Research On Transmission And Optimization Strategy In Two-Way Relay Networks With RF Energy Harvesting

With the development of Internet of Things(IoT)and wireless sensor networks,the transmission requires the communication design not only consider high efficiency,broaden coverage,but also consider the energy consumption issue.RF-based energy harvesting is a promising technique to figure out the energy problem.Meanwhile,the RF signal is a carrier of information used for information transmission,which results in a hot transmission technique named simultaneous wireless information and power transfer(SWIPT).Relay transmission is an important transmission mode for it can broaden transmission distance which is particularly suitable for IoT network's realization,the combination of energy harvesting technique and relay transmission technique deserves research.In this paper,we focus on designing the SWIPT strategy and resource allocation for some typical two way relay networks.The main description of our research works are listed in the following:Firstly,we investigate simultaneous wireless information and power transfer and corresponding optimization scheme for two way decode-and-forward(DF)relay network.Power splitting and DF relaying protocol are employed at the relay node.In order to enhance transmission effectiveness,we first establish an optimization problem aiming at maximizing achievable sum rate.Combined with case study,we propose an algorithm that solves optimal power splitting and obtain its closed-form value.Then,with the reliability requirement,we establish a joint optimization problem aiming at minimizing the system outage problem under transmit power constraint.The closed-form value of joint optimal power allocation and power splitting is solved by two-step optimization algorithm.Simulation results verify the correctness of the solved closed-form value,and analyze the effects of transmit power,relay location on optimization design.Furthermore,we verify that the proposed scheme outperforms the traditional SWIPT schemes.Secondly,we investigate the SWIPT and joint resource allocation with data rate fairness consideration for cognitive two way relay network.Consider that the cognitive relay network utilize underlay spectrum sharing,we establish a joint power control and resource allocation problem aiming at maximizing the max-min end-to-end rate without offending the interference temperature of primary user.We focus on designing the joint optimal transmit power,time allocation and power splitting to enhance the objectivefunction.Since the problem is non-convex,we propose a circular stepped alternate convex optimization method which can split the complex original problem into a convex problem and an alternate convex problem,and then find the joint optimal resource allocation by using circular iterative the split two problem.Simulation results show that the proposed scheme can offset transmission asymmetry,and analyze the effects of the interference temperature,the peak power on optimization design.Furthermore,we verify that the proposed scheme outperforms the traditional SWIPT schemes.Thirdly,we investigate SWIPT and joint resource optimization scheme with hardware impairments consideration.Consider that hardware impairments exists in the physical communication devices,we design the SWIPT transmission combined with the signal model with hardware impairments for two way AF and two way DF relay networks,and the optimization problems that aiming at maximizing achievable sum rate with data rate fairness are also established.For AF protocol,we derive the closed-form value of optimal power splitting.For the DF protocol,we focus on joint optimal time and power splitting,and propose two methods to solve it.Consider that the optimization problem are non-convex,we first propose an alternate convex optimization method,and since the alternate convex optimization method has high computation complexity,we further propose a sub-optimal method based on relaxed upper-bound.Simulation results analyze and compare the effects of hardware impairments on system performance for AF and DF protocols,and verify that the proposed sub-optimal method has the approximate performance compared with the alternate convex optimization method.Furthermore,we verify that the proposed scheme outperforms the traditional SWIPT schemes.