STB rules

As is widely known by now, the federal government has released details of the congressionally mandated coupon program for subsidizing digital-to-analog converter boxes. These soon-to-be-available set-top boxes will enable analog TV owners to continue receiving free OTA programming.

The coupon program specification defines the attributes of converter boxes eligible to receive a federally funded rebate. So, it makes sense to look more closely at what these boxes will — and won't — do. In the end, the program will affect how tens of millions of viewers receive and watch TV programs. Simple economics make it reasonable to expect that the majority of boxes sold will adhere to this specification.

Our lawmakers at work

As part of the Digital Television Transition and Public Safety Act of 2005, Congress empowered the National Telecommunications and Information Administration (NTIA) to define and manage the coupon program. The DTV act defines a digital-to-analog converter as “a stand-alone device that does not contain features or functions except those necessary to enable a consumer to convert any channel broadcast in the digital television service into a format that the consumer can display on television receivers designed to receive and display signals only in the analog television service, but may also include a remote control device.” The key phrase here is “functions except those necessary,” which left some interpretation to NTIA.

Last July, the administration released a Notice of Proposed Rulemaking and invited comments from the public. NTIA received more than 100 responses from the consumer electronics and broadcast industries, trade associations, public interest groups and private individuals, as well as from several members of Congress and congressional committees. NTIA then formulated its position and forwarded it in late January to the White House Office of Management and Budget for approval. The office then permitted the NTIA to release the specification in March.

The coupon program deals with three broad areas: eligibility of boxes for coupons, distribution of the coupons and coupon redemption requirements. The actual process of coupon distribution is being handled through a separate vendor process, which will address the logistical details of coupon availability, distribution, expiration and redemption, as well as box identification. This article will discuss the technical aspects of eligible converter boxes.

Box requirements

Analog TV viewers rely on various aspects of the medium for its ease of use. Channel selection, picture adjustment and antenna adjustment on portable sets are performed without a second thought. Many stakeholders urged for technical requirements for digital converters so that the user would have a similar experience when installing and using the STBs.

In the end, Congress mandated that coupon redemption would be limited to boxes meeting a specific set of technical requirements. It was ruled that manufacturers could self-certify compliance with these requirements, but must also supply units to NTIA (and FCC, if needed) for compliance verification.

The boxes must convert all ATSC formats to NTSC. The boxes should be designed “for ease of installation and operation,” though there is no absolute metric with which to measure this, other than the provision for a remote control.

The boxes must provide an antenna input and an RF output for display on channel 3 or 4. Baseband audio and video outputs must also be supplied. The boxes must consume no more than 2W when passive (no video or audio display), with an automatic power-down feature (defeatable) when operator input has not been detected for a certain time. Eligible boxes can optionally conform to the more stringent EnergyStar requirements of 8W when active and 1W when passive.

While a few respondents to the proposed rulemaking requested the inclusion of a software update feature, this was left as optional, presumably because of the cost and the relative immaturity of the technology. BTSC stereo inclusion at the RF output would also be at the discretion of the manufacturer. Support for closed captions and parental controls (i.e. the V-Chip) are required for coupon eligibility.

Two additional optional functions that can be added while retaining coupon eligibility include electronic programming guides (EPGs) and support for smart antennas. While the use of an EPG has become ubiquitous for cable and satellite subscribers, such a function does not exist for analog television. Thus, although there is value in providing a means with which to easily navigate the new DTV space, the inclusion of an elaborate EPG was not considered essential for all users. At the very least, coupon eligibility will require the ability to display channel number and simple program information for the channel being viewed.

There was also considerable support for the need for a smart antenna for viewers with problematic reception conditions. By electronically automating the aiming of the antenna and using an optimum reception pattern for each DTV station, the user's manual interaction with an antenna is essentially eliminated. Support for a smart antenna is achieved through the use of the CEA-909 Antenna Control Interface standard.

The boxes must also meet or exceed the guidelines specified in “ATSC Recommended Practice A/74: Receiver Performance Guidelines,” which is intended to assure reliable reception. Specifically addressing the RF front-end of a DTV receiver, A/74 outlines minimally acceptable performance levels for sensitivity, selectivity, interference rejection and multipath management. Performance is also specified for specific input levels, phase noise immunity, interference rejection and burst noise immunity. The multipath requirements are given as a template of echo delays for specific desired-to-undesired ratios, as well as the recommendation that receivers appropriately process signals simulated by several field-captured ensembles available from MSTV.

Several groups — most notably CEA, MSTV and NAB — advocated receiver requirements slightly beyond that of ATSC A/74, with stricter requirements in such areas as RF dynamic range and taboo channel rejection. Overwhelming cross-industry support resulted in the inclusion of these extended requirements. In addition, the requirements also describe the minimum number of multipath field ensembles that must be tolerated by an eligible converter.

Other features, however, are specifically excluded from coupon eligibility, including HD video output and DVR. These features are beyond the intent of the program, which is simply to avoid legacy TV obsolescence and the disenfranchisement of OTA viewers. Digital cable and satellite boxes were similarly excluded from the program.

User requirements

NTIA originally proposed restricting coupon eligibility to those households that exclusively receive OTA television signals (thus excluding cable and satellite service subscribers), but overwhelming response from the industry, the public and lawmakers resulted in the decision that all households would initially be eligible. If the non-contingent wave of 22.25 million coupons is exhausted, a second, contingent wave would then be sponsored, with an additional 11.25 million coupons, limited to households without cable or satellite subscriptions.

The first of these units should be available at retail markets later this year. On this timetable, viewers will have a little more than one year in which to upgrade their homes to digital broadcast. In the meantime, broadcasters should begin to educate viewers on the upcoming transition and coupon program. NAB and other groups have started such a campaign.

From the technical standpoint, it would be a good idea for stations to acquire some of these units to determine how viewers will be accessing their programming. One final note: No manufacturer is required to build converters meeting the above requirements — that is unless they wish their boxes to be eligible for the subsidy!

Aldo Cugnini is a consultant in the digital television indusry.

Capture description Antenna type Capture parameters Antenna direction optimization • Log-periodic
• Dipole
• Double bow-tie • Optimal
• Random • AGC on/off
• A/D precision
• Others Site description Antenna location Neighborhood Site location Miscellaneous • In-home
• Outdoor, up to 30ft • Rural
• Industrial park
• Suburban
• Others • Distance from transmitter
• Latitude and longitude of the site location • Channel name
• Date of capture
• Weather conditions
• On-site temperature
• Construction type
• Others Channel description Upper and lower adjacent channel Channel dominant characteristics • DTV
• None • Multiple echoes
• Dynamic or static channel
• In-band interference
• Band-edge distortion
• Pilot distortion
• Others