Global positioning method, terminal, and system

Abstract

A Global Positioning System forms a C/A code sequence by summing up, beginning from a polarity inversion boundary determined by a correlation peak position detector, chips at corresponding positions in PN frames constituting each bit of navigation data; calculates pseudo ranges by computing correlation between the C/A code sequence and a reference C/A code sequence generated by a GPS terminal; and determines the position of the GPS terminal using the pseudo ranges and navigation data. The navigation data detected inside the GPS terminal is used when a received electric field detected by a received electric field intensity detector is greater than a predetermined level, and the navigation data received from an external system is used when the received electric field is below the predetermined level. This makes it possible to solve following problems of a conventional system: the number of PN frames to be integrated is limited because the conventional system does not detect the polarity inversion boundaries of the navigation data, and hence the sensitivity (S/N ratio) is insufficient; and the communication between a terminal and a base station is required for determining the position because the GPS terminal always obtains the Doppler information from the base station, increasing the communication cost.