On the Impact of Phase Shifting Designs on IRS-NOMA

Abstract

In this letter, the impact of two phase shifting designs, namely coherent phase shifting and random discrete phase shifting, on the performance of intelligent reflecting surface (IRS) assisted non-orthogonal multiple access (NOMA) is studied. Analytical and simulation results are provided to show that the two designs achieve different tradeoffs between reliability and complexity. To further improve the reception reliability of the random phase shifting design, a low-complexity phase selection scheme is also proposed in this letter.

Smart Radio Environments Empowered by Reconfigurable Intelligent Surfaces: How It Works, State of Research, and The Road Ahead

“…In [216], the authors study the performance of two phase shifting designs, i.e., random phase shifting and coherent phase shifting, for application to RIS-assisted NOMA systems. Simulation results prove the accuracy of the obtained analytical results and are used to compare RIS-NOMA with respect to conventional relaying and RIS-OMA.…”

Ergodic Secrecy Rate of RIS-Assisted Communication Systems in the Presence of Discrete Phase Shifts and Multiple Eavesdroppers

“…Lemma 2: When N is large, γ E k can be approximated as an exponential random variable with mean λ [20,Lemma 2] and the fact that {ψ k,n } N n=1 are independent and identically distributed (…”

IRS-Assisted UAV Communications with Imperfect Phase Compensation

“…Moreover, the error and outage probabilities are not considered. The authors in [21] considered the outage probability of IRS-NOMA with coherent and random phase processing. For the coherent case, the phase estimation and compensation were considered ideal, while the random phase was considered uniform and discrete.…”

“…14] actually correspond to the case of uniform phase distribution [48], [49]. Consequently, the analysis is applicable to the random phase scenario considered in [21].…”

“…Although IRS may lead to significant SNR gain, such gain is highly dependent on the system capability to accurately estimate and compensate the end-to-end phase for each IRS element, which is one of the main challenges for such technology. Therefore, channel estimation, phase shift design, and performance evaluation with imperfect phase have received extensive attention [13], [21]- [29].…”