A-GPS im UMTS Handy!

Hallo zusammen,

ich bekomme in Kürze das UMTS Handy Motorola E 1000. Ich habe im Internet gelesen, dass in diesem Handy ein A-GPS Modul eingebaut ist! Bis jetzt weis ich nur das es ein Mix aus Satelitten Navigation und Navigation über das Funknetz (Cell ID und Timing Advanced) sein soll.
Weis von euch jemand etwas genaueres und ob es schon praktische Anwendungen hierfür gibt?

Liebe Grüsse, Georg

Genau die selbe Frage stelle ich mir auch gerade. Weiß da jemand was genaueres drüber?

Gerade gefunden:

Zur Erklärung: A-GPS funktioniert im Zusammenspiel von eingebautem GPS-Empfänger im Handy und einer GPRS - oder UMTS - Datenverbindung zu einem A-GPS-Server beim Netzbetreiber. Dadurch kann die Position auch bei schlechten Bedingungen noch exakt bestimmt werden. A-GPS wird bisher nur von Motorola-Handys unterstützt Es gibt bisher, keine kommerzielle Navigations-Lösung, die A-GPS verwendet. Der Netzbetreiber müsste eben auch A-GPS unterstützen. Tut er aber noch nicht

Zitat

Original von Mike_DUS
Hallo,

leider ist im E1000 die Funktion durch die von Vodafone gebrandete SW geblockt (habe leider noch keine andere SW gefunden und Motorola gibt keine raus).

Aber nun zurück zum Thema AGPS dazu habe ich folgendes gefunden:

AGPS steht für "Assisted Global Positioning System" und findet mittlerweile auch Einzug in mobile Endgeräte wie Handys, PDAs oder Pkw-Navigationssysteme. Die Hardware fällt hierbei wesentlich kleiner aus, da sämtliches Kartenmaterial nicht im RAM des Geräts gespeichert, sondern vom Mobilfunkbetreiber zu Verfügung gestellt wird. Die Software des Handsets verbindet GPS-Information mit Kartenmaterial aus dem Web und kann die Postition des Nutzers metergenau anzeigen.

Der wahre Vorteil des Assisted GPS liegt jedoch nicht nur in der Größe, sondern in der Geschwindigkeit der Satellitenortung. Die Suchzeit, die die 24 Satelliten für die Lokalisierung des Nutzers bei der normalen GPS-Ortung benötigen, fällt beim AGPS-Modell weg. Da das Mobilfunknetzwerk in Funkzellen gegliedert ist, und jede Basisstation eine gewisse Anzahl von Zellen versorgt, ist bereits die ungefähre Position des Nutzers bekannt. Startet man jetzt eine AGPS-Lokalisierung, übermittelt die Basisstation dem GPS System den ungefähren Aufenthaltsort des Empfängers, was es für die Satelliten deutlich leichter macht, die genaue Position zu ermitteln. Ein weiterer Vorteil gegenüber herkömmlichen GPS-Lösungen ist auch die Schonung der Akkuleistung, da weniger Daten mit den Satelliten ausgetauscht werden müssen.

Weiterhin benötigt AGPS immer Sichtkontakt zu den Satelliten, leichte Störungen, wie schlechte Wetterverhältnisse, können das Ergebnis erheblich beeinträchtigen. Gerade die Ortung im Auto, bei der man das Gerät schräg zur Windschutzscheibe stellt, ist nur sehr eingeschränkt möglich und daher noch nicht für sinnvolle Anwendungen wie Navigationssysteme brauchbar, da eine permanente GPS-Ortung höchstens über Drittsoftware ermöglicht wird. Eine Ortung in Gebäuden ist generell nicht möglich.

mfg

Mike

Alles anzeigen

Hallo zusammen,

Details über A-GPS und UMTS finden sich hier: http://www.3gpp.org/ftp/Specs/2004-12/R1999/25_series/25305-3b0.zip

Kleiner Auszug:

10 Network-assisted GPS positioning method
When GPS is designed to inter-work with the UTRAN, the network assists the UE GPS receiver to improve the performance in several respects. These performance improvements will:
- reduce the UE GPS start-up and acquisition times; the search window can be limited and the measurements sped up significantly;
- increase the UE GPS sensitivity; positioning assistance messages are obtained via UTRAN so the UE GPS can operate also in low SNR situations when it is unable to demodulate UE GPS signals;
- allow the UE to consume less handset power than with stand-alone GPS; this is due to rapid start-up times as the GPS can be in idle mode when it is not needed.
The Network-assisted GPS methods rely on signalling between UE GPS receivers (possibly with reduced complexity) and a continuously operating GPS reference receiver network, which has clear sky visibility of the same GPS constellation as the assisted UEs. GPS reference receivers may be connected to the UTRAN to enable derivation of UE assistance signals.
10.1 Timing calibration
Timing calibration is achieved by using UE or UTRAN GPS timing measurements as specified in [15].
10.2 Timing assistance
The UTRAN may derive the estimated UE position using UTRAN parameters (e.g. Cell-ID or IPDL) and may use this information, in conjunction with satellite specific ephemeris data received from the GPS reference receiver network, to derive the estimated times of arrival (code phases) for equivalent GPS satellite signals received by the UE-based GPS receiver functionality. For the UE-assisted method, the estimated code phase data may be conveyed, together with TUTRAN-GPS (as specified in [15] and [16]), from the UTRAN to the UE using higher layer signalling. The estimated code phase data value is uncertain to a degree depending on the accuracy of the UTRAN timing calibration and initial position determination methods used.
Alternatively, for the UE-based method, the UE itself may derive its location aided by assistance messages. The ephemeris data are transmitted from UTRAN to the UE using higher layer signalling. The UE may use this information, in conjunction with the UE's reference location, to derive the times of arrival (code phases) for GPS satellite signals received by the UE-based GPS receiver functionality.
10.3 GPS assistance data
The UE may receive GPS information through the UTRAN radio interface, using higher layer signalling. Once a UE Positioning measurement is setup by the SRNC the UE is responsible to maintain valid and up to date GPS assistance data in order to report the requested measurement results. In case that the UE has not sufficient assistance data or the data is out of date then the UE should indicate it to the SRNC and additionally request for assistance data.
When the UE is unable to detect a sufficient number of satellites, the assisted GPS method can be combined with other positioning methods. Altitude assistance can compensate for one satellite measurement.
The assistance data signalled to the UE may include all information listed below or a selected subset:
- data assisting the measurements; e.g. reference time, visible satellite list, satellite signal Doppler, code phase, Doppler and code phase search windows. This data can be valid for a few minutes (e.g., less than 5 minutes) or longer depending on the code phase and Doppler search window size that can be accommodated by the UE;
- data providing means for position calculation; e.g. reference time, reference position, satellite ephemeris, clock corrections. Satellite ephemeris and clock corrections data can be used for up to six hours.
NOTE: Certain types of GPS Assistance data may be derived, wholly or partially, from other types of GPS Assistance data.
If DGPS is utilised, then differential corrections may also be transmitted. If Selective Availability is turned off, these corrections can be valid for a few minutes or more. The DGPS data is valid for a large geographical area, so one centrally located reference receiver can be used to service this large region.
10.4 UE search
Provided that timing assistance, data assistance, and/or frequency reference is available in the UE, they should be applied in the GPS signal search procedure. The UE search procedure involves a three-dimensional search for a satellite pseudorandom code, time of arrival of a signal and the associated carrier Doppler.
"Modulation wipe-off" is defined here to mean a removal of the GPS navigation data bit modulation to GPS signals received at the UE, through the application of UTRAN timing and data assistance provided from the UTRAN to the UE. This process allows the UE to coherently integrate received GPS signals beyond 1 data bit period (i.e., 20 milliseconds).
10.5 Position determination
There are two types of network-assisted GPS methods, namely UE-based and UE-assisted, which differ according to where the actual position calculation is carried out.
Computation of the position fix can either be performed in UTRAN (i.e. SRNC) for UE-assisted or in the UE for UE based.
The UE-based method maintains a full GPS receiver functionality in the UE, and the position calculation is carried out by the UE, thus allowing stand-alone position fixes.
In the UE-assisted method, the UE employs a reduced complexity GPS receiver functionality. This carries out the pseudorange (code phase) measurements. These are signalled, using higher layer signalling, to the specific network element that estimates the position of the UE and carries out the remaining GPS operations. In this method, accurately timed code phase signalling (as specified in [15] and [16]) is required on the downlink. If DGPS is performed in the UE, then differential corrections must be signalled to it. On the other hand, DGPS corrections can be applied to the final result in the network to improve the position accuracy without extra signalling to the UE.
10.5.1 Information to be transferred between UTRAN elements
Table 10.1 lists information for both UE-assisted and UE-based modes that may be sent from SRNC to UE. This information can be signalled to the UE either in a broadcast channel or as dedicated signalling.
Table 10.1: Information that may be transferred from UTRAN to UE('Yes' = information applicable 'No' = information not applicable
Information UE-assisted UE-based
Number of satellites for which assistance is provided Yes Yes
reference time for GPS (TUTRAN-GPS) (specified in [15] and [16]) Yes Yes
3-d reference position (specified in [11]) No Yes
ionospheric corrections No Yes
satellite ID for identifying the satellites for which assistance data is provided Yes Yes
Ephemeris & clock corrections Yes Yes
UTC offset No Yes
DGPS corrections No Yes
almanac data Yes Yes
real-time integrity (e.g. a list of unusable satellites) No Yes
doppler (0th order term) Yes No
Doppler Search Window width Yes No
doppler (1st order term) Yes No
azimuth Yes No
elevation Yes No
code phase Yes No
code phase centre and search window width Yes No

The information that may be signalled from UE to SRNC is listed in table 10.2.
Table 10.2: Information that may be transferred from UE to SRNC
Information UE-assisted UE-based
reference time for GPS (TUE-GPS) (specified in [15] and [16]) Yes Yes
serving cell information No Yes
Latitude/Longitude/Altitude/Error ellipse No Yes
velocity estimate in the UE No Yes
satellite ID for which measurement data is valid Yes No
Whole/Fractional chips for information about the code-phase measurement Yes No
C/N0 of the received signal from the particular satellite used in the measurements Yes No
doppler frequency measured by the UE for the particular satellite Yes No
pseudorange RMS error Yes No
multipath indicator Yes No
number of Pseudoranges Yes No

Table 10.3 shows the information that may be transferred from Node B to its CRNC. If the CRNC is not the SRNC the information is also forwarded from CRNC to SRNC.
Table 10.3: Information that may be transferred from Node B/LMU to CRNC and between RNCs
Information UE-assisted UE-based
reference time for GPS (TUTRAN-GPS) (specified in [15] and [16]) Yes Yes

10.5.1.1 Almanac data
The almanac parameters specify the coarse, long-term model of the satellite positions and clocks. These parameters are a subset of the ephemeris and clock correction parameters in the Navigation Model, although with reduced resolution and accuracy. The almanac model is useful for receiver tasks that require coarse accuracy, such as determining satellite visibility. The model is valid for up to one year, typically. Since it is a long-term model, the field should be provided for all satellites in the GPS constellation.
Optionally, "SV Global Health" information may accompany this almanac information. This additional information is composed of the sequence of all non-parity data bits contained in words 3-10 of page 25 of subframe 4 of the GPS navigation message followed by the sequence of all non-parity bits contained in words 3-10 of page 25 of subframe 5 of the GPS navigation message. The following GPS navigation message fields are excluded when constructing these sequences: "Data ID", "SV (Page) ID", and "t".
10.5.1.2 DGPS corrections
In order to allow a UE to estimate its position more accurate, biases in the pseudorange measurements may be provided to the UE.
Status/Health
This information indicates the status of the differential corrections contained in the message.
IODE
This is the sequence number for the ephemeris for the particular satellite. The UE can use this information to determine if new ephemeris is used for calculating the corrections that are provided in the broadcast message. This eight-bit IE is incremented for each new set of ephemeris for the satellite and may occupy the numerical range of [0, 239] during normal operations. More information about this field can be found from [24].
User Differential Range Error (UDRE)
The UDRE provides an estimate of the uncertainty (1-*) in the corrections for the particular satellite. The value in this field shall be multiplied by the UDRE Scale Factor in the common Corrections Status/Health field to determine the final UDRE estimate for the particular satellite. More information about this field can be found from [24].
Pseudo-Range Correction (PRC)
The PRC indicates the correction to the pseudorange for the particular satellite at the GPS Reference Time, t0. The PRC definition here is different from the one given in [24].
Pseudo-Range Rate Correction (RRC)
This information indicates the rate-of-change of the pseudorange correction for the particular satellite, using the satellite ephemeris identified by the IODE IE. The RRC definition here is different from the one given in [24].
10.5.1.3 Ionospheric corrections
The Ionospheric Model contains information needed to model the propagation delays of the GPS signals through the ionosphere. Proper use of these information allows a single-frequency GPS receiver to remove approximately 50% of the ionospheric delay from the range measurements. The Ionospheric Model is valid for the entire constellation and changes slowly relative to the Navigation Model.
10.5.1.4 Ephemeris data and clock correction
Ephemeris data and clock corrections provide an accurate model of the satellite positions to the UE.
10.5.1.5 Real Time integrity monitor function
An Integrity Monitor (IM) function in the network should detect unhealthy (i.e., failed/failing) satellites. Excessively large pseudo range errors, as evidenced by the magnitude of the corresponding DGPS correction determined by the IM, may be used to detect unhealthy satellites. Unhealthy satellites should be detected very close to the occurrence of the satellite failure (e.g. 10 seconds) and marked in an unhealthy satellite list as unusable/bad. When unhealthy satellites are detected, the assistance and/or DGPS correction data should not be supplied for these satellites. Upon receiving the list of unhealthy satellites from the SRNC, the UE shall consider the data associated with these satellites to be invalid.
The IM function should also inform the UE of measurement quality in DGPS modes when satellites are healthy. This can be done by computing the position of the DGPS reference receiver using its derived pseudo ranges and differential corrections at the IM, and differencing the IM computed position with the known location of the DGPS reference receiver to compute a position error. When the error in the IM computed position is excessive for solutions based upon healthy satellites only, DGPS users should be informed of measurement quality through the supplied User Differential Range Error (UDRE) adjusted values based on the operation of the IM. The UE should use the measurement quality as a factor in weighing data obtained from associated satellites in its position calculation.
NOTE: UDRE is one of the IEs contained in the DGPS information ([19]).
The real-time Integrity Monitor function provides the following information to a UE:
- BadSATid;
- UDRE value adjusted based on the measurement quality.
BadSATid is a lit of unhealthy (i.e., failed/failing) satellites. The UE shall consider any assistance or DGPS data of these satellites as invalid.
Adjusted UDRE value reports the measurement quality of the corresponding satellites. The UE should consider the quality while calculating its position.
10.5.1.6 GPS reference time
GPS reference time may be used to provide a mapping between UTRAN and GPS time.
GPS TOW Assist
This information contains several fields in the Telemetry (TLM) Word and Handover Word (HOW) that are currently being broadcast by the respective GPS satellites. Combining this information with GPS TOW helps the UE with time-recovery needed to predict satellite signal.
TLM Message
This information contains a 14-bit value representing the Telemetry Message (TLM) being broadcast by the GPS satellite identified by the particular SatID, with the MSB occurring first in the satellite transmission.
Anti-Spoof/Alert
These information contain the Anti-Spoof and Alert flags that are being broadcast by the GPS satellite identified by SatID.
TLM Reserved
These information contain the two reserved bits in the TLM Word being broadcast by the GPS satellite identified by SatID, with the MSB occurring first in the satellite transmission.
10.5.1.7 UTC
UTC parameters may be used to provide Coordinated Universal Time to the UE.
10.5.1.8 Reference Location
The Reference Location contains a 3-D location (with uncertainty) specified as per [11]. The purpose of this field is to provide the UE with a priori knowledge of its position in order to improve GPS receiver performance.
10.5.1.9 Additional non-GPS related information
Additional non-GPS measurements performed by UTRAN or UE may be used by the SRNC to improve the performance of the UE-assisted GPS method. This information may be RTT in FDD or Rx Timing Deviation in TDD, UE receiving transmitting time (UE Rx-Tx), SFN-SFN observed time difference or CPICH Ec/No. All the additional measurements are defined in [15] and [16] and can be made available through RRC signalling for UE measurements or NBAP signalling for UTRAN measurements.
Furthermore, to those UE technologies requiring externally provided sensitivity and time aiding data, some navigation bits may be sent from UTRAN to UE for sensitivity assistance and time recovery.
10.6 Network Assisted GPS positioning Procedure
The diagram in Figure 10.1 illustrates the operations for the network assisted GPS when the request for position information is initiated by a LCS application signalled from the Core Network. A detailed description of the positioning procedure is given as follows. Note that the procedure is for illustration purpose and actual implementations may vary.


Figure 10.1: Network-assisted GPS methods
1. The operation begins with an authenticated request for positioning information about a UE from an application in the core network being received at the SRNC. The SRNC acts as interface between the Core Network and the UE Positioning entities in the UTRAN. The SRNC considers the request and the capabilities of the UE and the network.
2. Depending on the UE capabilities, the SRNC sends to the UE certain GPS assistance information. This information may include: the reference time for GPS, the satellite IDs, the Doppler frequency, the search window and its centre, the ephemeris and clock corrections, the almanac, and other information specified in 10.5.1. If the UE has not enough assistance data to perform the measurements, the UE should indicate it to the SRNC and additionally request for assistance data.
For UE-based method, jump to step 8.
For UE-assisted method, the SRNC may optionally request the following information before sending the assistance message(s) to the UE: the LMU update (see NOTE), the RTT measurements (from the Node Bs in the active set) to compensate for the one-way propagation delays. The LMU (associated or stand-alone) returns the information containing the time difference between the Node B and the GPS (e.g. UTRAN GPS timing of cell frames or SFN-SFN Observed Time Difference) to the CRNC. The Node B returns its RTT measurement to the CRNC. If the CRNC is not the SRNC, the CRNC forwards these information to SRNC.
4. The SRNC requests from the UE the measurement of GPS satellite pseudoranges and other information specified in 10.5.1. These measurements may be made while the UE is in RRC connected mode CELL_DCH state. The SRNC may request SFN-SFN Observed Time Difference measurements and Rx-Tx timing difference information from the UE to support the processing related to the RTT measurements.
5. The UE returns to the SRNC the measurement of GPS satellite pseudoranges and other information specified in 10.5.1. If requested, the UE may also return the SFN-SFN measurements and the Rx-Tx time difference information, together with a time stamp of when these values were obtained.
6 The UE position is calculated in the SRNC.
7. If there is insufficient information to yield a UE positioning estimate, the SRNC may start a new process from step 3.
8. In case of UE based method, UE returns the position estimate to the SRNC. This estimate includes the position, the estimated accuracy of the results and the time of the estimate.
9. The SRNC passes the position estimate to the CN.
NOTE: The LMU update (of the time difference between the GPS and the Node B) may be performed on a per-request basis (with respect to each UE Positioning request) or be performed timely that is independent of individual UE Positioning request. The latter is preferable when there is a large volume of UE Positioning requests.

Zitat

Original von Mike_DUS
Weiterhin benötigt AGPS immer Sichtkontakt zu den Satelliten, leichte Störungen, wie schlechte Wetterverhältnisse, können das Ergebnis erheblich beeinträchtigen. Gerade die Ortung im Auto, bei der man das Gerät schräg zur Windschutzscheibe stellt, ist nur sehr eingeschränkt möglich und daher noch nicht für sinnvolle Anwendungen wie Navigationssysteme brauchbar, da eine permanente GPS-Ortung höchstens über Drittsoftware ermöglicht wird. Eine Ortung in Gebäuden ist generell nicht möglich.

Dieses stimmt nicht ganz.
AGPS ist völlig richtig das sogenannte Assisted GPS, wobei das Assisted z.Zt. immer noch Auslegungssache ist.

Beim AGPS gibt es einen extrem empfindlichen GPS-Empfänger (ca. -160 dB), der eben gerade keinen Sichtkontakt benötigt. Es werden ca. 1000 mal mehr Korrelationen berechnet als bei den z.Zt noch üblichen (Sirf III ausgenommen, liegt knapp dahinter). Es kommt eben gerade auf die Ortung innerhalb von Bürokomplexen an, wo die Signale eben nur noch als Reflexionsreste vorhanden sind. Im zubetonierten Keller ist allerdings auch AGPS machtlos.
Das A, die Assistenz, wird vom Mobilfunkbetreiber zur Verfügung gestellt. Entweder leitet dieser die Signale aus bestehenden Netzwerken der Chiühersteller weiter oder er ermittelt eigene. Entscheidend ist, dass AGPS innerhalb 1 Sekunde zur Verfügung stehen soll (Notrufverordunung in den USA ab 2007), dazu werden dem GPS-Empfänger sowohl die sichtbaren Satelliten sowie ihre Bahnen und aktuellen Positinen mitgeteilt Vereinfacht kann man das so betrachten, als ob Kalt- und Warmstartphase entfallen würden.

Einer der Hauptentwickler von AGPS -> http://www.globallocate.com/
Ein bekannter deutscher Chipproduzent, der in Lizenz entsprechende Handychips fertigt ->
http://www.infineon.com/cgi/ecrm.dll/ecrm/scripts/prod_ov.jsp?oid=56435&cat_oid=-8480

Zur Navigation: Es ist beides möglich, sowohl herkömmlich, wobei die die Karte komplett auf einer Speicherkarte untergebracht ist und das "Smartphone" nebenbei ein als vollwertiger PDA zu gebrauchen ist, als auch mit "embedded Code", wobei die Routingabfrage an den Provider geschickt, dort berechnet und das Ergebnis zur Anzeige aufs Handy geschickt wird. Im letzteren wird es dann eine kostenpflichtige Dienstleistung werden.

Aber der primäre Gedanke hinter AGPS ist die Notfallortung: der Herzschrittmacher meldet Probleme und es wird beim auomatischen Notruf unmittelbar der exxakte Aufenthaltsort mitgeteilt, mit 2m Genauigkeit!

Zitat

Original von bianchifan

Beim AGPS gibt es einen extrem empfindlichen GPS-Empfänger (ca. -160 dB), der eben gerade keinen Sichtkontakt benötigt. Es werden ca. 1000 mal mehr Korrelationen berechnet als bei den z.Zt noch üblichen (Sirf III ausgenommen, liegt knapp dahinter). Es kommt eben gerade auf die Ortung innerhalb von Bürokomplexen an, wo die Signale eben nur noch als Reflexionsreste vorhanden sind. Im zubetonierten Keller ist allerdings auch AGPS machtlos.

Böse Zungen behaupten, dass diese hochempfindlichen GPS - Empfänger in alle mobilen Kommunikationsgeräte eingebaut werden müssen, die in den USA eine Zulassung haben wollen (homeland security act).

Hintergrund soll wohl sein, jederzeit das mobile Gerät ohne Mitwirken und Wissen des Nutzers orten zu können (und zwar wesentlich genauer als nur die Funkzelle und auch in geschlossenen Räumen)...

Diese Empfänger stehen nicht zwingend in Zusammenhang mit A(ssisted) GPS, sondern können natürlich genauso gut in normale GPS - Geräte eingebaut werden (es sei denn, diese Geräte verwenden zwecks genauer Ortung das militärische Signal, welches der Öffentlichkeit nicht zugänglich gemacht werden wird)...