Huayi Wu and Xiaohua Jia

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QoS Multicast Routing by Using Multiple
Paths/Trees in Wireless Ad Hoc Networks

• Huayi Wu and Xiaohua Jia
• Ad Hoc Networks, July 2007
• speaker Yu-Hsun Chen

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Outline

• Introduction
• Related Works
• Problem Formulation
• Multiple Paths/Trees Multicast Routing Protocol
• Three Multiple Paths/Trees Construction
  Strategies
• Simulations
• Conclusion

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Introduction 1

• Many applications require QoS multicast
• Multimedia group meeting
• Real-time multimedia data dissemination
• QoS multicast routing
• Find a multicast tree
• Rooted from the source node
• Spanning to all destination nodes
• Every path from the source to the destination
  satisfies the QoS requirements
• Limitation
• Limited bandwidth

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Introduction 2

• The QoS multicast routing in this paper
• Utilize multiple parallel paths or trees to meet
  the bandwidth and delay requirement of a QoS call
• Major advantages
• Reduce the system blocking probability
• Distributed scheme
• Similar to traditional on-demand routing protocols

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Outline

• Introduction
• Related Works
• Problem Formulation
• Multiple Paths/Trees Multicast Routing Protocol
• Three Multiple Paths/Trees Construction
  Strategies
• Simulations
• Conclusion

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On-Demand Multicast Routing Protocol 1

• S. J. Lee, W. Su, and M. Gerla, On-Demand
  Multicast Routing Protocol in Multihop Wireless
  Mobile Networks, Mobile Networks and
  Applications, 2002
• ODMRP is a mesh-based, rather than a tree-based
  multicast scheme
• Use a forwarding group concept
• The mesh provides richer connectivity compared
  with trees

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On-Demand Multicast Routing Protocol 2
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Multicast Operation of the Ad-hoc On-Demand
Distance Vector Routing Protocol 1

• E. M. Royer and C. E. Perkins, Multicast
  Operation of the Ad-hoc On-Demand Distance Vector
  Routing Protocol, IEEE/ACM International
  Conference on Mobile Computing and Networking,
  1999
• Extend AODV to offer multicast capabilities
• J_flag in RREQ
• Group Hello Messages
• Multicast Activation (MACT)

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Multicast Operation of the Ad-hoc On-Demand
Distance Vector Routing Protocol 2
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A Robust Multicast Routing Protocol

• G. H. Lynn and T. F. Znati, RoMR A Robust
  Multicast Routing Protocol for Ad-Hoc Networks,
  IEEE LCN, 2001
• Monitor the link and determine the percentage of
  time the link was available
• Build multiple reliable multicast trees
• m reliable multicast trees
• k edges in common

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Outline

• Introduction
• Related Works
• Problem Formulation
• Multiple Paths/Trees Multicast Routing Protocol
• Three Multiple Paths/Trees Construction
  Strategies
• Simulations
• Conclusion

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CDMA/TDMA and timeslot assignment

• MAC layer CDMA-over-TDMA channel model
• Conflict free fashion
• The number of timeslots ? free bandwidth over a
  link

• 2 free bandwidth of link AB
• Assigning free timeslots to a connection to
• maximize the available bandwidth of the
• connection is NP-hard

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Problem Statement 1

• Definition 1
• The available bandwidth of a link l
• Definition 2
• The bandwidth of a path P
• Definition 3
• The available bandwidth of a tree T

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Problem Statement 2

• Definition 4
• The network cost of a path P
• Definition 5
• The network cost of a multicast tree T
• Definition 6
• The delay of a tree, d(T), is the number of hops
  from the root to the farthest leaf node in T

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Problem Statement 3

• Problem
• Given a QoS multicast request
• Set up a multicast connection
• Using multiple paths/trees
• Minimize the network cost
• Meet the bandwidth and delay requirement

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Outline

• Introduction
• Related Works
• Problem Formulation
• Multiple Paths/Trees Multicast Routing Protocol
• Three Multiple Paths/Trees Construction
  Strategies
• Simulations
• Conclusion

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Route Discovery and Reply Phases 1

• Find candidate paths in parallel as many as
  possible
• Route discovery
• The source node floods the RREQ packets on-demand
• source, destination-list, seq-ID, type, route,
  freeslots, b, TTL
• When receiving a RREQ
• Check if there is any common free timeslots
• Append its own address to the route field and
  its free timeslot to the freeslots field
• Decrease TTL by 1
• Record duplicate RREQ but will not reflood

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Route Discovery and Reply Phases 2

• Route Reply
• The RREP packet
• source, node-ID, type, route, freeslots, b, TTL
• A non-destination node also needs to reply RREP
• Nodes wait either for a pre-specified timeout or
  the reception of a certain number of RREQs
• Send back a RREP including all the information
  about multiple paths going through the node

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Route Discovery and Reply Phases 3
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Maintenance Phases

• Route setup a new node join
• Flood a JO (join) packet
• Route prune a destination node leave
• Send PU (prune) packet to all the upstream nodes
  of it
• Route recovery
• Destination node is failed
• Its upstream nodes will detect it
• Forwarding node is failed
• Its downstream node floods JO for a new route

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Outline

• Introduction
• Related Works
• Problem Formulation
• Multiple Paths/Trees Multicast Routing Protocol
• Three Multiple Paths/Trees Construction
  Strategies
• Simulations
• Conclusion

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Shortest Path Tree Based Multiple-paths 1

• To find a shortest delay multicast routes
• The source node can easily find the SPT to all
  the destinations
• When bandwidth is not enough
• The source selects multiple paths parallel to the
  path-segment
• When there is a branch node
• Split the path-segment into two parts from the
  branch node

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Shortest Path Tree Based Multiple-Paths 2
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Least Cost Tree Based Multiple-Paths 1

• To find a least cost route
• The destination node is added first if it has the
  least network cost
• When bandwidth is not enough
• Find multiple parallel paths
• The multiple parallel paths are sorted by their
  network costs

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Least Cost Tree Based Multiple-Paths 2
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Multiple Least Cost Trees 1

• Find multiple trees directly
• Find a LCT first
• Those links that has no more bandwidth are
  removed
• The source will keep on searching for a LCT in
  the new network graph

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Multiple Least Cost Trees 2
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Outline

• Introduction
• Related Works
• Problem Formulation
• Multiple Paths/Trees Multicast Routing Protocol
• Three Multiple Paths/Trees Construction
  Strategies
• Simulations
• Conclusion

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Simulation Setup

• Range 100 100
• Number of nodes 100
• Transmission range 30
• Number of timeslots 16
• Network load 0 1
• Bandwidth requirement 2, 4, and 6 timeslots

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Simulation Results 1

• Network cost and success ratio versus multicast
  group size

• The MLCT and LCTM perform better in network cost
• Multiple paths/trees greatly increases the
  success ratio

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Simulation Results 2

• Success ratio versus network load

• The success ratio of SGT reaches the zero more
  quickly with the increase of network load
• The success ratio decreases sharply when the
  network load reaches a certain threshold

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Simulation Results 3

• Network cost versus network load

• The network cost is higher by using SPTM

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Conclusion

• Advantages of the protocol
• Reduce the system blocking probability
• Distributed scheme
• Similar to traditional on-demand routing
  protocols
• Comments
• Delay jitter might be an issue
• Network environment