Control Information Interaction Mechanism Design In Cognitive Radio Networks Based On Cyclic Difference Set

As a key technology for solving the problem of growing shortage of radio spectrum resources, cognitive radio technology allows the cognitive users access to authorized spectrum without interfering of the authorized ones, thus improving the utilization of limited spectrum resources.In the complex electromagnetic environment of spectrum heterogeneity, as the available spectrum between the adjacent cogonitive nodes may not be same,those adjacent nodes who want to communicate with each other must establish a common control channel available to both of them in advance to ensure the control information interaction as needed. To sovle the problem of difficulty in building a static common control channel and making full use of mutil-channel spectrum, a more efficient and reliable control information interaction method is to let each cognitive node in the network jumping periodically on all accessiable channel, thus those adjacent nodes jumping to the same channel at the same time can complete the control information iteraction process. The main contribution of this paper is to design different channel hopping systems for thecogonitive wireless network with or without clock synchronization based on the theory of cyclic difference set. That is to say, this paper aims to generate channel hopping sequence sets based on specific rules so as to realize the efficient channel hopping rendezvous on an arbitrary number of available channels.This paper gives a detail introduction to the several important metrics for evaluating the performance of a channel hopping system, including degree of rendezvous(DoR), maximum time to rendezvous(MTTR), average time to rendezvous(ATTR), maximum conditional time to rendezvous(MCTTR) and channel loading(CL). This paper alsosummarizethe metrics of existing algorithms for generating channel hopping system, thuslaying a foundation for the theory analysis and performance comparision for the channel hopping systems put forward afterwords.This paper extends the present concept of cyclic difference set(DS) to the union of disjoint difference set(UDDS). And based on this new concept, we proposes two new symmetric channel hopping system adjusting respectively to clock synchronous and clock asynchronous cognitive wireless networks, thus providing each cognitive node the ability of sending or receiving control information based on channel hopping. Besides, we deduced the performance metrics of the proposed synchronous and asynchronous channel hoppong system based on strict mathematical analysis, and the performance optimization can be relayed on finding disjoint minimum difference sets(MDS) as many as possible.As the problem of searching for disjoint minimum difference set has never been studied, this paper puts forward an efficient exhaustive search algorithm so as to achieve the maximum possible traversal search for the disjoint minimal cyclic difference set. And then, this paper further proposed a very efficient heuristic algorithm to find mutually disjoint difference set. Although the heuristic algorithm cannot guarantee to find the most disjoint difference sets, it can greatly reduce the high computational complexity using exhaustive search algorithm.Based on OPNET network simulation platform, this paper gives an analog simulation comparasion tonew channel hopping systems based on disjoint cyclic minimum difference set and many existing channel hopping systems.The result shows that the proposed channel hopping system can obtain better performance of cognitive wireless network average transmission throughput and average transmission delay.This paper also gives an experimental demonstration based on GNU Radio software platform and USRP hardware platform to the wireless transmission system based on asynchronous channel hopping rendezvous. The experiment results verified that the asynchronous channel hopping system proposed in this paper can meet the requirements of cognitive wireless transmission system, and the basic functions of spectrum sensing,spectrum switching and channel hopping rendezvous are guaranteed.