Hierarchical Bandwidth Phase Modulation for Reduced Peak-to-Average Power Ratio in Ultrabroadband Terahertz Communications

Hierarchical Bandwidth Modulations (HBMs) have been proposed to leverage the distance-dependent bandwidth of terahertz (THz) communication systems and allow singletransmitter multiple-receiver (STMR) systems to support users with different data rate requirements at the same time and frequency and in the same direction. HBM has much potential for purposes of multiplexing users, maximizing the overall system data rate, and accommodating each receiver’s channel. Up until now, HBM has been explored using quadrature and amplitude modulations. However, given the non-linearity of THz transmitters, modulations with high peak-to-average power ratios (PAPRs) are discouraged. In this paper, phase-only HBM is proposed, with the goal of solving the PAPR problem. In particular, after defining the key parameters affecting the performance of HBM using phase shift keying (PSK) constellations, an optimal constellation design is derived. The solution is numerically and experimentally tested and benchmarked. The results show the potential of PSK-HBM as a solution for THz communications to increase the data rate without increasing the PAPR.