Patent ID: 8681048

Claim:
An arrival angle estimation system comprising a transmitting device and a receiving device, the arrival angle estimation system estimating an arrival angle at which frames transmitted by radio from the transmitting device arrive at the receiving device, wherein: the transmitting device includes two first directional antennas being arranged so that corresponding directivities are tilted at ±θ degrees with respect to a front portion of the transmitting device, the transmitting device being configured to: select alternating ones of the first directional antennas to transmit a corresponding one of the frames to the receiving device; modify a portion of the corresponding frame in response to the selection, the modified portion identifying the selected first directional antenna; and transmit the corresponding frame from the first selected directional antenna to the receiving device; and the receiving device includes a second directional antenna having directivity toward a front portion of the receiving device, the receiving device being configured to: receive the corresponding frame from the transmitting device at a corresponding signal strength; identify the selected first directional antenna of the transmitting device, based on the modified portion of the corresponding frame; obtain (i) signal strength data for the first directional antennas and (ii) information identifying a correlation between differences in signal strength and arrival angles, the signal strength data comprising values of signal strength of previous transmissions received from at least one of the selected first directional antenna or the unselected first directional antenna; compute, based on the corresponding signal strength and the obtained signal strength data, a difference between a first mean signal strength of transmissions received from the selected first directional antenna and a second mean signal strength of transmissions received from the unselected first directional antenna; and estimate the arrival angle based on at least the computed difference and the obtained correlation information.