Energy-Efficient Communication in the Presence of Synchronization Errors

Communication systems are traditionally designed with tight transmitter-receiver synchronization. This requirement has negligible overhead in the high-SNR regime. In many applications, such as wireless sensor networks, communication needs to happen primarily in the energy-efficient regime of low SNR, where tight synchronization can be highly suboptimal. In this paper, we propose a new communication scheme that only requires loose synchronization. We show that the proposed scheme is asymptotically optimal for the Gaussian channel with synchronization errors in terms of energy efficiency as measured by the rate per unit energy. In the process, we also establish that the lack of synchronization causes negligible loss in energy efficiency. We further show that for a general discrete memoryless channel with synchronization errors and a general cost function on the input, the rate per unit cost achieved by the proposed scheme is within a factor of 2 of the information theoretic optimum.