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wireless networkswireless networks

Ilenia TinnirelloIlenia Tinnirello

Giuseppe Bianchi, Ilenia Tinnirello

Ilenia TinnirelloIlenia Tinnirello

[email protected]

Reti RadiomobiliReti Radiomobili

�Struttura corso� A: Pianificazione di sistemi cellulari

» Richiami propagazione/attenuazione; Ingegneria del traffico (Erlang)» Applicazioni alle reti cellulari(verificare cosa e’ noto e cosa no :-)

� B: GSM / WiFi» Interfaccia radio


» Protocolli» Infrastrutture di rete e reti ad hoc

� C: Tecnologie in evoluzione: UMTS/ LTE / IMS / WiMax» … in aumento/evoluzione» letteratura scientifica del settore

Supporti didatticiSupporti didattici

�Forum� Per Q/A, discussioni, informazioni

� Puntatori interessanti da studenti

�Lucidi lezioni� Su web

�Testi


�Testi� 2 capitoli libro Shankar per parte A

� Testo monografico per GSM, WLAN, WiMax, UMTS

� Articoli scientifici

�Lucidi + testi �� lingua inglese � (qualche piccolo problema riscontrato)

(fotocopie disponibili)

-Shankar, “Introduction to Wireless Systems”, (cap. 2 e 4), Wiley, 2001

-Stallings, “Wireless Communications and Networks”, Prentice Hall, 2001

(versioni elettroniche disponibili)

-Eberspacher, Vogel, Bettstetter, “GSM switching,

Testi


-Eberspacher, Vogel, Bettstetter, “GSM switching, services & protocols”, Wiley, 2001

-Matthew Gast, “802.11 Wireless Networks: The Definitive Guide”, O'Reilly

-Jeffreey G. Andrews, et al. “Fundamentals of WiMax”, Prentice Hall

-Mikka Poikselka, “The IMS IP multimedia concepts and services in the mobile domain”

Modalità esame (fino all’anno scorso..) Modalità esame (fino all’anno scorso..) A+BA+B o o C+oraleC+orale

�Prova A “quantitativa”�Pianificazione di sistemi cellulari

�Esercizi scritti (3)

�Prova B su parte monografica �su GSM/WLAN


�su GSM/WLAN

�7/8 domande scritte e/o prova orale

�Prova C su approfondimenti

� 2 esercizi su modelli e simulatore e 3 domande scritte

�Prova orale su articolo scientifico

Modalità esame nuova Modalità esame nuova

�Unica prova scritta con:

�3 esercizi su pianificazione di sistemi cellulare e/o modelli di

protocolli

�7 domande su GSM/WLAN/WiMax/UMTS approfondimenti

(volete mantenere le due prove separate??)


(volete mantenere le due prove separate??)

�Prova orale su articolo scientifico selezionato dalla letteratura del settore (da concordare con il docente a fine corso)

HistoryHistory

Lecture 0Lecture 0


Lecture 0Lecture 0

Wireless communicationWireless communication

�Early wireless communication: in the 400-900 TeraHertz Band!

�150 BC smoke signals (Greece)

�1794, optical telegraph, Claude Chappe


�What is wireless communication:

�Any form of communication that does not require the

transmitter and receiver to be in physical contact

�Electromagnetic wave propagated through free-space

�Radar, RF, Microwave, IR, Optical

types of communicationtypes of communication

�Simplex

�one-way communication

�radio, TV, etc

�Half-duplex:

�two-way communication but not simultaneous


�two-way communication but not simultaneous

�push-to-talk radios, etc

�Full-duplex:

�two-way communication

�cellular phones

�Frequency-division duplex (FDD)

�Time-division duplex (TDD): simulated full-duplex

Why wireless communication?Why wireless communication?

�User Mobility

�Reduced Cost (cheap infrastructure)

�Cabling very critical

�Developing nations utilize cellular telephony rather than

laying twisted-pair wires to each home


laying twisted-pair wires to each home

�Flexibility

�Can easily set-up temporary LANs

�Disaster situations

�Office moves

�Only use resources when sending or receiving a signal

Why wireless different than Why wireless different than wired?wired?

�Noisy, time-varying channel

�BER varies by orders of magnitude

�Environmental conditions affect transmission

�Shared medium


�Other users create interference

�Must develop ways to share the channel

�Bandwidth is limited

�spectrum allocated by state rules

�ISM band for unlicensed use

History of wireless History of wireless communicationcommunication

� 1896: Marconi � first demonstration of wireless telegraphy � tx of radio waves to a ship at sea 29 km away � long wave transmission, high power req. (200 kW and +)

� 1901: Marconi� Telegraph across the atlantic ocean� Close to 3000 Km hop!

� 1907 Commercial transatlantic connections


� 1907 Commercial transatlantic connections� huge ground stations (30 by100m antennas)

� 1915: Wireless telephony established � NY – S. Francisco� Virginia and Paris

� 1920 Marconi:� Discovery of short waves (< 100m)� reflection at the ionosphere� (cheaper) smaller sender and receiver, possible due to the invention of the

vacuum tube (1906, Lee DeForest and Robert von Lieben)

History of wireless History of wireless communicationcommunication

� 1920's: Radio broadcasting became popular

� 1928: many TV broadcast trials

� 1930's: TV broadcasting deployment

� 1946: First public mobile telephone service in US

� St. Louis, Missouri

� Single cell system

� 1960's: Bell Labs developed cellular concept


� 1960's: Bell Labs developed cellular concept

� brought mobile telephony to masses

� 1960’s: Communications satellites launched

� Late 1970's: technology advances enable affordable cellular telephony

� entering the modern cellular era

� 1974-1978: First field Trial for Cellular System� AMPS, Chicago

1st generation mobile systems1st generation mobile systems

�First generation: 1980’s�Several competing standards in

different countries� NMT (Nordic Mobile Telephone)

�Scandinavian standard; adopted in most of Europe

�First european system (Sweden, 1981)

�Analog transmission� Frequency modulation

�Various bands:� NMT:

�450 MHz first�900 MHz later

� TACS


�First european system (Sweden, 1981)

� TACS (Total Access Communication Systems), starts in 1985�UK standard; A few of Europe, Asia,

Japan

� AMPS (Advanced Mobile Phone Service)�US standard

� C-Netz (Only in Germany)� Radiocom 2000 (Only in France)

� TACS�900 MHz

� AMPS�800 MHz

�Today still in use in low-technology countries� And not yet completely

dismissed in high-tech countries

2nd generation mobile systems2nd generation mobile systems

�4 systems

�Global System for Mobile (GSM)

�Digital AMPS (D-AMPS), US

�Code Division Multiple Access (IS-95) – Qualcomm,US

�Personal Digital Cellular

�Basic bands:

�900 MHz

�1800 MHz

�(Digital Cellular System: DCS-1800)

�1900 MHz


�Personal Digital Cellular (PDC),Japan

�GSM by far the dominant one

�Originally pan-european

�Deployed worldwide �(slow only in US)

�1900 MHz

�(Personal Communication System:PCS-1900,US only)

�Specifications for

�GSM-400 (large areas)

�GSM-800 (north america)

TimingTiming

�1982: Start of GSM-specification in Europe (1982-1990)

�1983: Start of American AMPS widespread deployment

�1984 CT-1 standard (Europe) for cordless telephones

�1991 Specification of DECT


�1991 Specification of DECT

�Digital European Cordless Telephone (today: Digital Enhanced Cordless Telecommunications)

- ~100-500m range, 120 duplex channels, 1.2Mbit/s data transmission, voice encryption, authentication

�1992: Start of GSM operation Europe-wide

�1994: DCS-1800

2 ½ generation mobile systems 2 ½ generation mobile systems GSM incremental extensionGSM incremental extension

�High speed circuit switched data (HSCSD)

�Circuit switched data communication�Uses up to 4 slots (1 slot = 9.6 or 14.4 Kbps)

�General Packet Radio Service (GPRS)�Packet data (use spectrum only when needed!)


�Packet data (use spectrum only when needed!)� dial-up comparable speed

�Enhanced Data-rates for Global Evolution (EDGE)

�Higher data rate available on radio interface (3x)» Up to 384 Kbps (8 slots)» Thanks to new modulation scheme (8PSK)» May coexist with old GMSK

3rd generation mobile systems3rd generation mobile systems

�UMTS (Universal Mobile TelecommunicationSystem)

�ITU standard: IMT-2000 (International Mobile Telecommunication – 2000)

�UMTS forum created in 1996�Later on 3GPP forum (bears most of


�Later on 3GPP forum (bears most of standardization activities)

�Wideband CDMA radio interface�But several other proposals accepted as

“compatible”

�Radio spectrum: 1885-2025 & 2110-2200 MHz

�Long Term Evolutions

History of Wireless DataHistory of Wireless Data� Early Wireless LAN proprietary products

� WaveLAN (AT&T) - the ancestor of 802.11

� HomeRF (Proxim)�45% of the home network in 2000; 30% in 2001, … ε% today�Abandoned by major chip makers (e.g. Intel: dismissed in april 2001)

� IEEE 802.11 Committee formed in 1990� Charter: specification of MAC and PHY for WLAN

� First standard: june 1997�1 and 2 Mbps operation


�1 and 2 Mbps operation� Reference standard: september 1999

� Multiple Physical Layers�2.4GHz Industrial, Scientific & Medical shared unlicensed band

» Legacy; 802.11b/g

�5 GHz ISM (802.11a)� 1999: Wireless Ethernet Compatibility Alliance

(WECA) certification� Later on named Wi-Fi

� Boosted 802.11 deployment!!

WLAN speedsWLAN speeds

�802.11a: PHY for 5 GHz

�802.11b: higher rate PHY for 2.4 GHz


�802.11g: OFDM for 2.4 GHz

�802.11n: ??? (Higher data rate)�Launched in september 2003�Minimum goal: 108 Mbps (but higher numbers

considered)

Why so much talking about of Why so much talking about of 802.11 today?802.11 today?

�802.11: no more “just” a WLAN�Hot-spots

�Where the user goes, the network is available: home, school, office, hotel, university, airport, convention center…

�Freedom to roam with seamless connectivity in every domain, with single client device

�May compete (complement) with 3G for


�May compete (complement) with 3G for Wireless Internet access

Which of these two is the proper (closer) picture

of Wireless Internet andMobile Computing?

Which technology is most suited?

The global pictureThe global picture

Wide Area

Local Area

Personal AreaLAN:

collection of secure “hot spot”

WAN:everywhere outside of the hotspots, where

wireless Internet connection are

provided802.11/UMTS

switchingMobile Broadband Internet

IEEE 802.11 (b)> 10 Mb/s �� 100 m

GPRS, 3G – UMTS< 400 Kb/s �� Kms


“hot spot” connections, providing broadband access to

the Internet

PAN:collection of secure

connections between devices in a

“very” local area

BT/802.11switching

Bluetooth< 800 Kb/s �� 10 m

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