Mobile positioning via fusion of mixed signals of opportunity

In this article, we investigated several SOOPs for mobile positioning without GPS and compared their signal characteristics for navigation and tracking. Critical issues in positioning with SOOP were discussed, which include the lack of independent SOOP (poor GDOP), SOOP clock errors, 2-D vs. 3-D solutions, multipath and NLOS signals, and signal integrity, among others. We described the development of mobile test-beds with hardware and software features and presented field test results. The signals of opportunity that we have successfully acquired and tracked with our test-beds and then used to derive navigation solutions include GPS, DTV, GSM, and IS95/CDMA2000 (1xRTT) signals. Based on the comparative assessments and test results, this article advocates the use of mixed (hybrid/fused) signals of opportunity, which has the potential to alleviate several technical difficulties faced by positioning with SOOP. Our ongoing effort is to expand our software radios to include other communication and broadcast signals and modulation schemes and to perform cooperative position localization.