120 likes | 274 Views
Reliability Characteristics of Differential GPS Transmission. Cezary Specht Institute of Navigation and Maritime Hydrography Naval University in Gdynia CSpecht@amw.gdynia.pl. The importance of the navigation systems comparable criteria during the last years.
E N D
Reliability Characteristics of Differential GPS Transmission Cezary Specht Institute of Navigation and Maritime Hydrography Naval University in Gdynia CSpecht@amw.gdynia.pl
The importance of the navigation systems comparable criteria during the last years International Association of Lighthouse, European Radionavigation Plan, Federal Radionavigation Plan. year 1995 year 2000 year 1990 • Accuracy • Fix rate • Capacity • Ambiguity • Fix dimension • Coverage • Availability • Reliability • Continuity • Integrity ?
Availability of Differential GPS transmission The availability will be the state in which the age of at least 4 pseudorange corrections related to various satellites is lower than the maximum.
Availability of DGPS transmission the process of PRCs transmission for Ns ={7,8,9} The binary state vectors of the system : and the functions of their structures
Availability of DGPS transmission the process of PRCs transmission for Ns ={7,8,9} After decomposition: AVAILABILITY:
DGPS RS signal strength level Transmission availability calculation (1) Noise level SNR=f(BER)
SNR=f(BER) Transmission availability calculation (2) Transmission model Transmission availability zones
Reliability and Continuity of Differential GPS transmission failure rate - renewal rate - any moment in time time period Reliability function
some comparative analyses ... Type of the message, bit rate vs BER The increase in the number of satellites, for which the reference station transmits pseudorange corrections by message RTCM type 9-3, improves the availability
Conclusions • The aim of this presentation has been to develop a mathematical model of availability, reliability and continuity of differential GPS transmission based on probabilistic approach. • The problem was important because of the lack of methods, which would enable the parameter prognosis with regard to the process of navigation. In this light, the problem reliability characteristics constitutes one of the fundamental issues for multi-criteria assessment of modern systems at the stage of system testing and exploitation as well. • The theory the author worked out has been referred to the probabilistic characteristics of navigation systems functioning such as expected value, variance, or standard deviation. Specht C., (2003) Availability, Reliability and Continuity of Differential GPS Transmission, Annual of Navigation, no 5/2003, Polish Academy of Sciences, Gdynia, 2003, 85 pages.