On the number of pilots for OFDM system in multipath fading channels

The orthogonal frequency division multiplexing (OFDM) system has been demonstrated to be effective in a frequency selective multipath fading environment. To compensate the deleterious effects of the fading channels, pilot symbol assisted modulation (PSAM) technique has been used to obtain the channel estimate. In order to have an accurate estimate, a high percentage of pilot symbols is usually needed and thus reducing the spectrum efficiency. Therefore, the number of pilot symbols is a tradeoff between channel estimation accuracy and bandwidth efficiency. In this paper, we propose a novel method of deciding the optimal number of pilots in OFDM transmission. The method is based on the derivation and analysis of bit error rate (BER) of a PSAM-OFDM system in multipath fading channel in terms of the pilot spacing for a given block size.