Motorola Inc. will bring a revised ultrawideband (UWB) proposal to a meeting of the IEEE 802.15.3a task group in Orlando, Fla., this week, along with what it says is proof that the new scheme offers a tenfold efficiency improvement — at very short ranges — over a competing technology vying for the nod as the IEEE UWB standard.

The altered proposal reflects Motorola's be-lief that the application sweet spot for UWB is no longer full-room networked video distribution over distances of up to 10 meters, but wireless links for handheld devices and peer-to-peer cable replacement applications within a range of about 3 meters.

At the same time, the company maintains that multiple UWB physical layers (PHYs) are likely to emerge for different, or even the same, applications. With that in mind, Motorola has incorporated the recently developed Common Signaling Mode into its proposal. The CSM allows multiple, disparate UWB PHYs to coexist without obliterating one another and--in the context of the 802.15.3a debate--enables the derivation of a dual-PHY standard.

"We plan to share with the rest of the community a DS (direct-sequence) UWB solution that is head and shoulders above either our previous DS-UWB solution or the (multiband) OFDM solution" put forth by the rival Multiband-OFDM Alliance, said Martin Rofheart, director of UWB operations at Motorola. Led by Intel Corp. and Texas Instruments Inc., the MBOA, as the competing alliance is known, advocates orthogonal frequency-division multiplexing technology for UWB.

Thus armed, Motorola will again try to break the deadlock that has stalled what initially was rapid progress within the 802.15.3a task group (TG3a) toward developing a short-range, low-power physical-layer standard for wireless communications at rates of up to 480 Mbits/ second at 1-meter distances. Begun almost a year ago, the group's selection process has winnowed 32 proposals down to two: Motorola's DS-UWB and the MBOA's multiband OFDM. There it has stayed since September.

Some say the stalemate stems from questions over the MBOA's compliance with Federal Communications Commission rulings on power measurement. The compliance issue drove the MBOA to join Motorola in commissioning independent tests by ITS Labs (Boulder, Colo.) to evaluate the interference characteristics of their respective ultrawideband proposals.

The results of those tests are still six to eight months out, said Julius Knapp, deputy chief of the FCC's Office of Engineering and Technology (OET). "In the meantime, the OET is conducting its own tests of the MBOA waveform against that of others to gauge its relative interference potential," he said. Those results should be known in two to three months, he added.

"The success of the MBOA proposal depends on the FCC ruling on power," said Jim Zyren, director of marketing at what was once Intersil Corp.'s wireless-LAN group but is now part of Conexant Systems Inc. Zyren, a veteran of the 802.11g IEEE war, is evaluating UWB for potential inclusion in Conexant's portfolio of wireless links. "I think that the indecision over that (FCC ruling) is giving people a lot of second thoughts," he said.

Roberto Aiello, president of MBOA member Staccato Communications Inc., said the Motorola revision indicates that its earlier proposal can't meet the TG3a specification's 10-meter range requirement, "so now they're saying 3 meters is the sweet spot." The revised proposal will tip the time-to-market advantage to the MBOA camp, he said.

Both groups have vowed to bring their respective technologies to market by year's end, regardless of IEEE status.

At the core of the MBOA's case against Motorola's initial DS-UWB proposal has been the relatively unorthodox modulation scheme, M-ary bi-orthogonal keying (MBOK). In an open e-mail to all in the TG3a group, Staccato's Aiello detailed the concerns over that scheme. Aiello cited the need for a high-speed digital-to-analog converter and other issues that may hinder MBOK's ability to meet the complexity, power consumption and interference robustness requirements set out by TG3a.

But Motorola's revised proposal pre-emptively scuttles those concerns by dumping MBOK in favor of pushing further the relatively simple, biphase-shift keying already implemented in its current chip set. The company also claims to have halved the complexity of its proposal's forward error correction by moving from a K = 7 convolutional code to a K = 6 mode.

"We had focused to date almost exclusively on (applying UWB to) flat-panel displays and media centers, as the wire replacement for home theaters, with rates of 110 Mbits/s at 10 meters," said Motorola's Rofheart. "However, what we've seen happen over the last quarter is an upsurge in interest in handheld applications such as USB and 1394, and the idea that mobile handsets are central to UWB. So, we've revised and updated our proposal to include these handheld devices first and foremost."

The result, Rofheart said, is a proposal that is range-equivalent to MB-OFDM but "is 10x better in terms of speed/power product, so we can deliver data rates up to 3x faster, at power levels that are 1/3 lower for those shorter-range applications in the 5- to 6-foot range." The new scheme can reach rates between 1 and 1.3 Gbits/s at 6 feet, said Rofheart, "yet has the modes to serve the media server applications we originally set out to deliver upon at rates of up to 110 Mbits/s at 10 meters."

To get to those gigabit rates, according to a white paper Motorola is passing around to task group members, the scheme relies on the low-fading characteristics of the DS-UWB waveform, which allow uncoded operation over short distances with very low complexity. This allows the Viterbi decoder and interleaver to be powered down.

"By tweaking it this way, we can get really terrific performance for these handheld applications," said Rofheart, who took pains to point out that the scheme maintains the essential characteristics of the DS-UWB waveform, which the white paper lists as including inherent frequency diversity and precise ranging capabilities. "From a Motorola perspective, that's what we have a good position in--(namely) cell phones, PDAs, applications processors and things of that type."

Conexant's Zyren agreed that short-range applications are UWB's bread and butter. "We believe UWB will be limited to 2 or 3 meters for reliable operation," he said. "It's an inescapable conclusion, but that's still a tremendous market opportunity, as there's a lot of USB and 1394 nodes out there and UWB is ideal for that.

"But that wireless replacement has to be low-power and low-cost," he went on, "and we believe that the DS approach (historically) lends itself moderately to that."

Zyren's team is currently doing a peer review of the revised proposal. Shorter range, said Zyren, translates to less need for the robustness that OFDM offers in the face of multipath interference. That makes for lower complexity and low-power operation in jobs such as cable replacement.

The MBOA scheme, which he also sees as a good proposal, "is the same as 802.11g/a today and is perfect for longer range. But UWB is for shorter range, so why incur the same baseband complexity (as .11a/g) to go a couple of meters?"

As for the Common Signaling Mode that Motorola has rolled into its proposal, Intel et al. reiterated their objection to the concept to EE Times last week. That objection is based on a fundamental belief there should be one UWB communications PHY, and that it should be MB-OFDM based.

Rofheart disagrees. "Our solutions are going to market," he said. "It looks like the MBOA proposal will go to market too, so it's the responsibility of organizations such as ours and the MBOA to ensure there's harmony."

"It's fair to say there will be more than one radio at the end of the day," Conexant's Zyren said, "so we like the idea of the CSM."

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