Control Information Interaction Mechanism Design In Cognitive Radio Networks Based On The Same Frequency And The Same Time

In order to improve the utilization of limited spectrum resource, cognitive radio networks(CRNs) have to adopt efficient multi-channel MAC protocols for exchanging various kinds of control information, such as clock synchronization, spectrum sensing results, network topology, and channel reservation, among CR nodes so as to negotiate appropriate communication channels available to both transmitter and receiver without interfering the communication between primary users(PUs). Most existing cognitive MAC protocols rely on a common control channel(CCC) dedicated for control information exchange, which is free of PU occupancy. However, the increasingly complex electromagnetic environment makes it difficult to establish such a CCC. Moreover, accompanying with the increasing demand for control information exchange, the CCC itself will become a bottleneck for improving the performance of CRNs. In view of this, the present thesis is devoted to the design of efficient mechanisms for control information exchange within those CRNs without any CCC.Each of these mechanisms should adopt one common principle for each CR node to randomly generate a channel hopping(CH) sequence for hopping among multiple accessible channels. When neighboring CR nodes achieve a CH-based rendezvous, that is, they hop to a common channel at the same time, they can exchange control information with each other. Compared with the CCC-based exchange mechanism, the CH-based exchange mechanism has various advantages, e.g., independence of any fixed control channel, no need to know the CH sequence of neighboring CR nodes, and the effective alleviation of the saturation problem for control information exchange. The main contribution of this thesis is to design different CH systems, each including all CH sequences that can be generated according to a certain principle, for different application requirements of CRNs in control information exchange.First, based on the rendezvous property of circularly increasing and decreasing sequences, this thesis designs three new asymmetric synchronous CH systems to ensure that all CR nodes are equipped with a synchronized time clock and have the need to either transmitting or receiving control information only. Among these CH systems, the first one can flexibly generate different CH sequences to optimize the performance of control information exchange under different traffic loading, the second one is especially suitable for those CRNs with high traffic loading, and the third one can support different communication priorities for different CR nodes such that the high-priority CR nodes can always achieve a better performance of control information exchange than the low-priority ones and, meanwhile, the whole CRN can achieve a better overall performance than that without supporting node priorities. Numerical simulations based on MATLAB and OPNET show that, compared with the existing asymmetric synchronous CH systems, the proposed CH systems achieve better performance for control information exchange.Second, the present thesis further applies the basic idea of the proposed asymmetric synchronous CH system to the design of symmetric synchronization CH system subject to the constraints that all CR nodes should be synchronized and have the need for transmitting and receiving data. By replacing each bit in a certain binary expression with an appropriate asymmetric synchronous CH sequence, we proposed two symmetric synchronous CH systems, one for flexible rendezvous according to network traffic loading and the other for prioritized rendezvous. The OPNET-based simulation shows that the proposed symmetric synchronous CH systems also achieve better performance of control information exchange than the existing ones.Finally, we also designed an asymmetric asynchronous CH system, which, given a certain number of accessible channels, can generate more CH sequences than the existing CH system. The OPNET-based simulation shows that, for a CRN with relatively small number of nodes, the proposed asymmetric asynchronous CH system achieve better performance of control information exchange than the existing one.