Wireless Communications Lecture 1: Introduction

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ةبيط ةعماج

Wireless Communications Lecture 1: Introduction

Omar Siddiqui

Department of Electrical Engineering College of Engineering

Taibah University Madinah

Email:[email protected]

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- Wireless communication is the transfer of information or power between two or more points that are not connected by an electrical conductor.

Wireless Communications?

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Early Wireless Communications

Information transferred by pigeons

Information transferred by smoke

Information transferred by drum beat

College of Engineering, Taibah University Wireless Communications

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Wireless and Wireline Communications

Wireless

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Types of Wireless Systems

Cellular Systems (900 MHz to 2.5 GHz)

Radar

Wireless Local Area Network (WLAN or W-Fi)

2.4 GHz, 3.6 GHz, 4.9 GHz, 5 GHz, and 5.9 GHz

Cordless Phones

900 MHz, 2.4 GHz, 5.8 GHz

College of Engineering, Taibah University Wireless Communications GPS

Bluetooth (2.4 GHz) 2G, 3G, 4G, WiMax Satellite Communications (4 to 18 GHz)

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Input

(voice or picture)

Elements of a Basic Wireless system

Input

Transducer Modulation

Baseband signal (Low Frequency)

Wireless Signal (High Frequency)

Output baseband signal

Transmitter

Output

transducer Demodulatio n

Received Wireless signal

Output

(voice or picture)

Antenna

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Examples of Wireless Systems 1. Cellular Communications

Base station

Mobile

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Examples of Wireless Systems How does a cellular system work?

BSC: Basestation Controller MSC: Mobile switching center BTS: Base transceiver station

PSTN: Public switched telephone network

BTS

BTS BTS BTS

BTS

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Examples of Wireless Systems Cellular Evolution

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Examples of Wireless Systems

Cellular Evolution

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Radio Receiver TV receiver

2. Radio and TV Broadcasting

Radio Transmitter

Examples of Wireless Systems

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Satellite Communications

Satellite Receivers Satellite Transmitter

Examples of Wireless Systems

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Global Positioning Satellites (GPS)

GPS Receivers GPS Transmitters

Examples of Wireless Systems

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WLAN or Wi-Fi

Wifi Receivers Wifi Transmitter

Examples of Wireless Systems

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Radar Systems

Military

Speed Control

Examples of Wireless Systems

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André-Marie Ampère (French,

1775

-1836) – Ampere’s Law (1826)

t J D

H 

 







 

 _d_s

t s D

d J l

d H

S S

C

 

. .

.

 



^ ^ ^_

Important Historical Events in Wireless Communications

Electric Current produces magnetic field

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Michael Faraday (English, 1791-1867) – Faraday’s Law of Induction (1831)

t E B



 







 

s t d l B

d E

S C

 

.



^^ ^_

Question: If electric current (field) produces magnetic field, is the opposite possible?

 The static H does not induce any current

 Faraday wasted 10 years to produce electric field from magnetic field because he was looking at the static magnetic field

 In 1831, he used changing magnetic field and observed the current in the secondary coil

Faraday’s Experiment

Important Historical Events in Wireless Communications

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- Known as Father of Electromagnetics

- Solved Four equations of Electromagnetics (1865)

- Maxwell theoretically predicted wireless communication

If both E and H fields can produce each other then energy can propagate or travel!!!!!

Historical Events : James Clerk Maxwell (Scotland, 1831-1879)

Maxwell’s Equations

Maxwell’s Book

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Heinrich Hertz (

German

,

1857-1894

) – First transmission of waves

Birth of Radio: Practical Demonstration of Maxwell’s prediction of wave transmission

Important Historical Events in Wireless Communications

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Guglielmo Marconi (Italian, 1874-1937) – Commercial Radio

First transatlantic transmission of radio signal

Important Historical Events in Wireless Communications

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College of Engineering, Taibah University Wireless Communications 1923-1938 Television:

1936 Armstrong’s case of FM radio

1938-1945 World War II Radar and microwave systems 1948-1950 Information Theory and coding. C. E. Shannon 1962 Satellite communications begins with Telstar I.

1962-1966 High Speed digital communication 1972 Motorola develops cellular telephone.

Important Historical Events in Wireless Communications

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What will we study in this course?

Analog to Digital conversion Encoding

RF Modulation Inside a Mobile:

Communication Theory BSC-1

Losses

Radio Link (Electromagnetics) RF Link (Radio)

BSC-2 Fiber Links

Fiber or Microw

ave Link

BSC-2

Handoffs, Signalling, Channel Technology-dependent Protocols Cell

Site

BTS

MSC

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Focus of the Course

BSC-1

RF Link (Radio)

Fiber Link

Fiber/M

icrowave

BSC-2

• Focus will be on the radio link between the mobile and the base station

• We will study:

• Modulation (TDMA, CDMA, OFDMA etc)

• Technologies (2G, 3G, 4G etc)

• Radio wave propagation (Path loss models, fading etc)

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Some Definitions

- Cells and Frequency Reuse: same frequencies can be reused in other parts of the cellular system

f₁

f₂

f₃

f₁

f₁ is reused

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Some Definitions

- Cell sectorization: More users can be added by dividing the region served by single BTS into sectors served by several BTSs. Each sector uses a highly directional antenna

f_

f_

f_ f_

f_

f_ f_

f_

f_

f_

f_

f_ f_

f_

f_

Three Sector cell-sites

http://www.slideshare.net/NaveenKumar11/mobile-tower-radiation

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1. Frequency Division Multiple Access (FDMA) 2. Time Division Multiple Access (TDMA)

3. Code Division Multiple Access (CDMA)

4. Orthogonal Frequency Division Multiple Access (OFDMA)

FDMA

User 1User 2

User N

TDMA

User 1 User N

User M

User 1

Total Users = N Total Users = MXN

Some Definitions: Digital Modulation Techniques to

Multiplex various Channels (or Users)

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College of Engineering, Taibah University Wireless Communications Code Division Multiple Access (CDMA)

Example: UMTS System (3G)

Some Definitions: Digital Modulation Techniques to

Multiplex various Channels (or Users)

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Some Definitions

The Handoff or the Handover

A handoff refers to the process of transferring an active call or data session from one cell in a cellular network to another or from one channel in a cell to another.

(techopedia: https://www.techopedia.com/definition/16851/handoff)

BSC-1

Before Hand-off

BSC-1 After Hand-off break

break

make

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Some Definitions

Path Loss

College of Engineering, Taibah University Wireless Communications The path loss occurs due to the spread of the electromagnetic wave, absorption, moisture, vegetation etc

d

Free Space path Loss: It is only due to the spread of the wave without the effect of environment

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Some Definitions

Shadowing

Shadowing is caused by obstacles between the transmitter and receiver

that attenuate signal power through absorption, reflection, scattering, and diffraction.

Shadowing causes large-scale fading

d

Direct Path

Reflection Path

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Some Definitions

Multipath

College of Engineering, Taibah University Wireless Communications Multipath effect is caused due to several objects around the mobile that are

constantly in a changing environment. Mutipath causes small-scale fading

Complex environment

Difference between the signal received in the presence of shadowing and multipath

d

small-scale fading

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Course Outline and Textbook

4G Systems 1

3G Systems 3

RF Link, Path Loss, Fading, RF Budget 4

GSM Systems 2

Course Content Weeks

Textbook:

1. Wireless Communications: Principles and Practice (2nd Edition), by Rappaport 2. Wireless Communications by Andrea Goldsmith

4. Final Exam 40%

3. Mid Term Exam 2 20%

2. Mid Term Exam 1 20%

1. Class participation and homework, projects 20%

Grading