No abstract

No abstract

This paper describes a broadband (1MHz) digital HF transceiver for the HF band (3-30MHz) specifically designed for the transmission and reception of multicarrier and multichannel modulations. The wide modem bandwidth (1MHz) is not meant for the transmission of a single 1MHz wide signal, since the goal is to achieve flexible transmission and reception using several channels with a common standard bandwidth.

SUMMARYThe HF band data communication link has been traditionally desired by many of the large range transmission systems although it is associated to unfavourable 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 seconds, 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 ms (modem þ 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. Furthermore, these results are corroborated by real tests carried out in a 1800 Km link in the 18 MHz band.

Achieving reliable communication over HF channels is known to be challenging due to the particularly hostile propagation medium. To address this problem, diversity techniques were shown to be promising. In this paper, we demonstrate through experimental results the benefits of different diversity strategies when applied to multi-inputmulti-output (MIMO) multicarrier systems. The performance gains of polarisation, space and frequency diversities are quantified using different measurement campaigns.