SeminarSeminaronon

Joint Scheduling for Joint Scheduling for Wireless Sensor Wireless Sensor

NetworkNetwork

(Proposed by: Chong Liu, Kui Wu, Yang (Proposed by: Chong Liu, Kui Wu, Yang Xiao, Bo Sun)Xiao, Bo Sun)

Presented by:Presented by:

Saurav Kumar BenganiSaurav Kumar Bengani

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ContentsContents

• WSN Scheduling RequirementsWSN Scheduling Requirements• Assumptions for proposed MethodAssumptions for proposed Method• Randomized Scheduling AlgorithmRandomized Scheduling Algorithm• Joint Scheduling AlgorithmJoint Scheduling Algorithm• Extra-On RuleExtra-On Rule• Case StudyCase Study• ConclusionConclusion• ReferencesReferences

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WSN Scheduling WSN Scheduling RequirementsRequirements

• To optimize the energy consumption.To optimize the energy consumption.

• Sensor nodes are very small with Sensor nodes are very small with limited energy supplies.limited energy supplies.

• In WSN hard to replace batteries due In WSN hard to replace batteries due to large numbers and hostile to large numbers and hostile environment.environment.

• Sensing coverage and Network Sensing coverage and Network connectivity should not be reduced.connectivity should not be reduced.

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Assumptions for proposed Assumptions for proposed MethodMethod

• Flat Communication architecture.Flat Communication architecture.

• Sensor nodes are stationary.Sensor nodes are stationary.

• Sensor nodes are randomly deployed.Sensor nodes are randomly deployed.

• Sensor node’s radio transmission Sensor node’s radio transmission

range is fixed and independent from range is fixed and independent from

the sensing range.the sensing range.

• No assumption for accurate global No assumption for accurate global

time synchronization.time synchronization.

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Randomized Scheduling Randomized Scheduling AlgorithmAlgorithm

• It is a purely distributed algorithm It is a purely distributed algorithm with resilience to time asynchrony.with resilience to time asynchrony.

Example of Randomized Scheduling Algorithm

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Joint Scheduling AlgorithmJoint Scheduling Algorithm

• Guaranty the network connectivity after Guaranty the network connectivity after Randomized Coverage scheduling.Randomized Coverage scheduling.

• In addition to sensing coverage, the sensor network must remain connected.

• It enhance the above randomized scheduling algorithm such that both coverage quality and network connectivity can be met at any given time.

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Extra-On RuleExtra-On Rule• Extra-on rule: If a sensor node A has a downstream Extra-on rule: If a sensor node A has a downstream

node B, which is active in time slot i, and if none of node B, which is active in time slot i, and if none of node B’s upstream nodes is active in that time slot, node B’s upstream nodes is active in that time slot, then node A should also work in time slot i.then node A should also work in time slot i.

• Extra-on rule ensures that each sub network is Extra-on rule ensures that each sub network is connected, given that the original network before connected, given that the original network before scheduling is connected.scheduling is connected.

• This rule requires each sensor node to maintain its This rule requires each sensor node to maintain its minimum hop count to the sink node and the list of minimum hop count to the sink node and the list of its upstream nodes.its upstream nodes.

• Joint scheduling based on the extra-on rule works Joint scheduling based on the extra-on rule works correctly in face of network failure without requiring correctly in face of network failure without requiring periodical update of the minimum hop count values.periodical update of the minimum hop count values.

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Case StudyCase Study(An Example of Joint Scheduling Algorithm)(An Example of Joint Scheduling Algorithm)

Step 1: Select a Subset Randomly.Step 1: Select a Subset Randomly.

Step 2: Propagate Minimum Hop Count.Step 2: Propagate Minimum Hop Count.

Step 3: Exchange information with local Step 3: Exchange information with local neighbors.neighbors.

Step 4: Enforce the extra-on rule.Step 4: Enforce the extra-on rule.

Step 5: Work according to the new working Step 5: Work according to the new working schedule.schedule.

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ConclusionConclusion• It can achieve substantial energy saving and It can achieve substantial energy saving and

meet both constraints of coverage and meet both constraints of coverage and connectivity without relying on location connectivity without relying on location information or any assumptions on the information or any assumptions on the relationship between the sensing range and the relationship between the sensing range and the radio range.radio range.

• It is totally distributed and, thus, easy to It is totally distributed and, thus, easy to implement.implement.

• Each active sensor node knows at least one Each active sensor node knows at least one route with minimum hop count to the sink node. route with minimum hop count to the sink node. which solves the routing problem and eliminates which solves the routing problem and eliminates the system cost incurred by routing protocols.the system cost incurred by routing protocols.

• The scheduling method is resilient to time The scheduling method is resilient to time asynchrony.asynchrony.

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ReferencesReferences

• Chong Liu, Student Member, IEEE, Kui Wu, Member, IEEE, Yang Xiao, Senior Member, IEEE, and Bo Sun, Member, IEEE (IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS, VOL. 17, NO. 6, JUNE 2006).

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Thank YouThank You

Queries?Queries?