HF Modem for Secure Voice Communication and Its Real-time Performance Analysis

Inter-continential communication is possible using High Frequency (HF) due to the reflection of electromagnetic wave propagation from the ionosphere. In this paper, we present the MIL-STD-188-110D standard based HF modem design for narrowband voice communication, its real-time implementation and performance analysis. Decision Feedback Equalizer (DFE) was performed using the Recursive Least Square (RLS) method in order to eliminate time-varying channel distortions at the receiver. The interoperability of our HF modem implementation, which are developed using a fixed-point programming suitable for embedded processors, with the RapidM HF modem product is successfully demonstrated. In addition, we report the real-time performance results under ITU-R HF channel models using the RapidM channel simulator product.