It's expensive to access the internet in New Zealand.

Other nations laugh scornfully at the low speed and high cost of landline broadband access - not to mention the capped data. But the laughter stops when it comes to wireless broadband. Wherever you go wireless broadband access is more expensive than access via landline. And the blame doesn't lie with some global conspiracy of telecommunications companies but with the laws of physics.

There are many factors that affect the speed and capacity of access to the internet. Some of these are just accidents of history. In the US, for example, cable TV was widely deployed before the internet came along and became the standard means of broadband access there. Here, where cable TV barely exists, we were stuck with using the phone lines that just don't have the same capacity.

But other factors are more about physics than anything else, and the big limitations on wireless communications fall into this category.

The problem with wireless is its inefficient use of space. That may seem odd: after all wireless devices take up much less space than ones that require long, bulky and inconvenient cables. But it is space in a more general sense that wireless wastes. The whole point of wireless is that your mobile device can work properly anywhere within range of a base station. But if you can be anywhere within range then the base station has to transmit everywhere within range to make sure it finds you. This means that a given radio frequency can only be used to communicate with one device within range of the base station, to prevent interference between different devices.

Contrast this with wired communications. The radio waves (or light waves in the case of optical fibre) are constrained to the cable. There is little to no risk of interference between two cables so that two devices right next to each other can use the same frequency on different cables. A wired device can use any or all of the frequencies that can be transmitted over the cable, whereas a wireless device has to share the range of frequencies with other nearby devices.

A cell tower serving internet to a city block has to ration its set of frequencies among wireless subscribers in that block - while each occupant in the block could have their own landline connection using its own dedicated set of frequencies without affecting the access of their neighbours.

Ultimately wireless communication will always be limited by the need to share radio frequencies with other nearby users. This is a potential problem for all kinds of wireless communications, from wi-fi networks to satellite access. In the case of broadband internet it means that landline access can provide more capacity than wireless access - all other things being equal - and so by the law of supply and demand we can expect landline access to always be faster and cheaper than wireless access.

And anyone who says otherwise has their wires crossed.

Update: This story's headline has been corrected from its earlier version.

- © Fairfax NZ News

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