Impact of Distance on Outage Probability in IRS-NOMA for Beyond 5G Networks

Abstract

Non-orthogonal multiple access (NOMA) is envisioned as the solution for increasing capacity and serving exponentially increasing number of devices (users) in beyond 5G networks. Breaking orthogonality, with NOMA users having different channel gain (preferably a cell edge user (CEU) and a cell center user (CCU)) are selected and served on the same resource block. In urban areas, impact of blockages may limit the system performance. Impact of blockages is more prominent for the CEU because the CCU's close proximity to the base stations (BS) lowers probability of CCU being blocked. In order to overcome performance degradation due to blockages, the research interest have move towards intelligent reflecting surfaces (IRS). One of the prime utilization of IRS is to improve connectivity of the blocked users. Since IRS comprises of low-cost passive elements which reflect a signal incident on them using a certain phase shift, hence, are capable of effectively directing the signal from the BS towards the blocked CEU. Intuitively, the location of IRS from the BS, and from the user should play a vital role in directing the intended signal to the desired user. In the current literature, such phenomenon based on the location of IRS is not considered, and mostly fixed/dedicated IRS are considered for the users, which is not a practical approach, since, the users are mobile. The novel numerical results from the study of proposed NOMA-IRS network suggest strong relation between the distance of IRS from the BS and users on the performance of CEU using NOMA.