How to overcome challenges in LoRa® end node design?

How to overcome challenges in LoRa® end node design?

LoRa® (Long Range) technology combines long-range wireless connectivity with low-power performance to extend the reach of the Internet of Things (IoT). From smart cities to smart agriculture to supply chain tracking, LoRa meets a variety of needs and is ideal for building flexible IoT networks that can operate in both urban and suburban environments.

But how difficult is it to develop a completely new LoRa solution or migrate to a completely new LoRa solution?

This requires understanding new wireless technologies and being able to pick the right solution for your application, and the whole process can be daunting. Wireless radio frequency (RF) design typically requires deep RF expertise and takes up a significant amount of a designer's development time.

This article will introduce the four main elements of the LoRa network architecture and discuss in detail some of the most common challenges designers face when developing LoRa end nodes. We will also look at the role of regulatory-certified LoRa modules in helping to overcome these challenges and shorten time to market.

LoRaWAN Network Architecture

LoRa is a wireless modulation technology and physical layer that supports low-power terminal devices to communicate over long distances. LoRaWAN is a wireless networking protocol that is used as a medium access control (MAC) layer and is implemented on top of the LoRa physical layer. The LoRaWAN specification details the communication protocol and network architecture, designed to ensure secure communication between terminal devices and interoperability within the network.

There are four elements in the LoRa network, as shown in Figure 1.

Figure 1. The four elements of a LoRa network (Image source: LoRa Alliance)

1. End nodes are the building blocks of the LoRa ecosystem, used to collect sensor data and send/receive data. These elements are usually remotely connected and battery powered.

2. The gateway is a transparent bridge between the end node and the network server. Typically, the end node connects to the gateway via LoRaWAN, and the gateway connects to the network using high-bandwidth networks such as Wi-Fi®, Ethernet, or cellular.

3. A network server can be connected to multiple gateways, able to collect data from multiple gateways and filter out duplicate messages, decide which gateway should respond to the end node message, and adjust the data rate to extend the battery life of the end node.

4. The application server collects data from the terminal nodes and controls the actions of the terminal node devices.

Let’s take a closer look at the concept of LoRa terminal nodes and the challenges encountered when designing them.

Common Challenges in Designing LoRa End Nodes

End nodes are relatively simple objects, such as sensors and actuators. These objects are often referred to as "things" in the Internet of Things (IoT). In a LoRaWAN ecosystem, end nodes communicate with network servers through one or more gateways.

In most cases, LoRa end nodes are low-cost battery-powered applications that need to be cost-effective and energy-efficient. There are multiple options for building a LoRa end node, depending on development time, target cost, power consumption, and RF expertise. Before looking at the options for building a LoRa end node, let's take a look at some of the most common challenges designers face when designing an end node, which will help us choose the right product.

When designing this end node architecture, challenges in the following areas are most common:

1. RF design

Like all other wireless designs, designing a LoRa end node requires a lot of RF design expertise. When using a LoRa SoC/SiP, the end node device developer is responsible for the entire RF design, including schematics, BOM, PCB layout, antenna tuning, and other RF hardware. Even with the availability of solid and useful documentation and application design guides, RF design is not always easy. The design process not only requires in-depth RF expertise, but also takes up a lot of the designer's development time. Debugging RF designs often requires special equipment, which further increases development costs. To overcome RF design challenges, some vendors offer SoC/SiPs with a variety of support, including very useful documentation, regulatory-certified reference designs, and detailed chip-level design packages. However, to minimize development time and risk, LoRa modules that have been optimized, tested, and certified for RF are always the best choice. Such modules can be used as a single component to provide a complete solution, thereby reducing design risk and shortening development time.

2. Compliance and certification

LoRa/Sub-GHz radios typically operate in the unlicensed ISM bands, and frequencies vary by region, which presents a challenge for hardware and software designers. Designers must be careful to ensure that they design a fully compliant solution while keeping BOM costs as low as possible. Additionally, RF regulatory requirements are constantly changing, and keeping up with regulatory changes, retesting devices, and recertifying compliance can require end-node development companies to invest thousands of dollars and a significant amount of engineering time that could have been spent on new projects. Using certified LoRa modules can easily solve this problem, as the module manufacturer will take care of meeting the latest regulatory requirements and recertifying the module to meet the latest specifications. If you choose a LoRa module that is certified by regulations, you can completely avoid all the costs and time spent on ensuring compliance.

3. Multi-regional work

LoRa devices support multiple operating frequencies for different regions. End node manufacturers usually release their end products in one major region first. Once demand increases, companies will consider expanding the application scope of the same design to cover other regions. If you have a SKU that supports multiple regions, the final product can be seamlessly ported and expanded to different countries and regions. Regulatory-certified LoRa modules are suitable for multiple frequency bands and are ideal for such product expansion.

4. Reliable software

Typically, the LoRa module integrates the entire LoRaWAN protocol stack inside the module, and the terminal node developer only needs to implement the initialization and communication of the module. For LoRa SoC/SiP and independent LoRa modules, the protocol stack must be provided by the manufacturer. If it is not provided, the developer must develop the protocol stack by himself. In order to minimize the software development work, it is recommended to select a LoRa module/IC supported by the manufacturer's LoRaWAN protocol stack. The verified LoRaWAN protocol stack provided by the manufacturer ensures the interoperability between the terminal node and the main LoRaWAN networks and gateways, enabling the terminal node to work on different networks while reducing risks.

5. Migration from module to SoC

Many companies start prototyping and initial production runs based on certified modules to reduce risk and get their products to market faster. After their products begin to ramp up in production, companies may decide to switch to LoRa SoC/ICs for increased flexibility or reduced BOM costs. Migration is not always easy, so it is important to consider standalone modules that allow for simple software migration between modules and ICs. In addition, it is important to choose a vendor that sells both modules and SoCs so that the development platform, software migration, and support structure can remain the same.

Regulatory-certified LoRa modules help overcome challenges and simplify LoRa end-node designs

LoRa modules contain all the necessary radio components as well as the LoRaWAN protocol stack and RF circuitry, making them ideal for accelerating the development of LoRaWAN end devices. RF development and certification are performed by the module manufacturer, so any changes to the certification specifications or component replacements are completely handled by the manufacturer, saving end device manufacturers significant development time and re-certification costs.

Standalone LoRa modules feature highly integrated LoRa ICs that provide enough memory to run application code as well as the LoRaWAN protocol stack. This eliminates the need for an external microcontroller, saving board space and system cost. Figures 2 and 3 below show a simple example of such a standalone module. Based on Microchip's SAM R34/35 series ICs, the WLR089U0 module is a compact module with 256 KB flash and 40 KB RAM, making it ideal for space-constrained applications. In addition, the module has an integrated RF switch that enables multi-band operation and allows the same module to be used in multiple regions, making it easier to expand the market for end products. The WLR089U0 is also supported by Microchip's proven LoRaWAN protocol stack and proprietary point-to-point software, which can simplify the software development process for end users who are developing LoRa applications. These modules are based on the SAM R34/35 IC, so migration between modules and ICs is also simpler. Choosing such a module can help overcome all common design challenges when developing LoRa end nodes, thereby simplifying the entire design process.

Figure 2. Block diagram of WLR089U0 LoRa module

Figure 3. WLR089U0 LoRa module

in conclusion

Developing LoRa terminal nodes is complex and time-consuming. Highly integrated and certified LoRa modules provide a simple, proven way to overcome the complex challenges involved in designing these terminal nodes. Reliable software, larger memory, integrated RF switches, and regulatory certifications are some of the key features of LoRa modules. Choosing a LoRa module with rigorous certification not only helps simplify the design process, but also enables terminal node developers to successfully differentiate their products and bring them to market faster.