Weak GPS Signal Acquisition Using Antenna Diversity

GNSS Acquisition in fading and attenuated environments is challenging. In these situations, additional processing gain is required. A common method is to extend the coherent integration time. However, in weak signal situations, using only long coherent integration is limited by navigation data bit transitions and receiver oscillator instability. Using non-coherent and differentially coherent integration mitigates the bit transition problem but has lower processing gain as compared to coherent integration. Coherent, non-coherent and differentially coherent combining methods are not effective in dense multipath fading situations where the carrier-to-noise ratio (C/N0) varies significantly. Spatial antenna diversity provides additional processing gain to overcome multipath fading since multiple antennas detect signal components from independent fading channels. This thesis evaluates equal gain combining of two independent antennas in a standalone acquisition process. Traditionally acquisition has been evaluated at the cell level, which considers only a single cell, but in this thesis acquisition is assessed at the system level, where the complete acquisition process including the entire search space is examined. Receiver Operating Characteristic (ROC) curves in both cell and system levels are presented and compared both theoretically and using real data. Overall detection probability, probability of false alarm and acquisition time are investigated in terms of the mean and variance values. Optimal values for the integration time as well as combination of coherent and non-coherent integration that minimizes the mean acquisition time are obtained. The theoretical analysis is compared with Monte Carlo simulations and real GPS data results. Compared to a single antenna, smoother signal-to-noise ratio (SNR) values which show the fading mitigation were observed by applying diversity combining. Experimental results demonstrate the improvement of detection probability, enhanced immunity against false alarms, and significant reduction of the mean and variance of acquisition time in dense multipath environments.

Name thesis:degree_name

Master of Science (MSc)

Discipline thesis:degree_discipline

Geomatics Engineering

Grantor dc:publisher.institution

Graduate Studies

Year dc:date.issued

2014

Author dc:creator

• Mozaffari, Mohammad

Advisor dc:contributor.advisor

• O'Keefe, Kyle

• Engineering--Electronics and Electrical

Statement dc:rights

• University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

eng

DOI

http://dx.doi.org/10.11575/PRISM/28677

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:11023/1945