[Paper Review] Optimal Joint Power and Subcarrier Allocation for Full-Duplex Multicarrier Non-Orthogonal Multiple Access Systems

Yan Sun, Derrick Wing Kwan Ng+2 more|arXiv (Cornell University)|Jul 9, 2016

Advanced Wireless Communication TechnologiesEngineering21 citations

TL;DR

This paper proposes an optimal joint power and subcarrier allocation algorithm for full-duplex multicarrier non-orthogonal multiple access (FD-MC-NOMA) systems to maximize weighted sum throughput. Using monotonic optimization, the method achieves near-optimal performance with high spectral efficiency and fairness, significantly outperforming conventional half-duplex orthogonal multiple access systems.

ABSTRACT

In this paper, we investigate resource allocation algorithm design for multicarrier non-orthogonal multiple access (MC-NOMA) systems employing a full-duplex (FD) base station (BS) for serving multiple half-duplex (HD) downlink (DL) and uplink (UL) users simultaneously. The proposed algorithm is obtained from the solution of a non-convex optimization problem for the maximization of the weighted sum system throughput. We apply monotonic optimization to develop an optimal joint power and subcarrier allocation policy. The optimal resource allocation policy serves as a system performance benchmark due to its high computational complexity. Furthermore, a suboptimal iterative scheme based on successive convex approximation is proposed to strike a balance between computational complexity and optimality. Our simulation results reveal that the proposed suboptimal algorithm achieves a close-to-optimal performance. Besides, FD MC-NOMA systems employing the proposed resource allocation algorithms provide a substantial system throughput improvement compared to conventional HD multicarrier orthogonal multiple access (MC-OMA) systems and other baseline schemes. Also, our results unveil that the proposed FD MC-NOMA systems achieve a fairer resource allocation compared to traditional HD MC-OMA systems.

Motivation & Objective

• Address the underutilization of spectral resources in conventional half-duplex multicarrier orthogonal multiple access (HD-MC-OMA) systems.
• Overcome the limitations of suboptimal resource allocation in existing non-orthogonal multiple access (NOMA) systems by enabling simultaneous uplink and downlink transmissions via full-duplex (FD) base stations.
• Design an optimal joint power and subcarrier allocation policy that maximizes the weighted sum system throughput in FD-MC-NOMA systems.
• Provide a performance benchmark for FD-MC-NOMA systems through a globally optimal solution, despite high computational complexity.
• Propose a low-complexity suboptimal iterative scheme based on successive convex approximation to balance performance and complexity.

Proposed method

• Formulate a non-convex optimization problem to maximize the weighted sum throughput in FD-MC-NOMA systems with joint power and subcarrier allocation.
• Apply monotonic optimization theory to solve the non-convex problem and derive the globally optimal resource allocation policy.
• Introduce a dual problem formulation using Lagrangian relaxation and exploit weak duality to establish optimality conditions.
• Leverage the monotonicity of the dual function in the dual variable to prove that the duality gap is zero under optimal conditions.
• Propose a suboptimal iterative algorithm based on successive convex approximation (SCA) to reduce computational complexity while maintaining near-optimal performance.
• Ensure feasibility and convergence by iteratively solving convex approximations of the original non-convex problem.

Experimental results

Research questions

• RQ1 What is the maximum achievable spectral efficiency gain of optimal FD-MC-NOMA systems over conventional HD-MC-OMA systems?
• RQ2 How does joint power and subcarrier allocation impact system fairness and throughput in FD-MC-NOMA systems?
• RQ3 Can a suboptimal iterative algorithm achieve performance close to the optimal solution with significantly reduced complexity?
• RQ4 What role does monotonic optimization play in solving the non-convex resource allocation problem in FD-MC-NOMA?
• RQ5 How does the presence of self-interference and co-channel interference affect the design of resource allocation in FD-MC-NOMA systems?

Key findings

• The proposed optimal resource allocation policy achieves a substantial system throughput gain over conventional HD-MC-OMA systems and suboptimal baseline schemes.
• The suboptimal iterative scheme based on successive convex approximation achieves performance very close to the optimal solution, making it a practical alternative.
• FD-MC-NOMA systems with the proposed algorithms provide a fairer resource allocation compared to traditional HD-MC-OMA systems.
• The optimal solution is derived using monotonic optimization, ensuring global optimality despite the non-convex nature of the problem.
• The duality gap is proven to be zero under the optimal solution, confirming the validity of the dual-based approach.
• Simulation results confirm that the proposed FD-MC-NOMA system significantly improves spectral efficiency by exploiting both multiuser diversity and full-duplex operation.