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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 COMPASS is called “BeiDou Time” (BDT) and it is aligned with UTC. | 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 COMPASS 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 Documents, SIS ICD. As an example, the satellites transmit information that allows the receiver to compute their positions. | Each GNSS System transmits its own navigation message, defined in the respective Signal In Space Interface Control Documents, SIS ICD. As an example, the satellites transmit information that allows the receiver to compute their positions. The [http://www.beidou.gov.cn/attach/2011/12/27/201112273f3be6124f7d4c7bac428a36cc1d1363.pdf BeiDou Navigation Satellite System Signal In Space Interface Control Document (Test Version)] was released in December 2011<ref>[http://www.beidou.gov.cn/attach/2011/12/27/201112273f3be6124f7d4c7bac428a36cc1d1363.pdf BeiDou Navigation Satellite System Signal In Space Interface Control Document (Test Version)], China Satellite Navigation Office, December 2011</ref>. | ||
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. COMPASS (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, COMPASS supports a [[COMPASS 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. | 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. COMPASS (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, COMPASS supports a [[COMPASS 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. | ||
Revision as of 12:26, 25 January 2012
| COMPASS | |
|---|---|
| Title | BeiDou Receivers |
| Author(s) | GMV |
| Level | Basic |
| Year of Publication | 2011 |
The Compass Navigation Satellite System (CNSS), also named BeiDou-2,[1] 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[1][2]. The first and second generation of COMPASS receivers are already available, including the combination of GPS and COMPASS systems - currently limited to the available regional services - with already over a thousand users.
COMPASS Receiver
The COMPASS User Segment consists of COMPASS/Beidou user terminals[3]. The first generation of BeiDou-1 terminals emerged in 2003 with full RDSS function and communication terminal based on General Purpose ICs. The second generation appeared in 2009 based in ASIC and comprising already GPS integration[4].
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 COMPASS-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 COMPASS 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 Documents, SIS ICD. As an example, the satellites transmit information that allows the receiver to compute their positions. The BeiDou Navigation Satellite System Signal In Space Interface Control Document (Test Version) was released in December 2011[5].
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. COMPASS (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, COMPASS 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.
Notes
References
- ^ a b Compass Satellite Navigation System (Beidou), on Sinodefence.com, updated on August 6th, 2011.
- ^ COMPASS Navigation system in Wikipedia
- ^ China Satellite Navigation Office, Development of BeiDou Navigation Satellite System, Munich Satellite Navigation Summit, 2011
- ^ "Status of COMPASS Development", M. Lu, Stanford PNT Symposium 2010
- ^ BeiDou Navigation Satellite System Signal In Space Interface Control Document (Test Version), China Satellite Navigation Office, December 2011