Issue No.07 - July (2006 vol.39)
Published by the IEEE Computer Society
DOI Bookmark: http://doi.ieeecomputersociety.org/10.1109/MC.2006.247
There are two principal approaches to UWB technology, and companies have held off making products, hoping an IEEE standardization effort could yield one protocol on which they could focus their efforts.
Ultrawideband technology has been regarded with considerable promise for several years. Vendors want to use the short-range, high-speed wireless UWB for many potentially popular applications, such as home networks, connectivity between PCs and peripherals or monitors, and the transfer of large files between devices. In these areas, they see UWB as having significant advantages over similar technologies such as Bluetooth and Wi-Fi.
Vendors haven't released UWB products yet. But according to analyst Stuart Carlaw with ABI Research, a market-analysis firm, global UWB hardware shipments will reach 300 million units by 2011.
Currently, though, the lack of a unified standard has hurt UWB adoption. There are two principal approaches to the technology, and companies have held off making products, hoping an IEEE standardization effort could yield one protocol on which they could focus their efforts.
However, the IEEE was unable to get the UWB Forum and the WiMedia Alliance—proponents of the two main approaches—to agree to merge their widely divergent technologies into a single standard.
Vendors are now preparing to release products, such as dongles or wireless hubs, based on one or the other UWB version. But products based on one version will be incompatible with devices based on the other because the two approaches are so different. This will cause problems for products used within the same network or that must communicate with one another.
Meanwhile, vendor Freescale Semiconductor recently left the UWB Forum and decided to promote its own ultrawideband version.
Thus, just when it seemed poised to take off, the UWB market is facing considerable division and uncertainty.
University and government researchers in the US and the then-Soviet Union worked separately in the late 1960s on the first UWB-like technologies, for applications such as radar and secure communications. As chips have become more powerful and less expensive over the years, UWB has become affordable and sufficiently powerful for commercial use.
UWB appeals to vendors because, as a wireless, short-range technology, it is faster than Bluetooth or Wi-Fi. UWB is also power-efficient and, unlike Wi-Fi, doesn't use a complex security scheme. This makes it ideal for handheld devices, which use batteries and have limited processing power.
However, UWB works by transmitting across multiple frequencies, which increases the possibility of interference with other signals. Because of this, most countries have banned UWB.
In 2002, though, the US Federal Communications Commission (FCC) authorized commercial use at low power levels to limit interference. And recently, Europe's Electronic Communications Committee announced support for UWB, while Japan appears poised to do the same.
How UWB works
UWB works via chip-based radios that modulate signals across the entire available ultrawideband spectrum, which in the US is from 3.1 to 10.6 GHz, explained WiMedia Alliance president Stephen Wood. This is different than most wireless technologies, which operate only in a single assigned band within a frequency spectrum.
The UWB Forum's version of ultrawideband provides a maximum data rate of 1.35 Gbits per second and a maximum transmission range of 3 meters. The WiMedia Alliance's version offers 480 Mbps and 10 meters.
Bluetooth—a short-range radio device-connectivity technology that operates in the 2.45-GHz frequency band—sends data at only up to 3 Mbps but offers a transmission range of up to 100 meters. Wi-Fi—a family of wireless LAN and Internet-connectivity technologies operating in the 2.4- or 5-GHz frequency bands—provides transmission rates up to 54 Mbps and sends data up to 92 meters, although this range might increase considerably in the near future.
Thus, noted Michael J. Marcus, director of the Marcus Spectrum Solutions radio-technology consultancy, UWB will offer much more bandwidth than Bluetooth and Wi-Fi.
UWB doesn't have its own scheme for data security, so devices must provide it via encryption or other separate approaches.
UWB can function as an underlying transport platform over which other technologies will operate. With this in mind, the WiMedia Alliance and the Bluetooth Special Interest Group are working together on a combined technology. They expect prototypes to be available by 2007 and products by 2008.
UWB would be good for transferring large files, like those used in multimedia, quickly and wirelessly over short ranges between nearby devices, such as a PC and a digital camera or MP3 player.
Thus, Wood noted, UWB could work with mobile e-commerce. For example, a smart phone could use UWB to buy a DVD from a kiosk and subsequently upload it to an MP3 player.
Proponents also want to use the technology to replace wires that connect PCs to monitors and that connect DVD players and set-top boxes to TVs, according to Pulse∼Link president Bruce Watkins, a member of the UWB Forum's board of directors.
UWB's first commercially successful implementation may be in WiMedia-based wireless universal serial bus connections, predicted Christopher Kissel, an analyst with In-Stat, a market research firm. USB—which, like Bluetooth, could operate over UWB—is an external bus that connects computers and consumer electronics with peripherals.
Some supporters hope to use UWB to enable mesh networks, which devices could automatically form whenever they are within range of one another. In mesh networks, each node can communicate peer-to-peer with the other nodes without having to use a hub, explained Wood. UWB mesh networks could function as wireless LANs.
A Tale of Two Approaches
The two primary UWB versions use very different technical approaches.
The UWB Forum, originally led by Freescale, has 220 members including international telecommunications vendors and service providers, universities, and wireless companies. Participants include Fujitsu, Johnson Controls, Siemens, and Vodafone.
The forum is now led by Pulse∼Link and supports the company's CWave binary-phase-shift-keying UWB technology. BPSK modulates a signal into two phases, representing the ones and zeros of binary data. This enables the signal to carry data.
Pulse∼Link's technology sends signals in continuous waves over the entire UWB band and assigns different codes to separate transmissions. Each transmission goes only to the receiver configured to accept signals with the appropriate code. This approach increases bandwidth by letting a single channel carry multiple transmissions simultaneously.
The technology uses chipsets with two or three radio chips: one to transmit and receive signals, an optional one to amplify incoming signals, and one to control the physical and media access control (MAC) layers, explained Watkins.
"We will combine them into one chip over time," he said, "but they were broken into [multiple] chips initially to reduce engineering risk and to speed time to market."
The UWB Forum is focusing on technology for television-centric, home-multimedia connectivity, eliminating the wires between home-entertainment devices such as TVs, set-top boxes, and DVD players, he noted.
The group is also targeting broadband radios in cell phones that have MP3 players so that users can easily upload and download large MP3 files, added Robert Eisses, the forum's marketing manager and also vice president of sales and marketing for vendor Icron Technologies.
High-definition multimedia content delivery requires quality-of-service guarantees to ensure clear images and uninterrupted service. Thus, Pulse∼Link's technology uses an isochronous MAC, which guarantees data delivery within set time constraints, thereby providing continuous, uninterrupted bandwidth.
In addition, CWave lets devices form their own networks, with one of the participating nodes acting as a controller.
The Intel-led WiMedia Alliance has 214 members, consisting of PC, consumer electronics, and cellular service providers and handset makers. Participants include Hewlett-Packard, Hitachi, Microsoft, Nokia, Panasonic, Sony, and Texas Instruments. The alliance is focused on using UWB for computer, consumer electronics, and mobile-phone connectivity.
ECMA International (also known as the European Computer Manufacturer's Association) has already adopted WiMedia as a standard, and the International Organization for Standardization and the European Telecommunications Standards Institute are in the process of doing the same.
WiMedia transmits data via high volumes of low-power electromagnetic pulses. The technology also uses multiband orthogonal frequency-division multiplexing (MBOFDM), which splits a signal into 14 500-MHz-wide bands, shown in Figure 1, and uses OFDM to increase bandwidth.
According to the WiMedia Alliance's Wood, having many bands provides flexibility and makes it easier for users to work only with specific narrow bands, if required by an application or a governmental regulation.
OFDM increases bandwidth by dividing a larger channel into multiple narrow channels, which can each simultaneously carry signals, explained Charles Razzell, a senior principal engineer with Philips Semiconductors. The channels are orthogonal to their neighbors and thus many of them can be packed close together without interfering with one another.
Developers designed WiMedia to work well with CMOS manufacturing processes and thus the necessary components can be integrated easily onto a single radio chip, noted Wood. "A single-chip solution is cheaper, consumes less power, and can be included in smaller devices," he said.
Users can change the chip's functionality, if required by government regulations or technical advances, via software updates.
WiMedia's MAC approach allows PCs, TVs, and other devices to form their own networks without a centralized controller. Consumer-electronics vendors lobbied for this capability, which enables their products to work together directly without the need for additional equipment, thereby enhancing their marketplace appeal.
Between 2003 and earlier this year, the IEEE tried to merge the UWB Forum's and the WiMedia Alliance's technologies into a single standard. However, the groups backing each major version never came close to agreeing on a compromise approach.
The two UWB versions are very different, which made it difficult to bring them together into one standard, noted Stan Bruederle, research vice president for wireless connectivity with Gartner Inc., a market research firm.
In addition, said the WiMedia Alliance's Wood, the IEEE began its standardization attempt after companies had already begun serious design work for chips based on one or the other UWB version. This made them less likely to support a compromise, he explained.
Two subsequent compromise proposals failed to garner consensus. Freescale wanted the IEEE to certify both major approaches and let manufacturers decide which technology they want to use. The UWB Forum proposed a specification that would have let devices support both technologies and use whichever is most appropriate for a given application.
Freescale's Cable Free
In April of this year, Freescale pulled out of the UWB Forum to start initiative promoting Cable Free, the company's ultrawideband version.
Freescale wanted to concentrate on developing a market-ready technology, while the UWB Forum and WiMedia Alliance are geared more toward developing specifications, contended Calvin Harrison, the company's UWB marketing manager.
Cable Free uses Direct-Sequence UWB. The technology works in one wide frequency band, giving it a large area over which to spread its signals, according to Matt Welborn, senior wireless architect for Freescale's UWB operations.
Cable Free also sends data as high volumes of low-power electromagnetic pulses. To increase bandwidth, the technology can handle multiple transmissions simultaneously within a single channel. It assigns different codes to each transmission passing through the channel to make sure each goes only to the proper recipient.
The technology offers a maximum data rate of 110 Mbps and a maximum range of 10 meters.
UWB Forum and WiMedia Alliance vendors are continuing to develop their technologies by, for example, making them faster. They are also demonstrating prototypes and applying for FCC approval for individual products.
Later this year, Wood said, WiMedia chips will ship to manufacturers and appear in devices.
The UWB Forum's technology will hit the marketplace during the next few months, predicted Kirsten West, principal analyst for West Technology Research Solutions, a wireless-market analysis firm.
Proponents of each approach are trying to get as many manufacturers as possible to use their technology to establish a strong marketplace position. Commercial success could turn one approach into a de facto standard, according to West.
WiMedia has the edge because the key proponents are important companies with considerable marketing resources, she stated. However, Wood said, both approaches will find success at least in some niche applications.
Explained Watkins, "They will coexist because we live in a market-driven, competitive economy that always has and always will enable a foothold for compelling, sufficiently differentiated products."
David Geer is a freelance technology writer based in Ashtabula, Ohio. Contact him at email@example.com.