Signal Multiplex Techniques for GNSS - Revision history

Filipe.Pelica at 17:54, 26 May 2014

2014-05-26T17:54:27Z

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	:::: Similarly, Galileo will provide on E1 the Public Regulated Service (PRS) and the E1 OS data and pilot signals.		:::: Similarly, Galileo will provide on E1 the Public Regulated Service (PRS) and the E1 OS data and pilot signals.
	:::: GLONASS transmits the C/A Code and P-Code, and plans new CDMA signals		:::: GLONASS transmits the C/A Code and P-Code, and plans new CDMA signals
	:::: and ~~Compass~~ plans to provide two additional signals with services that are still to be specified.		:::: and BeiDou plans to provide two additional signals with services that are still to be specified.

	::*In L2		::*In L2
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	:::: Galileo plans to transmit four signals using the Alt-BOC modulation,		:::: Galileo plans to transmit four signals using the Alt-BOC modulation,
	:::: GLONASS plans to transmit new open CDMA signals in the L5 band,		:::: GLONASS plans to transmit new open CDMA signals in the L5 band,
	:::: and ~~Compass~~ plans to provide two additional signals with services that are still to be specified.		:::: and BeiDou plans to provide two additional signals with services that are still to be specified.
	::* In E6		::* In E6
	:::: Galileo plans to transmit the Public Regulated Service (PRS) and a Commercial Service (CS) with improved characteristics with respect to the free Open Service (OS),		:::: Galileo plans to transmit the Public Regulated Service (PRS) and a Commercial Service (CS) with improved characteristics with respect to the free Open Service (OS),
	:::: and ~~Compass~~ plans to provide two additional signals with services that are still to be specified.		:::: and BeiDou plans to provide two additional signals with services that are still to be specified.

	::* Finally in L3		::* Finally in L3

Carlos.Lopez at 09:18, 25 November 2011

2011-11-25T09:18:25Z

← Older revision		Revision as of 09:18, 25 November 2011
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	==References==		==References==
	<references/>		<references/>


			== Credits ==
			The information presented in this NAVIPEDIA’s article is an extract of the PhD work performed by Dr. Jose Ángel Ávila Rodríguez in the FAF University of Munich as part of his Doctoral Thesis “On Generalized Signal Waveforms for Satellite Navigation” presented in June 2008, Munich (Germany)


	[[Category:Fundamentals]]		[[Category:Fundamentals]]
	[[Category:GNSS Signals]]		[[Category:GNSS Signals]]

Carlos.Lopez at 09:30, 21 November 2011

2011-11-21T09:30:25Z

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	\|Category=Fundamentals		\|Category=Fundamentals
	\|Authors=J.A Ávila Rodríguez, University FAF Munich, Germany.		\|Authors=J.A Ávila Rodríguez, University FAF Munich, Germany.
	\|Level=~~Advanced~~		\|Level=Basic
	\|YearOfPublication=2011		\|YearOfPublication=2011
	\|Title={{PAGENAME}}		\|Title={{PAGENAME}}

Carlos.Lopez: /* Multiplexing Schemes */

2011-11-18T11:28:54Z

Multiplexing Schemes

← Older revision		Revision as of 11:28, 18 November 2011
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	::* [[Majority Signal Voting]]		::* [[Majority Signal Voting]]
	::* [[Hard Limiting]]		::* [[Hard Limiting]]
	::* [[Quadrature Product Sub-carrier Modulation (QPSM)]]		::* [[Quadrature Product Sub-carrier Modulation]] (QPSM)
	:::: Interplex and CASM		:::: Interplex and CASM
	:::: Modified Interplex Modulation		:::: Modified Interplex Modulation
	::* [[Intervoting]]		::* [[Intervoting (Interplex plus Majority Voting)\|Intervoting]]


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	::<math>\eta = \frac{P_{useful}}{P_{total}}</math>		::<math>\eta = \frac{P_{useful}}{P_{total}}</math>

	==References==		==References==

Carlos.Lopez at 14:12, 7 November 2011

2011-11-07T14:12:47Z

← Older revision		Revision as of 14:12, 7 November 2011
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	{{Article Infobox2		{{Article Infobox2
	\|Category=Fundamentals		\|Category=Fundamentals
	~~\|Title={{PAGENAME}}~~		\|Authors=J.A Ávila Rodríguez, University FAF Munich, Germany.
	\|Authors= J.A Ávila Rodríguez, University FAF Munich, Germany.
	\|Level=Advanced		\|Level=Advanced
	\|YearOfPublication=2011		\|YearOfPublication=2011
			\|Title={{PAGENAME}}
	}}		}}

	== Introduction ==		== Introduction ==

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	::*In L2		::*In L2
	:::: GPS will be transmitting the L2 Civil Signal (L2C) together with the P(Y) Code and M-Code,		:::: GPS will be transmitting the L2 Civil Signal (L2C) together with the P(Y) Code and M-Code,
	:::: and GLONASS transmits the C/A Code and P-Code.		:::: and GLONASS transmits the C/A Code and P-Code.

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	The availability of spectrum allocations is a limited resource as we have seen in previous chapters and thus the existing bands have to be reused. As new services are demanded, new signals are also required to ~~fulfil~~ needs that did not exist previously. Moreover it is highly desirable and of greatest importance that the new navigation signals that are introduced do not cause significant distortion on other signals sharing the frequency. In other words, they have to be compatible with the already existing ones. Additional constraints are that we can transmit the new signals through the same High Power Amplifier (HPA), to be able to accommodate new data messages and new Pseudo Random Noise (PRN) code families, to have spectral isolation with the rest of signals in the band and to be capable of providing flexibility to control the distribution of power between the signals in and outside of the allocated band.		The availability of spectrum allocations is a limited resource as we have seen in previous chapters and thus the existing bands have to be reused. As new services are demanded, new signals are also required to fulfill needs that did not exist previously. Moreover it is highly desirable and of greatest importance that the new navigation signals that are introduced do not cause significant distortion on other signals sharing the frequency. In other words, they have to be compatible with the already existing ones. Additional constraints are that we can transmit the new signals through the same High Power Amplifier (HPA), to be able to accommodate new data messages and new Pseudo Random Noise (PRN) code families, to have spectral isolation with the rest of signals in the band and to be capable of providing flexibility to control the distribution of power between the signals in and outside of the allocated band.

	If we take a look at all these constraints, we can clearly recognize the importance of developing good signal multiplex techniques based on a high efficiency constant-envelope. Multiplexing aims at providing a multiplicity of signals that must coexist on the same carrier without mutual interference [A.R. Pratt and J.I.R. Owen, 2005]<ref name="AP_2005">[A.R. Pratt and J.I.R. Owen, 2005] A.R. Pratt and J.I.R. Owen, Signal Multiplex Techniques in Satellite Channel Availability - Possible Applications to Galileo, Proceedings of the International Technical Meeting of the Institute of Navigation, ION-GNSS 2005, 13-16 September 2005, Long Beach, California, USA.</ref>. Moreover, we cannot ignore that there are clear constraints to fulfil at payload level and that the multiplex technique must therefore be carefully selected to avoid undesirable sources of degradation. In this chapter we will study the characteristics of current and future multiplexing techniques and the recently proposed modifications for GPS and Galileo in order to be capable of accommodating the optimized MBOC signal modulation.		If we take a look at all these constraints, we can clearly recognize the importance of developing good signal multiplex techniques based on a high efficiency constant-envelope. Multiplexing aims at providing a multiplicity of signals that must coexist on the same carrier without mutual interference [A.R. Pratt and J.I.R. Owen, 2005]<ref name="AP_2005">[A.R. Pratt and J.I.R. Owen, 2005] A.R. Pratt and J.I.R. Owen, Signal Multiplex Techniques in Satellite Channel Availability - Possible Applications to Galileo, Proceedings of the International Technical Meeting of the Institute of Navigation, ION-GNSS 2005, 13-16 September 2005, Long Beach, California, USA.</ref>. Moreover, we cannot ignore that there are clear constraints to fulfil at payload level and that the multiplex technique must therefore be carefully selected to avoid undesirable sources of degradation. In this chapter we will study the characteristics of current and future multiplexing techniques and the recently proposed modifications for GPS and Galileo in order to be capable of accommodating the optimized MBOC signal modulation.

Carlos.Lopez: Created page with "{{Article Infobox2 |Category=Fundamentals |Title={{PAGENAME}} |Authors= J.A Ávila Rodríguez, University FAF Munich, Germany. |Level=Advanced |YearOfPublication=2011 }} == Intr..."

2011-11-07T13:59:56Z

Created page with "{{Article Infobox2 |Category=Fundamentals |Title={{PAGENAME}} |Authors= J.A Ávila Rodríguez, University FAF Munich, Germany. |Level=Advanced |YearOfPublication=2011 }} == Intr..."

New page

{{Article Infobox2
|Category=Fundamentals
|Title={{PAGENAME}}
|Authors= J.A Ávila Rodríguez, University FAF Munich, Germany.
|Level=Advanced
|YearOfPublication=2011
}}

== Introduction ==

All the existing and planned Global Satellite Navigation Systems will be transmitting more than two services in each transmission band.

::*In E1/L1
:::: GPS plans to transmit at least four signals: The old C/A Code and P(Y) Code, the modernized military M-Code and the new L1 Civil signal (L1C).
:::: Similarly, Galileo will provide on E1 the Public Regulated Service (PRS) and the E1 OS data and pilot signals.
:::: GLONASS transmits the C/A Code and P-Code, and plans new CDMA signals
:::: and Compass plans to provide two additional signals with services that are still to be specified.

::*In L2
:::: GPS will be transmitting the L2 Civil Signal (L2C) together with the P(Y) Code and M-Code,
:::: and GLONASS transmits the C/A Code and P-Code.

::* In E5/L5
:::: GPS L5 will provide data and pilot signals, while
:::: Galileo plans to transmit four signals using the Alt-BOC modulation,
:::: GLONASS plans to transmit new open CDMA signals in the L5 band,
:::: and Compass plans to provide two additional signals with services that are still to be specified.
::* In E6
:::: Galileo plans to transmit the Public Regulated Service (PRS) and a Commercial Service (CS) with improved characteristics with respect to the free Open Service (OS),
:::: and Compass plans to provide two additional signals with services that are still to be specified.

::* Finally in L3
:::: GLONASS will also transmit one civil signal (C/A Code) and the military P-Code.

The availability of spectrum allocations is a limited resource as we have seen in previous chapters and thus the existing bands have to be reused. As new services are demanded, new signals are also required to fulfil needs that did not exist previously. Moreover it is highly desirable and of greatest importance that the new navigation signals that are introduced do not cause significant distortion on other signals sharing the frequency. In other words, they have to be compatible with the already existing ones. Additional constraints are that we can transmit the new signals through the same High Power Amplifier (HPA), to be able to accommodate new data messages and new Pseudo Random Noise (PRN) code families, to have spectral isolation with the rest of signals in the band and to be capable of providing flexibility to control the distribution of power between the signals in and outside of the allocated band.

If we take a look at all these constraints, we can clearly recognize the importance of developing good signal multiplex techniques based on a high efficiency constant-envelope. Multiplexing aims at providing a multiplicity of signals that must coexist on the same carrier without mutual interference [A.R. Pratt and J.I.R. Owen, 2005]<ref name="AP_2005">[A.R. Pratt and J.I.R. Owen, 2005] A.R. Pratt and J.I.R. Owen, Signal Multiplex Techniques in Satellite Channel Availability - Possible Applications to Galileo, Proceedings of the International Technical Meeting of the Institute of Navigation, ION-GNSS 2005, 13-16 September 2005, Long Beach, California, USA.</ref>. Moreover, we cannot ignore that there are clear constraints to fulfil at payload level and that the multiplex technique must therefore be carefully selected to avoid undesirable sources of degradation. In this chapter we will study the characteristics of current and future multiplexing techniques and the recently proposed modifications for GPS and Galileo in order to be capable of accommodating the optimized MBOC signal modulation.

Finally, it is interesting to note that, as shown in [A.R. Pratt and J.I.R. Owen, 2005] <ref name="AP_2005"/>, alternative multiplexing methods to those discussed in this chapter could be used. In fact, separate antenna and amplifier chains (that is separate aperture) which allow for signal combination in the far field of the satellite antenna system could be employed. In addition, different signals could be multiplexed on the carrier frequency on several different antenna beams as suggested in [G.L. Cangiani, 2005]<ref>[G.L. Cangiani, 2005] G.L. Cangiani, Methods and Apparatus for Multi-beam Multi-signal Transmission for Actively Phased Array Antenna, Patent US 6856284, granted 15 February, 2005.</ref>. Nevertheless, the extra complexity that the spacecraft payload would have to deal with would be of consideration and the antenna design would suffer from poor efficiency and important cost and weight drawbacks. Moreover, the more challenging problem of transmitting these signals would be the development of a general modulation approach with a single modulator, up-converter, power amplifier chain and antenna aperture [P.A. Dafesh et al., 2006]<ref name="PD_2006">[P.A. Dafesh et al., 2006] P.A. Dafesh, Nguyen, M. Tien, Quadrature product sub-carrier modulation system, Patent US 7120198, Granted 10 October 2006.
</ref>.

== Multiplexing Schemes ==

The first multiplexing technique used in navigation (GPS) was employed to send the C/A Code and the P(Y) Code providing two bi-phase signals on the same carrier frequency in phase quadrature (QPSK). Demultiplexing was relatively simple. However, the need to have more navigation signals has made this multiplexing scheme obsolete for future modernized implementations. In fact, the possible solution of adding another signal slightly offset in frequency would give rise to a non-constant envelope with the consequent distortion after passing through the High Power Amplifier (HPA). The following multiplexing techniques are further described:

::* [[Linear Modulation (Spatial Combining)]]
:::: Tri-code Hexaphase Modulation
::* [[Majority Signal Voting]]
::* [[Hard Limiting]]
::* [[Quadrature Product Sub-carrier Modulation (QPSM)]]
:::: Interplex and CASM
:::: Modified Interplex Modulation
::* [[Intervoting]]

In spite of the important advances realized in the past years, the research field on signal multiplex is still subject to active studies as shown in [T. Fan et al, 2005]<ref>[T. Fan et al, 2005] T. Fan, V. S. Lin, G. H. Wang, K. P. Maine, P. A. Dafesh and B. Myers, The RF Compatibility of flexible Navigation Signal Combining Methods, Proceedings of the National Technical Meeting of the Institute of Navigation, ION-NTM 2005, January 2005, San Diego, California, USA.</ref>. Out of all the multiplex techniques presented above, the Linear Modulation and the Tri-code Hexaphase Modulation have maximum efficiencies limited to roughly seventy-one percent [P.A. Dafesh et al., 2006] <ref name="PD_2006"/>, what is an important disadvantage. Moreover, they are limited to multiplexing only binary signals. The rest of multiplex techniques offer a superior performance as we will see in next chapters. The efficiency is defined as the sum of the effective transmitted power <math>P_{useful}</math> plus any band limiting losses, divided by the total transmitted power <math>P_{total}</math>.

::<math>\eta = \frac{P_{useful}}{P_{total}}</math>

==References==
<references/>

[[Category:Fundamentals]]
[[Category:GNSS Signals]]