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
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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 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
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