Navigation Solution Using HD Radio Signals

摘要

It is well known that the GPS signals are weak and are therefore subject to interference and blockage due to obstruction. Signals of Opportunity (SOO), on the other hand, are those signals which have been dedicated for other purposes such as communication, but are utilized here for navigation. SOO have relatively greater signal power than GPS, and are plentifully available, relatively more resistant to blockage and jamming compared to GPS. Many papers presented methods and algorithms utilizing SOO such as WiFi, AM radio, TV, etc. However, to our knowledge no published work exists using HD radio, i.e., digital AM radio, for navigation. Unlike analog AM radio signals, digital radio signals are well structured, having a wider bandwidth than the analog AM radio signals, and hence could be better adapted for navigation. In this paper we present a study in using digital AM radio signals in the 540-1700 kHz band of the frequency spectrum to locate and track receiver locations that are otherwise unknown. It is assumed that the locations of digital AM transmitters are known prior to localization. A technique called differential Time Difference of Arrival (dTDOA) is employed, which overcomes the problem of lack of synchronization in digital AM radio signals, as well as unknown clock offsets in digital AM radio receivers. The relatively narrow bandwidths and hence long symbol durations of the digital AM radio signals pose a problem as it gives rise to potentially large timing errors, thereby greater localization errors. To improve the location accuracy, strong digital AM signal levels are utilized to our advantage so methods such as curve fitting and time averaging can be performed. Moreover, problems in real-time application such as poor signal reception, signal attenuation, zone change of AM transmitters while in transit, different SNR levels, are all modeled. A comprehensive simulation study has been performed incorporating the above methods and models. Although the setting and the actual data obtained in a real world environment may be different, an attempt has been made to simulate them in this paper to the largest extent possible. The simulation study shows that location accuracy could achieve within a few meters.