs. This estimation is best done jointly using both the de-noised measurements of the original reference signal and measurements (the noisy, i.e., affected with phase noise) of the new reference signal and possibly in conjunction with the noisy measurements of other reference signals that might be present in the transmission interval such as PT-RS. Once this estimation of the phase noise realization is done, the result can be used to de-noise the other ports of the original reference signal. Indeed, when (an estimate of) the phase noise affecting the time-frequency resources of those other ports is available, its effect can be compensated, e.g., by simple division.

[0141] In the case where not all the reference signal ports share the same local oscillator, e.g., when the transmitter or the receiver is equipped with multiple panels of antenna elements with each of these panels having its own local oscillator, then some of the ports of the original reference signal can be affected by a different phase noise process than the one affecting some other ports. In that case, multiple CD-RS ports are needed (a number at least equal to the number of local oscillators), each of them associated with a different port of the original reference signal.

[0142] FIG. 4 shows a terminal device 110 according to an embodiment of the disclosure.

[0143] The terminal device 110 may comprise processing circuitry (not shown) configured to perform, conduct, or initiate the various operations of the terminal device 110 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field- programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors. The terminal device 110 may further comprise memory circuitry, which stores one or more instruction(s) that can be executed by the processor or by the processing circuitry, in particular under the control of the software. For instance, the memory circuitry may comprise a non- transitory storage medium storing executable software code which, when executed by the processor or the processing circuitry, causes the various operations of the terminal device 110 to be performed. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to one or more processors. The non-transitory memory may carry executable program code which, when executed by one or more processors, causes the terminal device 110 to perform, conduct, or initiate the operations or methods described herein.

[0144] The terminal device 110 is configured to receive resource configuration information 102 from a network device 100, wherein the resource configuration information 102 indicates one or more first resources 101 for transmitting or receiving at least one first reference signal, wherein the at least one first reference signal is for channel phase de-noising.

[0145] This disclosure further proposes a terminal device 110 for assisting the joint channel and phase noise estimation. The terminal device 110 may either be configured to be the transmitter of the new reference signal, i.e., the at least one first reference signal, or to be the receiver of the new reference signal.

[0146] Possibly, the resource configuration information 102 indicates a first set of symbols occupied by the one or more first resources 101, a first set of subcarriers occupied by the one or more first resources 101, and at least one first antenna port for transmitting the at least one first reference signal.

[0147] According to an embodiment of this disclosure, the terminal device 110 is further configured to send the at least one first reference signal and at least one second reference signal to the network device 100, based on the one or more first resources 101 and one or more second resources, wherein the one or more second resources are for transmitting or receiving the at least one second reference signal, wherein the at least one second reference signal is for channel estimation.

[0148] It may be understood that the at least one second reference signal comprises one of the following: a DM-RS, a CSI-RS, and an SRS. The one or more first resources 101 for at least one first reference signal are associated with the one or more second resources of at least one second reference signal. In particular, the at least one first reference signal for channel phase de-noising is supposed to be transmitted in a subset of the subcarriers occupied by the at least one second reference signal for channel estimation. In addition, the at least one first reference signal and the at least one second reference signal are transmitted in different OFDM symbols. Further, the at least one first reference signal and the at least one second reference signal transmit using the same antenna port. Notably, when the at least one second reference signal has multiple antenna ports, the at least one first reference signal may be transmitted using one or more of these ports.

[0149] Notably, the resource configuration information 102 received by the terminal device 110 may further indicate one or more second resources for transmitting or receiving at least one second reference signal.

[0150] According to an embodiment of this disclosure, the terminal device 110 is further configured to receive the at least one first reference signal the at least one second reference signal from the network device, based on the one or more first resources and one or more second resources, wherein the one or more second resources are for transmitting or receiving the at least one second reference signal, wherein the at least one second reference signal is for channel estimation; and perform channel estimation based on the received at least one first reference signal and the received at least one second reference signal to obtain a phase de-noised channel estimate.

[0151] According to an embodiment of this disclosure, the terminal device 110 is further configured to receive a port hopping indication from the network device 100. The port hopping indication indicates the at least one first antenna port with its associated transmission periods and its associated first subset resource, and at least one second antenna port for transmitting the at least one first reference signal with its associated transmission periods and its associated second subset resource. In particular, the at least one second antenna port and the at least one first antenna port are associated with different transmission periods. The first subset resource occupies a first subset of symbols from the first set of symbols and a first subset of subcarriers from the first set of subcarriers, and the second subset resource occupies a second subset of symbols from the first set of symbols and a second subset of subcarriers from the first set of subcarriers. Accordingly, the terminal device 110 is further configured to send the at least one first reference signal and the at least one second reference signal to the terminal device 110, further based on the port hopping indication.

[0152] Similarly, the terminal device 110 may be further configured to receive the at least one first reference signal and the at least one second reference signal from the terminal device 110, further based on the port hopping indication.

[0153] According to an embodiment of this disclosure, the terminal device 110 is further configured to send the at least one first reference signal, the at least one second reference signal, and at least one third reference signal to the network device 100, based on the one or more first resources 101, the one or more second resources and one or more third resources. The one or more third resources are for transmitting or receiving the at least one third reference signal, wherein the at least one third reference signal is for phase noise estimation based on a channel estimate. Notably, the at least one third reference signal may be a PT-RS.

[0154] According to an embodiment of this disclosure, the terminal device 110 is further configured to receive the at least one first reference signal, the at least one second reference signal, and at least one third reference signal from the network device 100, based on the one or more first resources 101, the one or more second resources, and one or more third resources, wherein the one or more third resources are for transmitting or receiving the at least one third reference signal, wherein the at least one third reference signal is for phase noise estimation based on a channel estimate; and perform channel estimation or joint channel and phase noise estimation based on the received at least one first reference signal, the received at least one second reference signal, and the received at least one third reference signal.

[0155] When antenna hopping is enabled, i.e., if the terminal device 110 receives the port hopping indication, the terminal device 110 is further configured to send the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal to the terminal device 110, further based on the port hopping indication. Alternatively, the terminal device 110 is further configured to receive the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal from the terminal device 110, further based on the port hopping indication. According to an embodiment of this disclosure, to perform the channel estimation, the terminal device 110 is configured to estimate a channel based on measurements associated with the at least one first reference signal and the at least one second reference signal, to obtain a first phase de-noised channel estimate; and estimate a phase noise realization based on measurements associated with the at least one third reference signal and the first channel estimate. The terminal device 110 may be configured to further de-noise the channel phase based on the estimated phase noise realization to obtain a channel estimation result.

[0156] Optionally, the terminal device 110 is further configured to send a request to the network device 100, wherein the request indicates that the one or more first resources 101 are to be assigned for the at least one first reference signal.

[0157] FIG. 5 shows a wireless communication system according to an embodiment of this disclosure. The system is composed of a network device 100 and a number of communication devices, some of which (including possibly the network device) may be integrated sensing and communications (ISAC) devices, i.e., also capable of sensing, network device 100 may be the network device shown in FIG. 1 or FIG. 4. The number of communication devices may include the terminal device 110 as shown in FIG. 1 or FIG. 4. In this figure, the terminal device 110 is shown as an example of a communication device. The signals transmitted by the different components of the system are OFDM signals or discrete Fourier transform spread OFDM (DFT-s-OFDM) signals.

[0158] The module “CD-RS pattern determination” determines for uplink (UL) or downlink (DL) CD- RS the time and frequency domain densities of the CD-RS, i.e., the at least one first reference signal as mentioned in the previous embodiments, and its position of the time-frequency resources within the resource grid. The time and frequency domain densities may be determined based on factors such as the maximum delay shift and the maximum Doppler frequency shift, a target RMSE for the channel estimation, the MCS to be used for data transmission, the SNR or the SINR, etc.

[0159] In the case of port hopping for CD-RS, this module also determines which port of the original reference signal the CD-RS should be associated with in which transmission interval, e.g., slot. The module “CD-RS insertion” then generates the CD-RS based on the determined pattern and inserts it in the transmission resource grid.

[0160] The network device 100 may send the CD-RS resource configuration information to the terminal device 110 through a physical downlink control channel (PDCCH) or by using higher- layer signaling, e.g., radio resource control (RRC) signaling. The terminal device 110 may send the CD-RS resource request message to the network device 100 using a physical uplink control channel (PUCCH) or some higher-layer signaling.

[0161] The module “joint channel (CH) and phase noise (PN) estimation” could simply be a two-step procedure consisting of first estimating the channel of the reference signal port having a CD- RS associated with it based on the channel estimation reference signal in conjunction with the associated CD-RS, followed by estimating the phase noise realization based on PT-RS (or some combination or reference signals) based on the thus obtained channel estimate. Or it can be an iterative procedure involving repeating the above two-step estimation a number of times to refine the result. Finally, it can be a more complex non-linear joint estimation method. The thus obtained phase noise estimate can be used to de-noise those other ports of the original reference signal (in case of reference signals with multiple ports) that do not have an associated CD-RS but which share the same local oscillator with the port having an associated CD-RS of its own.

[0162] The following embodiments of the invention show how it integrates with the transmitter part and the receiver part of a terminal device 110 or a network device 100.

[0163] FIG. 6 shows two time-frequency patterns for a CD-RS associated with a DM-RS port, according to an embodiment of this disclosure.

[0164] In particular, two time-frequency patterns within a transmission slot of a CD-RS associated with a DM-RS port are shown in this figure. Each of these patterns has a different frequency domain density. This figure is an illustration of the adaptation of CD-RS frequency domain density to the frequency selectivity level of the channel of the reference signal port with which it is associated, e.g., by making the number of CD-RS subcarriers at least equal to the number of the most significant delay taps of that channel. The time-frequency patterns shown in FIG. 6(a) has a larger frequency domain density, possibly to accommodate de-nosing a DM-RS port channel that has a higher frequency selectivity. It should be noted that this density adaptation is not exclusive to this embodiment, i.e., not exclusive to CD-RS associated with downlink DM- RS, but can apply to all the subsequent embodiments.

[0165] FIG. 7 shows the time-frequency resources of a CD-RS associated with one port out of multiple DM-RS ports, according to an embodiment of this disclosure. In particular, the time-frequency pattern of the CD-RS associated with one DM-RS port out of multiple DM-RS ports sharing the same local oscillator and the resources of which span two consecutive OFDM symbols for each DM-RS time instance. It can be seen that in this example, there are two time instances per slot in this example, possibly to handle moderate mobility.

[0166] It may be worth mentioning that the DM-RS port with which the CD-RS is associated might be different from the port with which the PT-RS is associated.

[0167] FIG. 8 shows a flow chart for the transmission of CD-RS associated with a DM-RS port in the downlink of a wireless communication system, according to an embodiment of this disclosure. This wireless communication system comprises a network device 100 and a terminal device 110. In one implementation, the network device 100 may be the network device shown in FIG. 1 or FIG. 4. The terminal device 110 may be the terminal device 110 shown in FIG. 1 or FIG. 4.

[0168] Optionally, the transmission procedure may be started with the terminal device 110 requesting CD-RS resources for DM-RS phase denoising. Then, the network device 100 configures resources corresponding to at least one DM-RS and one CD-RS port. In particular, the DM-RS is mapped to at least one of a plurality of symbols, the CD-RS is mapped to at least another one of the plurality of symbols, and a subcarrier to which the CD-RS is mapped on at least one of the plurality of symbols has a same frequency domain location as a subcarrier to which the DM- RS is mapped on at least one of the rest of the plurality of symbols. The network device 100 provides resource configuration information 102 for the DM-RS, PT-RS, and CD-RS to the terminal device 110. Notably, the resource configuration information may include DM-RS port number(s) to which CD-RS is associated, CD-RS symbol(s), and subcarrier indexes. The network device 100 further sends the DM-RS, PT-RS, and CD-RS samples to the terminal device 110. The terminal device 110 performs phase denoising of the DM-RS port based on the samples received on it and the CD-RS associated with it accordingly. The terminal device 110 then estimates phase noise based on PT-RS and denoised DM-RS samples or performs joint channel and phase noise estimation based on the DMRS and the PT-RS samples.

[0169] Optionally, the network device 110 may send the CD-RS resource configuration information to the terminal device 110 through a PDCCH or by using higher-layer signaling such as RRC signaling. The terminal device 110 may send the CD-RS resource request message to the network device 100 using a PUCCH or some higher-layer signaling.

[0170] FIG. 9 shows a flow chart for the transmission of CD-RS associated with a DM-RS port in the uplink of a wireless communication system, according to an embodiment of this disclosure. This wireless communication system comprises a network device 100 and a terminal device 110. In one implementation, the network device 100 may be the network device shown in FIG. 1 or FIG. 4. The terminal device 110 may be the terminal device 110 shown in FIG. 1 or FIG. 4.

[0171] In this embodiment, the transmitter of the terminal device 110 is configured to transmit CD-RS associated with uplink DM-RS to the receiver of the network device 100.

[0172] Similar to the downlink case, the transmission procedure may be started with the terminal device 110 requesting CD-RS resources for DM-RS phase denoising. Then, the network device 100 configures resources corresponding to at least one DM-RS and one CD-RS port. In particular, the DM-RS is mapped to at least one of a plurality of symbols, the CD-RS is mapped to at least another one of the plurality of symbols, and a subcarrier to which the CD-RS is mapped on at least one of the plurality of symbols has a same frequency domain location as a subcarrier to which the DM-RS is mapped on at least one of the rest of the plurality of symbols. The network device 100 provides resource configuration information 102 for the uplink DM- RS, PT-RS, and CD-RS to the terminal device 110. Notably, the resource configuration information may include DM-RS port number(s) to which CD-RS is associated, CD-RS symbol(s), and subcarrier indexes. The terminal device 110 then sends the DM-RS, PT-RS, and CD-RS samples to the network device 100 based on the resource configuration information 102. Then, the network device 100 performs phase denoising of the DM-RS port based on the samples received on it and the CD-RS associated with it accordingly. The network device 100 then estimates phase noise based on PT-RS and denoised DM-RS samples or performs joint channel and phase noise estimation based on the DMRS and the PT-RS samples.

[0173] Optionally, the network device 110 may send the CD-RS resource configuration information to the terminal device 110 through a PDCCH or by using higher-layer signaling such as RRC signaling. The terminal device 110 may send the CD-RS resource request message to the network device 100 using a PUCCH or some higher-layer signaling.

[0174] In another embodiment, the transmitter of a network device 100 may be configured to transmit CD-RS associated with downlink CSI-RS to the receiver of a terminal device 110.

[0175] FIG. 10 shows the time-frequency pattern in two slots (not necessarily consecutive) of a CD- RS associated with a CSI-RS transmitted in these two slots.

[0176] This figure shows the time-frequency resources of CD-RS associated with a CSI-RS port that is scheduled in transmission slots n and n+p for some integer values slots n and p. The scheduling of the same port in two different transmission slots can for example be used to estimate the Doppler frequency shifts associated with the wireless link in case of mobility of the terminal device 110 with respect to the network device 100. The transmission of a CD-RS associated with such a CSI-RS port can help in reducing the effect of phase noise on the estimation of these Doppler frequency shifts.

[0177] FIG. 11 shows a different time-frequency pattern for CD-RS with respect to the pattern shown in FIG. 10. The difference is introduced due to enabling the CD-RS port hopping feature in this embodiment.

[0178] In particular, FIG. 11 shows an example of the time-frequency pattern of a CD-RS associated with CSI-RS in the case where “port hopping” is enabled for CD-RS. In this example, the CD- RS is associated with CSI-RS port number 1 in slots n+2p and n+3p (as opposed to being associated with CSI-RS port number 3 in slots n and n+p in the previous figure). The timefrequency resources of the CD-RS signal are changed accordingly within slots n+2p and n+3p. FIG. 12 shows a flow chart for the transmission of CD-RS associated with a CSI-RS port in the downlink of a wireless communication system according to an embodiment of this disclosure. Similar to the previous embodiments, this wireless communication system comprises a network device 100 and a terminal device 110. In one implementation, the network device 100 may be the network device shown in FIG. 1 or FIG. 4. The terminal device 110 may be the terminal device 110 shown in FIG. 1 or FIG. 4.

[0179] Optionally, the transmission procedure may be started with the terminal device 110 requesting CD-RS resources for CSI-RS phase denoising. Then, the network device 100 configures resources corresponding to at least one CSI-RS and one CD-RS port. In particular, the CSI-RS is mapped to at least one of a plurality of symbols, the CD-RS is mapped to at least another one of the plurality of symbols, and a subcarrier to which the CD-RS is mapped on at least one of the plurality of symbols has a same frequency domain location as a subcarrier to which the CSI- RS is mapped on at least one of the rest of the plurality of symbols. The network device 100 provides resource configuration information 102 for the CSI-RS and CD-RS to the terminal device 110. Notably, the resource configuration information may include CSI-RS port number(s) to which CD-RS is associated, CD-RS symbol(s), and subcarrier indexes. The network device 100 further sends the CSI-RS and CD-RS samples to the terminal device 110.

[0180] The terminal device 110 performs phase denoising of the CSI-RS port based on the samples received on it and the CD-RS associated with it accordingly. Optionally, the terminal device 110 deduces a phase noise estimate and uses it to denoise, i.e., compensate phase noise on, the other CSI-RS ports. The terminal device 110 then performs DL MIMO channel estimation based on the denoised CSI-RS samples.

[0181] Optionally, the network device 110 may send the CD-RS resource configuration information to the terminal device 110 through a PDCCH or by using higher-layer signaling such as RRC signaling. The terminal device 110 may send the CD-RS resource request message to the network device 100 using a PUCCH or some higher-layer signaling.

[0182] In another embodiment, the transmitter of a terminal device 110 may be configured to transmit CD-RS associated with uplink SRS to the receiver of a network device 100. FIG. 13 shows the time-frequency pattern of a CD-RS associated with one SRS port for uplink channel estimation based on four SRS ports from a terminal device 110 with four antennas. In this embodiment, the signal of two of these SRS ports is transmitted in a slot different than the other two ports and the signal of all the ports has a comb pattern in the frequency domain to allow multiplexing multiple SRS signals from multiple terminal devices. In the presence of phase noise, channel estimates from each terminal antenna will be affected by a different realization of the phase noise process, leading to large MIMO channel estimation errors. CD- RS transmitted from one of the terminal antennas (port 4 in this example) on the time-frequency resources of the pattern shown in the figure can help reduce these errors.

[0183] FIG. 14 shows a flow chart for the transmission of CD-RS associated with an SRS port in the uplink of a wireless communication system according to an embodiment of this disclosure. Similar to the previous embodiments, this wireless communication system comprises a network device 100 and a terminal device 110. In one implementation, the network device 100 may be the network device shown in FIG. 1 or FIG. 4. The terminal device 110 may be the terminal device 110 shown in FIG. 1 or FIG. 4.

[0184] Optionally, the transmission procedure may be started with the terminal device 110 requesting CD-RS resources for SRS phase denoising. Then, the network device 100 configures resources corresponding to at least one SRS and one CD-RS port. In particular, the SRS is mapped to at least one of a plurality of symbols, the CD-RS is mapped to at least another one of the plurality of symbols, and a subcarrier to which the CD-RS is mapped on at least one of the plurality of symbols has a same frequency domain location as a subcarrier to which the SRS is mapped on at least one of the rest of the plurality of symbols. The network device 100 provides resource configuration information 102 for the SRS and CD-RS to the terminal device 110. Notably, the resource configuration information may include SRS port number(s) to which CD-RS is associated, CD-RS symbol(s), and subcarrier indexes. The terminal device 110 sends the SRS and CD-RS samples to the network device 100 accordingly.

[0185] The network device 100 performs phase denoising of the SRS port based on the samples received on it and the CD-RS associated with it accordingly. Optionally, the network device 100 deduces a phase noise estimate and uses it to denoise, i.e., compensate phase noise on, the other SRS ports. The network device 100 then performs UL MIMO channel estimation based on the denoised SRS samples. Optionally, the network device 110 may send the CD-RS resource configuration information to the terminal device 110 through a PDCCH or by using higher-layer signaling such as RRC signaling. The terminal device 110 may send the CD-RS resource request message to the network device 100 using a PUCCH or some higher-layer signaling.

[0186] FIG. 15 shows a method 1500 according to an embodiment of the disclosure, particularly for controlling event-based traffic handling. In a particular embodiment, the method 1500 is performed by the network device 100 shown in one of FIG. 1, FIG. 4, FIG. 5, FIG. 8, FIG. 9, FIG. 12, or FIG. 14. The method 1500 comprises a step 1501 of determining one or more first resources 101 for at least one first reference signal based on one or more second resources of at least one second reference signal, wherein the at least one first reference signal is for channel phase de-noising, and the at least one second reference signal is for channel estimation. Further, the method 1700 comprises a step 1502 of providing resource configuration information 102 to a terminal device 110, wherein the resource configuration information 102 indicates the one or more first resources 101 for transmitting or receiving the at least one first reference signal. Possibly, the terminal device 110 may be the network entity shown in one of FIG. 1, FIG. 4, FIG. 5, FIG. 8, FIG. 9, FIG. 12, or FIG. 14.

[0187] FIG. 16 shows a method 1600 according to an embodiment of the disclosure. In a particular embodiment, the method 1600 is performed by the terminal device 110 shown in one of FIG. 1, FIG. 4, FIG. 5, FIG. 8, FIG. 9, FIG. 12, or FIG. 14. The method 1600 comprises a step 1601 of receiving resource configuration information 102 from a network device 100, wherein the resource configuration information 102 indicates one or more first resources 101 for transmitting or receiving at least one first reference signal, wherein the at least one first reference signal is for channel phase de-noising. Possibly, the network device 100 may be the network device shown in one of FIG. 1, FIG. 4, FIG. 5, FIG. 8, FIG. 9, FIG. 12, or FIG. 14.

[0188] To summarize, embodiments of the present application propose:

[0189] A communications device (which may be a network device or a terminal device) configured to:

[0190] • Send a CD-RS on determined time and frequency domain positions and use the same antenna port as the reference signal port with which the CD-RS is associated during the current transmission interval.

[0191] • Receive a CD-RS on determined time and frequency domain positions and perform channel estimation or joint channel and phase noise estimation based on the measurements associated with the CD-RS and with the reference signal ports with which the CD-RS is associated.

[0192] A terminal configured to:

[0193] • Send a signal to a network device requesting the assignment of a CD-RS and the indexes of the reference signal ports with which the CD-RS is requested to be associated.

[0194] A network device configured to

[0195] • Determine time and frequency domain densities and positions of a channel denoising reference signal (CD-RS) associated with one or more ports of another reference signal e.g., DM-RS, SRS our CSI-RS to be transmitted to or from a terminal device.

[0196] • Select the time and frequency positions of the CD-RS based on 1) the time-frequency pattern of the pilot ports with which it is associated e.g., sharing some of the sub-carrier indexes of that port but on different time indices, and 2) the time-frequency pattern of other scheduled reference signals e.g., avoiding transmitting on positions occupied by those other signals.

[0197] • Select the time domain density of the CD-RS based on a phase noise level and a modulation and coding scheme (MCS).

[0198] • Select the frequency domain density of the CD-RS based on the scheduled bandwidth, the sub-carrier spacing and the frequency selectivity (power-delay profile) of the channel of the ports with which the CD-RS is associated.

[0199] • Send a signal to a terminal indicating the CD-RS time-frequency pattern (density and positions) and the indexes of the reference signal ports with which the CD-RS is associated.

[0200] • Determine whether port hopping is required for CD-RS. If yes, send a signal to the terminal indicating the hopping pattern to be adopted.

[0201] Based on the embodiments proposed in the application, this disclosure allows:

[0202] • Better precision in channel estimation based on “demodulation reference signals” and phase noise compensation in high-mobility scenarios for communications in high- frequency bands thus enabling the use of high modulation and coding schemes (MCS) in and higher spectral efficiency for these scenarios. • Better precision in MIMO channel estimation based on “channel status information reference signals” and “sounding reference signals” in high-mobility scenarios for communications in high-frequency bands thus enabling better MIMO precoding and beamforming resulting in less inter-stream interference and inter-user interference and hence higher spectral efficiency.

[0203] • Better target range and velocity estimation performance for bi-static sensing subject to phase noise.

[0204] The present disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed embodiments of the disclosure, from the studies of the drawings, this disclosure, and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutually different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.

[0205] Furthermore, any method according to embodiments of the disclosure may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer-readable medium of a computer program product. The computer-readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

[0206] Moreover, it is realized by the skilled person that embodiments of the network device 100 or the terminal device 110 comprise the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the solution. Examples of other such means, units, elements, and functions are processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, trellis-coded modulation (TCM) encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the solution.

[0207] Especially, the processor(s) of the network device 100 or the terminal device 110 may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression “processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some, or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

Claims

CLAIMS1. A network device (100), configured to: determine one or more first resources (101) for at least one first reference signal based on one or more second resources of at least one second reference signal, wherein the at least one first reference signal is for channel phase de-noising, and the at least one second reference signal is for channel estimation; and provide resource configuration information (102) to a terminal device (110), wherein the resource configuration information (102) indicates the one or more first resources (101) for transmitting or receiving the at least one first reference signal.

2. The network device (100) according to claim 1, wherein the resource configuration information (102) indicates a first set of symbols occupied by the one or more first resources (101), a first set of subcarriers occupied by the one or more first resources (101), and at least one first antenna port for transmitting the at least one first reference signal.

3. The network device (100) according to claim 2, configured to: determine the first set of symbols based on a second set of symbols occupied by the one or more second resources, wherein the first set of symbols and the second set of symbols do not overlap.

4. The network device (100) according to claim 2 or 3, configured to: determine the first set of subcarriers based on a second set of subcarriers occupied by the one or more second resources, wherein the first set of subcarriers is a subset of the second set of subcarriers.

5. The network device (100) according to one of the claims 2 to 4, configured to: determine the at least one first antenna port based on one or more antenna ports for transmitting the at least one second reference signal, wherein the at least one first antenna port is one of the one or more antenna ports for transmitting the at least one second reference signal.

6. The network device (100) according to one of the claims 2 to 5, configured to: determine whether to enable antenna port hopping for the at least one first reference signal; and if antenna port hopping is enabled, determine at least one second antenna port for transmitting the at least one first reference signal based on the one or more antenna ports for transmitting the at least one second reference signal, wherein the at least one second antenna port and the at least one first antenna port are associated with different transmission periods, and the at least one second antenna port is one of the one or more antenna ports for transmitting the at least one second reference signal.

7. The network device (100) according to claim 6, configured to: determine a first subset resource associated with the at least one first antenna port, wherein the first subset resource occupies a first subset of symbols from the first set of symbols and a first subset of subcarriers from the first set of subcarriers, and / or determine a second subset resource associated with the at least one second antenna port, wherein the second subset resource occupies a second subset of symbols from the first set of symbols and a second subset of subcarriers from the first set of subcarriers.

8. The network device (100) according to claim 7, configured to: provide a port hopping indication to the terminal device (110), if it is determined to enable antenna port hopping for the at least one first reference signal, wherein the port hopping indication indicates at least one first antenna port with its associated transmission periods and its associated first subset resource, and the at least one second antenna port with its associated transmission periods and its associated second subset resource.

9. The network device (100) according to one of the claims 1 to 8, configured to: determine a time-domain density of the at least one first reference signal based on a phase noise level and / or a modulation and coding scheme.

10. The network device (100) according to claim 9 and claim 3, configured to: determine the first set of symbols further based on the time-domain density of the at least one first reference signal.

11. The network device (100) according to one of the claims 1 to 10, configured to: determine a frequency-domain density of the at least one first reference signal based on one or more of the following conditions: a bandwidth scheduled for the at least one first reference signal, a subcarrier spacing, a frequency selectivity of a channel for the at least one second reference signal, and a frequency-domain density of the one or more second resources.

12. The network device (100) according to claim 11 and 4, configured to: determine the first set of subcarriers further based on the frequency-domain density of the at least one first reference signal.

13. The network device (100) according to one of the claims 1 to 12, configured to: send the at least one first reference signal and the at least one second reference signal to the terminal device (110), based on the one or more first resources (101) and the one or more second resources.

14. The network device (100) according to one of the claims 1 to 13, configured to: receive the at least one first reference signal and the at least one second reference signal from the terminal device (110), based on the one or more first resources (101) and the one or more second resources; and perform channel estimation based on the received at least one first reference signal and the received at least one second reference signal to obtain a phase de-noised channel estimate.

15. The network device (100) according claim 14 and claim 8, configured to: receive the at least one first reference signal and the at least one second reference signal from the terminal device (110), further based on the port hopping indication.

16. The network device (100) according to one of the claims 2 to 15, configured to: determine the first set of symbols and the first set of subcarriers further based on one or more third resources for transmitting or receiving at least one third reference signal, wherein the at least one third reference signal is for phase noise estimation based on a channel estimate.

17. The network device (100) according to claim 16, configured to: send the at least one first reference signal, the at least one second reference signal, and at least one third reference signal to the terminal device (110), based on the one or more first resources (101), the one or more second resources and the one or more third resources.

18. The network device (100) according claim 17 and claim 8, configured to: send the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal to the terminal device (110), further based on the port hopping indication.

19. The network device (100) according to claim 16, configured to: receive the at least one first reference signal, the at least one second reference signal, and at least one third reference signal from the terminal device (110), based on the one or more first resources (101), the one or more second resources and the one or more third resources; and perform channel estimation or joint channel and phase noise estimation based on the received at least one first reference signal, the received at least one second reference signal, and the received at least one third reference signal.

20. The network device (100) according claim 19 and claim 8, configured to: receive the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal from the terminal device (110), further based on the port hopping indication.

21. The network device (100) according to claim 19 or 20, to perform the channel estimation, the network device (100) is configured to: estimate a channel based on measurements associated with the at least one first reference signal and the at least one second reference signal, to obtain a first phase de-noised channel estimate; and estimate a phase noise realization based on measurements associated with the at least one third reference signal and the first channel estimate; and optionally further de-noise the channel phase based on the estimated phase noise realization to obtain a channel estimation result.

22. The network device (100) according to one of the claims 16 to 21, wherein the at least one third reference signal is a phase tracking reference signal.

23. The network device (100) according to one of the claims 1 to 22, wherein the at least one second reference signal comprises one of the following: a demodulation reference signal, a channel satet information reference signal, and a sounding reference signal.

24. The network device (100) according to one of the claims 1 to 23, configured to: receive a request from the terminal device (110), wherein the request indicates that the one or more first resources (101) are to be assigned for the at least one first reference signal.

25. A terminal device (110), configured to: receive resource configuration information (102) from a network device (100), wherein the resource configuration information (102) indicates one or more first resources (101) for transmitting or receiving at least one first reference signal, wherein the at least one first reference signal is for channel phase de-noising.

26. The terminal device (110) according to claim 25, wherein the resource configuration information (102) indicates a first set of symbols occupied by the one or more first resources (101), a first set of subcarriers occupied by the one or more first resources (101), and at least one first antenna port for transmitting the at least one first reference signal.

27. The terminal device (110) according to claim 25 or 26, configured to: receive a port hopping indication from the network device (100), wherein the port hopping indication indicates the at least one first antenna port with its associated transmission periods and its associated first subset resource, and at least one second antenna port for transmitting the at least one first reference signal with its associated transmission periods and its associated second subset resource, wherein the at least one second antenna port and the at least one first antenna port are associated with different transmission periods, wherein the first subset resource occupies a first subset of symbols from the first set of symbols and a first subset of subcarriers from the first set ofsubcarriers, and the second subset resource occupies a second subset of symbols from the first set of symbols and a second subset of subcarriers from the first set of subcarriers.

28. The terminal device (110) according to one of the claims 25 to 27, configured to: send the at least one first reference signal and at least one second reference signal to the network device (100), based on the one or more first resources (101) and one or more second resources, wherein the one or more second resources are for transmitting or receiving the at least one second reference signal, wherein the at least one second reference signal is for channel estimation.

29. The terminal device (110) according to claim 28 and claim 27, configured to: send the at least one first reference signal and the at least one second reference signal to the terminal device (110), further based on the port hopping indication.

30. The terminal device (110) according to one of the claims 25 to 27, configured to: receive the at least one first reference signal and the at least one second reference signal from the network device (100), based on the one or more first resources (101) and one or more second resources, wherein the one or more second resources are for transmitting or receiving the at least one second reference signal, wherein the at least one second reference signal is for channel estimation; and perform channel estimation based on the received at least one first reference signal and the received at least one second reference signal to obtain a phase de-noised channel estimate.

31. The terminal device (110) according to claim 30 and claim 27, configured to: receive the at least one first reference signal and the at least one second reference signal from the terminal device (110), further based on the port hopping indication.

32. The terminal device (110) according to one of the claims 25 to 31, configured to: send the at least one first reference signal, the at least one second reference signal, and at least one third reference signal to the network device (100), based on the one or more first resources (101), the one or more second resources and one or more third resources, wherein the one or more third resources are for transmitting or receiving the at least onethird reference signal, wherein the at least one third reference signal is for phase noise estimation based on a channel estimate.

33. The terminal device (110) according to claim 32 and claim 27, configured to: send the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal to the terminal device (110), further based on the port hopping indication.

34. The terminal device (110) according to one of the claims 25 to 31, configured to: receive the at least one first reference signal, the at least one second reference signal, and at least one third reference signal from the network device (100), based on the one or more first resources (101), the one or more second resources, and one or more third resources, wherein the one or more third resources are for transmitting or receiving the at least one third reference signal, wherein the at least one third reference signal is for phase noise estimation based on a channel estimate; and perform channel estimation or joint channel and phase noise estimation based on the received at least one first reference signal, the received at least one second reference signal, and the received at least one third reference signal.

35. The terminal device (110) according to claim 34 and claim 27, configured to: receive the at least one first reference signal, the at least one second reference signal, and the at least one third reference signal from the terminal device (110), further based on the port hopping indication.

36. The terminal device (110) according to claim 34 or 35, to perform the channel estimation, the terminal device (110) is configured to: estimate a channel based on measurements associated with the at least one first reference signal and the at least one second reference signal, to obtain a first phase de-noised channel estimate; and estimate a phase noise realization based on measurements associated with the at least one third reference signal and the first channel estimate; and optionally further de-noise the channel phase based on the estimated phase noise realization to obtain a channel estimation result.

37. The terminal device (110) according to one of the claims 32 to 36, wherein the at least one third reference signal is a phase tracking reference signal.

38. The terminal device (110) according to one of the claims 28 to 37, wherein the at least one second reference signal comprises one of the following: a demodulation reference signal, a channel state information reference signal, and a sounding reference signal.

39. The terminal device (110) according to one of the claims 25 to 38, configured to: send a request to the network device (100), wherein the request indicates that the one or more first resources (101) are to be assigned for the at least one first reference signal.

40. A method performed by a network device (100), the method comprising: determining one or more first resources (101) for at least one first reference signal based on one or more second resources of at least one second reference signal, wherein the at least one first reference signal is for channel phase de-noising, and the at least one second reference signal is for channel estimation; and providing resource configuration information (102) to a terminal device (110), wherein the resource configuration information (102) indicates the one or more first resources (101) for transmitting or receiving the at least one first reference signal.

41. A method performed by a terminal device (110), the method comprising: receiving resource configuration information (102) from a network device (100), wherein the resource configuration information (102) indicates one or more first resources (101) for transmitting or receiving at least one first reference signal, wherein the at least one first reference signal is for channel phase de-noising.

42. A computer program product comprising a program code for carrying out, when implemented on a processor, the method according to claim 40 or 41.

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