An IEEE 802.11 DCF-based optimal data link layer spectrum sensing scheme in cognitive radio networks

In cognitive radio networks (CRNs), spectrum sensing is the key functionality for unlicensed users to detect the unused spectrum. Currently, almost all the spectrum sensing schemes for CRNs are implemented at the physical layer. However, one serious problem with current physical layer spectrum sensing is that it can only detect the presence of licensed user signals but it cannot distinguish between the licensed transmitter and the licensed receiver. This may lead to spectrum sensing inaccuracies that cause interference at the licensed receiver or a waste of spectrum resources for unlicensed users. These issues make physical layer spectrum sensing inadequate in certain practical scenarios. In this paper, a novel data link layer spectrum sensing scheme based on the IEEE 802.11 DCF is proposed to improve the spectrum sensing accuracy. Moreover, an optimal spectrum sensing duration is derived to balance the trade-off between the spectrum sensing accuracy and the spectrum sensing overhead. Simulation results show that the proposed data link layer spectrum sensing scheme outperforms the physical layer sensing scheme in terms of lower collision probability between the licensed and unlicensed transmissions. To the best of our knowledge, this is the first work that investigates the data link layer spectrum sensing in CRNs.