Distributed time and frequency synchronization: USRP hardware implementation

In device-to-device communications timing and carrier frequency synchronization is crucial for guaranteeing efficient communications within dense networks. A distributed synchronization method without any external reference agent is suitable for these dense networks. This paper presents hardware validation of a recently proposed distributed synchronization algorithm based on consensus paradigms. Identical synchronization frames are sent from all transmitting nodes, and the synchronization configuration is estimated from these superimposed waveforms. This method greatly simplifies the carrier frequency offset (CFO) and timing offset (TO) estimation procedure when implemented in hardware. A real-time algorithm is implemented on software defined radios (SDR), and is tested in various configurations to investigate the tracking and accuracy abilities of the algorithm. The hardware tests verified the algorithm as a suitable candidate for synchronization in dense networks, with accurate estimation of the timing and frequency offsets of the transmitting nodes. Its ability to decouple the estimations was also demonstrated with experiments.