its running on HSPA+ wish is 3G ( even doh most carriers call it 4G )
here is out it works!
G = Generation
1G = analog
2g = EVDO , CDMA
3G = GSM , HSPA , HSPA+
4G = LTE
basicly HSPA+ supoort up to 41MB/sec speeds
LTE (4G ) can go up to 75mb/sec
but in the end no phone can go faster then 21mb/sec on the market
(unless the new NEXUs has more )...
SO EVEN if you have LTE its a waist.
in other words 4G is really useless aside from a strong signal for calls witch is also useless cause its only in MAJOUR cities where you get best reception ANY WAYS. LOL
if you go to this link you can see its on GSM (wish is the same thing as HSPA but not as powerful) the frequency support up to HSPA+
Samsung Focus S specs