jason ernst – university of guelph prepared for cs6650 - mobile & wireless networks
TRANSCRIPT
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
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
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Jason [email protected] of Guelph