Traffic Manager

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Wireless Media Distribution and Cross-Layer
QoS. Intel Infrastructure Processor Division
(IPD) David Romano - Architect Xiancheng Yuan -
Architect
Intel's 2004 IXA University Summit
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Multimedia networking is driving the mass-market
adoption of a new class of Consumer Electronics
(CE) and residential networks.
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• Intel Digital Home Initiative
• The digital home vision integrates entertainment
  and media usages across the Internet and
  broadcast islands in the home through a seamless,
  interoperable network which will provide unique
  opportunities for manufacturers and consumers
  alike. This network is the communications and
  control backbone for the digital home and is
  based on IP networking and UPnP technology.
• The IP family of protocols is the foundation of
  networking and connectivity in the digital home.
  IP also provides the underlying network
  communications for devices on the Internet.
• Digital Home Guidelines
• for 2004
• A Proposal from Intel Corporation

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Example of a possible Wireless home media
distribution model
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WLAN Background

• Wireless LANs are very different from wired LANs
• Throughput drops off rapidly with distance and
  obstacles
• Time division duplex Tx or Rx (not both at the
  same time)
• Collision avoidance (collisions are expensive,
  need to ensure that they rarely occur)
• Interference
• Changing link conditions
• Legacy system overhead

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Technical Barriers

• Shared / limited bandwidth
• Best effort delivery
• Transmission errors
• Channel variations
• Heterogeneous connections / clients

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• Cross-Layer QoS includes
• 802.11e (Wi-Fi WMM) - MAC Layer QoS
• Multi-Channel PHY technology - Physical Layer QoS
• Error Concealment
• Hybrid Automatic Repeat Request (ARQ) Transport
  Layer QoS
• Jitter Concealment (Program Clock Sync)
  Transport Layer QoS
• Dynamic Rate Adaptation Application Layer QoS

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Wi-Fi Wireless Multimedia (WMM)802.11e/WME
Enhanced Distributed Channel Access(EDCA)

• QoS based on priority of access to the wireless
  medium, and it supports priority based
  best-effort service such as DiffServ
• Prioritized QoS is realized through the
  introduction of four access categories (AC)
• AC is realized by setting different values for
  the AC parameters. The most important of which
  are
• Arbitrary inter-frame space number (AIFSN) The
  minimum time interval between the wireless medium
  becoming idle and the start of transmission of a
  frame.
• Contention Window (CW) A random number is drawn
  from this interval, or window, for the backoff
  mechanism.
• TXOP Limit The maximum duration for which a QSTA
  can transmit after obtaining a TXOP.

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Multi-Channel PHY

• For an 11b/g WLAN, the 2.4-MHz frequency band is
  divided up into 11 channels.
• Only three of these channels 1, 6, and 11 - are
  "far enough apart" in radio terms to avoid
  overlapping signals and a resultant loss in
  throughput.
• Conventional access points are assigned one of
  these channels for client connections, ignoring
  the others.
• Some chipsets vendors offer proprietary
  techniques for doubling the 11g data rate to just
  over 100M bit/sec.

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Multi-Channel PHY
HW Integrated Chip Set Solution
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3x 11b/g Simultaneous channels
Controller
Digital Base-Band
RF
Analog Base-Band
6
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HW Spectrum Analysis (Fast Interference detection)
SW 3x Single Channel Chip Set Solution
Digital Base-Band
RF
Analog Base-Band
1
Controller
3x 11b/g Simultaneous channels
6
SW Spectrum Analysis (Interference detection)
Digital Base-Band
RF
Analog Base-Band
11
Digital Base-Band
RF
Analog Base-Band
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Error Concealment

• Hybrid ARQ (HARQ) data transfer protocol
• The basic idea of Automatic Repeat ReQuest (ARQ)
  is to detect erroneous packets and to retransmit
  these packets until they are correctly received.
• Errors are typically detected by applying a
  Forward Error Correction (FEC) code that has good
  error detection capabilities (and may have weak
  error correction performance).
• Hybrid ARQ techniques combine FEC and ARQ for
  more effective video streaming.

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Jitter Concealment

• Program Clock Synchronization
• Recovery of a high-quality system clocks is
  crucial to the decoding of quality Audio and
  Video media.
• Audio and video sample clocks in an MPEG-2
  decoder are derived from the system clock at the
  encoder.

• Ideal method - Be insensitive to packet en-route
  delays and packet losses.

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Adaptive Rate Control

• A rate control algorithm dynamically adjusts
  encoder parameters to achieve a target bitrate.
• It allocates a budget of bits to each group of
  pictures, individual picture and/or sub-picture
  in a video sequence.

Uncompressed Source
Compressed Video
Encoder
Rate Controller
Bit Rate
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Example of a possible Wireless Video Networking
stack w/Cross Layer QoS
Application Layer
Network Layer
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IPD Lab Set-UP
Clients
Server
Test console 3
Video
PCI
10/100
WAP
Test console 2
IXP 425 development board
Data
Test console
Monitor
Test console 1
Voice