OLD LYME, CT – Joe Ciaudelli, Sennheiser’s expert on “white spaces” issues, shared the company’s May 4 response to the FCC’s recent Notice of Proposed Rulemaking (NPRM). Ciaudelli also noted that NPRM reply comments are due by June 2, 2020. Sennheiser advocated for several modifications, urging the FCC to expand Part 74 license eligibility and improve the interference registration process, while cautioning against other changes in rules such as the WSD antenna height above ground level limit (AGL).
More details from Sennheiser (www.sennheiser.com):
Attached is Sennheiser’s filing in response to the open FCC white space Notice of Proposed Rulemaking (NPRM). Reply comments are due on June 2, 2020. Those who are interested can contact me with any questions or remarks. — Joe Ciaudelli, Sennheiser Director, Spectrum & Innovation, (860) 848-3132.
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Before the Federal Communications Commission, Washington, DC 20554
In the Matter of Unlicensed White Space Device Operations in the Television Bands, ET Docket No. 20-36
COMMENTS OF SENNHEISER ELECTRONIC CORPORATION
Sennheiser Electronic Corporation (“Sennheiser”) provides the following comments on the Notice of Proposed Rulemaking in the above captioned proceedings (NPRM). Sennheiser supports implementation of the proposals in this NPRM with minor adjustments and requests that the Commission simultaneously address pending issues regarding Part 74 license eligibility and the white space database system.
BACKGROUND
Sennheiser Electronic Corporation is part of Sennheiser Electronic GmbH & Co. KG, headquartered in Germany, which is a global leader in advanced microphone technology, RF- wireless and infrared sound transmission, headphone and speaker technology, and active noise cancellation. Sennheiser Electronic Corporation is the main U.S. sales and marketing office, located in Old Lyme, Connecticut. Sennheiser also has a research center in San Francisco, California, and a manufacturing plant in Albuquerque, New Mexico, that produces the majority of Sennheiser wireless microphones sold in North America, South America, Canada, and Asia.
Wireless microphones are essential tools with proven benefits that are used daily within every echelon of society. The definition of wireless microphone includes a wide variety of wireless audio production tools. Wireless microphones are unique in that they are fault- intolerant, real-time devices (i.e. must exhibit negligible latency).
Wireless microphones are indispensable in modern content creation. Content is a key component of the U.S. economy and is a major source of cultural enrichment. Many professional applications don’t provide an opportunity for a “second take.” Thus, they require interference protection from unlicensed operations, including white space devices (WSDs).
Countless schools, municipalities, houses-of-worship, and businesses also rely on unlicensed wireless microphone operations in the TV-band. Although they have no priority over WSDs, compatible spectrum sharing should be maintained with any forthcoming rulemaking.
DISCUSSION
Bridging the digital divide to provide broadband services to rural America is an urgent priority. Sennheiser fully supports any means to achieve this noble objective, which will most likely be achieved by a combination of solutions including satellite and 5G technologies, as well as WSDs. After all, when great content is created all Americans should have access to it, regardless of where they reside.
- The Commission Should Expand Part 74 License Eligibility.
The Commission should, simultaneously with this proceeding, follow through on its
pending Further Notice of Proposed Rulemaking in GN Docket No. 14-166 to permit certain professional theater, music, performing arts, or similar organizations that meet certain criteria to obtain a Part 74 license, thereby allowing them to register in the white space database system for interference protection from unlicensed white space devices at venues where their events or productions are performed.
Currently, non-broadcast content creators are required to routinely operate fifty or more wireless microphones to be eligible for a license. The Commission has recognized that this current benchmark precludes many venues and performing arts companies that have a need for high-quality audio that is integral to their events or productions. Many such venues are required by the federal Americans with Disabilities Act (ADA) to operate assistive listening systems to aid hearing and visually challenged patrons. The front end of these systems are microphones. Thus, any interference to the microphones undermines the intent of this civil rights law. As Shure Incorporated has pointed out, “…it logically follows that rural areas with comparatively low population density would comprise a larger percentage of the unlicensed users incapable of meeting the arbitrary minimum threshold of 50 microphones.” Increased WSD power and antenna height and high power mobile geo-fenced WSD operation pose a significant threat of interference to microphone operations in rural areas. All professional events and productions should be granted the opportunity for interference protection, regardless of where they are staged and the number of wireless microphones they operate.
- Improvements are Needed in the Interference Registration Process.
The Commission adopted rules that allowed the introduction of white space devices with
the prerequisite that incumbent services such as TV broadcast and wireless microphones would be protected. The database system was intended to provide licensed broadcast and wireless microphone operators a means of registering for interference protection by reserving channels in the locale where productions were taking place. However, it’s currently very difficult to determine where to register. All of the original administrators seem to have ceased operation. Currently, the Commission lists three approved administrators on the White Space Database Administrators Guide web page: LStelcom / RadioSoft, Inc., Key Bridge Global LLC, and Nominet (we suggest that this list also appear on the White Space Database Administration Q & A Page where information related to wireless microphones is found). LStelcom / RadioSoft, Inc. accepts a registration but the channel availability function results in an infinite loop marked “loading”, which begs the question of whether the protection is operating properly. Key Bridge Global LLC has a web page but it doesn’t appear to have any functionality. It seems that Nominet is the only company operating a fully functional database.
Furthermore, there is no direct link from the FCC web site to the Nominet database. It is extremely difficult to find the Nominet database via an internet search (e.g. Google and Bing) or even a search within their own website (e.g. it’s not included on their TV White Space page). Once the portal is found, the Part 74 licensee seeking interference protection only sees an on-screen message of registration without any confirmation number, email, or print option.
This current situation, together with the cessation of operation by the original database administrators, has caused considerable confusion. The lack of reported instances of interference to date is a reflection of the minimal deployment of WSDs rather than an affirmation that interference protection is working properly. Simple improvements would help instill a higher degree of confidence in Part 74 licensees.
- No Changes Should Be Made to Height Above Ground Level (AGL).
In paragraph 24, the Commission seeks comment on whether it should increase or
remove the limit on WSD antenna height above ground level. However, the Commission has already considered and rejected this proposal, noting that “…it is generally not necessary to mount an antenna at heights greater than 30 meters (100 feet) AGL to avoid shadowing by trees and other obstructions in rural areas,4 [and thus] we are not increasing the antenna height in less congested areas beyond the current 30 meter AGL limit.” 5 The premise of that decision remains sound, and there is no evidence of a need to change it at this time in any areas, rural or otherwise.
- Separation Distances Should Be Adjusted Based on Original White Space Device Rules Original WSD rules established 4W EIRP (1 W conducted power with 6 dBi antenna gain) as the maximum transmit power for a fixed WSD. The corresponding appropriate interference protection requirement from registered licensed microphone operations was determined to be 1 km. Subsequently, the Commission revised permitted power limit to 10 W EIRP when operating in less congested areas. In that same Report and Order, the Commission stated, “To ensure that television stations, 600 MHz service licensees, and other protected operations are protected from interference due to a fixed white space device operating at more than 4 watts EIRP, we are changing the rules to increase the minimum separation distances between those services and the locations where fixed white space devices can operate.” Further noting that, “…the 4 dB increase in radiated power will provide roughly a 1.5 times increase in range.” The Commission accordingly increased the interference protection requirement for affected services, other than licensed wireless microphones. This seems to have been an oversight. The NPRM under consideration now has the opportunity to rectify this.
Factoring in the proposed increase in power and permitted HAAT, and using the Commission’s conservative assumption of free space propagation, Sennheiser proposes the following interference protection requirement be incorporated for Low Power Auxiliary Services, Including Wireless Microphones in §15.712(f), consistent with separation distances of the original rules:
- The Definition of Less Congested Areas Should Remain Unchanged.
The Commission defines a “less congested area” in 47 C.F.R. § 15.703(h) as:
(h) Less congested area. Geographic areas where at least half of the TV channels for the bands that will continue to be allocated and assigned only for broadcast service are unused for broadcast and other protected services and available for white space device use. Less congested areas in the UHF TV band are also considered to be less congested areas in the 600 MHz service band.
The NPRM seeks comments on any necessary changes to the definition. None are necessary. Since the goal in this proceeding is to allocate limited spectrum resources, it is proper to define less congested areas in terms of the spectrum resources rather than population density.
There are areas just outside major cities, such as New York, that are sparsely populated where the TV-band spectrum is densely packed. These areas are properly served by the standard WSD rules governing non-rural areas.
- A Speed and Antenna Gain Limit Should Be Set, or Recheck Times and Buffer Zone Sizes Should Vary with Mobile WSDs in Geo-Fenced Areas.
Sennheiser agrees with the Commission’s basic approach to preventing harmful interference of protected services from WSDs in geo-fenced areas:
To limit the potential of movable devices to cause harmful interference, we propose that a device may not use channel availability information for multiple locations if/when it moves closer than 1.6 kilometers to the boundary of the geo- fenced area in which the device operates, or at any point outside that boundary. This proposed limitation is designed to ensure that a device moving at 60 miles per hour (1.6 kilometers per minute) does not cross outside the boundary between device re-checks of its location.
School buses and agricultural equipment are cited as examples for geo-fenced applications in the NPRM. For safety reasons, we hope school buses don’t exceed 60 miles per hour. To our knowledge agricultural equipment doesn’t reach this speed. Thus, Sennheiser recommends that a 60 mile per hour limit be imposed such that the WSD would stop transmitting until the vehicle reduces speed below this limit and the WSD refreshes its available channel list. An alternate solution would be to increase the refresh rate (i.e. less than 60 seconds) in a variable fashion that is commensurate with the proposed rule.
Likewise, vehicles operating WSDs should only be permitted to use omnidirectional, zero gain antennas if the 1.6 km buffer zone is to be a constant. Otherwise, the buffer zone should increase accordingly if antennas with directional gain are used. Vehicles make turns. Thus, the focused energy of a high gain antenna wouldn’t be confined to a specific direction. Sennheiser has no objections to detachable antennas.
- Narrowband WSDs Should Be Limited to Less Congested Areas, or Rules Should Be Modified to Enhance Protection and Spectrum Sharing, or the Issue Should Be Considered in a Separate Proceeding.
The Commission should be flexible regarding bandwidth rules as a technology matures and different incarnations provide new benefits. Microsoft proposed a new class of WSDs that is narrowband for applications related to the Internet-of-Things (IoT). In its Petition for Rulemaking, Microsoft provided a test example and three topologies related only to agriculture in rural America. Sennheiser has no issues with narrowband WSDs operated in farms and other rural environments. Our concern lies in the fact that Microsoft’s desired rule is not limited to less congested areas like the other provisions found in its petition. The National Association of Broadcasters noticed this as well, stating “[t]his proposal appears to be directed at urban IoT applications rather than expanding rural broadband access–the justification for Microsoft’s other proposals.”
Microsoft asserted that “…by requiring all narrowband WSDs to comply with the separation distances that apply to 4 W devices…this will also effectively confine most narrowband operations to rural areas where the interference risk is minimal.” If it’s truly the intention to confine the use of these devices to rural areas, then their deployment should be limited to less congested areas by rule.
Internet-of-Things in urban and suburban areas is a far different situation. There are billions of “Things” in urban and suburban America. Any rule change that governs this broad and embryonic technology should be considered with great care.
One solution would be to more precisely define a transmit time plus idle period that, when the multiples are added together, could total up to the proposed ten seconds per hour of operation for narrowband WSDs. Any audible interference is unacceptable in wireless microphone operations. It’s not only annoying and distracting, it can pose a danger to hearing if it occurs in amplified sound systems or assistive listening systems for the hearing or visually challenged. Microsoft provides an example of narrowband WSD that wakes from a “deep sleep” to transmit only a few bytes of data and takes no longer than a fraction of a second.20 If the transmit time was short enough and the idle period was significantly longer, this could enable digital wireless microphones to mitigate audible interference through error concealment (noting that this does not mean error correction). Sennheiser proposes a three millisecond transmit time with a one second idle period, so that the proposed rule be revised to read:
(4) Narrowband white space devices. …
(v) Transmit time shall be limited to a maximum of 3 ms followed by an idle period of at least 1 second. Total channel occupancy shall be limited to 10 seconds per hour.
Sennheiser is willing to work with Microsoft on calculating other combinations that achieve the same result. Although licensed wireless microphone operators can register for interference protection from WSDs in the database system, this approach would provide another layer of protection. It would also facilitate co-channel operation of narrowband WSDs with unlicensed microphones, thus fulfilling the Commission’s goal of efficient spectrum sharing.
Other than these two options, it would be more appropriate to consider this complex issue in a separate proceeding that studies IoT comprehensively. After all, narrowband WSDs do little to address the more urgent need of providing broadband to citizens residing in rural America. A separate proceeding would provide proponents an opportunity to introduce additional tests outside rural environments. Except for agriculture and a limited number of other rural applications, IoT is primarily a short-range application. Thus, IoT in urban and suburban environments should be considered in light of the Commission’s recent ruling that opened an extremely large amount of spectrum for unlicensed operation in the 6 GHz band, as well as other technological developments. The non-broadcast portions of the 6 GHz band would be suitable for IoT applications. This is not the case for unlicensed wireless microphones because they are low power devices and body absorption severely impacts their operating range, especially in frequencies above the UHF band.
CONCLUSION
Providing broadband service to citizens in rural America is a national priority. Sennheiser supports any changes in WSD rules that achieve this objective, while maintaining the Commission’s mandate to prevent WSDs from causing interference to incumbent services, including wireless microphones. Updates to Part 74 license eligibility and improvements in the database system should be addressed simultaneously with this NPRM. No changes should be made to the WSD antenna height above ground level limit or the definition of less congested areas. Separation distances should be adjusted commensurate with increased WSD transmit power and HAAT based on original white space device rules and consistent with other protected services. Additional provisions should be included to ensure that high powered mobile WSD operation is confined to the defined geo-fenced area. The rules surrounding narrowband WSDs for IoT should be reconsidered, if they are not limited to less congested areas.
Respectfully submitted,
Joe Ciaudelli
Director, Spectrum & Innovation
Sennheiser Electronic Corporation. 1 Enterprise Drive, Old Lyme, CT 06371
(860) 848-3132
May 4, 2020
