Research On The Optimization Of Wireless Energy-carrying And Backscatter Hybrid Communication

The Internet of Things(Io T)is one of the key technologies for the development of wireless communication in the future,which can connect billions of daily equipment objects,such as smart watches and sweeping robots at anytime and anywhere.However,the amount of energy of Io T nodes is very limited.Backscatter communication technology remarkably enhances the energy efficiency in wireless communication networks through radio frequency modulation,which has the characteristics of low power consumption,low cost and low complexity.Meanwhile,wireless-powered communication is a technique which can power wireless nodes via radio-frequency energy in long distance,and thus it can effectively address the energyconstrained issue in wireless networks.By considering both the wireless-powered communication and backscatter communication techniques,the related issues on system models,hybrid communication schemes and throughput performance are studied in this thesis.Firstly,with regard to energy scheduling-based hybrid wireless-powered and backscatter communication systems,the throughput maximization problem is studied by designing a novel protocol and a communication scheme.Specifically,the upper bound of throughput performance is obtained based on the ideal situation of non-causal channel state information.Then,the finite state Markov channel model is introduced to maximize the system throughput performance based on the actual situation of causal channel state information by jointly optimizing the backscatter reflection coefficient,transmission power and time slot allocation.Based on the two situations mentioned above,a dynamic programming algorithm and an approximate dynamic programming algorithm are proposed,respectively.Convex optimization and layered optimization technique are utilized to obtain the optimal solution in this thesis.Secondly,a novel multi-relay hybrid communication scheme based on buffer-aided wireless-powered communication and backscatter communication is designed to maximize the system throughput performance.Specifically,the system optimization problem is first formulated,which aims to maximize the system throughput by jointly optimizing the backscatter coefficient and transmission power of each relay as well as system mode selection and relay selection.By solving the optimization problem,the corresponding system optimization scheme is proposed to achieve the optimal system throughput performance based on the value iteration-based dynamic programming algorithm.Furthermore,in order to reduce the computational complexity caused by dynamic programming algorithm,a policy iterationbased approximate dynamic programming algorithm is proposed,and the near-optimal throughput performance is obtained.Finally,the simulation results show that the designed hybrid communication schemes in these two hybrid communication systems proposed in this thesis can achieve superior throughput performance as well as realize green low-power communication and efficient information transmission,which is better than the existing pure schemes and other benchmark schemes.