A Vector Differential Coding for Hybrid RIS Aided Zero-Padded OTFS Systems

This paper presents a vector differential encoding for the recently proposed orthogonal time frequency space (OTFS) modulation scheme applied in hybrid Reconfigurable Intelligent Surface (RIS) aided wireless communication. The basic idea is to eliminate the need to estimate the channel and simplified the symbol detection at the user equipment. The design of initial symbol vector and differential scheme result in constant modulus transmission. The maximum likelihood(ML) detector with interference cancellation is derived with low complexity. Simulation results show the the uncoded bit error ratio is below 10
⁻²
for SNR over 18 dB with data rate 1.26Mbps, despite the strong Doppler effect caused by the high speed at 120 km/hr.