Multi-carrier connection design via intelligent exploitation of multi-user diversity in delay-doppler domain

Abstract

Disclosed is a multicarrier (MC) connection design via an intelligent exploitation of the multi-user diversity in delay-Doppler domain. Overall, the technology can play a key role as an enabler technology toward 5G and beyond communications systems with applications of NR-Lite, mMTC, eMBB, URLLC and SURLLC.

Claims

1. A method for a multicarrier connection design in a system with a single orthogonal time frequency space (OTFS) with active users that are served by one base station in a downlink transmission and in which a scheduling of user equipments is organized on a slot-by-slot basis, a queue of packets being stored at the base station for each user equipment of the user equipments, the method comprising: employing an algorithm having an objective function of max(Pu), u[1, 2, 3, . . . , Nu], wherein Nu is a number of the user equipments and Pu is a number of channel taps of a given user equipment, the algorithm assigning priority for transmission to the user equipment with a maximum number of channel taps; applying an inverse symplectic Fast Fourier Transform (ISFFT) to data symbols selected by the algorithm, wherein the ISFFT converts the selected data symbols into a time-frequency domain by applying an N-point inverse Fast Fourier Transform (IFFT) to rows of the selected data symbols and applying an M-point FFT to columns of the selected data symbols; performing a Heisenberg transform to the converted data symbols by using an M-point inverse Fast Fourier Transform over the time-frequency data symbols; adding a cyclic prefix of a length L to the Heisenberg transformed converted data symbols, where L is a number of channel paths to a transmission of an OTFS signal; removing the cyclic prefix after receiving the transmitted OTFS signal; preforming a Wigner transform to the cyclic prefix removed transmitted OTFS signal to recover a time-frequency representation of the received cyclic prefix removed transmitted OTFS signal; performing a symplectic Fast Fourier Transform to the received cyclic prefix removed transmitted OTFS signals so as to move the received signals into a delay-Doppler domain; and mapping the delay-Doppler domain received signals into received data symbols after performing channel equalization.

2. The method of claim 1, wherein the method is used in a wireless system.

Description

EXPLANATION OF FIGURES

(1) FIG. 1: Scheme showing Invention for Multi-user OTFS system in downlink transmission P.sub.1: The number of channel taps for the UE number 1 P.sub.2: The number of channel taps for the UE number 2 P.sub.Nu: The number of channel taps for the UE number N.sub.u H.sub.1[k,l]: The channel gain for the UE number 1 in delay-Doppler grid with indices k,l h.sub.2[k,l]: The channel gain for the UE number 2 in delay-Doppler grid with indices k,l h.sub.Nu[k,l]: The channel gain for the UE number N.sub.u in delay-Doppler grid with indices k,l

(2) FIG. 2: Block diagram of the proposed design for OTFS system in doubly dispersive channel A: Time-frequency domain B: Delay-Doppler domain 201: ISFFT 202: Heisenberg Transform 203: Wireless channel 204: Wigner transform 205: SFFT x[k,l]: k,l-th element of X s[n,m]: transmitted signal in time-frequency domain x(t): transmitted signal in time domain y(t): received signal in time domain r[n,m]: received signal in time-frequency domain y[k,l]: received signal in delay-Doppler domain

DETAILED DESCRIPTION OF THE INVENTION

(3) As mentioned above, the invention relates to a method for a multicarrier (MC) connection design via an intelligent exploitation of the multi-user diversity in delay-Doppler domain, in a system with a single OTFS cell with N.sub.u active users that are served by one base station (BS) in downlink transmission and the scheduling of the user equipment (UEs) is organized on a slot-by-slot basis, where a queue of packets is stored at the BS for each Ues wherein said method comprises the steps of; i. Employing an algorithm with the objective function given as
max(Pu),u[1,2,3, . . . ,Nu], where Nu is the number of the UEs and wherein the algorithm gives priority for transmission to the UE with the maximum number of channel taps, herein P.sub.1 is the number of channel taps of a given user, ii. Applying inverse symplectic fast fourier transform (ISFFT), iii. Converting the data symbols to time-frequency domain through applying N-point inverse Fast Fourier Transform (IFFT) and M-point FFT operation over the rows and columns of X, respectively, iv. Performing Heisenberg transform by using M-point IFFT over time-frequency data symbols v. Adding a cyclic prefix (CP) of L length in order to mitigate the inter-symbol interference between the OTFS signals where L denotes the number of channel paths, wherein after the transmission the OTFS signal undergoes the time-varying wireless channel vi. Removing the CP at the receiver side to recover the transmitted signal, vii. Performing Wigner transform to recover the time-frequency representation of the signal viii. Performing SFFT operation to get the received signal in the delay-Doppler domain ix. Mapping the received symbols to data information after performing channel equalization.

(4) Herein within the method of the invention, the inventors provide a novel scheduling algorithm for multi-user with orthogonal time frequency space (OTFS) signaling that assigns the radio resources to the users with the largest channel diversity in accordance with the user's demands.

(5) For the application of the method of invention a single OTFS cell with multi active users (N.sub.u) that perform communication with one base station in downlink transmission is considered.

(6) In the method of the invention, the proposed algorithm in step (i) gives priority for transmission to the UE with the maximum number of channel taps.

(7) In a preferred embodiment of the invention, for the method of the invention, a system of single antennas at both the transmitter (Tx) and the receiver (Rx) is considered.

(8) The system frame consists of N number of symbols and M number of subcarriers with T symbol duration and f subcarrier spacing (SCS), respectively. Therefore, the OTFS frame occupies a total bandwidth of B=Mf with a frame duration of T.sub.f=TN. The data in delay-Doppler domain is given by x[k,l] with k and 1 index representing Doppler and delay, respectively. FIG. 2 illustrates the block diagram of OTFS frame for the invention.

(9) In the method of the invention, Heisenberg transformation is performed in step (iv) to generate the time domain OTFS signal.

(10) Also, a cyclic prefix (CP) of L length is added in step (v) to mitigate the intersymbol interference between the OTFS signals where L denotes the number of channel paths.

EXAMPLES

Example 1: Application of the Method According to Present Invention

(11) A. In this patent, we consider a single OTFS cell with Nu active users that are served by one base station in downlink transmission, as illustrated in FIG. 1. The scheduling of the UEs is organized on a slot-by-slot basis, where a queue of packets is stored at the BS for each UE. In this invention, we propose an algorithm that gives priority for transmission to the UE with the maximum number of channel taps, which is given as follows
max(P.sub.u),u[1,2,3, . . . ,N.sub.u], where P.sub.u is the number of channel taps of a given user. B. Regarding the system design, we consider a system model with single antennas at transmitter (Tx) and receiver (Rx), where FIG. 1 shows the block diagram of OTFS systems. The system frame consists of N number of symbols and M number of subcarriers with T symbol duration and f subcarrier spacing (SCS), respectively. Therefore, the OTFS frame occupies a total bandwidth of B=Mf with a frame duration of T.sub.f=TN. The data in delay-Doppler domain is given by x[k,l] with k and 1 index representing Doppler and delay, respectively. C. After we apply Inverse Symplectic Fast Fourier Transform (ISFFT), we convert the data symbols to time-frequency domain. Accordingly, we apply N-point inverse Fast Fourier Transform (IFFT) and M-point FFT operation over the rows and columns of X, respectively. Note that k,l-th element of X is x[k,l]. D. To generate the time domain OTFS signal, we perform Heisenberg Transform by using M-point IFFT over time-frequency data symbols. We add a cyclic prefix (CP) of L length in order to mitigate the inter-symbol interference between the OTFS signals where L denotes the number of channel paths. After the transmission, the OTFS signal undergoes the time-varying wireless channel. E. At the receiver side, first we remove the CP to recover the transmitted signal. Later, we perform the Wigner transform to recover the time-frequency representation of the received signal. Following that, we perform SFFT operation to get the received signal in the delay-Doppler domain. After the equalization process, we map the received symbols to data information.

INDUSTRIAL APPLICABILITY OF THE INVENTION

(12) The invention is applicable to industrialization, and it represents an algorithm that can be applied to any signal performing transmission in delay-Doppler domain to exploit multi-user diversity.

(13) The method of the invention aims to design multi-carrier (MC) connection via an intelligent exploitation of the multi-user diversity in delay-Doppler domain and therefore this technology can play a key role as an enabler technology toward 5G and beyond communications systems with applications of NR-Lite, mMTC, eMBB, URLLC and SURLLC

(14) Around these basic concepts, it is possible to develop several embodiments regarding the subject matter of the invention; therefore, the invention cannot be limited to the examples disclosed herein, and the invention is essentially as defined in the claims. Separate embodiments of the invention can be combined where appropriate.

(15) It is obvious that a person skilled in the art can convey the novelty of the invention using similar embodiments and/or that such embodiments can be applied to other fields similar to those used in the related art. Therefore, it is also obvious that these kinds of embodiments are void of the novelty criteria and the criteria of exceeding the known state of the art.