NCTA Ex Parte Letter on White Space Devices


NCTA last week filed an ex parte letter with the FCC regarding the so called “white space” devices and interference with cable systems. While much of the media coverage of these devices has focused on interference with broadcast signals, an often overlooked aspect is the negative impact they can have on cable systems.

The good news, however, is we believe there are steps that can be taken by device manufacturers and the FCC to mitigate those concerns and bring these devices to market. The use of white spaces holds promise for new wireless services. And while we support use of this innovative technology, the FCC must first ensure that no harm is done to millions of cable customers.

White space devices, for those unfamiliar, identify and use unused TV channels for transmission of data. They identify the TV channels in use in a given area, and use the unused TV channels within that area for data transfer.

Broadcasters and makers of wireless devices such as microphones are concerned that the devices may not properly identify used TV channels and cause interference with everything from over the air television reception to concert hall sound systems. Testing currently underway gives a certain amount of legitimacy to this fear. Some devices improperly identified every frequency as being in operation or improperly identified frequencies in use as not in use.

Beyond these issues, however, cable subscribers have unique interference issues that can arise from white space devices, and they have gone largely unreported.

For instance:

  • Cable television systems have no ‘white spaces.’ Cable systems use all of the channels in the broadcast television band for the delivery of programming and other services to their customers. As consumers with TVs connected directly to cable (without a set-top) tune up and down the dial, they may experience significant interference as they tune past channels utilized by white space devices.
  • The proposed unlicensed TV band devices pose a significant threat to cable’s reception of distant over-the-air television programming at headends. If white space devices operate between a distant broadcast facility and a cable head-end, the device may not recognize the distant signal, and prevent the cable headend from receiving the signal at all.

In many cases, the most serious concerns about white space devices as they impact cable have more to do with the power of the devices. Higher power “fixed” white space antennas could impact consumers with cable ready TVs as far away as three miles from the antenna.

The use of white spaces is just one of the innovative solutions that cable and other industries are exploring to provide consumers more access to content when and where they want. These efforts are exciting but we should ensure that any new technology shouldn’t interfere with the right of consumers to enjoy the services to which they already subscribe.

To help resolve some of these technical challenges, we have proposed some steps that will mitigate the interference from this new technology. These solutions include:

  1. Restrict the operation of portable devices to a maximum of 10 mW and prohibit transmissions in the VHF channels given the high probability of direct pickup interference to TV receivers.
  2. Prohibit operations, at a minimum, on channels 2- 4.
  3. Restrict the operation of fixed devices to at least 400 feet from the external walls of residential buildings.
  4. Prohibit operation of fixed devices in VHF channels.
  5. Require spectrum coordination before operation of portable devices on channels adjacent to those being received at headends.
    1. Of the suggested methods by which fixed and portable devices might automatically determine channel availability, it appears that auto-location (GPS or equivalent), combined with regular access to a reliable database containing geographically-indexed lists of available channels, has the potential to provide the flexibility and reliability required to protect headend reception.

By incorporating these recommendations on the operation of white space devices, we believe the benefits of the technology can be balanced against the probable impact it will have on millions of cable television customers.