Two years ago I wrote about an FCC Notice of Proposed Rule Making allocating four UHF bands, 413-419 MHz, 426-432 MHz, 438-444 MHz, and 451-457 MHz for use by medical micro-power networks (MMN) comprised of multiple implanted medical devices employing wideband function electrical stimulation to relieve pain and improve healing in limbs and organs. This week, the FCC adopted a Report and Order allowing MMN systems to use these frequency bands on a secondary basis under the MedRadio service, which the FCC notes includes the legacy Medical Implant Communications Service (MICS) authorized to use the 402-405 MHz band. The MedRadio service represents "an umbrella framework to regulate the operation of both implanted and body-worn wireless medical devices used for diagnostic and therapeutic purposes in humans."
The main opposition to this secondary allocation came from users of this spectrum that were concerned their high power operations would interfere with the MMN systems, possibly leading to restrictions on their use of this spectrum. The 454-455 MHz portion of the 451-457 MHz band is used by broadcasters for remote pickup services, sometimes inside hospitals, and this prompted concerns from multiple broadcast organizations.
In the Report and Order, the FCC dismisses these concerns, noting that tests by AMF, a manufacturer of MMN systems, found their devices were able to avoid interference by moving to one of the other UHF bands. Requests to use other frequency bands were rejected because frequencies in the 400 MHz band penetrated the body with the least loss, allowing operation at very low power levels. Other bands required more power and larger batteries or more frequent replacement of implanted devices.
Devices must be registered and must contain circuitry that prevents interference to incumbent operations in these bands and is able to avoid interference by shifting frequencies, by safely shutting down or other means. Devices must be able to monitor the other frequencies' bands to determine which band they can safely operate on. The devices are allowed a maximum emission bandwidth of 6 MHz and the EIRP is limited to the lesser of 1 mW or (10 log B – 7.782) dBm where B is the 20 dB emission bandwidth of the transmitted signal in MHz. The maximum duty cycle is limited to 3 percent.
The FCC notes in the introduction to the Report and Order, "we expand the Medical Device Radiocommunication (MedRadio) Service under Part 95 of the Commission's rules to permit the use of new wideband medical implant devices that employ neuromuscular microstimulation techniques to restore sensation, mobility, and other functions to paralyzed limbs and organs." Commenters did not oppose the service itself. Most agreed with the FCC's statement that "These medical devices hold enormous promise to advance the state of medical care, lower health costs, and improve the quality of life for countless Americans."
