Relay Mode of Operation Extending LoRaWAN Coverage

Relay Mode of operation is a powerful brand-new feature of LoRaWAN technology to extend the range and coverage of LoRaWAN networks and improve their dependability. This new LoRaWAN feature has two main benefits: first, it will extend the range of LoRaWAN networks, and, second, it will improve the coverage and dependability for LoRaWAN devices that have a poor connection with the gateways because of their distant locations (examples are water and gas meters in basements, parking meters.) The LoRaWAN relay feature will also help with massive IoT adoption and deployments. Relay nodes, similar to the LoRaWAN devices and sensors, operate on batteries and are therefore simple to deploy and low cost. Moreover, relay nodes will help to achieve robust network coverage and dependability for all LoRaWAN devices and sensors, reduce the number of re-transmissions and in some cases significantly reduce the network costs as operators will not have to deploy additional gateways for a few devices or sensors. For a better understanding of the new Relay Mode of operation and Relay Nodes, let’s focus on the particular benefits they can bring and the ways they do that.

How Does Standard LoRaWAN Connectivity Work?

The LoRaWAN protocol supports deployments of gateways, which are designed to receive and send messages from and to end devices and sensors. The LoRaWAN standard implies that the gateway receives the messages and forwards them to the network server. The gateway can support multiple channels, so typically, a single gateway will receive responses from thousands of LoRaWAN devices and sensors and pass those messages to the network server. Conversely, the messages received from the network server are sent to each LoRaWAN device and sensor. This is why the term gateway is used instead of the base station – the latter would imply the processing of messages similar to 4G-5G technologies before sending them to the network server or devices and sensors.

Security Protocol

The LoRaWAN standard communication protocol uses encryption for secure relay data transfer. LoRa transmissions are secured with a 128-bit encryption scheme. This encryption is achieved by using two session keys, one held by the network server and the other held by the application server. Each session key is generated during the join exchange between the end device and the network server. Once a device has joined the network, it can send and receive data securely. The NwkSKey provides integrity protection of messages and the AppSKey provides encryption.

Activation

During the LoRaWAN network activation process, a network server and end node must each derive the same session keys using exchanged device information, nonce values, and the shared secret key(s). The session keys are used for only this session of the end node. As the session keys are re-generated during any subsequent join-procedure the loss or theft of these keys is not as critical as that of the root key(s). It would be reasonable to mention that adding a relay node will not compromise LoRaWAN security by any means, so it shouldn’t be a point of concern.

How Does LoRaWAN Relay Feature Work?

The relay mode of operation is a new LoRaWAN feature that helps ensure that a gateway is receiving data from a device that might be too far away to transfer it without a relay node. In order to extend network coverage, LoRaWAN can use a new relay feature, which is simple to implement and inexpensive. LoRaWAN relays use LoRaWAN uplink and downlink messages to transfer data. Once the end-devices uplink has been received; the relaying mechanism wraps the initial message with some added information and sends an uplink to the gateway. Then, the gateway forwards this uplink to the network server that recognizes it as a relayed message. Ideally, a well-positioned, robust, and noise-resistant relay module will enable bi-directional communication to devices that were out of reach of the original network coverage.

In order to use the new relay feature, LoRaWAN devices must support class A communication. This is bi-directional and asynchronous wireless communication, allowing each uplink transmission to happen at any time, followed by downlink windows. Class A communication is also used to send and receive network control commands. It allows a LoRaWAN end device to enter a low-power sleep state for as long as the application specifies.

The current LoRaWAN standard based on the LoRaWAN link layer standard consists of end devices and gateways. While the existing LoRa network specification allows only a single hop between end devices and gateways, the two-hop approach available with a relay module has the advantage of significantly improving the coverage area. As we already mentioned, a battery-operated relay module is extremely low-cost and is able to transfer LoRaWAN frames to achieve the coverage needed.

What Problems Will New Relay Feature Solve?

Adding a relay feature to the IoT network will help achieve robust network coverage extension in a broad range of key verticals. If you have the Internet of Things network and want to achieve excellent coverage, you should include either the gateway to a LoRaWAN node or a relay feature. Tomorrow you will look at the requirements for network coverage and be surprised how it is different from today, so if you want to have stable grounds in the technology sector, you should think about having this essential building block in your Internet connectivity.

The relay specification feature has a significant benefit for remote devices requiring extremely challenging underground coverage or for cases requiring deep indoor coverage. Network coverage extensions are necessary for meters inside metal closets, highly challenging environments such as around turns, building fire alarms, forest fires, flood/avalanche/earth movement, and similar cases requiring deep indoor and robust network coverage. Environmental challenges surrounding many spheres in smart cities and remote areas do not let devices perform at their best as they can lack full network coverage. Enabling the relay feature tomorrow, in turn, will let us enable massive IoT deployment. With relay end-points, long-range communications will be available even in extremely challenging underground, concrete and metal surroundings.

Why is it Better to Use LoRaWAN Relays rather than Additional Gateways?

You may ask this question, and it will be completely justified. You may think that it will be simpler and more effective to add one more gateway to the system rather than adopt a relay. But when you are aiming to extend network coverage, there is no such choice as either the gateway or relay receiver module. If you add one more gateway to achieve the coverage needed, you will put in more effort matching power and backhaul connection needs and pay more. With a relay node, in turn, you can have the same coverage more easily using the batteries power supply and LoRaWAN connection.

Lower Cost

The LoRaWAN relay feature, in turn, is less expensive than traditional IoT gateways, easier to integrate, and way more efficient in network coverage extension. In addition to being a low-cost solution, this mode of operation is a good choice for enterprises that already have their IoT architecture and know its physical limits. Furthermore, a robust LoRaWAN certification program with an integrated relaying mechanism allows enterprises to reduce the number of gateways needed, which is a key factor when trying to save some money.

Relay endpoints create a multi-hop communication method that improves the coverage of LoRaWAN in highly challenging environments when gateways cannot receive sensor signals themselves to ensure long-range communications. LoRa Alliance members identified that adding relay specification has a number of advantages, including low cost and increased range of coverage. It is also an excellent choice for use in the utilities sector as metering sensors require underground coverage, which represents a huge market opportunity for battery-operated relay devices.

Full Network Coverage

A relay network coverage extension can dramatically increase communication range. Adding a relay module can also simplify the deployment of LoRaWAN networks and help enable massive IoT deployment in smart cities and remote areas. The advantage of the relay mode of operation over mesh networks is that fewer nodes are needed.

The new relay feature has all the grounds to become a key component of LoRa networks. It can improve the performance of sensors and solve the problem of insufficient coverage. A relay module will ensure smooth end-to-end communications for water meters inside metal closets, underground parking devices, and outdoor Internet of Things components affected by extreme weather conditions. Relays will use feedback from a gateway to determine when to transmit data to the end device and when to transfer LoRaWAN frames further. This technology is planned to be compatible with most LoRaWAN standard applications, so it should become a common choice for most of the key verticals.

In What Ways Do Gateways Prevail over Relay Nodes?

It is important to still look at the option of adding more gateways for setting up smooth monitoring. Gateways have higher capacity, better performance capabilities, and lower power consumption than the newly introduced relay feature.

Higher capacity

The network capacity is a function of the density of the gateways. To maximize the capacity of the network while preserving the battery power of LoRa end nodes, LoRaWAN gateways employ an adaptive data rate mechanism. This mechanism sends packets at the lowest rate when sensors are closest to the gateway. The higher rate is used when sensors are farther from the gateway. So, gateways and devices work at full capacity in this framework.

Lower Power Consumption

Low power consumption is one of the key requirements for a LoRa module. There are several factors, which can determine energy consumption, such as the operation mode and the amount of time a device is active. Generally, operation modes consume more power than sleep modes. Thus, it is necessary to consider both these factors when calculating the energy consumption of a LoRaWAN device.

LoRaWAN networks are always set up in a star topology, where gateways act as relays between end devices and send messages to the network server. Adding one more gateway instead of the relay mode of operation in LoRaWAN, you will be able to maximize the amount of data transferred and minimize energy usage. Gateways’ low-power mode allows end devices to enter a low-power sleep mode. Moreover, the device can enter a low-power sleep mode for as long as it is required by the application.

LoRaWAN endpoints should be low-power systems. It is essential to avoid feature creep, which causes the system to consume more power than it should. The clock speed and memory size should also be kept low, as these factors affect the power consumption of LoRaWAN endpoints. Adding one more gateway require paying only a nominal cost of a device itself when power expenses will be extremely low.

Better Performance

Gateways are way more powerful than relay nodes can ever be because of the robust hardware, transmitting and receiving capabilities, and RF filters. In any way, gateways can handle more devices and ensure the better performance of the whole smart system you have.

What are the Important Points for Consideration of the Relay Feature?

At the first glance, looking at the information provided on the relay mode, it may seem the perfect solution to all the issues existing in the IoT market. However, we should stay objective and apply critical thinking to this matter not being blinded by a promotional campaign. First of all, in order to extend coverage with the relays, companies will need to integrate new devices with relay-capable FW. It might not be an issue for small-sized enterprises but if we are talking about global companies or smart cities, buying a whole bunch of new devices just to start using relay mode may appear too costly and unreasonable.

Another major point of concern is battery life reduction. End devices, which will be operating based on the relay feature, are expected to have ½-¼ of battery life if compared to a normal class A device. Such battery reduction is expected due to extra processes involved in relay mode operation. For example, a device will need to send a “power hungry” WakeOnRadio signal to notify the relay, which is expected to result in the biggest addition to the power consumption. Of course, we cannot say that it will be like this for sure before real-life testing but these estimates are likely and have to be taken into consideration.

The important thing to keep in mind is that even though a relay can extend coverage and is way cheaper than an additional gateway, it will always consume network capacity. Gateways are a more stable and superior option in terms of performance. So, to choose or not to choose this new relay feature mainly depends on the goals you have.

How is TEKTELIC Going to Address New Relay Feature?

TEKTELIC leads the LoRaWAN market with its largest portfolio of Carrier Grade Gateways, Devices, Sensors, and solutions and always investigates how to increase value to our customers and the LoRaWAN ecosystem at large. We listen to our customers to understand their pain points. We believe the Relay Mode will address a number of issues current customers face in some way, and reduce the operator TCO. We assist its development and introduction within the LoRaWAN standard and decided to share it with you and start working in this direction. We know of many applications where relay mode will help monitor static assets in smart cities, the utilities sector, parking, and others. As a Sponsor member of the LoRaWAN association, TEKTELIC today has over 450 customers, leads massive IoT adoption, and believes this feature will be used by many of its current and future customers. At the same time, we want to be an objective side here and that is why telling you all the pros and cons.

Main Takeaways

LoRa devices offer many compelling features for IoT applications. They are designed to be low-power and can be deployed on both public and private networks. LoRa devices can also easily integrate into existing infrastructure. The new relay mode, in turn, can become a total groundbreaker for difficult environments. A battery-operated node will solve the problem of transporting LoRaWAN packets from the gateway to LoRaWAN end devices and sensors through thick walls, ground metal covers, underground parking, metal frames, and other hard-to-reach environments.

Currently all the LoRa Alliance Sponsor and Contributor members, including TEKTELIC, closely collaborate to finalize the relay module specification so companies can build, test, and make them available to their customers. While our R&D team is working on the real relay device, our goal here is to give you a clear and easy-to-follow understanding of this new feature and its benefits.

We still see the list of challenges, which might be important to address, such as:

• Compatibility of relays with current devices and the necessity to buy new ones supporting relay-capable FW;
• Lower battery life of end devices expected (½-¼ of battery life compared to current class A device);
• Increased consumption of network capacity;
• Inability to build a MESH network; (rather its goal is to provide significant coverage extension to the star architecture that LoRaWAN is based on).

It is difficult to say now how effective this relay mode will turn out to be but when we see all the benefits and possible drawbacks on the same plate, it will be way easier to make decisions.

Do not hesitate to visit our website and check the news section for updates. Feel free to write to our sales team if you have any questions as well, they’ll be happy to help.