Energy Efficient Resource Allocation in Terahertz Downlink NOMA Systems

Terahertz (THz) band has attracted considerable interest recently due to its superior high frequency and large available bandwidth. THz could act a vital part in the sixth generation (6G) mobile communication networks. In this paper, we introduce the downlink non-orthogonal multiple access (NOMA) technology into THz band small cell networks, where the total performance is optimized considering the two key enabling technologies. In order to decrease the energy consumption triggered by increasing of wireless services, we pay great attention to energy efficiency (EE) optimization and resource allocation in the THz-NOMA downlink systems by solving the subchannel assignment and power optimization. We first exploit a channel model for the THz-NOMA downlink system by using the key features of THz-NOMA networks. Then we utilize Dinkelbach-style algorithm to solve the resource allocation problem and decompose it into two subproblems. A subchannel assignment algorithm and a power optimization based on alternative direction method of multipliers (ADMM) algorithm are developed to get the solution. Finally, to embody the strengths of THz-NOMA performance, we compare our proposed schemes against the conventional schemes. Simulation results yield substantially higher EE and further prove the availability of our proposed schemes.

I. Introduction

The demands for omnipresent access to information and entertainment with high data rates are growing. The data rates of wireless communications are expecting to 100 Gigabit-per-second (Gbps) or more [1]. However, the available spectrum resources currently are too scarce to support such high data rates. This fact makes it critical to exploit new and broad spectral band for alleviating the spectrum bottleneck. Hence, Terahertz (THz) band has attracted considerable interest with researches from academia due to its broad bandwidth. THz band’s frequency is from 0.1 THz to 10 THz, and its available bandwidth is more than one order of magnitude over mmWave communication signals [2]. Specially, THz band also has the characteristics of narrow beam and large communication capacity. Further, THz communications technique has been regarded as the fundamental technique in the sixth generation (6G) mobile communication networks [3].