CDMA2000 Signaling
R&S
®
CMW-KM8xx/-KS8xx
472
User Manual 1173.9511.02 ─ 12
The OVSF spreading factor SF corresponds to the Walsh function of order
N
. For a
given spreading factor SF, Walsh codes and OVSF codes can be derived from each
other via the binary representation of the channelization code numbers. The Walsh
code with code number
n
is equal to the OVSF code with code number
m
, where
m
has the inverse binary representation of
n
(
n
is converted into
m
by reversing the order
of bits in the binary representation of
n
). For numbers with symmetrical binary repre-
sentation (e.g. 00 or 1001), the Walsh code and OVSF code numbers are equal.
Table 4-4: Example for SF=4 and N=4
Hadamard (Walsh codes)
after mapping to +1/-1
Code number
Bit reverse (OVSF codes)
decimal
binary
1 1 1 1
0
00
1 1 1 1
1 -1 1 -1
1
01
1 1 -1 -1
1 1 -1 -1
2
10
1 -1 1 -1
1 -1 -1 1
3
11
1 -1 -1 1
Quasi-Orthogonal Functions
To increase the number of possible channels the IS-2000 standard defines alternative
sets of orthogonal functions. These functions are called Quasi-Orthogonal Functions
(QOF) and can be used in parallel to the Walsh functions. QOF are defined for radio
configurations 3 to 9. For the purpose to generate a new channelization code the
Walsh code is multiplied with one of the three QOF. All channelization codes which are
generated with the same quasi-orthogonal function are orthogonal amongst them-
selves. All other channelization codes have a constant and minimal cross correlation to
these codes. Thus the name quasi-orthogonal functions.
QOF is only used for the following forward physical channels: Forward Fundamental
Channel (F-FCH), Forward Supplemental Channel (F-SCH) and Forward Dedicated
Control Channel (F-DCCH). For more details see 3GPP2 C.S0002-C, chapter
3.1.3.1.15.
General Description
深圳德标仪器
135-1095-0799
