Certifying an End Device for LoRaWAN®: European Sub-Bands

The European radio regulations can be ambiguous when it comes to certifying and understanding LoRaWAN® network operation. Here we take a look at how an end device built with a LoRa® chipset should be certified for regulatory compliance, as well as the duty-cycle capacity we can expect from an end device deployed in a practical LoRaWAN network.

The EU ISM band is separated into sub-bands, each with specific requirements and limitations on their use. These limitations are governed by the ERC-REC 70-03 [1]; the excerpt for operation in the European 863 to 870MHz band is shown below:

Table 1:  Excerpt of the ERC-REC 70-03 [1] Band Plan for the EU 868MHz band (Page 8)

The LoRaWAN standard was conceived with the intention of using these sub-bands.

The benefit of addressing multiple sub-bands, instead of covering the entire band (such as h1.0 or h1.2) is that the duty cycle allocations per sub-band can be aggregated, and some of the lower output power limits are removed, allowing the medium access to be simplified (for example avoiding the use of FHSS).

Sub-Bands Used by LoRaWAN

The figure below shows the sub-bands targeted by LoRaWAN [2]. All of the light-blue bands permit almost complete coverage of the EU ISM band at the full 25mW of RF output power. We also benefit from the aggregation of 3.2% of duty cycle (over the sliding one hour window imposed by the ETSI regulations [3]).

Figure 1:  Sub-Bands Relevant to End Devices on a LoRaWAN Network in Europe

The remaining h1.7 band, also relevant to LoRaWAN, is only used by the gateway for transmission on 869.525MHz. Therefore, it would not feature in the transmission testing for an end device in the EU. For clarity, in the figure above, the three mandatory join channels required by the LoRaWAN are shown as green lines in the h1.5 band.

LoRa Basics Modem Implementation

At the time of writing, the test houses providing LoRaWAN certification (administered by the LoRa Alliance®) are in the process of transitioning from the LoRaMAC-Node implementation of a reference LoRaWAN stack for the end device [4], to the LoRa Basics Modem implementation [6]. For the European region only, both stack implementations check that any frequency requested of the end device falls within a legal sub-band. Each sub-band is identified by a band number with a lookup table that is used to specify (and enforce) the duty cycle restriction in that sub-band. (For completeness, in Figure 1 above, the band identifiers are numbered from B0 to B5).

Certification and Regional Parameters

The regulatory certification test coverage required depends upon the final intended use. If the final use case is a private network, where only a subset of these bands is to be addressed, then the certification coverage could be reduced. Note, however, that the aggregated duty cycle may end up being reduced, depending upon the bands targeted. If the final application is a public LoRaWAN network, then your end device could be asked to operate on any one of these sub-bands upon joining the network.

To simplify your final application, both LoRa Basics Modem and LoRaMAC-Node, take care of the duty cycle management process for you. It cumulates the time spent in each band and informs the application layer when a specific sub-band’s duty cycle allocation has been used up.

A Final Word: Duty Cycle in the Application

When considering duty cycle management in the final application, we should also consider gateway capacity. The LoRaWAN gateway employs a low cost, low power consumption architecture that permits the placement of a pair of 1MHz bandwidth radios anywhere in the EU ISM band [5]. The eight LoRa receive channels are placed within those two 1MHz bands. In terms of your final application, it is therefore worth considering that you’ll typically have access to the duty cycle allocation from two sub-bands. In most deployed networks these focus on the 1% uplink allocations. This means that you can reasonably expect 2% of the aggregated duty cycle available to the end-device in your final application.

For additional information about getting devices ready for deployment in Europe, see How to Qualify a LoRaWAN Device in Europe.

References

[1] Edition of February 2021 ERC Recommendation70-03 Relating to the use of Short Range Devices (SRD) Tromsø https://docdb.cept.org/download/2464

[2] LoRaWAN 1.1 Specification, Authored by the LoRa Alliance Technical Committee, version: 1.1 Date: Oct. 11, 2017 https://lora-alliance.org/wp-content/uploads/2020/11/lorawantm_specification_-v1.1.pdf

[3] ETSI EN 300 220-1 V3.1.1 (2017-02)

[4a] https://github.com/Lora-net/SWL2001

[4b] https://github.com/Lora-net/LoRaMac-node

[5] LoRa® Corecell Gateway Reference Design LoRa® Corecell Gateway Reference Design for Listen Before Talk and Spectral Scan | Semtech

[6] https://github.com/Lora-net/SWSD001

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