Effects of multiple-access interference on the noncoherent delay lock loop

This paper presents a performance analysis of the noncoherent delay lock loop (NC-DLL) in the presence of multiple-access interference (MAI). A renewal theory approach is applied along with the more familiar linear theory. The effect of the MAI on performance is evaluated in terms of the mean-time-to-lose-lock and the root-mean-square (RMS) tracking error. The analysis is made tractable by approximating the aperiodic cross-correlation function between two pseudonoise (PN) code sequences. The results are compared with those which assume that the MAI can be approximated as Gaussian noise. As expected, the results indicate a drastic decrease in performance as the number of users in a system is increased. The effect of the near-far ratio, PN code sequence length, system load, and signal-to-noise ratio on the performance of the NC-DLL in MAI are also examined.