Outline & Introduction
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Transcript Outline & Introduction
NETW 701:Wireless
Communications
Course Instructor
Instructor Office
Instructor Email
Teaching Assistants
Emails
: Tallal Elshabrawy
: C3.321
: [email protected]
: Eng. Phoebe Edward
: [email protected],
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
© Tallal Elshabrawy
2
Course Pre-Requisites
Review communication theory COMM 502
© Tallal Elshabrawy
3
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
© Tallal Elshabrawy
4
Course Contents Overview
Wireless Communication Channels
Signal
Interference
Power
PT
d (Km)
© Tallal Elshabrawy
Frequency
6
Wireless Communication Channels
Large-Scale Parameters
Signal
Interference
Distance Pathloss
Power
PT
PT+PL(d)
d (Km)
© Tallal Elshabrawy
Frequency
7
Wireless Communication Channels
Large-Scale Parameters
Signal
Interference
Distance Pathloss
Lognormal Shadowing
Power
PT
PT+PL(d)
d (Km)
© Tallal Elshabrawy
Frequency
8
Wireless Communication Channels
Large-Scale Parameters
Signal
Interference
Distance Pathloss
Lognormal Shadowing
Power
PT
PT+PL(d)
d (Km)
© Tallal Elshabrawy
Frequency
9
Wireless Communication Channels
Large-Scale Parameters
Signal
Interference
Distance Pathloss
Lognormal Shadowing
Power
PT
PT+PL(d)
d (Km)
© Tallal Elshabrawy
Frequency
10
Wireless Communication Channels
Large-Scale Parameters
Signal
Interference
Distance Pathloss
Lognormal Shadowing
Power
PT
PT+PL(d)
PT+PL(d)+X
d (Km)
© Tallal Elshabrawy
Frequency
11
Wireless Communication Channels
Large-Scale Parameters
Signal
Interference
Distance Pathloss
Lognormal Shadowing
Small-Scale Parameters
Multi-Path Fading
Power
PT
PT+PL(d)
PT+PL(d)+X
d (Km)
© Tallal Elshabrawy
Frequency
12
Wireless Communication Channels
100
100
90
90
80
Distance Pathloss
Mobile Speed 3 Km/hr
PL=137.744+
35.225log10(DKM)
80
70
70
60
60
50
50
40
40
20
30
0
10
20.1
20.2
20.3
20.4
20
10
20.5
20.6
20.7
20.8
30
20.9
21
40
50
60
50
60
50
60
d
15
0
Lognormal
Shadowing
Mobile Speed 3 Km/hr
ARMA Correlated
Shadow Model
10
-10
5
-20
0
-30
-5
-40
-10
-15
-50
20
0
10
10
20.1
20.2
20.3
20.4
20
20.5
20.6
20.7
20.8
30
20.9
21
40
d
20
0
10
-10
0
Small-Scale Fading
Mobile Speed 3 Km/hr
Jakes’s Rayleigh Fading
Model
-10
-20
-30
-30
-40
-40
-50
20
-50
-60
© Tallal Elshabrawy
-20
0
10
20.1
20
20.2
20.3
20.4
20.5
30
20.6
20.7
20.8
20.9
40
21
d
13
Wireless Medium Access Techniques
FDMA (Frequency Division Multiple Access)
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)
Channel bandwidth divided into frequency bands
At any given instant each band should be used by only one user
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
© Tallal Elshabrawy
14
Signal Reception and SINR
Signal
Interference
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
© Tallal Elshabrawy
S
I
15
Signal Reception and SINR
Signal
Interference
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
© Tallal Elshabrawy
S
I
16
Signal Reception and SINR
Signal
Interference
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
© Tallal Elshabrawy
I
17
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
© Tallal Elshabrawy
18
Advances in Wireless Comm.: Multi-Carrier Modulation
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
© Tallal Elshabrawy
19
Advances in Wireless Comm.: MIMO
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
© Tallal Elshabrawy
20
Wireless Communications
Channels: Large-Scale Pathloss
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
Power Flux Density
Tx Power
R
Surface Area of Sphere
PT
2
R
W
m
4 d 2
d
From “Wireless Communications”
Edfors, Molisch, Tufvesson
© Tallal Elshabrawy
22
Power Reception by an Isotropic Antenna
Power Received by Antenna
PR R Ae W
Ae=ARx Effective Area of Antenna
2
Ae iso =
4
Power Received by Isotropic
Antenna
PR
PT
4 d
2
PT
LP
W
From “Wireless Communications”
Edfors, Molisch, Tufvesson
LP Free-space Path-loss between
two isotropic antennas
© Tallal Elshabrawy
23
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.
Maximum transmit or receive
antenna Gain
Main Lobe
3 dB Beam
Width
A e Dir
G
A e iso
G=
4
2
A e Dir
Maximum (Peak)
Antenna Gain
Side Lobes
Antenna Pattern for Parabolic (dish-shaped)
antenna
© Tallal Elshabrawy
24
The Friis Equation
Friis Equation
PT G T G R
PR
LP
PR dB PT dB G R dB G T dB L P 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
df
2 D2
© Tallal Elshabrawy
D is the largest linear dimension
of the transmitting antenna
aperture
Note:
df must also satisfy df>>D, df>>λ
25
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
d0
PR d PR d0
d
© Tallal Elshabrawy
2
d d0 d f
26
Relating Power to Electric Field
Alternative formula for power flux density
Power Flux Density
2
2
E
E
PT G T
2
R
W
m
120 ( )
4 d 2
where E depicts the
electric field strength
and η is the intrinsic
impedance of freespace
Power Received by Antenna
PR d
© Tallal Elshabrawy
PT G T G R
2
4
d
2
2
2
2
GR
W
120
4
E
27