Evolution of Integrity Concept – From Galileo to Multisystem - Global Navigation Satellite Systems: Signal,Theory and Applications - page 91

(30)

σ = f σ

SISA GPS , SISA GPS , UDRE

(31)

σ = f σ

SISMA GPS , SISMA GPS , UDRE

Taking into account the different integrity allocation between the Galileo concept, which
implies the use of four failure mechanisms, and the EGNOS concept, based on a failure
assumption, the contribution of the GPS satellite to IR computation is reduced only to the
faulty free mode.

Then it is possible to assume f = and 0 f = , that is: 1

SISMA GPS , SISA GPS ,

(32)

σ = σ

SISA GPS , UDRE

Moreover, in order to estimate the standard deviation of the error, the following equation
can be used:

2 2 2 2

σ = σ + ( σ + σ ) (33)

uLGPS ,, UIRE Air Tropo

GPS
(USA)

EGNOS
(Europe)

GPS
Navigation Message

EGNOS
Integrity Message

EGNOS/Galileo
Converter

EGNOS Converted
Integrity Message

Consistency
Check
(FD)

RAIM Integration

IR
(Integrity Risk)

Galileo Integrity
Algorithm:

Galileo
Navigation Message

HPCA

Galileo
Integrity Message

Galileo
(Europe)

Fig. 5. Galileo-based integrity algorithm

5.3 Multisystem integrity (MSI) algorithm implementation
In this section, we describe a new proposed multisystem integrity algorithm. The algorithm
merges integrity data originated by the Galileo and EGNOS systems and employs a Receiver