In situations ranging from mobile phone use to grocery shopping, the usual procedure is to set up some type of centralized system to manage the service. For example, the person who runs your local Walmart doesn't have to spend the day trying to find goods to sell in the store; there are people in Arkansas who take care of such things.
But what if something happens? What if Ontario, California's water supply becomes contaminated, and everyone runs to the local Walmart to buy water?
Or what if a bomb goes off in central London, and everyone in the area wants to use their mobile phones? And I mean EVERYONE.
At times of crisis communications are essential. The emergency services need to coordinate their response while the general public want to contact loved ones and find out what’s happening. The problem is that there simply isn’t enough capacity for everyone to use the networks simultaneously, particularly in densely populated areas like central London.
Networks of all types are designed to cope with typical traffic demands, and so in exceptional circumstances they become massively overloaded.
Economics teaches you that there are ways to resolve spikes in demand. For example, when everyone is running to the local Walmart to get water, Walmart can respond by raising the price of water.
In the case of central London, where a bomb did go off in 2005, a different scheme was used - not allocation by money, but allocation by power.
On July 7 2005, police requested O2 to invoke...Access Overload Control or ACCOLC...within one square kilometre of the Aldgate Tube Station for a period of four hours.
For the benefit of dumb Americans like me, O2 is a British mobile phone service provider, and ACCOLC (since replaced by MTPAS) is a privileged access scheme that allows the mobile phone network to be limited to privileged users, such as police and emergency personnel.
So when the police requested O2 to invoke ACCOLC, most people were shut out of the phone network. While this prevented your average Nigel or Ian from ringing up their wives to say that they hadn't been blown up, it did allow police and emergency personnel to get their calls through. Mostly.
Unfortunately this was only partially successful because not all emergency service personnel at the time had [the correct SIM cards in their phones to access the privileged network], which meant their calls were blocked too.
Much of the material in this post is based upon a Nigel Linge post entitled "When the phones went dead: 7/7 showed how disasters call for tomorrow’s tech." Professor Linge's post discussed the issues of allocation of scarce network space in the event of a crisis, and how the technology - and the demand - have moved forward since 2005.
But what if you didn't need the central authority to allocate the service? What if the local Walmart manager ignored Bentonville and bought a few million gallons of water directly? And what if the mobile phones on 7/7 didn't depend upon towers? In the comments to Professor Linge's post, Louis Lavery raised the second possibility:
Mobiles receive and transmit and can, if so rigged, contact one another direct, maybe hopping from one to another to make a more remote connection - without use of a service provider. What we have is a centralised system, we ignore totally the other half - a decentralised system. If we had both, or hybrids, we'd have a far better and a more robust system capable of functioning even if fixed relay points go down. But who's going to start up such a system when there's no easy way to cornering the profits? Crowd funding maybe?
Lavery notes the problem - O2 or Verizon or AT&T or whoever isn't going to want to invest a ton of money into the development of peer-to-peer communications. What's in it for them? When a Swedish company (TerraNet) pioneered the idea in 2007, most large companies stayed away. TerraNet is still around today, but I see a distinct lack of customer success stories on the site.
Of course, a really big customer - such as the police - could tell the phone vendor that they have to provide peer-to-peer communication in emergencies, or else the police won't buy phones from them.
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