Challenges in designing testbed for evaluating delay-tolerant hybrid networks

Challenged networking applications such as rural internet, battlefield communication, post-disaster communication etc. cannot rely on mere DTN for its unpredictable delay and unreliable delivery probability. To meet application specific QoS constraints, in addition to DTN-enabled mobile nodes (smart phones/tablets), an ad hoc backbone infrastructure is essential. Such backbone components include the use of laptops or custom-built storage units as Information Dropboxes and/or Data Mules and wireless mesh, long range Wi-Fi etc. as long range wireless communication units. Evaluation of such systems through simulation is not enough as there are problems related to compatibility and interoperability. Hence design of a testbed for evaluating a DTN-based hybrid system is a non-trivial problem. In this paper we attempt to reveal some of the system related challenges/issues for above and present DTHN-Test, a low-cost testbed prototype developed for evaluating challenged network scenarios, in general. As a case study we show some initial results on performance of a Delay-constrained Four-Tier Hybrid Ad hoc Network Architecture using DTHN-Test.