Improved Navigation Solution Utilizing Antenna Diversity Systems in Multipath Fading Environments.

摘要

There is an intense effort on increasing the signal detection and tracking capabilities of Global Navigation Satellite System (GNSS) receivers in shaded areas where receivers suffer significant degradation due to attenuation and multipath. In order to overcome signal attenuation and multipath fading, more processing gain is required. Increasing the coherent integration time is traditionally known as the main source of processing gain. However, the mobile user is typically in motion while using the receiver, which limits the coherent integration gain. Diversity schemes constitute another source of processing gain that can be utilized to enhance signal detection and parameter estimation performance by providing additional processing gain.;Given the coherent integration time limit and spatial/temporal characters of indoor GNSS channels, a diversity system composed of spatially separated antennas is developed and tested in this thesis. The performance of this diversity system is assessed at three different levels namely signal detection, parameter estimation and navigation solution. The performance of different combining methods at different levels is assessed theoretically and practically using real GPS L1 data collected in different indoor environments.;An analysis of different metrics such as deflection coefficients, ROC curves and satellite availability, shows that the detection performance is considerably enhanced when utilizing the above diversity scheme.;Proposing an analytical model based on sphere of scatterers model and considering the antenna gain pattern, Doppler measurements error sources in multipath environment are characterized. It is shown that Doppler measurements are of limited value for positioning purpose in harsh multipath environments.;Combining pseudoranges of diversity branches based on their instantaneous qualities, represented by their epoch-by-epoch SNR, the pseudorange precision is enhanced significantly. Finally, improved satellite availability, along with enhanced pseudorange, makes a remarkable improvement in positioning accuracy.