A hybrid positioning system that combines Global Navigation Satellite System (GNSS) and Digital Video Broadcast-Terrestrial (DVB-T) is introduced in this dissertation. GNSS are satellites based positioning systems, which contain four global navigation systems(GPS,GLONASS,GALILEO and BEIDOU) and several regional systems. DVB-T is an European TV standard but it is world wide used. Although it is originally designed for TV service, but it can be used as Signal-of-Opportunity (SoO) to assistant or replace GNSS for positioning in some areas. GNSS can provide a very good performance in rural areas. However the performance in terms of accuracy and availability is degraded due to the obstacles in urban and indoor environments. Due to these obstacles, the number of visible satellites is greatly decreased and the received signals power may be highly attenuated. Also the multipath is a big problem for range based positioning techniques. Fortunately in these areas DVB-T signals can be received with high power comparing with the received GNSS signals. Since DVB-T is a terrestrial based system, the signals may experience different multipath environment with the satellite based signals. Because of these properties, the integrated hybrid GNSS and DVB-T positioning system is expected to provide enhanced positioning performance over the individual systems. The development of the hybrid system begins with the design of DVB-T positioning receiver. Considering the structure of GNSS receiver, the DVB-T receiver also achieves the position fix in two steps: first it estimates the TOA of signals and then computes the position with a Kalman filter. In order to estimate the TOA of signals, a classical acquisition and tracking block is implemented. Since DVB-T adopts Orthogonal Frequency-Division Multiplexing (OFDM) technique, the pilot subcarriers are used for autocorrelation. Since the DVB-T emitters in a Single Frequency Network (SFN) transmit the same frequency on the same band simultaneously, the signal association is a big issue during the positioning process. The association is achieved based on the information obtained from initialization phase. In the next step, we have considered low complexity. A one shot receiver is designed. The receiver stays in hibernation until position fix request arrived and it achieves TOA estimation through acquisition and some simple interpolation methods instead of tracking comparing with the one designed before. The linear interpolation and sinc interpolation are used after the acquisition stage. The performance is compared with the normal tracking receiver. Third, we investigate the path ambiguity solution. Since the receiver associates the signals on the basis of propagation delay, in case of some signals with similar or the same propagation delay several different paths will be estimated. Two different methods are introduced, one is pseudorange comparison and the other is Doppler aiding decision. Both methods take the benefit from an additional GNSS satellite. Lastly, we test the integrated hybrid GNSS and DVB-T system. In this test, we present a positioning method based on two GNSS satellites, which are not difficult to 'see' in an urban environment, cooperating with a DVB-T system. By calculating the TDOA between the two satellites, the receiver clock error can be eliminated and a hyperboloid surface can be generated. The user location will result on a line generated by intersecting the hyperboloid surface with the earth surface. A similar approach is used with DVB-T signals. By intersecting these two lines, the receiver position will be obtained.

Positioning Techniques with Signal of Opportunity: a Focus on Digital Television Systems / Huang, Jie. - (2014).

Positioning Techniques with Signal of Opportunity: a Focus on Digital Television Systems

HUANG, JIE
2014

Abstract

A hybrid positioning system that combines Global Navigation Satellite System (GNSS) and Digital Video Broadcast-Terrestrial (DVB-T) is introduced in this dissertation. GNSS are satellites based positioning systems, which contain four global navigation systems(GPS,GLONASS,GALILEO and BEIDOU) and several regional systems. DVB-T is an European TV standard but it is world wide used. Although it is originally designed for TV service, but it can be used as Signal-of-Opportunity (SoO) to assistant or replace GNSS for positioning in some areas. GNSS can provide a very good performance in rural areas. However the performance in terms of accuracy and availability is degraded due to the obstacles in urban and indoor environments. Due to these obstacles, the number of visible satellites is greatly decreased and the received signals power may be highly attenuated. Also the multipath is a big problem for range based positioning techniques. Fortunately in these areas DVB-T signals can be received with high power comparing with the received GNSS signals. Since DVB-T is a terrestrial based system, the signals may experience different multipath environment with the satellite based signals. Because of these properties, the integrated hybrid GNSS and DVB-T positioning system is expected to provide enhanced positioning performance over the individual systems. The development of the hybrid system begins with the design of DVB-T positioning receiver. Considering the structure of GNSS receiver, the DVB-T receiver also achieves the position fix in two steps: first it estimates the TOA of signals and then computes the position with a Kalman filter. In order to estimate the TOA of signals, a classical acquisition and tracking block is implemented. Since DVB-T adopts Orthogonal Frequency-Division Multiplexing (OFDM) technique, the pilot subcarriers are used for autocorrelation. Since the DVB-T emitters in a Single Frequency Network (SFN) transmit the same frequency on the same band simultaneously, the signal association is a big issue during the positioning process. The association is achieved based on the information obtained from initialization phase. In the next step, we have considered low complexity. A one shot receiver is designed. The receiver stays in hibernation until position fix request arrived and it achieves TOA estimation through acquisition and some simple interpolation methods instead of tracking comparing with the one designed before. The linear interpolation and sinc interpolation are used after the acquisition stage. The performance is compared with the normal tracking receiver. Third, we investigate the path ambiguity solution. Since the receiver associates the signals on the basis of propagation delay, in case of some signals with similar or the same propagation delay several different paths will be estimated. Two different methods are introduced, one is pseudorange comparison and the other is Doppler aiding decision. Both methods take the benefit from an additional GNSS satellite. Lastly, we test the integrated hybrid GNSS and DVB-T system. In this test, we present a positioning method based on two GNSS satellites, which are not difficult to 'see' in an urban environment, cooperating with a DVB-T system. By calculating the TDOA between the two satellites, the receiver clock error can be eliminated and a hyperboloid surface can be generated. The user location will result on a line generated by intersecting the hyperboloid surface with the earth surface. A similar approach is used with DVB-T signals. By intersecting these two lines, the receiver position will be obtained.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11583/2545742
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