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

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

• IEEE Wireless Commun., Aug. 2005
• Mihaela Van Der Schaar, UC Davis
• Sai Shankar N, Qualcomm Inc., USA

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Outline

• Introduction
• The Cross-Layer Design Problem
• Classification of Cross-Layer Solutions
• More Problems
• New Paradigm

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Introduction

• Existing wireless networks provide only limited,
  time-varying quality of service (QoS) for
  delay-sensitive, bandwidth-intense, and
  loss-tolerant multimedia applications.
• Real-time multimedia applications need that the
  application layer cooperate with the lower layers
  to select the optimal wireless transmission
  strategy that maximizes multimedia performance.

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Introduction (cont.)

• Layered optimization leads to a simple
  independent implementation, but results in
  suboptimal multimedia (objective and/or
  perceptual quality) performance.

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The Cross-Layer Design Problem

• The cross-layer design problem is formulated as
  an optimization with the objective to select a
  joint strategy across multiple OSI layers.

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The Cross-Layer Design Problem (cont.)

• Let NP, NM, and NA denote the number of
  adaptation and protection strategies available at
  the PHY, MAC, and APP layers, respectively.

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The Cross-Layer Design Problem (cont.)
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The Cross-Layer Design Problem (cont.)
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The conceptual framework
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Challenging

• The functions of Q, Delay, and Power are
  non-deterministic and non-linear, and there are
  dependencies between some of the strategies.
• The traditional algorithms and protocols at the
  various layers are often designed to optimize
  each layer independently and often have different
  objectives.

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Challenging (cont.)

• Formal procedures are required to establish
  optimal initialization, grouping of strategies at
  different stages and ordering. ??????,
  ????????????? Buffer size vs Delay vs re-try
• Different practical considerations for the
  deployed wireless standard.

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Classification Of Cross-Layer Solutions

• Top-down approach
• Bottom-up approach
• Application-centric approach
• MAC-centric approach
• Integrated approach

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Top-down approach

• The higher-layer protocols optimize their
  parameters and the strategies at the next lower
  layer.
• This solution has been deployed in most existing
  systems.

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Bottom-up approach

• The lower layers try to insulate the higher
  layers from losses and bandwidth variations.
• Not optimal for multimedia transmission.
  (unnecessary delays and throughput reductions)

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Application-centric approach

• The APP layer optimizes the lower layer
  parameters one at a time in a bottom-up or
  top-down manner, based on its requirements.
• Not always efficient.

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MAC-centric approach

• The APP layer passes its traffic information and
  requirements to the MAC, which decides which APP
  layer packets/flows should be transmitted and at
  what QoS level.
• The MAC decides the PHY layer parameters based on
  the available channel information.

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Integrated approach

• Exhaustively trying all the possible strategies
  and their parameters is impractical.
• A possible solution to solve this complex
  cross-layer optimization problem in an integrated
  manner is to use learning and classification
  techniques

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More problems

• Fairness
• Time
• Air
• MULTIMEDIA QUALITY

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New Paradigm

• Wireless stations can exchange information and
  distribute resources.
• Mixture of competition and cooperation.
• D. Krishnaswamy and M. van der Schaar, Adaptive
  Modulated Scalable Video Transmission over
  Wireless Networks with a Game Theoretic
  Approach, Proc. IEEE MMSP. Wksp., Sept. 2004.
• A Larcher et al., Decentralized Transmission
  Strategy for Delay-Sensitive Applications over
  Spectrum Agile Network, Packet Video 2004.

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VoIP
Video
RTP/RTCP
SCTP/UDP/TCP
IPv4/IPv6 MIP/HMIP
Mobile Management