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 Physical Random Access Channel spans 6 resource blocks of spectrum. PRACH formats 0, 1, 2, and 3 have a narrower subcarrier spacing of 1.25 kHz kiloHertz: A radio frequency measurement (one kilohertz = one thousand cycles per second).. This means that the OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. 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 Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format. (in % or dB), Power (in dB or dBm deciBels referenced to a milliWatt: dB relative to 1 milliwatt dissipated in the nominal input impedance of the analyzer), modulation format (Mod Fmt), number of resource blocks (Num RB Resource Block) and Preamble ID (PID, only visible when Sync Type is set to PRACH).
See Also
