Adaptive GNSS Receiver Design for Highly Dynamic Multipath Environments

Abstract

Ubiquitous navigation requires timely, uninterrupted and accurate estimate of receiver's position at all times, in all environments and for all modes of transportation and it is highly dependent on satellite availability, geometry and accurate positioning estimation. However, the availability, continuity and accuracy of a GNSS can be severely affected in a highly dynamic environment due to blockage, fading and multipath. This results in positioning information inaccurate, unreliable and sometimes unavailable. This paper presents a study on the potential vulnerabilities that can affect a multi-constellation multi-frequency GNSS receiver in low to highly dynamic multipath environments such as clear line-of-sight, partially and highly obstructed environments to characterize the distortions/anomalies which could significantly affect the satellite signals and their impact on positioning and navigation. The multi-constellation multi-frequency GNSS receiver configuration in this paper is set to GPS, GLONASS, Galileo and BeiDou for the first time at full capacity and performance comparison is made with the GPS based on satellite availability, blockage, continuity, precision and accuracy parameters. These parameters are then used in this paper to detect and characterize the type of environment for the multi-constellation GNSS receiver without using any external aiding devices or sensors. Based on environment detection and characterization, a new Adaptive Environment Navigation (AEN) based GNSS receiver design is proposed which can work in real time and has achieved an overall availability and accuracy factor of 94% in highly dynamic multipath/NLOS environment along with a reduction in the blockage coefficient, β, by almost 11% resulting in more accuracy and precision than the standard multi-constellation GNSS receiver where the availability factor was found to be 57% only.

Area-Efficient Universal Code Generator for GPS L1C and BDS B1C Signals

“…Lastly, Legendre sequence-based codes show excellent correlation characteristics, and they have recently been used in GPS L1C and BDS B1C signals. As the fields of the application of the GNSS have expanded along with the recent development of the industries, studies to provide high precision and additional functions of GNSS receivers have been extensively conducted [8][9][10][11][12][13][14][15][16][17]. In addition to the simple role of receiving signals and performing navigation calculations, advanced signal technologies, such as anti-jamming [8] and anti-spoofing [9], are applied, and studies on multiconstellation and multi-frequency receivers [10][11][12] are being conducted for high-precision high-reliability location calculations.…”

“…As the fields of the application of the GNSS have expanded along with the recent development of the industries, studies to provide high precision and additional functions of GNSS receivers have been extensively conducted [8][9][10][11][12][13][14][15][16][17]. In addition to the simple role of receiving signals and performing navigation calculations, advanced signal technologies, such as anti-jamming [8] and anti-spoofing [9], are applied, and studies on multiconstellation and multi-frequency receivers [10][11][12] are being conducted for high-precision high-reliability location calculations. Especially, studies on single code generators that support various codes are actively conducted for the implementation of multi-constellation and multi-frequency receivers so that single receivers can support multiple codes [13][14][15][16][17].…”

“…Especially, studies on single code generators that support various codes are actively conducted for the implementation of multi-constellation and multi-frequency receivers so that single receivers can support multiple codes [13][14][15][16][17]. As shown in Table 1, since LFSR-based code generation is the most widely applied, studies on LFSR-based codes have been steadily conducted [10][11][12][13]. According to one study [13], many LFSR-based PRN codes can be generated using a single LFSR structure.…”

“…In order to implement the GNSS receiver in hardware, the implementation of a code generator is essential. Whereas existing studies on code generators were conducted focusing on LFSR-based codes [10][11][12][13], a few studies on Legendre sequencebased codes have recently been conducted [14][15][16][17]. Figures 2-4 show the structure of Legendre sequence-based code generators.…”

Investigation of Using Sky Openness Ratio as Predictor for Navigation Performance in Urban-like Environment to Support PBN in UTM

“…An additional experimental setup for hemispheric photography was made at different altitudes to investigate if a correlation exists between GNSS performance and geometric blockage, or the sky openness ratio (SOR), independent from the multipath error in urban airspace. While previous studies have demonstrated a relationship between the visible sky (blockage factor) and positional accuracy, the contribution by the sky openness ratio was not isolated [ 6 ]. While no formal correlation had been specified, the building geometries and their blockage of visible sky were included as a parameter in the evaluation of GNSS performance in urban environments, as specified by the European Telecommunications Standards Institute (ETSI) [ 7 ].…”