Before the FEDERAL COMMUNICATIONS COMMISSION Washington, DC 20554 In the Matter of ) ) Unlicensed Use of the 6 GHz Band ) ET Docket No. 18-295 ) Expanding Flexible Use in Mid-Band Spectrum Between ) GN Docket No. 17-183 3.7 and 24 GHz ) COMMENTS OF NOKIA Nokia respectfully submits these Comments in response to the Further Notice of Proposed Rulemaking (FNPRM) issued in the above-captioned proceeding.1 Nokia has been extremely active in this proceeding, submitting several technical studies and advocating to reach a result that will support new robust unlicensed operations while protecting critical incumbent Fixed Service (FS) use of the band, which is substantial and growing.2 As a provider of best in class incumbent FS equipment as well as new high- performance unlicensed equipment such as Wi-Fi and New Radio (NR-U) in the 6 GHz band,3 Nokia is well-positioned to advise the Commission on the technical interference aspects of these two services sharing the band. In these Comments, Nokia submits in the attached Appendix technical studies and analysis regarding two proposals in the FNPRM: (1) very low power (VLP) devices to operate across the entirety of the 6 GHz band (5.925-7.125 GHz), both indoors and outdoors, without 1 Unlicensed Use of the 6 GHz Band, Order and Notice of Proposed Rulemaking, GN docket No. 18-295, et al., FCC 20-51 (rel. Apr. 24, 2020) (“FNPRM”). 2 See Id., Appendix E (citing three technical studies submitted by Nokia). 3 See Nokia blends 5G and WiFi 6, while WBA lays claim to 6 GHz band, Caroline Gabriel (Mar. 16, 2020) available at https://rethinkresearch.biz/articles/nokia-blends-5g-and-wifi-6-while-wba-lays-claim-to-6-ghz-band/. using an AFC; and (2) increasing the Power Spectral Density (PSD) EIRP for low power indoor (LPI) operations from 5 dBm/MHz to 8 dBm/MHz. Nokia is pleased that the Commission continues to explore ways to increase the utility of the 6 GHz band, but the results of our technical studies advise caution. The studies we submit today demonstrate that VLP operations present a high risk of interference unless at power limits in the 4 dBm EIRP range for a 160 MHz channel (PSD EIRP in the -18dBm/MHz range). Further, the attached studies show that raising power limits for LPI operations when not subject to Automated Frequency Coordination (AFC), as proposed in the FNPRM, also poses a high risk of interference. A. Very Low Power Operation In the FNPRM, the Commission proposes to permit VLP devices to operate across the entirety of the 6 GHz band (5.925-7.125 GHz), both indoors and outdoors, without using an AFC. The Commission also seeks comment on the appropriate power level for VLP unlicensed devices in the 6 GHz band, noting that certain Wi-Fi advocates are seeking power levels as high as 14 dBm EIRP.4 As demonstrated in the Appendix, such operations – especially at or near 14 dBm – are likely to cause interference into incumbent FS systems. Thus, Nokia recommends that VLP operations intended for use without an AFC should not be permitted at power levels that high as they will cause interference, and a 4 dBm limit would be advisable for such operations. Nokia has analyzed the coexistence between FS Links and VLP U-NII devices operating across the 6 GHz band (5.925-7.125 GHz), both indoors and outdoors, without using an AFC. Numerical analyses are presented for three interference scenarios involving a single 4 FNPRM, ¶ 243. - 2 - VLP U-NII device and an FS receiver antenna. In the first scenario, the VLP U-NII device and the FS receiver antenna are placed in the same building, with the VLP U-NII device considered at the highest floor of the building. In the second interference scenario, the VLP U-NII device is also considered at the highest floor of the building, but the FS receiver antenna is placed in a neighboring building. In the third interference scenario, the VLP U-NII device is considered at the street level, in the neighborhood of the building where a FS receiver antenna is placed. The Commission is generally considering power levels in the range of 4 dBm up to 14 dBm (for a 160 MHz channel).5 Considering the desirable and foreseen characteristics of VLP devices, including small size and simple operation, the VLP U-NII device is assumed to transmit with fixed 14 dBm power, i.e. power spectral density of -8 dBm/MHz (for a 160 MHz channel). Propagation models include free space path loss for short distances, body loss, and building entry loss, when applicable. The FS receiver is modeled according to international standards Rec. ITU-R F.7586 and 47 C.F.R. § 101.115 (Directional Antennas). The numerical analyses performed for the described three interference scenarios indicate potential for co-channel interference to an FS receiver due to transmissions of a single VLP U-NII device at power spectral density level of -8 dBm/MHz. Adoption of a power limit for VLP U-NII device operation on the lower side of the power range considered by the Commission, e.g. 4 dBm EIRP (-18 dBm/MHz PSD EIRP), would minimize the potential for co- channel interference to a FS receiver due to such devices. 5 See id. Appendix C, Initial Regulatory Flexibility Analysis at ¶ 2. 6 Recommendation ITU-R F.758-7, System parameters and considerations in the development of criteria for sharing or compatibility between digital fixed wireless systems in the fixed service and systems in other services and other sources of interference, Nov. 2019, available at https://www.itu.int/dms_pubrec/itu-r/rec/f/R-REC-F.758-7-201911- I!!PDF-E.pdf (“Rec. ITU-R F.758”). - 3 - B. Power Spectral Density Increase for Low Power Indoor Operation In our study of the Commission’s proposal to increase power spectral density (PSD) EIRP from 5 dBm/MHz to 8 dBm/MHz for LPI operations, we analyzed the coexistence between FS Links and LPI U-NII devices using numerical analyses as well as system simulations. Numerical analyses are presented for two interference scenarios involving a single LPI U-NII Access Point (AP) and an FS receiver antenna. In the first scenario, the LPI U-NII AP and the FS receiver antenna are placed in the same building, with the LPI U-NII AP considered at the highest floor of the building. In the second interference scenario, the LPI U- NII AP is also considered at the highest floor of the building, but the FS receiver antenna is placed in a neighboring building. Propagation models include free space path loss for short distances and building entry loss. The FS receiver is modeled according to international standards Rec. ITU-R F.7587 and 47 C.F.R. § 101.115 (Directional Antennas). The numerical analyses performed for the described two interference scenarios indicate potential for co-channel interference to an FS receiver due to transmissions of a single LPI U-NII device even at the current power spectral density level of 5 dBm/MHz. The 3 dB increase of power spectral density to 8 dBm/MHz would proportionally increase the potential for interference. We recommend that if the Commission determines to increase the PSD EIRP limit to 8dBm/MHz, then an AFC should be used. Nokia also performed system simulations to analyze interference caused by LPI U-NII networks to FS receivers with more realistic assumptions. The dynamic system simulator models the U-NII radio access at a detailed level with realistic traffic loads, medium access protocols, transmit output power levels, transceiver impairments, propagation models and device 7 Id. - 4 - antenna patterns. The study focuses on two different deployment scenarios of neighboring building interference. In the first scenario, a network of LPI U-NII devices is considered at the highest floor of a building in the neighborhood of the building where the FS receiver antenna is placed, in the direction of the FS receiver antenna boresight azimuth. Full buffer traffic and FTP3 traffic are considered for different distances between the buildings. Interference assessment at the FS receiver shows high potential of co-channel interference for the considered range of distances between the buildings, i.e. 20 m to 500 m. Potential for adjacent channel interference is shown to be low for non-full buffer traffic. The second scenario is similar to the first one, but in this case a single LPI U-NII device is considered to provide video streaming to a client device at an apartment in the highest floor of a building in the neighborhood of the building where the FS receiver antenna is placed. Distance between the buildings as well as azimuth offset relative to the FS receiver antenna boresight are considered. Interference assessment at the FS receiver shows high potential of co-channel interference for a range of distances between the buildings and azimuth offset relative to the FS receiver antenna boresight. For both scenarios simulated, it was assumed a 5 dBm/MHz power spectral density for LPI U-NII AP. The 3 dB increase of power spectral density to 8 dBm/MHz would proportionally increase the potential for interference. Again, we recommend the use of an AFC to mitigate the interference potential. From the results of our studies, Nokia understands that a 3 dB increase in the power spectral density for LPI U-NII AP would increase the existing high potential for co- channel interference in some scenarios and that an AFC would be needed if the Commission adopts this increase in the PSD EIRP limit from 5dBm/MHz to 8dBm/MHz.