RSS-244 — Medical Devices Operating in the Band 413-457 MHz

Issue 1

Posted on Industry Canada website:

Preface

Radio Standards Specification 244, Issue 1, Medical Devices Operating in the Band 413-457 MHz, sets out the minimum requirements for the certification of transmitters and receivers used in radiocommunication systems that are part of Medical Micropower Networks (MMNs). MMNs operate in the bands 413-419 MHz, 426-432 MHz, 438-444 MHz and 451-457 MHz. These devices are defined as Category I equipment as per RSS-Gen.

This document will be in force as of the publication date of Notice SMSE-001-13 in the Canada Gazette, Part I. Upon publication, the public has 120 days to submit comments. Comments received will be taken into account in the preparation of the next version of the document.

Issued under the authority of
the Minister of Industry


Marc Dupuis
Director General
Engineering, Planning and Standards Branch



1. Scope

This Radio Standards Specification (RSS) sets out the minimum requirements for the certification of transmitters and receivers used in radiocommunication systems that are part of Medical Micropower Networks (MMNs). MMNs operate in the bands 413-419 MHz, 426-432 MHz, 438-444 MHz and 451-457 MHz. These devices are defined as Category I equipment as per RSS-Gen.


2. General Information

RSS-244, Issue 1, must be used in conjunction with RSS-Gen, General Requirements and Information for the Certification of Radiocommunication Equipment, for general specifications and for information relevant to the equipment for which this standard applies.

Devices under the scope of this standard are classified as Category I equipment. A technical acceptance certificate (TAC) issued by the Certification and Engineering Bureau of Industry Canada or a certificate issued by a recognized Certification Body (CB) is required.

Devices covered by this standard produce very low emission levels such that they can coexist with the primary and secondary radio services within the bands 413-419 MHz, 426-432 MHz, 438-444 MHz and 451-457 MHz.

Only medical devices that are part of an MMN shall be designed to operate in the frequency bands 413-419 MHz, 426-432 MHz, 438-444 MHz and 451-457 MHz.

The medical devices subject to this standard operate on a “no-interference, no-protection” basis.

No antenna for a transmitter certified under this standard shall be configured for permanent outdoor use.

The antenna associated with any MMN transmitter must be supplied with the transmitter and shall be considered part of the transmitter subject to certification.

All medical devices falling under the scope of this standard are subject to the radio frequency (RF) exposure requirements specified in RSS-102, Radio Frequency (RF) Exposure Compliance of Radiocommunication Apparatus (All Frequency Bands).

2.1 Licensing Requirements

Medical radiocommunication systems covered by this standard are licence-exempt.

2.2 Definitions

The following terms and definitions apply to this standard:

Access protocol/ Protocole d’accès: is a specification for measuring natural and man-made ambient background levels for the purpose of providing a technique for spectrum access that reduces the potential for harmful interference to/from other users of the spectrum.

Listen Before Talk (LBT)/ Contrôle avant communication: is a performance requirement, usually in the form of a protocol, that requires a communications system to determine if the frequency band it intends to communicate in is occupied by another user, and selects from the available spectrum a frequency band for communication that reduces, to the extent possible, the potential for interference to/from another user of the spectrum.

MMN programmer/control transmitter/ Émetteur programmeur/contrôleur MMN: is a transceiver that is designed to monitor the frequency band(s) that the MMN system devices intend to occupy by selecting an authorized frequency band for a link to a medical implant, based on the use of the LBT access protocol and by transferring information to/from the MMN system devices after initiating the communications link.

Medical Micropower Network (MMN)/ Réseau de faible puissance à usage medical: An ultra-low power wideband network consisting of a MMN programmer/control transmitter and medical implant transmitters, all of which transmit or receive non-voice data or related device control commands for the purpose of facilitating functional electric stimulation, a technique using electric currents to activate and monitor nerves and muscles.

Monitoring system/ Système du surveillance: is the circuitry in a programmer/control transmitter that assures conformity with LBT spectrum access protocol requirements.

Threshold power level/ Niveau de seuil de puissance: is the ambient signal power level in a LBT system, as defined above, which is used by the monitoring system to determine if the spectrum is free and can be selected in a communication session.


3. Measurement Methods

3.1 References

In addition to the requirements of RSS-Gen, the following additional requirements apply:

Equipment intended to be implanted in or worn on the human body shall be tested in/on a simulated human torso in order to replicate operation of the device under actual operating conditions. For further information related to the simulated human torso, please refer to Annex A of the most recent version of ETSI EN 301 839-1, Electromagnetic Compatibility and Radio Spectrum Matters (ERM); Short Range Devices (SRD);Ultra Low Power Active Medical Implants (ULP-AMI) and Peripherals (ULP-AMI-P) operating in the frequency range 402 MHz to 405 MHz; Part 1: Technical characteristics and test methods, or to Annex A of the most recent version of ETSI EN 302 537-1, Electromagnetic compatibility and Radio Spectrum Matters (ERM); Short Range Devices (SRD); Ultra Low Power Medical Data Service Systems operating in the frequency range 401 MHz to 402 MHz and 405 MHz to 406 MHz; Part 1: Technical characteristics and test methods.

The tissue dielectric properties of the material (based on human muscle tissue) shall be suitable at 416 MHz, 429 MHz, 441 MHz and 454 MHz.Footnote 1 The tolerance of the relative permittivity and conductivity properties of the material shall be within ± 5%.

3.2 Occupied Bandwidth

The occupied bandwidth measurement method outlined in RSS-Gen shall be used.

3.3 Frequency Stability

The following temperatures and supply voltage ranges apply:

  1. For external devices:
    1. normally used outdoors: at temperatures of -30°C, +20°C and +50°C, and at the manufacturer’s rated supply voltage;
    2. normally used indoors: at temperatures of 0°C, +20°C and +50°C, and at the manufacturer’s rated supply voltage; and
    3. when the temperature is at +20°C: at ± 10% of the manufacturer’s rated supply voltage.
  2. For internal and body-worn medical devices:

    at temperatures of +25°C, +37°C and +45°C, and at the manufacturer’s rated operating voltage using a new battery only.

If the frequency stability limits are only met at a different temperature range from those specified in (a)(i) and (ii) or in (b), the frequency stability requirement will be deemed met if the transmitter is automatically inhibited from operating outside this different temperature range and if the published equipment operating characteristics are revised to reflect this different temperature range.

3.4 Equivalent Isotropically Radiated Power

The maximum equivalent isotropically radiated power (e.i.r.p.) shall be determined by measuring the radiated field at three metres and calculating the e.i.r.p. The maximum e.i.r.p. shall be measured using a peak detector when the transmission is continuous and at maximum power level. For transmitters intended to be implanted in or worn on the human body, the e.i.r.p. shall be measured using the simulated human torso per the ETSI standards outlined in Section 3.1.

3.5 Transmitter Unwanted Emissions

In addition to the requirements of RSS-Gen, unwanted emissions of transmitters intended to be implanted in or worn on the human body shall be measured using the simulated human torso as per the ETSI standards outlined in Section 3.1.

3.6 Receiver Spurious Emissions

In addition to the requirements of RSS-Gen, spurious emissions of receivers intended to be implanted in the human body or worn on the human body shall be measured using the simulated human torso as per the ETSI standards outlined in Section 3.1. As an alternative, the conducted measurement method may be used when the antenna is detachable. In such a case, the receiver spurious signal may be measured at the antenna port.

3.7 Monitoring System Measurements

Manufacturers of MMN shall share the spectrum on an equal basis in order to protect the health and safety of the patients who these systems are designed to serve. To accomplish this goal, the medical implant shall operate under the control of a programmer/control transmitter that incorporates a mechanism for monitoring all authorized frequency bands. The occupied frequency band selected for operation must have an ambient noise level below the threshold power level of the system.

The system must rely on a programmer/controller external to the body in order to schedule the implant transmissions. Multiple MMNs can exist within a patient. Each network can have multiple implanted devices with their own programmer/controller. In a case where an individual has two or more implanted devices, implant-to-implant communication is not permitted. The MMN programmer/controller transmitters and the medical implant transmitters cannot relay information in the bands 413-419 MHz, 426-432 MHz, 438-444 MHz and 451-457 MHz to a receiver that is not part of the same MMN. However, programmer/controller-to-programmer/controller communication is allowed in order to facilitate sharing of the spectrum and to avoid interference between two MMNs.

The measurement methodsFootnote2 described in Section 10 of ETSI EN 301 839-1 shall be used to determine compliance with the monitoring requirements of the MMNs devices outlined in Section 4.7 of this standard.

Specifically, the following parameters shall be measured:

  1. system threshold power levels;Footnote3
  2. monitoring system bandwidth;Footnote4
  3. system scan time and minimum monitoring period;Footnote5
  4. frequency access;Footnote6 and
  5. discontinuation of a MMN session.Footnote7

4. Transmitter and Receiver Standard Specifications

4.1 Authorized Bandwidth

For MMNs operating in the frequency bands 413-419 MHz, 426-432 MHz, 438-444 MHz and 451-457 MHz, the authorized bandwidth shall not exceed 6 MHz.

Each medical device that is part of an MMN must be capable of operating in each of these frequency bands: 413-419 MHz, 426-432 MHz, 438-444 MHz and 451-457 MHz. All medical devices that are part of a single MMN must operate in the same frequency band.

4.2 Types of Modulation

Equipment certified under this standard shall use digital modulation. Transmission of digitized or analog voice communication is prohibited.

4.3 Frequency Stability

The carrier frequency shall not depart from the reference frequency in excess of ±100 parts per million.

4.4 Equivalent Isotropically Radiated Power

The peak e.i.r.p of a MMN programmer/controller transmitter and an implanted transmitter over the frequency bands 413-419 MHz, 426-432 MHz, 438-444 MHz and 451-457 MHz shall not exceed 10 log B -7.782 dBm, where B is the 99% emission bandwidthFootnote8 in MHz. The peak power spectral density shall not exceed 800 microwatts per megahertz (μW/MHz) in any 1 megahertz (MHz) band.

4.5 Transmitter Unwanted Emissions

In addition to the requirements of RSS-Gen, the following transmitter unwanted emissions shall apply:

  1. In the first 2.5 MHz above or below any of the MMN bands (413-419 MHz, 426-432 MHz, 438 444 MHz and 451-457 MHz), the e.i.r.p level of any unwanted emission shall be attenuated by at least 20 dB below the maximum e.i.r.p within any 1 MHz of the fundamental emission. These measurements are performed using a peak detector with a resolution bandwidth of approximately 1.0% of the emission bandwidth of the device under measurement.
  2. Emissions from MMN devices more than 2.5 MHz outside of the MMN bands (413-419 MHz, 426-432 MHz, 438-444 MHz and 451-457 MHz) shall not exceed the transmitter spurious emission limits for licence-exempt devices, specified in RSS-Gen. At the band edges, the tighter limit applies.

4.6 Receiver Spurious Emissions

Receiver spurious emissions shall comply with the limits specified in RSS-Gen.

4.7 Monitoring System Specifications

MMN programmer/control transmitter shall incorporate a mechanism for monitoring the authorized bandwidth of the frequency bands which the MMN transmitter intends to occupy. The monitoring system antenna shall be the same antenna used by the programmer/control transmitter for a communication session.

4.7.1 System Threshold Power Levels

The system threshold power levels are defined as -60 dBm, as received by a 0 dBi gain antenna in any 12.5 kHz bandwidth within the MMN programmer/controller transmitter’s occupied bandwidth.

4.7.2 Monitoring System Bandwidth

The monitoring system bandwidth measured at its 20 dB down points shall be equal to, or greater than, the occupied bandwidth of the intended transmission.

4.7.3 Scan Cycle Time and Minimum Monitoring Period

A MMN programmer/control transmitter shall be capable of monitoring its occupied frequency band at least once every second (1 sec), and shall be capable of monitoring alternate frequency bands within two seconds (2 sec) prior to executing a change to the frequency band.

A MMN programmer/control transmitter shall be capable of monitoring the occupied frequency band and of determining whether either direction of the communications link is becoming degraded to the extent where the link will be lost for more than 45 milliseconds. Upon making such a determination, a MMN programmer/controller shall move to another frequency band.

4.7.4 Frequency Band Access

If the system threshold power levels are greater than -60 dBm as defined in Section 4.7.1 of this document, the MMN programmer/control transmitter shall move to another frequency band within one second of detecting a persistent signal (i.e. duration of more than 50 milliseconds).

4.7.5 Discontinuation of a MMN Session

MMN transmitters shall incorporate a programmable means to implement a system shutdown process in the event of communication failure, on command from the MMN programmer/controller transmitter, or when no frequency band is available. The shutdown process shall commence within 45 milliseconds after loss of the communication link occurs or after receipt of the shutdown command from the MMN programmer/controller transmitter.

4.8 Duty Cycle

For the purposes of this standard, the duty cycle is defined as the ratio, expressed as a percentage, of the maximum transmitter “on” time of one carrier frequency, relative to a one-hour period.

The duty cycle of all MMN programmer/control transmitters operating in the bands 413-419 MHz, 426-432 MHz, 438-444 MHz and 451-457 MHz shall not be greater than 3%.


5. User Manual

The user manuals for all transmitters covered by this standard shall contain the following statement in a conspicuous location:

“This device may not interfere with stations that are authorized to operate on a primary basis in the bands 413-419 MHz, 426-432 MHz, 438-444 MHz and 451-457 MHz, and it must accept any interference received, including interference that may cause undesired operation.”

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