Ilenia Tinnirello

wireless networks 

Ilenia Tinnirello 

Ilenia.tinnirello@tti.unipa.it 

Giuseppe Bianchi, Ilenia Tinnirello

Reti 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 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) 


Testi 

(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, 

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..) 

A+B o C+orale 

Prova A “quantitativa” 

Pianificazione di sistemi cellulari 

Esercizi scritti (3) 

Prova B su parte monografica 

su 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 

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??) 

Prova orale su articolo scientifico 

selezionato dalla letteratura del 

settore (da concordare con il 

docente a fine corso) 


History 

Lecture 0 


Wireless 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 communication 

Simplex 

one-way communication 

radio, TV, etc 

Half-duplex: 

two-way 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? 

User Mobility 

Reduced Cost (cheap infrastructure) 

Cabling very critical 

Developing nations utilize cellular telephony rather than 

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 

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 

communication 

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 

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 

communication 

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 

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 systems 

First generation: 1980’s 

Several competing standards in 

different countries 

NMT (Nordic Mobile Telephone) 

Scandinavian standard; adopted in most 

of Europe 

First 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) 

Giuseppe Bianchi, Ilenia Tinnirello 

Analog transmission 

Frequency modulation 

Various bands: 

NMT: 

450 MHz first 

900 MHz later 

TACS 

900 MHz 

AMPS 

800 MHz 

Today still in use in lowtechnology 

countries 

And not yet completely 

dismissed in high-tech 

countries

2nd generation mobile systems 

4 systems 

Global System for Mobile (GSM) 

Digital AMPS (D-AMPS), US 

Code Division Multiple Access 

(IS-95) – Qualcomm,US 

Personal Personal Digital Cellular 

(PDC),Japan 

GSM by far the 

dominant one 

Originally pan-european 

Deployed worldwide 

(slow only in US) 


Basic bands: 

900 MHz 

1800 MHz 

(Digital Cellular System: 

DCS-1800) 

1900 1900 MHz 

(Personal Communication 

System:PCS-1900,US only) 

Specifications for 

GSM-400 (large areas) 

GSM-800 (north america)

Timing 

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 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 Europewide 

1994: DCS-1800 


2 ½ generation mobile systems 

GSM 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 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 systems 

UMTS (Universal Mobile 

TelecommunicationSystem) 

ITU standard: IMT-2000 (International Mobile 

Telecommunication – 2000) 

UMTS forum created in 1996 

Later 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 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 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 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 

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 May compete (complement) with 3G for 

Wireless Internet access 

Which of these two is the 

proper (closer) picture 

of Wireless Internet and 

Mobile Computing? 

Which technology is most suited? 


GPRS, 3G – UMTS 

< 400 Kb/s Kms 

Mobile Broadband Internet 

IEEE 802.11 (b) 

> 10 Mb/s 100 m 

Bluetooth 

< 800 Kb/s 10 m 

The global picture 

Wide Area 

Local Area 

Personal Area 


802.11/UMTS 

switching 

BT/802.11 

switching 

PAN: 

collection of secure 

connections between 

devices in a 

“very” local area 

WAN: 

everywhere outside of 

the hotspots, where 

wireless Internet 

connection are 

provided 

LAN: 

collection of secure 

“hot spot” 

connections, providing 

broadband access to 

the Internet

Ilenia Tinnirello

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