GPS World, April 2014

Receiver Design GALILEO FIGURE 11 Galileo only mobile fix computed on March 12 2013 of 1 s as summarized in FIGURE 10 However there are some situations where the receiver may stay in fullpower mode for example during the initialization phase to collect important data from the navigation message such as the ephemeris and to perform RTC calibration 7KHUH DUH EHQH WV RI XVLQJ WKLV approach coupled to Galileo signals the main impact is the usage of the pilot codes Indeed a longer integration time allows reducing the active period length which most impacts the total power consumption being usually performed at higher repetition rate Some simulations were carried out to assess the performance of DC algorithms in the software receiver While in hardware LPSOHPHQWDWLRQV WKH GLUHFW EHQH W LV the power computation in a software implementation it is not possible to see such an improvement The reduced power demand is translated into a shorter processing time for each single processing channel The DC approach can facilitate the implementation of a real time or quasi real time software receiver The main drawback of using techniques based on DC tracking is the decrease of the rate of observables and PVT solution However this depends on the application for some a solution every second is more than enough Real Signal Results On March 12 2013 for the first time the four Galileo IOV satellites were broadcasting a valid navigation message at the same time From 9 02 CET all the satellites were visible at ESTEC premises and the first position fix of latitude longitude and altitude took place at the TEC Navigation Laboratory at ESTEC ESA in Noordwijk the Netherlands At the same time we were able to acquire track and compute one of the first Galileo only mobile navigation solutions using the receiver under test Thanks to its small size and portability it was installed on a mobile test platform embedded in ESAs Telecommunications and Navigation Testbed vehicle Using a network connection we could follow from the Navigation Lab the real time position of the van moving around ESTEC FIGURE 11 shows the vans track obtained by post processing NMEA data stored by the receiver evaluation board The accuracy achieved in these tests met all the theoretical expectations taking into account the limited infrastructure deployed so far In addition the results obtained with the receiver have to be considered SUHOLPLQDU VLQFH LWV UPZDUH supporting Galileo was in an initial test phase for example absence of a proper ionospheric model E1B only tracking Conclusions Analysis of a receivers test results confirms the theoretical benefits of Galileo OS signals concerning TTFF and sensitivity Future work will include the evolution of the software receiver model and a detailed analysis of power saving tracking capabilities with a comparison of duty cycle tracking techniques in open loop and in closed loop Acknowledgments This article reflects solely the authors views and by no means represents official European Space Agency or Galileo views The article is based on a paper first presented at ION GNSS 2013 Research and test campaigns related to this work took place in the framework of the ESA Education PRESTIGE programme thanks to the facilities provided by the ESA TECETN section The LMS multipath channel model was developed in the frame of the MiLADY project funded by the ARTES51 Programme of the ESA Telecommunications and Integrated Applications Directorate Manufacturers The tests described here used the STMicroelectronics www st com gps Teseo II receiver chipset and a Spirent www spirent com signal simulator NICOLA LINTY is a Ph D student in electronics and telecommunications at Politecnico di Torino In 2013 he held an internship at the European Space Research and Technology Centre of ESA PAOLO CROSTA is a radio navigation system engineer at the ESA TEC Directorate where he provides support to the EGNOS and Galileo programs He received a MSc degree in telecommunications engineering from the University of Pisa PHILIP G MATTOS received an external Ph D on his GPS work from Bristol University He leads the STMicroelectronics team on L1C and BeiDou implementation and the creation of totally generic hardware that can handle even future unknown systems FABIO PISONI has been with the GNSS System Team at STMicroelectronics since 2009 He received a masters degree in electronics from Politecnico di Milano Italy www gpsworld com April 2014 GPS World 43