Channel Estimation in HF Encryptor Modem Based on OFDM

Abstract
Since a secure voice or data session is very important in military HF communication, it needs a HF modem designed with cipher capability. Whereas multipath and Doppler affection are very adverse in HF sky-wave mode, so the production ofa robust modem is essential for military application to compensate channel distortion. Then channel estimation block is very important and this paper proposes an enhanced method for channel estimation. The OFDM pilot based channel estimation with wiener filtering is a robust method that estimates channel excellently with minimum pilot density. The result show that proposed method can increase bit rate with decrement in pilot density, which allows use of a stronger channel coding and subsequently a lower bit error rate. Simulation shows that the bit-error rate of the proposed method passes the American military standards.