DTN-based Delivery of Word-of-Mouth Information with Priority and Deadline

In this paper, we propose a DTN (Delay Tolerant Network) based data delivery method for an environment without communication infrastructures (e.g., disaster area, event place, etc) that takes into account relative importance and deadline of users’ data requests. In this paper, as a target application, we suppose a system that allows users in a sightseeing area to exchange word-of-mouth information including photos on each sightseeing spot. We assume that multiple portable servers called “InfoBoxes” that collect/disseminate data from/to user terminals via short range wireless communication (e.g., Bluetooth) are deployed at sightseeing spots. In our proposed system, each user terminal sends, to an InfoBox, a query specifying (1) a destination spot on which the user wants to get information, (2) the importance of the query (to what extent the user satisfies when getting the query response), and (3) a receiving spot where the user wants to receive the query response. We propose a carry-and-forward based technique for delivering queries/responses so that the overall user satisfaction is maximized. Depending on a given probability of user movement between two spots, the proposed method appropriately adjusts the number of data replicas copied from each InfoBox to user terminals. In addition, the method discards the data which cannot meet the delivery deadline for efficient bandwidth utilization. Through computer simulations, we confirmed that the proposed method achieves better overall user satisfaction than other conventional methods.