Receiver Operations - Revision history

Filipe.Pelica: Included editor logo.

2014-09-18T16:34:02Z

Included editor logo.

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	\|Level=Intermediate		\|Level=Intermediate
	\|YearOfPublication=2011		\|YearOfPublication=2011
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	\|Title={{PAGENAME}}		\|Title={{PAGENAME}}
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Carlos.Lopez at 11:01, 23 February 2012

2012-02-23T11:01:51Z

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	{{Article Infobox2		{{Article Infobox2
	\|Category=Receivers		\|Category=Receivers
	\|Editors=GMV ~~A.D.~~		\|Editors=GMV
	\|Level=Intermediate		\|Level=Intermediate
	\|YearOfPublication=2011		\|YearOfPublication=2011

Carlos.Lopez at 10:35, 23 February 2012

2012-02-23T10:35:24Z

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	{{Article Infobox2		{{Article Infobox2
	\|Category=Receivers		\|Category=Receivers
	\|~~Title={{PAGENAME}}~~		\|Editors=GMV A.D.
	~~\|Authors~~=GMV
	\|Level=Intermediate		\|Level=Intermediate
	\|YearOfPublication=2011		\|YearOfPublication=2011
	\|~~Logo~~=~~GMV~~		\|Title={{PAGENAME}}
	}}		}}

	In the first years of GNSS, when only GPS was available for public use, a receiver was not expected to perform as the navigation devices we see today. In fact, a first-generation GPS receiver could be designed to only process 4 or 5 signals at any given time, and it was deemed suitable for positioning applications. Today, with the increased availability and potential of different GNSS signals and constellations, any receiver is expected to support at least 10 or 12 channels up to hundreds, resulting in a solution with improved performance. However, at their core - and despite the many differences in target applications or implementation philosophy - most receivers still share common control and processing flow management properties, resulting in common operations<ref><i>Borre, K. et al, "A Software-Defined GPS and Galileo Receiver - A Single-Frequency Approach", Birkhäuser, chapter 5</i>.</ref> performed. The following sections describe these common operation modes in which a receiver functions.		In the first years of GNSS, when only GPS was available for public use, a receiver was not expected to perform as the navigation devices we see today. In fact, a first-generation GPS receiver could be designed to only process 4 or 5 signals at any given time, and it was deemed suitable for positioning applications. Today, with the increased availability and potential of different GNSS signals and constellations, any receiver is expected to support at least 10 or 12 channels up to hundreds, resulting in a solution with improved performance. However, at their core - and despite the many differences in target applications or implementation philosophy - most receivers still share common control and processing flow management properties, resulting in common operations<ref><i>Borre, K. et al, "A Software-Defined GPS and Galileo Receiver - A Single-Frequency Approach", Birkhäuser, chapter 5</i>.</ref> performed. The following sections describe these common operation modes in which a receiver functions.

Timo.Kouwenhoven: Text replace - "|Level=Medium" to "|Level=Intermediate"

2011-11-06T07:46:38Z

Text replace - "|Level=Medium" to "|Level=Intermediate"

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	\|Authors=GMV		\|Authors=GMV
	\|Level=~~Medium~~		\|Level=Intermediate
	\|YearOfPublication=2011		\|YearOfPublication=2011
	\|Logo=GMV		\|Logo=GMV

Rui.Pereira at 15:02, 31 May 2011

2011-05-31T15:02:59Z

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	==Overview==		==Overview==
	One thing most GNSS receivers have in common is how they operate in terms of processing chain, from reception of signals to solution outputs. Although their [[Receiver Types\|types]], [[System Design Details\|architectures]], and ~~[[Applications Processing\|~~applications]] may vary, the operations (illustrated in Figure 1) apply transversely.		One thing most GNSS receivers have in common is how they operate in terms of processing chain, from reception of signals to solution outputs. Although their [[Receiver Types\|types]], [[System Design Details\|architectures]], and applications may vary, the operations (illustrated in Figure 1) apply transversely.

	[[File:Receiver_operations.png\|center\|thumb\|650px\|'''''Figure 1:''''' GNSS receiver operations diagram.]]		[[File:Receiver_operations.png\|center\|thumb\|650px\|'''''Figure 1:''''' GNSS receiver operations diagram.]]
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	*[[Generic Receiver Description]]		*[[Generic Receiver Description]]
	*[[Receiver Types]]		*[[Receiver Types]]
	*[[Applications Processing]]

	==References==		==References==

Rui.Sarnadas: /* Overview */

2011-04-05T17:14:54Z

Overview

← Older revision		Revision as of 17:14, 5 April 2011
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	One thing most GNSS receivers have in common is how they operate in terms of processing chain, from reception of signals to solution outputs. Although their [[Receiver Types\|types]], [[System Design Details\|architectures]], and [[Applications Processing\|applications]] may vary, the operations (illustrated in Figure 1) apply transversely.		One thing most GNSS receivers have in common is how they operate in terms of processing chain, from reception of signals to solution outputs. Although their [[Receiver Types\|types]], [[System Design Details\|architectures]], and [[Applications Processing\|applications]] may vary, the operations (illustrated in Figure 1) apply transversely.

	[[File:Receiver_operations.png\|~~none~~\|thumb\|650px\|'''''Figure 1:''''' GNSS receiver operations diagram.]]		[[File:Receiver_operations.png\|center\|thumb\|650px\|'''''Figure 1:''''' GNSS receiver operations diagram.]]

	After start-up procedures (e.g. loading necessary data, initializations and resource allocations), the antenna and the front-end blocks start providing digitized data continuously to the signal processing channels, also referred to as [[Baseband Processing\|baseband processing]].		After start-up procedures (e.g. loading necessary data, initializations and resource allocations), the antenna and the front-end blocks start providing digitized data continuously to the signal processing channels, also referred to as [[Baseband Processing\|baseband processing]].

Rui.Sarnadas: /* Advanced Operations */

2011-04-01T09:18:25Z

Advanced Operations

← Older revision		Revision as of 09:18, 1 April 2011
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	Following these principles, acquisition is often sub-categorized in: cold, warm and hot start mode.		Following these principles, acquisition is often sub-categorized in: cold, warm and hot start mode.

	*<b>In cold start</b>, the receiver has no prior information about its own position or which satellites are in view. As a consequence, each channel has to perform extensive search of all possible signals/ satellites over all possible code delay/ Doppler frequency pairs. It is only when (at least) one full navigation message is decoded that the receiver can infer the remaining satellites in view (through almanac information), and may redirect the other channels to follow them.		*<b>In cold start</b>, the receiver has no prior information about its own position or which satellites are in view. As a consequence, each channel has to perform extensive search of all possible signals / satellites over all possible code delay / Doppler frequency pairs. It is only when (at least) one full navigation message is decoded that the receiver can infer the remaining satellites in view (through almanac information), and may redirect the other channels to follow them.

	*<b>In warm start</b>, the receiver has access to rough initial position (e.g. last position before powering down the receiver), and to almanacs relatively up to date (e.g. via external sources or stored at power down). With this information, the receiver is able to predict which satellites are most likely to be in view, and estimate their rough code delay and Doppler frequency, hence being able to narrow down the acquisition search space.		*<b>In warm start</b>, the receiver has access to rough initial position (e.g. last position before powering down the receiver), and to almanacs relatively up to date (e.g. via external sources or stored at power down). With this information, the receiver is able to predict which satellites are most likely to be in view, and estimate their rough code delay and Doppler frequency, hence being able to narrow down the acquisition search space.

Rui.Sarnadas: /* Advanced Operations */

2011-04-01T09:17:08Z

Advanced Operations

← Older revision		Revision as of 09:17, 1 April 2011
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	On top of the basic operations at channel and receiver level, the overall receiver can further benefit from information either collected from past operations or recently decoded. For example, the receiver can use the information conveyed in the navigation message of a given satellite – e.g. [[GNSS signal\|almanacs]] from other satellites – in order to estimate which satellites are visible and therefore assign channels to those satellites that have a higher probability to be in view.		On top of the basic operations at channel and receiver level, the overall receiver can further benefit from information either collected from past operations or recently decoded. For example, the receiver can use the information conveyed in the navigation message of a given satellite – e.g. [[GNSS signal\|almanacs]] from other satellites – in order to estimate which satellites are visible and therefore assign channels to those satellites that have a higher probability to be in view.
	Following these principles, acquisition is often sub-categorized in: cold, warm and hot start mode.		Following these principles, acquisition is often sub-categorized in: cold, warm and hot start mode.

	*<b>In cold start</b>, the receiver has no prior information about its own position or which satellites are in view. As a consequence, each channel has to perform extensive search of all possible signals/ satellites over all possible code delay/ Doppler frequency pairs. It is only when (at least) one full navigation message is decoded that the receiver can infer the remaining satellites in view (through almanac information), and may redirect the other channels to follow them.		*<b>In cold start</b>, the receiver has no prior information about its own position or which satellites are in view. As a consequence, each channel has to perform extensive search of all possible signals/ satellites over all possible code delay/ Doppler frequency pairs. It is only when (at least) one full navigation message is decoded that the receiver can infer the remaining satellites in view (through almanac information), and may redirect the other channels to follow them.

	*<b>In warm start</b>, the receiver has access to rough initial position (e.g. last position before powering down the receiver), and to almanacs relatively up to date (e.g. via external sources or stored at power down). With this information, the receiver is able to predict which satellites are most likely to be in view, and estimate their rough code delay and Doppler frequency, hence being able to narrow down the acquisition search space.		*<b>In warm start</b>, the receiver has access to rough initial position (e.g. last position before powering down the receiver), and to almanacs relatively up to date (e.g. via external sources or stored at power down). With this information, the receiver is able to predict which satellites are most likely to be in view, and estimate their rough code delay and Doppler frequency, hence being able to narrow down the acquisition search space.

	*<b>In hot start</b>, the receiver has access not only to its rough initial position, but also to the ephemerides of the satellites, hence greatly reducing the acquisition search space, improving the time to acquire and therefore the final Time To First Fix (TTFF).		*<b>In hot start</b>, the receiver has access not only to its rough initial position, but also to the ephemerides of the satellites, hence greatly reducing the acquisition search space, improving the time to acquire and therefore the final Time To First Fix (TTFF).

Rui.Sarnadas at 09:16, 1 April 2011

2011-04-01T09:16:43Z

← Older revision		Revision as of 09:16, 1 April 2011
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	}}		}}

	In the first years of GNSS, when only GPS was available for public use, a receiver was not expected to perform as the navigation devices we see today. In fact, a first-generation GPS receiver could be designed to only process 4 or 5 signals at any given time, and it was deemed suitable for positioning applications. Today, with the increased availability and potential of different GNSS signals and constellations, any receiver is expected to support at least 10 or 12 channels up to hundreds, resulting in a solution with improved performance. However, at their core - and despite the many differences in target applications or implementation philosophy - most receivers still share common control and processing flow management properties, resulting in common operations performed. The following sections describe these common operation modes in which a receiver functions.		In the first years of GNSS, when only GPS was available for public use, a receiver was not expected to perform as the navigation devices we see today. In fact, a first-generation GPS receiver could be designed to only process 4 or 5 signals at any given time, and it was deemed suitable for positioning applications. Today, with the increased availability and potential of different GNSS signals and constellations, any receiver is expected to support at least 10 or 12 channels up to hundreds, resulting in a solution with improved performance. However, at their core - and despite the many differences in target applications or implementation philosophy - most receivers still share common control and processing flow management properties, resulting in common operations<ref><i>Borre, K. et al, "A Software-Defined GPS and Galileo Receiver - A Single-Frequency Approach", Birkhäuser, chapter 5</i>.</ref> performed. The following sections describe these common operation modes in which a receiver functions.

	==Overview==		==Overview==

Rui.Sarnadas: /* Channel Level */

2011-04-01T08:59:11Z

Channel Level

← Older revision		Revision as of 08:59, 1 April 2011
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	A typical GNSS receiver controls independent channels that are assigned to a specific signal from a specific satellite. Each channel can be in two modes: acquisition or tracking. In acquisition mode, each channel conducts a rough [[Generic Receiver Description\|2D search]] (code delay and Doppler frequency) of the signal in order to assess whether the signal is present or not. The channel remains in acquisition mode until a signal is detected and a first estimate of the code delay and Doppler frequency is computed. At that point, the channel goes into tracking mode where the estimates of the code delay and the Doppler frequency are continuously refined and the navigation message is decoded.		A typical GNSS receiver controls independent channels that are assigned to a specific signal from a specific satellite. Each channel can be in two modes: acquisition or tracking. In acquisition mode, each channel conducts a rough [[Generic Receiver Description\|2D search]] (code delay and Doppler frequency) of the signal in order to assess whether the signal is present or not. The channel remains in acquisition mode until a signal is detected and a first estimate of the code delay and Doppler frequency is computed. At that point, the channel goes into tracking mode where the estimates of the code delay and the Doppler frequency are continuously refined and the navigation message is decoded.

	In tracking mode, the channel monitors the quality of the tracking results in order to assess if the signal is present and is being correctly tracked. If the [[Lock Detectors\|lock ~~detectors~~]] indicators fall below a threshold, the signal is considered lost and the channel goes back to acquisition mode and re-starts the whole process. The signal can be lost due to several factors such as shadowing of the satellite, cycle slips on the signal, or simply due to noisy initial estimates provided by the acquisition mode.		In tracking mode, the channel monitors the quality of the tracking results in order to assess if the signal is present and is being correctly tracked. If the [[Lock Detectors\|lock detection]] indicators fall below a threshold, the signal is considered lost and the channel goes back to acquisition mode and re-starts the whole process. The signal can be lost due to several factors such as shadowing of the satellite, cycle slips on the signal, or simply due to noisy initial estimates provided by the acquisition mode.

	==Receiver Level==		==Receiver Level==

← Older revision		Revision as of 17:14, 5 April 2011
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	One thing most GNSS receivers have in common is how they operate in terms of processing chain, from reception of signals to solution outputs. Although their [[Receiver Types\|types]], [[System Design Details\|architectures]], and [[Applications Processing\|applications]] may vary, the operations (illustrated in Figure 1) apply transversely.		One thing most GNSS receivers have in common is how they operate in terms of processing chain, from reception of signals to solution outputs. Although their [[Receiver Types\|types]], [[System Design Details\|architectures]], and [[Applications Processing\|applications]] may vary, the operations (illustrated in Figure 1) apply transversely.

	[[File:Receiver_operations.png\|~~none~~\|thumb\|650px\|'''''Figure 1:''''' GNSS receiver operations diagram.]]		[[File:Receiver_operations.png\|center\|thumb\|650px\|'''''Figure 1:''''' GNSS receiver operations diagram.]]

	After start-up procedures (e.g. loading necessary data, initializations and resource allocations), the antenna and the front-end blocks start providing digitized data continuously to the signal processing channels, also referred to as [[Baseband Processing\|baseband processing]].		After start-up procedures (e.g. loading necessary data, initializations and resource allocations), the antenna and the front-end blocks start providing digitized data continuously to the signal processing channels, also referred to as [[Baseband Processing\|baseband processing]].