Stability Analysis of Wireless Powered Communication Networks

In RF-based wireless powered communication networks (WPCNs), wireless devices can receive energy from electromagnetic waves radiated by dedicated energy transmitters or hybrid access points for operation. However, the energy charging rate at a wireless device is usually unstable or low because of time-varying characteristics of wireless channels or health concerns. When the wireless charging rate is low, the data backlog at a wireless device may be continuously growing, leading to data loss and system performance degradation. To maintain a finite data backlog and keep a wireless powered device stable, the data acquisition/arrival rate at a wireless powered device must be constrained under the given wireless charging rate and data transmission rate. Thus, this paper theoretically analyzes the stability condition of a wireless powered device using a two-dimensional continuous-time Markov chain model. The considered model with a finite energy storage buffer is never investigated in the literature, and thus the proposed model and analytical result in this paper are completely novel. Simulations are also conducted to validate the analytical result and show that the derived stability condition is necessary and sufficient for a wireless powered device.