Download - NETW 701:Wireless Communications
NETW 701:Wireless Communications
Course Instructor : Tallal ElshabrawyInstructor Office : C3.321Instructor Email : [email protected] Assistants : Eng. Phoebe Edward Emails : [email protected],
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Text Book and References
Text Book:
“Wireless Communications: Principles and Practice 2nd Edition”, T. S. Rappaport, Prentice Hall, 2001
Reference Books:
“Modern Wireless Communications”, S. Haykin and, M. Moher, Prentice Hall, 2004
“Mobile Wireless Communications”, M. Schwartz Cambridge University Press, 2005
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Course Pre-Requisites
Review communication theory COMM 502
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Course Instructional Goals Build an understanding of fundamental components of
wireless communications
Investigate the wireless communication channel characteristics and modeling
Discuss different access techniques to the shared broadcast wireless medium
Highlight measures of performance and capacity evaluation of wireless communication networks
Provide an insight to different practical wireless communication networks
Course Contents Overview
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SignalInterference
Power
Frequency
PT
d (Km)
Wireless Communication Channels
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Large-Scale Parameters Distance Pathloss
SignalInterference
Power
Frequency
PT
d (Km)
PT+PL(d)
Wireless Communication Channels
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Large-Scale Parameters Distance Pathloss Lognormal Shadowing
SignalInterference
Power
Frequencyd (Km)
PT
PT+PL(d)
Wireless Communication Channels
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SignalInterference
Power
Frequencyd (Km)
PT
PT+PL(d)
Wireless Communication Channels
Large-Scale Parameters Distance Pathloss Lognormal Shadowing
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Large-Scale Parameters Distance Pathloss Lognormal Shadowing
SignalInterference
Power
Frequencyd (Km)
PT
PT+PL(d)
Wireless Communication Channels
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Large-Scale Parameters Distance Pathloss Lognormal Shadowing
SignalInterference
Power
Frequencyd (Km)
PT
PT+PL(d)
PT+PL(d)+X
Wireless Communication Channels
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Large-Scale Parameters Distance Pathloss Lognormal Shadowing
Small-Scale Parameters Multi-Path Fading
SignalInterference
Power
Frequencyd (Km)
PT
PT+PL(d)
PT+PL(d)+X
Wireless Communication Channels
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0 10 20 30 40 50 6030
40
50
60
70
80
90
100
0 10 20 30 40 50 60-15
-10
-5
0
5
10
15
0 10 20 30 40 50 60-60
-50
-40
-30
-20
-10
0
10
20
Lognormal ShadowingMobile Speed 3 Km/hrARMA Correlated Shadow Model
Distance PathlossMobile Speed 3 Km/hrPL=137.744+ 35.225log10(DKM)
Small-Scale FadingMobile Speed 3 Km/hrJakes’s Rayleigh Fading Model
d
d
d
20 20.1 20.2 20.3 20.4 20.5 20.6 20.7 20.8 20.9 21-50
-40
-30
-20
-10
0
10
20 20.1 20.2 20.3 20.4 20.5 20.6 20.7 20.8 20.9 21-50
-40
-30
-20
-10
0
10
20 20.1 20.2 20.3 20.4 20.5 20.6 20.7 20.8 20.9 2140
50
60
70
80
90
100Wireless Communication Channels
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Wireless Medium Access Techniques
FDMA (Frequency Division Multiple Access) Channel bandwidth divided into frequency bands At any given instant each band should be used by only one user
TDMA (Time Division Multiple Access) System resources are divided into time slots Each user uses the entire bandwidth but not all the time
CDMA (Code Division Multiple Access) Each user is allocated a unique code to use for communication Users may transmit simultaneously over the same frequency band
SDMA (Space Division Multiple Access) System resources are reused with the help of spatial separation
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SignalInterference
Reliable Signal Reception requires adequate SINR (Signal to Interference and Noise Ratio)
S
I
Signal Reception and SINR
Factors influencing SINR: Number of Interferers Identity of Interferers Interference Power Interference Channels
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SignalInterference
S
I
Signal Reception and SINR
Reliable Signal Reception requires adequate SINR (Signal to Interference and Noise Ratio)
Factors influencing SINR: Number of Interferers Identity of Interferers Interference Power Interference Channels
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SignalInterference
I
Signal Reception and SINR
Reliable Signal Reception requires adequate SINR (Signal to Interference and Noise Ratio)
Factors influencing SINR: Number of Interferers Identity of Interferers Interference Power Interference Channels
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System Capacity
Maximum number of customers that may be satisfactorily supported within the wireless network
Example Criteria for a Satisfied-User: Number of Interfering sessions < N Outage Probability < ψTH
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Subdivide wideband bandwidth into multiple Orthogonal narrowband sub-carriers
Each sub-carrier approximately displays Flat Fading characteristics
Flexibility in Power Allocation & Sub-carrier Allocation to increase system capacity
Advances in Wireless Comm.: Multi-Carrier Modulation
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Frequency and time processing are at limits Space processing is interesting because it does not
increase bandwidth MIMO technology is evolving in different wireless
technologies
Cellular Systems
WLAN
Advances in Wireless Comm.: MIMO
Wireless Communications Channels: Large-Scale Pathloss
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Isotropic Radiation An Isotropic Antenna:
An antenna that transmits equally in all directions An isotropic antenna does not exist in reality An isotropic antenna acts as a reference to which other
antennas are compared
R
TR
Tx Power
Surface Area of Sphere
PW m
d2
24
Power Flux Density
From “Wireless Communications” Edfors,
Molisch, Tufvesson
d
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2
e isoA =
4
R R eP A WPower Received by Antenna
T T
RP
P PP W
Ld2
4
From “Wireless Communications” Edfors,
Molisch, Tufvesson
Ae=ARx Effective Area of Antenna
Power Received by Isotropic Antenna
LP Free-space Path-loss between two isotropic antennas
Power Reception by an Isotropic Antenna
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Directional Radiation A Directional Antenna:
Transmit gain Gt is a measure of how well an antenna emits radiated energy in a certain direction relative to an isotropic antenna.
Receive gain Gr is a measure of how well the antenna collects radiated energy in a given area relative to an isotropic antenna.
Side Lobes
Maximum (Peak) Antenna
GainMain Lobe
3 dB Beam Width
e Dir
e iso
e2 Dir
AG
A
G= A4
Maximum transmit or receive antenna Gain
Antenna Pattern for Parabolic (dish-shaped) antenna
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The Friis Equation
T T RR
P
R T R T P
P G GP
L
P dB P dB G dB G dB L dB
The received power falls off as the square of the T-R separation distance
The received power decays with distance at a rate of 20 dB/decade
Valid for Line of Sight (LOS) satellite communications The Friis free-space model is only valid for values of d in the far
field. The far field is defined as the region beyond the far field distance df
Friis Equation
f
Dd
22
Note:
df must also satisfy df>>D, df>>λ
D is the largest linear dimension of the transmitting antenna aperture
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PR(d) in the Far Field
The Friis equation is not valid at d=0 PR(d) could be related to a power level PR(d0) that
is measured at a close in distance d0 that is greater than df
R R f
dP d P d d d d
d
2
00 0
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Relating Power to Electric Field
Alternative formula for power flux density
T TR
E EP GW m
(d
2 2
22 120 )4
Power Flux Density
T T R
R R
EP G GP d G W
d
22 2
2 2 120 44
where E depicts the electric field strength and η is the intrinsic impedance of free-space
Power Received by Antenna