The FCC also proposed new rules for implantable wireless neuromuscular micro-stimulation devices.
By a Report and Order released on March 20, 2009, the Federal Communications Commission (FCC) established a new Medical Device Radiocommunication Service (MedRadio Service) and adopted technical and service rules for advanced wireless medical radiocommunication devices used for diagnostic and therapeutic purposes in humans. The FCC also allocated a total of five megahertz of spectrum at 401-406 MHz for such devices. Most significantly, the rules will permit manufacture and marketing of a variety of devices that are either implanted or body-worn, and that operate either with “listen-before-talk” (LBT) technologies or at reduced power and low duty cycle. In a companion Notice of Proposed Rulemaking, the FCC has proposed to allocate up to 24 megahertz of spectrum in the 413-457 MHz band for implantable micro-stimulation devices using wireless technologies. The following is a summary of the new and proposed rules.
Medical Device Radiocommunication Service
The FCC has established the new MedRadio Service in Part 95 of its Rules, and has incorporated into this new radio service the rules that currently govern the Medical Implant Communications Service (MICS) at 402-405 MHz. It also allocated to the MedRadio Service two new megahertz of spectrum in adjacent “wing” bands at 401-402 MHz and 405-406 MHz. Typical MICS operations involve a medical implant device that includes a radiofrequency transmitter operating in conjunction with an external programmer/control transmitter. Examples of such devices include cardiac pacemakers and defibrillators, and devices used for diabetic glucose monitoring and control. The rules for MICS did not accommodate body-worn devices, and all such devices had to incorporate LBT technologies.
In response to requests from the manufacturers of such devices, the FCC has expanded both the spectrum available for such devices as well as the types of devices that may be used.
In addition to 402-405 MHz, devices may be operated in the 401-402 MHz and 405-406 MHz bands. There are slight differences in the types of devices that may be accommodated in each band segment.
These devices are defined as having an antenna on the patient-worn device that is placed upon or within a few centimeters of the body. Body-worn devices may operate only at 401-402 or 405-406 MHz. However, in order to allow physicians to evaluate the efficacy of a proposed treatment involving implanted devices, temporary body-worn devices may also operate in the 402-405 MHz band subject to certain time limits and power limits.
Eligibility and Permissible Communications
MedRadio Service devices may only be used for non-voice communications for diagnostic and therapeutic purposes, and only when the device is provided to a human patient by an authorized health care professional. The FCC specifically declined to extend authorization to applications involving non-human test subjects in a research laboratory.
Bandwidths of up to 300 kHz may be used in the 402-405 MHz band, but operations in the 401-402 and 405-406 MHz bands will generally be limited to a bandwidth of up to 100 kHz. Up to 150 kHz may be used at 401.85-402 MHz in order to accommodate some body worn devices, such as glucose monitors, that already operate pursuant to an earlier rule waiver. The FCC will not allow multiple transmission channels in a MedRadio device if the total bandwidth would exceed the maximum per-channel bandwidth in each band segment.
The FCC retained the current requirement for devices at 402-405 MHz to monitor for other transmissions and to select an unoccupied channel on which to operate (i.e., LBT). However, the FCC will allow non-LBT access methods at 401-402 and 405-406 MHz for both implant and body-worn devices, subject to a power limit of 250 nanowatts EIRP, a maximum duty cycle limit of 0.1 percent and a maximum of 100 communication sessions per hour. In order to conform with international standards, non-LBT methods may also be used for implant devices within a maximum 300 kHz bandwidth channel centered at 403.65 MHz, with a maximum EIRP of 100 nanowatts, and maximum duty-cycle and session limits of 0.01 percent and 10 per hour, respectively. To accommodate some existing body-worn devices, non-LBT devices may operate up to 25 microwatts EIRP at 401.85-402 MHz.
The FCC retained the existing in-band and out-of-band emission limits in the 402-405 MHz band, and adopted a similar emission mask for the wing bands but modified to account for the fact that maximum channel bandwidth will be 100 kHz in these band segments.
The FCC retained the existing standards and procedures for evaluating the RF safety effects for implanted devices, and indicated that body-worn devices will generally be evaluated under the same requirements as other hand-held transmitting devices.
The new rules will become effective 90 days after they are published in the Federal Register.
Medical Micro-Power Networks
In a companion Notice of Proposed Rulemaking, the FCC proposed to adopt rules for the operation of wideband medical micro-power networks (MMNs), which are tentatively defined as ultra-low power radio services for the purpose of transmitting non-voice data to and from medical implant devices in order to facilitate functional electric stimulation (FES) and sensing. An MMN is comprised of multiple medical implant devices under the control of an MMN control transmitter.
The service would involve implanting anywhere between one to 100 (on average two to 12) micro-stimulators in a patient suffering from spinal cord injuries, stroke, traumatic brain injuries, multiple sclerosis, polio, cerebral palsy or other neurological disorders. These micro-stimulators (approximately 3.4 mm in diameter and 24 mm long) would create within the body a wireless network capable of delivering electrical stimulation and acting as sensors of various in-body attributes and functions, potentially including sensation of and control over next-generation prosthetic limbs. An external master control unit would coordinate the activities of the network components. Unlike other implantable wireless devices, MMNs would be characterized by relatively wide emission bandwidth.
The FCC is proposing to allocate up to 24 megahertz of bandwidth in the 413-419, 426-432, 438-444 and 451-457 MHz bands for MMN. This spectrum is currently used in a variety of federal and non-federal government radio services, including land mobile, radiolocation, space research and radar. The FCC invites comment on a number of issues concerning this proposed allocation, including the following:
- Frequency bands – Would MMNs cause interference to incumbent users, or could other users result in adverse effects in patients with MMNs?
- Licensing – Should MMNs be licensed “by rule” instead of individual station licensing?
- Permissible communications and eligibility – Should the FCC use the same definitions for eligibility and permissible communications as used in the MedRadio Service? Should implant-to-implant communications be allowed, and should all implants in a patient be controlled by a single master control unit even if the implants serve different functions?
- Bandwidth – Should the FCC allow up to 6 megahertz of bandwidth for each system, or should a smaller bandwidth, such as 3 megahertz, be adopted to improve spectrum efficiency?
- Channelization – Should the FCC refrain from adopting a specific channel plan as it has done with other MedRadio Services?
- Contention protocol – Should a contention protocol be applied to these devices so that conflicts are minimized if two or more MMNs are in close proximity?
- Transmitter power – Should EIRP be limited to 200 microwatts, and should each implanted MMN transmitter be limited to transmitting approximately five microseconds every 11 milliseconds, and to receiving data for approximately six microseconds every 11 milliseconds?
The FCC is accepting comments on these proposals up to 90 days after publication of the Notice of Proposed Rulemaking in the Federal Register, with reply comments due within 120 days after Federal Register publication.