Comparison of three spectrum access schemes in cognitive radios

In cognitive radio networks, the process of sensing the potential channels and choosing free ones to access in is called spectrum access. In this paper, three spectrum access schemes are compared. They are sensing-all before accessing scheme, Partially Observable Markov Decision Process (POMDP) based scheme and sequential channel sensing scheme. The efficacy of these schemes is studied by both theoretical analysis and simulations. The results show that the sensing-all before accessing scheme can find the largest spectrum opportunity, but has the lowest slot effectiveness. And the POMDP scheme can get the highest slot effectiveness, but the lowest spectrum opportunity. However, the sequential channel sensing scheme can make a good balance between spectrum opportunity and slot effectiveness.