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Why 3G?


jimcarter

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Last week I was involved in a product refresh with the senior engineers of one of our UK National security companies. We covered off our new SPT.6 hardware in both its “Pro” and “Mini” versions which was all very nice, but it was the 3G capability of the new devices that drew much attention and I thought it would be useful to share some of the topics we covered.

When you are in the business of data communications you have to constantly revisit and re-evaluate the old technologies, how they compare with the new and what operational differences there may be. Looking back on my piece written around radio installations I realise that some of what I wrote at the time (3 years ago) may not be relevant to today!

What is apparent is that the wireless data network is improving with the release of 3G and 4G. Incidentally I saw a development 5G device on the BBC news website last week, its worth looking up. I am not about to go as far as saying that wireless will take over from broadband anytime soon, it will be quite a few years before mobile communications will mirror the last mile resilience and data speeds of a fixed line circuit. But from what I have seen, 3G is enough to consider radio only communications favourably for critical data transmission where circumstances require it and with a potential to reduce reporting times below what we would consider a 2G device capable of.

Let us take a look at some basic comparisons between 2G & 3G. The switch from analogue GSM services to digital took place in the 90’s or in generation terms, from 1G to 2G. 2G was designed as a voice service with a basic data transmission capability, primarily for text and very limited Internet connectivity. Bandwidth is low but suited to applications where the packet data is small, such as a poll or alarm message in an alarm transmission system. However error correction is quite poor and inefficient and it is often necessary for devices to resend and validate data that has not been correctly received. This can lead to extended download times or a “timeout” to occur where the devices can no longer continue to communicate in the same “session”. This means the communication process has to begin again.

2G requires the last mile (between the base station and the module) to be stable, reliable and have a very good quality of service.

3G differs in that the service has been constructed around mobile data operations as well as voice. It came into its own when the rise in smart phone demand exploded. It is a protocol that has vastly improved error correction (less retries and “timeouts”), improved building penetration and at least double the download speeds. Resilience is improved too; a fall back to Edge (2.5G; or the stop-gap between 2G & 3G) and GPRS when 3G is not available maintains data connectivity.

In operation, 3G (so my Development team tell me) is like DAB radio in that if you have a “signal” (literally any signal) it will work, where as 2G is more akin to Long Wave radio where signal and direction are required to obtain service.

Translate this into a Security application and we find that our usual indicators are not entirely valid. For example signal strength has been used as a guide to 2G service availability (although not an entirely reliable one). On a scale of 1 to 10, anything indicating 3 or below could suggest a potential problem. In 3G terms, signal strength is meaningless. If the module has a good connection it will work as long as that connection is “up” regardless of signal, whether it be a 1 or a 10.

How do we survey a site of this is the case? It can be argued that a survey is obsolete in its own right as the device has an ability to intelligently roam between service providers and incorporates a secondary roaming feature that can hop between technologies and frequencies (which makes jamming almost impossible by the way). But there are tools we can utilise and what is even better they are free! The network providers publish coverage maps on their websites. Some include service availability notifications as well. Or there are Apps that you can download to your Smartphone such as “Open Signal”. This App uses data gathered from its users to populate a service coverage map based on actual availability data as opposed to what the operators would like you to believe. It constantly updates, shows local serving cells and the more users there are the better the data mapping becomes.

Building a next generation mobile data module into a security product has several challenges. Cost is the leading factor. New generations of devices carry a premium and it has only just become viable for WebWayOne to incorporate a 3G module as standard and retain a competitively priced SPT. Migrating to 4G will come but it will be the module price that determines when this will be.

Next are the changes in software. You cannot simply bolt a 3G module onto a piece of hardware and expect it to work. The Development team have to “tame the beast”, working with the modules design teams; not only to make it work, but to maximise the features that the module can support, for example the ability for the module to manage the SIM cards connectivity to the network.

Operationally the results are quite staggering. 3G coverage is excellent and the download speeds for a 650K file are 25 minutes on 2G compared to 6 to 8 minutes over 3G.

Let me provide you with some hard information. I have two test SPTs at home, both are operating in radio only mode, both are configured for a 3-minute reporting time, have the same software and a Telefonica Roaming SIM card installed. I can share with you the comparison over the past month of testing that is revealing.

My home is a particularly good testing ground as I live in a rural part of Berkshire with very poor radio reception and just two providers available, O2 & Vodafone. Below is the diagnostics I can retrieve from the SPT showing 3G operation on a 900 frequency band with a signal strength of just 2.

blogentry-7774-0-07546900-1418141204_thu

And here are the comparisons in signal strength over the past month (scale 0 to 10 where 10 is the maximum signal). You will see they are very low, generally below 3.

blogentry-7774-0-20807200-1418140015_thu

3G Signal

blogentry-7774-0-57160800-1418140096_thu

2G Signal

The 2G device is obviously struggling to maintain a connection and since the 22nd November it has lost registration to the core network to all services, whereas the 3G device has been online all of the time. This is reflected in the circuit availability.

blogentry-7774-0-56982700-1418140143_thu

2G network availability for the month is 81%

blogentry-7774-0-52881500-1418140214_thu

3G network availability is 99.79%

When you translate the availability figures into the number of failures that would have been reported to the end user the scale of the difference is aparent. The 3G device would have reported just 3 fails (of which 2 of these were during tests I carried out with the device), compared to 385 fails from the 2G device.

I would not advocate rushing out and installing 3G only with 3 minute reporting times or consider replacing broadband devices with radio only. But certainly where longer reporting times are concerned and a landline is not available or impractical then the stability figures we are seeing gives confidence. Coupled with a fixed line circuit, especially Broadband provides an incredibly robust solution.

Looking to the future, the speeds that are being achieved and the reliability of the circuits demonstrate that high bandwidth applications can access the 3G to. Where Imaging or CCTV is concerned the speed in which you can transmit images to an operator is critical and therfore 3G is a viable backup path to broadband.

So to conclude. 3G:-

  • Supports faster Upload/Download speeds - future applications such as Imaging and CCTV have access to a viable backup network
  • Has better building penetration
  • Signal strength is not as operationally critical
  • Will automatically drop to Edge or 2G if a 3G service is unavailable
  • Frequency hopping renders jamming almost impossible
  • Global SIM cards provide additional resilience in network roaming
  • Additional software controls on the module allow for intelligent roaming (as opposed to letting the SIM card and network operators determine connectivity)
  • Network coverage is excellent, before the ability to roam providers comes into the equation

But remember; it is the GSM module and not the SIM that determines what technology can be accessed.

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