ADVANCES IN SIGNAL PROCESSING FOR GLOBAL NAVIGATION SATELLITE SYSTEMS Sana U. Qaisar and Craig R. Benson Processing Cost of Doppler Search in GNSS Signal Acquisition Measuring Doppler shift in navigation satellite signals T o acquire a global navigation satellite system (GNSS) signal, the receiver must determine the Doppler offset experienced by the signal. The time and resources consumed in the Doppler search contribute to the cost and efficiency of the receiver, which is fundamentally dependent on signal processing techniques adapted for the search. In this article, we address the cost of signal processing for a Doppler search in GNSS signal acquisition. We describe the standard signal processing approaches of the Doppler search and present a signal averaging technique for reducing the processing cost. We select the modernized global positioning system (GPS) L2C signal to facilitate conceptual discussions and to produce experimental validations. Introduction GNSS signal acquisition ©ISTOCKPHOTO.COM/COFOTOISME Digital Object Identifier 10.1109/MSP.2017.2715979 Date of publication: 6 September 2017 1053-5888/17©2017IEEE GNSS signal acquisition is the process of finding the correct code delay and carrier Doppler offset experienced by the satellite signal along the propagation to establish early synchronization between the received and the local replica signals. The signal search is accomplished by comparing the received and local replica signals, typically over an interval of one ranging code period over a complete range of potential code delays and carrier Doppler offsets. As illustrated in Figure 1, the signal is declared detected once both the correct code delay and Doppler offset are determined through strong correlation between the received and local signal and the correlation energy level exceeds the detection threshold. The efficiency of signal acquisition can be realized through smart processing in both the code delay and the Doppler dimensions. There are two fundamental strategies of the Doppler search: the time-domain, also known as the serial search, where each potential Doppler is tried one by one [1]-[3], and the frequency-domain or parallel search, where a single fast Fourier transform (FFT) is applied to simultaneously examine the full range of possible Doppler offsets IEEE SIGNAL PROCESSING MAGAZINE | September 2017 | 53http://www.ISTOCKPHOTO.COM/COFOTOISME