A practical multichannel multiradio MAC

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A practical multi-channel multi-radio MAC

• Song Wei 1983.song.wei_at_gmail.com
• _at_
• WiSeR Group http//wireless.cs.uh.edu

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Introduction

• For multi-channel multi-radio wireless network
  (MCMR)?
• Distributed
• An up to date MAC framework with a clear design
  to handle MCMR
• Intelligent Decision Making Compnent

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Background

• Assumptions
• Multiple interfaces for one node
• Off the shelf hardware
• Number of channels gt Number of interfaces per
  node
• No centralized control
• Trade offs
• simplicity vs flexibility
• throughput vs delay

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Motivation

• Intelligent decisions needed in distriubted MCMR
  network
• Channel switching
• Avoid crowded channels
• Packet scheduling
• Balance among multiple links
• Traditional MAC CSMA/CA
• How to avoid collison when you can't hear from
  all the neighbours?

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Related Work with Numeric Results

• Capacity of MultiChannel Wireless Networks
  Impact of Number of Channels and Interfaces,
  Pradeep Kyasanur, Nitin H. Vaidya
• performance bounds for static multi-channel
  wireless network
• Decentralized Cognitive MAC for Opportunistic
  Spectrum Access in Ad Hoc Networks A POMDP
  Framework, Qing Zhao, Lang Tong, Ananthram Swami,
  and Yunxia Chen
• simpfied assumptions, partial observable markov
  chain

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Related Work with simulation results

• Multichannel MAC Protocols for Wireless Networks,
  Ritesh Maheshwari, Himanshu Gupta and Samir R.
  Das
• one node is equipped with one packet interface
  and a busy tone interface

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Related Work with testbed implementation

• Design and Implementation of a MultiChannel
  MultiInterface Network, Chandrakanth Chereddi,
  Pradeep Kyasanur, and Nitin H. Vaidya
• net-x framework channel/load balancing
  abstraction layer above device driver, fixed
  interface switchable interface
• device driver enhancements for faster channel
  switching
• MadMAC Building a Reconfigurable Radio Testbed
  using Commodity 802.11 Hardware, Ashish Sharma,
  Mohit Tiwari, Haitao Zheng
• fine grained control over madwifi driver
• McMAC A Multi-Channel MAC Proposal for Ad-Hoc
  Wireless Networks, Hoi-Sheung Wilson So, Jean
  Walrand
• 1 hop ad hoc network with 1 radio per node
• Rendezvous based

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What's special about us?
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(No Transcript)
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An attempt to bridge theory and implementation
PMODP Machine learning ...
NET-X
?
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Goal

• MCMR MAC framework
• easy linux integration
• hide details from network layer
• fine grained control
• separate basic infranstructure and algorithmic
  module
• Decision making module
• channel switching, packet scheduling, load
  balancing
• acheive better distributed coordination between
  nodes
• utilize detailed wireless statistics

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Design Choices

• One switchable interface(hopper) one fixed
  interface(anchor)?
• flexibility vs simplicity
• A bonding driver above device drivers
• hide hardware details
• can handle different devices more easily
• utilize standard wireless interface in current
  linux
• link level hello protocal
• Update customization upon NET-X work
• Focus on decision making module

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Improvements upon NET-X
NETX
WiSer MAC

• Add on to bonding driver
• Link level contains routing functionality
• Invokation of scheduling/channel switching code
  is simple
• Linux 2.4

• Clean slate code
• Link level modification is hidden from upper
  level
• Flexible ways to invoke scheduling/channel
  switching code
• Linux 2.6

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Design Choices

• Decision making module
• Objective
• channel switching
• packet scheduling
• load balancing
• harness RSSI and other detailed wireless info for
  every packet

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System Architecture
Network layer
Linux packet interface
Control utility in user space
Wiser bonding driver
IOCTL
Linux packet interface
Linux wireless framework
Slave Network Driver
Slave Network Driver
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System ArchitectureWiser bonding driver
Channel switching timer
Packet buffer queue
Packet scheduling channel switching module
Interface/channel assignment interface
wireless device interface
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System Architecturehello protocol
Hello protocal timer
Hello protocol module
Slave device control
wireless device interface
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System Architecturemeasurement
wireless device interface
Measurement componenet
Wireless node
Wireless node
Wireless node
Centralized experiment control data gathering
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Decision Making module

• Design will be driven by measurement result
• May need to be merged with hello module
• Major concerns
• reduction of in-network interference efficient
  distributed coordination
• capture of external interference/link quality
  variation pattern
• guess what's happening on other channels with
  limited observation
• Candidate tools
• markov chain, coding theory, dynamic programming,
  Q learning, neural network

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Decision Making module

• Current idea
• Which channel to switch to
• Bandwitdth expectation
• Load balancing requirement
• Lookihood of channel state estimation
• When to switch
• Current channel state
• Load balancing needs
• Channel switching time

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Current status

• Done
• Related work survey
• Design goal formulation
• Design choice
• In progress
• Implementation debugging of MAC infranstruture
  prototype
• ToDo
• Measure throughput delay on testbed
• measurement driven design of decision making
  module

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Conclusion

• The bridge between theory and system work is a
  weak link in current research in this area.
• This work is both an exploration as well as
  ground work for our group
• Importance of investment in system development
• Grateful for critiques and suggestions!