This paper proposes a novel geometric framework for the network-centric localization of statics Internet-of-Remote-Things (IoRT) nodes using multiple Round Trip Time (RTT) measurements by a single satellite. This framework is motivated by two primary reasons, viz: i) the benefits of obtaining reliable RTT measurements using simple and cost-effective hardware, independent of environmental factors, and ii) the unsuitability of Global Navigation Satellite System (GNSS) receivers in IoRT terminals due to their low-cost and ultra-high-powerefficiency requirements. The localization of such devices is only feasible to be conducted on the network/satellite side. First, a probabilistic relationship of the satellite transmit and receive positions with the target node position is derived. Next, closed-form analytical expressions to describe the distribution of RTT measurement error and its translation into other channel parameters such as the Line-of-Sight (LoS) path length and Angle-of-Arrival (AoA) are derived. Subsequently, mathematical expressions for the likelihood function of node coordinates and Mean Squared Error (MSE) are derived. Furthermore, a thorough analysis of the influence of the number of considered measurement instances, relative satellite positions for channel probing, and satellite altitude/velocity on the performance of the proposed localization scheme is conducted. A minimum of two measurements are necessary to perform the localization, while additional measurements narrow down the Region of Interest (RoI) and enhance the accuracy. Precise IoRT node positioning relies on obtaining an accurate estimate of RTT measurements and satellite position. Notably, the positioning error increases as the satellite altitude increases, indicating that the proposed scheme is more suitable for lower-altitude satellites.
