Tony Abbott has said he thinks it is "hugely implausible" that the speeds on the National Broadband Network could easily increase by a factor of 10 to the 1 gigabit per second maximum speed now being claimed by the NBN. For his benefit (and the benefit of confused voters), we're here to explain in simple terms why such a scenario is plausible, even though it doesn't necessarily mean you'll get that speed directly into your house.
Picture by NBN Co
The National Broadband Network plan is based around a fibre-optic network. Simply put, this uses fibre-optic cables to transmit data in the form of light waves, rather than the copper cabling which currently connects your telephone line (and ADSL service) to the nearest telephone exchange.
Fibre has two big advantages over copper. Firstly, it experiences much lower levels of data loss and interference than copper cables, which makes it much more suitable for use over long distances. Fibre is already one of the main technologies used for backhaul (transmitting information across the network between exchanges; see our previous explanation of why backhaul matters),
The second advantage of fibre (and the one which particularly matters here) is that it can transmit data much faster than alternative technologies. To put the current Australian argument into perspective, fibre optic networks can theoretically run at up to 14 terabits per second (that's 14000 gigabits, or 14000 times faster than the newly-claimed maximum speed). While that requires very careful construction, building a network that runs at 1 gigabits per second (Gbps) isn't particularly difficult or expensive.
While fibre has huge theoretical speeds, in practice the speed is largely determined by another element: the equipment in the exchanges connected to the fibre cabling at either end. Unsurprisingly, getting higher speeds requires more complex and more expensive equipment at the exchange level. However, that equipment can be replaced or upgraded to allow higher speeds without requiring the fibre itself to be altered. Determining network speed thus becomes a trade-off between speed and the cost of equipment -- which is why the NBN originally set itself a goal of delivering 100 megabits per second (Mbps) to end users.
As with most areas of technology, however, equipment gets more efficient and cheaper over time, making it feasible to deliver higher speeds as the network is built and evolves. Planning for the NBN has been going on for more than a year, so the increase in speed is not that surprising or remarkable, especially given the much higher speeds fibre networks can actually handle. It might well be debatable whether the announcement of that speed increase is a matter of political expediency, but the physics and engineering are well-established and tested.
It's worth remembering that 1Gbps is a maximum potential speed. The actual speed experienced by the user will be affected by numerous other factors, including the rate at which data is being transmitted from a given site or application, and the speed of networking equipment at the customer end. For instance, if you've got a high-speed connection but an old slow wireless router, your maximum speed will be dictated by the router. If you're accessing an overseas web site, the number of other customers using the same ISP as you also trying to access overseas sites will be a constraint.
However, those same variables also apply to any other kind of Internet connection you can think of, whether that's ADSL or wireless or cable. It's also important to remember that while most of us think of the Internet in terms of browsing web sites (and downloading torrents), it can also be used to transmit other data using other protocols, some of which can be much more efficient than those current applications.
New use cases also continue to emerge. A decade ago, few people would have imagined that video content could be routinely served onto sites; today, that's the rather mundane reality of YouTube. Video on demand services are already being promoted by ISPs, but those would be much more accessible on a high-speed network.
While the NBN has promoted 'fibre to the premises', this doesn't actually mean a single unique fibre connected directly to your home for your exclusive use. The NBN uses a network infrastructure known as GPON (gigabit passive optical networking), which uses one fibre to deliver to a group of locations and only splits it close to the premises. This is much cheaper and easier to maintain than a direct fibre connection to every location.
In the case of the NBN, each fibre will serve 32 households. Even if all 32 are connected simultaneously, however, NBN Co calculates that users will get a typical maximum speed of 78Mbps. (In the case of larger premises such as hospitals and universities, the NBN will offer direct fibre connections for better speed.)
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