Adaptive sensing time and decision threshold based on interferencereduction in cognitive OFDM network

Cognitive Radio (CR) systems allow unlicensed users to dynamically access licensed spectrum bands. CR systems are expected to detect unoccupied spectrum bands (spectrum holes). Therefore spectrum sensing is the main task of CR users. One important challenge in CR network is to select sensing time such that transmission time increases as much as possible and also interference to primary users decreases. It is also obvious that increasing sensing time will increase accuracy but decrease useful time for spectrum utilization. So there is a trade-off between sensing time and transmission time, and assuming a constant sensing time in all situation is not effective. In this paper we consider an OFDM system in which continuous time Markov chain is used to model the behavior of channel, and calculate optimum sensing time based on interference reduction. Then according to this optimum sensing time and cyclostationary feature of signals, we find an expression for decision threshold. We assume an adaptive decision threshold that varies with size of sensing window. Simulation results show that this method will increase detection probability and decrease miss detection probability compared to non-adaptive spectrum sensing and decision threshold.

کلیدواژه ها:

cognitive radio ، adaptive spectrum sensing ، adaptive decision threshold ، OFDM ، continuous time Markov.