Machine-type communications in NOMA-based terahertz wireless networks

Terahertz (THz) band is one of the most promising aspects of wireless communication systems because of its potential to meet the growing demands for the envisioned next-generation of cellular communications. THz band connectivity can alleviate bandwidth shortages and transmit power constraints using multiple-input multiple-output (MIMO) systems. To obtain better throughput and enhanced spectral efficiency, non-orthogonal multiple access (NOMA) configuration can be incorporated into MIMO systems, as NOMA uses non-orthogonal resource allocation by assigning the same carrier frequency to multiple devices in the power domain. In this paper, we focus on 2 × 1 MIMO-NOMA and cooperative 2 × 1 MIMO-NOMA systems for THz spectrum in the downlink transmission. In order to evaluate the effectiveness of the proposed system architecture, we derive accurate data rate, transmission latency, and reliability expressions for 2 × 1 MIMO-NOMA system consists of critical and non-critical devices by leveraging finite block length theory. Moreover, we derive the closed-form expressions for power splitting coefficients, data rate, transmission latency, and reliability for the considered cooperative 2 × 1 MIMO-NOMA system. Extensive numerical results are presented to validate the feasibility of the proposed 2 × 1 MIMO-NOMA as well as the cooperative 2 × 1 MIMO-NOMA systems in the THz band.