Impact of Hidden Collision on primary users´ performance in Dynamic Spectrum Access

Dynamic Spectrum Access (DSA) allows Secondary Users (SUs) to access a shared medium when it is in idle state, however, several challenges may be encountered. In this paper, we will focus on the Hidden Collision problem (HC) which occurs when Primary Users (PUs) are using Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) procedure, such as 802.11 protocol, and when SUs are trying to access the medium during the Backoff Window (BW) as they wrongly perceived the medium as available. As a consequence, PUs´ performance may be negatively affected. In previous work, we proposed a new model that adresses this HC problem and allows better control of its effect. In this paper, we extend our work and study the effect of HC on PUs´ performance in terms of throughput and delays under controlled and uncontrolled HC. Our results show that both throughput and delays decrease with the increase of SU transmission activity. The number of PUs has little effect on their throughput and a more significant impact on their traffic delays.