1. Lecture 3 LAN Transmission Media
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2. Transmission Media
Transmission medium: the physical path between transmitter and receiver.
Repeaters or amplifiers may be used to extend the length of the medium.
Communication of electromagnetic waves is guided or unguided.
Guided media :: waves are guided along a physical path (e.g, twisted pair, coaxial cable and optical fiber).
Unguided media:: means for transmitting but not guiding electromagnetic waves (e.g., the atmosphere and outer space).
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3. Transmission Media Choices
Twisted pair
Coaxial cable
Optical fiber
Wireless communications
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4. Digital Transmission Media Bit Rates
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5. Twisted Pair
Consists of two insulated copper wires arranged in a regular spiral pattern to minimize the electromagnetic interference between adjacent pairs
Often used at customer facilities and also over distances to carry voice as well as data communications
Low frequency transmission medium
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6. Twisted Pair
Limited in distance, bandwidth and data rate due to problems with attenuation, interference and noise
Issue: cross-talk due to interference from other signals
“shielding” wire (shielded twisted pair (STP)) with metallic braid or sheathing reduces interference.
“twisting” reduces crosstalk.
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7. Types of Twisted Pair STP (shielded twisted pair)
the pair is wrapped with metallic foil or braid to insulate the pair from electromagnetic interference
UTP (unshielded twisted pair)
each wire is insulated with plastic wrap, but the pair is encased in an outer covering
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8. Ratings of Twisted Pair
Category 3 UTP
data rates of up to 16mbps are achievable
Category 5 UTP
data rates of up to 100mbps are achievable
more tightly twisted than Category 3 cables
more expensive, but better performance
STP
More expensive, harder to work with
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9. UTP categories Category 1 Voice only (Telephone) Category 2
Data to 4 Mbps (Localtalk)
Category 3
Data to 10Mbps (Ethernet)
Category 4
Data to 20Mbps (Token ring)
Category 5
Category 5e
Data to 100Mbps (Fast Ethernet)
Data to 1000Mbps (Gigabit Ethernet)
Category 6
Data to 2500Mbps (Gigabit Ethernet)
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10. Twisted Pair Advantages
Inexpensive and readily available
Flexible and light weight
Easy to work with and install
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11. Twisted Pair Disadvantages
Susceptibility to interference and noise
Attenuation problem
For analog, repeaters needed every 5-6km
For digital, repeaters needed every 2-3km
Relatively low bandwidth (3000Hz)
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12. Coaxial Cable (or Coax)
Used for cable television, LANs, telephony
Has an inner conductor surrounded by a braided mesh
Both conductors share a common center axial, hence the term “co-axial”
Traditionally used for LANs, but growth of twisted pair for local nets and optical fiber for larger nets has reduced coax use
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13. Coaxial Cable Center conductor Dielectric Braided material Outer outer
cover
Copyright ©2000 The McGraw Hill Companies
Leon-Garcia & Widjaja: Communication Networks
Figure 3.39
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14. Coaxial Cable Divided into two basic categories for coax used in LANs:
50-ohm cable [baseband]
75-ohm cable [broadband or single channel baseband]
In general, coax has better noise immunity for higher frequencies than twisted pair.
Coaxial cable provides much higher bandwidth than twisted pair.
However, cable is ‘bulky’.
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15. Baseband Coax
50-ohm cable is used exclusively for digital transmissions
Uses Manchester encoding, geographical limit is a few kilometers.
10Base5 Thick Ethernet :: thick (10 mm) coax
10 Mbps, 500 m. max segment length, 100 devices/segment, awkward to handle and install.
10Base2 Thin Ethernet :: thin (5 mm) coax
10 Mbps, 185 m. max segment length, 30 devices/segment, easier to handle, uses T-shaped connectors.
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16. Broadband Coax 75-ohm cable (CATV system standard)
Used for both analog and digital signaling.
Analog signaling – frequencies up to 500 MHZ are possible.
For long-distance transmission of analog signals, amplifiers are needed every few kilometers.
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17. Fiber Optic Cable
Thin (2 to 125 µm), flexible medium capable of conducting an optical ray
Advantages
Greater capacity
Smaller size/lighter weight
Lower attenuation
Electromagnetic isolation
Attenuation in the fiber can be kept low by controlling the impurities in the glass.
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18. Fiber Optic Layers plastic jacket glass or plastic cladding fiber core
consists of three concentric sections
plastic jacket
glass or plastic
cladding
fiber core
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19. Optical Fiber
Three standard wavelengths : 850 nanometers (nm.), 1300 nm, 1500 nm.
First-generation optical fiber :: 850 nm, 10’s Mbps using LED (light-emitting diode) sources.
Second and third generation optical fiber :: and 1500 nm using ILD (injection laser diode) sources, gigabits/sec.
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20. Optical Fiber Attenuation loss is lower at higher wavelengths.
There are two types of detectors used at the receiving end to convert light into electrical energy (photo diodes):
PIN detectors – less expensive, less sensitive
APD detectors
ASK is commonly used to transmit digital data over optical fiber {referred to as intensity modulation}.
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21. Optical Fiber Three techniques:
Multimode step-index
Multimode graded-index
Single-mode step-index
Presence of multiple paths  differences in delay  optical rays interfere with each other.
A narrow core can create a single direct path which yields higher speeds.
WDM (Wavelength Division Multiplexing) yields more available capacity.
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22. Fiber Optic Types multimode step-index fiber
the reflective walls of the fiber move the light pulses to the receiver
multimode graded-index fiber
acts to refract the light toward the center of the fiber by variations in the density
single mode fiber
the light is guided down the center of an extremely narrow core
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23. Fiber Optic Signals fiber optic multimode step-index
graded-index
fiber optic single mode
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24. Structured Cabling System
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25. Structured Cabling System
Standards for cabling within a building (EIA/TIA-568 and ISO 11801)
Includes cabling for all applications, including LANs, voice, video, etc
Vendor and equipment independent
Designed to encompass entire building, so that equipment can be easily relocated
Provides guidance for pre-installation in new buildings and renovations
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26. Structured Cabling Subsystems
Six subsystems:
Entrance Facilities are where the building interfaces with the outside world.
Equipment Room:  A room with equipment that serves the users inside the building.
Telecommunications Room: This room contains the telecommunications equipment that connects the backbone and horizontal cabling subsystems.
Backbone Cabling: A system of cabling that connects the equipment rooms and telecommunications rooms.
Horizontal Cabling: The system of cabling that connects telecommunications rooms to individual outlets or work areas on the floor.
Work Area Components: These connect end-user equipment to outlets of the horizontal cabling system.
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27. Transmission Media - Aseel Alhadlaq

28. Backbone Cabling
The backbone cabling is also called vertical cabling or wiring.
It provides interconnection between telecommunication rooms, equipment rooms and entrance facilities.
These backbone cablings typically are done from floor to floor to floor.
Cables: unshielded twisted-pair (UTP) cable, shielded twisted-pair (STP) cable, fiber optic cable, or coaxial cable.
Equipment should be connected by cables of no more than 30 meters.
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29. Horizontal Cabling
The horizontal cabling system extends from the work area’s telecommunications information outlet to the telecommunications room.
Horizontal cabling is usually installed in a star topology that connects each work area to the telecommunications room.
Cables: Twisted pair and fiber optic cable can be used for horizontal cabling
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30. Horizontal Cabling
To comply with EIA/TIA wiring standards, individual cables should be limited to 90 meters in length between the outlet in the work area and the patch panels in the telecommunications room.
Patch cords for connecting the patch panel to hubs and switches in the telecommunications room should be no longer than 6 meters total distance.
Cables connecting users’ computers to outlets should be limited to 3 meters in length.
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31. Horizontal Cabling
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32. Backbone vs Horizontal Cabling
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33. Backbone vs Horizontal Cabling
The main difference between backbone cabling and horizontal cabling is that they cover different telecommunication service areas.
Backebone cabling is to connect the entrance facilities, equipment rooms and telecommunication rooms.
Horizontal cabling connects telecommunication rooms to individual outlets on the floors.
Backbone runs between floors. While horizontal is on one floor.
The cables used for backbone cabling have very different requirement from the horizontal cabling:
Backbone cables must meet particular fire-rating specifications.
Backbone cable must have sufficient strength to support its own weight.
Horizontal cabling system cable will be simpler.
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34. Ethernet Cable
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35. Ethernet Cable
The name, Ethernet Cable, always refers to the following category:
Category 5
Category 5e
Category 6
Or more than those categories.
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36. Ethernet Cable It is composed of 4-pair twist wirings. Orange Green
Blue
Brown
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Cat5e cable

37. Ethernet Cable
Color
Pin (T568B)
White/Orange 1
Orange 2
White/Green 3
Blue 4
White/Blue 5
Green 6
White/Brown 7
Brown 8
You can use the order of rainbow colors to memorize the order of this wiring.
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38. Ethernet Cable
Pin
Usage 1
Transmission (Tx+) 2
Transmission (Tx-) 3
Receive (Rx+) 4 -- 5 6
Receive (Rx-) 7 8
We can use the concept to justify the order of the wiring colors of straight through and crossover.
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39. How to wire Prepare the materials and tools. Cable & RJ-45 plugs
Scissors
Crimping tool
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For RJ-45 plug.
Crimping tool

40. How to wire Strip off suitable length of the cable sheath.
About cm
You can mark the position first.
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41. How to wire
Align the colored wires according to the specific order. (Later we will talk about.)
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42. Straight Through And Crossover Wiring
Wiring within a twisted pair cable is configured as either
Straight through, where each wire (or pin) is attached to the same contact point at each end
Crossover, where transmit contacts on each end of the cable are connected to the receive contact at the other end
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43. Straight Through Wiring
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44. Crossover Wiring
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45. How to wire 1→8 Straight Through
All order of the wirings is the same as the other side.
1→8
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46. Straight Through Host A Host B Pin Usage Color 1 Tx+ 2 Tx- 3 Rx+ 4 --5 6
Rx- 7 8
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47. How to wire
Crossover
We need to change the order of the transmission and receiving wirings.
1→8
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48. Crossover Host A Host B Pin Usage Color 1 Tx+ 2 Tx- 3 Rx+ 4 -- 5 6 Rx-7 8
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49. How to wire Trim all the wires to the same length.
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50. How to wire Insert the wires into the RJ45 plug.
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51. How to wire Crimp the RJ45 plug with the crimping tool.
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52. How to wire Correct Incorrect
Verify the order of the wires is correct and all the wires are correctly making good contact with the metal contacts in the RJ45 plug.
Correct
Incorrect
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53. How to wire
Cut the cable into suitable length and repeat the below steps for the other side.
Please be sure what kind of the cable you are wiring.
Testing
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