<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.