Secondary user transmission protection optimisation in sensing-transmission scheduling under varying channel noise in cognitive radio networks

Abstract

Secondary user transmission maximisation and primary user contention minimisation are opposing targets with a constantly existing trade-off between them. A design that simultaneously prevents harmful interference caused to license possessing primary users while efficiently utilising spectrum gaps for secondary user is the premise of cognitive radio networks. When left unused the radio spectrum licensed to permanent users gets wasted and constraints imposed on wireless communication by the limitation of frequency spectrum are very daunting. For a secondary user, both sensing and transmitting is important so as to avoid collisions, packet loss and enhance successful transmission. This paper considers both low and high channel noise in the optimisation of secondary user sensing-transmission scheduling for strategically accessing the spectrum in cognitive radios. The need to maximise the secondary user access is represented by exponential variations in its packet length and the need to minimise primary user contention is represented by exponential variations in collision cost in a threshold-based sensing-transmission structure using Matlab simulations. The results for varying channel noise provide an insight into the optimum scheduling of sensing-transmission.