Cooperative synchronization and channel estimation in wireless sensor networks

A critical issue in applications involving networks of wireless sensors is their ability to synchronize and mitigate the fading propagation channel effects. Especially when distributed "slave" sensors (nodes) reach-back to communicate with the "master" sensor (gateway), low-power cooperative schemes are well motivated. Viewing each node as an antenna element in a multi-input multi-output (MIMO) multi-antenna system, we design pilot patterns to estimate the multiple carrier frequency offsets (CFO), and the multiple channels corresponding to each node-gateway link. Our novel pilot scheme consists of non-zero pilot symbols along with zeros, which separate nodes in a TDMA fashion, and lead to low-complexity estimators because CFOs and channels per node are decoupled. The resulting training algorithm is not only suitable for wireless sensor networks, but also for synchronization and channel estimation of single-carrier MIMO systems. We investigate the performance of our estimators analytically, and with simulations.