WO2021028612A2 - One bit small scale fading tracing - Google Patents

Abstract

A method may include collecting, by a user equipment, channel coefficients of a communication channel in a frequency and time domain. The method may also include creating a channel matrix based on the collected channel coefficients. The method may further include performing a two-dimensional Fast Fourier Transform to the channel matrix. The method may also include transforming the channel matrix into a delay-doppler domain. The method may further include reporting, based on a first periodicity, one or more positions of one or more taps in the delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The method may also include reporting, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase.

Description

TITLE:

ONE BIT SMALL SCALE LADING TRACING

CROSS-RELERENCE TO RELATED APPLICATIONS:

This application claims priority from U.S. provisional patent application no. 62/884,836 filed on August 9, 2019. The contents of this earlier filed application are hereby incorporated by reference in their entirety.

FIELD:

Some example embodiments may generally relate to mobile or wireless telecommunication systems, such as Long Term Evolution (LTE) or fifth generation (5G) radio access technology or new radio (NR) access technology, or other communications systems. For example, certain embodiments may relate to apparatuses, systems, and/or methods for one bit small scale fading tracing for channel state information (CSI) reporting.

BACKGROUND:

Examples of mobile or wireless telecommunication systems may include the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN), LTE- Advanced (LTE-A), MulteFire, LTE-A Pro, and/or fifth generation (5G) radio access technology or new radio (NR) access technology. Fifth generation (5G) wireless systems refer to the next generation (NG) of radio systems and network architecture. 5G is mostly built on a new radio (NR), but the 5G (or NG) network can also build on E- UTRAN radio. It is estimated that NR will provide bitrates on the order of 10-20 Gbit/s or higher, and will support at least enhanced mobile broadband (eMBB) and ultra reliable low-latency-communication (URLLC) as well as massive machine type communication (mMTC). NR is expected to deliver extreme broadband and ultra- robust, low latency connectivity and massive networking to support the Internet of Things (IoT). With IoT and machine-to-machine (M2M) communication becoming more widespread, there will be a growing need for networks that meet the needs of lower power, low data rate, and long battery life. It is noted that, in 5G, the nodes that can provide radio access functionality to a user equipment (i.e., similar to NodeB in UTRAN or eNB in LTE) are named gNB when built on NR radio and named NG-eNB when built on E-UTRAN radio. SUMMARY:

Some example embodiments are directed to a method. The method may include collecting, by a user equipment, channel coefficients of a communication channel in a frequency and time domain. The method may also include creating a channel matrix based on the collected channel coefficients. The method may further include performing a two-dimensional Fast Fourier Transform to the channel matrix. In addition, the method may include transforming the channel matrix into a delay-doppler domain. Further, the method may include reporting, based on a first periodicity, one or more positions of one or more taps in the delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The method may also include reporting, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase.

Other example embodiments may be directed to an apparatus. The apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and computer program code may be configured to, with the at least one processor, caused the apparatus at least to collect channel coefficients of a communication channel in a frequency and time domain. The apparatus may also be caused to create a channel matrix based on the collected channel coefficients. The apparatus may further be caused to perform a two-dimensional Fast Fourier Transform to the channel matrix. In addition, the apparatus may be caused to transform the channel matrix into a delay-doppler domain. Further, the apparatus may be caused to report, based on a first periodicity, one or more positions of one or more taps in the delay- doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The apparatus may also be caused to report, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase.

Other example embodiments may be directed to an apparatus. The apparatus may include means for collecting channel coefficients of a communication channel in a frequency and time domain. The apparatus may also include means for creating a channel matrix based on the collected channel coefficients. The apparatus may further include means for performing a two-dimensional Fast Fourier Transform to the channel matrix. In addition, the apparatus may include means for transforming the channel matrix into a delay-doppler domain. Further, the apparatus may include means for reporting, based on a first periodicity, one or more positions of one or more taps in the delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The apparatus may also include means for reporting, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase.

Other example embodiments may be directed a non-transitory computer readable medium which may be encoded with instmctions that may, when executed in hardware, perform a method. The method may include collecting, by a user equipment, channel coefficients of a communication channel in a frequency and time domain. The method may also include creating a channel matrix based on the collected channel coefficients. The method may further include performing a two-dimensional Fast Fourier Transform to the channel matrix. In addition, the method may include transforming the channel matrix into a delay-doppler domain. Further, the method may include reporting, based on a first periodicity, one or more positions of one or more taps in the delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The method may also include reporting, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase.

Other example embodiments may be directed to a computer program product that performs a method. The method may include collecting, by a user equipment, channel coefficients of a communication channel in a frequency and time domain. The method may also include creating a channel matrix based on the collected channel coefficients. The method may further include performing a two-dimensional Fast Fourier Transform to the channel matrix. In addition, the method may include transforming the channel matrix into a delay-doppler domain. Further, the method may include reporting, based on a first periodicity, one or more positions of one or more taps in the delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The method may also include reporting, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase.

Other example embodiments may be directed to an apparatus that may include circuitry configured to collect channel coefficients of a communication channel in a frequency and time domain. The apparatus may also include circuitry configured to create a channel matrix based on the collected channel coefficients. The apparatus may further include circuitry configured to perform a two-dimensional Fast Fourier Transform to the channel matrix. In addition, the apparatus may include circuitry configured to transform the channel matrix into a delay-doppler domain. The apparatus may also include circuitry configured to report, based on a first periodicity, one or more positions of one or more taps in the delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The apparatus may further include circuitry configured to report, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase.

Certain example embodiments may be directed to a method. The method may include receiving, at a network node, a report of one or more positions of one or more taps in a delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The method may also include creating a channel matrix in a delay- doppler plane based on the report. The method may further include collecting, based on a second periodicity, a differential report including a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase. In addition, the method may include updating the amplitude and the phase of the one or more taps based on the collected bits for the differential tap amplitude and the differential tap phase, and preconfigured stepsizes. The method may also include performing an inverse two-dimensional Fast Fourier Transform to the channel matrix in the delay-doppler plane to generate a channel matrix in a frequency- time domain.

Other example embodiments may be directed to an apparatus. The apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and computer program code may be configured to, with the at least one processor, cause the apparatus at least to receive a report of one or more positions of one or more taps in a delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The apparatus may also be caused to create a channel matrix in a delay-doppler plane based on the report. The apparatus may further be caused to collect, based on a second periodicity, a differential report including a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase. In addition, the apparatus may be caused to update the amplitude and the phase of the one or more taps based on the collected bits for the differential tap amplitude and the differential tap phase, and preconfigured stepsizes. The apparatus may also be caused to perform an inverse two- dimensional Fast Fourier Transform to the channel matrix in the delay-doppler plane to generate a channel matrix in a frequency-time domain. Other example embodiments may be directed to an apparatus. The apparatus may include means for receiving, at a network node, a report of one or more positions of one or more taps in a delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The apparatus may also include means for creating a channel matrix in a delay-doppler plane based on the report. The apparatus may further include means for collecting, based on a second periodicity, a differential report including a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase. In addition, the apparatus may include means for updating the amplitude and the phase of the one or more taps based on the collected bits for the differential tap amplitude and the differential tap phase, and preconfigured stepsizes. The apparatus may also include means for performing an inverse two-dimensional Fast Fourier Transform to the channel matrix in the delay-doppler plane to generate a channel matrix in a frequency- time domain.

Other example embodiments may be directed to a non-transitory computer readable medium that may be encoded with instructions that may, when executed in hardware, perform a method. The method may include receiving, at a network node, a report of one or more positions of one or more taps in a delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The method may also include creating a channel matrix in a delay-doppler plane based on the report. The method may further include collecting, based on a second periodicity, a differential report including a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase. In addition, the method may include updating the amplitude and the phase of the one or more taps based on the collected bits for the differential tap amplitude and the differential tap phase, and preconfigured stepsizes. The method may also include performing an inverse two- dimensional Fast Fourier Transform to the channel matrix in the delay-doppler plane to generate a channel matrix in a frequency-time domain.

Other example embodiments may be directed to a computer program product that performs a method. The method may include receiving, at a network node, a report of one or more positions of one or more taps in a delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The method may also include creating a channel matrix in a delay-doppler plane based on the report. The method may further include collecting, based on a second periodicity, a differential report including a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase. In addition, the method may include updating the amplitude and the phase of the one or more taps based on the collected bits for the differential tap amplitude and the differential tap phase, and preconfigured stepsizes. The method may also include performing an inverse two- dimensional Fast Fourier Transform to the channel matrix in the delay-doppler plane to generate a channel matrix in a frequency-time domain.

Other example embodiments may be directed to an apparatus that may include circuitry configured to receive a report of one or more positions of one or more taps in a delay- doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The apparatus may also include circuitry configured to create a channel matrix in a delay-doppler plane based on the report. The apparatus may further include circuitry configured to collect, based on a second periodicity, a differential report including a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase. In addition, the apparatus may include circuitry configured to update the amplitude and the phase of the one or more taps based on the collected bits for the differential tap amplitude and the differential tap phase, and preconfigured stepsizes. The apparatus may also include circuitry configured to perform an inverse two-dimensional Fast Fourier Transform to the channel matrix in the delay-doppler plane to generate a channel matrix in a frequency-time domain.

BRIEF DESCRIPTION OF THE DRAWINGS:

For proper understanding of example embodiments, reference should be made to the accompanying drawings, wherein:

FIG. 1 illustrates a delay-doppler plane after 2-D Fast Fourier Transform (FFT), according to an example embodiment.

FIG. 2(a) illustrates a portion of a reporting scheme, according to an example embodiment.

FIG. 2(b) illustrates another portion of the reporting scheme, according to an example embodiment.

FIG. 2(c) illustrates a further portion of the reporting scheme, according to an example embodiment.

FIG. 3 illustrates a setting of reporting periodicity for one tap reporting, according to an example embodiment.

FIG. 4 illustrates a flow diagram of a method, according to an example embodiment. FIG. 5 illustrates a flow diagram of another method, according to an example embodiment.

FIG. 6(a) illustrates an apparatus, according to an example embodiment. FIG. 6(b) illustrates another apparatus, according to an example embodiment. DETAILED DESCRIPTION:

It will be readily understood that the components of certain example embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. The following is a detailed description of some example embodiments of systems, methods, apparatuses, and computer program products for one bit small scale fading tracing for channel state information (CSI) reporting.

The features, structures, or characteristics of example embodiments described throughout this specification may be combined in any suitable manner in one or more example embodiments. For example, the usage of the phrases “certain embodiments,” “an example embodiment,” “some embodiments,” or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment. Thus, appearances of the phrases “in certain embodiments,” “an example embodiment,” “in some embodiments,” “in other embodiments,” or other similar language, throughout this specification do not necessarily all refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more example embodiments.

Additionally, if desired, the different functions or steps discussed below may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the described functions or steps may be optional or may be combined. As such, the following description should be considered as merely illustrative of the principles and teachings of certain example embodiments, and not in limitation thereof.

Channel state information (CSI) feedback may play a part in a multiple-input and multiple-output (MIMO) transmission system. In addition, CSI feedback may include one or a combination of CSI estimation at a user equipment (UE), CSI reporting, and CSI reconstructing at a 5G or NR base station (gNB). In certain situations, CSI feedback may be implemented to seek the best tradeoff between UE implementation complexity/reporting overhead and CSI reconstructing accuracy.

3^rd Generation Partnership Project (3GPP) NR Rel-16 discusses overhead reduction, and targets the Type II CSI overhead issue while maintaining the CSI feedback accuracy to support a higher order of multi-user (MU) transmission. Rel-16 also describes a progress of CSI reporting where a simplified version of frequency domain channel hardening is applied to reduce the reporting overhead. Further, channel-hardening beams may be selected from a group of predefined Discrete Fourier Transform (DFT) beams and reported in a wideband manner. After channel-hardening, a Type II CSI reporting may be applied with one or more minor modifications.

Additionally, 3GPP NR Rel-15 describes Type II CSI reporting which may include two parts. The first part (parti) is reporting the index of predefined wideband beams, and the second part (part2) is reporting the combining coefficients associated with the wideband beams for each sub-band, which may be known as linear combination codebook. Additionally, part2 reporting may occupy the most bits of CSI reporting. This may be at least because within part2, one coefficient may have to be reported by amplitude and phase for each beam, each polarization, and each layer. Further, the number of bits may scale with the number of beams, polarizations, and layers.

According to certain example embodiments, it may be possible to scale down the number of part2 coefficients by, for example, channel hardening, the selection of the beams, and the reporting periodicity of parti and part2. In other example embodiments, the number of part2 coefficients may also be scaled down by part2 coefficient quantization. However, a defect in part2 coefficient quantization may be that the quantization bitwidth may be predefined and independent to reporting granularity. The report granularity may, according to certain example embodiments, refer to a report period, report sub-band size, and report distance. In addition, since the reporting may refer to a MIMO channel, spatial position may also be considered in this context. Furthermore, the distance between two reporting instances may be referred to as the spatial position information of a UE for a MIMO channel.

In view of some of the challenges described above, certain example embodiments may address the quantization bitwidth for part2 coefficients reporting, and provide a means to quantize and save reporting overhead. For instance, in certain embodiments, quantization of bitwidth may be associated with correlation granularity. In an example embodiment, correlation granularity may be accomplished in terms of correlation time, bandwidth, and length/distance of a UE channel as well as the reporting granularity. Further, the quantization bitwidth may be associated with reporting granularity. According to an example embodiment, if the reporting granularity is smaller than the correlation granularity, the UE channel updates may be small, and differential reporting may be implemented between two reporting instances to reduce overhead. In an example embodiment, 1 bit reporting for amplitudes and phase updates of the coefficients may be provided. According to one example embodiment, based on data mining theory, 1 bit to indicate the trend of changes may be sufficient to follow-up UE channel updates within the correlation granularity. According to another example embodiment, adaptive stepsize may be used to interpret the 1 bit reporting. Although explicit feedback with two-dimensional (2-D) Fast Fourier Transform (FFT) channel hardening may be used, certain example embodiments may also be applicable to Rel- 15 Type II CSI part2 coefficient reporting or the ongoing Rel-16 CSI reporting design.

According to an example embodiment, a 2-D FFT based frequency-time domain channel hardening may be applied by which the channel matrix may be transformed into a delay-doppler plane. Further, according to other example embodiments, it may be possible to report the aggregated channel matrix, the taps in the delay-doppler plane, with least bits, which corresponds to the best quantization method of the taps. In one example embodiment, the taps may be seen as coefficients with position information in a delay-doppler plane.

FIG. 1 illustrates a delay-doppler plane after 2-D FFT, according to an example embodiment. In the delay-doppler plane illustrated in FIG. 1, each of the taps may correspond to one multipath ray. Further, the position of each tap in terms of coordinates with a delay and doppler value may be determined by a small-scale fading characteristic of the UE channel. That is, in an example embodiment, the amplitude and phase of the tap capture the path loss and shadowing effect, both of which may be determined by the UE position. Further, the variation of the taps between two UE reporting time instances may represent UE position updates.

In an example embodiment, the path loss may be a continuous function of UE distance, and the shadow fading of the UE channel may be correlated within a correlation length. These modellings may be interpreted as the path loss and shadowing of the UE channel may be continuous functions, and may only change slightly within a correlation length.

According to an example embodiment, in channel modeling, the updated distance of the UE may be limited within 1 meter including, for example, v At < 1 m, to keep the channel correlated. For a moving UE with a speed of about 60 km/h and a reporting period of about 20ms, between the two reporting time instances, the UE position updates may remain within a correlation length. In other words, the path loss and shadowing changes of the UE channel may be very small between two reporting time instances, which may also suggest that the taps, in terms of amplitude and phase, in the delay- doppler plane, are a continuous function. In addition, the taps may slightly change between two reporting instances.

In an example embodiment, the UE may be configured to report CSI in steps and with different reporting periodicities. According to an example embodiment, within a period, the UE may first report the whole channel information, and may report only the differential part to update the channel matrix in certain instances. Since the differential part is expected to be minor, in an example embodiment, the UE may report only 1 bit to indicate the trend of the changes.

FIGs. 2(a) - 2(c) illustrate various portions of a reporting scheme, according to an example embodiment. In an example embodiment, the UE reporting of CSI may include the UE collecting channel coefficients in the frequency and time domain. The UE may also form a channel matrix, and perform a 2-D FFT to the channel matrix. In addition, the UE may transform the channel matrix to a delay-doppler domain.

In another example embodiment, the UE may report any tap positions in the delay- doppler plane. In certain example embodiments, the tap positions may correspond to coordinates with a delay, and a doppler value. Furthermore, the UE may report the amplitude and the phase of the taps based on a periodicity known as periodicity A. According a further example embodiment, the UE may report the differential tap amplitude and phase (delta value to step 2 reported tap amplitude and phase), with 1 bit for the differential amplitude and 1 bit for the differential phase rotation. In an example embodiment, the report of the differential tap may be based on another periodicity known as periodicity B.

As previously mentioned, FIGs. 2(a) - 2(c) illustrate a reporting scheme. In particular, FIG. 2(a) illustrates a procedure where the best reporting granularity of channel coefficients may be with the correlation frequency and correlation time. The combination of the correlation frequency and the correlation time brings the best compression with 2-D FFT.

Further, FIG. 2(b) illustrates a procedure where some, but not all of the taps are reported. In other words, as illustrated in FIG. 2(b), there is no need to report all the taps. Further, in an example embodiment, thresholding may be applied to remove the non-significant taps to compress the reporting overhead in the delay-doppler plane. FIG. 2(c) illustrates a procedure where the UE may report a 1 bit value of “1” if the amplitude of a tap increases compared to a previous reported value, and the UE may report a 1 bit value of “0” if the amplitude of a tap decreases compared to the previous reported value. Similarly, the UE may report a 1 bit value of “1” if the phase of a tap rotates clockwise compared to the previous reported value, and the UE may report a 1 bit value of “0” if the phase of a tap rotates counter-clockwise compared to the previous reported value. According to an example embodiment, when the amplitude or the phase have the same value, the UE may report nothing to save power or flip a coin to send a reporting of “0” or “ 1 ” to keep the reporting format.

FIG. 3 illustrates a setting of reporting periodicity for one tap reporting, according to an example embodiment. As illustrated in FIG. 3, the reporting periodicity A may be a multiple of periodicity B. In an example embodiment, the reporting periodicity A may be configured so that the UE position changes within a correlation length between two step2 reporting.

According to an example embodiment, the channel at the gNB may be reconstructed. The reconstruction may be performed by the gNB which collects the reporting from the UE. In an example embodiment, the reporting collected from the UE may include the position of the taps as well as their amplitudes and phases. With the report, the gNB may form the channel matrix in a delay-doppler plane. However, for the positions without a tap, the gNB may insert zeros as the channel coefficients.

In an example embodiment, the gNB may also collect the differential tap amplitude and phase bits, and update the tap amplitude and phase with the reported bits and preconfigured stepsizes. In an example embodiment, the stepsize may be adapted to the UE reporting in running time. Further, if continuous 0s or Is are received, the stepsize may be increased to catch up with the channel variation.

According to another example embodiment, the gNB may perform an inverse 2-D FFT to the channel matrix in the delay-doppler plane, and obtain the channel matrix in the frequency-time domain. According to an example embodiment, explicit feedback may be implemented, and other example embodiments may be applied to all legacy reporting mechanisms with attention paid to the periodicity configuration.

According to other example embodiments, the CSI reporting described herein may be applied to Rel-15 Type II CSI reporting, with a minor modification. For example, the UE may report parti and part2 with periodicity A and the differential value of part2 (the change of the coefficient per layer/polarization/beam) by 1 bit for the amplitude, and 1 bit for the phase with periodicity B. In addition, the reporting granularity may be configured with periodicity A to be smaller than the correlation time, and the UE position update may be smaller than the correlation length.

Certain example embodiments may also be applied to Rel-16 new CSI reporting design. For example, a version of frequency domain channel hardening may be performed, and the selected DFT beams may be reported in a wideband manner. Then, Rel-15 Type II reporting may be applied on top of the hardened channel with a modified part2. Although there may be phase shifting of the taps in the part2 report, the differential amplitude and phase of the taps may be reported once the shifting order is fixed. Furthermore, in another example embodiment, the channel hardening beams and part 1/2 report may be reported with periodicity A, and the differential of part2 may be reported with periodicity B. In another example embodiment, the configuration of reporting granularity may be selected with periodicity A that is smaller than the correlation time, and the UE position update may be smaller than the correlation length.

FIG. 4 illustrates a flow diagram of a method, according to an example embodiment. In certain example embodiments, the flow diagram of FIG. 4 may be performed by a mobile station and/or UE, for instance similar to apparatus 10 illustrated in FIG. 6(a). According to one example embodiment, the method of FIG. 4 may include initially, at 400, collecting, by a user equipment, channel coefficients of a communication channel in a frequency and time domain. The method may also include, at 405, creating a channel matrix based on the collected channel coefficients. In addition, the method may include, at 410, performing a two-dimensional Fast Fourier Transform to the channel matrix. The method may further include, at 415, transforming the channel matrix into a delay-doppler domain. Further, the method may include, at 420, applying a thresholding to the one or more taps to remove non-significant taps. In addition, the method may include, at 425, reporting, based on a first periodicity, one or more positions of one or more taps in the delay doppler plane, and an amplitude and a phase of the one or more taps. The method may also include, at 430, reporting, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase. Furthermore, the method may include, at 435, receiving, from a network node, a stepsize configuration for the differential tap amplitude and the differential tap phase.

In another example embodiment, the differential tap amplitude may be a difference between a current tap amplitude and a previously reported tap amplitude, and the differential tap phase may be a difference between a current tap phase and a previously reported tap phase. According to a further example embodiment, the reporting of the amplitude of the one or more taps may include reporting, for each of the one or more taps, a 1 bit value of 1 if the amplitude of the one or more taps increases compared to a previously reported amplitude, and reporting a 1 bit value of 0 if the amplitude of the one or more taps decreases compared to a previously reported amplitude. In another example embodiment, the reporting of the phase of the one or more taps may include reporting, for each of the one or more taps, a 1 bit value of 1 if the phase of the one or more taps rotates clockwise compared to a previously reported phase, and reporting a 1 bit value of 0 if the phase of the one or more taps rotates counter-clockwise compared to a previously reported phase. According to an example embodiment, first periodicity may be a multiple of the second periodicity. According to another example embodiment, the differential tap amplitude and the differential tap phase may be reported when a reporting granularity is smaller than a correlation granularity.

FIG. 5 illustrates a flow diagram of another method, according to an example embodiment. In an example embodiment, the method of FIG. 5 may be performed by a network entity or network node in a 3GPP system, such as LTE or 5G-NR. For instance, in an example embodiment, the method of FIG. 5 may be performed by a base station, eNB, or gNB for instance similar to apparatus 20 illustrated in FIG. 6(b).

According to an example embodiment, the method of FIG. 5 may include initially, at 500, receiving, at a network node, a report of one or more positions of one or more taps in a delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The method may also include, at 505, creating a channel matrix in a delay-doppler plane based on the report. The method may further include, at 510, collecting, based on a second periodicity, a differential report including a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase. In addition, at 515, the method may include updating the amplitude and the phase of the one or more taps based on the collected bits for the differential tap amplitude and the differential tap phase, and preconfigured stepsizes. The method may further include, at 520, performing an inverse two- dimensional Fast Fourier Transform to the channel matrix in the delay-doppler plane to generate a channel matrix in a frequency-time domain. The method may also include, at 525, adapting, in a running time, a stepsize configuration based on the received report, the differential tap amplitude, and the differential tap phase. The method may further include, at 530, transmitting the stepsize configuration to the UE. According to an example embodiment, the differential tap amplitude is a difference between a current tap amplitude and a previously collected tap amplitude, and the differential tap phase is a difference between a current tap phase and a previously collected tap phase. According to another example embodiment, the first periodicity may be a multiple of the second periodicity. In a further example embodiment, in the differential report, the amplitude of the one or more taps may include a 1 bit value of 1 if the amplitude of the one or more taps increases compared to a previously collected amplitude, and a 1 bit value of 0 if the amplitude of the one or more taps decreases compared to a previously collected amplitude. According to an example embodiment, in the differential report, the phase of the one or more taps may include a 1 bit value of 1 if the phase of the one or more taps rotates clockwise compared to a previously collected phase, and a 1 bit value of 0 if the phase of the one or more taps rotates counter-clockwise compared to a previously collected phase.

FIG. 6(a) illustrates an apparatus 10 according to an example embodiment. In an embodiment, apparatus 10 may be a node or element in a communications network or associated with such a network, such as a UE, mobile equipment (ME), mobile station, mobile device, stationary device, IoT device, or other device. As described herein, UE may alternatively be referred to as, for example, a mobile station, mobile equipment, mobile unit, mobile device, user device, subscriber station, wireless terminal, tablet, smart phone, IoT device, sensor or NB-IoT device, or the like. As one example, apparatus 10 may be implemented in, for instance, a wireless handheld device, a wireless plug-in accessory, or the like.

In some example embodiments, apparatus 10 may include one or more processors, one or more computer-readable storage medium (for example, memory, storage, or the like), one or more radio access components (for example, a modem, a transceiver, or the like), and/or a user interface. In some embodiments, apparatus 10 may be configured to operate using one or more radio access technologies, such as GSM, LTE, LTE-A, NR, 5G, WLAN, WiFi, NB-IoT, Bluetooth, NFC, MulteFire, and/or any other radio access technologies. It should be noted that one of ordinary skill in the art would understand that apparatus 10 may include components or features not shown in FIG. 6(a).

As illustrated in the example of FIG. 6(a), apparatus 10 may include or be coupled to a processor 12 for processing information and executing instructions or operations. Processor 12 may be any type of general or specific purpose processor. In fact, processor 12 may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples. While a single processor 12 is shown in FIG. 6(a), multiple processors may be utilized according to other embodiments. For example, it should be understood that, in certain example embodiments, apparatus 10 may include two or more processors that may form a multiprocessor system (e.g., in this case processor 12 may represent a multiprocessor) that may support multiprocessing. According to certain example embodiments, the multiprocessor system may be tightly coupled or loosely coupled (e.g., to form a computer cluster).

Processor 12 may perform functions associated with the operation of apparatus 10 including, as some examples, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus 10, including processes illustrated in FIGs. 1-4.

Apparatus 10 may further include or be coupled to a memory 14 (internal or external), which may be coupled to processor 12, for storing information and instructions that may be executed by processor 12. Memory 14 may be one or more memories and of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and/or removable memory. For example, memory 14 can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, hard disk drive (HDD), or any other type of non-transitory machine or computer readable media. The instructions stored in memory 14 may include program instructions or computer program code that, when executed by processor 12, enable the apparatus 10 to perform tasks as described herein.

In an embodiment, apparatus 10 may further include or be coupled to (internal or external) a drive or port that is configured to accept and read an external computer readable storage medium, such as an optical disc, USB drive, flash drive, or any other storage medium. For example, the external computer readable storage medium may store a computer program or software for execution by processor 12 and/or apparatus 10 to perform any of the methods illustrated in FIGs. 1-4. In some embodiments, apparatus 10 may also include or be coupled to one or more antennas 15 for receiving a downlink signal and for transmitting via an uplink from apparatus 10. Apparatus 10 may further include a transceiver 18 configured to transmit and receive information. The transceiver 18 may also include a radio interface (e.g., a modem) coupled to the antenna 15. The radio interface may correspond to a plurality of radio access technologies including one or more of GSM, LTE, LTE-A, 5G, NR, WLAN, NB-IoT, Bluetooth, BT-LE, NFC, RFID, UWB, and the like. The radio interface may include other components, such as filters, converters (for example, digital-to-analog converters and the like), symbol demappers, signal shaping components, an Inverse Fast Fourier Transform (IFFT) module, and the like, to process symbols, such as OFDMA symbols, carried by a downlink or an uplink.

For instance, transceiver 18 may be configured to modulate information on to a carrier waveform for transmission by the antenna(s) 15 and demodulate information received via the antenna(s) 15 for further processing by other elements of apparatus 10. In other embodiments, transceiver 18 may be capable of transmitting and receiving signals or data directly. Additionally or alternatively, in some embodiments, apparatus 10 may include an input and/or output device (I/O device). In certain embodiments, apparatus 10 may further include a user interface, such as a graphical user interface or touchscreen.

In an embodiment, memory 14 stores software modules that provide functionality when executed by processor 12. The modules may include, for example, an operating system that provides operating system functionality for apparatus 10. The memory may also store one or more functional modules, such as an application or program, to provide additional functionality for apparatus 10. The components of apparatus 10 may be implemented in hardware, or as any suitable combination of hardware and software. According to an example embodiment, apparatus 10 may optionally be configured to communicate with apparatus 10 via a wireless or wired communications link 70 according to any radio access technology, such as NR.

According to certain example embodiments, processor 12 and memory 14 may be included in or may form a part of processing circuitry or control circuitry. In addition, in some embodiments, transceiver 18 may be included in or may form a part of transceiving circuitry.

As discussed above, according to certain example embodiments, apparatus 10 may be a UE for example. According to certain embodiments, apparatus 10 may be controlled by memory 14 and processor 12 to perform the functions associated with example embodiments described herein. For instance, in one embodiment, apparatus 10 may be controlled by memory 14 and processor 12 to collect channel coefficients of a communication channel in a frequency and time domain. Apparatus 10 may also be controlled by memory 14 and processor 12 to create a channel matrix based on the collected channel coefficients. Apparatus 10 may further be controlled by memory 14 and processor 12 to perform a two-dimensional Fast Fourier Transform to the channel matrix. In addition, apparatus 10 may be controlled by memory 14 and processor 12 to transform the channel matrix into a delay-doppler domain. Further, apparatus 10 may be controlled by memory 14 and processor 12 to report, based on a first periodicity, one or more positions of one or more taps in the delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. In addition, apparatus 10 may be controlled by memory 14 and processor 12 to report, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase.

FIG. 6(b) illustrates an apparatus 20 according to an example embodiment. In an example embodiment, the apparatus 20 may be a RAT, node, host, or server in a communication network or serving such a network. For example, apparatus 20 may be a satellite, base station, a Node B, an evolved Node B (eNB), 5G Node B or access point, next generation Node B (NG-NB or gNB), and/or WLAN access point, associated with a radio access network (RAN), such as an LTE network, 5G or NR. It should be noted that one of ordinary skill in the art would understand that apparatus 20 may include components or features not shown in FIG. 6(b).

As illustrated in the example of FIG. 6(b), apparatus 20 may include a processor 22 for processing information and executing instructions or operations. Processor 22 may be any type of general or specific purpose processor. For example, processor 22 may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples. While a single processor 22 is shown in FIG. 6(b), multiple processors may be utilized according to other embodiments. For example, it should be understood that, in certain embodiments, apparatus 20 may include two or more processors that may form a multiprocessor system (e.g., in this case processor 22 may represent a multiprocessor) that may support multiprocessing. In certain embodiments, the multiprocessor system may be tightly coupled or loosely coupled (e.g., to form a computer cluster.

According to certain example embodiments, processor 22 may perform functions associated with the operation of apparatus 20, which may include, for example, precoding of antenna gain/phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatus 20, including processes illustrated in FIGS. 1-3 and 5.

Apparatus 20 may further include or be coupled to a memory 24 (internal or external), which may be coupled to processor 22, for storing information and instructions that may be executed by processor 22. Memory 24 may be one or more memories and of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and/or removable memory. For example, memory 24 can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, hard disk drive (HDD), or any other type of non-transitory machine or computer readable media. The instructions stored in memory 24 may include program instructions or computer program code that, when executed by processor 22, enable the apparatus 20 to perform tasks as described herein.

In an embodiment, apparatus 20 may further include or be coupled to (internal or external) a drive or port that is configured to accept and read an external computer readable storage medium, such as an optical disc, USB drive, flash drive, or any other storage medium. For example, the external computer readable storage medium may store a computer program or software for execution by processor 22 and/or apparatus 20 to perform the methods illustrated in FIGs. 1-3 and 5.

In certain example embodiments, apparatus 20 may also include or be coupled to one or more antennas 25 for transmitting and receiving signals and/or data to and from apparatus 20. Apparatus 20 may further include or be coupled to a transceiver 28 configured to transmit and receive information. The transceiver 28 may include, for example, a plurality of radio interfaces that may be coupled to the antenna(s) 25. The radio interfaces may correspond to a plurality of radio access technologies including one or more of GSM, NB-IoT, LTE, 5G, WLAN, Bluetooth, BT-LE, NFC, radio frequency identifier (RFID), ultrawideband (UWB), MulteFire, and the like. The radio interface may include components, such as filters, converters (for example, digital-to- analog converters and the like), mappers, a Fast Fourier Transform (FFT) module, and the like, to generate symbols for a transmission via one or more downlinks and to receive symbols (for example, via an uplink).

As such, transceiver 28 may be configured to modulate information on to a carrier waveform for transmission by the antenna(s) 25 and demodulate information received via the antenna(s) 25 for further processing by other elements of apparatus 20. In other embodiments, transceiver 18 may be capable of transmitting and receiving signals or data directly. Additionally or alternatively, in some embodiments, apparatus 20 may include an input and/or output device (I/O device).

In an embodiment, memory 24 may store software modules that provide functionality when executed by processor 22. The modules may include, for example, an operating system that provides operating system functionality for apparatus 20. The memory may also store one or more functional modules, such as an application or program, to provide additional functionality for apparatus 20. The components of apparatus 20 may be implemented in hardware, or as any suitable combination of hardware and software.

According to some embodiments, processor 22 and memory 24 may be included in or may form a part of processing circuitry or control circuitry. In addition, in some embodiments, transceiver 28 may be included in or may form a part of transceiving circuitry.

As used herein, the term “circuitry” may refer to hardware-only circuitry implementations (e.g., analog and/or digital circuitry), combinations of hardware circuits and software, combinations of analog and/or digital hardware circuits with software/firmware, any portions of hardware processor(s) with software (including digital signal processors) that work together to cause an apparatus (e.g., apparatus 10 and 20) to perform various functions, and/or hardware circuit(s) and/or processor(s), or portions thereof, that use software for operation but where the software may not be present when it is not needed for operation. As a further example, as used herein, the term “circuitry” may also cover an implementation of merely a hardware circuit or processor (or multiple processors), or portion of a hardware circuit or processor, and its accompanying software and/or firmware. The term circuitry may also cover, for example, a baseband integrated circuit in a server, cellular network node or device, or other computing or network device. As introduced above, in certain embodiments, apparatus 20 may be a radio resource manager, RAT, node, host, or server in a communication network or serving such a network. For example, apparatus 20 may be a satellite, base station, a Node B, an evolved Node B (eNB), 5G Node B or access point, next generation Node B (NG-NB or gNB), and/or WLAN access point, associated with a radio access network (RAN), such as an LTE network, 5G or NR. According to certain embodiments, apparatus 20 may be controlled by memory 24 and processor 22 to perform the functions associated with any of the embodiments described herein.

For instance, in one embodiment, apparatus 20 may be controlled by memory 24 and processor 22 to receive a report of one or more positions of one or more taps in a delay- doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. Apparatus 20 may also be controlled by memory 24 and processor 22 to create a channel matrix in a delay-doppler plane based on the report. Apparatus 20 may further be controlled by memory 24 and processor 25 to collect, based on a second periodicity, a differential report including a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase. Apparatus 20 may also be controlled by memory 24 and processor 25 at least to update the amplitude and the phase of the one or more taps based on the collected bits for the differential tap amplitude and the differential tap phase, and preconfigured stepsizes. In addition, apparatus 20 may be controlled by memory 24 and processor 25 to perform an inverse two-dimensional Fast Fourier Transform to the channel matrix in the delay-doppler plane to generate a channel matrix in a frequency-time domain.

Certain example embodiments described herein provide several technical improvements, enhancements, and /or advantages. In some example embodiments, it may be possible to modify a channel reconstruction procedure with an additional step of updating the channel matrix by differential report bits together with stepsizes. It may also be possible to set CSI reporting configuration based on UE channel characteristics, and correlation granularity including correlation time/bandwidth/length. In other example embodiments, it may be possible to perform CSI reporting in a stepwise manner with first the whole channel information report with periodicity A, and then only the differential part may be reported with periodicity B to update the whole channel information or part of it. As for differential reporting, the UE may report only 1 bit to indicate the trend of the change.

According to other example embodiments, it may be possible to achieve overhead saving. In further example embodiments, it may be possible to implement 2D-FFT to compress the channel coefficients in a time-frequency domain. It may also be possible to provide one bit tracking of the spatial domain, which may further compress the report overhead in the spatial domain. In other example embodiments, it may be possible to achieve the best tradeoff between overhead and accuracy since reporting the channel may be managed with the least overhead. Additionally, in certain example embodiments, the methods described herein may be applied to Type II CSI reporting and explicit reporting, and have flexibility.

A computer program product may comprise one or more computer-executable components which, when the program is run, are configured to carry out some example embodiments. The one or more computer-executable components may be at least one software code or portions of it. Modifications and configurations required for implementing functionality of an example embodiment may be performed as routine(s), which may be implemented as added or updated software routine(s). Software routine(s) may be downloaded into the apparatus.

As an example, software or a computer program code or portions of it may be in a source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers may include a record medium, computer memory, read-only memory, photoelectrical and/or electrical carrier signal, telecommunications signal, and software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers. The computer readable medium or computer readable storage medium may be a non-transitory medium.

In other example embodiments, the functionality may be performed by hardware or circuitry included in an apparatus (e.g., apparatus 10 or apparatus 20), for example through the use of an application specific integrated circuit (ASIC), a programmable gate array (PGA), a field programmable gate array (FPGA), or any other combination of hardware and software. In yet another example embodiment, the functionality may be implemented as a signal, a non-tangible means that can be carried by an electromagnetic signal downloaded from the Internet or other network.

According to an example embodiment, an apparatus, such as a node, device, or a corresponding component, may be configured as circuitry, a computer or a microprocessor, such as single-chip computer element, or as a chipset, including at least a memory for providing storage capacity used for arithmetic operation and an operation processor for executing the arithmetic operation.

One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although certain example embodiments have been described, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of example embodiments. Although certain example embodiments refer to 5G NR and LTE technology, certain example embodiments may also apply to any other present or future 3 GPP technology, such as LTE-advanced, and/or fourth generation (4G) technology.

A first embodiment is directed to a method that may include collecting, by a user equipment, channel coefficients of a communication channel in a frequency and time domain. The method may also include creating a channel matrix based on the collected channel coefficients. The method may further include performing a two-dimensional Fast Fourier Transform to the channel matrix. In addition, the method may include transforming the channel matrix into a delay-doppler domain. The method may also include reporting, based on a first periodicity, one or more positions of one or more taps in the delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The method may further include reporting, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase.

In a variant, the method may further include applying a thresholding to the one or more taps to remove non-significant taps.

In a variant, the differential tap amplitude may be a difference between a current tap amplitude and a previously reported tap amplitude, and the differential tap phase may be a difference between a current tap phase and a previously reported tap phase.

In a variant, the reporting of the amplitude of the one or more taps may include reporting a 1 bit value of 1 if the amplitude of the one or more taps increases compared to a previously reported amplitude, and reporting a 1 bit value of 0 if the amplitude of the one or more taps decreases compared to a previously reported amplitude. In a variant, the reporting of the phase of the one or more taps may include reporting a 1 bit value of 1 if the phase of the one or more taps rotates clockwise compared to a previously reported phase, and reporting a 1 bit value of 0 if the phase of the one or more taps rotates counter-clockwise compared to a previously reported phase.

In a variant, the first periodicity may be a multiple of the second periodicity.

In a variant, the differential tap amplitude and the differential tap phase are reported when the reporting granularity is smaller than the correlation granularity.

In a variant, the method may also include receiving, from a network node, stepsize configuration for the differential tap amplitude and the differential tap phase.

A second embodiment may be directed to a method that may include receiving, at a network node, a report of one or more positions of one or more taps in a delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity. The method may also include creating a channel matrix in a delay-doppler plane based on the report. The method may further include collecting, based on a second periodicity, a differential report including a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase. In addition, the method may include updating the amplitude and the phase of the one or more taps based on the collected bits for the differential tap amplitude and the differential tap phase, and preconfigured stepsizes. Further, the method may include performing an inverse two-dimensional Fast Fourier Transform to the channel matrix in the delay-doppler plane to generate a channel matrix in a frequency-time domain.

In a variant, the differential tap amplitude may be a difference between a current tap amplitude and a previously collected tap amplitude, and the differential tap phase may be a difference between a current tap phase and a previously collected tap phase.

In a variant, the first periodicity may be a multiple of the second periodicity.

In a variant, in the report, the amplitude of the one or more taps may include a 1 bit value of 1 if the amplitude of the one or more taps increases compared to a previously collected amplitude, and a 1 bit value of 0 if the amplitude of the one or more taps decreases compared to a previously collected amplitude. In a variant, in the report, the phase of the one or more taps may include a 1 bit value of 1 if the phase of the one or more taps rotates clockwise compared to a previously collected phase, and a 1 bit value of 0 if the phase of the one or more taps rotates counter-clockwise compared to a previously collected phase.

In a variant, the method may also include adapting, in a running time, a stepsize configuration based on the received report, the differential tap amplitude, and the differential tap phase.

In a variant, transmitting the stepsize configuration to the user equipment.

Another embodiment is directed to an apparatus including at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured, with the at least one processor, to cause the apparatus at least to perform the method according to the first embodiment or the second embodiment or any of their variants discussed above.

Another embodiment is directed to an apparatus that may include circuitry configured to perform the method according to the first embodiment or the second embodiment or any of their variants.

Another embodiment is directed to an apparatus that may include means for performing the method according to the first embodiment or the second embodiment or any of their variants.

Another embodiment is directed to a computer readable medium including program instructions stored thereon for performing at least the method according to the first embodiment or the second embodiment or any of their variants

Partial Glossary

CSI Channel State Information

DFT Discrete Fourier Transform eNB Enhanced Node B

FFT Fast Fourier Transform

FR2 Frequency Range 2 gNB 5G or NR Base Station

LTE Long Term Evolution

MIMO Multiple-input and Multiple-output

MU Multi-User NR New Radio

UE User Equipment

Claims

CLAIMS:

1. A method, comprising: collecting, by a user equipment, channel coefficients of a communication channel in a frequency and time domain; creating a channel matrix based on the collected channel coefficients; performing a two-dimensional Fast Fourier Transform to the channel matrix; transforming the channel matrix into a delay-doppler domain; reporting, based on a first periodicity, one or more positions of one or more taps in the delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity; and reporting, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase.

2. The method according to claim 1, further comprising applying a thresholding to the one or more taps to remove non-significant taps.

3. The method according to claims 1 or 2, wherein the differential tap amplitude is a difference between a current tap amplitude and a previously reported tap amplitude, and the differential tap phase is a difference between a current tap phase and a previously reported tap phase.

4. The method according to any of claims 1-3, wherein the reporting of the amplitude of the one or more taps comprises reporting a 1 bit value of 1 if the amplitude of the one or more taps increases compared to a previously reported amplitude, and reporting a 1 bit value of 0 if the amplitude of the one or more taps decreases compared to a previously reported amplitude.

5. The method according to any of claims 1-4, wherein the reporting of the phase of the one or more taps comprises reporting a 1 bit value of 1 if the phase of the one or more taps rotates clockwise compared to a previously reported phase, and reporting a 1 bit value of 0 if the phase of the one or more taps rotates counter-clockwise compared to a previously reported phase.

6. The method according to any of claims 1-5, further comprising receiving, from a network node, stepsize configuration for the differential tap amplitude and the differential tap phase.

7. A method, comprising: receiving, at a network node, a report of one or more positions of one or more taps in a delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity; creating a channel matrix in a delay-doppler plane based on the report; collecting, based on a second periodicity, a differential report including a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase; updating the amplitude and the phase of the one or more taps based on the collected bits for the differential tap amplitude and the differential tap phase, and preconfigured stepsizes; and performing an inverse two-dimensional Fast Fourier Transform to the channel matrix in the delay-doppler plane to generate a channel matrix in a frequency-time domain.

8. The method according to claim 7, wherein in the report, the amplitude of the one or more taps comprises a 1 bit value of 1 if the amplitude of the one or more taps increases compared to a previously collected amplitude, and a 1 bit value of 0 if the amplitude of the one or more taps decreases compared to a previously collected amplitude.

9. The method according to claims 7 or 8, wherein in the report, the phase of the one or more taps comprises a 1 bit value of 1 if the phase of the one or more taps rotates clockwise compared to a previously collected phase, and a 1 bit value of 0 if the phase of the one or more taps rotates counter-clockwise compared to a previously collected phase.

10. The method according to any of claims 7-9, further comprising adapting, in a running time, a stepsize configuration based on the received report, the differential tap amplitude, and the differential tap phase.

11. The method according to any of claims 7-10, further comprising transmitting the stepsize configuration to a user equipment.

12. An apparatus, comprising: at least one processor; and at least one memory comprising computer program code, the at least one memory and the computer program code are configured, with the at least one processor to cause the apparatus at least to collect channel coefficients of a communication channel in a frequency and time domain; create a channel matrix based on the collected channel coefficients; perform a two-dimensional Fast Fourier Transform to the channel matrix; transform the channel matrix into a delay-doppler domain; report, based on a first periodicity, one or more positions of one or more taps in the delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity; and report, based on a second periodicity, a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase.

13. The apparatus according to claim 12, wherein the at least one memory and the computer program code are further configured, with the at least one processor to cause the apparatus at least to apply a thresholding to the one or more taps to remove non significant taps.

14. The apparatus according to claims 12 or 13, wherein the differential tap amplitude is a difference between a current tap amplitude and a previously reported tap amplitude, and the differential tap phase is a difference between a current tap phase and a previously reported tap phase.

15. The apparatus according to any of claims 12-14, wherein the reporting of the amplitude of the one or more taps comprises reporting a 1 bit value of 1 if the amplitude of the one or more taps increases compared to a previously reported amplitude, and reporting a 1 bit value of 0 if the amplitude of the one or more taps decreases compared to a previously reported amplitude.

16. The apparatus according to any of claims 12-15, wherein the reporting of the phase of the one or more taps comprises reporting a 1 bit value of 1 if the phase of the one or more taps rotates clockwise compared to a previously reported phase, and reporting a 1 bit value of 0 if the phase of the one or more taps rotates counter-clockwise compared to a previously reported phase.

17. The apparatus according to any of claims 12-16, wherein the at least one memory and the computer program code are further configured, with the at least one processor to cause the apparatus at least to receive, from a network node, stepsize configuration for the differential tap amplitude and the differential tap phase.

18. An apparatus, comprising: at least one processor; and at least one memory comprising computer program code, the at least one memory and the computer program code are configured, with the at least one processor to cause the apparatus at least to receive a report of one or more positions of one or more taps in a delay-doppler plane, and an amplitude and a phase of the one or more taps based on a first periodicity; create a channel matrix in a delay-doppler plane based on the report; collect, based on a second periodicity, a differential report including a differential tap amplitude and a differential tap phase with 1 bit for the differential tap amplitude and 1 bit for the differential tap phase; update the amplitude and the phase of the one or more taps based on the collected bits for the differential tap amplitude and the differential tap phase, and preconfigured stepsizes; perform an inverse two-dimensional Fast Fourier Transform to the channel matrix in the delay-doppler plane to generate a channel matrix in a frequency-time domain.

19. The apparatus according to claim 18, wherein in the report, the amplitude of the one or more taps comprises a 1 bit value of 1 if the amplitude of the one or more taps increases compared to a previously collected amplitude, and a 1 bit value of 0 if the amplitude of the one or more taps decreases compared to a previously collected amplitude.

20. The apparatus according to claims 18 or 19, wherein in the report, the phase of the one or more taps comprises a 1 bit value of 1 if the phase of the one or more taps rotates clockwise compared to a previously collected phase, and a 1 bit value of 0 if the phase of the one or more taps rotates counter-clockwise compared to a previously collected phase.

21. The apparatus according to any of claims 18-20, wherein the at least one memory and the computer program code are further configured, with the at least one processor to cause the apparatus at least to adapt, in a running time, a stepsize configuration based on the received report, the differential tap amplitude, and the differential tap phase.

22. The apparatus according to any of claims 18-21 , wherein the at least one memory and the computer program code are further configured, with the at least one processor to cause the apparatus at least to transmit the stepsize configuration to a user equipment.

23. An apparatus comprising means for performing a process according to any of claims 1-11.

24. A non- transitory computer readable medium comprising program instructions stored thereon for performing the method according to any of claims 1-11.

25. An apparatus comprising circuitry configured to cause the apparatus to perform a process according to any of claims 1-11.