Cross-Layer Wireless Multimedia Transmission: Challenges, Principles - - PowerPoint PPT Presentation

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Cross-Layer Wireless Multimedia Transmission: Challenges, Principles - - PowerPoint PPT Presentation

Feb 14, 2024 28 likes •291 views

Cross-Layer Wireless Multimedia Transmission: Challenges, Principles and New Paradigms Mihaela Van Scharr, Sai Shankar Overview of Presentation Multimedia transmission in wireless networks. Part 1: meeting QoS constraints Part 2:

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Cross-Layer Wireless Multimedia Transmission: Challenges, Principles and New Paradigms

Mihaela Van Scharr, Sai Shankar

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Overview of Presentation

  • Multimedia transmission in wireless networks.
  • Part 1: meeting QoS constraints
  • Part 2: fairness and “coopetition”
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Multimedia Transmission

  • Quality of Service (QOS) constraints in

multimedia:

  • Can tolerate some errors / dropped packets
  • Sensitive to delay
  • High Bandwidth
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Cross-layer Optimization Background

  • Link adaptation
  • Channel-aware scheduling
  • Optimal power control
  • Don't consider characteristics of multimedia.
  • Redesign existing protocols?
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Layers being considered

  • Applications (APP)
  • Medium Access Control (MAC)
  • Physical Layer (PHY)
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PART 1: meeting QoS constraints

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Definitions

  • denotes the number of PHY,

MAC, APP adaptation and prediction strategies.

  • Joint cross-layer strategy is defined as:
  • denotes multimedia quality.
  • = (SNR, contention) represents the

instantaneous channel condition

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Cross-Layer Optimization Problem

  • Optimal strategy denoted as:

with constraints:

  • Many approaches to this optimization problem.
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Cross-Layer Optimization Problem

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Minimum required APP-layer packet length as a function of SNR

R denotes MAC retry limit

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Joint MAC/PHY Optimization

  • Use received signal strength indicator (RSSI)

via ACK to adapt modulation at PHY.

  • Increase throughput.
  • But this is not optimal for multimedia.
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Joint MAC/PHY Optimization

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Joint APP/MAC/PHY Optimization

  • denote the base layer and

enhancement layer rates at the APP.

  • : MAC packet size.
  • : modulation strategy at PHY.
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Joint APP/MAC/PHY Optimization

  • Optimal strategy becomes:

with

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Joint APP/MAC/PHY Optimization

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Joint APP/MAC/PHY Optimization

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PART 2: Fairness

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Ideal Fair Scheduler Based on Generalized Processor Scheduler

  • : amount of video flow from WSTA

at time interval .

  • : weight based on requirements.
  • Optimal policy is
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Proposed Idea: Time Scheduling

  • : time allocated to video stream of

during time interval .

  • : weight based on requirements.
  • Fairness policy becomes
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Scenario 1: same cross-layer strategies for both WSTAs

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Scenario 2: WSTA1 experiences more severe fading and interference

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Scenario 3: WSTA1 located further away from access point

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Multimedia Quality Fairness

  • Use information at APP to partition streams into

multiple sub flows.

  • Enforce minimum quality constraint for all

stations.

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Multimedia Quality Fairness

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Conclusions

  • Traditional cross-layer paradigms need to be

adapted for multimedia transmission.

  • Cross-layer optimization problem is exhaustive

to solve deterministically.

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Questions?