Simple, zero-feedback, collaborative beamforming for emergency radio

Collaborative beamforming among a set of distributed terminals is studied, assuming a) no specialized RF hardware for carrier frequency synchronization, and b) zero feedback from destination (either in the form of pilot signals or explicit messages). A solution is provided for conventional radios in relevant critical applications, such as emergency radio. The proposed scheme simply exploits lack of synchronization among distributed carriers, operating at the same nominal carrier frequency. It is shown that such beamforming is possible and its performance is analytically quantified.