Design And Implementation Of Centralized Cognitive Radio Verification System

With the rapid development of communication technology,spectrum resources have become increasingly scarce resources.As a technology that can effectively solve the problem of insufficient spectrum resources,cognitive radio technology has received extensive attention and research.Cognitive radio system has two system architectures:distributed and centralized.Distributed cognitive radio system allocates spectrum resources in the system through negotiation between secondary users.In centralized cognitive radio system,the cognitive center is responsible for coordinating the resource allocation in the system.Compared with distributed spectrum resource allocation,centralized spectrum resource allocation can synthesize the results of each detection node,make more accurate perception,and allocate resources to each node,so as to improve the efficiency of spectrum resource utilization of the whole system.The difficulty is how to design the scheduling algorithm of data and response provided by cognitive center.In this paper,we focus on this problem and carry out the corresponding theoretical research,and construct a verification system to verify the algorithm.In this paper,a centralized cognitive radio system model is constructed,and according to its characteristics,based on queuing theory,it is transformed into a queuing model with two queues and multiple servers.In view of the state changes in the system in the model,we used the two-dimensional Markov chain to analyze the queuing model.We obtained steady state probabilities of all states in system according to steady state equations,and based on this,the blocking coefficient and other performance indicators of the system are derived.In this paper,a dynamic spectrum allocation algorithm based on dynamic change of priority factor which depends on the user changing in the system is proposed.The simulation results of MATLAB shows that the proposed dynamic spectrum allocation algorithm can improve the blocking state of the system and reduce the blocking coefficient of the system.Based on theoretical derivation and simulation results,the steady-state probabilities and corresponding system states under different arrival rates are obtained.Combined with the proposed dynamic spectrum allocation algorithm,we built a cognitive radio verification system,to verify the feasibility of system steady-state probability for system state decision under different arrival rates,and complete the spectrum allocation process of cognitive center.Cognitive radio verification system is developed based on exynos4412 and stm32F103.Wireless communication is implemented using 2.4GHz module nRF24L01.In wireless communication,we overcomes the shortcomings of 2.4GHz module nRF24L01 that modules can't communicate well at the same frequency,innovatively constructs networking mode and data frame structure,and effectively reduces mutual interference.Development boards representing the central base station and two types of secondary users constitute a centralized cognitive radio verification system.An algorithm lookup table is set up in the central base station.According to the simulation results,the cognitive center judges the allocation of spectrum according to steady state probability of each state,and verifies the proposed algorithm.Data is displayed through hyper terminal,TFT display and LCD 1602.This research is part of National Science Foundation of China "Research on Unauthorized Spectrum Sensing and Resource Allocation Algorithms for Marine Cognitive Wireless Communication Systems"(NO.61501078),it mainly studies the spectrum allocation algorithms in cognitive radio systems.