A Study Of Dynamic Spectrum Access Practical Algorithm In Cognitive Radio

During these years, with the rapid development of wireless communication technology, wireless communication services increased substantially, and the application of the wireless business has put forward higher requirements. The appropriate allocation of the spectrum resources has become the focus of people's attention. Most of the spectrum assigned to the user has not been fully utilized, and it causes a serious waste of spectrum resources. How to effectively improve the utilization of scarce spectrum resource becomes a hot research. Cognitive radio technology is to solve the imbalance between spectrum resource utilization and it is an effective way. The so-called cognitive radio technology is the wireless network technology by detecting the external environment, searching idle frequency band, accessing spectrum dynamic, thus it can alleviate the acute shortage of spectrum resources. But the secondary user is required to not interfere with the primary user's communication, thus the problem of dynamic spectrum access has become the key technology of cognitive radio.This article's the mainly idea is POMDP(Partly Observation Markov Decision Processes)-based model for dynamic spectrum access algorithms and secondary users in case of energy constraint algorithm for dynamic spectrum access.First, this thesis introduces the background of cognitive radio technology, and the definition of cognitive radio technology is described. It also summarizes the domestic and international research on the status of cognitive radio systems, and introduces cognitive radio technology in the future applications. In the second chapter, the system framework of cognitive radio and the variety models of cognitive radio dynamic spectrum access are introduced.Then, it focuses on the process which is the secondary users use POMDP framework to finish dynamic spectrum access under the accurately network model. Given the POMDP framework for dynamic spectrum access, we introduce the optimal algorithm and sub-optimal algorithm in the case of non-detection error, and analyze two algorithms'the advantages and disadvantages through simulation curves. We also analyze the secondary user's performance when the primary users switch frequency frequently. Secondly, we discuss the dynamic spectrum access algorithm based on non-accurate model error, and analyze the performance of the secondary users in the case of non-accurate model.At last, we describe dynamic spectrum access process in case of the error-free detection, accurate model and the energy limitation. Numerical examples are provided to study the impact of spectrum occupancy dynamics, channel fading statistics, and energy consumption characteristics of the secondary user on the optimal sensing and access decisions.