Spark fired up five cellular towers to give Queenstown the fastest mobile data speeds in the country. The company says users have managed 400Mbps downloads during testing.

The towers are in Queenstown's tiny CBD, as well as in Frankton and Arrowtown with other towers filling the gaps between these sites. It turns out users in the Queenstown area are data gluttons. One of the sites in the town numbers among the top ten nationwide.

Spark already has towers using the same technology in central Christchurch and in Silverdale. They are one-offs. This is the first time Spark has kitted out an entire region for faster mobile data.

The reported speeds are impressive, but that's not the whole story. During a test held in Christchurch last year, a custom-made receiver managed to download data at 1.1Gbps.

Spark describes the wireless technology deployed in Queenstown as 4.5G. That's controversial in some circles. But is the simplest way to describe a stepping stone between the 4G mobile service found in most of New Zealand and the next generation 5G services expected to debut in 2020.

The technology is LTE-Advanced Pro. It offers about four times the speed and capacity as everyday 4G. One key feature is the ability to aggregate spectrum giving users more bandwidth to play with.

The other controversy is today's devices can't make full use of Spark's 4.5G technology. Vodafone used an interview opportunity in the NBR to sneer at Spark's claims.

Most recent phones can get speeds in the 400Mbps range.

Spark says it roll out its 4.5G technology to another 10 towns over the next year.