SENSOR SEnsor Network desigN and ORganization Sameer Tilak Advisor- Dr. Nael Abu-Ghazaleh Committee Members- Dr. Michael Lewis Dr. Wendi Heinzelman Copyright 2002 Sameer Tilak

Problem Overview Efficient protocol architectures for sensor networks Copyright 2002 Sameer Tilak

Introduction to Sensor Nets What is a sensor -network ? What are real world applications ? Copyright 2002 Sameer Tilak

Real World Applications Remote surveillance Temperature sensing Animal tracking in a forest Taxi-cab for traffic condition information Tornado motion/pattern study Copyright 2002 Sameer Tilak

Motivation Embed numerous distributed devices to monitor and interact with physical world: hospitals, homes, vehicles, and “the environment” Disaster Response Circulatory Net Network these devices so that they can coordinate to perform higher-level tasks. Requires robust distributed systems of hundreds or thousands of devices. Copyright 2002 Sameer Tilak

Challenges Low Battery power Low bandwidth Error-prone air medium Low computing power and memory Copyright 2002 Sameer Tilak

Unique Characteristics No end-to-end communication Co-operative operation Redundancy in information Application specific specialized networks Copyright 2002 Sameer Tilak

End-to-end Communication Client A Elton John Music www.mp3.com Can you ??? Client B Knuth’s book www.cs.stanford.edu Copyright 2002 Sameer Tilak

Co-operative + Redundancy Sensor network for animal tracking Copyright 2002 Sameer Tilak

Performance Metrics Life-time Accuracy Latency Scalability Fault-tolerance Copyright 2002 Sameer Tilak

Taxonomy Need Application specific nature Systematic classification to aid development of protocols Helpful to sensor network designer Insight into sensor-network working model Isolation of important factors Fair comparison of different protocols Copyright 2002 Sameer Tilak

Components of Sensor-Net Observer Phenomenon Copyright 2002 Sameer Tilak

Taxonomy Sensor Network Architecture Communication Models Data-delivery Models Network Dynamics / Mobility Copyright 2002 Sameer Tilak Copyright 2002 Sameer Tilak

Sensor Network Architecture Infrastructure:- Sensors and current deployment, H/W properties of sensors Network Protocol:- Creating paths for communication Observer/Application:- “Interested” in phenomenon. We classify issues that influence Network Protocol. Copyright 2002 Sameer Tilak

Communications Models Application Level Communication:- Transferring information regarding Phenomenon towards observer. Infrastructure level communication:- Communication for configure, maintain and optimize sensor network itself. (Overhead). Network protocol should support both. Copyright 2002 Sameer Tilak

Data-delivery Model Continuous:- example temperature sensing Event-driven:- example animal tracking Observer-driven:- request/reply Hybrid:- Combination of any of the above. Copyright 2002 Sameer Tilak

Network dynamics Important from comm. since degree and type of comm. Is dependant on dynamics. Mobile observer (Plane flying) Mobile phenomenon (Animal tracking) Mobile sensors (taxicab) Each of the above requires different organization, data delivery models and thus different protocols. Copyright 2002 Sameer Tilak

Addressing Mobility in SN Again no End-to-End communication so solutions for ad-hoc mobility are not applicable. Reactive approach e.g. Observer initiated. Proactive approach e.g. sensor initiated patching procedure similar to soft handoff. Copyright 2002 Sameer Tilak

Importance of these factors Protocol Development heavily depends on traffic characteristics Efficient/optimized protocols are possible with insight of accurate model Application specific knowledge and infrastructure knowledge both used Copyright 2002 Sameer Tilak

Infrastructure tradeoffs study Why ? Non-Intuitive results Expectations:- High Accuracy, low delay, longer lifetime Solution:- More sensors -> More information, high accuracy, high fault tolerance and longer life-time…. Is this solution right ??? Copyright 2002 Sameer Tilak

Infrastructure Features Sensor Capabilities Number of Sensors Deployment strategies Copyright 2002 Sameer Tilak

Number of Sensors Simple Analysis Copyright 2002 Sameer Tilak

Meaning of equations Channel capacity upper bound Application specific criteria (e.g., accuracy lower bound). Copyright 2002 Sameer Tilak

Deployment strategies Grid like Random uniform Biased deployment Copyright 2002 Sameer Tilak

Sensor Network As 15x15 Grid Copyright 2002 Sameer Tilak

Random Deployment of 100 Sensors Copyright 2002 Sameer Tilak

Biased Deployment of 100 Sensors Copyright 2002 Sameer Tilak

Evaluation Environment Framework extends ns-2 Flexibility, realistic modeling Separation of Phenomenon, sensors and observer Copyright 2002 Sameer Tilak

Parameters to study Continuous and phenomenon driven model Traditional:- Goodput, delay, energy expenditure New:- accuracy as a proof of concept for any application specific performance metric. Copyright 2002 Sameer Tilak

Accuracy model Relative distance determines accuracy Lion(10,15) Someone(25,30) I enjoy my sleep Sensing range Copyright 2002 Sameer Tilak

Goodput Study Copyright 2002 Sameer Tilak Grid Random

Delay Study Copyright 2002 Sameer Tilak Grid Random

Accuracy Study Copyright 2002 Sameer Tilak

Energy Expenditure study Copyright 2002 Sameer Tilak

Energy Depletion Study Copyright 2002 Sameer Tilak

Continuous data model Copyright 2002 Sameer Tilak 10 x 10 Grid

Biased Versus Uniform Copyright 2002 Sameer Tilak

Copyright 2002 Sameer Tilak Effect of Bandwidth Goodput Accuracy

Capacity versus Path length Goodput drops with increase in avg. path length Copyright 2002 Sameer Tilak

Network Protocol Effect Copyright 2002 Sameer Tilak DSR, AODV similar DSDV Bad

Congestion Management Defining congestion management Same problem as in internet then why not use the same solution ??? Again no end-to-end communication. Copyright 2002 Sameer Tilak

Background for CM Desired goals:- Internet:- Maximize aggregate throughput with fairness. Sensor Networks:- Get information that satisfies application requirements. Why is this so different then ? Copyright 2002 Sameer Tilak

Internet Congestion Copyright 2002 Sameer Tilak Elton John Music Client A Elton John Music www.mp3.com Can you cut off either one??? Client B Knuth’s book www.cs.stanford.edu

Co-operative + Redundancy Sensor network for animal tracking Copyright 2002 Sameer Tilak

Optimal region of operation Copyright 2002 Sameer Tilak

Optimal region of operation Copyright 2002 Sameer Tilak Optimal region of operation To keep the system operating in this optimal region

CM Alternatives Feedback based (some communication) Who detects congestion ??? 1. Observer based feedback 2. In-network feedback 3. Hybrid No feedback [No communication] Copyright 2002 Sameer Tilak

Basic points Co-operative communication pattern. Redundant information. Basically As long as lower threshold determined by application is maintained observer is happy. Fairness in not the goal. Copyright 2002 Sameer Tilak

Our Solution Congestion Avoidance Unbiased Algorithm: No application knowledge is used. Every sensor is treated accuracy. Biased Algorithm: Application knowledge is used. Application specific policy is used. We just provide mechanism to do it. Policy versus mechanism separation, cleaner solution. Copyright 2002 Sameer Tilak

Unbiased Algorithm Probabilistic algorithm. All sensors are equal. Each sensor after sensing the phenomenon sends with certain probability. However this sending probability is same for all sensors. Is this the best way to do ??? Copyright 2002 Sameer Tilak

Problem with Unbiased model Copyright 2002 Sameer Tilak Problem with Unbiased model Relative distance determines accuracy Don’t send Lion(10,15) Send Lion(5,5) Lion(4,4) Someone(25,30) I enjoy my sleep Sensing range

Biased model Relative distance determines accuracy Copyright 2002 Sameer Tilak Biased model Relative distance determines accuracy Send Lion(10,15) Don’t send Lion(5,5) Lion(4,4) Someone(25,30) I enjoy my sleep Sensing range

Advantages Completely localized solution. Copyright 2002 Sameer Tilak Advantages Completely localized solution. No local/global communication required. Minimum overhead simplicity desirable for SN. Does this solve all problems ???

Disadvantages No guarantee that at least one sensor will report because: Probabilistic nature. Does not adopt dynamically to the changing conditions very much. Copyright 2002 Sameer Tilak

Copyright 2002 Sameer Tilak Preliminary results

Future work for CM Feed-back based methods: More adoptive. More complex. Require communication overhead. Tradeoff might be worth studying….. Copyright 2002 Sameer Tilak

Future Work Making taxonomy more comprehensive. Development of better Congestion Management strategies (discussion and Implementing phase). Exploring novel protocols, that support data-fusion (Discussion phase). Copyright 2002 Sameer Tilak

Conclusions Copyright 2002 Sameer Tilak Overall communication in sensor network is application driven and data-centric. Taxonomy will be helpful in designing and evaluation of protocols for sensor-nets. Taxonomy will assist development of simulation models to study performance of different sensor-net organization and making design and deployment decisions.

Conclusions continued. Copyright 2002 Sameer Tilak Conclusions continued. SN organization: Infrastructure, Network protocol, Application/Observer. Communication models, data delivery models, Network dynamics influence network protocol. Mobility is SN should be handled differently than in Ad-Hoc e.g. reactive, proactive approach...

Conclusions continued…. Copyright 2002 Sameer Tilak Conclusions continued…. Infrastructure tradeoffs study shows: If not properly managed, deploying more sensors may end-up in harming performance of network according to both network and application metrics. Channel capacity id the upper bound on collective data communication and application requirements is the lower bound.

Conclusions continued…. Different deployment strategies studied show: No appreciable difference in terms of application and n/w metrics between grid and uniform random then random = low cost and effort. Biased network deployment if managed properly can be a better alternative. Copyright 2002 Sameer Tilak

Conclusions continued... Copyright 2002 Sameer Tilak Congestion could be a real problem for SN. Network protocol should do “Intelligent management of sensors” e.g., Congestion Management. There exists an optimal region of operation from both application and network point of view. Network protocol should operate SN in this region.