<FONT face=Verdana>Based on the analyses of the recent routing research productions of the cognitive radio networks (CRN)
this paper identifies five critical challenges on the routing research of CRN: neighbor discovery
deafness problem
neighbor disappearance
routing problem and cross-layer design
then some topics about common control channel
path delay and the technical metrics are discussed from the view of research method
which must be considered on the routing research of CRN. After that
we summarize and analyze the scenario design patterns of routing research from four aspects: medium
channel
node and network; study and discuss the main research productions from the views of optimization scheme and routing topology algorithm / protocol in detail at the end of this paper.