  Clock synchronization is ubiquitous in wireless systems for communication,
sensing and control. In this paper we design a scalable system in which an
indefinite number of passively receiving wireless units can synchronize to a
single master clock at the level of discrete clock ticks. Accurate
synchronization requires an estimate of the node positions. If such information
is available the framework developed here takes position uncertainties into
account. In the absence of such information we propose a mechanism which
enables simultaneous synchronization and positioning. Furthermore we derive the
Cramer-Rao bounds for the system which show that it enables synchronization
accuracy at sub-nanosecond levels. Finally, we develop and evaluate an online
estimation method which is statistically efficient.
