Orthogonal Time Frequency Space Index Modulation based on Non-Orthogonal Multiple Access

Wireless communication techniques always strive for advanced spectral efficiency in highly mobile environments. A recently developed Orthogonal Time Frequency Space (OTFS) modulation is considered an appropriate candidate to combat time and frequency offset in signals received from the doubly selective channels by employing the Delay Doppler domain. This paper presents a novel technique that utilizes the spectral advantage of Non-Orthogonal Multiple Access (NOMA) with OTFS-based Index Modulation (OTFS-IM), aiming to increase the spectral efficiency while reducing the transmit power and bit error rate (BER). Compared to conventional OTFS and OTFS-IM, the simulation results of OTFS-IM-NOMA reveal that it can accommodate more than one user using the same DD resources. The simulation results also show that the BER of OTFS-IM-NOMA users outperforms the conventional OTFS technique.