Post on 27-Dec-2014
description
Performance Comparison Of Mobile
Ad-Hoc Networks
By
Josh Broch, David A. Maltz, David B.Johnson, Yih-Chun Hu, Jorjeta Jetcheva
Presented by
Santhosh Ramaraju & Pradeep Godhala
Overview• Introduction
• Destination Sequenced Distance Vector (DSDV).
• Temporally Ordered Routing Algorithm (TORA).
• Dynamic Source Routing (DSR).
• Ad-hoc On-Demand Distance Vector Routing (AODV).
• Performance Metrics.
• Simulations.
• Conclusion.
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Introduction
• Ad-Hoc Network (Infrastructureless Networking).
• DSDV, TORA, DSR, AODV.
• ns-2 Network Simulator to include• Node Mobility
• Realistic Physical Layer• Radio propagation model supporting propagation delay
• Capture effects
• Carrier sense
• Radio network interfaces• Transmission power
• Antenna gain
• Receiver sensitivity
• 802.11 MAC using DCF
• ARP
• Packet Buffering
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DSDV
• Table driven
• Hop by hop routing
• Sequence numbers to routes
• Increase or decrease route fidelity based on sequence numbers
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Implementation decisions in DSDV
DSDV-SQ (Used for paper results):
•New sequence number triggers updates
•Broken links detected faster
•More overhead
DSDV:
•New metric triggers updates
•Less detected not as fast ov
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TORA
• On demand routing
• Information flows like water flowing downhill
• Each node is assigned a "height" and information flows from nodes with greater height to nodes with lower height
• Three functions:
1) Route Creation
2) Route Maintenance
3) Route Erasure
• Builds DAG
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Implementation Decisions in TORA
• Aggregation Delay
• Retransmission period and Timeout period
• IMEP's method of link status sensing is improved
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Table: constants used in TORA
DSR
• DSR uses source routing rather than hop-by-hop routing.
• The Key Advantage of the source routing is that intermediate nodes do notneed to maintain up-to-date routing information in order to route thepacket.
• Route Discovery
• Route Request
• Route Reply
• Route Maintenance
• Reducing Route discovery process by maintain route cache.
• Route Error.
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Implementation Decisions in DSR
• DSR protocol uses Unidirectional routes, since 802.11 is used it usesRTS/CTS/DATA/ACK exchange for all unicast packets limiting theprotocol to using bidirectional links.
• Implemented DSR to avoid Unidirectional links by using Route Reply toreverse back the same path as Route Request.
• Route Request packet maximum propagation limit (hop limit) set to zero,prohibiting form rebroadcasting it.
Table: Constants used in DSR
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AODV
• Combination of DSR and DSDV.
• ROUTE REQUEST packets contain last known sequence number fordestination.
• When a node receives a ROUTE REQUEST packet for a destinationit has a route to it generates a ROUTE REPLY with the updatedsequence number and number of hops. Reverse route is also createdbefore forwarding the ROUTE REQUEST.
• Each node that forwards the reply back to the originator creates aforward path to the destination.
• Hello messages are used to maintain link state.
• Nodes remember only the next hop
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Implementation Decisions in AODV
• Dropped periodic HELLO packets in favor of link layer breakagedetection (AODV-LL) thereby reducing Overhead.
• Problem with AODV-LL is its On Demand (link breakages can be detectedonly if there is a packet to be transmitted).
• Reduced ROUTE REPLY timeout to 6 seconds from 120 seconds.
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Table: constants used in AODV
Methodology• Simulated network
• Took scenario files as input
• 210 total scenario files
• Describe motion of each node
• Exact sequence of packets(4 packets a second) to send from each node
• Exact Time change (in motion or packet origination) is to occur 50 wirelessnodes
• Flat rectangular area (1500m x300m)
• 900 seconds test time
• Following improvements made to all protocols:• Jittered response to periodic broadcast packets
• Routing packets queued ahead of other packets
• 802.11 MAC layer link breakage detection (except DSDV)Performance Comparison Of Mobile Ad-Hoc Networks 12
Movement Model and Communication
• Random Way-point Model
• 7 different pause times (0, 30, 60, 120, 300, 600, and 900 seconds)
• Nodes moved with a speed from 0-20m/s
• Also use simulations with max 1m/s for comparison
• Networks contained 10,20,30 CBR sources
• Did not use TCP
• 4 packets per second
• 64 byte packets
• Connections started uniformly between 0-180s
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Performance Metrics
Fig: Packet delivery Ratio Fig: Routing Overhead
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Performance metrics contd…..
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Table: Rate of connection changes
Fig: Path Optimality between 1m/s and 20m/s
Simulation Results
Packet Delivery Ratio for DSDV and DSR
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Packet Delivery Ratio for TORA and AODV-LL
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Routing Overhead for DSDV and DSR
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Routing Overhead for TORA and AODV-LL
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Path Optimality
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Fig: Path optimality for Different Protocols
Lower speed of node movement
Packet delivery ratio when packets
moving at 1m/s.
Routing Overhead when packets
moving at 1m/s.
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Conclusion• ns network simulator can now evaluate ad-hoc routing protocols
• DSDV
• Good with low mobility and fails to converge when node mobility increases.
• TORA
• Large overhead; fails to converge with 30 sources but does good when using 10 and 20 sources. Large overhead but can deliver 95% of the data for 10 and 20 sources.
• DSR
• Very good at all rates + speed, but large packet overhead.
• AODV
• Almost as good as DSR, but has more transmission overhead
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Thank youQuestions….?
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