Topology Management Framework for Highly Dynamic MANETs Ricardo Sanchez, Joseph Evans Mobile Ad Hoc Networks (MANETs) Recap Self-organizing, self-configuring Wireless Networks No fixed infrastructure, no centralized control All nodes are mobile, all links are wireless All/some nodes function as “mobile routers” (or relay nodes) Nodes join/leave network arbitrarily Applications: battlefield operations, disaster relief, etc. Physical models: flat and hierarchical (shown below) Motivation What happens in Highly Dynamic MANETs? Intermittent and fast link activations and failures cause high rates of topology state changes  due to internal/external node conditions such as sudden mobility, power failure, harsh weather, high load, etc. Most protocol approaches to end-to-end routing in MANETs typically tackle one condition: mobility, energy, …. assume rates of changes of short (insignificant) duration Embed complexity at the routing protocol level to operate end-to- end over ANY underlying topology – does not always work! But routing performance is significantly affected by high rates of changes [as reported in the research literature] => Can we improve the responsiveness/efficiency of MANET routing protocols under highly dynamic conditions? Research Ideas Decouple network topology structure from routing problem Provide better representation of topology to routing protocols Distinguish between physical and logical representation Organize logical topology into connected/non-partitioned clusters Characterize dynamic nature of topology with vector metrics Require positioning/velocity/signal-strength information plus more Metric values are essential to measure link/node/cluster quality… … but metric vectors provides also an estimation for stability May offer better resource utilization and/or savings capabilities Construct and maintain stable cluster-based topology Use mechanisms to merge/split clusters with the aid of resilient control structure Goal: development of resilient and adaptive cluster-based topology management framework Topology Management Framework MOBILE BASE STATION MOBILE HOST BACKBONE WIRELESS LINK LAST-HOP WIRELESS LINK Challenges Dynamic topology  Mobility, terrain, weather, … Limited resources  BW, energy, processing load, … Problem: MANET routing over multi-hop paths is difficult! Building blocks: resilient link/cluster level control protocols Cross-layer interactions with Routing/MAC functional blocks (i) Link-level control protocol Operate over any two neighboring nodes using special beacons Distinguish link quality/stability between neighboring nodes Establish “safe” links between “stable” neighboring nodes based on vectorized node-level (relative) metric Tune node’s transmission range according to “stable” condition (ii) Cluster-level control protocol Operate over selected “safe” links among specific “stable” nodes Construct/maintain variable-diameter clusters using vectorized cluster-level (aggregated) metric Rely on special structure for dissemination of control information to minimize impact of signaling overhead during merge/split ops (i) + (ii) = foundation for versatile MANET routing protocol