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“Firstly, there’s the role of satellite in providing backhaul from very remote places where it’s not economically or technically feasible to install terrestrial infrastructure. “Secondly, some key sites will require high levels of redundancy and physical separation of fixed plant, antennas and connectivity. “And finally, there’s always the need for rapid deployment of additional connectivity for special events or when maintenance or re-engineering work is planned.” Integrated TETRA To manage such special events or respond more effectively to emergency situations, that TETRA-satellite connectivity is also being more closely integrated with command and control vehicles on the ground. As part of a major recent contract with Abu Dhabi police, UK systems vendor APD Communications equipped seven mobile command vehicles with a full suite of control systems and communications links including satellite connectivity to support the terrestrial TETRA system. Dan Ellis, development manager at APD takes up the story: “We’ve used the Etisalat satellite – initially using their Ku-band service – to link in with our Cortex system to provide a range of communications options for the Abu Dhabi police. “When you’re integrating TETRA with satellite systems, you do need to take a very disciplined approach to the engineering issues and we found the use of a network emulator from iTrinegy invaluable in optimizing the communications paths that use satellite. It’s important, however, to remember that satellite systems themselves can’t always be fully relied on and a fall-back option is always required.” Paralleling this, 2011 saw the deployment of a fleet of dual-mode TETRA-satellite emergency response vehicles by Afcom Satellite Networks for a major multinational oil company in Nigeria. Using a Motorola TETRA system, the users are able to stream live, broadcast-quality video and data files between an event and the company’s network while supporting voice calls from on the ground. Once again, special features were needed to provide reliable communications links in the worst rain-fade conditions. Networking networks While satellite performance can be managed relatively straightforwardly when a single TETRA-satellite network is involved, things can become more problematic when systems need to be interlinked – whether different TETRA networks on the ground or where other wireless technologies such as GSM, 3G and Wi-Fi are also in use. As ever, building this ‘network of networks’ is a complex challenge and organizations such as ETSI, the Public Safety Communications Europe Forum, and the European Commission sponsored Integral Satcom Initiative are currently engaged in co-ordinating activities in at least one continent. One early example of this kind of work was the WISECOM (Wireless Infrastructure over Satellite for Emergency Communications) project in 2008, which looked at the hard-core engineering issues involved in satellite-terrestrial interworking for emergency situations, focusing in particular on Inmarsat’s BGAN and DVB-RCS links. Given the current increasing interest in broadband by the whole TETRA and critical communications community, it’s not surprising that interworking between broadband cellular and satellite systems is emerging as a hot topic. Mobile satellite service provider Solaris Mobile is seeking to exploit its unique spectrum licence – adjacent to 3G frequencies – to provide a number of enhanced services to both enterprise and public safety customers using a satellite located at the 10° East orbital location. Matt Child, chief executive of the company, explains: “Hybrid solutions are going to become increasingly important in the public safety arena in terms of both broadcasting alerts to the public and in providing broadband connectivity to the emergency services. Advances in both antenna design and spectrum allocation are bringing much-needed flexibility and the 3GPP community is already considering S-Band as an extension to existing mobile broadband frequencies.” Service innovations This drive for broadband is also echoed by Inmarsat’s government services business development manager, Dave Robertson. “Given the TETRA and critical communications community’s aspirations for broadband – both in its public safety roles as well as enterprise applications such as transport, utilities and oil and gas – it’s natural for them to look at satellite technology to enhance existing solutions. “We have a number of new satellite launches planned over the next year to expand coverage and connectivity, such as our Inmarsat-5 constellation, which will be capable of delivering 50 Mbit/s to a 60?cm dish. We already provide support for Télécoms Sans Frontières and recently worked with US 4G provider LightSquared during Hurricane Irene last autumn.
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