Towards a Sensor Network Architecture: Issues and Challenges. Muneeb Ali LUMS, Pakistan SICS, Sweden

Transcription

1 Towards a Sensor Network Architecture: Issues and Challenges Muneeb Ali LUMS, Pakistan SICS, Sweden Talk at Knuth SICS, Sweden, November 2005

2 Outline Introduction Internet vs Sensor Networks Towards a Sensor Network Architecture Sensor-Net Protocol (SP) IP over SP Mobility-Management in Sensor-Net Architecture SP and Naming Issues Future Work Conclusion

3 Introduction How might the computing and communications world be materially different in 10 years? Image courtesy SATCON - USA

4 Introduction In 10 years, there should be a ubiquitous, low cost, open infrastructure suited for communication with lowcost computing devices such as sensors and controllers. (David Clark et al., "Making the world (of communications) a difference place", ACM Computer Communication Review, July 2005) Image courtesy Prof Kris Pister, UC Berkeley

5 Internet vs Sensor-Nets What they have learned, What we have learned, and we have forgotten. and they have ignored. (BIG) (small) Reference: Philip Lewis, ICSI Talk, May 2004

6 Internet vs Sensor-Nets The Internet Sensor Networks Independent hosts End to end flows Two tier architecture Wired (generally) Latency Throughput Bandwidth is relatively cheap Limited in-network state Collaborative use Collect, disseminate,... Ad-hoc (more homogeneous) Low power wireless Wake time Very low utilization Bandwidth is expensive RAM is limiting physical resource Reference: Philip Lewis, ICSI Talk, May 2004

7 Internet vs Sensor-Nets Philip Scott I have an algorithm. What does it do? It s for propagating code in sensor networks. Is that important? I ll take your word for it. It has some nice properties. Such as? It suppresses redundant messages! It avoids floods! It spreads like a virus! So, there is this thing called SRM. Have you ever heard of pbcast? Oh, it s an epidemic algorithm. Reference: Philip Lewis, ICSI Talk, May 2004

8 Internet vs Sensor-Nets Lessons Learned Internet solutions generally do not apply apply to sensor networks Their underlying techniques do Apply, change and adapt to the peculiarities of sensor networks Example: Muneeb Ali et al.,"csn: A Network Protocol for Serving Dynamic Queries in Large-Scale Wireless Sensor Networks", In CNSR 2004, Fredericton, N.B, Canada, May Reference: Philip Lewis, ICSI Talk, May 2004

9 Towards a Sensor-Net Architecture The primary factor currently limiting progress in sensor-nets is not any specific technical challenge (although many remain, and deserve much further study) but is instead the lack of an over-all sensor network architecture. Reference: David Culler et al., Towards a Sensor Network Architecture: Lowering the Waistline, In Proc. HotOS-X, June 2005.

10 Towards a Sensor-Net Architecture Traditional view of the sensor network protocol stack Application layer Transport layer Network layer Data link layer Power management Mobility management Task management Physical layer

11 Towards a Sensor-Net Architecture Alphabet soup of protocols and subsystems Widely differing assumptions about: - the rest of the system and, - how its part should interact Vertically integrated designs - work with own set of components - unable to inter-operate No standards that the protocols and solutions need to conform to - good for research - bad for interoperability

12 Towards a Sensor-Net Architecture Sensor-Net Application Power Management System Management Mobility Management Discovery Security Timing In-Network Storage Address-Free Protocols Name-Based Protocols Suppression Custody Transfer Triggers Estimation Caching Naming Graphs Sensor-Net Protocol Data Link Media Access Time Stamping ACK Physical Architecture Sensing Carrier Sense Transmit Receive

13 Sensor-Net (SP) Protocol Unlike IP, SP sits between the network layer and the data link layer REASON: processing potentially occurs at each hop not just at end points Allows multiple network protocols and link technologies to co-exist Abstraction could be implemented in any OS SP performs three main operations: a) Data SEND b) Data RECEIVE c) Neighbor Management Main differences from IP a) feedback e.g. Congestion, phase shift b) network protocols can request urgent/reliable service c) allow network and link layer to share link information

14 Sensor-Net (SP) Protocol Network Service Manager Network Protocol 1 Network Protocol 2 Network Protocol 3 Neighbors Send Receive SP Neighbor Table Msg Pool SP Adaptor A SP Adaptor B Data Link A Data Link B

15 SP vs ZigBee ZigBee proposes a classic layered architecture, but each layer assumes a specific instance of the surrounding layers: e.g., the routing layer assumes the IEEE link and physical layers. An architecture build on static technologies is destined for obsolescence Reference: Joe Polastre et al., A Unifying Link Abstraction for Wireless Sensor Networks, In Proc. ACM SenSys 2005.

16 IP over SP Internet Sensor Network Gateway Normal User

17 IP over SP Internet Sensor Network Gateway Normal User

18 Open Issues: IP over SP? Sensor-Net Application Power Management System Management Mobility Management Discovery Security Timing TCP or UDP Internet Protocol (IP) Address-Free Protocols Name-Based Protocols Sensor-Net Protocol Data Link Media Access Time Stamping ACK Physical Architecture Sensing Carrier Sense Transmit Receive

19 Mobility-Management Image courtesy CodeBlue - Harvard

20 Mobility-Management High network dynamics in medical and emergency health care Lot of different hardware platforms for Body Sensor Networks Mobility-management as a cross-layer service in sensor network architecture AR-1 model for mobility prediction [Zainab et al, SECON 04, Globecom 04] Computation costs vs communication costs (nodes need mobility information for other nodes as well)

21 Naming Issues SP does not take any stance on naming yet assumes that all interfaces have unique-link-addresses. How to provide energy-efficient unique link-identifiers? Globally Unique vs Locally Unique Naming

22 Naming Issues [ DATA] [ DATA] [A 3 DATA] [A 12 DATA] [Attribute-Based Name NextHop Locally Unique DATA]

23 Naming Issues Scalability Problem Two-hop Naming Problem

24 Naming Issues Encoded MAC, RETRI and naming (64 and 16 bit modes) Naming for Cluster-Based sensor networks Issues and Solutions 4-plus-4 addressing Use the inherent 6% cluster heads mechanism provided by clustering approaches and break free from the two-hop naming problem!

25 Future Work "Towards a Sensor Network Architecture: Experiences with the Sensornet Protocol (SP)", Manuscript in preparation. "On the Energy-Efficiency of Node Address Naming Schemes for Wireless Sensor Networks", Manuscript in preparation. "Medium Access Control Issues in Sensor Networks", Editorial in preparation (ACM CCR April 2006 Issue). "Mobility-management in Sensor Networks", Manuscript in preparation (workshop with DCOSS 2006).

26 Further Information Muneeb Ali Thank You!