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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.
Pengenalan Kepada Sistem Perhubu
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
Pengenalan Kepada Sistem Perhubu
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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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
Pengenalan Kepada Sistem Perhubu
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)
Pengenalan Kepada Sistem Perhubu
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.
Pengenalan Kepada Sistem Per
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/Frequency8/14/2019 b1 -Intro Noise -comm theorem
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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.
Pengenalan Kepada Sistem Perhubu
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_noise8/14/2019 b1 -Intro Noise -comm theorem
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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._Johnson8/14/2019 b1 -Intro Noise -comm theorem
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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.
Pengenalan Kepada Sistem Perhubu
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=
Pengenalan Kepada Sistem Perhubu
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
Pengenalan Kepada Sistem Perhubu
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.
Pengenalan Kepada Sistem Perhubu
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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32Pengenalan Kepada Sistem Perhubu
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)