Accounting for Receiver Performance in Improving Spectrum Efficiency:
The GAO Report

The Middle Class Tax Relief and Job Creation Act of 2012 (referred to informally by broadcasters as the Spectrum Act) was signed into law on February 22 2012 and, among other things, authorized the use of "incentive auctions" of broadcast spectrum. As a result, the FCC has issued a Notice of Proposed Rule Making on various aspects of conducting incentive auctions of broadcast spectrum; comments were filed on January 25 and reply comments are due on March 12. However, another part of the Spectrum Act that perhaps got fewer headlines, headed "Study on Receiver Performance and Spectrum Efficiency," required the U.S. Comptroller General (essentially the Government Accountability Office or GAO) to conduct a study that has just been released on the effect of adjacent spectrum on wireless transmission systems, encompassing all telecommunications, broadcast, satellite, commercial mobile service, or other communications systems that employ radio spectrum.

Specifically, the GAO study was required to consider:

"(1) the value of-

(A) improving receiver performance as it relates to increasing spectral efficiency;
(B) improving the operation of services that are located in adjacent spectrum; and
(C) narrowing the guard bands between adjacent spectrum use;

(2) the role of manufacturers, commercial licensees, and government users with respect to their transmission systems and the use of adjacent spectrum;

(3) the feasibility of industry self-compliance with respect to the design and operational requirements of transmission systems and the reasonable use of adjacent spectrum; and

(4) the value of action by the Commission and the Assistant Secretary to establish, by rule, technical requirements or standards for non-Federal and Federal use, respectively, with respect to the reasonable use of portions of the radio spectrum that are adjacent to each other."

The deadline for the report was one year after the date of enactment of the Spectrum Act, and GAO released its report to Congress and the public on time on February 22, 2013.

The 48-page report details the results of GAO's interviews with industry and government representatives and their own analysis conducted between July 2012 and February 2013 on the relationship of receiver performance with interference mitigation and spectrum efficiency.

The report notes that the FCC and NTIA have primarily focused on setting emission limits on transmitters and/or establishing spectrum guard bands to control interference. Mandates on receiver performance have been routinely used by NTIA for federal spectrum users, but rarely used by the FCC for commercial services. NTIA indicated that their mandatory standards for receivers apply to about 60 percent of federal spectrum assignments. In commercial industry, it has been more popular for industry-led organizations to adopt voluntary standards for receivers. For instance, for television service, the Advanced Television Systems Committee (ATSC) developed and maintains the A/74 "Recommended Practice on Receiver Performance Guidelines."

The GAO report summarized their research and found several challenges to further improvements in receiver performance:

Lack of coordination across industries:
While members of a particular industry coordinate with each other, they may have little or no communication with services operating in adjacent spectrum bands. The report uses the FM radio industry and the aviation community (which operates above the FM radio band) as an example where there are discussions within the groups but a general lack of coordination and information sharing between the groups.

Lack of incentives to improve receivers:
Manufacturers generally have little incentive to build more robust receivers, primarily because the manufacturers will not receive the benefits. Rather, those who want to make more spectrum available or share spectrum will benefit. Improved receiver performance can result in increased size, weight, power consumption and/or cost, all of which may competitively disadvantage a receiver product.

Difficulty accommodating a changing spectrum environment:
Incumbent services function well with receivers that don't have interference problems in the current spectrum environment. However, if that environment changes, for example when previously unused adjacent spectrum is occupied by a new user, receivers currently in use may experience increased interference. Manufacturers, on the other hand, find it difficult to build receivers to accommodate an unknown future, where predictability of the future interference environment is not certain.

The report documents various efforts that have been taken over the years by industry and the FCC with regard to receiver performance. However, the Recommendation at the end of the report implies that more needs to be done at the government level:

"To improve receiver performance and spectrum efficiency, we recommend that the Chairman of the FCC consider collecting information on the practical effects of various options to improve receiver performance, including consideration of small-scale pilot tests of these options."

The GAO report "Spectrum Management: Further Consideration of Options to Improve Receiver Performance Needed" can be downloaded here.

In the year that the GAO report was being prepared, work in other venues on the subject was also ongoing. On November 29, 2012 the House Energy and Commerce Committee's Subcommittee on Communications and Technology held a hearing on "The Role of Receivers in a Spectrum Scarce World." During that hearing, the FCC's Deputy Chief of the Office of Engineering and Technology noted that "receiver performance is becoming increasingly important as a limiting factor as we move to repurpose spectrum and pack services closer together on the spectrum chart." He also indicated that the FCC planned to review the upcoming report from GAO, as well as output expected from the FCC Technological Advisory Council (TAC).

The FCC TAC consists of approximately 50 telecommunications experts that provide technical advice and recommendations to the FCC. At the December 10, 2012 TAC meeting, the TAC Working Group on Receivers and Spectrum recommended that the FCC investigate implementing an "interference limits" policy. This refers to establishing ceilings, called harm claim thresholds, on in-band and out-of-band interfering signals that must be exceeded before a radio system can claim that it is experiencing harmful interference. Manufacturers then determine on their own how to build receivers that can tolerate such interference, on a voluntary basis. Following a peer review process within the TAC, a white paper on the topic was made publicly available from the TAC working group in early February. The FCC TAC white paper "Interference Limits Policy: The Use of Harm Claim Thresholds to Improve the Interference Tolerance of Wireless Systems" can be downloaded here.

Webinar on Ultra-HD

Join this free webinar on Thursday February 28 at 1:00 pm Eastern for an executive summary of the state of "4K' and "8K" versions of Ultra-HD technology and a view on what must be done to enable Ultra-HD service. Sponsored by US Telecom, the webinar will be led by consultant Greg DePriest (former VP, Technology for NBC Universal) who led the Washington, D.C. private demonstrations of "8K" Ultra-HD technology during the recent London Olympic Games in cooperation with NHK, BBC and OBS. For more information and to register for the webinar, click here.

On a related note for those attending the NAB Show, be sure to visit the NAB Labs Futures Park, where Japanese national public-service broadcaster NHK will demonstrate its 8K Super Hi-Vision (SHV) system, including content recorded at the 2012 Olympic Games in London, displayed on a 300-inch screen with 22.2 channel sound playback. The NHK exhibit will also include portable and 120 Hz studio cameras recently developed for SHV, and production tools for the system's 22.2 channel audio format. In addition, the NHK exhibit will feature the first demonstration outside Japan of over-the-air broadcast transmission and reception of the Super Hi-Vision service, using two 6MHz TV channels.

The Korean Electronics and Telecommunications Research Institute (ETRI) also will show Ultra HD at the NAB Labs Futures Park, including a proposed next-generation TV broadcast system that provides 4K service to fixed receivers and HD service to mobile receivers, in a single multiplexed transmission.

The February 25, 2013 TV TechCheck is also available in an Adobe Acrobat file. Please click here to read the Adobe Acrobat version of TV TechCheck.