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Ultrawideband Takes on Wi-Fi

Capable of zapping data many times faster than the common home networking technology, ultrawideband is moving closer to commercial reality. Now there’s just that pesky fight over standards to resolve.
September 2, 2004

In a move that could portend a major shakeup in wireless networking, the Federal Communications Commission last month licensed the first chipset based on ultrawidebanda technology born in the U.S. military that can deliver huge amounts of data quickly over short distances. Ultrawideband, or UWB, would enable you to swap data between your digital camcorder and desktop computer. Or you could send signals from your digital cable box to portable flat panel displays scattered around your house. Whats more, youd be able to do so at speeds that are five to ten times faster than with Wi-Fi, now the dominant technology in wireless home networking.

There’s just one hitch: the FCC’s ultrawideband license, which was given to Motorola spinoff Freescale Semiconductor, applies only to one of two evenly matched rival formats vying to be the ultrawideband standard.

Standards wars are common in wireless technology, but this battle stands out for both its bitterness and its duration. And as UWB dawdles at the starting gate, it becomes more and more likely that its impact will be muted by a new version of Wi-Fi.

On September 13, the IEEE (Institute of Electrical and Electronic Engineers) will meet in Berlin to begin sorting through rival proposals for the new Wi-Fi, known officially as 802.11n (the Wi-Fi now in common use is 802.11b; a more advanced version just starting to be used is 802.11g). This next-generation Wi-Fi will be less power-efficient than ultrawideband, and may well be more prone to signal interference. On the other hand, it will work over longer distancesup to 90 meters compared to UWB’s 10 to 20 meters.

More importantly, the new version of Wi-Fi offers compatibility with the wireless networking technology that has spread rapidly in the last few years. Not only is Wi-Fi a winner in the corporate world and growing fast both in the home and in public “hotspots,” it will soon invade cell phones and may extend Internet telephony into the wireless realm. A delayed or split UWB standard could mean Wi-Fi will win the home entertainment networking market. That would leave UWB to battle it out with Bluetooth and other technologies for the significant, but less far-reaching role as a very-short-range cable replacement for PCs and consumer electronics. UWB should win that battle (and we’d all be thankful if someone would win it soon), but it may well miss out on a greater destiny as a multimedia networking technology for homes and offices.

Even if ultrawideband loses ground to Wi-Fi, though, the technology offers so many benefits that it’s unlikely to fade away. Unlike narrowband wireless technologies such as Wi-Fi, which beam signals within a defined frequency band, UWB scatters its transmissions over several gigahertz of the spectrum using short pulses. The broadband potential of UWB lies in the sophisticated transmission scheme, not in the strength of the transmitting technologythat’s why UWB transmitters can be simple devices that use very little electrical power. Moreover, due to its spectrum-scattered approach to communications, UWB is theoretically less susceptible to interference and offers an inherently more secure channel that is difficult to jam. Unlike with Wi-Fi, you could set up multiple independent UWB networks within the same household, so your PC-to-peripherals network won’t interfere with transmission between your cable set-top box and your TV.

Ultrawideband also offers an interesting extra: the ability to precisely identify the location of transmitters, conceivably down to the centimeter. This feature could open up a variety of applications where Wi-Fi is less suitable. For example, a wearable cardiac monitor endowed with a UWB transmitter could not only alert hospital workers to an emergency event, put pinpoint the patient’s location. Or a “smart highway” might someday be equipped with UWB transmitters posted at regular intervals to communicate with UWB-equipped cars and keep them moving in unison.

Yet before this illustrious future can be achieved, there’s a little thing called a standard to settle.

The ultrawideband standard that’s under contention is what IEEE dubs 802.15.3a. Freescales UWB technology, which could arrive in home entertainment systems as early as year-end, adheres to the UWB Forum. Backed by Motorola and about 60 other (mostly smaller) companies, the UWB Forum is pushing a variant of ultrawideband that transmits data in a continuous sequence; it’s called DS, for Direct Sequence. The rival group is called the MultiBand OFDM Alliance (MBOA); it is being promoted by Intel and an even longer list of companies, including Hewlett Packard, Philips, Samsung, and Texas Instruments. MBOA proposes a technique that hops rapidly between multiple frequency bands to improve performance; such multiband orthogonal frequency division multiplexing, or OFDM, is used already in digital subscriber line and other communications technologies.

There is no clear technological winner between the two standards. The UWB Forum technology is farther along in its development and may be easier to integrate into smaller devices such as smart phones. The MBOA, meanwhile, claims to be able to sell its technology at a lower cost since it boasts so many consumer electronics companies on its side. Both offer roughly equal performance specs. And both sides are also calling each other names and slamming doors.

By comparison, the emerging battle over the next Wi-Fi looks to be relatively mild. One contender, the Worldwide Spectrum Efficiency (WWISE) group, is backed by Airgo Networks, Broadcom, Conexant, Mitsubishi, Motorola, STMicroelectronics and Texas Instruments. It will compete with a rival proposal from an organization called TGn Sync, backed by companies including Agere, Atheros, Cisco, Intel, Matsushita, Nokia, Philips, and Sony. The IEEE’s roadmap for a draft specification in 2005 and a final spec by 2007 seems reasonable since the two Wi-Fi proposals are similar. Both use variations on a technique called MIMO, which boosts performance by sending and receiving data over multiple antennas (MIMO stands for multiple input, multiple output). So far, TGn Sync seems to have the edge on speed and power efficiency while WWISE appears to offer better compatibility with existing Wi-Fi networks. Participants on both sides seem willing to compromise and speed the process along so that the technology can make its mark before UWB takes root.

The next Wi-Fi will require a data rate of 200 megabits per second, which translates into a real-world throughput of 100 megabits per second. (Similarly, the 802.11g standard’s throughput is only half its 54-megabit-per-second data rate.) This 100-megabit-per-second mark, which is where UWB products will start out, essentially brings Wi-Fi up to the level of a typical fast Ethernet wired network. Both camps offer optional extensions to their standards that could eventually boost performance to more than 500 megabits per second, making them equivalent to where ultrawideband is expected to be in a few years.

The new Wi-Fi has one more advantage: because it is based on a proven standard, it should encounter less scrutiny from regulators. Theoretically, UWB users should experience less signal interference than Wi-Fi users. But this has yet to be proven to the satisfaction of regulatory agencies, which are concerned about the wide frequency range that UWB covers. To ensure that there’s no interference with fire and police radio systems, the FCC has authorized UWB usage only in the 3.1- to 10.6-gigahertz band. This limits UWB’s effective range to about 10 to 20 meters. 

Eventually, UWB boosters say, regulators will discover there’s little threat of interference and they’ll open up a wider range for UWB, making it easier to reach higher speeds and at ranges up to 30 meters. But first things first: a standard.

Standards wars serve their purpose, bringing the best (or at least the most feasible) technology to the fore while broadening corporate participation. Yet for this magic to work, a single standard must emerge in the end. In the immortal words of James T. Kirk when he was split into two beings, “Somebody…please…make…the decision!”

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