An introduction to LoRa gateways

Published on by Alexis Leibbrandt
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What is a LoRa gateway?

LoRa gateways are radio modules that serve as communication devices within a LoRa network between end-devices and a LoRaWAN network server (LNS).

A LoRa gateway is mostly used to transmit sensor data from an electrical device to the cloud. Especially in environments where other types of networks are not viable due to technical limitations, LoRa gateways can be used to establish a network implementation of relevant electrical devices. LoRa technology itself is only used for communication between the respective end devices and the gateways connected to them.

LoRa has the advantage that the wireless range for data transmission is exceptionally high and the energy consumption is very low – thus allowing for exceptionally long battery life.

How does a LoRa gateway work?

LoRa gateways are radio modules whose devices are fitted with a LoRa concentrator that allows LoRa packets to be received.

LoRa gateways include an operating system where the packet forwarding software runs in the background. In this way, the network administrator has more leeway in managing his gateway. The data rate between the end node (node or end device) and the LoRa gateway is comparatively low, but this is a necessary sacrifice to enable long-lasting battery life and a high radio range.

The gateway itself is connected to a LoRaWAN network server through high-bandwidth networks such as WiFi, Ethernet or cellular to provide end-to-end connectivity between LoRa end nodes and the application server.

Diagram lorawan

A typical LoRaWAN infrastructure

In a nutshell: All LoRa gateways within range of an end node receive data from the device. Then, the gateways forward this data to the LoRaWAN network server. The network server is in charge of removing duplicate data packets, verifying data integrity, and performing security checks before sending the message to the application server.

In the other direction, the LNS is also responsible for selecting the best LoRa gateway to forward all messages queued for the next downlink session.

How does a LoRa gateway connect to the LoRa Network Server?

LoRa gateways can be seen as transparent bridges that forward the radio data packets to IP packets and vice versa. Hence, gateways are connected to the LoRaWAN network server (LNS) via standard IP connections. Typically, the LoRa gateway communicates with the LNS via Wi-Fi, hardwired Ethernet, or cellular connection.

Indoor vs outdoor LoRa gateways

Indoor gateways are less sturdy and not weatherproof compared to outdoor gateways. They are typically equipped with case vents, which makes them not ideal for deployment outdoors as water can enter through these vents triggering corrosion.

Outdoor gateways on the other hand are robust and they are engineered to be weatherproof. Many outdoor waterproof gateways are IP67 certified, meaning they are completely protected against dust and may even survive temporary immersions in the water of up to 30 minutes in depths between 15cm and 1m. Another attribute that makes a LoRaWAN gateway “weatherproof” is the larger temperature ranges covered by the installed chips.

Similar to other outdoor hardware, these devices are typically 3 to 6 times more expensive than their indoor counterpart.

Single-channel vs multi-channel gateways

All LoRaWAN gateways can be categorized into 2 groups: Single-channel and multi-channel gateways. Single-channel gateways typically use cheaper transceivers such as the SX1276 and the SX1272. These savings in hardware are reflected in the overall price, making single-channel gateways an attractive choice, as they lower the barrier of entry for network enthusiasts wanting to give LoRaWAN a try without too much of a financial commitment.

Multichannel LoRaWAN gateways may be considered as the “real deal”, as they are LoRa Alliance compliant powered by much more expensive, but versatile transceivers. These gateways can receive on 8 or 10 channels and 6 spreading factors simultaneously.

The problem with single-channel gateways

In terms of functionality, single-channel gateways are very limited. This leads to less than ideal approaches to various network solutions. They can only receive on a single spreading factor and one channel at the same time. While some single-channel gateways can switch between different spreading factors and frequencies to simulate multi-channel gateways, most of them only have around 2% of the capacity of a multi-channel gateway.

Another problem with single-channel gateways is the lack of downlink support. This can lead to messages getting lost if a network attempts to schedule a downlink. Devices close to a single-channel gateway without downlink support will not switch to more efficient spreading factors, but instead “clogging” the spectrum with unnecessary transmissions.

Gateways antennas

LoRaWAN gateways can feature different types of antennas. There is not a single perfect type of antenna, each one has its pros and cons depending on the use case in the network, as the transmission signal is never equally pronounced in every direction. This is described by the so-called radiation pattern.

The most commonly used type of antenna is the rod antenna. Its waves are transmitted in a donut shape. Thus, most of the transmission power is directed horizontally while vertical transmission remains relatively poor. The radiation characteristics of the antenna must be taken into account when positioning the gateway. Here are few tips on placing gateways with a rod antenna in different scenarios:

End devices are located indoors on a single level:

If the connected sensors and actuators are located on a single level in a building, the LoRa antenna on the gateway should be mounted vertically. Ideally, your gateway should be located in the center of the intended coverage area.

End devices on multiple levels inside a building:

If you want to cover several levels or floors with one gateway, the gateway should be placed in the center of the building and the antenna should be aligned horizontally.

End devices are located outdoors:

If your end devices are located outdoors, make sure that the gateway is mounted at a reasonable height and is not obscured by anything objects, such as trees, buildings or fences in the immediate vicinity. The higher the gateway is positioned, the further the LoRa connection will reach. Ideally, therefore, the gateway should be mounted on a free-standing mast overlooking the terrain.

How many devices can connect to a LoRa gateway?

The number of end devices a single LoRa gateway can support depends on a few factors. Most importantly the data volume of the payload transmitted by the sensor and the transmission interval set on these end devices. These two factors can be used to determine the total amount of air time the gateway has to process. However, environmental factors also influence this equation.

Because it is hard to predict capacities of a gateway, it is usually best to find out through trial and error at the actual site of deployment, and verify the maximum number of supported devices without risking data packet loss.

Typically, a single LoRaWAN gateway can receive messages from several hundred devices.

How to install a LoRa gateway?

Previously, we’ve already discussed the importance of the antenna’s orientation, depending on the setting (indoor, outdoor, number of walls etc) and the location of the respective end devices. However there are many other aspects one needs to consider, when setting up a LoRa Network with gateways and sensors.

If your sensors are located in a concrete-dense building with particularly thick walls and a decent amount of windows, you may want to consider placing your gateway outdoors next to the building, with the Antenna aligned vertically. This may seem counterintuitive, however your gateway’s reception will benefit from the lower attenuation of glass compared to concrete walls and ceilings. The disadvantage to this strategy is that you will need an outdoor gateway which is much more expensive and maybe also harder to maintain than an indoor gateway.

Basic rules of thumb for installing gateways and end devices indoors:

Make sure there’s a reasonable gap between the device and the closest wall. Installing a device directly next to or inside a wall will greatly inhibit its transmission capabilities.
Do not install the device on the floor of the room. Deploy them at a height of at least 150cm.
If possible, try to place your device towards an opening in the room, like a window or a door frame.

What are common LoRa gateways in the market?

There is already a wide variety of gateways on the market ensuring a healthy level of competitiveness amongst certified manufacturers. There are gateways for all kinds of budgets, but due to the aforementioned constraints, a single-channel gateway should be avoided for most use cases.

This page of available gateways on the official LoRa-Alliance website provides the most informative overview of the different gateways currently available for purchase. If you want to “test the waters” with LoRaWAN without too much financial commitment The Things Indoor Gateway may be the best choice for you. It is a beginner-friendly, yet multi-channel gateway, that can be setup in less than 5 mins and can be powered with any USB-C cable.

Another example is the KONA Micro Gateway from Tektelic with Ethernet and cellular 3G/4G Backhaul. This gateway was designed for Mission-Critical Deployments and is also supported by the Loriot LoRaWAN network server.

If you want to learn more about LoRaWAN, be sure to check out our previous article:

LoRaWAN Explained

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