Interpolation-based maximum likelihood channel estimation using OFDM pilot symbols

An interpolation-based maximum likelihood channel estimation scheme using OFDM pilot symbols is proposed. Instead of direct estimation of the frequency response on each subchannel, an interpolation filter is used on the pilot symbols to estimate a smaller set of coefficients that are sufficient to characterize the multipath channel. The actual frequency responses on the subchannels are then computed through inverse filtering of these coefficients. Because the same amount of signal energy is used to estimate a reduced set of unknowns, the estimation accuracy is improved. The scheme is well suited for packet-based OFDM communication systems where pilot symbols instead of pilot tones are usually used at the beginning of each packet for fast synchronization and channel estimation.