Outage Behaviors of Active Intelligent Reflecting Surface Enabled NOMA Communications

Active intelligent reflecting surface (IRS) is a novel and promising technology that is able to overcome the multiplicative fading introduced by passive IRS. In this paper, we consider the application of active IRS to non-orthogonal multiple access (NOMA) networks, where the incident signals are amplified actively through integrating amplifier to reflecting elements. More specifically, the performance of active/passive IRS-NOMA networks is investigated over large and small-scale fading channels. Aiming to characterize the performance of active IRS-NOMA networks, the exact and asymptotic expressions of outage probability for a couple of users, i.e., near-end user n and far-end user m are derived by exploiting a 1-bit coding scheme. Based on approximated analyses, the diversity orders of user n and user m are obtained for active IRS-NOMA. In addition, the system throughput of active IRS-NOMA is discussed in the delay-sensitive transmission. The simulation results are carried out to verify that: i) The outage behaviors of active IRS-NOMA networks are superior to that of passive IRS-NOMAnetworks; ii) As the reflection amplitude factors increase, the active IRS-NOMAnetworks are capable of furnishing the enhanced outage performance; and iii) The active IRS-NOMA has a larger system throughput than passive IRS-NOMA and conventional communications.