I want to ask about the uplink grant for UE while attempting random access procedure. How the eNB decide the uplink grants of msg3? (Which subframe and which resource blocks). And the UE perform HARQ when transmitting and receiving the step 3 and step 4 messages. Some source said that, each step in HARQ is performed at 4 subframes intervals. If i get to the root of the problem, how many subframes ( or ms) does the random access procedure take?