Adaptive Modulation for THz Communications Under Hardware Impairments: Design and Analysis

Terahertz (THz) band is widely nominated to be exploited in next wireless networks to meet the high demand on data rates. However, unlike lower frequency bands, several challenges come up while designing a transmission system over the THz band. Among these challenges is the hardware impairments at the transmitter front-end. It is well known that hardware impairments limit the error performance of any transmission system, where a lower bound on the error rate is usually noticed. Such an impact becomes more severe as the operating frequency increases, which significantly degrades the transmission over THz band. To this end, this paper proposes an adaptive modulation scheme that is able to overcome this problem. Moreover, the optimal detector for the proposed adaptive modulation scheme is presented. Mathematical modeling and analysis of the performance of the conventional QAM and the proposed modulation scheme are included along with simulation results that verify the analytical findings. Results indicate that the error performance of the proposed scheme is much better than conventional QAM where no error floor is noticed.