Set Top Box

Digital set top box technology

The set top box (STB) has evolved from the analogue box (used on U.S. cable systems) to BMAC/DMAC technology (which was a hybrid of digital audio and analogue video used by AUSSAT for `Sky Channel) to a fully digital product which includes sophisticated integrated hardware and software.

The STB is utilised in various delivery technologies including Cable, Satellite and Digital Television (DTV) The basic technology is the same in these cases; the change is in the `front end" or demodulator with Quadrature Phased Shift Keying (QPSK) for satellite, Quadrature Amplitude Modulation (QAM) for Cable and DTV.

The basic STB consists of the tuner and baseband converter, filters, QPSK or QAM demodulator, channel

Decoder (FEC), microcontroller and power supply. However the `heart' of the box is the chip set, which is, currently down to two chips. For subscription or payTV condition access and smart card(s) are added.

The Interactive STB incorporates a cable modem, two tuners a CPU and sufficient memory to run special Web browsers and other software. It may also house other client software tools such as TV mail and TV chat applications. These components enable the STB to perform the function of integrating Web content, voice and video and displaying it on the subscriber's screen, As such the STB is the key component allowing operators to deliver cost effective, branded and centrally managed services to their subscribers.

The latest developments in STB technology are the Personal Video Recorder (PVR) and the Multimedia Home Platform (MHP) which are integral to Open TV or Interactive TV which is discussed further.

The cost of STBs will vary depending on the degree of sophistication, quality, and quantities ordered by the operator. In quantity a reasonable quality STB will vary from US$ 200 to US$ 400 each

At the heart of digital transmission is the MPEG toolkit, a core concept that defines how a particular digital decoder may behave, where it means the efficient transfer of video information, audio information and data services through the production chain

However new platforms have been developed which allow interoperability and interactivity in order to deliver multiple services (data, voice and video) in a single cost effective medium, creating compelling services for consumers and generating additional revenue for broadcasters from these services. These propriety platforms include OpenTV and Liberate.

These platforms provide interactivity providing Internet access, personalised programme delivery, video on demand (VOD), e-commerce transactions, Internet telephony, games, banking, pay per view (PPV) and other services on demand.

The Multimedia Home Platform (MHP), a DVB system, comprises the STB, integrated TV set, multimedia PC, in-home digital network which supplies the subscriber with enhanced broadcasting with local interactivity, interactive services using a return channel and internet access.

For enhanced broadcasting, the built in navigator and electronic program guide (EPG) were identified as benchmarked applications. The navigator identifies and allows selection of all events to which the subscriber is entitled, including all services, in the clear, for all networks that the MHP is connected to. The EPG constitutes the second level of the subscriber navigation system giving detailed information of programmes/services and their events. The STB integrates a computer to manage the EPG and its interface to the end user.

When writing about the future in digital STBs, the future often happens as one puts words to paper so some of the following developments may have been deployed as I write.

Hard disk storage has recently been deployed by "Pace" with 20Gb of storage and their XTV technology applied to the Personal Video Recorder (PVR) which enables the viewer to enter their personal profile in regards to favourite types of programming. XTV will then automatically record selected broadcasts in DVD format. Within the next few years it is predicted that 600-800 hours of viewing choice may be stored. Other developers including "Scientific Atlanta" are working on head end storage, which gives viewers access through remote control and a return-path link.

Cable STBs will incorporate cable modems to integrate internet access into the box, similarly satellite STBs will have internet access integrated in the STB with a return path, initially, through the telephone line.

As the STB sits on the TV set while the PC, or Mac, is usually located in another room there is a necessity for a connection when the modem is contained in the STB. New Bluetooth and 801.11b technology will enable wireless connections. This technology may also be applied when there is more than one TV to feed off the STB as broadband wireless will be available in the near future.

Future end-to-end solutions comprise advanced and emerging technologies and protocols for merging video, web-based content and telephony. The set top box, incorporating advanced modem technology, represents the key piece of equipment for displaying enhanced programme content on the subscriber's TV.