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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 44540 (05)
- University: Sharif University of Technology
- Department: Electrical Engineering
- Advisor(s): Pakravan, Mohammadreza
- Abstract:
- In the present thesis we will design and study some rendezvous algorithms for cognitive radio networks. In cognitive radio networks, secondary users try to access the spectrum of primary users in an opportunistic manner. Each secondary user constructs a channel list of accessible resources by channel sensing. These resources are not necessarily the same for different users; therefore, in order to make a connection in absence of a fixed control channel, different secondary users should find each other properly and quickly after entering the network. This is known as the blind rendezvous problem. We will develop and examine a new sequence based algorithm for blind rendezvous. Moreover, some available important blind rendezvous methods will be analyzed and compared with each other. Also, it will be shown that the proposed algorithm has significantly smaller average and maximum time to rendezvous compared to other methods. Then, some developments on the blind rendezvous algorithms are introduced to improve their performance in situations which some channels are used by primary users. Available algorithms, when faced with a busy channel, replace this busy channel with a randomly accessible channel or eliminate it from their sequence. Our proposed channel replacement methods are based on substitution with a predetermined channel; hence, channel replacement is equal for different radios, and this can increases the rendezvous chance for the radios. In addition, a novel method for channel prioritization will be presented. It will be verified that knowing the channel status, the channel prioritization can be utilized to decrease the time to rendezvous. Majority of the available rendezvous algorithms are designed and studied for rendezvous of two radios and they have not examined the issue of rendezvous for multiple radio networks. Available solution for multiple radio rendezvous is based on two-by-two synchronization of radios until complete synchronization in the network. This approach performs poorly in networks with large number of users. We present a method based on construction of rendezvous tables for multiuser and multi hop rendezvous that significantly decreases the convergence time of the network. At the end, by designing a rendezvous simulator in cognitive radio networks, we will study the performance of the available and proposed methods
- Keywords:
- Opportunistic Spectrum Access ; Multiuser Network ; Cognitive Radio ; Spectrum Sensing ; Rendezvous Algorithm
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