Add “LoRa” to your list of abbreviated tech terms.
Meet our friend LoRa. LoRa is kind of new to the area and is making an impact on the wireless IoT options available. The company Semtech acquired this proprietary modulation technique, and major chipmakers (Microchip for example) are creating tools using LoRa that are worth learning about for a variety of reasons. The roots of LoRaWAN (short for Long Range, Wide Area Network) are in the CSS (Chirp Spread Spectrum) space. So this becomes a nice alternative when device situations call for long range wireless connectivity. Additionally, the low power requirements make it realistic to operate node devices with long battery life or smaller batteries. Think remote locations or already established industrial environments that could benefit from groups of sensor nodes reporting lower amounts of data to an independent cloud structure for routine monitoring or ongoing data analysis.
As an electronics design engineering services company, DE Design Works has tested initial assessment prototypes for an industrial customer and achieved connected nodes at 1 mile distance to the gateway that indicate 400 days of battery life on a charge. That’s correct – getting your facilities or machinery monitored is no longer limited by Bluetooth or ANT+ measurements in the sub-100 foot category, nor do you need to intrude upon existing Wi-Fi networks.
- When compared to alternatives for industrial wireless communication in remote environments, the advantages of LoRa are distance, battery life, and features for security.
LoRaWAN is an open standard that allows for off-the-shelf or custom router infrastructure.
- DE Design Works has worked with the LoRa radio for the IoT node supplied by a well-established industry leader (Microchip) with proven tools and support. The SiP (System in Package) is an integration of a radio, memory, and processor. This means it will scale to manufacturing well in cost, battery life, and size. These factors could help you create a low-risk technology platform choice.
- The Microchip SAMR34/R35 SiP has an ARM core processor, memory, and radio integrated onto the die at the silicon chip level, making it a smaller package, lower power, and lower cost when compared to a separate board-level radio module.
Range and Bandwidth
The theoretical range cited for LoRa is around 6 miles. This extreme distance wireless range requires line-of-sight. Objects will impair this range – wireless waveforms are absorbed by obstructions, such as walls, metal structures, and machinery.
LoRa hardware is designed to use license-free sub-GHz frequencies (433/868/915/865/867/923 MHz) and can achieve data rate from 27 Kbps to 0.3 Kbps. This low frequency operation means it can penetrate objects and travel much further, however the LoRa tradeoff is lower data rates so it would not be suitable for voice or video. In comparison, Bluetooth and standard Wi-Fi use 2.4GHz for faster data rates but less range and penetration.
Bandwidth is a function of packet size and data rate. LoRa has multiple channels for spread spectrum, this can be used as a sliding scale in firmware to favor bandwidth or range through channel configuration. This can serve as a powerful feature in reliability of the product to communicate in a challenging environment if the data packet size and bandwidth of transmissions are acceptable.
With any radio technology, the most energy is consumed when the radio is transmitting RF energy.
Reducing the time spent transmitting results in lower energy consumption and extended battery life. Also, for the radio to receive data it must be powered up and waiting for the message to arrive. When the radio is in a sleep state, depending on what sensor activity the remainder of your node needs to monitor, a very low energy consumption can be achieved.
The average total energy consumption of the device is determined by the weighted time ratio of power consumed during activities vs power in sleep state. The goal is then to minimize the time and frequency spent performing energy consuming activities and radio operation.
LoRa is a good choice for reducing power consumption due to its protocol design, allowing a choice of energy consumption vs. communication latency and speed. In LoRa development, three classes of operation are defined:
- Class A – Sensor sends data as needed, right after which the gateway can send data back. The node can sleep until it needs to send. This has the lowest energy requirement.
- Class B – Gateway polls sensor devices for data at a fixed interval during which the node is awake and listening, then the node responds. The node must wake up periodically to receive the messages. This has medium energy requirements, and medium response time.
- Class C – Nodes can receive data from the gateway at any time, requiring the node to be listening always. This has the highest energy requirements, but lowest response time.
Along with a light-weight protocol with low processing overhead, LoRa offers low-power operation with short messaging and short listening windows which allow low-energy operation.
Power consumption is also a function of the voltage at which the devices are designed to operate (P=V*I). A successful low power optimized design is the purposeful system architecture design of the entire PCB hardware sub-system, sensor, firmware, data packet size, transmit times and speeds and use-case implementation in a culmination of practical programming architecture to achieve an optimum balance between use-case and battery life. With a professional custom electronics hardware design to meet environmental challenges, architects of the system can provide the flexibility and resources needed for specific goals. The firmware and the use-case then become the critical factors in optimizing battery life.
Key tradeoff adjustment impacts are
- How often the device can be in sleep state
- How often the device must transmit data
- How much data the device must transmit
- How big is the battery
- Any thermal impacts or life degradation environments to the battery chemistry
- Outlier use-cases that impact the device such as listening events or mode changes need to be considered and optimized
Should you need to offer the data open source and provide interoperability with off-the-shelf devices, the LoRa Alliance provides standards and certification testing to the standards. (https://lora-alliance.org/)
- LoRa is built on a sub-GHz FCC approved radio spectrum, speaking a defined message set
- LoRaWAN is a Wide Area Network implementation of LoRa, not just a radio, but an open protocol designed for interoperability – that can be public or private use.
A LoRa enabled product does not have to be open source, it can be protected and proprietary. LoRa messages can be received by 3rd party devices – if the system is architected to the LoRaWAN standard and if the 3rd party device is configured to use the messages.
- The LoRaWAN grand vision is for LoRaWAN devices to use public infrastructure to communicate to the cloud. https://lora-alliance.org/lorawan-coverage
- The use of LoRa radios today adds potential long-term additional advantages in lower cost of infrastructure in the future.
LoRa is one of several types of sub-GHz bi-directional radio technologies that may meet the requirements of the application. Other choices for wireless radios and underlying hardware platforms are available. The main considerations for an application include the following:
|Technology||Why is this better than LoRa?||Why LoRa is better|
|Proprietary Sub-GHz 878,900 MHz||
|BLE 5.2 (Mesh and Long-Range Options)||
|Wi-Fi 2.4/5 – dual band||
(CAT-m or NBIoT)