A novel frequency domain reciprocal modulation technique for HF channel

Frequency domain reciprocal modulation (FDRM) is a new digital transmission technique that offers an advantage in a high frequency (HF) radio channel afflicted with dynamic multipath. Adaptive equalizers allow high-speed bandwidth-efficient communications through the channel with multipath. However, when the multipath is dynamic, bandwidth-efficient digital transmission is very difficult because the adaptive equalizers frequently cannot adapt fast enough. The proposed new modulation technique employs two blocks of correlated data to cancel the effects of all linear distortion. Cancellation of all linear distortion is an intrinsic property of this modulation technique. Additionally FDRM is useful for transmission of bursty data packet because demodulation is simplified by using two blocks of data. This technology is similar to OFDM, but has the ability to tolerate much faster changes in the multipath distortion. The performance of the proposed modulation technique is studied through simulations, and comparison of the performance with OFDM is described in this paper.