On the 20th May 2015, Applied Satellite Technology Ltd (AST) held its first Technology Day, inviting key resellers and customers to see some of the latest industry products and solutions in action. Mark Blount-Stonham, Engineer from Inmarsat Global Government, attended the event with a GCS Cheetah II terminal, and supported AST with a live Global Xpress (GX) demonstration.
Inmarsat’s GX service is the first high speed broadband network to span the world.
The event was held at Down Hall Country House Hotel, a 20 minute drive from Stansted Airport. On 1st April, Mark had visited the venue with AST technical staff to ensure the site was suitable for a demonstration of the GX service on Inmarsat’s I5 F1 satellite.
An 8° look angle was needed to connect with the satellite and an area on the roof of the building was identified as a viable location for the Cheetah terminal.
Mark arrived at Down Hall on the 19th May, the day before the event, to meet with staff from AST and to set up and test the KA connection. They were greeted by dark clouds and rain, and Mark had the challenge of setting up the Cheetah terminal on the roof during the dry spells.
GX makes use of Adaptive Coding and Modulation (ACM) on the forward carrier and despite the rain and the low look angle on the 19th, the ACM was working well and in real time.
Due to the poor weather, the modulation coding (MODCOD) had to be adjusted, along with the error coding, to ensure the Committed Information Rate (CIR) was still delivered. This allowed the antenna to stay on the network, although with a lower throughput.
Despite the stormy weather, a rate of just over 1Mbps was achieved and the network connection was not lost. With brighter weather on the day of the event, higher MODCOD was achieved allowing the terminal to hit the Maximum Information Rate (MIR) of around 8Mbps.
GX has been developed to be more robust against rainfade than other VSAT networks. The GX system adjusts the MODCOD scheme to use additional satellite power, if available, or reduce data-rate to overcome rain-fade.
AST was delighted with the success of the GX demonstration, and attendees were impressed with the performance, particularly taking into account the difficult location and previous days weather.