Wireless Systems Design

UWB's Promises Hold Industry-Wide Appeal

As it works to prove that it won't interfere, this emerging technology is attracting many consumer and industrial applications.

Ultra Wideband (UWB) is one of the latest radio-frequency device technologies to hit the news. Yet a number of people are still unaware of what sets this technology apart. To send information through the air over short distances, UWB uses the low-power transmission of a high-speed pulsed radio signal. Because UWB pulses are very short or narrow, they result in a wide transmission bandwidth. As a result, UWB devices intend to operate using the RF spectrum that's presently occupied by existing radio services.

With the proliferation of wireless communication devices, the available RF spectrum is growing scarce. Ideally, UWB devices should allow more efficient utilization of the airwaves. Ultra Wideband is already catching the eyes of areas ranging from imaging radar to communications. The technology could spawn applications and devices that weren't even thought possible. If it lives up to its promises, it will bridge the gap between many industry and technology segments. Within the next year, expect UWB technology to show up in laptop computers and cellular telephones for high-speed data transmission. It also will emerge in short-range radar-imaging devices.

When it comes to interference, however, this much-celebrated technology seems to have caused some debate along the way. Last year, an article printed in a popular magazine explained how a UWB device was mock-tested by NASA in a Boeing 737. The testing was prompted by concern over UWB transmitting over all bands, including aeronautical frequencies. According to the test results, key cockpit safety devices were "knocked out from virtually every seat in the plane." Admittedly, the levels that were transmitted were higher than the levels permitted by the FCC for consumer devices. Yet the results were enough to convince United Airlines to require additional testing.

Other interested parties, however, take different stances on UWB. The U.S. Congress, for example, feels that the technology could be hindered because the power levels permitted by the FCC are too low. Extensive independent testing also has been done to determine the effect of UWB transmissions on GPS receivers, PCS communications, amateur radio, and government radio services. Some testing did show potential interference. From the results, however, the FCC concluded that interference from UWB devices to these services is unlikely.

For its part, the FCC has clearly stated that it is taking cautious steps regarding UWB technology. Currently, few production UWB devices are available for study. It is therefore difficult to determine UWB's impact on other radio services. In addition, the new standards that were adopted by the FCC are largely based on standards from the National Telecommunications and Information Administration (NTIA). The NTIA created those standards because it believes that they're needed to protect vital federal government operations against interference.

To address new issues and the operation of additional types of UWB devices, the FCC intends to review the standards. On April 22, 2002, the commission released ET Docket 98-153. It amends Part 15 of the FCC rules, thereby permitting the marketing and operation of certain types of UWB technology. It also establishes different technical standards and operating restrictions for three types of UWB devices: imaging systems, vehicular radar systems, and communications and measurement systems. They were categorized according to their potential to cause interference.

UWB devices operate in frequency bands that are allocated to both U.S. government and non-government operations. The FCC regulates non-government operations. Government operations are regulated by the NTIA. As stated, the regulations adopted by the FCC for imaging systems are largely based on the NTIA standards. Imaging systems also are restricted for use by certain parties, such as law enforcement and fire and rescue.

Imaging systems include the following technologies:

  • Ground-penetrating-radar (GPR) systems are allowed to operate below 960 MHz or in the frequency band from 3.1 to 10.6 GHz (FIG. 1). They may only operate when in contact with or in close proximity to the ground for the purpose of detecting or obtaining images of buried objects. The energy from the GPR must be directed down into the ground. Operation is restricted to law-enforcement agencies, fire and rescue organizations, scientific-research institutions, commercial mining companies, and construction companies.
  • Wall-imaging systems are generally used to detect images within a wall. They can only be operated below 960 MHz or in the frequency band from 3.1 to 10.6 GHz (FIG. 1). Operation is restricted to law-enforcement agencies and fire and rescue organizations. Surveillance systems also may be operated by public utilities and industrial entities.
  • Through-wall imaging systems are utilized to detect objects or persons on the other side of a wall or structure. They must be operated below 960 MHz or in the band of 1.99 to 10.6 GHz (FIG. 2). Operation is restricted to law-enforcement and fire and rescue organizations.
  • Surveillance-system devices generate a stationary RF perimeter field. The intrusion of persons or objects can then be detected within the field. Operation is restricted to law enforcement, fire and rescue organizations, public utilities, and industrial parties. The devices aren't really considered imaging systems. For regulatory purposes, however, the FCC opted to treat them the same as through-wall imaging systems. It permits operation in the 1.99-to-10.6-GHz frequency band (FIG. 2).
  • Medical imaging systems can be used for medical scans inside a person or an animal. The systems are allowed to operate in the band from 3.1 to 10.6 GHz (FIG. 1). They must be used in accordance with the direction or supervision of a licensed healthcare practitioner.
  • Communications and measurement systems include a variety of UWB applications, such as high-speed networking and storage-tank measurements. These devices must operate in the 3.1-to-10.6-GHz frequency band. They are subject to other frequency and power limitations as defined in Part 15 of the FCC Rules (FIG. 3 and FIG. 4). Handheld devices are allowed for peer-to-peer operation and other short-range, high-speed data transmission. Otherwise, indoor-only operation must be ensured by design.

    Handheld devices can only transmit when they're in communication with an associated receiver. The transmission must cease within 10 sec. unless it receives acknowledgement from the associated receiver. That acknowledgement will continue during the transmission at 10-sec. intervals. The limits are even more stringent for handheld devices that can be used outdoors.

  • Vehicular radar systems operate in the 24-GHz frequency band. Their bandwidth is 22 to 29 GHz. The center frequency and the frequency at which the highest radiated emission occurs must be over 24.075 GHz (FIG. 5). These systems are used in terrestrial transportation vehicles to detect the location and movement of nearby objects. Using directional antennas, they enable features like collision avoidance; improved airbag activation; and suspension systems that better respond to road conditions.

As long as they operate within their permitted frequency bands, the regulations for UWB devices call for operation at the levels specified in CFR FCC Part 15.209. The limits for imaging systems operating above 960 MHz vary with the type and frequency range of device operation. In addition, some imaging systems can only be operated by parties that are eligible for licensing under the provisions of Part 90 of the FCC rules. Others require government coordination for operation.

Each rule section has a table. That table lists the emission limits that pertain to specific UWB applications. The UWB device must comply with all applicable limits for all frequency bands associated with the device (see table).

In the United States and worldwide, Ultra Wideband technology will become a significant factor in the future of communications. This technology can lead to advances in safety and rescue operations and medical imaging. It also could enable broadband communications to devices in our homes and offices. However, the impact of UWB communications on existing communications infrastructure is still unknown. For this reason, the FCC has approached the UWB technology cautiously. It has imposed what some believe to be overly stringent regulations.

The FCC understands that UWB technology will be used globally. Throughout the world, other countries will impose their own, possibly less stringent regulations. Because it understands the urgency in releasing this new technology, the FCC will initiate further review with public input within the year. Hopefully, a heightened review will provide information on the effects that UWB will have on current communications technologies. Then, the industry will know whether the FCC regulations can be relaxed or stand as written.

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