This paper summarizes studies on the utilization of precise clock synchronization in satellite-based navigation and communication. The user's clock synchronization with one of the precise clocks installed in a navigation satellite or ground radio station, which maintains the time standard for the generation of range measurement signals, enables the adoption of new satellite navigation concepts, and the simplicity will open up avenues for efficient methods of mobile communications. Precise clock synchronization between two radio stations, which really means the detection of the time offset between two clocks, is performed, in principle, by using bi-directional communication between these stations and by detecting the difference in radio propagation times between one direction and its opposite. Satellite positioning based on clock synchronization will reduce the number of deployed satellites and mitigate geometrical requirements for satellite placement. Application of synchronized timing to spread-spectrum communications will produce a technology combining Code Division Multiple Access (CDMA) with Time Division Multiple Access (TDMA), with which optional communications between radio stations and multiple access circuit control for mobile message communications can be achieved efficiently. Another subject of this paper is the formulation and integration of several kinds of satellite-based navigation algorithms. Such formation and integration can be skillfully achieved by applying the Weight Least Squares (WLS) method. Nearly optimal estimation of positioning is done by regulating the weights of the WLS algorithm, referring to the numerical values of Dilution Of Precision (DOP), which are calculated from the covariance matrix of the position error discussed in this paper. Characteristics of the WLS navigation algorithm are discussed in relation to the geometry of satellite placement.
Studies on satellite-based navigation and communication utilizing precise clock synchronization between radio stations
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