Riots and looting in several English cities during August placed heavy demands on Airwave, the national TETRA network for the emergency services. Martin Benké, network services director, explained to Richard Lambley how the emergency was handled

In our service centre we have, on the wall, TV channels showing Sky News and BBC News, so we were across [the disturbances] very quickly.

As soon as we spotted that something was kicking off, the first thing that we did was we got on the phone to our customers and asked them if there was anything we could do to help. And we started to monitor proactively, and give an additional look at sites in the affected areas. We saw the traffic on the network starting to build up and we saw additional usage, predominantly by the police.

The real growth in traffic didn’t start to occur until Tuesday, August 9, which was the day after the Croydon fire [when a furniture showroom was burned down by rioters]. David Cameron [Prime Minister] got up and talked about putting 16?000 police on the streets of London. That’s when we noticed a real surge in capacity.

We’ve done a comparison between what the network looked like on Tuesday August 2 and what the network was like on Tuesday August 9, when it was clear that there were going to be lots more police on the streets.

Fundamentally, the network was twice as busy as it was the previous Tuesday. So on August 2 we carried about two million calls on our London switch and on August 9 that number became four million calls.

Call minutes also doubled – more than doubled, in fact. They went up from 450?000 on August 2 to 950?000 on August 9. And of that 500?000 increase – we’ve done the analysis – we can clearly see that the vast majority, 470?000 of those, came from police users. A significant increase.

There were many additional police users on the streets causing many additional call minutes. It doubled the usage of the network, effectively.

Dynamic changes

Once we’d studied the problems, we started to put in place additional resource – extra people looking at the network, extra people available 24 hours a day to do dynamic changes to the network.

We put additional resource in to monitor the [radio] sites more closely than we would do normally, particularly in the areas of high usage. And we then put in place what we call our parameter change team – these are the people who are responsible for the actual configuration of the network – and they were making dynamic changes to the network to ensure that capacity was managed carefully.

One of the things that eats up capacity on a TETRA network is where people drag their talk groups on to a site, so that you end up with – for example – police from Manchester providing mutual aid [reinforcement] to the Metropolitan Police [the main London police force].

They come down to London to provide help – but what they actually do is sit and listen to their home talk groups, so they can understand what’s going on at home! But they are taking capacity away from the Met, because they are listening to Manchester talk groups in London.

So we had to put in place what we call a valid site profile, which restricts the use of the base station to the specific talk groups a customer wants to use on it. It effectively stops police from Manchester in London listening to Manchester talk groups. We have to manage the use of it because there is a finite capacity out there. If the talk groups are being used ineffectively, then of course it eats into capacity.

The other thing we did was we put additional engineers on the ground in London in case of problems, to fix faults on base stations. But I’m glad to say we didn’t have any of those. So our additional engineering resource was there and available, but it wasn’t actually used to go out and fix anything, because nothing broke.

Peak allowance

In terms of capacity, the way we configure the network is we look at the average usage and then we put an allowance over the top of that to deal with unexpected peaks. We’ve also put in some additional capacity for the Olympics [the London 2012 Games]. So we have additional capacity in the network right now because of the Olympics, and we didn’t suffer any capacity issues at all during the unrest.

As well as the additional resource we put in place to monitor the network, as well as the parameter change team, as well as the additional field engineering support, we did do some other things which are perhaps worthy of note.
We stopped all planned work on the network. Obviously we have to do upgrades, we have to go and swap out faulty equipment and things like that, but we stopped all of that during the period of the unrest. So there was no disruption to the network for any adds, moves or changes.

And we held a series of daily conference calls with our customers, at two o’clock every afternoon, to ensure that they were up to date with the status of the network, to take any intelligence that they might be able to provide us with as to where unrest was. We also sent out, on an hourly basis during the evenings, the status of the network so that our customers would know if there was a site down that might impact their ability to respond.
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