PRACH (LTE-Advanced)
is the Physical Random Access Channel and is used by UEs to request an uplink allocation from the base station.
In the frequency domain, PRACH spans 6 resource blocks of spectrum. PRACH formats 0, 1, 2, and 3 have a narrower subcarrier spacing of 1.25 kHz. This means that the OFDM symbol duration is 800 ms. PRACH format 4 has a subcarrier spacing of 7.5 kHz and a symbol duration of ~133 ms.
The frequency location of PRACH is determined by upper layers.
For each PRACH Resource detected, the Frame Summary trace shows the PRACH resource index (ResourceN), EVM (in % or dB), Power (in dB or dBm), modulation format (Mod Fmt), number of resource blocks (Num RB) and Preamble ID (PID, only visible when Sync Type is set to PRACH).
See Also