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{{Article Infobox2
{{Article Infobox2
|Category=COMPASS
|Category=BEIDOU
|Title={{PAGENAME}}
|Editors=GMV
|Authors=GMV.
|Level=Basic
|Level=Basic
|YearOfPublication=2011
|YearOfPublication=2011
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|Logo=GMV
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The [[BeiDou_General_Introduction|BeiDou Navigation Satellite System (BDS)]], also known as BeiDou-2<ref name=BDS_STATUS> Compass/BeiDou Status, Jun Shen, BNStar Navigation Technology & System, Inc., Rome (Italy), June 11, 2009</ref>, is China’s second-generation satellite navigation system<ref name=BDS_STATUS/><ref>[https://en.wikipedia.org/wiki/Beidou_Navigation_Satellite_System BeiDou Navigation Satellite System in Wikipedia]</ref> that will be capable of providing positioning, navigation, and timing services to users on a continuous worldwide basis<ref name=BDS_WORLDWIDE> BeiDou China’s Rapidly Emerging GNSS, InsideGNSS, May/June 2014</ref>. The first and second generation of BeiDou receivers are already available, including the combination of GPS and BeiDou systems - currently limited to the available [[BeiDou Services|regional services]] - with already over a thousand [[BeiDou User Segment|users]].


The [[Work in Progress:COMPASS General Introduction|Compass Navigation Satellite System (CNSS)]], also named BeiDou-2,<ref name=Chinese_today>[http://www.sinodefence.com/space/satellite/compass-beidou2.asp Compass Satellite Navigation System (Beidou), on Sinodefence.com, updated on August 6th, 2011.] </ref> 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.<ref name=Chinese_today/><ref name=COMPASS_Wiki>[http://en.wikipedia.org/wiki/Compass_navigation_system COMPASS Navigation system in Wikipedia]</ref>


Although the upgrade of its regional navigation system towards a global solution started in 1997, the formal approval by the Government of the development and deployment of BeiDou-2/CNSS was done in 2004.<ref name=Chinese_today/> The system is currently under development evolving from a regional system called [[Work in Progress:Other Regional Systems|BeiDou-1]], and in the first phase will provide high-accuracy positioning services for users in China and its neighbouring regions by 2012.<ref name=Chinese_today/> In a second stage, the system will evolve to provide global navigation services by 2020, similarly to the [[GPS General Introduction|GPS]], [[GLONASS General Introduction|GLONASS]] or [[GALILEO General Introduction|Galileo]] systems.<ref name=Chinese_today/>
==BeiDou Receiver==


As of August 2011, nine satellites for Compass have been launched, the first eight of which completed the deployment foreseen for the first phase of BeiDou-2.<ref name=Chinese_today/><ref name=BEIDOU_MUNICH_2011>China Satellite Navigation Office, ''Development of BeiDou Navigation Satellite System'', Munich Satellite Navigation Summit, 2011.</ref><ref name="Compass-IGSO3">[http://business.globaltimes.cn/industries/2011-04/642763.html ''China completes basic Beidou (Compass) Navigation Satellite System''], 2011-04-10 by Globaltimes.cn</ref>
The BeiDou User Segment consists of Beidou user terminals<ref name=BEIDOU_MUNICH_2011>China Satellite Navigation Office, Development of BeiDou Navigation Satellite System, Munich Satellite Navigation Summit, 2011</ref>. The first user terminals appeared in 2009  based in ASIC and comprising already GPS integration<ref>"Status of COMPASS Development", M. Lu, Stanford PNT Symposium 2010</ref>.


==COMPASS Receiver==


The COMPASS User Segment consists of COMPASS/Beidou user terminals,<ref name=BEIDOU_MUNICH_2011/> which receive Compass navigation signals, determine pseudoranges (and other observables) and solve the navigation equations in order to obtain their coordinates.
==Particularities==
Each GNSS system uses a specific [[Reference Frames in GNSS|Reference Frame]]; although a multi-constellation receiver is able to convert all information to the same common frame, a BeiDou-only receiver uses the China Geodetic Coordinate System 2000 (CGCS2000), consistent with the International Terrestrial Reference System (ITRS).


A COMPASS receiver is a user terminal capable of determining the user position, velocity and precise time (PVT) by processing the signal broadcasted by COMPASS satellites. It receives COMPASS navigation signals, determines pseudoranges (and other observables) and solves the navigation equations in order to obtain their coordinates. Any navigation solution provided by a [[GNSS Receivers General Introduction|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.<ref name="GNSS-Book ">J. Sanz Subirana, JM. Juan Zornoza and M. Hernández-Pajares, ''Global Navigation Satellite Systems: Volume I: Fundamentals and Algorithms''</ref> In June 2011, the test-beds for ground segment and also the test section of the user terminal development have been completed.<ref>[http://www.cnkeyword.info/compass-system-10-months-to-complete-a-comprehensive-test-covering-the-asia-pacific-region-next-year/ ''Compass system 10 months to complete a comprehensive test covering the Asia Pacific region next year''] China news, 20th June 2011.</ref> There is also international cooperation in terms of Compatibility and Interoperability between BeiDou and other GNSSs, which will lead to interoperable terminals compatible with other GNSSs.<ref name=BEIDOU_MUNICH_2011/>
In an analogous way, each system has its own [[Time References in GNSS|time reference]] defined by the respective control segments; the time reference for BeiDou is called “BeiDou Time” ([[Time References in GNSS#BeiDou Time (BDT)|BDT)]] and it is aligned with UTC.


For completeness, the main characteristics of COMPASS signals are shown in the following table and figure, extracted from the presentation on the status of COMPASS in Munich Satellite Navigation Summit 2011 by the China Satellite Navigation Office:<ref name=BEIDOU_MUNICH_2011/>
Each GNSS System transmits its own navigation message, defined in the respective Signal In Space Interface Control Document, SIS ICD, and whose content is used by receivers to compute their positions. The [http://gge.unb.ca/test/beidou_icd_english.pdf first version of the SIS ICD] for BeiDou B1I open service signal on 1561.098 MHz was released December 27 at a news conference held in Beijing by the Chinese State Council Information Office<ref>http://www.gpsworld.com/beidou-icd-released GPS World, January 2013</ref>.
[[File:CompassSpectrum.PNG‎|COMPASS Signals Spectrum|450px|thumb]]


[[File:CompassSignals.png‎|COMPASS Signals characteristics|500px]]
GNSS signals modulation, structure, navigation message contents and formats are often different among signals from the same system and from different systems. Most of these characteristics are easily implemented at the receiver (e.g. requiring only “software modifications”, such as the use of different PRN codes or the ability to cope with different message structures). The main difference among GNSS receivers falls into the specific characteristics that have impact at RF level, such as the [[CDMA FDMA Techniques|Multiple Access Techniques]] employed. BeiDou (as GPS and Galileo) uses CDMA techniques allowing a simpler RF module (than for example GLONASS), since all signals in the same frequency band have a common carrier. Nevertheless, BeiDou supports a [[BeiDou Services|regional short message service]], which allows the user to send information to the stations. This additional communication link adds complexity to the receiver, and therefore potentially higher costs.


The COMPASS services are further described in the article [[Work in Progress:COMPASS Services|COMPASS Services]].
It should be noted that the current trend consists on facilitating the access of each system to the receivers, i.e. fomenting multi-constellation receivers. Hence, most discussions and agreements among the systems’ responsibles are conducted in the sense of taking this effort out of the user segment, focusing on [[Principles of Compatibility among GNSS|compatibility]] and [[Principles of Interoperability among GNSS|interoperability]] aspects in the system design.


==Notes==
<references group="footnotes"/>
==References==
==References==
<references/>
<references/>


[[Category:COMPASS]]
[[Category:BEIDOU]]

Latest revision as of 15:47, 10 August 2018


BEIDOUBEIDOU
Title BeiDou Receivers
Edited by GMV
Level Basic
Year of Publication 2011
Logo GMV.png

The BeiDou Navigation Satellite System (BDS), also known as BeiDou-2[1], is China’s second-generation satellite navigation system[1][2] that will be capable of providing positioning, navigation, and timing services to users on a continuous worldwide basis[3]. The first and second generation of BeiDou receivers are already available, including the combination of GPS and BeiDou systems - currently limited to the available regional services - with already over a thousand users.


BeiDou Receiver

The BeiDou User Segment consists of Beidou user terminals[4]. The first user terminals appeared in 2009 based in ASIC and comprising already GPS integration[5].


Particularities

Each GNSS system uses a specific Reference Frame; although a multi-constellation receiver is able to convert all information to the same common frame, a BeiDou-only receiver uses the China Geodetic Coordinate System 2000 (CGCS2000), consistent with the International Terrestrial Reference System (ITRS).

In an analogous way, each system has its own time reference defined by the respective control segments; the time reference for BeiDou is called “BeiDou Time” (BDT) and it is aligned with UTC.

Each GNSS System transmits its own navigation message, defined in the respective Signal In Space Interface Control Document, SIS ICD, and whose content is used by receivers to compute their positions. The first version of the SIS ICD for BeiDou B1I open service signal on 1561.098 MHz was released December 27 at a news conference held in Beijing by the Chinese State Council Information Office[6].

GNSS signals modulation, structure, navigation message contents and formats are often different among signals from the same system and from different systems. Most of these characteristics are easily implemented at the receiver (e.g. requiring only “software modifications”, such as the use of different PRN codes or the ability to cope with different message structures). The main difference among GNSS receivers falls into the specific characteristics that have impact at RF level, such as the Multiple Access Techniques employed. BeiDou (as GPS and Galileo) uses CDMA techniques allowing a simpler RF module (than for example GLONASS), since all signals in the same frequency band have a common carrier. Nevertheless, BeiDou supports a regional short message service, which allows the user to send information to the stations. This additional communication link adds complexity to the receiver, and therefore potentially higher costs.

It should be noted that the current trend consists on facilitating the access of each system to the receivers, i.e. fomenting multi-constellation receivers. Hence, most discussions and agreements among the systems’ responsibles are conducted in the sense of taking this effort out of the user segment, focusing on compatibility and interoperability aspects in the system design.

References

  1. ^ a b Compass/BeiDou Status, Jun Shen, BNStar Navigation Technology & System, Inc., Rome (Italy), June 11, 2009
  2. ^ BeiDou Navigation Satellite System in Wikipedia
  3. ^ BeiDou China’s Rapidly Emerging GNSS, InsideGNSS, May/June 2014
  4. ^ China Satellite Navigation Office, Development of BeiDou Navigation Satellite System, Munich Satellite Navigation Summit, 2011
  5. ^ "Status of COMPASS Development", M. Lu, Stanford PNT Symposium 2010
  6. ^ http://www.gpsworld.com/beidou-icd-released GPS World, January 2013