User`s guide

Chapter 15 393
W-CDMA Uplink Digital Modulation for Receiver Test
Setting Up a Multiple PRACH Signal
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 382, 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.
The second PRACH transmission will need to begin, at a minimum, in the 12th access
slot (access slot number 11 (0 + 11 = 11)). If you started the second transmission in
access slot 10, it would be ignored since the first transmission occupies part of that
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