BeiDou User Segment

BEIDOU
Title	BeiDou User Segment
Edited by	GMV
Level	Basic
Year of Publication	2011

The BeiDou Navigation Satellite System (BDS), also known as BeiDou-2, is China’s second-generation satellite navigation system that will be capable of providing positioning, navigation, and timing services to users on a continuous worldwide basis. With continuous efforts put on compatibility and interoperability of the system, the BeiDou user segment and respective applications are expected to be very similar to all other GNSSs for the open service. BeiDou has one particularity over all the other GNSSs: the capability of allowing exchange of short message services between ground stations and users.

BeiDou User Segment

The BeiDou User Segment consists of Beidou user terminals, which receive BeiDou navigation signals, determine pseudoranges (and other observables) and solve the navigation equations in order to obtain their coordinates. A BeiDou receiver is a device capable of determining the user position, velocity and precise time (PVT) by processing the signal broadcasted by BeiDou satellites. Any navigation solution provided by a GNSS Receiver is based on the computation of its distance to a set of satellites, by means of extracting the propagation time of the incoming signals traveling through space at the speed of light, according to the satellite and receiver local clocks. It should be noted that in the first version of the system, BeiDou-1, the user position is computed by the ground station and relayed back to the user via GEO satellite. This concept was not adopted in the BeiDou evolution that uses the usual way of computing user position on receiver side.

In June 2011, the system has completed the ground segment commissioning, including the test section of the user terminal development. However the first terminals appeared in 2009 based in ASIC and comprising already GPS integration.

There is also an international cooperation in terms of Compatibility and Interoperability between BeiDou and other GNSSs. The China Satellite Navigation Office has been publishing ICD updates on an annual basis being the definition of the Open Service (OS) in a very advanced status.

Applications

GNSS applications are all those applications that use GNSS signals to collect position, velocity and time information to be used by the application. For instance, the position and velocity provided by a BeiDou user terminal may be used for different kinds of applications (civil, military, scientific) such as:

• Fishery: fishermen safety, oceanic and economic security, protection of sovereignty and resources: 14000 fisher users were reported and more than 500 vessel rescue and costal alarm systems have been equipped with BeiDou terminals;
• Disaster Prevention and Mitigation: improvement of rescue response and decision-making capability due to rapid and timely disaster alert, support to rescue operations regarding command scheduling and rapid communication. BeiDou terminals were used in the operations that followed the earthquakes in Wenchuan (Sichuan Province) and Yushu (Qinghai Province);
• Timing: Beidou/GPS multi-mode time synchronization devices, with a reported synchronization accuracy better than 100 ns;
• Other applications include transportation, water management, meteorology, forest fire prevention, soil monitoring and coal mine safety monitoring.

In August 2015, Alibaba, China’s e-commerce counterpart to Amazon, announced that it will start providing Location Based Services (LBS) based on the BeiDou Navigation Satellite System (BDS).

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