Receiver-side processing of orthogonal time frequency space modulated signals
Wireless communication techniques for transmitting and receiving reference signals is described. The reference signals may include pilot signals that are transmitted using transmission resources that are separate from data transmission resources. Pilot signals are continuously transmitted from a base station to user equipment being served. Pilot signals are generated from delay-Doppler domain signals that are processed to obtain time-frequency signals that occupy a two-dimensional lattice in the time frequency domain that is non-overlapping with a lattice corresponding to data signal transmissions.
1. A method for wireless communication, comprising:
receiving, by a wireless communication receiver, a wireless signal comprising information bits that are modulated using an orthogonal time frequency and space (OTFS) modulation scheme;
generating a baseband signal from the wireless signal;
generating digital samples that correspond to an output of applying a discrete Symplectic Fourier transform or an inverse discrete Symplectic Fourier transform to the baseband signal;
performing a linear equalization of the digital samples resulting in an equalized signal;
producing a decision feedback equalizer (DFE) output signal by inputting the equalized signal to a DFE comprising a feedforward filter and a feedback filter, wherein the feedforward filter is implemented in a time-frequency domain and the feedback filter is implemented in the delay-time domain;
extracting symbol estimates from the DFE output signal in a delay-Doppler domain; and
recovering the information bits from the symbol estimates.
2. The method of claim 1 , wherein the generating the baseband signal comprises:
down-converting the wireless signal from a radio frequency signal to generate the baseband signal.
3. The method of claim 2 , further comprising:
applying automatic gain control (AGC) to the baseband signal to generate a gain-corrected baseband signal.
4. The method of claim 3 , further comprising:
converting the gain-corrected baseband signal from an analog domain to the digital samples in the time-frequency domain.
5. The method of claim 1 , wherein the performing the linear equalization comprises performing the linear equalization to minimize a mean square error of an error criterion.
6. The method of claim 1 , wherein the equalized signal comprises inter-symbol-interference (ISI), and wherein the DFE output signal suppresses the ISI.
7. The method of claim 1 , wherein the producing the DFE output signal comprises performing a multi-input multi-output (MIMO) decision feedback equalization (DFE) to produce the DFE output signal.
8. The method of claim 1 , the producing the DFE output signal comprises
performing a multi-input multi-output (MIMO) decision feedback equalization (DFE) using successive interference cancellation (SIC) to produce the DFE output signal.
9. An apparatus for wireless communication, comprising:
a receiver configured to receive a wireless signal comprising information bits that are modulated using an orthogonal time frequency and space (OTFS) modulation scheme; and
a processor, coupled to the receiver, configured to:
generate a baseband signal from the wireless signal;
generate digital samples that correspond to an output of applying a discrete Symplectic Fourier transform or an inverse discrete Symplectic Fourier transform to the baseband signal;
perform a linear equalization of the digital samples resulting in an equalized signal;
produce a decision feedback equalizer (DFE) output signal by inputting the equalized signal to a DFE comprising a feedforward filter and a feedback filter, wherein the feedforward filter is implemented in a time-frequency domain and the feedback filter is implemented in the delay-time domain;
extract symbol estimates from the DFE output signal in a delay-Doppler domain; and
recover the information bits from the symbol estimates.
10. The apparatus of claim 9 , wherein the processor is further configured, as part of generating the baseband signal, to:
down-convert the wireless signal from a radio frequency signal to generate the baseband signal.
11. The apparatus of claim 10 , wherein the processor is further configured to:
apply automatic gain control (AGC) to the baseband signal to generate a gain-corrected baseband signal.
12. The apparatus of claim 9 , wherein performing the linear equalization comprises performing the linear equalization to minimize a mean square error of an error criterion.
13. The apparatus of claim 9 , wherein the performing the linear equalization includes performing Wiener filtering of the digital samples.
14. The apparatus of claim 9 , wherein the equalized signal comprises inter-symbol-interference (ISI), and wherein the DFE output signal suppresses the ISI.
15. A method for wireless communication, comprising:
receiving, by a wireless communication receiver, a wireless signal comprising information bits that are modulated using an orthogonal time frequency and space (OTFS) modulation scheme;
generating a baseband signal from the wireless signal;
generating digital samples that correspond to an output of applying a two-dimensional windowing function to the baseband signal;
performing a linear equalization of the digital samples resulting in an equalized signal;
producing a decision feedback equalizer (DFE) output signal by inputting the equalized signal to a DFE comprising a feedforward filter and a feedback filter, wherein the feedforward filter is implemented in a time-frequency domain and the feedback filter is implemented in the delay-time domain;
extracting symbol estimates from the DFE output signal in a delay-Doppler domain; and
recovering the information bits from the symbol estimates.
16. The method of claim 15 , wherein the two-dimensional windowing function is applied over a grid in the time-frequency domain.
17. The method of claim 15 , wherein the performing the linear equalization comprises performing the linear equalization to minimize a mean square error of an error criterion.
18. The method of claim 15 , wherein the equalized signal comprises inter-symbol-interference (ISI), and wherein the DFE output signal suppresses the ISI.
19. The method of claim 15 , wherein the producing the DFE output signal comprises performing a multi-input multi-output (MIMO) decision feedback equalization (DFE) to produce the DFE output signal.
20. The method of claim 15 , the producing the DFE output signal comprises performing a multi-input multi-output (MIMO) decision feedback equalization (DFE) using successive interference cancellation (SIC) to produce the DFE output signal.