Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position ac...Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position accuracy is affected by several factors such as satellite clock error, propagation path delays and receiver noise due to which the GPS does not meet the requirements of critical navigation applications such as missile navigation and category I/II/III aircraft landings. This paper emphasizes on modelling the satellite clock error and orbital solution (satellite position) error considering the signal emission time. The transmission time sent by each satellite in broadcast ephemerides is not accurate. This has to be corrected in order to obtain correct satellite position and in turn a precise receiver position. Signal transmission time or broadcast time from satellite antenna phase center is computed at the receiver using several parameters such as signal reception time, propagation time, pseudorange observed and satellite clock error correction parameters. This corrected time of transmission and broadcast orbital parameters are used for estimation of the orbital solution. The estimated orbital solution was validated with the precise ephemerides which are estimated by Jet Propulsion Laboratory (JPL), USA. The errors are estimated for a typical day data collected on 11th March 2011 from dual frequency GPS receiver located at Department of Electronics and Communication Engineering, Andhra University College of Engineering, Visakhapatnam (17.73°N/83.319°E).展开更多
Based on the deep analysis of the wide area differential principle on the separation of satellite ephemeris errors and clock errors, the similarities and differences between the absolute separation of satellite epheme...Based on the deep analysis of the wide area differential principle on the separation of satellite ephemeris errors and clock errors, the similarities and differences between the absolute separation of satellite ephemeris errors under time synchronization among the differential stations and relative separation of them under no time synchronization among them are analyzed. A one-station correction method of satellite clock errors including the 1st and the 2nd step correction is given under no time synchronization among these secondary stations, and the backward inference algorithm of the second correction of satellite clock errors is proposed. Through simulation analysis, satellite time service accuracy with code phase measurement can reach 5―7 ns, and that with carrier phase smoothing pseudo-range can reach 1―3 ns.展开更多
The performance degradation of an orthogonal frequency division multiplexing (OFDM) systems due to clock synchronization error is analyzed and a pilot-aided maximum likelihood (ML) estimating method is proposed to cor...The performance degradation of an orthogonal frequency division multiplexing (OFDM) systems due to clock synchronization error is analyzed and a pilot-aided maximum likelihood (ML) estimating method is proposed to correct it. The proposed algorithm enables clock synchronization error estimation from a pilot whose duration is only two symbol periods. The study shows that this method is simple and exact. The clock synchronization error can be corrected almost entirely.展开更多
为了提升星地一体化通信用户接收终端钟差的同步校正准确度,提出基于正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术的星地一体化通信用户接收终端钟差同步校正方法。解析星地一体化通信过程中相对论效应产生的通...为了提升星地一体化通信用户接收终端钟差的同步校正准确度,提出基于正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术的星地一体化通信用户接收终端钟差同步校正方法。解析星地一体化通信过程中相对论效应产生的通信钟差干扰;根据校正的需求,求解接收信道的最优方向角,优化用户接收终端的接收信道;在此基础上,结合OFDM信号特点,根据通信信号的发射周期,将信号划分为不同的时间窗;建立同步校正的度量函数,估计OFDM信号的符号起始位置,通过预估误差补偿实现了对钟差的同步校正。经过实验测试可知,应用该方法进行OFDM信号校正处理后,通信信号波形更加规律;应用该方法进行钟差校正后钟差值较小,提升了星地一体化通信用户接收终端钟差同步校正的准确度。展开更多
文摘Global Positioning System (GPS) is a satellite-based navigation system that provides a three-dimensional user position (x,y,z), velocity and time anywhere on or above the earth surface. The satellite-based position accuracy is affected by several factors such as satellite clock error, propagation path delays and receiver noise due to which the GPS does not meet the requirements of critical navigation applications such as missile navigation and category I/II/III aircraft landings. This paper emphasizes on modelling the satellite clock error and orbital solution (satellite position) error considering the signal emission time. The transmission time sent by each satellite in broadcast ephemerides is not accurate. This has to be corrected in order to obtain correct satellite position and in turn a precise receiver position. Signal transmission time or broadcast time from satellite antenna phase center is computed at the receiver using several parameters such as signal reception time, propagation time, pseudorange observed and satellite clock error correction parameters. This corrected time of transmission and broadcast orbital parameters are used for estimation of the orbital solution. The estimated orbital solution was validated with the precise ephemerides which are estimated by Jet Propulsion Laboratory (JPL), USA. The errors are estimated for a typical day data collected on 11th March 2011 from dual frequency GPS receiver located at Department of Electronics and Communication Engineering, Andhra University College of Engineering, Visakhapatnam (17.73°N/83.319°E).
基金Supported by the National Natural Science Foundation of China (Grant No.10778715)National Basic Research Program of China (Grant No. 2007CB815502)Scientific Research Fund of Hunan Provincial Education Department (Grant No. 08B039)
文摘Based on the deep analysis of the wide area differential principle on the separation of satellite ephemeris errors and clock errors, the similarities and differences between the absolute separation of satellite ephemeris errors under time synchronization among the differential stations and relative separation of them under no time synchronization among them are analyzed. A one-station correction method of satellite clock errors including the 1st and the 2nd step correction is given under no time synchronization among these secondary stations, and the backward inference algorithm of the second correction of satellite clock errors is proposed. Through simulation analysis, satellite time service accuracy with code phase measurement can reach 5―7 ns, and that with carrier phase smoothing pseudo-range can reach 1―3 ns.
文摘The performance degradation of an orthogonal frequency division multiplexing (OFDM) systems due to clock synchronization error is analyzed and a pilot-aided maximum likelihood (ML) estimating method is proposed to correct it. The proposed algorithm enables clock synchronization error estimation from a pilot whose duration is only two symbol periods. The study shows that this method is simple and exact. The clock synchronization error can be corrected almost entirely.
文摘为了提升星地一体化通信用户接收终端钟差的同步校正准确度,提出基于正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术的星地一体化通信用户接收终端钟差同步校正方法。解析星地一体化通信过程中相对论效应产生的通信钟差干扰;根据校正的需求,求解接收信道的最优方向角,优化用户接收终端的接收信道;在此基础上,结合OFDM信号特点,根据通信信号的发射周期,将信号划分为不同的时间窗;建立同步校正的度量函数,估计OFDM信号的符号起始位置,通过预估误差补偿实现了对钟差的同步校正。经过实验测试可知,应用该方法进行OFDM信号校正处理后,通信信号波形更加规律;应用该方法进行钟差校正后钟差值较小,提升了星地一体化通信用户接收终端钟差同步校正的准确度。
