Pushing the envelope

Fast, reliable communications are a lifeline for disaster emergency workers operating in hostile environments around the world. But how do you keep the lines of communication open when the local telecoms infrastructure has been knocked out by an earthquake or flood?

Iridium PTT uses Iridium’s constellation of 66 cross-linked low-earth orbit satellites to extend the ‘walkie talkie’ model to a worldwide service – that’s still at the push of a button. This ‘one-to-many’ communication provides the fast response needed for groups of remote workers operating in challenging environments. Iridium PTT will also be compatible with Iridium NEXT, the company’s next-generation satellite constellation, which is scheduled for completion in 2017.

Traditional PTT systems are limited by range and coverage. But the Iridium PTT service provides pole-to-pole coverage using Iridium’s satellite network. “It sounds straightforward – until you realise it involves harnessing Iridium’s global constellation of satellites, flying 485 miles above the surface of the planet at a speed of 17,000mph,” said Richard Traherne, chief commercial officer at Cambridge Consultants.

“As the service designers, end-to-end system architects and system developers, we needed to do things differently. It meant designing new protocols and developing multiple new system components to meet not only the goals of the service but also the needs of users.”

A new satellite modem and handset were created, along with a high-availability, real-time, telecoms-grade broadcast controller in Iridium’s gateway. Cambridge Consultants also developed a scalable cloud-based web application – the Iridium PTT Command Center – which allows customers to configure and manage the service. User-friendly drag-and-drop controls, developed using Cambridge Consultants’ proprietary user experience design process, enable users to define coverage areas and talk groups quickly and easily – and, as situations evolve, changes can be made in just seconds.

“Cambridge Consultants has a long track record of technically challenging and mission-critical system design – and has been a trusted core technology partner for more than a decade,” said Scott Smith, chief operating officer at Iridium. “That combination of world-class expertise and close collaboration has been crucial in helping us to create the world’s first truly global PTT communication service.”

The Iridium PTT handsets are lightweight and fit in the palm of a hand – there’s no backpack antenna or heavy equipment. All transmissions are sent using AES-256 encryption. Users decide how many talkgroups they need – and how many handsets should operate in each group. In any talkgroup, up to 10 service areas can be defined across the globe. And the service is interoperable, allowing different organisations to communicate on an ‘as-needed’ basis.

With Iridium PTT, voice and data traffic is transmitted securely from the ‘talker’ across the satellite network and down to Iridium’s gateway. Here, the broadcast controller determines, in real time, the satellites to broadcast to for the listening users to hear the conversation or receive the data. “Each satellite is constantly changing position – covering nearly 8,000 metres every single second – so this low-latency, real-time system was a complex system design challenge,” said Traherne. “And there’s no margin for error when you’re dealing with mission-critical communications.”