User fairness for RSS-based positioning in uplink cooperative NOMA

Geolocation of mobile nodes with non-orthogonal multiple access (NOMA) is a crucial process for enabling advanced location-based services (LBSs) in 5G networks. In this study, the authors investigate the theoretical limits of received-signal-strength (RSS)-based positioning for uplink cooperative NOMA under different network conditions with special emphasis on the user fairness feature. In addition, they compare the performance of the RSS-based positioning of cooperative NOMA with that of orthogonal multiple access (OMA). The Cramer-Rao lower bounds are derived in order to show the fundamental limits of position estimation error by taking amplify-and-forward and decode-and-forward relaying into account. The numerical results for both schemes are presented and compared considering the effects of number of relays and user equipments, different relaying on the performance of RSS positioning. The effects of power allocation on the user fairness of cooperative NOMA are also investigated. The results show that the cooperative NOMA outperforms cooperative OMA in terms of positioning. It provides high precision position accuracy and user fairness under different network conditions. Hence, the results suggest that the RSS-based positioning for uplink cooperative NOMA is a promising technique for achieving user fairness and supporting diversified low-cost LBSs in 5G networks.