MAC Protocol Adaptation in Cognitive Radio Networks: An Experimental Study

This paper presents an adaptive MAC (AMAC) protocol for supporting MAC layer adaptation in cognitive radio networks. MAC protocol adaptation is motivated by the flexibility of emerging software-defined radios which make it feasible to dynamically adjust radio protocols and parameters. Dynamic changes to the MAC layer may be useful in wireless networking scenarios such as tactical or vehicular communications where the radio node density and service requirements can vary widely over time. A specific control framework for the proposed AMAC is described based on the "CogNet" protocol stack which uses a "global control plane (GCP)" to distribute control information between nearby radios. A proof-of-concept AMAC prototype which switches between CSMA and TDMA is implemented using GNU radio platforms on the ORBIT radio grid testbed. Experimental results are given for both UDP and TCP with dynamic traffic variations. The results show that adaptive MAC can be implemented with reasonable control protocol overhead and latency, and that the adaptive network achieves improved performance relative to a conventional static system.