PRACH (LTE-Advanced)

PRACH 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

LTE-Advanced Physical Layer Overview

About Frame Summary