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

Electromagnetic Spectrum K. Salah

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

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

Unshielded and Shielded TP 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 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 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

Transmission Characteristics 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

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

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

Comparison 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 185 meters Coaxial-Thicknet 4 3 500 meters UTP 1 10-100 Mbps 100 meters STP 16-155 Mbps Fiber-optic 5 100+ Mbps Multiple kilometers K. Salah

Wireless Transmission 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 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 K. Salah

Types of Radio Propagation K. Salah

Terrestrial 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

Wide Area: Satellite Systems Cover very large areas Different orbit heights GEOs (39000 Km), LEOs (2000 Km), MEOs (9000km) GEO is stationary. You need 3 to cover whole planet LEO and MEO orbit the earth every one hour Dish antennas, or bulky handsets Optimized for one-way transmission, location positioning, GPS systems, Satellite Radio Radio (XM, DAB) and movie (SatTV) broadcasting Killed MMDS wireless TV offerings. Future: satTV (eg: directTV) in your car Most two-way systems struggling or bankrupt Expensive alternative to terrestrial cellular system (2G) Trucking fleets, journalists in wild areas, Oil rigs K. Salah

LEO and MEO Used in GPS 24 MEOs are need to cover the whole planet 54 for LEOs to cover the whole planet Could have multiple readings for increased precision and reliability. K. Salah

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

Others IR (Infrared) Broadcast Radio 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

Cellular System Cellular Bands K. Salah