Over-the-Air Inter-Node Carrier Phase Synchronization for Coherent Transmission

This paper proposes new over-the-air inter-node carrier phase synchronization to maintain constant inter-node carrier phase offset among wireless nodes participating cooperative coherent transmission over slow Rayleigh fading channels. In the proposed method, one of the two nodes updates its carrier frequency and carrier phase periodically using the measured bi-directional channel parameters. In OFDMA systems, bi-directional channels are measured in distributed subcarriers to attain frequency diversity effect. In the presence of phase noise, one node can track the other node´s phase error using the proposed synchronization. Numerical results show that the proposed method maintains inter-node carrier phase alignment error less than 5 degrees. It is also revealed that the proposed method achieves accurate synchronization with feasible amount of signaling and complexity in LTE-advanced.