The Samsung GT-i9506 is believed to be an international version of the Galaxy S4 with LTE-Advanced connectivity. Like the S4 LTE-A that was exclusively launched in South Korea in July, the GT-i9506 seems to have a Snapdragon 800 chipset inside.
The existence of the GT-i9506 is now confirmed by the FCC. The Commission’s documents show that this is indeed an S4 variant, but can’t clarify if there’s any LTE-A flavor in it. The only LTE band mentioned by the FCC next to the i9506 is band 5 (850 MHz). This, however, does not mean the new handset supports just LTE band 5. We assume the FCC only mentions band 5 because the rest of the bands supported by the device aren’t usable in the US anyway.
LTE band 5 is scarcely used around the world, and only US Cellular relies on it Stateside.
The ability to use LTE-Advanced networks is not the the only advantage that the GT-i9506 would bring over the regular Qualcomm-based S4 (GT-i9505) — which comes with a Snapdragon 600 chipset. As AndroidBeat points out, Snapdragon 800 increases CPU performance by 20-30%, and GPU performance by up to 80% when compared to S600. That is something.