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The regulatory process for making UWB systems commercially available has taken a long road inside and outside the United States. Started in 1998, the U.S. regulatory process for UWB was completed in 2002, allowing UWB transmission in the 3.1 GHz to 10.6 GHz range. Subsequent updates followed, including a clarification that allowed multiband orthogonal frequency-division multiplexing technology to operate at normal operating power levels. This decision was the result of a series of interference studies provided by proponents and critics. Both factions supplied the data required by the Federal Communications Commission (FCC) to issue a set of rules to encourage technology innovation and protect the incumbent systems from interference.

Today, the worldwide regulatory process is still under way. International regulatory bodies continue discussions and interference studies to determine the best rules for meeting the requirements in their geographic regions. One of the differences is that many countries have allocated spectrum for fixed services/WiMAX systems in the 3.4 GHz to 3.8 GHz region. Since these fixed services/WiMAX systems can be placed in close proximity to UWB-enabled devices, there is a potential interference concern. Some studies show that UWB emission at the FCC levels of -41.3 dBm/MHz has the potential to create interference to those services in this part of the spectrum.

In an effort to harmonize the spectrum, while not posing interference to these fixed services/WiMAX systems operating in the 3.4 GHz to 3.8 GHz range, the concept of ‘detect and avoid’ (DAA) was proposed. This concept mandates UWB devices to reduce the level of emission in that band when they detect a nearby narrowband system. It has been promoted in Japan, Korea and Europe as a possible solution to allow existing and future services to share the spectrum below 5 GHz with UWB devices. In order to support the application requirements and future evolution, UWB systems require spectrum below 5 GHz and above 6 GHz. Products operating in the spectrum below 5 GHz will enter the U.S. market first. Products operating above 6 GHz will be introduced shortly thereafter in other geographic regions.

Japan is the only country outside the United States to issue spectrum regulations for UWB devices. An important part of the regulations is the immediate allocation of the 4.2 GHz to 4.8 GHz band that doesn't require DAA for a period of time (until Dec. 31, 2008 in Japan). Other parts of the spectrum that require DAA will be opened after the mechanism is defined. As shown in the figure, the Japanese mask differs from the European mask in two ways:

1. DAA may be required for all frequencies below 5 GHz starting in January of 2009 while Europe is considering allowing transmission-without DAA until 2010-2012.

2. The lower limit for the band above 5 GHz starts at 7.25 GHz rather than 6 GHz. This lower limit will make it difficult to develop a single harmonized radio able to operate worldwide.

The regulations for DAA are still being defined and must be proven to work before regulators will adopt them. Other geographies are in the process of regulating UWB, including Canada, Korea and China. From a UWB industry perspective, a common harmonized spectrum would enable multidevice interoperability in any geography and increase the adoption rate of the technology. Regardless, it is becoming apparent that most major geographies will have some spectrum opened up in 2007 to allow for the introduction of UWB on a worldwide basis.

Roberto Aiello is the founder and chief technical officer at Staccato Communications. Jeff Foerster is an engineer with Intel Architecture Labs at Intel Corporation.