Cognitive radio technology is regarded as the most promising technique to solve the problem of ultra-low utilization efficiency of wireless spectrum resources. Based on this technology, cognitive radio networks (CRNs) effectively improve utilization efficiency of licensed spectrum through dynamic spectrum access. However, the resultant dynamic channel availability significantly increases the difficulty in networking for CRNs. Rendezvous aims at providing common media for communication between users, which is the foundation of networking in wireless networks. This paper introduces the basic concept and characteristics of rendezvous in CRNs and dissect the challenges and concerned performance metrics in design of rendezvous schemes. According to the proposed classification criteria and system models, the related research work on rendezvous schemes are analyzed in depth. Finally, open problems in rendezvous schemes design are discussed to point out future research trends and focuses.