Broadband cognitive radio transmission based on sub-channel sensing and NC-OFDM

Abstract

Cognitive Radio (CR) has now been applied for broadband communication systems, so its spectrum sensing technique should be in a broadband signal detection framework. Conventional sensing algorithms such as energy detection are only effective for narrow-band signals or a single broadband signal in the detection range of the spectrum. In this paper a channellization receiver based on DCT filter banks is adopted, which can divide a wide frequency scope into a number of small sub-channels, so energy detection or other sensing algorithm can be used to determine the existence of the primary user within these sub-channels. Then the non-contiguous orthogonal frequency division multiplexing (NC-OFDM) technique is introduced to open or close some sub-channels according to the detection results, so as to make sure the sending carriers of the sub-channels should not jam the authorized users. In this way the effective transmission of broadband CR signals can be acquired, accompanying with which the efficiency of the algorithm resources is markedly increased since the FFT module is adopted in this system for both signal detection and transmission.