9 1 FALL 2000 Rob Wolfe Telecommunications Ch.11-A,B,C

9 DIT Wolfe 2Goal Explain Shannons comm model Explain Shannons comm model Define bandwidth and effects Define bandwidth and effects Difference between: Difference between: simplex, half duplex, full duplex, echoplex Odd/even parity Odd/even parity Synchronous/asynchronous comms Synchronous/asynchronous comms

9 DIT Wolfe 3 Goal (continued) Packet and circuit switching Packet and circuit switching LAN standards/protocols LAN standards/protocols Adv/Disadv of Internet over Adv/Disadv of Internet over POTS, Cell, cable TV, satellite

9 DIT Wolfe 4 Data Communications (A)

9 DIT Wolfe 5 Model of Communication Systems Simplex Half Duplex Full Duplex

9 DIT Wolfe 6 Communication Signals Signal frequency is measured in Signal frequency is measured in Hertz (Hz) Megahertz (MHz) Gigahertz (GHz) Hertz = one wave (oscillation) per second Hertz = one wave (oscillation) per secondwave

9 DIT Wolfe 7 Data Communications (cont) Communications Channel Communications Channel Communications Medium Communications Medium twisted pair, coax, fiber-optic Bandwidth Bandwidth Digital(bps), Analog (Hz) Transmission Speed Transmission Speed Serial, Parallel transmission Signal Direction Signal Direction Simplex, Half-duplex, Duplex, Echoplex Parity Protocol (even/odd parity) Parity Protocol (even/odd parity) Synchronous/Async Protocols Synchronous/Async Protocols

9 DIT Wolfe 8 Communications Links (B) Twisted Pair Cable Twisted Pair Cable Coaxial Cable Coaxial Cable Fiber Optic Cable Fiber Optic Cable

9 DIT Wolfe 9 Twisted Pair Cable Terminates with RJ-45 connector Terminates with RJ-45 connector Note: Twisted pair cable used for telephones use smaller RJ-11 connector Shielded (STP) wires are coated with a foil shield that reduces signal noise that might interfere with data transmission. Shielded (STP) wires are coated with a foil shield that reduces signal noise that might interfere with data transmission. Unshielded (UTP) contain no shielding and are... Unshielded (UTP) contain no shielding and are... less expensive more susceptible to noise

9 DIT Wolfe 10 RJ-45 connector RJ-45 wall outlet Each wire is coated with plastic so wires dont have direct contact. To computer Usually contains four pairs of copper wires Plastic sheath protects wires Twisted Pair Cable

9 DIT Wolfe 11 Twisted Pair Cable Category 1: Category 1: UTP are recommended for analog voice communication but not data Referred to as voice-grade cable Category 2: Category 2: Higher grade of UTP suitable for voice and data Categories 3-5: (16, 20, 100Mbps) Categories 3-5: (16, 20, 100Mbps) Higher grade of UTP and STP Suitable for voice and data Referred to as data grade cable

9 DIT Wolfe 12 Copper wire core Metal BNC connector links cable to a T- shaped connector on back of a computer Copper wire conductor Copper wire conductor Non conducting insulator Non conducting insulator Foil shield Foil shield Woven metal outer shielding Woven metal outer shielding Plastic outer coating Plastic outer coating Coaxial cable a high-capacity communications cable that consists of: Coaxial Cable

9 DIT Wolfe 13 Coaxial Cable Called Category 6 cable Called Category 6 cable Has a bandwidth greater than twisted pair cable(100mbps+) Has a bandwidth greater than twisted pair cable(100mbps+) Thin coax (3/16 inch) Thin coax (3/16 inch) Found in local area networks Used in home cable TV wiring Thick coax (3/8 inch) Thick coax (3/8 inch) Found in older local area networks Used in cable TV trunk lines

9 DIT Wolfe 14 Twisted Pair Coaxial Coaxial Cable vs. Twisted Pair Cable Category 5 Category 5 Used more in networks today Used more in networks today More durable More durable Cheaper Cheaper Used to be widely used in LAN Used to be widely used in LAN Excellent bandwidth Excellent bandwidth Less durable Less durable More expensive More expensive

9 DIT Wolfe 15 Fiber Optic Cable a bundle of extremely thin tubes of glass called optical fibers. Optical fibers are: Fiber Optic Cable Thinner than the diameter of a human hair Thinner than the diameter of a human hair A relatively new development- since 1980s A relatively new development- since 1980s Purified glass without traces of water or metals Purified glass without traces of water or metals

9 DIT Wolfe 16 Fiber is wrapped in cladding to reflect light that travels through the fiber. Category 7 Cable Core of each fiber is a perfectly formed glass tube. Metal wire strengthens the cable. Plastic coating protects the bundle of glass fibers. Fiber Optic Cable

9 DIT Wolfe 17 How fiber optic cables work: Miniature lasers (LEDs) send pulses of light through the fibers Miniature lasers (LEDs) send pulses of light through the fibers Electronics at the receiving end convert light pulses into electrical signals Electronics at the receiving end convert light pulses into electrical signals Each fiber is a one-way communications channel Each fiber is a one-way communications channel Fiber Optic Cable

9 DIT Wolfe 18 Low Earth Orbit Satellite Networks A low earth orbit communications system requires a web of satellites to provide continual coverage over an area such as North America. A low earth orbit communications system requires a web of satellites to provide continual coverage over an area such as North America.

9 DIT Wolfe 19 Communications Systems(C) POTS POTS Integrated Services Digital Network (ISDN) Integrated Services Digital Network (ISDN) T1, T3 T1, T3 Cellular Phones Cellular Phones CATV CATV Internet/Intranet Internet/Intranet LANS (Ethernet, Token Ring) LANS (Ethernet, Token Ring)

9 DIT Wolfe 20 Communication via Telephone Creates dial-up connection when you dial Creates dial-up connection when you dial Stops connection when you hang up Stops connection when you hang up Uses analog audio signals Uses analog audio signals Must use a modem to send data signals Must use a modem to send data signals Modulation Modulation Changing the characteristics of a digital pulse into an analog signal Demodulation Demodulation Changing the signal back to its original state Plain Old Telephone Service (POTS)

9 DIT Wolfe 21 Internet Access via Telephone System

9 DIT Wolfe 22 Internet Access Speed Cable Modems (30 Mbps) Cable Modems (30 Mbps) DSL (1.5-8 Mbps) DSL (1.5-8 Mbps) T1/T3 (1.5/45 Mbps) T1/T3 (1.5/45 Mbps) ISDN ( Mbps) ISDN ( Mbps) Modems Modems 56 Kbps 28.8 Kbps 14.4 Kbps 8-20 sec sec 52 sec 10 min 24 min 46 min 90 min

9 DIT Wolfe 23 Local Area Networks (LANs) Topology Topology Three Types Three Types Star Ring Bus Network Standard Network Standard Ethernet Token Ring Network Communications Protocol Network Communications Protocol TCP/IP, IPX, LAT, AFP

9 DIT Wolfe 24 Whats Happening in Telecom? How long it took to reach 50 million people How long it took to reach 50 million people Radio … 38 years TV … 13 years PC … 16 years Internet … 4 years

9 DIT Wolfe 25 Whats Happening in Telecom? Cause of Information Overload Cause of Information Overload Average US office worker … Average US office worker … Communicates with 24 different people per day Six to 20 incoming messages per hour Average UK office worker … Average UK office worker … Receives 48 phone calls, 23 s, 11 voice mails, 20 letters, 15 memos, 11 faxes, 13 post-it- notes, 8 beeps Snail mail growth … less than 2% a year Snail mail growth … less than 2% a year The culprit is … The culprit is …

9 DIT Wolfe 26 Whats Happening in Telecom? Cost of Long-Distance Communication Cost of Long-Distance Communication 1974 … NY to LA, 3 minutes, $1.45 Today … same call, about a quarter Volume of Long-Distance Communication Volume of Long-Distance Communication 1984 … AT&T, 90% market share, 25 million calls per day Today … AT&T, 50% market share, 250 million calls per day

9 DIT Wolfe 27 Whats Happening in Telecom? How about Faxes … How about Faxes … In 1997, 3.2 billion pages were faxed. US Postal Service estimates that fax drove USPS market share (for correspondence industry) from 77% in 1988 to less than 59% in Wireless Communications Wireless Communications More than 21 million sign-ups for wireless account every month in the US Wireless penetration in US is 21%. In Finland, over 50%.

9 DIT Wolfe 28 Whats Happening in Telecom? Digital Convergence Digital Convergence Honey, would you please answer the TV? Im watching the phone. JAVA C&C Convergence (Japanese) ?

9 DIT Wolfe 29Goal Explain Shannons comm model Explain Shannons comm model Define bandwidth and effects Define bandwidth and effects Difference between: Difference between: simplex, half duplex, full duplex, echoplex Odd/even parity Odd/even parity Synchronous/asynchronous comms Synchronous/asynchronous comms

9 DIT Wolfe 30 Goal (continued) Packet and circuit switching Packet and circuit switching LAN standards/protocols LAN standards/protocols Adv/Disadv of Internet over Adv/Disadv of Internet over POTS, Cell, cable TV, satellite