Introduction to Digital Subscriber Line (DSL)

1. EE4220 Communications system  Introduction to Digital Subscriber Line (DSL) Dr. Hassan Yousif Electrical Engineering Department College of Engineering Salman Bin Abdulaziz University Lect no-5

2. Introduction Internet Digital Subscriber Line (DSL) Broadband Access DSLAM downstream Central Office DSL modem DSL modem upstream VoiceSwitch LPF LPF Customer Premises Telephone Network DSLAM - Digital Subscriber Line Access Multiplexer LPF – Low Pass Filter (passes voiceband frequencies)

3. DSL Flavors DSL is often called xDSL since there are many varieties (different x) e.g. ADSL, HDSL, SHDSL, VDSL, IDSL, etc. There were once many unconnected types but now we divide them into three main families The differentiation is by means of the application scenario • HDSL (high bit rate, mainly business, data + telephony) • ADSL (asymmetric, mainly residential, Internet access) • VDSL (very high rate, but short distance)

4. More xDSL flavors

5. Not DSL More xDSL flavors (cont.)

6. History of wireless communication • Guglielmo Marconi invented the wireless telegraph in 1896 • Communication by encoding alphanumeric characters in analog signal • Sent telegraphic signals across the Atlantic Ocean • 1914 – first voice communication over radio waves • Communications satellites launched in 1960s • Advances in wireless technology • Radio, television, mobile telephone, communication satellites • More recently • Satellite communications, wireless networking, cellular technology

8. What is Wireless Communication ? • Transmitting voice and data using electromagnetic waves in open space (atmosphere) • Electromagnetic waves • Travel at speed of light (c = 3x108 m/s) • Has a frequency (f) and wavelength (l) • c = f x l • Higher frequency means higher energy photons • The higher the energy photon the more penetrating is the radiation

9. Types of wireless communication celullar wireless computer network radio service

10. Electromagnetic radiation spectrum

11. Wavelength of Some Technologies • GSM Phones: • frequency ~= 900 Mhz • wavelength ~= 33cm • PCS Phones • frequency ~= 1.8 Ghz • wavelength ~= 17.5 cm • Bluetooth: • frequency ~= 2.4Gz • wavelength ~= 12.5cm

12. Types of electromagnetic carriers • when the distance between the sender and receiver is short (e.g. TV box and a remote control) infrared waves are used • for long range distances between sender and receiver (e.g. TV broadcasting and cellular service) both microwaves and radio waves are used • radio waves are ideal when large areas need to be coverd and obstacles exist in the transmission path • microwaves are good when large areas need to be coverd and no obstacles exist in the transmission path

13. Wireless applications (services)

14. Advantages and disadvantages of wireless communication • advantages: • mobility • a wireless communication network is a solution in areas where cables are impossible to install (e.g. hazardous areas, long distances etc.) • easier to maintain • disadvantages: • has security vulnerabilities • high costs for setting the infrastructure • unlike wired comm., wireless comm. is influenced by physical obstructions, climatic conditions, interference from other wireless devices

15. Frequency Carries/Channels • The information from sender to receiver is carrier over a well defined frequency band. • This is called a channel • Each channel has a fixed frequency bandwidth (in KHz) and Capacity (bit-rate) • Different frequency bands (channels) can be used to transmit information in parallel and independently.

16. Wireless System Architecture

17. Evolution of Wireless Technology • Nikola Tesla • Invented radio communications • Guglielmo Marconi • Sent telegraphic signals across the Atlantic Ocean • Communications satellites launched in 1960s • Advances in wireless technology • Radio, television, mobile telephone, communication satellites • More recently • Satellite communications, wireless networking, cellular technology

18. Broadband Wireless Technology • Higher data rates achievable with broadband wireless technology • Graphics, video, audio • Shares same advantages of all wireless services

19. Wireless Technologies • Unlicensed Frequency Spectrum • Industrial, Scientific and Medical (ISM) • 915 MHz • 2.45 GHz • 5.8 GHz • Wireless Fidelity (Wi-Fi) • Based on IEEE 802.11 standards • Refers to 802.11-compatible products certified as interoperable by the Wi-Fi Alliance • Covers office and home based LANs as well as hotspots

21. Comparison of Wi-Fi Standards

22. Comparison of Wi-Fi Standards

23. Wireless Technologies (cont.) • Unlicensed Frequency Spectrum • Unlicensed National Information Infrastructure (U-NII) • U-NII devices do not require licensing • Designated to provide short-range, high-speed wireless networking communication at low cost • Three frequency bands (100 MHz each) were set aside by the FCC in 1997 • Objective was to help schools connect to the Internet without the need for hard wiring

24. Wireless Technologies (cont.) • Unlicensed Frequency Spectrum • Unlicensed National Information Infrastructure (U-NII)

25. Wireless Technologies (cont.) • Worldwide Interoperability for Microwave Access (WiMAX) • Similar to Wi-Fi • Range of 40-50 Km • Wireless alternative to cable, DSL, and T1/E1 for last-mile broadband access • Initial developments were in fixed locations but a mobile version was also developed

26. Wireless Technologies (cont.) • ZigBee • Standard ratified on Dec 9, 2004 • Enables reliable, cost-effective, low-power, wirelessly networked, monitoring and control products based on an open global standard • Targeted to sensors and control devices that do not require high bandwidths but do require low latency and very low power consumption • Initial markets • Home control • Building Automation • Industrial Automation

27. Wireless Technologies (cont.) • Ultrawideband • According to the FCC, ultrawideband is any radio technology with a spectrum that occupies greater than 20% of the center frequency or a minimum of 500MHz • An UWB system provides a wireless PAN • Data payload communication capabilities of 53.3, 80, 110, 160, 200, 320, 400, and 480 Mb/s • Employs orthogonal frequency division multiplexing (OFDM) • Technology specification developed by MultiBand OFDM Alliance (MBOA) • Over 170 member companies

28. Limitations and Difficulties • Limitations as well as political and technical difficulties inhibit wireless technologies • Lack of an industry-wide standard • Device limitations • Small LCD on a mobile telephone can only display a few lines of text • Browsers of most mobile wireless devices use wireless markup language (WML) instead of HTML

29. Standards Organizations • National Technical Standard-Setting Organizations: • American National Standards Institute • Institute of Electrical and Electronic Engineers, Inc • National Institute of Standards and Technology • International Standard-Setting Organizations: • International Telecommunication Union • International Standards Organization • European Telecommunications Standards Institute

30. Wireless Technology & Governance • Federal Communications Commission • National Telecommunications and Information Administration • Cellular Telecommunications Industry Association