Augmentation of GPS/LAAS with GLONASS: Performance Assessment

GLONASS has been proposed as an augmentation to GPS/LAAS. This paper will examine the incremental benefits of the additional signals from GLONASS to the availability of service for precision approaches. The methodology used for the modeling of availability is the same as that adopted previously for the analysis of GPS/LAAS. The inclusion of GLONASS signals requires provision for adapting the models of measurement errors to account for the differences between GPS and GLONASS. The main difference of significance to LAAS is due to the frequency division multiple access scheme used by GLONASS, and the resultant inter-frequency biases in the measurements. The errors introduced by such biases at the reference and user receivers are uncorrelated, and have to be accounted for in the error models. As expected, the availability of service improves considerably with the additional ranging sources. The combined GPS and GLONASS signals provide consistent and robust performance with high levels of availability of service for the most demanding precision approaches.