FIRMS URGE FINE-TUNING ON FCC PROPOSAL FOR UNLICENSED DEVICE RULES

To bolster the availability of broadband wireless technologies through more-efficient spectrum sharing, the FCC in Sept. proposed updates to parts of its Part 2 and Part 15 rules for unlicensed devices. In part, the proposal would: (1) Allow the use of advanced antenna technologies with spread spectrum devices at 2.4 GHz and would alter the replacement antenna restriction for Part 15 devices. (2) Update equipment authorization procedures to allow more flexibility to configure transmission systems without needing to obtain separate authorizations for every combination of system components. (3) Harmonize measurement procedures for digital modulation systems under Part 15 and change channel spacing requirements for frequency hopping spread spectrum devices at 2.4 GHz to remove hurdles to the introduction of new technologies using wider bandwidths. (4) Spell out equipment authorization requirements for modular transmitters.

Microsoft urged the Commission to adopt unlicensed sharing rules in new bands where these devices would be used for broadband data networks. The FCC has stipulated the duties of unlicensed devices to protect licensed services but has been reluctant to weigh in on conflicts among unlicensed services, it said. Spectrum etiquette among unlicensed devices is now critical, Microsoft said. The proposal sought comment on such an etiquette, based on 1.9 GHz unlicensed PCS rules that require devices in this band to monitor the spectrum and only transmit when no signal above a particular threshold is detected. Increased use of unlicensed spectrum for critical wireless networks and the evolution of such devices toward higher bandwidths has shown current rules “systematically favor narrowband devices over broadband devices since the latter devices encounter more difficulty in finding an open channel in which to operate,” Microsoft said. As an example of systems that can use new technology to exploit unregulated public networks, Microsoft cited the “Wi-Fi Hog” developed by MIT. The system consists of a laptop linked to different sniffing and jamming devices, which can take “complete control” of a public Wi-Fi network by blocking other users, Microsoft said.

Microsoft called for rules to compel unlicensed devices, especially in more crowded lower bands, to use spectrum more efficiently. It called for unlicensed devices: (1) To observe a “non-greedy occupancy” rule for spectrum sharing, meaning no user should occupy any channel when it has no data to send. (2) To refrain from transmitting on a particular channel unless they can do so without causing harmful interference to devices already operating there. This could be done through an “interference threshold,” which would be the aggregate interference level that can be sensed by a network node at which the node must consider that channel unavailable. This would be band-specific and based on the actual interference environment. (3) To incorporate a minimum amount of dynamic range and “to reduce transmit power to the minimum necessary to achieve the link margin they desire.” Microsoft said the proposed rules “are framed as performance requirements rather than as design specifications.”

Meanwhile, Intel argued spectrum sharing etiquettes aren’t necessary right now. “Today’s sharing allocations are successful because they create a structure of primary and secondary users and give de facto control of the secondary use to the owner of the immediate physical area (business, campus or home),” it said. Attempts by the FCC to mandate etiquettes in this area likely would delay the rollout of new services and impede innovation, Intel argued. Crowding problems that could be expected from “co- equal” unlicensed devices have been mitigated, it said, citing Wi-Fi deployments in which a homeowner controls the deployment of such devices. In other areas, it told the FCC that while there is a need for some boundaries around the beamwidths of advanced antenna technology, a minimum beamwidth of 120 deg. isn’t the best scenarios for all cases. The NPRM sought feedback on the characteristics a system would need to exhibit to be classified as a sectorized or phased array antenna system and proposed limiting the total simultaneous beamwidth radiating from an antenna to 120 degrees.

Motorola said that for now, it didn’t back a spectrum etiquette for unlicensed bands outside 1.9 GHz unlicensed PCS spectrum. “The risk that a spectrum etiquette may stifle innovation and product development outweighs any apparent benefits,” it told the FCC. Motorola said such sharing rules aren’t needed at 2.4 GHz. “While such an etiquette may be appropriate in future bands available for unlicensed operations, depending on the circumstances, the lack of an etiquette in current bands has allowed innovation and should not be altered at this time,” it said.

Citing recent changes to Part 15 rules to accommodate new digital technologies, Cisco argued against having 2 sets of rules apply to identical devices operating in virtually identical spectrum. Cisco urged the FCC to adopt a single measurement procedure for digital modulation systems in the (Unlicensed National Information Infrastructure) U-NII band. It noted the FCC proposal indicated unlicensed digitally modulated systems can operate under unlicensed rules at Part 47 of Sec. 15.407 of the Communications Act or under spread spectrum rules in Sec. 15.247. The FCC previously altered its spread spectrum rules to accommodate devices that use the advanced digital modulation techniques already allowed by the U-NII rules. “As a result of these rule changes, identical unlicensed devices can now operate in the same spectrum under 2 different sets of rules,” Cisco said. The NPRM noted different measurement procedures apply to these 2 rule sections, which means the 2 sections can treat identical devices operating in identical spectrum differently. Cisco backed the FCC proposal to apply the compliance testing procedures of Sec. 15.407 to the authorization of devices under the spread spectrum rules of Sec. 15.247.

Hewlett-Packard told the FCC it generally supported the proposed new rules on advanced antenna technologies but had concerns about the interference risk to “normal” users and access point devices on Wi-Fi networks. H-P reflected concerns of several other commenters, saying the FCC’s Part 15 rules have been successful but offer no protection against interference to unlicensed devices. H-P suggested some additional controls or guidelines, such as location and frequency restrictions, to keep interference from “eventually becoming a problem.” It singled out the advanced antenna systems for point-to-multipoint service under the NPRM, which H-P said will clearly have increased power density at the intended receiving points compared to devices with omnidirectional antennas. “Point-to-multipoint services with steerable or sectored antenna beams and relatively higher power may present an unacceptable level of interference to regular users of 802.11 WLAN [wireless local area network] systems,” it said. H-P said this represents a different interference risk than fixed point-to-point services where the interference potential is limited to fixed locations. To help control interference, H-P suggested restricting the operation of point- to-multipoint systems to certain sub-bands or frequencies, “perhaps with some geographical overlay.” This would keep other frequencies available for normal WLAN use, it said.

CEA lauded the proposals to allow use of phased array and adaptive sectorized antennas, saying this would bolster the reliability of communications carried by unlicensed devices and increase spectrum efficiency by letting the signals be directed toward the devices “with which the communication is desired and away from other devices and users.” CEA called for the FCC to extend these provisions to other unlicensed bands, including bands at 5 GHz. It also backed proposals to let professional installers and service providers customize their systems with different antennas and to use amplifiers of up to 1 W when that power level is permitted. Such changes would promote wireless broadband access, CEA said. In other areas, CEA urged the FCC not to consider spectrum etiquettes for unlicensed bands beyond unlicensed PCS spectrum at 1.9 GHz. In the unlicensed PCS spectrum, equipment and services failed to flourish, despite the prime location of this band, CEA said. “This stands in marked contrast to the success of a wide variety of unlicensed devices in the unlicensed bands neighboring the UPCS bands,” it said. CEA recommended against spectrum etiquettes except in “very narrow circumstances where specific methods are required to protect a primary user in the same band.”

The Technology Industry Council (ITI) backed the proposed streamlining of antenna approvals under Part 15 and said the changes wouldn’t increase interference to other services in that unlicensed band or adjacent frequencies. But ITI objected to an FCC requirement for unique antenna connectors, saying multiple radio vendors will use the same connectors to reduce cost. The group said the requirement shouldn’t be applicable to the unlicensed devices covered by these rules. The requirement adds additional costs for the end user “with no demonstrable benefit,” it said. ITI also raised concerns about the extent to which FCC rules require unlicensed devices to accept interference from other unlicensed devices, some of which are serving as “last- mile” broadband networks. “A challenge for policy-makers is to ensure that the interference environment permits unlicensed broadband devices to operate with great reliability,” ITI said.