Posts Tagged ‘Communications’

As part of my full-time employment I am currently working on replacing an aging proprietary trunked radio system with a new P25 system.  P25 (APCO Project 25) is the modern standard for a communications system that supports an open multi-vendor environment.  In the course of speaking with vendors and discussing requirements for interoperability many vendors are shocked to learn my demands for continuing to support “legacy” analog communication paths ranging from VHF Low Band to 800MHz when discussing a modern “interoperable” trunked radio system.  The fact is that there is nothing more “interoperable” than analog conventional radio system.

MESIN Interoperability Site

As we are in a time when many regions are spending significant funding to move toward 800MHz P25 system in the name of interoperability, many people forget the basics of meeting such a goal.  In my home state of Maryland two employees from the Department of Budget and Management authored a paper many years ago titled “TAC Stack — Or No Band Left Behind” nearly 15 years ago that has all but disappeared from the internet these days.  Their concept was quite simple – what if we could use existing nationally designated interoperability channels in each frequency band and bridge them together? What if we could do this on incident, regional and statewide scales?

In the days of significant funding for interoperability from the federal government many such regional projects were developed. In the case of the Maryland Eastern Shore Interoperability Network (MESIN) a system was deployed to provide for portable on street coverage along Maryland’s Eastern Shore bridging available interoperability frequencies on VHF, UHF and 800MHz public safety spectrum.  The beauty of such a system is that it considers the question of interoperability at a fundamental level. While many areas built similar interoperability infrastructure they did so generally on only one frequency band, the one used by them and their direct neighbor.  Such a deployment however ignores the case for when such systems are needed most – the day that help comes from hundreds of miles away.

Consider for a moment the amount of out of region and out of state support a jurisdiction may require when responding to a large or catastrophic event such as a hurricane, earthquake or major tornado outbreak.  When you request support that arrived by EMAC do you know what kind of radios they will be bringing? In a catastrophic scenario do you have enough cache radios to give each responder and the personnel to train them in their operation? The answer to each of these questions, if answered honestly, will be no.  With that in mind, take the time and effort to ensure that your radio system design makes use effectively of the national interoperability channels for all frequency bands and is able to support the monitoring and patching of those channels into your system(s).  The good news is that analog convention equipment is rather inexpensive and easy to integrate into radio system upgrade projects.  The bad news is that if your luck is much like mine, you may find sales staff looking at you like you have three heads when you ask for it.


I have been working on a few projects lately that involve providing redundant processes, particularly related to communications circuits.  What I have been finding with a great deal of regularity is that in almost all cases the technology that has been implemented over the years has replaced technologies that are still practical and effective.  In most cases, radio systems for example, low-band VHF radio systems provided noisy coverage that didn’t work from portable radios but was very reliable.  These systems were replaced by modern trunked radio systems that are very robust, offer many talkpaths, perform well in buildings but depend on complex IP based infrastructure to function.  While the upgrade path to these systems was cost effective and generally makes sense, sending hundreds or thousands of those old radios to a landfill may not be the best idea the first time you have a glitch in the new system.


Each time these issues come up someone always will say – “If only we had kept….”. Let this be the warning to each individual responsible for system lifecycles, always keep the previous generation of your networks in place and operational the greatest extent possible. Having a redundant layer is ALWAYS advisable.