Opportunistic Scheduling for Wireless Network Coding H' Yomo

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Opportunistic Scheduling for Wireless Network
CodingH. Yomo P. Popovski IEEE ICC June,
2007

• Chengzhi Li May 25, 2007

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Outline

• Background Motivation
• System Model Basic Assumptions
• Adaptive rate and Opportunistic Scheduling with
  Network Coding
• Numeric Results
• Several Comments

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Background Motivation

• Network coding has been extended to wireless
  networks
• e.g., XORs in the air practical wireless
  network coding by S. Katti, et. al. Sigcomm
  2006
• Most existing results exploit the
  broadcast nature
  of wireless
  communications, but ignore the
  corresponding feature
  heterogeneous
  and unreliable wireless channels
• Motivation
• exploit network coding gain
  in more
  realistic wireless network
  environment

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Main Contribution

• Propose an opportunistic scheduling for network
  coding to increase the throughput of wireless
  networks in more realistic environments
• First paper investigates the possible
  transmission rate adaptation and opportunistic
  scheduling for network coding

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System Model

• Only considers a network
  
  coding group
• One relay node and N receiving nodes
• Relay node has the packets to
  
  forward to all receiving nodes
• Each receiving node has the packets
  
  that will be forwarded to
  other N-1
  
  receiving nodes
• Constant transmission power
• Wireless channels
• stationary
• slow fading
• white Gaussian noise
• rn(t) instantaneous SNR
  
  at time t for node n,
  1lt n lt N
• are i.i.d. random variables
• follow Rayleigh distribution
• available at relay node
• Node n can successfully decode the transmitted
  packet only if
• transmission rate lt Blog2(1 rn) for frequency
  bandwidth B

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Rate Adaptation and Opportunistic Scheduling with
Network Coding

• Re-order rn(t), 1lt n lt N,
• Given k, relay node opportunistically select
  N-k1 nodes with and XOR their
  packets and broadcast at the rate
• Instantaneous capacity
• Average capacity
• Two special cases
• k 1 classical wireless network coding
• k N classical opportunistic scheduling for
  cellular networks
• Opportunistic scheduling for wireless network
  coding
• Dynamically choose kop according to time-varying
  SNRs of N receiving nodes

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Experimental Results

• For opportunistic scheduling
• Only simulation results
• For fixed k scheduling
• Theoretical and simulation results
• The authors claim
• For fixed k scheduling, the theoretical results
  closely match the simulation results

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Final Remarks

• Is it worth to study wireless network coding in
  more realistic environment by taking into account
  about
• Channel fading in door and out door
• Narrowband and wideband
• Packet error rate
• Wireless networks based on standards s.t. IEEE
  802.11

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Questions ?
Thanks You!