A New Multipath Routing Protocol for Ad Hoc Wireless Networks

1
A New Multipath Routing Protocol for Ad Hoc
Wireless Networks

• Amit Gupta and Amit Vyas

2
Outline

• Motivation
• Intuition and Previous Work
• Problem Statement
• Analysis
• Simulations
• Conclusion

3
Motivation

• Ad Hoc Wireless networks
• Very quickly deployable
• Less costly than infrastructure networks
• Applications
• Internet connectivity in buildings
• Connecting computers at a conference
• Video-conferencing
• Wireless sensor networks
• Military communications and emergency services

4
Motivation

• Interactive Applications place stringent demands
  on delay requirements (e.g. telnet or multimedia
  communication)
• Lower delays might be more important than
  bandwidth used
• Can we achieve lower delays by sending same
  packet over multiple paths ?
• What is the trade-off between decrease in delays
  and increase in bandwidth ?

5
Outline

• Motivation
• Intuition and Previous Work
• Problem Statement
• Analysis
• Simulations
• Conclusion

6
Intuition

• Send same packets along multiple paths
• Lowers end-to-end probability of losses
• In turn reduces expected number of
  retransmissions and number of timeouts
• Hence decreases expected end-to-end delay
• More relevant for wireless networks
• They are more lossy than wired networks
• But increases bandwidth requirements
• Let us try to quantify this trade-off

7
Previous Work

• Old work
• Dispersity Routing Maxemchuk (1975)
• Efficient Dispersal of Information Rabin (1989)
• More recently
• Apostolopoulos (2001)
• Split a video into multiple streams and send
  different streams over different paths to achieve
  better quality
• Liang, Steinbach, Girod (2001)
• Real-time voice communication over the internet
  using packet path diversity.
• Experimental setup in which they send packets
  over two paths using a relay server.
• Also simulated two CBR voice streams via two
  paths using ns simulator

8
Outline

• Motivation
• Intuition and Previous Work
• Problem Statement
• Analysis
• Simulations
• Conclusion

9
Problem Statement

• But no one has looked at
• Impact of using extra paths on bandwidth
• Trade-off between reduction in delay and extra
  bandwidth used
• Optimal number of redundant paths
• Depends on loss probability, time out values,
  number of hops
• Application to routing protocols

10
Problem Statement

• Outline of Work
• Analysis of delay-bandwidth tradeoff
• Study of loss models for wireless networks
• Impact of various parameters on the optimum
  choice
• Study of current Ad Hoc Wireless Routing
  Protocols
• Design of a new protocol
• Simulations using ns-2 network simulator

11
Outline

• Motivation
• Intuition and Previous Work
• Problem Statement
• Analysis
• Simulations
• Conclusion

12
Analysis

• Loss model for wireless networks
• Nguyen et. al. (1996)
• Trace-based approach for modeling wireless
  channel behavior
• For ATT WaveLAN, average packet error rate of
  2-3
• Improved two-state model (error, error-free)
• Two Three segment curves respectively for
  distribution
• Konrad et. al (2001)
• Markov based channel model
• Algorithm to divide trace into stationary
  components
• These models are very complicated and need very
  specific parameters
• Simple probability model is good enough for our
  study
• Burst losses and outages will only make our
  results better

13
Analysis

• Important parameters
• Loss probability over a link
• Timeout for end-to-end retransmission
• Number of hops
• Number of paths
• Additional delay of alternate path(s)
• Metrics
• Expected end-to-end delay
• Expected bandwidth used
• Delay-bandwidth product

14
Analysis

• Variation of number of paths

15
Analysis

• Variation of number of paths

16
Analysis

• Variation of number of hops

17
Analysis

• Variation of number of hops

18
Analysis

• Variation of additional delay of alternate paths

19
Outline

• Motivation
• Intuition and Previous Work
• Problem Statement
• Analysis
• Simulations
• Conclusion

20
Current Ad Hoc Wireless Routing Protocols

• Table-Driven Routing Protocols
• Destination-Sequenced Distance Vector Routing
  (DSDV)
• Clusterhead Gateway Switch Routing (CGSR)
• The Wireless Routing Protocol (WRP)
• Source-Initiated On-Demand
• Ad Hoc On-Demand Distance Vector Routing (AODV)
• Dynamic Source Routing (DSR)
• Temporally Ordered Routing Algorithm (TORA)
• Associativity-Based Routing
• Signal Stability Routing

21
Simulations

• To validate the analysis results
• Used the ns-2 simulator with wireless extensions
• Modified DSR protocol to allow multiple paths
  Dynamic Multipath Source Routing (DMSR)
• Simulation Setup
• Interested in study of delay-BW tradeoff for
  end-to-end error-recovery protocols (e.g. TCP)
• Effect of number of hops and network load
• Two scenarios deterministic 16 nodes and
  uniform randomly distributed 30 nodes

22
Simulations

• Scenario of 16 nodes
• Relatively low network load

23
Outline

• Motivation
• Intuition and Previous Work
• Problem Statement
• Analysis
• Simulations
• Conclusion

24
Conclusion

• Use of multiple paths for achieving lower
  expected delays
• Studied effect of various parameters on the
  delay-bandwidth trade-off
• Determined optimal number of redundant paths
• Implemented scheme as DMSR Wireless Routing
  Protocol
• Validated results using simulations

25

• THE END