Saturday, September 26, 2009

Wireless data coverage is uneven

We discuss evolving cellular data generations. Today's third generation equipment provides for speeds of up to 2 mbps, but, as shown in this figure, download speed varies considerably from one city or neighborhood to another. The download speed to your iPhone 3G might be as low as 400 kbps or as high as 1,600 kbps.



The plot was generated by ARCchart, a wireless market research firm, and described by Brough Turner in a blog post. ARCchart monitored over two million performance tests using iPhone, Blackberry and Android phones, then filtered them to focus on major cities. This graph is based on 648,374 downloads from major cities in 103 nations between August 2008 and June 2009.

(Gizmodo performed a more limited test of Sprint, AT&T and Verizon 3G networks in eight US cities and also found considerable variance in download speed).

Of course, in some places there is no GSM coverage. Consider the coverage by AT&T, the GSM provider supporting the Apple iPhone in the US -- there is no coverage in the light-colored regions:



This map was taken from AT&T's coverage viewer in early September 2009, and coverage has continued expanding since then.

However, AT&T states that the maps are only an approximation, not a guarantee, of their coverage, which may be effected by terrain, weather, foliage, buildings and other construction, signal strength, customer equipment and other factors. There are many anecdotal reports of inability to use an iPhone in parts of San Francisco and the bay area.