Why LTE requires low latency

There are two obvious reasons why LTE networks will require both lower latency and higher bandwidth backhaul: LTE simply is the lowest latency air interface and features bandwidth that cannot be supported by legacy backhaul protocols.

Edge and EVDO networks can handle average peak data rates using two or three T1 links, but need more than that to handle peak rates. But HSPA networks cannot do so, either efficiently or conveniently. To support peak rates on an HSPA network, about 45 Mbps is required.
An LTE network using a 10-MHz channel requires nearly a DS-3 (45 Mbps) just to handle average load, and needs an Ethernet connection to handle peak loads.
Also, where older GPRS or EDGE data networks featured round-trip latencies in the 600 millisecond to 700 msec. range, LTE networks feature round-trip latencies in the 50 msec. range.
That means Ethernet speed backhaul and lower-latency performance is required.