White spaces could affect medical telemetry devices

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Next year, when cable converts to a digital signal, wireless frequencies called white spaces will be up for grabs and hospitals using remote patient monitoring through radio frequency could be impacted if other devices using the unlicensed white space generate signals that could interfere with medical telemetry devices.

The Federal Communications Commission (FCC) in 2000 allocated spectrum and established rules for a Wireless Medical Telemetry Service (WTMS) that allows potentially life-critical equipment to operate on an interference-protected basis, according to the American Society of Healthcare Engineers. Medical telemetry devices operate on channel 37 of the white space spectrum.

The white space channels were originally designed to prevent radio waves from adjoining channels from bleeding into each other. As the United States moves toward digital television conversion, technology companies and TV broadcasters are fighting over the remote, with different ideas on what to do with the unused airwaves.

Tim Kottak, engineering general manager for System and Wireless, GE Healthcare, however, told Health Imaging News that there are healthcare implications if the white spaces adjacent to the WMTS spectrum were left unprotected.

“From our perspective the current proposed FCC rule making is not adequate to protect patients in hospitals around the country and we endeavor to educate the industry on the effects it could have on patient safety,” Kottak said. “With the digital conversion in 2009 and without changes to the existing rule, there is a risk of interference and a threat to patient safety.”

The crux of the problem lies in the channels bordering channel 37, which is dedicated to healthcare, he said. If there is a really strong device using channel 36, the power could bleed over and interfere with medical telemetry devices.

“We are talking about stronger devices that work in this spectrum, thousands of times more powerful which could interfere with monitoring,” Kottak said.

To prevent this from happening, GE has recommended to the FCC that channel 36 and 38 be established as guard bands and not be used so that spurious emissions cannot bleed over into channel 37.

Problems with interferences on medical telemetry from TV broadcasting were why the protected spectrum was established. For example, a hospital in Texas had its medical telemetry system go down when a local TV station went live—the TV station was broadcasting with a signal that was strong enough to interfere with the hospital’s remote patient monitoring system.

Kottak said that there is still older equipment used today that on different channels than channel 37. Medical telemetry devices are the only unlicensed product allowed to operate in these broadcast channels. A second risk is that facilities using these older devices might be affected if commercial devices are allowed to operate in the white spaces—even outside of channel 37.

Kottak said GE has recommended to the FCC to grant a one-year extension for channels 33-35 to give hospitals using older equipment that operates on those channels another year to migrate systems into channel 37.

For newer telemetry devices, the channel 37 issue is simply an adjacent channel power concern, however, with older devices it would be flat out interference, Kottak said.