When the FCC gave its blessing to unlicensed ultrawideband, or UWB, technology in 2002, it envisioned myriad potential uses, ranging from short-range high-speed data transmissions suitable for broadband access to the Internet to radar imaging of objects buried under the ground or behind walls. It also recognized how UWB would benefit police, fire and rescue personnel to enable covert, secure communications.

Yet, two years later, UWB technology stakeholders are deadlocked within the Institute of Electrical and Electronics Engineers' (IEEE) standards-setting process, unable to reach a consensus on a single standard. The outcome is of consequence to the public-safety wireless industry. Commercial acceptance has a direct correlation to the technology's cost-effective potential in the public-safety sector.

“Public safety will benefit from the commercialization of UWB chips driving innovations in the consumer market and then translating into public-safety applications,” said Gary Grube, corporate vice president and chief technology officer of Motorola's commercial, government and industrial solutions segment. “The commercial sector is where the volume is, and it will make a nice, attractive add-on to public-safety communications when that happens.”

Computer- and electronics-industry heavyweights such as Intel, Toshiba and Sony are anxious to see UWB replace almost every data cable in the consumer's home, revolutionizing home media networking by assuming such tasks as distributing HDTV signals from a receiver to multiple television sets and connecting printers to computers.

This is possible through the technology's promise of delivering data at speeds of almost a gigabit per second or at least a guaranteed speed of 100 Mb/s by using a wide frequency range at very low power-10 millionth of a watt per megahertz of occupied bandwidth. Fearing interference with other wireless devices such as public-safety radios and global positioning system receivers, the FCC set some strict limitations on the amount of power that can be generated by this technology. UWB signals must occupy at least 500 MHz of bandwidth in the 7.5 GHz band of spectrum between 3.1 GHz and 10.6 GHz, spectrum already occupied by existing radio services. Because UWB systems transmit low-power streams of short pulses in a large swath of spectrum, their energy is spread over a large amount of spectrum, and the signal can penetrate crowded and noisy radio environments, which translates into a higher quality of service without signal fading.

“UWB brings to the picture the ability to do a couple of different things. One, provide horrendously high data rates over short distances, like gigabits per second, or providing the ability to instead run megabits and get substantially more range,” said John Adams, director of radio technology and strategy with Free-scale Semiconductor, Motorola's chip spinoff.

Gigabit speeds can be accomplished within 10 meters, but turning down the data rates to even 500 Mb/s can increase the range to almost 50 meters, said Adams. And the IEEE is planning to create specifications for mesh networking to extend the range even further via peer-to-peer networking. Artimi, a fabless semiconductor company developing silicon solutions for UWB technology, says its first products will contain a native mesh-networking capability.

UWB technology's characteristics bode well for the public-safety community.

“We've shown in the lab that you can get radar distancing accuracy within inches,” said Motorola's Grube. That characteristic translates into a whole new level of visibility for first responders such as fire-safety personnel.

UWB radios connected to tiny cameras mounted on firefighters' helmets could transmit images back to a vehicle sitting at the fire site and immediately identify the location of any firefighter within a burning building because signals can penetrate through walls, said Tom Cooper, senior vice president of marketing for Artimi. Location is determined by sharing range information with a network of transceivers.

Grube envisions embedded UWB devices inside hand-held trunked radios that will be capable of sending data, pictures and video as well as enabling voice-over-IP communications.

“If UWB can start to take off, allowing us to drive down the overall cost of deployment, then I think you'll see something like an APCO standard come forward and take advantage of the volume out there instead of developing something new,” said Adams. “Public safety can be equipped with the technology they need to have without having to pay $50,000 per fireman.”

Aether Wire & Location has already developed small, low-power transceivers capable of providing position location. The company recently won a contract with the Marine Corps to provide an ad hoc UWB network consisting of several pager-sized units and software that runs on a laptop to pinpoint the location of the units, which is useful for covert operations. Aether Wire & Location President Patrick Houghton said the coverage of such a network can extend kilometers with a node-to-node range of 130 meters.

“The current device is not a single-chip solution yet, but it's going to get to a lower cost,” said Houghton, who also said the company is less focused on high-speed data communications via UWB technology. “Our view is that here is something you can't do with any other type of existing radio. You can get location outside with GPS, but inside, it disappears.”

Aether Wire & Location has approached homeland security officials, the Federal Emergency Management Agency, the U.S. Department of Justice and local police and firefighters with the solution. For first responders, the issue is one of funding, said Houghton.

The standards conundrum

UWB technology has sat in a black hole of sorts with the IEEE for nearly a year, locked in a debate over which of two technologies should become the 802.15.3a standard.

On one side, Intel is one of more than 170 computer and electronics manufacturers comprising the Multi-band OFDM Alliance that favor orthogonal frequency division multiplexing (OFDM), which carves a UWB signal into several chunks. The benefit, say the technology's backers, is an increase in range and less interference because the chunks causing static can be controlled.

The other camp, known as the UWB Forum, is led by Motorola and Freescale and includes some 60 start-up companies. This group endorses direct sequence (DS)-CDMA technology, which sends out a continuous stream of data and already has been used by the U.S. military. DS-CDMA also has the backing from the International Tele-communication Union. Proponents of DS-CDMA claim the technology uses less power than OFDM and tout the technology's head start. Freescale recently announced FCC certification of its first UWB DS-CDMA chip. Artimi, which claims to be neutral in the entire debate, will introduce its first chips based on DS because of the maturity of the technology. Other generations of chips will incorporate OFDM, said Cooper.

“[DS-CDMA is] better known and has been used by the military for so long,” said Cooper. “It ought to contain less core memory and processing power and, therefore, get out the door quicker. That's what we've discovered in our work.”

Still, with the Multiband OFDM Alliance supporting more members, many believe the vote would swing its way. Yet, neither technology camp has been able to win the 75% of the IEEE votes needed to ratify the standard. During the first four meetings, OFDM won initial votes by 60% to 40%. At the next meeting DS-CDMA won the initial vote by 50.3% to 49.7%, and there wasn't a consensus at the meeting last month.

“Both technologies are well understood in the marketplace,” said Robert Sanchez, vice president of technology and wireless lab technology director for inCode, a wireless communications consultancy firm in San Diego. “This has become an economic decision. This is all purely intellectual property behind it.”

Sanchez said the debate ultimately could become a Betamax vs. VHS situation, where economies of scale win.

And while the UWB market stalls, public-safety agencies are proceeding with plans for high-speed wireless data deployments in the 4.9 GHz band.

“Public safety will be happy with the speeds in 4.9 GHz for many years,” noted Motorola's Grube. Motorola and Mesh-Networks recently agreed to work to-gether to provide an ad hoc mobile broadband networking solution that also includes position-location solutions.

However, 4.9 GHz deployments and UWB could complement each other because UWB transmits signals better within a multipath environment, said Freescale's Adams.

“We might find 4.9 doing some of the backhaul and overall support, but UWB functionality could end up driving the real worker-to-worker communications because it's a lot stronger when you get into a difficult environment.”

Interference still a concern with UWB signals

Despite placing stringent power limitations on ultrawideband signals, the FCC remains concerned about potential interference with commercial wireless systems, global positioning system receivers and public-safety communications.

“The FCC is still suspicious of the potential interference and appropriately so. It's a new thing for the wireless industry,” said Gary Grube, corporate vice president and chief technology officer for Motorola's commercial, government and industrial solutions segment. “The FCC has, of course, appropriately put together a mask designed to minimize energy of a UWB transmitter, but it really hasn't been used in practice, and the technology is now being developed.”

Freescale Semiconductor, the chipmaker spun off from Motorola, announced a collaboration agreement with the National Telecommunications and Information Administration's (NTIA) testing labs to help determine whether UWB poses a significant interference risk. The study will look at the interference potential of both competing UWB standard proposals — OFDM and direct sequence-CDMA, the proposal supported by Freescale. The project will be conducted in four phases to address the following topics: UWB signal generation, how to develop measurement methods on emission, how it affects a receiver's actual measurements of emissions characteristics, and how digital and analog downlink receivers react to interference.

As for potential interference from incompatible UWB radios in the same market, the topic has yet to be addressed among the UWB factions battling for supremacy on the standards front. However, UWB start-up Pulse Link proposes a spectrum-allocation scheme that assigns times slots to UWB equipment. The company claims a common signaling mode would ensure that multiple incompatible UWB systems could operate in the same physical space.
— Lynnette Luna

Could OFDM be the world standard?

Developed more than 40 years ago and first used in broadcast television stations in Europe, orthogonal frequency division multiplexing, or OFDM, technology could eventually emerge as the dominant world standard for high-speed wireless data transmission.

The name of the game is continually increasing data transmission speeds. OFDM promises high spectral efficiency, resiliency to radio-frequency interference and high data speeds because a radio signal is split into several narrowband channels at different frequencies.

OFDM is already transforming fixed wireless standards, moving 802.11-based technologies from practical speeds of 11 Mb/s to real-world transmission speeds of 50 Mb/s and beyond in standards such as 802.11a or 802.11g. The technology also is the basis for the emerging metro-area fixed wireless technology known as WiMAX, or 802.16a Revision D, which is expected to attract a variety of telecom players globally by extending the reach of DSL and cable, offering broadband competition to wireline services and even serving as a complement to mobile technologies. And vendor Flarion is pushing its own flavor, known as flash-OFDM, into the mobile environment. The company, in conjunction with Motorola, is building a high-speed wireless data broadband network for the District of Columbia (see story on page 46.

Motorola, a major advocate of OFDM technology, is developing a specialized version for the public-safety 4.9 GHz band that accommodates the limited amount of spectrum located in the band, said Gary Grube, corporate vice president and chief technology officer for Motorola's commercial, government and industrial solutions segment.

Only 50 MHz of spectrum is available in the band compared with 600 MHz in the unlicensed band. That leaves public safety vulnerable to interference if it uses off-the-shelf 802.11 equipment, according to Motorola, but several public-safety officials and vendors in the unlicensed space have claimed the tighter mask Motorola has proposed for the band is unnecessary.
— Lynnette Luna

Fast access to spectrum through secondary markets

At a time when little or no spectrum for some uses is being auctioned, the ability for wireless operators to lease frequencies from existing spectral holders is giving new players access to licensed spectrum while providing incumbents a new way to make a return on their investments in airwaves.

Since February, when the FCC spectrum leasing policy became effective, “over 60” leasing deals have been reached, according to FCC spokesperson Lauren Patrich. “It's going to take some time to find [spectrum leasing's] level, but people like the flexibility and the streamlined process,” she said.

Jonathan V. Cohen, a partner of the Wilkinson Barker Knauer law practice, agreed. “The FCC is clearly interested in getting people access to spectrum. Leasing is an easier way to do this with less regulatory delay,” he said. “The latest order demonstrates the Commission's desire to use all avenues to promote new technology to access spectrum as quickly as possible.” Cohen noted it has taken the FCC several years of proceedings to get to this point. “A lot of people in the business world are looking at this as another tool in the toolbox to access spectrum.”

Two options exist for leasing spectrum usage. A licensee can become a spectrum manager, retaining both legal and de facto control over the spectrum and lease usage of spectrum to other parties; or a licensee can transfer de facto control of a spectrum license for a period of time to another party.

In September, the FCC released another notice of proposed rulemaking to expand its spectrum-leasing policy. The agency will provide immediate processing for certain types of qualifying spectrum lease arrangements and immediate processing procedures for qualifying license assignments and transfer transactions. Parties that want to engage in leasing spectrum can now “get overnight processing for a plain vanilla transaction,” said Patrich. Now, a variety of spectrum holders are testing the waters for leasing. “It's been spread around [among all spectrum holders], not just the PCS companies,” said Patrich.

There are several ways to arrange a spectrum lease, ranging from directly approaching a spectrum holder or dedicated spectrum band manager to seeking out a spectrum broker. A spectrum holder is the party that is assigned the licenses by the FCC; they have legal and practical control of the spectrum. A spectrum band manager is explicitly leasing out the spectrum that's been assigned to them by the FCC. And a spectrum broker is an entity that connects people who have spectrum with people who need spectrum.

Spectrum band manager First Avenue Networks has about 30 customers leasing spectrum in the 24 and 39 GHz fixed wireless bands. “We're leasing to ISPs, WISPs and cellular carriers,” said Dean Johnson, president of First Avenue Networks. “Cellular carriers want to replace their terrestrial networks for backhaul.” First Avenue bought the assets of Advanced Radio Telecommunication out of bankruptcy in 2002 and is in the process of acquiring the licenses of former wireless phone carrier Teligent.

Some are reluctant to call current spectrum leasing policy a complete success. “A lot of firms have shied away from doing secondary spectrum licensing,” said Carri Bennet, managing partner and principal at Bennet & Bennet, a Washington law firm specializing in rural telecommunications issues. “Without bankruptcy protection, it's very scary. Firms could end up building out an entire network, and if the company holding spectrum goes bankrupt, you'd be stuck,” she said, citing WinStar Communication's recent business difficulties as an example. “There's no protection for firms leasing spectrum if the spectrum holder loses its license. The FCC needs to deal with bankruptcy protection.” Cohen dismissed concerns over bankruptcy. “It's no different than any other business,” he said,.

The FCC also would like to ratify rules enabling “dynamic” leasing arrangements, in which a smart radio using advanced technologies could use a licensed band and “jump in” when spectrum is available. The FCC also took the opportunity in the recent report to define a “private commons” concept allowing licensees to make spectrum available for use to individual users or groups of users outside the traditional options for spectrum leasing in a model similar to the existing use of 2.4 GHz and 5 GHz unlicensed bands.