  In cognitive radio mobile ad hoc networks (CR-MANETs), secondary users can
cooperatively sense the spectrum to detect the presence of primary users. In
this chapter, we propose a fully distributed and scalable cooperative spectrum
sensing scheme based on recent advances in consensus algorithms. In the
proposed scheme, the secondary users can maintain coordination based on only
local information exchange without a centralized common receiver. We use the
consensus of secondary users to make the final decision. The proposed scheme is
essentially based on recent advances in consensus algorithms that have taken
inspiration from complex natural phenomena including flocking of birds,
schooling of fish, swarming of ants and honeybees. Unlike the existing
cooperative spectrum sensing schemes, there is no need for a centralized
receiver in the proposed schemes, which make them suitable in distributed
CR-MANETs. Simulation results show that the proposed consensus schemes can have
significant lower missing detection probabilities and false alarm probabilities
in CR-MANETs. It is also demonstrated that the proposed scheme not only has
proven sensitivity in detecting the primary user's presence, but also has
robustness in choosing a desirable decision threshold.
