Minimising TTR for Frequency Rendezvous using Channel Hopping

Abstract

With increasing number of users and limited frequency spectrum, the scarcity of the spectrum has been the real problem in the communication field. It has been analysed that most of the spectrum are not always occupied by the users. It introduces the concept of Dynamic spectrum Access (DSA). DSA is a smart way of using those spectrums which is not being currently used by any other user. This brings Secondary Users (SU) into the picture. SU are those which can use the currently vacant spectrum with a condition that they should leave the spectrum once the licensee of the spectrum comes again. Cognitive Radios are the smart radios which help to achieve DSA. When DSA is implemented another problem of rendezvous comes. The SU don’t have fixed spectrum, they occupy those which they find that are vacant. This leaves it and its peers to find each other in the band of frequency. Another important factor with rendezvous is Time to Rendezvous (TTR). TTR simply means how much time SUs take to rendezvous and it should be as low as possible. Many algorithms have been designed for rendezvous and to minimise TTR. In this thesis optimized algorithm for low TTR is proposed with a guarantee of rendezvous. The algorithm is based on decentralised network with no control channel. This rendezvous process is also called blind rendezvous. It depends on the number of available channels and has been developed for shared model where radios have frequency numbering, number of available channels in common with no synchronisation with each other. Mathematical analysis has been done. Simulations results are compared with the proposed algorithm. Simulation show the performance of the proposed algorithm is much better than the other. For example, if we take 3 number of PUs, the TTR of the proposed algorithm is 3 but for the other one is 10.