1. NT1210 Introduction to Networking
Unit 4:
Chapter 4, Transmitting Bits 1

2. Class Agenda 1/12/16 Learning Objectives
Lesson Presentation and Discussions.
Class Quiz: Quiz 1
Lab Activities will be performed in class.
Assignments will be given in class.
Break Times. 10 Minutes break in every 1 Hour.
Note: Submit all Assignment and labs due today.

3. PHYSICAL LAYER NETWORK CONCEPTS

4. Objectives Explain the fundamentals of electrical circuits.
Identify different types of physical cabling.
Identify wireless network communication needs.
Distinguish among the different needs for wired and wireless networks. 4

5. Objectives
Differentiate among major types of LAN and WAN technologies and specifications and determine how each is used in a data network.
Explain basic security requirements for networks. 
Install a network (wired or wireless), applying all necessary configurations to enable desired connectivity and controls.
 Explain the fundamentals of electrical circuits.
Identify different types of physical cabling. 5

6. Transmitting Bits: Communication Analogy
In networks, nodes send data to each other over link: Sending node acts like person talking; receiving node acts like person listening. 6

7. Sending Bits with Electricity and Copper Wires: Electrical Circuits
Electrical circuit must exist as complete loop of material (medium) over which electricity can flow.
Material used to create circuit can’t be just any material; must be good electrical conductor (e.g., copper wire).
Simple Direct Current Circuit Using a Battery 7
Figure 4-2

8. Sending Bits with Electricity and Copper Wires: Electrical Circuits
Direct Current (DC) electrical circuits
Electrical current: Amount of electricity that flows past single point on circuit (amount of electron flow in circuit).
Current always flows away from negative (-) lead in circuit and towards positive (+) lead.
Powering a Light Bulb with a DC Circuit 8
Figure 4-3

9. Sending Bits with Electricity and Copper Wires: Frequency, Amplitude, Phase
DC circuit (on left) and AC circuit (on right) both use 1 volt.
DC shows constant +1 volt signal.
AC circuit slowly rises to +1 volt, falls to 0 then falls to -1 volt (1 volt, but in opposite direction), repeating over time.
Resulting AC wave: Sine wave
Graphs of 1 Volt (Y-Axis) over time: DC (Left) vs AC (Right) 9
Figure 4-4

10. Sending Bits with Electricity and Copper Wires: AC Frequency, Amplitude, Phase
To send data, networking Physical layer standards can change amplitude, frequency, phase, period of AC electrical signal .
Graphs of AC Circuit: Amplitude, Period, Frequency 10
Figure 4-5

11. Frequency is the rate of change with respect to time.
Sending Bits with Electricity and Copper Wires: AC Frequency, Amplitude, Phase
Frequency is the rate of change with respect to time.
Change in a short span of time
means high frequency.
Change over a long span of time means low frequency.
Encoding Options: Frequency, Amplitude, and Phase Shifts 11
Figure 4-6

12. Table 3.1 Units of period and frequency

13. Sending Bits with Electricity and Copper Wires: AC Frequency, Amplitude, Phase, Period
Wave Feature
Definition of the Graph
Electrical Feature it Represents
Amplitude
Maximum height of the curve over the centerline.
Voltage
Frequency
Number of complete waves (cycles) per second (in Hertz).
Speed with which current alternates directions.
Phase
Single location in repeating wave.
Voltage jumps, which makes signal graph jump to new phase.
Period
Time (width on x-axis) for one complete wave to complete.
Time for voltage to change from maximum positive voltage back to same point again.
Common Features Used by Encoding Schemes 13
Table 4-1

14. Comparison of analog and digital signals

15. The bandwidth of a composite signal is the difference between the
Note
The bandwidth of a composite signal is the difference between the
highest and the lowest frequencies contained in that signal.

16. Sending Bits with Electricity and Copper Wires: Circuit Bit Rates
Bit rate (link speed): Defines number of bits sent over link per second (bps).
Impacts how nodes send data over circuit.
Example where Encoder Changes Signal Every Bit Time 16
Figure 4-10

17. Sending Bits with Electricity and Copper Wires: Using Multiple Circuits
Simplex transmissions are one way: If encoding scheme works in only one direction (on single circuit):
Devices must take turns using that circuit or …
Devices must use different circuits for each direction.
Half-duplex transmissions take turns: Node1 sends while Node2 listens; when Node1 finishes, Node2 sends while Node1 listens.
Full duplex transmissions can send/receive simultaneously: Both endpoints can send at same time because they use multiple wire pairs.
Full Duplex Using Two Pair, One for Each Direction 17
Figure 4-13

18. Sending Bits with Electricity and Copper Wires: Problems with Electricity
Noise: Electro-Magnetic Interference (EMI)
Cables help prevent effects of EMI in many ways, including shielding.
Twisting of wire pairs creates “cancellation” effect to help stop EMI effect.
Attenuation: Signals fade away over distance to point where devices can’t interpret individual bits
Ethernet standards limit copper links to 100 meters.
Very important when designing network. 18

19. Sending Bits with Electricity and Copper Wires: Unshielded Twisted Pair (UTP)
10Base-T, 100Base-T & 1000Base-T uses Unshielded Twisted Pair (UTP).
Cable contains twisted pairs of wires and no added shielding materials.
Twisting reduces EMI effects between pairs in same jacket and in nearby cables.
Lack of shielding makes cables less expensive, lighter, easier to install.
Supports full-duplex.
Note: Twisted pair cables with shielding are called Shielded Twisted Pair (STP). 19

20. Note
Baseband transmission of a digital signal that preserves the shape of the digital signal is possible only if we have a low-pass channel with an infinite or very wide bandwidth.

21. Figure 3.18 Baseband transmission

22. Sending Bits with Electricity and Copper Wires: LAN Standards Progression
Ethernet has long history (developed in 1970s and is still used today).
IEEE standardized Ethernet in standard in early 1980s.
Has added many more Ethernet standards since then.
Each standard took years to grow in marketplace and eventually drive prices down.
Timeline of the Introduction of Ethernet Standards 22
Figure 4-14

23. Transmission medium and physical layer

24. Classes of transmission media

25. Sending Bits with Electricity and Copper Wires: Unshielded Twisted Pair (UTP)
10Base-T, 100Base-T & 1000Base-T uses Unshielded Twisted Pair (UTP).
Cable contains twisted pairs of wires and no added shielding materials.
Twisting reduces EMI effects between pairs in same jacket and in nearby cables.
Lack of shielding makes cables less expensive, lighter, easier to install.
Supports full-duplex.
Note: Twisted pair cables with shielding are called Shielded Twisted Pair (STP). 25

26. Twisted-pair cable

27. UTP and STP cables

28. UTP connector

29. Sending Bits with Electricity and Copper Wires: RJ-45 Connectors, Ports
Ethernet standards allow use of RJ-45 connectors on twisted pair cable and matching RJ-45 ports (sockets) on NICs, switch ports, and other devices.
Again, RJ-45 connectors and ports accommodate 8 wires (pins) in single row.
Example RJ-45 Connectors and Sockets 29
Figure 4-15

30. Sending Bits with Electricity and Copper Wires: Cable Pinouts
Straight-through: Each wire connects to the same pin number on both ends of the cable.
Conceptual Drawing of Straight-Through Cable 30
Figure 4-17

31. Sending Bits with Electricity and Copper Wires: Cable Pinout Standards
Ethernet uses TIA (Telecommunications Industry Association) standards to define specific wires to use for pinouts.
UTP cables have four pairs of wires, each using a different color: green, blue, orange, brown.
Each pair has 1 wire with solid color and other one with white stripe.
TIA Cable Pinouts – T568A On Each End Creates a Straight-Through Cable 31
Figure 4-18

32. Sending Bits with Electricity and Copper Wires: Cable Pinout Standards—568A/568B
NOTE: 568B switches green and orange wires.
TIA Cable Pinouts – T568A On Each End Creates a Straight-Through Cable 32
Figure 4-18

33. Figure 7.7 Coaxial cable

34. Break
Take 15 34

35. Sending Bits with Light and Fiber Optic Cables
Fiber optics transmission like turning light switch on and off: ON = 1, OFF = 0.
Endpoints agree to use same speed and same basic encoding scheme.
Encoding Bits Using Light On/Off 35
Figure 4-20

36. Sending Bits with Light and Fiber Optic Cables
Fiber cables contain several parts that wrap around glass or plastic fiber core.
Core is about as thin as human hair.
Fiber breaks easily without some type of support.
Core and cladding have direct effect on how light travels down cable.
Optical transmitter (laser or LED) shines light into core to transmit data.
Components of a Fiber Optic Cable 36
Figure 4-21

37. Optical fiber

38. Figure 7.12 Propagation modes

39. Wireless transmission waves

40. Sending Bits with Radio Waves and No Cables: Radio Basics
A Radio Station Broadcasting a Radio Signal to a Car Radio 40
Figure 4-28

41. Figure 16.1 Cellular system
Typical Radius = 1-12 miles

42. Mobile phone Standard GSM: Global System for Mobiles
CDMA: Code Division Multiple Access
UMTS: Universal Mobile Telephone System

43. Sending Bits with Radio Waves and No Cables: WLAN IEEE Standards
IEEE WLAN Standard
Maximum Stream Rate (Mbps)
Frequency Range
Number of Non-overlapping Channels
802.11b 11
2.4 GHz 3
802.11a 54
5 GHz 23
802.11g
802.11n 72 21
802.11n*
150 9
802.11ac**
1000 Plus 12
* When using bonded 40 MHz channel, instead of 20 MHz channel (as used by other standards outlined in table). **
WLAN Standards and Speeds 43
Table 4-4

44. Unit 4 Assignment
Complete the following tasks using the Chapter Review Activities at the end of Chapter 4 in the Odom textbook (answers can be found in the textbook):
Respond to the multiple-choice questions.
Complete the Define Key Terms table.

45. Lab and Project
Assignment Unit 4 Assignment 1: Physical Layer Network Concepts Review
Unit 4 Lab 4.1: Copper Cabling
Unit 4 Lab 4.2: Data Link Connections
Unit 4 Lab 4.3: Cabling Exploration
Unit 4 Lab 4.4: Cable Troubleshooting
Unit 4 Research Project 1: Chapter 5 Mind Maps