Active interference cancellation technique for MB-OFDM cognitive radio

Ultra Wideband transmit power (in-band) is regulated to be -41.25 dBm/MHz (in the United States), but in the future, it may be flexibly relaxed subject to the cognitive-radio spectrum policy. However, in close proximity of a protected radio service, transmission at the relaxed power might inflict an excessive degradation on the service quality. Applying the general analog or digital notch filter in the UWB transmitter (baseband) is the simplest but not a favorable approach due to the increased cost and the power consumption of the device. In OFDM, turning off the interfering tones has been studied as the alternative solution, but the inter-carrier interference may limit the notch depth to 5-10 dB. This paper discusses a new approach that enables the accurate notch bandwidth and depth control for the general OFDM transmitter. The technique demonstrates the fundamental advantage of the OFDM-based UWB solution[l] for the future cognitive ratio.