Zebroids: Carrier-based Replacement Policies to Minimize Availability Latency in Vehicular Ad-hoc Networks

Zebroids are mobile devices that carry a referenced data item from a server containing that data item to a client that requested it. An environment employs zebroids in order to minimize the availability latency incurred by the client. A device acts as a zebroid when it is in close vicinity of a server and travels along a path that rendezvous with the client. Over time, the storage capacity of the zebroid might become occupied with data items. To carry the requested data item, it must evict one or more of its existing data items. The primary contribution of this study is to quantify the latency-overhead tradeoff associated with alternative replacement policies that might be employed by a zebroid. We employ a simulation study to quantify the tradeoffs associated with policies such as Least Recently Used (LRU), Least Frequently Used (LFU), and a simple random policy. Obtained results highlight the parameter space where the use of zebroids provides superior performance when compared with a static data placement strategy that does not use zebroids. We verify this and the other observed trends using a simple analytical approximation of latency for a 2D random walk mobility model.