Weak GNSS Signal Acquisition for Indoor Environments

Weak GNSS Signal Acquisition for Indoor Environments

Seung-Hyun Kong (KAIST, South Korea)
Copyright: © 2018 |Pages: 30
DOI: 10.4018/978-1-5225-3528-7.ch012
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High sensitivity and fast acquisition are two important goals that must be considered in the development of signal processing techniques for a GNSS acquisition function to meet the demands for LBS in GNSS-challenged environments, such as indoor and urban canyon. This chapter introduces the fundamentals of GNSS acquisition functions, GNSS acquisition techniques for new GNSS signals, and GNSS acquisition techniques achieving high sensitivity and fast acquisition. Therefore, this chapter contains useful information for engineers who study the fundamentals and principles of GNSS acquisition and the state-of-the-art GNSS signal acquisition techniques for weak signals.
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Fundamentals Of Gnss Signal Acquisition

GNSS (signal) acquisition function searches and detects incoming GNSS signals to initialize the tracking function that actually produces fine GNSS signal measurements for positioning. In general, the GNSS signals are spread by periodic long spreading codes, and the GNSS satellite motion relative to the receiver generates a Doppler frequency shift in the incoming signal as large as 5kHz to 10kHz depending on the receiver’s motion. Since the precise time and location of a GNSS receiver is not initially known, the GNSS acquisition function of the receiver cannot estimate the code phase and Doppler frequency of the incoming signals. Therefore, the task of the GNSS acquisition function is to identify the prompt code phase and Doppler frequency of the incoming GNSS signals, as quickly as possible, within a resolution which is fine enough to initialize the tracking function successfully. Since the code phase and Doppler frequency of an incoming GNSS signal can have any value within the 2-dimensional (2D) hypothesis plane (aka, the search space) which includes all possible combinations of code phase and Doppler frequency hypothesis, the acquisition function needs to test each hypothesis within the 2D plane using a matched filter (e.g., correlator) (Kaplan, 2005; Van Diggelen, 2009; Parkinson & Spilker, 1996) until the detection of the incoming GNSS signal.

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