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Terahertz (THz) wireless technology is envisioned to enable terabit-per-second (Tbps) and secure transmissions in sixth-generation (6G) communication networks and has attracted attention from academia and industry in recent years. Because the transmission range of THz radios is restricted compared to that of microwave radios, frequency reuses in the THz band become much more flexible and even possible among transceiver pairs in close proximity. However, without appropriate spatial arrangement and coordination, the frequency reuse in the THz band can also lead to severe co-channel interference and result in a low signal-to-interference-plus-noise ratio (SINR) or a signal-to-interference ratio (SIR), which finally degrades signal detection and network reliability. To thoroughly study the co-channel interference in the THz band, we model the co-channel interference by the compound channel model and analyze it in detail. The adopted channel model captures the key features of THz communication, such as, spreading loss, molecular absorption loss, and dynamic shadowing, which is much different and complicated than those used in the low-frequency band. The resulted SINR and SIR are investigated by approximating the sum of co-channel interference as a gamma distribution. The generalized analytical results are also reduced to specialized forms for two special cases, i.e., the single-interferer case and the case of multiple independent and identically distributed (i.i.d.) interferers. Due to the generalized nature of the THz interference model constructed in this paper, the results play a meaningful role in practical implementation and can be easily extended to advanced performance analyses for THz communication systems. [ABSTRACT FROM AUTHOR]

Hardware distortions (HWDs) render drastic effects on the performance of communication systems. They are recently proven to bear asymmetric signatures; and hence can be efficiently mitigated using improper Gaussian signaling (IGS), thanks to its additional design degrees of freedom. Discrete asymmetric signaling (AS) can practically realize the IGS by shaping the signals’ geometry or probability. In this paper, we adopt the probabilistic shaping (PS) instead of uniform symbols to mitigate the impact of HWDs and derive the optimal maximum a posterior detector. Then, we design the symbols’ probabilities to minimize the error rate performance while accommodating the improper nature of HWD. Although the design problem is a non-convex optimization problem, we simplified it using successive convex programming and propose an iterative algorithm. We further present a hybrid shaping (HS) design to gain the combined benefits of both PS and geometric shaping (GS). Finally, extensive numerical results and Monte Carlo (MC) simulations highlight the superiority of the proposed PS over conventional uniform constellation and GS. Both PS and HS achieve substantial improvements over the traditional uniform constellation and GS with up to one order magnitude in error probability and throughput. [ABSTRACT FROM AUTHOR]