Intelligent Reflecting Surface Aided NOMA-HARQ Based IoT Framework for Future Wireless Networks

In sixth-generation (6G) wireless networks, non-orthogonal multiple access (NOMA) technology is widely used to improve the spectrum efficiency. Along with NOMA, hybrid automatic repeat request (HARQ) technique is used to enhance the reliability of communication system. Recently, intelligent reflecting surfaces (IRS) are a futuristic transmission technology that can achieve high spectral and energy efficiency at low cost. In this paper, an IRS aided downlink NOMA-HARQ based Internet of Things (IoT) framework is proposed to enhance the IoT devices' performance in non-line-of-sight (NLoS) region. Further, to enhance the performance of NLoS IoT device/users, two NOMA-HARQ aided IRS schemes are proposed namely: NOMA-selection combining (SC) with IRS and NOMA-maximum ratio combining (MRC) with IRS. This paper formulates and examines the IoT user/device performance in terms of the achievable data rates, outage probability, bit error rate (BER) and diversity order in IRS aided downlink NOMA-HARQ environment with variable signal-to-noise ratio (SNR). With the help of the simulation results, it is demonstrated that in dynamic wireless channels, the proposed schemes outperform the conventional NOMA with HARQ (NOMA-HARQ) in terms of achievable data rates, outage probability, BER and diversity order.

I. Introduction

The interesting suggestion of connecting every gadget or “thing” to the Internet has resulted in the development of an innovation known as the Internet of Things (IoT), which is gradually overtaking every part of our modern life. In sixth generation (6G) the application of IoT technologies and the demands call for fundamental changes in wireless technologies need to be increased to meet the communication links, latency and reliability requirements of the expected massive number of connected devices [1]. From first generation (1G) to fifth generation (5G), wireless technologies are built on the idea that the wireless environment cannot be manipulated or changed. As a result, the only way to solve the problem is to create efficient communication technology. However, beyond 5G, traditional wireless communication system design methods are unsuitable to support demanding wireless systems and services. Therefore, 6G ideas can be obtained by considering the wireless environment as a variable that can be adjusted and controlled. This can be obtained by Intelligent reflecting surfaces (IRS), large intelligent surfaces (LISs) [2] and 6G supporting technologies [3].