Introduction to Mobile Communications TCOM 552, Lecture #1 Hung Nguyen, Ph.D. 28 August, 2006.

Introduction to Mobile Introduction to Mobile CommunicationsCommunications

TCOM 552, Lecture #1Hung Nguyen, Ph.D.

28 August, 2006

08/28/2006Hung Nguyen, TCOM 552, Fall 20062

Chapter 10: Cellular Wireless NetworksChapter 10: Cellular Wireless Networks

Cellular wireless network design issues First generation analog (traditional

mobile telephony service) Second generation digital cellular networks

– Time-division multiple access (TDMA)– Code-division multiple access (CDMA)

Third generation networks


Chapter 2: Transmission FundamentalsChapter 2: Transmission Fundamentals

Basic overview of transmission topics Data communications concepts

– Includes techniques of analog and digital data transmission

Channel capacity Transmission media Multiplexing


Chapter 6: Signal Encoding TechniquesChapter 6: Signal Encoding Techniques

Wireless transmission– Analog and digital data– Analog and digital signals


Chapter 5: Antennas and PropagationChapter 5: Antennas and Propagation

Principles of radio and microwave– Antenna performance– Wireless transmission modes– Fading


Chapter 8: Coding and Error ControlChapter 8: Coding and Error Control

Forward error correction (FEC) Using redundancy for error detection Automatic repeat request (ARQ) techniques


Chapter 7: Spread SpectrumChapter 7: Spread Spectrum

Frequency hopping Direct sequence spread spectrum Code division multiple access (CDMA)


Chapter 13: Wireless LAN TechnologyChapter 13: Wireless LAN Technology

Overview of LANs and wireless LAN technology and applications

Transmission techniques of wireless LANs– Spread spectrum– Narrowband microwave– Infrared


Chapter 12: Mobile IP and Wireless Chapter 12: Mobile IP and Wireless Access ProtocolAccess Protocol

Modifications to IP protocol to accommodate wireless access to Internet

Wireless Application Protocol (WAP)– Provides mobile users access to telephony and

information services including Internet and Web– Includes wireless phones, pagers and personal

digital assistants (PDAs)


Chapter 11: Cordless Systems and Chapter 11: Cordless Systems and Wireless Local LoopWireless Local Loop

Cordless systems Wireless local loop (WLL)

– Sometimes called radio in the loop (RITL) or fixed wireless access (FWA)

Introduction to WirelessIntroduction to Wireless


Wireless Comes of AgeWireless Comes of Age

Marconi invented the wireless telegraph in 1896– Communication by encoding alphanumeric characters in

analog electromagnetic signal– Sent telegraphic signals across the Atlantic Ocean

Communications satellites launched in 1960s Before 1980’s: wireless technology usage

– Radio, television, communication satellites, paging More recently

– Cellular services started in early 1980’s in the US– Wireless data at low rates available in the 1990’s (e.g.,

ARDIS, Bell South), higher data rates underway– WLAN came of age in late 1990’s, WiFi hotspots


Cellular/PCS EvolutionCellular/PCS Evolution

Bell Labs proposes cellular in 1968 First cellular system begins operation in early

1980’s using analog (AMPS) system, by ATT -- First Generation systems (1G) --’Cellular’– These are called cellular systems, in the 800 and 900 MHz

range mostly. Large, bulky phones Digital system using TDMA starts early 1990’s (2G)

– Both in 800 and 900 MHz, and around 1800 and 1900 MHz

– These, along with GSM and CDMA below, labeled PCS, when in the 1800 and 1900 MHz range


Cellular/PCS Evolution (Cont’d)Cellular/PCS Evolution (Cont’d)

European GSM starts operation early 1990’s (2G)– Similar frequency range as TDMA but not exactly--- US and

Europe usually differ– GSM used nearly worldwide, more users than US standards -- in

US Voicestream uses it First CDMA operation 1996-1997 -- Qualcomm holds ‘key’

patents (2G)– Used by half of 2G systems in US, S. Korea, parts of Latin

America First (very) limited 3G operation in Japan in May 2001-

Wideband CDMA – Worldwide (semi) standardization agreed to in 1999, for data rate

services to 2 Mbps – Frequency allocation around 1800 MHz in most of world, US just

set 90 MHz 2.5G, in the form of GPRS (GSM/TDMA) and 1XRTT (IS-95)

out in 02– Some pictures, higher data rates


Mobile Comms -- Anywhere/AnytimeMobile Comms -- Anywhere/Anytime

Personal Communications -- Inexpensive use of cellular and wireless to communicate anywhere, anytime --- Personal: for individual use– Cellular in 1983 was expensive, PCS in 90’s it became

cheap, commonplace– Terms: Wireless, Mobile, PCS, etc

Comms for access to people (voice) and information (data, services)

Essential Requirements– Mobility >>> untethered >>> wireless– Mobility also meant having access to the network (the

PSTN) -- will get you anywhere– Personal (e.g., not just corporate) >>> cheap small

terminals, cheap services


Mobile Comms -- Anywhere/Anytime Mobile Comms -- Anywhere/Anytime (cont’d)(cont’d)

Essential Ingredients– Infrastructure (Comms systems and networks)– User terminals (for personal use)– Standards (multiple systems need to interoperate)– Spectrum (availability and use)– Services (over the infrastructure) --- From voice to smart

phones to data -- value added– Subscribers (enough to make it financially attractive)


CATEGORIES OF MOBILITYCATEGORIES OF MOBILITY

PortableTransportable

Untethered Mobile

In BuildingWirelessLAN


Wireless ExamplesWireless Examples

Mobile wireless systems– Cellular/PCS (Personal Communications Systems)

Terrestrial microwave transmission Satellite transmission Broadcast radio and TV Fixed wireless WLAN Paging Wireless Data

– Including email/Web/News/Video on personal units


Limitations and Issues in Wireless Limitations and Issues in Wireless TechnologiesTechnologies

Political and economic limitations affect wireless technologies– Spectrum limitations, infrastructure costs, standards,

politics and policies Spectrum is limited, best portions allocated,

expensive --- legal/political – 3G US spectrum a problem, 90 MHz to be reallocated from

DOD/MDS (asked for more) – NextWave bought for $5B, bankrupt, FCC sold spectrum

for $16B, lost in court, still in litigation, asked to be relieved of debt burden

Expensive infrastructure (15K base stations) needed for national coverage


Limitations and Issues in Wireless Limitations and Issues in Wireless Technologies (cont’d)Technologies (cont’d)

Standards evolve slowly, require international consensus, and involve multiple incompatible variants --- seamless roaming is not always possible

Telecom infrastructure and industry are important national policy issues

Current wireless woes: low market valuations due to very competitive cellular market, debt burdens, too many carriers, expensive/limited spectrum, wireless data build up is expensive and unprofitable

Technical– Wireless propagation is error prone and forces complex

radio equipment – Small devices for mobility, hard on technology and battery


Mobile Telephone & Internet UsersMobile Telephone & Internet Users

0

100

200

300

400

500

600

700

1993 1994 1995 1996 1997 1998 1999 2000 2001

Source: Ericsson Radio Systems, Inc.

Mobile TelephoneUsers

Internet Users

Millions

Year

BUT: SLOWED DOWN, OVERHYPED, AND ARPU IS DOWN


NOTE: Subscribers, Cell Sites, ARPU

137,458,902 currentU.S. Wireless Subscribers

Aug. 24, 2002, 2AM, per CTIA

From CTIA sitehttp://www.wow-com.com/industry/stats/surveys/


From CTIA web site


Other Wireless Status DataOther Wireless Status Data

Wireless companies market cap– March 2000 --- $794B

– March 2001 --- $265B Wireless industry layoffs, Dec.2000-Jan2002: 352,000 Wireless subscribers still growing, but slower

– Sales in one year period expected at 540 million handsets down to less than 400 million, globally

DOCOMO (Japan) continues to add subscribers, including iMode (Internet) accounts -- ARPU is $71.86, much higher than in US

China to have 132 million wireless users by the end of2001, a gain of 46.4 million over a year before, 2nd to the US, Europe about 100 million -- Asia Pacific biggest growth area


Nokia 3G Concept PhoneNokia 3G Concept Phone---Where Cellular Might Be Going------Where Cellular Might Be Going---

Nokia concept phone, from

http://www.3g-generation.com/index.htm


Mobile Wireless Data ServicesMobile Wireless Data Services

Mobile messaging, two way paging, email/news– e.g., Motorola 2-way, Blackberry RIM, other specialized services

Mobile cell-phone-based data– Currently on WAP enabled phones (messaging, news, sports, wireless

Internet promise) – iMode in Japan --- better/faster, growing use– SMS based on GSM in Europe --- messaging– Coming: GPRS-based and 1xRTT-based services to few 10’s Kbps --

wireless Internet, email, pictures, etc– Later higher with EDGE, and to 2 Mbps with 3G (Europe Japan first, later in

US) -- 3G will do all services above plus voice and video simultaneously WLAN -- WiFi spreading like a virus, many public AP’s

– Some say it will do VOIP, go mobile/wide-area, do away with 3G


Public WLAN Service: Mobile Operators Must not Miss the Boat (#IN020286MD)


Broadband Wireless TechnologyBroadband Wireless Technology

Higher data rates obtainable with mobile broadband wireless technology– Broadband = more than messaging or paging or voice– Fixed broadband wireless --- to home/office, Internet – But mobile applications more difficult --- GPRS 1st

Shares same advantages of all wireless services: convenience and reduced cost– Service can be deployed faster than other fixed service– No cost of cable plant

But so far not a commercial success (some exceptions), service is spotty for wireless data


Why Is Wireless Different?Why Is Wireless Different?

Why is there a ‘send’ or ‘call’ button on a cell phone?

Why can’t you make a cell phone call from some places?

Why does a cell connection break up sometimes? Why does a cell phone battery last less time than a

pager battery? Why are cell phone calls becoming cheaper?


Cellular System OverviewCellular System Overview


Why is Mobile Wireless Difficult?Why is Mobile Wireless Difficult?

Coverage limitations (blank spots in coverage, shielding in buildings, shadowing)

Signal losses and fading, due to propagation, blockage, and multipath, while still or while moving (lower received signal power, causes bit errors, lower voice quality, can fade out)

Call blocking, due to having no available channel (number of channels in a cell, busy hours, busy spots)

Small user terminals desired, battery (talktime, ontime, and lifetime)

Infrastructure (base stations and switches) needs to be built up and connected to phone network --- expensive

Spectrum needs to be acquired --- expensive


From iec.org


From Rappaport & Ref. there


Wireless -- The Technical Good NewsWireless -- The Technical Good News

Radio propagation effects can be offset– Use of modulation, coding and processing techniques

Continuously improving techniques (e.g., smart antennas)

– Coverage can be expanded and filled in with additional base stations (if there are enough customers to pay for it)

Battery power is sufficient because of highly power efficient techniques and power control in most units– Problems persist for higher data rates, such a 3G

Spectrum allocations do exist and additional spectrum is/will be auctioned off or allocated

Standards do exist and large areas allow roaming Current infrastructure works OK for voice (mostly),

data expansion underway


Typical Cellular NumbersTypical Cellular Numbers

Base Station Transmitted Power: 10-100 watts (= 20 dBW = 50 dBm)

Base Station Antenna Gains: 10-17 dB (i.e., X10-50) US: Base stations: about 100K --- Users: 130M Voice Transmission BW or Data Rates:

– Analog (FM): 25 or 30 KHz

– Digital: 8-14 Kbps 3 dB = X2; 10 dB = X10; 20 dB = X100; 30 dB = X1000; 100

dB = X10,000,000,000 (or 10^10 = 10 Billion) Receiver Sensitivities: -100 to -117 dBm (dB below a milliwatt)

(-100 dBm = 10^-10 mW) -- pretty good ah!! Propagation Losses: 80-180 dB over 1-10 kms US Cellular and PCS Frequencies: 824-894 MHz, and 1850-

1990 MHz


Source: Ericsson Radio Systems, Inc.


BooksBooks

Stallings– Online resources at www.WilliamStallings.com/Wireless1e.html– Has signals and comms basics, comms technical topics on

modulation, coding, spread spectrum, others– Has cellular and other wireless topics such as satellite and WLAN– Not deep into cellular/mobile topics, but good introduction for

TCOM major Rappaport

– More technical than Stallings. Often used for EE major– Deeper into cellular and mobile and much more physical layer – A bit dry and a good reference for working engineer

Lee– Preceded Rappaport and provided mathematical and theoretical

foundation for mobile communications


Some Internet and Web ResourcesSome Internet and Web Resources

Web page for Stallings Book– WilliamStallings.com/Wireless1e.html

Useful web sites, errata sheet, figures, tables, slides, internet mailing list, wireless courses

Wireless devices and items http://www.zdnet.com/special/filters/wireless/

Web proforum telecom, wireless and other simple tutorials http://www.iec.org/online/tutorials/

Washington area centric, telecom at http://www.washtech.com/news/telecom/

Qualcomm CDMA Technology Home Page at http://www.cdmatech.com/

Regulatory: FCC and ITU at www.fcc.gov and www.itu.int Wireless News --- wirelessweek.com CTIA --- http://www.wow-com.com/ More Complete Online References, next page


Online References (cont’d)Online References (cont’d)

http://comet.columbia.edu/cellularip/ Cellular IP protocol research

http://delson.org/wc/ 3G Wireless Conference http://www.tiaonline.org/ Telecom Industry Association http://www.thestandard.com/section/0,1970,813,00.html The

Industry Standard, on Tech and Telecomm, Latest http://www.openwave.com/ Makers of WAP wireless phone

microbrowser http://www.itu.int/home/index.html ITU page on IMT2000 http://www.3gpp2.org/ 3G Partnership consortia – 2 (1 was

Europe, 2 US) http://www.ietf.org/html.charters/wg-dir.html Active IETF

Working Groups http://www-daedalus.cs.berkeley.edu/ Berkeley wireless

project More Complete Online References, next page


Online References (cont’d)Online References (cont’d)

http://www.ieee-wcnc.com/ IEEE Wireless Comms and Networking Conference

http://www.sss-mag.com/ Online spread spectrum and RF magazine

http://www.analysys.com/vlib/ Virtual library, telecomunications

Wireless Design Online (Review site in general – 'a vertical net marketplace for industry professionals') http://www.wirelessdesignonline.com/content/hubs/dir.asp?hub=news

http://www.iec.org/tutorials/cell_comm/index.html Tutorials, this one on cellular communications

http://www.washtech.com/news/telecom/ Washington Tech online, Latest

http://www.zdnet.com/enterprise/filters/resources/0,10227,6016597,00.html zdNet wireless resources

http://www.cdmatech.com/ Qualcomm CDMA Technology Home Page

Introduction to Mobile Communications TCOM 552, Lecture #1 Hung Nguyen, Ph.D. 28 August, 2006.

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