The Design Space of Wireless Sensor Networks

Xin-Xian Liu

2005 03 22

Outline

Background Performance Metrics Sensor Network Architecture Design Space Conclusion

Background

Initial research into WSN was mainly motivated by military application

A de facto definition of WSN as a large-scale, ad hoc, multihop, tiny, resource-constrained

Sensor network

The components of a sensor node

Performance Metrics

Energy efficiency / system lifetime Latency Accuracy Fault-tolerance Scalability

Sensor Network Architecture

The network protocol is responsible for supporting all communication between the sensors and the observer

The performance of the protocol will be highly influenced by the network dynamics and by the specific data delivery model employed

Communication Models

Communication within a sensor network can be classified into two categories– Application communication– Infrastructure communication

Application communication is related to the transfer of sensed data with the goal of informing the observer about the phenomena

Communication Models

Within application communication, there are two models:– Cooperative– Non-cooperative

Communication Models

Infrastructure communication refers to the communication needed to configure, maintain and optimize operation

In sensor networks, an initial phase of infrastructure communication is needed to set up the network

Data Delivery Models

Sensor networks can be classified in terms of the data delivery required by the application interest as:– Continuous– Event-driven– Observer-initiated– hybrid

Data Delivery Models

Continuous– The sensors communicate their data continuously

at a prespecified rate Event-driven

– The sensors report information only if an event of interest occurs

Observer-initiated– The sensors only report their results in response t

o an explicit request from the observer

Data Delivery Models

The actual flow of data packets between the sensors and the observer– Flooding– Unicast– Multicast

Network Dynamics Models

The approach to construct and maintain a path between observer and phenomenon will differ depending on the network dynamics, which we classify as – Static sensor networks– Dynamic sensors networks

Static Sensor Networks

In static sensor networks, there is no motion among communication sensor, the observer and the phenomenon

Dynamic Sensor Networks

In dynamic sensor networks, either the sensors themselves, the observer, or the phenomenon are mobile

Dynamic sensor networks can be further classified by considering the motion of the components– Mobile observer– Mobile sensors– Mobile phenomena

Design Space

We informally characterize each of the dimension and, where appropriate, identify property classes in order to support a coarse-grained classification of sensor network application

Design Space

Deployment– Random vs. Manual– One-time vs. Iterative

Mobility– Immobile vs. Partly vs. All– Occasional vs. Continuous– Active vs. Passive

Design Space

Cost – The cost of a single device may vary from

hundreds of Euros to a few cents

Size– The form factor of a single sensor node may vary

from the size of a shoebox to a microscopically small particle

Design Space

Resources and Energy– Varying size and cost constrains directly result in

corresponding varying limits on the energy available, as well as on computing, storage and communication resources

– We partition sensor nodes roughly into four classes based on their physical size

brick, matchbox, grain, and dust

Design Space

Heterogeneity– Homogeneous vs. Heterogeneous

Communication Modality– Radio vs. Light vs. Inductive vs. Capacitive vs.

Sound

Infrastructure– Infrastructure vs. Ad Hoc

Design Space

Network Topology– Single-hop vs. Star vs. Networked Start vs. Tree

Coverage– Sparse vs. Dense vs. Redundant

Connectivity– Connected vs. Intermittent vs. sporadic

Design Space

Network Size– The network size may vary from a few nodes to

thousands of sensor nodes or even more

Lifetime– Depending on the application, the required

lifetime of a sensor network may range from some hours to several years

Design Space

Other QoS Requirement– Depending on the application, a sensor network

must support certain QoS aspects such as Real-time Robustness Tamper-resistance Eavesdropping resistance

Conclusion

Clearly, a single hardware platform will most likely not be sufficient to support the wide range of possible applications

A modular approach, where the individual components of a sensor node can easily exchanged

References

[1] S. Tilak, N. B. Abu-Ghazaleh, and W. Heinzelman, “A Taxonomy of Wireless Micro-Sensor Network Models,”MR2C, vol. 6, no. 2, Arp.2002, pp. 28-36

[2] Kay Romer and Friedemann Mattern, ETH Zurich, “The Design Space of Wireless Sensor Networks,” IEEE Communications Magazine, pp.54-61,December 2004