Introduction to

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• In the name of God
• University of Tehran
• School of Electrical and Computer Engineering

Introduction to
802.11 Protocol(WLan Standard)
By Noushin Behboudi 810188190 Supervisor Prof.
S. M. Fakhraei Spring 2010
Class presentation for the course Custom
Implementation of DSP Systems All the materials
are copy rights of their respective authors as
listed in references.
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Outline

• Introduction
• IEEE 802.11 Protocol Layers
• IEEE 802.11 standards
• ATHEROS Product
• Summary
• References

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Introduction

• Access anytime, anywhere internet.
• IEEE 802.11 is a set of standards for wireless
  Local Area Networks
• (WLANs) computer communication, developed by
  the IEEE
• LAN/MAN Standards Committee.
• 1997 working group approved IEEE 802.11 as the
  worlds first
• wireless LAN standard.
• IEEE 802.11 is a subset of IEEE 802 LAN
  standard.
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IEEE 802.11 Protocol

• Covers physical and data link layer acc. to OSI
• Physical layer

• FHSS
• DSSS

• Data Link layer

Spread Spectrum

• Logic Link Control (LLC)
• Media Access Control (MAC)

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IEEE 802.11 standards

• IEEE 802.11 standards
• IEEE 802.11 b
• IEEE 802.11 a
• IEEE 802.11 g
• IEEE 802.11 n

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IEEE 802.11 standards
IEEE 802.11 b

• Frequency 2.4 GHz (ISM band)
• Maximum Speed 11 Mbps
• Range about 38meters(Varies)
• Encoding Scheme DSSS
• Modulation Technique BPSK(1 Mbps),
• DQPSK(2 Mbps), CCK(5.5 Mbps,11Mbps)
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www.cisco.com
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IEEE 802.11 standards

• IEEE 802.11 standards
• IEEE 802.11 b
• IEEE 802.11 a
• IEEE 802.11 g
• IEEE 802.11 n

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IEEE 802.11 standards
IEEE 802.11 a

• Frequency 5 GHz
• Maximum Speed 54 Mbps
• Range about 35 meters(Varies)
• Encoding Scheme OFDM
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www.cisco.com
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IEEE 802.11 standards
IEEE 802.11 a
Multipath Effect(Multipath Fading) is simply
a term used to describe the multiple Paths the
radio wave may follow between transmitter and
receiver

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IEEE 802.11 standards
IEEE 802.11 a
Orthogonal Frequency Division Multiplexing(OFDM)

• OFDM a digital multi-carrier modulation method. A
  large
• number of closely-spaced orthogonal sub-carrie
  rs are used to
• carry data.
• Although the principles and some of the benefits
  have
• been known since the 1960s, OFDM is popular
  for
• wideband communications today by way of
  low-cost digital
• signal processing components that can
  efficiently calculate
• the FFT.

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IEEE 802.11 standards
IEEE 802.11 a A simple idealized OFDM
system (Implementation using FFT Algorithm)
Transmitter
Receiver

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IEEE 802.11 standards

• IEEE 802.11 a
• OFDM Pros Cons
• Robust against narrow-band co-channel
  interference.
• Robust against intersymbol interference (ISI) and
  fading caused by multipath propagation.
• High spectral efficiency as compared to
  conventional modulation schemes, spread spectrum,
  etc.
• Efficient implementation using Fast Fourier
  Transform (FFT).
• Sensitive to Doppler shift.
• Sensitive to frequency synchronization problems.
• High peak-to-average-power ratio (PAPR),
  requiring linear transmitter circuitry, which
• suffers from poor power efficiency.

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IEEE 802.11 standards

• IEEE 802.11 standards
• IEEE 802.11 b
• IEEE 802.11 a
• IEEE 802.11 g
• IEEE 802.11 n

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IEEE 802.11 standards
IEEE 802.11 g
www.cisco.com

• Frequency 2.4 GHz
• Maximum Speed 54 Mbps
• Range about 38 meters(Varies)
• Encoding Scheme OFDM

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IEEE 802.11 standards

• IEEE 802.11 standards
• IEEE 802.11 b
• IEEE 802.11 a
• IEEE 802.11 g
• IEEE 802.11 n

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IEEE 802.11 standards
IEEE 802.11n

• Frequency 5 GHz,2.4 GHz
• Modulation OFDM
• Addition of Mimo
• Maximum Speed 150 Mbps
• Range about 70 meters(Varies)
• Encoding Scheme OFDM

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IEEE 802.11 standards
IEEE 802.11 n Multiple Input Multiple Output(MIMO)

• In radio, Multiple-input and
• Multiple-output is used of
• multiple antennas at both the
• transmitter and receiver to
• improve communication
• performance. It is one of
• several forms of smart antenna
• technology.

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ATHEROS Product

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ATHEROS Product
ATHEROS 9285 Spec

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Summary

• IEEE 802.11n standard Significantly improves
  throughput and range compared with older 802.11
  standards.
• 802.11n is the only 802.11standard that operates
  in either the 2.4 GHz and 5 GHz frequency bands.
• It is the first to standardize the use of
  multiple input, multiple output (MIMO) antenna
  design.

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References

• www.atheros.com/pt/bulletins/ar9285Bulletin.pdf
• www.howstuffworks.com/wireless-network.htm
• Pankos,Tutorial Wireless LANs (WLANs),
  Business Data Networks and Telecommunications,
  2007
• Pablo brenner ,A technical tutorial of the IEEE
  802.11 protocol ,2007
• http//en.wikipedia.org/wiki/802.11
• Dr.S.Srikanth , Tutorial on OFDM,AU-KBC
  Research Centre Anna University Chennai,2007
• K. F. Lee and D. B. Williams, A space-frequency
  coded transmitter
• diversity technique for frequency
  selective fading channels, in Proc.IEEE
• Sensor Array and Multichannel Signal
  Processing Workshop, Cambridge, MA, Mar, pp.
  149-152,2000.
• Tanenbaum Andrews ,Computer networks (fourth
  edition) book
• 9. Hardware Implementation of a ???.??n MIMO
  OFDM Transceiver, Zoha
• Pajouhi, Seid Mehdi Fakhraie, Seid
  Hamidreza Jamali. IEEE ????

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Thanks for your attention !
Any Question?