Performance-enhanced orthogonal time frequency space system based on probabilistic shaping

In this paper, a probabilistically shaped orthogonal time frequency space (PS-OTFS) modulation is proposed and experimentally demonstrated in a photonics-assisted millimeter-wave system. The probabilistic amplitude shaping (PAS) architecture is employed to generate PS quadrature amplitude modulation (PS-QAM) symbols, which are subsequently mapped into the delay-Doppler (DD) domain for OTFS modulation. At the receiver, pilot-assisted channel estimation is utilized to estimate the channel, and a message passing (MP) detector is adopted for symbol detection. Under the condition of a normalized generalized mutual information (NGMI) threshold of 0.92, the experimental results show that PS-16QAM achieves a 0.3 dB improvement in receiver sensitivity compared to uniform 16QAM, while PS-64QAM achieves a 0.5 dB improvement over uniform 64QAM. Furthermore, a net rate of 13.82 Gbit/s is achieved in the experiment over a 0.8-meter wireless link under delay and Doppler spread channels, demonstrating the potential of the proposed system for future 6G wireless communication networks.