User Guide

PAMS
Technical Documentation
NHD–4
System Overview
Page 3–32
Original 11/97
Walsh Encoding ExampleUser A
–1
+1
+1
–1
For a 0 input,
use Code 11
For a 1 input,
use Code 00
0
0
11
Channel A
Voice data
111
0
+1
Channel A
Walsh Encoded
Voice Data
0
0
0
11
0000
User A data 1011
User B data 0110
User B
For a 1 input
use code 01
For a 0 input
use code 10
Channel B
Voice Data
Channel B
Walsh encoded
Voice data
W
2
=
0 0 – User A
0 1 – User B
+1
–1
–1
+1
+1
0
0
1
1
0
0110
1
00
111
00
+1
–1
+2
–2
Sum of A & B
Walsh Encoded
Data Streams
CDMA13.DRW
Figure 31. Walsh Encoding Example
The example in Figure 31 uses Walsh Code set 2 that has two unique orthogonal
codes, “00” and “01”. Walsh code “00” will be assigned to User A and code “01” to
User B. Now in order for the Walsh code addition to work, bipolar values must be
used, so that a binary “0” has a value of “–1”. Also unless some higher math is
utilized one more convention must be used. If the voice data is a “0”, User A’s
Walsh code is “+1,+1”.