Introduction to 802.11 Protocol(WLan Standard) In the name of God University of Tehran School of Electrical and Computer Engineering By: Noushin Behboudi.

Introduction to

802.11 Protocol(WLan Standard)

In the name of GodUniversity of Tehran

School of Electrical and Computer Engineering

By:

Noushin Behboudi 810188190Supervisor :

Prof. S. M. FakhraeiSpring 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]3

IEEE 802.11 Protocol:

4

Covers physical and data link layer acc. to OSI

Physical layer:

Data Link layer

Spread Spectrum

FHSS

DSSS

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

[5]

IEEE 802.11 standards :

5 [5]

IEEE 802.11 standards :

IEEE 802.11 b

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Frequency = 2.4 GHz (ISM band)Maximum Speed =11 MbpsRange = about 38meters(Varies)Encoding Scheme = DSSSModulation Technique= BPSK(1 Mbps), DQPSK(2 Mbps), CCK(5.5 Mbps,11Mbps)

[5]

www.cisco.com

IEEE 802.11 standards :

7 [5]

IEEE 802.11 standards :

IEEE 802.11 a

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Frequency = 5 GHzMaximum Speed = 54 MbpsRange = about 35 meters(Varies)Encoding Scheme = OFDM

[5]

www.cisco.com

IEEE 802.11 standards :

9

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]

IEEE 802.11 standards :

10

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]

IEEE 802.11 standards :

IEEE 802.11 a

A simple idealized OFDM system(Implementation using FFT Algorithm)

11

TransmitterReceiver

[6]

IEEE 802.11 standards :

IEEE 802.11 a

OFDM Pros &ConsRobust 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. 12 [6]

IEEE 802.11 standards :

13 [5]

IEEE 802.11 standards :

IEEE 802.11 g

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

www.cisco.com

[5]

IEEE 802.11 standards :

15 [5]

IEEE 802.11 standards :

IEEE 802.11n

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

[5]

IEEE 802.11 standards :

IEEE 802.11 n

Multiple Input Multiple Output(MIMO)

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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]

ATHEROS Product :

18 [1]

ATHEROS Product :

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ATHEROS 9285 Spec:

[1]

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.

20 [2]

References :

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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. Tanenbaum Andrews ,”Computer networks (fourth edition) book”9. Hardware Implementation of a .٨٠٢ ١١n MIMO OFDM Transceiver, Zoha Pajouhi, Seid Mehdi Fakhraie, Seid Hamidreza Jamali. IEEE ٢٠٠٨

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