Strategic Mobility and Cooperative Caching in DTN: A Social Dilemma Perspective

Content sharing in Delay Tolerant Networks is largely contingent on the cooperation of participating nodes as message dissemination is executed in a store-carry-forward approach. The scope of the term cooperation has largely been limited to content forwarding in prior work. This work considers a universe of distributed content- sources that generate disjoint contents. A population of users who are capable of moving from one source to another are interested only in some selected subset of the localized contents. Interest of users is assumed to vary from one another; being rational entities, they are solely interested in collecting their preferred content(s) at the expense of minimum cost. With solutions like Direct Reciprocity been proposed earlier to force a user to be altruistic in message forwarding, our work starts in this backdrop where preference-based content caching and deletion strategy comes into play even if a user is forced to share her contents with all other encountered users. Alongside, we introduce mobility as a user strategy to characterize the non-cooperation of a user along with deletion of non-preferred cached contents. Under this premise, we explore the optimal strategies that a user can exercise to maximize her benefit corresponding to the strategies adopted by other users. More specifically, we investigate the joint impact of user's mobility and caching strategy on self and overall network performance using a Public Goods game in the Social Dilemma framework evincing the condition when non-cooperation is costlier than cooperation.