Channel stacking switch technology for residential DBS reduces cabling and STBs

Deploying multi-viewer packages, digital/personal video recorders (PVR), high definition (HD) content, and home media centers requires new or additional set-top boxes (STBs) or multi-tuner STBs in the home, and an efficient method to receive the content from the satellite outdoor unit (ODU). Traditionally, multiple tuners have meant an increase in cabling into the home to connect the ODU to each tuner. New tuners or STBs, each requiring a new cable drop, introduce substantial cost burdens and a barrier for achieving higher ARPU.

Channel Stacking Switch (CSS) technology reduces installation cabling complexity and cost for new DBS installations, and provides a simple upgrade capability for add-on STB installations or replacement of multi-tuner STB installations. This technology also creates new markets for both operators and free-to-air installers and retailers by making satellite television viable for many more multi-dwelling units (MDU).

Media trends driving STB demand
Digital and high-definition broadcasting trends drive demand for STBs and other multi-tuner media center devices. Viewing preferences are simultaneously changing, as consumers discover the freedom of being able to view content at the time and place of their choosing. Content providers are fueling these demands with an ever-increasing array of high-definition programs and event broadcasts. The advertising revenues associated with these high-end broadcast events further drive the industry in the direction of more content-rich, viewer-controlled programming.

All of these trends depend on the proliferation of a wide variety of STBs and PVRs, many equipped with multiple tuners. Each tuner requires a separate channel feeding it. Without CSS, this means a separate cable from the ODU to each tuner. PVR-STB combinations and multi-tuner STBs require multiple cables per box. With CSS technology, a single cable can run to the house with splitters installed to feed multiple STBs and multi-tuner STBs.

Central servers that enable entertainment enthusiasts to enjoy satellite TV throughout the home are currently being produced. CSS technology combined with a media server solution provides the easiest of all installations with a single cable running from the ODU to the multi-tuner media server. The media server can then process multiple channels from the single cable for display, storage, or distribution to networked devices around the home.

Many avid consumers are willing to upgrade and add-on to take advantage of the latest viewing technologies, but are hampered by complex cabling of non-CSS configurations.

The cable challenge
As mentioned above, in a traditional DBS installation, each tuner is connected directly to the ODU with a separate coaxial cable. Cabling must be added in situations where additional STBs or multi-tuner STBs (e.g., simultaneous watch and record) are added or services are extended to numerous units in an MDU.

Installing additional cabling introduces many drawbacks:

• Installation visits (truck rolls) are very expensive.
• Wiring and installation procedures become more complex and time consuming.
• Potentially ugly wiring is introduced around the dwelling.
• Some customers become unserviceable due to access limitations or other wiring restrictions imposed by home owners' associations or local ordnances.

CSS technology: stacking channels on a cable
All of these drawbacks are eliminated by the use of channel stacking systems. CSS technology implements a channel-stacking scheme --multiple channels can be transmitted on a single cable based on the demands from multiple STBs and tuners connected to that cable. A single cable drop from the ODU provides each STB tuner with dedicated channels, eliminating the need for multiple cables. (See Figure 1.)

Figure 1: CSS technology enables a single cable to drive multiple STBs and tuners.

In-home receivers communicate with a CSS-enabled ODU to request specific channels. The CSS translates a particular satellite channel of interest and passes thru a dedicated SAW filter. The desired channels are then combined, or in other words, CSS 'stacks' them, onto the single cable. The ODU also tells each receiver where a requested channel is located.

Bandwidth and STB capacity per cable
These DBS systems typically transport programming from the ODU to STB using a frequency range of 950 to 2150 MHz, which provides a useable bandwidth of 1.2 GHz. Individual transponders are typically only 20 to 36 MHz wide, depending on satellite transmission symbol rates. For example, if a CSS system converts and passes desired channels with a typical surface acoustic wave (SAW) bandpass filter, about 12 individual channels can be stacked on a single cable. This translates into the ability to support at least 12 separate, active STBs or tuners on a single cable drop. With narrower separation between SAW filters, up to 30 channels can be stacked on a single cable.

Industry standards
Stacking channels on a single cable requires an extension to the existing communications protocol between the STBs and the ODU. CENELEC, the European Committee for Electrotechnical Standardization, is currently ratifying a proposed extension of a Digital Satellite Equipment Communications (DiSEqC) standard incorporating CSS technology into the specifications that define communications between an STB and the CSS ODU. STB manufacturers have already endorsed the emerging standard, and currently marketed STBs incorporate support for CSS technology. Firmware upgrades will enable the functionality. Other efforts are under way, driven by interested companies and consortiums, to develop a standard for performance requirements pertaining to the ODU.

The standards efforts uniformly recognize CSS technology as a viable solution. Additionally, CSS technology will be included in emerging satellite broadcast standards. As such, broadcast service operators and installation service companies alike can confidently take advantage of the more intelligent cabling options enabled by CSS technology.

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