1. Transmission Basics and Networking Media
Chapter Four
Transmission Basics and Networking Media

2. Objectives
Explain data transmission concepts including full-duplexing, attenuation, and noise
Describe the physical characteristics of coaxial cable, STP, UTP, and fiber-optic media
Explain the benefits and limitations of different networking media
Identify the best practices for cabling buildings and work areas
Describe the methods of transmitting data through the atmosphere

3. Transmission Basics Transmission has two meanings:
Refers to process of issuing data signals on a medium
Refers to progress of data signals over a medium
On a data network, information can be transmitted via one of two methods:
Analog
Digital

4. Transmission Basics
Both analog and digital signals are generated by electrical current, pressure of which is measured in volts
In analog signals, voltage varies continuously
In digital signals, voltage turns off and on repeatedly

5. Figure 4-1: Example of an analog signal
Transmission Basics
Figure 4-1: Example of an analog signal

6. Transmission Basics Amplitude Frequency Wavelength
Measure of a signal’s strength
Frequency
Number of times a signal’s amplitude changes over a period of time
Expressed in hertz (Hz)
Wavelength
Distances between corresponding points on a wave’s cycle

7. Figure 4-2: Phase differences
Transmission Basics
Phase
Refers to progress of a wave over time in relationship to a fixed point
Figure 4-2: Phase differences

8. Figure 4-3: A complex analog signal representing human speech
Transmission Basics
Figure 4-3: A complex analog signal representing human speech

9. Transmission Basics Binary system encodes using 1s and 0s
Bits can only have a value of either 1 or 0
Eight bits together form a byte
Noise or any interference that may degrade signals affects digital signals less than analog signals

10. Figure 4-4: Example of a digital signal
Transmission Basics
Figure 4-4: Example of a digital signal

11. Data Modulation Modem Modulation Frequency modulation (FM)
Name reflects function as modulator/demodulator
Modulation
Technique for formatting signals
Frequency modulation (FM)
Method of data modulation in which frequency of carrier signal is modified by application of a data signal
Amplitude modulation (AM)
Modulation technique in which amplitude of carrier signal is modified by application of a data signal

12. Figure 4-5: A carrier wave modified by frequency modulation
Data Modulation
Figure 4-5: A carrier wave modified by frequency modulation

13. Transmission Direction
Simplex
Signals travel in only one direction
Half-duplex
Signals may travel in both directions over a medium but in only one direction at a time
Full-duplex
Signals are free to travel in both directions over a medium simultaneously
Also referred to just as duplex

14. Transmission Direction
Channel
Distinct communication path between two or more nodes
Figure 4-6: Simplex, half-duplex, and full-duplex transmission

15. Transmission Direction
Multiplexing
Allows multiple signals to travel simultaneously over one medium
To accommodate multiple signals, single medium is logically separated into subchannels
For each type of multiplexing:
Multiplexer (mux) is required at sending end of channel
Demultiplexer (demux) separates the combined signals and regenerates them in original form

16. Transmission Direction
Time division multiplexing (TDM)
Divides channel into multiple intervals of time
Figure 4-7: Time division multiplexing

17. Transmission Direction
Wavelength division multiplexing (WDM)
Used only with fiber-optic cable
Data is transmitted as pulses of light
Fiber-optic modem (FOM) is a demultiplexer used on fiber networks that employ WDM
Figure 4-9: Wavelength division multiplexing

18. Relationships Between Nodes
Point-to-point
Transmission involving one transmitter and one receiver
Broadcast
Transmission involving one transmitter and multiple receivers
Webcasting
Broadcast transmission used over the Web

19. Relationships Between Nodes
Figure 4-10: Point-to-point versus broadcast transmission

20. Throughput and Bandwidth
Throughput is amount of data the medium can transmit during a given period of time
Also called capacity
Bandwidth measures difference between highest and lowest frequencies a media can transmit
Range of frequencies is directly related to throughput

22. Transmission Flaws Electromagnetic interference (EMI)
Interference that may be caused by motors, power lines, television, copiers, fluorescent lights, or other sources of electrical activity
Radiofrequency interference (RFI)
Interference that may be generated by motors, power lines, televisions, copiers, fluorescent lights, or broadcast signals from radio or TV towers

23. Figure 4-11: An analog signal distorted by noise
Transmission Flaws
Figure 4-11: An analog signal distorted by noise

24. Figure 4-12: A digital signal distorted by noise
Transmission Flaws
Figure 4-12: A digital signal distorted by noise

25. Transmission Flaws Attenuation
Loss of signal strength as transmission travels away from source
Analog signals pass through an amplifier, which increases not only voltage of a signal but also noise accumulated
Figure 4-13: An analog signal distorted by noise, and then amplified

26. Transmission Flaws Regeneration Repeater
Process of retransmitting a digital signal
Repeater
Device used to regenerate a signal
Figure 4-14: A digital signal distorted by noise, and then repeated

27. Coaxial Cable
Consists of central copper core surrounded by an insulator, braiding, and outer cover called a sheath
Figure 4-15: Coaxial cable

28. Table 4-2: Some types of coaxial cable

29. Thicknet (10Base5) Also called thickwire Ethernet
Rigid coaxial cable used on original Ethernet networks
IEEE designates Thicknet as 10Base5 Ethernet
Almost never used on new networks but you may find it on older networks
Used to connect one data closet to another as part of network backbone

30. Thicknet Characteristics
Throughput
According to IEEE 802.3, Thicknet transmits data at maximum rate of 10 Mbps
Cost
Less expensive than fiber-optic but more expensive than some other types of coaxial cable
Connector
Can include a few different types of connectors, which are very different from those used on modern networks

31. Thicknet Characteristics
Attachment Unit Interface (AUI)
Ethernet standard establishing physical specifications for connecting coaxial cables with transceivers and networked nodes
An AUI connector may also be called a DIX or DB-15 connector
Figure 4-17: AUI connectors

32. Thicknet Characteristics
N-series connector (or n connector)
Screw-and-barrel arrangement securely connects coaxial cable segments and devices
Figure 4-18: N-Series connector

33. Thicknet Characteristics
Noise immunity
Because of its wide diameter and excellent shielding, has the highest resistance to noise of any commonly used types of network wiring
Size and scalability
Because of its high noise resistance, it allows data to travel longer than other types of cabling

34. Thinnet (10Base2) Also known as thin Ethernet Characteristics:
Throughput
Can transmit at maximum rate of 10 Mbps
Cost
Less expensive than Thicknet and fiber-optic cable
More expensive than twisted-pair wiring
Connectors
Connects wire to network devices with BNC T-connectors
A seen in Figure 4-19, BNC barrel connectors are used to join two Thinnet cable segments together

35. Thinnet (10Base2) Characteristics (cont.): Size and scalability
Allows a maximum of 185 m per network segment (see Figure 4-20)
Noise immunity
More resistant than twisted-pair wiring
Less resistant than twisted-pair wiring
Figure 4-19: Thinnet BNC connectors

36. Thinnet (10Base2) Signal bounce
Caused by improper termination on a bus network
Travels endlessly between two ends of network
Prevents new signals from getting through
Figure 4-20: A 10Base2 Ethernet network

37. Twisted-Pair (TP) Cable
Color-coded pairs of insulated copper wires twisted around each other and encased in plastic coating
Twists in wire help reduce effects of crosstalk
Number of twists per meter or foot known as twist ratio
Alien Crosstalk
When signals from adjacent cables interfere with another cable’s transmission
Figure 21: Twisted-pair cable

38. Shielded Twisted-Pair (STP)
STP cable consists of twisted wire pairs that are individually insulated and surrounded by shielding made of metallic substance
Figure 4-22: STP cable

39. Unshielded Twisted-Pair
Consists of one or more insulated wire pairs encased in a plastic sheath
Does not contain additional shielding
Figure 4-23: UTP cable

40. Unshielded Twisted-Pair
To manage network cabling, it is necessary to be familiar with standards used on modern networks, particularly Category 3 (CAT3) and Category 5 (CAT5)
Figure 4-24: A CAT5 UTP cable

41. Comparing STP and UTP Throughput Cost Connector Noise immunity
Both can transmit up to 100 Mbps
Cost
Typically, STP is more expensive
Connector
Both use RJ-45 connectors (see Figure 4-27) and data jacks
Noise immunity
STP is more noise-resistant
Size and scalability
Maximum segment length for both is 100 meters

42. Figure 4-27: An RJ-45 connector

43. Fiber-Optic Cable Contains one or several glass fibers at its core
Surrounding the fibers is a layer of glass called cladding
Figure 4-28: A fiber-optic cable

44. Figure 4-29: Single-mode and multimode fiber-optic cables
Single-mode fiber
Carries light pulses along single path
Multimode fiber
Many pulses of light generated by LED travel at different angles
Figure 4-29: Single-mode and multimode fiber-optic cables

45. Fiber-Optic Cable Throughput Cost
Reliable in transmitting up to 1 gigabit per second
Cost
Most expensive type of cable

46. Fiber-Optic Cable Noise immunity Size and scalability
Unaffected by either EMI or RFI
Size and scalability
Network segments made from fiber can span 100 meters
Signals transmitted over fiber can experience optical loss

47. Fiber-Optic Cable Two popular connectors used with fiber-optic cable:
ST connectors
SC connectors
Figure 4-30: ST and SC fiber connectors

48. Atmospheric Transmission Media
Infrared transmission
Infrared networks use infrared light signals to transmit data through space
Direct infrared transmission depends on transmitter and receiver remaining within line of sight
In indirect infrared transmission, signals can bounce off of walls, ceilings, and any other objects in their path

49. Atmospheric Transmission Media
RF transmission
Radio frequency (RF) transmission relies on signals broadcast over specific frequencies
Two most common RF technologies:
Narrowband
Spread spectrum

50. Choosing the Right Transmission Media
Areas of high EMI or RFI
Corners and small spaces
Distance
Security
Existing infrastructure
Growth

51. Chapter Summary
Information can be transmitted via analog or digital methodology
Throughput is the amount of data a medium can transmit during a given period of time
Noise is interference that distorts an analog or digital signal
Costs depend on many factors
There are three specifications that dictate size and scalability of networking media
Connectors connect wire to the network device

52. Chapter Summary
Coaxial cable consists of central copper core surrounded by an insulator and a sheath
Thicknet cabling is a rigid coaxial cable used for original Ethernet networks
Both Thicknet and Thinnet coaxial cable rely on bus topology and must be terminated at both ends with a resistor
Twisted-pair cable consists of color-coded pairs of insulated copper wires, twisted around each other and encased in plastic coating

53. Chapter Summary
STP cable consists of twisted pair wires individually insulated and surrounded by a shielding made of metallic substance
UTP cabling consists of one or more insulated wire pairs encased in a plastic sheath
Fiber-optic cable contains one or several glass fibers in its core
On today’s networks, fiber is used primarily as backbone cable