Orthogonal time frequency space modulation techniques
Orthogonal Time Frequency Space (OTFS) is a novel modulation scheme with significant benefits for 5G systems. The fundamental theory behind OTFS is presented in this paper as well as its benefits. We start with a mathematical description of the doubly fading delay-Doppler channel and develop a modulation that is tailored to this channel. We model the time varying delay-Doppler channel in the time-frequency domain and derive a new domain (the OTFS domain) where we show that the channel is transformed to a time invariant one and all symbols see the same SNR. We explore aspects of the modulation like delay and Doppler resolution, and address design and implementation issues like multiplexing multiple users and evaluating complexity. Finally we present some performance results where we demonstrate the superiority of OTFS.
1. A wireless communication method, comprising:
receiving multiple data streams, each data stream representing data for a separate user equipment;
generating information symbols by multiplexing the multiple data streams;
modulating the information symbols onto one of a set of two dimensional (2D) orthogonal basis functions that span at least a portion of bandwidth and time duration of an orthogonal time frequency space, OTFS, frame, wherein the set of 2D orthogonal basis functions comprises OTFS basis functions defined along a delay dimension and a Doppler dimension; and
further processing and transmitting the transmission burst.
2. The method of claim 1 , wherein the modulating operation includes performing at least one of a quadrature amplitude modulation (QAM) and a quadrature phase shift keying (QPSK) modulation.
3. The method of claim 1 , wherein the transmitting the transmission burst includes transmitting the transmission burst using an orthogonal frequency division multiplexing (OFDM) physical layer.
4. The method of claim 1 , wherein the modulating includes giving different ones of the set of 2D orthogonal basis functions within the OTFS frame to each user equipment to achieve multiplexing of the multiple data streams.
5. The method of claim 1 , wherein the modulating each of the information symbols includes:
applying window functions to the set of 2D orthogonal basis functions to generate windowed basis functions; and
modulating each of the information symbols using a corresponding windowed basis functions.
6. The method of claim 1 , wherein the modulating the information symbols includes:
placing each information symbol on a grid along the delay dimension and the Doppler dimension;
multiplying, using a symplectic Fourier Transform, each information symbol with a corresponding 2D orthogonal basis function; and
superpositioning results of the multiplying operation for the information symbols.
7. A wireless communication apparatus, comprising a processor configured for:
receiving multiple data streams, each data stream representing data for a separate user equipment;
generating information symbols by multiplexing the multiple data streams;
modulating the information symbols onto one of a set of two dimensional (2D) orthogonal basis functions that span at least a portion of bandwidth and time duration of a transmission burst, wherein the set of 2D orthogonal basis functions comprises OTFS basis functions defined along a delay dimension and a Doppler dimension; and
further processing and transmitting the transmission burst.
8. The apparatus of claim 7 , wherein the module for modulating includes a module for performing at least one of a quadrature amplitude modulation (QAM) and a quadrature phase shift keying (QPSK) modulation.
9. The apparatus of claim 7 , wherein the module for further processing and transmitting the transmission burst includes a module for processing transmitting the transmission burst using an orthogonal frequency division multiplexing (OFDM) physical layer.
10. The apparatus of claim 7 , wherein the processor is further configured to performing the modulating by:
placing each information symbol on a grid along the delay dimension and the Doppler dimension;
multiplying, using a symplectic Fourier Transform, each information symbol with a corresponding 2D orthogonal basis function; and
superpositioning results of the multiplying operation for the information symbols.
11. A wireless communication method, implemented at a user equipment, comprising:
receiving and processing an orthogonal time frequency space, OTFS, frame that includes information symbols for multiple user equipment that are multiplexed using a multiplexing scheme;
recovering, from the OTFS frame, information symbols based on one of a set of two dimensional (2D) orthogonal basis functions that span a portion of the bandwidth and time duration of the OTFS frame, wherein the set of 2D orthogonal basis functions comprises OTFS basis functions defined along a delay dimension and a Doppler dimension; and
recovering information bits by demodulating the information symbols.
12. The method of claim 11 , wherein the demodulating operation includes performing at least one of a quadrature amplitude modulation (QAM) demodulation and a quadrature phase shift keying (QPSK) demodulation.
13. The method of claim 11 , wherein the receiving the transmission burst includes receiving the transmission burst using an orthogonal frequency division multiplexing (OFDM) physical layer.
14. The method of claim 11 , wherein the demodulating includes:
performing a matched filtering operation on a portion of the OTFS frame assigned to the user equipment, followed by a symplectic fast Fourier transform operation to generate time-frequency samples of the information symbols.
15. A wireless communication apparatus, comprising a processor, wherein the processor is configured for:
receiving and processing a transmission packet that includes information symbols for multiple user equipment that are multiplexed using a multiplexing scheme;
recovering, from the transmission packet information symbols based on one of a set of two dimensional (2D) orthogonal basis functions that span at least a portion of the bandwidth and time duration of a transmission burst, wherein the set of 2D orthogonal basis functions comprises OTFS basis functions defined along a delay dimension and a Doppler dimension; and
recovering information bits by demodulating the information symbols.
16. The apparatus of claim 15 , wherein the set of orthogonal basis functions comprise orthogonal time frequency space (OTFS) transform.
17. The apparatus of claim 15 , wherein the processor is further configured for demodulating by performing at least one of a quadrature amplitude modulation (QAM) demodulation and a quadrature phase shift keying (QPSK) demodulation.
18. The apparatus of claim 15 , wherein the processor is further configured for receiving the transmission burst using an orthogonal frequency division multiplexing (OFDM) physical layer.
19. The apparatus of claim 15 , wherein the processor is further configured for demodulating by performing a matched filtering operation on a portion of the OTFS frame assigned to the user equipment, followed by a symplectic fast Fourier transform operation to generate time-frequency samples of the information symbols.