A Distance and Bandwidth Dependent Adaptive Modulation Scheme for THz Communications

Abstract

In this paper, we provide a novel distance and frequency dependent adaptive modulation scheme, which is suitable for communication systems operating in the terahertz (THz) band. After determining the transmission bandwidth, the proposed scheme evaluates the subcarrier bandwidth of the orthogonal frequency division modulated (OFDM) transmission signal, in order to countermeasure the frequency selectivity of the THz channel. Next, the power is allocated to the OFDM subcarriers and the modulation order of the quadrature modulated (QAM) symbol loaded in each subcarrier is selected, based on the instantaneous channel conditions and a predetermined bit error rate (BER) requirement. The proposed link adaptation algorithm has low computational complexity and can significantly increase the link's throughput.