Spectrum Detection And Allocation Research Of Cognitive Radio System

Cognitive Radio is a revolutionary spectrum sharing technology, which can significantly improve the spectrum utilization. Cognitive radio system follow such a mechanism, the cognitive users can use the spectrum when the primary user doesn't use them. This shows that the spectrum sensing technology is the key technology of CR, which means that the accuracy of test results can directly affect the communication quality of the primary users or full use of idle spectrum.Now the test result of single-node spectrum detection technology depends on the channel condition between the cognitive user and the primary user, which is not reliable. Collaborative spectrum detection algorithm use the single-node test results in the service area to draw a conclusion, which can avoid the effect of "dead pixels" and improve the detection reliability. These schemes evaluate or estimate reliability of each local sensing result, which needs much time and may not meet the need of practice CR system, especially when the reliability of local sensing result often changes. These CR systems include the CR systems with mobile CR users and the CR systems of which the primary user can appear at an arbitrary location.This paper presents a likelihood ratio test algorithm for the spectrum sencing of cognitive radio systems. The algorithm, which uses energy detection as single-node detection method, takes the channel fading and path loss between the primary user and multiple users into consideration and builds the decision model according to the likelihood ratio, and then uses the pdf to reduce the complexity of the algorithm. Experiments show that the algorithm can get a good sencing result as soon as possible.After studying spectrum detection technology in, the article also has a research on spectrum allocation. This paper presents a spectrum allocation strategy based on GA, which can achieve maximum benefit.This paper will use likelihood ratio test selection algorithm for spectrum sencing. The algorithm is an effective spectrum sensing technology but with complexity. To solve the problem, this paper presents a mathematical model with considering actual reasonable aspects to ensure high detection performance, and then using the probability distribution simplifying the model, which can help CR get accurate results as soon as posssible.After studying spectrum sensing techniques, the paper also has a research on spectrum allocation techniques. The paper uses the concept of GA to solve the problem of spectrum allocation and get a good result.The subject belongs to the basic theoretical research, aimed at the existing shortcomings of spectrum sensing and allocation techonology. which has a problem of not accuracy and fast enough. This paper presents a likelihood ratio test selection algorithm model with considering path loss and channel fading and a spectrum allocation algorithm based on GA, which will help CR get a good sensing and allocation results as quickly as possible.Summary this work in the following:1. Summarizing the spectrum detection and allocation techonology for CR. Analyzing the shortcomings of current spectrum sensing and allocation algorithm.2. This paper presents a likelihood ratio test selection algorithm model with considering path loss and channel fading.3. This paper presents a spectrum allocation algorithm based on GA.