Cognitive radio technology: From distributed spectrum coordination to adaptive network collaboration

This paper presents an integrated view of cognitive radio technologies for efficient wireless services in dense spectrum environments. The rationale for cognitive radio based systems is discussed, leading to an identification of the available design space that ranges from reactive interference avoidance to spectrum etiquette and eventually network collaboration. After reviewing prior work in the dynamic spectrum area, a specific distributed spectrum etiquette protocol called ''common spectrum coordination channel (CSCC)'' is introduced. Performance gains achieved with CSCC relative to simpler reactive time/frequency/power control algorithms are evaluated for example in WiFi/Bluetooth and WiFi/WiMax co-existence scenarios. The next level of system performance can be achieved through opportunistic collaboration between radios to form ad hoc multi-hop networks in which neighboring nodes associate with each other at high bit-rate and low power. Adaptive wireless networks of this type will require new protocol architectures which integrate flexible PHY/MAC and cross-layer capabilities with ad hoc network discovery and multi-hop routing. A specific ''CogNet'' protocol architecture based on the concept of a ''global control plane (GCP)'' is described. Major CogNet protocol modules for bootstrapping, discovery, data path setup and naming/addressing are outlined, and representative ns-2 simulation results are provided for validation. In conclusion, the paper gives a preview of the network-centric WiNC2R prototype under development at WINLAB as an experimental cognitive radio platform.