Outage Probability Expressions for an IRS-Assisted System with and without Source-Destination Link for the Case of Quantized Phase Shifts

In this work, we study the outage probability (OP) at the destination of an intelligent reflecting surface (IRS) assisted communication system in the presence of phase error due to quantization at the IRS when a) source-destination (SD) link is present and b) SD link is absent. First,an exact expression is derived and then we derive three simple approximations for the OP using the following approaches: (i) uni-variate dimension reduction, (ii) moment matching and,(iii) Kullback-Leibler divergence minimization. The resulting expressions for OP are simple to evaluate and quite tight even in the tail region. The validity of these approximations is demonstrated using extensive Monte Carlo simulations.