Agilent Technologies E4428C, User Manual, Page: 500 / 700

476 Chapter 16
W-CDMA Uplink Digital Modulation for Receiver Test
Multiple PRACH Overview
Figure 16-21 Transmitting PRACHs
If a third PRACH transmission was configured that overlapped the second PRACH transmission for UE1,
the third transmission would occur because the second transmission is ignored/not transmitted.
The multiple PRACH feature is configured from the factory to have UE 1 on and set to start in access slot
zero. This is so you can have a PRACH signal just by turning on the W-CDMA format and the RF output,
assuming that the
MOD Off On
hardkey is set to on (
MOD ON
annunciator is showing in the display).
In accordance with the 3GPP standards, there are 16 different signatures to choose from for each UE, and the
different signatures point to the appropriate channel codes for the control part and data part. These codes are
automatically selected when a signature is chosen and are listed in the
ChCode Ctl Dat
column. The
control part is always spread with the channelization code of spread factor 256. The spread factor for the
data part is determined by the slot format, but the node that the channelization code resides on is determined
by the signature.
As seen in Figure 16-20 , there are eight positions per UE for assigning access slot numbers. When a position
has not been assigned an access slot, a dash is showing. If all eight positions have dashes, this has the same
affect as turning the UE off. This is because there are no PRACHs to transmit for the UE. You can transmit
eight PRACHs per UE by transmitting only the preamble. Since a preamble only occupies one access slot,
there would be no overlapping of the PRACH transmissions for an individual UE.