TOBB ETU Bil557 – Kablosuz Ağlar

1. TOBB ETU Bil557 – Kablosuz Ağlar Bahar 2007 Çarşamba 08:30 – 12:00 Sınıf: 175 Bülent Tavlı Oda: 169 btavli@etu.edu.tr

2. Ders Bilgileri - I • Bu derste neler öğreneceğiz? • Geleneksel cep telefonu (cellular networks) ve kablosuz ağları (wireless networks) olanaklı kılan kavramlar nelerdir? • Kablosuz iletişim sistemi tasarımlarındaki temel yapılar ve sistem performansını yükseltme yöntemleri nelerdir? • Kablosuz iletişimi konusunda en son aşama (state-of-the-art) araştırma nasıl yapılır? • Bu ders için nasıl bir altyapı gerekli? • Temel matematiksel analiz • İşaret işleme (signal processing) • Elektronik iletişim (Telecommunications) • Programlama (C/C++ ve Matlab) • Eğer bu konularda yetersizseniz  • Bu dersi yine de alabilirsiniz • Ama ek çaba ve zaman harcamanız gerekecek • Bilgi dağarcığınızı genişletmek için ve son derece popüler bir konuda verimli araştırma yapabilmek için mükemmel bir fırsat

3. Ders Bilgileri - II • Ana kaynak • Wireless Communications and Networks, 2nd Edition, Prentice Hall by W. Stallings • Bu kitaptan kesinlikle bir tane edinmelisiniz! • http://williamstallings.com/Wireless/Wireless2e.html • Yardımcı kaynaklar • Wireless Communications: Principles and Practice , 2nd Edition, Prentice Hall by T. Rappaport • Ad Hoc Wireless Networks: Architectures and Protocols, Prentice Hall by C. S. R. Murthy and B. S. Manoj • Mobile Ad Hoc Networks: Energy-Efficient Real-Time Data Communications, Springer by B. Tavlı and W. B. Heinzelman • Derste dağıtılacak makaleler ve diğer belgeler • Network Simulator (ns-2) • http://nsnam.isi.edu/nsnam/index.php/User_Information

4. Ders Bilgileri - III • Notlandırma • Ödevler (iki haftada bir): %20 • Proje (rapor + sunum): %30 • Arasınav: %25 • Sonsınav: %25 • Projeler kablosuz iletişim ve ağlar hakkında olmalı • Derinlemesine literatür taraması, Benzetim (simulation), Analiz, Uygulama • Tek başınıza veya en fazla üç kişilik gruplar halinde • Dönem sonunda konferans bildirisi formatında bir rapor verilecek ve konferans sunumu şeklinde bir sunum yapılacak • Proje takvimi • Şubat sonuna kadar projenizi belirleyip onay alın • Dönemin son haftası proje sunumu yapılacak • Akademik ahlak • Yardımlaşmanız teşvik edilmekle beraber kopye çekmeniz kesinlikle yasaktır

5. Introduction to Wireless Chapter 1

6. What is wirelesscommunication? • Any form of communication that does not require the transmitter and receiver to be in physical contact through guided media • Electromagnetic wave propagated through free-space • Radar, RF, Microwave, IR, Optical • Simplex: one-way communication (e.g., radio, TV) • Half-duplex: two-way communication but not simultaneous (e.g.,push-to-talk radios) • Full-duplex: two-way communication (e.g., cellular phones) • Frequency-division duplex (FDD) • Time-division duplex (TDD): simulated full-duplex

7. Electromagnetic Specturm 1017 1019 109 1012 4.3x1014 7.5x1014 http://imagine.gsfc.nasa.gov/docs/ science/know_l1/emspectrum.html

8. Why use wireless communication? • Provides mobility • A user can send and receive messages no matter where he/she is located • Added convenience / reduced cost • Enables communications without adding expensive infrastructure • Can easily setup temporary wireless LANs (disaster situations) • Developing nations use cellular telephony rather than laying wires to each home • Use resources only when sending or receiving signal

9. Why is wireless different than wired? • Noisy, time-varying channel • BER varies by orders of magnitude • Enviromental conditions affect transmission • Shared medium • Other users create interference • Must develop ways to share the channel • Bandwidth is limited • TÜK, FCC determines the frequency allocation • ISM band for unlicensed spectrum (902-928 MHz, 2.4-2.5 GHz, 5.725-5.875 GHz) • Requires intelligent signal processing and communications to make efficient use of limited bandwidth in error-prone environment

10. Early forms of wireless communication • Primitive • Sound (e.g., beating of drums) • Sight (e.g., smoke signals) • PA (public address) system • Disadvantages of these forms of communication • Limited alphabets • Noisy • Broadcast (no privacy or security) • Limited distance (or requires relaying which is unreliable) • Require line-of-sight between transmitter and receiver

11. Wireless Comes of Age • 1893: Nikola Tesla demonstrated the first ever wireless information transmission in New York City • 1897: Marconi demonstrated transmission of radio waves to a ship at sea 29 km away • 1915: Wireless telephony established-- VA and Paris • 1920's: Radio broadcasting became popular • 1930's: TV broadcasting began • 1946: First public mobile telephone service in US • 1960's: Bell Labs developed cellular concept-- brought mobile telephony to masses • 1960’s: Communications satellites launched • Late 1970's: IC technology advances enable affordable cellular telephony-- ushers in modern cellular era • Early 1990’s: Cellular telephony in Türkiye • 2007: İŞTCell cellular service is introduced by TürkCell 

12. Some Milestones in Wireless Communications

13. Modern Cellular Standards • First generation (1G) systems (analog) • 1979: NTT (Japan), FDMA, FM, 25 kHz channels, 870-940 MHz) • 1981: NMT (Sweden and Norway), FDMA, FM, 25 kHz, 450-470 MHz • 1983: AMPS (US), FDMA, FM, 30 kHz channels, 824-894 MHz • 1985: TACS (Europe), FDMA, FM, 25 kHz channels, 900 MHz • Second generation (2G) systems (digital) • Supported voice and low-rate data (up to 9.6 kbps) • 1990: GSM (Europe), TDMA, GMSK, 200 kHz channels, 890-960 MHz • 1991: USDC/IS-54 (US), TDMA, π/4 DQPSK, 30 kHz channels, 824-894 MHz • 1993: IS-95 (US), CDMA, BPSK/QPSK, 1.25 MHz channels, 824-894 MHz and 1.8-2.0 GHz • 1993: CDPD (US) FHSS GMSK 30 kHz channels 824-894 Mhz • Enhanced 2G (2.5G) systems • Increased data rates • General Packet Radio System (GPRS): packet-based overlay to GSM, up to 171.2 kbps • Enhanced Data rates for GSM Evolution (EDGE): modulation enhancements to GSM to support up to 180 kbps • 3rd generation (3G) systems • Up to 2 Mbps • Internet, VoIP • 2004-2005: IMT-2000, 2000 MHz range - W-CDMA (UMTS), cdma2000, TD-SCMA

14. Fast facts – Cellular subscribers

15. Fast facts – cellular growth

16. Wireless data standards • IEEE 802.11: wireless LAN/ad-hoc networking, 1, 2 or 11 Mbps, DSSS or FHSS with CSMA/CA RTS-CTS-ACK, 2.4 - 2.4835 GHz • Bluetooth: replacement for cables, short low power (1 or 100 mW), low cost, 1 piconets with master-slave operation • HomeRF: wireless home networking, 150 feet range, up to 10 devices, SWAP protocol • IEEE 802.15: wireless PAN, modes for low (< 10 kbps, ZigBee), medium (up to 200 kbps), and high (> 20 Mbps) data rates • CDPD: TCP/IP compatible packet transmission via digital overlay to existing analog cellular network, 19.2 kbps • PCS: modified cellular protocols, goals--low power, voice and moderate-rate data, small, inexpensive terminals, large coverage area • MobileIP: "routing support to permit IP nodes (hosts and routers) using either IPv4 or IPv6 to seamlessly roam among IP subnetworks and media types...maintenance of active TCP connections and UDP port bindings." • WAP: communications protocol and application environment, enables viewing of Internet content in special text format on special WAP-enabled devices

17. Underlying concepts • Electromagnetics • Antennas, wave propagation, channel modeling • Signals and systems • Filtering, Fourier transforms, block-diagram design • Digital signal processing • Equalization, spread-spectrum, source coding • Communications • Modulation, noise analysis, channel capacity, channel coding

18. Enabling Technologies • Digital integrated circuits • RF generation devices (efficient power amps, sleep modes, improved oscillators, smart antennas) • Source coding (data compression) • Modulation (improved efficiency) • Multiple-access techniques (increase number of users) • Channel coding/forward error correction (improve probability of successful reception) • Software programmable radios

19. Protocol stack - I Source coding Application • Provides abstraction when designing layers • We'll discuss each layer in turn... Packet re-ordering (e.g., TCP) Transport Routing (e.g., IP) Network Error correction, encryption Data Link (MAC) Modulation, power control, filtering Physical Channel

20. FTP - A A B C D E FTP - E TCP - A TCP - E Protocol Stack - II Application Transport Network MAC Physical Channel

21. Course Outline

22. Part One: Background • Provides preview and context for rest of the course • Covers basic topics • Data Communications • TCP/IP

23. Chapter 2: Transmission Fundamentals • Basic overview of transmission topics • Data communications concepts • Includes techniques of analog and digital data transmission • Channel capacity • Transmission media • Multiplexing

24. Chapter 3: Communication Networks • Comparison of basic communication network technologies • Circuit switching • Packet switching • Frame relay • ATM

25. Chapter 4: Protocols and the TCP/IP Protocol Suite • Protocol architecture • Overview of TCP/IP • Open systems interconnection (OSI) reference model • Internetworking

26. Part Two: Wireless Communication Technology • Underlying technology of wireless transmission • Encoding of analog and digital data for wireless transmission

27. Chapter 5: Antennas and Propagation • Principles of radio and microwave • Antenna performance • Wireless transmission modes • Fading

28. Chapter 6: Signal Encoding Techniques • Wireless transmission • Analog and digital data • Analog and digital signals

29. Chapter 7: Spread Spectrum • Frequency hopping • Direct sequence spread spectrum • Code division multiple access (CDMA)

30. Chapter 8: Coding and Error Control • Forward error correction (FEC) • Using redundancy for error detection • Automatic repeat request (ARQ) techniques

31. Part Three: Wireless Networking • Examines major types of networks • Satellite-based networks • Cellular networks • Cordless systems • Fixed wireless access schemes • Use of mobile IP and Wireless Access Protocol (WAP) to provide Internet and Web access

32. Chapter 9: Satellite Communications • Geostationary satellites (GEOS) • Low-earth orbiting satellites (LEOS) • Medium-earth orbiting satellites (MEOS) • Capacity allocation

33. Chapter 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

34. Chapter 11: Cordless Systems and Wireless Local Loop • Cordless systems • Wireless local loop (WLL) • Sometimes called radio in the loop (RITL) or fixed wireless access (FWA)

35. Chapter 12: Mobile IP and Wireless Access 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)

36. Part Four: Wireless Local Area Networks • Examines underlying wireless LAN technology • Examines standardized approaches to local wireless networking

37. Chapter 13: Wireless LAN Technology • Overview of LANs and wireless LAN technology and applications • Transmission techniques of wireless LANs • Spread spectrum • Narrowband microwave • Infrared

38. Chapter 14: IEEE 802.11 Wireless LAN Standard • Wireless LAN standards defined by IEEE 802.11 committee

39. Chapter 15: Bluetooth • Bluetooth is an open specification for wireless communication and networking • Personal computers • Mobile phones • Other wireless devices

40. Advanced Topics • Ad Hoc Networks • Sensor Networks

41. Part One Technical Background

42. Transmission Fundamentals Chapter 2

43. Electromagnetic Signal • Function of time • Can also be expressed as a function of frequency • Signal consists of components of different frequencies

44. Time-Domain Concepts • Analog signal - signal intensity varies in a smooth fashion over time • No breaks or discontinuities in the signal • Digital signal - signal intensity maintains a constant level for some period of time and then changes to another constant level • Periodic signal - analog or digital signal pattern that repeats over time • s(t +T ) = s(t ) -¥< t < +¥ • where T is the period of the signal

47. Time-Domain Concepts • Aperiodic signal - analog or digital signal pattern that doesn't repeat over time • Peak amplitude (A) - maximum value or strength of the signal over time; typically measured in volts • Frequency (f ) • Rate, in cycles per second, or Hertz (Hz) at which the signal repeats

48. Time-Domain Concepts • Period (T ) - amount of time it takes for one repetition of the signal • T = 1/f • Phase () - measure of the relative position in time within a single period of a signal • Wavelength () - distance occupied by a single cycle of the signal • Or, the distance between two points of corresponding phase of two consecutive cycles

49. Sine Wave Parameters • General sine wave • s(t ) = A sin(2ft + ) • Figure 2.3 shows the effect of varying each of the three parameters • (a) A = 1, f = 1 Hz,  = 0; thus T = 1s • (b) Reduced peak amplitude; A=0.5 • (c) Increased frequency; f = 2, thus T = ½ • (d) Phase shift;  = /4 radians (45 degrees) • note: 2 radians = 360° = 1 period

50. Sine Wave Parameters