Interference, Multipath, and Scintillation - Understanding GPS: Principles and Applications - page 292

1.2

BPSK-R(1), 8 MHz BPSK-R(1), 24 MHz BPSK-R(10), 24 MHz

1

0.8

0.6

0.4

0.2

0

5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0
Satellite elevation angle (deg.)

Figure 6.15 RMS ranging error for diffuse multipath model, for signals received from satellites at different
elevation angles (numerical results from [19]).

7

6

BPSK-R(1), 8 MHz BPSK-R(1), 24 MHz BPSK-R(10), 24 MHz

5

4

3

2

1

0

5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0 5 0
Satellite elevation angle (deg.)

Figure 6.16 RMS carrier phase tracking error for diffuse multipath model, for signals received from satel-
lites at different elevation angles (numerical results from [19]).

The results in this section demonstrate that smaller errors from multipath can be
obtained through use of wider signal bandwidths, wider precorrelation bandwidths,
and narrower early-late spacing (when used in conjunction with wider
precorrelation bandwidths). The quantitative amount of improvement depends crit-
ically on the specific multipath environment, including the time variation of the
multipath and smoothing of errors within the receiver processing. In some applica-
tions, shadowing of the direct path is common, and the errors that result from track-
ing of a multipath can be more important than the errors from multipath when the
direct path is present. When wider precorrelation bandwidths and narrower
early-late spacing are employed, the complexity of receiver processing increases, as
discussed in Chapter 5.

6.3.3 Multipath Mitigation
The dominance of multipath-induced errors in some applications has motivated
considerable investigation into development of multipath mitigation techniques that
go beyond the straightforward strategies described in Section 6.3.2. Some multipath