BeiDou Navigation Satellite System
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  • LI Dehai

    Associate Professor, Chinese Academy of Surveying & Mapping

  • LI Nan

    Brand director, strategic development center, Beijing BDStar Navigation CO., LTD.

As one of the original countries that developed astronomy, China recorded the observation of Big Dipper. Big Dipper consists of seven stars named as Dubhe, Merak, Phecda, Megrez, Alioth, Mizar and Alkaid, respectively. Ancient Chinese people linked these stars into an archaic hopper used for spooning out the wine, in order to indicate the direction and calculate the time. The BeiDou culture is rooted deeply in Chinese culture with five thousand years, and also is a cultural symbol of realistic significance truly strengthening the national self-confidence. BeiDou Navigation Satellite System (BDS) is a global navigation satellite system developed by China, which is the third mature navigation satellite system in the wake of following the Global Positioning System (GPS) of USA and Global Navigation Satellite System (GLONASS) of Russia. BDS, GPS of USA, GLONASS of Russia and GALILEO of the EU are suppliers affirmed by the International Committee on Global Navigation Satellite System.

With the development of construction and service ability for BeiDou System, it has been successfully applied in many domains including surveying and mapping, telecommunication, water conservancy, fishery, transportation, forest fire protection, disaster mitigation and public security, bringing remarkable economic and social benefits. For better understanding of BDS, the International Publishing Center (IPC) of China National Knowledge Infrastructure (CNKI) specially invited Mr. Dehai Li, the associate research fellow from Chinese Academy of Surveying and Mapping, and Mr. Nan Li, brand director of Beijing BeiDou Star (BDStar) strategic development center, to provide forefront viewpoints on various aspects of BDS such as system composition, strengths and characteristics, independent research and development and civil promotion.

1. System composition

BeiDou System implements the "three-step" development strategy. In 1994, the engineering construction of BeiDou I System started and BeiDou Navigation Satellite test system was preliminarily established, which adopted active positioning mechanism to provide communication services like positioning, navigation, timing service and short message for Chinese users; in 2004, the engineering construction of BeiDou II System was initiated, and 14 satellites were launched to form the network and passive positioning mechanism was added, providing aforementioned services for users in the Asia-Pacific region; in 2009, the construction of global BeiDou System started, inheriting the active and passive services with a view to providing services for countries along "the Belt and Road" and surrounding countries in 2018. Thirty five satellites will be launched for the network to render services for global users.

BeiDou System is composed of three parts: the space section, the ground section and the user section. The space section is a hybrid constellation navigation composed of some geostationary orbit satellites, inclined geo-synchronization orbit satellites and medium earth orbit satellites. The ground section consists of a certain number of stations, including the main control stations, the injection stations and the monitoring stations. The user section covers fundamental products (e.g., chips, modules and antennas), compatible with other satellites, as well as terminal products, application systems and application services.

At present, the BeiDou II System in operation broadcasts B1 and B2 public service signals, providing open services for the Asia-Pacific region for free. The service area covers 55 degrees north to south, 55 to 180 degrees east longitude. The positioning accuracy is beyond 10 meters; the velocity accuracy is better than 0.2 m/s and the timing accuracy is better than 50 nanoseconds.

2. Strengths and characteristics

In comparison with other navigation satellite systems (e.g., GPS), BeiDou System has advantages in three aspects. First of all, the space section of BeiDou System adopts the hybrid constellation navigation consisting of three orbiting satellites, embracing more high orbit satellites than other navigation satellite systems with better anti-occluding, which performs more noticeably in low latitude regions. Mr. Dehai Li introduced that the altitude of GPS orbit is about 20 thousand to 24 thousand kilometers. BeiDou has five GEO satellites at a height of 36 thousand to 38 thousand kilometers. Secondly, BeiDou System has offered navigation signals with multiple frequency points. By means of combining the multi-frequency signals, BeiDou system enhances the control of data quality to ensure service accuracy. Thirdly, BeiDou System creatively integrates navigation and communication ability, possessing five functions: real-time navigation, rapid positioning, precise timing services, location reports and short-message communication service. Mr. Nan Li, the brand director of Beijing BDStar strategic development center, introduced that the short-message function is exclusively possessed by BDStar. In the past, the fishermen had no signals for cell phones when they put out to the sea and they would spend even more than ten dollars per second on a maritime telephone. Nowadays, the fishermen can use the short message service of BeiDou System to communicate with administrative departments, BeiDou terminals and any users of mobile communication.

3. Independent research and development

Navigation Satellite System is an important strategic resource for a country. A successful navigation satellite system not only needs mature and complete satellites and terrestrial infrastructure, but also needs the development of industrialization application. At present, China has realized fully independent controllability in some core technology areas of navigation satellite industrialization. On the 8th China Satellite Navigation Conference in May 2017, BDStar released 28 nm GNSS-UFirebird, the first and smallest chip in China. Mr. Nan Li introduced that UFirebird chip was developed by a holding subsidiary of BDStar Navigation, Unicore Communications Inc. (Beijing), leading domestic multimode chips into 28 nm era. The smallest chip is 1.9 mm × 2.9 mm, only the size of pencil tip, which features ultra-low power consumption and supports WAAS/QZSS/EGDOS/MSAS/GAGAN enhancement signals, in addition to global navigation satellite signals.

In July 2017, China Satellite Navigation Office published the National BDS Augmentation System Service Performance Standard (Version 1.0). National Administration of Surveying, Mapping, and Geoinformation has newly built and restructured more than 360 CORS stations through the modern geomatics engineering project, and the program of national fundamental surveying and mapping. By collecting the data flow from nationwide CORS stations, real-time solution and precision processing are conducted with the wide-area differential correction information experimentally issued, and thus the users can receive differential correction information so as to carry out positioning resolve and improve positioning accuracy to sub-meter through Internet.

4. Civil promotion

As a mature system, BeiDou is gradually perceived and accepted by the community. Recent years have witnessed accelerated industrial development of BeiDou. Along with the introduction of some previous industrial demonstration projects, such as marine fishery, buses for tourism/passengers and vehicles carrying dangerous chemical products, and driving test, BeiDou system has received preference from users in different fields with technology, user scale and other aspects improved constantly. The smallest GNSS chip (28 nm) of BDStar received the preference of the Internet-of-Things market once released. Mr. Nan Li introduced that, OFO Bicycle signed the strategic partnership agreement with BDStar at the chip briefing, and aimed at the further application of BeiDou in sharing bicycle area, in order to push forward BeiDou toward the community acceleratedly.

The Chinese Academy of Surveying and Mapping mainly conducts the civil promotion of BeiDou System in three major fields, according to the introduction of Mr. Dehai Li. First of all, data processing of the reference station and application of China Geodetic Coordinate System 2000 based on BeiDou are studied. By developing softwares including GPASS, they conduct the non-difference and dual-difference BDS/GPS data processing, achieving the maintenance of national coordinate reference frame in which BDS is incorporated. Secondly, they take on the mission to construct the analysis center of International GNSS Monitoring and Assessment System (IGMAS), and to conduct the monitoring and evaluation service platform covering BDS/GPS/Glonass/Galileo. Besides, they operationally generate and issue products like precise orbit, clock error and earth rotation parameter (ERP), tropospheric delay, ionospheric delay, and monitoring sequence of station coordinates. Thirdly, by collaborating with other organizations, such as National Administration of Surveying, Mapping, and Geoinformation, they jointly develop the BeiDou wide-area differential enhanced service system, and experimentally broadcast the BDS/GPS wide-area enhancement information.

JTP's LIU Kang contributed to this report.

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