Asynchronous Pseudolite Navigation Using C/N₀Measurements

Abstract

The problem of indoor navigation is investigated using a Commercial Off-the-Shelf (COTS) pseudolite system. The system is operated in synchronous and asynchronous mode. It is shown that, when the system is operated in synchronous mode, it is unsuitable for deep indoor operations: in complex propagation environments, the synchronisation required for metre level navigation is difficult to achieve and different solutions have to be adopted. Two asynchronous approaches are thus considered and indoor navigation with metre level accuracy is demonstrated using C/N 0 measurements. The approaches use a modified Receiver Signal Strength (RSS) navigation algorithm and a weighted centroid technique, respectively. In both cases, a pre-filtering stage has been adopted to enhance the quality of C/N 0 measurements. The two methods have been compared under different operating conditions and the advantages and drawbacks of the two techniques have been analysed. The experiments demonstrate that metre level accuracy can be achieved using asynchronous pseudolites. These results are particularly encouraging since they were obtained without exploiting map constraints and prior knowledge of the user position. K E Y WO R D S1. Asynchronous signals.2. Pseudolite. 3.

Stand-Alone and Hybrid Positioning Using Asynchronous Pseudolites

“…Such error is mitigated by C / N 0 filtering, and it is not evident in the filtered distances (blue lines). This result confirms the findings obtained in [7]. …”

“…Such measurements are, however, noisy, and significant performance improvement can be obtained by pre-filtering them. The benefits of C / N 0 filtering has been investigated in [7], and a comparison between filtered and unfiltered solutions is provided in Section 5.3. If not differently specified, the C / N 0 measurements are at first pre-processed using a filter with a triangular impulse response of a length of five.…”

“…If not differently specified, the C / N 0 measurements are at first pre-processed using a filter with a triangular impulse response of a length of five. Justifications for the usage of such a filter can be found in [7]. …”

“…Synchronization, however, requires a complex architecture, which increases the complexity of the pseudolite system and, consequently, its cost. Thus, alternative solutions have been considered, where each pseudolite operates independently, as described in [7,8]. This has led to the development of asynchronous pseudolite technologies characterized by a simplified system design and reduced costs.…”

Evaluating the Vulnerability of Several Geodetic GNSS Receivers under Chirp Signal L1/E1 Jamming

“…For the benefit of the experiment, a commercially available in-car jammer was used. With regard to Borio et al [35], it was a sub-miniature version A (SMA) unlabelled jammer L1/E1 jammer, with no manufacturer's data, powered by a battery, its external antenna with omnidirectional radiation pattern was connected through a SMA connector (see Figure 3), which emitted a single saw-tooth chirp signal, according to References [44][45][46], belonging to the class II group. According to their tests, the jammer's output features a period of 10 µs, while according to our test it, the device raises noise power up to 50 dB in a frequency band of 1570 MHz ± 20 MHz.…”