OFDM based 802.11g Wireless Local Area Networks (WLAN) operate in the 2.4 GHz ISM band. Various other wireless systems use the same band which causes interference and leads to significant performance degradation. Hence, Cognitive Radio's (CR) could better determine free spectrum and coordinate the spectrum usage in this band. Apart from this, to reduce the interference due to spectral leakage, Filter Bank Multicarrier (FBMC) type of system is considered as an alternative to FFT based systems. In this study, FFT and filter bank based spectrum sensing methods are compared by applying them for detecting spectral holes between WLAN and FBMC channels, considering also the spectral leakage effects appearing practical WLANs. Also the performance of alternative multicarrier techniques regarding the efficiency of spectrum utilization is studied.