1. IEEE INFOCOM 2005, Miami, FL RID: Radio Interference Detection in Wireless Sensor Networks Gang Zhou, Tian He, John A. Stankovic, Tarek F. Abdelzaher Computer Science Department, University of Virginia March 2005

2. Outline Motivation, State of the Art, and Contributions Radio Interference Detection Protocols RID protocol RID-B protocol Using Radio Interference Detection in TDMA Designs Conclusions and Future Work

3. Motivation Use Communication Topology as the Basis of TDMA Designs One popular example: Assume collision free by allowing one node, within two communication hops, to transmit packets at a time. Using Communication Topology is Misleading Case B: Not Bandwidth Efficient BDC Case A: Not Collision Free DBA A’s Comm. Range AC How about K hops communication topology? K needs to be > 2 !K needs to be < 2 ! We Need to Detect Radio Interference!

4. State of the Art Communication Topology is Widely used as the Design Basis of TDMA Protocols In MANET: NAMA protocol [Bao and Garcia-Luna-aceves 2001] In WSN: TRAMA protocol [Rajendran et al. 2003] Pervasive Existence and Complexity of Radio Interference are Reflected in Recent WSN Experiments: Shadowing Phenomena [Woo et al. 2004] Radio irregularity [Zhou et al. 2004] Packet delivery performance [Zhao and Govindan 2003] Reliable multihop routing [Woo et al. 2003] Connectivity assessment tool [Cerpa et al. 2003]

5. Contributions To the best of our knowledge, our protocols, RID and RID-B, are the first to detect radio interference topology in runtime systems Apply radio interference detection in TDMA design (take NAMA as a case study) NAMA-RID-B keeps 100% packet delivery ratio In heavy load, NAMA can have packet loss up to 60% Analyze the application of radio interference detection in backoff algorithms. (See paper for detail) Study the relationship between communication range and interference range in MICA2 devices, in both strong link case and weak link case. (See paper for detail)

6. RID Protocol RID Phases: HD-ND Detection Information Sharing Interference Calculation Range 1: A’s High Sending Power Communication Range Range 2: A’s Normal Sending Power Interference Range B AC Range 1 Range 2 HD ND

7. RID Protocol System wide solution: Random back off

8. RID Protocol System wide solution: Random back off Add-on rule Condition A: Stable power level during T1 Condition B: Stable low power level (background noise power) during T2

9. RID Protocol System wide solution: Random back off Add-on rule Condition A: Stable power level during T1 Condition B: Stable low power level (background noise power) during T2

10. RID Protocol System wide solution: Random back off Add-on rule Condition A: Stable power level during T1 Condition B: Stable low power level (background noise power) during T2

11. RID Protocol System wide solution: Random back off Add-on rule Multi-round Detections

12. RID Phases: HD-ND Detection Information Sharing Interference Calculation ID1Power1 ID2Power2 ID3Power3 …… Interference_In Table Record: Who can interfere with me and how much it is ID10Power10 ID11Power11 ID12Power12 …… Interference_Out Table ID21Power21 ID22Power22 ID23Power23 …… Interference_HTP Table Record: Who I can interfere with and how much it is Record: Who can interfere with one of my neighbors and how much it is This Phase generates two more tables

13. Goal: Figure out All Collision Cases by Local Calculation Basic Step: Calculate possible interference cases at receiver D, when there are only two simultaneous transmitters RID Phases: HD-ND Detection Information Sharing Interference Calculation (1) Node i 1 ’s signal can be disturbed by node i 2 ’s signal (2) Without interference, node i 1 ’s signal is able to be received by node D (1)(2)

14. Interference Calculation --- Extension Step Extension: How about k simultaneous transmitters? (1)(2) (3) (1) Node i 1 ’ signal can be disturbed by the sum of node set {i 2, ……, i k } (2) Without interference, node i 1 ’s signal is able to be received by node D (3) Any proper subset of node set {i 2, ……, i k } can not generate enough interference

15. Interference Calculation --- Properties Two interesting properties of : Is complete Has no Redundancy

16. RID-B Protocol Motivation of RID-B Future traffic information is needed to take full use of N k (D) in RID. Very expensive, especially in WSN RID-B’s concern: Detect nodes that can interrupt the receiver’s reception of the weakest packet from nodes within its communication neighborhood. J R E D C G F

17. RID-B Calculation How to achieve that? The same way to build Interference_In table Reorganize the Interference_In table Replace entry (transmitter ID, power level) with entry (transmitter ID) if the following condition is met Entry is removed, if the condition is not met Weakest signal power level from R’s communication neighbors (C here) J R E D C G F

18. Using RID-B in NAMA Protocol NAMA Protocol Scheduling is based on 2 hops communication topology. Each node makes local decision whether it can have the current time slot, based on IDs in two communication hops. Without communication, there comes a consensus. Only one node wins the time slot. NAMA-RID-B Protocol Scheduling is based on 2 hops of interference topology. Each node makes local decision whether it can have the current time slot, based on IDs in two interference hops. Without communication, there comes a consensus. Only one node wins the time slot.

19. Simulation Configuration ComponentsSetting SimulatorGloMoSim Terrain(144m X 144m) Square Node Number144 Node PlacementUniform Payload Size32 Bytes ApplicationMany-to-one CBR streams Routing ProtocolGF MAC ProtocolNAMA/NAMA-RID-B (ACK added, Max #Retransmission is 8) Radio ModelRADIO-ACCNOISE Radio Bandwidth250Kb/s Radio Range25m (Adjust parameter values to set different interference range) Confidence IntervalsThe 90% confidence intervals are shown in each figure

20. Performance Evaluation Performance with Different System Load

21. Overhead Performance with Different System Load

22. Performance with Different ICR and SNR (a) Performance with Different ICR ( ICR=R I /R c ) (b) Performance with Different SNR Threshold

23. Conclusions To the best of our knowledge, our protocols, RID and RID-B, are the first to detect radio interference topology in runtime systems Apply radio interference detection in TDMA design. It improves NAMA’s packet delivery ratio from 40% to 100%, in heavy load. Analyze the application of radio interference detection in backoff algorithms. Study the relationship between communication range and interference range in MICA2 devices, in both strong link case and weak link case.

24. Future Work Predict future traffic information, and combine it with RID to design more bandwidth efficient TDMA Explore the use of RID-B in backoff algorithms in detail Analyze the combination of RID with topology control protocols Implement and evaluate radio interference detection in a large-scale sensor network system Explore the interaction between radio interference and radio irregularity

25. The End! Thanks to anonymous reviewers for their valuable comments!