A Hybrid Spatial Adaptive Modulation and Frequency Stochastic Approach for MU-MIMO-OFDM Systems in the Context of Underlay Cognitive Radios

In this paper, low complexity rate and power optimization schemes operating in the spatial frequency domains are proposed a cognitive radio (CR) setting involving multi-user multiple-input-multiple-output-orthogonal division multiplexing (MU-MIMO-OFDM). Under assumption of perfect secondary channel state information (CSI) at receiver, presented architectures encompass two main stages. first one, waterfilling-like method is performed per each MIMO subchannel pertaining to subcarrier user (SU). The resulting allocated eigen-channel considered as budget second stage. latter, stochastic algorithm-based approach wherein transmit parameters SU adapted such that maximize achievable sum-rate capacity SUs. Three different introduced work. First, derivation continuous MU-MIMO-OFDM-CR version, referred C-MU-MIMO-OFDM-CR presented. Obviously, proposition theoretical taken benchmark for remaining counterparts. we called discrete-rate MU-MIMO-OFDM-CR, briefly designated D-MU-MIMO-OFDM-CR which round provided rate. Finally, third modified solution, denoted P-D-MU-MIMO-OFDM-CR proceeds similar way alternative, but superimposes non/over-used amount next iteration. simulation results show that, compared discrete exhibits an approximate gain 1 dB when SNR level low, 5 high range.