Low-power wide area networks (LPWANs) provide many benefits for IoT and are gaining wide acceptance. But the LPWAN landscape is vastly different from a few years ago. The technologies have coalesced into a few dominant ones. The two undisputed leaders are LoRaWAN and LTE. Two other newcomers, Wi-SUN and Weightless, are gaining significant traction.
A unique characteristic of LPWANs is the long battery life of LPWAN end devices, including smart sensors. Typical LPWAN batteries last from five to ten years, depending on the application, and up to 20 years (theoretically) for smart meter applications. This longevity is very attractive for enterprises seeking low maintenance costs for devices installed in remote locations. LPWANs require infrequent machine-to-machine (M2M) communication at a low data rate, less than one megabit per second. They are not designed for high-throughput applications such as video streaming.
The Industrial IoT (IIoT), transportation, smart factories, smart cities and buildings, and security and surveillance use LPWANs. As do healthcare, smart energy, retail, smart agriculture and animal farming. New applications are added every day.
This article will provide an update on these technologies and the applications they are most suitable for.
Long-Term Evolution (LTE)
LTE LPWAN is by far the leader in the cellular-based licensed spectrum segment. LTE category M (LTE-M) and Narrowband-IoT (NB-IoT) are the two most popular versions. The main difference between the two is that LTE-M has a higher speed of 370kbps typical (theoretical speed is 1Mbps) compared with NB-IoT at 108kbps. It is good to note that speed offerings among different carriers may vary. LTE-M supports voice within the range of LTE, while NB-IoT can support a distance up to 10km without voice capability. Additionally, users will need to pay a license fee to the carriers.
Use case
While asset tracking has been around for a long time, the introduction of LTE-M has revolutionized its applications. Traditionally, cargo or raw materials are moved from one location to another. The sellers and/or buyers keep track of where the trucks are. They will always know the approximate arrival time. However, to track the contents’ conditions, especially if the contents are perishable products such as milk or meat, requires monitoring indicators such as the refrigerator truck’s temperature. With LTE LPWAN, smart sensors can be installed to measure new parameters including temperature, humidity, motion, and location and can be tracked in real-time over the cloud. As shown in Figure 1, LTE-M based smart sensors will send data through the cloud platform to the enterprise’s servers. The data will then be updated in real-time as long as LTE coverage is present. Asset tracking can be very useful. With the technology, users can monitor the temperature in the refrigerator truck to ensure that the contents are within the temperature profile. A motion sensor will indicate if a fragile product has undergone excess shock. Additionally, location monitoring reveals exactly where the cargo is to calculate the delivery time.
Cellular-based IoT providers such as NimbeLink have given users a great deal of freedom to implement solutions. Users can acquire and install the asset tracking devices, acquire the API to interface with their own enterprise or rely on NimbeLink to provide the complete solution, including the cloud platform.
Long Range Wide Area Network (LoRaWAN)
The LoRa Alliance, with more than 500 members, is the organization behind LoRaWAN technology, which operates on an unlicensed spectrum. Today LoRaWAN network operators are in 157 countries. LoRa Alliance members include tech heavyweights such as IBM, Cisco, HP, Foxconn, Schneider, and Bosch. LoRaWAN operates at a lower data rate than LTE does, in the 50kbps range. Typical range is 10km. It could be as low as 2 to 3km, depending on the gateway and antenna design and message type, as well as indoor or outdoor location of the gateways. (This is also true with other LPWANs. The range figures in the comparison chart below are for reference only.)
Use case
Smart agriculture’s objective of maximizing crop production by monitoring the growing environment makes this an ideal LoRaWAN application. Some of the parameters need to be monitored using smart wireless sensors including those for temperature, humidity, and soil moisture. Additionally, it is important to monitor the temperature of the soil and its growing environment of the crops so as to avoid frost damage as well as overexposure to the sun. Another benefit is that smart sensors make irrigation monitoring and control possible, preventing harmful overwatering and saving irrigation costs.
Sensoterra, based in the Netherlands, uses LoRaWAN sensors and solar-powered gateways to help potato and almond farmers to reduce water consumption as much as 30 percent. The savings can be significant.
Weightless FAN
The power grid and industrial metering are a very important part of today’s economy. For the most part, LPWANs focus on industrial applications. The exceptions are the Weightless protocol and Wi-SUN. Among other things, the American Reinvestment and Recovery Act of 2009 has motivated the industry to invest in advanced metering infrastructure (AMI) or smart meters. However, transitioning from existing infrastructure to LPWAN is not easy. Over time, as LPWAN development has matured, power utilities have started to migrate to digital LPWAN grid-edge field area networks (FANs).
Weightless, an open standard LPWAN for public or private networks, is a bidirectional, star topology network that can deliver a theoretical data rate of 100kbps over a distance of up to 17km. These characteristics make Weightless suitable for AMI. Weightless makes it possible to connect a large number of smart meters or nodes at a data upload frequency from 1 to 15 minutes. Other LPWANs, including LoRaWAN and LTE, transmit data less frequently, e.g. hourly.
Use case
The state-owned Taiwan Power Company (Tai-Power), which provides electricity to the entire nation of Taiwan, conducted a technology trial. The goal was to select the best LPWAN technology for its AMI implementation. The project tested multiple LPWANs, including Weightless, LoRaWAN, LTE, and IEEE 802.15.4g (Wi-SUN) side by side over 13 months. In the end, Weightless was selected to be the technology of choice. The first phase of installation will be 285,000 electric meters.
In this trial approximately 6.7 million uplinks/day took place, for a total of 300MB/day from 61,000 meters. One Weightless station can support 1000 smart meters. Weightless proved its capability to support millions of smart meters in a power grid application.
Wireless Smart Utility Network (Wi-SUN)
The Wi-SUN Alliance’s initial focus was on smart utility network applications such as smart metering. Over time, the Wi-SUN FAN has evolved to support infrastructure for smart cities, including street lighting, smart parking, and waste management. Its specifications call for the design of product life cycles lasting from 15 to 20 years, including the battery. Additionally, its IEEE 802.15.4e based mesh network with hopping capability is suitable for utility grids that have to withstand rough environments and events such as storms. With the mesh network topology, if one part of the grid is damaged, the data can be rerouted through hopping to other nodes.
The Wi-SUN data rate is among the highest, about 300kbps. With low latency of less than one second, it is more suitable than other LPWANs for smart city applications in which fast responses are required. Other networks have latency of 10 to 20 seconds.
Use case
Florida is known for its destructive hurricanes. Every year, users face the possibility of power outages. Florida Power & Light Company serves 5 million customer accounts. By installing Wi-SUN based AMI meters and fault indicators, the utility was able to use the AMI automatic feeder switches to reroute electricity. This rerouting enabled Florida Power & Light to restore power to 1,500,000 customers within 48 hours in 2016. The mesh technology has proved to be very useful in rerouting electricity.
As shown in Figure 3, Wi-SUN has the potential to leverage its technology to make the connection to provide services in smart metering, smart lighting, and smart parking in future smart cities. Since power and utility companies provide lighting and electricity to the city, it makes sense to integrate smart technology to run smart cities.
Don’t Forget Your Certification
Apart from governmental certification such as that required by the FCC, LPWAN vendors will need to get certification based on their technologies. The LoRa Alliance, as well as the organizations behind Wi-SUN and Weightless, all have their own certification processes. This is to ensure that their products will be interoperable with other LPWAN products. For example, LoRa Alliance wants to make sure that certified products manufactured by one member will be able to work with products produced by another LoRa Alliance member.
LTE carriers, on the other hand, require certification to ensure that their network will not be affected by unwanted RF waves generated by the devices. Note that the LTE carriers require the PTCRB certification in North America, except for Verizon which has its own unique certification process.
LPWAN certification is an important step before a commercial product can be shipped.
The Future of LPWAN
There are many other LPWAN technologies around, and each has carved out its own unique niche market. LoRaWAN and LTE will continue to dominate the industrial segments. Both Wi-SUN and Weightless will accelerate in the power grid and AMI markets. The wildcard is smart city applications. Each of these technologies can be part of a smart city solution. The big question is which one will dominate. Most likely, a mixture of LPWAN solutions will coexist. But Wi-SUN is trying hard to be the leader.
Note 1: Wi-Sun FAN, based on the mesh topology, can hop from one node to another reaching a distance longer than 4km.
Note 2: Range figures are for reference only. Actual distances depend on multiple factors including antenna design, message type, and indoor or outdoor location of the gateways.
For more on LPWANs, read The Guide to Low-Power Wide Area Networks.