This paper focuses on the performance of time of arrival estimators for distress beacon signals which are defined by pulses with smooth transitions. These signals are used in the satellite-based search and rescue Cospas-Sarsat system. We propose a signal model based on sigmoidal functions. Closed-form expressions for the modified Cramér-Rao bounds associated with the parameters of this model are derived. The obtained expressions are easy to interpret since they analytically depend on the system parameters. Simulations conducted on realistic search and rescue signals show good agreement with the theoretical results.
The International Cospas-Sarsat Programme provides accurate, timely, and reliable distress alert and location data to help search and rescue authorities assist persons in distress. To achieve this objective, Cospas-Sarsat Participants implement, maintain, coordinate and operate a satellite and ground system capable of detecting distress alert transmissions from radiobeacons that comply with Cospas-Sarsat specifications and performance standards, and of determining their position anywhere on the globe. The distress alert and location data is provided by Cospas-Sarsat Participants to the responsible SAR services. Cospas-Sarsat co-operates with the International Civil Aviation Organization (ICAO), the International Maritime Organization (IMO), the International Telecommunication Union (ITU) and other international organizations to ensure the compatibility of the Cospas-Sarsat distress alerting services with the needs, the standards and the applicable recommendations of the international community.
With the multiplication of GNSS and the increasing complexity of the new GNSS applications, such as LocationBased Services applications, it will be essential in the coming years to have access to receivers test benches providing a series of test procedures being reproducible and standardized, enabling localization performance assessment. GNSS receiver test benches have to fulfill a twofold need: first, to provide a standardized methodology to enable comparison, in various controlled conditions, of different products that seem to have similar performance specifications on paper. And secondly, to provide a platform to test the functions of receivers in conditions closed to the real targeted environment.
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