For the phone utilities, M2M represents a great opportunity. For one thing, the amount of data a device is likely to send is very small – it won’t put a great strain on the network capacity. And much of the communication is not time critical. Like other public services, phone networks experience a rush hour – typically at the end of the working day, when commuters call home to say they’re on their way and then dial up some tasty video stream. But in the middle of the night, the airwaves are almost silent, a wasted resource.
It would be no problem for low-priority messages to be scheduled for off-peak periods, effortlessly increasing revenue, while more urgent data could be squeezed into temporary lulls in mostly busy traffic.
What scares providers is the prospect of large numbers of machines trying to establish contact with a base station at the same moment – instantaneously congesting the system, and interfering with regular callers’ access. When the internet of things grows well into the billions of connections, that’s going to be a common issue. Unsurprisingly, redesigning the connection protocols to accommodate machine communications is a high priority in wireless research.
Of course, there are many other ways machines can connect into the internet – through wi-fi access, Bluetooth and so on. Much of the connectivity takes those paths at the moment. But where cellular wireless scores over these is in autonomy: not only devices with solar power (or other forms of energy harvesting) that can be freed from the electrical grid, but with mobile connectivity, they can be put in relatively remote locations, or can be free to roam.
Cars are a classic case. With vehicles already extensively run by computer, wired for infotainment, guided by connected satnavs, it’s only natural that they should each become another node in the internet of things. It’s only with the mobile infrastructure they can maintain continuous contact as they move from zone to zone down the street.
There was already interest in using wireless communications between cars as a safety measure. A leading car is less likely to get shunted if it can wirelessly message the one behind that it’s slowing sharply before the brake lights come on. Indeed, in 1999 a band of the radio spectrum – called the Dedicated Short Range Communications (DSRC) band - was allocated specifically for this purpose.
Though Professor Mario Gerla of the University of California in Los Angeles, who’s been looking at vehicle networking for the past decade, thinks auto manufacturers may lose their exclusive access because these safety systems have been so slow to come on the market.
“DSRC was developed to have plenty of bandwidth so that it wouldn’t have to fight [radio] congestion and competition with commercial traffic, to give a clean channel for the safety applications. But the rumours are that it will be taken away. So the challenge now will be to develop safety applications using spectrum that is not totally dedicated to you.”
Among the concepts Professor Gerla is working on is the “cognitive car” – one that uses intelligent spectrum sensing on the fly to identify free bandwidth as it speeds down the freeway (it is a concept similar to cognitive radio, described in the second of this five part series). In the past he’s proposed CarTorrent – a vehicular equivalent of the popular BitTorrent software used to share large files on the internet. In cars, it would allow cars to connect in a flexible way.