WIRELESS NETWORKING RIVALS TAKE AIM AT INTERFERENCE ISSUES

While industry officials contend instances of interference still are rare, they are working in standards groups to minimize it. Thrust of technologies is to connect computing, audio and video devices and phones in homes and offices. Another layer of complexity that technology developers cite is Bluetooth wireless technology, which also operates at very short ranges in band and is projected to grow significantly. Part 15 issues teed up at Commission include: (1) Petition by 3Com, Cisco, Ericsson, Intel, Lucent, Nokia, Texas Instruments (TI) and others for clarification or partial reconsideration of decision by Commission to allow companies such as Proxim to operate higher data rate, wideband frequency-hopping devices at 2.4 GHz. (2) Application for review by Calgary-based Wi-Lan to operate its Orthogonal Frequency Division Multiplexing (OFDM) transmitter at 2.4 GHz. (3) Ex parte communications from Texas Instruments touting ability of its Wi-Fi LAN technology, also known as IEEE 802.11b high rate, to operate at 2.4 GHz.

“We are looking at what’s the best way of going forward,” FCC official said. Agency has been weighing possibility of holding industry forum to discuss Part 15 issues more broadly, but no decision has been made, official said. “The idea of a forum would have been to just have a dialog with the industry,” Commission source said. FCC’s interest has been in examining issues in band and whether rule changes are appropriate, several sources said. “It’s a little bit early” to ascertain whether such meeting would lead to notice of inquiry, FCC official said.

“These devices are generally designed to withstand some interference. Spread spectrum technology tends to be robust,” FCC official said. While more attention has been focused on risk of interference as use of band increases, Part 15 requirements are tailored to have multiple devices operating in same place “without any problems,” official said. “The question that people are concerned about is will there get to be so many products in the band that interference will increase,” official said. “Much of that is speculative.” While Part 15 requirements provide “great deal of freedom” in how products for that band are designed, “some systems might not be as immune as others” to interference.

Pending petition by 3Com and others asks FCC to clarify that Part 15 rules allow frequency hopping spread spectrum (FHSS) to use adaptive hopping techniques. As alternate, petition asks reconsideration of Aug. 31 order to permit use of adaptive hopping of those systems at 2.4 GHz to avoid interference with other systems. Last summer’s decision cleared way for FHSS systems developed by Home RF consortium members, including Proxim, to operate in band with spread spectrum devices that use wider frequency hopping channels. Home RF technology has been backed by Motorola and Hewlett-Packard. Petition by 3Com asks that adaptive hopping include parameters such as no fewer than 15 nonoverlapping hopping frequencies. Proxim has argued in ex parte filings that such clarification isn’t needed because rules specify FHSS systems can’t use less than 75 MHz of spread bandwidth at 2.4 GHz if channel bandwidth is at least 1 MHz. Proxim said petition would allow devices to operate over smaller portion of band, essentially using same amount of power in less bandwidth. It also contended petition didn’t offer guidance on minimum spectrum block that hopping technologies should use.

One group examining multiple users of 2.4 GHz band is IEEE’s Bluetooth Coexistence Committee. Bluetooth Special Interest Group is having “active conversations” with both Wi-Fi and Home RF developers as well as other users of 2.4 GHz band to promote coexistence, said Tod Sizer, researcher at Lucent Technologies’ Bell Labs and chmn. of Bluetooth Coexistence Committee. “My working group is simulating and doing live tests to look at co- existence between Bluetooth and those other systems -- not only their effect on Bluetooth but Bluetooth’s effect on other systems,” he said. While group hasn’t made decisions yet on techniques to minimize risk of interference, Lucent at FCC has been promoting use of adaptive hopping, Sizer said. Specifically, in 3Com petition for partial reconsideration, companies such as Lucent are asking FCC to change Part 15 requirements to allow adaptive hopping over bandwidth that’s less than 75 MHz, with understanding that operators would reduce power levels and that technology would hop only to that reduced number of slots on band in cases of interference, he said. Of discussions among industry stakeholders, Sizer said: “I am confident that we are going to come to consensus. I don’t see any showstoppers left.”

Point of industry discussions has been to try to reach agreement on some of technical details of what 3Com put forward in petition. Proxim and others in ex parte filings still have argued that they think any significant changes in those requirements should be subject to full rulemaking process rather than clarification.

“What the FCC has done is essentially created spectrum which has been an incubator for extensive research and technology development for devices rolled out for Part 15 spectrum,” said Washington attorney Scott Harris, former FCC staffer who represents companies that petitioned for partial reconsideration of Proxim order. At the time that Part 15 requirements were put in place, systems that operated in band “were not nearly as technologically advanced” as today, Harris said. “Anytime you have a burst of technological development, existing rules at some time become something of a constraint,” he said, and FCC was cognizant of trend in way it was examining unlicensed spectrum issues.

In “vast, vast majority of cases,” there will be no co- existence issues between technologies such as Bluetooth and 802.11 cards operating in same computer at same time. There remain some cases where there’s room for improvement, which typically means increasing throughput to 100% rather than 80%. “Our studies have shown that the dominant interferer to Bluetooth will be Bluetooth itself. That’s our major worry -- how does it work when you get extremely dense with other systems,” Sizer said. Still, simulation tests have shown that in environments with up to 70 simultaneous Bluetooth users in 10 m radius, which is “unthinkable density,” technology still works, he said.

How FCC addresses 3Com petition will affect future of Part 15 unlicensed spectrum and small business “that are seeking to create technical innovations,” wireless technology developer Mobilian argued in ex parte filing at FCC. 3Com petition could “open the door for increased interference by FH systems,” company said. Specifically, Mobilian said 15-channel proposal at 2.4 GHz wasn’t consistent with Commission policy at 900 MHz and 5 GHZ. It said its support for 3Com request hinged on “a more detailed study” of technical impact of proposals.

Some companies are leveraging increased interest in 2.4 GHz as marketing tool, citing user fears of congested airwaves. Atheros Communications, whose wireless technology operates in 5 GHz band, touts equipment for wireless LANs on its Web site by exhorting users to “avoid the crowds and confusion at 2.4 GHz.” Company is focusing on chipsets based on IEEE 802.11a standards. While that band also falls under FCC’s Part 15 unlicensed spectrum requirements, Atheros CEO Rich Redelfs said unlike Part 15 requirements at 2.4 GHz, operators at 5 GHz cannot use spread spectrum technology. So equipment can use higher power limits over given length of spectrum, unlike frequency hopping devices that are confined to successive narrow bands of spectrum, Redelfs said. “It lends itself to the broadband communications that we are doing,” he told us.

IEEE ratified 802.11b standard for 2.4 GHz about same time approval was granted for 802.11a specification at 5 GHz, Redelfs said. At time, “everybody in the industry thought 5 GHz would be way too expensive and power consuming to be competitive,” he said. While some industry observers have speculated that some systems operating at 2.4 GHz might see that upper band as attractive to migrate to, “not all the applications can move,” Redelfs said. “So microwave ovens won’t move. Cordless phones won’t move. It won’t be as polluted as 2.4 GHz.”

Meanwhile, at FCC, Calgary-based Wi-Lan has pending order for reconsideration to operate as direct sequence spread spectrum (DSSS) device under Part 15. FCC has turned down Wi-Lan’s request for certification to operate under Part 15 and request for waiver to deploy systems in that band. Company has been seeking certification of its wideband OFDM transmitter. FCC Equipment Authorization Branch told Wi-Lan in last year that its technology didn’t meet “intent” of definition of DSSS system. Commission said spread spectrum systems used occupied bandwidth greater than what they actually needed to transmit information. Agency has said that W-OFDM systems take opposite approach by minimizing occupied bandwidth needed to send information.

Industry Canada cleared Wi-Lan to operate in Part 15 spectrum under requirements that essentially are same as those of FCC for that frequency, Industry Canada’s Veena Rawat said. Regulators based decision on “spectrum management perspective,” even though Wi-Lan devices “may not meet every letter in the definition of direct sequence devices,” she said. Industry Canada concluded “the impact was the same on the use of the spectrum as all the other devices which have been approved in this band,” Rawat said. Devices were seen as on par in terms of power outputs and ability to absorb interference from other operations in band as other systems approved for that spectrum: “It’s more spectrally efficient from a spectrum management perspective.”

“There is no serious question in my mind that this does comply” with FCC requirements for DSSS systems to operate in Part 15 band, said Mitchell Lazarus, attorney for Wi-Lan. Pending application for review asks full Commission to review OET decision, he said. “As demand increases, the Commission needs to think about how it regulates” in this area, Lazarus said: “Our biggest problem is not the rules as such, but the length of time it takes to change the rules. The engineers are always 2 years ahead of the lawyers.”

In other areas, Texas Instruments, which is member of Bluetooth wireless specifications group, unveiled offer of royalty-free licenses under TI patents needed to implement IEEE 802.11g standard. Last year TI bought Alantro Communications, which develops both 802.11b LANs and next-generation 802.11g LANs. It has told FCC that higher speed of that technology, 802.11g, can be certified based on agency’s current Part 15 rules, without changes. TI described 802.11g standard as doubling data rate of IEEE 802.11b products to 22 Mbps.

Potential for interference raises “serious issues among all the players, Home RF, Wi-Fi and Bluetooth” Parks Assoc. analyst Kurt Scherf said. Bluetooth, in particular, has support of broad range of companies and is likely to be embedded in broad range of wireless products, he said. “Bluetooth is going to be there and Home RF and Wi-Fi are going to have to deal with it.” Rather than regulatory changes, Scherf said he expected market would sort out potential interference issues. Because 2.4 GHz is cluttered, technology that succeeds in winning consumers over may not ultimately emerge from that band, he said: “The ultimate winner may actually fall out at the 5 GHz space.”