Distributed Beamforming Using Multi-Antenna Backscattering Network

This paper proposes two novel beam-forming methodologies, which employ passive RF devices to enhance received signal through a passive, scattering based beam forming. Currently available backscattering systems, e.g. the radio frequency identification (RFID), suffer from a poor communication in an environment with multiple passive devices. The intermediate antennas create severe scattering environment with nulls. In contrast, the proposed approach changes the scattering properties of a subset of the multiple antennas such that the received signal strength and quality is maximized. The schemes employ Taguchi system and Learning Automaton to quickly identify such a suitable set of scattering intermediate devices. The theoretical limits of these schemes are studied mathematically and in simulations. For a 100-device network, the proposed schemes achieve power improvements over the line of sight equal to 37.5dB and 33dB for Taguchi and Learning Automaton-based schemes respectively. Moreover, the schemes are shown to perform well in an environment with the Rayleigh fading.