On the Use of Filter Shape Index Modulation for Downlink NOMA Systems Over Fading Channels

In our work, we investigate the use of an index modulation technique for Non-Orthogonal Multiple Access (NOMA) systems within the terahertz communication context. This modulation is called Filter Shape Index Modulation (FSIM), and it is considered to be a single-carrier modulation. We focus on a downlink NOMA scenario with two users, where both of these users and the Base Station (BS) are equipped with a single antenna. In our system, we consider to have frequency selective fading channels. We compare the Bit Error Rate (BER) performance of our system with that of a two-user NOMA system that uses Quadrature Phase Shift Keying (QPSK) modulation. We present the effect of multipath fading channels on the BER performance and investigate the case of imperfect Inter-Symbol Interference (ISI) cancellation at the receiver side.