On the Theoretical Capacity of Cooperative Amplify and Forwards MIMO Sparse Code Multiple Access Systems

Novel capacity analysis for cooperative amplify and forward (AF) sparse code multiple access (SCMA) Multiple–input multiple–output (MIMO) system is presented in this study. SCMA is the code domain approach of Non–orthogonal multiple access (NOMA) schemes that attracted substantial research interest in the past few years. SCMA is combined with MIMO techniques and studied for cooperative AF network. In particular, spatial multiplexing (SMX), Spatial modulation (SM) and Space shift keying (SSK) MIMO techniques are considered. Theoretical capacity formulas are derived for the overall system and substantiated through Monte Carlo simulation results over variant fading channel distributions. As well, the conditions under which the theoretical capacity can be achieved are analyzed and discussed. Reported results reveal that AF–SCMA-SSK system outperforms other techniques and near capacity performance can be achieved over the Rayleigh fading channel.