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Welcome

Overview of

DOCSIS

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DOCSIS

Data Over Cable Service Interface Specification

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INTRODUCTION TO DOCSIS

• CABLELABS®

- An organization that govern the DOCSIS

certification for Cable TV Industry equipments

- Defined several standards for cable TV industry

- One such standard is for Cable Modem and is known as DOCSIS (Data Over Cable Service Interface Specification)

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MAIN COMPONENTS OF DOCSIS

• HeadEnd

• Distribution Hub (resides in HeadEnd)

• Cable Modem

• Computer/TV

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HEADEND

• Contains the major equipment for the network

• Talks to different Video Sources as well as Data traffic, assembles and sends to Distribution Hub

• Contains Cable Modem Terminating System (CMTS)

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HeadEnd

CMTS

Distribution Hub

Distribution Hub

Optical F

ibre

Optical Fibre

Video Source 1

Video Source2

Data Packets

DataSource2

Video PacketsVideo PacketsAssembly of Video + Data packets

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Distribution Hub

• Receives Assembled data from the Head End. Assembled Data Contains Video Packets + Data Packets

The function of the Hub contains – – “Modulator” which modulates the Video

packets to different Channels

– “Receiver” to receive data from the subscriber.

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Distribution Hub

HEAD END

RECEIVER

MODULATOR

CHANNEL 1

CHANNEL 2

CHANNEL n

From Sub 1

From Sub 2

From Sub n

UPSTREAM

DOWNSTREAM

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HEADEND

CABLE MODEM

CMTS Cable Modem

Cable Modem

Cable Modem

Cable Modem

Cable Modem

Cable Modem

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General Architecture of Cable Modem

Burst Modulator

Demodulator MAC Interfaces

USBEthernet

PCI

TUNER

Extracts data from MPEG frames, Filter data from CMs,Times transmission of upstream bursts

A/D Conversion, Demodulation, Error Correction, MPEG synchronization.

Converts TV Channel to a fixed lower frequency

-In the transmit direction-D/A conversion -Reed Solomon encoding of each burst

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Interesting Question

Why did we talk about Cable Modem?

DOCSIS is the standard that govern the – Cable Modem, – Cable Modem Terminating System and– their environment.

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DOCSIS• Standard that defines passing of data (IP),

over Hybrid Fiber Coax (HFC) networks.

• Data goes along with Video packets.

• Main purpose is to ensure interoperability between Cable Modem at Subscriber’s location and Cable Modem Terminating System at operator’s headend.

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Three Generations of DOCSIS

• DOCSIS 1.0

• DOCSIS 1.1

• DOCSIS 2.0

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DOCSIS 1.0• Primary Internet access service to the

Subscribers

• A single cable is shared by multiple subscribers

• Includes Baseline privacy features to provide the subscriber security over the shared HFC access network.

• Most of the BW is reserved for Downstream (from CMTS to CM)

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DOCSIS 1.0

• Introduces

- Efficient utilization of BW, through Web browsing and email.

- Supports best effort transmission of data

- Baseline Privacy Features (SP-CMTS-SMI)

- Security Management Interface (SMI)

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DOCSIS 1.1

• Adds ability to delivery data very accurately

• Supports Telephone Services

• Backward compatibility to DOCSIS 1.0

• Have Quality of Service and management of network equipment.

• When used in DOCSIS 1.0 environment, it doesn’t assure accurate delivery of data.

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DOCSIS1.1• Introduces

•Quality of Service

-Dynamic Service

-Concatenation

-Fragmentation

-Payload Header Suppression

•IP Multicast

•SNMP Version3

- Fault Management

•CM Authentication

•CM Account Mgmt

Enhanced Security Software

(Difference between DOCSIS 1.0 and DOCSIS 1.1)

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DOCSIS 2.0

• Since DOCSIS 1.1 provides the QOS and enhanced Security, that was lacking in DOCSIS 1.0,

• DOCSIS 2.0 mainly focuses on

- Improvement of performance

- more efficient use of network capacity.

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DOCSIS 2.0• Features Improved in DOCSIS 2.0:• Upstream Capacity: + Triples the maximum capacity when compared to DOCSIS 1.1 + Increased Upstream throughput to 30.72Mbps. - Uses a fewer timeslots to transmit a given

amount of BW than DOCSIS 1.x cable modems. The saved TS are used by other CMs, which increases the throughput.

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DOCSIS 2.0• Higher Modulation

(Improved Signal Processing)- DOCSIS 1.0 provide modulation rate of

QPSK- DOCSIS 1.1 provide modulation rate of 16

QAM- DOCSIS 2.0 provide modulation rate of

64QAM or 128QAM• Allows more subscribers and services on a

single channel ->increased revenues to operators.

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DOCSIS 2.0

• Advanced PHY layer modulation

techniques that allows operators to run higher modulation levels.

• Supports immunity to Ingress Noise.

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DOCSIS SPECIFICATION

• There are different specifications for each piece of the system.

• A DOCSIS reference model is defined to understand the layout of different specifications.

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DOCSIS REFERENCE MODEL

PSTN

Backbone Network

Network Termination

MOD

DEMOD

Security & Access Controller

O/ENode

O/ENode

O/ENodeC

ombiner

Splitter

Transmitter

Receiver

5 –

42 M

Hz

50 - 860 MHz

Fiber

Cable Modem

Operations Support System

CMTS

HEAD END

CMTS-NSI

DOCS-OSSI

CM-RFIcoax

CMCI

CMTS-PRI

Remote Access Server

BackboneTransport AdapterWAN

T1/T3

Video

Data

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The Existence of DOCSISDOCSIS covers many aspects of the Cablenetwork. Included in the architecture are:• The link between the PC and the Cable

Modem (CM)• The link between the CM and the Cable

Modem Termination System (CMTS)• Network Management• Link Privacy• Generic information about the network

beyond the CMTS

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DOCSIS SPECIFICATIONS

• The link between PC and the Cable Modem (CMCI)

• The link between the CM and the CMTS

• Network Management (CMTS-OSSI)

• Link Privacy (CMTS-SMI)

• Generic information about the network beyond the CMTS (CMTS-NSI)

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CMRFI

• Cable Modem to RF Interface

- Defines the messages that flow over Coax and into Cable Modem

- Description of those messages

- Description of Electrical modulators and PHY layer Techniques.

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CMCI

• Cable Modem to Computer Interface

- Defines the protocol between the PC to Cable Modem

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CMTS-SMI

• Cable Modem Termination System – Security Management Interface

• Also known as DOCS – SS (Security System)

- Allows only the Valid users to use the system

- Data is encrypted so that a user is assured of privacy of their data

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OSSI

• Operation System Service Interface- Network Management activities- Allows the operator to detect problems in

the network and determine the following* - Status

* - Capability * - Provisioning of the parameters for

Cable Modem

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Thank You