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 document
NB-IoT has 6 RBs for sending preambles. In the frequency range, subcarrier spacing of 3.75 kHz is applied. NPRACH resources occupy a contiguous set of either 12, 24, 36 or 48 subcarriers and are located on a discrete set of subcarrier ranges. The preamble is based on symbol groups on a single subcarrier. Each symbol group has a cyclic prefix (CP) followed by 5 symbols. Two preamble formats are defined, format 0 and format 1, which differ in their CP
length. The five symbols have a duration of 1.333 ms, prepended with a CP of 67 μs for format 0 and 267 μs for format 1, giving a total length of 1.4 ms and 1.6 ms, respectively. The preamble format to be used is broadcasted in the system information.The preamble is composed of 4 symbol groups transmitted without gaps. Frequency hopping is applied on symbol group granularity, i.e. each symbol group is transmitted on a different subcarrier. By construction, this hopping is restricted to a contiguous set of 12 subcarrier. Depending on the coverage level, the cell may indicate that the UE shall repeat the preamble 1, 2, 4, 8, 16, 32, 64, or 128 times, using the same transmission power on each repetition.