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 services to global users.

(II) Main Composition of the BDS

The BDS is mainly comprised of three segments: space segment, ground segment and user segment.

– The space segment. The BDS space segment is a hybrid navigation constellation consisting of GEO, IGSO and MEO satellites.

– The ground segment. The BDS ground segment consists of various ground stations, including master control stations, time synchronization/ uplink stations, and monitoring stations.

– The user segment. The BDS user segment consists of various kinds of BDS basic products, including chips, modules and antennae, as well as terminals, application systems and application services, which are compatible with other systems.

(III) Characteristics of the BDS

The BDS development follows a model of developing regional service capacities, then gradually extending the service globally. This practice has enriched the development models for navigation satellite systems worldwide.

The BDS possesses the following characteristics: First, its space segment is a hybrid constellation consisting of satellites in three kinds of orbits. In comparison with other navigation satellite systems, the BDS operates more satellites in high orbits to offer better anti-shielding capabilities, which is particularly observable in terms of performance in the low-latitude areas. Second, the BDS provides navigation signals of multiple frequencies, and is able to improve service accuracy by using combined multi-frequency signals. Third, the BDS integrates navigation and communication capabilities for the first time, and has five major functions – real-time navigation, rapid positioning, precise timing, location reporting and short message communication services. 6