FCC APPROVES ORDER THAT ADDS FLEXIBILITY TO PART 15 RULES
FCC Thurs. at its agenda meeting approved order designed to update Part 15 rules to permit new digital systems to operate at 915 MHz, 2.4 GHz and 5.7 GHz under current rules for spread spectrum devices. Order, approved unanimously, also adds flexibility in design and operation of frequency- hopping spread-spectrum systems such as Bluetooth at 2.4 GHz and did away with a processing gain requirement for direct- sequence spread-spectrum systems such as 802.11b wireless LAN. Agency has said these changes, in part, are meant to address extent to which there are increased high-speed wireless applications at 2.4 GHz. But Commission didn’t take additional step sought by several wireless applications developers. Several developers of Bluetooth and 802.11b systems, including Lucent spin-off Agere, had asked FCC to require smart hopping or so-called adaptive frequency-hopping techniques in exchange for system using fewer frequency- hopping channels. Officials said order gives manufacturers flexibility to design more diverse array of products for band.
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Bluetooth Special Interest Group (SIG) urged Commission in filing last week to adopt order allowing reduced hopsets for frequency-hopping spread-spectrum decisions. While FCC did that in Thurs. order, it didn’t agree to another requirement sought by that group and others, which was that devices taking advantage of those reduced hopsets be mandated to do adaptive or smart hopping to prevent interference. “We created flexibility within the band,” said FCC Office of Engineering & Technology Chief Edmond Thomas at press briefing. Questions this entails involve regulators examining whether such decisions should be made on the basis of average or peak power and what power level is chosen as basis for comparison, he said. IEEE or another accredited standards body is more appropriate place to examine adaptive hopping, which order suggests that operators do, Thomas said. “We didn’t tell them how,” he said: “My suggestion is that almost out of self-preservation, manufacturers will get together and try to figure out the best way to do it and they are much better equipped to do it than we are here in Washington.” Once Commission begins evaluating issues such as whether one service is more susceptible than another as result of such policy choices, “very quickly you get in a position where you have to start establishing standards,” Thomas said: “It’s inconsistent with innovation within the band because we like industry to find ways to build very robust systems. Frankly, we didn’t know how to do it in a way that we were comfortable with.”
“It is a legitimate concern,” said Washington attorney Scott Harris, who represented Bluetooth SIG in proceeding. “However, had the private sector known that OET had that concern it might have been able to provide an appropriate response,” he said. “One problem with the way the system is operating now is that the private sector finds it increasingly difficult to learn what concerns FCC staff have about particular issues and thus is unable to be responsive to those concerns,” said Harris, who is former FCC International Bureau chief.
Existing Part 15 rules allow operation of direct- sequence spread-spectrum systems (DSSS) and frequency-hopping spread-spectrum systems (FHSS) on non-licensed basis. Both systems reduce power density of transmitted signal, lowering possibility that the transmitter will cause interference to other devices in band. Order concludes that because new digital modulation technologies have spectrum characteristics akin to DSSS systems, they can operate under same rules as DSSS devices at 915 MHz, 2.5 GHz and 5.7 GHz “without posing additional risk of interference,” FCC said. Order removes rule that systems in these bands be limited to just DSSS or FHSS technology.
Commission adopted further notice of proposed rulemaking last year that would allow spread spectrum devices at 2.4 GHz to use fewer hops than 75 that have been required under existing Part 15 rules. Order approved Thurs. would permit use of as few as 15 hopping channels for FHSS in 2.4 GHz band. To reduce risk of interference, these systems can use channel bandwidth up to 5 MHz wide if they reduce their output power to 125 mW if fewer than 75 hopping channels are used. This is 8 times less than power limit allowed for systems that do not reduce their hopsets, said OET attorney Neal McNeil. Rule change will allow technology developers to design FHSS systems that have a greater ability to avoid interference with other systems, he said. For example, equipment manufacturer now is free to include both Bluetooth and 802.11 technology in same device, he said.
“This action will allow new FHSS systems to better avoid interference than today’s systems by enabling them to avoid occupied channels,” Commission said. Order also did away with a minimum processing gain requirement for DSSS systems. It found that “manufacturers have market-driven incentives to design products that can withstand interference from other radio frequency devices,” Commission said.
FCC Comr. Martin said order continues trend at Commission of allowing applications such as Bluetooth and 802.11 to flourish by sharing spectrum under Part 15 rules. “Increased spectral efficiency -- particularly through spectrum sharing -- is becoming more and more important as we face ever increasing demands for spectrum,” he said. “I have thus encouraged the Commission to move toward policies that enable and encourage sharing.” Comr. Abernathy said key point underlying order is that FCC “is making sure that there is adequate flexibility to design and market a wide variety of consumer devices.” Comr. Copps said Part 15 has been critical to the FCC’s attempts to address the “spectrum crunch.”