New rules authorize body-worn networks for medical monitoring and treatment.
It was impressive enough when medical engineers started mass-producing complex devices for use inside the human body. Now those devices are talking not only to the physician, but also to each other.
The FCC has authorized Medical Body Area Network (MBAN) devices that will operate in the 2360-2400 MHz region, immediately below the heavily-used unlicensed band that houses Bluetooth, and most Wi-Fi, along with many other applications. We told you about the proposed rules three years ago. The new Report and Order took a while because, like all useful spectrum, this band already has incumbent users, many of whom have to be protected.
An MBAN, as the FCC envisions it, is a little like a cellular wireless system in miniature, worn on a patient’s body. Sensors around the body monitor various functions, depending on the patient’s needs, and communicate their data to a central hub, worn by the patient or located close by. The hub aggregates data from the various sensors, and transmits those data using the health care facility’s network (possibly over Wi-Fi or Ethernet) to a central control point, from where the data are made available to the professional staff for interpretation and appropriate response.
The 40 MHz identified for MBANs is a lot of spectrum, and moreover is located in the “sweet spot” of frequencies best suited to mobile communications. The FCC defends its allocation of this wide swath by explaining that the need to avoid interference to other users will limit the frequencies available at any given time and place. Moreover, it says, adequate bandwidth will both increase reliability and allow room for multiple vendors, thus increasing competition and reducing costs.
Other users of the 2360-2390 MHz segment include the U.S. Government, which has long employed the band for the flight-testing of aircraft, missiles, and such. The people in charge of such functions prefer not to receive interference from patients’ monitoring systems. So MBAN communications will have to run “downstream” as well: an FCC-designated frequency coordinator will tell the facility’s central control point what frequencies (if any) are safe to use for that time and location, and the central control point will send the frequency information to the patient’s hub, which will transmit it back to the various sensors.
Interestingly, what the FCC calls a “sensor” need not only sense, but can also deliver therapy. The FCC does not give examples, but we can imagine such a system releasing medication or even stimulating the patient’s heart, when needed.
Any health care facility wishing to use the 2360-2390 MHz segment must register with the frequency coordinator, and its devices may not operate in this band until they receive a control message with a go-ahead for specific frequencies. The FCC declined to adopt a “listen-before-talk” requirement, although it encourages the industry to do so as part of the standards-setting process.
To further protect the Government users, 2360-2390 MHz spectrum can be deployed only indoors. Near the large radio astronomy facility at Arecibo, Puerto Rico, which also uses part of the same band, MBAN users will have to notify the facility before beginning operation.
The other MBAN frequencies, at 2390-2400 MHz, are part of an amateur band. To no one’s surprise, the amateurs opposed MBANs as possibly interfering with amateur “weak signal” operations, and also warned about amateur transmitters causing interference into MBAN devices. Again, to no one’s surprise, the FCC concluded that MBANs and amateur users could successfully coexist. Because use of the lower band at 2360-2390 MHz is limited to hospitals and similar facilities, any in-home use must occur in the amateur band. No coordination is required.
In considering whether and how to license MBANs, the FCC confronted a familiar dilemma. The Communications Act, as interpreted by the courts, requires a license for any transmitter having significant potential to cause harmful interference. In calling for MBAN users to coordinate with Government users, the FCC concedes that harmful interference is possible. Yet to process individual license applications for every facility using MBANs would impose a burden with little benefit. Fortunately, Congress allows the FCC to license four kinds of users “by rule” – that is, simply to deem that they have licenses, without actually mailing out pieces of paper. A cynic might carp that MBAN is not among the applications listed in the statute. But that detail has never stopped the FCC in the past. Two of the services authorized for license-by-rule – Citizens Band and Radio Control – are both in Part 95 of the FCC rulebook, so the FCC has always reasoned that anything else it puts into Part 95 can similarly be licensed by rule. Part 95 is where the MBAN rules will go.
Power limits are relatively generous: 1 milliwatt at 2360-2390 MHz, with a higher limit of 20 milliwatts at 2390-2400 MHz, in part to give patients greater mobility within their homes.
There remains one loose end in the process: the selection of a coordinator for MBAN operation in the 2360-2390 MHz band. Make that two loose ends: before a coordinator can be selected, the FCC will have to establish criteria for the coordinator position and the selection process. To that end the FCC has included a “notice of proposed rulemaking” section in its Report and Order in which it lays out its thinking on those points and invites comments from the public. No deadline for those comments has yet been established. Check back here for updates. (Similarly, the rules which have been adopted will not take effect until the Report and Order is published in the Federal Register – but even then, because they’re subject to the Paperwork Reduction Act, a couple of the new rules won’t take effect even then.)
The new MBAN rules join MedRadio devices in the 413-457 MHz band, in addition to the Wireless Medical Telemetry Service at 308-614, 1395-1400, and 1427-1432 MHz. We won’t be surprised if our next hospital bill, like a cell phone bill, shows a charge for megabytes used.
