WiFi, i.e., IEEE 802.11 is one of the most widely used technologies to implement internet access in today's networks. Typical frame error rates in IEEE 802.11 are much higher than in wired links. This negatively impacts the behavior of TCP, which assumes that packet loss is due to congestion. This paper presents LN-MAC, a cross-layer solution based on explicit loss notification (ELN), where the IEEE 802.11 MAC is enhanced to provide loss notifications to the TCP layer. Extensive simulation results demonstrate the benefits of LN-MAC. Numerical results demonstrate that under any condition TCP throughput is always higher when using LN-MAC than when using conventional IEEE