b1 -Intro Noise -comm theorem

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SZE 3533SZE 3533COMMUNICATION PRINCIPLECOMMUNICATION PRINCIPLE

ByByMohd Taufik Bin Jusoh @ TajudinMohd Taufik Bin Jusoh @ Tajudin

Topic 1Topic 1Introduction to CommunicationIntroduction to Communication

SystemSystem


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1.0 Introduction1.0 Introduction

How do you want to send data/information tosomeone who is far from you?

If the information that you want to send is yourvoice, how to make sure that what you are

saying is understood by your friend?

What is the source and technology available

surround you that can help?

Pengenalan Kepada Sistem Perhubu


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1.1 Communication System History1.1 Communication System History 1837 Samuel Morse invented telegraph. 1858 First telegraph cable across Atlantic (Canada Ireland) 1876 Alexander Graham Bell invented telephone. 1988 Heinrich Hertz introduce electromagnetic field theory. 1897 Marconi invented wireless telegraph. 1906 Radio communication system was invented. 1923 Television was invented.

1938 Radar and microwave system was invented for World War II. 1950 TDM was invented. 1956 First telephone cable was installed across Atlantic. 1960 Laser was invented 1962 Satellite communication 1969 Internet DARPA

1970 Corning Glass invented optical fiber. 1975 Digital telephone was introduced. 1985 Facsimile machine. 1988 Installation of fiber optic cable across Pacific and Atlantic. 1990 World Wide Web and Digital Communication. 1998 Digital Television.



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1.2 Communication System1.2 Communication System Communication system Process of sending information

signal from one point to another point - involve 3 important

processes ie:Transmission

Receiving

Processing Eg: Telegraphy, telephony, facsimile, radio, satellite, optical

fiber system, cellular mobile.

Analog System: Information signal is analog signal andsensitive to noise.

Digital System: Information signal can be digital or analoguesignal (through discrete process) and less sensitive to noise.


mtx(t)

Comm

System

mrx(t)

Input

Transducer

Output

Transducers(t) r(t)

Fig. 1.1 Basic communication system


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1.3 Types of Signal1.3 Types of Signal Signal Classification:

Continuous-time and discrete-time

Analog and digital

Periodic and Aperiodic

Periodic :x(t)=x(t+To)

Aperiodic:x(t) no repetition, eg: audio signal


An example of a periodic signal is a sinusoidal signal:

)2sin()( += tfAtx o

002 f =

00

0

12

fT ==

)2sin()2

(sin)2

( 00

0

0

++=

++=+ tAtAtx

[ ])2sin()cos()2cos()sin( 00 +++= ttA

But cos(2 ) =1 and sin(2 )=0

;

)()sin()2

( 00

txtAtx =+=+

Periodic signal: A sinusoidal signal

Aperiodic signal: Unit pulse signal


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6Pengenalan Kepada Sistem Perhubu

t

g(t)

g(t)

t

t

g(t)

t

g(t)

Analog, continuous-time Digital, continuous-time

Analog, discrete-time Digital, discrete-time


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1.3.1 Harmonic signal1.3.1 Harmonic signal



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1.4 Basic Communication System1.4 Basic Communication System


TransmitterTransmission

MediumReceiver

Input

Transducer

OutputTransducer

Noise

wired / wireless

mtx(t)

s(t) r(t)

ptx(t)

n(t)

mrx(t)prx(t)

s(t) Input signal; audio, video, image, data etc.

mtx(t) Modulating signal; input signal that has been converted to electrical

signal.ptx(t) Modulated signal transmit by the transmitter.

n(t) Noise signal.

prx(t) Modulated signal receive by the receiver.

mrx(t) Modulating signal at the receiver.

r(t) Output signal.


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1.5 Transmission Medium (Guided)1.5 Transmission Medium (Guided)

Kabel Terpiuh (Twisted pair)

Unshielded Twisted Pair (UTP)

Shielded Twisted Pair (STP)

Kabel Sepaksi (Coaxial)

Kabel Gentian Optik (Fiber Optic)

Singlemode step index

Multimode step index Multimode graded index

Pandu Gelombang (Waveguide)



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1.6 Transmission Medium (Unguided)1.6 Transmission Medium (Unguided)


Ruang Bebas (Free Space)


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1.7 Frequency Spectrum1.7 Frequency Spectrum

Pengenalan Kepada Sistem Per

100M

Hz

WaveguideCoaxial CableTwisted PairCable

Infrared

Visible

Ultraviolet

Optical Fiber

ExtraHigh

Frequency

EHF

SuperHigh

Frequency

SHF

Ultra

High

Frequenc

yUHF

VeryHigh

Frequency

VHF

High

Frequen

cy

HF

Medium

Frequen

cy

MF

Low

Frequen

cy

LF

VeryLow

Frequency

VLF

Audio

Line-of-sightradio

Skywaveradio

Groundwaveradio

Wavelength

Frequencydesignations

Transmissionmedia

Propagationmodes

Representativeapplications

Frequency

Laser beam

100km 10km 1km 100m 10m 1m 10cm 1cm 10-6m

Telephone

Telegrap

h

Mobilrad

io

VHFT

VandFM

Mobilan

dAerona

utical

UHFTV

CBradio

Amateur

radio

AMbroad

casting

Aero

nautical

Submarin

ecable

Navigation

Transoceanicrad

io

Broad

bandPCS

Wireless

c

ommunication

Cellular,Pager

Satellite-satellite

Microwaverelay

Earth

-sat e

llite

R

adar

Wide

banddata

1kHz

10kHz

100kH

z

1MHz

10MH

z

1GHz

10GH

z

1G0H

z

10

14Hz

10

15Hz


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1.8 Communication System Efficiency1.8 Communication System Efficiency

We can measure the level of efficiency of communication system

through several ways:

How close the received signal to the transmitted input signal?

s(t) , r(t) ; Needs high quality of transmission.

s(t) Analog Signal to Noise Ratio (SNR).

s(t) Digital Bit Error rate (BER).

How much power needed to transmit modulated signal?

Low power; Lifespan of a battery is longer.

High power; Lifespan of a battery is shorter.

How much Bandwidth,BWis needed to transmit the modulated

signal?

Low BWmeans more users can share the communication

medium.

How much signal or signal size needs to transmit?

Analog system depends on s(t) BW.

Digital system depends on bit rate, bit/s.Pengenalan Kepada Sistem Perhubu


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1.8.1 Obstacle to Communication System1.8.1 Obstacle to Communication System

Technology Problem

Hardware

Economy

Law and Regulation

Physical Problems

BW

Signal Power

Noise



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1.8.2 Types of Transmission1.8.2 Types of Transmission

Simplex

One way transmission

Half-Duplex

Two way transmission but only one user can transmit the

signal at one time. Full-Duplex

Two way transmission, both users can transmit the signal at

the same time.



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1.9 Noise1.9 Noise

In practice, we cannot avoid the existence ofunwanted signal together with the modulated signal

transmitted by the transmitter. This unwanted signal is called noise. Noise is a random signal that exists in a

communication system. Random signal cannot be represented with a simple

equation. The existence of noise will degrade the level of

quality of the receive signal at the receiver.



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1.9.1 Types of noise1.9.1 Types of noise An undesired disturbance within the frequencyband of interest; the summation

of unwanted or disturbing energy introduced into a communications systemfrom man-made and natural sources.

A disturbance that affects a signal and that may distort the information carriedby the signal.


Noise

Internal Noise External Noise

Due to random movement ofelectrons in electronic circuit

Thermal noise/Johnson noise Shot noise

Man-made noise andnatural resources

Lightning Solar noise Ignition Crosstalk
http://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Band_%28radio%29http://en.wikipedia.org/wiki/Communications_systemhttp://en.wikipedia.org/wiki/Signal_%28information_theory%29http://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Informationhttp://en.wikipedia.org/wiki/Signal_%28information_theory%29http://en.wikipedia.org/wiki/Communications_systemhttp://en.wikipedia.org/wiki/Band_%28radio%29http://en.wikipedia.org/wiki/Frequency


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1.9.2 Noise Effect1.9.2 Noise Effect

Degrade system performance for both analog anddigital systems.

The receiver cannot understand the original signal.

The receiver cannot function as it should be.

Reduce the efficiency of communication system.



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1.9.3 Thermal Noise1.9.3 Thermal Noise JohnsonNyquist noise (thermal noise, Johnson noise, or

Nyquist noise) is the Electronicnoise - generated by thethermal agitation of the charge carriers (the electrons) insidean electrical conductorin equilibrium, which happensregardless of any applied voltage.

Movement of the electrons will forms kinetic energy in the conductorrelated to the temperature of the conductor.

When the temperature increases the movement of free electrons willincreases and the current flows through the conductor.

Current flows due to the free electrons will creates noise voltage, n(t).

Noise voltage, n(t) is influenced by the temperature and therefore it iscalled thermal noise.

Also known as Johnson noise or white noise.

http://en.wikipedia.org/wiki/Electronic_noisehttp://en.wikipedia.org/wiki/Noise_%28physics%29http://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Electrical_conductorhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Noise_%28physics%29http://en.wikipedia.org/wiki/Electronic_noise


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kTBP

TBP

n

n

=

Watt

where

Pn = noise power (Watt)

k = Boltzmanns constant (1.38 x 10-23 J/K)

T = Temperature (K)

B = BW spectrum system (Hz)

In 1928, J. B. Johnson have proven that noise power generated isproportional to the temperature and the BW.

Noise power can be modeled using voltage equivalent circuit (Thevenin

equivalent circuit) or current equivalent circuit(Norton equivalent circuit)

This type of noise was first measured by John B. Johnson at Bell Labs in 1928. He described his

findings to Harry Nyquist, also at Bell Labs, who was able to explain the results.
http://en.wikipedia.org/wiki/John_B._Johnsonhttp://en.wikipedia.org/wiki/Bell_Labshttp://en.wikipedia.org/wiki/Harry_Nyquisthttp://en.wikipedia.org/wiki/Harry_Nyquisthttp://en.wikipedia.org/wiki/Bell_Labshttp://en.wikipedia.org/wiki/John_B._Johnson


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Noise source will be connected to a system with the input resistance RL.

Therefore, total noise power isPn.

With the concept of maximum power transfer ie whenRn=R

Lall the

power will be transferred to the load. Also called as impedance matching.


Rn, Noise

source

Vn, Noise

voltage source

Rn, noise

free

=

(b) Thevenin equivalent circuit(a) Noise source circuit

It can be modeled by a voltage source representing the noise of the non-ideal

resistor in series with an ideal noise free resistor.


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RL, system inputresistance

Vn, Noise

voltage source

Rn, Noise

free

(c) Thevenin equivalent circuit with the load

VL

RRR Ln ==

R

V

R

V

R

VP n

n

LL

4

22

2

2

=

==

kTBPPLn==2

n

n

Ln

L

L

V

VRR

RV

=

+=

Note: Vn = Vrms

kTBRV

kTBRV

kTBR

V

n

n

n

4

4

42

2

=

=

=

Given

Voltage acrossRL :

=>

and

=>


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1.9.4 How to determine noise level in1.9.4 How to determine noise level in

communication system?communication system?

Noise effect can be determined by measuring:

- Signal to Noise Ratio, SNR for analog system

- probability of error or bit error rate, BER for digital system

To determine the quality of received signal at the receiver or anantenna,SNRiis used.

SNRois always less thanSNR

i, due to the facts that the

existence of noise in the receiver itself. In the receiver usuallyconstitute a process offiltering, demodulation and

amplification.

Another parameters that can be used is Noise Factor, FandNoise Temperature, T

e.



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1.10 Noise Calculation1.10 Noise Calculation

SNR is a ratio of signal power,Sto noise power,N.

Noise Figure, F

Noise factor,NF

dBN

SSNR log10=


dBNS

NS

FNF

oo

iilog10

log10

=

=

oo

ii

NS

NSF= dB


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1.10.1 Noise calculation in Amplifier1.10.1 Noise calculation in Amplifier

To simplify the analysis two types of noise model are used. - Amplifier with noise

- Amplifier without noise


aioNGNN +=

GNa

Ni No GNi NoNai

(a) Model Penguat Berhingar (b) Model Penguat Tanpa Hingar

( )aiio

NNGN +=

whereG

NN

a

ai= BkTNP iin ==and


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1.10.2 Analysis Amplifier with Noise1.10.2 Analysis Amplifier with Noise

ioGSS =

( )aii

a

i

aio

NNG

G

NNG

NGNN

+=

+=

+=

G

Na

Model Penguat Berhingar

Ni

So

No

Si(1)

( )

i

ai

i

aii

aii

i

i

i

o

i

N

N

N

NN

NNG

GS

N

S

SNR

SNR

+=

+=

+=

1

i

ai

N

NF +=1

io SNRSNR

(3)


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1.10.3 Analysis Amplifier Without Noise1.10.3 Analysis Amplifier Without Noise

GSi So

NoNi+Nai

Model Penguat Tanpa Hingar( )

aiio

io

NNGN

GSS

+==

( )

i

ai

i

aii

aii

i

i

i

o

i

N

N

N

NN

NNG

GS

N

S

SNR

SNR

+=

+=

+=

1

i

ai

N

NF +=1

io SNRSNR

(3)

(1)


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1.10.4 Cascaded Connection1.10.4 Cascaded Connection

In communication system cascaded connection is commonlyused:

Below is the example of cascaded connection.


G3SoNo

G1 F2, G2, Te2

antenna

pre-amplifier demodulate amplifier

F1 , Te1F

3, T

e3SiNiT

iNai1 Nai2 Nai3

S1N1

S2N2


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( )

( )11

111

111

ei

ei

aii

TTkBG

BkTGBkTG

NNGN

+=+=+=

( )

( )

( ) BkTGTTkBGG

BkTGBkTGGBkTGG

NGNNGG

NNGN

eei

eei

aiaii

ai

22121

2212121

22121

2122

++=++=

++=

+=

( )( )

( ) BkTGBkTGGTTkBGGG

BkTGBkTGGBkTGGGBkTGGG

NGNNGG

NNGN

eeei

eeei

aiai

aio

332321321

332321321321

332132

323

+++=+++=

++=+=

Level 1: Level 2:

Level 3:

iSGS 11 =i

SGG

SGS

21

122

==

iSGGG

SGS

321

230

=

=

S1N1

G1

F1 , Te1SiNi

Ti Nai1N

ai2

S2

N2

S1

N1

F2, G

2, T

e2

G3 SoNo

F3 , Te3

Nai3

S2N2


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31i

e

T

TF +=1

( )( )

i

e

i

e

i

e

i

e

i

e

i

ei

i

eeei

eeei

i

i

i

o

o

i

i

o

i

tot

TGG

T

TG

T

T

T

TGG

T

TG

T

T

TT

BkTGGG

BkTGBkTGGTTkBGGG

BkTGBkTGGTTkBGGG

SGGG

BkT

S

N

S

N

S

SNR

SNRF

21

3

1

21

21

3

1

21

321

332321321

332321321

321

1 +++=

+++=

+++=+++

=

=

==

( ) ( )

21

3

1

21

11

GG

F

G

FFFtot

+

+=

We have: Therefore:


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12121

3

1

2

1

......

++++=n

neeeetot

GGG

T

GG

T

G

TTT

( )ie TFT 1=To calculate Noise Temperature: From:

We have: ( ) ( )

21

3

1

21

21

3

1

21

21

3

1

2

1

21

3

1

21

1111

11

11

GG

T

G

TTT

TGG

T

TG

T

T

T

T

T

GG

T

T

G

T

T

T

T

T

T

GG

F

G

FFF

ee

eetot

i

e

i

e

i

e

i

etot

i

e

i

e

i

e

i

etot

tot

++=

++=

+

+

+

++=+

++=

Friss formula: ( ) ( ) ( )

12121

3

1

21

...

1...

11

++++=n

n

tot

GGG

F

GG

F

G

FFF


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E l 1 1


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Example 1.1

Calculate signal power if its value in dBm is 0 dBm.

Example 1.2

Calculate signal power in dB if its value is 1 mW.

Example 1.3

A carrier signal, vc(t) = 100 cos 10 t Volt was suppressed by 20 dB.

dBm = 10 log P2 / P1 = 10 log P2 / 1 mW = 0

P2 = 1 mW

dB = 10 log P2 / P1 = 10 log P2 / 1 W = 10 log 1 mW / 1 W = - 30 dB

dB = 20 log V2 / V1 = 20 log 100 / 1 = 40 dB

New carrier amplitude = 40 dB 20 dB = 20 dB ;

20 log V = 20 dB ; V = log-1 1 = 10 Volt.

Therefore, vc

(t)new

= 10 cos 10 t Volt


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Example 1.4

One operational amplifier with a frequency range of (18-20) MHz has

input resistance 10 k . Calculate noise voltage at the input if theamplifier operate at ambient temperature of 270C.

Vn2 = 4KTBR

= 4 x 1.38 x 10-23 x (273+ 27) x 2 x 106 x 104

Vn = 18 volt

E l 1 5


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Example 1.5

Noise generated in amplifier of 5 MHz bandwidth is represented by

amplifier input noise power of 0.082 pW. Calculate noise factor and

noise figure if the amplifier was fed with the

(a) source input signal match the temperature of 300 K

(b) source input signal match the temperature of 100 K

NoNi

Ne = 0.082PW

(a) Noise power from the source input = KTiB

= 1.38 x 10-23 x 300 x 5 x 106

= 0.021 pW

9.4021.0103.0

021.0082.0021.0hingarFaktor ==+=+=

NiNeNi

Noise figure = 10log10

4.9 = 6.9 dB


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(b) Noise power from the source input = KT iB

= 1.38 x 10-23 x 100 x 5 x 106

= 0.007 pW

7.12

007.0

103.0

007.0

082.0007.0hingarFaktor ==

+=

+=

Ni

NeNi

Noise Factor = 10log10

12.7 = 11.04 dB

Noise factor and noise figure were less when operated at roomtemperature.

NoNi

Ne= 0.082

PW


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Example 1.6

An antenna is connected to an amplifier with noise temperature, Te

= 125 oK,

gain, G = 108. Given the bandwidth, B = 10 MHz and output receiver noise, No

= 10 W. Determine the antenna temperature, Ti and noise factor, F of thereceiver.

( )

( )

( )( )

KT

T

GTTKB

GBKTBKT

GNNN

i

i

ei

ei

eio

o

8623

600

1012510101038.110

=

+=

+=

+=

+=

2.1600

12511 =+=+=

i

e

T

TF or 2.1

8.82

100==

+=

i

ei

N

NNF


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Example 1.7

Three amplifiers, ABC was connected in series. Noise figure and power

gain of the amplifiers are given below:

Amplifier A : GA = 20 dB FA = 3 dB

Amplifier B : GB

= 10 dB FB

= 5 dB

Amplifier C : GC

= 5 dB FC

= 10 dB

An input signal of 50 dB higher than noise level was fed at the input of the

network. Calculate:

(a)Total noise factor

(b) SNR at the output


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03.2

1090216.099.1

1000

110

100

116.399.1

10100

110

100

11010

11

3

10/5103

21

3

1

2

1

=++=

+

+=

+

+=

+

+=

GG

F

G

FFF

(b) Di beri, SNRmasukan

= 50 dB

Solution:

keluarkandiSNR

masukandiSNRF =

FdB

= SNRmasukan

(dB) SNRkeluaran

(dB)

SNR keluaran= 50 dB 3.05 dB = 46.95 dB

A B C

Amplifier A : GA

= 20 dB FA

= 3 dB

AmplifierB : GB

= 10 dB FB

= 5 dB

Amplifier C : GC

= 5 dB FC

= 10 dB

(a) Angka hingar = 10 log10

2.03 = 3.05 dB

Summary


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Protocol Release Date Op. Frequency Throughput(Typ)

Data Rate(Max)

ModulationTechnique

Range (RadiusIndoor)Depends, #and type ofwalls

Range (RadiusOutdoor) Lossincludes onewall

Legacy 1997 2.4 GHz 0.9 Mbit/s 2 Mbit/s ~20 Meters ~100 Meters

802.11a 1999 5 GHz 23 Mbit/s 54 Mbit/s OFDM ~35 Meters ~120 Meters

802.11b 1999 2.4 GHz 4.3 Mbit/s 11 Mbit/s DSSS ~38 Meters ~140 Meters

802.11g 2003 2.4 GHz 19 Mbit/s 54 Mbit/s OFDM ~38 Meters ~140 Meters

802.11n June 2009[4](est.)

2.4 GHz5 GHz

74 Mbit/s 248 Mbit/s ~70 Meters ~250 Meters

802.11y June 2008[4]

(est.)3.7 GHz 23 Mbit/s 54 Mbit/s ~50 Meters ~5000 Meters
http://en.wikipedia.org/wiki/IEEE_802.11_(legacy_mode)http://en.wikipedia.org/wiki/IEEE_802.11a-1999http://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexinghttp://en.wikipedia.org/wiki/IEEE_802.11b-1999http://en.wikipedia.org/wiki/Direct-sequence_spread_spectrumhttp://en.wikipedia.org/wiki/IEEE_802.11g-2003http://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexinghttp://en.wikipedia.org/wiki/IEEE_802.11nhttp://en.wikipedia.org/wiki/IEEE_802.11yhttp://en.wikipedia.org/wiki/IEEE_802.11yhttp://en.wikipedia.org/wiki/IEEE_802.11nhttp://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexinghttp://en.wikipedia.org/wiki/IEEE_802.11g-2003http://en.wikipedia.org/wiki/Direct-sequence_spread_spectrumhttp://en.wikipedia.org/wiki/IEEE_802.11b-1999http://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexinghttp://en.wikipedia.org/wiki/IEEE_802.11a-1999http://en.wikipedia.org/wiki/IEEE_802.11_(legacy_mode)

Documents

b1 -Intro Noise -comm theorem