Li et al. Satell Navig (2020) 1:12 https://doi.org/10.1186/s43020-020-00010-2 Satellite Navigation https://satellite-navigation.springeropen.com/ REVIEW Open Access Advances in BeiDou Navigation Satellite System (BDS) and satellite navigation augmentation technologies Rui Li1,2, Shuaiyong Zheng1, Ershen Wang3*, Jinping Chen4, Shaojun Feng5, Dun Wang6 and Liwen Dai7 Abstract Several noteworthy breakthroughs have been made with the BeiDou Navigation Satellite System (BDS) and other global navigation satellite systems as well as the associated augmentation systems, such as the commissioning of the BDS-3 preliminary system and the successful launch of the frst BDS-3 GEO satellite which carries the satellite- based augmentation payload. Presently, BDS can provide basic services globally, and its augmentation system is also being tested. This paper gives an overview of BDS and satellite navigation augmentation technologies. This overview is divided into four parts, which include the system segment technologies, satellite segment technologies, propaga- tion segment technologies, and user segment technologies. In each part, these technologies are described from the perspectives of preliminary information, research progress, and summary. Moreover, the signifcance and progress of the BeiDou Satellite-based Augmentation System (BDSBAS), low earth orbit augmentation, and the national BeiDou ground-based augmentation system are presented, along with the airborne-based augmentation system. Further- more, the conclusions and discussions covering popular topics for research, frontiers in research and development, achievements, and suggestions are listed for future research. Keywords: BeiDou Navigation Satellite System, Satellite navigation augmentation systems, System segment technologies, Satellite segment technologies, Propagation segment technologies, User segment technologies Introduction the rapid development of BDS in all aspects, the chief GPS came into full operation in 1995, when Russia, designer of BDS, Yang Changfeng, announced the ini- Europe, and China subsequently put their satellite navi- tial operation of BDS-3 at the state council information gation systems into full use (Elliott and Christopher ofce of China in early 2019, and since this time BDS-3 2006). In recent years, China has been actively promoting has been ofcially providing global positioning, naviga- the construction and development of the BeiDou Navi- tion, and timing services. Completion of the construction gation Satellite System (BDS), and by the end of the year of BDS-3 is expected to occur around 2020, after which 2000 the construction of BDS-1 was complete and BDS-1 BDS-3 will be able to provide services to the world on a began to provide GPS services for China. Te construc- wider basis. tion of BDS-2 was completed at the end of 2012, after It is well known that the navigation service provided by which BDS-2 was utilized to provide service for regions GNSS covers use with bicycles, cars, and trains, which all over the Asia–Pacifc region. China is also working on require adequate position accuracy. As GNSS is gradually applying its BDS to serve users all over the world. With applied to civil aviation, stricter requirements need to be satisfed for safe fight. In addition to accuracy, integrity *Correspondence: [email protected] is also emphasized for the safe navigation of aircraft. Te 3 College of Electronic and Information Engineering, Shenyang Aerospace civil aviation authority has produced the requirements University, No. 37 Daoyi South Street, Daoyi District, Shenyang, China for satellite navigation systems in terms of required navi- Full list of author information is available at the end of the article gation performance (RNP), including accuracy, integrity, © The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creat iveco mmons .org/licen ses/by/4.0/. Li et al. Satell Navig (2020) 1:12 Page 2 of 23 continuity, and availability. Tese requirements in terms facilities, they are also known as external augmentation of accuracy and integrity (Guo et al. 2019) are illustrated systems. ABAS is built with an internal receiver or other in Fig. 1. Te requirements for accuracy in civil aviation airborne navigation sources and is hence also sometimes vary from the kilometer level to the meter level, for safety called the internal augmentation system. en-route and when carrying out CAT-III approaches, and Satellite navigation augmentation technology is tech- the requirements for integrity risk probability lie between nology that can further improve the accuracy, integrity, 10−4/h and 10−9/approach level. continuity (Li et al. 2018), and availability of GNSS by Te International Civil Aviation Organization (ICAO) generating augmentation information or adding a signal has recommended specifc GNSS requirements for difer- source. More specifcally, satellite navigation augmenta- ent phases of fight (Anonymous 2006), which are listed tion technologies mainly include: satellite integrity moni- in Table 1. Te ICAO divides the satellite navigation aug- toring and alarms, GNSS signal propagation technologies mentation systems into three categories: the Satellite- such as ionospheric propagation modeling, monitoring, Based Augmentation System (SBAS), the Ground-Based and alarms, wide area integrity monitoring, local area Augmentation System (GBAS), and the Airborne-Based integrity monitoring, GNSS diferential correction, Augmentation System (ABAS). Generally speaking, as pseudolite augmentation, the design and implementa- GBAS and SBAS are built with corresponding auxiliary tion of the GNSS augmentation system, the analysis and verifcation of accuracy, integrity, continuity, availabil- ity, the accurate detection of faults and alarms, integrity risk modeling, anti-spoofng, and other augmentation technologies. Integrity Point Pseudorange Carrier positioning difference phase According to the principle of GNSS augmentation technologies, satellite navigation augmentation tech- 10-9 CAT-III nology is divided into two categories: information augmentation technologies and signal augmentation -8 10 CAT-II technologies. For information augmentation technolo- -7 10 CAT-I gies, the ground tracking network calculates GNSS sig- En-route NPA (oceanic) nal error corrections and integrity information. Te Marine affairs ground tracking network then broadcasts these data to 10-6 Continent Geodesy users through the internet or satellite communication GIS channels, and the user utilizes the received corrections 10-5 and integrity information to process the GNSS signal received. For instance, the augmentation technology of 10-4 1000m 100m 10m 1m 10cm 1cm 1mm GBAS is denoted information augmentation technology. Accuracy Signal augmentation technologies refer to technology Fig. 1 Performance requirements in terms of accuracy and integrity which provides additional ranging signals to complement Table 1 ICAO GNSS requirements for diferent phases of fight Typical operation Accuracy (H,V) Integrity Continuity Availability Integrity probability Alert limit (H,V) 7 4 8 En route 3700 m, – 1–1 10− /h 3700 m, – 1–10− to 1–10− /h 0.99–0.99999 × 7 4 8 Terminal 740 m, – 1–1 10− /h 1850 m, – 1–10− to 1–10− /h 0.99–0.99999 × 7 4 8 NPA 220 m, – 1–1 10− /h 556 m, – 1–10− to 1–10− /h 0.99–0.99999 × 7 6 APV-I 16 m, 20 m 1–2 10− /APCH 40 m, 50 m 1–8 10− /15 s 0.99–0.99999 × 7 × 6 LPV 16 m, 20 m 1–2 10− /APCH 40 m, 50 m 1–8 10− /15 s 0.99–0.99999 × 7 × 6 LPV200 16 m, 4 m 1–2 10− /APCH 40 m, 35 m 1–8 10− /15 s 0.99–0.99999 × 7 × 6 APV-II 16 m, 8 m 1–2 10− /APCH 40 m, 20 m 1–8 10− /15 s 0.99–0.99999 × 7 × 6 CAT-I 16 m, 4–6 m 1–2 10− /APCH 40 m, 10–15 m 1–8 10− /15 s 0.99–0.99999 × 9 × 6 CAT-II/IIIA 6.9 m, 2.0 m 1–2 10− /APCH 17.3 m, 5.3 m 1–4 10− /15 s 0.99–0.99999 × 9 × 7 CAT-IIIB 6.1 m, 2.0 m 1–2 10− /APCH 15.5 m, 5.2 m 1–1 10− /15 s 0.99–0.99999 × × APCH APproaCH, H Horizontal, V Vertical Li et al. Satell Navig (2020) 1:12 Page 3 of 23 those already provided by GNSS. Trough the use of sig- 2013). Te geometric range can be computed using the nal augmentation technologies, users can obtain accurate navigation message and the position of the monitor sta- and reliable information concerning position in situ- tion. Common view time transfer is used to estimate the ations where GNSS cannot usually be used or does not clock ofset of the monitor station and the synchronized work sufciently (Ge et al. 2018; Wang et al. 2018a, b). pseudorange (Chen et al. 2017; Tsai 1999). Finally, the For example, Low Earth Orbit (LEO) augmentation tech- monitor stations forward the resultant data to the master nology is a type of signal augmentation technology (Li stations. Master stations generate diferential corrections et al. 2019a; Ma 2018; Reid et al. 2016). SBAS is a com- and integrity information with regard to each monitored bination of information augmentation technologies and satellite and each monitored ionosphere grid point (IGP). signal augmentation technologies, providing multiple Diferential corrections include long-term corrections, augmentations including ranging signals, corrections, fast corrections, and ionospheric corrections.