Good explanation about how scattered the LTE spectrum is, why there will be different iPhone 5 models and how other LTE handsets handle this challenge.
The need to simultaneously support different systems (LTE, WCDMA, HSPA, MC-GSM etc.) in one handset, while simultaneously supporting an increasing number of frequency bands (LTE will be available in 18 bands by the end of 2012), has resulted in a significant increase in RF system complexity for mobile handsets.
This article also explains very well that LTE PA’s need double the power of 3G. So I wonder how Apple can claim that battery time for 3G and LTE is both 8 hours in the iPhone 5.