Robust Physical Layer Security for Power Domain Non-orthogonal Multiple Access-Based HetNets and HUDNs, SIC Avoidance at Eavesdroppers

TL;DR

This paper proposes a novel physical layer security scheme for Power Domain NOMA-based HetNets and HUDNs, preventing eavesdroppers from SIC to enhance secrecy rates in 5G networks.

Contribution

It introduces a joint subcarrier and power allocation optimization with SIC avoidance at eavesdroppers, considering perfect and imperfect CSI scenarios.

Findings

Significant increase in sum secrecy rate compared to conventional methods.

Effective SIC avoidance scheme for eavesdroppers in NOMA HetNets.

Validation of the approach in massive connectivity scenarios for 5G.

Abstract

In this paper, we investigate the physical layer security in downlink of Power Domain Non Orthogonal Multiple Access based heterogeneous cellular network in presence of multiple eavesdroppers. Our aim is to maximize the sum secrecy rate of the network. To this end, we formulate joint subcarrier and power allocation optimization problems to increase sum secrecy rate. Moreover, we propose a novel scheme at which the eavesdroppers are prevented from doing Successive Interference Cancellation, while legitimate users are able to do it. In practical systems, availability of eavesdroppers Channel State Information is impractical, hence we consider two scenarios: 1 Perfect CSI of the eavesdroppers, 2 imperfect CSI of the eavesdroppers. Since the proposed optimization problems are nonconvex, we adopt the well known iterative algorithm called Alternative Search Method. In this algorithm, the optimization problems are converted to two subproblems, power allocation and subcarrier allocation. We solve the power allocation problem by the Successive Convex Approximation approach and solve the subcarrier allocation subproblem, by exploiting the Mesh Adaptive Direct Search algorithm. Moreover, in order to study the optimality gap of the proposed solution method, we apply the monotonic optimization method. Moreover, we evaluate the proposed scheme for secure massive connectivity in 5G networks. Numerical results highlight that the proposed scheme significantly improves the sum secrecy rate compared with the conventional case at which the eavesdroppers are able to apply SIC.