Interactive end-of-chapter exercises


CDMA - Advanced

This time, assume there are 3 senders whom interfere with eachother and that the interfering transmitted bit signals are additive. The value received at a receiver, however, is now the sum of the transmitted bits from all senders.

Assume that sender 1 has a CDMA code of (1, -1, 1, -1, 1, -1), sender 2 has a CDMA code of (-1, -1, 1, 1, -1, -1), and sender 3 has a CDMA code of (-1, 1, 1, -1, 1, -1) and their combined output is: (1, 1, 1, -3, 3, -1)



Question List


1. Assuming you are receiver 1, what is the decoded bit? If it can't be done, answer with 'n/a'

2. Assuming you are receiver 2, what is the decoded bit? If it can't be done, answer with 'n/a'

3. Assuming you are receiver 3, what is the decoded bit? If it can't be done, answer with 'n/a'




Solution


1. Because the CDMA codes weren't well chosen, interference will render the receiver unable to decode the original bit

2. The decoded bit is: -1 for sender 2

3. Because the CDMA codes weren't well chosen, interference will render the receiver unable to decode the original bit



That's incorrect

That's correct

The answer was: n/a

Question 1 of 3

The answer was: -1

Question 2 of 3

The answer was: n/a

Question 3 of 3

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We greatly appreciate the work of John Broderick (UMass '21) in helping to develop these interactive problems.

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