Methods for CSI enhancements and CSI feedback reduction in medium and high speed devices

Abstract

A method (200) of Channel State Information (CSI) reporting by at least one second node (104) in a wireless communication system is described. The method (200) comprises receiving a refer-ence signal by the at least one second node(104) from at least one first node (102). The reference signal is at least one of a Channel State Information-Reference Signals (CSI-RS) and a Tracking Reference Signals (TRS). The at least one second node (104) estimates a Channel State Infor-mation (CSI) based on the received reference signal. The at least one first node (102) configures a first periodicity and a second periodicity for reporting of the CSI. A value of the first periodicity is greater than a value of the second periodicity. The at least one second node (104) reports a full CSI feedback with the first periodicity and a partial CSI feedback with the second periodicity.

Description

FIELD OF THE INVENTIONThe present invention relates to a wireless communication system, and more particularly to methods for reducing CSI feedback overhead in medium and high speed devices of wireless communication system.BACKGROUND OF THE INVENTIONThe ever-increasing demand for wireless broadband services leads to design and deployment of 5G and beyond cellular systems for providing high data rates and lower latencies. The third generation partnership project (3GPP) New Radio (NR) air interface is a scalable and flexible air interface designed to meet requirements, such as enhanced Mobile Broadband (eMBB), Ultra-Reliable Low Latency Communications (URLLC) and massive Internet of Things (m-IOT) of 5G communications. The NR air interface supports bands below 6 GHz in addition to new spectrum in the mm Wave frequency bands. Massive Multiple-Input Multiple-Output (MIMO) is an emerging technology that can scale up performance by possibly orders of magnitude compared to the current state of the art. Massive MIMO has all properties of conventional MIMO, but on a much larger scale. Overall, massive MIMO is an enabler for the development of the future broadband (fixed and mobile) networks. Further, massive MIMO is energy-efficient, secure, and robust, and will use the spectrum efficiently.Massive MIMO systems may enhance coverage and capacity performance by supporting various Reference Signals (RS), Channel State Information (CSI) measurement and feedback, precoder selection, link adaptation, efficient receiver algorithms etc. Massive MIMO system requires CSI at transmitter in closed loop. In Frequency Division Duplex (FDD) systems, due to the absence of channel reciprocity, User Equipment (UE) has to feedback the Downlink (DL) CSI to a Base Station (BS). The BS transmits pilot / reference signals to the UE. The UE estimates channel responses based on the pilot / reference signals to obtain CSI feedback. Further, the UE quantizes the CSI feedback and feed them back to the BS. The BS may build a DL precoding scheme based on the CSI feedback. The BS may utilize the DL precoding scheme to reduce interference from other co-scheduled users and cells, and to improve Signal to Interference plus Noise Ratio (SINR) for the user. Therefore, for efficient operation, massive MIMO systems rely on the availability of good channel knowledge at the BS in uplink (UL) and the downlink (DL).The optimal precoder in a MIMO system is based on the singular vectors of the MIMO channel matrix. However, transmission of singular vectors involves huge feedback overhead. This necessitates a compression mechanism for feedback. In general, singular vectors of the MIMO channel matrix can be represented in terms of 2D DFT vectors. The 2D DFT enables the CSI feedback in form of beam selection, thereby reducing the feedback overhead. In case of low-resolution CSI feedback, selected beam indices, and Phase Shift Keying (PSK) based co-phase combining coefficients between two polarizations are fed back from the UE to the BS. In case of high-resolution CSI feedback, the coefficients to linearly combine the beams, in addition to selected beam indices, are also fed back. The beam selection is performed for the wideband, while Linear Combining (LC) coefficients are calculated for the sub bands separately. In 3GPP NR system, Type-I and Type-II codebook-based CSI feedback have been standardized to support advanced MIMO transmission. The Type I codebook corresponds to the low-resolution CSI feedback and has low feedback overhead. The Type II CSI corresponds to the high-resolution feedback and has high feedback overhead. Type-II is a dual-stage codebook, where in the first stage a spatial DFT basis subset is selected, and the second stage includes choosing a set of LC coefficients that approximate the channel's right singular vectors. As a result, it is envisioned that more accurate CSI can be obtained from Type-II codebook-based CSI feedback so that better precoded MIMO transmission can be employed by the network.Consider a scenario, where 'L' beams are selected to represent a singular vector and there are N sub bands. In that case, '2LN' LC coefficients need to be fed back, which is huge for large N. However, the channels of neighboring sub bands often have a significant mutual correlation. Therefore, the LC coefficients would also be correlated across the sub bands. This property can be utilized to compress the LCs in the Frequency Domain (FD) leading to reduced feedback. As an illustration, the LC coefficients are reported separately for each sub band in NR Rel. 15 Type II CSI. However, in NR Rel.16, enhanced Type II CSI was proposed, where the correlations in the FD is utilized to reduce the reporting overhead. The precoding structure with the FD compression can be written as Eq. (1):W=W_1 W_2 W_f^H (1)where W is the precoder matrix, W1 and W2 are the matrices that represents the wideband and sub band characteristics of the channel, and WfH, which is a Hermitian of a matrix Wf is a FD compression matrix consisting of a set of row vectors from a DFT basis.The demand for seamless connectivity and high-capacity links in UE high mobility scenarios is growing rapidly. In such cases, adequate CSI feedback schemes used for link adaption are of major importance. However, conventional NR Type-II CSI feedback schemes lack performance in scenarios where UEs move even at moderate speeds (10 to 30 km / h). Enhancements in CSI feedback are required to improve the performance for medium and high speed UEs. This necessitates more frequent CSI-RS transmission from BS and frequent CSI measurement and reporting from the UE and leads to huge feedback overhead in case of high speed UEs. Thus, there is a need of a method of CSI feedback reporting, which address the above-mentioned shortcomings. OBJECTS OF THE INVENTIONA general objective of the present invention is to provide a method for enhancing Channel State Information (CSI) feedback mechanism.Another objective of the present invention is to provide a method to reduce CSI feedback overhead for a user equipment moving with medium and high velocities.Another objective of the present invention is to provide a method for dynamic switching between different CSI reporting mechanisms.SUMMARY OF THE INVENTIONThe summary is provided to introduce aspects related to a signalling method for reducing CSI feedback overhead in medium and high speed devices of wireless communication system, and the aspects are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.The present invention relates to method of reporting Channel State Information (CSI) in a wireless communication system is described. The method comprises receiving, by at least one second node, a reference signal from at least one first node. The at least one second node estimates at least one CSI based on the reference signal. The at least one second node receives configuration information about a first periodicity and a second periodicity for reporting of the at least one CSI to the at least one first node, wherein a value of the first periodicity is greater than a value of the second periodicity. The at least one second node reports a full CSI feedback with the first periodicity and a partial CSI feedback with the second periodicity to the at least one first node.In one aspect, the full CSI feedback may comprise indices of Two-Dimensional (2D) Discrete Fourier Transform (DFT) vectors of a first matrix, indices of a 2D DFT vectors in the compression matrix in the frequency domain, and linear combining coefficients in a second matrix.In one aspect, the partial CSI feedback may comprise differential values of the second matrix.In one aspect, the precoder matrix may be represented as:W=W_1 W_2 W_fHwhere W represents a precoder matrix, W1 represents the first matrix, W2 represents the second matrix, and WfH represents Hermitian of the compression matrix in the frequency domain.In one aspect, the differential values of the second matrix may be calculated using:W_2 (t)=aW_2 (t-1)+Δwhere a denotes a scalar quantity, Δ denotes a difference matrix or an error matrix of the second matrix and 't' denotes CSI reporting instance.In one aspect, a range of magnitude of a values may be incorporated in a first pre-defined vector and a range of phase of a may be incorporated in a second pre-defined vector. An index of the first pre-defined vector corresponding to the magnitude of optimal value of a may be reported to the at least one first node and an index of the second pre-defined vector corresponding to the phase of the optimal value of a may be reported to the at least one first node.In one aspect, the optimal value of a may be an average of ratios between corresponding elements of matrices W2(t) and W2(t-1).In one aspect, the optimal value of a may be calculated using:a=((vec(W_2 (t)))H (vec(W_2 (t-1)))) / ||(vec(W_2 (t-1)))||2 where elements in matrices W2(t) and W2(t-1) are arranged in vector form using the vector operator, vec, and the optimal value of a is calculated as a minimum Euclidean distance between matrices W2(t) and W2(t-1).In one aspect, the at least one first node may signal at least one first reference signal to the at least one second node for reporting the full CSI feedback with the first periodicity. Also, the at least one first node may signal at least one second reference signal to the at least one second node for reporting the partial CSI feedback with the second periodicity.In one aspect, the at least one first reference signal may be one of tracking reference signal and channel state information (CSI) reference signal. In one aspect, the at least one second reference signal may be one of tracking reference signal and channel state information (CSI) reference signal.In one aspect, the at least one first node may signal the value of the first periodicity and the value of the second periodicity to the at least one second node.In one aspect, the full CSI feedback may comprise values of all channel taps of the multiple path channel.In one aspect, the partial CSI feedback may comprise a first group having autocorrelation values of channel values between the current and previous CSI estimated by the at least one second node in first significant tap locations. Also, the partial CSI feedback may comprise a second group having absolute values of channel values in second significant tap locations. The first significant tap locations may match with current and previous CSI estimated by the at least one second node and the second significant tap locations may be different between the current and previous CSI.In one aspect, the at least one second node may identify the locations and values of significant channel taps of the multi path channel.A method of dynamic switching between Channel State Information (CSI) mechanisms in a wireless communication system is described. The method comprises receiving, by at least one second node, an indication of a CSI feedback parameter and a Reference Signal (RS) from at least one first node based on the capability information, wherein the CSI feedback parameter is associated with at least one of an autocorrelation function and a Doppler frequency. The at least one second node determines at least one of autocorrelation values based on the RS when the CSI feedback parameter is associated with the autocorrelation function, and Doppler frequency values based on the RS when the CSI feedback parameter is associated with the Doppler frequency. The at least one second node reports to the at least one first node, index of at least one of a vector comprising autocorrelation values and a vector comprising Doppler frequency values, wherein the index corresponds to the value in the vector that is closest to the calculated value.In one aspect, the at least one second node may transmit capability information of the at least one second node to a at least one first node.In one aspect, the at least one first node may perform channel prediction for current instance based on the indices of the vector values obtained from previous CSI reporting instances.In one aspect, the at least one first nodemay compare the indexes of vector values with pre-defined threshold values. Also, the at least one first node may switch between compressed CSI and full CSI based on comparison between the indexes of vector values and the pre-defined threshold values.BRIEF DESCRIPTION OF THE DRAWINGSThe accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. Fig. 1 illustrates an implementation diagram of a wireless communication network, in accordance with an embodiment of the present invention.Fig. 2 illustrates a flow chart of a method of reporting Channel State Information (CSI) in a wireless communication system, in accordance with an embodiment of the present invention.Fig. 3 illustrates a flow chart of a method of dynamic switching between different Channel State Information (CSI) reporting mechanisms in a wireless communication system, in accordance with an embodiment of the present invention.DETAILED DESCRIPTION OF THE INVENTIONAs used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This disclosure may however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those of ordinary skill in the art. Moreover, all statements herein reciting embodiments of the disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure).Fig. 1 illustrates an implementation diagram of a wireless communication network 100, in accordance with an embodiment of the present invention. The wireless communication network 100 comprises Base Stations (BSs), such as a first BS 102-1 through nth BS 102-n and User Equipments (UEs), such as a first UE 104-1 through nth UE 104-n. The first BS 102-1 through nth BS 102-n are cumulatively referred as a BS 102 and the first UE 104-1 through nth UE 104-n are cumulatively referred as a UE 104 for the ease of labelling and explanation. The BS 102 may communicate with each other for coordinating and communicating with the UE 104. The UE 104 may be either stationary or mobile and may be dispersed throughout the wireless communication network 100. Fig. 2 illustrates a flow chart 200 of a method of reporting CSI in the wireless communication system 100, in accordance with an embodiment of the present invention. It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the drawings. For example, two blocks shown in succession in Fig. 2 may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Alternate implementations are included within the scope of the example embodiments in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved.The UE 104 may receive a reference signal from the BS 102, at step 202. The reference signal is a Channel State Information-Reference Signals (CSI-RS) and / or a Tracking Reference Signals (TRS). The UE 104 may estimate a Channel State Information (CSI) based on the reference signal, at step 204. The BS 102 may configure a first periodicity and a second periodicity to the UE 104 for reporting of the CSI, at step 206. A value of the first periodicity may be greater than a value of the second periodicity. The UE 104 may report a full CSI feedback with the first periodicity and a partial CSI feedback with the second periodicity, at step 208. To reduce the CSI feedback overhead, the method illustrated in Fig. 2 employs a differential feedback mechanism based on time correlation. The first periodicity is represented by 'p1' and the second periodicity is represented by 'p2'. For every p1 slots, the UE 104 may report the full CSI feedback with the first periodicity comprising indices of Two-Dimensional (2D) Discrete Fourier Transform (DFT) vectors of a first matrix representing wideband characteristics of a channel between the BS 102 and the UE 104, indices of 2D DFT vectors of a compression matrix in a frequency domain, and coefficients of a second matrix representing sub-band characteristics of the channel between the BS 102 and the UE 104. The optimal 2D-DFT vectors are calculated, for example, using orthogonal matching pursuit algorithm.For every p2 slots, the UE 104 may report the partial CSI feedback with the second periodicity comprising only the differential values of the second matrix W2, assuming dominant DFT vectors in W1 and Wf do not change within short period. The differential values of the second matrix W2 may be calculated using Eq. (3):W_2 (t)= αW_2 (t-1)+Δ (3)where α denotes a scalar quantity and denotes a difference matrix or an error matrix of the second matrix W2. The UE 104 may report a and Δ every p2 slots as the partial CSI feedback to the BS 102. Using the values of {a and Δ} and W2 at 't-1', BS 102 may reconstruct an approximate version of W2(t) for precoding purposes.A first pre-defined vector may include a range of magnitude of a values and a second pre-defined vector may include a range of phase of a represented as "Δ". The UE 104 may report the index of the suitable values of magnitude of a and Δ from the corresponding vectors to the BS 102. For instance, a quantized from of magnitude of parameter a (|a |), such as, {0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8} may be stored in the first pre-defined vector. The value in the vector that is closest to the calculated value of |a | is found and the index of that value is fedback. Since there are 16 entries in the vector, 4 bits can be used to represent the value of | a |. If the value of | a | is beyond the range of the first pre-defined vector, the UE 104 may report all the indices of the second matrix W2, instead of reporting only the differential values of the second matrix W2. The UE 104 may report an index of an optimal value of a to the BS 102 using the first pre-defined vector and the second pre-defined vector. In an implementation, the optimal value of a may be calculated based on the average of ratios between corresponding values of W2(t) and W2(t-1). In another implementation, the optimal value of a may be calculated using the Least-squares approach. In the least squares approach, the elements in matrices W2(t) and W2(t-1) may be arranged in vector form using the vector operator vec. The optimal value of a may be calculated as a minimum Euclidean distance between matrices W2(t) and W2(t-1) using Eq. (4):a=((vec(W_2 (t)))H (vec(W_2 (t-1)))) / ||(vec(W_2 (t-1)))||2 (4)where (vec (W2(t)))H is a Hermitian of a vector (vec (W2(t))) and ||vec (W2(t-1))|| is a norm of a vector vec (W2(t-1)). The vectors vec (W2(t)) and vec (W2(t-1)) are reshaped according to the sizes of matrices W2(t) and W2(t-1). The optimal value of a may be used to calculate the final matrix of W2(t) using the Eq.(5):W2(t)=a W2 (t-1) +Δ (5)For every p1 slots, CSI-RS with higher frequency density may be used to improve the measurement accuracy of the CSI. As the periodicity of p1 slots are longer than p2 slots, there would not be a significant increase in the CSI-RS overhead. For every p2 slots, the UE 104 may report the partial CSI feedback for updating the channel variations in time.The TRS may be used as the reference signal in the full CSI feedback. The TRS is a resource set consisting of multiple periodic CSI-RS. The UE 104 may report the full CSI feedback based on the TRS, which is denser in time and frequency, thereby increasing the measurement accuracy of the CSI. The values in the difference matrix Δ are much smaller than the actual values of the second matrix W2. Therefore, it is sufficient to signal the values in Δ that are significant and leave the rest of the values that are not significant. The BS 102 may signal the maximum limit on the number of values in Δ that need to be fedback. This leads to reduction in the feedback overhead.The BS 102 may signal the TRS to the UE 104 for reporting the full CSI feedback with the first periodicity. The BS 102 may signal the CSI-RS to the UE 104 for reporting the partial CSI feedback with the second periodicity. The value of first periodicity and the value of the second periodicity are provided by the BS 102 to the UE 104.The UE 104 may employ a sparsity recovery algorithm, for example, to reduce the CSI feedback overhead by reducing uplink (UL) resources used for reporting the CSI feedback. A compression scheme may be applied at the UE 104 to compress an explicit CSI feedback to reduce the feedback overhead. The received CSI feedback is decompressed at the BS 102 to build a downlink (DL) CSI needed for precoding the DL resources. An explicit feedback of multi path channel values may be used for channel prediction at the BS 102. Channel prediction may help to combat the effect of channel aging. The explicit multi path channel feedback may reduce the DL resources consumed in training periods.The UE 104 may report the multi path channel values to the BS 102 using significant channel taps in the time domain. The UE 104 may estimate the multi path channel using the CSI-RS received from the BS 102. The UE 104 may identify locations and values of significant time-domain channel taps using a spatial recovery algorithm.The UE 104 may report the full CSI feedback using the first periodicity. The full CSI feedback may comprise full multipath channel tap values. The UE 104 may report the partial CSI feedback using the second periodicity. The partial CSI feedback may comprise a first group and a second group. The first group may include the autocorrelation values of channel values in first significant tap locations. The first significant tap locations may match with current and previous CSI estimated by the UE 104. The second group contain the actual channel values of second significant tap locations. The second significant tap locations are different from the current and previous CSI estimated by the UE 104.The present invention provides a method to adapt with channel aging with reduced overhead. The method as illustrated in Fig. 2 is proposed to compress the CSI feedback in order to reduce the CSI feedback overhead by employing at least one of the differential feedback mechanism based on time correlation. The method may be primarily required for medium and high speed UEs. In case of stationary or low speed UEs, existing CSI reporting methods such as a full CSI feedback can be employed. Therefore, a mechanism may be required to switch between a full CSI feedback and a compressed CSI feedback based on the speed of the UEs. The speed of the UEs may be measured based on at least one of a Doppler frequency and a time domain auto correlation of channel estimates. The measurement of Doppler frequency and the time domain auto correlation may be used for switching between the full CSI feedback and the compressed CSI feedback mechanisms. The Doppler frequency and the time domain auto correlation may also be used for assisting the UE 104 and the BS 102 to predict the channel between the UE 104 and the BS 102.Fig. 3 illustrates a flow chart 300 of a method of dynamic switching between Channel State Information (CSI) mechanisms in a wireless communication system, in accordance with an embodiment of the present invention. It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the drawings. For example, two blocks shown in succession in Fig. 3 may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Alternate implementations are included within the scope of the example embodiments in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved.The UE 104 may transmit its capability information to the BS 102.The UE 104 may receive a CSI feedback parameter and a Reference Signal (RS) from the BS 102 based on the capability information, at step 304. The CSI feedback parameter may be associated with at least one of an autocorrelation function and a Doppler frequency. The UE 104 may determine whether the CSI feedback parameter is associated with autocorrelation, at step 306. The UE 104 may determine autocorrelation values based on the RS when the CSI feedback parameter is associated with the autocorrelation function, at step 310. The UE 104 may determine Doppler frequency values based on the RS when the CSI feedback parameter is associated with the Doppler frequency, at step 308. The UE 104 may report indexes of vector values comprising the autocorrelation values to the BS 102, at step 314. The UE 104 may report indexes of vector values comprising the Doppler frequency values to the BS 102, at step 312.The TRS may include four symbols containing pilots to enable measurement of channel values in different time instants, even within one TRS instance. Therefore, the TRS may be used by the UE 104 to measure the autocorrelation values between the channel estimates at successive TRS symbols. The channel estimated at different TRS symbols can be subsequently used for calculation of the Doppler frequency value also.The BS 102 may select the CSI feedback parameter to be feedback (time domain autocorrelation or Doppler frequency) based on the capability information of the UE 104 and channel traffic conditions. The BS 102 may configure the CSI feedback parameter as auto correlation values. A vector of possible auto correlation values is predefined. The vector may include values between -1 to 1. The UE 104 may compute the auto correlation value and compares the calculated value with the values in the predefined vector. The UE 104 may find the value in the vector that is closest to the calculated auto correlation. The UE 104 may signal the index of closest value in the vector to the BS 102.The BS 102 may configure the CSI feedback parameter as Doppler frequency values. A vector with range of Doppler frequency values is predefined. The UE 104 may compute the Doppler frequency using channel estimates at RS and may compare the computed value with the values in the predefined vector. The UE 104 may compute the value in the vector that is closest to the calculated Doppler frequency. The UE 104 may signal the index of the vector value to the BS 102.For low speed UEs, the CSI measurement and feedback may be performed with a low periodicity. When the speed of UE increases, the channel estimates would get outdated before the next CSI reporting instant. Therefore, in order to update channel estimates between CSI reporting instants, the BS 102 may predict the channel values for future time instants (using either auto correlation or Doppler frequency). Using the predicted channel, the CSI accuracy is improved. In case of auto correlation feedback, BS 102 can use either the autocorrelation values directly for prediction or calculate the Doppler frequency values from the auto correlation values and use that for prediction.The autocorrelation or Doppler frequency values may be used to alter the CSI-RS, TRS or DMRS periodicity. The BS 102 may configure the RS with higher periodicity when the auto correlation values are high, or the Doppler frequency is less. The BS 102 may configure the RS with lower periodicity when the auto correlation is low or Doppler frequency may be high. The BS 102 may signal the UE 104 to switch from the full CSI feedback mechanism to the compressed CSI feedback mechanism when the Doppler frequency increases. The BS 102 signals the UE 104 to switch from the compressed CSI feedback mechanism to full CSI feedback mechanism when the Doppler frequency decreases, in order to the transmit full CSI in every CSI-RS period.In the above detailed description, reference is made to the accompanying drawings that form a part thereof, and illustrate the best mode presently contemplated for carrying out the invention. However, such description should not be considered as any limitation of scope of the present invention. The structure thus conceived in the present description is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence.

Claims

1. A method (200) of reporting Channel State Information (CSI) in a wireless communication system, the method comprising: receiving, by at least one second node (104), a reference signal from at least one first node (102); estimating, by the at least one second node (104), at least one CSI based on the reference signal; receiving, by the at least one second node (104), configuration information about a first periodicity and a second periodicity for reporting of the at least one CSI to the at least one first node (102), wherein a value of the first periodicity is greater than a value of the second periodicity; and reporting, by the at least one second node (104) to the at least one first node (102), a full CSI feedback with the first periodicity and a partial CSI feedback with the second periodicity.

2. The method as claimed in claim 1, wherein the full CSI feedback comprises indices of Two-Dimensional (2D) Discrete Fourier Transform (DFT) vectors of a first matrix, indices of a 2D DFT vectors in the compression matrix in the frequency domain, and linear combining coefficients in a second matrix.

3. The method as claimed in claim 1, wherein the partial CSI feedback comprises differential values of the second matrix.

4. The method as claimed in claim 2, wherein the precoder matrix can be represented as: W=W_1 W_2 W_fH where W represents a precoder matrix, W1 represents the first matrix, W2 represents the second matrix, and WfH represents Hermitian of the compression matrix in the frequency domain.

5. The method as claimed in claim 3, wherein the differential values of the second matrix are calculated using: W_2 (t)=aW_2 (t-1)+Δ where a denotes a scalar quantity, Δ denotes a difference matrix or an error matrix of the second matrix and 't' denotes CSI reporting instance.

6. The method as claimed in claim 5, wherein a range of magnitude of a values is incorporated in a first pre-defined vector and a range of phase of a is incorporated in a second pre-defined vector, and wherein an index of the first pre-defined vector corresponding to the magnitude of optimal value of a is reported to the at least one first node (102) and an index of the second pre-defined vector corresponding to the phase of the optimal value of a is reported to the at least one first node (102).

7. The method as claimed in claim 5, wherein the optimal value of a is an average of ratios between corresponding elements of matrices W2(t) and W2(t-1).

8. The method as claimed in claim 5, wherein the optimal value of a is calculated using: a=((vec(W_2 (t)))H (vec(W_2 (t-1)))) / ||(vec(W_2 (t-1)))||2 where elements in matrices W2(t) and W2(t-1) are arranged in vector form using the vector operator, vec, and the optimal value of a is calculated as a minimum Euclidean distance between matrices W2(t) and W2(t-1).

9. The method as claimed in claim 1, further comprises: signaling, by the at least one first node (102), at least one first reference signal to the at least one second node (104) for reporting the full CSI feedback with the first periodicity; and signaling, by the at least one first node (102), at least one second reference signal to the at least one second node (104) for reporting the partial CSI feedback with the second periodicity.

10. The method as claimed in claim 9, wherein the at least one first reference signal is one of tracking reference signal and channel state information (CSI) reference signal.

11. The method as claimed in claim 9 wherein the at least one second reference signal is one of tracking reference signal and channel state information (CSI) reference signal.

12. The method as claimed in claim 1, wherein the at least one first node (102) signals the value of the first periodicity and the value of the second periodicity to the at least one second node (104).

13. The method as claimed in claim 1, wherein the full CSI feedback comprises values of all channel taps of the multiple path channel .

14. The method as claimed in claim 1, wherein the partial CSI feedback comprises a first group having autocorrelation values of channel values between the current and previous CSI estimated by the at least one second node (104) in first significant tap locations and a second group having absolute values of channel values in second significant tap locations, wherein the first significant tap locations match with current and previous CSI estimated by the at least one second node (104) and the second significant tap locations are different between the current and previous CSI.

15. The method as claimed in claim 13 and 14, wherein the identifying by the at least one second node (104), the locations and values of significant channel taps of the multi path channel..

16. A method (300) of dynamic switching between Channel State Information (CSI) mechanisms in a wireless communication system, the method comprising: receiving, by at least one second node (104), an indication of a CSI feedback parameter and a Reference Signal (RS) from at least one first node (102) based on the capability information, wherein the CSI feedback parameter is associated with at least one of an autocorrelation function and a Doppler frequency; determining, by the at least one second node (104), at least one of autocorrelation values based on the RS when the CSI feedback parameter is associated with the autocorrelation function, and Doppler frequency values based on the RS when the CSI feedback parameter is associated with the Doppler frequency; and reporting, by the at least one second node (104) to the at least one first node (102), index of at least one of a vector comprising autocorrelation values and a vector comprising Doppler frequency values, wherein the index corresponds to the value in the vector that is closest to the calculated value.

17. The method as claimed in claim 16, comprising transmitting, by the at least one second node (104), capability information of the at least one second node (104) to the at least one first node (102).

18. The method as claimed in claim 16, further comprising performing, by the at least one first node (102), channel prediction for current instance based on the indices of the vector values obtained from previous CSI reporting instances.

19. The method as claimed in claim 16, further comprising: comparing, by the at least one first node (102), the indexes of vector values with pre-defined threshold values; and switching, by the at least one first node (102), between compressed CSI and full CSI based on comparison between the indexes of vector values and the pre-defined threshold values.