I keep mentioning in posts on HSPA data speeds that one has to be very careful when using such numbers as they represent the theoretical maximum that is only reached very close to the base station. In various presentations, one can often see graphs where speeds are shown over the percentage of users, i.e. what speeds 95% of the users are experiencing to the speed only experienced by 5% of the users. But what does that mean when plotted over a geographical area?
Ericsson has done a great job of visualizing this in their 1/2009 edition of the Ericsson review on page 8 figure 2. I can't reproduce it here, but I encourage you to follow the link and check it out for yourself, it's very insightful! As you can see in the 3 pictures, which represent various stages of the HSPA+ evolution, the direct benefit of adding higher top speeds gets more and more limited the higher the speed.
What the pictures don't show, however, is that subscribers not enjoying the best radio coverage do also benefit from higher speeds, in a different way though. By having at least some users in the zones where data can be transmitted faster, users under ordinary conditions benefit because the overall cell capacity has increased, as some uses can transfer their data faster, thus leaving more time to serve other users.
Great visualizations, thanks to Stefan Ström, Dirk Gerstenberger, Johan Bergman and Fredrick Gunnarsson for the article!