Distributed Cooperative Synchronization for Large-Scale 4G Wireless Sensor Networks Using CAZAC Sequences

Clock synchronization is an important requirement of wireless sensor networks (WSNs). Synchronization is crucial to maintain data consistency, coordination, and perform fundamental operations. Many application scenarios exist where external clock synchronization may be required because WSN itself may not consist of an infrastructure for distributing the clock reference. In distributed systems the clock of a reference node is synchronized with GPS time tag or UTC as conventional external clock sources. The rest of the nodes estimate the offset and drift based on a synchronization protocol. For vast WSN, where the topology introduces propagation delay and fast drift rate of clock over sampling periods, synchronizing the WSN nodes and maintaining the synchronization is difficult. To maintain an accurate synchronization across the WSN, the authors propose a cooperative synchronization method, which uses Constant Amplitude Zero Auto Correlation (CAZAC) sequences for OFDM symbols. The proposed method is part of a class of distributed methods known as Gossip or Consensus. These protocols are robust and self-correcting to topology changes and link failure. In this paper, the authors introduce a specific type of power-law topology called scale-free and compare the synchronization performance of the proposed method in random and scale-free topologies.