Analysis of the throughput of random-access multichannel CDMA systems with multiuser detection

This paper analyzes the asymptotic behavior of the throughput of random-access (RA) multichannel CDMA (MCDMA) systems with multiuser detection. It is proved that as the maximum number K of users which the multiuser detector can handle at the same time increases, the normalized throughput function, i.e., the collision-free transmission probability for each channel, approaches a unit step function exponentially fast. This unit step function is defined as 1.0 if the average number r of simultaneous users in each channel is less than K, as 0.50 if r=K, and as zero for r>K. The maximum throughput of a RA/MCDMA system is found to be reached approximately at a traffic load value of rˆ_m (K)=K-2√K+1 for K>9