  Clock asynchronism is a critical issue in integrating radar sensing into
communication networks. It can cause ranging ambiguity and prevent coherent
processing of dis-continuous measurements in integration with asynchronous
transceivers. Should it be resolved, sensing can be efficiently realized in
communication networks, requiring little network infrastructure and hardware
changes. This article provides a systematic overview of existing and potential
new techniques for tackling this fundamental problem. We first review existing
solutions, including using a fine-tuned global reference clock, and
single-node-based and network-based techniques. We then examine open problems
and research opportunities, offering insights into what may be better realized
in each of the three solution areas.
