Research issues in wireless Sensor Research issues in wireless Sensor networksnetworks

Presented by: Brajendra Kumar Singh

Course: Wireless Communications Systems 88-563 Winter 2007 Semester

Instructor: Dr. Kemal E. Tepe

Department of electrical and computer engineeringUniversity of Windsor,

Windsor, Ontario, Canada

Introduction Wireless sensor network:

Massively distributed, untethered, and unattended systems to cover spatially distributed phenomena in natural & obstructed environments

A sensor node is a Single-chip systems with Low-power CPU and less memory, Radio or optical communication MEMs-based on-chip sensors Referred to as “motes” or “smart dust” Mote applications are deeply tied to hardware Each mote runs a single application at a time.

Driven by interaction with environment Event arrival and data processing are concurrent activities

Reliability It must collect data without human interaction for months at a time. No real

recovery mechanism in the field except for automatic reboot. In-network processing Self configuring system

Sensor nodes scattered in a sensor field

The components of a sensor nodeSource: Ref[1]

Example of some sensorsSource: Ref[4]

OS and ProgrammingOS and Programming TinyOS

designed for network embedded systems. the core OS requires 400 bytes of code and data memory, combined. a component-based architecture, a simple event-based concurrency model

nesC nesC is an extension of C Whole-program analysis nesC is a static language nesC supports and reflects TinyOS’s design two types of components in nesC: modules and configurations.

Simulators: Tossim Emstar Others: Shawn, VisualSense, J-Sim etc.

Group of sensor nodes in action

Source: Ref[6]

Sensors on field

Base Station

Source: Ref[6]

Tight resource constraints Energy Communications range, bandwidth Computation, storage (but not as constrained as energy

and communications – computation is often used to reduce communication)

Dynamically changing network topology Battery depletion Node failure Node mobility Unreliable links (noise, jamming)

Dynamically changing bandwidth, range, and computation power Interactions

Computation constraints lead to uneven power depletion which leads to network topology changes

Correlated bursts of traffic across neighboring nodes not a collection of independent point-to-point flows violating the design assumptions of common media

access protocolsWireless transmission is unreliable

Sensor Network ChallengesSensor Network Challenges

Factors influencing design of WSNFactors influencing design of WSN

Fault tolerance, Scalability, Production costs, Operating environment, Sensor network topology, Hardware constraints, Transmission media, Power consumption Data Management Geographic routing challenges Monitor and Maintenance

Sensor network modelSensor network model

THE PHYSICAL LAYEROPEN RESEARCH ISSUES Modulation schemes:

Simple and low-power modulation schemes needed can be either baseband or passbandSolution Strategy: overcome signal propagation effects

Hardware design: Tiny, low-power, low-cost transceiver, sensing, and

processing units needed Power-efficient hardware management strategies Solution Strategy: managing frequencies of operation reducing switching power predicting work load in processors

DATA LINK LAYEROPEN RESEARCH ISSUES

MAC for mobile sensor networks: Self-Organizing Medium Access Control for Sensor Networks (SMACS)

and the Eavesdrop-And-Register (EAR) Algorithm perform well for mainly static sensor networks. It is assumed in the connection schemes that a mobile node has many static nodes as neighbors.

In CSMA-based scheme, the mobility issues and carrier sensing mechanisms remain largely unexplored.

Determination of lower bounds on the energy required for sensor network self-organization

Error control coding schemes: Convolution coding effects have been explored. The feasibility of other

error control schemes in sensor networks needs to be explored. Power-saving modes of operation:

a sensor node must enter into periods of reduced activity when running low on battery power. The enumeration and transition management for these nodes is open to research.

NETWORK LAYEROPEN RESEARCH ISSUES Existing protocols need to be improved or new protocols

developed to address higher topology changes higher scalability

An overview of network layer schemes

• Exploit Redundancy

• Tiered Architectures

• Exploit spatial diversity and density of sensor networks

• Achieve desired global behavior with adaptive localized algorithms

• Leverage data processing inside the network and exploit computation

near data sources

• Time and location synchronization

• Self-configuration

• Secure routing

Source: Ref[5]

Open Research Issues for routingOpen Research Issues for routing

NETWORK LAYERContinued…..

Fruits are not so low in the Routing research area

TRANSPORT LAYER

OPEN RESEARCH ISSUES

Acknowledgments are too costly (As needed in TCP/IP)

Split the end-to-end communication UDP-type protocols are used in the sensor network traditional TCP/UDP protocols in the Internet or

satellite network

THE APPLICATION LAYER

Open research issues Three possible protocols

Sensor Management Protocol (SMP),

Task Assignment and Data Advertisement Protocol (TADAP)

Sensor Query and Data Dissemination Protocol (SQDDP)

SQDDP is explored a lot, but SMP and TADAP are still open for research.

• Routing Algorithms with secure foundations

• Optimize Secure Data Management Algorithms (Aggregation)

• Social and Network privacy

• Mobile nodes, Mobile Base Stations

• Delegation of privileges

• Tolerate the lack of physical security

• Intrusion Detection techniques, integrated IDS

Efficient Data Dissemination Protocols

Reliable Transport Protocols

Congestion Control and Avoidance Techniques

Sensor Network Measurements

Open Research Areas - 1Open Research Areas - 1

• Programming models, architectures, tools Programming abstractions, service architecture, resource mgmt

• Computing with uncertainties Uncertainties about environment and system itself Models of reliability, resource-aware and task-oriented

computation, software architectures Consider both application and networking

Simultaneously Vs Separately

• Quality of service guarantees built in to the network protocols

Real-time support in sensor networks- Network support for classes of traffic not for specific applications

- Precise network provisioning not realistic in sensor networks Innovative applications

In areas such as security, transportation, healthcare

Open Research Areas - 2Open Research Areas - 2

Scheduling Challenges Uncertainty:

nondeterministic processing algorithms, communication noise

Dynamics: robustness to topology and resource changes

Deep, multi-hop data flows Scale Providing decision-theoretic objective tradeoffs

Some Approaches to Handling Scheduling Problems Static schedules that are robust to uncertainty and time-varying

constraints Network provisioning for redundant paths On-line scheduling

- Not practical in tight computation nodes - Introduces latency

Off-line construction of conditional schedules that adapt to sensor feedback, topology changes, and task changes

Open Research Areas - 3Open Research Areas - 3

Integrated Communication and Computation Scheduling Problem (Load balancing problem)

Parallel, distributed computation Sensor processing Task data flow, e.g. aggregation, in-network processing

Communication Broadcast links: interference, range

Synchronization of computation and communication to satisfy task Objective Function:

Minimize computationMinimize computation convergenceconvergence time time Minimize latencyMinimize latency in responding to in responding to new sensor datanew sensor data Minimize total energyMinimize total energy consumed consumed Balance distribution of energyBalance distribution of energy consumed consumed

Open Research Areas - 4Open Research Areas - 4

Sensor ApplicationsSensor Applications

Just the tip of the icebergJust the tip of the iceberg

o A Wireless Sensor Network for Structural Monitoring

o For monitoring health of power lines

o Smart paint

o Wireless Sensor Networks for Habitat Monitoring

o Biomedical Sensors

o Military surveillance

Conclusion

Optimize, Optimize, Optimize!Optimize, Optimize, Optimize!

(memory constraints, energy usage…)

References

1. Ian Akyildiz., W. Su, Y. Sankarasubramaniam, E. Cayirci, "A Survey on Sensor Networks", IEEE Communications Magazine, August 2002

2. David Culler, Deborah Estrin, and Mani Srivastava, "Overview of Sensor Networks", IEEE Computer, August 2004

3. Chee.-Yee. Chong and Kumar, S.P., "Sensor Networks: Evolution, Opportunities, and Challenges," Proc IEEE, August 2003

4. David Gay, Phil Levis, Rob von Behren, Matt Welsh, Eric Brewer, and David Culler, "The nesC Language: A Holistic Approach to Networked Embedded Systems", Programming Language Design and Implementation (PLDI) 2003, June 2003

5. Al-Karaki, J.N. Kamal, A.E., Routing techniques in wireless sensor networks: a survey, Wireless Communications, Volume 11, Issue 6, Dec. 2004

6. Deepak Ganesan , Alberto Cerpa , Wei Ye , Yan Yu ,Jerry Zhao , Deborah Estrin, "Networking Issues in Wireless Sensor Networks" Slides Slides internet, 2005

ThanksThanks

Questions and suggestions?

Some facts

TinyDB a sensor network query processing engine,

Mate a small virtual machine that allows rapid reprogramming of sensor networks.

nesC Vs C: C does have significant disadvantages: it provides little help in writing safe code or in structuring applications. nesC addresses safety through reduced expressive power and structure through components.

Differences between sensor networks and ad hoc networks are:

The number of sensor nodes in a sensor network can be several orders of magnitude higher than the nodes in an ad hoc network.

Sensor nodes are densely deployed. Sensor nodes are prone to failures. The topology of a sensor network changes very

frequently. Sensor nodes mainly use a broadcast communication

paradigm, whereas most ad hoc networks are based on point-to-point communications.

Sensor nodes are limited in power, computational capacities, and memory.

Sensor nodes may not have global identification (ID) because of the large amount of overhead and large number of sensors.

Transmission media based on RF circuit design

The uAMPS wireless sensor node uses a Bluetooth-compatible 2.4 GHz transceiver with an integrated frequency synthesizer.

The low-power sensor device uses a single-channel RF transceiver operating at 916 MHz.

based on infrared. Infrared communication is license-free robust to interference from electrical devices. cheaper and easier to build. Smart Dust mote computing Both infrared and optical require a line of sight between the

sender and receiver.

Power Consumption A limited power source (< 0.5 Ah, 1.2 V). Power-aware protocols and algorithms for sensor networks.

The main task of a sensor node detect events, perform quick local data processing transmit the data

Power consumption can hence be divided into three domains:

sensing communication data processing

Embaded Network Sensing Research focus

Network Self-Network Self-OrganizationOrganization

Programming Programming modelsmodels

Database policiesDatabase policiesand architectureand architecture

SensorsSensors

Connection toConnection toinfrastructureinfrastructure

Cooperative DetectionCooperative DetectionCommunicationCommunication

LinksLinks

TheoreticalTheoreticalframeworkframework

Node LocalizationNode Localization

Mobility andMobility andnavigationnavigation Target IdentificationTarget Identification

AlgorithmsAlgorithms

System EnergySystem EnergyManagementManagement ActuationActuation

HumanHumaninterfaceinterface

Modeling ofModeling ofEnvironmentEnvironment

CalibrationCalibration