A Framework to Provide a Bidirectional Abstraction of the Asymmetric Network to Routing Protocols

Wireless links are often asymmetric due to heterogeneity in the transmission power of devices, non-uniform environmental noise, and other signal propagation phenomenon. Because of the variable and unpredictable capacity of wireless links, packet loses may happen frequently. Several routing protocols have been proposed for Mobile Adhoc networks, yet there is no one for all schemes that works well in all link conditions with different network sizes, traffic loads and node mobility patterns. This paper first presents a study of various routing protocols and the impact of asymmetric links on network connectivity. It then presents a framework that provides a bidirectional abstraction of the asymmetric network to routing protocols. This new framework works by maintaining multi-hop reverse routes for unidirectional links and provides three new abilities: improved connectivity by taking advantage of the unidirectional links, reverse route forwarding of control packets to enable off-the shelf routing protocols, and detection packet loss on unidirectional links. This framework takes the approach of discovering and maintaining reverse paths for unidirectional links. Experiments were conducted in ns2 simulator with the design of bidirectional routing abstraction to maintain reverse routes for unidirectional links in an efficient and scalable manner. Performance evaluation shows how a typical routing protocol, such as the well-known AODV, layered on this framework achieves superior connectivity in asymmetric networks.