Medical Devices

Wireless Medical Telemetry Systems: Implementation in the Real World

MedSun Telemetry Audioconference

May 24, 2006

Rick Hampton
Wireless Manager
Partners HealthCare
Information Systems



Partners Healthcare System: Brigham and Women's Hospital, Massachusetts General Hospital, North Shore Medical Center, Faulkner Hospital, McLean Hospital, Dana-Farber/Partners Cancer Care, Newton-Wellesley Hospital, and Spaulding Rehabilitation Hospital.


  • Important EMI Case Histories
  • FCC Regulations
  • Spectrum Management
  • Reference Sites

Important EMI Cases

  • Part 90 Medical Telemetry in the 460-470 MHz Land Mobile Radio Band
  • Part 15 Medical Telemetry in the TV “White Spaces”
  • Part 15 Spread Spectrum systems in the ISM Bands
  • Part 95 Personal Radio (WMTS)
    (Part xx refers to the section of the FCC rules governing the radio service indicated.)

Important EMI Cases (cont.)

  • Part 90 Medical Telemetry in the 460-470 MHz Land Mobile Radio Band
    • Hurley Medical Center - 1989
      • Frequency Coordinator assigned telemetry channel to digital paging system located on hospital roof
    • New Jersey Hospital
      • Recent report of telemetry suffering intermittent interference
      • Manufacturer claims LMR interference but provided no supporting evidence or data
      • Still under investigation

Important EMI Cases (cont.)

  • Part 15 Medical Telemetry in the TV “White Spaces”
    • Baylor & Methodist Hospitals
    • FCC is still issuing new licenses for digital and low power TV stations
    • Pending proposal to allow advanced wireless services to use TV “White Spaces”
      • Will these systems “hear” medical telemetry and avoid it… or not?

Important EMI Cases (cont.)

  • Part 15 Spread Spectrum systems in the ISM Bands
    • No known issues from external interference
    • The issue isn’t “medical vs. microwave” but “network device vs. network device”
      • Telemetry/monitoring vs. Voice over IP
    • Hospitals need to plan for sensible wireless network use

Important EMI Cases (cont.)

  • Part 95 Personal Radio (WMTS)
    • Brigham & Women’s Hospital, Boston
      • WSBK – Analog TV38
    • Anonymous Hospital, New Jersey
      • DTV36 & DTV38
    • Anonymous Hospital, Kansas
      • DTV36 & Analog TV38
    • Anonymous Hospital, Ohio
      • DTV36 & DTV38

WSBK Spectrogram

This is a screen image from a Spectrum Analyzer instrument that shows the frequency spectrum between 602 mhz and 620 mhz on the horizontal axis, and signal strength in dBm on the vertical axis. Frequency markers provided by the instrument are shown at 608, 610, 612, and 614 mhz. (marked 1, 2, 3 and 4, respectively). Between markers 2 and 3 (610 and 612 mhz), several spikes can be seen illustrating the presence of medical telemetry signals. Just to the right of marker 4 (just above 614 mhz) is a large signal spike, greater in amplitude than the medical telemetry signals. Between markers 3 and 4 (between 612 and 614 mhz) other signal spikes of varying amplitude can be discerned on the display.

Slide Notes:

Notice the four diamond-shaped “markers” on the trace. The signals between markers 2 and 3 are actual patient telemetry signals. The signals between markers 3 and 4 is the “bleed over” from WSBK and, though allowed by the FCC, interferes with hospital telemetry.

FCC Regulations

FCC’s Final Rule establishing WMTS says:

“We note that medical telemetry service providers operating on 608–614 MHz (television channel 37) currently must accept adjacent channel interference from broadcast television stations operating on channels 36 and 38. With this allocation, we are not requiring television broadcasters to protect WMTS from adjacent band interference.”

FCC Regulations (Cont.)

  • L-band issues (1395-1400 MHz and 1427-1429.5 & 1429-1431.5 MHz)
  • “(1427-1429.5 & 1429-1431.5 MHz) are shared by WMTS with non-medical telemetry operations, such as utility telemetry operations, that are regulated under Part 90 of the FCC's Rules.”
    • Depending on your geographic location, WMTS operations are always treated as secondary to non-medical telemetry operations in one of those two bands.
  • Again from the Final Rule, “The rules also require operators in the 1395–1400 MHz and 1429–1432 MHz bands to protect certain government operations.”

Other Important EMI Cases

  • FCC does not require any particular communications protocol within WMTS
  • Without standards, incompatible telemetry systems have interfered with each other
    • Channelized vs. Channelized
    • Frequency hopping vs. Channelized
    • Frequency hopping vs. Smart hopping?

Spectrum Management: The Key to Prevention

  • Know your environment
    • Preferably, you will have a spectrum analyzer and can perform periodic spectrum sweeps to establish baselines and changes.
    • Alternatively, hire a consultant to perform the spectrum sweep.
    • At the very least, you should have a detailed frequency list for every radio/wireless/RF system used in your hospital and their locations.

Spectrum Management: The Key to Prevention (cont.)

  • Monitor your environment
    • Periodically, redo spectrum sweeps
    • Learn to use FCC databases and monitor critical frequencies
      • Universal Licensing System
      • FCC General Menu Reports
      • TV Database Query
      • FCC ID Query

Spectrum Management: The Key to Prevention (cont.)

  • Register all WMTS deployments
    • Urban hospitals in close proximity should also coordinate exact frequencies with their neighbors
  • License all remaining Part 90 Medical Telemetry in the 460-470 MHz Land Mobile Radio Band
    • Licensing does NOT guarantee exclusive use of a frequency
    • Licensing does let frequency coordinators know you are there

Spectrum Management: The Key to Prevention (cont.)

  • Plan ahead
    • Have an escape plan to replace or reconfigure equipment, if needed.
    • Use of unlicensed technology is growing in medical devices. Begin working with your IS team NOW to ensure smooth operations between departments
  • Report ALL incidents of interference!
    • To FDA
    • To ECRI
    • Encourage friends at other facilities to do the same


Contact Information

Rick Hampton
Wireless Communications Manager
Partners HealthCare System
One Constitution Center, OCC210
Charlestown, MA 02129
Office: 617-726-6633
Cell: 617-968-2262

Transcript for "WMTS: Implementation in the real world"

Rick is the Wireless Communications Manager for Partners Healthcare System in Boston, Massachusetts. He’s responsible for the overall coordination of activities relating to the safe and effective use of wireless communication technologies at Partners Healthcare and its affiliates.

In addition to leading the wireless task force, he coordinates efforts to provide safe and effective wireless deployment, educate Partners departments on proper wireless deployment methods and technologies, maintain and disseminate all policies regarding wireless technologies, and investigate electromagnetic compatibility and interference issues.

Rick is also active with IEEE and other organizations trying to develop standards and guidelines for implementation of such safe wireless medical systems.

Go ahead Rick.

Rick Hampton: Thank you Terrie and it was very nice of you to ask me to be on this conference call.

Okay, so we’ve heard a little bit about me, we’ll go to Slide 2.

And for those of you who have not heard of Partners Healthcare systems, just a brief introduction: We’re a group of hospitals up in the Boston area; you may have heard of Mass General and Brigham and Womens, some of the others are community hospitals. But we are basically a group of hospitals like yourselves trying to deal with this issue of telemetry and interference.

Let’s go on to Slide 3.

So there are a few things I’m going to discuss. I’m going to play off of Rich’s very well done introduction to the history of telemetry, I’m going to discuss some important EMI case histories, some of the FCC regulations and what they really mean, touch a little bit on spectrum management, and like Rich, I have a couple of reference sites for everyone to use.

Slide 4 - So it’s interesting to note that none of these telemetry systems are without risks. You know Rich has covered how some of - how the WMTS systems came about and where we’re going with those, and everyone when WMTS came out thought that that was going to provide protected spectrum. Well it does but protected should be in quotes, and I have a few definitions and I’ll give those to you.

So, we’re going to look at the different telemetry systems and I’ve referred to them here as Part 90, Part 15, and Part 95. Those part numbers refer to the section of the FCC’s rules that govern the radio service indicated. So if you really -- if you wanted to look up the actual rules, and I would suggest anyone that’s interested do this, there’s a site online where you can go to the Federal Register and you can browse the different sections and you’d look and CFR 47 which is the rules promulgated by the federal communications commission. You could look in these different parts to find the exact rules as they are today that govern these different systems.

So we’re going to look at EMI cases in all of them.

So going to Slide 5, Part 90 is the oldest of the telemetry services and at one point in time you actually had to have a license in order to operate each and every transmitter that you use. And back in those days I was a clinical engineer with Hurley Medical Center in Flint, Michigan and in 1989, we had an incident where one of our telemetry channels started having severe interference.

To make a long story short, it turns out that the frequency coordinator responsible for assigning frequencies to the different radio systems in that part of the world had assigned the same frequency as our telemetry system to a paging company who had a digital paging system located on the roof of our hospital. So as you might imagine every time a page was sent from this system it basically destroyed that particular channel.

So this is not really a new instance and it points out to the fact that the operation in Part 90 has never been completely risk-free or trouble-free.

Most recently though with the release of the newer licenses that Rich talked about, I’ve received reports from a hospital in New Jersey and I was in contact with them as late as yesterday afternoon. They are suffering from interference to their Part 90 medical telemetry in the land mobile radio band. It is intermittent at this point in time. It is something that they can live with while they investigate whether or not that they need to replace the system. I think it’s a pretty simple question to answer myself.

But they had the manufacturer come in. The manufacturer did a quick study, basically told them that they were suffering interference from land mobile radio and provided them no supporting evidence or data at all. So the hospital is trying to collaborate this with a third party investigator and that will probably take about another two weeks then I think it will probably wind up moving.

But the point here is the interference came on quickly, it is intermittent, they’re not sure when they’re going to have problems with the telemetry system and when they’re not, but as this point in time it’s only some of the telemetry channels are affected, but they are seeing this problem and they were not able to predict it.

Let’s go on to Slide 6.

Part medical or Part 15 medical telemetry and the TV white spaces; this was the stuff that Rich mentioned earlier in the Baylor and Methodist Hospital incidents.

It’s important to note that there’s a false assumption that there is a list of TV stations out there and if you don’t have a TV station in your area that’s on that list, you are safe. That is not true.

Again, as Rich mentioned earlier, the FCC is still issuing new licenses for digital and low power TV stations. The last contact I had with the FCC’s Media Bureau Division, the group that regulates TV stations, indicated that once the analog stations are done away with and the conversion to digital is fully implemented, they will probably be issuing many new TV licenses throughout the United States.

So do not think that just because you have an empty TV station now or an empty TV channel now that it will remain that way. That can change relatively quickly.

There is also a pending proposal to advance - to allow advance wireless services to use the TV white spaces. Primarily the biggest issue here is the new WiMAX service that you may have heard about that will provide wireless coverage, you know, in metropolitan areas. They’re looking for spectrum space.

The talk is that the proposal that the WiMAX systems and these other advanced wireless systems will have to use sophisticated cognitive radio systems that will listen before they transmit. If they hear another station, they will not transmit. If they do not hear a station, they will transmit.

And the question is will these advanced systems be able to hear the very weak signals that are coming from our medical telemetry systems. It is a real problem and you will probably not know that you’re going - that these things are going to be installed because at this point in time, they may be unlicensed.

Let’s go to Slide 7.

If we look at the Part 15 spread-spectrum systems and the ISM band, there are a couple of companies using these systems. As of right now, I’ve not heard any issues of external interference to these systems, however, the issue isn’t the medical system versus the microwave that everyone discusses, it’s more of the medical device versus the network device, the telemetry monitoring voice versus the wireless voice over IP systems.

It’s something that can be managed. Our hospital is using actually just about all of the telemetry systems except the land mobile radio stuff; we’ve converted our telemetry out of that. But we do have spread-spectrum systems in the ISM bands operating in the same floors, in the same geographic areas as our wireless LAN for the IS system. It can be done, it needs planning, and we’ll touch upon that in a little bit.

So the point here is if you plan to use spread-spectrum systems in the ISM bands, it can be done. The biggest interference is the stuff that you’re going to have internally and operating amongst your own systems. So hospitals need to plan for sensible wireless network usage there.

Slide 8 goes back to Part 95, the new WMTS bands. As luck would have it, of all the places that would have to have problems with WMTS, it had to be one my hospitals here in Boston and it has to do with Channel 38 which is an analog TV station and the TV station is WSBK, and I’ll show you a slide from that in a second. But we currently have some pretty severe interference in the upper portion of the WMTS band and it actually meets all of the FCC rules and regulations as they govern TV stations, and we’ll discuss how that happened in a little bit.

There were also three other instances from a hospital in New Jersey, one in Kansas, and one in Ohio. I was contacted by each of these hospitals -- all of them requested anonymity. We’ll get into that if someone wants me to. But the point is that they all have problems with TV 36 and TV 38 stations in their locality.

And it turns out that even these hospitals didn’t have the same problem that we have here in Boston. The problem at these other hospitals seems to be that the telemetry system was not designed to withstand close proximity to these TV stations and so in each case the manufacturer had to come back in and remediate the problem. But until that was done, the hospitals were severely handicapped by the interference.

Go to Slide 9.

Here’s a spectrogram showing you what the situation is here at our hospitals. There are four triangular markers here in this spectrogram. The first marker is at 608 megahertz, the second is at 610, the third is at 612, and the fourth is at 614 megahertz.

All of the spikes you see in the middle of the screen between Markers 2 and 3 are actual telemetry channels. The large spike just to the right of Marker 4 is a carrier for the TV station that’s nearby; it’s actually about 6 miles away. And all of the signals between Markers 3 and 4 are actually the legitimate and legal signals coming from the TV transmitter. And you’ll notice that some of those are of equal amplitude or greater amplitude than some of the telemetry signals and that causes a problem for us in that we cannot use the upper one-third of our telemetry band there.

Go to Slide 10.

So how can this happen?

The FCC’s final rule that established WMTS discussed this a little bit, and I’m just going to cut to the chase to the section that I highlighted. This is with this allocation, grading telemetry to Channel 37, it says, “With this allocation, we are not requiring television broadcasters to protect WMTS from adjacent band interference.”

Basically that means if you have interference from a nearby TV station and that TV station is transmitting according to the FCC rules, there is no recourse for you to have that station either fix the problem, move, reduce the power or anything. The rules -- the FCC rules governing WMTS plainly state that it’s up to the hospital and the manufacturer of the device to remediate all the problems and if they can’t, they are to move to a different band -- the L-band or the 1300 megahertz band.

Let’s go to Slide 11.

And if we look at the regulations that govern the L-band, as Rich discussed earlier, this section is still shared with other operators. There are non-medical telemetry operators such as utility companies that monitor meter reading equipment -- that operates up here.

That has -- I’ve heard but I’ve not been able to confirm that there’s been an issue already in licensing a WMTS system up in this part of the band. I don’t think it was a true interference issue; it was an issue in that the utility company had already staked their claim to this part of the band and was refusing to share it with the telemetry. I believe that was worked out. Again, that’s -- I’ve heard that from a reliable source, but I’ve not heard it firsthand from a hospital.

So there can be some issues with the registering of this.

And then again, the final rule says that we have to share and protect certain government operations. There are some military radar installations as well as radio astronomy here as well.

(Switch) Slide 12, some other important EMI cases.

Basically what I want to say here is that the FCC doesn’t require any particular communication protocol within WMTS and what that means is there are no standards for what particular protocol is used in these telemetry systems by manufacturers. You can have a channelized system like Rich discussed earlier; you can have a frequency hopping system which is the ISM band stuff; and you can have a newer version that’s come out that’s called Smart Hopping and it doesn’t actively hop across frequencies but it only changes frequencies when it receives interference.

The question is how do these things interact if you have several different versions in one hospital or you have two hospitals quite near each other? And there have been cases where hospitals have installed frequency hopping equipment in one portion of their hospital and found that it jammed and interfered with the channelized equipment they had operating in a different part of the hospital. And there’s also been a few cases where hospitals in urban settings where you have basically a hospital, you know, across the street from another one where one hospital will install frequency hopping equipment and it will, you know, interfere with the channelized equipment at the other hospital.

There are ways to mitigate this, but the point is you have to plan ahead and find out what everyone is using in the area before you turn these things on. You can cause interference just by using a different brand of medical telemetry.

Slide 13. I want to talk a little bit about spectrum management and the key to preventing some of these instances.

The first thing you need to do is you need to know your environment. Preferably, you’ll have a spectrum analyzer and you’ll be able to perform periodic spectrum sweeps to establish baseline, you know, electromagnetic environment for your facility and to be able to see any changes. Alternatively, you can hire a consultant to come in and perform these very same functions. At the very least, you need to have a detailed frequency list of every radio and wireless system used in your hospital, and don’t forget to include things like microwave ovens, know where those are, you don’t have to pinpoint those down specifically but you need to be aware of where they are.

There are a lot of hospitals buying these coaster pagers to, you know, help alert patients and visitors when they need to be at certain places. Many of these things can be bought off the shelf and it’s -- you really need to know what systems are being used and where they’re at.

One other thing you can do, and I would strongly suggest it, is when you consider purchasing a new telemetry system, have to manufacturer of that system come in and do an environmental sweep in the region of the spectrum where their system operates to help prevent some of these issues.

Go to Slide 14.

Again, continue to monitor your environment, periodically redo the spectrum sweeps, learn to use the FCC databases and monitor critical frequencies. I’ve got a few other resources you can use, but some of them are the same that Rich had earlier.

The Universal Licensing System will tell you every land mobile radio system in use within a certain radius of your facility, all you’ve got to do is plug in your geographic coordinates and give it a radius and it will spit out everything that’s in use. You can track -- I’m sure your hospital probably has walkie-talkie systems and some other radio systems, you can track those as well using the general menu reports and the Universal Licensing System.

Again, the TV database query will tell you what TV stations are in the area and which ones have just gotten construction permits.

The FCC ID query will actually let you take any device that someone brings in and presents to you as a possible item to purchase. There’s an FCC ID number on that device if it’s supposed to transmit radio frequency. You can look up the ID number on that and there’s a plethora of information that’s available to you when you use those. So I suggest you learn how to use these databases.

Slide 15. Register all of your WMTS deployments. Urban hospitals in close proximity should also coordinate the exact frequency with their neighbors.

This is another fallacy of the WMTS that if you register your stuff, everyone knows what frequency you’re operating. But that’s not the way WMTS registration works.

When you register your telemetry equipment, you simply tell us what block or what range of frequencies that you intend to use. You do not enter every exact frequency. And so, if you have neighboring facilities nearby, you need to talk with them to find out what frequencies they’re using so you can adjust yours around that and not share them.

You need to license any land mobile radio telemetry that you still have. The option now is if you’re going to stay there, you should license it. Licensing does not guarantee exclusive use of a frequency, but it does let the local frequency coordinators know that you’re there. If they don’t know that you’re there, they cannot even begin to think about protecting you.

Slide 16. Plan ahead. Have an escape plan, replace or reconfigure your equipment as needed. This is particularly important if you are still using land mobile radio systems because you never know when that stuff is going to start receiving interference that you can no longer deal with.

Use of unlicensed technology is growing in medical devices. Begin working with your IS team now to ensure that there is smooth operation between the departments.

I’m working with a lot of the device manufacturers and several of the IT companies trying to figure out how we can tie the medical devices with some of the IS systems because there’s only one chunk of spectrum to share and the best way to do that is by tying some of the systems together. So you need to get on good relations with your IS team now to help ensure that that happens.

Most importantly, report all of these incidences of interference to the FDA and ECRI and encourage your friends at other facilities to do the same.

Luckily I’ve talked with a bunch of MedSun hospitals who know the importance of this. But the reason some of -- the three hospitals I’ve mentioned earlier who request to remain anonymous is there’s still a lot of fear, uncertainty, and doubt in what happens when you report these things.

So as silly as it is, people are calling me rather than calling the FDA. You know if I’m the reporting of last resource that’s okay, but I do so reluctantly. The stuff really needs to be reported to the FDA and ECRI and please encourage the other folks to do this.

Slide 17 are some references for the different things I mentioned earlier. Visit these sites, learn how to use these tools. And there are some other documents, if you haven’t already downloaded them on the MedSun registration site, some articles from ECRI, and a couple from (AAMI) that deal with some of these issues, and there’s a better accounting of some of the telemetry issues that I ran into available in one of those articles.

And that’s my presentation, Terrie.

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