Code division multiplexing

[TheRealAndyCook]

I understand CDM but really don't get this part, of the wiki example.

code0 = (1, –1), data0 = (1, 0, 1, 1)
encode0 = 2(1, 0, 1, 1) – (1, 1, 1, 1) = (1, –1, 1, 1)
signal0 = encode0 ⊗ code0
= (1, –1, 1, 1) ⊗ (1, –1)
= (1, –1, –1, 1, 1, –1, 1, –1)

yellow - why is it multiplied by 2? wouldn't that be more of a polar - frequency division multiplex? because your adding the depth of 2?

red - is that inverse code0.(1,1)

code0 = (1, –1), signal = (0, –2, –2, 0, 2, 0, 2, 0)
decode0 = pattern.vector0
decode0 = ((0, –2), (–2, 0), (2, 0), (2, 0)).(1, –1)
decode0 = ((0 + 2), (–2 + 0), (2 + 0), (2 + 0))
data0=(2, –2, 2, 2), meaning (1, 0, 1, 1)

is there some XOR operation im completely missing? why does red change positive and yellow not turn negative?

 

[Gearhead]

My head is spinning.

 

[TheRealAndyCook]

basically you have a stream of data...if someone changes that data...you minus the stream XOR there token and you get there data.

that way you can have 2 people sending data on one stream of data. you just XOR there token and the stream and you get there data

 

[Gearhead]

That helped me 0%. I'll just let someone that understands chime in.

 

[TheRealAndyCook]

and i just realized that i was thinking ⊗ (kronecker) was an ⊕ (XOR)

 

[TheRealAndyCook]

back from the movies, i keep trying to solve that equation correctly but there is no way to do it, unless im missing something its encoding it wrong. there is no way to solve it with out already knowing it.

 

[TheRealAndyCook]

However this makes sence. B is your encription, C is your data stream.

your xor your data (a) with b and you get which is your data c

A B C
1 XOR 0 1 {true}
XOR 1 0 {false}
XOR 1 0 {false}

since A is 1, it is (either 1 or 0) and not (either 1 or 1) and not (either 1 or 1)

as A is 1, so it is 1 NAND 1, not 1 OR 1


A B C

1 XOR 1 0 {false}
0 1 {true}
1 0 {false}


since 1 isn't 1 or 1, its NAND...it cant be XOR its false
since 1 is 1 or 0 its XOR and thus is true
since 1 isn't 1 or 1 its NAND it cant be XOR its false

 

[TheRealAndyCook]

So there seems to be no logical data on how CDM works. Just some brief theory and some unsupported code where they have used numbers to fix there equations.

I'm going to give up now, and cry in the corner because I legitimately cant figure it out.


In real terms, figuring this out is like a caveman figuring out fire after everyones been doing it for years...then again cave men didn't have cell phones, YOU KNOW WHAT I MEAN.

 

[Gearhead]

Hey, you what to do my homework? It'll make you feel smart, at least smarter than me.

 

[TheRealAndyCook]

don't think so, im legitimately broken inside, this is bugging me so much...I could actually see going to university now, just to figure this out.