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Communications Satellites

At a recent conference on satellite application and services organised by techUK the progress made in providing broadband by satellite surprised many. Pushing the frequencies higher – to Ka band – and the ability to provide multiple spot beams has made high bit rates not only possible but also competitive. Companies like ViaSat and Avanti are finding their service attractive in the middle of cities, not just in rural areas.

Most people have an expectation that communications – including rural and mobile services – will continue to improve for the foreseeable future. Given that a simple explanation of GPS is “satellites telling you where you are” it is not surprising that most people believe that if they have a couple of bars of a signal they should be able to navigate too. Navigation services – the logic says – will also continue to improve.

Navigation Is Hard

If only it were that simple. At the techUK conference Steve Gardner, CEO of ViaSat, described his own career including working in the famous Linkabit company with such great names as Andrew Viterbi. These giants of the industry invented signal protection and error correction schemes which kept information intact despite the signal being mangled by fading and noise effects.

This is great for digital communication but not much help for navigation systems where the information is not carried in digital form but in the signal structure itself. If basic phase or timing information is lost the navigation performance is affected. Furthermore, four good clean signals are needed to fix a position, not just one spot beam. Radio navigation is hard.

Down to Earth

Navigation services will improve but the answer may well lie with terrestrial systems and even autonomous systems such as inertial using the next generation of quantum sensors. For most people GPS has solved navigation, not only because of the work of the visionaries who created the system 40 years ago but the smartphone technology which has put it in the pocket of almost everyone on the planet. The lesson is, if one is going to keep one eye on the heavens the other ought to be fixed firmly on developments here on earth.

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