A lot of the comments filed on the FCC's Notice of Inquiry (NOI) into the use of spectrum bands above 24 GHz were positive, praising the commission for launching the proceeding to investigate potential opportunities for using millimeter wave (mmW) bands to accelerate 5G services. But many interested parties are calling for caution as well, especially when it comes to framing rules around the use of the mmW bands.
CTIA urges the commission to make the bands above 24 GHz available on a licensed, exclusive-use basis and said that "where spectrum is not easily used for mobile wireless services, it could be made available on an unlicensed basis."
T-Mobile US (NYSE:TMUS) sounded similar concerns about licensing. "When the commission establishes licensing and authorization mechanisms for mobile operations above 24 GHz, exclusive use licenses will strike the right balance between the benefits of competition and the efficiencies of scale and scope needed to justify investments in the band," the company said in its filing.
T-Mobile also said that any 5G mobile technologies will complement, not be a replacement for, 4G technology, and it notes that LTE is in the early stages of its life cycle, which for cellular technologies historically has been about 20 years from launch to peak penetration. T-Mobile noted that it has already launched carrier aggregation, a widely used technique in the LTE-Advanced standard, to create wider channels and produce more capacity and higher speeds.
CTIA also wants to make sure licensees have the flexibility to experiment with wider-bandwidth technologies without penalty. In particular, it is telling the commission not to adopt out-of-bandwidth emission (OOBE) rules that penalize technologies that use larger bandwidths.
Part of the purpose of the FCC's NOI is to revisit the service rules in the mmW bands, with the main goal of developing flexible rules that accommodate as wide a variety of services as possible. The inquiry is taking place within the context of broader efforts to develop technical standards for 5G services.
Although standards bodies such as 3GPP have not yet embarked on mmW spectrum standards, current thinking is that the "phantom cell" concept is likely to be used, according to NYU Wireless' filing. The phantom-cell idea would use today's incumbent UHF and microwave CMRS frequencies to carry extensive and increasing data communication needs, but also would provide a "control plane" to enable the use of a much-higher-data-rate "user plane" at mmW frequencies that could carry new types of traffic and applications far greater in bandwidth than anything used today, according to NYU Wireless, which has conducted significant mmW research, including on propagation measurements, radio-channel modeling, system simulation and antennas.
The NYU researchers are urging the commission to quickly make mmWave spectrum available for commercial use and note that with suitable FCC regulations, new non-cellular-type providers could spring up almost instantly. NYU Wireless founder Ted Rappaport and his colleagues say that the technology exists today to create products and services such as Wi-Fi-like broadband, backhaul-network support in rural areas and new content-distribution businesses.
Verizon's (NYSE: VZ) comments lean toward a decidedly more conservative approach, telling the commission that it should avoid making determinations at this time about the appropriate regulatory framework or frameworks, as it's unclear what technologies and business models may eventually emerge for frequencies above 24 GHz. In addition, "the Commission should also avoid making prescriptive assumptions about what '5G' means today," the filing said, adding that the commission should be cautious in using "5G" merely as shorthand for the unbounded technologies that may emerge in the proceeding.
Some of the most widely publicized field trials of mmW mobile service have been conducted at New York University and the University of Texas with funding from the U.S. Army and Samsung.
Samsung says the commission should focus on allocating the 28 GHz and 39 GHz LMDS bands as well as 37/42 GHz for 5G, with a secondary eye toward other bands, such as 60 GHz. If the commission moves forward with permitting 5G mobile networks in the LMDS band, base stations should be permitted to operate at the same power levels (85dBm) and mobile stations should be permitted to operate at the subscriber-station power levels, the company says. That would enable the 5G network to provide services similar to, or better than, what a current licensee is serving.
Qualcomm (NASDAQ:QCOM) is urging the FCC to issue multiple and specific Notices of Proposed Rulemaking proposing to exclusively license large blocks of spectrum currently assigned to LMDS, 39 GHz and 37/42 GHz services. It also wants the commission to take steps to extend the current 60 GHz unlicensed band to include the 64 GHz to 71 GHz swatch of spectrum.
The NOI is the first step in the FCC's process to examine the use of innovative technologies that could enable the use of frequencies above 24 GHz for mobile services. Reply comments are due by Feb. 17.
- see the FCC's NOI
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NYU Wireless' Rappaport envisions a 5G, millimeter-wave future