Research On Energy-Efficient Transmission Of Energy Harvesting D2D Communication In Heterogeneous Networks

In order to deal with the rapid growth of mobile terminal equipment and cellular traffic,existing heterogeneous networks need to integrate other communication technologies to improve the energy efficiency of wireless communication systems.D2D(Device-to-Device)communication technology is an effective technology that can be adapted to future demand for low power consumption.However,since D2 D communication equipment is usually energy limited,the advantages of direct communication cannot be fully exploited.Therefore,if combined with the current RF energy harvesting technology,it can effectively improve the disadvantage,and further enhance the energy efficiency of wireless communication systems.In order to solve the problem of effective transmission of D2 D transmitter without initial energy,this paper studies the energy efficiency allocation of device-to-device(D2D)communication in an overlay wireless cellular networks,where a D2 D transmitter first harvests energy from a base station(BS)and then communicates with a D2 D receiver.The corresponding resource allocation algorithm design is formulated as a non-convex optimization problem for the maximization of the energy efficiency(bits/Joule)of the D2 D system.As to the constraints of the proposed optimization problem,we take consideration of the minimum required harvested energy,maximum duration of signal transmission,and minimum required system throughput and so on.Exploiting fractional programming theory,we transform the nonconvex problem into a standard convex optimization problem.This allows us to characterize the optimal solution structure of joint time,frequency,and power allocation and to derive an efficient iterative algorithm for obtaining the optimal solution.We reveal that the optimal energy-efficient D2 D communication in this framework should occur if the D2 D transmitter consumes all the harvested energy from the BS.Simulation results demonstrate the energy efficiency improved brought by the proposed joint time and frequency optimization compared to two baseline schemes.Finally,in order to study the robust performance of energy-efficient D2 D communication system,this paper analysis the problem of resource allocation in the case that all links have only imperfect channel state information.Based on the fractional programming technique and SDP relation technique,the original non-convex optimization problem is transformed into convex optimization problem.In order to reduce the complexity of the optimal algorithm,a suboptimal resource allocation algorithm is proposed which can find the local optimal solution of the original robust optimization problem.The simulation results show that the suboptimal algorithm can get the system efficiency which is nearly close to the global optimal value,and greatly reduce the computational complexity.