On Friday, Nov. 14, the FCC issued the full text of its Second Report and Order and Memorandum Opinion and Order. Commonly referred to as the white spaces decision, the 130-page document primarily details the rulings and the reasoning that will govern the operation of non-broadcast devices in the TV broadcast band.
This document was eagerly awaited for by wireless microphone manufacturers seeking full details of future spectrum access for users of professional wireless mics since the commission’s Nov. 4 decision. While many details remain to be uncovered from within the full 130-page document, the essence of the Report and Order contained few major surprises.
As expected, the report and order allows unlicensed radio transmitters to operate in the unused portions of the broadcast TV spectrum (known as the “white spaces”). The FCC characterized this as a “conservative first step” aimed at enabling new technologies and encouraging development of broadband wireless Internet access, but with a focus on safeguarding incumbent services — notably broadcast television.
White space devices are described as unlicensed TV band devices. These new devices will be required to avoid other users through a combination of two methods, a geolocation database and spectrum sensing, and they will come in two varieties, fixed and portable. Fixed devices (presumably wireless network base stations) will operate at up to 4W EIRP (effective isotropic radiated power), while handheld units will be restricted to 100mW of power (40mW on broadcast-adjacent channels).
In essence, TV band devices are authorized throughout the TV spectrum through 698MHz (Channels 2-51). Fixed devices may operate throughout this range, while portable devices are restricted to Channels 21-51. (All users of TV band devices and wireless mics, including broadcasters, must avoid Channel 37, which is reserved for radio astronomy and medical devices, and Channels 3 and 4, on which DVDs, VCRs, satellite and cable boxes operate.)
The most profound and needed change mandated in the report is the creation of a national radio frequency database, accessible via the Internet. This database will be populated with the frequencies and locations of all broadcast TV stations, all fixed-location TV band devices and registered wireless microphone users. All TV band devices will be required to access the frequency database before the transmit capabilities are engaged.
Wireless microphones will be protected in a number of ways. Channels 2 through 20 will be limited to only fixed TV band devices, so the FCC anticipates that “many of these channels will remain available for wireless mics on an itinerant basis.” In the 13 major markets where land mobile operators already occupy selected channels in the 14-20 range, two channels between 21 and 51 (one above Channel 37 and one below) will be reserved for wireless microphones — meaning those channels will be restricted from TV band devices use.
In addition, wireless mics will be protected by the sensing capabilities of TV band devices and can be registered in the national frequency database. The details of these arrangements are not yet fully revealed, but wireless mic registration, while available for both permanent and temporary events/locations, “will be limited to facilities with wireless microphone use at well-defined times and locations,” according to the Report and Order. So while this bodes well for sports and entertainment event venues and houses of worship, the fate of mobile ENG teams and local rock bands (described as “itinerant microphone operations”) are less certain.
And while TV band devices become legal for FCC consideration on Feb. 18, 2009, development of a “proof of performance” standard to detect and avoid incumbent devices remains to be completed. It is reassuring, however, that the report specifically states that the TV band devices that detect wireless microphones in operation will be required to avoid those frequencies.
While this capability has yet to be reliably demonstrated in prototype devices, the FCC seems convinced that this performance standard can and will be attained. Specifically, the FCC noted that “...work is under way to improve the performance of this technology in sensing wireless microphones and we believe that, at this time, it is satisfactory as a complement to the database system and for providing a capability for the detection of unregistered wireless microphone operations. Accordingly, we will require that all unlicensed TV band devices incorporate a spectrum sensing capability to detect wireless microphones and to use that capability in determining the available channels in their area.” The FCC has requested comments from concerned parties to help determine the certification standards for TV band devices.
The commission is adamant that certification requirements of such devices will be stringent, and strictly enforced, to avoid unwanted interferences. Specifically, the Report and Order promises that the FCC will “take whatever actions may be necessary to avoid, and if necessary correct, any interference that may occur.”
So while the future of wireless microphones is likely to become more complicated in the post-DTV world of spectrum allocations, it seems clear that the FCC’s intent is for all existing systems — including wireless microphones — to remain legal and operational, even in the coming era of shared frequency access with unlicensed TV band devices. Whether that intent remains a reality once these devices proliferate the market remains to be seen.
The full Report and Order document can be downloaded in links dated Nov. 14 at www.fcc.gov.