With the advent of new high data rate wireless applications, as well as growth of existing wireless services, demand for additional spectrum is rapidly increasing. Existing “command-and-control” spectrum allocations defined by government regulatory authorities, such as federal communications commission (FCC), prohibit unlicensed access to licensed spectrum, constraining them instead to several heavily populated, interference-prone frequency bands. Though several report shows that still the spectrum is not utilized efficiently across time and frequency. To use spectrum efficiently, a new intelligent wireless communication system has been developed termed as cognitive radio network. Multi-carrier techniques, such as orthogonal frequency division multiplexing (OFDM) transceiver have a big role in such advance wireless standard. However an OFDM or NC-OFDM may have several subcarriers that are deactivated i.e. zero valued input that means many FFT calculations are there which are not... Это и многое другое вы найдете в книге An Advance FFT Pruning Algorithm For OFDM Based Wireless Systems (Niladri Mandal and Himadri Mandal)