Maximum likelihood delay estimation in a navigation receiver for aeronautical applications

The potential of the SAGE (Space Alternating Generalized Expectation Maximization) algorithm for navigation systems in order to distinguish the line-of-sight signal (LOSS) is to be considered. The SAGE algorithm is a low-complexity generalization of the EM (Expectation-Maximization) algorithm, which iteratively approximates the maximum likelihood estimator (MLE) and has been successfully applied for parameter estimation (relative delay, incident azimuth, incident elevation, Doppler frequency, and complex amplitude of impinging waves) in mobile radio environments. This study discusses receivers using a single antenna or an antenna array. Whereas we estimate the complex amplitudes, relative delays, and Doppler frequencies of the impinging waves, in the latter additionally the spatial signature of the impinging waves (incident azimuth and elevation) is estimated. The results of the performed computer simulations and discussion indicate that the SAGE algorithm has the potential to be a very powerful high resolution method to successfully estimate parameters of impinging waves for navigation systems. SAGE has proven to be a promising method to combat multipath for aircraft navigation applications due to its good performance, fast convergence, and low complexity.