Projects:2017s1-102 HF Radio Automated Link Establishment (ALE) Model

Introduction

High Frequency (HF) radio communications are able to transmit information such as voice wirelessly over long distances. These distances are achieved by refracting HF waves off layers in the ionosphere. The Radio Division of Codan limited produce a range of HF Radio's which use the 2G-ALE protocol. A tool was made which predicts the call blocking probability for a given system. The tool can also be used to propose a range of channels, for a desired call blocking probability. The ionosphere’s refractive properties vary due to factors such as time of day which in-turn change the channel availabilities of the system. Statistical models were developed to predict a system without ionospheric effects, these were verified on hardware to validate results. The model was then adapted to add probabilities of channels being viable. Online tools are then able to predict the channels viability for a given location and time.

Background

High Frequency radio communications

HF radio communications uses 3MHz to 30MHz electromagnetic waves to transmit information such as voice wirelessly over long distances. The waves emit from the antenna will either be absorbed or refracted by the ionosphere layers, allowing the waves to travel several hundred kilometres. The refracted waves will travel to the destination radio station while the absorbed waves will vanish in space. The layers include innermost layer (D layer), middle layer (E layer), Appleton–Barnett layer (F1,F2 layer).

Automated Link Establishment (ALE)

ALE is a standard used in HF radio communications to initiate link from one station to another. This standard is used to provide a quick and reliable method for a network of stations to contact each other. The system automatically selects a channel based on the data collected from previous links and external data to achieve higher quality links. Station with receivers will also scan through a list of channels for calls.

Project Team

• Supervisors
  • Langford White
  • Paul Hirschausen
• Students
  • Xuyang Jie
  • Andrew Thornton
  • Chung Seng Foong