Combination of Asynchronous Array Pseudolites and GNSS for Outdoor Localization

Abstract

Global navigation satellite systems (GNSS) are usually unable to provide location-based service (LBS) in urban canyons, thus the pseudolite positioning system has become an important way to enhance the availability and the accuracy of GNSS in such environments. However, the challenge of the traditional pseudolite positioning system is time synchronization, which requires complex hardware and visibility between pseudolites and reference receiver. Thus, the positioning in the urban environment becomes very difficult and complex. To solve this problem, a new asynchronous array pseudolites system is proposed in this paper. Multi-channel transmitters in array pseudolites system have an identical clock source and are based on an identical 1 pulse per second (1PPS) as well. The clock deviation of pseudolites' pseudorange can be eliminated by making the difference between array channels. The minimum positioning system consisting of one array pseudolite and three navigation satellites is used for positioning experiment in this paper. The results of the simulation verify the effectiveness of the minimum positioning system based on combined positioning. Compared with four navigation satellites, the horizontal positioning accuracy is improved slightly by exploiting the minimum positioning system. INDEX TERMS Array pseudolites, satellite navigation, asynchronous, combined positioning. I. INTRODUCTION

RSS-Based Indoor Localization System with Single Base Station

“…2. The matrix in (5) shows the NLOS distances of reflected signals from the whole walls, where each column represents the distances for the same RPs for different MS. Moreover, the minimum value of the nearest RP along each column is calculated to get a raw vector of minimum distances for the shortest possible NLOS path length.…”

“…Typically, the Global Navigation Satellite Systems (GNSS) only works for outdoor environments with wide geographic coverage. They are widely applied for navigation of vehicles, ships, and airplanes [5,6], however not for indoor applications [7][8][9]. Meanwhile, the demand for indoor localization in wireless networks becomes significant.…”

Precise Point Positioning Algorithm for Pseudolite Combined with GNSS in a Constrained Observation Environment

“…Using the observation equation above, public users have difficulty getting their own precise position with only pseudolite carrier phase measurements as result of a lack of pseudolite pseudorange measurements, which includes a large multi-path error, To solve this problem, the KPI (Known Point Initialization [19][20][21]) method has been proposed to achieve integer ambiguity of the pseudolite in advance, and the public user has to wait for a minute at a known precise position, which is very inconvenient for public users in motion. Fortunately, with more than four GNSS satellites available, public users can easily get a precise position, which provides important a priori knowledge for integer ambiguity resolution of a pseudolite in a constrained environment, such as an urban canyon.…”

GDOP-based analysis of suitability of LEO constellations for future satellite-based positioning

“…Various complementary solutions have been studied in detail so far, such as positioning solutions relying on cellular terrestrial networks, and in particular on 5G networks promising high accuracy, pseudolite-based positioning [2], WiFi-based positioning, sensor-based augmentation, positioning via longrange low-power Internet of Things (IoT) signals such as LoRa and NB-IoT, or Ultra Wide Band (UWB)-based positioning [3], [4], [5], [6]. Among the above-mentioned complementary techniques, the standalone systems able to achieve the submeter accuracy currently offered by GNSS are the 5G-based and UWB-based solutions, but both have limited coverage and a relatively large energy consumption at the receiver side.…”