Research On The Link Setup Procedure In Cognitive Radio Systems

In recent years, there is a conflict between the lack of spectrum resources and spectrum utilization efficiency in wireless communication. With artificial intelligence through learning and the ability of reconfiguration, cognitive radio is a potential solution for this problem. It senses the surrounding environment, learns, and adjusts the transmission parameters so as to adapt to the changes in wireless channels.Based on the adaptive interference avoidance characteristics of Rateless Code, in this article, we applies Rateless packet transmission scheme in the cognitive link setup procedure. And we emphasize on the multiple access control of packet and propose an effective link setup procedure which can be implemented in cognitive OFDM system.Firstly, this paper summarizes the development status of cognitive radio. Because the protocol design and engineering application is still little at present, we select the wireless link setup procedure of cognitive radio as the research direction.Next, we analyze the application feasibility of Rateless packet transmission in cognitive link setup as well as the implementation details. To make the packet access effective and real-time, we propose a simplified handshake mechanism of Rateless packet transmission. And according to the practical application demand, we explore relevant supporting physical layer techniques and put forward the NC-OFDM modulation for data transmission as well as the TDCS for control channel. These techniques provide a guarantee for the implementation of cognitive link setup.In addition, we focus on the key technique of multiple access control in the Rateless packet transmission and propose a solution which is based on reinforcement learning and an adaptive transmission control method. To reduce the dependence on the common control channel and adapt to fast-varying channel, We propose two kinds of opportunistic spectrum access mechanism, the Markov Decision and Statistical Averaging, based on the core idea of autonomous learning and decision-making. According to the theoretical analysis and simulation results, we compare these methods. They both have advantages and disadvantages in terms of performance, stability and application scene. In practical link setup procedures, we can select one according to the need or use a flexible mix mechanism of opportunistic access. On the transmission duration control, in contrast to current study which simplifies the scenario, we propose an online adaptive transmission duration control method which can be applied in the multi-PU and multi-SU scenario.Finally, we apply the above techniques to design the cognitive OFDM link setup protocol. We build a simulation platform which contains the VG and MATLAB tool and acquire the indicators of link setup delay, equity indices and successful ratio of access for secondary user, which can be used to guide practical design of link setup procedures.