634 Chapter 17
W-CDMA Downlink Digital Modulation for Receiver Test
W-CDMA Downlink Concepts
Scramble Codes
The real-time I/Q baseband 3GPP W-CDMA personality implements scrambling codes for downlink OCNS
and DPCH channels in compliance with the 3GPP specifications. This is done through the use of the
Scrambling Code (primary scramble code) field, located in the BS setup menu, and the SecScr Code
OS (secondary scramble code offset) fields located in the OCNS and DPCH Physical Channel Setup menus.
These fields are linked so that an entry to any field affects the actual scramble code. To better understand the
relationship, refer to the following formula:
The primary and secondary sets are determined by the SecScr Code OS field values. If the SecScr Code
OS field value is zero, then the scramble code is in the primary set. Any non-zero entry enables the
secondary set. The SecScr Code OS field value has a range of
0 through 15.
A primary scramble code is the product of the Scrambling Code field value and 16. Therefore, the
primary scramble code set contains all the multiples of 16, from 0 through 8176.
A secondary scramble code is the sum of the non-zero SecScr Code OS field value and the primary
scramble code. The secondary scramble code set uses the numbers in between the multiples of 16.
Thus, all numbers from 0 through 8191 are available for scramble codes.
Refer to the following for examples of scramble codes generated with the primary and secondary sets:
Tabl e 17- 4
Where n = scramble code Range: 0 to 8191
i = Primary Scrambling Code field input Range 0 to 511
k = SecScr Code OS field input Range: 0 to 15
Tabl e 17- 5
Where n = scramble code
i = Scrambling Code field input
k = SecScr Code OS field input
n 16 i×()k+=
n 16 i×()k+=
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