This is another interesting question. In order to answer this question. You need to understand the context. Meaning Latency or round trip time involves not only the radio but also the core network and the user equipment (UE).
For user plane, the 3GPP target is to have latency less than 10 msec in a fully evolved LTE -SAE system.
User Plane is shown below.
Over Channel Setup
For overall channel setup time i.e., going from idle to active (connected mode) the latency is supposed to be less than 100 msec
Now remember this 10 msec and 100 msec latencies are expected to be applicable in ideal conditions, You may not see these values always in the usually in the field practice.