CDMA Network...PLEASE help(homework)

[The_Other_One]

OK... So I'm in this networking class and the crap's nothing like I expected. It's all about the internals of the network... Well, we had some homework, but I'm totally baffled. The book has no direct examples, our lecture notes have no similar examples, our teacher's impossible to understand, and examples/answers make no sence to me! Here's what I found online...

CDMA. Chapter 2.53. Page 181. A CDMA receiver gets the following chips: (-1 +1 -3 +1 -1 -3 +1 +1). Assume the chip sequences defined in Figure. 2-45 (b), which stations transmited, and which bits did each one send?

Ans: Just compute the four normalized inner products between the signal and the four chip seuqnces:
(-1+1-3+1-1-3+1+1)•(-1-1-1+1+1-1+1+1)/8=1
(-1-1-1+1+1-1+1+1) is A's chip sequence.

(-1 +1 -3 +1 -1 -3 +1 +1) • (-1 -1 +1 -1 +1 +1 +1 -1)/8 =-1
(-1 -1 +1 -1 +1 +1 +1 -1) is B's chip sequence.

(-1 +1 -3 +1 -1 -3 +1 +1) • (-1 +1 -1 +1 +1 +1 -1 -1)/8 = 0
(-1 +1 -1 +1 +1 +1 -1 -1) is C's chip sequence.

(-1+1-3+1-1-3+1+1) •(-1+1-1-1-1-1+1-1)/8=1
(-1+1-1-1-1-1+1-1) is D's chip sequence.

The result is that A and D sent bit-1s, B sent bit-0, and C was silent.

That is the question and answer. While I can just write down the answer and be fine, I'm sure this will come up later and I really want to know how it came about... From the looks of it, I just need to add them up and muliply the two things. However, I get nothing like the posted answer...

 

[codeman0013]

Wow man i'm in a networking class and i dont think i will ever see anything like that our school must be behind or something lol!