Indoor Positioning with GNSS-Like Local Signal Transmitters - Global Navigation Satellite Systems: Signal,Theory and Applications - page 317

evaluation purposes, since this situation is clearly not representative of reality), the envelope
of the resulting error in pseudo-range measurement is drawn. The upper curve corresponds
to reflected path in phase with the direct signal, when the lower curve is related to the case
where the reflected path is out of phase with the direct path. Note that SDLL is absolutely
not suitable for indoor environments since errors as high as 60 meters are possible 17 . The
same almost applies to the Narrow Correlator 18 since errors of 10 metres are still possible: if
the goal of accuracy is in the range of a few metres, this approach is also not viable.
Pseudo-range error in m
80
SDLL
40
NC
0
-40
-80
0 100 200 300 400 500
Delay of reflected path in m
Fig. 10. Multipath effect of the pseudo-range measurement
Fig. 11. Typical multipath environment indoors
17 Here one has the explanation why no commercial solutions are available in the field of code phase
pseudolites!
18 Another constraint of the Narrow Correlator is the need for a receiving bandwidth of at least 8 MHz,
which is not the current standard. Nevertheless, the standard is bound to evolve with the advent of
Galileo in the frequency band L1/E1 since the current 2 MHz are too narrow for an acceptable detection
of their signals.