On cooperative NOMA relay selection under Nakagami‐m fading and imperfect channel estimation

Abstract

Nonorthogonal multiple access (NOMA), which is an effective technique to achieve high spectral efficiency, has been emerging as a candidate for the fifth‐generation multiple access. In addition, NOMA reflects a transition on the forms of power allocation comparing with the orthogonal multiple access (OMA). In this paper, two relay selection schemes are considered to evaluate the achieved performance of a NOMA‐based relaying network, ie, the max‐min relay selection (MMRS) and the two‐stage relay selection (TSRS) schemes. Exact expression analyses for the system outage probability using the MMRS and TSRS schemes are derived to evaluate the system performance under Nakagami‐m fading. The existence of the error floor, caused by the estimation error, is confirmed by the detailed analysis of the asymptotic result. By comparing NOMA with OMA, and comparing the MMRS scheme with the TSRS scheme, one can reveal that cooperative NOMA under Nakagami‐m fading and imperfect channel estimation can maintain superior performance gain than OMA.

Enhancing physical layer security via a UAV friendly jammer for NOMA‐based IoT systems with imperfect CSI

“…Taking channel uncertainties into consideration in cooperative NOMA networks is particularly important since the encoding and decoding of NOMA highly depend on the quality of CSI. 38 In the work of Zhang et al, 39 the authors investigated the outage probability performance of a NOMA-based relaying system under imperfect CSI and Nakagami-m fading, and derived the exact expressions of the outage probability in the case of deploying the max-min relay selection and the two-stage relay selection schemes. Making an assumption that there exist direct links between the source and the destinations, for a cooperative NOMA network over Nakagami-m fading channels with channel uncertainties, the closed form expressions for the exact and lower bound of the outage probability was discussed by Men et al 40 To this end, the analysis of the physical layer security in UAV-aided cooperative NOMA IoT systems is rarely addressed.…”

Minimum Variance Maximum Mean Relay Selection Scheme for Cooperative NOMA Networks

“…In [19], two optimal RS schemes are proposed viz., twostage weighted max-min (TSWMM) and max-weightedharmonic-mean (MWHM) for C-NOMA with static and dynamic power distributions at the relays. C-NOMA with the two-stage RS scheme (TSRS) and max-min RS scheme (MMRS) are analyzed over Nakagami-m fading channel [20], and it is shown that TSRS outperforms MMRS. Investigation on three RS scheme, namely round robin, centralized and distributed for C-NOMA, have also been carried out [21].…”