Focal Design Issues Affecting The Deployment Of Wireless Sensor Networks For Pipeline

MonitoringPresented By:

K Sandeep

Dept. of Computer Science & Engineering,

Navodaya Institute of Technology

A seminar on

AbstractWireless sensor networks (WSNs) are a target

technology for oil and gas pipeline monitoring because they offer benefits of low cost, ease of deployment and ability to cater for data acquisition at great spatial and temporal scales.

It discusses the concept of cooperative communication

for pipeline- monitoring sensor networks deployed in sub-sea environments.

Content

IntroductionEnd-User View of Manufacturing WSNFeatures of WSN’SCritical RequirementsPipeline monitoring wireless sensor networkArchitectureOverview of key design issuesConclusionReferences

IntroductionWireless Sensor Networks (WSN)

Autonomous sensing networks comprised of many cheap sensing nodes.

Energy ConstrainedOften deployed in remote

or hard to access.

In this ppt we identify vital design issues that must be considered to facilitate the employment of WSN for pipeline monitoring.

End-User View of Manufacturing WSN

LikesMobilityCompactnessFlexibilityLow costShort range (security)Ease of installation

Dislikes Complexity High cost for coverage in

large plants Portability issues (power) Too risky for process control Lack of analysis tools

Features of WSN’s

The following are the features of WSN’s

Small SizeWireless ArchitectureEase of deploymentUbiquitous nature

(0,0) (4,0)

(0,4) (4,4)

S1 S2

S4S3

S5

Fields of application of wireless sensor

networks

Critical Requirements

Oil and gas pipelines transverse several kilometers of hazardous inaccessible terrains.

The cost implications of a wired sensor network will be counter-productive.

Due to longer distances, it makes it difficult and uneconomical to access.

Architecture of Pipeline Monitoring Wireless Sensor Network

Made up of sensor nodes to accomplish a common task.

Breaks long distances into a series of shorter hops.

Finds alternative routes to maintain data transmission.

Capable of event localization to determine where an incident has occurred.

Overview Of Key Design issues

The surveillance part collects information from the environment.

Acquiring information is a fundamental design issue for every network.

Affected by highly non-linear spatial and temporal processes.

Must differentiate one type of physical anomaly from the other.

Classification Of Issues

We can classify these issues in the following categories:

Sensing ModalityPower EfficiencyEnergy HarvestingNetwork ReliabilityLocalization

Sensing modality

Sensors are of different type – uni-directional, multi-directional, omni-directional.

Coverage of each sensor is determined by the kind of sensing.

The sensor placement is in-deterministic

The sensor however are not dynamic enough to assume a deterministic position to assume maximum coverage.

Sensing Modality cont…Sensors are employed for pipeline monitoring using:

Steady-state detection methodsTransient detection methods

Steady-state detection methods are used when the physical condition of pipelines are expected to remain relatively unchanged over time.

Required to distinguish between the normal operational and anomaly.

Ineffective for pipelines that undergo continuous transient changes and also for long transmissions.

Transient detection methods on the other hand are useful for scenarios where the variables experienced by operational pipelines change rapidly over time.

The method exploits the hydraulic behavior of the pipeline.

Transient based methods have been increasingly used for pipeline monitoring.

Pipeline monitoring WSN technologies must however utilize suitable detection methods to facilitate effective monitoring.

Power ConservationMore concern where the gateway nodes have access to

dedicated power supply.

Such scenarios may occur when the infrastructure is deployed at certain environments where power is available, for instance at reservoirs, pumping stations or heat stations.

However in most scenarios, dedicated power supply is unavailable such that the nodes rely entirely on battery power.

The key design issue is thus to consider factors that can sustain battery life.

Factors that can sustain battery life.

Sensor type and cell capacityCommunication standardCommunication protocolData fusionPhysical deployment

Energy HarvestingIncrease the field lifetime of the nodes.Energy harvesting allows on-site charging of rechargeable batteries,

which can be cycled hundreds of times before their performance degrades.

With proper hardware and energy management, the lifetime can be extended almost indefinitely. For example, a NiMH battery will decrease to 80% of its rated capacity after about 500 full cycles. However, if it is cycled daily at only 10% of its capacity, the lifetime will increase to 5000 cycles, or about 13 years.1

The critical issue is the need to harvest and store these energies in small-scale magnitudes that are applicable to WSN.

Thus the focus is to investigate energy harvesting technologies for self-sustainable pipeline monitoring battery powered sensor nodes.

Localization in WSNWhat?

To determine the physical coordinates of a group of sensor nodes in a wireless sensor network (WSN)

Due to application context, use of GPS is unrealistic, therefore, sensors need to self-organize a coordinate system

Why?

To report data that is geographically meaningful

Services such as routing rely on location information; geographic routing protocols; context-based routing protocols, location-aware services

Localization cont….Location information is taken for granted in many network

designs, e.g. geographic routing

Nodes can often measure their distances to nearby nodes, e.g. ultra-wideband ranging

The network localization problem is to determine the positions of all the nodes.

Equipping each node with GPS is not always feasible due to power constraints and other limitations inherent to sensor networks

The cost implication of sensor nodes with GPS capability may increase the overall cost of the WSN.

GPS signals may be unable to penetrate concrete or metal pipe walls.

Localization cont…Mapping technique on the pipeline where each sensor node is

required to provide a form of unique identification.

The shortcoming of this method is that a problem of scalability

may arise in large networks.

In Crossbow Technology it uses combination of ultra-sound and RF signal strength to determine the location of nodes and relative defects.

It’s results indicate an accuracy of a couple of centimeters.

RIPS is also used where two radio transmitters operating at slightly different frequencies to provide an interference signal capable of determining ranging information for localization.

Network ReliabilityMajor challenges is to ensure end-to-end data delivery.

Creating increased redundancy paths is invaluable for pipeline monitoring because some nodes are expected to experience hardware failure during the lifetime of the network.

Sparse deployment results in limited routing alternatives and inability to cater for node and link failures.

It may also create power inefficiency due to long range transmission.

A high density of sensor nodes may not be completely advantageous because it may increase the overall cost of the network.

Network Reliability cont…

Sensor node failure is a major issue that hampers network reliability.

During the lifetime of the technology, some nodes will become inactive as a result of energy depletion.

Failure also be caused by hardware malfunction, node displacement, and by external factors like environmental changes and security breach.

It results in holes which are created in the network topology causing loss of connectivity.

Network Reliability cont…To achieve network reliability, 2 mechanisms are used packet

loss recovery network congestion control.

Packet loss recovery:Packets may get lost in transit as a result of collision, resulting

in node failure and link failure. The aim of packet loss recovery is to detect and correctly

reinstate lost packets.

Network congestion control:Occurs when the magnitude of the acquired data supersedes

the capacity. Congestion can hamper data detection at the gateway node

even when the sensor node effectively collects data.

Conclusion

The low cost, simple deployment and flexible attributes of WSN makes the technology impeccable for pipeline monitoring.

Their ease of installation allows easy distribution in inaccessible terrains where pipelines may transverse.

In order for WSN to meet present day pipeline- monitoring requirements, certain design requirements are inevitable.

ReferencesN. Graham, Smart infrastructure: wireless sensor networks for

condition assessment and monitoring of civil engineering infrastructure, MESSAGE, EPSRC Joint Project Between Imperial College London and University of Cambridge, 2010.

Y. Jin, A. Eydgahi, Monitoring of distributed pipeline systems by wireless sensor networks, in: Proceedings of the 2008 IAJC-IJME International Conference, 2008.

N. Baker, The Four Rs of Reliability, Article of Sensicast Systems,2006.

A. Sabata, Remote Monitoring of Pipelines Using Wireless Sensor Networks, United States Patent, Patent No. 7526994B2, May 2009.

C. Ludlow, Energy Harvesting with Piezoelectric Sensors, Mide Engineering Smart Technologies Article, May 2008

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