The concept of spectrum sensing is in the broad sense, the ability to detect and interpret other signals in the band and take appropriate actions by implementing adaptive techniques in the MAC layer in addition to traditional interference cancellation techniques applied in the PHY layer. In this paper we present algorithms to detect interference to WLAN systems in the 2.4GHz spectrum originating from microwave ovens or frequency hopping devices like cordless phone, and methods to mitigate the interference. The concept can be extended to other coexistence issues as well as spectrum sharing between primary and secondary users of a spectrum.