Efficient Pilot Pattern for OFDM-based Cognitive Radio Channel Estimation - Part 2

This paper is the extension of the first paper (Rashad et al., 2007) that described the modification of rectangular pilot pattern applied in OFDM-based cognitive radio system. In this paper, a new concept for pilot symbols arrangement in OFDM transmission system is introduced. The new idea is the virtual pilot symbols concept which is based on the interpolation of the received pilot symbols. Further in the paper virtual pilot symbols concept together with the modified hexagonal pilot pattern are proposed as a new pilot symbols arrangement technique for OFDM-based cognitive radio system. Using the proposed pilot patterns, the channel estimation based on two cascaded one dimensional (2times1-D) Wiener filter is investigated by simulation. Both narrowband and wideband Licensed Users are considered. The results have shown more than 15 dB SNR gain is achieved by the hexagonal pilot pattern with virtual pilot symbol at channel estimate mean square error (MSE) 2 times 10^-3 compared to the regular rectangular pilot pattern.