Devices and Methods for Multicarrier Modulation Schemes

Abstract

A transmitter device, a receiver device and a transceiver device for a multicarrier modulation scheme. The transmitter device is configured to obtain a plurality of signature roots based on receiving a feedback message from a receiver device, construct a Lagrange matrix or a Vandermonde matrix from the plurality of signature roots, and generate a multicarrier modulated signal based on the Lagrange matrix or the Vandermonde matrix. The receiver device is configured to determine a plurality of signature roots, construct a Lagrange matrix or a Vandermonde matrix from the plurality of signature roots, and perform a demodulation of a multicarrier modulated signal based on the Lagrange matrix or the Vandermonde matrix. The transceiver device comprises a transmitter device configured to generate a multicarrier modulated signal, and a receiver device configured to perform a demodulation of the multicarrier modulated signal.

Claims

1. A transmitter device for a multicarrier modulation scheme, the transmitter device configured to: obtain a plurality of signature roots (ρ.sub.k) based on a feedback message received from a receiver device, wherein each signature root of the plurality of signature roots (ρ.sub.k) is a nonzero complex point; construct, from the plurality of signature roots (ρ.sub.k), at least one of a Lagrange matrix or a Vandermonde matrix; and generate a multicarrier modulated signal based on at least one of the Lagrange matrix or the Vandermonde matrix.

2. The transmitter device according to claim 1, wherein the feedback message indicates a radius (a) of a circle, wherein signature roots of the plurality of signature roots (ρ.sub.k) are uniformly distributed on a circumference of the circle.

3. The transmitter device according to claim 2, wherein the transmitter device is further configured to: allocate a determined transmit power to each subcarrier of the multicarrier modulated signal according to a tuning factor (κ.sub.k) estimated based on the radius (a) of the circle.

4. The transmitter device according to claim 2, wherein the plurality of signature roots (ρ.sub.k) are obtained based on ${\rho }_k=a{e}^{\frac{j2\pi k}{K}}$ wherein ρ.sub.k corresponds to a signature root related to the k.sup.th subcarrier, wherein a corresponds to the radius of the circle, and wherein K is the number of the subcarriers.

5. The transmitter device according to claim 1, wherein the feedback message indicates at least one vector for the plurality of signature roots (ρ.sub.k).

6. The transmitter device according to claim 5, wherein the transmitter device is further configured to: allocate a determined transmit power to each subcarrier of a multicarrier modulated signal according to a tuning factor (κ.sub.k) estimated based on the plurality of signature roots (ρ.sub.k).

7. The transmitter device according to claim 1, wherein the transmitter device is further configured to perform at least one of: perform, in response to constructing the Lagrange matrix, a zero-padding procedure on the multicarrier modulated signal; or perform, in response to constructing the Vandermonde matrix, a cyclic-prefix procedure on the multicarrier modulated signal.

8. A receiver device for a multicarrier modulation scheme, the receiver device configured to: determine a plurality of signature roots (ρ.sub.k), wherein each signature root is a nonzero complex point; construct, from the plurality of signature roots (ρ.sub.k), at least one of a Lagrange matrix or a Vandermonde matrix; and perform demodulation of a multicarrier modulated signal based on the at least one of the Lagrange matrix or the Vandermonde matrix.

9. The receiver device according to claim 8, wherein the receiver device is further configured to: determine a radius (a) of a circle based on channel state information of a communication channel, wherein signature roots of the plurality of signature roots (ρ.sub.k) are uniformly distributed on a circumference of the circle.

10. The receiver device according to claim 9, wherein the receiver device is further configured to: send, to a transmitter device, a feedback message indicating the radius (a) of the circle.

11. The receiver device according to claim 9, wherein the receiver device is further configured to: compute, based on the channel state information of the communication channel, a metric for evaluating at least one of the radius (a) of the circle or the plurality of signature roots (ρ.sub.k).

12. The receiver device according to one of the claim 8, wherein the receiver device is further configured to: modify, individually, each signature root from the plurality of signature roots (ρ.sub.k) based on a machine learning algorithm, using a gradient descent algorithm.

13. The receiver device according to claim 12, wherein the receiver device is further configured to: determine at least one vector for the plurality of signature roots (ρ.sub.k) based on the individual modification of each signature root; and send a feedback message to the transmitter device indicating the at least one vector for the plurality of signature roots (ρ.sub.k).

14. The receiver device according to claim 8, wherein performing the demodulation of the multicarrier modulated signal results in a demodulated signal; and wherein the receiver device is further configured to: perform a one-tap equalization on the demodulated signal based on the plurality of signature roots (ρ.sub.k).

15. A transceiver device comprising: a transmitter configured to: obtain a plurality of signature roots (ρ.sub.k) based on a feedback message received from a receiver device, wherein each signature root of the plurality of signature roots (ρ.sub.k) is a nonzero complex point; construct, from the plurality of signature roots (ρ.sub.k), at least one of a Lagrange matrix or a Vandermonde matrix; and generate a multicarrier modulated signal based on the at least one of the Lagrange matrix or the Vandermonde matrix; and a receiver device configured to: determine a plurality of signature roots (ρ.sub.k), wherein each signature root of the plurality of signature roots (ρ.sub.k) is a nonzero complex point; construct, from the plurality of signature roots (ρ.sub.k), at least one of a Lagrange matrix or a Vandermonde matrix; and perform demodulation of a multicarrier modulated signal based on the at least one of the Lagrange matrix or the Vandermonde matrix.

16. A transceiver device for a multicarrier modulation scheme, the transceiver device comprising: a transmitter device configured to generate a multicarrier modulated signal based on constructing at least one of a Lagrange matrix or a Vandermonde matrix; and a receiver device configured to perform a demodulation of the multicarrier modulated signal based on constructing the other matrix from the at least one of the Lagrange matrix or the Vandermonde matrix constructed by the transmitter device.

17. A method, comprising: obtaining, by a transmitter device, a plurality of signature roots (ρ.sub.k) based on a feedback message received from a receiver device, wherein each signature root of the plurality of signature roots (ρ.sub.k) is a nonzero complex point; constructing, from the plurality of signature roots (ρ.sub.k), at least one of a Lagrange matrix or a Vandermonde matrix; and generating a multicarrier modulated signal based on the at least one of the Lagrange matrix or the Vandermonde matrix.

18. A method for being implemented at a receiver device, the method comprising: determining a plurality of signature roots (ρ.sub.k), wherein each signature root of the plurality of signature roots (ρ.sub.k) is a nonzero complex point; constructing, from the plurality of signature roots (ρ.sub.k), at least one of a Lagrange matrix or a Vandermonde matrix; and performing demodulation of a multicarrier modulated signal based on the at least one of the Lagrange matrix or the Vandermonde matrix.

19. A method, comprising: generating, at a transmitter device of a transceiver device, a multicarrier modulated signal based on constructing a Lagrange matrix or a Vandermonde matrix; and performing, at a receiver device of the transceiver device, demodulation of the multicarrier modulated signal based on constructing the other matrix from the at least one of the Lagrange matrix or the Vandermonde matrix constructed by the transmitter device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0088] The above described aspects and implementation forms of the present invention will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which

[0089] FIG. 1 is a schematic view of a transmitter device for a multicarrier modulation scheme, according to an embodiment of the present invention.

[0090] FIG. 2 is a schematic view of a receiver device for a multicarrier modulation scheme, according to an embodiment of the present invention.

[0091] FIG. 3 is a schematic view of a transceiver device for a multicarrier modulation scheme, according to an embodiment of the present invention.

[0092] FIG. 4 is an exemplarily scheme of a transceiver device comprising a transmitter device using a Lagrange matrix for modulation and a receiver device using a Vandermonde matrix for demodulation, according to an embodiment of the invention.

[0093] FIG. 5 is an exemplarily scheme of a transceiver device comprising a transmitter device using a Vandermonde matrix for modulation and a receiver device using a Lagrange matrix for demodulation, according to an embodiment of the invention.

[0094] FIG. 6 is a schematic view for signaling exchange indicating a radius of a circle.

[0095] FIG. 7 is a schematic view for signaling exchange indicating the signature root refinement.

[0096] FIG. 8a and FIG. 8b illustrate two exemplarily channel realization.

[0097] FIG. 9a and FIG. 9b illustrate the performance results for a uniform and an optimized power allocation at the transmitter device being based on a frequency selective channels with uniform (FIG. 9a) and exponential (FIG. 9 b) power delay profile.

[0098] FIG. 10a and FIG. 10.b illustrate comparison of performance results under perfect and imperfect CSI, when the transmitter device is using a uniform power allocation (FIG. 10a) or an optimal power allocation (FIG. 10b).

[0099] FIG. 11a and FIG. 11b illustrate determining a radius of a circle (FIG. 11a) and further determining the signature roots using the radius of the circle (FIG. 11b).

[0100] FIG. 12a and FIG. 12b illustrate modifying the plurality of signature roots, when the plurality of signature roots migrating toward new positions (FIG. 12a) and when the MSE decreases with the GDA iterations (FIG. 12b).

[0101] FIG. 13 shows the overall performance of the LV modulator of the invention compared to the performance of a conventional ZP-OFDM.

[0102] FIG. 14 is a flowchart of a method for being implemented at a transmitter device, according to an embodiment of the invention.

[0103] FIG. 15 is a flowchart of a method for being implemented at a receiver device, according to an embodiment of the invention.

[0104] FIG. 16 is a flowchart of a method for being implemented at a transceiver device, according to an embodiment of the invention.

[0105] FIG. 17 schematically illustrates a conventional Zero Padding Orthogonal Frequency Division Multiplexing (ZP-OFDM) block diagram.

[0106] FIG. 18 schematically illustrates a conventional Cyclic Prefix Orthogonal Frequency Division Multiplexing (CP-OFDM) block diagram.

[0107] FIG. 19 schematically illustrates a conventional Mutually-Orthogonal Usercode-Receiver (AMOUR) block diagram.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0108] FIG. 1 is a schematic view of a transmitter device 100 for a multicarrier modulation scheme, according to an embodiment of the present invention.

[0109] The transmitter device 100 for the multicarrier modulation scheme is configured to obtain a plurality of signature roots ρ.sub.k based on receiving a feedback message 11 from a receiver device 110, wherein each signature root is a nonzero complex point.

[0110] The transmitter device 100 is further configured to construct a Lagrange matrix 101-L or a Vandermonde matrix 101-V from the plurality of signature roots ρ.sub.k.

[0111] The transmitter device 100 is further configured to generate a multicarrier modulated signal 102-L, 102-V based on the Lagrange matrix 101-L or the Vandermonde matrix 101-V.

[0112] The transmitter device 100 may comprise processing circuitry (not shown) configured to perform, conduct or initiate the various operations of the transmitter device 100 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the transmitter device 100 to perform, conduct or initiate the operations or methods described herein.

[0113] Moreover, in some embodiments, the transmitter device 100 may further be incorporated in a transceiver device.

[0114] FIG. 2 is a schematic view of a receiver device 110 for a multicarrier modulation scheme, according to an embodiment of the present invention.

[0115] The receiver device 110 for the multicarrier modulation scheme is configured to determine a plurality of signature roots ρ.sub.k, wherein each signature root is a nonzero complex point.

[0116] The receiver device 110 is further configured to construct a Lagrange matrix 111-L or a Vandermonde matrix 111-V from the plurality of signature roots ρ.sub.k

[0117] The receiver device 110 is further configured to perform a demodulation 112-V, 112-L of a multicarrier modulated signal 102-L, 102-V based on the Lagrange matrix 111-L or the Vandermonde matrix ill-V.

[0118] The receiver device 110 may comprise processing circuitry (not shown) configured to perform, conduct or initiate the various operations of the receiver device 110 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the receiver device 110 to perform, conduct or initiate the operations or methods described herein.

[0119] Moreover, in some embodiments, the receiver device 110 may further be incorporated in a transceiver device.

[0120] FIG. 3 is a schematic view of a transceiver device 300 for a multicarrier modulation scheme, according to an embodiment of the present invention.

[0121] The transceiver device 300 comprises a transmitter device 100 configured to generate a multicarrier modulated signal 102-L, 102-V based on constructing a Lagrange matrix 101-L or a Vandermonde matrix 101-V.

[0122] The transceiver device 300 further comprises a receiver device 110 configured to perform a demodulation 112-V, 112-L of the multicarrier modulated signal 102-L, 102-V based on constructing the other matrix 111-V, 111-L from the Lagrange matrix or the Vandermonde matrix constructed by the transmitter device 100.

[0123] For example, the transceiver device 300 may be based on a LV multicarrier modulation scheme. For instance, the transmitter device 100 of the transceiver device 300 may generate the multicarrier modulated signal 102-L based on constructing a Lagrange matrix 101-L. Moreover, the receiver device 110 may obtain the multicarrier modulated signal 102-L and may further construct the Vandermonde matrix 111-V from the plurality of signature roots ρ.sub.k. Furthermore, the receiver device 110 may perform the demodulation 112-V of the multicarrier modulated signal 102-L based on the Vandermonde matrix ill-V.

[0124] Similarly, the transceiver device 300 may be based on a VL multicarrier modulation scheme. For instance, the transmitter device 100 of the transceiver device 300 may generate the multicarrier modulated signal 102-V based on constructing a Vandermonde matrix 101-V. Moreover, the receiver device 110 may obtain the multicarrier modulated signal 102-V and may further construct the Lagrange matrix 111-L from the plurality of signature roots ρ_k. Furthermore, the receiver device 110 may perform the demodulation 112-L of the multicarrier modulated signal 102-V based on the Lagrange matrix 111-L.

[0125] The transceiver device 300 may comprise processing circuitry (not shown) configured to perform, conduct or initiate the various operations of the transceiver device 300 described herein. The processing circuitry may comprise hardware and software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors. In one embodiment, the processing circuitry comprises one or more processors and a non-transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the transceiver device 300 to perform, conduct or initiate the operations or methods described herein.

[0126] In the following, some mathematical basics and notation are briefly discussed, that may be used by the transmitter device 100 and/or the receiver device 110 and/or the transceiver device 300, without limiting the present invention.

[0127] For example, from a set of K distinct nonzero complex points {ρ.sub.k}.sub.k=1.sup.K, that are referred to as signature roots, a Vandermonde matrix may be constructed. The Vandermonde matrix, is a K×P matrix, given by Eq. 10:

[00011]$\begin{array}{cc}{V}_{K\times P}=\left[\begin{array}{cccc}1& {\rho }_0^{-1}& \mathrm{.Math.}& {\rho }_0^{1-P}\\ 1& {\rho }_1^{-1}& \mathrm{.Math.}& {\rho }_1^{1-P}\\ \mathrm{.Math.}& \mathrm{.Math.}& & \mathrm{.Math.}\\ 1& {\rho }_{K-1}^{-1}& \mathrm{.Math.}& {\rho }_{K-1}^{1-P}\end{array}\right],v_{k,p}=\left({\rho }_{k-1}^{1-p}\right)& \mathrm{Eq}.10\end{array}$

[0128] Moreover, note that, if

[00012]${\rho }_k=\frac{1}{\sqrt{K}}\exp \left(j\frac{2\pi k}{K}\right)=\frac{1}{\sqrt{K}}{w}^{-k},$

therefore, V.sub.K×K=F.sub.K×K which is the Discerete Fouriuer Transofrm (DFT) matrix given above.

[0129] Furthermore, the Lagrange basis polynomials (e.g., a K polynomials) may be obtained according to Eq. 11

[00013]$\begin{array}{cc}{F}_k\left(z\right)={\kappa }_k\underset{\underset{n\ne k}{n=0}}{\overset{K-1}{.Math.}}\frac{1-{\rho }_n{z}^{-1}}{1-{\rho }_n{\rho }_k^{-1}}=\underset{i=0}{\overset{K-1}{.Math.}}{r}_{k,i}{z}^{-i}=\left[\begin{array}{cccc}1& z^{-1}& \mathrm{.Math.}& z^{1-K}\end{array}\right]{\underset{\_}{r}}_k& \mathrm{Eq}.11\end{array}$

[0130] where, κ.sub.k is a tuning factor that normalizes the transmitter device filter (F.sub.k) energy. Moreover, a Lagrange matrix may be constructed, given by Eq. 12:

[00014]$\begin{array}{cc}R=\left[\begin{array}{cccc}{\underset{\_}{r}}_0& {\underset{\_}{r}}_1& \mathrm{.Math.}& {\underset{\_}{r}}_{K-1}\end{array}\right]=\left[\begin{array}{cccc}{r}_{0,0}& r_{1,0}& \mathrm{.Math.}& r_{K-1,0}\\ r_{0,1}& r_{1,1}& \mathrm{.Math.}& r_{K-1,1}\\ \mathrm{.Math.}& \mathrm{.Math.}& \mathrm{.Math.}& \mathrm{.Math.}\\ r_{0,K-1}& r_{1,K-1}& \mathrm{.Math.}& r_{K-1,K-1}\end{array}\right]& \mathrm{Eq}.12\end{array}$

Note that, F.sub.k(ρ.sub.l)=κ.sub.kδ(k−l) where k,l∈[0, K−1]. Furthermore, the following identity may be verified:

[00015]$\begin{array}{cc}{V}_{K\times K}R=\left[\begin{array}{ccc}{\kappa }_o& & \\ & \ddots & \\ & & {\kappa }_{K-1}\end{array}\right]& \mathrm{Eq}.13\end{array}$

[0131] where κ.sub.k are the tuning factors defined above.

[0132] Reference is made to FIG. 4 which is an exemplarily scheme of the transceiver device 300 comprising the transmitter device 100 using a Lagrange matrix for modulation and the receiver device 200 using a Vandermonde matrix for demodulation, according to an embodiment of the invention.

[0133] In the block diagram of the LV modulator of FIG. 4, the transceiver device 300 (i.e., being based on a LV modulator) is exemplarily shown for K signature roots. The transceiver device 300 comprises the transmitter device 100 which includes a precoder 401, a modulator 402 and a ZP block 403.

[0134] The precoder 401 may apply the tuning factors κ.sub.k, for example, for allocating the determined transmit power, which may be K×K diagonal matrix (n) in FIG. 4.

[0135] Moreover, the modulator 402 uses the Lagrange matrix (R in FIG. 4) which has a size of K×K (for example, it may construct a Lagrange matrix 101-L and may further generate a multicarrier modulated signal 102-L based on the Lagrange matrix 101-L).

[0136] Furthermore, the ZP block 403 may be used for the zero-padding procedure, where every input block of K symbols will be trailed by L zeros. Therefore, it may provide and may further output block symbols with the length of P, where P=K+L.

[0137] Moreover, the communication channel of the transceiver device 300 comprises the transmitter filter (Tx filter) 404 and the receiver filter (Rx filter) 406 (for example, they may be raised cosine filters). In addition, the parameter C 405 which is a propagation channel of order L may be obtained according to Eq. 14:

C(z)=Σ.sub.l=0.sup.Lh.sub.lz.sup.−1  Eq. 14

[0138] Furthermore, the convolution of the Tx filter 404, the C 405 and the Rx filter may be given by a channel matrix H.

[0139] The transceiver device 300 further comprises the receiver device (Rx) 110 which includes the demodulator 407, the one-tap Equalizer unit 408 and the decision block 409.

[0140] The demodulator 407, perform a demodulation based on constructing a matrix E which is a Vandermonde matrix having a size of K×P. The one-tap equalizer 408 uses a K×K diagonal matrix (for example, it may construct a Vandermonde matrix 111-V and may further perform a demodulation 112-V of a multicarrier modulated signal 102-L based on the Vandermonde matrix 111-V).

[0141] Furthermore, a convolution of the modulation, channel, and demodulation, is given by Eq. 15:

[00016]$\begin{array}{cc}\underset{\underset{E=V_{K\times P}}{︸}}{\left[\begin{array}{cccc}1& {\rho }_0^{-1}& \mathrm{.Math.}& {\rho }_0^{1-P}\\ 1& {\rho }_1^{-1}& \mathrm{.Math.}& {\rho }_1^{1-P}\\ \mathrm{.Math.}& \mathrm{.Math.}& & \mathrm{.Math.}\\ 1& {\rho }_{K-1}^{-1}& \mathrm{.Math.}& {\rho }_{K-1}^{1-P}\end{array}\right]}\underset{\underset{H:P\times K}{︸}}{\left[\begin{array}{ccc}{h}_0& \mathrm{.Math.}& 0\\ \mathrm{.Math.}& \ddots & \mathrm{.Math.}\\ h_L& \ddots & 0\\ 0& \ddots & \mathrm{.Math.}\\ \mathrm{.Math.}& \ddots & h_0\\ \mathrm{.Math.}& \ddots & \mathrm{.Math.}\\ 0& \mathrm{.Math.}& h_L\end{array}\right]}R=\left[\begin{array}{ccc}{\kappa }_{0}C\left({\rho }_0\right)& & \\ & \ddots & \\ & & {\kappa }_{K-1}C\left({\rho }_{K-1}\right)\end{array}\right]& \mathrm{Eq}.15\end{array}$

[0142] Note that, the following operations or conditions may be performed or satisfied.

[0143] This result is true ∀ρ.sub.k.Math.For example, the plurality of signature roots ρ.sub.k may further be determined (e.g., an operation to obtain or determine or choose the plurality of signature roots ρ.sub.k).

[0144] If C(ρ.sub.k)≠0, ∀k.Math.a perfect recovery condition may be satisfied.

[0145] It may be determined, e.g., how to choose the tuning factor (it may be depend on the signature roots) in order to satisfy the transmit power constraint, normalization of the modulator: Trace(R.sup.HR)=K.

[0146] Overall, it may further be determined, how to choose e.g., modify, optimize) the plurality of signature roots in order to boost the system performance (such as minimize the bit error rate (BER)).

[0147] The proposed multicarrier modulation scheme (e.g., the Lagrange-Vandermonde multicarrier modulation scheme presented in FIG. 4) may generalize the conventional ZP-OFDM modulation, and may further satisfy the PR condition. At next, an exemplarily procedure is provided which discusses that this generalization may be achieved while satisfying the transmit power constraint.

[0148] As discussed above, in some embodiments, the plurality of signature roots may be modified (e.g., they may migrate, refined, optimized, or the like). However, if the transceiver device send using K signature roots, the optimization should be carried out over .sup.K where the complexity increases with the K.

[0149] This problem may be solved based on operations performed in the following two steps including step 1 and step 2.

[0150] Step I: choosing the plurality of signature roots.

[0151] For example, the plurality of signature roots (ρ.sub.k) may be uniformly distributed on the circumference of the circle, e.g., uniformly spread over a circle of radius a, such that

[00017]${\rho }_k=a{e}^{\frac{j2\pi k}{K}}.$

[0152] In the embodiment of FIG. 4 in which the transceiver device is based on an LV Modulator, all of the Tx Filters (F.sub.k) may have the same energy and may be normalized by

[00018]${\kappa }_k=\kappa =K\sqrt{\frac{1-a^2}{1-a^{2K}}},\forall k$

and Eq. 16 may further be obtained:

[00019]$\begin{array}{cc}{F}_k\left(z\right)=\kappa \underset{\underset{n\ne k}{n=0}}{\overset{K-1}{.Math.}}\frac{1-{\rho }_n{z}^{-1}}{1-{\rho }_n{\rho }_k^{-1}}=\underset{i=0}{\overset{K-1}{.Math.}}{r}_{k,i}{z}^{-i}=\frac{\kappa }{K}\underset{q=0}{\overset{K-1}{.Math.}}{\rho }_k^q{z}^{-q}& \mathrm{Eq}.16\end{array}$

[0153] Furthermore, The Lagrange matrix R reduces to a Vandermonde, given by Eq. 17:

[00020]$\begin{array}{cc}R=\frac{\kappa }{K}\left[\begin{array}{cccc}1& {\rho }_0& \mathrm{.Math.}& {\rho }_0^{K-1}\\ 1& {\rho }_1& \mathrm{.Math.}& {\rho }_1^{K-1}\\ \mathrm{.Math.}& \mathrm{.Math.}& & \mathrm{.Math.}\\ 1& {\rho }_{K-1}& \mathrm{.Math.}& {\rho }_{K-1}^{K-1}\end{array}\right],& \mathrm{Eq}.17\\ \mathrm{EHR}=\underset{\underset{D}{︸}}{\kappa \left[\begin{array}{ccc}C\left({\rho }_0\right)& & \\ & \ddots & \\ & & C\left({\rho }_{K-1}\right)\end{array}\right]}& \end{array}$

[0154] Note that, when R reduces to a Vandermonde matrix, a low-complex transceiver may be implemented (for example, based on a simple one-tap equalization and no matrix inversion is required as the AMOUR system 1900 in FIG. 19).

[0155] Moreover, if a=1, therefore, the following operation is satisfied:

[00021]$\begin{array}{cc}\frac{\kappa }{K}=\frac{1}{\sqrt{K}},R=F^H\mathrm{and}{E}_{K\times P}=\stackrel{•}{F}=\left[FF\left(:,1\text{:}L\right)\right]& \mathrm{Eq}.18\end{array}$

[0156] From the above operations (e.g., the Eq. 18) it may be determined that the LV modulator (i.e., the Lagnrange-Vandemonde multicarrier modulation scheme of the invention) generalizes the conventional ZP-OFDM multicarrier modulation scheme.

[0157] Furthermore, if a=1 is considered, therefore, D may be the Channel frequency response while satisfying the PR condition.

[0158] Moreover, a procedure for modifying the radius of the circle may be provided. For example, the transceiver device 300 (e.g., its receiver device 100) may modify (e.g., optimize) the radius of the circle, for example, determine the optimal radius as a.sub.opt

[0159] Without loss of generalities, it may be derived that both LV and VL modulators end up with the same optimization metric's expression. In the following, the LV modulator scheme is discussed, while VL modulator may be deduced accordingly.

[0160] Referring to FIG. 4, the received signal (at the input of the demodulator E) may be given by:

[00022]$\begin{array}{cc}y=\frac{1}{K}{\underset{\underset{H}{︸}}{\left[\begin{array}{ccc}{h}_0& \mathrm{.Math.}& 0\\ \mathrm{.Math.}& \ddots & \mathrm{.Math.}\\ h_L& \ddots & 0\\ 0& \ddots & \mathrm{.Math.}\\ \mathrm{.Math.}& \ddots & h_0\\ \mathrm{.Math.}& \ddots & \mathrm{.Math.}\\ 0& \mathrm{.Math.}& h_L\end{array}\right]}\left[\begin{array}{cccc}1& {\rho }_0& \mathrm{.Math.}& {\rho }_0^{K-1}\\ 1& {\rho }_1& \mathrm{.Math.}& {\rho }_1^{K-1}\\ \mathrm{.Math.}& \mathrm{.Math.}& & \mathrm{.Math.}\\ 1& {\rho }_K& \mathrm{.Math.}& {\rho }_{K-1}^{K-1}\end{array}\right]}^T\Omega s+\eta ,& \mathrm{Eq}.19\\ \mathrm{where}\Omega =\left[\begin{array}{ccc}{\kappa }_0& & \\ & \ddots & \\ & & {\kappa }_{K-1}\end{array}\right]& \end{array}$

[0161] Therefore, the demodulated signal is given by:

[00023]$\begin{array}{cc}\tilde{y}=\underset{\underset{E}{︸}}{\left[\begin{array}{cccc}1& {\rho }_o^{-1}& \mathrm{.Math.}& {\rho }_0^{1-P}\\ 1& {\rho }_1^{-1}& \mathrm{.Math.}& {\rho }_1^{1-P}\\ \mathrm{.Math.}& \mathrm{.Math.}& & \\ 1& {\rho }_{K-1}^{-11}& \mathrm{.Math.}& {\rho }_{K-1}^{1-P}\end{array}\right]}y=\underset{\underset{D}{︸}}{\left[\begin{array}{ccc}{\kappa }_{0}C\left({\rho }_0\right)& & \\ & \ddots & \\ & & {\kappa }_{K-1}C\left({\rho }_{K-1}\right)\end{array}\right]}s+\left[\begin{array}{cccc}1& {\rho }_o^{-1}& \mathrm{.Math.}& {\rho }_0^{1-P}\\ 1& {\rho }_1^{-1}& \mathrm{.Math.}& {\rho }_1^{1-P}\\ \mathrm{.Math.}& \mathrm{.Math.}& & \\ 1& {\rho }_{K-1}^{-11}& \mathrm{.Math.}& {\rho }_{K-1}^{1-P}\end{array}\right]\eta & \mathrm{Eq}.2O\end{array}$

[0162] Moreover, the one tap-equalization is given by:

[00024]$\begin{array}{cc}{D}^1\tilde{y}=s+\underset{\underset{u}{︸}}{\left[\begin{array}{ccc}{\kappa }_0^{-1}{C\left({\rho }_0\right)}^{-1}& & \\ & \ddots & \\ & & {\kappa }_{K-1}^{-1}{C\left({\rho }_{K-1}\right)}^{-1}\end{array}\right]}E\eta & \mathrm{Eq}.21\end{array}$

here, it may be determined that, a perfect recovery of s is satisfied.

[0163] In addition, a method, among other, for optimizing the radius “a” is to minimize the mean squared error (MSE) given by Eq. 22 as follow:

MSE=K.sup.−1E[Trace(uu.sup.H)]  Eq. 22

[0164] Moreover, in some embodiments, a uniform power allocation over subcarriers (defined by signature roots) may be used, and by using the same tuning factor

[00025]${\kappa }_k=\kappa =K\sqrt{\frac{1-a^2}{1-a^{2K}}},$

the MSE expression is given by the MSE=K.sup.−1E{u.sup.HU} and according Eq. 23:

[00026]$\begin{array}{cc}\mathrm{MSE}=\frac{{\sigma }_{\eta }^2\left(1-a^{2K}\right)\left(1-a^{2\left(K+L\right)}\right)}{{\sigma }_s^2{K}^3\left(1-a^2\right)\left(1-a^{-2}\right)}\underset{k=0}{\overset{K-1}{.Math.}}{.Math.C\left({\rho }_k\right).Math.}^{-2}& \mathrm{Eq}.23\end{array}$

[0165] Therefore, the a.sub.opt may be determined as

[00027]$a_{\mathrm{opt}}=\arg \underset{a}{\min }\mathrm{MSE}.$

[0166] Additionally, in some embodiments, the power allocation may be optimized, for example, by using different κ.sub.k that minimize the MSE given by Eq. 24 as follow:

[00028]$\begin{array}{cc}{\mathrm{MSE}=\frac{{\sigma }_{\eta }^2\left(1-a^{-2\left(K+L\right)}\right)}{{\sigma }_s^2\left(1-a^{-2}\right)K}\underset{k=0}{\overset{K-1}{.Math.}}{.Math.{\kappa }_k.Math.}^{-2}.Math.C\left({\rho }_k\right).Math.}^{-2}.& \mathrm{Eq}.24\end{array}$

[0167] The x.sub.k=|κ.sub.k|.sup.−1|C(ρ.sub.k)|.sup.−1 may be set, and the problem formulation may be according to Eq. 25 as follow:

[00029]$\begin{array}{cc}\begin{array}{cc}\underset{x}{\mathrm{minimize}}& \underset{k=0}{\overset{K-1}{.Math.}}{x}_k^2\\ \mathrm{subjectto}& \underset{k=0}{\overset{K-1}{.Math.}}\frac{E_0}{{.Math.C\left({\rho }_k\right).Math.}^2{x}_k^2}=K.\end{array}& \mathrm{Eq}.25\end{array}$

[0168] Furthermore, the optimal κ.sub.k and the MSE.sub.min may be given by Eq. 26 and Eq. 27 as:

[00030]$\begin{array}{cc}{\kappa }_k=\sqrt{{K\left(E_0.Math.C\left({\rho }_k\right).Math.\underset{i=0}{\overset{K-1}{.Math.}}{.Math.C\left({\rho }_i\right).Math.}^{-1}\right)}^{-1}},\mathrm{and}& \mathrm{Eq}.26\\ \mathrm{MS}{E}_{\min }=\frac{{\sigma }_{\eta }^2\left(1-a^{-2\left(K+L\right)}\right)\left(1-a^{2K}\right)}{K^4{\sigma }_s^2\left(1-a^{-2}\right)\left(1-a^2\right)}(\underset{k=0}{\overset{K-1}{.Math.}}{.Math.C\left({\rho }_k\right){|}^{-1})}^2& \mathrm{Eq}.27\end{array}$

[0169] Consequently, the a.sub.opt may be determined as

[00031]$a_{opt}=\arg \underset{a}{\min }MSE.$

[0170] Step 2: modifying the plurality of the signature roots

[0171] For example, the signature roots that uniformly spread over a circle of radius a.sub.opt may be used, and an algorithm may further be applied that may optimize the signature roots individually following a specific optimization metric. In particular, a machine learning techniques may be used in this step.

[0172] In the following this step is exemplarily referred to as the “signature roots refinement”. A detailed description of this step is provided, for example, in FIG. 7 and FIG. 12.

[0173] Reference is made to FIG. 5 which is an exemplarily scheme of the transceiver device 300 comprising the transmitter device 100 using a Vandermonde matrix for modulation and the receiver device 110 using a Lagrange matrix for demodulation, according to an embodiment of the invention.

[0174] In the block diagram of the VL modulator of FIG. 5, the transceiver device 300 (i.e., being based on a VL modulator) is exemplarily shown for K signature roots. The transceiver device 300 comprises the transmitter device 100 which includes a precoder 401 and a modulator 402.

[0175] The precoder 401 of the transmitter device 100 may apply the tuning factors κ.sub.k, for example, for allocating the determined transmit power, which may be K×K diagonal matrix (Ω).

[0176] Moreover, the modulator 402 of the transmitter device 100 uses the Vandermonde matrix V (in FIG. 5) of size P×K, where P=K+L. For example, it may construct a Vandermonde matrix 101-V and may further generate a multicarrier modulated signal 102-V based on the Vandermonde matrix 101-V.

[0177] Moreover, the communication channel of the transceiver device 300 comprises the transmitter filter (Tx filter) 404 and the receiver filter (Rx filter) 406 (for example, they may be raised cosine filters). In addition, the parameter C 405 which is a propagation channel of order L may be obtained according to Eq. 28:

C(z)=Σ.sub.l=0.sup.Lh.sub.lz.sup.−1  Eq. 28

[0178] Furthermore, the convolution of the Tx filter 404, the C 405 and the Rx filter may be given by a channel matrix H.

[0179] The transceiver device 300 further comprises the receiver device (Rx) 110 which includes CP removal block 501, the demodulator 407, the one-tap Equalizer unit 408 and the decision block 409.

[0180] The CP removal block 501 may be given by [0.sub.K×L I.sub.K×K] where I.sub.K×K is the identity matrix.

[0181] The demodulator 407, perform a demodulation based on constructing a matrix L which is a Lagrange matrix of size K×K. For example, it may construct a Lagrange matrix 111-L and may further perform a demodulation 112-L of a multicarrier modulated signal 102-V based on the a Lagrange matrix 111-L.

[0182] The one-tap equalizer 408 uses a K×K diagonal matrix, and its output is provided to the decision block 409.

[0183] Furthermore, a convolution of the modulation, channel, and demodulation, is given by Eq. 29:

[00032]$\begin{array}{cc}\underset{\underset{L:K\times K}{︸}}{\left[\begin{array}{cccc}{r}_{\kappa -1,0}& r_{\kappa -2,0}& \mathrm{.Math.}& r_{0,0}\\ r_{\kappa -1,1}& r_{\kappa -2,1}& \mathrm{.Math.}& r_{0,1}\\ \mathrm{.Math.}& \mathrm{.Math.}& \mathrm{.Math.}& \mathrm{.Math.}\\ r_{\kappa -1,K-1}& r_{\kappa -2,K-1}& \mathrm{.Math.}& r_{0,K-1}\end{array}\right]}\underset{\underset{\left[0_{K\times L}I\right]H:K\times P}{︸}}{\left[\begin{array}{cccccc}{h}_L& \mathrm{.Math.}& h_0& 0& \mathrm{.Math.}& 0\\ 0& \ddots & \ddots & \ddots & & \mathrm{.Math.}\\ \mathrm{.Math.}& \ddots & \ddots & \ddots & \ddots & 0\\ 0& \mathrm{.Math.}& 0& h_L& \mathrm{.Math.}& h_0\end{array}\right]}\underset{\underset{V:P\times K}{︸}}{\left[\begin{array}{cccc}{\rho }_0^{1-P}& {\rho }_1^{1-P}& \mathrm{.Math.}& {\rho }_{K-1}^{1-P}\\ {\rho }_0^{2-P}& {\rho }^{2-P}& \mathrm{.Math.}& {\rho }_{K-1}^{2-P}\\ \mathrm{.Math.}& \mathrm{.Math.}& \mathrm{.Math.}& \mathrm{.Math.}\\ 1& 1& 1& 1\end{array}\right]}=\left[\begin{array}{ccc}C\left({\rho }_0\right)& & \\ & \ddots & \\ & & C\left({\rho }_{K-1}\right)\end{array}\right]& \mathrm{Eq}.29\end{array}$

[0184] Note that, the following operations or conditions may be performed or satisfied. This result is true ∀ρ.sub.k.Math.For example, the plurality of signature roots ρ.sub.k may further be determined (e.g., an operation to obtain or determine or choose the plurality of signature roots ρ.sub.k).

[0185] If C(ρ.sub.k)≠0, ∀k.Math.a perfect recovery condition may be satisfied.

[0186] It may be determined, e.g., how to choose the tuning factor (it may be depend on the signature roots) in order to satisfy the transmit power constraint, normalization of the modulator: Trace(V.sup.HV)=K.

[0187] Overall, it may further be determined, how to choose e.g., modify, optimize) the plurality of signature roots in order to boost the system performance (such as minimize the bit error rate (BER)).

[0188] The proposed multicarrier modulation scheme (e.g., the Vandermonde-Lagrange multicarrier modulation scheme presented in FIG. 5) may generalize the conventional CP-OFDM modulation scheme, and may further satisfy the PR condition.

[0189] As discussed above, the plurality of signature roots may be modified. However, if sending using K signature roots, the modification (e.g., optimization) may be carried out over .sup.K where the complexity increases with K.

[0190] This problem may be solved based on operations performed in the following two steps including step 1 and step 2:

[0191] Step I: choosing the plurality of signature roots.

[0192] For example, the plurality of signature roots (ρ.sub.k) may be uniformly distributed on the circumference of the circle, e.g., uniformly spread over a circle of radius a, such that

[00033]${\rho }_k=a{e}^{\frac{j2\pi k}{K}}.$

[0193] In the embodiment of FIG. 5 in which the transceiver device is based on a VL Modulator, a Lagrange basis polynomials may be used at the receiver device, given by Eq. 30:

[00034]$\begin{array}{cc}{F}_k\left(z\right)=\frac{\kappa }{K}\underset{q=0}{\overset{K-1}{.Math.}}{\rho }_k^q{z}^{-q},\mathrm{where}\kappa =K\sqrt{\frac{1-a^2}{1-a^{2K}}}\mathrm{tuning}\mathrm{factor}& \mathrm{Eq}.30\end{array}$

[0194] Moreover, the Lagrange matrix L reduces to a Vandermonde, given by Eq. 31:

[00035]$\begin{array}{cc}L=\frac{\kappa }{K}\left[\begin{array}{cccc}{\rho }_0^{K-1}& {\rho }_0^{K-2}& \mathrm{.Math.}& 1\\ {\rho }_1^{K-1}& {\rho }_1^{K-2}& \mathrm{.Math.}& 1\\ \mathrm{.Math.}& \mathrm{.Math.}& \mathrm{.Math.}& \mathrm{.Math.}\\ {\rho }_{K-1}^{K-1}& {\rho }_{K-1}^{K-2}& \mathrm{.Math.}& 1\end{array}\right],L\underset{\underset{\mathrm{after}\mathrm{CP}\mathrm{Rem}}{︸}}{V\left(L+1\text{:}P,\text{:}\right)}=\kappa I,D={\kappa }_F\underset{\underset{\mathrm{Freq}.\mathrm{response}\mathrm{of}\mathrm{the}\mathrm{channel}}{︸}}{\left[\begin{array}{ccc}C\left({\rho }_0\right)& & \\ & \ddots & \\ & & C\left({\rho }_{K-1}\right)\end{array}\right]}& \mathrm{Eq}.31\end{array}$

[0195] Note that,

[00036]$a.Math.V=\underset{\underset{\mathrm{CP}\mathrm{add}}{︸}}{\left[0I_L;I_K\right]}{F}^H$

and L=F.

[0196] From the above operations it may be determined that the VL modulator (i.e., the Vandemonde-Lagnrange multicarrier modulation scheme of the invention) generalizes the conventional CP-OFDM multicarrier modulation scheme.

[0197] Similar to the embodiment of FIG. 4 (i.e., being based on the LV modulator), it may be derived that both LV and VL modulators end up with the same optimization metric's expression. A repeated derivation of equations for the VL modulator is omitted, as it can be derived by the skilled person.

[0198] Step 2: modifying the plurality of the signature roots

[0199] For example, the signature roots that uniformly spread over a circle of radius a.sub.opt may be used, and an algorithm may further be applied that may optimize the signature roots individually following a specific optimization metric. In particular, a machine learning techniques may be used in this step.

[0200] In the following this step is exemplarily referred to as the “signature roots refinement”. A detailed description of this step is provided, e.g., in FIG. 7 and FIG. 12.

[0201] Reference is made to FIG. 6 which is a schematic view for signaling exchange indicating a radius a.sub.opt of a circle.

[0202] The present invention may provide (e.g., identify and propose) a new waveform that may satisfy the perfect recovery condition while keeping a low complex transceiver implementation. Without limiting the present invention, the signaling exchange indicating the radius of the circle is exemplarily discussed for a transceiver device 300 being based on a transceiver device 300 comprising a transmitter device 100 using a Lagrange matrix 101-L for modulation 102-L and a receiver device 110 using a Vandermonde matrix 111-V for demodulation 112-V. However, such a signaling exchange for a transceiver device 300 being based on a VL modulator can also be deduced accordingly and a repeated description (i.e., for a transceiver being based on a VL modulator) is omitted, since the VL modulator will follow same steps.

[0203] Step I: choosing the plurality of signature roots.

[0204] For example, the plurality of signature roots (ρ.sub.k) may be uniformly distributed on the circumference of the circle, e.g., uniformly spread over a circle of radius a, such that

[00037]${\rho }_k=a{e}^{\frac{j2\pi k}{K}}.$

[0205] In the signalling exchange the following three operations may be performed.

[0206] 1. For example, an optimization block 602 is provided that needs the channel state information (can be obtained from the channel estimation unit 601) in order to compute the optimization metric (e.g., the MSE detailed above), and it may further compute the a.sub.opt.

[0207] 2. Moreover, a signalling may be sent to feedback a.sub.opt to the transmitter device 100 which may be required for the modulator 402 and the precoder block 401.

[0208] 3. Furthermore, the receiver device 110 may use the a.sub.opt to compute the demodulation matrix.

[0209] In some embodiments of the invention, the above mentioned step 1 (i.e., Step I: choosing the plurality of signature roots) may only be performed (i.e., the above step may be enough).

[0210] Moreover, in some embodiments, (e.g., depending on the use case), the above mentioned step 2 (i.e., Step 2: modifying the plurality of the signature roots) may further be performed, which is exemplarily discussed, e.g., in FIG. 7 and FIG. 12.

[0211] Reference is made to FIG. 7 which is a schematic view for signaling exchange indicating the signature root refinement.

[0212] Without the limiting the present invention, the signaling exchange indicating the signature root refinement is exemplarily discussed for a transceiver device 300 being based on a transceiver device 300 comprising a transmitter device 100 using a Lagrange matrix 101-L for modulation 102-L and a receiver device 110 using a Vandermonde matrix 111-V for demodulation 112-V. However, such a signaling exchange for a transceiver device 300 being based on a VL modulator can also be deduced accordingly and a repeated description (i.e., for a transceiver being based on a VL modulator) is omitted, since the VL modulator will follow same steps.

[0213] Step 2: modifying the plurality of the signature roots

[0214] For example, the signature roots that uniformly spread over a circle of radius a.sub.opt may be used, and an algorithm may further be applied that may optimize the signature roots individually following a specific optimization metric. In particular, a machine learning techniques may be used in this step. FIG. 7 illustrates the signalling exchange corresponding to the Step 2.

[0215] For the signalling exchange of the signature roots refinement, the following operations may be performed.

[0216] 1. The optimization block 602 that needs the channel state information (which may be obtained using the channel estimation unit 601) in order to compute the optimization metric (for instance, the MSE detailed above) and it may further compute the a.sub.opt.

[0217] 2. Moreover, a refinement block 603 (for example, it may use a refinement algorithm) that needs to refine the signature roots individually following a specific optimization method and using a specific metric.

[0218] 3. In addition, a signal may be sent, in order to feedback the modified signature roots ρ (vector of K complex values) to the transmitter device 100 which may be necessary for the modulator 402 and the precoder block 401.

[0219] 4. Furthermore, the receiver device 100 may use the modified plurality of signature roots ρ to compute the demodulation matrix.

[0220] References are made from FIG. 8a and FIG. 8b which illustrate two exemplarily channel realization.

[0221] At a first step, the signature roots may be obtained (e.g., determined, generated) such that they are uniformly spread over a circle of radius a, for example, according to

[00038]${\rho }_k=a{e}^{\frac{j2\pi k}{K}}.$

The significance of a.sub.opt and its impact on the overall system performance is exemplarily described.

Channel realization1:C(z)=1+z.sup.−4

Channel realization 2:C(z)=1−z+z.sup.−4

[0222] Furthermore, considering the optimization metric, the MSE (by using a uniform power allocation, therefore, same κ over the subcarriers may be applied).

[0223] In the example of channel realization 1 which is illustrated in FIG. 8a, the optimum radius is 1.1 (i.e., a.sub.opt=1.1). Note that, if using the ZP-OFDM (a=1), the signal cannot be efficiently recovered since

[00039]${\mathrm{SNR}}_{eq}=\frac{1}{MSE}$

is almost 0 (see FIG. 8a).

[0224] However, in the example of channel realization 2 which is illustrated in FIG. 8b, the best choice is when the radius is equal to 1, then the LV scheme reduces to the ZP-OFDM.

[0225] In the following, the performance results are presented, in terms of BER as a function of the signal-to-noise ratio (SNR).

[0226] References are made from FIG. 9a and FIG. 9b which illustrate the performance results for a uniform and an optimized power allocation at the transmitter device based on a frequency selective channels with uniform (FIG. 9a) and exponential power delay profile (FIG. 9 b).

[0227] When using K=32 subcarriers, the channel spread L of 4 (i.e., L=4), and further carrying out the performance where the transmitter device uses the uniform and the optimized power allocation (for example, a precoder with different tuning factors) and assuming the frequency selective channels with uniform (e.g., FIG. 9a) and exponential power delay profile (pdp) (e.g., FIG. 9 b).

[0228] With reference to FIG. 9a (the uniform pdp) and FIG. 9b (Exponential pdp with factor α=0.2), it can be derived that, both of the LV scheme (represented by the dashed curves) including for the LV (uniform power allocation) and the LV (optimized power allocation) (e.g., always) outperforms the ZP-OFDM schemes (represented by the solid lines).

[0229] Moreover, the performance of both schemes increases when using the optimal power allocation.

[0230] FIG. 8a, FIG. 8b, FIG. 9a and FIG. 9b have been depicted using perfect channel state information (CSI) at the receiver device. In the following, the performance results are shown using imperfect CSI at the receiver device (i.e., channel estimation errors). Without limiting the present invention, the performance results (i.e., FIG. 10a and FIG. 10b) are presented for the frequency selective channels using uniform power delay profile.

[0231] References are made from FIG. 10a and FIG. 10b which illustrate comparison of performance results under perfect and imperfect CSI, when the transmitter device is using uniform power allocation (FIG. 10a), and when the transmitter device is using optimal power allocation (FIG. 10b).

[0232] As can be derived from FIG. 10a and FIG. 10b, the LV modulation scheme outperforms the ZP-OFDM under the imperfect CSI conditions. This result also illustrates the robustness of the present invention to the channel conditions.

[0233] As discussed, in some embodiments, the signature roots may be modified (e.g., refined, migrated, optimized, etc.). For example, the “Step 2: modifying the plurality of the signature roots may be performed”.

[0234] References are made from FIG. 11a and FIG. 11b which illustrate determining the radius of the circle (FIG. 11a) and further determining the signature roots using the radius of the circle (FIG. 11b).

[0235] For example, the Gradient descent algorithm may be used in order to perform the individual signature roots optimization (i.e., modifying the signature root). For instance, at first, the radius of the circle a.sub.opt may be used (i.e., which has been provided by Step 1) and considering the K=16 and the L=4 (e.g., the results given by Step 1). The determined radius of the circle in FIG. 11a may be used and the plurality of the signature roots may further be obtained (e.g., determined, generated, etc.), as it is illustrated in FIG. 11b.

[0236] Moreover, the plurality of the signature roots represented in FIG. 11b may further be modified (e.g., refined) using Gradient Descent algorithm (GDA). The results of signature roots refinement (using Step 2) are depicted in FIG. 12a and FIG. 12b, for the same channel realization.

[0237] FIG. 12a shows the plurality of signature roots migrating toward new positions, and FIG. 12b shows the MSE decreasing with the GDA iterations.

[0238] As it can be derived from FIG. 12b, the MSE degrades while the GDA algorithm is optimizing the plurality of the signature roots positions from an iteration to another.

[0239] FIG. 13 shows the overall performance of the LV modulator of the invention compared to the conventional ZP-OFDM performance.

[0240] The comparison of the performance is performed based on considering K=32, L=4, and using frequency selective channel following a uniform pdp (the results can be derived for a more general channel). Moreover, the comparison of performance results is performed using Step 1 only, and step 1 along with the Step 2 (which uses Step 1 as an intermediate results).

[0241] A performance gain of 5 dB at 10.sup.−5 may be obtained (using Step 1 with optimized power allocation)

[0242] 2 dB additional gains may be obtained when using Step 2, signature roots refinement.

[0243] LV multicarrier modulation scheme of the present invention outperforms the ZP-OFDM.

[0244] FIG. 14 shows a method 1400 according to an embodiment of the invention for being implemented at a transmitter device 100. The method 1400 may be carried out by the transmitter device 100, as it described above.

[0245] The method 1400 comprises a step 1401 of obtaining a plurality of signature roots ρ.sub.k based on receiving a feedback message 11 from a receiver device 110, wherein each signature root is a nonzero complex point.

[0246] The method 1400 further comprises a step 1402 of constructing a Lagrange matrix 101-L or a Vandermonde matrix 101-V from the plurality of signature roots ρ.sub.k.

[0247] The method 1400 further comprises a step 1403 of generating a multicarrier modulated signal 102-L, 102-V based on the Lagrange matrix 101-L or the Vandermonde matrix 101-V.

[0248] FIG. 15 shows a method 1500 according to an embodiment of the invention for being implemented at a receiver device 110. The method 1500 may be carried out by the receiver device 110, as it described above.

[0249] The method 1500 comprises a step 1501 of determining a plurality of signature roots ρ.sub.k, wherein each signature root is a nonzero complex point;

[0250] The method 1500 further comprises a step 1502 of constructing a Lagrange matrix 111-L or a Vandermonde matrix 111-V from the plurality of signature roots ρ.sub.k.

[0251] The method 1500 further comprises a step 1503 of performing a demodulation 112-L, 112-V of a multicarrier modulated signal 102-V, 102-L based on the Lagrange matrix 111-L or the Vandermonde matrix 111-V.

[0252] FIG. 16 shows a method 1600 according to an embodiment of the invention for being implemented at a transceiver device 300. The method 1600 may be carried out by the transceiver device 300, as it described above.

[0253] The method 1600 comprises a step 1601 of generating, at a transmitter device 100, a multicarrier modulated signal 102-L, 102-V based on constructing a Lagrange matrix 101-L or a Vandermonde matrix 101-V.

[0254] The method 1600 further comprises a step 1602 of performing, at a receiver device 110, a demodulation 112-V, 112, L of the multicarrier modulated signal 102-L, 102-V based on constructing the other matrix 111-V, 111-L from the Lagrange matrix or the Vandermonde matrix constructed by the transmitter device 100.

[0255] The present invention has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed invention, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation.