it doesn't control your data speeds, its just a data plan.. your tower & phone determines if u will get GPRS/EDGE/UMTS/HSPA/HSPA+
GPRS (56kbps) = 2.5G
EDGE (237kbps) = 2.75G
UMTS (384kbps) = 3G
HSDPA (3.6mbps) = 3.25G
HSPA (7.2mbps) = 3.5G
HSPA+ (14.4/21mbps+) = 3.75G
LTE = 3.9G/pre-4G
LTE Advance = 4G
56k for GPRS lol. Usually wont see more than 32k unless in a popular area which doubles.
237k for EDGE lol. Usually wont more than 70k w/ possibly of 128k max unless in a popular area which doubles to 256k.
HSPA 7.2 has extended its speeds beyond capacity. In a 7.2 area ive calculated from the 2.4Mbps max to 3.6Mbps max enhanced capabilities from the tower.
In a HSPA+ 21 area on a 7.2 only capable device ive calculated lil over 6Mbps max
In a HSPA+ 21 area on a 10.2 device ive calculated lil over 9Mbps max.
In a HSPA+ 21 area on a 21 device ive calculated lil over 11Mbps max.