With the emergence of self-interference cancellation techniques, wireless full-duplex communication at the same frequency channel and time slot has become possible. The gain of full-duplex communication over half-duplex depends on the success of self-interference cancellation or the amount of residual self-interference. In this paper, we propose a medium access control (MAC) protocol, named Synchronized Contention Window Full-Duplex (S-CW FD) protocol for enabling full duplex in wireless local area networks (WLANs) and we evaluate its performance under a realistic self-interference model and a realistic network model with hidden nodes. The proposed S-CW FD protocol can not only work both in ad hoc and infrastructure modes of IEEE 802.11 WLANs, but with the legacy nodes as well. Our performance analysis considering various network scenarios and different self-interference cancellation levels show that, when there are no hidden nodes in the network, the S-CW FD protocol can at most double the throughput of half-duplex IEEE 802.11. In the presence of hidden nodes, the advantages of full-duplex are further emphasized, as the throughput gain can get as high as an order of magnitude even for moderate SI cancellation levels.