A geocast is a type of data transmission where data is sent from one sender to a group of recipients in a specific geographical location. The group of recipients may only consist of one member – the important part is the identification by location. When connecting, this casting type can only happen in a peer-to-peer network that uses geographical location data.
Some mobile ad hoc routing protocols work this way. Although it is possible to target users based on IP addresses and their physical locations on the internet, geocasting is NOT a type of Internet routing. Technically, geocasting is a sub-form of multicasting, as it addresses multiple recipients on the same network with one sender.
Geographic destination addresses are used in geocasting and are expressed in shapes – point, circles, and polygons. Polygons are used to set the target area or location – for example, a city or continent. The points and circles are then used to determine individual users in the polygon that defines the general area.
Routers are organized by a hierarchy, unlike those used in Internet traffic, where individual routers are essentially all equals, and distinction is more likely to be made by signal strength.
Geocasting can be helpful in things such as geographic messaging (messages relevant only to people in a particular state, for example), geographic advertising (offers only available in one city, not outside it), or geographically restricted services (such as a pizza place with a limited delivery area).
Abiding Geocast
The subset of Abiding geocast also referred to as stored geocast, offers some interesting additional functionality. A standard geocast message is sent to any connected device within the configured location when the message is sent. Abiding geocast stores the network message long-term in the network. It’s then sent to any device that enters the configured range before the timer expires.
This offers potentially helpful use cases such as hazard warnings and road signs. Taken to an extreme, however, a shop could also use precise location distinctions to deliver ads to customers based on the products they are near. Geocast could also be particularly useful after natural disasters.
These tend to affect traditional communications infrastructure, but an Adhoc network may be able to spring up. Then being able to communicate with devices within a particular area might be able to help direct search and rescue operations and supply deliveries to where they’re needed.
Conclusion
Geocast is a subset of multicast. Instead of sending messages to a preselected group of devices, messages are sent to any device within a configured location. Geocast is not generally implemented and is only really found on ad hoc mobile networks.
The availability of the concept and the inherent unreliability of mobile ad hoc networks limits the potential usefulness of geocast. If it were more widely implemented, it could offer several positive use cases. Unfortunately, the same functionality could be used for further invasive ad tracking and other less desirable outcomes.
