The market for Internet Protocol delivery of digital television (IPTV) by telecommunications service providers promises to become sizable in the next few years. Today, however, this market is a welter of competing hardware and software solutions, complicated by a variety of compression technologies and the potential convergence with home network applications. These factors make decisions difficult when it comes to designing IP set-top boxes (STBs), so original equipment manufacturers (OEMs) need to select processing technology that lets them keep their implementation options open.
As the focal point of delivery, the STB must be able to adapt to the particular IPTV "ecosystem" in which it is deployed. Interoperability is therefore vital for these systems, as well as the performance needed to handle the high throughput of video. With the many new applications that IPTV networks may offer, scalability becomes important as well, and cost is always an issue with consumer appliances. STB designers are finding that these requirements are met by highly integrated digital signal processors (DSPs), which not only supply high real-time performance affordably, but can also be reprogrammed easily for new configurations, updates, upgrades and applications.
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Figure 1: The IPTV ecosystem
The IPTV ecosystem
The STB has to interact with all the equipment and software in an IPTV ecosystem, the major items of which are shown in Figure 1. At the head end, the service provider encodes video for IPTV transmission from sources such as terrestrial broadcast, pre-recorded specialty content, and satellite TV channels. Content can also be provided directly from the VOD server. To insure proper access, all of this content delivery is tied closely to the Conditional Access Server (CAS), which provides transmission security through measures such as encryption, verification and authorization. Coordinating these elements is the middleware server, which monitors client requests, communicates with the other servers, schedules transmissions, and interfaces to network administration for provisioning, billing, maintenance and other necessary services. This server also communicates with the middleware in the client Set Top Box (STB) to manage these requests and provide a friendly graphical user interface (GUI).
The client end of the figure shows a DSL modem and the STB --functions that in some cases may be combined in a single box. The STB receives and decodes the IPTV signal from the broadband connection, then outputs one or more streams for TV display. It should be noted that most schemes proposed today do not include wide-open access to the Internet through the STB, but this capability is likely to be supported in the future.
Next: STB browsers and middleware
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