Handling Asymmetry in Power Heterogeneous Ad Hoc Networks: A Cross Layer Approach

Power heterogeneous ad hoc networks are characterized by link layer asymmetry: the ability of lower power nodes to receive transmissions from higher power nodes but not vice versa. This not only poses challenges at the routing layer, but also results in an increased number of collisions at the MAC layer due to high power nodes initiating transmissions while low power communications are in progress. Previously proposed routing protocols for handling unidirectional links largely ignore MAC layer dependencies. In this paper, we propose a cross layer framework that effectively improves the performance of the MAC layer in power heterogeneous ad hoc networks. In addition, our approach seamlessly supports the identification and usage of unidirectional links at the routing layer. The framework is based on intelligently propagating low power MAC layer control messages to higher power nodes so as to preclude them from initiating transmissions while the low power communications are in progress within their sensing range. The integrated approach also constructs reverse tunnels to bridge unidirectional links thereby facilitating their effective usage at the routing layer. Extensive simulations are performed to study the proposed framework in various settings. The use of our framework improves the overall throughput of the power heterogeneous network by as much as 25 % over traditional layered approaches. In summary, our framework offers a simple, yet effective and viable approach for media access control and to support routing in power heterogeneous ad hoc networks.