EP4699268A1 - Methods and apparatuses for pilot symbol transmission - Google Patents

Abstract

Methods and apparatuses for pilot symbol transmission are provided. According to an embodiment, a first communication device determines arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols, wherein the plurality of pilot symbols are distanced from each other. The first communication device communicates, with a second communication device, a signal comprising the plurality of pilot symbols superimposed on the set of data symbols based on the arrangement information. In this way, the overall spectrum efficiency and channel estimation accuracy can be improved.

Description

METHODS AND APPARATUSES FOR PILOT SYMBOL TRANSMISSION Technical Field [0001] Embodiments of the represent disclosure relate to the field of telecommunication and in particular, to methods, devices, apparatuses and computer readable storage medium for pilot symbol transmission. [0002] This section introduces aspects that may facilitate better understanding of the present disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art. [0003] High-speed mobile communication technologies, such as vehicle-to-vehicle (V2V) and train communication, are becoming increasingly important with the advancement of automated driving, for example, and are needed to enable connectivity in broader use cases. Orthogonal Frequency Division Multiplexing (OFDM) is a widely used communication standard for communication networks such as Wi-Fi, long term evolution (LTE) and fifth- generation (5G) networks. It offers near-optimal performance in static channels. However, it suffers from severe performance degradation in high-speed mobile environments due to double selectivity caused by delay and Doppler spread. In other words, such delay and/or Doppler shifts can cause inter-symbol and inter-carrier interferences, resulting in performance degradation. A new modulation scheme, Orthogonal Time-Frequency Space (OTFS), which can be implemented on top of current OFDM and is therefore compatible with OFDM, can overcome this challenge by multiplexing data and pilot symbols in the delay-Doppler domain. OTFS can be implemented based on the OFDM modulation scheme and it is suitable for dealing with doubly dispersive channels in high-speed mobile environments. [0004] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. [0005] One of the objects of the disclosure is to provide an improved solution for superimposed pilot (SP)-based communication for transmitting pilot symbols superimposed 1 F1231100 on data symbols. Another one of the objects of the disclosure is to provide an improved solution for channel estimation for SP-based communication. In particular, one of the problems to be solved by the disclosure is to optimally map data-carrying pilot symbols while considering the trade-off between channel estimation accuracy and overall spectral efficiency (SE). [0006] According to a first aspect of the disclosure, a method implemented at a first communication device is provided. The first communication device may determine arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols, wherein the plurality of pilot symbols are distanced from each other. The first communication device may communicate, with a second communication device, a signal comprising the plurality of pilot symbols superimposed on the set of data symbols based on the arrangement information. In this way, the overall spectrum efficiency can be improved by sending additional information bits by data-carrying pilot symbols and the demodulation performance of data and channel information accuracy can be improved through the arrangement of the plurality of pilot symbols among the data symbols. [0007] In some embodiments, the plurality of pilot symbols may be distanced from each other to avoid interference from each other. [0008] In some embodiments, the arrangement information may indicate respective locations of the plurality of pilot symbols. [0009] In some embodiments, the first communication device may determine arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols based on at least one of the following: an optimal distance between adjacent pilot symbols in a delay-Doppler domain, the number of pilot symbols to be superimposed on the set of data symbols, a maximum number of pilot symbols to be superimposed on the set of data symbols. [0010] In some embodiments, the first communication device may determine the arrangement information based on the maximum delay shift and/or the maximum Doppler shift for a communication channel, and communicating the signal with the second communication device comprises: communicating the signal with the second communication device over the communication channel. In some mobile environments, the communication channel between the communication devices may suffer from delay and/or Doppler shifts, which may cause inter-symbol and inter-carrier interferences and thus lead to performance 2 F1231100 degradation. The maximum delay shift and/or Doppler shifts can reflect the mobility characteristics (e.g., the device velocities) in the environment where the communication device are located. In the embodiments of the present disclosure, by taking into account the expected maximum delay shift and/or Doppler shifts for a communication channel, the arrangement information, for example, the locations of pilot symbols in the delay-Doppler domain, may be determined in a proper way to avoid the interferences and performance degradation. [0011] In some embodiments, the first communication device may determine an optimal distance between adjacent pilot symbols in a delay-Doppler domain based on the maximum delay shift and/or the maximum Doppler shift, wherein the optimal distance is determined such that inference between the adjacent pilot symbols is eliminated; and determining the arrangement information based on the optimal distance between adjacent pilot symbols in the delay-Doppler domain. [0012] In some embodiments, the optimal distance in the delay-Doppler domain indicates at least one of the following: a first guard space corresponding to the maximum delay shift, and/or a second guard space corresponding to the maximum Doppler shift. [0013] In some embodiments, the first communication device may transmit the signal from the first communication device to the second communication device, and/or receive the signal by the first communication device from the second communication device. [0014] In some embodiments, the first communication device may be a first terminal device or a first network device, and wherein the second communication device may be a second terminal device or a second network device. [0015] In some embodiments, the first communication device may receive the arrangement information from the second communication device. In this case the first communication device is the first terminal device and the second communication device is the second network device. In some embodiments, the first communication device may transmit the arrangement information from the first communication device to the second communication device. In this case, the first communication device is the first network device and the second communication device is the second terminal device. 3 F1231100 [0016] In some embodiments, the arrangement information may be received or transmitted via radio resource control (RRC) signaling or via downlink control information (DCI). [0017] In some embodiments, the arrangement information may be comprised in an information element for downlink configuration in the RRC signaling. [0018] In some embodiments, the first communication device may receive the signal from the second communication device. In this case, the first communication device may further perform the following acts for at least one iteration until a termination criterion is met, determining at least one estimated delay shift and at least one estimated Doppler shift by comparing an aggregated power of the received signal in a delay-Doppler domain with a power threshold, estimating channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated Doppler shift, estimating the set of data symbols based on the channel information, and cancelling an interference from the received signal, to generate an updated received signal for use in a next iteration, the interference being determined based on the channel information and the set of estimated data symbols. In this way, the first communication device may obtain the estimated channel information and the set of estimated data symbols after the at least one iteration is completed. In this way, the channel information and data symbols carried by the data- carrying pilots are estimated in an iterative manner. In the iterative detection process, the channel information accuracy can be improved while taking into account the delay and Doppler shifts. [0019] In some embodiments, to determine at least one estimated delay shift and at least one estimated Doppler shift, for a given propagation path of the signal in the delay-Doppler domain, the first communication device may, in accordance with a determination that the aggregated power of the received signal in the given propagation path exceeds the power threshold, determine an estimated delay shift and an estimated Doppler shift corresponding to the given propagation path. In these embodiments, by applying a threshold criterion, the communication device can identify whether any propagation path(s) is located at a given delay-Doppler grid and use the estimated delay shift and an estimated Doppler shift corresponding to the delay-Doppler grid to facilitate the channel information estimation. [0020] In some embodiments, the power threshold may be determined based at least in part on at least one of the following: a noise power, an average transmit power of the set of data 4 F1231100 symbols, and the number of pilot symbols in the plurality of pilot symbols. In some embodiments, the power threshold may be constant over the at least one iteration and is determined further based on an expected symbol error rate (SER). In some embodiments, the power threshold for use in an iteration may be updated based on an expected symbol error rate (SER), to generate an updated power threshold for use in a next iteration. Since the power threshold is used for estimating the delay shift(s) and Doppler shift(s) and thus may impact the detection performance, the determination of the power threshold is important. If the power threshold is simply set to a ground/earth level, this leads to considering all delay- Doppler grids as “active” (i.e., all delay-Doppler grids are considered to receive propagation paths). This means that no matter how actual propagation paths are, all delay-Doppler grids have some propagations path(s), leading to poor channel estimation performance. Thus, in some embodiments of the present disclosure, some proper methods are provided to set the power threshold, by considering the specific parameters involved in the pilot symbol transmission, such as the noise power, the transmit power of data symbols, the number of pilot symbols, and the expected SER. By properly setting the power threshold, the detection performance can be further improved. [0021] In some embodiments, the termination criterion may be determined based on at least one of the following: a pre-defined number of iterations having been performed, or a difference between values of a parameter generated in a current iteration and a previous iteration falling below a threshold, the parameter comprising one of the channel information, the set of estimated data symbols, the received signal. [0022] According to a second aspect of the disclosure, a method implemented at a communication device is provided. The communication device may receive a signal comprising a plurality of pilot symbols superimposed on a set of data symbols. The communication device may perform the following acts for at least one iteration until a termination criterion is met, determining at least one estimated delay shift and at least one estimated Doppler shift by comparing an aggregated power of the received signal in a delay- Doppler domain with a power threshold, estimating channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated Doppler shift; estimating the set of data symbols based on the channel information; cancelling an interference from the received signal, to generate an updated received signal for use in a next iteration, the interference being determined based on the 5 F1231100 channel information and the set of estimated data symbols. The communication device may obtain the estimated channel information and the set of estimated data symbols after the at least one iteration is completed. In this way, the channel information and data symbols carried by the data-carrying pilots are estimated in an iterative manner. In the iterative detection process, the channel information accuracy can be improved while taking into account the delay and Doppler shifts. [0023] In some embodiments, to determine at least one estimated delay shift and at least one estimated Doppler shift, for a given propagation path of the signal in the delay-Doppler domain, the communication device may, in accordance with a determination that the aggregated power of the received signal in the given propagation path exceeds the power threshold, determine an estimated delay shift and an estimated Doppler shift corresponding to the given propagation path. [0024] In some embodiments, the power threshold may be determined based at least in part on at least one of the following: a noise power, an average transmit power of the set of data symbols, and the number of pilot symbols in the plurality of pilot symbols. [0025] In some embodiments, the power threshold may be constant over the at least one iteration and is determined further based on an expected symbol error rate (SER). [0026] In some embodiments, the power threshold for use in an iteration is updated based on an expected symbol error rate (SER), to generate an updated power threshold for use in a next iteration. [0027] In some embodiments, the termination criterion may be determined based on at least one of the following: a pre-defined number of iterations having been performed, or a difference between values of a parameter generated in a current iteration and a previous iteration falling below a threshold, the parameter comprising one of the channel information, the set of estimated data symbols, the received signal. [0028] In some embodiments, the communication device may comprise a terminal device or a network device. [0029] According to a third aspect of the disclosure, a first communication device is provided. The first communication device may comprise: a processor and a memory, said 6 F1231100 memory containing instructions executable by said processor whereby said first communication device is operative to determine arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols, wherein the plurality of pilot symbols are distanced from each other; and communicate, with a second communication device, a signal comprising the plurality of pilot symbols superimposed on the set of data symbols based on the arrangement information. [0030] According to a fourth aspect of the disclosure, a communication device is provided. The communication device may comprise: a processor and a memory, said memory containing instructions executable by said processor whereby said communication device is operative to receive a signal comprising a plurality of pilot symbols superimposed on a set of data symbols; perform the following acts for at least one iteration until a termination criterion is met, determining at least one estimated delay shift and at least one estimated Doppler shift by comparing an aggregated power of the received signal in a delay-Doppler domain with a power threshold, estimating channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated Doppler shift, estimating the set of data symbols based on the channel information, and cancelling an interference from the received signal, to generate an updated received signal for use in a next iteration, the interference being determined based on the channel information and the set of estimated data symbols; and obtain the estimated channel information and the set of estimated data symbols after the at least one iteration is completed. [0031] According to a fifth aspect of the disclosure, there is provided a method implemented in a communication system including at least one communication device. The method may comprise steps of the method according to any of the above first and second aspects. [0032] According to a sixth aspect of the disclosure, there is provided a communication system including at least one communication device according to any of the above third and fourth aspects. [0033] According to a seventh aspect of the disclosure, a computer readable storage medium is provided. The computer readable storage medium may comprise instructions, which, when executed on at least one processor, cause the at least one processor to carry out the method according to any of the above first and second aspects. 7 F1231100 [0034] According to an eight aspect of the disclosure, an apparatus is provided. The apparatus may comprise a processing module that is configured to determine arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols, wherein the plurality of pilot symbols are distanced from each other. The apparatus may also comprise a transceiver module that is configured to communicate, with a second communication device, a signal comprising the plurality of pilot symbols superimposed on the set of data symbols based on the arrangement information. [0035] According to a ninth aspect of the disclosure, an apparatus is provided. The apparatus may comprise a transceiver module that is configured to receive a signal comprising a plurality of pilot symbols superimposed on a set of data symbols. The apparatus may also comprise a processing module that is configured to perform the following acts for at least one iteration until a termination criterion is met, determining at least one estimated delay shift and at least one estimated Doppler shift by comparing an aggregated power of the received signal in a delay-Doppler domain with a power threshold, estimating channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated Doppler shift, estimating the set of data symbols based on the channel information, and cancelling an interference from the received signal, to generate an updated received signal for use in a next iteration, the interference being determined based on the channel information and the set of estimated data symbols; and obtain the estimated channel information and the set of estimated data symbols after the at least one iteration is completed. [0036] These and other objects, features and advantages of the disclosure will become apparent from the following detailed description of illustrative embodiments thereof, which are to be read in connection with the accompanying drawings. [0037] FIG.1 shows a communication system in which embodiments of the disclosure can be implemented; [0038] FIG. 2 illustrates a block diagram of a single-input single-output (SISO)-based Orthogonal Time-Frequency Space (OTFS) system model; 8 F1231100 [0039] FIGS. 3A-3C illustrate some traditional frame structure with superimposed pilot symbols; [0040] FIG. 4 illustrates a signaling chart for communications in accordance with some embodiments of the present disclosure; [0041] FIG.5 illustrates a schematic diagram of a frame structure in accordance with some embodiments of the present disclosure; [0042] FIG. 6 illustrates a block diagram of a system for channel and data estimation in accordance with some embodiments of the present disclosure; [0043] FIG. 7 illustrates a flow chart of a process for channel and data estimation in accordance with some embodiments of the present disclosure; [0044] FIG. 8A and FIG. 8B illustrate performance comparisons for conventional pilot transmission schemes with the pilot transmission scheme in accordance with some embodiments of the present disclosure; [0045] FIG. 9 is a flowchart of a method implemented at a first communication device in accordance with an embodiment of the present disclosure; [0046] FIG. 10 is a flowchart of a method implemented at a communication device in accordance with some embodiment of the present disclosure; [0047] FIG.11 is a block diagram showing an apparatus suitable for use in practicing some embodiments of the present disclosure; [0048] FIG. 12A shows a block diagram showing a terminal device suitable for use in practicing some embodiments of the present disclosure; [0049] FIG. 12B shows a block diagram showing a network device suitable for use in practicing some embodiments of the present disclosure; [0050] FIG. 13 shows an example of a communication system in accordance with some embodiments of the present disclosure; [0051] FIG. 14 shows a block diagram of a host in accordance with some embodiments of the present disclosure; and 9 F1231100 [0052] FIG.15 shows a communication diagram of a host communicating via a network node with a user equipment (UE) over a partially wireless connection in accordance with some embodiments. [0053] Throughout the drawings, the same or similar reference numerals represent the same or similar element. Detailed Description [0054] For the purpose of explanation, details are set forth in the following description in order to provide a thorough understanding of the embodiments disclosed. It is apparent, however, to those skilled in the art that the embodiments may be implemented without these specific details or with an equivalent arrangement. [0055] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art. [0056] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description. [0057] Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present 10 F1231100 disclosure should be or are in any single embodiment of the disclosure. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Furthermore, the described features, advantages, and characteristics of the disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the disclosure. [0058] As used herein, the terms “first”, “second” and so forth refer to different elements. The singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises”, “comprising”, “has”, “having”, “includes” and/or “including” as used herein, specify the presence of stated features, elements, and/or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. The term “based on” is to be read as “based at least in part on”. The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment”. The term “another embodiment” is to be read as “at least one other embodiment”. Other definitions, explicit and implicit, may be included below. The term “one or more elements” used is to be read as “only one element” or “a plurality of elements”. The term “at least element” used is to be read as “only one element” or “more than one element”. [0059] As used herein, the term “terminal device”/ “communication device” may be any device intended for accessing services via an access network and configured to communicate over the access network. For instance, the terminal device/communication device may be, but is not limited to: mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, television, radio, lighting arrangement, tablet computer, laptop, or PC. The terminal device/communication device may be a portable, pocket storable, hand- held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data, via a wireless or wireline connection. The term “terminal device” may be referred to as a mobile station (MT). Alternatively, the term “terminal device” may be referred to as 11 F1231100 a user equipment (UE). The terms “terminal device” and “UE” can be used interchangeably hereinafter. [0060] The term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (IAB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, an aircraft network device, and so forth, depending on the applied terminology and technology. [0061] FIG. 1 illustrates a communication system 100 in which embodiments of the disclosure can be implemented. As shown in FIG.1, the communication system 100 includes a network device 120. The communication system 100 also includes a terminal device 110- 1, a terminal device 110-2, ... , a terminal device 110-N (collectively referred to as “terminal device(s) 110”), where N is an integer number. The terminal device 110 is currently served by a cell 101. [0062] It can be understood that the number of devices and their connections shown in FIG. 1 are only for the purpose of illustration without suggesting any limitation. The communication system 100 may include any suitable number of devices configured to implementing embodiments of the present disclosure. Although not shown, it would be appreciated that one or more additional terminal devices may be located in the cell 101, and one or more additional cells may be deployed in the communication system 100. [0063] In some embodiments, a channel from the network device 120 to the terminal device 110 is referred to as a downlink (DL), while a channel from the terminal device 110 to the network device 120 is referred to as an uplink (UL). In the DL, the network device 120 is a transmitting (TX) device (or a transmitter) and the terminal device 110 is a receiving (RX) device (or a receiver). In the UL, the terminal device 110 is a TX device (or a transmitter) and the network device 120 is a RX device (or a receiver). In some embodiments, device-to- device (D2D) or sidelink (SL) communication may be conducted between terminal devices 110. A direct link may be established between the terminal devices 110 for the D2D or SL 12 F1231100 communication. The direct link may also be referred to as a SL or D2D link. In the D2D or SL communication, a terminal device 110 may act as a TX device (or a transmitter), and one or more terminal devices 110 may act as a TX device(s) (or a receiver(s)). [0064] Communications in the communication system 100 may be implemented according to any proper communication protocol(s), comprising, but not limited to, cellular communication protocols of the first generation (1G), the second generation (2G), the third generation (3G), the fourth generation (4G), the fifth generation (5G), the sixth generation (6G), and the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and/or any other technologies currently known or to be developed in the future. [0065] Many communication systems use pilot symbols (sometimes also called “reference signals”), which are pre-determined signals that are transmitted over a communication channel and used in the receiver to improve the quality of reception by allowing estimation of unknown parameters such as the channel response (also referred to as channel information). Pilot symbols may be transmitted in UL, DL, or SL. In UL, a transmitter of pilot symbols is a terminal device, and a receiver of the pilot symbols is a network device. For example, at least one terminal device may transmit pilot symbols to at least one network device for estimation of channel information about the corresponding channel from the at least one terminal device to the network device. In DL, a receiver of pilot symbols is a network device, and a transmitter of the pilot symbols is a terminal device. For example, at least one network device may transmit pilot symbols to at least one terminal device for estimation of channel information about the corresponding channel from the at least one network device to the terminal device. In SL, a transmitter of pilot symbols may be a terminal device, and one or more other terminal devices may be a receiver(s) of the pilot symbols. The pilot symbols transmitted between the terminal devices may be similarly used to estimate the channel between the terminal devices. 13 F1231100 [0066] As mentioned above, considering delay and/or Doppler shift in high-speed mobile environments, a OTFS modulation scheme is developed to overcome this challenge by multiplexing pilot symbols and data symbols in the delay-Doppler (DD) domain. OTFS can be implemented based on the OFDM modulation scheme. It is suitable for dealing with doubly dispersive channels in high-speed mobile environments. [0067] For the purpose of better understanding, FIG.2 illustrates a block diagram of a single- input single-output (SISO)-based OTFS system model 200 using simple matrix notations. As illustrated, the OTFS system model 200 comprises an inverse symplectic finite Fourier transform (SFFT) unit 210, a Heisenber transformation unit 220, a Wigner transformation unit 240, and a SFFT unit 250. The OTFS system model 200 is to model signal transmission of N OFDM symbols over a channel 230. [0068] The SFFT unit 250 is configured to convert the time-frequency (TF)-domain received signal ^^^TF ∈ ℂ ^{^^× ^^} into the DD-domain signal ^^^DD ∈ ℂ ^{^^× ^^} by ^^^DD = ^^_M ^H _^^ ^TF _^^N, ⁽¹⁾ where ^^_N ∈ ℂ ^{^^× ^^} and ^^_M ∈ ℂ ^{^^× ^^} are the discrete Fourier transform (DFT) matrixes, respectively. Similarly, the ISFFT unit 210 is configured to convert the DD-domain transmitted signal ^^^DD ∈ ℂ ^{^^× ^^} into the TF-domain transmitted signal ^^^TF ∈ ℂ ^{^^× ^^} by ^^^TF = ^^_M ^^^DD ^^_N ^H _. (2) [0069] The Heisenberg transformation unit 220 is configured to convert the transmitted signal ^^^TF in the TF domain into a time-domain signal ^^ ∈ ℂ ^{^^× ^^} by ^^ = ^^_tx ^^_M ^H _^^ ^TF _. ⁽³⁾ [0070] For rectangular waveforms, pulse shaping matrices ^^_tx and ^^_rx are equal to the identity matrix ^^_M. After the time-domain signal ^^ is transmitted over the channel 230, the Wigner transformation unit 240 is configured to convert the time-domain received signal ^^ ∈ signal ^^^TF by ^^^TF = ^^_M ^^_rx ^^. ⁽⁴⁾ 14 F1231100 [0071] As can be seen from the above Equations (1)-(4), the Wigner transformation is inverse transformation of the Heisenberg transformation. These operations can compose an OTFS system. [0072] For OTFS modulation, the DD-domain transmitted signal ^^ ∈ ℂ ^{^^× ^^} is converted into the time-domain signal ^^ ∈ ℂ ^{^^× ^^} by ISFFT and the Heisenberg transformation of ^^ = ^^_tx ^^_M ^H( ^^_M ^^ ^^_N ^H) = ^^_tx ^^ ^^_N ^H _. (5) [0073] A vectorized form of the time-domain signal ^^ can be written as follows: ^^ = vec( ^^) = ( ^^_N ^H _{⊗ ^^tx) ^^.} ⁽⁶⁾ [0074] For OTFS demodulation, the time-domain received signal ^^ ∈ ℂ ^{^^× ^^} is converted into the DD-domain signal ^^ ∈ ℂ ^{^^× ^^} by the Wigner transformation and SFFT of ^^ = ^^_M ^H( ^^_M ^^_rx ^^) ^^_N. ⁽⁷⁾ [0075] A vectorized form of the DD-domain signal ^^ can be written as ^^ = ( ^^_N⊗ ^^_rx) ^^. (8) [0076] In this way, an OTFS system performs signal domain conversion. Specifically, the- DD domain transmitted signal is converted into the time-domain signal, and the time-domain signal returns to the DD-domain signal again. [0077] The input-output relationship in the time domain in the OTFS system model 200 is given by ^^ = ^^ ^^ + ^^, (9) where each element of ^^ ∈ ℂ ^{^^ ^^×1} follows a distribution of ^^ ^^(0, ^^²). ^^ ∈ ℂ ^{^^ ^^× ^^ ^^} is a channel matrix defined by [0078] Here, ^^ denotes a permutation matrix with forward cyclic shift of 15 F1231100 and Δ denotes a diagonal matrix of with ^^ = exp Let ^^ be the number of propagation paths. ℎ _^^ , ^^ _^^ and ^^ _^^ are the channel gain, delay shift, and Doppler shift for the ^^-th propagation path, respectively. The delay shift ^^ _^^ and the Doppler shift are given by where Δf is the sampling rate in the frequency domain, and ^^ is the sampling duration in the time domain. It is assumed that delay-Doppler taps ⁽ ^^ _^^, ^^ _^^ ⁾ are integers. [0079] Overall, the input-output relationship in the DD domain in the OTFS system model 200 is described by ^^ = ^^_eff ^^ + ^^, (14) where ^^ _{^^ ^^ ^^} = ( ^^ _^^⊗ ^^ _^^x) ^^( ^^ _^ ^{^} ^^{^}⊗ ^^_tx) is an effective channel matrix and ^^̃ = ( ^^ _^^⊗ ^^ _^^x) ^^ is an effective noise vector. The noise vector ^^̃ also follows the distribution of ^^ ^^(0, ^^²) if ( ^^ _^^⊗ ^^ _^^x) is an unitary matrix. That is why the rectangular waveforms are considered as ⁽ ^^_tx = ^^ _^^x = ^^ _^^ ⁾ for simplicity. [0080] The channel matrix, also called channel information or channel response, may be estimated from the received signal. As mentioned earlier, the OTFS modulation scheme is developed to multiplex pilot symbols and data symbols in the delay-Doppler (DD) domain. A traditional embedded pilot (EP)-based scheme is to embed one pilot symbol in a frame. However, such OTFS channel estimation requires sufficient guard space to prevent interference between data and pilot symbols. [0081] FIG. 3A shows an EP-based frame structure 310. As shown, a pilot symbol is embedded in the center, with many guard symbols to separate the pilot symbol from the data symbols. In the EP-based scheme, a transmission signal ^^ in the DD domain is defined by: 16 F1231100 where ^^ _{^^ ^^ ^^} and ^^ _{^^ ^^ ^^} correspond to the maximum delay shift ^^ _{^^ ^^ ^^} and maximum Doppler shift ^^ _{^^ ^^ ^^} , respectively, as defined below: [0082] It can be seen that the transmission signal ^^ contains three components: data symbols, a pilot symbol, and a guard space. To completely avoid interference between the data symbols and the pilot symbol, transmission symbols ^^[ ^^, ^^] for ^^ _^^ − 2 ^^ _{^^ ^^ ^^} ≤ ^^ ≤ ^^ _^^ + 2 ^^ _{^^ ^^ ^^} and ^^ _^^ − ^^ _{^^ ^^ ^^} ^^ _{^^ ^^ ^^} are allocated to guard symbols. [0083] However, the EP-based transmission scheme is a challenge in high-speed mobile environments, where more guard space is required as the moving speed increases. This reduces the number of data symbols per OTFS frame (equivalent to time-frequency resource blocks in OFDM) and lowers the overall spectral efficiency (SE). [0084] A potentially promising solution to the problem of SE lowering is to adopt the superimposed pilot (SP)-based scheme for the OTFS system. The SP-based scheme proposes data-carrying pilot symbols by superimpose pilot symbols to data symbols. As used herein, “superimpose” means that a transmission pilot is used for carrying both a pilot symbol and a data symbol. A pilot symbol superimposed on a data symbol may also be referred to as a data-carrying pilot symbol. The superimposing refrains from increasing transmission bandwidth required for transmission of the pilot symbol. [0085] The SP-based scheme improves SE by allocating all transmission symbols to data symbols and superimposing data and pilot on top of each other, thus eliminating the need for guard space. This scheme has been applied to the OTFS system and shown to improve SE. [0086] A traditional OTFS channel estimation solution proposes to transmit a single superimposed pilot (SP) symbol, which achieved an accuracy comparable to the embedded pilot (EP)-based scheme. FIG.3B shows such a SP-based frame structure 320. As shown, all symbols in a frame are allocated to data symbols. A single pilot symbol is superimposed on 17 F1231100 one data symbol in the frame. In this SP-based scheme, the pilot symbol ^^ ^^× ^^ ^_^ ∈ ℂ is superimposed on the data symbol ^^ ^^× ^^ ^_^ ∈ ℂ as: ^^ = ^^ _^^ + ^^ _^^. (17) [0087] Similarly, another traditional method proposes an OTFS frame structure with only superimposed pilot symbols. FIG.3C shows such a SP-based frame structure 330. As shown, all the OTFS symbols are replaced by SP pilot symbols, with the pilot symbols carried on all the data symbols. Therefore, it limits the overall spectrum efficiency due to 1) limited channel estimation performance due to inter-symbol interference and 2) limited number of encoded bits of SP data symbols. [0088] A remaining challenge is how to optimally map data-carrying pilot symbols while considering the trade-off between channel estimation accuracy and overall SE. For example, if a single SP is transmitted in an OTFS frame as in FIG.3B, it may result in limited channel estimation and associated data demodulation performance. The other solution uses only superimposed pilot symbols as in FIG. 3C, which avoids the use of conventional digital modulation such as Quadrature Amplitude Modulation (QAM) and Phase Shift Keying (PSK), resulting in limited overall SE. [0089] Some embodiments of the disclosure provide an improved SP-based OTFS transmission solution in which multiple pilot symbols are superimposed on data symbols. The proposed solution exploits the advantages of multiple superimposed pilots, which can effectively eliminate the interference between data symbols and pilot symbols and improve the accuracy of channel estimation. In this solution, the multiple superimposed pilot symbols are scattered from each other such that adjacent pilot symbols do not interfere each other, resulting in the improvement on the overall spectrum efficiency and channel estimation accuracy. [0090] Some further embodiments of the disclosure also provide, among other things, a solution at a receiver side to estimate channel information and data from the SP-based transmission signal, to improve the demodulation performance of data by enhanced channel estimation performance. Some implementations of the disclosed technique may be incorporated into an system that includes a transmitter, an unknown channel, and a receiver. [0091] Embodiments of the present disclosure will be described in detail below with 18 F1231100 reference to the accompanying drawings. [0092] Reference is now made to FIG. 4, which shows a signaling chart 400 for communications according to some embodiments of the present disclosure. As shown in FIG. 4, the signaling chart 400 involves a communication device 405-1 and a communication device 405-2 between which a signal carrying pilot and data symbols is communicated. The communication devices 405-1 and 405-2 may sometimes be collectively or individually referred to as communication devices 405. [0093] In an embodiment, the communication device 405-1 may be implemented as a transmitter of the pilot and data symbols, and the communication device 405-2 may be implemented as a receiver of the pilot and data symbols. In an embodiment, the communication device 405-1 may be the receiver and the communication device 405-2 may be the transmitter. [0094] In some embodiments, the communication device 405-1 may be implemented as or included in a terminal device 110 or a network device 120 in the communication system 100. The network device 220 may be implemented as or included in a network device 120 or a terminal device 110 in the communication system 100. In some embodiments, in UL communication in the communication system 100, a transmitter of the pilot and data symbols may be a terminal device 110, and a receiver of the pilot and data symbols may be a network device 120. In DL communication in the communication system 100, the transmitter may be a network device 120, and the receiver may be a terminal device 110. In some cases, both the communication device 405-1 and the communication device 405-2 may be implemented as or included in terminal devices 110, e.g., in the scenario of sidelink (SL) communications. [0095] In the signaling flow 400, the communication device 405-1 determines (410) arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols. The plurality of pilot symbols are distanced from each other. Similarly, the communication device 405-2 determines (420) the arrangement information. Any one of the communication devices 405-1 and 405-2 may be a transmitter of the pilot symbols, while the other one may be a receiver of the pilot symbols. [0096] The proposed solution exploits the advantages of multiple superimposed pilots, which can effectively eliminate the interference between data symbols and pilot symbols and improve the accuracy of channel estimation. In this solution, the multiple superimposed pilot symbols are scattered from each other such that adjacent pilot symbols do not interfere each other, resulting in the improvement on the overall spectrum efficiency and channel estimation. 19 F1231100 [0097] In some embodiments, the plurality of pilot symbols may be distanced from each other to avoid interference from each other. In some embodiments, the communication device 405- 1 and/or 405-2 may determine the arrangement information based on an optimal distance between adjacent pilot symbols in a delay-Doppler domain. In some embodiments, the communication device 405-1 and/or 405-2 may determine the arrangement information based on a maximum delay shift ^^ _{^^ ^^ ^^} (a maximum shift in the delay domain) and/or a maximum Doppler shift ^^ _{^^ ^^ ^^} (a maximum shift in the Doppler domain) for a communication channel over which the signal is to be communicated. It is noted that the shifts in delay and Doppler domains will induced by the propagation delay and Doppler shift over a communication channel. Before transmission, the maximum delay shift and maximum Doppler shift are thus needed to be estimated. [0098] In some embodiments, the optimal distance between adjacent pilot symbols in a delay-Doppler domain may be determined based on the maximum delay shift ^^ _{^^ ^^ ^^} and/or the maximum Doppler shift ^^ _{^^ ^^ ^^} . The optimal distance may be determined such that inference between the adjacent pilot symbols is eliminated. The communication device 405- 1 and/or 405-2 may determine the arrangement information based on the optimal distance between adjacent pilot symbols in the delay-Doppler domain. In some embodiments, the optimal distance in the delay-Doppler domain indicates at least one of the following: a first guard space (or called guard interval) ^^ _{^^ ^^ ^^} corresponding to the maximum delay shift ^^ _{^^ ^^ ^^}, and/or a second guard space ^^ _{^^ ^^ ^^} corresponding to the maximum Doppler shift ^^ _{^^ ^^ ^^}. For example, the pilot symbols may be assigned on delay-Doppler grids according to the computed optimal distance in the delay-Doppler domain. [0099] FIG. 5 illustrates a schematic diagram of a frame structure 500 relying on multiple superimposed pilots in accordance with some embodiments of the present disclosure. As shown, sufficient guard spaces based on ^^ _{^^ ^^ ^^} , ^^ _{^^ ^^ ^^} are required to avoid interference between adjacent pilot symbols. A general principle is to locate plurality of pilot symbols on a delay-Doppler grid such that one pilot symbol does not interfere with the others even if that pilot symbol is shifted by ^^ _{^^ ^^ ^^}, ^^ _{^^ ^^ ^^}. [00100] Alternatively, or addition, depending on optimal distance between adjacent pilot symbols and the total number of data symbols to be transmitted, e.g., the total number of transmission symbols in a frame, the communication device 405-1 and/or 405-2 may determine a maximum number of pilot symbols to be superimposed on the data symbols that 20 F1231100 can allow the optimal distance. In some embodiments, the communication device 405-1 and/or 405-2 may determine the exact number of pilot symbols to be superimposed on the set of data symbols, which may be the same as or equal to the maximum number. In some embodiments, the arrangement information may be determined to indicate respective locations of the plurality of pilot symbols, e.g., in a frame to be transmitted. [00101] As a specific example, it is assumed that a frame includes NxM transmission symbols where ⁽ ^^, ^^⁾ = ⁽16,16⁾ . It is further assumed that ⁽ ^^ _{^^ ^^ ^^}, ^^ _{^^ ^^ ^^} ⁾ = ⁽5,2⁾, one of the pilot arrangements is ( ^^ _^^, ^^ _^^) = ^{(0,2⁾, ⁽0,7⁾, ⁽0,13⁾, ⁽10,2⁾, ⁽10,7⁾, ⁽10,13^)}, then the maximum number of pilot symbols is six. Then any suitable number of pilot symbols that is lower than or equal to six may be selected from the pilot index set ( ^^ _^^, ^^ _^^) = {(0,2), (0,7), (0,13), (10,2), (10,7), (10,13)}. It is noted that the SP-based transmission scheme proposed in the embodiments of the present disclosure can be applicable to any OTFS frame structure. [00102] In some examples, if the first guard space (in the delay domain) ^^ _{^^ ^^ ^^} is used to determine the optimal distance for the pilot symbols (and thus the locations of the pilot symbols), the pilot symbols may be allocated in such a way that there is one superimposed pilot symbol in the Doppler domain while considering the guard space in the delay domain. In this way, it can guarantee that there is no inter-SP interference in the delay-Doppler even if there is a shift in Doppler (as there is only one superimposed pilot symbol in Doppler so there is no collision if the superimposed pilot symbol is shifted by Doppler shifts). [00103] In some examples, if the second guard space (in the Doppler domain) is used to determine the optimal distance for the pilot symbols (and thus the locations of the pilot symbols), similarly, the pilot symbols may be allocated in such a way that there is only one superimposed pilot symbol in the delay domain while considering the guard space in the Doppler domain. [00104] In some embodiments, the communication device 405-1 and/or 405-2 may determine the maximum delay shift ^^ _{^^ ^^ ^^} and/or the maximum Doppler shift ^^ _{^^ ^^ ^^} based on relevant information of at least one of the communication device 405-1 and/or 405-2, and/or any other communication device that may be involved in receiving the pilot symbols. The relevant information may indicate a set of parameters that can be used for determining the delay and Doppler shifts. 21 F1231100 [00105] In some embodiments, the relevant information may indicate the velocity of at least one terminal device involved in receiving the pilot symbols and/or the velocity of the receiver in case of the moving receiver. Note that this is for a case where the receiver is also moving. Thus, the relative speed with respect to at least one terminal device needs to be taken into consideration. More specifically, in the example of FIG. 4, the relevant information may indicate a velocity of the communication device 405-1, a velocity of the communication device 405-2, and/or a velocity of any other communication device that may be involved in receiving the pilot symbols. [00106] In some embodiments, as an alternative or in addition to the velocity information, other parameters may be considered in determining the maximum delay shift ^^ _{^^ ^^ ^^} and/or the maximum Doppler shift ^^ _{^^ ^^ ^^}. The other parameters may include a frequency range over the communication channel. For example, a high frequency may correspond to a small delay shift and will cause a few propagation paths. As a contrary, a low frequency may correspond to a high delay shift and will cause a lots of propagation paths. The other parameters may include a communication scenario in which the communication devices 405-1, 405-2 are located. For example, in different scenarios such as micro urban, macro urban, and suburb urban, the propagation paths and reflection paths of signals may be different due to the different buildings and obstacles in the corresponding scenarios. [00107] It would be appreciated that some example information for determining the maximum delay shift ^^ _{^^ ^^ ^^} and/or the maximum Doppler shift ^^ _{^^ ^^ ^^} in a communication channel is provided above, and there may be various other information that can also be taken into account. [00108] In some embodiments, the arrangement information for the plurality of pilot symbols may be determined by one of the communication devices 405-1 and 405-2 and transmitted to the other one the communication devices 405-1 and 405-2. In some embodiments, the arrangement information may be configured by either the transmitter or the receiver, depending on the role of the network device. In some embodiments, if the communication device 405-1 is a terminal device, e.g., the terminal device 110 in FIG.1, and the communication device 405-2 is a network device, e.g., the network device 120 in FIG.1, then the communication device 405-2 may determine the arrangement information and transmit the arrangement information to the communication device 405-1. Alternatively, if the communication device 405-1 is the network device 120 in FIG.1, and the communication 22 F1231100 device 405-2 is a terminal device 110 served by the network device 120, then the communication device 405-1 may determine the arrangement information and transmit the arrangement information to the communication device 405-2. [00109] The arrangement information may be communicated in any suitable signaling or messages. In some embodiments, the arrangement information may be received or transmitted via radio resource control (RRC) signaling from the network device. The parameters for defining the locations of the pilot symbols may be included in the communication standard for the RRC signaling. In an example, the arrangement information may be comprised in an information element for downlink configuration in the RRC signaling. In some embodiments, the arrangement information may be received or transmitted via downlink control information (DCI) in physical downlink control channel (PDCCH). Although this requires additional overhead on control channels, it enables more frequent update on the allocation of data-carrying pilots. [00110] Referring back to FIG. 4, the communication device 405-1 communicates (430), with the second communication device (404), a signal comprising the plurality of pilot symbols superimposed on the set of data symbols based on the determined arrangement information. In some embodiments, if the communication device 405-1 acts as a transmitter (which may be either a network device 120 or a terminal device 110 in FIG. 1), it may transmit the signal to the communication device 405-2 acting as a receiver (which may be either a network device 120 or a terminal device 110 in FIG. 1). Alternatively, if the communication device 405-1 acts as the receiver, it may receive the signal from the communication device 405-2. In some embodiments, although not illustrated, the transmitter may transmit the signal to more than one receiver. [00111] In some embodiments, the transmitter (e.g., the communication device 405-1 or the communication device 405-2) may allocate the data symbols to respective transmission symbols in an OTFS frame. According to the arrangement information, the transmitter may allocate the indicated number of pilot symbols to their respective locations in the OTFS frame, superimposing the pilot symbols on the data symbols at those locations. The transmitter may then transmit the OTFS frame as the signal. In some embodiments, the transmitted signal may be conveyed over a communication channel as multiple OFDM symbols over multiple subcarriers in time-frequency channel resources. [00112] Correspondingly, the receiver (e.g., the communication device 405-2 or the 23 F1231100 communication device 405-1) may receive the multiple OFDM symbols over the multiple subcarriers in time-frequency channel resources. The receiver may converting the time- frequency domain received signal into the delay-Doppler domain via linear transformation techniques. The receiver may determine the plurality of pilot symbols superimposed on data symbols according to the arrangement information. The receiver may estimate channel information using the plurality of superimposed pilot symbols and then demodulate data symbols in the plurality of superimposed pilot symbols, and demodulate other data symbols in the received signal using the plurality of superimposed pilot symbols. [00113] According to embodiments described with reference to FIGS.4-5, the proposed SP- based transmission scheme can improve the overall spectrum efficiency by sending additional information bits by data-carrying pilot symbols and improving the demodulation performance of data and channel information accuracy through the optimal configuration of pilot symbol allocation among the data symbols. [00114] Some further embodiments of the disclosure also provide a solution for channel information and data estimation at a receiver side to mitigate the error floor in high signal- noise ratio (SNR) region and improve the demodulation performance of data by enhanced channel estimation performance. In those embodiments, the channel information and data symbols carried by the data-carrying pilot symbols may be estimated in an iterative manner. [00115] FIG.6 illustrates a block diagram of a system 600 for channel and data estimation in accordance with some embodiments of the present disclosure. The channel and data estimation system 600 may be included in or implemented at a receiver of pilot and data symbols. As discussed above, either the communication device 405-1 or the communication device 405-2 may be a receiver which receives that the signal comprising the set of data symbols and the plurality of pilot symbols superimposed on data symbols. For the purpose of illustration only, it is assumed that the communication device 405-1 receives the signal from the communication device 405-2, e.g., over a communication channel between the two communication devices. However, it would be appreciated that the same process may be implemented at the communication device 405-2 if it is the receiver. [00116] From the perspective of the receiver, the pilot symbols are known signals, but the data symbols and channel information of the communication channel are unknown to the communication device 405-1. In order to demodulate the data symbols, the communication device 405-1 may estimate the channel information using the known pilot symbols 24 F1231100 configured according to the arrangement information. As shown in FIG. 6, the system 600 includes a channel estimator 610, a symbol detector 620, and an interference canceller 630, which are configured to perform an iterative detection process to estimate channel information and data symbols. [00117] The iterative detection process will be discussed in detail with reference to a process 700 as illustrated in FIG.7. The process 700 may be implemented at a receiver of pilot and data symbols, e.g., the communication device 405-1 by using the system 600. [00118] In the process 700, the communication device 405-1 may performs the acts at blocks 710, 720, 730, and 740 until a termination criterion is met. [00119] At block 710, the communication device 405-1, e.g., the channel estimator 610 in the system 600, determines at least one estimated delay shift and at least one estimated Doppler shift by comparing an aggregated power of the received signal in a delay-Doppler domain with a power threshold. [00120] In some embodiments, for the case ^^ ≥ ^^ _^^, the delay-Doppler input-output relation is given by: ^^ (18) ^^^[ ^^, ^^^] = ∑ℎ _^^ ^^ ^{^^ ^^( ^^− ^^ ^^)} _^^ ^[[ _{^^ − ^^ ^^} ^] _^^, ^[ _{^^ − ^^ ^^} ^] _^^ ^] _. ^^=1 where ^^ is a transmitted signal, ^^ is the received signal, ℎ _^^ is channel information to be estimated. It is assumed an estimated delay shift in the delay domain ^^ = ^^ _^^ + ^^ _^^ and an estimated Doppler shift in the Doppler domain ^^ = ^^ _^^ + ^^ _^^ , the received pilot symbols for the ^^-th ( ^^ = 1,2,⋯ , ^^) propagation path can be rewritten as [00121] In some embodiments, an accurate estimation of the channel information ℎ _^^ may be defined as follows: 25 F1231100 where ^^ denotes the number of pilot symbols, ( ^^ _{^^ ^^} , ^^ _{^^ ^^}) denotes a pair of delay-Doppler indices for ^^ = 1,2,⋯ , . The average of the channel information is calculated from multiple pilot symbols. While the total energy is kept constant, the multiple pilot symbols can cancel the data-pilot interference. [00122] In some embodiments, the communication device 405-1 may apply a threshold criterion to estimate the delay-Doppler indices ( ^^ _^^, ^^ _^^). The communication device 405-1 may evaluate the sum of the amplitude/power of the received signal over the delay-Doppler domain in comparison with a threshold. More specifically, for a given propagation path of the signal in the delay-Doppler domain, the communication device 405-1 may determine whether the aggregated power of the received signal in the given propagation path exceeds the power threshold. If the aggregated power of the received signal in the given propagation path exceeds the power threshold, the communication device 405-1 may determine an estimated delay shift and an estimated Doppler shift corresponding to the given propagation path. Let ^^[ ^^, ^^] denote whether a path with an estimated delay shift ^^ and estimated Doppler shift ^^ exist or not, which is given by: ^^ (21) ^^^[ ^^, ^^^] = {1, ∑| ^^ [ ^^ _{^^ ^^} + ^^, ^^ _{^^ ^^} + ^^]| ≥ ^^, ^^=1 0, otherwise. The number of propagation paths is estimated by ^^̂ = ^∑ _^^ ^∑ _^^ ^^[ ^^, ^^] , and the delay-Doppler indices ( ^^ _^^, ^^ _^^) correspond to the indices ( ^^, ^^) having ^^[ ^^, ^^] = 1. With the delay-Doppler indices ( ^^ _^^, ^^ _^^) determined, the estimated delay shift(s) may be determined as ^^ = ^^ _^^ + ^^ _^^ and the estimated Doppler shift in the Doppler domain may be determined as ^^ = ^^ _^^ + ^^ _^^. [00123] In some embodiments, the power threshold ^^ to determine the estimated delay shift and estimated Doppler shift may be determined by computing the expected amplitude of the signal including the noise power and the transmitted signal, which may be indicated by an average transmit power of the set of data symbols, and the number of pilot symbols in the plurality of pilot symbols. In some embodiments, power threshold ^^ may be determined as follow: (22 √ ^{( 2} _^ ² ) ^^ = 3 ^^ ^^ + ^^_^ ⁾, 26 F1231100 where ^^² is the variance of the noise power, and ^^ _^ ² ^ is the average power of data symbols, and ^^ denotes the number of pilot symbols. The threshold is defined to distinguish received symbols that contain a part of multiple pilot symbols. [00124] At block 720, the communication device 405-1, e.g., the channel estimator 610 in the system 600, estimates channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated Doppler shift. The communication device 405-1 may estimate the channel information from the received signal and the data-carrying pilot symbols while considering the estimated delay shift(s) and/or the Doppler shift(s) estimated at block 710. The communication device 405-1 may average over multiple pilot symbols with the delay-Doppler locations. [00125] At block 730, the communication device 405-1, e.g., the symbol detector 620 in the system 600, estimates the set of data symbols based on the channel information. The communication device 405-1, e.g., the symbol detector 620, may estimating the data symbols by equalizing the channel information estimated at block 720. In some examples, the communication device 405-1 may apply the well-known minimum mean square error (MMSE) detector to the proposed method. Considering the system model in the DD domain, an MMSE estimate of data symbols is given by −1 ^^̂ _^^ = ( ^^̂_e ^H f_f ^^̂_eff + λ ^^_MN) ^^̂_e ^H f_f ^^ _^^, (23) where ^^̂_eff is the estimated channel information, ^^_MN is an identity matrix with dimensions of M and N , ^^ = ^^²/ ^^ _^ ² ^ is the coefficient depends on SNR, ^^̂ _^^ are estimated data symbols, and the received data symbols ^^ _^^ is given by ^^ _^^ = ^^ − ^^̂_eff ^^ _^^. (24) where ^^ _^^ are the pilot symbols. [00126] At block 740, the communication device 405-1, e.g., the interference canceller 630 in the system 600, cancels an interference from the received signal, to generate an updated received signal for use in a next iteration, the interference being determined based on the channel information and the set of estimated data symbols. The communication device 405- 27 F1231100 1, e.g., the interference canceller 630, may subtracting the interference from the received signal by the estimated channel information and data symbols. [00127] In some examples, after obtaining estimates the channel information ^^̂_eff and the data symbols ^^̂, the interference cancellation is performed using: ^^̃ = ^^ − ^^̂_eff ^^̂ _^^. (25) The received signal ^^̃ with the interference cancelled may be further provided from the interference canceller 630 to the channel estimator 610 for use in a next iteration. [00128] In some cases, the received signal ^^̃ consisted of only the multiple pilot symbols and noise may be obtained. But in some other cases, ^^̃ contains interference that could not be removed in the previous iteration. In some embodiments, the power threshold ^^ may be determined by computing the expected amplitude of the signal including the noise power and the transmitted signal while considering the cancelled signal power during the iteration which may be indicated through an expected symbol error rate (SER). [00129] Specifically, before the next iteration, the power threshold ^^ may be updated to mitigate remaining interference. However, deriving an optimal threshold in the practical channel model is a challenging task. For example, in some traditional solutions, a threshold is updated using the number of propagation paths. The residual amount of interference depends on estimation errors, i.e., ^^̂ and ^^̂. Therefore, it is desirable to consider both channel estimation and symbol detection errors for an accurate threshold decision. Here, an improved threshold using symbol error rate (SER) is determined. In some embodiments, the power threshold for use in an iteration may be updated based on an expected symbol error rate (SER), to generate an updated power threshold for use in a next iteration. In an example, the power threshold ^^ may be determined as follows: [00130] It is assumed that SER is known in advance because the theoretical SER can be approximated under ideal conditions given a specific SNR. In some examples, this SNR may be (approximately) computed by expected channel power (e.g., pathloss), transmit power, and noise power. 28 F1231100 [00131] In some embodiments, alternatively, the power threshold ^^ for use in an iteration may be constant over the iterations and determined by the expected symbol error rate (SER) for a given received SNR, e.g., the power threshold ^^ determined according to Equation (26) may be constant over the iterations. [00132] At block 750, the communication device 405-1 determines whether the termination criterion is met. If the termination criterion is not met, the communication device 405-1 may return to block 710. Otherwise, if the termination criterion is met, the communication device 405-1 may proceed to block 760. [00133] In some embodiments, the termination criterion is met if a pre-defined number of iterations of the acts at blocks 710, 720, 730, and 740 have been performed. In some examples, the pre-defined number of iterations may be determined by either the transmitter(s) or the receiver(s) before the communication. [00134] Alternatively, or in addition, the termination criterion may be based on a difference between values of a parameter generated in a current iteration and a previous iteration falling below a threshold, the parameter comprising one of the channel information, the set of estimated data symbols, the received signal. The communication device 405-1 may measure a certain value over iterations and terminating the iteration when the measured value satisfies a pre-defined threshold. For example, the communication device 405-1 may measure the power of the received signal after subtracting the interference at block 740, and may terminate the iteration when the difference between the measured signal power at the current iteration and that at the previous iteration falls below a pre-defined threshold (e.g., 10⁻⁵). To elaborate, let the received signal after interference cancellation (i.e., ^^̃) be indexed by , where ^^ denotes the iteration index. Then, the iterations may end when ‖ ^^̃^{( ^^)}‖ − ‖ ^^̃^{( ^^−1)}‖ < ^^ , where ^^ is a threshold. Similarly, the communication device 405-1 may measure the channel information and/or the set of estimated data symbols in a similar way to decide whether to terminate the iteration. [00135] The acts at blocks 710, 720, 730, and 740 may be performed for at least one iteration until the termination criterion is met. After the termination criterion is met, at block 760, the communication device 405-1 obtains the estimated channel information and the set of estimated data symbols after the at least one iteration is completed. 29 F1231100 [00136] According to embodiments described with reference to FIGS. 6-7, the channel information accuracy can be improved by optimally configuring allocation of data-carrying reference signaling while taking into account the expected maximum delay and Doppler shifts. improving the demodulation performance of data. [00137] Note that the channel estimation solution proposed for the SP-based scheme of FIG. 3C (where all data symbols are superimposed with pilot symbols) differs from the channel estimation solution proposed in the embodiments of the present disclosure. Specifically, the channel estimation solution of FIG.3C estimates the channel gain ℎ _^^ with a MMSE estimator. The major problem with the channel estimation solution of FIG.3C is that it cannot estimate the delay-Doppler index ( ^^ _^^, ^^ _^^). [00138] To better understanding the performance improvements, the proposed SP-based scheme in accordance with an embodiment of the present disclosure is compared against the conventional EP-based scheme in FIG. 3A and the single SP-based scheme in FIG. 3B in terms of bit error rate (BER) and normalized mean squared error (NMSE). [00139] The comparison results are obtained from an OTFS system with Quadrature Phase Shift Keying (QPSK) signaling where the number of time slots is ^^ = 16, the number of subcarriers is ^^ = 64, the maximum relative speed is ^^ = 500 km/h, the carrier frequency is ^^ _^^ = 4 GHz, and the subcarrier spacing is Δ ^^ = 15 kHz. Table I: 5-tap Delay-Doppler Channel Parameters Path index ^^ 1 2 3 4 5 Delay [μs] 2.08 5.20 8.328 11.46 20.8 Relative power [dB] 1 -1.804 -3.565 -5.376 -8.860 [00140] A 5-tap delay-Doppler channel model shown in Table I. Each propagation path has a Doppler shift calculated from the Jakes formula of ^^ _^^ = ^^ _{^^ ^^ ^^} cos⁽ ^^ _^^ ⁾, (27) where ^^ _^^ is the angle parameter following uniform distribution in [0,2 ^^] . Following the conventional schemes as in FIG. 3A and FIG. 3B, data SNR and pilot SNR are defined separately as 30 F1231100 where ^^ _^ ² ^ = E[^| ^^ _^^ ^[ ^^, ^^^]|2] denotes the average power of data symbols and ^^ _^ ² _^ = 2 | ^^ _^^| denotes the power of pilot symbols. For simplicity, the noise variance is defined as ^^² = 1. The pilot power per symbol is multiplied by 1/ ^^ to keep the total energy constant. It is assumed that SNR _^^ = 50 dB and ^^ = 3 in the simulations. [00141] FIG.8A and FIG.8B illustrate performance comparisons 810, 820 for conventional pilot transmission schemes with the pilot transmission scheme in accordance with some embodiments of the present disclosure. The performance for the conventional EP-based scheme is denoted as “Conv.EP”, and the performance for the conventional single SP-based scheme is denoted as “Conv.SP w/1 pilot”. The proposed performances of the pilot transmission scheme are is denoted as “Prop.SP w/3 pilot” (i.e., three pilot symbols are transmitted), “Prop.SP w/6 pilot” (i.e., six pilot symbols are transmitted), and “Prop.SP w/9 pilot” (i.e., nine pilot symbols are transmitted). [00142] As can be seen from FIG. 8A, the BER performance improved by increasing the number of superimposed pilots. However, compared to the EP-based scheme, all SP-based schemes exhibited performance deterioration in high SNR _^^ region because of inevitable interference between data and pilot symbols. [00143] As can be seen from FIG.8B, similar to FIG.8A, the proposed SP-based schemes achieved better NMSE performance than the conventional SP-based scheme, and EP-based scheme achieved stable performance in all SNR _^^ regions. From these results, it can be seen that the advantage of the proposed scheme using multiple superimposed pilot symbols in terms of BER and NMSE. In BER and NMSE comparisons, similar trends were observed. This was because ^^̂_eff and ^^̂ are used in the proposed iterative detection scheme. [00144] Additionally, the SE is evaluated based on transmission rate. Transmission rates of EP-based scheme and SP-based scheme can be written as ^^ ^^ − ^^ _{^^ ^^ ^^ ^^ ^^} − 1) (29) and log( ^^) ^^ ^^ (30) ^^ _{^^ ^^} = , ^^Δ _^^ ^^ ^^ 31 F1231100 where ^^ denotes the modulation order and ^^ _{^^ ^^ ^^ ^^ ^^} = (2 ^^ _{^^ ^^ ^^} + 1)(4 ^^ _{^^ ^^ ^^} + 1) denotes the amount of guard space for EP-based scheme. In our simulations, transmission rates were ^^ _{^^ ^^} = 2 bit/s/Hz and ^^ _{^^ ^^} = 1.28 bit/s/Hz . Thus, the proposed SP-based scheme improved the transmission rate by 56%. [00145] Overall, the proposed SP-based scheme is expected to improve channel estimation accuracy and SE, especially in high-mobility scenarios. [00146] FIG. 9 is a flowchart of an example method 900 implemented at a first communication device in accordance with an embodiment of the present disclosure. For the purpose of discussion, the method 900 will be described from the perspective of a communication device 405-1 in FIG.4. [00147] At block 910, the communication device 405-1 determines arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols, wherein the plurality of pilot symbols are distanced from each other. In some embodiments, the plurality of pilot symbols may be distanced from each other to avoid interference from each other. [00148] At block 920, the communication device 405-1 communicates, with a further communication device (e.g., the communication device 405-2), a signal comprising the plurality of pilot symbols superimposed on the set of data symbols based on the arrangement information. [00149] In some embodiments, the arrangement information may indicate respective locations of the plurality of pilot symbols. [00150] In some embodiments, the communication device 405-1 may determine arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols based on at least one of the following: an optimal distance between adjacent pilot symbols in a delay-Doppler domain, the number of pilot symbols to be superimposed on the set of data symbols, a maximum number of pilot symbols to be superimposed on the set of data symbols. [00151] In some embodiments, the communication device 405-1 may determine the arrangement information based on the maximum delay shift and/or the maximum Doppler shift for a communication channel. In some embodiments, the communication device 405 32 F1231100 may communicate the signal with the further communication device over the communication channel. [00152] In some embodiments, the communication device 405-1 may determine an optimal distance between adjacent pilot symbols in a delay-Doppler domain based on the maximum delay shift and/or the maximum Doppler shift, wherein the optimal distance is determined such that inference between the adjacent pilot symbols is eliminated; and may determine the arrangement information based on the optimal distance between adjacent pilot symbols in the delay-Doppler domain. [00153] In some embodiments, the optimal distance in the delay-Doppler domain may indicate at least one of the following: a first guard space corresponding to the maximum delay shift, and/or a second guard space corresponding to the maximum Doppler shift. [00154] In some embodiments, the communication device 405-1 may determine the maximum delay shift and the maximum Doppler shift based on relevant information of at least one of the communication device 405-1 or the communication device 405-2. [00155] In some embodiments, the relevant information indicates at least one of the following: a velocity of the communication device 405-1 and/or a velocity of the communication device 405-2. [00156] In some embodiments, the communication device 405-1 may transmit the signal from the first communication device to the second communication device. In some embodiments, the communication device 405-1 may receive the signal by the first communication device from the communication device 405-2. [00157] In some embodiments, the communication device 405-1 may be a first terminal device or a first network device. In some embodiments, the communication device 405-2 with which the signal is communicated may be a second terminal device or a second network device. [00158] In some embodiments, the communication device 405-1 may receive the arrangement information from the communication device 405-2. In this case, the communication device 405-1 may be the first terminal device and the communication device 405-2 may be the second network device. 33 F1231100 [00159] In some embodiments, the communication device 405-1 may transmit the arrangement information to the communication device 405-2. In this case, the communication device 405-1 may be the first network device and the communication device 405-2 may be the second terminal device. [00160] In some embodiments, the arrangement information may be received or transmitted via radio resource control (RRC) signaling or via downlink control information (DCI). In some embodiments, the arrangement information may be comprised in an information element for downlink configuration in the RRC signaling. [00161] In some embodiments, the communication device 405-1 may receive the signal from the communication device 405-2. The communication device 405-2 may perform the following acts for at least one iteration until a termination criterion is met: determining at least one estimated delay shift and at least one estimated Doppler shift by comparing an aggregated power of the received signal in a delay-Doppler domain with a power threshold, estimating channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated Doppler shift, estimating the set of data symbols based on the channel information, and cancelling an interference from the received signal, to generate an updated received signal for use in a next iteration, the interference being determined based on the channel information and the set of estimated data symbols. The communication device 405-1 may obtain the estimated channel information and the set of estimated data symbols after the at least one iteration is completed. [00162] In some embodiments, to determine at least one estimated delay shift and at least one estimated Doppler shift, or a given propagation path of the signal in the delay-Doppler domain, the communication device 405-1 may, in accordance with a determination that the aggregated power of the received signal in the given propagation path exceeds the power threshold, determine an estimated delay shift and an estimated Doppler shift corresponding to the given propagation path. [00163] In some embodiments, the power threshold may be determined based at least in part on at least one of the following: a noise power, an average transmit power of the set of data symbols, and the number of pilot symbols in the plurality of pilot symbols. [00164] In some embodiments, the power threshold may be constant over the at least one iteration and is determined further based on an expected symbol error rate (SER). 34 F1231100 [00165] In some embodiments, the power threshold for use in an iteration may be updated based on an expected symbol error rate (SER), to generate an updated power threshold for use in a next iteration. [00166] In some embodiments, the termination criterion may be determined based on at least one of the following: a pre-defined number of iterations having been performed, or a difference between values of a parameter generated in a current iteration and a previous iteration falling below a threshold, the parameter comprising one of the channel information, the set of estimated data symbols, the received signal. [00167] FIG.10 is a flowchart of an example method 1000 implemented at a communication device in accordance with an embodiment of the present disclosure. For the purpose of discussion, the method 1000 will be described from the perspective of a communication device 405 in FIG.4 (e.g., either the communication device 405-1 or communication device 405-2 which acts as a receiver). [00168] At block 1010, the communication device 405 receives a signal comprising a plurality of pilot symbols superimposed on a set of data symbols. [00169] At block 1020, the communication device 405 performs the acts at blocks 1021, 1022, 1025, and 1027 for at least one iteration until a termination criterion is met. [00170] Specifically, at block 1021, the communication device 405 determines at least one estimated delay shift and at least one estimated Doppler shift by comparing an aggregated power of the received signal in a delay-Doppler domain with a power threshold. At block 1023, the communication device 405 estimates channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated Doppler shift. At block 1025, the communication device 405 estimates the set of data symbols based on the channel information. At block 1027, the communication device 405 cancels an interference from the received signal, to generate an updated received signal for use in a next iteration. The interference is determined based on the channel information and the set of estimated data symbols. [00171] At block 1030, the communication device 405 obtains the estimated channel information and the set of estimated data symbols after the at least one iteration is completed. 35 F1231100 [00172] In some embodiments, to determine at least one estimated delay shift and at least one estimated Doppler shift, for a given propagation path of the signal in the delay-Doppler domain, the communication device 405 may, in accordance with a determination that the aggregated power of the received signal in the given propagation path exceeds the power threshold, determine an estimated delay shift and an estimated Doppler shift corresponding to the given propagation path. [00173] In some embodiments, the power threshold may be determined based at least in part on at least one of the following: a noise power, an average transmit power of the set of data symbols, and the number of pilot symbols in the plurality of pilot symbols. [00174] In some embodiments, the power threshold may be constant over the at least one iteration and is determined further based on an expected symbol error rate (SER). [00175] In some embodiments, the power threshold for use in an iteration may be updated based on an expected symbol error rate (SER), to generate an updated power threshold for use in a next iteration. [00176] In some embodiments, the termination criterion may be determined based on at least one of the following: a pre-defined number of iterations having been performed, or a difference between values of a parameter generated in a current iteration and a previous iteration falling below a threshold, the parameter comprising one of the channel information, the set of estimated data symbols, the received signal. [00177] In some embodiments, the communication device may comprise a terminal device or a network device. [00178] FIG.11 is a block diagram showing an apparatus 1100 suitable for use in practicing some embodiments of the disclosure. For example, any one of communication devices described above, including the terminal devices and the base station, may be implemented through the apparatus 1100. As shown, the apparatus 1100 may include a processor 1110, a memory 1120 that stores a program, and optionally a communication interface 1130 for communicating data with other external devices through wired and/or wireless communication. 36 F1231100 [00179] The program includes program instructions that, when executed by the processor 1110, enable the apparatus 1100 to operate in accordance with the embodiments of the present disclosure, as discussed above. That is, the embodiments of the present disclosure may be implemented at least in part by computer software executable by the processor 1110, or by hardware, or by a combination of software and hardware. [00180] The memory 1120 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor- based memory devices, flash memories, magnetic memory devices and systems, optical memory devices and systems, fixed memories and removable memories. The processor 1110 may be of any type suitable to the local technical environment, and may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architectures, as non- limiting examples. [00181] FIG. 12A shows a block diagram showing an apparatus 1200 suitable for use in practicing some embodiments of the present disclosure. For example, the apparatus 1200 may be the terminal device 110 or the network device 120 shown in FIG. 1. As shown in FIG. 12A, the apparatus 1200 may include a transceiver module 1210 that is configured to receive, from a network device, a first indication indicating system information to be changed. The transceiver module 1210 may also be configured to receive, via a broadcast signaling from the network device, the system information indicated to be changed by the first indication. The system information may include a first measurement configuration. The apparatus 1200 may also include a processing module 1220 that is configured to update an existing measurement configuration based on the first measurement configuration. The transceiver module 1210 and the processing module 1220 may also be configured to perform the method described with reference to FIG.9 and/or the method described with reference to FIG.10. [00182] FIG. 12B shows a block diagram showing an apparatus 1201 suitable for use in practicing some embodiments of the present disclosure. For example, the apparatus 1201 may be the network device 120 shown in FIG.1. As shown in FIG.12B, the apparatus 1201 may include a transceiver module 1211 that is configured to transmit, to at least one terminal device, a first indication indicating system information to be changed. The transceiver module 1211 may also be configured to transmit, via a broadcast signaling to the at least one terminal device, the system information indicated to be changed by the first indication. The 37 F1231100 system information comprises a first measurement configuration that is used to update an existing measurement configuration at the at least one terminal device. The network device 1201 may also include other modules, for example, a processing module 1221. The modules in the apparatus 1201 (for example, the transceiver module 1211 and the processing module 1221) may also be configured to perform the method described with reference to FIG. 9 and/or the method described with reference to FIG.10. [00183] FIG. 13 shows an example of a communication system 3100 in accordance with some embodiments. [00184] In the example, the communication system 3100 includes a telecommunication network 3102 that includes an access network 3104, such as a radio access network (RAN), and a core network 3106, which includes one or more core network nodes 3108. The access network 3104 includes one or more access network nodes, such as network nodes 3110a and 3110b (one or more of which may be generally referred to as network nodes 3110), or any other similar 3rd Generation Partnership Project (3GPP) access node or non-3GPP access point. The network nodes 3110 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs 3112a, 3112b, 3112c, and 3112d (one or more of which may be generally referred to as UEs 3112) to the core network 3106 over one or more wireless connections. [00185] Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 3100 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. The communication system 3100 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system. [00186] The UEs 3112 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with the network nodes 3110 and other communication devices. Similarly, the network nodes 3110 are arranged, capable, configured, and/or operable to communicate directly or indirectly with 38 F1231100 the UEs 3112 and/or with other network nodes or equipment in the telecommunication network 3102 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in the telecommunication network 3102. [00187] In the depicted example, the core network 3106 connects the network nodes 3110 to one or more hosts, such as host 3116. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 3106 includes one more core network node (e.g., core network node 3108) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 3108. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and/or a User Plane Function (UPF). [00188] The host 3116 may be under the ownership or control of a service provider other than an operator or provider of the access network 3104 and/or the telecommunication network 3102 and may be operated by the service provider or on behalf of the service provider. The host 3116 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server. [00189] As a whole, the communication system 3100 of FIG. 13 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), 39 F1231100 and/or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and/or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox. [00190] In some examples, the telecommunication network 3102 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 3102 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 3102. For example, the telecommunications network 3102 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and/or Massive Machine Type Communication (mMTC)/Massive IoT services to yet further UEs. [00191] In some examples, the UEs 3112 are configured to transmit and/or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 3104 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 3104. Additionally, a UE may be configured for operating in single- or multi-RAT or multi- standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e., being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio – Dual Connectivity (EN-DC). [00192] In the example, the hub 3114 communicates with the access network 3104 to facilitate indirect communication between one or more UEs (e.g., UE 3112c and/or 3112d) and network nodes (e.g., network node 3110b). In some examples, the hub 3114 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 3114 may be a broadband router enabling access to the core network 3106 for the UEs. As another example, the hub 3114 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 3110, or by executable code, script, process, or other instructions in the hub 3114. As another example, 40 F1231100 the hub 3114 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 3114 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub 3114 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 3114 then provides to the UE either directly, after performing local processing, and/or after adding additional local content. In still another example, the hub 3114 acts as a proxy server or orchestrator for the UEs, in particular in if one or more of the UEs are low energy IoT devices. [00193] The hub 3114 may have a constant/persistent or intermittent connection to the network node 3110b. The hub 3114 may also allow for a different communication scheme and/or schedule between the hub 3114 and UEs (e.g., UE 3112c and/or 3112d), and between the hub 3114 and the core network 3106. In other examples, the hub 3114 is connected to the core network 3106 and/or one or more UEs via a wired connection. Moreover, the hub 3114 may be configured to connect to an M2M service provider over the access network 3104 and/or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 3110 while still connected via the hub 3114 via a wired or wireless connection. In some embodiments, the hub 3114 may be a dedicated hub – that is, a hub whose primary function is to route communications to/from the UEs from/to the network node 3110b. In other embodiments, the hub 3114 may be a non-dedicated hub – that is, a device which is capable of operating to route communications between the UEs and network node 3110b, but which is additionally capable of operating as a communication start and/or end point for certain data channels. [00194] FIG.14 is a block diagram of a host 3200, which may be an embodiment of the host 3116 of FIG. 13, in accordance with various aspects described herein. As used herein, the host 3200 may be or comprise various combinations hardware and/or software, including a standalone server, a blade server, a cloud-implemented server, a distributed server, a virtual machine, container, or processing resources in a server farm. The host 3200 may provide one or more services to one or more UEs. [00195] The host 3200 includes processing circuitry 3202 that is operatively coupled via a bus 3204 to an input/output interface 3206, a network interface 3208, a power source 3210, and a memory 3212. Other components may be included in other embodiments. Features of 41 F1231100 these components may be substantially similar to those described with respect to the devices of previous figures such that the descriptions thereof are generally applicable to the corresponding components of host 3200. [00196] The memory 3212 may include one or more computer programs including one or more host application programs 3214 and data 3216, which may include user data, e.g., data generated by a UE for the host 3200 or data generated by the host 3200 for a UE. Embodiments of the host 3200 may utilize only a subset or all of the components shown. The host application programs 3214 may be implemented in a container-based architecture and may provide support for video codecs (e.g., Versatile Video Coding (VVC), High Efficiency Video Coding (HEVC), Advanced Video Coding (AVC), MPEG, VP9) and audio codecs (e.g., FLAC, Advanced Audio Coding (AAC), MPEG, G.711), including transcoding for multiple different classes, types, or implementations of UEs (e.g., handsets, desktop computers, wearable display systems, heads-up display systems). The host application programs 3214 may also provide for user authentication and licensing checks and may periodically report health, routes, and content availability to a central node, such as a device in or on the edge of a core network. Accordingly, the host 3200 may select and/or indicate a different host for over-the-top services for a UE. The host application programs 3214 may support various protocols, such as the HTTP Live Streaming (HLS) protocol, Real-Time Messaging Protocol (RTMP), Real-Time Streaming Protocol (RTSP), Dynamic Adaptive Streaming over HTTP (MPEG-DASH), etc. [00197] FIG. 15 shows a communication diagram of a host 3302 communicating via a network node 3304 with a UE 3306 over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with various embodiments, of the UE (such as a UE 3112a of FIG.13), network node (such as network node 3110a of FIG. 13), and host (such as host 3116 of FIG. 13 and/or host 3200 of FIG. 14) discussed in the preceding paragraphs will now be described with reference to FIG.15. [00198] Like host 3200, embodiments of host 3302 include hardware, such as a communication interface, processing circuitry, and memory. The host 3302 also includes software, which is stored in or accessible by the host 3302 and executable by the processing circuitry. The software includes a host application that may be operable to provide a service to a remote user, such as the UE 3306 connecting via an over-the-top (OTT) connection 3350 extending between the UE 3306 and host 3302. In providing the service to the remote user, 42 F1231100 a host application may provide user data which is transmitted using the OTT connection 3350. [00199] The network node 3304 includes hardware enabling it to communicate with the host 3302 and UE 3306. The connection 3360 may be direct or pass through a core network (like core network 3106 of FIG.13) and/or one or more other intermediate networks, such as one or more public, private, or hosted networks. For example, an intermediate network may be a backbone network or the Internet. [00200] The UE 3306 includes hardware and software, which is stored in or accessible by UE 3306 and executable by the UE’s processing circuitry. The software includes a client application, such as a web browser or operator-specific “app” that may be operable to provide a service to a human or non-human user via UE 3306 with the support of the host 3302. In the host 3302, an executing host application may communicate with the executing client application via the OTT connection 3350 terminating at the UE 3306 and host 3302. In providing the service to the user, the UE's client application may receive request data from the host's host application and provide user data in response to the request data. The OTT connection 3350 may transfer both the request data and the user data. The UE's client application may interact with the user to generate the user data that it provides to the host application through the OTT connection 3350. [00201] The OTT connection 3350 may extend via a connection 3360 between the host 3302 and the network node 3304 and via a wireless connection 3370 between the network node 3304 and the UE 3306 to provide the connection between the host 3302 and the UE 3306. The connection 3360 and wireless connection 3370, over which the OTT connection 3350 may be provided, have been drawn abstractly to illustrate the communication between the host 3302 and the UE 3306 via the network node 3304, without explicit reference to any intermediary devices and the precise routing of messages via these devices. [00202] As an example of transmitting data via the OTT connection 3350, in step 3308, the host 3302 provides user data, which may be performed by executing a host application. In some embodiments, the user data is associated with a particular human user interacting with the UE 3306. In other embodiments, the user data is associated with a UE 3306 that shares data with the host 3302 without explicit human interaction. In step 3310, the host 3302 initiates a transmission carrying the user data towards the UE 3306. The host 3302 may 43 F1231100 initiate the transmission responsive to a request transmitted by the UE 3306. The request may be caused by human interaction with the UE 3306 or by operation of the client application executing on the UE 3306. The transmission may pass via the network node 3304, in accordance with the teachings of the embodiments described throughout this disclosure. Accordingly, in step 3312, the network node 3304 transmits to the UE 3306 the user data that was carried in the transmission that the host 3302 initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step 3314, the UE 3306 receives the user data carried in the transmission, which may be performed by a client application executed on the UE 3306 associated with the host application executed by the host 3302. [00203] In some examples, the UE 3306 executes a client application which provides user data to the host 3302. The user data may be provided in reaction or response to the data received from the host 3302. Accordingly, in step 3316, the UE 3306 may provide user data, which may be performed by executing the client application. In providing the user data, the client application may further consider user input received from the user via an input/output interface of the UE 3306. Regardless of the specific manner in which the user data was provided, the UE 3306 initiates, in step 3318, transmission of the user data towards the host 3302 via the network node 3304. In step 3320, in accordance with the teachings of the embodiments described throughout this disclosure, the network node 3304 receives user data from the UE 3306 and initiates transmission of the received user data towards the host 3302. In step 3322, the host 3302 receives the user data carried in the transmission initiated by the UE 3306. [00204] One or more of the various embodiments improve the performance of OTT services provided to the UE 3306 using the OTT connection 3350, in which the wireless connection 3370 forms the last segment. More precisely, the teachings of these embodiments may improve the data rate and thereby provide benefits such as relaxed restriction on file size, improved content resolution, and better responsiveness. [00205] In an example scenario, factory status information may be collected and analyzed by the host 3302. As another example, the host 3302 may process audio and video data which may have been retrieved from a UE for use in creating maps. As another example, the host 3302 may collect and analyze real-time data to assist in controlling vehicle congestion (e.g., controlling traffic lights). As another example, the host 3302 may store surveillance video uploaded by a UE. As another example, the host 3302 may store or control access to media 44 F1231100 content such as video, audio, VR or AR which it can broadcast, multicast or unicast to UEs. As other examples, the host 3302 may be used for energy pricing, remote control of non-time critical electrical load to balance power generation needs, location services, presentation services (such as compiling diagrams etc. from data collected from remote devices), or any other function of collecting, retrieving, storing, analyzing and/or transmitting data. [00206] In some examples, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 3350 between the host 3302 and UE 3306, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection may be implemented in software and hardware of the host 3302 and/or UE 3306. In some embodiments, sensors (not shown) may be deployed in or in association with other devices through which the OTT connection 3350 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 3350 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not directly alter the operation of the network node 3304. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling that facilitates measurements of throughput, propagation times, latency and the like, by the host 3302. The measurements may be implemented in that software causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 3350 while monitoring propagation times, errors, etc. [00207] In an aspect of the disclosure, there is provided a method implemented in a host configured to operate in a communication system that further includes a network node and a user equipment (UE). The method may comprise providing user data for the UE. The method may further comprise initiating a transmission carrying the user data to the UE via a cellular network comprising the network node. The network node may perform the following operations to transmit the user data from the host to the UE. The network node may schedule, for a first terminal device whose capability of whether supporting FDM of a first physical channel for transmitting traffic data and a second physical channel for transmitting control 45 F1231100 information is unknown to the network node, one or more transmissions each using the first physical channel that is multiplexed with the second physical channel in an FDM manner. The network node may perform the one or more transmissions to the first terminal device, based on the scheduling. The network node may receive, from the first terminal device, one or more reception feedbacks on the one or more transmissions. The network node may determine whether the first terminal device supports FDM of the first and second physical channels, based on the one or more reception feedbacks. [00208] In an embodiment of the disclosure, the method may further comprise, at the network node, transmitting the user data provided by the host for the UE. [00209] In an embodiment of the disclosure, the user data may be provided at the host by executing a host application that interacts with a client application executing on the UE. The client application may be associated with the host application. [00210] In another aspect of the disclosure, there is provided a host configured to operate in a communication system to provide an over-the-top (OTT) service. The host may comprise processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a network node in a cellular network for transmission to a user equipment (UE). The network node may have a communication interface and processing circuitry. The processing circuitry of the network node may be configured to perform the following operations to transmit the user data from the host to the UE. The processing circuitry of the network node may be configured to schedule, for a first terminal device whose capability of whether supporting FDM of a first physical channel for transmitting traffic data and a second physical channel for transmitting control information is unknown to the network node, one or more transmissions each using the first physical channel that is multiplexed with the second physical channel in an FDM manner. The processing circuitry of the network node may be configured to perform the one or more transmissions to the first terminal device, based on the scheduling. The processing circuitry of the network node may be configured to receive, from the first terminal device, one or more reception feedbacks on the one or more transmissions. The processing circuitry of the network node may be configured to determine whether the first terminal device supports FDM of the first and second physical channels, based on the one or more reception feedbacks. 46 F1231100 [00211] In an embodiment of the disclosure, the processing circuitry of the host may be configured to execute a host application that provides the user data. The UE may comprise processing circuitry configured to execute a client application associated with the host application to receive the transmission of user data from the host. [00212] In yet another aspect of the disclosure, there is provided a communication system configured to provide an over-the-top service. The communication system may comprise a host. The host may comprise processing circuitry configured to provide user data for a user equipment (UE). The user data may be associated with the over-the-top service. The host may further comprise a network interface configured to initiate transmission of the user data toward a cellular network node for transmission to the UE. The network node may have a communication interface and processing circuitry. The processing circuitry of the network node may be configured to perform the following operations to transmit the user data from the host to the UE. The processing circuitry of the network node may be configured to schedule, for a first terminal device whose capability of whether supporting FDM of a first physical channel for transmitting traffic data and a second physical channel for transmitting control information is unknown to the network node, one or more transmissions each using the first physical channel that is multiplexed with the second physical channel in an FDM manner. The processing circuitry of the network node may be configured to perform the one or more transmissions to the first terminal device, based on the scheduling. The processing circuitry of the network node may be configured to receive, from the first terminal device, one or more reception feedbacks on the one or more transmissions. The processing circuitry of the network node may be configured to determine whether the first terminal device supports FDM of the first and second physical channels, based on the one or more reception feedbacks. [00213] In an embodiment of the disclosure, the communication system may further comprise the network node; and/or the user equipment. [00214] In an embodiment of the disclosure, the processing circuitry of the host may be configured to execute a host application, thereby providing the user data. The host application may be configured to interact with a client application executing on the UE. The client application may be associated with the host application. 47 F1231100 [00215] In a first aspect of the disclosure, there is provided a method implemented at a first communication device. The method comprises: determining arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols, wherein the plurality of pilot symbols are distanced from each other; and communicating, with a second communication device, a signal comprising the plurality of pilot symbols superimposed on the set of data symbols based on the arrangement information. [00216] In some embodiments, the plurality of pilot symbols are distanced from each other to avoid interference from each other. [00217] In some embodiments, the arrangement information indicates respective locations of the plurality of pilot symbols. [00218] In some embodiments, determining arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols comprises: determining arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols based on at least one of the following: an optimal distance between adjacent pilot symbols in a delay-Doppler domain, the number of pilot symbols to be superimposed on the set of data symbols, a maximum number of pilot symbols to be superimposed on the set of data symbols. [00219] In some embodiments, determining the arrangement information further comprises: determining the arrangement information based on the maximum delay shift and/or the maximum Doppler shift for a communication channel, and communicating the signal with the second communication device comprises: communicating the signal with the second communication device over the communication channel. [00220] In some embodiments, determining the arrangement information based on the maximum delay shift and/or the maximum Doppler shift comprises: determining an optimal distance between adjacent pilot symbols in a delay-Doppler domain based on the maximum delay shift and/or the maximum Doppler shift, wherein the optimal distance is determined such that inference between the adjacent pilot symbols is eliminated; and determining the arrangement information based on the optimal distance between adjacent pilot symbols in the delay-Doppler domain. 48 F1231100 [00221] In some embodiments, the optimal distance in the delay-Doppler domain indicates at least one of the following: a first guard space corresponding to the maximum delay shift, and/or a second guard space corresponding to the maximum Doppler shift. [00222] In some embodiments, communicating the signal with the second communication device comprises: transmitting the signal from the first communication device to the second communication device, and/or receiving the signal by the first communication device from the second communication device. [00223] In some embodiments, the first communication device is a first terminal device or a first network device, and wherein the second communication device is a second terminal device or a second network device. [00224] In some embodiments, the method further comprises: receiving, by the first communication device, the arrangement information from the second communication device, wherein the first communication device is the first terminal device and the second communication device is the second network device, or transmitting the arrangement information from the first communication device to the second communication device, wherein the first communication device is the first network device and the second communication device is the second terminal device. [00225] In some embodiments, the arrangement information is received or transmitted via radio resource control (RRC) signaling or via downlink control information (DCI). [00226] In some embodiments, the arrangement information is comprised in an information element for downlink configuration in the RRC signaling. [00227] In some embodiments, the first communication device receives the signal from the second communication device, the method further comprising: performing the following acts for at least one iteration until a termination criterion is met, determining at least one estimated delay shift and at least one estimated Doppler shift by comparing an aggregated power of the received signal in a delay-Doppler domain with a power threshold, estimating channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated Doppler shift, estimating the set of data symbols based on the channel information, and cancelling an interference from the received signal, to generate an updated received signal for use in a next iteration, the interference being 49 F1231100 determined based on the channel information and the set of estimated data symbols; and obtaining the estimated channel information and the set of estimated data symbols after the at least one iteration is completed. [00228] In some embodiments, determining at least one estimated delay shift and at least one estimated Doppler shift comprises: for a given propagation path of the signal in the delay- Doppler domain, in accordance with a determination that the aggregated power of the received signal in the given propagation path exceeds the power threshold, determining an estimated delay shift and an estimated Doppler shift corresponding to the given propagation path. [00229] In some embodiments, the power threshold is determined based at least in part on at least one of the following: a noise power, an average transmit power of the set of data symbols, and the number of pilot symbols in the plurality of pilot symbols. [00230] In some embodiments, the power threshold is constant over the at least one iteration and is determined further based on an expected symbol error rate (SER). [00231] In some embodiments, the power threshold for use in an iteration is updated based on an expected symbol error rate (SER), to generate an updated power threshold for use in a next iteration. [00232] In some embodiments, the termination criterion is determined based on at least one of the following: a pre-defined number of iterations having been performed, or a difference between values of a parameter generated in a current iteration and a previous iteration falling below a threshold, the parameter comprising one of the channel information, the set of estimated data symbols, the received signal. [00233] In a further aspect, there is provided method implemented at a communication device. The method comprises: receiving a signal comprising a plurality of pilot symbols superimposed on a set of data symbols; performing the following acts for at least one iteration until a termination criterion is met, determining at least one estimated delay shift and at least one estimated Doppler shift by comparing an aggregated power of the received signal in a delay-Doppler domain with a power threshold, estimating channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated Doppler shift; estimating the set of data symbols based on the channel 50 F1231100 information; cancelling an interference from the received signal, to generate an updated received signal for use in a next iteration, the interference being determined based on the channel information and the set of estimated data symbols; and obtaining the estimated channel information and the set of estimated data symbols after the at least one iteration is completed. [00234] In some embodiments, determining at least one estimated delay shift and at least one estimated Doppler shift comprises: for a given propagation path of the signal in the delay- Doppler domain, in accordance with a determination that the aggregated power of the received signal in the given propagation path exceeds the power threshold, determining an estimated delay shift and an estimated Doppler shift corresponding to the given propagation path. [00235] In some embodiments, the power threshold is determined based at least in part on at least one of the following: a noise power, an average transmit power of the set of data symbols, and the number of pilot symbols in the plurality of pilot symbols. [00236] In some embodiments, the power threshold is constant over the at least one iteration and is determined further based on an expected symbol error rate (SER). [00237] In some embodiments, the power threshold for use in an iteration is updated based on an expected symbol error rate (SER), to generate an updated power threshold for use in a next iteration. [00238] In some embodiments, the termination criterion is determined based on at least one of the following: a pre-defined number of iterations having been performed, or a difference between values of a parameter generated in a current iteration and a previous iteration falling below a threshold, the parameter comprising one of the channel information, the set of estimated data symbols, the received signal. [00239] In some embodiments, the communication device comprises a terminal device or a network device. [00240] In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in 51 F1231100 firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. [00241] As such, it should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be practiced in various components such as integrated circuit chips and modules. It should thus be appreciated that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit, where the integrated circuit may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor, a digital signal processor, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this disclosure. [00242] It should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be embodied in computer-executable instructions, such as in one or more program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device. The computer executable instructions may be stored on a computer readable medium such as a hard disk, optical disk, removable storage media, solid state memory, RAM, etc. As will be appreciated by one skilled in the art, the function of the program modules may be combined or distributed as desired in various embodiments. In addition, the function may be embodied in whole or in part in firmware or hardware equivalents such as integrated circuits, field programmable gate arrays (FPGA), and the like. [00243] References in the present disclosure to “one embodiment”, “an embodiment” and so on, indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in 52 F1231100 connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. [00244] It should be understood that, although the terms “first”, “second” and so on may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of the disclosure. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed terms. [00245] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and/or “including”, when used herein, specify the presence of stated features, elements, and/or components, but do not preclude the presence or addition of one or more other features, elements, components and/ or combinations thereof. The terms “connect”, “connects”, “connecting” and/or “connected” used herein cover the direct and/or indirect connection between two elements. It should be noted that two blocks shown in succession in the above figures may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. [00246] The present disclosure includes any novel feature or combination of features disclosed herein either explicitly or any generalization thereof. Various modifications and adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-Limiting and exemplary embodiments of this disclosure. 53 F1231100

Claims

Claims 1. A method (400, 900) implemented at a first communication device (405-1), comprising: determining (410, 910) arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols, wherein the plurality of pilot symbols are distanced from each other; and communicating (430, 920), with a second communication device (405-2), a signal comprising the plurality of pilot symbols superimposed on the set of data symbols based on the arrangement information.

2. The method (400, 900) of claim 1, wherein the plurality of pilot symbols are distanced from each other to avoid interference from each other.

3. The method (400, 900) of claim 1 or 2, wherein the arrangement information indicates respective locations of the plurality of pilot symbols.

4. the method (400, 900) of claim 3, wherein determining arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols comprises: determining arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols based on at least one of the following: an optimal distance between adjacent pilot symbols in a delay-doppler domain, the number of pilot symbols to be superimposed on the set of data symbols, a maximum number of pilot symbols to be superimposed on the set of data symbols.

5. The method (400, 900) of any of claims 1 to 4, wherein determining the arrangement information further comprises: determining the arrangement information based on the maximum delay shift and/or the maximum doppler shift for a communication channel, and communicating the signal with the second communication device comprises: communicating the signal with the second communication device over the communication channel. 54 F1231100

6. The method (400, 900) of claim 5, wherein determining the arrangement information based on the maximum delay shift and/or the maximum doppler shift comprises: determining an optimal distance between adjacent pilot symbols in a delay-doppler domain based on the maximum delay shift and/or the maximum doppler shift, wherein the optimal distance is determined such that inference between the adjacent pilot symbols is eliminated; and determining the arrangement information based on the optimal distance between adjacent pilot symbols in the delay-doppler domain.

7. The method (400, 900) of claim 6, wherein the optimal distance in the delay- doppler domain indicates at least one of the following: a first guard space corresponding to the maximum delay shift, and/or a second guard space corresponding to the maximum doppler shift.

8. The method (400, 900) of any of claims 1 to 7, wherein communicating the signal with the second communication device comprises: transmitting the signal from the first communication device (405-1) to the second communication device (405-2), and/or receiving the signal by the first communication device (405-1) from the second communication device (405-2).

9. The method (400, 900) of claim 8, wherein the first communication device is a first terminal device (110) or a first network device (120), and wherein the second communication device is a second terminal device (110) or a second network device (120).

10. The method (400, 900) of claim 9, the method further comprising: receiving, by the first communication device (405-1), the arrangement information from the second communication device (405-2), wherein the first communication device (405-1) is the first terminal device (110) and the second communication device (405-2) is the second network device (120), or transmitting the arrangement information from the first communication device (405- 1) to the second communication device (405-2), wherein the first communication device (405-1) is the first network device (120) and the second communication device (405-2) is the second terminal device (110). 55 F1231100

11. The method (400, 900) of claim 10, wherein the arrangement information is received or transmitted via radio resource control (RRC) signaling or via downlink control information (DCI).

12. The method (400, 900) of claim 11, wherein the arrangement information is comprised in an information element for downlink configuration in the RRC signaling.

13. The method (400, 700, 900) of claim 8, wherein the first communication device (405-1) receives the signal from the second communication device (405-2), the method (400, 700, 900) further comprising: performing the following acts for at least one iteration until a termination criterion is met, determining (710) at least one estimated delay shift and at least one estimated doppler shift by comparing an aggregated power of the received signal in a delay- doppler domain with a power threshold, estimating (720) channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated doppler shift, estimating (730) the set of data symbols based on the channel information, and cancelling (740) an interference from the received signal, to generate an updated received signal for use in a next iteration, the interference being determined based on the channel information and the set of estimated data symbols; and obtaining (760) the estimated channel information and the set of estimated data symbols after the at least one iteration is completed.

14. The method (400, 700, 900) of claim 13, wherein determining (710) at least one estimated delay shift and at least one estimated doppler shift comprises: for a given propagation path of the signal in the delay-doppler domain, in accordance with a determination that the aggregated power of the received signal in the given propagation path exceeds the power threshold, determining an estimated delay shift and an estimated doppler shift corresponding to the given propagation path. 56 F1231100

15. The method (400, 700, 900) of claim 13 or 14, wherein the power threshold is determined based at least in part on at least one of the following: a noise power, an average transmit power of the set of data symbols, and the number of pilot symbols in the plurality of pilot symbols.

16. The method (400, 700, 900) of any of claims 13 to 15, wherein the power threshold is constant over the at least one iteration and is determined further based on an expected symbol error rate (SER).

17. The method (400, 700, 900) of any of claims 13 to 15, wherein the power threshold for use in an iteration is updated based on an expected symbol error rate (SER), to generate an updated power threshold for use in a next iteration.

18. The method (400, 700, 900) of any of claims 13 to 17, wherein the termination criterion is determined based on at least one of the following: a pre-defined number of iterations having been performed, or a difference between values of a parameter generated in a current iteration and a previous iteration falling below a threshold, the parameter comprising one of the channel information, the set of estimated data symbols, the received signal.

19. A method (700, 1000) implemented at a communication device (405), comprising: receiving (1010) a signal comprising a plurality of pilot symbols superimposed on a set of data symbols; performing (1020) the following acts for at least one iteration until a termination criterion is met, determining (710, 1021) at least one estimated delay shift and at least one estimated doppler shift by comparing an aggregated power of the received signal in a delay-doppler domain with a power threshold, estimating (720, 1023) channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated doppler shift, estimating (730, 1025) the set of data symbols based on the channel information, and 57 F1231100 cancelling (740, 1027) an interference from the received signal, to generate an updated received signal for use in a next iteration, the interference being determined based on the channel information and the set of estimated data symbols; and obtaining (760, 1030) the estimated channel information and the set of estimated data symbols after the at least one iteration is completed.

20. The method (700, 1000) of claim 19, wherein determining (710, 1021) at least one estimated delay shift and at least one estimated doppler shift comprises: for a given propagation path of the signal in the delay-doppler domain, in accordance with a determination that the aggregated power of the received signal in the given propagation path exceeds the power threshold, determining an estimated delay shift and an estimated doppler shift corresponding to the given propagation path.

21. The method (700, 1000) of claim 19 or 20, wherein the power threshold is determined based at least in part on at least one of the following: a noise power, an average transmit power of the set of data symbols, and the number of pilot symbols in the plurality of pilot symbols.

22. The method (700, 1000) of any of claims 19 to 21, wherein the power threshold is constant over the at least one iteration and is determined further based on an expected symbol error rate (SER).

23. The method (700, 1000) of any of claims 19 to 21, wherein the power threshold for use in an iteration is updated based on an expected symbol error rate (SER), to generate an updated power threshold for use in a next iteration.

24. The method (700, 1000) of any of claims 19 to 23, wherein the termination criterion is determined based on at least one of the following: a pre-defined number of iterations having been performed, or a difference between values of a parameter generated in a current iteration and a previous iteration falling below a threshold, the parameter comprising one of the channel information, the set of estimated data symbols, the received signal. 58 F1231100

25. The method (700, 1000) of any of claims 19 to 24, wherein the communication device (405) comprises a terminal device (110) or a network device (120).

26. A first communication device (1100) comprising: at least one processor (1110); and at least one memory (1120), the at least one memory (1120) containing instructions executable by the at least one processor (1110), whereby the first communication device (1100) is operative to: determine arrangement information for a plurality of pilot symbols to be superimposed on a set of data symbols, wherein the plurality of pilot symbols are distanced from each other; and communicate, with a second communication device, a signal comprising the plurality of pilot symbols superimposed on the set of data symbols based on the arrangement information.

27. The first communication device (1100) of claim 26, wherein the first communication device (1100) is operative to perform the method according to any of claims 2 to 18.

28. A communication device (1100) comprising: at least one processor (1110); and at least one memory (1120), the at least one memory (1120) containing instructions executable by the at least one processor (1110), whereby the communication device (1100) is operative to: receive a signal comprising a plurality of pilot symbols superimposed on a set of data symbols; perform the following acts for at least one iteration until a termination criterion is met, determining at least one estimated delay shift and at least one estimated doppler shift by comparing an aggregated power of the received signal in a delay-doppler domain with a power threshold, estimating channel information based on the received signal, the plurality of pilot symbols, the at least one estimated delay shift and the at least one estimated doppler shift, 59 F1231100 estimating the set of data symbols based on the channel information, and cancelling an interference from the received signal, to generate an updated received signal for use in a next iteration, the interference being determined based on the channel information and the set of estimated data symbols; and obtain the estimated channel information and the set of estimated data symbols after the at least one iteration is completed.

29. The communication device (1100) of claim 28, wherein the first communication device (1100) is operative to perform the method according to any of claims 20 to 25.

30. A communication system, comprising: at least one communication device (405-1, 405-2) that is operative to perform the method according to any of claims 1-18, and/or the method according to any of claims 19- 25.

31. A computer readable storage medium comprising instructions which when executed by at least one processor, cause the at least one processor to perform the method according to any of claims 1-18, and/or the method according to any of claims 19-25. 60 F1231100