GPS navigation message parameter improvement

Navigation message design will influence the system's performance including accuracy and receiver's satellite selection. To summarize the GPS navigation message improvement in its modernization, the main parameters: ephemeris, clock and user range accuracy (URA) in NAV (L1), CNAV (L2C/A), CNAV-2 (L1C) are compared and contrasted. Utilizing the corresponding user algorithms, different parameters' performances are simulated and analyzed. Results show that, the improvement highlights the accuracy and satellite selection. The new ephemeris and clock parameters will cause smaller orbit error. The further fractionized URA could discriminate the satellite errors, moreover improve user position precision and satellite selection performance.