LoRaWAN is a low power, long range radio network used to collect readings from meters that have no wired connection back to a data logger. This article explains how it works, what the common terms mean and why a LoRaWAN meter can stop reporting. If you are standing in a plant room with a meter that is not reporting, go straight to Quick Approach to LoRaWAN Fault Finding.
What LoRaWAN is
LoRa is the radio technique (a chirp spread spectrum modulation) that lets a very small signal travel a long way. LoRaWAN is the network protocol that runs on top of it and is maintained by the LoRa Alliance. A LoRaWAN meter wakes up, sends a short message and goes back to sleep, which is why a battery can last for many years.
Because the messages are tiny, LoRaWAN suits meters that report a few readings an hour or a day. It is not suited to streaming data or to anything that needs a fast reply.
The parts of a LoRaWAN system
| Part | What it does | What goes wrong |
|---|---|---|
| End device (the meter or a LoRaWAN module fitted to it) | Measures, wakes on a timer and transmits an uplink message. | Flat battery, radio switched off, wrong keys, poor antenna position. |
| Gateway | Listens on several channels and passes every message it hears to the network server. Most gateways do this over a mobile data connection using a SIM card fitted directly in the gateway, and some can also use Ethernet. It does not know which meter belongs to which customer. | Power loss, SIM or mobile signal problems (the backhaul), poor antenna or cable, bad location. |
| Network server | Checks each message is genuine, removes duplicates heard by more than one gateway, manages data rate and sends any reply. | Device not registered, wrong region or keys, frame counter errors. |
| Application server or platform | Decodes the payload into readings (a decoder or parser) and stores them for billing and reports. | Decoder does not match the meter firmware, so values are missing or wrong. |
A single meter message is often heard by two or three gateways. That is normal and is one of the strengths of LoRaWAN: a meter does not need to be tied to one gateway.
The words you will see on the platform
| Term | Plain meaning |
|---|---|
| Uplink and downlink | An uplink is a message from the meter to the network. A downlink is a message back to the meter. |
| DevEUI, JoinEUI (AppEUI) and AppKey | The identity and secret key of a meter. If any one is typed wrongly on the platform, the meter cannot join. |
| OTAA and ABP | Over the air activation (OTAA) means the meter joins the network and agrees fresh session keys. Activation by personalisation (ABP) uses fixed keys loaded in advance. |
| Spreading factor (SF7 to SF12) | The trade off between range and speed. A higher number reaches further but takes much longer on air and uses more battery. |
| ADR (adaptive data rate) | The network tells a meter with a strong signal to use a lower spreading factor, and a weak one to use a higher one. |
| RSSI | How strong the received signal is, in dBm. Closer to zero is stronger, for example minus 90 is stronger than minus 115. |
| SNR | How far the signal is above the background noise, in dB. LoRa can work with a negative SNR, which is one reason it reaches so far. |
| Frame counter | A number that rises with every message. The network rejects a message if the count goes backwards, which protects against replayed messages. |
| Class A, B and C | Class A devices only listen briefly after they transmit, which is how battery meters work. Class C devices listen all the time and need mains power. |
The radio rules in the UK
LoRaWAN in the UK uses the EU868 plan in the 863 to 870 MHz licence exempt band. Three default channels (868.1, 868.3 and 868.5 MHz) are used by every device. Transmissions are limited by a duty cycle, which is typically 1 percent on the default channels, so a device is only allowed to be on air for a small fraction of each hour. This is why a meter cannot simply send more often to make up for a missed message.
| Data rate | Spreading factor | Largest application payload | Typical effect |
|---|---|---|---|
| DR0 | SF12 | 51 bytes | Longest range, slowest, uses the most battery per message. |
| DR2 | SF10 | 51 bytes | Good range with moderate airtime. |
| DR5 | SF7 | 222 bytes | Shortest range, fastest, uses the least battery. |
Good to know: A meter that is struggling to be heard will fall back to a higher spreading factor, which makes each message take far longer on air. Many weak meters on one gateway can therefore crowd each other out, so coverage problems often get worse as more meters are added.
Why metering is hard for radio
- Meters are in cupboards, risers, basements and plant rooms behind metal doors, concrete floors and steel pipework.
- A signal that is fine in the street can lose most of its strength going through a basement ceiling or a dense riser.
- Metal enclosures act like a screen. An antenna pushed inside a closed metal cabinet will reach a fraction of the distance it should.
- Gateways on the roof or in a corridor may have excellent backhaul but poor sight of a meter in the basement.
Caution: Do not judge coverage from the meter alone. Always check what the gateway actually heard, using the RSSI and SNR shown against each message on the network server.
LoRaWAN on the Sycous range
The ZENNER B.One Gateway is the LoRaWAN gateway Sycous supplies, in Indoor and Outdoor versions. It sends messages to the application server over the mobile network using a SIM card fitted in the gateway itself, so there is no router to look after, and it changes to an Ethernet connection automatically if one is available. The gateway does not store meter readings, it only passes them on. It can be configured and updated remotely, and it is encrypted end to end with AES 128.
| Product | Role in a LoRaWAN system | Where to look |
|---|---|---|
| ZENNER B.One Gateway Indoor | Gateway. Built for coverage inside a building, including several floors and basements, without extra repeaters. | B.One Gateway Indoor |
| ZENNER B.One Gateway Outdoor | Gateway. Rugged coated aluminium housing for rural and urban coverage over a wide area. | B.One Gateway Outdoor |
| ZENNER C5 IUF heat and cooling meter | End device. LoRaWAN versions can be woken from sleep mode and sent a force join request. | Zenner C5 IUF |
| ThermaReach LoRaWAN relays, Pulse ATEX LoRaWAN sensor, ZENNER Easy Protect LoRa smoke alarm | End devices on the same LoRaWAN network. | Product sections in the Pay As You Go, Data Collection and Meter Hardware categories |
Good to know: A gateway only helps meters it can hear. For a basement or a riser, choose the Indoor gateway, place it with a clear view of the meters and keep its cellular antenna clear of metal.
What good looks like
- The meter joins the network within a few minutes of being powered and activated.
- Messages arrive at the expected interval with the frame counter rising by one each time.
- RSSI is comfortably above minus 110 dBm at the strongest gateway and the SNR is above zero.
- The spreading factor is stable and not stuck at SF12.
- More than one gateway hears the meter where the site allows.
For poor signal, see Improving Poor Radio Signal at a Site, and for any meter that is not reading start at Meters Not Reading or Poor Signal: Where to Start.
Frequently asked questions
What is the difference between LoRa and LoRaWAN?
LoRa is the radio signal. LoRaWAN is the network protocol that decides how meters join, how messages are secured and how the network manages data rate. A meter can be said to use LoRa radio and the LoRaWAN protocol.
How far can a LoRaWAN meter transmit?
Several kilometres in open country, but in a building the answer is the number of walls and floors the signal has to pass through, not the distance. A meter in a basement may need a gateway on the same site.
Does a LoRaWAN meter need its own SIM card?
No. The meter only needs the radio. The gateway needs the data connection, which on the ZENNER B.One Gateway is a SIM card fitted in the gateway, and one gateway can serve many meters.
Why does the meter show readings only once a day?
Most LoRaWAN meters are set to report on a long interval to save battery and stay within duty cycle limits. The interval is a setting of the meter, not a fault.
Can a LoRaWAN meter be read at any time?
Not usually. A battery powered Class A meter only listens just after it has sent a message, so any request has to wait for the next uplink.
Need a hand on site? Contact Sycous at info@sycous.com and have the details from the checklist above ready.