Wireless Access Research Congestion Avoidance in Source Routed Ad-Hoc Networks Bryan Hogan, Michael Barry, Ronan Skehill, Sean McGrath

Wireless Access Research Outline Ad-Hoc Networks Routing Congestion Solution Results

Wireless Access Research Lack centralised control Mobile and Transient Routing still a requirement for functionality Low: power, bandwidth, processing Ad-Hoc Networks

Wireless Access Research Table Driven Routing Store and maintain list of routes to all other nodes. Regardless of possible link use.

Wireless Access Research Dynamic Source Routing Open route only as needed –Broadcast route request Route maintenance Node involved responsible for successful hop –If failure: inform source

Wireless Access Research Congestion S2S2 S1S1 S2S2 D1D1 D2D2 D3D3

Wireless Access Research Congestion S2S2 S1S1 S2S2 D1D1 D2D2 D3D3

Wireless Access Research Congestion S2S2 S1S1 S2S2 D1D1 D2D2 D3D3

Wireless Access Research Congestion S2S2 S1S1 S2S2 D1D1 D2D2 D3D3

Wireless Access Research Congestion Expected throughput exceeds capability Congestion is local One node, too many routes Route eavesdropping

Wireless Access Research Algorithm If queue > QueueLimit –Broadcast congestion alert If forward > ForwardLimit and receive congestion alert –Perform route maintenance New route: If all nodes recently congested –Backoff

Wireless Access Research Simulation Environment NS-2 5 Source/Destination pairs CBR 100kbps (512 byte packets) Random waypoint Limits –Queue 35 packets –Forward 50,000 bytes SD S D 600m

Wireless Access Research Congestion Events

Wireless Access Research Packet delivery rate

Wireless Access Research Further work Queue Limit –Absolute –% buffer Forward Limit –50,000 bytes –70,000 bytes –Air interface dependant New routes in a congested scenario

Wireless Access Research Conclusions Congestion is local Node involved responsible for successful hop Local node must solve congestion