# BeiDou Augmented Navigation from Low Earth Orbit Satellites
## 1 Introduction
The second generation Iridium-NEXT satellites began to be deployed into the existing constellation in January 2017. Somewhat similar to the Iridium satellite constellation, Globalstar is also a LEO satellite constellation for satellite phone and low-speed data communications, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Constellation** & **No. Sats** & **Altitude [km]** & **Inclination [\({}^{\circ}\)]** & **Year** & **Country** \\ \hline Iridium & 66 & 781 & 86.4 & 1998 & USA \\ Globalstar & 48 & 1400 & 52 & 2000 & USA \\ LeoSat & 108 & 1400 & Not defined, yet & 2019/2020 & USA \\ Telesat & 117 & 1000–1245 & 99.5 & 2021 & Canada \\ Hongyun & 156 & 1000 & Not defined, yet & 2022 & China \\ Hongyan & 324 & 1100 & Not defined, yet & 2023 & China \\ OneWeb & 648 & 1200 & 88 & 2019 & USA/UK \\ Boeing & 2956 & 1200 & 45, 55, 88 & Not defined, yet & USA \\ SpaceX Starlink & 7518 & 1110–1325 & 53, 53.8, 74, 81, 70 & 2020 & USA \\ Astrome Technology & 150 & 1400 & Not defined, yet & 2020 & India \\ Samsung & 4600 & \textless{}1500 & Not defined, yet & Not defined & Korea \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The summary of some deployed or proposed commercial communication LEO constellations. the first generation Globalstar constellation have 48 satellites with an orbital height of approximately 1400 km and an inclination of 52\({}^{\circ}\). A Globalstar second-generation constellation consists of 24 LEO satellites, which were fully launched in 2013. To keep up with the rising demand for broadband, several new LEO constellations are being proposed. Proposed in 2013, LeoSat is designed to consist of 108 satellites in 1400 km orbit and use Ka-band for provide secure broadband links [9]. The Canadian Telesat proposed a LEO communication system consists of a constellation of 117 satellites in 11 orbital planes, with six planes (12 satellites per plane) inclined 99.5 degrees in a circular orbit at an approximate altitude of 1000 km and five planes (nine satellites per plane) inclined 37.4 degrees in a circular orbit at an approximate altitude of 1248 km [10]. In January 2015, OneWeb announced a partnership with Virgin and Qualcomm to produce a satellite internet constellation of approximately 720 satellites expected to provide global Internet broadband service to individual consumers as early as 2019. These satellites evenly distributed in 18 near-polar orbital planes, at an approximate altitude of 1200 km. Moreover, the system will be expended to accommodate additional 1260, which would double the number of orbital planes from 18 to 36, and increase the maximum number of satellites per plane from 40 to 55 [11]. SpaceX, with support from Google, announced a similar ambition for StarLink constellation with 4425 LEO satellites operating in 83 orbital planes at altitudes ranging from 1100 km to 1325 km in March 2018, and this new approval gives the green light for the planned 7518 satellites in the Starlink constellation [12; 13]. The prototype test-flight satellites were successfully launched on 22 February 2018. In August of 2015, Samsung expressed interest with a proposal for a LEO constellation of 4600 [14]. Boeing joined the race in June of 2016 announcing plans for a LEO constellation of 2956 satellites to provide broadband internet access globally. Boeing plans to deploy the first portion of the system, 1396 satellites operating at an altitude of 1200 km, and to subsequently increase the constellation to the total of 2956 satellites [15]. Moreover, China Aerospace Science and Industry Corporation (CASIC) have launched a project named 'Hongyun' to build a global wideband communications LEO satellite constellation consisting of 156 satellites with altitude 1000 km. The first phase of the project is expected to complete by 2021, and the first experimental satellite has been launched in 2017 [16].