AN2254 Freescale Semiconductor / Motorola, AN2254 Datasheet - Page 5

• Manufacturer Part Number: AN2254
• Description: Scrambling Code Generation for WCDMA
• Manufacturer: Freescale Semiconductor / Motorola

Freescale Semiconductor
3.
4.
Binary Gold sequence z
Real-valued Gold sequence:
a.
b.
Scrambling Code Generation for WCDMA on the StarCore™ SC140/SC1400 Cores, Rev. 1
The real-valued long scrambling sequences c
The complex-valued long scrambling sequence C
and denotes rounding to the nearest lower integer:
A more intuitive way of forming the complex-valued scrambling code from two real-valued codes,
c
with sequences w
The decimation factor for the second sequence is 2. Ultimately this way of creating the scrambling
sequence reduces the zero crossings in the constellation and further reduces the amplitude
violations in the modulation process. In conclusion, Equation 13 and Equation 14 give the same
complex scrambling code as is achieved through Equation 12.
1,n
and c
2,n
, with the decimation principle is:
Z
c1,n(i) = Zn(i), i=0, ..., 225-2
c 2,n (i) = Z n (i+16777232) modulo (2 25 –1), i=0, ..., 2 25 –2
C n (i) = c 1,n (i) ( 1 + j( -1 ) i c 2,n ( 2 * FLOOR(i/2) ) )
C scrambling = c 1,n ( w 0 + jc 2,n (2k) w 1 ), k = 0, 1, 2, ...
w 0 = {1 1}, w 1 = {1 -1}
n
0
(i) =
x n (i+25) = x n (i+3) + x n (i) modulo 2, i=0, ..., 2 25 -27
y(i+25) = y(i+3) + y(i+2) + y(i+1) + y(i) modulo 2, i=0, ..., 2 25 -27
z n (i) = x n (i) + y(i) modulo 2, i=0, ..., 2 25 -2
and w
n
:
1
given as chip rate sequences:
+1 if z
-1 if z
n
n
(i) = 1
.
(i) = 0
1,n
for i = 0, 1, 2, ..., 2
and c
n
, is defined as follows, where i = 0, 1, ..., 2
2,n
are defined as follows:
25
-2.
Scrambling Codes for WCDMA
Equation 10
Equation 11
Equation 12
Equation 13
Equation 14
Equation 6
Equation 7
Equation 8
Equation 9
25
-2
5