Using multi-hop acknowledgements to discover and reliably communicate over unidirectional links in ad hoc networks

Neighbor discovery protocols are based on the receipt of an acknowledgement in response to a node advertisement. Traditionally, the advertisement and acknowledgement are sent in opposite directions across the same link. As a result, these protocols are only able to discover bidirectional links. The exclusion of unidirectional links can reduce the network´s capacity and also lead to network partitioning. These concerns are particularly relevant to ad hoc networks, where bandwidth and transmission power are limited resources and links are not necessarily bidirectional. To support the discovery and subsequent use of unidirectional links, we propose the multi-hop broadcast and unicast relay of link layer acknowledgements. Through simulation of an ad hoc network with reduced transmission power support, we demonstrate that the proposed multi-hop feedback techniques are able to discover nearly all of the unidirectional links, improving network connectivity by 30% and reducing the length of shortest hop paths by 25%