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Transmission Media Wired –Coaxial –Twisted Pair (UTP / STP) –Optical Fibres Wireless –IR –Microwave signals –Radio Frequency.

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Presentation on theme: "Transmission Media Wired –Coaxial –Twisted Pair (UTP / STP) –Optical Fibres Wireless –IR –Microwave signals –Radio Frequency."— Presentation transcript:

1 Transmission Media Wired –Coaxial –Twisted Pair (UTP / STP) –Optical Fibres Wireless –IR –Microwave signals –Radio Frequency

2 Wired LAN (Coaxial cable) –high capacity communication cable –using BNC Connector –2 concentric conductor one inner (inner core) one outer (metal mesh) –nowadays mostly for cable TV transmission –disadv : much thicker not flexible more expensive (c.f. UTP / STP)

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5 Wired LAN (Twisted pair) –Using ordinary copper wire –the copper wires are twisted together to reduce crosstalk / electromagnetic interference –by electrical appliances (motors, transformers) –radio frequency interference –if the twisted pair is enclosed inside a shield –STP not enclosed inside a shield (unshield) –UTP –nowadays mostly for networking cabling

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8 Wired LAN (Twisted pair) … contd –Using RJ45 connector –Adv : more flexible less expensive (c.f. coaxial cable) –Categories Cat for analogue voice (old telephone system) Cat. 2 Cat baseT Ethernet (16Mbps) Cat. 4 Cat baseT Ethernet (100Mbps) –Ref : 10_twisted-pair_balanced_cabling.asphttp://www.siemon.com/us/standards/13- 10_twisted-pair_balanced_cabling.asp

9 Wired LAN (Twisted pair) … contd –Types of cables Straight through cable –connecting PC to network devices (hub / switch) Crossover cable –connection between PC & PC –connection between network device with network device Rollover cable –with connector –RJ45 to DB-9 converter then to COM 1 or COM 2 of PC

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26 Wired LAN (Optical fibres) –made up of a bundle of thin tubes of glass thinner than a human hair –do not conduct or transmit electrical signals not interfere by electromagnetic wave –Transmission of info via light pulse –Carry more info than copper wire at the same period of time –signal can travel a very long distance because no / little attenuation –But fragile … need more protection installation.. More labour intensive

27 Interference –Original Signal

28 –Noise

29 –When signal and noise combined together

30 –Resulting Signal detected

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32 Wireless LAN –use electromagnetic waves to transmit and receive data from one device to another –suitable to env. where cabling is difficult / not practical / not economical construction site warehouse school campus hospitals –usually as an extension or an alternative for a wired LAN –transmitter : Access Point (AP)

33 Wireless LAN … contd –Using IR / radio signals / microwaves Some of them require direct line of sight (e.g. : IR) –Signal travels in straight line Stations using antenna & satellite –To avoid the »curvature of the Earth »Mountains »Tall buildings »Other signal obstacles Advanced wireless technology –Eliminate the limitation of direct line-of-sight –More flexible

34 Wireless LAN … contd –Problems faced by wireless transmission Signals can be weakened by bad weather and solar activity A satellite can be used for around 7-10 years Anyone can detect the signal (Security problem) –Signal / data must be encrypted before sending

35 Wireless LAN … contd –Advantages –Easy installation –Flexibility in usage –Economical –Expandability –http://iclassroom.hkedcity.net/directory/index.phtml?iroom_id=1387&tool_id=853&folder _id=1520http://iclassroom.hkedcity.net/directory/index.phtml?iroom_id=1387&tool_id=853&folder _id=1520


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