Study On Power Allocation For Green Cognitive Networks With Energy Harvesting Technology

At present,under the background of the information age,the rapid development of wireless communication technology has become one of the key technologies in modern society.With the wide application of wireless communication devices and the wireless network access equipment,wireless mobile users increased rapidly as well as a variety of wireless communication services increased,leads to the contradiction between the demand of users and the scarce wireless spectrum resources is becoming more and more prominent,and it poses great challenges to the development of the wireless communication technology in the future.However,the Federal Communications Commission(FCC)survey shows that the spectrum utilization rate of authorized users is extremely low,resulting in a large number of spectrum void phenomena.How to satisfy the growing demand of wireless users and ensure the reliability of wireless network communication under the limited radio spectrum resources is an important topic for the future development of wireless communication technology.Cognitive radio(CR)technology brings dawn to solve this problem,as a new type of intelligent wireless communication system,it has intelligent perception of the surrounding wireless electromagnetic environment,and satisfies the spectrum sharing characteristics of various users,effectively improving the spectrum utilization.CR network composed by primary users(PU)and secondary users(SU)together,PUs has the priority right to use the licensed spectrum.Without affecting the normal communication of the PUs,the SUs are allowed to temporarily use the idle primary spectrum,which can realize spectrum sharing with PUs.At the same time,the contradiction between the huge energy consumption by wireless communication devices and the shortage of energy supply produced can not be ignored.Although cognitive radio networks can improve spectrum efficiency,they are more complex than other communication networks and therefore face more serious energy consumption problems.Therefore,under the premise of rapid growth of wireless communication demand,coordinating the effectiveness of radio spectrum resources and reducing the energy consumption of wireless communication has also become the core issue of the development of communication technology.Combining the energy harvesting(EH)technology with the cognitive radio,SUs has an energy harvesting device that can harvest other energy and convert it into power to supply the SU for data transmission,which is an effective technical solution to the low utilization of spectrum resources and energy consumption.The energy harvesting device can collect energy from the surrounding environment such as wind energy and solar energy,and also from radio frequency(RF)signals such as primary channel.This paper investigates optimal power allocation(OPA)problem in CR networks with EH technology and the main contents are as follows:1)In order to improve spectrum utilization and energy efficiency at the same time,the Radio frequency(RF)EH technology is introduced into CR network to study the optimal power allocation of secondary users.We assume that the SUs accesses energy harvesting devices that can harvest RF energy from the main user.We select the underlay spectrum access model,and the optimization goal is to minimize the SUs system bit error rate(BER).Considering the maximum transmission power constraint of SUs and the interference temperature constraint limited by PU,then the transmission power of SUs on each subcarrier is allocated.The effectiveness and convergence of our proposed power allocation algorithm is analyzed by computer simulation.It is verified that the algorithm can achieve the optimization of the transmission performance of CR network system.2)This paper propose an OPA policy for the EH CR network considering multi users with the underlay spectrum access model.Consider the system model with multiple SUs where each SU transmitter is equipped with an EH device.In our study,we focus on the maximization of the average throughput of the secondary system within multiple time slots under the maximum transmission power constraint,the minimum throughput constraint of SUs,and the interference power constraint defined by PU.Orthogonal frequency division multiplexing(OFDM)access scheme is used in the process of spectrum sharing,where the available spectrum is divided into a set of subcarriers.The optimal transmission power of each SU can be obtain by using Dynamic Programming(DP)algorithm and static OPA,which can be solved by the backward induction method and the Lagrange dual method respectively.The proposed algorithm can maximize average throughput and satisfy all constrains,so that the performance of the SUs system can be optimized under the premise of ensuring the transmission quality of the PU.