Is there an LPWAN in your future?

Jan. 28, 2021
Four contenders look to fill the gap between short-range WANs and LTE/5G options

One of the primary considerations for IoT end-devices is low power consumption. A second consideration is distance—can my signal make it from the device to an access point? Low-power wide-area networks (LPWAN) are designed to satisfy both low power and long distance requirements, claiming the gap between longer-distance cellular networks and short-distance local area networks (LAN), including industrial wireless sensor networks, Bluetooth, Zigbee and Wi-Fi.

Mesh networks like ZigBee and Bluetooth are being used in IoT applications. ZigBee isn’t the right fit for LPWAN applications, as mesh networks are only useful at medium distances. Conversely, local radio frequency (RF) applications like Bluetooth don’t have the required range.

LPWANs include several implementations and protocols, both proprietary and open-source, which share common characteristics of low power—operating on small, inexpensive batteries for years—and wide area, with a typical operating range of more than 2 km in urban settings.

The main players trying to capture the LPWAN market are LoRaWAN, Sigfox, NB-IOT and LTE-M. All LPWAN technologies use a star topology to conserve energy.

LoRaWAN (for Long Range Wide Area Network) is supported by the LoRa Alliance. It's deployed in a star-of-stars topology in which gateways relay messages between end-devices and a central network server. The gateways are connected to the network server via standard IP connections, and act as a transparent bridge, simply converting RF packets into IP packets and vice versa. The wireless communication takes advantage of the long range characteristics of the LoRaWAN physical layer, allowing a single-hop link between the end-device and one or many gateways. All modes are capable of bidirectional communication, and there's support for multicast addressing groups to make efficient use of spectrum during tasks such as Firmware Over-The-Air (FOTA) upgrades or other mass distribution messages.

Sigfox was developed by the French company of the same name to operate in the 200 kHz of the publicly available 900 MHz band. All network and computing complexity is managed in the Sigfox-operated cloud. Sigfox devices are constrained to a maximum of 140 (12-byte) uplink and four (eight-byte) downlink messages per day with limited coverage in Asia, which predominantly uses NB-IoT.

NB-IoT and LTE-M, which stands for LTE-Machine Type Communication (MTC), also known as Cat-M1, are both 3GPP projects. NB-IoT is part of the 5G technology family, while, as the name implies, LTE-M is based on the widely deployed LTE networks used by North American cellular providers and is also compatible with 5G.

NB-IoT uses DSSS (direct sequence spread spectrum) modulation instead of LTE; specifically engineered chipsets for NB-IoT protocols contribute to simpler device construction and result in reduced overall component costs. Due to its simpler waveform, NB-IoT consumes minimal power. It has potential advantages for smart-city applications, as it's well-suited for the static sensors associated with indoor coverage, utility meters and sensors, eliminates the need for a gateway, and allows connectivity of more than 100,000 devices per cell.

NB-IoT latency is typically around 1.6 to 10 seconds, while LTE-M delays are in the range of 100 to 150 ms.

Typical use cases for LTE-M include connected vehicles, wearable devices, trackers and alarm panels.

As you can see, each of these technologies has a target market by industry and/or geography. One thing is for certain, the market is growing rapidly. According to Global Market Insights, the global LPWAN market is set to surpass $65 billion by 2025.

Though the utilities and energy sectors will certainly be adopters, LPWAN will have a smaller impact on the process industry sector. But at least you're now aware of other options or tools to add to your wireless coverage quiver.

About the author: Ian Verhappen