 decreases the cost of the transaction also has to decrease. The interesting thing about mobile phones as a payment method is that potentially they combine both low transactional cost and a potentially robust authentication and security process. The obvious point to make here is that mobile phones can only do this if they are connected to a radio network that in turn provides connectivity to a banking network that can fulfil the transaction. The radio network can become a banking network and has some, if not all, of the billing and financial management procedures in place to realise this, but this brings us on to the narrative of the next ten chapters, network hardware and software. Part Three Network Hardware Wireless Radio Access Network Hardware 12.1 Historical Context The next five chapters review the technology and commercial dynamics of network hardware. This first chapter looks at wireless radio access network hardware, but in practice the topic has to be broader. A modern radio base station in a mobile broadband network has a similar amount of software code to a digital switch a few years ago and has an ability to make decisions on admission control that would have once upon a time been taken by the central switch. This is useful because many of these decisions have to be taken SO quickly that by the time the signalling had travelled to the centre and back again there would be too much decision-time latency. Given that signalling travels more or less at the speed of light or 300 million metres per second this might seem odd, but in practice a six-kilometre round trip adds 20 microseconds to a delay budget and several trips might be needed to make a decision. Add a few million clock cycles to the process and it can be seen that distance becomes a nuisance, particularly for decisions that have to be made every few milliseconds. Additionally, the once-clear distinction between computing networks and telecommunica- tions networks irrespective of whether those networks are fibre, cable, copper or wireless or a