Institute of Electrical & Electronic Engineers
Orthogonal Frequency Division Multiplex (OFDM) has been widely used in various wireless communications systems. Thus the detection of OFDM signals is of significant importance in cognitive radio and other spectrum sharing systems. A common feature of OFDM in many popular standards is that some pilot subcarriers repeat periodically after certain OFDM blocks. In this paper, sensing methods for OFDM signals are proposed by using such repetition structure of the pilots. Firstly, special properties for the Auto-Correlation (AC) of the received signals are identified, from which the optimal Likelihood Ratio Test (LRT) is derived.