GASIP

GASIP

(Galileo Signal Performance Simulation Tool)

Customer

European Commisssion

Duration

2010 - 2012

Projectleader at the Institute

Members involved

Matteo Paonni

Iva Bartunkova

Diana Fontanella

Marco Anghileri

 

The GASIP Project

The project main objective is to develop a software to assess performance of Galileo signals. The general design nervertheless gives to the user the possibility of assessing the performance of any CDMA-based GNSS system, e.g. GPS. The tool gives exhaustive overview of theoretical performance of a GNSS using wide set of figures of merit.

The tool is based on MATLAB without any additional toolboxes. Access to all functionality is arranged in a graphical user interface. Clear structure of the program and well-defined interfaces ensure flexibility and sustainability.

 

In the framework of the tool a GNSS is defined in terms of constellation, payload characteristics (antenna, clock and transmitted power), navigation signal modulation and message structure. Moreover an optional second signal, used for the evaluation of the performance in dual frequency mode, is also available.

The constellation characteristics can be input by means of custom user defined parameters or by means of a yuma file. A full orbit propagator is programmed into GASIP. A geodetic reference frame can be defined as well. The definition of a signal takes into account an arbitrary carrier frequency and several possible spreading modulations, including BPSK, BOC (sine and cosine phased), MBOC, AltBOC and GMSK. User defined spreading codes can be defined as well and their performance in terms of auto-correlation and cross-correlation properties evaluated.

Additionally, evil waveforms can be simulated as well and different types of models and its parameters can be defined by the user.

 

Two very complete input panels are dedicated to the receiver settings and one to the characterization of the transmission channel. Channel definition includes ionospheric and atmospheric influences, multipath models for single and multiple reflections and various interferences scenario, including inter-GNSS, wideband and bandlimited interferences, and also pulsed interferences, as DME/TACAN pulses or rectangular pulses.

 

The performance of a GNSS system is measured using figures of merit sorted into eight different groups:

*   Link budget, where EIRP, user received power and effective signal to noise ratio can be computed;

* Signal propagation, with the possibility of estimating the errors caused by atmosphere and multipath;

* Spreading codes performances are assessed by means of autocorrelation and crosscorrelation properties;

* Signal acquisition performance are evaluated by means of the minimum signal to noise ratio to acquire the signal (acquisition sensitivity) and acquisition time;

* Signal tracking is evaluated estimating DLL, PLL, FLL stability and mean time to cycle slip;

* BER and FER demodulation thresholds inform about the quality of data demodulation;

* TTFF: novel procedure for determination of time to first fix is included into GASIP, and the different contributions to the TTFF can be easily computed and visualized in different receiver conditions;

* Other system performance figures of merit are grouped into the last panel: dilution of precision, aggregate gain, number of visible satellites, power flux density, UERE budget and position accuracy.

 

The output of each computed  figure of merit can be visualized in  a very user friendly interface and  the possibility to export the results  in different formats is also offered  to the user.