Figure 7

In this scenario, the channel estimation algorithm has to cope with a LOS path (red) that is superimposed by several simultaneous multipath replicas. The DLL receiver (green) shows the typical multipath errors, whose magnitude varies due to the fading processes of the path amplitudes. If the multipath replicas are not taken into account by the estimator (, (a)), the LOS estimate (dark blue) shows still significant errors, but their magnitude is smaller than the DLL errors, since the dynamic model used in the estimator helps to constrain variation of the LOS estimate. With (b) the number of considered paths is too small to track all replicas and thus the multipath delay estimates (light blue) tend to jump between the respective multipath signals. Once the number of considered replicas is sufficient to take into account all present signals (, (c, d)), the estimation algorithm detects and tracks the channel, except for the period between 40 s and 80 s. During this interval, a proper resolution of the actual LOS does not seem feasible any more, due to the presence of an echo which is born with almost zero delay w.r.t. the LOS path which itself is strongly attenuated, hence its history does not allow to separate it suitably from the LOS component.