Communication terminal, method for allowing communication terminal to obtain position information, and program product for controlling communication terminal

A method for allowing a communication terminal to obtain position information, said communication terminal being 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, the method comprising:

• receiving each radio wave transmitted by said each base station;
• obtaining said identification information from said radio wave;
• storing said obtained identification information;
• obtaining 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;
• receiving a plurality of positioning signals for positioning;
• calculating position information indicating the position of said communication terminal based on said assist data or said plurality of positioning signals;
• and
• outputting said calculated position information,
• wherein said obtaining said assist data includes:
• comparing said identification information newly obtained with said identification information already stored, and thereby determining whether or not said communication terminal is present in said range,
• generating a transmission request for said assist data when it is determined that said communication terminal is present in said range,
• transmitting said generated transmission request to said information providing device, and
• extracting said assist data from said received signal,
• said obtaining said identification information includes the step of obtaining, 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 identification information from the radio waves received in said second range, and
• said obtaining said assist data includes obtaining said assist data based on said identification information 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.

A non-transitory computer readable medium for controlling a communication terminal, said communication terminal being 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 program causing said communication terminal to perform:

• receiving said each radio wave transmitted by said each base station;
• obtaining said identification information from said radio wave;
• saving said obtained identification information;
• obtaining 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;
• receiving a plurality of positioning signals for positioning;
• obtaining position information indicating the position of said communication terminal based on said assist data or said plurality of positioning signals;
• and
• outputting said obtained position information
• wherein said obtaining said assist data includes:
• comparing said identification information newly obtained with said identification information already stored, and thereby determining whether or not said communication terminal is present in said range,
• generating a transmission request for said assist data when it is determined that said communication terminal is present in said range,
• transmitting said generated transmission request to said information providing device, and
• extracting said assist data from said received signal,
• said obtaining said identification information includes obtaining, 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 identification information from the radio waves received in said second range, and
• said obtaining said assist data includes obtaining said assist data based on said identification information 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.