Diameter of Opportunistic Mobile Networks

Portable devices have more data storage and increasingcommunication capabilities everyday. In addition to classic infras-tructure based communication, these devices can exploit human mo-bility and opportunistic contacts to communicate. We analyze thecharacteristics of such opportunistic forwarding paths. We establishthat opportunistic mobile networks in general are characterized by asmall diameter, a destination device is reachable using only a smallnumber of relays under tight delay constraint. This property is firstdemonstrated analytically on a family of mobile networks which fol-low a random graph process. We then establish the validity of thisresult empirically with four data sets capturing human mobility, usinga new methodology to efficiently compute all the paths that impactthe diameter of an opportunistic mobile networks. We complete ouranalysis of network diameter by studying the impact of intensity ofcontact rate and contact duration. This work is, to our knowledge, thefirst validation that the so called “small world” phenomenon appliesvery generally to opportunistic networking between mobile nodes.