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.