Some of us remember when two-way radio vehicular equipment used valve transceivers and dynamo generators. Transistor technology eventually took over and transceivers became smaller, with handhelds also becoming available.
Time moves on, and we now have small and even tiny hand- held communicators. But back in the mid-1970s we wouldn’t have dreamt that a transportable cell- phone, the size of a small car battery, would shrink to the size of a Mars Bar 10 years later.
Likewise with handheld PMR transceivers: those went from the size of a house brick to the footprint of a credit card. PMR users are now increasingly us- ing digital terminals. These have considerably more facilities than their earlier analogue counter- parts, such as data communication like text messaging, along with integrated GPS receivers, Bluetooth connectivity and the like.
Trunked radio has also given us many advantages, not only for spectrum efficiency but also allowing multi-site operation. There are few, if any, modern medium- and wide-area networks not taking advantage of trunking. A well-known use of trunking with digital terminals and GPS location technology is Airwave’s TETRA system in the UK.
MPT1327 is certainly not dead though, a significant user of this technology is Transport for London (TfL) for its fleet of more than 7,600 buses. With 10 base stations covering Greater London and 66 traffic channels it has committed to continue using this for at least four more years before eventually migrating to a DMR system to give greater capacity.
The phrase of ‘if it isn’t broken don’t fix it’ certainly came up at a recent meeting between Ofcom, radio manufacturers and users. TfL also uses TETRA for the London Underground, and the Airwave Direct service for TfL-wide communication, which eliminates reliance on public mobile networks.
My own company helped with the migration of a major UK government agency from analogue FM to DMR a few years ago, with encrypted DMR being its decision as best for its needs following our presentation of various digital radio technologies.
Right now DMR is also the choice of many commercial two- way radio users as a migration to digital, although dPMR-based technology also fulfils specific needs for many. Interconnection between digital radio systems and other communication methods such as fire alarm panels, digital pagers, email, alert calls, text messaging, the internet, and digital telephone interconnect is not just a bonus, but to many users an absolute necessity for an integrated communication system.
What of the future? Most readers will be aware of the UK’s forthcoming Emergency Services Network (ESN), where fourth- generation cellular (4G) will be used for multimedia communication between terminals, dispatchers, and interconnection with other third party communication methods. On the commercial side a national DMR Tier III system is being rolled out and this may radically change the way small, medium and large businesses communicate. Past lessons from the two earlier national MPT1327 commercial networks, and the later Dolphin national TETRA commercial network, could show that this may be an interesting challenge. Once the ESN is fully in place what will become of the existing national TETRA infrastructure, as well as the vast number of TETRA terminals in current use that may become redundant?
Push-to-talk over cellular didn’t catch on in the past because of long latency times, often in the order of several seconds. However, with the ongoing rollout of 4G coverage it’s becoming more attractive to PMR users, with a much lower latency of around 600 to 700 milliseconds. Could this be an alternative and even a competitor to traditional PMR?
For the next step, the Next Generation Mobile Networks Alliance is encouraging “ecosystem players” to work together to make 5G available by 2020. But is this realistic considering current 5G technology development? Microwave frequencies including new spectrum bands above six GHz are intended to be used for 5G, which is likely to present interesting challenges for geographic coverage.
Many more base sites will also be required – is this realistic either? In January 2016 Google announced Project Skybender; an initiative to deliver a 5G network over solar-powered drones that would give ‘line of sight’ coverage to many outdoor locations.
No-one can predict exactly what the future of PMR communications is going to look like, but we certainly live in interesting times!
About the author
Chris Lorek is SMC Group’s CTO, and has been with the company for 28 years. He specialises in planning and arranging the manufacture and installation of bespoke radio systems, including city- wide and country-wide secure digital radio networks.
