USE WALSH TABLE TO GENERATE CHIP SEQUENCE FOR EACH OF THE FOLLOWING STATIONS WHICH WANT TO SEND DATA BIT WRITTEN AGAINST EACH

1. USE WALSH TABLE TO GENERATE CHIP SEQUENCE FOR EACH OF THE FOLLOWING
STATIONS WHICH WANT TO SEND DATABIT WRITTEN AGAINST EACH
Since there are 8 stations, so we need 8 x 8 walsh matrix each row of which represents
code for each station
𝑊1 = = [ +1 ]
𝑊2𝑁 = |
𝑊𝑁 𝑊𝑁
𝑊𝑁 𝑊 𝑁
|
𝑊2(1) = |
𝑊1 𝑊1
𝑊1 𝑊1
| = |
+1 +1
+1 −1
|
𝑊4 = 𝑊2(2) = |
𝑊2 𝑊2
𝑊2 𝑊2
| =
Similarly walsh matrix for 8 row and 8 columns can also be calculated
Here each row represents chip sequence for different stations on the channel
STATIONS DATA BIT
Station 1 1
Station 2 1
Station 3 1
Station 4 Silent
Station 5 1
Station 6 0
Station 7 1
Station 8 Silent
𝑊2 =
+1 +1
+1 -1
+1 +1 +1 +1
+1 -1 +1 -1
+1 +1 -1 -1
+1 -1 -1 -1
𝑊8 = 𝑊2(4)
+1 +1 +1 +1 +1 +1 +1 +1
+1 -1 +1 -1 +1 -1 +1 -1
+1 +1 -1 -1 +1 +1 -1 -1
+1 -1 -1 +1 +1 -1 -1 +1
+1 +1 +1 +1 -1 -1 -1 -1
+1 -1 +1 -1 -1 +1 -1 +1
+1 +1 -1 -1 -1 -1 +1 +1
+1 -1 -1 +1 -1 +1 +1 -1

2. Here data bits are encoded i-e if a station need to send a 0 bit, it encodes as -1 and if it needs to
send a 1 bit, it encodes it as +1. When a station is ide, it sends no signal, which is interpreted as 0.
Data bits Encoded in
0 -1
1 +1
Silent 0
Now, each station will multiply its chip sequence with data, if it wants to send data to
common channel
MUTIPLEXING:-
STATION CODE DATA RESULT CODE
Station 1  +1 +1 +1 +1 +1 +1 +1 +1
Station 2  +1 -1 +1 -1 +1 -1 +1 -1
Station 3  +1 +1 -1 -1 +1 +1 -1 -1
Station 4  +1 -1 -1 +1 +1 -1 -1 +1
Station 5  +1 +1 +1 +1 -1 -1 -1 -1
Station 6  +1 -1 +1 -1 -1 +1 -1 +1
Station 7  +1 +1 -1 -1 -1 -1 +1 +1
Station 8  +1 -1 -1 +1 -1 +1 +1 -1
STATIONS DATA BIT Code to be multiplied
with chip sequence
Station 1 1 +1
Station 2 1 +1
Station 3 1 +1
Station 4 Silent 0
Station 5 1 +1
Station 6 0 -1
Station 7 1 +1
Station 8 Silent 0
Station 1 [+1 +1 +1 +1 +1 +1 +1 +1] x +1 = [+1 +1 +1 +1 +1 +1 +1 +1]
Station 2 [+1 -1 +1 -1 +1 -1 +1 -1] x +1 = [+1 -1 +1 -1 +1 -1 +1 -1]
Station 3 [+1 +1 -1 -1 +1 +1 -1 -1] x +1 = [+1 +1 -1 -1 +1 +1 -1 -1]
Station 4 [+1 -1 -1 +1 +1 -1 -1 +1] x 0 = [0 0 0 0 0 0 0 0]
Station 5 [+1 +1 +1 +1 -1 -1 -1 -1] x +1 = [+1 +1 +1 +1 -1 -1 -1 -1]
Station 6 [+1 -1 +1 -1 -1 +1 -1 +1] x -1 = [-1 +1 -1 +1 +1 -1 +1 -1]
Station 7 [+1 +1 -1 -1 -1 -1 +1 +1] x +1 = [+1 +1 -1 -1 -1 -1 +1 +1]
Station 8 [+1 -1 -1 +1 -1 +1 +1 -1] x 0 = [0 0 0 0 0 0 0 0]

3. If all stations send data at the same time then data on the common channel will be sum of
all the corresponding elements of all result codes
After multiplexing we get data on channel i-e [4, 4, 0, 0, 2, -2, 2, -2]
***********
DEMULTIPLEXING:-
To demultiplex the code each station code will be multiplied to the data on
the common channel and then resultant code will be added up and divided by the total number of
stations.
Station 1
[+1 +1 +1 +1 +1 +1 +1 +1 ] x [4 4 0 0 2 −2 2 −2] / 8
= [4 4 0 0 2 −2 2 −2] / 8
= (4 + 4 + 0 + 0 + 2 -2 +2 -2) / 8 = 8/8 = +1 which is bit 1
Station 2
[+1 −1 +1 −1 +1 −1 +1 −1 ] x [4 4 0 0 2 −2 2 −2] / 8
= [4 −4 0 0 2 2 2 2] / 8
= (4 - 4 + 0 + 0 + 2 + 2 + 2 + 2) / 8 = 8/8 = +1 which is bit 1
Station 3
[+1 +1 −1 −1 +1 +1 −1 −1 ] x [4 4 0 0 2 −2 2 −2] / 8
= [4 4 0 0 2 −2 −2 2] / 8
= (4 + 4 + 0 + 0 + 2 - 2 -2 + 2) / 8 = 8/8 = +1 which is bit 1
Station 4
[+1 −1 −1 +1 +1 −1 −1 +1 ] x [4 4 0 0 2 −2 2 −2] / 8
= [4 −4 0 0 2 2 −2 −2] / 8
= (4 - 4 + 0 + 0 + 2 + 2 -2 - 2) / 8 = 0/8 = 0 which is silent
Station 5
[+1 +1 +1 +1 −1 −1 −1 −1 ] x [4 4 0 0 2 −2 2 −2] / 8
= [4 4 0 0 −2 2 −2 2] / 8
= (4 +4 + 0 + 0 - 2 + 2 -2 + 2) / 8 = 8/8 = +1 which is bit 1
Station 6
[+1 −1 +1 −1 −1 +1 −1 +1 ] x [4 4 0 0 2 −2 2 −2] / 8
= [4 −4 0 0 −2 −2 −2 −2] / 8
= (4 -4 + 0 + 0 - 2 + 2 -2 + 2) / 8 = -8/8 = -1 which is bit 0
Station 7
[+1 +1 −1 −1 −1 −1 +1 +1 ] x [4 4 0 0 2 −2 2 −2] / 8
= [4 4 0 0 −2 2 2 −2] / 8
= (4 + 4 + 0 + 0 - 2 + 2 -2 + 2) / 8 = 8/8 = +1 which is bit 1
Station 8
[+1 −1 −1 +1 −1 +1 +1 −1 ] x [4 4 0 0 2 −2 2 −2] / 8
= [4 −4 0 0 −2 −2 2 2 ] / 8
= (4 -4 + 0 + 0 - 2 + 2 -2 + 2) / 8 = 0/8 = -1 which is silent