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8.11.1 For double-delta correlators, the aircraft receiver tracks the strongest correlation peak over the full code
sequence for every ranging source used in the navigation solution.
8.11.2 For double-delta correlators, the precorrelation filter rolls off by at least 30 dB per octave in the transition band.
8.11.3 The following parameters are used to describe the tracking performance specific to each type of satellite:
a) the instantaneous correlator spacing is defined as the spacing between a particular set of early and late samples of
the correlation function;
b) the average correlator spacing is defined as a one-second average of the instantaneous correlator spacing. The
average applies over any one-second time frame;
c) the discriminator Δ is based upon an average of early-minus-late samples with spacings inside the specified range, or
is of the type Δ = 2Δd1 – Δ2d1, with both d1 and 2d1 in the specified range. Either a coherent or non-coherent
discriminator is used;
23/11/06 ATT D-46
Attachment D Annex 10 — Aeronautical Communications
d) the differential group delay applies to the entire aircraft system prior to the correlator, including the antenna. The
differential group delay is defined as:
c
d(f ) d(f )
d d
φ φ
−
ω ω
where
fc is the precorrelation band pass filter centre frequency;
f is any frequency within the 3dB bandwidth of the precorrelation filter;
φ is the combined phase response of precorrelation band pass filter and antenna; and
ω is equal to 2πf.
8.11.4 For aircraft receivers using early-late correlators and tracking GPS satellites, the precorrelation bandwidth of the
installation, the correlator spacing and the differential group delay are within the ranges defined in Table D-11.
8.11.5 For aircraft receivers using early-late correlators and tracking GLONASS satellites, the precorrelation
bandwidth of the installation, the correlator spacing, and the differential group delay are within the ranges as defined in Table
D-12.
8.11.6 For aircraft receivers using double-delta correlators and tracking GPS satellites, the precorrelation bandwidth of
the installation, the correlator spacing and the differential group delay are within the ranges defined in Table D-13.
8.11.7 For aircraft receivers using the early-late or double-delta correlators and tracking SBAS satellites, the
precorrelation bandwidth of the installation, the correlator spacing and the differential group delay are within the ranges
defined in Table D-14.
9. Status monitoring and NOTAM
9.1 System status
9.1.1 Degradation of GBAS usually has local effects and affects mainly approach operations. System degradation of
GBAS is to be distributed as approach-related information.
9.1.2 Degradation of core satellite constellation(s) or SBAS usually has not only local effects, but additional
consequences for a wider area, and may directly affect en-route operations. System degradation of these elements is to be
distributed as area-related information. An example is a satellite failure.
9.1.3 Degradation of GRAS may have local effects and/or wide area effects. Therefore, if the degradation has only
local effects, GRAS system degradation information is to be distributed in accordance with 9.1.1. If the degradation has wide
area effects, GRAS system degradation information is to be distributed in accordance with 9.1.2.
9.1.4 Information is to be distributed to indicate the inability of GNSS to support a defined operation. For example,
GPS/SBAS may not support a precision approach operation on a particular approach. This information can be generated
automatically or manually based upon models of system performance.
ATT D-47 23/11/06
Annex 10 — Aeronautical Communications Volume I
Table D-11. GPS tracking constraints for early-late correlators
Region
3 dB precorrelation
bandwidth,
BW
Average
correlator spacing
(chips)
Instantaneous
correlator spacing
(chips)
Differential
group delay
1 2 < BW ≤ 7 MHz 0.045 – 1.1 0.04 – 1.2 ≤ 600 ns
2 7 < BW ≤ 16 MHz 0.045 – 0.21 0.04 – 0.235 ≤ 150 ns
3 16 < BW ≤ 20 MHz 0.045 – 0.12 0.04 – 0.15 ≤ 150 ns
4 20 < BW ≤ 24 MHz 0.08 – 0.12 0.07 – 0.13 ≤ 150 ns
Table D-12. GLONASS tracking constraints for early-late correlators
Region
3 dB precorrelation
bandwidth,
BW
Average correlator
spacing range
(chips)
Instantaneous correlator
spacing range
(chips)
Differential
group delay
1 7 < BW ≤ 9 MHz 0.05 – 1.0 0.045 – 1.1 ≤100 ns
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