Comb-Type Pilot Aided Channel Estimation in Non-Contiguous OFDM Systems for Cognitive Radio

The Non-Contiguous (NC) OFDM is a promising candidate transmission scheme in cognitive radio (CR) system. However, the NC available sub-carriers bring new challenges on system design. The pattern of known signals in frequency domain, such as preamble and pilots is vulnerable by NC subcarriers. Several recent researches have studied synchronization issues for NC-OFDM. In this paper, we study the comb-type pilot channel estimation and interpolation for NC-OFDM transmission. Firstly, three types of channel estimation strategies are revealed. And then, we proposed the Shift Pilot (SP) scheme by inserting some punched pilots on other available sub-carriers of data at transmitter. A preprocessor is introduced between channel estimation and interpolation at receiver to estimate channel values of punched pilots. The enhanced strategy achieves better performance with a reasonable complexity in NC-OFDM.