Index Modulation Multiple-Access (IMMA): Efficient Techniques for Downlink Millimeter Waves Outdoor Channel

In this paper, we propose two new multiple-access schemes for downlink transmission based on the combination of orthogonal frequency division multiplexing (OFDM) with index modulation (IM), namely OFDM-IM. In the first proposed technique, namely, Index Modulation Multiple-Access (IMMA), the OFDM subcarriers are divided into multiple sets, and each set is assigned to a specific user, and their data bits are transmitted via the OFDM-IM technique. On the other hand, in the second proposed scheme, an extended version of IMMA is introduced where the different users are arranged into different pairs, and each pair of users shares a block of OFDM subcarriers. The two users of each pair are allocated into different domains: the index domain and the constellation domain. The focus in this paper is on the 28 GHz transmission band as it has been considered for an initial deployment of mm-waves wireless systems due to their relatively lower location within the mm-waves range and are hence characterized by lower attenuation. The fluctuating two ray model (FTR) was proposed as the propagation model for 28 GHz outdoor millimeter waves channels. Simulation results demonstrate that both schemes achieve improved average bit error rate (ABER) than classical OFDMA and NOMA-IM techniques.