Limitations, performance and instrumentation of closed-loop feedback based distributed adaptive transmit beamforming in WSNs

We study closed-loop feedback based approaches to distributed adaptive transmit beamforming in wireless sensor networks. For a global random search scheme we discuss the impact of the transmission distance on the feasibility of the synchronisation approach. Additionally, a quasi novel method for phase synchronisation of distributed adaptive transmit beam-forming in wireless sensor networks is presented that improves the synchronisation performance. Finally, we present measurements from an instrumentation using USRP software radios at various transmit frequencies and with differing network sizes.