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

2.  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.  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

5.  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.  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.  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.  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. GW MR 3 0 1245 012345010001110101112001111301110041110105111001012345010001110101112001111301110041110105111001

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

12.  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.  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.  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.  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.  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. Jason Ernst jernst@uoguelph.ca University of Guelph