| Summary: | 博士 === 國立臺灣海洋大學 === 資訊工程學系 === 104 === Cognitive radio network (CRN) has been widely studied because it significantly enhances spectrum access efficiency. An essence issue for CRN communications is to provide rendezvous between two nodes. Some existing works claim that rendezvous guarantee can be provided by using a dedicated common control channel to negotiate the channel being used. A serious problem of these mechanisms is that there may not exist a globally available channel. Some channel hopping protocols try to provide rendezvous guarantee without using a common control channel. However, these solutions may suffer from a poor number of rendezvous or uneven channel utilization. In this dissertation, we propose three novel distributed rendezvous guarantee channel hopping protocols: Quorum and Latin square Channel Hopping (QLCH), Randomized QLCH (RQL), and Hadamard matrix and Hash function Channel Hopping (HHCH), to efficiently provide rendezvous guarantee.
The QLCH scheme efficiently provides rendezvous guarantee by utilizing the concept of quorum systems and latin squares. The former is utilized to guarantee balanced rendezvous among nodes while the latter is adopted to share the rendezvous among channels. QLCH efficiently provides fast rendezvous guarantee and can also cooperate with other channel hopping protocols to enhance network throughput.
Utilizing the concepts of quorum systems, latin squares, and a pseudo random number generator linear congruential generator (LCG), RQL efficiently provides rendezvous guarantee and balanced channel utilization. The concept of quorum systems and latin squares are utilized similar to the QLCH while LCG is used to share the rendezvous among all channels at any moment. RQL is considered a flexible and robust solution that provides rendezvous guarantee for any pair of nodes in a CRN.
HHCH efficiently provides rendezvous guarantee and fair rendezvous opportunity by utilizing the concepts of Hadamard matrix and hash function. The Hadamard matrix is utilized to guarantee balanced rendezvous among nodes while the hash function is adopted to share the rendezvous among different channels. In addition to rendezvous guarantee and fairness, the HHCH scheme also provides high and even channel utilization.
Analytical and simulation results verify the improvement of proposed protocols. They performs better in terms of time to rendezvous (TTR) and network throughput when comparing to existing representative rendezvous protocols, L-QCH, ACH, JS, etc. In addition to TTR and throughput, HHCH also outperforms others in terms of variance of expected TTR. That is, any pair of nodes running HHCH have the same ETTR.
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