1. A Simple Neighbor Discovery Procedure for Bluetooth Ad Hoc Networks Miklós Aurél Rónai and Eszter Kail GlobeCom 2003 Speaker: Chung-Hsien Hsu Presented at TKU Group Meeting January 29, 2004

2. Outline Introduction Simple Neighbor Discovery Procedure Performance of the SND Procedure Comparison of SND and Inquiry Conclusion

3. Introduction Current Bluetooth neighbor discovery procedure Three weaknesses: Taking a lot of time. Transmitting data simultaneously with the inquiry is very inefficient. Assuming asymmetric roles is not well suited to an ad hoc network of peer nodes.

4. Simple Neighbor Discovery Procedure Main concept: Every node sends beacon messages regularly at pseudo-randomly selected slots. Containing BD_ADDR and clock A node wants to discover or update information about its neighbors: To perform Scanning

5. Simple Neighbor Discovery Procedure - Sending beacon packets Priority: Beacon packet > Data and ack packets

6. Simple Neighbor Discovery Procedure - Sending beacon packets Beacon Containing BD_ADDR and clock. Predictable. (option) Packet loss: Automatic Retransmission Query (ARQ) mechanism. Not every Bluetooth frequency is used as beacon frequency. To ensure faster discovery of nodes. Be sent with one of the 63 DIAC access code. The nodes are aware of SND.

7. Simple Neighbor Discovery Procedure - Scanning Scanning Objective To discover the neighbors. To update the status information about its neighbors. The length and the timing of the scan periods are not fixed. Randomly selects frequencies for scanning. During a scan period the node listens only on one frequency.

8. Simple Neighbor Discovery Procedure - Scanning

9. Performance of the SND procedure Environment: A discrete event driven. Simulator: Plasma (object oriented) Nodes: 2 The interval between scanning periods: 0 ~ 1000 slots Scanning duration: 10 slots Frequency used for scanning: 32 channels

10. Performance of the SND procedure - Experiment 1 If a node sends beacons more often, the probability of discovery is higher.

11. Performance of the SND procedure - Experiment 1 The reception of a beacon packet at a scanning node is successful: The number of beacon and scanning frequencies. The length of a timeslot. Beacon period length of the node performing the neighbor discovery. The probability of interference occurs.

12. Performance of the SND procedure - Experiment 1 The reception of a beacon packet at a scanning node is successful: The probability of using the same frequency. The probability that the beacon packet cannot be detected. The probability that the beacon packet be detected. The probability of having received the beacon successfully.

13. Performance of the SND procedure - Experiment 1 The probability of discovering: The period of a node performs scanning. The beacon period of a neighbor node sends a beacon. The total amount of time spent with scanning.

14. Performance of the SND procedure - Experiment 1 The probability of discovering: The probability of having a beacon in a scan period.

15. Performance of the SND procedure - Experiment 1 The probability of discovering:

16. Performance of the SND procedure - Experiment 1 2.9s 5.8s 99% 90%

17. Performance of the SND procedure - Experiment 2 Analyzing 2 different kinds of scanning schemes: Deterministic scanning periods. Random scanning periods.

18. Performance of the SND procedure - Experiment 2

19. Comparison of SND and Inquiry

20. Four difference: Inquiry messages vs. beacon packets. Asymmetric roles vs. equal roles. Deterministic vs. probabilistic. Guarantees 100% probability of the discovery in a fixed time interval vs. trade-off between the discovery time and overhead.

21. Comparison of SND and Inquiry Comparing procedures in two case: Asymmetric roles. Symmetric roles.

22. Comparison of SND and Inquiry - Asymmetric roles Wake-up period 16 slots 64 slots 10 slots

23. Comparison of SND and Inquiry - Asymmetric roles

24. Comparison of SND and Inquiry - Symmetric roles

26. Conclusion Proposed a Simple Neighbor Discovery procedure: Well suited to systems where peer nodes are communicating. Flexible mechanism. Be performed with low overhead during data transmissions. Taking less time than the Bluetooth inquiry. Be configurable in the trade-off between discovery time and overhead.