Network Technology CSE30201

Network Technology CSE3020

Week 13

Network Technology CSE30202

Network Technology

Local Area Networks• Ethernet and Token Passing Networks

Wireless Networks• Cellular Networks and Wireless LAN

Wide Area Networks• ATM and ISDN

Residential Area Networks• ADSL, Cable TV

Basic Data Communications Theories• Data transmission• Coding & Modulation• Multiplexing & Switching• Transmission Media

Network Technology CSE30203

Simplified Network Model

Network Technology CSE30204

OSI Model

Network Technology CSE30205

OSI Model

Network Technology CSE30206

TCP/IP Protocol Architecture

Network Technology CSE30207

OSI and TCP/IP

Network Technology CSE30208

Computer Networks

Token Ring, FDDI

Encoding & Modulation

Router

PCM

WLAN

Capacity

BridgeEthernet

Residential AreaNetworks

ATM

ApplicationPresentation

Session

Transport

Network

Data link

Physical

Backbone

Network Technology CSE30209

Sine Wave

Peak Amplitude (A) - maximum strength of signal, generally in volts.

Frequency (f) - rate of change of signal. - Hertz (Hz) or cycles per second.

- Period = time for one repetition (T). - T = 1/f

Phase () - relative position in time.

Wavelength () - Distance occupied by one cycle. - = vT where v is signal velocity.

General sine wave: s(t)=Asin(2 ft + ).

Network Technology CSE302010

Frequency Domain Concepts

Signal are usually made up of many frequencies.

Components are sine waves. Fourier analysis:

• Can plot frequency domain functions.

• Any signal is made up of sine waves.

Network Technology CSE302011

Transmission Impairments

AttenuationNoise

Delay Distortion

Signal received may differ from signal transmitted.

Analog - degradation of signal quality. Digital - bit errors

Impairments: Attenuation, Delay distortion & Noise

Network Technology CSE302012

Channel Capacity Maximum rate at which data can be transmitted.

Nyquist Theorem: Maximum bit rate on a noise-free channel.

Shannon Theorem: Maximum bit rate on a noisy channel.

C = 2 B log 2 M bits/sec

C = B log 2 (1 + S/N) bits/sec

channel bandwidthsignal-to-noise ratio

Network Technology CSE302013

Data Encoding

Digital data digital signal (Encoding/Decoding)

Analog data digital signal (Digitization/Conversion)

Digital data analog signal (Modulation/Demodulation)

Analog data analog signal (Modulation /Demodulation)

Data and Signals:

Network Technology CSE302014

Signaling/Modulation Rate

Signaling/Modulation rate– Rate at which the signal elements are transmitted.

– Measured in baud = signal elements per second.

– For binary signaling, bit rate = baud rate.

Data rate - Rate of data transmission in bits per second.

Bit rate = Baud rate Number of bits per signal element.

Network Technology CSE302015

Interpreting Signals• Need to know: Timing of bits/signals and Signal levels.

• Factors affecting successful interpreting of signals:

– Signal to noise ratio, Data rate and Bandwidth

• An increase in data rate increases bit error rate (BER).

• An increase in SNR decreases bit error rate.

• An increase in bandwidth allows an increase in data rate.

Network Technology CSE302016

Encoding Schemes

Nonreturn to Zero-Level (NRZ-L)

Nonreturn to Zero Inverted (NRZI)

Bipolar-Alternate Mark Inversion (Bipolar-AMI)

Pseudoternary

Manchester

Differential Manchester

Bipolar with 8-zeros substitution (B8ZS)

High-density bipolar-3 zeros (HDB3)

Signal Spectrum.

Clocking.

Error detection.

Signal interference and noise immunity.

Cost and complexity.

Network Technology CSE302017

Digitization

Analog to digital conversion: PCM & Delta Modulation. If a signal is sampled at regular intervals at a rate higher than twice

the highest signal frequency, the samples contain all the information of the original signal.

Voice data limited to below 4000Hz - Require 8000 sample/second. Samples are quantized: Quantizing error or noise. Each sample assigned digital value (4 bit system gives 16 levels). Equally spaced level: Uniform Quantization. Non-equally spaced level: Non-uniform Quantization

Network Technology CSE302018

Pulse Code Modulation(PCM)

Network Technology CSE302019

Modulation

Analog modulation: - Amplitude Modulation (AM) - Frequency Modulation (FM) - Phase Modulation(PM)

Why modulate analog/digital signals?– Higher frequency can give more efficient transmission.

– Permits frequency division multiplexing.

– Unguided Transmission needs high frequencies.

– For practical antenna size.

Digital modulation:– Amplitude shift keying (ASK)

– Phase shift keying (PSK)

– Frequency shift keying (FSK)

Network Technology CSE302020

Spread Spectrum Spread data over wide bandwidth.

Makes jamming and interception harder. Frequency hopping:

- Signal broadcast over seemingly random series of frequencies.

- Receiver hops between frequencies in synchronization with transmitter.

Direct Sequence:

- Each bit is represented by multiple bits in transmitted signal by a chipping code.

- Chipping code spreads the signal across a wider frequencies.

Network Technology CSE302021

Transmission Media• Guided Transmission:

– Twisted Pair - Unshielded Twisted Pair (UTP) - Shielded Twisted Pair (STP)

– Coaxial Cable– Optical Fiber

• Unguided (wireless) Transmission:– Terrestrial Microwave– Satellite Microwave– Broadcast Radio– Infrared

Network Technology CSE302022

Transmission Media• Electromagnetic waves. • Characteristics and quality determined by medium and

the transmitted signal.• Key concerns are data rate and distance.

• Design Factors:– Bandwidth.– Transmission impairments.– Interference.– Number of receivers.

• Each transmission media:– Limitations & characteristics.– Pros & Cons.– Applications.

Network Technology CSE302023

Asynchronous and SynchronousTransmission• Transmission requires cooperation and agreement between the

two sides.• Fundamental requirement is Synchronization: Receiver must

know the beginning and end of a bit/rate at which bits are received.– Asynchronous transmission– Synchronous transmission

• Asynchronous transmission:– Each character treated independently and begins with a start bit.– Not good for long block of data.

• Synchronous transmission:– Block of data is formatted as a frame with a starting and an ending flag.– Good for block of data.

Network Technology CSE302024

Multiplexing Multiplexing. Demultiplexing. Different types:

Frequency division multiplexing (FDM). Time division multiplexing (TDM).

Synchronous TDM Statistical TDM

Code division multiplexing (CDM).

Network Technology CSE302025

Switching• Circuit switching & Packet switching.• Circuit switching: designed for voice.

- Dedicated communication path between. - Data rate is fixed. Both ends must operate at the same rate.

• Packet switching: designed for data networks.

– Data transmitted in small packets.

– Longer messages split into series of packets.

– Each packet contains a portion of user data plus some control information: Routing (addressing).

– Packets handled in two ways.– Datagram: No call setup phase and More flexible

– Virtual circuit: Sequencing and error control, Fast, Less reliable.

Network Technology CSE302026

Data Link Control• Flow control: Preventing buffer overflow at the receiver.

- Stop-and-wait & Sliding window.

• Error control: Detecting and correcting transmission errors.- Parity check & Cyclic Redundancy Check (CRC).

• Automatic Repeat Request (ARQ): Error & Flow Control.- Error detection & Retransmission.- ARQ schemes.

- Stop-and-Wait.- Go-back-N (retransmission from error frame). - Selective Repeat (selective retransmission).

- ARQ efficiency:- Unnecessary waiting and sending unnecessary transmission.

• High Level Data Link Control (HDLC).

Network Technology CSE302027

Local Area Network (LAN)• LAN applications.• LAN Architecture:

- Protocol architecture.

- Topologies.

- Media Access Control.

- Logical Link Control.• LAN devices:

- Repeaters

- Bridges

- Hubs & Switches.

Network Technology CSE302028

Local Area Networks (LANs)

LAN

products

fiber twisted pair coaxair (wireless)

busstarringtree

FDDI Ethernet Token ring Wireless LAN

random accesstoken passing

polling

IEEE ISO, ATM Forum

MACprotocols

standardbodies

topologies

transmissionmedia

Network Technology CSE302029

LAN Types• Ethernet:

• Token ring network.

• FDDI

• ATM LANE.

• Backbone network.

Network Technology CSE302030

Wireless LAN (WLAN)

•WLAN advantages.

•WLAN design considerations.

•WLAN types/products.

•WLAN topology/architecture.

•WLAN MAC protocol (CSMA/CA).

•Hidden station & exposed station problem.

Network Technology CSE302031

Asynchronous Transfer Mode (ATM)

• ATM characteristics.

• ATM Protocol reference model.

• ATM logical connections: Virtual paths & circuits.

• ATM Cell.

• ATM Service characteristics.

Network Technology CSE302032

ATM Protocol Reference Model

Higher Layer

ATM Adaptation Layer (AAL)

ATM Layer

Physical Layer

Management PlaneControl Plane User Plane

Layer

Managem

ent

Pla

ne M

anagem

ent

Network Technology CSE302033

Residential Area Networks PSTN:

ISDN:

ADSL:

Cable modem: