Influence of multipath fading and mobile unit velocity on the performance of PN tracking in CDMA systems

Influence of multipath fading and the mobile unit velocity on the performance of the pseudo noise (PN) tracking system is evaluated and the ability of the PN tracking loop to maintain synchronization under different channel multipath conditions and mobile unit velocities is quantified. The approach used in this paper uses the probability that the tracking loop will lose lock-in (P_L) as a measure of performance which is evaluated as a function of multipath spread of the channel (τ_d) and mobile unit velocity. The results show that when τ_d>0.455 chip duration (T_c) the performance of the PN tracking loop degrades substantially; i.e., P_L>10^-5. Similarly, the mobile unit´s velocity has an influence on the performance of the PN tracking loop. Results indicate that for constant mobile unit velocity, the velocity affects the rate at which the loop responds to changes in tracking errors due to noise