LTE RACH procedure include 4 steps. In 1st step UE sends preamble to eNB. UE use 6 RB for sending preamble.

In NB-IoT same 4 steps exist. But I do not know how many RBs are needs for sending preamble.

Also I read it is hierarchical and it depend on repetition level. what is repetition level? 



I want to know about difference between LTE-A and NB-IoT. I say welcome for explain or introduce good documentSmile