System, computer-implemented positioning method, computer program and non-volatile data carrier

A system comprising:

• a set of mobile units (U1, U2, U3) each of the mobile units being configured to:
• be attached to a respective entity, and
• transmit, periodically, a first radio message (M1) including identity information (ID[U1]) of the respective entity to which the mobile unit (U1) is attached;
• at least three base stations (B1, B2, B3, B4, B5, B6, B7, B8), each of the base stations being configured to:
• receive the first radio message (M1);
• and
• based on the received first radio message, forward, via at least one transmission line communicatively connected to said base station, the identity information (ID[U1]) and timing information (U1(t1), U1(t2);
• U1(t3)) indicative of a point in time when the first radio message (M1) was received in the respective base station;
• and
• a central unit (CU) communicatively connected to the at least one transmission line, and configured to:
• receive, via the at least one transmission line, the identity information (ID[U1]) and the timing information (U1(t1), U1(t2), U1(t3)) from at least three of the base stations (B1, B2, B3);
• and
• based on the received identity information and the received timing information, determine a position of the respective entity relative to the at least three base stations,
• wherein each given one of the mobile units (U1, U2, U3) is configured to alter an energy density (PRF, P) at which subsequent said first radio messages (M1) is are transmitted by the given mobile unit in response to a trigger input being generated depending on a location of the mobile unit (U1) relative to a stationary reference (R1, R2, R3),
• wherein each of the mobile units is further configured to receive a second radio message (M2) as the trigger input of a given said mobile unit when the location of the given mobile unit (U1) is within an area (A1) defined by the stationary reference (R1);
• and in response to receiving the second radio message cause the given mobile unit (U1) to alter the energy density (PRF, P) at which subsequent said first radio messages are transmitted, and
• wherein at least one of the base stations is configured to:
• receive a first-area message (AM1) from the central unit (CU), which first-area message (AM1) is generated in response to a first said mobile unit (U1) having the location determined to be within a first said area (A1) defined by a first said stationary reference (R1);
• and in response thereto
• transmit the second radio message (M2) to the first mobile unit (U1).