  Time synchronization is important for a variety of applications in wireless
sensor networks including scheduling communication resources, coordinating
sensor wake/sleep cycles, and aligning signals for distributed
transmission/reception. This paper describes a non-hierarchical approach to
time synchronization in wireless sensor networks that has low overhead and can
be implemented at the physical and/or MAC layers. Unlike most of the prior
approaches, the approach described in this paper allows all nodes to use
exactly the same distributed algorithm and does not require local averaging of
measurements from other nodes. Analytical results show that the
non-hierarchical approach can provide monotonic expected convergence of both
drifts and offsets under broad conditions on the network topology and local
clock update stepsize. Numerical results are also presented verifying the
analysis under two particular network topologies.
