Access Tech

7/28/2019 Access Tech

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Why Broadband?

A non-technical perspective...


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Driving Factors cause & effect


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Bandwidth Requirement


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Broadband Connectivity

Connects Everything


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Broadband Access Techniques

Cable Modem

DSL

Fiber

2.5G and 3G Cellular Wireless

Wireless Ethernet


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Cable Modem

CMTS

Cable-modem Termination System Upload : ~ 128Kbps

Download : ~ 500 Kbps 2 Mbps

Aiming to Enable interactive Applications- videoconferencing, high-end on-line video

-Data Over Cable


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8/40 Broadband throughCable Modem

Cable Company Distribution Hub

Cable Splitter

Customer Premises

TV

Cable Modem

Hub

ComputerComputer

SharedCoaxCable

System

Combiner

Customer

Premises

CustomerPremises

TV VideoNetwork

Cable ModemTermination

System

ISP POP

Cable Company

Fiber Node

Optical/Electrical

Converter

Downstream

Upstream

Router

CableCompany

Fiber Node


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Cable Modem

Runs over cable TV wiring

Installed by cable company

Download speeds of 768K to 3M and higher

Upload speeds slower, about 300K Always on

Shared bandwidth - the more people on it, theslower it is

Unlimited use with Internet access (ISP)included in cost

Cost


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Cable Modem

Advantages

Usually quite fast

Always on

Somewhat reliable Broader availability

Does not interfere with

TV

Disadvantages

Shared bandwidth

Requires additional

hardware (cable box) Works only at the site

of installation

Upload slower than

download No choice in cable

company or ISP


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DSL

Runs over ordinary telephone wires

Digital signals use high frequencies not

used by analog phones

Installed by local phone company

Reliable download speeds of 128K to 7M

Always on Cheaper


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Types of DSL

Addresses

various network environments and

applications

trade-offs between reach and bandwidth


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Common Elements in DSL


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Common Elements in DSL


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DSL

Advantages Always on

Reliable

Requires no new wiring

Does not tie up phoneline

Fixed IP available

Can be used to host aweb site

Dial-up access whentraveling often included

Disadvantages Can be tough to switch

ISPs

Requires additional

hardware (DSL Router)

Can be difficult to getinstalled

Works only at the site

of installation Limited availability

Fast upload speedscost more


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Digital Subscriber Line

ADSL G.lite (UDSL)

SDSL

G.shdsl (G.991.2 an ITU-T standard) HDSL (High-bit rate DSL)

VDSL (very-high-data rate DSL)

RADSL (Rate Adaptive DSL) ISDN DSL (IDSL)


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Block Schematic of xDSL


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ADSL

Asymmetric DSL

Primarily used for residential services

- more downloads Download : Up to 8-9Mbps

Upload : ~1Mbps


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Block Schematic of ADSL


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Spectrum of Copper pair used

in last mile

0.3125K guardband

So 256 X 4 = 1024

255 X .3125 = 79.68

Total =1104 K


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DMT

Discrete multitone (DMT) is a method of separating a

Digital Subscriber Line signal so that the usable

frequency range is separated into 256 frequency

bands of 4.3125 KHz each. Within each channel,

modulation uses QAM.

By varying the number of bits per symbol within a

channel, the modem can be rate-adaptive. Both

G.DMT and G.lite use DMT


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Other modulation technologies for DSL are

carrierless amplitude modulation (CAP) and multiple

virtual line (MVL).

However, DMT is the most widely used and appears

to be becoming the industry standard like ANSI,ETSI

DMT


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SDSL

Cost-effective solution to small and

medium enterprises offering competitive

alternative to E1/T1

SHDSL Data rate :192 Kbps to 2.3Mbps

which is 30% larger than that of SDSL


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Can support Asymmetric/Symmetric DSL

ADSL mode can upload up to 52 Mbps

Suitable for High-speed applications suchas real-time video streaming

Mostly used in FTTH/B

VDSL


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FIBER FTTH/B(Fiber-to-the-Home/Building)

PON (Passive Optical Network) are used for one-to-many connectivity

Passive Optical Networking (PON)

PON, also called Fiber to the Home will unleash

the potential of optical fiber communications toend users.

With WDM hundreds or thousand of channels are

possible. Passive optical doesnt require

electricity, lowering cost, but limiting itsmaximum distance


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FTTH


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FTTH

Downstream : 51 Mbps

Upstream : 1.6 Mbps

FTTCab and FTTC coverts signal to provide

connectivity thro copper cable to achieve xDSL


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FTTCabinet/HFC


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The major difference between the

FTTC/VDSL and FTTC/HFC architecture VDSL every copper wire (subscriber

connection) can carry up to 52 Mbps

downstream With HFC, every channel on the coax cable

can carry up to 38 Mbps downstream

All subscribers serviced by an Optical Nodeshare channel capacity


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2 and 2.5 Generation Cellular

Wireless

2G Data rate: 9.6 Kbps

2.5 G supports- GPRS (General Packet Radio Service)

- EDGE (Enhanced Data rate for

Global(GSM) Evolution)


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Wireless Ethernet

Ethernet 802.11b offers 11 Mbps data rate

through DSSS(Direct sequence spread

Spectrum ) technique.

This is also known as Wi-Fi

Radio Transmission is in 2.4 GHz band


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802.11a operates in 5 GHz radio band

Data rate up to 54 Mbps using OFDM

802.11g up to 22 Mbps in 2.4 GHz band

using OFDM

Wireless Ethernet


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Wireless Ethernet


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Wireless Ethernet


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Advantages

High speed 11M

(802.11b) and higher

(802.11a & g)

Wiring unnecessary

Use with any computer

Many laptops are

wireless-ready

Disadvantages

May require a PC

Card

Requires extra stepsto increase security

Wireless Ethernet


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Thank You

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