LoRaWAN Overview and Diagnosis

What LoRaWAN is

LoRaWAN is a low power, long range radio network. Meters send small messages to gateways, which pass them to a network server and on to the application platform. It suits battery powered meters that only need to send a few readings a day.

How LoRaWAN works

• The meter has a LoRaWAN radio and sends a message at set intervals.
• Any gateway in range can hear it and forward it. The meter does not belong to one gateway.
• The meter must join the network using its keys, and the keys must match the ones on the network server.
• The network server forwards the message to the application platform, where a decoder turns it into readings.
• Coverage depends on the gateways, so building structure and gateway position matter.

For the full detail, read Understanding LoRaWAN for Smart Metering.

Where issues usually lie

• The meter has not joined the network, or its keys do not match.
• There is no gateway coverage, or the gateway is offline.
• The message arrives but the decoder cannot read it, so no readings appear.
• The battery is flat.
• The signal is weak because of the building or the position of the meter.

Diagnosis and quick approaches

Use this guide when a LoRaWAN meter has stopped reporting, never reported, or is reporting badly. Work through the sections in order. Each one starts from a symptom and takes you to the most likely cause. For background on the terms, read Understanding LoRaWAN for Smart Metering.

Not sure which guide you need? Start at Meters Not Reading or Poor Signal: Where to Start.

Before you start: collect the facts

• Meter serial number and DevEUI.
• The time of the last message received, and how often the meter should report.
• Whether one meter, several meters or every meter on the site is affected.
• The RSSI, SNR, spreading factor and gateway shown on the last few messages.
• Whether anything changed: a battery swap, a firmware update, a new gateway, a SIM or network change or building works.

Good to know: One meter offline is usually a meter or location problem. Many meters offline at the same time is almost always a gateway, backhaul or platform problem, so check that first.

1. Every meter on the site has stopped reporting

1. Check the gateway is online on the network server or application server. If it shows as disconnected, the fault is between the gateway and the internet, not with the meters.
2. Check the gateway has power and its status lights match the manufacturer documentation.
3. Check the SIM card fitted in the gateway. It should be seated properly, active and on a data plan. Gateways here use a SIM directly, so there is no router to check.
4. Check the mobile signal where the gateway is mounted. A gateway in a plant room or basement may need an external GSM antenna fitted outside the metalwork.
5. Check whether an Ethernet cable is also fitted. The B.One Gateway moves from mobile to Ethernet automatically when Ethernet is available, so if a cable is connected, check the cable and the network port as well as the SIM.
6. Ask Sycous to confirm the SIM is active if it looks healthy but the gateway will not connect. A suspended or expired SIM looks just like a dead gateway.
7. Reboot the gateway only after you have noted the status lights and the time, then watch for messages to return. If the gateway is still online through its SIM or network connection, try to fix it remotely before a site visit: the Elvaco CMe2100 can be configured, updated and rebooted by SMS or HTTP, the CMe3100 can be reached through its built in web interface, and the ZENNER B.One Gateway and the Elvaco Edge can be configured and updated remotely.

Warning: Check the mobile network the SIM uses is still live in that area. Equipment that can only use 2G or 3G stops working when those networks are switched off and needs a 4G capable unit.

2. A new meter will not join the network

1. Check the meter is actually switched on and activated. Many meters ship with the radio disabled until it is woken, so check the meter manual. For a ZENNER C5, see Waking a Zenner C5 from Sleep Mode and LoRaWAN Force Join Request.
2. Compare the DevEUI, JoinEUI and AppKey on the platform with the meter label, character by character. A single wrong character stops it joining.
3. Check the meter is registered on the correct network server and for the correct region (EU868 in the UK).
4. Look in the network server logs for join requests. If requests arrive but are rejected, the keys are wrong. If no requests arrive, the gateway is not hearing the meter.
5. Move closer to a gateway or into the open to test. If it joins there, the original location has a coverage problem.
6. Check the battery. A weak battery can power the meter display but not give the radio enough current to transmit.
7. Wait and watch. Some meters retry joining on a slow back off timer, so after a failed attempt the next try can be many minutes or hours away.

3. The meter reports, but with gaps

1. Look at the RSSI and SNR over time. If they hover near the edge, the meter is only heard some of the time.
2. Check the spreading factor. A meter stuck on SF12 is working hard to be heard and is probably in a poor location.
3. Check the meter antenna. It should not be inside a closed metal cabinet and should point as the manual describes.
4. Check for new obstructions: a new metal door, a boarded up riser or building works between the meter and the gateway.
5. Check the gateway antenna, cable and connectors for damage, water ingress or loose joints.
6. Check the battery level if the platform reports it. A tired battery shows up as gaps that get longer over time.
7. Add a gateway, or move the existing one, if the meter is correctly set up but simply too far from coverage.

4. The meter reports but the readings look wrong or are missing

1. Compare the raw payload with the decoded values. If the raw payload is present and the values are blank, the decoder is the problem, not the meter.
2. Check the decoder or parser version matches the meter firmware and hardware version. New firmware can add or reorder fields.
3. Check the units and scaling. A value that is ten or a thousand times out is usually a unit mismatch.
4. Check whether the meter was replaced. A new meter with a new DevEUI needs its own entry and the right decoder.
5. Check the reading against the meter display. If the display and the payload disagree, note the time of both and raise it with the meter manufacturer.

For practical fixes to weak signal, see Improving Poor Radio Signal at a Site.

5. When to call for support

Call for support if the gateway is online, the meter has good signal on the network server, the keys match and the meter still does not report. At that point you need the meter manufacturer logs or a firmware check.

Frequently asked questions

Why has my LoRaWAN meter stopped sending data?

The most common causes are a gateway or its internet connection going offline, a flat battery, a change in the building that blocks the signal, wrong keys after a change on the platform, and a decoder that no longer matches the meter.

How do I know if the problem is the gateway or the meter?

Check whether other meters near the same gateway are still reporting. If they are, the gateway is fine and the fault is with the meter or its location. If none are, check the gateway and its connection.

What does join failed mean?

The meter sent a join request but the network did not accept it, or the meter never heard the reply. Check the keys, the region setting and the signal strength in that order.

What does a frame counter error mean?

The network server received a message with a lower counter than expected and rejected it. It usually follows a meter reset or a battery change on a device using ABP.

What signal strength do I need?

As a rough guide an RSSI stronger than minus 110 dBm with an SNR above zero is healthy. Weaker than minus 120 dBm is marginal for most meters.

Need a hand on site? Contact Sycous at info@sycous.com and have the details from the checklist above ready.