FCC Commissioners to Discuss Medical Micropower Networks in 413-457 MHz Band
In their regular meeting on Wednesday, November 30, the four FCC Commissioners will hear from the Commission’s Office of Engineering and Technology (OET) regarding amending Parts 2 and 95 of the Commission’s Rules. In a Notice of Proposed Rule Making (NPRM) issued in March 2009, the FCC proposed to allocate spectrum and adopt service and technical rules for the utilization of new implanted medical devices that operate on 413-457 MHz (70 cm). The Amateur Radio Service has a secondary allocation in the 70 cm band.
According to the FCC, these devices -- called implanted neuromuscular microstimulators -- would greatly expand the use of functional electric stimulation to restore sensation, mobility and function to those persons with paralyzed limbs and organs; they would be implanted in a patient and function as wireless broadband medical micropower networks (MMNs). These devices would be used on the 70 cm band on a secondary basis as part of the Medical Data Radiocommunication Service in Part 95 of the FCC rules.
In its comments to the FCC regarding the NPRM, the ARRL said it believes that the choice of frequency bands for MMNs as proposed is “unfortunate and unnecessary” and that “the WMTS [Wireless Medical Telemetry Service] offers a far more suitable solution than does the 413-457 MHz band for MMNs.”
“The Alfred Mann Foundation argues that the frequency range just above 400 MHz is optimum for their application, which requires no more than 1 mW of RF spread across about 5 MHz of bandwidth,” ARRL Chief Executive Officer David Sumner, K1ZZ, wrote in “It Seems to Us: Coexistence,” published in the June 2009 issue of QST. “However, recognizing the presence of a variety of incumbent radio services in that range, specifically including the amateur service, they have proposed four channels for flexibility in avoiding localized interference. Two of the four channels are 426-432 and 438-444 MHz; the other two are above and below the 420-450 MHz band.” The Mann Foundation is the developer of the MMN technology.
Though the Mann Foundation has proposed that MMNs would be secondary to incumbent licensed operations in the subject bands, the Amateur Service is presently secondary to government radiolocation in this band; this represents a cooperative sharing arrangement that is satisfactory to both government agencies and the Amateur Service, the League contends.
The ARRL noted that there is Part 90 spectrum above 450 MHz available for low-power biomedical telemetry, but “the Alfred Mann Foundation argues that bands between 450 and 470 MHz are unsuitable due to the fact that the band is ‘congested and populated with commercial, high-power transmitters that could preclude reliable operation of lower-power, wireless medical implant devices.’” This, the ARRL said, “is a very worrisome contention, and not the argument that should be made by the proponent of a new service that is secondary to other incumbent licensees. ARRL contends that if the 450-470 MHz band hosts services that are incompatible with reliable operation of MMNs, then the 420-450 MHz band, and especially the segment proposed for MMNs at 438-444 MHz, is equally incompatible with MMNs.”
Sumner, in his June 2009 QST editorial, said that the FCC’s proposed rules raise two concerns: “First and foremost, the devices would be required to accept interference only from stations authorized to operate on a primary basis. The Mann Foundation has assured us that amateur stations will not cause its system to malfunction, so we see no reason why this cannot be reflected in the rules, even though our allocation is on a secondary basis. Second, while the Mann Foundation researchers appear to have done their homework, others who try to take advantage of the new rules may not be as rigorous.”
The ARRL did acknowledge in its comments that it thought the FCC was correct when it stated in the NPRM that “[g]iven the low transmitter power and duty cycle limits that would typically be used by either the implanted MMN device or the external MCU, we expect that the risk of interference from MMNs to incumbent operations in these frequency bands would be negligibly small.” The ARRL pointed out, however, that no testing has been done to verify this conclusion and “such testing should be concluded and the results analyzed before this anticipatory conclusion can be relied upon.”
While the ARRL is concerned about interference from the MMNs affecting radio amateurs, it is also concerned about RF from these radio amateurs affecting the MMNs. “The Amateur Service has a practical inability to protect patients wearing RF susceptible MMNs from interference from ongoing amateur operations in the 420-450 MHz band, and therefore all MMN operation is going to have to be conditioned on the ability to withstand and operate in the presence of such high-power signals, and thus subordinate in allocation status to the Amateur Service,” the ARRL said in its comments. “Unless this interference rejection capability is demonstrated by MMN proponents in advance, the devices should not be allowed to operate anywhere in the 420-450 MHz band.”