BEFORE THE
FEDERAL COMMUNICATIONS COMMISSION
In the Matter of Unlicensed Operation
in the TV Broadcast Bands, ET Docket No. 04-186
Additional Spectrum for Unlicensed Devices
Below 900 MHZ and in the 3 GHz Band, ET Docket No. 02-380
REPLY COMMENTS OF
New America Foundation
Media Access Project
Cuwin Foundation
Michael Marcus, Sc.D., F-IEEE
Dr. Paul Kolodzy
Dr. Joseph Evans
NAF, et al., applaud the FCC Office of Engineering and Technology (OET) for its recent report describing initial measurements of prototype TV white space devices (WSD). The goal of the OET effort was to "conduct a testing program, including field testing, to assess the potential for interference from low power devices operating in the TV bands." These tests were to provide a basis for understanding the current state of interference avoidance technology for WSD and whether the operational parameters selected by the developers of the prototype would provide sufficient protection from harmful interference to other devices accessing the TV broadcast spectrum. NAF, et al., are encouraged to see that the OET report clearly confirms the feasibility, based on current technologies, for WSD to detect and operate on vacant TV channels without causing harmful interference to over-the-air television viewers or wireless microphone systems.
The testing of two devices, while significant, does not represent of the capabilities of the entire electronics industry, nor does it reflect the potentials of these devices once a set of rules and device certification parameters are formulated and many more firms begin developing hardware. The reports released by OET, while providing valuable information, must by no means be mistaken as the sum total of necessary testing to determine appropriate standards for functioning WSD.
NAF, et al., therefore focus on the following general comments. First, how does the information from the prototype testing fit within the stated goal of the R&O/FNPRM to determine suitable standards for WSD (both stationary WSD and, if possible without creating undue risk of harmful interference, mobile devices). Second, NAF, et al., suggest which issues require further study.
The data reported by OET demonstrate conclusively that "listen-before-talk" (LBT) can detect digital television signals at a threshold that protects television reception. Given the extraordinary success of one of the prototypes under laboratory conditions, the OET experiments demonstrate conclusively that LBT is a feasible technology for interference avoidance. What remains is for OET to set a suitable sensitivity standard. In this regard, it is important to note that although the "B" Prototype (apparently submitted by Philips) detected signals at a threshold of -114 dBm, no one has empirically established that this level of sensitivity is necessary to protect viewers from harmful interference. OET should therefore regard the successful laboratory tests of the prototypes as establishing that even with today's sensing technology, devices can identify incoming signals at strength levels well below what is necessary to protect television reception. It is critical to distinguish between the technical ability to sense a DTV signal at -114 dBm and the practical policy wisdom of prohibiting the constructive use of spectrum when the signal is this low, particularly where the typical DTV cannot display the signal, or where the signal is originating from a non-local TV market.
The OET reports do not address the issue of transmission. This is why NAF stresses again that the OET reports make up only one part of the engineering data the Commission must consider. In the rush to declare the OET lab results a "failure" for unlicensed use of the white spaces, opponents of the Commission's proposal have ignored the previous engineering evidence submitted by NAF based on experiments at the University of Kansas (K.U.). As the K.U. experiments demonstrate, operation of WSD on adjacent vacant channels -- under appropriately stringent rules developed by the FCC -- did not create harmful interference for television viewers.
With regard to the overall TV Whitespace Proceeding, there are two essential questions for the OET to address: first, what operational parameters provide sufficient protection to harmful interference; and second, whether the technology for WSD to meet those parameters is technically feasible.
To view the full comments, please see the PDF document linked below.
