NETW 701:Wireless Communications

1
NETW 701Wireless Communications

• Course Instructor Tallal Elshabrawy
• Instructor Office C3.321
• Instructor Email tallal.el-shabrawy_at_guc.edu.eg
  
• Teaching Assistants Eng. Phoebe Edward
• Emails phoebe.edward2_at_guc.edu.eg,

2
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

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Course Contents Overview
6
Wireless Communication Channels
Signal Interference
Power
PT
Frequency
d (Km)
7
Wireless Communication Channels
Signal Interference

• Large-Scale Parameters
• Distance Pathloss

Power
PT
PTPL(d)
Frequency
d (Km)
8
Wireless Communication Channels
Signal Interference

• Large-Scale Parameters
• Distance Pathloss
• Lognormal Shadowing

Power
PT
PTPL(d)
Frequency
d (Km)
9
Wireless Communication Channels
Signal Interference

• Large-Scale Parameters
• Distance Pathloss
• Lognormal Shadowing

Power
PT
PTPL(d)
Frequency
d (Km)
10
Wireless Communication Channels
Signal Interference

• Large-Scale Parameters
• Distance Pathloss
• Lognormal Shadowing

Power
PT
PTPL(d)
Frequency
d (Km)
11
Wireless Communication Channels
Signal Interference

• Large-Scale Parameters
• Distance Pathloss
• Lognormal Shadowing

Power
PT
PTPL(d)
PTPL(d)X
Frequency
d (Km)
12
Wireless Communication Channels
Signal Interference

• Large-Scale Parameters
• Distance Pathloss
• Lognormal Shadowing
• Small-Scale Parameters
• Multi-Path Fading

Power
PT
PTPL(d)
PTPL(d)X
Frequency
d (Km)
13
Wireless Communication Channels
Distance Pathloss Mobile Speed 3
Km/hr PL137.744 35.225log10(DKM)
d
Lognormal Shadowing Mobile Speed 3 Km/hr ARMA
Correlated Shadow Model
d
Small-Scale Fading Mobile Speed 3 Km/hr Jakess
Rayleigh Fading Model
d
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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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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

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

S
I
17
Signal Reception and SINR
Signal Interference
Reliable Signal Reception requires adequate SINR
(Signal to Interference and Noise Ratio)
I

• 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 lt N
• Outage Probability lt ?TH

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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

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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

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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

Power Flux Density
d
From Wireless Communications Edfors, Molisch,
Tufvesson
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Power Reception by an Isotropic Antenna
Power Received by Antenna
AeARx? Effective Area of Antenna
Power Received by Isotropic Antenna
From Wireless Communications Edfors, Molisch,
Tufvesson
LP? Free-space Path-loss between two isotropic
antennas
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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.

Maximum (Peak) Antenna Gain
Main Lobe
Maximum transmit or receive antenna Gain
3 dB Beam Width
Side Lobes
Antenna Pattern for Parabolic (dish-shaped)
antenna
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The Friis Equation
Friis Equation

• 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

D is the largest linear dimension of the
transmitting antenna aperture
Note df must also satisfy dfgtgtD, dfgtgt?
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PR(d) in the Far Field

• The Friis equation is not valid at d0
• 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

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Relating Power to Electric Field

• Alternative formula for power flux density

Power Flux Density
where E depicts the electric field strength and
? is the intrinsic impedance of free-space
Power Received by Antenna