Jason Ernst – University of GuelphPrepared for CS6650 - Mobile & Wireless Networks

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

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

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

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

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)

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

GW

MR

MR

MR MR MRMR

30

1 2 4 5

0 1 2 3 4 50 1 0 0 0 1 11 0 1 0 1 1 12 0 0 1 1 1 13 0 1 1 1 0 04 1 1 1 0 1 05 1 1 1 0 0 1

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

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

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)

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)

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

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.

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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.

Jason Ernstjernst@uoguelph.caUniversity of Guelph