Design and Analysis for an 802.11-Based Cognitive Radio Network

This paper considers a distributed opportunistic spectrum access (D-OSA) scenario in which multiple cognitive radio (CR) users attempt to access a channel licensed to some primary network. CR users operate on a frame-by-frame basis and need to carry out spectrum sensing at the beginning of each frame to determine if the primary network is active or idle. Upon detecting the primary network being idle, each CR user employs a modified 802.11 DCF protocol for contention-based channel access. Spectrum sensing is imperfect and introduces false alarms and mis-detections. To protect primary users, it is required that the combined probability of mis-detection of all CR users must be below a specified threshold. We provide concrete protocol design, performance analysis, and extensive simulation results for our D-OSA design. Our results highlight the importance of taking a cross-layer view and jointly designing PHY-layer spectrum sensing and MAC-layer channel access.