Analysis of Waiting Probability of Secondary Users in Cognitive Radio Networks

Abstract

Cognitive Radio (CR) is an adaptive, intelligent radio and network technology that can automatically detect available channels in a spectrum and change transmission parameters enabling more communications to run concurrently. Thus the cognitive radio networks are emerging paradigm for future generation wireless networks where secondary users (SUs) opportunistically access the RF spectrum without causing harmful interference to primary users (PUs). SUs vacate the bands upon the arrival of licensed PUs. This thesis analyse the waiting probability of SUs to get channel access based on PUs activities. Multi-user cognitive radio system is considered where SUs contend for spectrum access using time division multiple access over idle PU channels. Secondary users of cognitive radio network would have no knowledge of activities of other users. Thus the probability of being idle of SUs in cognitive radio network has to be assigned according to the available local information. Further, this thesis focuses on SUs' waiting probability analysis, for which a systematic understanding is lacking. Analysis and results have revealed that the waiting probability increases when the arrival rate of SUs increases. The waiting probability of SUs decreases with increasing number of slots. Also it is noted that the probability of getting one or at least two slots by SUs increases with increasing number of slots. The average service rate also decreases with increase in number of SUs, and the average service rate is lowest among all when the number of SU is the highest. The trade-off between different parameters is required to make an efficient opportunistic dynamic spectrum access by SUs in CR.