Outage Performance of Pairwise NOMA Allowing a Dynamic Decoding Order and Optimal Pairs of Power Levels

Abstract

In this paper, we evaluate the overall outage probability (OOP) of pairwise Non-orthogonal Multiple Access (NOMA) for both uplink and downlink. We also propose a dynamic decoding order (DDO) together with a fixed pairwise power allocation (FPPA) scheme, in which the optimal decoding order is decided based on the instantaneous channel gains, and thereafter, a pair of power levels is assigned in accordance with the selected decoding order. Exact closed-form expressions of the OOPs for both uplink and downlink pairwise NOMA considering all proposed decoding orders over Nakagami-m fading are derived. Further, we find the optimal fixed power levels for different power allocation strategies so that the OOPs are minimized. Moreover, we investigate the influence of the distances between the source nodes and the access point (AP), the target transfer rates and the path-loss exponents on the OOPs for all cases of decoding orders. In addition, we benchmark our proposed DDO against other decoding orders in terms of the OOP. The results show that assigning optimal fixed power levels which takes the instantaneous decoding order into account not only improves the communication reliability, but also reduces the complexity and computational load at the AP.

Defeating Jamming Using Outage Performance Aware Joint Power Allocation and Access Point Placement in Uplink Pairwise NOMA

“…They also clarify that the power allocation significantly influences the decoding order in downlink NOMA, while the decoding order in uplink NOMA is decided based on both the power allocation and the channel gains. Moreover, a dynamic decoding order offers higher reliability compared to a fixed decoding order [16], [47], [48]. Therefore, we use the dynamic decoding order and fixed pairwise power allocation scheme proposed in [16] in this work, to reduce the complexity of the communication protocol without degrading the OOP.…”

“…Moreover, a dynamic decoding order offers higher reliability compared to a fixed decoding order [16], [47], [48]. Therefore, we use the dynamic decoding order and fixed pairwise power allocation scheme proposed in [16] in this work, to reduce the complexity of the communication protocol without degrading the OOP.…”

“…Moreover, in industrial automation, the NOMA-based systems in [14] are shown to be more predictable and provide higher reliability for the critical-service users than TDMA, even though the performance of the best-effort user has to be sacrificed a little. However, due to the complex nature of the successive interference cancellation (SIC) operation and the imperfect SIC experienced in practice, the number of nodes that are served simultaneously should not be too large [15], which makes pairwise NOMA a more practical option considering also hardware implementation [15], [16]. Therefore, using a mobile AP or a UAV in pairwise NOMA is a potential solution in many emerging scenarios of practical importance.…”

“…While the OOP can be used to evaluate the performance of larger wireless networks supporting shortterm user fairness, the IOP is best suited for evaluating the communication reliability of individual nodes. In [16], the OOP is derived with perfect channel state information (CSI) and without a jamming attack, and it is noted that if there exists any type of interferer which can be considered as noise, the OOP can be obtained directly from the OOP in [16]. However, in the presence of a jamming attack, the OOP cannot be derived directly from the obtained OOP in [16] because there exists multipath fading between the UAV and the jammer.…”

“…In [16], the OOP is derived with perfect channel state information (CSI) and without a jamming attack, and it is noted that if there exists any type of interferer which can be considered as noise, the OOP can be obtained directly from the OOP in [16]. However, in the presence of a jamming attack, the OOP cannot be derived directly from the obtained OOP in [16] because there exists multipath fading between the UAV and the jammer. Moreover, the estimated CSIs at the UAV are imperfect in this situation.…”