NETW 701:Wireless
Communications
Course Instructor
Instructor Office
Instructor Email
Teaching Assistants
Emails
: Tallal Elshabrawy
: C3.321
: tallal.el-shabrawy@guc.edu.eg
: Eng. Phoebe Edward
: phoebe.edward2@guc.edu.eg,
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