Joint Optimization of Power and Channel Allocation with Non-Orthogonal Multiple Access for 5G Cellular Systems

Abstract

Non-orthogonal multiple access (NOMA) with successive interference cancellation (SIC), is considered as a candidate multi-user access scheme for 5G cellular systems. In this paper, we provide theoretical insights and solution algorithm for optimizing multi-user power and channel allocation in NOMA systems. We mathematically formulate the NOMA resource allocation problem and prove its NP-hardness. For solving the problem, we propose an algorithm combining Lagrangian duality and dynamic programming to deliver a competitive suboptimal solution. Numerical results demonstrate that the proposed algorithmic solution can significantly improve the system performance over orthogonal frequency division multiple access (OFDMA) as well as over other existing NOMA resource allocation scheme.Index Terms-Non-orthogonal multiple access (NOMA), successive interference cancellation (SIC), 5G, power allocation

On fair power optimization in nonorthogonal multiple access multiuser networks

“…For successful SIC, a sufficient gap in transmit powers of different users is mandatory and must be ensured by the proposed solutions. However, related works did not guarantee such gap in transmit powers in their proposed frameworks, and hence the proposed solutions are less practical. In the work of Ali et al, authors studied power allocation to maximize sum throughput of the system subject to minimum rate requirements of the users, limited transmit power, and a constraint to ensure sufficient gap between transmitted powers for successful SIC.…”

“…In the work of Wang et al, the problem of power allocation for sum rate maximization in a two‐user NOMA assisted downlink system was solved under constraints of limited power budget and per user rate requirements. The work of Wang et al was extended for NOMA based cognitive radio networks in the work of Zabetian et al The sum rate maximization was further investigated under joint optimization of power allocation and channel assignment in the works of Lei et al and Di et al The optimization to maximize the overall throughput enhances the system performance, however may result in unfair QoS provision for different users . Moreover, the nature of power allocation in NOMA may introduce an additional degree of unfairness and, thus, investigating the fair NOMA designs becomes more important .…”

“…The main contributions of this paper are as follows. A max‐min–based power allocation problem is formulated to achieve fairness among different users. Unlike other works, we consider a more general framework for a practical multiuser NOMA transmission. The problem is solved for two cases. (1) A channel is shared by two users , and (2) a general NOMA system where a channel is shared among multiple users. In the case of two users, the problem is first transformed into a standard convex optimization problem and then dual decomposition is adopted to solve the problem. For more than two users, sequential quadratic programming (SQP) is exploited to find the solution of the nonconvex problem. …”

“…19 Power optimization in NOMA systems is necessary to exploit the potential benefits for future 5G systems and is a nontrivial problem. 20 Recently, the other works [21][22][23][24][25][26][27][28][29][30][31] have investigated the problem for power domain NOMA system under various objectives and constraints. The work of Zhang et al 21 has studied power allocation to maximize energy efficiency in a multiuser system.…”

“…• Unlike other works, [21][22][23][24][25][26][27][28][29][30][31][32][33] we consider a more general framework for a practical multiuser NOMA transmission. • The problem is solved for two cases.…”