CABLES AND RADIO RETURN PATHS

PRESENTED BY OYIBO, ALEWO MICHAEL

AMUZU-QUAIDOO, ISHMAEL

SATELLITE RETURN-PATH SYSTEMS

Cable Television Description

Cable television is a system of providing television programs to consumers via radio frequency (RF) signals transmitted to televisions through coaxial cables or optical fibers that connects subscriber's property

Introduction

When interactivity is implemented over the network, a Return Path is required.

Most cable operators choose a Set-Top box (popularly called a decoder ) with integrated cable modem with an Ethernet (utp), or powerline connection to the set-top box.

What is a Return Path?

A communications connection that carries signals from the subscriber back to the operator.

ExampleThe set-top box (STB) accepts commands from the user (often via the use of remote devices such as a remote control) and transmits these commands back to the network operator through some sort of Return Path or back channel

Cable TV return path contd.

The return path signal, which typically ranges from 5 to 42 MHz, originates in the home and flows through the fiber plant toward the headend.

Cable TV Return Path System

Cable television signals use only a portion of the bandwidth available over coaxial lines.

This leaves plenty of space available for other digital services such as

cable internet, cable telephony and wireless services, using

both unlicensed and licensed spectrum.

Contd.

The Return Path is achieved over coaxial cable by using Cable Modems built into the Set-Top box to convert the network data into a type of digital signal that can be transferred over coaxial cable.

The existing standards for Cable TV are-DVB-C (cable)DVB-C2DOCSIS (Data Over Cable Service Interface

Specification)

Typical Schematic Diagram of an HFC Network for CableTV

CableTV Network with Return Path

Radio Return Paths (DVB-RCT)

DVB-RCT (Return Channel Terrestrial) is the response that offers a wireless interaction channel for Interactive Digital Terrestrial Television, even in the congested UHF/VHF band.

This standard incorporates Multiple Access OFDM.

DVB-RCT does not require access to spectrum on a primary basis, the system has been designed to use any gaps or under-utilised spectrum anywhere without interfering with the primary analogue and digital broadcasting services

Multiple Access OFDM included in the DVB-RCT specification

Provides the following characteristics:Turbo Codes or Concatenated CodesTime InterleavingBand Segmentation (from 1 MHz slot up)Dynamically Assigned Adaptive ModulationPower Ranging to reduce interference

Schematic Diagram for DVB-RCT

Return Path Services

Return Path over the network is for example used in applications such as

Voting, Video on Demand, Pay-per-view,Shopping on TV, andWeb browsing on TV.

References

http://www.fiber-optics.info/articles/return_path_management_design_and_usage

Sosinsky, B. (2009). Network Bible (First Edit., p. 916). Indiana: Wiley Publishing, INC.

Cable Europe Labs. (2009). Cable Network Handbook ; (4th Editio., p. 27). Brussels: Cable Europe Labs.

Samaraweera, N. K. G. (2010). Return Link Optimization for Internet Service Provision Using DVB-S Networks. Retrieved May 15, 2012, from www.ndsuk.com