A Long Term Evolution required for public safety communications

Telecoms.com periodically invites expert third parties to share their views on the industry’s most pressing issues. In this piece Ingo Flomer, Product Manager at Cobham Wireless looks at what is needed to deliver a reliable modern public safety communication system.

Emergency service responders – such as the police, emergency medical services and fire and rescue crews – are tasked with keeping the public safe, rapidly addressing problems and finding solutions to man-made and natural disaster. They are reliant on infrastructure that supports rapid, reliable and high-quality communications.

TETRA – the old reliable

Today, most countries – including the UK – use TETRA (terrestrial trunked radio), or a very similar standard of professional mobile radio (PMR), to deliver dedicated public safety communications. These systems deliver very reliable services, providing coverage over huge distances. The technology is highly suitable for voice conversations – person to person and group calls – and basic messaging.

However, supporting only narrowband connectivity and kilobit throughput rates, these networks are not appropriate for large data packet transmission, including digitalised communication, something most of us now take for granted.

We store and share documents in the cloud, send images and stream live video, from almost any location. Emergency services can also greatly benefit from the use of data services, which can include image sharing for facial recognition and real-time video transmission for satellite surveillance or body cameras.

A more robust solution

LTE-based public safety networks can support a wide range of data-centric emergency communication services, future proofing networks for years to come. The technology has been proven in thousands of commercial mobile networks today, offering megabit throughput and latency better than 25ms.

As well as supporting data services, LTE can also support robust voice connectivity. It can change modulation and adapt it to the signal link quality available, so in bad link loss conditions a network can continue to provide a voice or low-data connection. This makes it ideal for most emergency situations where maintaining communications is imperative. Subsequently, many governments across the globe are exploring how they can utilise LTE technology to improve public safety communications. Deployments and network trials are happening today in countries including the UK, US, South Korea, Brazil, Chile and the UAE.

In the US, AT&T is building LTE public safety network FirstNet, which will eventually offer voice, video and data services across the country. The network will use a dedicated spectrum, band 14 in the 700MHZ spectrum, which can also support cellular communications. The UK plans to completely replace its legacy TETRA network with a new LTE-based ESN (Emergency Services Network) by 2020, with elements of the network due to be rolled out at the end of this year and throughout 2019. Unlike FirstNet, it will not leverage dedicated spectrum and will utilise the commercial wireless network of BT, using spectrum at 800MHz, as well as 2.6GHz and 1.8GHz in some locations. In this situation, public safety communications will be prioritised over traditional cellular calls, which can be dropped if necessary.

A timescale for change – LTE challenges

However, despite ambitious plans set-out by these countries, they are finding that developing new LTE public safety networks offers a number of complexities. The UK’s ESN network is already over budget and deadline, whilst in the US, building a standalone public safety network using Band 14 will likely take between five to ten years to complete. One of the complications could be due to the necessary development of new functionality within LTE public safety networks. This includes push-to-talk and group chat functionality, which are not standardised services in today’s LTE networks and require new core, signal processing and radio interface protocols to be developed, which will take time.

Another major challenge is ensuring widespread LTE public safety coverage – including deep penetration into buildings such as basements, large enterprises, and parking lots, as well as remote rural locations. TETRA communications use low frequency, narrowband spectrum – 400MHz in the UK – which delivers extremely effective coverage and in-building penetration in almost any environment. LTE public safety networks, on the other hand, are looking to utilise much higher frequency spectrum – 700Mhz and 800MHz respectively in the US and UK – which have less range and penetration. The result is that public safety networks must be densified in order to provide coverage in hard to reach areas, which has obvious cost implications.

These challenges will be overcome with time and the use of new innovative coverage solutions, yet it is clear to governments and communications companies that expectations of timescales and cost may need reconsidering. As such, TETRA will not instantly disappear and will have to coexist with LTE, in most cases for many years to come. In South Korea, for example, the LTE public safety network being built has interoperability with current TETRA equipment. In France, an LTE network is being built which will share infrastructure with the current TETRA network.

Furthermore, the lifecycle for TETRA is expected to be long, due to the time and cost to deploy the networks. In cases such as in Germany, it has taken almost a decade to complete the nationwide TETRA network. Therefore, the government will be in no hurry to deploy a brand-new LTE network for public safety and replace the existing system.

Almost every country will take a different approach to deploying LTE public safety networks, particularly given the low availability of LTE spectrum. Some will take a hybrid approach, using TETRA and LTE together, whilst others have full ambitions to move communications to LTE as rapidly as possible. What is clear is that new technology is needed to solve the issues associated with public safety communications.

Ingo Flomer is responsible for defining the product management strategy at Cobham Wireless. He has over 20 years’ experience in telecommunications infrastructure and is also an Advisory Board Member for several enterprises and research projects.