Ringing in interactive video: switched video services transform video into an offensive services opportunity using existing copper - Spotlight: broandband networks

Telecommunications Americas,  Sept, 2003  by Frank Wiener

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The combination of new opportunities and increasing competitive threats from cable MSOs has many historic wireline service providers considering entry into the video services delivery market. Fortunately, advancements in service delivery systems align with emerging consumer requirements to transition video from a defensive service bundle to an offensive services opportunity.

The concept of a switched video service is once again breathing new life into old copper phone lines. The principle benefit of this service architecture is that "channel selection" occurs in the network--before the programming is sent downstream to the individual subscriber. As a result, the bandwidth requirement for the delivery of video and other interactive services is minimized to a level supportable over the existing copper access lines with ADSL (see Figure 1).

[FIGURE 1 OMITTED]

As the video over DSL industry has matured, multiple vendors have developed products providing the functional components in a form compatible and interoperable with a broader range of services using IP signaling and ATM transport.

This framework sets the stage for interoperable economies of scale. It also positions the switched video services network to expand beyond basic video to include broadcast, video on demand (VOD) and an expanded set of interactive video services distributed from IPTV networks.

Switched video services are implemented using the following primary functional elements (see Figure 2):

[FIGURE 2 OMITTED]

* Digital Headend: Receives and formats video content from satellite and other sources for distribution over the service delivery network. The digital headend consists of equipment designed to receive, process and format various content streams into a switched video services network format.

Fundamentally, this results in MPEG video frames encapsulated in UDP/IP/Ethernet packets that are bridged onto ATM to support IGMP (Internet Group Management Protocol) video signaling for IP-based switching as well as the ATM service infrastructure of ADSL.

The MPEG encode rate determines the required DSL line rate, which correlates with service reach. Traditional content providers accept encoding plus overhead rates of 3.8 Mbps. At this rate, DSL will support delivery of a single stream of video, plus Internet access and POTS to approximately 13,000 feet on 24 AWG wire. Two streams of video are supported to approximately 10,000 feet and three streams are supported up to approximately 8,000 feet. As content providers approve the use of newer encoders with equivalent quality at rates of 2.6 Mbps and below, these service reach attributes improve significantly.

An increasingly important component of the digital headend is the VOD server, which stores prerecorded video content for on-demand streaming to individual consumers. As consumer behaviors track toward more instantaneous, on-demand services, VOD and IPTV usage will increase substantially.

In the case of IPTV content sources, the newer more efficient lower bit rate compression available with MPEG 4 Part 10/H.264 or Windows Media Player version 9, may become the preferred encoder technology, with similar picture quality at rates of 1.5 Mbps and below.

* Service delivery network: Aggregates and transports all video and associated service content and signaling for transport across the network, ultimately delivering the service to the subscriber's premises. This function may be implemented using an integrated access and transport network or with distinct networks.

a) Aggregation and transport network. The benefit of broadcast video is that one copy of each channel can be multicast across the network and replicated for viewing by all interested subscribers at the network edge. Even with this one-to-many transport efficiency, transporting 120 broadcast video channels each at 3.8 Mbps quickly adds up to over 450 Mbps. The addition of Internet access and voice traffic quickly consumes an OC-12 or GigE transport for basic broadcast video, Internet and voice. Unlike broadcast, VOD is a unicast service. The VOD server generates an individual video stream for every requesting subscriber set top box. Therefore, if 500 video subscribers watch VOD programs concurrently, the network will need to support the transport of 500 VOD streams, each at 3.8 Mbps for a incremental transport capacity of 1.9 Gbps. Combining even moderate VOD traffic with broadcast, Internet and voice traffic quickly exceeds GigE and consumes a full OC48 of transport.

As future IPTV services come on line, the take rate of these interactive services increases materially with similar capacity implications as VOD. The IPTV network may deliver broadcast video, VOD or bi-directional interactive services. The switched video services network delivery of IPTV content will be facilitated through a switched unicast service model similar to VOD--only with service termination on a router. Interactive IPTV services are anticipated to provide major service differentiation and a competitive advantage over cable. Therefore, service providers should plan carefully and deploy a switched video services infrastructure with the capacity to scale and support the requirements of VOD and IPTV as well as broadcast.