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Federal Register / Vol. 86, No. 7 / Tuesday, January 12, 2021 / Rules and Regulations
in a six-megahertz channel to no higher than the existing limits for a four-watt EIRP broadband white space device.
Although the Commission declined to propose requiring narrowband devices to use a listen-before-talk mechanism, it nonetheless sought comment on whether one would be necessary to prevent harmful interference to protected services in the TV bands. The Commission also sought comment on whether there is a need to increase the minimum separation distances from cochannel and adjacent channel TV
station contours as the rules require for personal/portable devices operating as clients.
57. The Commission modifies the rules to facilitate the development of new and innovative narrowband IoT
devices in the TV bands. Specifically, the Commission establishes a new class of narrowband white space device, which it defines as a type of fixed or personal/portable white space device operating in a bandwidth of no greater than 100 kilohertz. A number of parties support the proposals to modify the white space rules to permit narrowband IoT operations. In response to specific comment sought on the definition of a narrowband white space device, the Commission expands that definition to include master devices as well as clients. This change is suggested by Dynamic Spectrum Alliance and Microsoft to enable greater flexibility in the design of IoT networks. No party opposed this change. A narrowband device that operates as a client must communicate with a master device that contacts the white space database to obtain a list of available channels and operating powers at its location, while a narrowband device that acts as a master must incorporate a geo-location mechanism and be capable of obtaining lists of available channels and operating powers from the white space database.
The Commission permits all types of white space devices that incorporate geo-location and have database access fixed, Mode II, mobile, and narrowband to act as a master device to a narrowband client device. TV band frequencies are better able to penetrate foliage and other obstacles than higher frequencies, so this action will permit the development of IoT devices with improved transmission range.
58. As proposed in the NPRM, the Commission permits narrowband white space devices to operate with a conducted PSD of up to 12.6 dBm/100
kilohertz, which is the same maximum level permitted for fixed devices, and require narrowband devices to comply with the same maximum antenna gain requirements as fixed devices, i.e., a
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maximum antenna gain of 6 dBi with no reduction in transmitter conducted power, or higher antenna gain if the conducted power is proportionally reduced. The Commission also requires narrowband white space devices to comply with an emission limit of 42.8
dBm into adjacent channels, i.e., outside of the 6-megahertz channel in which they operate. These requirements will permit a white space device to operate with a single or several narrowband carriers rather than having to spread all of its energy across a six megahertz channel while ensuring that narrowband white space devices have no greater interference potential than wider bandwidth devices operating under the current rules. To prevent narrowband devices from being used for data intensive applications and to limit the potential for these devices to cause harmful interference, the Commission limits transmissions on each narrowband channel to a total of 36
seconds per hour, as suggested by Dynamic Spectrum Alliance and Microsoft, i.e., a 1% duty cycle.
59. The Commission will not, however, increase this transmission time limit for narrowband devices to allow for signaling overhead as suggested by Microsoft. Microsoft has not indicated how much additional transmission time would be necessary for this overhead. Further, to the extent that a narrowband device needs additional transmission time for functions such as contacting a white space database to obtain a list of available channels, there appear to be ways to perform these functions while still complying with the 36 second per hour per narrowband channel limit. For example, under the rules the Commission is adopting there will be up to 55 narrowband channels within one six-megahertz TV channel, and a device could use one or more of these narrowband channels for signaling purposes. In addition, any overhead associated with contacting the database could be accomplished by other means, such as a non-narrowband white space channel, Wi-Fi, a fixed link, or a fiber connection.
60. The Commission also requires narrowband devices to use the proposed channel plan that limits total transmitted power in a six-megahertz channel to no higher than the existing limits for a four-watt EIRP broadband white space device. This channel plan requires narrowband white space devices to operate at least 250 kilohertz from the edge of a six-megahertz TV
channel, unless the adjacent channel is also vacant, and requires narrowband white space devices to operate only on
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channels centered at integral multiples of 100 kilohertz between the 250
kilohertz guard bands. The net effect of these requirements is that narrowband devices will be permitted to operate within 55 possible 100-kilohertz channels in the center 5.5 megahertz of each six-megahertz channel. Even in the event that all 55 narrowband channels within a six-megahertz channel were occupied simultaneously by devices transmitting at maximum power, the total conducted and radiated power within that six-megahertz channel would be no greater than for a fixed device operating with one-watt conducted power and 4 watts EIRP.
Because of the transmission time limit of thirty-six seconds per hour a onepercent duty cycle, the interference potential of these narrowband white space devices will actually be significantly less than four-watt EIRP
fixed devices in most cases since it is extremely unlikely that devices would transmit at maximum power on all 55
narrowband channels simultaneously, and even if they did, that would occur for no more than 36 seconds per hour.
61. The Commission is not limiting operation of narrowband devices to less congested areas as suggested by wireless microphone interests. Since narrowband devices will operate under control of a master device that accesses a white space database to determine available channels at its location, narrowband devices will not be permitted to operate on the channels at locations where registered licensed wireless microphones operate.
Additionally, unlicensed wireless microphones and white space devices must already share spectrum with fixed white space devices operating at up to 4 watts EIRP in areas that do not meet the definition of less congested. Even under worst-case conditions, narrowband devices will have no greater interference potential than four-watt fixed devices and will have a significantly lower interference potential in the vast majority of cases.
For these reasons, the Commission does not agree with RADWIN that a proliferation of narrowband devices will prevent spectrum use for internet access.
62. The Commission declines to allow a greater transmission duty cycle for narrowband devices used only by public safety entities as requested by NPSTC.
While NPSTC does not indicate how much it wants the limit increased, the higher transmit duty cycle the Commission is permitting will benefit all narrowband device applications, including those used by public safety entities. Allowing different technical
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