A Deeper Understanding

Last issue I introduced LTE radios using PoC or Push-to-talk Over Cellular as the future of group communications.

This time we will take a deeper dive into the technology and look at some of the hardware available.

So how does it work?  Essentially, a PoC service is like any other client server system that you use.  Take Skype as an example that many people will be familiar with.  This is what is commonly referred to as a ‘client-server’ application.  The Skype app sits on you phone, tablet, laptop or desktop and is in constant communication with the Skype servers out there in the cloud.

When someone calls up your ID and initiates a message or a call, the server does the heavy lifting, to make sure the two are connected correctly, and that, as far as is possible, that call is secure end-to-end; that’s a client-server interaction.

PoC is the same, except it is made to look and feel like a regular, conventional two-way radio.  So you still have a client application that sits on an LTE radio terminal, talking to a server, and when you press the PTT button, all of the other users also within your talkgroup or channel, will hear your message.  Exactly like a regular two-way radio call, but with no limits on range or coverage.

Let’s bust a myth again!!  Some people will tell you this isn’t real radio, because it is using the cellular data network rather than UHF or VHF……wrong!!  As I pointed out last issue, a cellphone is nothing more than a fancy two-way radio.  It still uses radio waves to communicate from the phone to the cell tower and back again, so in this respect, the only significant difference from a UHF or VHF radio are the operating frequencies being used.

All PoC systems comprise three elements: service, airtime and hardware.  Let’s look in more detail at each one.

ServiceThe PoC service is the bit that gives you the client-server interaction.  There are a few options available to you, and very often it is a matter of personal preference that will decide which one you go for.

The most well known is probably Zello, and they have done a lot to further the use and understanding of PoC.  Zello is popular because it is free (up to a point!).  Everyone can have a free account, you can sign up as an individual, and it takes just a few minutes.  You can then set-up your own channel (more commonly called talkgroups) and give others access to it, and now you are on the air!

Zello has millions of users across the world taking advantage of the free service.  The upshot of this is that there can quite often be delays and disconnections; you aren’t expecting a premium service if you’re not paying anything for, right?

Having recognised that PoC represented the future of group communications, we invested in the development of our own client-server app called Lynx7, which offers a range of options over and above simple Push to Talk, and features end-to-end AES256 encryption and fully redundant servers to ensure security and continuity.

AirtimeThis is probably the most critical part of the whole equation, and deserves special consideration.  With most PoC systems you have two connection options, cellular data (3G/4G/LTE) and WiFi.  I say ‘most’ because there are one or two bespoke systems out there that do not offer WiFi as an option.

WiFi is a good choice if you are operating within a known geographic boundary, such as a house, large estate, shopping centre or other such location, already server with good WiFi coverage.  But be aware that you will be sharing this WiFi connection with many others, and when not gets busy, you may notice an impact on the performance.  In circumstances such as this, we would recommend configuring the WiFi to give priority to your devices, or to put in an overlyWiFi network purely for your PoC devices; both of these we regularly do for our PoC clients.

Cellular data is the right choice if you are on the move and are never sure where you are going to be headed.  Most first and second world countries are well served with 3G & 4G but take care in selecting your network.  We all have experience of poor coverage areas from our own airtime provider, so do your homework to ensure you pick the one most suited for your area, or better still, bring in a professional company to advise.

Make sure you go for contract SIM’s rather than pay as you go (PAYG) SIM’s to ensure continuity of service and reliability.  The network operators will insist they treat PAYG SIM’s no different to contract SIM’s but a mass of anecdotal evidence would argue differently.

Also beware of multi-network roaming SIM’s they are not always what they appear to be.  We have had horrendous performance results using multi-network SIM’s to the extent that we are now swapping all of our SIM’s for both our clients, and our extensive PoC hire fleet, back to single operator roaming SIM’s.

A final word in this section on data.  These services don’t use a huge amount of data, and if you are only using the devices for PoC, then 500MB per month is more than enough.  Find a plan that allows a set data bundle to be shared across a range of devices, and you will be even better covered.

HardwareHere we have an ever growing choice.  In the simplest of terms you can do what we call BYOD or Bring Your Own Device.  If you already have a smartphone, chances are you can download a PoC app onto it and get up and running.

However, approach with caution!  We all commonly use our smart devices for a whole range of things other than talking, so unless you are going to be doing very little of the latter, our advice to clients is to stick with a dedicated device for your PoC requirements.

The ever increasing range of bespoke devices has driven the rise of PoC use over the past 12-18 months.  This time two years age there was barely a handful of devices available, and now there are 100’s in all sorts of different form factors.

One of the challenges with the adoption of PoC as a mainstream comms service, was always going to be psychological.  If you give an operator a phone, they are going to use it like a phone.  Their voice procedure is going to be like they are talking on a phone.  They’ll use it for things other than voice comms, so when that critical call comes in, it may be missed, or at best the response may be delayed.

Give an operator a radio however, or what looks like a radio, and they will use it like a radio.  We’ve seen this phenomenon time and again, and it is real!

So choose your PoC hardware wisely.  We only offer hardware to our clients that we and our partner organisations have tested and approved for use with Lynx7, our PoC service.  The reality is that 95% of the devices are coming out of China, and as you’d expect, there are some very good ones, but there is also a lot of rubbish.

If you are bold enough to try to source hardware yourself, ensure you look for the CE marking indicating that it is certified for operation within the UK & Europe, but don’t stop there.  Insist on seeing the CE Certification itself.  If it cannot be produced then it probably hasn’t been through the approvals process so don’t touch it.

Better still, find a company that you trust and that has a good pedigree, not only in the technology but in the industry.  That doesn’t have to be us (but we’d be delighted if it was!), just make sure you take good advice before parting with you money!

Next time we will consider the interfacing of PoC networks with existing, conventional radio networks, and some of the things you need to take into consideration.

Communications Column – A Deeper UnderstandingBy Andy Clark

G6 Global has been delivering critical communications since 1999.  Communications connects everything that we do, and we will find the most robust and appropriate solution to your communications needs. We recently partnered with Syops Solutions who specialise in delivering communications training that will raise your teams communications skills to the next level.

For more information, email G6 Managing Director Andy Clark at:[email protected] – www.g6-global.com

The post A Deeper Understanding appeared first on Circuit Magazine.


or to participate.