GPS World, March 2014

SIMULATORS AND TOOLS GNSS Modernization FIGURE 8 Static position GPS L1 comparison live left replayed right FIGURE 9 GPS L1 L2 with GLONASS L1 comparison record and lead playback the real time signals in time and to take short breaks for housekeeping functions Data LV SDFNHG LQWR D ELQDU OH DFFRUGLQJ WR D SUH GHWHUPLQHG sequence which in turn is set by the number of channels DQG EDQGZLGWKV LQ XVH OH KHDGHU LV JHQHUDWHG ZKLFK contains all of the information necessary for reconstructing the data streams for replay A synchronization sequence is DGGHG DW WKH VWDUW RI WKH OH WR DOORZ UHFRYHU RI WKH FRUUHFW bits for each channel and each baseband quadrature arm and to the correct timeslots for each component Destroying the correct time reproduction is the most likely issue to FDXVH IDXOW UHSOD LQ DQ UHFRUG UHSOD GHYLFH 166 UHFHLYHUV GRQ W OLNH GLVFRQWLQXRXV RU VOHZLQJ WLPH This approach also allows the insertion of external digital GDWD LQWR WKH OH 3URYLGLQJ WKH GDWD SURFHVVLQJ KDUGZDUH LV DZDUH RI WKH LQGLYLGXDO ELWV LQWR ZKLFK WKLV GDWD LV SODFHG digital data recorded at the same time as the raw signals may be regenerated synchronously during replay Thus any GDWD WKDW LV DSSOLHG WR D UHFHLYHU LQ D UHDO WLPH WULDO FDQ EH DYDLODEOH IRU WKH VDPH WULDO DQ WLPH DIWHU WKH HYHQW 7ZR streams of synchronous data can be recorded per channel potentially making six serial data streams per chassis DYDLODEOH User Interfaces A final challenge presents itself in the case of user LQWHUIDFHV OWKRXJK WKH RSHUDWLRQDO RSWLRQV RI WKH GHYLFH are quite complex there is a requirement to be able to capture field data with just the equipment itself and any necessary antenna setup Consequently the product has a display and control keys implemented on the front panel DOORZLQJ WKH XVHU FRPSUHKHQVLYH DFFHVV WR WKH LQWHUQDO functions using a menu system and scrolling displays OWHUQDWLYHO IRU RSHUDWLRQ LQ D ODE HQYLURQPHQW D QHWZRUN connected user interface is specified and this requirement LV VXSSRUWHG E D ZHEVHUYHU UXQQLQJ RQ WKH PDLQ SURFHVVRU LQ WKH GHYLFH 7KXV VLPSO RSHQLQJ D ZHE EURZVHU DQG FRQQHFWLQJ WR WKH GHYLFH V 3 DGGUHVV DOORZV IXOO IXQFWLRQDO control Q DGGLWLRQ FRQQHFWLQJ D PRXVH NH ERDUG DQG PRQLWRU WR WKH GHYLFH DOORZV DFFHVV WR WKH PDLQ SURFHVVRU DOORZLQJ WKH UXQQLQJ RI VFULSWV WKXV SURYLGLQJ IXOO FRQWURO RI UHSOD V DQG UHFHLYHU IXQFWLRQV IRU UXQQLQJ FRQWLQXRXV WHVWV LQ DQ DXWRPDWHG ODERUDWRU HQYLURQPHQW 8VLQJ WKLV DSSURDFK UHFHLYHU PRGL FDWLRQV FDQ EH WHVWHG RYHU PDQ VFHQDULRV DQG ORFDWLRQV PDQ WLPHV HDFK WR SURYLGH VWDWLVWLFDOO UHOHYDQW UHVXOWV ZLWKRXW WDNLQJ XS RSHUDWRU WLPH 5HPRWH PRQLWRULQJ LV SRVVLEOH XVLQJ WKH ZHEVHUYHU Performance Testing UDQJH RI WHVWV DQG WULDOV KDYH EHHQ FDUULHG RXW WR YHULI that the product meets its specifications and to measure the performance in a number of real life scenarios Repeatability Degradation Attenuation 7KH UVW DQG PRVW REYLRXV WKLQJ WR H SORUH LV WKH HIIHFW RI WKH UHFRUG DQG SOD EDFN RQ VLJQDO WR QRLVH UDWLR 6LQFH WKH 5 FLUFXLWV DGG some noise to the signal recorded we would expect some degradation to take place here Also during replay the UHFHLYHU XQGHU WHVW DGGV PRUH QRLVH GHSHQGLQJ RQ LWV QRLVH JXUH DOWKRXJK WKLV VKRXOG EH WKH VDPH DV ZRXOG EH DGGHG ZKHQ XVLQJ OLYH VLJQDOV 0DQ UHFHLYHUV DGMXVW IRU WKHLU QRLVH JXUH ZKHQ UHSRUWLQJ 1 0 QXPEHUV 1 0 is a signal to noise measurement normalized to a 1 Hz bandwidth DQG LV WKH VWDQGDUG UHSRUWHG PHDVXUHPHQW IRU PRVW 166 UHFHLYHUV RZHYHU E UHSOD LQJ EDFN WKH UHFRUGHG VLJQDO DQG QRLVH DW D KLJKHU OHYHO WKDQ ZRXOG KDYH EHHQ UHFHLYHG LQ OLYH FRQGLWLRQV ZH FDQ HOLPLQDWH DOPRVW DOO RI WKH GHJUDGDWLRQ Q OLYH YHUVXV UHSOD HG WHVWV IRU LQGLYLGXDO VDWHOOLWHV XVLQJ D 9 UHFHLYHU ZKLFK DOORZV XV WR WHVW all of the supported bands and constellations we found that replay is possible within G RI WKH RULJLQDO OLYH VLJQDOV 5HSOD HG VLJQDOV ZHUH DERXW G DERYH WKH RULJLQDO UHFRUGHG OHYHO WR DFKLHYH WKLV HIIHFWLYHO VZDPSLQJ WKH UHFHLYHU V QRLVH FRQWULEXWLRQ Q LQWHUHVWLQJ DVSHFW RI FRQWUROOLQJ WKH 1 0 this way is the ability to attenuate the replayed signal and therefore LQFUHDVH WKH FRQWULEXWLRQ RI WKH WHVW UHFHLYHU V QRLVH JXUH 7KXV DOWKRXJK WKH UHFRUGHG 1 0 KDVQ W FKDQJHG ZH FDQ DWWHQXDWH WKH UHSOD OHYHO DQG XVH WKH UHFHLYHU WR DGG QRLVH 7KLV SURFHVV LV QRW OLQHDU DQG ZH REYLRXVO KDYH WR UHPRYH QHDUO DOO RI WKH G H FHVV WR JHW VWDUWHG 7KH GHYLFH NHHSV D WDEOH RI DWWHQXDWLRQ YV 1 0 reduction DOORZLQJ WKH XVHU WR VLPSO GLDO XS WKH UHTXLUHG 1 0 loss 6LQFH WKLV GHSHQGV RQ WKH UHFHLYHU QRLVH JXUH HIIHFWV PD GLIIHU VOLJKWO IURP UHFHLYHU WR UHFHLYHU 8VHIXOO WKH WDEOH LV XVHU GH QDEOH DOORZLQJ WDLORULQJ WR D VSHFL F UHFHLYHU GPS World March 2014 www gpsworld com 38