MANHASSET, N.Y. The FCC has declined to act on a request for a declaratory ruling on the means of compliance testing for ultrawideband devices. Instead, the Commission will leave it up to the IEEE 802.15.3a task group, which is working on an ultrawideband short-range communications solution, to ensure that whatever standard it approves meets the FCC's interference requirements.
In a statement issued late Thursday (Sept. 11), Julius Knapp, director of the FCC's office of engineering and technology, said, "We urge that IEEE perform technical analyses to ensure that any UWB standard it develops will not cause levels of interference beyond that already anticipated by the rules. This information will be needed to support any necessary FCC rules interpretations or other appropriate action for the chosen standard."
The statement extricates the FCC from an extremely contentious situation and places the onus back on the .15.3a task group to decide between two competing proposals for what looks to be a UWB-based standard. That group meets in Singapore next week to begin a second round of a contentious debate involving most of the world's leading semiconductor and consumer electronics manufacturers.
On one side is Xtremespectrum (XSI), Motorola and ParthusCeva with a single-band, direct-sequence-CDMA (DS-CMDA)-based proposal. On the other is a Texas Instruments/Intel-led umbrella group of 16 semiconductor and consumer electronics companies called the Multiband-OFDM Alliance (MBOA). They propose a multiband, frequency-hopping approach.
At the last meeting in July, the two sides argued over whether or not the MBOA can use a frequency-hopping technique and still meet the 802.15.3a's data and range requirements while remaining in compliance with the FCC's stated declarations on how frequency-hopping systems should be tested. According to an interpretation of the FCC regulations by Chris Fisher, XSI's vice president of marketing, frequency hopping should be "parked," or turned off, during test. In that case, the power output of the MBOA proposal would have to be cut by at least 5 dB, which would drastically reduce data rate and/or range.
However, the MBOA group has repeatedly said it is in compliance with the FCC frequency-hopping rulings, even though it performs its tests with frequency hopping turned on. "It's all about how you interpret the letter and the intent of the [frequency-hopping] rulings," said Roberto Aiello, CEO of MBOA member Staccato Communications Inc. (San Diego). "The original ruling was designed to prevent someone from using frequency hopping to allow a narrowband signal to meet the 500-MHz bandwidth needed [to be classified as an UWB signal]," he said. "But the overall intention was to ensure compliance with the FCC's interference and power-limit rules, and we've demonstrated that."
Aiello referred to compliance testing results announced this week on an MBOA-based system from Staccato, Samsung, General Atomics and Wisair by independent test lab TDK RF Solutions (Austin, TX). "We showed that we did not cause interference and are completely in compliance with the FCC's power limits," he said. According to Aiello, the test showed an over-the-air data rate of 320 Mbits/s, with a payload of 110 Mbits/s. With less robust error-correction coding, he said, the demo reached rates of up to 200 Mbit/s.
However, showing compliance with the FCC's UWB spectral mask may not be enough if the MBOA proposal is selected and, as a result, FCC rules on UWB test have to be changed. While the FCC has set precedents in terms of changing rules according to newly defined IEEE standards the 802.11 standard is a case in point few rules were as hotly debated as UWB's.
With cellular, military, GPS and radio operators all debating the original UWB rules and limits, the FCC will have its work cut out for it in calling for an UWB rule revision. "Frequency hopping has been shown to cause more interference than direct sequence," said Fisher, "that's why the FCC came down so hard on it. If they try and change the rules to meet the MBOA proposal, they're going to meet a lot of resistance from those other groups."