Top Banner
Network Media Chapter 4 Signal Transmission Network Media
39

Network Media Chapter 4 Signal Transmission Network Media.

Mar 27, 2015

Download

Documents

Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: Network Media Chapter 4 Signal Transmission Network Media.

Network Media

Chapter 4

Signal Transmission

Network Media

Page 2: Network Media Chapter 4 Signal Transmission Network Media.

Signal Transmission

Signaling—the way data is transmitted across the media

Digital signaling Two discrete states

• 0 or 1, on or off

Analog signaling Constantly changing electromagnetic waves

Page 3: Network Media Chapter 4 Signal Transmission Network Media.

Digital Signaling

Two different voltages are used. One voltage to represent on and another voltage to represent off

Data 0 0 1 1 0 1 0 0

Voltage

Time 0 1 2 3 4 5 6 7

Page 4: Network Media Chapter 4 Signal Transmission Network Media.

Analog Signaling Constantly changing electromagnetic

wave Characteristics:

Amplitude• Strength of signal (height of wave)

Frequency• Amount of time needed to complete one cycle of

the wave Phase

• Relative state of one wave in reference to another wave

Page 5: Network Media Chapter 4 Signal Transmission Network Media.

Attenuation/Noise

Loss of signal strength as signal travels across media

Signal must be amplified or regenerated to ensure that data is transmitted correctly

Noise on media can disrupt data signal Static, cross-talk, etc. Electromagnetic interference (EMI) Radio frequency interference (RFI)

Amplifiers and regenerators are used to increase the distance that signals can travel

Page 6: Network Media Chapter 4 Signal Transmission Network Media.

Converting Analog to Digital

Modems At sending computer, convert computer

digital signal to analog signal for transmission via media

At receiving computer, convert analog signal to digital signal

Modulator/Demodulator

Page 7: Network Media Chapter 4 Signal Transmission Network Media.

Transmission Direction

Simplex—transmission of data in one direction only (television)

Half-duplex—transmission of data in both directions but only one direction at a time (CB radio)

Full-duplex—simultaneous sending and receiving of data (telephone)

Page 8: Network Media Chapter 4 Signal Transmission Network Media.

Multiplexers

Enables multiple signals to travel simultaneously by combining two or more separate signals and transmitting them together.

Multiplexer (mux) at sending end combines signals and demultiplexer (demux) at receiving end separates signals Example: Cable TV--numerous signals travel through

coaxial cable; circuitry in the TV, VCR, or cable box separate the signals into different channels

Page 9: Network Media Chapter 4 Signal Transmission Network Media.

Multiplexing Methods

Time Division Multiplexing Divides channel into time slots--each

device is allotted a time slot Statistical Multiplexing

Number of time slots allotted for each device varies depending on priority and need

Wavelength Division Multiplexing Used for fiber-optic (light); different

wavelength used for each channel

Page 10: Network Media Chapter 4 Signal Transmission Network Media.

Throughput/Bandwidth Throughput is the amount of data that can be

sent across the network media in a given time. Measured in bits per second

Bandwidth is the range of frequencies that the media can transmit Frequently throughput and bandwidth are used

interchangable Two methods for allocating bandwidth:

Baseband Broadband

Page 11: Network Media Chapter 4 Signal Transmission Network Media.

Baseband

Transmission signals use the entire media bandwidth.

Commonly used for digital signaling. Most LANs use baseband signaling

Page 12: Network Media Chapter 4 Signal Transmission Network Media.

Broadband

Media bandwidth is divided into multiple channels.

Each channel can carry different analog signals

Broadband networks support multiple simultaneous signals over a single transmission medium

Page 13: Network Media Chapter 4 Signal Transmission Network Media.

Network Adapters (NICs or NACs)

Provide the physical connection between your computer and the network media

Transmit and receive data Prepare data for the network cable Send the data to another computer or device Control the flow of data between the

computer and the network media

Page 14: Network Media Chapter 4 Signal Transmission Network Media.

Media Characteristics Throughput/bandwidth Cost

Installation—cable cost, ease of installation Maintenance—troubleshooting, repairing, replacing

Scalability Node Capacity—max # of node, Attenuation—max length of segment, max number of

segments Noise immunity

electromagnetic interference, radio frequency interference, and eavesdropping

Connectors

Page 15: Network Media Chapter 4 Signal Transmission Network Media.

Network Media

Copper• Coaxial cable• Twisted-pair cable

Glass• Fiber-optic cable

Wireless (Air)• Radio waves• Microwaves• Infrared

Anything that carries the message through the network

Transmission media—Physical path through which computers send and receive signals

Page 16: Network Media Chapter 4 Signal Transmission Network Media.

Coaxial Cable (Coax)

Copper core surrounded by insulation and a sheath

Shielding makes it more resistant to interference

Two types of coax cable used in networks Thinnet (10Base2)—RG 58 A/U Thicknet (10Base5)—RG 62

Thicknet

Thinnet

Page 17: Network Media Chapter 4 Signal Transmission Network Media.

Coaxial cable showing various layers

Outer shield

Insulation (PVC, Teflon)

Conducting coreCopper wire mesh oraluminum sleeve

Page 18: Network Media Chapter 4 Signal Transmission Network Media.

Thicknet cable transceiver with detail of a vampire tap piercing the core

Thicknet

Transceiver

Drop Cable

Vampire tap

Page 19: Network Media Chapter 4 Signal Transmission Network Media.

BNC cable connector

Coaxial Cable

Terminators used at both ends of network to prevent signal bounce back

Used with bus topology BNC cable connector used for Thinnet cable; n-

connectors are used for Thicknet

BNC Terminator

BNC T-connector

Page 20: Network Media Chapter 4 Signal Transmission Network Media.

Coaxial Characteristics

Thinnet (10Base2) Thicknet (10Base5) Cost Relatively inexpensive More than Category 5 Installation Relatively easy More difficult Bandwidth 10 Mbps 10 Mbps Nodes 30 100 Attenuation 185 meters 500 meters EMI Better than UTP Better than UTP Connectors BNC n connectors

Page 21: Network Media Chapter 4 Signal Transmission Network Media.

Twisted-Pair Cable Similar to telephone wiring

Color-coded pairs of wire; twisted and encased in plastic coating

Unshielded twisted-pair and shielded twisted-pair cables

Shielding

UTP

STP

Page 22: Network Media Chapter 4 Signal Transmission Network Media.

RJ-45 connector and jack

Page 23: Network Media Chapter 4 Signal Transmission Network Media.

Twisted Pair Cable Categories Category 1-2: Voice communications and low speed data

communications. Category 3: Suitable for computer networks. Data

transmission rates up to 10 Mbps. Currently used for phone installations (home)

Category 4: Data transmission rates up to 20 Mbps Category 5: Data transmission rates up to 100 Mbps. Very

popular for LANs. Category 5E: Higher speeds are possible (200 Mbps);

more twists Category 6: Speeds up to six times faster than Cat 5 Category 7: Speeds up to 1 Ghz (Gigabit)

Page 24: Network Media Chapter 4 Signal Transmission Network Media.

UTP Characteristics Cost: Relatively inexpensive; depends on grade

of copper and any enhancements Installation: Easy to install Bandwidth: 10-100 Mbps (Cat 5)

Higher speeds are possible (up to 1000Mbps—Cat5E, Cat 6 and Cat 7)

Node Capacity: Two (computer to hub) Attenuation: 100 meters EMI: Very susceptible to EMI and

eavesdropping Connector: RJ-45

Page 25: Network Media Chapter 4 Signal Transmission Network Media.

STP Characteristics

Cost: Relatively inexpensive (more UTP, less than Thicknet or fiber-optic.

Installation: Slightly more difficult than UTP Bandwidth: same as UTP Node Capacity: Two Attenuation: 100 meters EMI: Susceptible to EMI (but less susceptible

than UTP) and eavesdropping Connector: RJ-45

Page 26: Network Media Chapter 4 Signal Transmission Network Media.

Plenum Cable

A plenum is the space between the false ceiling and the floor above.

Plenum-grade cable is fire resistant and produces a minimum of smoke

More expensive than PVC cable and less flexible

May be required by fire code

Page 27: Network Media Chapter 4 Signal Transmission Network Media.

Fiber-optic cable Contains one or more glass fibers (core) Data transmitted via pulsing light Two categories: Single-mode and multi-mode

Fiber-optic connectors:ST and SC

Optical fiber (core) Glass cladding

Protective outer sheath(jacket)

Page 28: Network Media Chapter 4 Signal Transmission Network Media.

Fiber-optic Characteristics Cost: More expensive than copper cable Installation: More difficult than copper cable Bandwidth: 100 Mbps to 1 Gbps Node: 2 Attenuation: Several kilometers EMI: Not subject to EMI; immune to

eavesdropping Connectors: ST and SC are popular

Page 29: Network Media Chapter 4 Signal Transmission Network Media.

Cable Media ComparisonFactor UTP STP Coaxial Fiber-optic Cost Lowest Moderate Moderate Highest Installation Easy Fairly easy Fairly easy Difficult Bandwidth 10-100 Mbps

(typical) 10-100 Mbps (typical)

Typically 10 Mbps 1 Gbps (100 Mbps)

Nodes 2 2 30 (10base2) 100 (10base5)

2

Attenuation High (100 meters)

High (100 meters)

Lower Thinnet--185 m Thicknet--500 m

Lowest (several kilometers)

EMI Yes Yes but less than UTP

Yes but less than UTP and STP

No

Connectors RJ-45 RJ-45 BNC (thinnet) N connectors (thicknet)

ST and SC

Page 30: Network Media Chapter 4 Signal Transmission Network Media.

Wireless Media (Atmospheric)

Infrared Radio Frequency (RF)

Narrow-band Spread-spectrum

Microwaves

Page 31: Network Media Chapter 4 Signal Transmission Network Media.

Wireless portable computer using an infrared light beam to print

Infrared

Page 32: Network Media Chapter 4 Signal Transmission Network Media.

Infrared Transmission Systems Use infrared light to transmit signals Point-to-Point (Direct) or Broadcast

(Indirect) Point-to-Point (Direct)—highly focused and

directed at a specific target• Line of Site

Broadcast—spread the signal to cover a wider area and allow reception of signal by several receivers

• Signal can be bounced off walls and ceilings

Page 33: Network Media Chapter 4 Signal Transmission Network Media.

Infrared Characteristics Line of site

Light must be able to reach target Bandwidth: 100 Kbps to 16 Mbps

Tested at up to 100Mbps but slower speeds are currently standard

Attenuation: Depends upon the quality of light and atmospheric conditions

EMI: Can be affected by intense light. Point-to-Point transmissions are fairly immune to eavesdropping. However, broadcast transmission are more easily intercepted.

Page 34: Network Media Chapter 4 Signal Transmission Network Media.

Wireless portable computer connecting to a cabled network access point

Network

Page 35: Network Media Chapter 4 Signal Transmission Network Media.

Radio Frequencies Characteristics

Narrowband Spread-spectrum Frequency range

Single frequency Multiple frequencies simultaneously

Cost Moderate Moderate Installation Simple Moderate Bandwidth Up to 10Mbps Up to 10Mbps Attenuation High High EMI Poor Fair

Page 36: Network Media Chapter 4 Signal Transmission Network Media.

Wireless bridge connecting two LANs

Page 37: Network Media Chapter 4 Signal Transmission Network Media.

Microwave Transmission Terrestrial Microwave

Line of site (max distance ~ 23 miles) Transmission can be affected by

atmospheric conditions (rain/fog). Vulnerable to EMI, jamming and eavesdropping

Bandwidth 1-10 Mbps Satellite Microwave

Can transmit data over vast distances Extremely expensive if you put up your

own satellite

Page 38: Network Media Chapter 4 Signal Transmission Network Media.

Example of Network Wiring

patch cable

Page 39: Network Media Chapter 4 Signal Transmission Network Media.

Example Wiring Closet