An overview on Global Positioning Techniques for Harsh Environments

Abstract This chapter presents strategies and techniques used to increase the sensitivity of global navigation satellite system (GNSS) receivers in order to make them usable in harsh environments, such as urban canyons, light indoor scenarios, deep forests, or space. It discusses the assistance that can be provided to the GNSS receiver through communication channels to ease the acquisition and tracking processes. Assisted GNSS is a consolidated standard, but other kinds of assistance and signal processing techniques can improve the ability of the receiver to process the signal at a low signal-to-noise ratio. The chapter introduces the common approaches to increase the sensitivity at the acquisition stage, discussing the impact on the accuracy of the delay and Doppler shift estimation, and the intrinsic limitation to coherent and noncoherent integration time extension. Techniques to increase robustness to low signal-to-noise ratio scenarios are presented, considering the structure of new and modernized GNSS signals.