Performance analysis of ABCom NOMA systems for 6G with generalized hardware impairments

With the continuous emergence of new smart applications, the number of smart devices is increasing exponentially. Therefore, it is a great challenge to meet the rising network demands for the sixth generation (6G) communication. To solve the above problem, non-orthogonal multiple access (NOMA) and ambient backscatter communication (AmBC) technologies are introduced. However, deploying a large number of low cost components, all nodes are prone to hardware non-ideal, and the system performance is limited by the imperfect factors of in-phase and quadrature-phase imbalance (IQI) and residual hardware impairments (RHIs). Motivated by this, this paper considers an AmBC-NOMA communication system with both IQI and RHIs. In particular, we derive the analytic expressions for outage probability (OP) and ergodic rate (ER) of each node for the cases of ideal and non-ideal conditions. In order to get further insights, we analyze the asymptotic behavior of OPs and ERs at high signal-to-noise ratios (SNRs). The comparison of theoretical analysis and Monte Carlo simulation show that: (1) IQI and RHIs have negative impacts on the effectiveness and reliability of the system; (2) As the transmit SNR increases, the OP of each node converges to a non-zero constant, resulting in the diversity order approaches zero; (3) The ER of Uf is less affected by these two non-ideal factors; (4) RHIs have a greater impact on the ER of Un than Uf.