A Pragmatic Approach towards the Improvement of Performance of Ad Hoc Routing Protocols

1. A Pragmatic Approach towards the Improvement of Performance of Ad Hoc Routing Protocols Rajesh Roy, Sudipto Das, Pradip K. Das Department of Computer Science & Engineering, Jadavpur University, Kolkata – 700 032 rajesh.roy@rediffmail.com, sudipto.das@rediffmail.com, pkdas@cse.jdvu.ac.in

2. Presentation Outline • Abstract • Motivation • Layer Description • Issues Addressed in this paper • Design Specifications • Conclusion

3. Abstract • Mobile ad hoc networks are characterized by high mobility and frequent link failures – Results in low throughput and high end-to-end delay • The primary goal of an ad hoc network routing protocol - correct and efficient route establishment between a pair of nodes. • Routing Protocol Implementations suffer from some inherent in-capabilities to cope with highly dynamic scenarios. • This paper proposes to introduce a New Layer in between network layer and IEEE 802.11 MAC sub layer. • This Layer interacts with the underlying MAC layer and provides link connectivity information as well as various other valuable parameters

4. Presentation Outline • Abstract • Motivation • Layer Description • Issues Addressed in this paper • Design Specifications • Conclusion

5. Motivation • Performance degradation of various Ad-hoc Routing protocol implementations due to Fluctuating Node Problem and Communication Gray Zone Problem • Specific requirements of certain routing algorithm e. g. Extended Device Driver Interface by Signal Stability based adaptive routing protocol for measuring received signal strength • Generic Platform for developing Ad-hoc Routing Protocols

6. Presentation Outline • Abstract • Motivation • Layer Description • Issues Addressed in this paper • Design Specifications • Conclusion

7. Our Solution – A New Layer • In this paper, we propose the introduction of a New Layer • Main function of the New Layer is to gather information about the Network • Information gathered by the Layer augments the Routing Entity • Shares a portion of the Routing Overhead from the Routing Entity Schematic Representation of the New Layer

8. Layer Description • The Layer requires some sort of beacon messages to detect the presence of a neighbor as well as gather Network statistics • Design Alternatives • Beacon messages inherent to the IEEE 802.11 MAC layer • Protocol specific Hello messages We use the latter option • Interface to Routing Entity • Lookup Table

9. Presentation Outline • Abstract • Motivation • Layer Description • Issues Addressed in this paper • Design Specifications • Conclusion

10. Issues addressed in this Paper • Fluctuating Neighbor Problem • At the transmission borderline, communication tends to be unreliable due to fluctuating quality of links. This leads to spurious HELLO messages, which, once received, do not reflect correctly whether consistent communication between two nodes is possible, or not. As a consequence this means that shorter but unreliable ones can replace stable and longer routes • Communication Gray Zone Problem • In IEEE 802.11b, broadcasting is always done at a basic bit rate while data transmissions normally are sent at higher rates (up to 11 Mbit/s in IEEE 802.11b). Transmissions at lower bit rates are more reliable and can reach further than at higher rates. As HELLO messages are broadcasted, this is the main cause to why gray zones appear Gray Zone Problem

11. B A C Fluctuating Neighbor Problem

12. A B Communication Gray Zone Problem • 802.11b transmits broadcast packets at a lower data rate (Usually at 1 or 2 Mbps) • Unicast Packets at 11 Mbps

13. Presentation Outline • Abstract • Motivation • Layer Description • Issues Addressed in this paper • Design Specifications • Conclusion

14. A Pragmatic SolutionStable Neighbor Detection • A N-consecutive periodic hello messages scheme • Minimum signal strength threshold value for hello messages • Neighbor Status • Unstable • Meta Stable • Stable Meta Stable State timeout N2 consecutive beacons N1 consecutive beacons Stable State Unstable State K consecutive timeout

15. Meta Stable Link A Pragmatic SolutionChanges to AODV • Changes over AODV to make it compatible with the New Layer Stable Link Destination Source A B B Marks all route replies as Meta stable received from A

16. Presentation Outline • Abstract • Motivation • Layer Description • Issues Addressed in this paper • Design Specifications • Conclusion

17. Conclusion • The mobility scenario in an Ad hoc network has led to the degradation in the performance of the routing algorithms • Unavailability of various parameters, like received signal strength, network resource usage etc., to the routing protocols, and • The need for enhancement in their performance - introduction of a new layer between the Network Layer and the MAC Layer becomes imperative • In addition to providing a solution to some problems like Fluctuating Neighbor & Communication Gray Zone – provides a Generic Platform for future enhancements

18. Acknowledgements The authors gratefully acknowledge the facilities provided and support given by all the staff members of the Centre for Mobile Computing and Communication, Jadavpur University formed by UGC under its “University with Potential for Excellence” program.