Input-Output Relation and Performance of RIS-Aided OTFS With Fractional Delay-Doppler
Vighnesh S Bhat, Gandhodi Harshavardhan, A. Chockalingam
Abstract
This letter presents an early investigation of reconfigurable intelligent surfaces (RIS)-aided orthogonal time-frequency space (OTFS) in high-Doppler channels. We derive the end-to-end delay-Doppler (DD) domain input-output relation of a RIS-aided OTFS system, considering rectangular pulses and fractional delay-Doppler values. We also consider a Zak receiver for RIS-aided OTFS that converts the received time-domain signal to DD domain in one step using Zak transform, and derive its end-to-end input-output relation. Our simulation results show that <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$i$ </tex-math></inline-formula> ) RIS-aided OTFS performs better than OTFS without RIS, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ii$ </tex-math></inline-formula> ) Zak receiver performs better than a two-step receiver, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$iii$ </tex-math></inline-formula> ) RIS-aided OTFS achieves superior performance compared to RIS-aided OFDM.