AODVBR: Backup Routing in

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AODV-BR Backup Routing in Ad hoc
Networks Sung-Ju Lee and Mario
Gerla http//www.cs.ucla.edu/NRL/wireless Wirele
ss Adaptive Mobility Laboratory Computer Science
Department University of California Los Angeles,
CA
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Multiple Routes

• Providing multiple paths is useful in mobile
  wireless networks
• Previous ad hoc multicast studies show that
  protocols with alternate routes are robust to
  mobility Lee et al INFOCOM 2000
• Related work
• DARPA Packet Radio Network Alternate Routing
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• Nasipuri and Das ICCCN 99
• TORA Park and Corson INFOCOM 97
• ROAM Raju and Garcia-Luna-Aceves ICCCN 99
• They all require additional control messages to
  construct multiple routes

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Backup Routing

• Can be applied to any on-demand routing protocol
• Provide alternate paths without transmitting
  additional control messages
• Nodes promiscuously overhear Route Reply packets
  sent by neighbors that are part of the route to
  form backup paths

Fishbone!
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Usage of Backup Routes

• Data packets are delivered through the primary
  route unless it is disconnected
• The node detecting the disconnection performs a
  one hop data broadcast with a special bit set,
  instead of simply dropping the packet
• Upon receiving this packet, nodes that have a
  route to the destination unicast the packet to
  the next hop
• the packet must not be from the next hop to the
  destination
• the packet must not be a duplicate
• Alternate path hence provides emergency bypass
• Route Error packet is also sent by the node that
  detects the route break

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Example (1/4)

• Primary route ltS-A-B-C-Dgt
• Node D send a Route Reply to node C
• Nodes Y and Z overhear the packet and become
  nodes of backup routes

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Example (2/4)

• Node C forwards the Route Reply to node B
• Nodes W and X overhear it and become backup
  routes
• Nodes D, Y and Z ignore it

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Example (3/4)

• The Route Reply has reached the source node S
• The primary route ltS-A-B-C-Dgt and backup routes
  (nodes W, X, Y, and Z) are established

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Example (4/4)

• Node B moves out of the range of node C, and
  detects a disconnection
• Performs a one hop broadcast to its neighbors
• Node W picks up the packet and sends it to node C

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Variant suppress redundant transmissions

• Nodes of the alternate path optionally may not
  relay salvaged data packets
• Consider the link between nodes A and B is broken
• Assume the node X picks up the packet and sends
  it to node B first
• If node W hears that transmission from node X to
  B, it can suppress its transmission

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Performance Evaluation

• Simulated in GloMoSim written in PARSEC
• Applied our scheme to AODV (Ad hoc On-demand
  Distance Vector) and evaluated the performance
  gain
• Our scheme AODV-BR (AODV with Backup Routes)
• 50 nodes in 1500 meter X 300 meter area
• Free space propagation model, IEEE 802.11 DCF
• Ten data sessions each with the rate of 4 pkt/sec
• Random waypoint mobility model
• min and max speed 0 and 20 m/s
• varied the pause time to simulate different
  mobility degree

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Packet Delivery Ratio
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Delay
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Conclusions

• Our scheme can be applied to any on-demand
  routing protocol that uses request/reply cycle
• Alternate routes are constructed without
  generating additional routing messages
• Backup routes improve packet delivery in AODV
• We plan to use more sophisticated and realistic
  channel models in our simulation backup routes
  will be more beneficial in those environments

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GloMoSim Simulator

• Event driven simulator written in PARSEC
• Detailed model of the network protocol stack
• Capability to simulate large network models
• Parallel execution
• http//pcl.cs.ucla.edu/projects/domains/glomosim.h
  tml

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The Number of Data Transmitted per Data Delivery
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Packet Delivery Ratio with Increased Number of
Data Sessions
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Packet Delivery Ratio vs Data Rate
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Proactive Routing Schemes

• Distance vector and link state algorithms
• Periodic and event triggered updates
• Update route changes of inactive routes and waste
  bandwidth
• Loops
• Too many event triggered updates as nodes move
  faster
• The network view does not converge or converges
  slowly
• Do not perform well in wireless mobile ad hoc
  networks