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  • Specifically, TATRC is interested in applying mobile and wireless information technologies to medical informatics and telemedicine applications at the point of care and rear-ward
  • Nodes have limited transmission range and so two nodes that are far apart can communicate through intermediate nodes which act as routers in forwarding data packets.
  • Since nodes are not bound to any centralized control they are free to move about arbitrarily and hence the topology changes dynamically. Also since communication is thru wireless links they have lower bandwidth compared to their wired counterparts. And the capacity of each link varies due to noise, fading & congestion. Ad hoc network nodes rely on batteries or some other exhaustive means for their energy. Hence the protocols designed for these networks must be optimized for lean power consumption. The absence of infrastructure in these networks make them very attractive for many applications. For example, they can be used in military battlefield networks, PANs, search and rescue operations and peer to peer networks.
  • Along with the wide variety of applications that ad hoc networks have they also have a number of vulnerabilities which makes security in these networks a challenging issue. Because of the lack of a centralized control key management becomes very difficult. It is very challenging to design a sophisticated routing protocols and designing a secure routing protocols is an even more challenging. Protecting the communication from eavesdropping is difficult to prevent. The presence of any non-cooperating nodes make the routing protocol prone to a number of attacks.
  • Transcript

    • 1. Wireless Sensor Network Prabhakar Dhekne Bhabha Atomic Research CentreAugust 24, 2006 Talk at SASTRA 1
    • 2. Why Talk About Wireless? Wireless communication is not a new technology but cell phones have brought revolution in wireless communication Wireless Technology has changed the way  Organizations & individuals work & live today In less than 10 years  World has moved from fixed to wireless networks  Allowing people, mobile devices & computers talk to each other, connect without a cable  Only available option for field data acquisition Interconnectivity with multiple devices  Using radio-waves, sometimes light  Frees user from many constrains of traditional computer & phone system August 24, 2006 Talk at SASTRA 2
    • 3. Ubiquitous Computing Future State of Computing Technology?  Mobile, many computers  Small Processors  Low Power Consumption  Relatively Low Cost August 24, 2006 Talk at SASTRA 3
    • 4. Ubiquitous Computing Small, mobile, inexpensive computers…..everywhere! Fade into the background of everyday life Computers everywhere provides potential for data collection….sensors!  Temperature  Light  Sound  Motion  Pressure  Many others!!!August 24, 2006 Talk at SASTRA 4
    • 5. Growth in Wireless Systems Rapid growth in cellular voice services  Cell phones everywhere! Several wireless technology options have been available for the last ~10-20 yrs  mini cell stations using existing standards like CDMA or GSM  wireless PABX using PCS standards such as DECT or PHS/PACS  satellite and microwave backhaul Above solutions OK for voice & low-speed data, but do not meet emerging needs for broadband access and mobile data August 24, 2006 Talk at SASTRA 5
    • 6. Mobile Computing Identify/develop mobile computing solutions and effector systems integrated with existing wireless infrastructure Improve health care via enhanced training and more effective decision making To maximize the amount of medical data available for health surveillance August 24, 2006 Talk at SASTRA 6
    • 7. Mobile Healthcare TechnologiesMobile Healthcare can be regardedas the integration of technologies ofmedical sensors, mobile computing,and wireless communications into asystem of medical assistance. August 24, 2006 Talk at SASTRA 7
    • 8. Application Examples Monitoring of patient’s vital signs  Diabetes  Asthma  Hypertension  ECG Predictive usage in order to minimize the needs for medication Improving the quality of life August 24, 2006 Talk at SASTRA 8
    • 9. Potential Benefits Increasing the physician productivity and Wireless sensors enable the patients’ freedom Providing clinicians remote access to patient’s Enabling telemonitoring in emergency August 24, 2006 Talk at SASTRA 9
    • 10. Mobile HealthcareThe provision of Real Time patient care. No matter where the clinician is No matter where the patient is To apply physiological and medical knowledge, advanced diagnostics, simulations, and effector systems integrated with information and telecommunications for the purposes of enhancing operational and medical decision-making, improving medical training, and delivering medical treatment across all barriersAugust 24, 2006 Talk at SASTRA 10
    • 11. Typical Demo System The patient is provided with a wearable wireless sensor. The signal from the sensor is captured in a Node situated in a mobile phone. The system allows ubiquitous access to patient’s data and medical information in real-time via the mobile phone. The medical data is stored & processed in a server, and can be used for establishing diagnostics and treatments. August 24, 2006 Talk at SASTRA 11
    • 12. Application server Application server centralises the received data and presents it to the user as:  Raw data  Formatted as graphs App Server DB August 24, 2006 Talk at SASTRA 12
    • 13. Wireless Technology Emerging mainstream wireless technologies provide powerful building blocks for next-generation applications  WLAN (IEEE 802.11 “WiFi”) hot-spots for broadband access, Bluetooth  PDAs and laptops with integrated WLANs  Broadband Wireless access technology- MAN (Alternative to DSL)  IEEE 802.16 10-30 Km 40 Mbps WiMax  Wide area wireless data also growing  SMS, GPRS, Edge, CDMA2000 1xEV-DO (2.4 Mbps data optimized)  Variety of interesting devices (e.g. Treo, Sidekick) Networking of embedded devices  Smart spaces, sensor networks (IEEE 802.15.4a- ZigBee)  Context-aware mobile data services and web caching for information services  Wireless sensor nets for monitoring and control  VOIP for integrated voice services over wireless data networks August 24, 2006 Talk at SASTRA 13
    • 14. IrDA: P2P wireless  Infra-red Data Association  Based on Half Duplex Point-to-Point concept  Frequency below the red end of spectrum making it invisible  Eliminate the need for cables  Clear line-of-sight  Short-range (few meters)  Simplest, most prevailing wireless standard  No fixed speed 9.6 Kbps, 4Mbps  Discovery Mode to find out data rate, size  Token based transmission  IrDA ports on PDA, Laptops USB sticks  Remote Control in TV, VCR, Air-conditionerPort costs less than Rs. 1000 August 24, 2006 Talk at SASTRA 14
    • 15. Bluetooth: Wireless PAN Bluetooth (Named after Danish King Harold Bluetooth)  Based on Master-Slave concept  Short-range (10 meters)  Eliminate the need for cables M1 S  Operates in 2.4 GHz ISM band S S 2  720 Kbps 1 S 1 M 1/S1  Three modes of operation park/hold/sniff 2 Piconet & Scatternet (master+7 slaves) Interference due to multiple piconets and IEEE 802.15.1 home/person LAN Piconet 1 Piconet 2 To eliminate interference frequency hoping technique used Ominidirectional with both voice & data Port costs about Rs. 2000 August 24, 2006 Talk at SASTRA 15
    • 16. Wi-Fi: Wireless LAN (Hot Spot)  Wireless Fidelity based LAN  Most popular on Laptops  Replacement to wired LAN  Connectivity on the move  Short-range (100 meters)  Ad Hoc and Base station mode  Security provided at physical layer  Operates in 2.4 GHz and 5 GHz  Collection of IEEE standards 802.11a/b/g 11 Mpbs & 54 Mbps  Low range, requires more powerAd Hoc Access hence not suitable for PDA’s Net Point Net  Difficult to control access & security  Set up is expensive August 24, 2006 Talk at SASTRA 16
    • 17. Wi-Max: Wireless MAN Wireless Max  High Speed 40-70 Mbps  Mid-range (30 Kmeters)  Eliminate the need for cables  Saving of wired cost  Operates in 2.4 GHz ISM band IEEE standard 802.16 August 24, 2006 Talk at SASTRA 17
    • 18. Issues in Wireless Networking Infrastructured networks  Handoff  location management (mobile IP)  channel assignment August 24, 2006 Talk at SASTRA 18
    • 19. Issues in WirelessNetworkingInfrastructureless networksWireless MAC Security (integrity, authentication, confidentiality) Ad Hoc Routing Protocols Multicasting and BroadcastingAugust 24, 2006 Talk at SASTRA 19
    • 20. Indoor Environments Three popular technologies - High Speed Wireless LANs (802.11b (2.4GHz, 11 Mbps), 802.11a (5GHz, 54 Mbps & higher) - Wireless Personal area Networks PANs (IEEE 804.14)  HomeRF  Bluetooth, 802.15 - Wireless device networks  Sensor networks, wirelessly networked robots August 24, 2006 Talk at SASTRA 20
    • 21. What is an Ad hoc Network Collection of mobile wireless nodes forming a network without the aid of any infrastructure or centralized administration Nodes have limited transmission range Nodes act as a routers August 24, 2006 Talk at SASTRA 21
    • 22. Ad Hoc Networks• Disaster recovery• Battlefield• ‘Smart’ office Rapidly deployable infrastructure  Wireless: cabling impractical  Ad-Hoc: no advance • Network of access devices planning • Wireless: untethered Backbone network : • Ad-hoc: random deployment wireless IP routers • Edge network: Sensor networks, Personal Area Networks (PANs), etc. August 24, 2006 Talk at SASTRA 22
    • 23. Ad Hoc Network Characteristics  Dynamic topologies  Limited channel bandwidth  Variable capacity links  Energy-constrained operation  Limited physical security Applications  Military battlefield networks  Personal Area Networks (PAN)  Disaster and rescue operation  Peer to peer networks August 24, 2006 Talk at SASTRA 23
    • 24. Security Challenges in Ad Hoc Networks Lack of Infrastructure or centralized control  Key management becomes difficult Dynamic topology  Challenging to design sophisticated & secure routing protocols Communication through Radio Waves  Difficult to prevent eavesdropping Vulnerabilities of routing mechanism  Non-cooperation of nodes Vulnerabilities of nodes  Captured or Compromised August 24, 2006 Talk at SASTRA 24
    • 25. Security Challenges in ad hoc network security  The nodes are constantly mobile  The protocols implemented are co-operative in nature  There is a lack of a fixed infrastructure to collect audit data  No clear distinction between normalcy and anomaly in ad hoc networks Secure the Routing Mechanism  A mechanism that satisfies security attributes like authentication, confidentiality, non-repudiation and integrity Secure the Key Management Scheme  Robust key certification and key distribution mechanism August 24, 2006 Talk at SASTRA 25
    • 26. Services while on moveSensor services servicesexercise monitorbiometrics Calendar+ servicetraffic information Integrate dynamic traffic & schedule Doctor prescription service track health indicators Doctor write prescription Follow me kiosk service Sensors mobile devices receive and transmit messages Fridge & shopping service Fridge records stock Scalable, reliable, consistent, Suggests shopping based on recipe Shopping guide in store distributed service August 24, 2006 Talk at SASTRA 26
    • 27. Tourist guide Stuttgart tourist guide  Like MapQuest except on mobile device Mapping local interests  Museums historical sites  Shopping & restaurants Sample Data  Small text with description, operating hours  Local map August 24, 2006 Talk at SASTRA 27
    • 28. How it works Info station  Island of wireless station  Embedded in area  Users have cheap low bandwidth components  Integrated to network with high quality connection  Requires some overlap to manage transition between stations for hand off Scaleable by load balancing  Each center contains unique information  Overhead of communication Initialize externally specified; adjusts quickly August 24, 2006 Talk at SASTRA 28
    • 29. Map-on-the-move Provide appropriate map County resolution driving in car Info stations small area high bandwidth Remainder lower bandwidthAugust 24, 2006 Talk at SASTRA 29
    • 30. Problems in a Mobile Environment Variable Bandwidth Disconnected Operation Limited Power Implications on distributed file system support? August 24, 2006 Talk at SASTRA 30
    • 31. Constraints in mobile computing PDA vs. Laptop vs. cell phones Cellular modem connection: Failure prone Space: office vs. city vs. county Not continuous connectivity required Data such as pictures text files not streaming audio and video Heterogeneous devices August 24, 2006 Talk at SASTRA 31
    • 32. MANET: Mobile Ad hoc NetworksA collection of wireless mobile nodes dynamically forming anetwork without any existing infrastructure and the relativeposition dictate communication links (dynamically changing). From DARPA Website August 24, 2006 Talk at SASTRA 32
    • 33. Rapidly Deployable Networks Failure of communication networks is a critical problem faced by first responders at a disaster site  major switches and routers serving the region often damaged  cellular cell towers may survive, but suffer from traffic overload and dependence on (damaged) wired infrastructure for backhaul In addition, existing networks even if they survive may not be optimized for services needed at site  significant increase in mobile phone traffic needs to be served  first responders need access to data services (email, www,...)  new requirements for peer-to-peer communication, sensor net or robotic control at the site Motivates need for rapidly deployable networks that meet both the above needs -> recent advances in wireless technology can be harnessed to provide significant new capabilities August 24, 2006 Talk at SASTRA 33
    • 34. Infostations Prototype: System for Rapid Deployment Applications Outdoor Infostations with radio backhaul  for first responders to set up wireless communications infrastructure at a disaster site  provides WLAN services and access to cached data  wireless backhaul link  includes data cache Project for development of:  high-speed short-range radios  802.11 MAC enhancements  content caching algorithm & software  hardware integration including solar panels, antennas and embedded computing device with WLAN card WINLAB’s Outdoor Infostations Prototype (2002) August 24, 2006 Talk at SASTRA 34
    • 35. Ad-Hoc Wireless Network  A flexible, open-architecture ad-hoc WLAN and sensor network testbed ...  open-source Linux routers, AP’s and terminals (commercial hardware)  Linux and embedded OS forwarding and sensor nodes (custom)  radio link and global network monitoring/visualization tools  prototype ad-hoc discovery and routing protocols 802.11b Management PDA stations Radio Monitor 802.11b Forwarding Node/AP Linux PC AP (custom) Commercial Router network 802.11Compute with arbitrary topology& storage servers Sensor Node PC-based (custom) August 24, 2006 PC Talk at SASTRA Linux router 35
    • 36. What is a WSN?Sensor: The device Observer: The end user/computer Phenomenon: The entity of interest to the observer  A network that is formed when a set of small sensor devices that are deployed in an “ad hoc fashion” no predefined routes, cooperate for sensing a physical phenomenon.  A Wireless Sensor Network (WSN) consists of base stations and a number of wireless sensors.  Is simple, tiny, inexpensive, and battery-powered August 24, 2006 Talk at SASTRA 36
    • 37. Why Wireless Sensors Now? Moore’s Law is making sufficient CPU performance available with low power requirements in a small size. Research in Materials Science has resulted in novel sensing materials for many Chemical, Biological, and Physical sensing tasks. Transceivers for wireless devices are becoming smaller, less expensive, and less power hungry (low power tiny Radio Chips). Power source improvements in batteries, as well as passive power sources such as solar or vibration energy, are expanding application options. August 24, 2006 Talk at SASTRA 37
    • 38. Typical Sensor Node Features A sensor node has:  Sensing Material  Physical – Magnetic, Light, Sound  Chemical – CO, Chemical Weapons  Biological – Bacteria, Viruses, Proteins  Integrated Circuitry (VLSI)  A-to-D converter from sensor to circuitry  Packaging for environmental safety  Power Supply  Passive – Solar, Vibration  Active – Battery power, RF Inductance August 24, 2006 Talk at SASTRA 38
    • 39. Sensor Node Hardware Sensor + Actuator + ADC + Microprocessor + Powering Unit + Communication Unit (RF Transceiver) + GPS 1Kbps- 1Mbps 3m-300m Transceiver Lossy Transmission 128Kb-1Mb Limited Storage Memory Embedded 8 bit, 10 MHz Processor Slow Computation Requires Supervision Sensor Multiple sensors Limited Lifetime Battery Portable and self-sustained (power, communication, intelligence). Capable of embedded complex data processing. August 24, 2006 Talk at SASTRA 39
    • 40. Sensors and Wireless Radio  Types of sensors: -Pressure, -Temperature -Light -Biological -Chemical -Strain, fatigue -Tilt  Capable to survive harsh environments (heat, humidity, corrosion, pollution etc).  No source of interference to systems being monitored and/or surrounding systems.  Could be deployed in large numbers.August 24, 2006 Talk at SASTRA 40
    • 41. Wireless SensorNetworks ZigBee Wireless Communication Protocol  Based on the IEEE 802.15.4 standard  Small form factor  Relatively Inexpensive  Low Power Consumption  Low Data Rate of Communication  Self Organising, Self-Healing…multi- hop nodes  Integrated Sensors  Ideal for Wireless Sensor Network ApplicationsAugust 24, 2006 Talk at SASTRA 41
    • 42. WSN APPLICATIONS Potential for new intelligent applications:  Smart Homes  Process monitoring and control  Security/Surveillance  Environmental Monitoring  Construction  Medical/Healthcare Implemented with Wireless Sensor Networks! August 24, 2006 Talk at SASTRA 42
    • 43. Medical and Healthcare Appln Remote Databases Backbone Backbone Net Switch Network NetworkIn HospitalPhysician Net Switch Wireless Remote consultation Possibility for Remote consulting (including Audio Visual communication) August 24, 2006 Talk at SASTRA 43
    • 44. Medical and Healthcare Applications Sensors equipped with BlueToothAugust 24, 2006 Talk at SASTRA Source: USC Web Site44
    • 45. iBadge - UCLA Investigate behavior of children/patient Features:  Speech recording / replaying  Position detection  Direction detection / estimation (compass)  Weather data: Temperature, Humidity, Pressure, Light August 24, 2006 Talk at SASTRA 45
    • 46. Other Examples MIT dArbeloff Lab – The ring sensor  Monitors the physiological status of the wearer and transmits the information to the medical professional over the Internet Oak Ridge National Laboratory  Nose-on-a-chip is a MEMS-based sensor  It can detect 400 species of gases and transmit a signal indicating the level to a central control station VERICHIP: Miniaturised, Implanted, Identification Technology August 24, 2006 Talk at SASTRA 46
    • 47. Structural Health Monitoring Accelerometer board prototype, Ruiz-Sandoval, Nagayama & Spencer, Civil E., U. Illinois Urbana-Champaign Semi-active Hydraulic DamperModel bridge with attached wireless sensors, (SHD), Kajima Corporation, Japan B.F. Spencer’s Lab, Civil E., U. Illinois U-C August 24, 2006 Talk at SASTRA 47
    • 48. Application in Environment Monitoring Measuring pollutant Pollutants monitored by sensors in concentration the river Pass on information to monitoring station Predict current ST location of pollutant volume based on Sensors report to the base monitoring station various parameters Take corrective action August 24, 2006 Talk at SASTRA 48
    • 49. August 24, 2006 Talk at SASTRA 49
    • 50. Vehicular Traffic ControlAugust 24, 2006 Talk at SASTRA 50
    • 51. Project at The University of California, DavisUS FCC allocated 5.850to 5.925 GHz dedicatedshort rangecommunication (DSRC) Road side toVehicle Vehicle to vehicle communication VMesh: Distributed Data Sensing, Relaying, & C Networks August 24, 2006 Talk at SASTRA 51
    • 52. Network characteristics of WSN Generally, the network:  Consists of a large number of sensors (103 to 106)  Spread over large geographical region (radius = 1 to 103 km)  Spaced out in 1, 2, or 3 dimensions  Is self-organizing  Uses wireless media  May use intermediate “collators” August 24, 2006 Talk at SASTRA 52
    • 53. Sensor Network Topology Hundreds of nodes require careful handling of topology maintenance. Predeployment and deployment phase  Numerous ways to deploy the sensors (mass, individual placement, dropping from plane..) Postdeployment phase  Factors are sensor nodes position change, reachability due to jamming, noise, obstacles etc, available energy, malfunctioning, theft, sabotage Redeployment of additional nodes phase  Redeployment because of malfunctioning of units August 24, 2006 Talk at SASTRA 53
    • 54. Organization into Ad Hoc Net Individual sensors are quite limited. Full potential is realized only by using a large number of sensors. Sensors are then organized into an ad hoc network. Need efficient protocols to route and manage data in this network. August 24, 2006 Talk at SASTRA 54
    • 55. Network Topologies Star  Single Hop Network  All nodes communicate directly with Gateway  No router nodes  Cannot self-heal  Range 30-100m  Consumes lowest powerAugust 24, 2006 Talk at SASTRA 55
    • 56. Network Topologies Mesh  Multi-hopping network  All nodes are routers  Self-configuring network  Node fails, network self- heals  Re-routes data through shortest path  Highly fault tolerant network  Multi-hopping provides much longer range  Higher power consumption…nodes must always listen!August 24, 2006 Talk at SASTRA 56
    • 57. Network Topologies Star-Mesh Hybrid  Combines of star’s low power and…  …mesh’s self-healing and longer range  All endpoint sensor nodes can communicate with multiple routers  Improves fault tolerance  Increases network communication range  High degree of flexibility and mobilityAugust 24, 2006 Talk at SASTRA 57
    • 58. Self-Organizing WLAN Opportunistic ad-hoc wireless networking concepts starting to mature…  Initial use to extend WLAN range in user-deployed networks  Based on novel auto-discovery and multi-hop routing protocols  extends the utility and reach of low-cost/high speed WiFi equipment Wired Network Wired Network AP1 Infrastructure Infrastructure AP2 802.11 Access to AP Ad-hoc radio link (w/multi-hop routing Ad-hoc Infrastructure links Ad-hoc access To FN Forwarding Node (FN) Mobile Node (MN) (end-user) Forwarding Node (FN)Self-organizingAd-hoc WLAN August 24, 2006 Talk at SASTRA 58
    • 59. How to get information from Data-centric Sensor Networks? Types of Queries:  Historical Queries: Analysis of data collected over time  One Time Queries: Snapshot view of the network  Persistent Queries: Periodic monitoring at long and regular intervals Routing required to respond to a Query:  Application specific  Data centric  Data aggregation capability desirable  Need to minimize energy consumption August 24, 2006 Talk at SASTRA 59
    • 60. Software FrameworkMAC layer (Tiny OS, routing)Configuration TablePower consumption status & replacement strategySensor Data ManagementMiddlewareApplication (passing parameters via API) August 24, 2006 Talk at SASTRA 60
    • 61. Technical challenges Sensor design Self-organizing network, that requires 0- configuration of sensors  Random or planned deployment of sensors, and collators Auto-addressing Auto-service discovery Sensor localization August 24, 2006 Talk at SASTRA 61
    • 62. Power Consumption Limited Power Source Battery Lifetime is limited Each sensor node plays a dual role of data originator and data router (data processor) The malfunctioning of a few nodes consumes lot of energy (rerouting of packets and significant topological changes) August 24, 2006 Talk at SASTRA 62
    • 63. Environmental Factors Wireless sensors need to operate in conditions that are not encountered by typical computing devices:  Rain, sleet, snow, hail, etc.  Wide temperature variations  May require separating sensor from electronics  High humidity  Saline or other corrosive substances  High wind speeds August 24, 2006 Talk at SASTRA 63
    • 64. Historical Comparison Consider a 40 Year Old ComputerModel Honeywell H-300 Mica 2Date 6/1964 7/2003CPU 2 MHz 4 MHzMemory 32 KB 128 KBSRAM ??? 512 KB August 24, 2006 Talk at SASTRA 64
    • 65. Advances in Wireless Sensor Nodes Consider Multiple Generations of Berkeley MotesModel Rene 2 Rene 2 Mica Mica 2Date 10/2000 6/2001 2/2002 7/2003CPU 4 MHz 8 MHz 4 MHz 4 MHz Flash 8 KB 16 KB 128 KB 128 KBMemorySRAM 32 KB 32 KB 512 KB 512 KBRadio 10 Kbps 10 Kbps 40 Kbps 40 Kbps August 24, 2006 Talk at SASTRA 65
    • 66. Summary Sensor networks will facilitate one to address several societal issues:  Early-warning systems  Disaster mitigation Applications in other sectors  Security, transportation, irrigation Technology is available today  Research into new sensors  Needs experimentation, pilot deployment  Lots needs to be done in Software (OS, MAC, Application)  While cost is an issue today, it will not be so tomorrow August 24, 2006 Talk at SASTRA 66
    • 67. References Wireless & Mobile Systems Prof Dharma Prakash Agrawal and H. Deng Integrating Wireless Technology in the Enterprise by Williams Wheeler, Elsevier Digital Press Circuits & Systems for Wireless Communications Edited by Markus Helfenstein and George S. Moschytz, Kluwer Academic Publishers August 24, 2006 Talk at SASTRA 67
    • 68. Any Questions?August 24, 2006 Talk at SASTRA 68