Indoor Adaptive GNSS Signal Acquisition--Theory and Simulations

Abstract

Indoors, GNSS signal encounters severe multipath power loss and fading which leads to significant signal degradation of the amplitude and phase to perform GPS (or GNSS) signal acquisition. To overcome these effects, piling up received GPS (or GNSS) data is a traditional (or conventional) method; however, it exhibits two shortcomings (drawbacks or limitations): instable detection performance, such as the probability of false alarm (PFA) fluctuates due to changes of the signal-to-noise ratio (SNR); and elongated acquisition time caused by extended accumulation duration and over repetitive FA occurrence (or “penalty”). To overcome the first shortcoming, an adaptive structure is employed in GNSS signal acquisition that enables constant FA rate (CFAR) criteria to guarantee a stable detection performance on the GNSS signal acquisition. To overcome the second shortcoming, an adaptive determination on accumulation length is employed to minimize the accumulation duration; therefore, a double-dwell structure (DDS) is used to reduce the processing time “penalty” caused by FA. Simulation results illustrate that an adaptive, stable detection implementation and DDS reduce the average acquisition time by almost fifty percent (or by half or a factor of two). Other important significant unique accomplishments found in this paper are as follows: Dr. Progri for the first time provides the closed form expressions of generalized modified Bessel function distributions of the cumulative distribution functions (cdf) of the first and second kinds and for the first time introduces the very powerful utility of the Kampe de Feriet function and parabolic cylinder function in the navigation community. Index Terms—Adaptive GNSS signal acquisition; weak GNSS signal; constant FA rate (CFAR); DDS; generalized modified Bessel function distribution; modified Bessel function; Kampe de Feriet function; parabolic cylinder function.