An Efficient Pilot Design Method for OFDM-Based Cognitive Radio ...

In orthogonal frequency-division multiplexing (OFDM)-based cognitive radio (CR) systems, the subcarriers already occupied by the primary users cannot be used by the secondary users. This leads to possibly non-contiguous positions of the available subcarriers for the secondary users. The conventional pilot design methods are no longer effective for such systems. In this paper, we propose a new practical pilot design method for OFDM-based CR systems. We first formulate the pilot design as a new op