Iptv Basics, Technology, Operation and Services by Lawrence Harte

Author:Lawrence Harte [Harte, Lawrence]
Language: eng
Format: azw3
Publisher: UNKNOWN
Published: 2017-03-11T05:00:00+00:00

Distribution Network

The distribution network is the part of an IPTV television system that connects the headend of the system (video and media sources) to the customer’s location. IPTV signals are transmitted over a broadband IP network or a network that can transport broadband IP packets (such as an ATM or Ethernet system). IPTV distribution networks may be divided into a core network and an access network. IPTV systems may use a combination of individual channels (unicasting) or through shared channels (multicasting) in the distribution network.

Unicasting is the delivery media or data to only one client per communication session. If unicasting is used to provide broadcast services, a separate communication session must be established and managed between each user (client) and the broadcast provider (media server). If each user were connected directly to the headend of the system, the amount of data transmission required at the headend of the system would be substantial. Several thousand or hundreds of thousands of viewers would require 2 to 4 MByte connections each. To overcome this bandwidth challenge, popular programming (e.g. network programming) that is watched by multiple viewers at the same time is copied and redistributed (multicast) locally to the simultaneous viewers.

Multicast service is a one-to-many media delivery process that sends a single message or information transmission that contains a multicast address (code) that is shared by several devices (nodes) in a network. Each device that is part of a multicast group needs to connect to a router (node) in the network that is part of the multicast distribution tree. This means that the multicast media (such as an IPTV channel) is only sent to the users (viewers) who have requested it. The benefit of multicasting is the network infrastructure near the user (e.g. a home) only needs to provide one or two channels at once, drastically reducing the bandwidth requirements.

IPTV distribution systems commonly locate media servers throughout the distribution network to temporarily store popular television content. This allows for the supply of popular content (such as sports programs) during and shortly after the program has been broadcasted from local media servers.

Media servers can only hold a limited amount of programs. This means that programs that are stored in media servers located throughout the IPTV distribution network must be deleted after a short time to make storage memory space available for additional programs. For users who want to watch a program after it has been removed from a nearby server, their viewing request will be forward up towards a higher level sever (e.g. a regional hub) which may still contain the program. If the program is not available from the regional or central headend, the program may be requested and obtained from the content provider (e.g. the movie studio).

Core Network The core network is the central network portion of a communication system. The core network primarily provides interconnection and transfer between edge networks. Core networks in IPTV systems are commonly set upas fiber rings and spurs. A fiber ring is an optical network of network topology with a connection that provides a complete loop.

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