Simulation of Asynchronous CDMA system
Repeat Problem 15.2 when the four users transmit asynchronously. For example, simulate the case when the four-user CDMA signals are offset in time by one chip relative to one of the other signals. That is, the CDMA signal of user 2 is delayed by one chip relative to the first user, the CDMA signal of user 3 is delayed by one chip relative to the signal of user 2, and the CDMA signal of user 4 is delayed by one chip relative to the signal of user 3. Compare the error probability obtained with asynchronous transmission to that obtained with synchronous transmission.
Problem 15.2
Simulation of Synchronous CDMA System
Write a MATLAB program that performs a Monte Carlo simulation of four time synchronous CDMA users when each user employs a distinct Gold sequence of length L = 31. The four Gold sequences are as follows:
The users employ the binary (±1) modulation of their representative Gold sequences with the number of chips per bit equal to 3 1. The receiver for each user correlates the composite CDMA received signal, which is corrupted by additive white Gaussian noise (added on a chip-by-chip basis) with their respective sequence. Using Monte Carlo simulation with N = 10,000 information bits, estimate and plot the probability of error for each user as a function of SNR.