Reference-aided distributed transmit beamforming with mobile radios

This paper describes a method to localize and synchronize a network of mobile radios and to localize a transceiver position so that the radios can steer a transmit beam to the transceiver. To achieve this, the radios must (a) synchronize their independent clocks, (b) estimate their positions relative to each other, and (c) estimate the range and angular orientation of their constellation to the steering direction. These parameters are estimated from GPS measurements and measurements of time-difference of arrival of inter-radio messages and of the transceiver emissions. A Kalman filter is used to blend the measurements and propagate the transmit node and transceiver states through the beamforming phase. In contrast with other distributed transmit beamforming methods, this technique does not require a cooperative transceiver or knowledge of its location.