Weight based Multicast Routing Protocol for Ad hoc Wireless Networks

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Weight based Multicast Routing Protocol for Ad
hoc Wireless Networks
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Introduction

• Multicasting consists of concurrently sending the
  same message from one source to multiple
  destinations.
• Several multicast routing protocols have been
  proposed for Ad hoc networks which are classified
  as either mesh based or tree based.

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Introduction

• In a mesh based multicast protocol, there may be
  more than one path between a pair of source and
  receiver, thus providing more robustness compared
  to tree based multicast protocols.

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Introduction

• In a tree based multicast protocol, there exists
  only a single path between a pair of source and
  receiver, thus leading to higher multicast
  efficiency.
• The construction of a multicast tree can be done
  starting either from the source(source-initiated)
  or from the receiver(receiver-initiated).

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Introduction

• The Ad hoc environment suffers from frequent path
  breaks due to mobility of nodes, and hence
  efficient group maintenance is necessary.
• Maintaining the multicast group can be done by
  either soft state approach or hard state approach.

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Introduction

• In the soft state approach, the multicast group
  membership and associated routes are refreshed
  periodically.
• In hard state approach, the routes are
  reconfigured only when a link breaks.

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Motivation

• Bandwidth efficient multicast routing protocol
  consumes the least bandwidth due to its hard
  state tree maintenance scheme.
• When a receiver wants to join the multicast
  group, it floods JoinReq control packets and
  receives a number of Reply packets from the
  forwarding nodes and receivers in the multicast
  tree.

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Motivation

• Then the receiver sends a Confirm packet to the
  nearest forwarding node and joins the multicast
  group.
• Thus it minimizes the number of added forwarding
  nodes and eventually leading to a high multicast
  efficiency.

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Protocol Description

• Our protocol involves two phases
• 1.Tree initialization phase
• 2.Tree Maintenance phase

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Tree Initialization Phase

• A node desires to join the multicast group.
• The aim here is to find the best point of entry
  into the multicast group.
• The approach we have taken for this is a
  receiver-initiated approach.

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Tree Initialization Phase

• When a new receiver R5 decides to join the
  group, it broadcasts a JoinReq packet with a
  certain time to live(TTL) entry.
• These JoinReq packets are forwarde until they are
  received by a tree node.
• Upon receiving a JoinReq packet, a tree node say
  I1, send a Replay packet.

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Tree Initialization Phase

• The Replay packet initally contains the distance
  of the node I1 from the source S.
• Upon the reply packet receipt at node R5 will
  have the hop distance of the node R5 from node I1
  and the hop distance of node I from the source S.

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Tree Initialization Phase
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Tree Initialization Phase

• The best replay minimizes the following quantity

Q(1-joinWeight)(hop distance of R5 from I1-1)

joinWeight(hop distance of R5 from I1

hop distance of I1 from S)
joinWeight0?1??
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Tree Maintenance Phase
Link failure
In the hard state
Node move
Data packets drop
Low packet delivery
overcome
Localized prediction technique
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Tree Maintenance Phase

• In which tree maintenance phase is executed for
  TriggerHandoff time period before the link is
  expected to break.
• The triggerHandoff is the time duration after
  which the downstream tree node starts the handoff
  procedure to reconfigure the multicast tree
  before the link breaks(link between downstream
  node and its parent node).

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Tree Maintenance Phase
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Tree Maintenance Phase

• In this scheme, each node maintains a Neighbor
  Multicast Tree table(NMT).
• A node refreshes the NMTExistence timer when it
  receives data packets from tree node.

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Tree Maintenance Phase

• When the downstream tree node receives data
  packets from its parent node, the node can
  predict the time duration for which the parent
  node would remain within its transmission range.

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Tree Maintenance Phase

• After receiving the data packets if the link life
  period is less than the TriggerHandoff time
  period , then the downstream node transmits the
  data packet after setting InitiateHandoff bit.

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Tree Maintenance Phase

• When a neighbor node promiscuously receives a
  data packet with InitateHandoff bit set,it sends
  Handoff control packet if the following two
  conditions are satisfied.
• 1.the neighbor node has tree node inforation for
  that particular multicast group in NMT table.
• 2.the NodeDistance value of the corresponding
  tree node entry in NMT be less than the distance
  of the node which requests for handoff procedure.

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Tree Maintenance Phase

• If the above two conditions are satisfied , then
  the neighbor node sends Handoff control packet to
  the interested tree node.
• When the tree node receives many Handoff control
  packets,it chooses the Handoff control packet
  with least NodeDistance value and immediately
  sends back a HandoffConf control packet to the
  neighbor node.

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Tree Maintenance Phase

• After receiving the HandoffConf control
  packet,the neighbor node forwards it to the tree
  node to rejoin the multicast tree.

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Tree Maintenance Phase

• There may be more than one neighbor which satisfy
  the above two conditions.
• They are also eligible to send Handoff control
  packets to the interested tree node to
  reconfigure the multicast tree.
• Due to this reason,there is a chance that these
  Handoff packets collide and not reach the
  destination node.

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Tree Maintenance Phase

• Sending Handoff control packets by many neighbor
  nodes may lead to increased control overhead.
• If any neighbor node hears a HandoffConf control
  packet,just before sending the Handoff control
  packet,then it discards its Handoff control
  packet.

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Tree Maintenance Phase

• There is no neighbor node satisfying the two
  conditions.
• Hence the downstream node in this case does not
  get any Handoff control packet from any neighbor
  nod,resulting in a link break.
• When such a situation arises, the downstream node
  of the broken link has to take measures to rejoin
  the multicast group.

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Tree Maintenance Phase

• To find the new route to any forwarding node in
  the multicast tree, the downstream node floods
  JoinReq with certain TTL value.

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Performance Evaluation

• A. simulation environment
• B. Metrics
• C. Simulation Results

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Simulation environment

• 50 mobile nodes move within a 1000m x 1000m area.
• The radio transmission range used is 250m.
• Channel capacit is assumed as 2Mbits/sec.
• The network traffic load is kept at
  10packets/sec.
• Source and receivers are chosen randomly and join
  the multicast seeion at the beginning.

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Metrics

• Data Packet Delivery Ratiothe percentage of data
  packets received by the receivers.
• Number of Control Packets Transmitted per Data
  Packet Receivedthe degree of control overhead.
• Number of Data Packets Received per Data Packet
  Transmittedthe multicast routing efficiency.

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Simulation Results
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Simulation Results
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Simulation Results
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Simulation Results
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Simulation Results
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Simulation Results
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Simulation Results
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Simulation Results
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Simulation Results
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Conclusions

• We consider not only the number of forwarding
  nodes but alst the distance between source and
  receiver.
• It makes the protocol efficient as well as
  robust.
• We use localized prediction scheme,hence it
  achieves high packet delivery ratio.