Stephen Berger: Here’s How Hospitals Can Prepare for Crucial Spectrum Change

The decision this past summer by the Federal Communications Commission (FCC) to allow TV White Space (TVWS) devices to share Channel 37 with Wireless Medical Telemetry Service (WMTS) systems changes the spectrum environment in an important way. Hospitals and other healthcare organizations have a three-to-five-year planning horizon to prepare for this change. While that may sound like a lot of time, as we all know time passes quickly. If a WMTS system needs significant redesign, it’s crucial to understand the implications of the FCC ruling now so that the needed changes can be made before there are problems. (It’s important to note that there are two other WMTS spectrum bands, at 1.4 GHz, and those WMTS systems are unaffected by the FCC decision.)

Running a coexistence test following the standard ANSI C63.27 will give organizations the information they need for their planning. A coexistence test helps to determine the sensitivity of a WMTS system to TVWS transmissions and also to digital television (DTV) and other WMTS systems that may be nearby. The result of the test will be a set of desired‑to‑undesired (D/U) signal ratios. There will be a D/U ratio for co‑channel transmissions and other D/U ratios for adjacent channel transmissions.

D/U ratios are then translated into threat distances. What is the greatest distance and therefore lowest intended signal level expected of a WMTS device? It is not advisable to operate any device at the absolute maximum range because other factors will result in erratic signal reception when the intended signal is very weak. A shorter, maximum recommended operating distance is needed to ensure reliable operation. From the maximum recommended operating distance, the D/U ratio will tell you how close a TVWS devices can come before it will cause a problem.

The new FCC rules require that TVWS devices stay 380 meters away from WMTS systems. If the threat distance is less than that, the risk of interference is greatly reduced, but not entirely eliminated. There is still the chance that a TVWS device might violate the FCC rules. WMTS systems should have a defense-in-depth risk management plan. There should be more than one layer of protection. Healthcare organizations will want to make sure that their WMTS systems provide additional layers of protection and ensure safe, reliable operation.

Stephen Berger is president of TEM Consulting. He also served on AAMI’s Wireless Strategy Task Force and is co-chair of the AAMI Wireless Eoexistence Work Group.

5 thoughts on “Stephen Berger: Here’s How Hospitals Can Prepare for Crucial Spectrum Change

  1. In my humble opinion, I think it is irresponsible of the FCC to allow this: forcing a field to react in an area that it should not have to react. The HTM and IT have enough to handle with in the area system integration problems. I believe that HIPAA will come into the picture before long if there is interference between WMTS system and TVWS transmissions. These 2 systems should not be allowed. What happens when you try to tune to a week radio signal from an analog dial, the stronger adjacent frequencies override. Yes, the interference went away when analog phones went digital.
    And the idea of registered and unregistered in this time of pirating and hackers.
    I would be glad to be told I was wrong when proven that I’m wrong. I have been in this field too long. My question is, does the FCC know all the requirements of HIPAA?

    • I am not sure I fully follow your comment, so feel free to educate me if I misunderstand you. By bringing in HIPAA I understand that you are introducing concerns about security and privacy. Those are indeed valid concerns, but they raise a fundamental question about WMTS systems. Modern communication systems are protected by robust encryption and authentication processes. Further, a variety of methods are routinely used to improve communications reliability. If the very limited introduction of TVWS that the FCC has allows is a problem it perhaps indicates that WMTS systems are badly out of date technologically. If that proves to be the case, then the FCC action may force WMTS to move to more current technology and thus provide a real benefit to heath care delivery. In other areas I have observed a tendency at times to protect poor engineering behind the nobility of the service. Important services such as heathcare should, and I am sure for the majority of us, do call for the continuing pursuit of excellence in engineering. Security, privacy, and reliability are routinely addressed in modern communication systems and should be no problem to address here.

  2. One of the allies the hospital industry can enlist in this is the American Radio Relay League, At the local level, a radio club or chapter can be contacted to track down a interfering signal source that may pop up in the spectrum and help the hospital get the offending transmitter shut down. Radio clubs love this type of challenge and refer to this activity as a “foxhunt.” I would highly encourage biomeds who take care of telemetry systems to get their technician class radio license and make friends with the local radio club. I wish I had got my radio license years ago. And I recommend it to any biomed. If you are studying for the CBET and need to study electronics, taking the radio license exam is a great fun way to do so:

    Give it a try – J Scot Mackeil CBET KC1CZX – (General class Amateur radio operator)

    • Scot,

      Great comment and let me extend it a bit. ARRL is a wonderful organization and a very useful source of help and information.

      With the way wireless is developing these days, it is increasingly important to have tools that work at multiple layers of the OSI stack and not just look at the physical RF level. Pretty much everything that transmits—Wi-Fi, Bluetooth and TVWS—will have unique MAC identifiers. If your tools allow you to decode the transmitted packets, you can get the MAC address. This is a lot like getting the license plate of the car that speeds through your kids school zone every afternoon. It is one thing to tell the police a car speeds through every afternoon, endangering your kids. It is far better if you can add the license plate number.

      The tools to grab packets and decode MAC addresses are increasingly available. You can get $20 USB SDR dongles with amazing capabilities. Put that with the software in GNU Radio and a new world opens up on what you can do to monitor and understand what is happening in the RF environment of your hospital.

      This might be a nice project to pursue, to take these components that are very affordable and available and develop them into tools for use by hospital engineers.

      Thanks for a great comment.

  3. It is also appropriate to make sure that any operating MTS systems are properly registered. It can be anticipated that complaints about interference from unregistered (rogue?) systems will not be enthusiastically received.

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