Medical technology firms are asking the Federal Communications Commission to finalize a proposed rule that would allocate prime radiofrequency spectrum for non-exclusive use by wireless patient monitoring networks.

At the request of GE Healthcare, FCC proposed in June that up to 40MHz in the 2360-2400 MHz band be allotted for operating the monitoring technology, which is still in development (¹ Also see "GE Healthcare Seeks Spectrum For Wireless Patient Monitoring Networks" - Medtech Insight, 14 September, 2009.).

According to GE, small, wireless body sensors could be designed to collect a series of vital signs and send them to a medical body area network (MBAN) receiver at the patient's bedside.

In recent comments to FCC on its proposal, GE writes that the commission's rulemaking could be a "major step in fostering revolutionary advances in patient monitoring and health care delivery ... thereby making an important contribution to health care reform."

GE-competitor Philips Healthcare Systems agrees. "Allocating the requested spectrum for MBAN devices will foster production of low cost sensors" that will alert health care providers earlier to changes in a patient's condition, Philips writes.

But the GE request is at odds with aerospace interests, which argue that spectrum sharing could cause radiofrequency interference to aeronautical mobile telemetry (AMT) stations, which monitor test flights using signals in the same spectrum.

Groups such as the Aerospace and Flight Test Radio Coordinating Council say the interference could jeopardize the lives of test pilots and compromise the quality of data gathered in military and commercial aircraft test flights.

"The notion of these two life-critical, but unlike, applications sharing spectrum is fraught with problems for the commission licensees and the public," AFTRCC writes. AFTRCC's corporate members include Boeing, Northrop Grumman and Lockheed Martin.

Medical technology firms counter that there are ways to mitigate interference and that by having access to a full 40MHz of spectrum, it would be easier to create protocols allowing an MBAN device to hop to another frequency channel if interference by the primary user of the spectrum was detected.

Exclusion Zone Enforceability Questioned

One way to minimize interference between medical and aerospace applications of the spectrum is to create geographic exclusion zones protecting existing AMT sites from interference by hospitals that adopt MBAN technology.

But the industries disagree on how large the exclusion zones would need to be to fully protect the technologies from interference.

AFTRCC views exclusion zones as impractical, arguing that zones large enough to ensure against interference would eliminate entire metropolitan areas such as Los Angeles; Wichita, Kansas; Seattle and St. Louis.

Medical device firms argue that the group is using worst-case scenarios rather than probability in recommending the scale of the exclusion zones that would be needed.

GE states that only 2.4% of hospital sites in the U.S. are located within 9.7 km of an AMT site, pointing out that hospitals are more likely to be located in densely populated areas, whereas test flight sites are often in very remote locations.

"By any objective measure, the 2360-2400 MHz band is extremely sparsely utilized in geography, frequency and time," GE writes.

"It is simply not in the public interest for this much spectrum to be left lying fallow in the majority of the U.S. at any given time, when a compelling, compatible and socially productive potential new use such as MBAN exists," GE adds.

Medtech firms propose that hospitals within exclusion zones be allowed to utilize a narrower, 10MHz band of spectrum for MBANs within 2390-2400 MHz. But the aerospace industry fears it would be difficult to enforce this restriction.

AFTRC envisions that device vendors would put pressure on their sales reps to "sell MBANs units with the widest possible spectrum flexibility. It is unrealistic to expect that these devices will be confined to use outside exclusion zones, or 2390-2400 MHz within exclusion zones."

While there is much debate over the structure of exclusion zones for existing AMT sites, there is also uncertainty about how to monitor the use of MBANs once new AMT sites come into play.

AdvaMed, which also submitted comments, proposes that hospitals registered for the 2360-2390 MHz band be protected from automatic placement in exclusion zones when new AMT sites are installed.

"We expect to use a coordination process based on the site-specific AMT frequency usage to develop appropriate exclusion criteria for the sites," AdvaMed says.

Philips says a hospital that has deployed MBAN devices would be informed through a coordinator if a new AMT site is established later, and would be "subject to the same restrictions as if it always had been within an AMT exclusion zone."

MedTech Discounts Feasibility Of Other Spectrums

FCC generally supports GE's spectrum request in its proposal, but the commission also suggests alternate bands. The device industry continues to press specifically for 40MHz in 2360-2400 MHz range.

Some of the other bands emit too much noise to be practical for medical devices, and others have applications likely to compete for bandwidth in a hospital setting, such as those used in Wi-Fi devices carried by doctors, patients or visitors, GE says.

Other bands require too much power to operate, which would lead to shorter battery life for the body sensors, the company argues.

Also, the 2360-2400 MHz range allows device makers to design MBANs with off-the-shelf electronic chips requiring little modification, something not possible in some of the alternative bands.

"The need for chip vendors to create new silicon is a significant barrier that would, at a minimum, increase MBAN costs and introduce significant development delays," GE writes.

- Monica Hogan ( ² m.hogan@elsevier.com )

Industry Urges FCC To OK Spectrum Sharing For Medical Body Area Networks

More from Archive

More from Medtech Insight