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.
Outline:
 Introduction
 IEEE 802.11 Protocol Layers
 IEEE 802.11 standards
 ATHEROS Product
 Summary
 References
2
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 world’s first
wireless LAN standard.
 IEEE 802.11 is a subset of IEEE 802 LAN standard.
 [5]
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IEEE 802.11 Protocol:
Covers physical and data link layer acc. to OSI
 Physical layer:
 FHSS
 Data Link layer
Spread Spectrum
 DSSS
 Logic Link Control (LLC)
 Media Access Control (MAC)
 [5]
4
IEEE 802.11 standards :
IEEE 802.11 standards
 IEEE 802.11 b
 IEEE 802.11 a
 IEEE 802.11 g
 IEEE 802.11 n
 [5]
5
IEEE 802.11 standards :
IEEE 802.11 b
Frequency = 2.4 GHz (ISM band)
www.cisco.com
Maximum Speed =11 Mbps
Range = about 38meters(Varies)
Encoding Scheme = DSSS
Modulation Technique= BPSK(1 Mbps),
DQPSK(2 Mbps), CCK(5.5 Mbps,11Mbps)
[5]
6
IEEE 802.11 standards :
IEEE 802.11 standards
 IEEE 802.11 b
 IEEE 802.11 a
 IEEE 802.11 g
 IEEE 802.11 n
 [5]
7
IEEE 802.11 standards :
IEEE 802.11 a
Frequency = 5 GHz
Maximum Speed = 54 Mbps
Range = about 35 meters(Varies)
Encoding Scheme = OFDM
[5]
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
 [7]
9
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-carriers 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.
 [6]
10
IEEE 802.11 standards :
IEEE 802.11 a
A simple idealized OFDM system
(Implementation using FFT Algorithm)
Transmitter
Receiver
 [6]
11
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.
 [6]
12
IEEE 802.11 standards :
IEEE 802.11 standards
 IEEE 802.11 b
 IEEE 802.11 a
 IEEE 802.11 g
 IEEE 802.11 n
 [5]
13
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
 [5]
14
IEEE 802.11 standards :
IEEE 802.11 standards
 IEEE 802.11 b
 IEEE 802.11 a
 IEEE 802.11 g
 IEEE 802.11 n
 [5]
15
IEEE 802.11 standards :
IEEE 802.11n






 [5]
Frequency = 5 GHz,2.4 GHz
Modulation = OFDM
Addition of Mimo
Maximum Speed = 150 Mbps
Range = about 70 meters(Varies)
Encoding Scheme = OFDM
16
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.
 [4]
17
ATHEROS Product :
 [1]
18
ATHEROS Product :
ATHEROS 9285 Spec:
 [1]
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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.
 [2]
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References :
1.
www.atheros.com/pt/bulletins/ar9285Bulletin.pdf
2.
www.howstuffworks.com/wireless-network.htm
3.
Panko’s,“Tutorial Wireless LANs (WLANs)”, Business Data Networks and
Telecommunications, 2007
4.
Pablo brenner ,”A technical tutorial of the IEEE 802.11 protocol ”,2007
5.
http://en.wikipedia.org/wiki/802.11
6.
Dr.S.Srikanth ,” Tutorial on OFDM’’,AU-KBC Research Centre Anna University
Chennai,2007
7.
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.
8.
9.
Tanenbaum Andrews ,”Computer networks (fourth edition) book”
Hardware Implementation of a ٨٠٢.١١n MIMO OFDM Transceiver, Zoha
Pajouhi, Seid Mehdi Fakhraie, Seid Hamidreza Jamali. IEEE ٢٠٠٨
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Thanks for your attention !
Any Question?
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