A couple of things: - It's not going to get fixed by a software-defined radio. You also need an antenna that can function acceptably at all these frequencies - it's hard enough getting one that'll work pentaband - and PAs that can output the required power at these frequencies. SDR doesn't solve those issues. - When mortals roam, they don't want LTE. They are paying so much for data roaming, LTE would bankrupt them in minutes. Worldwide roaming on WCDMA is frightening enough (says the person who clocked up $600 of charges in 3 hours in Taiwan by mistake). Ok, so this isn't applicable if your phone is unlocked, but still… there's a business issue besides the technical one. @Kai: voice and 3G data will be fine.