If a cable television network is available in a particular area, then consumers access IPTV from a network based on hybrid fiber/coax (HFC) technology. HFC technology refers to any network configuration of fiber-optic and coaxial cable that may be used to redistribute a variety of digital TV services. Most cable television companies are already using it. Networks built using HFC technology have many characteristics that make it ideal for handling the next generation of communication services:
. HFC networks are capable of simultaneously transmitting analog and digital services. This is extremely important for network operators who are rolling out digital and IPTV to their subscribers on a phased basis.
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HFC meets the expandable capacity and reliability requirements of an IPTV system. The expandable capacity feature of HFC based systems allows network operators to add services incrementally without major changes to the overall network infrastructure.
. HFC is essentially a “pay as you go” architecture that matches infrastructure investment with new revenue streams, operational savings, and reliability enhancements.
. The physical characteristics of coaxial and fiber cables support a network operating at several gigabits per second.
The topology of an end-to-end HFC network is illustrated in Fig. 2.4. From the diagram we can see that the HFC network architecture consists of a fiber based backbone connected via an optical node to a coaxial network. The optical node acts as an interface that connects upstream and downstream signals that traverse the fiber optic network with the coaxial cabling. The coaxial portion of the HFC network uses tree-and-branch topology and is used to connect cable TV subscribers via specialized devices called taps to the HFC network. The digital TV signal is transmitted from the headend in a star-like fashion to the fiber nodes.
The fiber nodes, in turn, distribute the signals over coaxial cable, amplifiers, andtaps throughout the customer serving area.
Deploying IPTV Over a Cable TV Network
The debate within the cable TV industry to start carrying video traffic across an IPbased architecture continues as of this writing. Threats to their core pay TV FIGURE 2.4 End-to-end HFC network.
business from telecommunication operators combined with bandwidth efficienciesassociated with IP delivery mechanisms are two of the key factors drivingcable operators toward a more IP centric model of delivering video content to endusers.
Switching a radio frequency based network over to an IP based switched digitalvideo (SDV) environment however requires the installation of a number of newpieces of equipment ranging from routers to IP set-top boxes and high speednetworking switches. Some of the advantages associated with deploying an SDVenvironment include:
. A large amount of network bandwidth is freed up due to the fact that theoperator is only required to transmit a sing le TV channel to a subscribers IPset-top box. This contrasts quite sharply from traditional systems where allchannels on the operator’s lineup are broadcasted across the network andunused channels still occupy bandwidth.
. Spare bandwidth allows cable operators to deliver advanced IPTV content andservices to their subscribers.
. Cable operators can accurately measure and monitor what video content iswatched by each of its subscribers. This is an important feature for operatorswho want to generate revenue through advertising.
From a technical perspective a typical cable IPTV system constitutes a mix of IPand RF based hardware devices that are used to carry the video signal across the networking infrastructure. Figure 2.5 shows an example of a cable IPTV architecture that constitutes a mix of IP and RF technologies.
As shown the network consists of a variety of hardware devices, including
. GigE routers or switches Gigabit Ethernet (GigE) is emerging as thetransport protocol of choice for connecting IP networking components. GigE is typically used by higher capacity applications, such as VoD. The GigErouter aggregates the IPTV traffic and provides interconnectivity to the coreaccess network.
. Optical transport network The core network provides the network pathbetween the video servers in the headend and the modulators at the edge ofthe network.
Synchronous optical network (SONET), ATM, and dense wavelength division multiplexing (DWDM) are examples of technologies that maybe used in the core network.
. Edge modulators The modulators located at the regional offices receive theIPTV content from the core network, convert the video content from IP basedpackets to RF, and distribute it via an HFC network to the set-top boxes.
This is an example of a large scale cable IPTV deployment and makes use of ahierarchical architecture through the establishment of regional distribution headends.
. HFC networks are capable of simultaneously transmitting analog and digital services. This is extremely important for network operators who are rolling out digital and IPTV to their subscribers on a phased basis.
HFC meets the expandable capacity and reliability requirements of an IPTV system. The expandable capacity feature of HFC based systems allows network operators to add services incrementally without major changes to the overall network infrastructure.
. HFC is essentially a “pay as you go” architecture that matches infrastructure investment with new revenue streams, operational savings, and reliability enhancements.
. The physical characteristics of coaxial and fiber cables support a network operating at several gigabits per second.
The topology of an end-to-end HFC network is illustrated in Fig. 2.4. From the diagram we can see that the HFC network architecture consists of a fiber based backbone connected via an optical node to a coaxial network. The optical node acts as an interface that connects upstream and downstream signals that traverse the fiber optic network with the coaxial cabling. The coaxial portion of the HFC network uses tree-and-branch topology and is used to connect cable TV subscribers via specialized devices called taps to the HFC network. The digital TV signal is transmitted from the headend in a star-like fashion to the fiber nodes.
The fiber nodes, in turn, distribute the signals over coaxial cable, amplifiers, andtaps throughout the customer serving area.
Deploying IPTV Over a Cable TV Network
The debate within the cable TV industry to start carrying video traffic across an IPbased architecture continues as of this writing. Threats to their core pay TV FIGURE 2.4 End-to-end HFC network.
business from telecommunication operators combined with bandwidth efficienciesassociated with IP delivery mechanisms are two of the key factors drivingcable operators toward a more IP centric model of delivering video content to endusers.
Switching a radio frequency based network over to an IP based switched digitalvideo (SDV) environment however requires the installation of a number of newpieces of equipment ranging from routers to IP set-top boxes and high speednetworking switches. Some of the advantages associated with deploying an SDVenvironment include:
. A large amount of network bandwidth is freed up due to the fact that theoperator is only required to transmit a sing le TV channel to a subscribers IPset-top box. This contrasts quite sharply from traditional systems where allchannels on the operator’s lineup are broadcasted across the network andunused channels still occupy bandwidth.
. Spare bandwidth allows cable operators to deliver advanced IPTV content andservices to their subscribers.
. Cable operators can accurately measure and monitor what video content iswatched by each of its subscribers. This is an important feature for operatorswho want to generate revenue through advertising.
From a technical perspective a typical cable IPTV system constitutes a mix of IPand RF based hardware devices that are used to carry the video signal across the networking infrastructure. Figure 2.5 shows an example of a cable IPTV architecture that constitutes a mix of IP and RF technologies.
As shown the network consists of a variety of hardware devices, including
. GigE routers or switches Gigabit Ethernet (GigE) is emerging as thetransport protocol of choice for connecting IP networking components. GigE is typically used by higher capacity applications, such as VoD. The GigErouter aggregates the IPTV traffic and provides interconnectivity to the coreaccess network.
. Optical transport network The core network provides the network pathbetween the video servers in the headend and the modulators at the edge ofthe network.
Synchronous optical network (SONET), ATM, and dense wavelength division multiplexing (DWDM) are examples of technologies that maybe used in the core network.
. Edge modulators The modulators located at the regional offices receive theIPTV content from the core network, convert the video content from IP basedpackets to RF, and distribute it via an HFC network to the set-top boxes.
This is an example of a large scale cable IPTV deployment and makes use of ahierarchical architecture through the establishment of regional distribution headends.
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