1. STATE-OF-THE-ART IN SENSOR NETWORKS RESEARCH Ian F. Akyildiz Broadband & Wireless Networking Laboratory School of Electrical and Computer Engineering Georgia Institute of Technology Tel: 404-894-5141; Fax: 404-894-7883 Email: ian@ece.gatech.edu Web: http://www.ece.gatech.edu/research/labs/bwn

2. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 2 Internet, Satellite, etc Sink Task Manager SENSOR NETWORKS Several thousand nodes Several thousand nodes Nodes are tens of feet of each other Nodes are tens of feet of each other Densities as high as 20 nodes/m3 Densities as high as 20 nodes/m3 I.F.Akyildiz, W.Su, Y. Sankarasubramaniam, E. Cayirci, I.F.Akyildiz, W.Su, Y. Sankarasubramaniam, E. Cayirci, “Wireless Sensor Networks: A Survey”, Computer Networks (Elsevier) Journal, March 2002.

3. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 3 A Sensor Node Power Unit Power Generator Sensor ADC ProcessorMemory Transceiver Location Finding System Mobilizer SENSOR NODE HARDWARE Small Small Low power Low power Low bit rate Low bit rate High density High density Low cost (dispensable) Low cost (dispensable) Autonomous Autonomous Adaptive Adaptive

4. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 4 Sensor Networks Communication Architecture Application Layer Transport Layer Network Layer Data Link Layer Physical Layer Power Management Plane Mobility Management Plane Task Management Plane n Used by sink and all sensor nodes n Combines power and routing awareness n Integrates data with networking protocols n Communicates power efficiently through wireless medium and wireless medium and n Promotes cooperative efforts

5. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 5 WHY CAN’T AD-HOC NETWORK PROTOCOLS BE USED HERE? Number of sensor nodes can be several orders of magnitude higher Number of sensor nodes can be several orders of magnitude higher Sensor nodes are densely deployed and are prone to failures Sensor nodes are densely deployed and are prone to failures The topology of a sensor network changes very frequently due to node mobility and node failure The topology of a sensor network changes very frequently due to node mobility and node failure Sensor nodes are limited in power, computational capacities, and memory Sensor nodes are limited in power, computational capacities, and memory May not have global ID like IP address. May not have global ID like IP address. n Need tight integration with sensing tasks.

6. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 6 SENSOR NETWORK APPLICATIONS Military, Environmental, Health, Home, Space Military, Environmental, Health, Home, Space Exploration, Chemical Processing, Disaster Relief…. Exploration, Chemical Processing, Disaster Relief…. SENSOR TYPES: Seismic, Low sampling rate magnetic, SENSOR TYPES: Seismic, Low sampling rate magnetic, Thermal, Visual, Infrared, Acoustic, Radar… Thermal, Visual, Infrared, Acoustic, Radar… SENSOR TASKS: Temperature, Humidity, Vehicular SENSOR TASKS: Temperature, Humidity, Vehicular Movement, Lightning Condition, Pressure, Soil Makeup, Movement, Lightning Condition, Pressure, Soil Makeup, Noise Levels, Presence or Absence of Certain Types of Noise Levels, Presence or Absence of Certain Types of Objects, Mechanical Stress Levels on Attached Objects, Objects, Mechanical Stress Levels on Attached Objects, Current Characteristics Speed, Direction, Size) of Current Characteristics Speed, Direction, Size) of an Object …. an Object ….

7. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 7 TRANSPORT LAYER Related Work Infrastructure Tradeoffs [1] Infrastructure Tradeoffs [1] RMST [2] RMST [2] PSFQ - Pump Slowly Fetch Quickly [3] PSFQ - Pump Slowly Fetch Quickly [3] MAC Level Reliability [4,5] MAC Level Reliability [4,5] [1] S. Tilak, N. B. Abu-Ghazaleh and W. Heinzelman, “Infrastructure Tradeoffs for Sensor Networks,” In Proc. ACM WSNA’02, September 2002. In Proc. ACM WSNA’02, September 2002. [2] F. Stann and J. Heidemann, “RMST: Reliable Data Transport in Sensor Networks,” In Proc. IEEE SNPA’03, May 2003. In Proc. IEEE SNPA’03, May 2003. [3] C. Y. Wan, A. T. Campbell and L. Krishnamurthy, “PSFQ: A Reliable Transport Protocol for Wireless Sensor Networks,” In Proc. ACM WSNA’02, September 2002. Sensor Networks,” In Proc. ACM WSNA’02, September 2002. [4] A. Woo and D. Culler, “A Transmission Control Scheme for Media Access in Sensor Networks”, In Proc. ACM MOBICOM’01, July 2001. In Proc. ACM MOBICOM’01, July 2001. [5] W. Ye, J. Heidemann and D. Estrin, “An Energy-Efficient MAC Protocol for Wireless Sensor Networks”, In Proc. IEEE INFOCOM’02, June 2002. Networks”, In Proc. IEEE INFOCOM’02, June 2002.

8. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 8 TRANSPORT LAYER Related Work Conclusions Wireless TCP variants NOT suitable !!! Wireless TCP variants NOT suitable !!! –End-to-end semantics –Huge buffering requirements –ACKing is energy draining Reliable multicast solutions NOT applicable Reliable multicast solutions NOT applicable –Multiple-sender single receiver transport problems traditionally solved as multiple unicast Traditional end-to-end guaranteed reliability (TCP/Multicast solutions) not appropriate… Traditional end-to-end guaranteed reliability (TCP/Multicast solutions) not appropriate… New Reliability Notion is required!!!

9. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 9 Event Radius Sink Sensor nodes Event-to-Sink Reliability Y. Sankarasubramaniam, O. B. Akan, I. F. Akyildiz, Proc. of ACM MobiHoc’03, Annapolis, Maryland, June 2003. Sensor networks are event-driven Sensor networks are event-driven Multiple correlated data flows from event to sink Multiple correlated data flows from event to sink Goal is to reliably detect/estimate event features from collective information Goal is to reliably detect/estimate event features from collective information Necessitates event-to-sink collective reliability notion Necessitates event-to-sink collective reliability notion

10. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 10 Open Research Issues Extend ESRT to address reliable transport of concurrent multiple events in the sensor field. Extend ESRT to address reliable transport of concurrent multiple events in the sensor field. Explore possible other reliability metrics Explore possible other reliability metrics –Total expected mean square distortion –Minimum mean squared error estimation. Develop unified transport layer protocols for sink-to-sensors and bi-directional reliable transport in WSN Develop unified transport layer protocols for sink-to-sensors and bi-directional reliable transport in WSN Research to integrate WSN domain into NGWI (Next Generation Wireless Internet) Research to integrate WSN domain into NGWI (Next Generation Wireless Internet) –Adaptive Transport Protocols for WSN-Ad Hoc environments

11. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 11 NETWORK LAYER Important considerations: Important considerations: n Sensor networks are mostly data centric n An ideal sensor network has attribute based addressing and location awareness n Data aggregation is useful unless it does not hinder collaborative effort n Power efficiency is always a key factor

12. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 12 NETWORK LAYER Related Work n Sensor Protocols for Information via Negotiation (SPIN) [1] n Directed Diffusion [2] [1] W. R. Heinzelman, J. Kulik, and H. Balakrishnan, “Adaptive Protocols for [1] W. R. Heinzelman, J. Kulik, and H. Balakrishnan, “Adaptive Protocols for Information Dissemination in Wireless Sensor Networks,” Proc. of the ACM Information Dissemination in Wireless Sensor Networks,” Proc. of the ACM MobiCom’99, pp. 174-185, Sept. 1999. MobiCom’99, pp. 174-185, Sept. 1999. [2] C. Intanagonwiwat, R. Govindan, and D. Estrin, “Directed Diffusion: A Scalable and Robust Communication Paradigm for Sensor Networks,” Proc. Scalable and Robust Communication Paradigm for Sensor Networks,” Proc. of the ACM MobiCom’00, pp. 56-67, Sept. 2000. of the ACM MobiCom’00, pp. 56-67, Sept. 2000.

13. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 13 Desired Features n Periodic update of routes not needed n Adaptive to failures n Cope with topology changes n No need for routing tables n Easy incorporation of new sensor nodes n Routes based on QoS requirements n One-to-one, many-to-one, one-to-many, and many-to-many communications communications

14. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 14 Open Research Issues Store and Forward Technique that combines data fusion and aggregation. Routing for Mobile Sensors Investigate multi-hop routing techniques for high mobility environments. Priority Routing Design routing techniques that allow different priority of data to be aggregated, fused, and relayed. 3D Routing

15. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 15 MEDIUM ACCESS CONTROL (MAC) Related Work n IEEE 802.11 S-MAC and EAR [1,2] S-MAC and EAR [1,2] Transmission Control Scheme [3] Transmission Control Scheme [3] Distributed Source Coding [4,5] Distributed Source Coding [4,5] Routing and Data Compression [6] Routing and Data Compression [6] [1] K.Sohrabi et al.,”Protocols for Self-Organization of a Wireless Sensor Network”, IEEE Personal Communications,October 2000. IEEE Personal Communications,October 2000. [2] W. Ye, J. Heidemann and D. Estrin, “An Energy Efficient MAC Protocol for Wireless Sensor Networks,” Proc. ACM MOBICOM ’01, pp.221 –235, July 2001. Proc. ACM MOBICOM ’01, pp.221 –235, July 2001. [3] A. Woo and D. Culler, “A Transmission Control Scheme for Media Access in Sensor Networks”, Proc. ACM MOBICOM’01, July 2001.. Proc. ACM MOBICOM’01, July 2001.. [4] S.S. Pradhan, K. Ramchandran, “Distributed Source Coding: Symmetric Rates and Applications in Sensor Networks,” in Proc. Data Compression Conference’00, pp. 363 –373, 2000. Networks,” in Proc. Data Compression Conference’00, pp. 363 –373, 2000. [5] S.S. Pradhan, J. Kusuma, K. Ramchandran, “Distributed Compression in a Dense Microsensor Network,” IEEE Signal Processing Magazine, vol.19, no.2, pp.51 –60, Mar 2002. IEEE Signal Processing Magazine, vol.19, no.2, pp.51 –60, Mar 2002. [6] A. Scaglione, S.D. Servetto, “On the Interdependence of Routing and Data Compression in Multi-Hop [6] A. Scaglione, S.D. Servetto, “On the Interdependence of Routing and Data Compression in Multi-Hop Sensor Networks,” Proc. MOBICOM’02, September 2002. Sensor Networks,” Proc. MOBICOM’02, September 2002.

16. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 16 Collaborative MAC Protocol M. C. Vuran, Y. Sankarasubramaniam, I.F. Akyildiz, “Collaborative Medium Access for Wireless Sensor Networks”, March 2003. Spatial correlation in sensor networks is exploited in the MAC layer Spatial correlation in sensor networks is exploited in the MAC layer Event MAC (E-MAC) filters out correlation whereas Network MAC (N-MAC) prioritizes the route-thru packets Event MAC (E-MAC) filters out correlation whereas Network MAC (N-MAC) prioritizes the route-thru packets Number of transmissions are reduced instead of number of transmitted bits Number of transmissions are reduced instead of number of transmitted bits

17. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 17 Optimal Packet Size for Wireless Sensor Networks Y. Sankarasubramaniam, I. F. Akyildiz, S. McLaughlin, ”Optimal Packet Size for Wireless Sensor Networks”, IEEE SNPA, May 2003.  Determining the optimal packet size for sensor networks is necessary to operate at high energy efficiencies.  The multihop wireless channel and energy consumption characteristics are the two most important factors that influence choice of packet size. Payload ( <=73) Header ( 2) Trailer (FEC) ( >=3)

18. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 18 PHYSICAL LAYER (Some Facts) n Low-lying antennae and near-ground channels result in fourth power decay of signal intensity with distance power decay of signal intensity with distance n Transmit power can be reduced by increasing node density n Multi-hop communication can also mitigate some signal propagation effects propagation effects n M-ary modulation reduces transmit on-time but requires greater output power to achieve same BER as binary modulation greater output power to achieve same BER as binary modulation

19. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 19 SYNCHRONIZATION Related Work Post-Facto Synchronization [1] Post-Facto Synchronization [1] Reference-Broadcast Reference-Broadcast Synchronization (RBS) [2] Synchronization (RBS) [2] [1] J. Elson and D. Estrin, “Time Synchronization for Wireless Sensor Networks,” [1] J. Elson and D. Estrin, “Time Synchronization for Wireless Sensor Networks,” Proceedings of the 15th International Parallel and Distributed Processing Symposium Proceedings of the 15th International Parallel and Distributed Processing Symposium (IPDPS-01), IEEE Computer Society, April 2001. (IPDPS-01), IEEE Computer Society, April 2001. [2] J. Elson, L. Girod, and D. Estrin, “Fine-Grained Network Time Synchronization using Reference Broadcasts,” Proceedings of the Fifth Symposium on Operating Reference Broadcasts,” Proceedings of the Fifth Symposium on Operating Systems Design and Implementation (OSDI 2002), December 2002. Systems Design and Implementation (OSDI 2002), December 2002.

20. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 20 PERCEPTIVE LOCALIZATION Related Work N. Patwari et. al., “Relative Location Estimation in Wireless Sensor Networks,” IEEE Transactions on Signal Processing, August 2003. N. Patwari et. al., “Relative Location Estimation in Wireless Sensor Networks,” IEEE Transactions on Signal Processing, August 2003. - Mathematical analysis of sensor location accuracy based on fixed base-stations capable of - Mathematical analysis of sensor location accuracy based on fixed base-stations capable of peer- to-peer time-of-arrival or received signal strength measurements peer- to-peer time-of-arrival or received signal strength measurements R. Moses et.al., “A Self-Localization Method for Wireless Sensor Networks,” Eurasia Journal on Applied Signal Processing, No. 4, pp. 348-358, 2003. R. Moses et.al., “A Self-Localization Method for Wireless Sensor Networks,” Eurasia Journal on Applied Signal Processing, No. 4, pp. 348-358, 2003. - A self-location method that uses base-stations with known positions as references - A self-location method that uses base-stations with known positions as references A. Savvides et.al., “Dynamic Fine-Grained Localization in Ad-Hoc Networks of Sensors,” Proc. Of ACM MobiCom’01, pp. 166-179, 2001. A. Savvides et.al., “Dynamic Fine-Grained Localization in Ad-Hoc Networks of Sensors,” Proc. Of ACM MobiCom’01, pp. 166-179, 2001. - Use fixed-base stations for fine-grained location - Use fixed-base stations for fine-grained location OPEN RESEARCH ISSUE: Non Fixed Base-Station based Techniques: Enable location of sensor nodes without the need for location beacons

21. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 21 Some Applications MAN  for Meteorological Observations SpINet  for Mars Surface Airport Security  Sensors/Actors Sensor Wars Wide Area Multi-campus Sensor Network

22. Ne X tworking’03 June 23-25,2003, Chania, Crete, Greece The First COST-IST(EU)-NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING Akyildiz NeXtworking'03 - Chania, Crete, Greece, The First COST-IST(EU)- NSF(USA) Workshop on EXCHANGES & TRENDS IN NETWORKING AKYILDIZ 22 Basic Research Needs An Analytical Framework for Sensor Networks More theoretical investigations of the Protocol developments Realistic Demos Integration with other network paradigms ….