492 Chapter 16
W-CDMA Uplink Digital Modulation for Receiver Test
Setting Up a Multiple PRACH Signal
Access slot numbers can be entered into positions that either contain dashes or that already contain an access
slot number.
Conversely there are also two ways to eliminate access slot numbers:
• Highlight the position for a UE that contains the unwanted access slot within the 80 ms time period.
Press the
Edit Item softkey and then the Off softkey that appears.
You will see a dash inserted in place of the access slot number. The dash means that the current position
within the 80 ms period has been turned off.
• Highlight any position/item on a UE’s row, and press the
Clear All Pos of Selected UE softkey.
You will see a dash inserted in place of all access slot numbers for the selected UE.
When all positions for a UE are occupied by dashes, the UE can no longer transmit any PRACHS. This has
the same affect as turning off the UE.
In this task you will learn how to use access slots for determining the placement of the PRACHs within the
80 ms time period.
This task assumes factory preset conditions for the timing setup display.
1. Setup UE1 for two PRACH transmissions.
For this task, we will use the factory default access slot of zero for the first UE1 PRACH transmission.
Using the parameters that can be set in the PRACH code setup display, you can calculate the number of
access slots required for each UE1 PRACH transmission. This calculated value can then be used to
determine the placement for each repeated PRACH within the 80 ms period. This avoids overlapping the
retransmitted PRACHs. Remember a PRACH that is repeated and overlaps a previous transmission for
the same UE, is ignored.
In the section, “Configuring the PRACH Code Setup” on page 481, we set the Tp-m to 4 access slots and
the message part TTI to 10 ms (7.5 access slots). These values are used in the following steps to
determine the access slot for the second UE1 PRACH transmission.
a. Highlight the second access slot position for UE1.
b. Calculate the number of access slots occupied by a single PRACH.
Message part TTI = 10 ms One access slot = 1.33 ms
10 ms / 1.33 ms = 7.5 access slots
Tp-m = 4 access slots
One PRACH transmission = 7.5 + 4
= 11.5 access slots
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