Real-link Performance of a SS-MC-MA High Frequency Radio Modem

Abstract

The HF band data communication link has been traditionally desired by many of the large range transmission systems although it is associated to unfavorable performances as low transmission rate, large delay and low confidence in terms of link establishment and maintenance. Although transmission rates may be high enough to transmit digital voice, delay, usually over several second, has been the main handicap to let the systems provide interactive digital voice links. Indeed, there is no unclassified equipment with this capability. The main achievement of this proposal is that we are able to guarantee digital voice transmission with low latency, around 135 msec (modem+codec), providing a full interactive digital voice link. Performances of two new 2460 bps. HF modems are presented versus the 39-tone 2400 bps MIL-STD-188-110A modem, working over an ITU-R moderate channel. Futhermore, these results are corroborated by real tests carried out in a 1800 Km. link.