CE RED Testing and Certification of Helium Compatible Gateways
Introduction
Helium hotspots (miners) operate in the EU868, also known as the EU863-870 MHz unlicensed band, as modified LoRaWAN compatible gateways. Currently the Helium system operates on 200 kHz channel frequencies from 868.1 to 868.8 MHz in the EU868 band.
The CE Radio Equipment Directive, also known as CE RED, covers regulatory certification for all EU member states. Other regulatory country bodies, such as Australia, some Middle Eastern, and African countries also accept CE RED certification testing. CE RED is the most commonly accepted testing in many countries around the world.
Using CE pre-certified LoRaWAN gateway concentrator modules based on Semtech Corcell card designs from marketplace suppliers can assist in the development of a new gateway product but these may or may not include all the required certifications for Helium system support. As discussed in several sections of this application note, not all EU member states are harmonised with their technical specifications. It is the ultimate responsibility of manufacturers providing Helium compatible network products that proper regulatory testing and certification or recertification is obtained for countries of intended operation.
In this application note the term gateway and hotspot are used interchangeably.
Glossary
- BW: Bandwidth
- e.r.p.: Effective Radiated Power
- ETSI: European Telecommunications Standards Institute
- EU: European Union
- EUT: Equipment Under Test
- LoRa: Long Range radio modulation technique
- LoRaWAN™: LoRa low power Wide Area Network protocol
- mW: milli-Watts
- PoC: Helium Proof of Coverage function
- RED: Radio Equipment Directive
- RF: Radio Frequency
- RX: Receive / Receiver
- SF: Spreading Factor
- TX: Transmit / Transmitter
References
- ETSI EN 300 220-1 V3.1.1 (2017-02) Short Range Devices
- ETSI EN 300 220-2 V3.1.1 (2017-02) SRD Part 2 Essential requirements
- LoRa Alliance TS001-1.0.4 LoRaWAN® L2 1.0.4 Specification
- LoRa Alliance RP002-1.0.3 LoRaWAN® Regional Parameters
- Semtech TN1300.01 How to Qualify a LoRaWAN Device in Europe
- Semtech Corecell Gateway Reference Design EU Version Performance Report
CE RED Certification Requirements
Helium gateways currently operate on 9 frequencies in the 867 to 869 MHz range and are regulated by ETSI standards. An additional channel at 869.525 MHz is supported by the gateway as a downlink receive slot 2 (RX2) frequency. The Helium gateways meet current LoRaWAN specifications TS001-1.0.4 and RP002-1.0.3, the document links are given in the references section above. To meet ETSI requirements transmissions are duty cycle limited and do not use listen-before-talk protocol which require different testing.
The Helium frequency chart for EU868 operation is shown below. Note that uplink (transmissions to the gateway) and downlink (transmissions from the gateway) frequencies are the same with no offsets. These are the minimum frequencies required for operation on the Helium network. Developers may want to test and certify for a wider EU868 frequency range of 863 through 870 MHz, 35 channels with separations of 200 kHz, for possible future frequency expansions or the use of alternate frequencies in some regions. It is important to note that additional frequency ranges, such as band K (863 – 865 MHz), have lower transmit duty cycle requirements.
Helium Uplink and Downlink (RX1) Frequencies
| Frequency (MHZ) | Spreading Factor |
|---|---|
| 868.1 | SF7BW125 to SF12BW125 |
| 868.3 | SF7BW125 to SF12BW125 and SF7BW250 |
| 868.5 | SF7BW125 to SF12BW125 |
| 867.1 | SF7BW125 to SF12BW125 |
| 867.3 | SF7BW125 to SF12BW125 |
| 867.5 | SF7BW125 to SF12BW125 |
| 867.7 | SF7BW125 to SF12BW125 |
| 867.9 | SF7BW125 to SF12BW125 |
| 868.8 | FSK |
Helium Downlink RX2
| Frequency (MHZ) | Spreading Factor |
|---|---|
| 869.525 | SF12BW125 |
ETSI Testing Requirements
ETSI standards define acceptable test procedures and limits. There are two applicable ETSI specifications, EN 300-220-1 V3.1.1 (Part 1) and EN 300-200-2 V3.1.1 (Part 2). Note that the ETSI specification EN 300-220-1 was split into these two parts with the latest versions V3.1.1 in 2017. The Part 2 specification provides a “Harmonised Standard” for short range devices in the 25 to 1000 MHz frequency range while the Part 1 specification gives details for “Technical characteristics and methods of measurement”. Overall, Part 2 lists frequency bands and RF regulations for these bands and points the reader to the applicable sections in Part 1 for specifics of measurement methods. The EU868 (863 – 870 MHz) frequency range is broken up into many sub-bands with different power and duty cycle requirements which are defined in the Part 2 specification.
Since these specifications are linked, the required test explanations below for LoRaWAN / Helium gateway certification will have the applicable sections of EN 300-220-2 and EN 300-220-1 listed.
ETSI EN 300-220-1 4.3.3 defines normal test conditions and the following section 4.3.4 defines extreme test conditions. Extreme conditions require additional testing over temperature and source voltage variations depending on the operational profile defined by the manufacturer. Some standards only require testing at normal conditions while others also require testing at extreme testing conditions.
EN 300-220-2 4.2.1 / EN 300-220-1 5.1.1 Operating Frequency
The manufacturer will declare the operating band or bands, frequencies, and operating channel widths in the certification filing. See EN 300-220-2, Annex B and C, for tables of allowable frequencies and bands of operation. Annex B lists the frequencies for EU wide national harmonised radio and Annex C for radio interfaces not EU wide harmonised. The Annex C (not harmonised) is for operational frequencies that may be allowed in some EU countries, but not all. It is up to the manufacturer to determine which EU countries that the gateway may operate in and the requirements of that country. Additional insight on this subject is given in the Semtech TN1300.01 technical note with a link in the References.
EN 300-220-2 4.2.2 / EN 300-220-1 5.9 Spurious Emissions
Unintended spurious emissions are measured in both transmit and receive / standby modes with different limits for each operational mode. EN 300-220-1 5.9.1 defines a spectral mask when transmitting with varying spurious limits depending on the frequency spacing from the intended channel. Spurious emissions are measured in both conducted and radiated modes with the exception of devices without antenna connectors (permanent antenna) are permitted to have radiated only measurements. The ETSI specification covers a wide range of frequencies depending on the test mode from 9 kHz to 6 GHz. The equipment under test must be measured at the lowest and highest operating frequencies at maximum power. Normal test conditions are only required for spurious emissions measurements.
EN 300-220-2 4.3.1 / EN 300-220-1 5.2 Effective Radiated Power
Effective radiated power is measured by direct connection to the EUT when an external antenna port is available. The power may be measured by radiated means when there is no external antenna connector available. The maximum gain of the antenna, referenced to an ideal dipole, to be used with the equipment is included in the test report. For conducted results of effective radiated power the gain of the antenna must be added to the measured conducted power. This test is measured in transmit mode at the lowest and highest frequencies of operation and also under normal and extreme test conditions.
EN 300-220-2 4.3.2 / EN 300-220-1 5.3 Maximum e.r.p. Spectral Density
Effective radiated power spectral density is defined as the maximum power radiated when transmitting in units of power per hertz over the power envelop. Antenna gain referenced to a dipole, as in the effective radiated power test, must be included in the calculation. It is important to note that the e.r.p. spectral density test may be the limiting factor for the power setting of the gateway.
Since gateways operate operate on several ETSI defined band “L” frequencies, specific limits may apply depending on the EU country where it is intended for operation. In EN 300-220-2 Annex C, certain “not EU harmonised” countries may not require the EUT to meet this regulation for spectral density and allow 25 mW effective radiated power. For LoRaWAN / Helium operation in regions that require this test the power will be limited to approximately 5 mW. The applicant should contact the regulatory agencies of each EU country for the current rules and work with a testing service facility to determine the proper limits.
This test is measured in transmit mode at the lowest and highest frequencies of operation under normal test conditions only.
EN 300-220-2 4.3.3 / EN 300-220-1 5.4 Transmit Duty Cycle
The intent of the maximum transmitter duty cycle test is to not exceed the duty cycle limits given in ETSI 300-220-2 Annex B and C. The EUT should be in “normal use” mode and the duty cycle observational period is 1 hour of normal operation.
EN 300-220-2 4.3.4 / EN 300-220-1 5.6 Transmit Occupied Bandwidth
Transmit occupied bandwidth is defined as the frequency range in which 99% of the total power of an emission falls. This parameter is tested at the lowest and highest frequencies of operation and under normal and extreme test conditions.
EN 300-220-2 4.3.5 / EN 300-220-1 5.8 Transmit Out of Band Emissions
Two out of band emissions requirements are defined in ETSI specifications: The operating channel and operational frequency band. The operating channel mask defines the emissions near the channel of operation while the frequency band emissions include everything out to the operating band limits. These spectrum masks may overlap. ETSI 300-220-1 5.8.1 defines the masks for both specifications. Out of band emissions are tested at the lowest and highest frequencies of operation and also under normal and extreme test conditions.
EN 300-220-2 4.3.6 / EN 300-220-1 5.10 Transmit Transient Power
Transmit transient power is defined as the transmit power falling outside the current operating channel when the transmitter is switched on and off. Transient power is measured at the lowest and highest frequencies of operation at normal operating conditions only.
EN 300-220-2 4.4.2 / EN 300-220-1 5.18 Receiver Blocking
Receiver blocking is defined as the capability of the receiver to receive a wanted modulated signal without exceeding a given degradation due to the presence of a stronger unwanted input signal other than a spurious response or an adjacent channel. The test is performed with 2 signal generators, one on-channel with the wanted modulated signal and an offset generator with an unmodulated carrier. EN 300-220-2 specifies the minimum performance standard is a category 2, and EN300-220-2 5.18.3 defines the levels for category 2. Blocking is measured at normal test conditions only but ETSI requires at least 1 measurement per band that the EUT operates in.
Conducted and Radiated Tests, Antenna Requirements
The effective radiated output power, EN 300-220-1 5.2, as discussed above takes into account antenna gain. The maximum antenna gain, with respect to a dipole reference, must be added to output power to determine the effective radiated output power. Gateways with antennas that have gain over a standard dipole will need to reduce their maximum conducted power settings to meet this specification.
ETSI certification testing is mostly written around conducted methods where a cable is attached to the antenna port or a test port. The specifications do allow for radiated testing of most parameters which may be the case for EUTs that do not have readily available test connections. See EN 300-220-1 sections 4.3.7, 4.3.8, and 4.3.9 for requirements. Spurious emissions is a notable exception to conducted only test procedures where a radiated measurement must be taken.
While radiated testing for most parameters is allowed, it is usually not practical to attempt extreme test conditions with this test method especially over temperature extremes. Most gateway designs are stationary devices and are assumed to have access to an antenna connector or an internal test connector.
Summary of Certification Testing Requirements
| EN 300-220-2 | EN 300-220-1 | Tests | Limits | Results |
|---|---|---|---|---|
| 4.2.1 | 5.1.1 | Operating Frequency | Declared | |
| 4.2.2 | 5.9 | Spurious Emissions | See -1 5.9 | |
| 4.3.1 | 5.2 | Effective Radiated Power | See -2 Annex B, C | |
| 4.3.2 | 5.3 | e.r.p. Spectral Density | Depends on EU country | |
| 4.3.3 | 5.4 | TX Duty Cycle | See -2 Annex B, C | |
| 4.3.4 | 5.6 | TX Occupied Bandwidth | See -2 Annex B, C | |
| 4.3.5 | 5.8 | TX Out of Band Emissions | See -1 5.8.2 Table 15 | |
| 4.3.6 | 5.10 | TX Transient Power | See -1 5.10.2 Table 23 | |
| 4.4.2 | 5.18 | Receiver Blocking | See -1 5.18.3 category 2 min |
Helium Foundation Expected Minimum Performance
While all Helium gateways for operation in the EU must meet CD RED standards as presented in the sections above, additional performance parameters not regulated by ETSI standards are expected to ensure the intended operation of the Helium network. Maximum output power for the operational modes is regulated by ETSI regulations, however, ETSI does not specify minimum power output. Likewise, the EU does not regulate receiver minimum sensitivity levels for duty cycle limited devices.
For the proper operation of the Helium network, minimum power outputs and receiver sensitivity are expected for Helium’s hotspot approval process (see HIP19). The minimum performance levels are based on Semtech Corecell reference design using the SX1302 baseband processor and SX1250 RF transceiver. The Semtech performance report (link in the references) shows typical power outputs in section 4 and receiver performance for various spreading factors in section 8. Helium expects power output to be within 1 dB of the Corcell reference design and receiver sensitivities to be no worse than 2 dB above the reference design levels.