Patent ID: 8125917

Claim:
A method of optimising radio frequency field strength in a radio communications network, the network comprising a wireless access point arranged to transmit a signal at a configurable power level, the radio frequency field strength being dependent on the transmitted signal power level, and the network further comprising a plurality of sensors, each sensor having a defined location with respect to a designated zone of wireless coverage, the method comprising: receiving at each sensor the signal transmitted from the wireless access point; measuring the power of said received signal at each sensor, the received signal power being dependent on the radio frequency field strength at the location of the sensor; and controlling transmitted power from the wireless access point in dependence on a difference between said power measured at each sensor and an expected level of power at each sensor, said expected level of power at each sensor being a function of the location of each sensor with respect to said designated zone of wireless coverage; controlling the transmitted power from the wireless access point in dependence on minimizing an objective function, in which the objective function comprises contributions from two or more sensors selected from a group comprising: a first sensor at the edge of the designated zone of coverage, the contribution of the first sensor having a characteristic that that increases with increasing as deviation from a target received signal power; a second sensor, the second sensor being within the designated zone of coverage, the contribution of the second sensor having a characteristic that decreases with increasing received signal power up to the target received signal power and that is substantially constant when the signal power is above the target signal power; and a third sensor, the third sensor being outside the designated zone of coverage, the contribution of the third sensor having a characteristic that increases with increasing received signal power above to a threshold of received signal power and that is substantially constant when the signal power is below the threshold, the threshold being lower than the target received power, in which at least one of said sensors is located at the edge of or outside the designated zone of wireless coverage.