Blind detection and estimation of OFDM signals in cognitive radio contexts

Cognitive radio has been seen as a promising technique to address the frequency resource scarcity problem. It is a key issue to reliably detect the activity of primary users´ (PUs) for cognitive radio users. As orthogonal frequency division multiplexing (OFDM) has becoming a popular technique for modern wireless communications systems. It is necessary to identify the existence and estimate the key parameters OFDM systems in cognitive radio contexts. In this paper, we propose a scheme to identify the Pus signals with OFDM. This scheme involves three steps. Firstly, we propose a method to identify the activity of signals through spectrum sensing. Then, we provide a scheme to distinguish whether an active signal is OFDM signal or single-carrier signal. At last, the key parameters of OFDM such as the number of subcarriers and the cyclic prefix length are estimated blindly. Simulation results validate the proposed method.