In this Letter, the problems associated with routing for conference size ad-hoc mobile networks are presented. While conventional link-state and distance-vector Bellman–Ford routing proto-cols function well in a wired network, they incur extensive bandwidth, power and computation overheads for MHs in an ad-hoc mobile network. Hence, a simple and bandwidth-efficient distributed routing protocol based on a new concept of associativity is proposed. The asso-ciation property allows the routing protocol to exploit the spatial and temporal relationships of ad-hoc MHs to construct long-lived routes, resulting in fewer route re-constructions and hence higher attainable throughput.
The proposed protocol uses a combination of point-to-point and broadcast routing approach.
Routes are initiated by the source and are set-up based on demand. The protocol is free from loops since “seen” tables, single route selection and ultimate single route re-construction
mechanisms are employed. Because a route is explicitly selected prior to usage (with all other possible alternate routes remaining passive), packet duplicates are avoided. Since there is no need to maintain alternate route information, problems associated with stale routes are absent.
To ensure transmission integrity, a data flow acknowledgement and retransmission scheme is incorporated into the routing protocol.
The route re-construction process exploits the advantage of locality of neighbouring MHs to quickly construct alternate and even shorter routes, i.e. route optimisation. To fairly distribute the route relaying functions among ad-hoc MHs, the route relaying load is identified as a new routing metric, so is the longevity of a route. Neighbouring tables used to support associativity-based routing (ABR) can be simultaneously used to support “neighbour-aware” applications, such as nomadic collaborative computing. In addition, the integration of ABR routing with BS-oriented WLANs allows packets to be re-routed to another nearby BS via other MHs during a BS failure.
To evaluate the protocol performance during the cases when the associativity interlock property is violated, the routing protocol is implemented within a migration-based ad-hoc mobile simulator. From the results obtained out of 113 ad-hoc mobile networks simulations, we found that the re-constructed route can be shorter than its original route and the number of localised query operations are less than its worst possible value. In addition, as the route neighbouring factor is increased, the probability of a localised query success is also increased.
We have also proposed a new dynamic cell size adjustment scheme for ABR, which provides further improvement in throughput and reduction in transmission power in a manner that is independent of the underlying MAC layer protocols.
While conventional networks have static topologies, ad-hoc mobile networks have chang-ing topologies. While conventional packet-level network simulators can evaluate traffic per-formance as a result of node and link failures, they however cannot possibly model nodes in migration with respect to space. In addition, their operations are mainly synchronous and the ability to test for all possible route re-constructions are limited. This explains our approach in developing a migration-based ad-hoc mobile network simulator. Although the traffic per-formance is not evaluated in our simulator, we believe that the property of having long-lived routes has already enhanced the communication throughput considerably and the capability of the routing protocol to quickly locate an alternative shorter route enhances the response time to link changes.
Future work includes the implementation of the proposed routing protocol into existing WLANs (such as AT&T/NCR WaveLAN and Wi-LAN WiLAN) and the development of adaptive mobile applications so that ad-hoc mobile computing can be better supported.
Acknowledgements
I wish to thank Prof. D.R. McAuley (Computer Science Department, Glasgow University), Dr. David Greaves (Cambridge University Computer Laboratory), Benny Lee and Mike Webb for their interesting comments on this work. I am grateful to Prof. A. Ephremides (Electrical Engineering Department, University of Maryland) and Dr. Sanjiv Nanda (AT&T Bell Labs) for allowing me to use some of their published research results. Prof. Mario Gerla, Jack Tsai and Keith Scott from UCLA have also assisted in providing me with the relevant publications.
I am also thankful to the researchers at Networked Computing Research Group at AT&T Bell Labs for their valuable feedback. Finally, I am indebted to King’s College Cambridge for funding my research work.
References
1. A. Sugikawa, Y. Morioka, K. Iwamura, Y. Tajika and M. Nakamura, “A computerized support system for nomadic collaboration”, in Proceedings of MoMuC2: Second International Workshop on Mobile Multi-Media Communications, April 1995.
2. D. Nielson, F. Tobagi and B. Leiner, “Issues in packet radio design”, Proceedings of the IEEE, Vol. 75, No. 1, pp. 6–20, 1987.
3. K.L. Scott and N.D. Bambos, “A fully distributed algorithm for the creation and maintenance of wireless networks of mobile users”, Technical Report, TR UCLA-ENG-95-112, Department of Electrical Engineering, University of California at Los Angeles, 1994.
4. C. Perkins and P. Bhagwat, “Highly dynamic destination-sequenced distance vector routing (DSDV) for mobile computers”, in Proceedings of ACM SIGCOMM’94, September 1994, pp. 234–244.
5. K.-C. Chen, “Medium access control of wireless LANs for mobile computing”, IEEE Network – Special Issue on Nomadic Personal Communications, Vol. 8, No. 5, pp. 50–63, 1994.
6. C. R. Lin and M. Gerla, “A distributed architecture for multi-media in dynamic wireless networks”, in Proceedings of IEEE GlobeCom’95, November 1995, pp. 1468–1472.
7. A. Ephremides, J.A. Flynn and D.J. Baker, “The design and simulation of a mobile radio network with distributed control,” IEEE Journal of Selected Area in Communications, Vol. 2, No. 1, pp. 226–237, 1984.
8. M. S. Corson and A. Ephremides, “A distributed routing algorithm for mobile radio networks”, ACM Wireless Networks Journal, Vol. 1, No. 1, pp. 61–81, 1995.
9. K. Scott and N. Bambos, “The self-organising wireless network protocol for communication among mobile users”, in Proceedings of IEEE GlobeCom’95, November 1995, pp. 355–359.
10. H. Takagi and L. Kleinrock, “Optimal transmission ranges for randomly distributed packet radio terminals”, IEEE Transactions on Communications, Vol. 32, No. 3, pp. 246–257, 1984.
11. K.Y. Eng, M.J. Karol, M. Veeraraghavan, E. Ayanoglu, C.B. Woodworth, P. Pancha and R.A. Valenzuela, “A wireless broadband ad-hoc ATM local area network”, ACM Journal on Wireless Networks (WINET), Vo. 1, No. 2, pp. 161–174, 1995.
12. K. Lee, “Adaptive network support for mobile multi-media”, in Proceedings of ACM First International Conference on Mobile Computing and Networking (MOBICOM’95), November 1995, pp. 62–72.
13. D. B. Johnson and D. A. Maltz, “Dynamic source routing in ad hoc wireless networks”, in Mobile Computing, Thomasz Imielinski and Hank Korth (eds.), Kluwer Academic Publishers: Dordrecht. 1996.
14. D.R. McAuley, Private Communications. 1995.
15. A. DeSimone and S. Nanda, “Wireless data: Systems, standards, applications”, ACM Journal on Wireless Networks (WINET), Vol. 1, No. 2, pp. 241–252, 1995.
16. P. Agrawal, E. Hyden, P. Krzyzanowsji, M.B. Srivastava and J. Trotter, “Multimedia information processing in the SWAN mobile networked computing system”, in Proceedings of Multimedia Computing and Networking (MMCN’96), January 1996.
17. P. Agrawal, E. Hyden et al., “SWAN: A mobile multimedia wireless network”, IEEE Personal Communica-tions Magazine, Vol. 3, No. 2, pp. 18–33, April 1996.
18. P. Agrawal et al., “A testbed for mobile networked computing”, in Proceedings of IEEE International Conference on Communications (ICC’95), June 1995, pp. 410–416.
19. P. Agrawal, P.P. Mishra and M.B. Srivastava, “Network architecture for mobile and wireless ATM”, in Proceedings of 16th International Conference on Distributed Computing Systems (ICDCS ’96), May 1996.
20. P. Krishna, M. Chatterjee, N.H. Vaidya and D.K. Pradhan, “A cluster-based approach for routing in ad-hoc networks”, in Proceedings of 2nd USENIX Symposium on Mobile and Location-Independent Computing, April 1995, pp. 1–10.
21. J. Burchfiel, R. Kunzelman, R. Kahn and S. Gronemeyer, “Advances in packet radio technology”, Proceedings of the IEEE, Vol. 66, No. 11, pp. 1468–1496, 1978.
22. A. Bhatnagar and T.G. Robertazzi, “Layer Net: A new self-organizing network protocol”, in Proceedings of MILCOM’90: IEEE Military Communications Conference, June 1990, pp. 845–849.
23. P. Merlin and A. Segall, “A failsafe distributed routing protocol”, IEEE Transactions on Communications, Vol. 27, No. 9, pp. 1280–1287, 1979.
24. T.A. Wilkinson, “HIPERLAN: An air interface designed for multi-media”, in Proceedings of MoMuC2:
Second International Workshop on Mobile Multi-Media Communications, April 1995.
25. T. Izumoto, H. Shigeno, T. Yokoyama and Y. Matsushita, “A self-organizing wireless LAN system”, in Proceedings of IEEE 18th Conference on Local Computer Network, September 1993, pp. 467–473.
26. J. Jubin and J. Tornow, “The DARPA packet radio network protocols”, Proceedings of the IEEE, Vol. 75, No. 1, pp. 21–32, 1987.
27. J. T.-C. Tsai, Private Communications. 1996.