GIGABIT WLANS

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GIGABIT WLANS

• RAGHAVENDER JOGARAJU

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WHAT IS GWLAN ?

• Gigabit WLAN is a fourth generation system based
  on high-data-rate Orthogonal Frequency Division
  Multiplexing(OFDM), Multi Input Multi
  Output(MIMO) and Efficient MAC protocol
  techniques

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WHY GWLAN ?

• Modern Users of the Wireless networks expect the
  same service and quality from wireless networks
  as offered by wired networks.
• few of the things that a typical user of a
  wireless network might expect are E-mail,
  Internet, Voice, Video and Multimedia
  applications.

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• 2G and 3G technologies are not able to cope with
  these networks.
• 802.11n does not completely close the gap, hence
  we need a Gigabit WLAN.

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WiGLAN Architecture

• Network Controller
• Allocates channels
• Measures SNR
• Space-Time Diversity

Network Controller
NGI
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Network Controller with Space-Time Diversity
Receiver Chain
Transmitter Chain
Receiver Chain
Transmitter Chain
Receiver Chain
Transmitter Chain
Receiver Chain
Transmitter Chain

• Digital Modulation
• Digital Space-Time Diversity Processing
• Improves channel capacity
• Replicated Transmit/Receive Chain

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Network Adapter Block Diagram
Network adapter
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PREVIOUS WORK

• Wireless networking is an important media for
  computer connectivity, there have been numerous
  innovations since its introduction through the
  IEEE 802.11 standard in 1999.
• competition and innovation in wireless networking
  has produced greater capabilities with 802.11a,b
  and g.

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• The biggest change in wireless over the past
  10yrs has been the availability of the unlicensed
  wireless spectrum.
• Before this, the evolution of wireless
  technologies was tied to a specific spectrum and
  specific protocols.
• Because of concerns about interference, the
  transmission of electromagnetic energy was highly
  regulated.

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• It has now become possible to connect a radio to
  a computer that could control signals in new and
  complicated ways, at rates much greater than ever
  before.
• In the past 10 years the data rate available over
  unlicensed wireless systems has changed by four
  orders of magnitude.

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WHERE CAN IT BE USED ?

• The main application area is the transmission of
  multimedia content in so-called hot-spots in home
  scenarios, and in large offices where an enormous
  data rate back-off is necessary
• In order to be able to include a high data rate
  air-interface into a future heterogeneous mobile
  communications system, also high mobility
  applications are covered.

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TECHNOLOGIES

• Two Technologies that help realize GWLAN are,
• Multiple Input Multiple Output (MIMO)
• System-On-a-Package(SOP)

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MIMO

• MIMO wireless is an emerging cost effective
  technology that offers substantial leverages in
  making 1Gbps wireless links a reality.
• we can, in principle, meet the 1Gbps data rate
  requirement if the product of bandwidth (measured
  in Hz) and spectral efficiency (measured in
  bps/Hz) equals 109.

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• MIMO wireless constitutes a technological
  breakthrough that will allow Gbps speeds in NLOS
  wireless networks.
• The performance improvements resulting from the
  use of MIMO systems are due to,
• Array gain
• Diversity gain
• Spatial Multiplexing Gain
• Interference Reduction

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• In general it is not possible to exploit
  all the leverages of MIMO technology
  simultaneously due to conflicting demands on the
  spatial degrees of freedom (number of antennas).
• The degree to which these conflicts are resolved
  depends upon the signaling scheme.

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System-On-a-Package

• SOP approach for the next-generation wireless
  solution is a more feasible option than SOC .
• Recent development of materials and processes in
  packaging area makes it possible to bring the
  concept of SOP into the RF world to meet the
  stringent needs in wireless communication area.

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• Wireless devices implementing complex
  functionality require a large amount of circuitry
  and consequently, require a large conventional
  package or MCM real estate.
• SOP goes one step beyond Multi Chip Module (MCM)
  by enhancing overall performances and adding more
  functionalities.

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SOP
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• SOP is the art of bringing together at the system
  level ICs and embedded components following a co
  design philosophy.
• The SOP evolution for gigabit wireless
  applications involves systems, technology and
  materials consideration.
• Research is targeting 3-D high density module
  technologies for SOP based solutions for wireless
  communication applications.

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ISSUES

• Integrate unlicensed wireless securely and
  transparently into existing networking systems
• Provide the fast handoffs that will be required
  for continuous mobile connectivity, as cell sizes
  will continue to decrease
• Power Consumption.

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INTEGRATION WITH EXISTING SYSTEMS

• The wireless meshed network must intercommunicate
  with all the existing legacy systems out there.
  The interconnections need to be efficient and
  economically practical.
• The meshed network can't require the legacy
  systems to be extensively modified

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So What is the issue?

• Several unexpected problems have come up.
• TCP/IP was originally designed to run over lossy,
  highly variable delay networks and still deliver
  reasonable performance.
• The biggest problem for most users of TCP/IP,
  however, turned out to be that it was not
  efficient under the load of multiple users (which
  is what GWLAN would be serving).

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Whats the Solution ?

• There are two avenues of attack for these types
  of problems, and both should be followed through
  in parallel,
• Modify the existing protocols to be more
  flexible.
• Make the wireless mesh network look more like a
  wired network with predictable delays and minimal
  losses.

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HANDOFF

• One of the greatest system design concepts in the
  evolution of wireless technology is the notion of
  cellular deployment and the huge reuse of
  spectrum it provides.
• Reusing spectrum every few miles or every few
  hundred feet provides an essentially unlimited
  capacity for wireless communications.
• Handoff is the transition for any given user of
  signal transmission from one base station to a
  geographically adjacent base station as the user
  moves around

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• The smaller the cell size, the larger the
  communication capacity per unit area. This
  imposes huge pressure for very high-speed,
  short-distance radios.
• Thus, as cell size naturally shrinks, the
  available data rate increases.

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The Problem

• Since a GWLAN gives very high data rates we need
  to use more number of cells.
• The main limiting factor is the ability to
  provide fast handoffs over cells sized a few
  hundred feet in diameter.
• Typical vehicle speeds of a hundred feet per
  second mean switching cells every few seconds.

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• So We need a mechanism that takes care of these
  fast handoffs.
• For that we will need faster processors .
• Standards bodies today are defining the
  interfaces required to make the faster handoffs
  possible .

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POWER CONSUMPTION

• The need to reduce power consumption is one of
  the most challenging and interesting topics in
  wireless engineering.
• We require complicated physical solutions before
  any real system can be implemented

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• Today's cellphone solutions have made huge
  strides in conserving battery power, which has
  been achieved with fixed Throughput.
• The next challenge for GWLAN is to keep this
  trend intact while increasing the throughput by
  several orders of magnitude

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• One method of decreasing power consumption is to
  bring the radios closer together or, in other
  words, to create a ubiquitous mesh network .
• To bring radios closer together, they must become
  exponentially cheaper, as the number required
  increases (at best) by the square of the ratio of
  decrease in their average separation .

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• There is also a great push to increase the power
  density of batteries or other power-storage
  devices for reasons of portability.
• GWLANS should always strive to minimize power
  consumption, because the loss of one node would
  mean loss of a whole lot of Data.

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OTHER ISSUES

• ADC
• DIRTY RF
• MIMO Techniques
• MAC

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ADC

• Given todays analog-to-digital conversion
  technology and its only moderate evolution speed
  over the last decades, a digitization bandwidth
  of 100 MHz appears to be a reasonable assumption
  for GWLAN
• But For this a spectral efficiency of at least 10
  bit/s/Hz will be required.

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Dirty RF

• In view of the high system bandwidth requirements
  for Gigabit Wireless, carrier frequencies can be
  expected to be significantly higher in the
  future.
• In combination with decreasing supply voltages
  and high SNR requirements for MIMO techniques,
  non-linear effects in the RF front-end (e.g.,
  phase-noise, clock jitter, non-linear amplifiers)
  will have a strong impact on system performance
  making RF an issue.
• Appropriate analog predistortion as well as
  digital compensation techniques have to be
  developed in order to compensate the error
  effects.

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MIMO Techniques

• The use of multiple antenna techniques is a
  prerequisite to achieving a spectral efficiency
  of at least 10 bits/s/Hz within reasonable SNR
  limits.
• The main design challenges that have to be
  addressed to make the inclusion of MIMO
  techniques possible are channel estimation and
  base band signal processing complexity.

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MAC

• In todays WLAN systems, the reception of a
  packet is usually confirmed by an acknowledgement
  message of no more than 14 bytes.
• The transmission of such very short messages,over
  a conventional MAC is highly inefficient, due to
  minimum burst sizes and additional overhead
  (e.g., for authentication,request to send, clear
  to send, channel estimation,etc.).
• It is obvious that, if we follow the conventional
  approach, achieving a payload rate of 1 Gbit/s
  could require data rates of as much as 2 Gbit/s
  over the air which is neither feasible nor
  reasonable.

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SO ARE WE THERE ?

• If WiMAX -- an extension of Wi-Fi's reach -- is
  still more than a year from full use, Gi-Fi is a
  glimmer in the eyes of wireless enthusiasts.
• Regardless of the time it might take Gi-Fi to
  gain wide use, its promoters argue Gi-Fi has a
  tangible purpose and could find a willing market.

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OTHER ADVANTAGES OF GWLANS

• Lower Deployment and Production Costs.
• Indoor/Outdoor mobility.
• Availability .
• Security comparable to Wired Networks.

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CONCLUSION

• If the success of Wi-Fi and the imminent wide
  usage of WiMAX is any indication, Gi-Fi
  potentially can bring wireless broadband to the
  enterprise in an entirely new way.

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References

• Paving the Way for Gigabit Networking
• By Jean-Pierre Ebert, Eckhard Grass, Ralf
  Irmer, Rolf Kraemer, and Gerhard Fettweis,Karl
  Strom, Günther Tränkle, Walter Wirnitzer, Reimund
  Witmann, Hans-Jürgen Reumerman, Egon Schulz,
  Martin Weckerle, Peter Egner, and Ulrich Barth
• An Overview of MIMO Communications - A Key to
  Gigabit Wireless
• A. J. Paulraj, D. Gore, R. U. Nabar, and H.
  Bolcskei
• The Future of WLAN
• ACM Queue vol. 1, no. 3 - May 2003 by
  Michael W. Ritter, Mobility network systems
• Gigabit Wireless System-on-a-Package Technology
• RAO R. TUMMALA, FELLOW, IEEE AND JOY LASKAR,
  SENIOR MEMBER, IEEE
• http//www.wigwam-project.de/

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• Challenges and Opportunities in Broadband and
  Wireless Communication Designs
• Jan M. Rabaey1, Miodrag Potkonjak2, Farinaz
  Koushanfar3, Suet-Fei Li1,TimTuan11 EECS
  Department, University of California, Berkeley,
  CA 94720 2 CS, 3 EE Departments, University of
  California, Los Angeles, CA 90095
• http//www.theregister.co.uk/2004/11/19/gigabit_wi
  -fi_promised/
• System Concept for 1 Gbit/sand Beyond
• Tutorial IEEE 802 Plenary, Vancouver,
  November 2005
• Gerhard Fettweis Vodafone Chair Mobile
  Communications Systems
• TechnischeUniversitätDresden, Germany
• WIGWAM-A Wireless Gigabit System with Advanced
  Multimedia Support
• Gerhard Fettweis, Tim Hentschel, Ernesto
  Zimmermann, Technische Universität Dresden,
  Germany