POC (PTT Over Cellular).

PTT over Cellular or POC is a form of radio communication that relies on the use of the existing cellular telephone network. It isn’t a particularly new technology but in recent years it has become much more attractive as an alternative to conventional two radio communications.

What Can POC do that radio can’t?

Using a POC system you can communicate wherever you have cell phone coverage or a data connection such as WiFi. That opens up the possibility to communicate over huge distances without needing your own complex infrastructure such as trunking or repeaters. As well as walkie talkie style communication you can send text messages, pictures and even stream live video. You can also track a users location using GPS. Calls can be made to individuals, groups or everyone. There is a lot you can do with POC.

What can’t POC do that radio can?

POC’s biggest problem is that it need a cellular or data connection and a connection to a control server. It doesn’t need a particularly fast data connection, but if you don’t have one or the server is out it won’t work. So POC won’t work in remote areas and even in well developed countries there can still be gaps in the cellular networks. In a disaster situation the cellular network or server center may be damaged or overloaded and this can make POC unusable. While there are special sims for emergency service providers that have priority network access in emergency or overload situations it is possible that in an emergency the police or government may restrict access to the cellular networks. So those with regular sims will be locked out. For these reasons you must be very careful before choosing a POC system for safety to life applications.

Cost?

POC can work out expensive as each device will require a sim card with some sort of airtime or data agreement. The devices themselves are no more expensive than other good quality walkie talkies but each device requires a sim card or data plan with on-going charges which can build up. There will also be a cost, normally per user for the server and control system for the network. But as you don’t need to have towers, repeaters or any other infrastructure it will often work out cheaper than a trunked radio system. But when direct radio to radio communication is possible POC is typically more expensive, often a lot more!

Hybrid.

In the last few years a number of suppliers have started to produce POC devices that also have traditional walkie talkie capabilities. These devices are generally based on an Android phone so have all the functionality of a phone, POC device and walkie talkie. Although quite expensive these devices give you the best of both worlds.

POC Networks.

There are many to choose from. You can get free accounts with Zello if you just have a few users and are happy with the basic PTT platform that Zello offers. But many organisations want their own system as this gives them absolute control. We run and can install servers from ProPTT. These are fully scalable from 10 users to 1000’s and include options such as live video streaming between users, live tracking and mapping. For our disaster and emergency communications we have a portable fly-away server and a mesh network that can cover a very large area and we use hybrid POC/DMR devices.