  Network coding and opportunistic routing are two recognized innovative ideas
to improve the performance of wireless networks by utilizing the broadcast
nature of the wireless medium. In the last decade, there has been considerable
research on how to synergize inter-flow network coding and opportunistic
routing in a single joint protocol outperforming each in any scenario. This
paper explains the motivation behind the integration of these two techniques,
and highlights certain scenarios in which the joint approach may even degrade
the performance, emphasizing the fact that their synergistic effect cannot be
accomplished with a naive and perfunctory combination. This survey paper also
provides a comprehensive taxonomy of the joint protocols in terms of their
fundamental components and associated challenges, and compares existing joint
protocols. We also present concluding remarks along with an outline of future
research directions.
