Sunday, September 11, 2011

Opportunistic Networks (Oppnets) - Basis for Ubiquitous Networks

Opportunistic Networks (oppnets) is a rather new concept borned around 6 years ago. The key idea behind this kind of networks is to use mobile devices to build a network to transfer data from a source node to a destination one without knowing the path or route to follow. Moreover, the message has no guarantee of reaching destiny. The whole thing relays on a best effort policy but nevertheless results quite effective. An oppnet can be seen as a subset of a Delay-Tolerant Network where communication opportunities are intermittent, so an end-to-end path between the source and the destination may never exist.

A source node passes its message to a nearby node following a gossip fashion. Nodes move around and while being near to others pass the messages they have to them and at some point the destiny node is reached. The basic characteristic is that the nodes may enter and leave the oppnet at any time, they can move and take with them the messages. All these things are done without the interaction of people. Usual elements to become part of an oppnet are cell phones, PADs, netbooks, or any electronic device with communication capacity. The oppnet may be based on any kind of communication technology, WI-FI, Bluetooth, RFID, etc.

The oppnets are part of what has been known as ubiquitous computing and later as pervasive computing. Basically these concepts are related to the use of computing devices in everyday activities without explicit knowledge of the user of its existence. Oppnets appear then to link these devices in a friendly an easy way to help people. They differ from traditional network standards in that the size and structure of the network is unknown. Actually, the oppnet starts with a seed oppnet of one or just a few nodes and grows dynamically with the incorporation of friendly devices. The growth of the network is guided from the application layer that requires information to be retrieved/sent from/to other nodes. In this aspect it is essentially different to the previous approach of Mobile ad-hoc Networks (MANET). In Manets, each device is a”router” that has to keep in someway information about the possible paths to reach a specific destination. In a certain way, a device entering a MANET assumes a compromise for routing messages according to a certain transport and routing protocol. In oppnets instead, devices act as vectors propagating the information as they move. The main thing in oppnets is related to the application layer and not to the transport layer and there is no constraint on the underlying communication standard.
Oppnets bring new problems in their implementation as privacy and security are two main issues that are still not resolved.

They may turn to be an incredible tool to monitor different variables and as an alternative communication path when the main lines are dropped after an incident like an earthquake or hurricane. They can also be used in traffic jams, crowd management, environmental monitoring, etc. The devices should be prepared to hold information and pass it at the proper moment to other friendly devices. In this message passing, like a gossip chain, information can travel across the city and reach the destination nodes. Obviously, this implies that people, cars, buses, trains, etc, act like vectors carrying the data and in this way the privacy of a person may be violated by revealing the geographical position in a certain instant. People may want to share a public profile in such a way that while moving around the city can collect information on different subjects like shop offers, traffic delays, entertainment activities, etc. By making a public profile of interests, the person may reveal sensible data that may be used maliciously. These aspects are still to be solved.

Addressing key research challenges and open issues, this complete technical guide reports on the latest advancements in the deployment of stationary relay nodes on vehicular opportunistic networks. It also illustrates the use of the service location and planning (SLP) technique for resource utilization with quality of service (QoS) constraints in opportunistic capability utilization networks. The book introduces a novel prediction-based routing protocol, and supplies authoritative coverage of communication architectures, network algorithms and protocols, emerging applications, industrial and professional standards, and experimental studies—including simulation tools and implementation test beds.
1420088122 Mobile Opportunistic Networks: Architectures, Protocols and Applications

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