It has been announced in a recent Inside AdSense blog that ad units served on cellphones, mainly the high-end models will now be more optimized to fully utilize the display capabilities of the phone. Earlier, AdSense mobile publishers were only able to serve smaller text and images on the mobile content.
If you are an AdSense publisher, you won't be require to load extra features to run the larger AdSense ad units on the cellphone. If a user is browsing content through his/her high-end phone, Google AdSense will automatically detect it and serve the larger AdSense units. The new feature is expected to increase AdSense revenue.