Multi-Dimensional Modulation for Data Rate Maximization in Non-Orthogonal Spatial-Time-Frequency Domains

Loss of orthogonality among radio resource blocks in different domains introduces additional interference such as inter carrier interference (ICI) in frequency domain, and inter symbol interference (ISI) in time domain, and inter antenna correlation (IAC) in spatial domain. Such interference due to imperfect time/frequency synchronization and spatial separation are usually tolerated in LTE, and 5G communication systems. However, with the ongoing wireless evolution towards beyond 5G and 6G networks that operate in mmWave bands with significantly higher data rates, these interference will become more severe, and deteriorate the system performance significantly. Based on these observations, this paper is motivated to maximize the communication data rate under non-orthogonality conditions that occur in spatial, time and frequency domains. We propose a novel multi-dimensional modulation (MDM) scheme to achieve our objective. The simulation results demonstrated that our proposed MDM scheme achieves maximized data rate in spatial-time-frequency domains and it outperforms the state-of-art spatially multiplexed MIMO-OFDM system. We also show that the proposed MDM scheme is highly advantageous for mmWave and massive MIMO applications.