EE 442 Analog & Digital Communication Systems Spring 2020 ... · ES101A Communication in the Digital Age Spring 2015 2 The Evolution of the Telephone Wired Landline Telephone –Started

Department of Engineering Science

EE 442 Analog & Digital Communication Systems

Spring 2020

Lecture Notes: Chapter 14

Wireless Cellular Telephone Networks

References

• These slides at http://www.sonoma.edu/esee/courses/es442/ .

• http://en.wikipedia.org/wiki/Wireless_network

• Preston Gralla, “How Wireless Works,” 2nd ed., Que Publishing, Indianapolis, IN, 2005.

• Wikipedia: http://en.wikipedia.org/wiki/History_of_mobile_phones

• V. H. MacDonald, “The Cellular Concept,” Bell System Technical Journal, Vol. 58,

January 1979

http://www.cellularconcepts.com/Home.html

ES101A Communication in the Digital Age Spring 2015 2

The Evolution of the Telephone

Wired Landline Telephone – Started in 1876 with switchboards &

operators; Automated switching began in the 1920s, but PSTN reached

full automation in 1980s. First cellular telephone in 1983. First digital

cellular phone in 1991 (GSM).

https://www.reddit.com/r/nostalgia/comments/8r25ei/evolution_of_the_mobile_phone/

ES101A Communication in the Digital Age Spring 2015 3

Why Wireless Networks?

❑ Mobility: Liberated from a wired connection; Communicate from

almost anywhere.

❑ Convenience: People can easily carry cellular telephones for

communication with almost anyone, anytime, anywhere.

❑ To provide a network with an air interface allowing for large

numbers of mobile cell phones to simultaneously operate as users

roam almost anywhere.

❑ Cellular concept uses massive ”frequency reuse” to get around

the electromagnetic bandwidth limitation.

Why Cellular Networks?

ES101A Communication in the Digital Age Spring 2015 4

Cellular Telephony in the “Wireless Landscape”

WPAN WLAN WMAN WWAN

3G cellular

4G cellular

Telephony

SensorNetworks

ResourceSharing

VoiceData

InternetMedia

VoiceData

Mobile InternetMobile Media

Access&

Distribution

Both Fixed &Mobile WiMAX

Sensing& Tracking

Wireless Wide

Area NetworkWireless Local

Area Network

Wireless

Metropolitan

Area Network

Wireless

Personal

Area Network

RFIDNetworks

ES101A Communication in the Digital Age Spring 2015 5

First Four Generations in Cellular Telephony

https://www.electronicsforu.com/technology-trends/mobile-communication-1g-4g

ES101A Communication in the Digital Age Spring 2015 6

Five Generations in Cellular Telephony

IP

ES101A Communication in the Digital Age Spring 2015 7

Two Parts of Cellular Telephone System

1. It is a radio (handsets are both transmitters and receivers)

2. It is a computer-controlled data communication network

ES101A Communication in the Digital Age Spring 2015 8

Walkie-Talkie Communication (Is Not Cellular)

Radio handset to handset

Limited range of radio

Limited number of channels

22 bands near 466 MHz with a range of several miles.

ES101A Communication in the Digital Age Spring 2015 9

The First Mobile “Radio Telephone” System (1945)

The first mobile radio telephone system (AT&T) was developed and

inaugurated in the United States in St. Louis, Missouri, in 1945.

It consisted of six channels and did not work well due to interference.

A better idea was needed – the cellular telephone concept emerged!

It used a single high-power

base station which all use

to communicate.

POTSTelephone

System

Its

coverage area

was called a

“small zone system”

Base

Station

ES101A Communication in the Digital Age Spring 2015 10

❑ Cellular networks were developed to provide mobile telephony

Goal: telephone access “anytime and anywhere.”

❑ AT&T’s idea was a mobile phone system involving the division

of the coverage area into "cells." These "cells" were intended

to reduce bandwidth interference and expand number of users.

❑ Core Principles:

1. Small cells “tessellated” over entire coverage area

2. Must have call handoff as cell phones moved from one cell to

another cell

3. Incorporate “frequency reuse” over the entire cellular network to

increase number of users in network

AT&T’s Cellular Network Concept (1947)

handoff

1

2

3

4

ES101A Communication in the Digital Age Spring 2015 11

An Array of Cells Forms a Cellular Network

www.ece.lehigh.edu/~skishore/research/lucid/lucid_2.ppt

BTSBase Station

Transceiver System

A tessellation of small functional cells over the entire coverage area.

Definition: Tessellation is the process of creating a

two-dimensional pattern using the repetition of a

geometric shape with no overlaps and no gaps.

Cellular

Network

ES101A Communication in the Digital Age Spring 2015 12

Each BTS (Base Transceiver Station) cell serves those users within the cell itself. Users located beyond the edge of the cell receive weak signals and are served by adjacent cells.

Benefits:(1) Smaller cell size means that a (1) lower power is required for Base

Transceiver Station and (2) for each cell phone(2) Result: A greater number of customers can be accommodated with

frequency reuse

Single Cell in the Cellular Telephone Network

www.ece.lehigh.edu/~skishore/research/lucid/lucid_2.ppt

Cell phone

Cell phone

hexagonal shaped cell

BTS

ES101A Communication in the Digital Age Spring 2015 13

BSC

BTS

BTS

BTS

BTS

BSC

BTS

BTS

BTS

BTS

To wireline

services

HLR

VLR

EIR

AUC

Register

MSC GMSC

BSS

BSS

SGSN

GMSN

Internet

MS

MS

PSTN

GSM Cellular Network PSTN = public switched telephone

network

ISDN = integrated services digital

network

PSDN = packet-switched digital

network

HLR = home location register

VLR = visitor location register

EIR = equipment identity register

ISDN

BTS = base transceiver station

BSC = base station controller

BSS = base station subsystem

MS = mobile station

GMSC = gateway mobile switching center

GMSN = gateway mobile switching network

AUC = authentication center

ES101A Communication in the Digital Age Spring 2015 14

Efficient Use of Radio Spectrum Achieved By

❑ Frequency Reuse – Repeats the use of the same frequencies by physically separating cells from each other

❑ Dynamic channel assignment – One cell can borrow channels from an adjacent cell if that cell is under-utilized

❑ Cell splitting – In areas of high population density, cells can be made smaller to accommodate the greater number of users

(Note: Setup of “microcells” and “picocells”)

❑ Cell sectoring – Uses directionalized radio signals (typically cell are divided into two or three sectors per cell)

❑ Offload to Wi-Fi – Allows Wi-Fi enabled cell phones use Wi-Fi hotspots connected to cellular network (this is big part of 5G)

ES101A Communication in the Digital Age Spring 2015 15

A “cluster of 7” has six neighbors which forms the “reuse pattern.” The cellular network repeats this reuse pattern over and over. Using the same frequencies again in each “cluster of 7” allows a service provider to support many more cell phone users in the area.

Frequency Reuse in a Cellular Network

1

2

3

4

5

“Cluster of 7”

BTS Cells

BTS = Base Station Transceiver System

ES101A Communication in the Digital Age Spring 2015 16

Cell Splitting

Expanding the capacity of a

cellular system can be achieved

by increasing the number of cell

sites covering the entire

geography. With cells covering

smaller areas the reuse of the

same frequencies can be

applied more often within the

whole geographic coverage

area. Smaller cell sizes also

allows lower power operation.

Parameter Macrocell Microcell Picocell

Cell Radius 1 to 10 km 0.1 to 1 km < 0.1 km

Transmission Power 1 to 20 W 0.1 to 1 W < 0.2 W

Maximum Bit Rate 0.3 Mbps 1 Mbps > 1 Mbps

http://ironbark.bendigo.latrobe.e

du.au/subjects/DC/lectures/22/

Region of higher

population density

Region of lower

population density

Macrocell

Microcell

Picocell

ES101A Communication in the Digital Age Spring 2015 17

Principle:

An increase in network capacity can be

achieved by reducing the number of

interfering co‐channel cells. If sectoring is

done so that all channels assigned to a

particular sector are always it the same

direction in the other cells, then the

interference is reduced which allows the

cluster size to be reduced – that increases

the network’s capacity.

Cell Sectoring (Smart Antennas)

3-sector base station antenna

3-sector base station antenna

pattern can be optimized by

directing signal beams

(Spatial Division Multiple Access)

http://en.wikipedia.org/wiki/History_of_mobile_phones

ES101A Communication in the Digital Age Spring 2015 18

https://www.researchgate.net/figure/Wireless-technology-evolution_fig1_322584266

Wireless Evolution (Mobile and LAN)

ES101A Communication in the Digital Age Spring 2015 19

Cellular Telephone Generations

1980 1990 2000 2010 2020

1G

Ca

pa

city E

nh

an

ce

me

nts

by G

en

era

tio

n

2G

3G

Voice Telephony

Analog Cellular

Digital voice, Data

and Messaging

Wideband Digital,

Enhanced Data &

Multimedia Services

Digital Voice, Data

and Multimedia, &

Very High Data Rates

4G

LTE

2.5G

Much higher

Data Rates

LTE is “Long

Term Evolution”

Outdated & Retired Today

G generation

ES101A Communication in the Digital Age Spring 2015 20

https://www.researchgate.net/figure/Comparison-between-MCS-base-rates-

per-RAT-and-Shannons-limit-for-an-AWGN-channel_fig1_321638086

Shannon Limit with AWGN vs. LTE and Wi-Fi

( )log SNR

710

ES101A Communication in the Digital Age Spring 2015 21

http://en.wikipedia.org/wiki/Motorola_DynaTAC

Martin Cooper (31 years ago) designed

the Motorola DynaTAC 8000X

First Commercial Cell Phone: Motorola DynaTAC

❑ Introduced by Motorola, it was …First Generation* (1G)“analog voice-only phone”

❑ First sale in March 1983

❑ Battery – 30 minutes of talk time & 8 hours of standby

❑ Weighed ~ 2 pounds and 13 inches high (tall)

❑ Stored up to 30 phone numbers; 10 hours to recharge

❑ Price started at $3,995

The

“Brick”

* Known as AMPS for “Advanced

Mobile Phone System”

AMPS*

1G used

800 MHz &

900 MHz

radio bands

ES101A Communication in the Digital Age Spring 2015 22

Martin Cooper formulated the Law of Spectral Efficiency,

otherwise known as Cooper's Law. The law states that the

maximum number of voice conversations or equivalent data

transactions that can be conducted in all of the useful radio

spectrum over a given area doubles every 30 months.

Cooper’s Law

ES101A Communication in the Digital Age Spring 2015 23

Second Generation (2G) Mobile Phones

http://en.wikipedia.org/wiki/Global_System_for_Mobile_Communications

❑ Second Generation (2G) introduced in early 1990s to replace 1G

❑ Digital (rather than analog) transmission of voice

❑ Designed for circuit-switched networks (voice centric)

❑ Uses 900 MHz and 1800 MHz frequency bands

❑ Dominant 2G phone standard: GSM (Global System for Mobile)

❑ Introduced SMS (aka “text messaging”)

❑ GSM uses SIM card containing user ID (Subscriber Identity Module)

❑ Began in Europe; rapidly expanded around the World

http://sharingmythoughts-

ben.blogspot.com/2010/09/histor

y-of-mobile-phone.html

Nokia 2G

Mobile

Phones

GSM is still

widest used

cell phone

standard

Worldwide!

ES101A Communication in the Digital Age Spring 2015 24

GSM Band Uplink Frequency Band

GSM850

GSM/PCS1900

GSM900

GSM/DCS1800

824.2 to 849.2 MHz

1850.2 to 1909.8 MHz

880 to 915 MHz

1710.2 to 1784.8 MHz

Downlink Frequency Band

869.2 to 894.2 MHz

1930.2 to 1989.8 MHz

925 to 960 MHz

1805.2 to 1879.8 MHz

GSM Frequency Bands

ES101A Communication in the Digital Age Spring 2015 25

Third Generation (3G) Mobile Phones

❑ Third Generation (3G) introduced in early 2000s to upgrade 2G

❑ Wider range of advanced mobile services & better quality of service

(e.g., delivers multimedia with broadband access to Internet)

❑ Digital transmission using data packets

❑ Uses both circuit-switched & packet-switched networks

❑ Uses 1800 MHz, 1900 MHz and 2100 MHz frequency bands

❑ Faster data rates:

144 kbps – wide area vehicular (rapid motion) environment

384 kbps – pedestrian or urban environment

2,000 kbps (2 Mbps) – stationary (e.g., within buildings) environment

http://www.cheap3gphones

.net/samsung-3g-phones/

ES101A Communication in the Digital Age Spring 2015 26

Fourth Generation (4G) Mobile Phones

❑ Fourth Generation (4G) introduction began in 2011

❑ Known broadly as LTE (Long Term Evolution)

❑ Provides for much faster data rates

❑ It is an all IP – uses only packet-switched networks

❑ Uses 700 MHz, 1,700 MHz, and 2,100 MHz frequency bands

❑ Greater than 100 Mbps data rates possible (with max 20 MHz channel)

❑ Will take some years to fully implement

http://www.droid-life.com/2011/01/10/chart-verizon-4g-lte-android-

phone-lineup/

Verizon 4G LTE Android phonesDroid Bionic, HTC Thunderbolt, LG Revolution, Samsung SCH-I510

ES101A Communication in the Digital Age Spring 2015 27

From John Harmon’s Presentation (Nov. 13, 2013)

John Harmon (11/2013)

WLAN

Cellular

Gen

era

tion

ES101A Communication in the Digital Age Spring 2015 28

Multi-X: Radios, Bands & Applications

• Cellular (3GPP: GSM/EDGE/ W-

CDMA/HSDPA/HSUPA);

450/800/800/1700/1900/2100 MHz

Cellular Diversity

• Audio

✓ 15 Radios ✓ 41 Bands ✓ 2M Apps

• FM Stereo

• A-GPS • DAB

WLAN

Diversity • WLAN • 802.11a/b/g

• Bluetooth

• Infrared

From John Harmon (11/2013)

DAB = digital audio broadcast;

The modern smartphone has multiple capabilities!

There are cellular radios, usually a voice radio, an SMS radio, a 2G radio, a 3G radio, a 4G radio, and a 4G LTE radio. Also, a Wi-Fi radio, a GPS radio, a Bluetooth radio, and an NFC radio.

ES101A Communication in the Digital Age Spring 2015 29

Base

Transceiver

System (BTS)

Mobile Station (MS)

multi-path

propagation

Path Delay

Po

we

r

path-2

path-2

path-3

path-3

path-1

path-1

Challenges to Cellular: Multi-Path Propagation

Your cell phone must contend with multiple signals to properly operate.

path -2

path -1Note delay of path -2

ES101A Communication in the Digital Age Spring 2015 30

Challenges to Cellular: Signal Attenuation

http://en.wikipedia.org/wiki/Terrestrial_Trunked_Radio

Radio signal strength becomes weaker as energy spreads out.

Cell 1 Cell 2

RSS = received signal strength

distance

ES101A Communication in the Digital Age Spring 2015 31

Automatic Number Identification (ANI) and Automatic Location Information

(ALI) data are sent to the PSAP for 911 response.

GPS with assistance of cellular base station location methods give greater

precision to locating the cellular device. This is known as “assisted GPS.”

Your location data may be a matter of record.

Enhanced 911 Calls (E911)

MSC PSAP

E911

Call

Cellular

network

determines

location

Public-Safety

Answering

Point

Land line phones already have a location, but cell

phones do not.

ES101A Communication in the Digital Age Spring 2015 32

Cell Phone Location Tracking

There is an app (e.g., AT&T Family

Maps) allowing all cell phones and

smartphones on the plan to be tracked

using Assisted GPS.

It works as long as the cell phone is on.

Eventually all cell phones will be able to

be tracked. It requires a GPS chip

embedded within the cell phone.

ES101A Communication in the Digital Age Spring 2015 33

Summary

▪ Cellular networks became practical beginning in the 1980s

▪ Cellular concept allows for frequency reuse (smaller cells allow for

greater frequency reuse over service area)

▪ In the 1990s data delivery (mostly video) became important –

faster data rates then became important

▪ Smartphones today represent the state of the art with respect to the

number of services and applications

▪ Over the next few years service providers installing 4G LTE networks

▪ “Wireless Web” or “Mobile Internet” is the primary growth today

▪ We will see cellular networks combined with Wi-Fi networks for

better bandwidth utilization

ES101A Communication in the Digital Age Spring 2015 34

Additional Slides

(including cell phone

radiation effects)

ES101A Communication in the Digital Age Spring 2015 35

Electromagnetic Radiation Hazards

Mobile phone hazard

▪ As of 2009 there were ~ 2.5 billion mobile phone users worldwide.

Mobile phones use EM radiation in the radio spectrum. There is

controversy about such emissions being harmful to human health.

▪ Dr. Keith L. Black, a preeminent brain surgeon and author of the

book, Brain Surgeon: A Doctor's Inspiring Encounters with

Mortality and Miracles, 2009, has said,

“While some studies showed no correlation between cell phone use and

brain tumors, other credible studies show brain tumor incidence that is

250% greater than non-cell phone users.”

He recommends using a Bluetooth ear piece with your cell phone

to reduce radiation intensity around your head as a precaution.

Some cell phones emit approximately one watt of transmit power.

http://en.wikipedia.org/wiki/Electromagnetic_radiation_and_health

ES101A Communication in the Digital Age Spring 2015 36

EM radiation distributions in head @ 1900 MHz.

(a) 11 % larger head size, (b) average head size, and (c) smaller head

size (such as in a child – note proportionally larger heating).

Gandhi & Kang, Phys. Med. Biol., 47, 1501-18, 2002.

Head Models for Electromagnetic Energy Absorption

SAM (is “standard anthropomorphic mannequin”)

DECT 6.0 1900 MHz cordless phones

Large

Adult Child

ES101A Communication in the Digital Age Spring 2015 37

Some simple steps you can take to substantially reduce

exposure to cell phone radiation:

1. Use a wired headset or wireless Bluetooth headset, or use

phone in speaker-phone mode. Better yet, send text messages.

2. Keep cellphones away from your body (particularly

pant/trouser or shirt pockets) or use a belt holster designed to

shield your body. When not in use, put in it in “stand-by mode.”

3. Avoid using in a moving car, train, bus, or in areas with weak

reception – results in an increase in EM power by the cell phone.

4. Use the cellphone like an answering machine. Keep it off until

you want to see who has called. Then return calls you want to.

5. Do not allow children under 18 to use cellphones except in

emergencies or very limited circumstances.

How to reduce EM exposure in using cell phones

ES101A Communication in the Digital Age Spring 2015 38

If Interested in this Topic Suggest You Read:

Disconnect

by Devra Davis

Publisher: Dutton

2010

Paperback price from

Amazon is about $11.00

ES101A Communication in the Digital Age Spring 2015 39

Cellular Telephone Generations

Generation

Technology

Network

Service

Data rate

Coverage

1G

Analog

Circuit-

Switched

Voice

Telephony

No Data

Limited

Coverage

2G

Digital

Circuit-

Switched

Voice &

Limited Data

(Narrowband)

Slow Data

Trans-

national &

Limited

Global

Roaming

2.5G

Digital

Circuit &

Packet-

Switched

Voice +

Higher Data

Rates

Fast Data

Global

Coverage &

Global

Roaming

3G

Digital

Circuit &

Packet-

Switched

Voice +

Advanced

Data (MM)

Faster Data

Global

Coverage &

Global

Roaming

4G

Digital

All IP Packet-

Switched

Voice &

Advanced

Multimedia

Even Faster

Global

Coverage &

Global

Roaming

Transition

Phase