| Summary: | 碩士 === 國立臺灣海洋大學 === 資訊工程學系 === 103 === In a cognitive radio network (CRN), a premise for two nodes to communicate is having a rendezvous which means that they switch to the same channel simultaneously. Most existing channel hopping solutions for the rendezvous problem is for a homogeneous CRN where nodes have the same type of cognitive radio and thus can sense the same spectrum. In reality, nodes have different types of cognitive radios and hence the spectrums being sensed are different. In such a heterogeneous CRN, designing a channel hopping mechanism to provide rendezvous guarantee is challenging. Besides, while determining the channel hopping sequences, existing channel hopping protocols enable nodes to switch to all the channels with the same probability. Such mechanisms are suboptimal since they do not consider different channel conditions of different channels. In this paper, we propose a channel hopping protocol for heterogeneous CRNs, RACH, which provides rendezvous guarantee between any pair of nodes and enables a node to dynamically adjust the ratio of each channel being used. Nodes running RACH use three consecutive odd numbers to determine the schedule for a particular channel. Utilizing the property that two different sets of three consecutive odd numbers are relatively primes, RACH provides rendezvous guarantee on each channel for two nodes. RACH allows nodes to change the set of consecutive odd numbers to adjust the ratio of a channel being switched to. Such a mechanism enables a node to tune to a better channel more to enhance its rendezvous probability to other nodes. Simulation results verify that RACH improves network performance in terms of time to rendezvous and throughput when compared with an existing channel hopping protocol for heterogeneous CRNs.
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