Enhanced Capacity and Reliability With OAM and Multi-Dimensional Constellation Over Time-Variant Channel for Beyond 5G Systems

With the growth of the 5G network, a wide range of heterogeneous systems have become an integral part of it. The perspective of heterogeneity has made the 5G new radios (NRs) waveform-hungry to meet the system capacity and reliability in highly mobile environments. Conventional NR systems use orthogonal frequency division multiplexing (OFDM), which suffers from the Doppler effect in high-mobility environments. This paper presents the novel waveforms for the NR system using orbital angular momentum (OAM) modes to make the MIMO system even more spectral efficient. The waveforms are orthogonal time-frequency space mode (OTFSM) and orthogonal time-sequency multiplexing mode (OTSMM). In OTFSM, the symbols are in the delay-Doppler-mode domain, and in OTSMM, they are in the delay-sequency-mode domain. Further, we significantly improve the system’s performance in terms of bit error rate at higher modulation orders by incorporating the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i>-dimensional (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i>-D) mapper into the OTFSM and OTSMM modulation methods. A low-complex detector is also designed for these waveforms, and its performance is compared with that of the orthogonal frequency mode division multiplexing waveforms. The simulation results depict the superiority of our novel waveforms in terms of enhanced system capacity and reliability in high-mobility environments.