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Module 3.2: Transmission Media

Module 3.2: Transmission Media. Electromagnetic Spectrum Guided Transmission Media Twisted Pair Coaxial cable Optical fiber Unguided Transmission Media Terrestrial Microwave Satellite Radio IR Cellular Telephony. Electromagnetic Spectrum. Guided Transmission Media. Twisted Pair

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Module 3.2: Transmission Media

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  1. Module 3.2: Transmission Media • Electromagnetic Spectrum • Guided Transmission Media • Twisted Pair • Coaxial cable • Optical fiber • Unguided Transmission Media • Terrestrial Microwave • Satellite • Radio • IR • Cellular Telephony K. Salah

  2. Electromagnetic Spectrum K. Salah

  3. Guided Transmission Media • Twisted Pair • Coaxial cable • Optical fiber K. Salah

  4. Twisted Pair • Most common medium • Telephone network • Between house and local exchange (subscriber loop) • Within buildings • To private branch exchange (PBX) • For local area networks (LAN) • 10Mbps or 100Mbps • Pros and Cons: • Cheap • Easy to work with • Low data rate • Short range, about 100 meters. K. Salah

  5. Unshielded and Shielded TP • UTP Categories • Cat 3 • up to 16MHz • Voice grade found in most offices • Cat 4 • up to 20 MHz • Cat 5 • up to 100MHz • Commonly pre-installed in new office buildings • Unshielded Twisted Pair (UTP) • Ordinary telephone wire • Cheapest • Easiest to install • Suffers from external EM interference • Shielded Twisted Pair (STP) • Metal braid or sheathing that reduces interference • More expensive • Harder to handle (thick, heavy) • Capacity 10-155 Mbps • RJ-11 vs. RJ-45 • RJ-11 is a typical UTP phone connector. Has 2 pairs. • RJ-45 is a UTP connector. Has 4 pairs. K. Salah

  6. Coaxial Cable • Most versatile medium • Television distribution • Ariel to TV • Cable TV • Long distance telephone transmission • Can carry 10,000 voice calls simultaneously • Being replaced by fiber optic • Short distance computer systems links • Local area networks • Transmission Characteristics • Analog • Amplifiers every few km • Closer if higher frequency • Up to 500MHz • Digital • Repeater every 1km • Closer for higher data rates K. Salah

  7. Optical Fiber • Greater capacity • Data rates of hundreds of Gbps • Smaller size & weight • Lower attenuation • Electromagnetic isolation • Greater repeater spacing • 10s of km at least K. Salah

  8. Transmission Characteristics • Act as wave guide for 1014 to 1015 Hz • Portions of infrared and visible spectrum • Light Emitting Diode (LED) used in MMF • Cheaper • Wider operating temp range • Last longer • Injection Laser Diode (ILD) used in SMF • More efficient • Greater data rate • Wavelength Division Multiplexing (WDM) using light prisms. MMF vs. SMF K. Salah

  9. Cable Type Cost 1 = lowest 5 = highest Typical Capacity Installation 1 = easy 5 = hard Max Cable Length EMI Resistance 1 = low 5 = high Coaxial-Thinnet 2 10 Mbps 2 185 meters 2 Coaxial-Thicknet 4 10 Mbps 3 500 meters 2 UTP 1 10-100 Mbps 1 100 meters 1 STP 3 16-155 Mbps 2 100 meters 2 Fiber-optic 5 100+ Mbps 5 Multiple kilometers 5 Comparison K. Salah

  10. Wireless Transmission • Frequencies • 2GHz to 40GHz • Microwave • Highly directional • Point to point • Satellite • 30MHz to 1GHz • Omnidirectional • Broadcast radio • 3 x 1011 to 2 x 1014 • Infrared • Local pt-pt confined area • Unguided media • Transmission and reception via antenna • Directional • Focused beam • Careful alignment required • Omnidirectional • Signal spreads in all directions • Can be received by many antennae K. Salah

  11. Types of Radio Propagation K. Salah

  12. Microwave Satellite Microwave • Satellite is relay station • Satellite receives on one frequency, amplifies or repeats signal and transmits on another frequency • Requires geo-stationary orbit • Height of 35,784km • GEO vs. LEO • Frequency Bands: C, Ku, and Ka • Television • Long distance telephone • Private business networks Terrestrial Microwave • Parabolic dish • Focused beam • Line of sight • Long haul telecommunications • Higher frequencies give higher data rates K. Salah

  13. WLAN • Benefits of Ethernet WLAN • Cheap • Faster to deploy • Mobility • Watch for security • Need for authentication • Need for encryption during transmission • What is an Access Point? • A typical diameter is a room for one AP about 40 meters • Frequencies used and data rate • IEEE 802.11b operates at 2.4 GHz range and gives 11Mbps • IEEE 802.11a operates at 5 GHz range and gives 54Mbps • IEEE 802.11g operates at 2.4 GHz range and gives 54Mbps • Bluetooth gives 1Mbps. Bluetooth networks PDAs or cell phones with PCs. Operates in a short diameter (10 meters). • Operates at 2.4 - 2.4835 GHz • May have interference with Ethernet WLAN APs K. Salah

  14. Others IR (Infrared) • Modulate noncoherent infrared light • Line of sight (or reflection) • Blocked by walls • e.g. TV remote control, IRD port Broadcast Radio • Omnidirectional • FM radio • UHF and VHF television • Line of sight • Suffers from multipath interference • Reflections K. Salah

  15. Cellular System Cellular Bands K. Salah

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