Research On Power Allocation Algorithm In Cognitive Radio Networks

Cognitive radio is an intelligent spectrum sharing system which can adjust and reconstruct the working parameters according to the communication environment.If the interference to primary user is lower than the tolerance,cognitive user has access to the authorized spectrum allocated to the primary user by opportunistic approach or controlling transmit power.In cognitive radio network,in order to allocate transmit power reasonably and use wireless spectrum efficiently,radio resource management(RRM)takes the function,such as access control,channel allocation,spectrum switching and power control,etc.To ensure the normal communication and primary user's priority of using spectrum resources,strict transmit power control must be performed for cognitive users,and power allocation is one of the key factors for cognitive users to share the spectrum of primary users.In this paper,we study on power allocation algorithm in cognitive radio networks.We aim at underlay cognitive radio networks,and study on optimal power allocation algorithm based on user fairness and priority.In view of the relevance of energy efficiency(EE)and spectral efficiency(SE)in a wireless communication system,we should use joint optimization for them.We aim at cognitive radio network based on hybrid sharing,and study on energy efficient power allocation algorithm that based on transmit power and interference power constraint.(1)Underlay spectrum sharing mode is a kind of interference limited spectrum sharing mode.In this mode,the cognitive user is allowed to coexist with the primary user in the same spectrum,but does not allow to exceed primary users' interference tolerance.In the underlay cognitive radio network,since the primary users' interference tolerance is a common constraint for all cognitive users,however,cognitive users may have priority and act selfishly.A power allocation algorithm based on non-uniform pricing is proposed,considering the priority difference of cognitive users,we adopt a non-uniform pricing mechanism to reduce the equilibrium point,so that the higher priority of cognitive users can get higher transmission rate;The sufficient conditions for the algorithm to obtain the unique equilibrium point are derived;The performance of the algorithm is simulated.(2)Hybrid spectrum sharing mode is a kind of underlay and overlay interleave sharing mode.According to the result of spectrum sensing,if the primary user exists,we adopt underlay mode to reduce the interference to primary user by controlling the transmit power.If the primary user is idle,we adopt overlay mode to improve spectrum utilization.In hybrid cognitive radio network,we study on power allocation algorithm for energy efficiency and spectral efficiency equalization,which aim at average power constraint and peak power constraint of the primary user.Firstly,we take the signal processing power consumption as part of the total power consumption,and establish the optimization model with the average interference power constraint and the peak interference power constraint of primary user.Then,we use weighted sum method to transform the multiple objective function of the optimization problem into a weighted sum form of the objective function.Finally,we use sub-gradient method to finish power allocation.The effects of spectrum sensing performance,different types of CSI and the influence of transmission power constraint on the energy efficiency and spectral efficiency of the system are simulated.