Multicorrelator - Revision history

Filipe.Pelica: Included editor logo.

2014-09-18T16:37:01Z

Included editor logo.

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Carlos.Lopez at 11:01, 23 February 2012

2012-02-23T11:01:38Z

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	\|Category=Receivers		\|Category=Receivers
	\|Editors=GMV ~~A.D.~~		\|Editors=GMV
	\|Level=Advanced		\|Level=Advanced
	\|YearOfPublication=2011		\|YearOfPublication=2011

Carlos.Lopez at 10:35, 23 February 2012

2012-02-23T10:35:02Z

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	\|Category=Receivers		\|Category=Receivers
	\|~~Title={{PAGENAME}}~~		\|Editors=GMV A.D.
	~~\|Authors~~=GMV
	\|Level=Advanced		\|Level=Advanced
	\|YearOfPublication=2011		\|YearOfPublication=2011
	\|~~Logo~~=~~GMV~~		\|Title={{PAGENAME}}
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	It is commonly said that correlation is the key operation in GNSS receivers, in order to achieve synchronization with the incoming signals from each satellite. However, a single correlator is not enough to fulfill this purpose: in fact, even the simplest GNSS receiver supports multiple correlators to achieve synchronization and / or improve the accuracy of the generated observables.		It is commonly said that correlation is the key operation in GNSS receivers, in order to achieve synchronization with the incoming signals from each satellite. However, a single correlator is not enough to fulfill this purpose: in fact, even the simplest GNSS receiver supports multiple correlators to achieve synchronization and / or improve the accuracy of the generated observables.

Rui.Pereira: moved Work in Progress:Multicorrelator to Multicorrelator over redirect

2011-05-27T15:51:59Z

moved Work in Progress:Multicorrelator to Multicorrelator over redirect

← Older revision	Revision as of 15:51, 27 May 2011
(No difference)

Rui.Pereira: moved Multicorrelator to Work in Progress:Multicorrelator

2011-05-11T13:21:23Z

moved Multicorrelator to Work in Progress:Multicorrelator

← Older revision	Revision as of 13:21, 11 May 2011
(No difference)

Rui.Sarnadas at 12:20, 6 May 2011

2011-05-06T12:20:32Z

Show changes

Teresa.Ferreira: /* Further Applications */

2011-05-05T17:06:57Z

Further Applications

← Older revision		Revision as of 17:06, 5 May 2011
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	*Tracking of BOC modulations		*Tracking of BOC modulations
	The bump jumping algorithm <ref>P. Fine, W. Wilson, “Tracking Algorithm for GPS Offset Carrier Signals,” ION NTM 1999, San Diego, MA, pp. 671-676</ref> is designed to track BOC modulated signals. In fact, the autocorrelation function of the BOC signals presents more than one peak, as illustrated in Figure 3. Thus, the receiver needs to implement a mechanism that ensures it is tracking the correct autocorrelation peak and not a side peak.		The bump jumping algorithm <ref>P. Fine, W. Wilson, “Tracking Algorithm for GPS Offset Carrier Signals,” ION NTM 1999, San Diego, MA, pp. 671-676</ref> is designed to track BOC modulated signals. In fact, the autocorrelation function of the BOC signals presents more than one peak, as illustrated in Figure 3. Thus, the receiver needs to implement a mechanism that ensures it is tracking the correct autocorrelation peak and not a side peak.
	The bump jumping mechanism consists in adding two extra correlators to the receiver [[Tracking Loops\|tracking loops]] structure: the very early (VE) and the very late (VL) correlators.		The bump jumping mechanism consists in adding two extra correlators to the receiver [[Tracking Loops\|tracking loops]] structure: the very early (VE) and the very late (VL) correlators. Then their powers are used to assess whether the main peak is being tracked or if the receiver has locked into a side peakl.

	==Related articles==		==Related articles==

Teresa.Ferreira: /* Further Applications */

2011-05-05T17:05:58Z

Further Applications

← Older revision		Revision as of 17:05, 5 May 2011
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	==Further Applications==		==Further Applications==

	Although ~~the~~ basic receivers use three correlators to track the incoming signal, one can imagine that the number of correlators could be increased (at the cost of power and resources consumption~~, of course~~) in order to extract further information.		Although basic receivers use three correlators to track the incoming signal, one can imagine that the number of correlators could be increased (at the cost of power and resources consumption) in order to extract further information.
	These kind of techniques are actually used in advanced signal processing receivers to achieve higher performances.		These kind of techniques are actually used in advanced signal processing receivers to achieve higher performances.

	Two examples are:		Two examples are:
	*Multipath Mitigation		*Multipath Mitigation
	The Multipath Estimating Delay Lock Loop (MEDLL) was first proposed in 1992 by Van Nee<ref>R. Van Nee, “The Multipath Estimating Delay Lock Loop”, IEEE ISSSTA 92, 1992, Japan, pp 39-42</ref>. The MEDLL estimates the amplitude, delay and phase of each multipath component using maximum likelihood criteria. The contribution to the correlation function is in turn subtracted from the measured correlation function. When this process is complete, the estimate of the direct path correlation function is left~~. Finally, a standard E-L DLL is applied in order to estimate optimally~~ the code ~~loop tracking~~ error<ref>B. Townsend, P. Fenton, K. Van Dierondonck, R.Van Nee, “Performance Evaluation of the Multipath Estimating Lock Loop”, ION Navigation, VOL. 42, No. 3, fall 1995,pp 503-514</ref>.		The Multipath Estimating Delay Lock Loop (MEDLL) was first proposed in 1992 by Van Nee<ref>R. Van Nee, “The Multipath Estimating Delay Lock Loop”, IEEE ISSSTA 92, 1992, Japan, pp 39-42</ref>. The MEDLL estimates the amplitude, delay and phase of each multipath component using maximum likelihood criteria. The contribution to the correlation function is in turn subtracted from the measured correlation function. When this process is complete, the estimate of the direct path correlation function is left and the code error can be computed<ref>B. Townsend, P. Fenton, K. Van Dierondonck, R.Van Nee, “Performance Evaluation of the Multipath Estimating Lock Loop”, ION Navigation, VOL. 42, No. 3, fall 1995,pp 503-514</ref>.
	In practice, 10 or more correlators ~~are employed in order~~ to increase the resolution of the correlation function ~~obtained by sampling~~		In practice, the MEDLL uses 10 or more correlators to increase the resolution of the correlation function and extract further information on its shape.


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	*Tracking of BOC modulations		*Tracking of BOC modulations
	The bump jumping algorithm ~~proposed in~~ <ref>P. Fine, W. Wilson, “Tracking Algorithm for GPS Offset Carrier Signals,” ION NTM 1999, San Diego, MA, pp. 671-676</ref> is designed to track ~~the~~ BOC modulated signals. In fact, the autocorrelation function of the BOC signals presents more than one peak, as illustrated in Figure 3~~, leading to several zero crossings of the discriminator response~~. Thus, the receiver needs to implement a mechanism that ensures it is tracking the correct autocorrelation peak.		The bump jumping algorithm <ref>P. Fine, W. Wilson, “Tracking Algorithm for GPS Offset Carrier Signals,” ION NTM 1999, San Diego, MA, pp. 671-676</ref> is designed to track BOC modulated signals. In fact, the autocorrelation function of the BOC signals presents more than one peak, as illustrated in Figure 3. Thus, the receiver needs to implement a mechanism that ensures it is tracking the correct autocorrelation peak and not a side peak.
	The bump jumping mechanism consists in adding two extra correlators to the receiver tracking loops structure: the very early (VE) and the very late (VL) correlators.		The bump jumping mechanism consists in adding two extra correlators to the receiver [[Tracking Loops\|tracking loops]] structure: the very early (VE) and the very late (VL) correlators.




	==Related articles==		==Related articles==

Teresa.Ferreira: /* Mathematical Model */

2011-05-05T17:01:28Z

Mathematical Model

← Older revision		Revision as of 17:01, 5 May 2011
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	*<math>\tau_e</math> is the error of the code delay estimated at the receiver		*<math>\tau_e</math> is the error of the code delay estimated at the receiver
	*<math>\phi_e</math> is the error of the carrier phase estimated at the receiver		*<math>\phi_e</math> is the error of the carrier phase estimated at the receiver
	*E, P, L ~~indeces~~ stand for Early, Prompt and Late respectively		*E, P, L indexes stand for Early, Prompt and Late respectively
	*<math>\delta</math> is the Early-Late spacing		*<math>\delta</math> is the Early-Late spacing

Teresa.Ferreira: /* Block Diagram */

2011-05-05T17:00:12Z

Block Diagram

← Older revision		Revision as of 17:00, 5 May 2011
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	==Block Diagram==		==Block Diagram==

	Figure 2 ~~depicted~~ the block diagram for ~~the baseband processing of~~ a single channel, with focus on the correlators.		Figure 2 depicts the baseband processing block diagram for a single channel, with focus on the correlators.


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	This is an iterative process that the receiver supports continuously. The Integrate and Dump (I&D) blocks are used to integrate the correlation outputs over time, either coherently or non-coherently, as discussed [[Baseband Processing\|here]].		This is an iterative process that the receiver supports continuously. The Integrate and Dump (I&D) blocks are used to integrate the correlation outputs over time, either coherently or non-coherently, as discussed [[Baseband Processing\|here]].
	In parallel, [[Lock Detectors\|lock detectors]] use these correlators’ outputs to assess whether or not the incoming signal is actually being tracked. In noisy conditions ~~it might happen that~~ the tracking loops diverge from the real peak or that a false acquisition ~~has occurred.~~
	~~Finally, the sign of the prompt correlator output can be used to infer the sign of the navigation data bit (or symbol for FEC coded signals such as Galileo)~~.		In parallel, [[Lock Detectors\|lock detectors]] use these correlators’ outputs to assess whether or not the incoming signal is actually being tracked. This is justified by the fact that, in noisy conditions, the tracking loops may diverge from the real peak or that a false acquisition may occur.

	==Mathematical Model==		==Mathematical Model==