CROSS-LAYER%20OPTIMIZATION

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CROSS-LAYER OPTIMIZATION

• PRESENTED BY M RAHMAN
• ID100746402

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Outline

• Introduction
• What it is?
• Why Cross-Layer ?
• Optimization Goals
• Pros and Cons
• What are the Challenges
• What are the research problems
• Future tasks
• Conclusions

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Introduction

• A significant recent advances that demonstrate
  that wireless resources such as (time, frequency,
  power, link data rates, and end-user data rates),
  across multiple layers can be incorporated into a
  unified optimization framework.

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What it is?

• To create infrastructure and algorithms to enable
  more optimal performance of the wireless system,
  by adopting an integrated, multi-layer approach.
• The design and optimization process will combine
• Innovations at physical layers
• Control and scheduling at MAC layer
• Efficient routing and admission control at
  network layer
• Dynamics and flow control at transport layer
• Specific requirements at application layers.

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Optimization Goals

• Lengthen system lifetime
• Enable large scale networks
• Low cost
• High efficiency
• Improve power efficiency
• Prevent system deconstruction
• Support node versatility
• Multiple functionality
• Multiple applications

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Why Cross-Layer?

• Possibility
• Optimization goals can be pursued in multiple
  layers
• layered optimizations assume cross-layer
  cooperation
• Some applications do not need all layers
• Multi-hop Local Positioning System (MLPS)
• Necessity
• Optimizing single layer is not enough
• Optimizations may be conflict with each other
• One-for-all consolidate design for feasible
  applications

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Why Cross-Layer? (Contd.)

• Heterogeneity
• Intra connection vs. Inter connection
• Scalability
• Correctness verification
• Reusability
• Code reuse
• Module reuse

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Pros

• Service Consistency Stable, consistent service
  quality is a basic requirement. If the consumers
  experience is inconsistent, he or she will be
  less likely to continue subscribing to the
  service.
• Connection Reliability Reliable connections are
  extremely important to build consumer confidence
  in 3G services. A dropped connection during a
  wireless data session is more disruptive than a
  dropped voice call.
• Consistent Multimedia Streaming Streaming video
  and audio are the key services that differentiate
  3G from 2G/2.5G networks. In a wireless WAN, RF
  variations can lead to long, initial buffering
  times and additional interruptions during
  viewing.

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Cons

• While applying Congestion control algorithms in a
  wireless environment, network efficiency problems
  occur
• Redundant data is transmitted Congestion
  control algorithms induce retransmissions
  resulting in redundant data transmissions and
  multiple acknowledgements of data already
  received.
• Less bandwidth is utilized When congestion
  control kicks in (break down/smash), the rate at
  which packets are sent is reduced, thereby
  failing to exploit valuable bandwidth.
• Sessions are terminated When the protocol
  inaccurately determines that a connection has
  timed out, the session will terminate. Due to
  this response, some applications, like
  e-commerce, may be impossible to use.

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What are Challenges?

• Improved Coverage Transport optimization can
  increase effective cell coverage so that in areas
  where a user previously could not download a Web
  page due to poor signal quality, a user now can
  do so quickly. Carriers are able to deliver
  consistent service quality over a larger area
  without having to increase base station density.
• More Capacity, Higher Returns Wireless networks
  have limited capacity due to limited spectrum.
  With a cross-layer optimization approach, mobile
  service providers increase network and spectrum
  utilization, freeing up usable bandwidth and
  available capacity.
• Increased Throughput (document sending) and
  Improved Multimedia Performance Cross-layer
  optimization can increase application throughput
  up to nine times, improving the user experience
  and resulting in faster browsing, shorter
  buffering times for multimedia, and fewer
  interruptions in all cell areas.

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Research Problems

• Cross-Layer Design With Fairness
• Constant-Overhead/Low-Overhead Implementation
• Tightness of Throughput-Loss Bounds
• Nonconcave Utility Functions
• The Congestion-Control Problem
• The Scheduling Problems
• Propagation Delays and Connection-Level Stability
  Analysis
• Traffic Arriving at all Nodes on the Route
  Instantaneously
• Complexity Issues and Distributed Algorithms for
  General Physical Interference Models

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Future Tasks

• Do some theoretical study on the system
  limitations
• System Throughput Network Scale
• Node Synchronization and Positioning accuracy
• Channel allocation and Mode decision
• Identify and justify feasible application models
• Implement the applications
• Complete the protocol stacks
• Tune the protocols and functional modules
• Optimize the applications
• Developing the research platform

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Conclusions

• While the progress in this area has been
  substantial over the last few years, there are
  still several open problems, especially in the
  area of multihop wireless networks, where
  scalability becomes a critical issue.
• While the application can adapt to a
  rate-delay-performance tradeoff curve offered by
  the network and underlying links, by making the
  lower layer protocols aware of the tradeoffs
  inherent to the application adaptation, that
  tradeoff curve might be adjusted to improve
  end-to-end performance without using up more
  resources in the network.
• In other words, if the application is aware of
  the lower layer protocol tradeoffs and these
  protocols aware of the application tradeoffs,
  these tradeoffs curves can be merged to operate
  at the best point relative to end-to-end
  performance.

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Conclusions (contd.)

• While implementing this philosophy, in spite of
  open research problem, it holds significant
  promise for the performance of ad hoc wireless
  networks
• In todays wireless world, consumers are
  demanding secure, high-quality wireless data
  services to access their most important business,
  news and entertainment content while they are
  mobile.
• By employing a cross-layer optimization solution
  that works transparently at the transport and
  application layer, the Web, streaming multimedia,
  e-mail and other applications perform at a level
  users expect.

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• 
  
• Thank you
  

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QUESTION SESSION

• QUESTIONS?