Robust time-slotted round-trip carrier and timing synchronization for distributed beamforming

Distributed beamforming has arisen as a significant approach in multi-user wireless communication systems. It allows several transmitters with common information to emulate an antenna array and focus their transmissions towards an intended destination. However, carrier and timing synchronization among the transmitters is necessary to ensure that the information is aimed in the desired direction. In this work we present a robust time-slotted round-trip carrier and timing synchronization protocol that is valid in dynamic environments in the sense that sensors can disappear from the network without affecting the performance severely. The protocol is based on the execution of simple rules at each sensor and leaves freedom to choose those signals that provide better timing synchronization. Numerical results show that a large fraction of the maximum beamforming gain can be maintained for death ratios as high as 50%.