Optimal power allocation in NOMA-based two-path successive AF relay systems

Abstract

Due to the characteristic of transmitting multiplexed signals in superposed mode over the same spectrum, non-orthogonal multiple access (NOMA) technology is deemed as a promising way to improve spectral efficiency in fifth generation (5G) networks. In this paper, we develop a NOMA cooperative system based on the two-path successive relaying concept, in which the data at the source node is divided into two parallel parts and is transmitted to the destination in superposed mode via the assistance of two amplify-and-forward (AF) relays. On the condition that the transmit power of the individual nodes and the entire system are all constrained, the maximization of achievable rate is formulated as an optimization problem. Following the guidelines of Karush-Kuhn-Tucher (KKT) conditions, the dual decomposition method is adopted to obtain the closed-form expressions of the optimal power allocation. Moreover, to balance the achievable rate between two superposed signals, which is equivalent to minimizing the required spectrum bandwidth, a power allocation scheme between the superposed signals is proposed. In order to verify the effectiveness and efficiency of the proposed power allocation scheme, we conduct extensive numerical simulation on some realistic system setup. The results demonstrate that our analytical insights about the optimal power allocation are aligned with the simulation outcome.

5G Technology: Towards Dynamic Spectrum Sharing Using Cognitive Radio Networks

“…The framework utilises the sum rate to provide QoS and guarantee an effective SIC constraint whilst managing the power to reduce interference within a cluster. Furthermore, a NOMA two-way relaying method was developed by [42] by using Karush-Kuhn-Tucker conditions with dual composition techniques. The relay divides singlesource data into two parallel parts, which are then transmitted using amplify-and-forward relay.…”

Joint Power Allocation for NOMA-Based Diamond Relay Networks With and Without Cooperation

“…• Case 1: λ 3 = 0 and λ 4 = 0. We need to check if inconsistency occurs among (20), (21), (22), and (23). For this case, we rearrange the terms in (20) to obtain g 1 λ 1 = P 4 g 2 g 4 λ 2 +λ 5 .…”

“…The authors in [19] consider a new way for selecting an optimal relay mode and optimal transmission power levels simultaneously in NOMA-based relay networks to achieve a better network throughput. Furthermore, the spectral efficiency of amplify-and-forward (AF)-based NOMA cooperation is investigated in [20], while a similar problem is tackled for decode-and-forward (DF)-based NOMA cooperation as well in [22]. The problem of joint resource allocation, involving the subcarrier pair, subcarrier-user assignment, and power levels, is examined to maximize the network throughput in [21].…”

Full-Duplex NOMA Transmission with Single-Antenna Buffer-Aided Relays

“…More specifically, a range-division user relay selection scheme was devised, dividing the circular cell in continuous annular areas and performing ORS in each one. Other works, targeted the sum-rate of two-hop NOMA relay networks, jointly studying NOMA and SuR [25,26]. The proposed solutions created virtual FD relay networks by employing two dedicated relays to perform SuR and serve two users through NOMA.…”