Stored Geocast

For many location based services like location based advertising, location based information services, or in particular, realizing a virtual traffic sign, which is bound to a location over time, we need a stored geocast solution. A stored geocast is a time stable geocast, which is delivered to all nodes that are inside a destination region within a certain period of time. The period of time starts at the time of sending plus network propagation delay and ends at a user defined time or is boundless. This paper discusses the design space, the semantics, and three reasonable solutions for stored geocast in an ad hoc network. The first approach is an infrastructure-based server solution to store the messages. The second is an infrastructure-less approach that may be more suitable for an ad hoc network. A node inside the geocast destination region is elected to act temporarily as a server for geocast messages. The last approach works infrastructure-less, too, by complementing the exchange of neighbor information necessary for many geographic unicast routing protocols with geocast information.