Reliable Message Forwarding in Opportunist Networks: A New Horizon
In mobile ad-hoc networks, before information sharing, devices have partial or complete knowledge of routes to the destinations using ad-hoc routing protocols. This kind of communication can only be realised if nodes follow a certain pattern. However, in reality, mobile ad-hoc networks are highly unpredictable as any node can join or leave the network at any time. This ubiquitous nature makes these networks unsafe in terms of for reliable communication. This issue is addressed by introducing new breed of ad-hoc networking termed as opportunistic networks.
In opportunistic networks, nodes have no prior knowledge of routes to intended destinations. Any node in the network can be used as potential forwarder with the anticipation of taking information one step closer to intended destination. The forwarding decision is based on the information gathered from the source node or encountering node. The opportunistic forwarding can only be achieved if message forwarding is carried out in store-and-forward fashion. Although, opportunistic networks are more flexible than traditional MANETs, however, due to little insight of network, it poses distinct challenges such as intermittent connectivity, variable delays, short connection duration and dynamic topology. Addressing these challenges in opportunistic network is the basis for initiatives to develop novel efficient protocols for information sharing.
One of the major research directions in this regard is to design routing/forwarding techniques for improving overall message delivery at destinations while keeping the communication cost very low. Some assumptions are considered to improved directivity of message flow towards intended destinations. These assumptions exploit human social relationship analogies, approximate awareness of the location of nodes in the network and use of hybrid communication by combining several routing concepts to gain maximum message directivity.
Enhanced message forwarding in opportunistic networks can be achieved by targeting key nodes that show high degree of influence, popularity or knowledge inside the network. Discussing the following protocols with regards to forwarding in opportunistic networks is important;
Lobby Influence based protocols, in which the forwarding decision is based on two important factors, popularity of node and popularity of node’s neighbour. [1]
Enhanced Lobby Influence, where the forwarding decision depends on the intermediate node selection criteria and on the knowledge of previously directed message delivery of intended destination. [2]
Location-aware opportunistic content forwarding (LOC) that depends on the knowledge of nodes position in the network, resulting in high message directivity primarily through use of direction vectors. [3]
Hybrid content forwarding (HCF) that combines the characteristics of social centrality based forwarding techniques used in opportunistic networks with traditional MANETs protocols used in Bluetooth scatternets. [4]
Future Research
There is a lot going on in the area of social sciences that can be used for the purposes of opportunistic forwarding. For instance, the way humans behave socially evolves every now and then, can be incorporated with technology to further enhance opportunistic routing/forwarding protocols.
These days, most of the mobile phones are capable of communicating using various communication technologies simultaneously. The use of multiple communication technologies to learn about the location of intended destination in an opportunistic network can further enhance the node’s ability to locate a desired node. Exploring this area has lot of potential for development of new enhanced location aware techniques.
There is an incentive in using opportunistic communication as an alternate communication infrastructure. In disaster situations or during the war for instance, when the main telecom infrastructure is no more operational, opportunistic networking can be used as an alternative for a rather quicker and cheaper communication.
References
[1] S. K. A. Khan et. al., “Lobby Influence: Opportunistic forwarding algorithm based on Human social relationship”, proceedings of the International Workshop on the Impact of Human Mobility in Pervasive Systems and Applications, 2012
[2] S. K. A. Khan et. al., “Enhanced Lobby Influence: Knowledge based content forwarding algorithm for opportunistic communication networks”, proceedings of the 20th International Conference on Software, Telecommunications and Computer Networks, 2012.
[3] S. K. A. Khan et. al., “LOC: Location-aware opportunistic content forwarding using direction vectors”, proceedings of the IEEE Symposium on Computers & Informatics, 2013
[4] S. K. A. Khan, J. Loo, M.A. Azam, H. Sardar, M. Adeel & L. N. Tokarchuk (2012), “Hybrid content forwarding technique for Bluetooth communication environment”, proceedings of the 20th International Conference on Software, Telecommunications and Computer Networks, 2012.
Author’s Profile
Sardar Kashif Ashraf Khan holds MPhil degree in Electronic Engineering from Queen Mary University of London and a PhD degree in from Middlesex University. He has vast industrial and academic research experience in telecoms and networking sectors. He has remained associated with organisations like Ericsson UK and Huawei UK on various consultancy roles. His research interests include IP routing & switching, ad hoc networks, sensor networks, social Networks, ubiquitous computing and IP based 2G/3G/4G technologies.
