Design And Implementation Of Protocol In LTE-Based Cognitive Wireless Networks

The scarcity of spectrum resources has become an urgent problem that restricts the development of wireless networks towards wideband and ubiquitous networks. For the purpose of solving the problem, researchers have proposed the concept of cognitive wireless network, which mainly contains a cognitive loop including a cognitive phase, a learning and decision-making phase and an executive phase, back and forth. With this cognitive loop, the network can achieve higher spectrum efficiency.Therefore, the focus of this thesis is how to introduce the cognitive loop into LTE while bringing about minimal changes to the existing LTE protocol stack, with the objectives of minimizing interference to primary users and maximizing the throughput of cognitive users. In order to solve this problem, this thesis puts forward a hierarchical spectrum sensing method of taking full advantage of the special subframe in TD-LTE frame structure for low-level spectrum sensing. On the basis of that, it also introduces the cognitive loop into radio resource control (RRC) layer, and adds L1/L2 control signaling and the corresponding RRC signaling message as a support. In addition, we build a demo system to verify the function of the designed protocol.The remainder of this thesis is organized as follows: First, we summarize the background and key technologies of cognitive wireless networks, and give a brief introduction to the architecture and air interface of LTE. According to that, we clarify the necessity of incorporating cognitive function in LTE protocol.Second, after deep analysis of each layer of LTE, we propose a hierarchical spectrum sensing mechanism based on TD-LTE, a scheme that can transport cognitive related information on RRC layer and their corresponding signaling design supporting the mechanism and the scheme mentioned above. Then, the feasibility and possible complexity of the methods are concluded with our careful evaluation.Third, in terms of the simplified standard of the demo system, we reasonably simplify LTE R8 protocol and extend it with cognitive features. Furthermore, the overall software architecture of the protocol stack is also designed. Besides, module design and corresponding implementation scheme are detailedly described.Finally, a conclusion is made at the end of this thesis, and the future directions are also presented.