  In cognitive radio (CR) networks, the secondary users (SUs) sense the
spectrum licensed to the primary users (PUs) to identify and possibly transmit
over temporarily unoccupied channels. Cooperative sensing was proposed to
improve the sensing accuracy, but in heterogeneous scenarios SUs do not
contribute equally to the cooperative sensing result because they experience
different received PU signal quality at their sensors. In this paper, a
two-layer coalitional game is developed for distributed sensing and access in
multichannel CR ad hoc networks where the SUs' transmission opportunities are
commensurate with their sensing contributions, thus fostering cooperation and
eliminating free-riders. Numerical results show that the proposed two-layer
game is computationally efficient and outperforms previously investigated
collaborative sensing and spectrum access approaches for heterogeneous
multichannel CR networks in terms of energy efficiency, throughput, SU
fairness, and complexity. Moreover, it is demonstrated that this game is robust
to changes in the network topology and the number of SUs in low-mobility
scenarios. Finally, we propose a new physical-layer approach to distributing
the network-level miss-detection (MD) constraints fairly among the interfering
SUs for guaranteed PU protection and demonstrate the performance advantages of
the AND-rule combining of spectrum sensing results for heterogeneous SUs.
