Highly-Resilient, Energy-Highly-Resilient, Energy-EEffifficient Multipath Routing cient Multipath Routing ininWireless Sensor NetworksWireless Sensor Networks

Computer Science Department, UCLAComputer Science Department, UCLAInternational Computer Science Institute, BerkeleyInternational Computer Science Institute, Berkeley

ACIRI, BerkeleyACIRI, Berkeley

AboutAboutPeriodic low-rate flooding of data in

order to allow recovery from failure.Multipaths for energy efficient

recoveryDisjoint multipath schemeBraided multipath schemeBraided multipaths are viable

alternative for energy-efficient recovery from isolated and patterned failures

IntroductionIntroductionDirected DiffusionEarlier work has explored the

design of mechanisms for single-path routing in sensor networks

To route around failed nodes, this work assumed periodic, low-rate, flooding of events that enabled local re-routing around failed nodes

IntroductionIntroductionMultipath routingDisjoint multipathBraided multipathResilienceMaintenance OverheadEvaluating the two mechanisms:

isolated node failures and patterned failures

Direct DiffusionDirect DiffusionDirected Diffusion

Direct DiffusionDirect DiffusionUsing directed diffusion to perform

energy-efficient and robust dissemination of surveillance data samples from sources to sinks

Low rate samplesPath reinforcementRecovery from failure along

reinforcement pathThe problem is low-rate flooding

scheme

Direct DiffusionDirect DiffusionDirect Diffusion for energy-

efficient data samples from source to sinks.

Multipath RoutingMultipath RoutingClassic Multipath Routing usageUsing multipath routing in this paperPrimary pathConstruct and maintain a small

number of alternate paths (without periodic flooding)

When primary path is set up, alternate paths also sets up multipaths which data is send low-rate

No network wide flooding needed

Disjoint MultipathsDisjoint MultipathsSmall number of alternate paths

that are node-disjoint with the primary path, and with each other

How do we realize node disjoint multipaths using localized information alone, and not relying on global topology information?

Primary and alternate path reinforcement

Localized disjoint multipaths are differ from idealized multipaths

Construction of Localized Construction of Localized Disjoint PathsDisjoint Paths

Braided MultipathsBraided MultipathsDisjoint multipaths can be energy

inefficientAlternate paths in a braid are partially

disjoint from the primary path, not completely node-disjoint

For each node on the primary path, find the best path from source to sink that does not contain that node

All paths are called idealized braided

Braided MultipathsBraided MultipathsLocalized technique for

constructing braids. Nodes send reinforcement to

route neighbours.The alternate paths can rejoin

the primary path

Braided MultipathsBraided Multipaths

Braided MultipathsBraided Multipaths

Qualitative ComparisonQualitative ComparisonEnergy/resilience tradeoffs of the two

multipath schemesThe energy cost of alternate disjoint

paths depends on the network densityThe resilience of these multipaths to

failure (isolated failures and patterned failures)

Disjoint paths give us independence, but the failure of a single node on each alternate path results in the failure of the multipath.

Qualitative ComparisonQualitative ComparisonBy contrast, in braided multipaths, the

various alternate paths are not independent, and a combination of failures on the primary path could sever all alternate paths

How much additional energy must one expend in order to increase resilience by a fixed amount?

How does the energy/resilience tradeoff vary with density or with the extent and frequency of patterned failures?

How closely do the localized schemes approximate their idealized counterparts?

Evaluation MethodologyEvaluation MethodologyMaintenance overheadResilienceFailure models for which we

evaluated the resilience of our multipath mechanisms

Isolated FailuresPatterned Failures

FailuresFailures

Details of MethodologyDetails of MethodologyThe idealized and localized

constructions of disjoint and braided multipath in ns-2

Uniformly distributing a number of sensor nodes on a finite plane of dimension 400 meters square

Node transmission radius: 40 metersDensityThe spatial separation between source

and sink (represented by the length of the shortest-hop path between the two

Details of MethodologyDetails of MethodologyThe failure probability for isolated

failures pithe arrival rate of patterned failures

is lamda pRadius of patterned failures REach run of our experiment

corresponded to one choice of number of nodes N and and spatial separation between source and sink d

In each run, we randomly selected a large number of source-sink pairs separated by d hops

Simulation ResultsSimulation Results Impact of failure probability on resilience:

400 nodes, 6-hop source-sink separation

Simulation ResultsSimulation ResultsResilience to Isolated Failures

Simulation ResultsSimulation ResultsThe impact of density and

source-sink separation on resilience to isolated failure

Simulation ResultsSimulation ResultsResilience to Patterned Failures

Simulation ResultsSimulation ResultsThe impact of density and source-sink

separation on resilience to patterned failure

Simulation ResultsSimulation ResultsMaintenance Overhead - Density

Simulation ResultsSimulation ResultsMaintenance Overhead – Path

Length

ConclusionsConclusionsMultipath routing for energy-efficient

recoveryNo need network-wide flooding for path

discory on failureDisjoint and braided multipaths are similar,

but braided multipaths have about %50 higher resilience to isolated failures

It is harder to design localized energy-efficient mechanisms for constructing disjoint alternate paths, because the localized algorithms lack the information to find low latency disjoint paths

Increasing the number of disjoint paths does increase the resilince but this needs higher energy cost.

Questions ?Questions ?