Position information providing system indoor transmitter and method for providing position information

An indoor transmitter capable of providing position information by use of a first positioning signal which is a spread spectrum signal from each of a plurality of satellites, and a second positioning signal compatible with the first positioning signal, comprising:

• a first storage section which stores therein position data for identifying an installation location of the indoor transmitter;
• a generation section for generating an second positioning signal including the position data, as a spread spectrum signal;
• and
• a transmitting section for transmitting the generated spread spectrum signal,
• wherein the generation section is adapted to generate the second positioning signal in such a manner as to repeat a same content message in a cycle shorter than that of the first positioning signal,
• wherein the second positioning signal comprises a plurality of frames each including a one or more words, each of which is a transmission unit of data to be subjected to error detection, and
• wherein:
• the number of the words included in each of the frames is variably set,
• a leading one of the words in each of the frames includes a preamble for establishing frame synchronization during receiving,
• the leading one of the words in each of the frames comprises a message-type identification information indicative of the number of the words constituting the frame, and further indicative of whether the frame includes position information or other information, and
• if the frames include more than one word, the remaining one or more words other than at least the leading word, in each of the frames, include count data which is updated every time the word data is generated.

A method of providing position information by use of a first positioning signal which is a spread spectrum signal from each of a plurality of satellites, comprising:

• the step of loading position data for identifying an installation location of an indoor transmitter;
• the step of generating an second positioning signal including the position data, as a spread spectrum signal;
• the step of transmitting the generated spread spectrum signal;
• the step of receiving the transmitted spread spectrum signal;
• the step of, based on a plurality of code patterns related to the first and second positioning signals, identifying one of the code patterns which corresponds to the received spread spectrum signal;
• the step of, based on a signal obtained by demodulating the received spread spectrum signal using the identified code pattern, determining which of the first and second positioning signals is received;
• the step of deriving position information, while switching between processing modes depending on a result of the determination;
• and
• the step of outputting the derived position information,
• wherein the second positioning signal is generated to repeat a same content message in a cycle shorter than that of the first positioning signal,
• wherein the second positioning signal comprises a plurality of frames each including a one or more words, each of which is a transmission unit of data to be subjected to error detection, and
• wherein:
• the number of the words included in each of the frames is variably set,
• a leading one of the words in each of the frames includes a preamble for establishing frame synchronization during receiving,
• the leading one of the words in each of the frames comprises a message-type identification information indicative of the number of the words constituting the frame, and further indicative of whether the frame includes position information or other information, and
• if the frames include more than one word, the remaining one or more words other than at least the leading word, in each of the frames, include count data which is updated every time the word data is generated.