Fair Scheduling for Wireless Mesh Networks

1. Fair Scheduling for Wireless Mesh Networks Jason Ernst – University of Guelph Prepared for CS6650 - Mobile & Wireless Networks

2. Presentation Outline • Introduction & Background • WMN, Fair Scheduling, Mobility • Motivation • Limitations of Current Implementations • Related Work & Applications • Current Progress • FS Implementation in C++ • Fair Scheduling algorithm • Future Work & Project Goals • NS2 Implementation Challenges • What will be simulated • Questions

3. Introduction and Background • Wireless Mesh Network: • Ad-hoc network consisting of mesh routers and mesh clients. • Mesh routers • have more resources (power, memory, bandwidth) than the mesh clients and are used for forwarding packets • Mesh Clients • A wireless node which may be or may not be mobile, may be constrained by resources such as battery life

4. Introduction & Background

5. What this work tries to address • Three Assumptions in Hubaux and Salem paper “A Fair Scheduling for WMN” • Static and known topology of the network • Nodes are not mobile (both clients and mesh routers) • Nodes cannot be added or removed • One gateway • Huge bottleneck point, both for traffic and scheduling • Mesh Routers are not mobile • Mobile mesh routers allow for interesting applications such as mobile transit networks and military applications

6. Motivation • Wireless Mesh Networks • Fewer gateways required compared to single-hop APs spread around • Redundant paths in case of congestion, failure • If properly designed can support self* properties of autonomic networks • Fair Scheduling • Ensure every user gets equal service for equal money, control greedy or malicious nodes, prevent starvation • Mobile WMN: • Moving nodes can be grouped with a mobile MR to minimize the number of handoffs since they are all moving together (ex: bus scenario) • A type of clustering where moving nodes are paired with a moving MR

7. Related Work & Applications • Applications • WMN transit system • Mobile military applications • Community Mesh Networks • “Last-Hop” solutions for ISPs • Related Work • Wireless Local Area Networks (WLAN) • Mobile Ad-hoc Networks (MANET) • Operating System Scheduling • Distributed Computing (SHARCNET)

8. Current Progress • Implementation of “A Fair Scheduling for WMN” by Hubaux and Salem in c++ • Uses concept of “compatibility matrix” to produced a collision-free STDMA scheduling for the network • In their paper they do not allow for any mobility (mesh clients or mesh routers) • They do not provide a mechanism for distributing the scheduling to the MRs

9. Compatibility Matrix GW 3 0 MR MR 1 2 4 5 MR MR MR MR 0 1 2 3 4 5 0 1 0 0 0 1 1 1 0 1 0 1 1 1 2 0 0 1 1 1 1 3 0 1 1 1 0 0 4 1 1 1 0 1 0 5 1 1 1 0 0 1

10. Fair Scheduling • The Fair Scheduling is determined using the compatibility matrix and a concept of ‘gain’ where the links are weighted based on the number of clients using the link • The gain is calculated by the sum of all the gains minus the max gain for each group of links • The group with the maximal gain which does not intersect with existing selected groups of links is chosen to be added to the scheduling

11. Fair Scheduling Figure 1: Example STDMA Scheduling taken from “A fair Scheduling for WMN” by Hubax and Salem

12. NS2 Implementations Challenges • Current MAC implementations in NS2 • Many make use of RTS/CTS mechanism for collision avoidance (802_11) and are complicated • Some of the more basic TDMA scheduling MAC implementations are meant for single-hop • Some MAC implementations don’t work with existing routing protocols such AODV (WiMax module)

13. What will be Simulated • Small to medium sized network (up to about 50 nodes) • Increasing number of mobile mesh routers, performance will be evaluated with an increasing number of mobile mesh routers • Similarly, increasing number of gateways to see the performance changes • Dynamic network topology (adding, removing and moving nodes)

14. Future Work & Project Goals • Continue to work on distribution method to get the scheduling to the MRs in the network • Either centralized via gateway control (as in the Hubaux and Salem paper) or a more distributed approach where the matrix is split up at each layer of the hierarchy • Implement new features • Support for multiple gateways (requires distributed solution if GW controls the scheduling • Add mobility support for MRs • Allow dynamic topology changes

15. References • Agrawal et Al. Achieving Load Balancing in Wireless Mesh Networks Through Mulitple Gateways. IEEE. 2006. 807-812. • Bejerano, Yigal., Han, S-J., Kumar, Amit. Efficient Load-Balancing Routing for Wireless Mesh Networks. 2007. Computer Networks. 51. 2450-2466. • Chandranmenon et. Al. On the Design and Implementation of Infrastructure Mesh Networks. IEEE Workshop on Wireless Mesh Networks (WiMesh) 2005. • Cheng, S-M., Lin, Phone., Huang, Di-Wei., Yang, Shun-Ren. A Study on Distributed / Centralized Scheduling for Wireless Mesh Network. 2006. IWCMC ’06. ACM. 599-604. • Gupta, Piyush., Sankarasubramaniam, Yogesh., Stolyar, Alexander. Random-Access Scheduling with Service Differentiation in Wireless Networks. 2005. IEEE. 1815-1825. • Erwu, Liu., Shan, Jin., Gang, Shen., Luoning, Gui. Fair Scheduling in Wireless Multi-Hop Self-Backhaul Networks. IEEE AICT/ICIW 2006. • Hubaux, J-P., Salem, Ben Naouel. A Fair Scheduling for Wireless Mesh Networks. WIMESH. 2005 • Koutsonikolas, Dimitrios., M. Das., Saumitra., Hu, Charlie, Y. An Interference-aware Fair Scheduling for Multi-cast in Wireless Mesh Networks. 2008. Journal of Parallel and Distributed Computing. 68. 372-286. • Popa, Lucian., Rostamizadeh, Afshin., Karp, Richard, M., Papadimitriou, Christos., Stoica, Ion. Balancing Traffic Load in Wireless Networks with Curveball Routing. 2007. Mobihoc ‘07. ACM. 170 – 179.

16. References cont’d • J. Thomas, “Cross-Layer Scheduling and Routing For Unstructured And Quasi-Structured Wireless Networks” • M.S. Kuran, G. Gur, T. Tugcu, F. Alagoz, “Cross-Layer Routing-Scheduling in IEEE 802.16 Mesh Networks”, in Mobilware’08. Austria, 2008. • M. Neely, R. Urgaonkar, “Cross-layer adaptive control for wireless mesh networks,” in Ad Hoc Networks Vol . 5, pp 719-743, 2007. • J. Tang, G. Xue, W. Zhang, “Cross-Layer Design for End-To-End Throughput and Fairness Enhancement in Multi-Channel Wireless Mesh Networks,” in IEEE Transactions on Wireless Communications, Vol. 6. pp 3482-3486. October 2007. • X. Wang, K. Kar, “Cross-Layer Rate Control for End-to-End Proportional Fairness in Wireless Networks with Random-Access,” in MobiHoc ’05. Illinois, USA, 2005. • J. Tang, G. Xue, C. Chandler, W. Zheng, “Link Scheduling with Power Control for Throughput Enhancement in Multihop Wireless Network • V. Kawadia, P.R. Kumar, “A Cautionary Perspective on Cross-Layer Design,” in IEEE Wireless Communications, pp 3-11, February 2005. • I.F. Akyildiz, X. Wang, “Cross-Layer Design in Wireless Mesh Networks,” in IEEE Transactions on Vehicular Technology, Vol. 57, 2, pp 1061- 1076, March 2007.

17. Questions & Comments? Jason Ernst jernst@uoguelph.ca University of Guelph