Patent ID: 8285301
Filing Date: 2012-10-09
Classification: G01S

Abstract:
1. A communication terminal capable of wirelessly communicating with each of a plurality of base stations, said each base station being connected to an information providing device via a communication line, said information providing device being capable of transmitting assist data for assisting to specify a position of said communication terminal in response to a request, said each base station being capable of transmitting a radio wave including identification information for identifying itself and a radio wave including said assist data, said communication terminal comprising: a first receiver configured to receive said each radio wave transmitted by said each base station; a processor; and a memory connected to said processor, wherein said processor is configured to obtain said identification information from said radio wave; said memory is configured to store said obtained identification information; said processor is configured to obtain said assist data from said information providing device when said communication terminal is present in a range in which said communication terminal can communicate with the base station specified by said identification information; said communication terminal further comprising: a second receiver configured to receive a plurality of positioning signals for positioning, wherein said processor is configured to calculate position information indicating the position of said communication terminal based on said assist data or said plurality of positioning signals, said communication terminal further comprising: an output device configured to output said calculated position information, wherein said processor compares newly obtained said identification information with said identification information already stored in said memory, and thereby determines whether or not said communication terminal is present in said range, generates a transmission request for said assist data when it is determined that said communication terminal is present in said range, transmits said generated transmission request to said information providing device, and extracts said assist data from a signal received by said first receiver, and wherein, when said communication terminal moves from a first range in which said communication terminal cannot receive the radio waves transmitted by said base stations to a second range in which said communication terminal can receive the radio waves, said processor is configured to obtain said identification information from the radio waves received in said second range, and when said communication terminal moves to said first range after said identification information is obtained, and then moves from said first range to be present again in said second range in which said communication terminal can receive the radio wave from the base station specified by said identification information, said processor is configured to obtain said assist data based on said identification information.