Supporting a secure terrestrial transmitter based positioning

A system comprising at least one processor and at least one memory, wherein the at least one memory includes computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause at least one apparatus at least to:

• receive a positioning request from a mobile device, the positioning request including:
• an identifier of a transmitter, an indication of a timing of transmissions currently used by the transmitter for broadcasting packets and a result of measurements by the mobile device on radio signals of the transmitter conveying the packets;
• generate for the transmitter at least one expected timing of transmissions using a cryptographic function, based on a signal of a master clock and based on a secret code assigned to the transmitter, wherein the at least one apparatus has access to a plurality of stored secret codes assigned to a plurality of transmitters;
• determine whether there is a match between the indicated timing of transmissions and the at least one expected timing of transmissions;
• and
• provide position information as trusted position information only in the case of a match, wherein the position information is determined based on the results of measurements in the positioning request.

A method comprising, performed by a mobile device:

• detecting radio signals used by at least one transmitter for broadcasting packets and performing measurements on the detected radio signals;
• extracting identifiers of transmitters from the packets;
• determining, based on the detected radio signals, a timing of transmissions currently used by each of the at least one transmitter for broadcasting packets, wherein the timing of transmissions is based on a secret code assigned to the at least one transmitter and on signals of a clock that is synchronized with a master clock;
• assembling a positioning request including for each of the at least one transmitter at least:
• an identifier of the transmitter, results of measurements on the detected radio signals and an indication of the determined timing of transmissions;
• and
• causing transmission of the positioning request to a server.

An apparatus comprising at least one processor and at least one memory, wherein the at least one memory includes computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause a mobile device at least to:

• detect radio signals used by at least one transmitter for broadcasting packets and performing measurements on the detected radio signals;
• extract identifiers of transmitters from the packets;
• determine, based on the detected radio signals, a timing of transmissions currently used by each of the at least one transmitter for broadcasting packets, wherein the timing of transmissions is based on a secret code assigned to the at least one transmitter and on signals of a clock that is synchronized with a master clock;
• assemble a positioning request including for each of the at least one transmitter at least:
• an identifier of the transmitter, results of measurements on the detected radio signals and an indication of the determined timing of transmissions;
• and
• cause transmission of the positioning request to a server.