LoRa®-Based Solution from Renesas to Develop IoT Applications with Low Power Consumption

PublishTime： 2022-11-10 Article Source：Renesas Blogs

Renesas provides LoRA-based solutions for the RL78 and RA microcontroller (MCU) families, including communication software that realizes features like low power and easy design, and wireless evaluation tools that enable easy evaluation. In this blog, I would like to provide an overview of LoRa and LoRaWAN^® communications suitable for IoT for those unfamiliar with them and the LoRa-based solutions with low power consumption that are available from Renesas.

Requirements for IoT Application Development

Considering IoT applications that collect information from devices and control them while installed across a wide area in the field, there are generally the following requirements.

◇ Requires using long-range wireless communications to easily build a network

◇ Requires lower power consumption to reduce the capacity and replacement frequency of the battery

◇ Requires collecting device information in the cloud service, and analyzing and visualizing the data

LoRa and LoRaWAN are attracting attention as communication methods that can realize such requirements.

Long-Range Wireless Communication (LoRa)

LoRa is a wireless modulation technique and its biggest feature is that it can communicate over long distances. It might be a few kilometers in urban areas where there are many obstacles, and it could be even more than 20km under some line-of-sight conditions. It is suitable for transmitting small-sized data such as that used for monitoring and control, rather than large-size data such as images. Example applications are as follows:

Long-Range, Low-Power Wide Area Wireless Communication Protocol (LoRaWAN)

LoRaWAN is a communication protocol, which defines communication procedures, that uses LoRa wireless modulation technique, and is standardized by the LoRa Alliance^®. The LoRaWAN network consists of the following components.

◇ LoRaWAN device (Smart meter with LoRaWAN wireless communication functions, etc. Hereinafter, referred to as the device)

◇ LoRaWAN gateway (Hereinafter referred to as the gateway)

◇ LoRaWAN network server (Hereinafter referred to as the network server)

The device communicates wirelessly with the gateway using the LoRaWAN protocol. After that, the gateway communicates with the network server via the internet network, etc. The network server manages the entire LoRaWAN network and controls the radio-related parameters (frequency, data rate, transmission/reception timing, etc.) used for each device and gateway to enable efficient and stable communication.

Major features of LoRaWAN include the following four points.

Long-Range Communication, Low-Power Consumption: Use of LoRa, Availability of Intermittent Operation

The long-range communication feature of LoRaWAN is realized by using the wireless modulation technique of LoRa. In addition, the low power consumption feature of LoRaWAN is mainly realized by intermittent operation. In a typical operation mode for LoRaWAN, the device does not need to be in the receiving state except for during the predetermined periods after a transmission. Besides, it does not require periodic communication with the network server to maintain the network. So, the device can employ an intermittent operation where it keeps a sleep state, the state with the lowest power consumption, for most of the time, performs transmission and reception only when necessary, and returns back to the sleep state. Low power consumption performance can be achieved by extending the interval of the intermittent operation and reducing the power consumption in the sleep state which accounts for most of the time as much as possible.

Improvement of Communication Quality and Efficiency: Dynamically Switching Frequency and Data Rate

By switching the frequency each time the device transmits, reduces the negative impact of radio wave interferences and improves robustness. Besides, if the communication environment is not good, the data rate is lowered to improve the reachability to the gateway at the cost of increased communication time. If the communication environment is good, the data rate is increased and the communication time is shortened. As a result, communication traffic is suppressed and communication efficiency is improved by optimizing (minimizing) the communication time while maintaining the communication quality depending on the communication environment.

Obstacle Avoidance: Dynamically Switching Gateway

When the device transmits, it transmits data to all neighboring gateways. The network server selects the optimal gateway in consideration of the parameters such as the signal strength at the gateways that received the data from the device and sends data to the device via the gateway. In this way, by dynamically switching to the gateway with a good communication condition depending on the communication environment, the communication is less likely affected by obstacles, etc., and the communication stability can be improved.

Easy to Work with Cloud Service: Connection to Cloud Service by Network Server

In general, communication with a cloud service requires complex communication protocols for the processes such as authentication and encryption, but in LoRaWAN, the network server is responsible for these complex processes and communicates with the cloud service. So, the device side is not required to implement the protocol for the cloud service. That's why LoRaWAN makes it easy for devices to work with the cloud service.

LoRa-based Solutions from Renesas

Renesas provides LoRa-based solutions for the RL78 and RA MCU families, including communication software that realizes features like low power and easy-to-design, and wireless evaluation tools that enable easy evaluation.

By combining Renesas' ultra-low power microcontroller (RL78/RA2) with Semtech's LoRa transceiver (SX1261/SX1262), it is easy to build systems that require long-term operations with battery power.

Low Power

The combination of Renesas' ultra-low power microcontroller (RL78/RA2), Semtech's LoRa transceiver (SX1261/SX1262), and the communication software designed for the low power consumption achieves the total current of the microcontroller and the LoRa transceiver in the sleep mode is less than 1µA (0.55µA in the case of RL78/G23*1). Since the current in sleep mode can be minimized, which accounts for most of the time that LoRaWAN is in operation, benefits like a reduction in system cost via reducing the capacity/number of batteries and LoRaWAN devices experiencing a longer lifetime can be enabled.

Easy to Design

The communication software is compliant with the LoRaWAN protocol, sample applications that can be controlled by AT commands, and sample applications working with various cloud services (AWS, Azure, etc.) to visualize sensor data are provided. The software fully utilizes the power-saving features of the RL78 and RA2 MCUs and has been optimized to meet the timing constraints of the LoRaWAN protocol. So, it makes it easy to design IoT applications with low power consumption utilizing the LoRaWAN protocol.

Easy to Evaluate

Evaluation tools are useful to estimate power consumption before development, evaluate the wireless performance after prototyping, and analyze the protocol in the event of issues. So, they make it easy to evaluate developed applications. Since the software can work on the RL78 and RA2 evaluation boards (Fast Prototyping Board), the evaluation of the applications can be started immediately.

Summary

In this blog, Renesas explained the overview of LoRa and LoRaWAN communications suitable for IoT, and LoRa-based solutions with low power consumption from Renesas.

Please take advantage of our LoRa-based solutions when developing IoT applications with low power consumption utilizing LoRa/LoRaWAN.

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