Research On Resource Allocation Of Cognitive Radio Based On OFDM

Up to the present,the wireless communication services have experienced tremendous changes from the traditional single voice call service to the current mobile Internet,car networking and other various services from the first use.It is foreseeable that more types of wireless communications will emerge in the future.With the change of wireless communication services,the demands for communication bandwidth and communication service quality are getting higher and higher,but the spectrum resources they support are limited and non-renewable,which makes the shortage of spectrum bandwidth resources and huge communication demand has intensified.In this situation,the efficient use of existing spectrum resources has become the focus of research.The concept and research of cognitive radio provide a new direction for resolving and solving the problem of the utilization of spectrum resources.This article based on the existing OFDM cognitive radio system research,this paper does the following work:(1)Resource allocation problem when considering the proportional rate constraint in non-real-time servicesUnder the premise of considering multi-cognitive users and individual primary users,we propose an OFDM cognitive radio model which considers the fairness of the cognitive user's transmission rate.The objective is to satisfy the total transmit power constraint of cognitive users and the interference temperature limit of primary users.The power allocation method is optimized to maximize the total data transmission rate of cognitive users,and rate ratio constraints are used to ensure that each cognitive user can achieve fairness of transmission opportunities.For non-convex optimization problems in the process of power allocation,it can be converted into a convex optimization problem without introducing auxiliary variables;in order to reduce the burden of information exchange and computational complexity,the primary user interference temperature constraint is decoupled into the average interference constraint;using Lagrange multiplier method to solve the mathematical calculation problem of optimal transmission power.Through numerical simulation experiments and analysis,it is found that the algorithm not only improves the rate fairness of each cognitive user,but also guarantees the quality of the communication service of primary users.(2)Resource allocation problem when considering the minimum protection rateconstraint in real-time servicesWe consider the data transmission problem of real-time wireless communication services,by aiming at maximizing the throughput of system users as the objective function,and applying the constraint of the total transmit power of cognitive users and the interference threshold of primary users,then we adopt the minimum protection rate constraint of cognitive users at the same time Guarantee the service quality of real-time wireless communication services.According to the constructed OFDM cognitive radio model,the convex optimization method is used to obtain the optimal power allocation algorithm.Finally,we simulate the performance of the proposed algorithm.The results show that the adopted minimum protection rate constraint can guarantee the continuity and stability of real-time service data transmission.In addition,by comparing with non-real-time services,it is found that combining the two methods will improve spectrum utilization and save resources.