| 摘要 |
Disclosed is the estimation of the position of a user device (18) using radio beacons (B1-B4) which are operable at a plurality of transmit power levels. The radio beacons (B1-B4) may transmit their position and current transmit power level. Estimates of distance between a user device and a radio beacon can take into account both received signal strength and the current transmit power level of the radio beacon. The position of the user device (18) can be estimated taking into account whether a radio beacon (B1-B4)) can be detected at a given transmit power level. The transmit power level of the radio beacon may vary according to a cycle. The transmit power level of the radio beacon may be changed to facilitate positioning, for example in response to a signal from a user device. A radio beacon (B1-B4) changes transmit power level in a cycle. The radio beacon can reduce transmit power level responsive to a signal. The radio beacon (B1-B4) may be compatible with Bluetooth short range wireless connectivity standard core specification version 4.0. |
