Wireless interference: An inconvenient truth for MBANs



What do you get when you install wireless networking of body transmitters used for capturing a wide range of physiological data in healthcare facilities? Medical Body Area Networks (MBANs) with the potential for interference, both from legacy wireless networks and neighboring MBANs, that can disrupt hospital operations and adversely impact patient safety.

Last year, the Federal Communications Commission unanimously voted to allocate 40 megahertz of spectrum in the 2360-2400 MHz band for MBANs and in September posted its final rules. In allocating airwaves for these wireless networks, the FCC believes body-worn medical sensors can help cut healthcare costs and improve patient care by increasing patient monitoring and physically untethering a "messy jumble" of cables, replacing them with short-length radio waves. 

"The only cost resulting from these new regulations is the risk of increased interference, and we have minimized that risk by adopting rules that permit an MBAN device to operate only over relatively short distances and as part of a low power networked system," states the FCC's report and order. "This approach will permit us to provide frequencies where an MBAN can co-exist with existing spectrum users and engage in robust frequency re-use, which will result in greater spectral efficiency." 

Though the FCC acknowledges that the potential for signal interference exists, the agency has said the benefits "greatly outweigh" the risks. However, I'm not convinced that the FCC has mitigated the transmission interference risks posed by hundreds of wireless sensors transmitting data around a hospital, particularly high-density settings such as waiting rooms, elevator lobbies and preparatory areas, as well as from Wi-Fi and other high-powered devices. After all, the upper end of the allocated MBAN spectrum band sits adjacent to that used by Wi-Fi, wireless local area network devices and industrial, scientific and medical (ISM) equipment.

The most widely used ISM band is already filled with many cross-technology interference sources, including WiFi, Bluetooth devices, and appliances such as microwave ovens, cordless phones, baby monitors, and garage doors, according to a 2013 paper

In addition, one can't help but be skeptical that the allocated spectrum will prevent transmission interference and support the coexistence of multiple and competitive MBAN networks. "Today, I don't think that your average community hospital would have a very good grasp on, for instance, what the interference issues would be if they had two or three MBANs and lots of other wireless things going on,"  Matthew Quinn, the FCC's Director of Health Care Initiatives, admitted in a recent interview with FierceMobileHealthcare.

A 2012 paper analyzing MBAN interference asserts that unlike cellular networks, MBANs are randomly distributed networks where two or more MBANs may overlap and interfere with each other due to the limited available frequency bands. "Severe interference will decrease the [Signal to Interference plus Noise Ratio] dramatically and as a result cause throughput degradation and packet loss," states the paper. 

While it's admirable that the U.S. is the first country in the world to dedicate spectrum for MBANs, there remain serious concerns that the increasing use of wireless, radio-frequency (RF) wireless medical devices and other wireless systems operating nearby will interfere with each other. If interference and spectrum congestion were to occur, data packets transmitted by medical devices could be delayed or blocked, potentially interfering with timely transmissions of critical patient data. 

Complicating matters is the fact that the FCC has yet to name, let alone develop the criteria for selecting, a frequency coordinator to remove or mitigate RF interference between MBANs and other wireless systems which utilize the same operational frequency. If MBANs are to realize the agency's vision for enhanced patient safety and increased patient mobility, the FCC must address these outstanding issues. - Greg (@Slabodkin)  

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