End-to-end congestion control in multi-hop cognitive radio ad hoc networks: To timeout or not to timeout?

End-to-end congestion control, aiming to find out how much traffic load offered by the source can be handled by a network, is an essential function of a transport layer protocol. In traditional wireless ad hoc networks, numerous solutions have been proposed to solve this issue. However, in cognitive radio (CR) ad hoc networks, the end-to-end congestion control issue still remains unexplored. More importantly, due to the nonuniform channel availability in CR ad hoc networks, unique challenges of end-to-end congestion control are introduced. In this paper, a comprehensive end-to-end congestion control framework that considers the non-uniform channel availability is proposed. In addition, we investigate two types of existing congestion control approaches: 1) the explicit feedback mechanism without timeouts and 2) the timeout mechanism. Through extensive simulations, we observe that both mechanisms have limitations and cannot be simply applied in multi-hop CR ad hoc networks. To the best of our knowledge, this is the first work that studies the end-to-end congestion control issue in CR ad hoc networks that considers the non-uniform channel availability.