Notes
Slide Show
Outline
1
"WWRF12 Meeting,"
  • WWRF12 Meeting,
  • 4-5 November 2004,
  • Toronto, Canada
2
Introduction
  • Routing in wireless Ad Hoc network
    • Proactive (DSDV)
    • Reactive (DSR, AODV)
  • Problems in Reactive Routing Protocols
    • Finding the shortest path between sender and receiver by flooding the requests
    • Shortest path leads to network congestion in central areas
    • Caching mechanisms for storing the routes causes the traffic load to concentrate on certain nodes
    • Traffic load is unevenly distributed
3
Capacity
  • Estimation
    • Theoretical estimation for per node capacity is given by P. Gupta et al.
    • A simple estimation is geometrically given as:
4
Capacity
  • One example
    • The 1500*1500 m*m network with 550 m interference range can have capacity around 2.36*K Mbps. If K = 2 Mbps, the capacity of the network is around 4.72 Mbps.
    • The utilization measured from simulations:
5
Traffic Balancing
  • Why Traffic Balancing?
    • Unevenly distributed traffic waste bandwidth
    • Congestion cause long backoff period
  • Fundamental Idea:
6
Traffic Balancing
  • Implementation
    • Two parameters and one counter:
      • the medium usage threshold
      • the measurement time period
      • overThresholdCounter
    • Functions:
      • For the router: Upon receiving a route request, checking the medium usage. If the medium usage is over the medium usage threshold, the node increases the overThresholdCounter by one.
      • For the sender: Upon receiving the route replies, the sender chooses the route with the smallest overThresholdCounter. If more than one path has the same smallest overThresholdCounter, the one with fewer hops is chosen. If more than one path has the same overThresholdCounter and the same number of hops, the sender randomly chooses one.
7
Simulation Results
  • Simulation Environment
    • Network Simulator 2 (NS2)
    • IEEE 802.11 MAC
    • Constant Bit Rate Traffic (CBR)
    • 100 nodes
8
Simulation Results
  • Results (network size 1000*1000 m*m):
9
Simulation Results
  • Medium Threshold
10
Conclusion
  • System throughput is improved by routing traffic away congested area
  • Traffic Balancing collects more information during route discovery
  • System resources is used efficiently in two aspects:
    • Bandwidth in edge area of network
    • Bandwidth saved from backoff period
11
Future Work
  • Adaptive Traffic Balancing
    • Dynamic Medium Threshold
    • Dynamic Measurement Period
  • Physical Layer Model
  • Traffic Model
  • Wireless Mesh Network