Bandwidth Efficient Channel Estimation Using Super-Imposed Pilots in OFDM Systems

This paper proposes a channel estimation algorithm using super-imposed pilots for OFDM systems. The pilot symbols are added linearly to the modulated data symbol at a fraction of the total transmit power, making the method spectrally efficient. We present a series of iterative and non-iterative receivers in which complexity is traded for performance. In particular, a high complexity non-iterative receiver that achieves the theoretically lowest BER and a low complexity iterative receiver that show near-optimal performance are presented. The proposed iterative receiver offers a 50 - 98% reduction in complexity over a non- iterative receiver having equivalent performance, depending on the modulation used. We observe that the performance of the receiver is independent of the channel´s Doppler frequency and delay spread. Finally, we compute an analytic bound for the bit error rate of the proposed non-iterative receiver.