Routing VoIP over Multichannel, MultiRadio Wireless Networks

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Routing VoIP over Multichannel, Multi-Radio
Wireless Networks
Illinois Center for Wireless Systems

• Vijay Raman and Nitin H. Vaidya
• University of Illinois at Urbana-Champaign

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Net-X Testbed

• Multi-channel, multi-interface wireless testbed
• 20 Soekris net4521 boards
• Linux 2.4 kernel
• Two 802.11a radiosper node (1 mini-PCI and 1
  PCMCIA)
• Runs a suite of multi-channel protocols

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Multichannel Protocol (HMCP)Kyasanur and Vaidya
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• One interface fixed on a channel the other
  capable of switching channels
• Channel allocation algorithm assigns only fixed
  interface channels
• Switchable interface switches to neighbors fixed
  channel for sending data
• Fixed interface used for receiving data

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Multichannel Routing

• Modified AODV routing protocol
• Next hop information includes channel and
  interface to use
• Channel diverse paths preferred

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Problem Definition

• HMCP optimized for throughput
• Provides network connectivity
• Multichannel protocols enhances throughput
• Switch to transmit incurs delay
• Channel switching delay, 5 ms
• Service a channel for a minimum duration, 20 ms
• Adds up over a multihop route!
• Such high delays not suitable for RT applications
• Eg. VoIP lt 150 ms delay preferred

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Alternative Mechanism

• Static Channel Allocation
• At least one channel common between two neighbors
• No channel switches
• Downside
• Requires topology knowledge
• Idea
• Use static channel mechanism for RT applications

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SHORT Static-Hybrid Approach

• Source indicates RT flow during route discovery
• Destination and intermediate nodes fix
  switchable radio to previous hops fixed channel
• No more channel switches during RT flow
• Even for broadcast!

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• DEMO

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Performance Results
Single Flow Case
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Performance Results
Multi Flow Case
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Performance Results
VoIP with TCP
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Thank You!

• http//www.crhc.illinois.edu/wireless/