Protection and fairness oriented cognitive radio MAC protocol for ad hoc networks (PROFCR)

Spectrum scarcity and underutilized frequency bands are the most challenging wireless networking problems in the last decade. Cognitive radio (CR) is the promising solution for these two problems. We propose a protection and fairness oriented cognitive radio MAC protocol (PROFCR) for ad hoc networks. PROFCR allows secondary users (SU) to utilize the unused and underutilized frequency bands while bounding the harm against the QoS of primary users (PU). An important advantage of PROFCR is that it completely eliminates the spectrum sensing process. Each SU decides next operating channel by calculating state variables of channels using only local information. Instead of choosing another data channel after each collision, PROFCR tries to utilize the same data channel until a state variable reaches the limit. This process reduces the number of handovers and decreases the delays that arise from changing channels frequently. The proposed protocol includes three protection schemes, which limit the harm caused by SUs against the QoS of PUs. These protection schemes are: limiting the packet size of SUs, assigning larger congestion window size to SUs that compete for channel resources with PUs, and requiring SUs to wait before attempting to access the channel. We have created a discrete time simulator to analyze the efficiency of the proposed protocol. The simulation results indicate that PROFCR utilizes the spectrum holes efficiently while protecting primary transmission.