PASSSERBY®  takes advantage of passers-by to distribute information. It uses wireless technology to make short hops between devices, and then exploits the fact that users are moving around (walking, taking a bus, driving) to provide longer-range communication. By selectively taking advantage of both, PASSERBY achieves fast, long-range communication with without any long-range infrastructure.

 

 

PASSERBY is a file-exchange and distribution technology, It is able to distribute anything that can be stored as a file, and every PASSERBY device can distribute any file type, even if the device can't actually process that file type. So PASSERBY can easily distribute audio, images, documents, and much more. 

 

Each device continuously monitors which other PASSERBY devices are visible (that is, within wireless range). By doing so, it forms a picture of its direct social network. As devices come into range of each other, they share their social networks with each other, so that each device knows not just its direct social network (the other devices it regularly sees), but also its indirect social network (the devices that devices it sees regularly see, and so on). This means that each device can make a good guess about how likely it it to be able to help route a file or a message towards a particular destination. 

 

When two devices come into range of each other, they first exchange their current social profiles. This allows each device to work out which of the messages or files it has currently stored could be successfully routed via the other device. These files are exchanged, and copied onto the receiving device for distribution to other PASSERBY devices it may meet later in the day.

 

Messages might be passed to multiple devices to give the best chance that a message reaches its destination, but devices that aren't likely to be able to help don't copy the files, so that the system doesn't get swamped. Messages find their way quickly but efficiently to where they intended.

 

While not able to provide "cellphone-like" voice communications, PASSERBY can provide efficient distribution for email, voice-mail, bulletin-boards, copying image files, sending documents, and a whole host of other communication and information activities. The time a message takes to reach its destination, and the probability of success, are dependent on the activity of the community in which they are used. But in general, PASSERBY brings a radical improvement in communication at a very low-cost for rural environments.