Channel Estimation Algorithms Comparison for Multiband-OFDM

This paper studies the effects of channel estimation in ultra wideband (UWB) systems using a multiband-OFDM (MB-OFDM) approach. The system used consists of a three-band OFDM transmitter, each band having 128 equally spaced subcarriers, which carry both the information data and the pilot signals. The channel estimation is based on the principle of pilot-symbol aided channel estimation (PACE), and it has been implemented using comb-type and block-type pilot subcarrier arrangements. The algorithms used here are based on the least squares (LS) and the linear minimum mean-square error (LMMSE) approaches supported by linear and cubic interpolation, and an IFFT-based time channel estimation, which uses a zero-padding interpolation approach with and without Wiener filtering. In frequency domain algorithms, phase compensation is also taken into account. Bit error rate (BER) versus signal-to-noise ratio E_b/N₀ results show that the frequency based methods generally perform better than the corresponding time based ones. Furthermore, the performances of LS and LMMSE methods are quite similar, leading us to suggest the use of LS estimator for uncoded MB-OFDM systems. Phase compensation is required in comb-type pilot sub-carrier arrangement when a low number of pilot sub-carriers is used