CDMA2000 Signaling
R&S
®
CMW-KM8xx/-KS8xx
471
User Manual 1173.9511.02 ─ 12
4.2.10.2
Channelization Codes
The forward CDMA2000 channel is spread using orthogonal Walsh functions W
n
N
defined in terms of the order
N
of the function and the index
n
ranging from
0
to
N–1
.
This index is also called channelization code number. The Walsh functions are con-
structed from a
N x N
Hadamard matrix, generated by means of the following recursive
procedure defined in 3GPP2 C.S0002:
For the spreading operation the binary symbols of the Walsh function are mapped as
follows:
0
is mapped to
+1
and
1
is mapped to
-1
.
Orthogonal Variable Spreading Factor (OVSF) codes provide an alternative scheme of
generating codes that preserve orthogonality between channels. They are derived from
a hierarchical tree.
Channelization codes are used to separate different physical channels of the same
carrier frequency, cell and user. They are defined in terms of the spreading factor (SF)
and a code number
m
ranging from
0
to SF
–1
. The codes c
SF,m
are called Orthogonal
Variable Spreading Factor (OVSF) codes and are derived from a hierarchical tree:
The following rule has to be observed for assignment of channelization codes in order
to avoid code conflicts. Within each branch only one code can be used at the same
time. This means:
●
1. Other codes on the path between the code and the root of the tree must not be
used.
●
2. Codes in sub-branches of the code (to the right of the code) must not be used.
For an example see the figure below. The red parts are blocked when c
4,3
is used.
General Description
深圳德标仪器
135-1095-0799
