Code TrackingBiasCompensation Scheme fortheGalileoEl OS signal
Seungsoo Yoo · 2008
Galileo systemusesdirectsequence/spread spectrum (DS/SS) asitsmodulation method. Single delta delay lockloop(A-DLL), whereA issampleduration between early andlatecorrelation values, hasbeenwidely usedforcode tracking inDS/SSsystems. When theA-DLLisusedforcode tracking inideal environments, codetracking biasdoesnotarise because thesymmetry ofthecorrelation function isnotdestroyed. However, inmultipath (MP)environments, alarge codetracking biasarises owingtotheasymmetrical correlation function. An MP signal always hasapropagation delay timeafter thatofthe lineofsight signal. Thus,correlation values intheadvanced offset region arelessdistorted thanthoseinthedelayoffset region. Fromthis observation, wepropose aneffective tracking biascompensation schemefortheGalileo Elopenservice signal. KeywordsGalileo system, codetracking, single delta delay lock loop, tracking bias, biascompensation