Global Positioning System Reference
In-Depth Information
the lab window, so to have and indication of the available GPS constellation. The distance
between the antenna of the auxiliary receiver and the test indoor antenna is
≤
10 m. The sky
Fig. 10. Skyplot, indoor, Rb
plot relative to this case-study is depicted in Fig. 10. PRN6 and PRN30 are considered in this
section. The assistance log is summarized in Table 4. Then the 3-step procedure in Section 5.2
is applied. Firstly, the strongest signal, which is PRN6 as seen in Table 4, is determined. After
that, FFT-based acquisition is activated to search for PRN6 in the signal snapshot collected in
indoor environment. Then the following procedure has been used to determine the assistance
offsets and the corrected aiding data. For PRN6 the code phase from the assistance log is
6
τ
p
6
τ
=120 chips.
The preliminary fast acquisition on PRN6 estimated a code-phase
= 1000.3
chips (Table 6). The code-phase offset is:
p
6
6
=
τ
− τ
=
δτ
6
880.3 chips
(47)
As the signal snapshot is the same for the two PRNs, there are no time drifts to take into
account. Therefore:
p
30
30
30
τ
=
δτ
30
+
τ
=
δτ
6
+
τ
=
1060.3 chips
(48)
p
30
It should be noted that because the full code length is 1023 chips, therefore,
τ
can also equal
to 37.3 chips.
The same approach is used to compute the aiding value of Doppler frequency,
f
D
,30
=
−
0.6025
kHz. Finally, after step 2, the aiding parameters are listed in Table 5.
The aiding parameters are used for acquiring the weaker satellite, PRN30, in indoor
environment. The correlation results are shown in Fig. 11 and in Table 5, it can be noticed
that the 3 dB rule still holds. In fact The signal of PRN 30 pass through the roof and the walls
of the laboratory. Thus, it was good realizations of typical indoor signals and and it is detected
by assisted coherent correlation.
6. Channel combination approach: Joint data/pilot acquisition strategies
In this section, the channel combination approach to improve the sensitivity of the acquisition
is described. The considered signal is Galileo E1 Open Service signal. The current definition
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