Post on 30-May-2018
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Opportunistic Networking :Data Forwarding indisconnected mobile ad
hoc networks
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Abstract
Opportunistic networks are on of the mostinteresting evolution of MANETs
Opportunistic network mobile nodes areenabled to communication with each node
Routes are built dynamicallymessage are en route between sender a
destinationNode can opportunistically be used as next
hop This method is to bring message closer to the
final destination
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Introduction
Research on multihop ad hoc network has afocused on a number of applicationenvironment
Originally conceived for military application,and aimed at improving battlefieldcommunication
Two main evolutions of multihop ad hocnetwork are mesh network and
opportunistic networkOpportunistic network no assumption is
made with regard to the existence of complete path between two nodes wishing
to communicationConce t of o ortunistic network come from
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Taxonomy of routing/forwardingtechniques for Opportunistic Network
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Delay-tolerant network
Delay-tolerant network (DTN) architectureconsists of
DTN RegionDTN Gateway
Use protocol stack that best suit theparticular infrastructure
DTN node overlay protocol is added on top of the traditional transport layer
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6
Delay-tolerant network
Architecture
Region A - InternetRegion A - Internet
Region B Sensor networkRegion B Sensor network
data
data
data
data
UserHost{A, UserHost}
{A, R1}
{B, R2}
{B, R3}
{D, R4}
{A, R2}
{C, R3}
{C, R4}
DTN gatewaySource : http://www-net.cs.umass.edu/~shyang/presentation_slides/DTN.ppt
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Delay-tolerant network
Example of delay-tolerant network
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Opportunistic Network
Opportunistic networking
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Realistic Case Studies
PSNs in the Haggle ProjectWildlife Monitoring :
ZebranetSWIM
Opportunistic Network for Developing AreasDarkNetSaami Network Connectivity (SNC)
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Realistic Case Studies
Research on opportunistic network isdevoting particular attention to realisticcase study
On of the basic component realistic casestudies are mobility models
Design of efficient forwarding algorithm aswell as to perform realistic simulation
Researchers are also implementing a numberof real-application scenarios inopportunistic network
For example, with wildlife trackingapplication
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Haggle Project
It targets solutions for communication inopportunistic network
Funded by European Commission in theframework of the FET-SAC
Studying the properties on Pocket SwitchedNetworks (PSNs)
Pair-wise modeling contacts between devices
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Wildlife Monitoring : ZebraNet
Biologists want to track animalsLong-termOver long distances
Questions:Interactions within a species?Interactions between species?Impact of human development?
Source : http://www.princeton.edu/~mrm/zebranet.html
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Wildlife Monitoring : ZebraNet
Source : http://www.princeton.edu/~mrm/ZNetASPLOS.pdf
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ZebraNet Protocols
Two peer-to-peer protocols evaluated hereFlooding : Send to everyone found in peer
discovery.History-Based : After peer discovery, choose
at most one peer to send to per discoveryperiod: the one with best past history of delivering data to base.
Simulation results show that both protocolsoutperform the directly protocol
History-based protocol outperforms floodingin term of bandwidth and energyconsumption
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Wildlife Monitoring : SWIM
In the Shared Wireless Infostation Model(SWIM) whales are monitored.
Data is replicated and diffused (similar to theflooding protocol in ZebraNet)
Both whale-to-whale and whale-to-base-station communications are allowed
No experimental result are actually availablebut simulation results are quite realisticsince simulation parameter set accordingto studies conducted by biologist whalesreal habits
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Opportunistic Network for DevelopingAreas : Darknet
It aims to provide a low-cost InternetConnectivity to rural villages in India
Kiosks are built up and equipped digitalstorage and short-range wirelesscommunication
MAPs exchange data with the kioskswirelessly
MAPs can download/upload data to theInternet when passing by APs in a nearbytown
It supports Internet/Intranet messaging,distribution and collection information
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Opportunistic Network for DevelopingAreas : SNC
It aims to provide network connectivity to thenomadic Saami population of the reindeerherders
Providing network connectivity is a mean toprotect their habits, culture and tradition
In its initial stage, it focused on providingemail, file transfer, and cached webservices
It should finally be noted that the SNC projectfocuses on a pure DNT architecture
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Dissemination-Based Routing
Based on data dissemination performdelivery a message to destination bydiffusing it all over the network.
No knowledge of a possible path todestination and nor of appropriate of next-hop
Works well on mobile networkLimits message delay but is resource hungry.May lead to network congestion
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Dissemination-Based Routing
Such asEpidemic Routing ProtocolMV Routing ProtocolNetwork Coding-Based Routing Protocol
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Epidemic Routing protocol
Goal is to deliver messages with highprobability even when there is never a fullyconnected path.
Give a message copy to every nodeencountered
essentially: flooding in a disconnectedcontext
Source : http://www.cise.ufl.edu/~helmy/cis6930-09/Epidemic-and-Ferry.ppt
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Mv routing protocol
A further step beyond epidemic routingMessages exchanged during pair-wise
contacts as in epidemic routing but usemore sophisticated method to selectmessages to forward to a
Deliver probability is relied on recent-pastobservation of both meeting betweennodes and the visits of nodes to
geographical locationA similar approach is followed in PROPHET
routing protocol
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Network coding-based protocol
Takes an original approach to limit messageflooding
Outperform flooding as it is able to deliverthe same information with a fewer numberof messages infected into the network
See example on next slide
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Example of network-coding efficiency
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Context-based routing
Exploits more information about the contextso as to identify suitable next hops towardsthe destinations (e.g., the home address of a user)
Reduce messages duplication Tend to increase the delay that each
message experience during deliveryDue to errors and inaccuracies in selecting
the best relays
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Context-based routing (contd.)
Nodes maintain a state in order to keep trackof the utility values
Need storage capacity for both state andmessages
Cost to hold and update the state at eachnode (overhead)
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Context-aware routing (CAR) Protocol
Each node is in charge of producing deliveryprobabilities towards each destination host
Delivery probabilities are exchanged so thatnode compute the best carrier fordestination node based on the nodescontext
When the best carrier receives a message, itstores it in a buffer and forwards it to the
destination node when metCAR provides a framework for computing
next hop based on the multiattribute utilitytheory
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Mobyspace : mobility pattern spacerouting protocol
The nodes mobility pattern is the contextinformation used for routing
The protocol builds up a high dimensionalEuclidean space
Each axis represents a possible contactbetween a couple of nodes
The distance along an axis measures theprobability of that contact to occur
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Example scenario
Source : http://jeremie.leguay.free.fr/lip6/files/poster_sigcomm05.pdf
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Node mobility pattern
Source : http://jeremie.leguay.free.fr/lip6/files/poster_sigcomm05.pdf
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Routing with infrastructure
Routing based on fixed infrastructureRouting based on mobile infrastructure
(carrier-based routing)
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Routing based on fixed infrastructure
A source node delivery a message keeps ituntil it reach a base station belonging tothe infrastructure
Then forwards the message to itBase station are gateways towards less
challenged networks (e.g. connected to aLAN)
The goal of an opportunistic routingalgorithm is to delivery messages to thegateways, which are able to find thedestination more easily
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Two variations of the protocol
1. First, only node-to-base-stationcommunications
Work as described abovemessages experience high delays
The example of this approach is theInfostation model
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Routing based on mobile infrastructure(carrier-based routing)
Nodes of the infrastructure are mobile datacollectors
They move around in the network area andgather messages from the nodes they passby
These special nodes are referred to ascarriers, supports, forwarders, MULEs, oreven ferries
They are entities responsible for messagesdelivery
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Routing based on mobile infrastructure(carrier-based routing) contd.
Node-to-carrier communicationshelp increasing connectivity in sparse
network and guaranteeing that isolatednodes be reached
delivery of messages is accomplishedBoth by carriers and ordinary nodesBoth node-to-node and node-to-carrier
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The data-mule system
Focus on data retrieval from sparse wirelesssensor networks
Consist of a three-tire architecture:The lower level : sensor nodes periodically
perform data sampling from the surroundingenvironment
The middle level : mobile agents (MULEs)move around in the area to gather theirdata
The upper level : a set of wired Aps and datarepositiories which receive information fromthe MULEs and connected to a central datawarehouse
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The message-ferrying approach
Extra mobile nodes (message ferries) areexploited to offer a message relayingservice
Nodes move around in the network They collect messages from source nodes
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Message collection happen intwo ways:
Node-initiated message ferrying :the ferry node moves around a predefined and
known pathEach node has knowledge of the path by
ferriesnode moves to meet ferries when it has data
to deliver
Ferry-initiated message ferrying :source node sends a ServiceRequest and
current position to the ferrythe ferry changes trajectory to meet the
source node
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Conclusion
Taxonomy of routing/forwarding techniquesfor opportunistic networks : without andwith infrastructure
Interesting is how to design multitieropportunistic networks
The data MULEs and message-ferryingarchitectures are the most promisingapproach
In the data MULEs approach, lower levelnodes exploit the higher level and mobiledevice(the MULEs)
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Future trends
Each level of the infrastructure is anopportunistic network in which nodes mayexploit routing algorithms to communicate
and may rely on the upper levels of theinfrastructure to reach nodes are too faraway
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Future trends (contd.)
For example, lower level : devices (e.g. PDA,smart phone)
An opportunistic routing algorithm makedevices to communicate with each other
Higher level : city-bus network might be used, bus act as MULEs
City-bus network might exploit further levelsuch as mesh network
Opportunistic network might representa fundamental building block for the next-generation internet