Data transfer in IoT systems
A typical IoT system is illustrated in Figure 1. The IoT system has some sensors/end-nodes located out in the world, these sensors are typically powered by a battery and communicate via radio signals to a base station (LPWAN). The base station transforms the radio signals into internet communication (TCP/IP) and sends data over the regular internet. The part that deals with the radio communication is called Low Power
Wide Area Network (LPWAN).
LPWAN - Low Power Wide Area Network
We normally think of networks as something where the goal is to send as much data as quickly as possible. This works fine when there is plenty of power available. But an IoT device doesn't need to be able to send/receive a lot of data, as is needed when streaming a movie, for example, it just needs to be able to send/receive small data packets over several years. And IoT devices do not have unlimited power, they usually run on batteries and are placed in places where you can't just pull a power cord or easily change a battery. That's why Low Power Wide-Area Networks (LPWAN) have been developed. These are radio technologies that use very little power and can send a small amount of data over long distances (much further than your cell phone). The three main LPWAN technologies are Sigfox, LoRaWAN and NB-IoT.
Sigfox
SigFox was founded in 2009 in Labège, France. SigFox has had great success with its successful marketing campaigns in Europe, and also boasts a large ecosystem of suppliers including Texas Instruments, Silicon Labs and Axom. SigFox is based on a proprietary technology. Sigfox is used in more than 70 countries worldwide and by over 7 million devices across many different industries. Sigfox collaborates with local network operators in the different countries.
The network came to Denmark in 2016, when the Danish company IoT Denmark began the rollout of the Danish Sigfox IoT network, which is now nationwide.
LoRa and LoRaWAN
The story of LoRa also began in France in 2009, when three friends set out to develop a long-range, low-power radio technology. They founded the company Cycleo and initially focused on the metering industry, for example for gas, water and electricity meters. In 2012, Cycleo was acquired by the American company Semtech and LoRA and LoRaWAN took off. In 2015, the international LoRA Alliance was founded. The alliance is non-profit and operator-independent and has over 500 members including IBM, Everynet, Actility, MicroChip, Orange, Cisco, KPN, KPN, Swisscom, Semtech, Proximus, The Things Industries and Cavagna Group. The LoRaWAN standard is today the fastest growing IoT network standard globally. The standard is based on hardware from electronics manufacturer Semtech and others producing LoRa chips and has evolved into a large ecosystem of manufacturers of
both gateways and sensors. The LoRaWAN network can be found in over 170 countries worldwide and with over 150 different network operators. Since LoRaWan technology is open, there are a multitude of LoRaWAN gateways around the world. The LoRaWAN standard defines 3 classes of devices class a, b and c. All 3 classes can send and receive data, but there is a difference in how much they "listen" for messages, which affects their battery life.
Class-A devices: Uploads data occasionally and does not listen for downlink messages. Typical Class-A devices are: smoke detectors, water leak detectors, environmental data and GPS trackers. In other words, devices that need to send a status once in a while, but do not need to receive data. Class-A devices are often battery powered and have minimal energy consumption as they are in sleep mode most of the time.
Class-B devices: Class-B devices are an extension of Class-A devices. Class-B devices listen to the downlink at fixed times. Class-B devices use more battery than Class-A as they use the radio more. Typical Class-B devices are: temperature meters and power meters. Class-B devices are typically connected to a power source.
Class-C devices: Class-C devices are also an extension of the Class-A type. Class-C devices have their radio on all the time and are constantly listening for messages. This results in low latency as you can ask the device to send data when you need it. On the other hand, Class-C devices consume much more power than Class-A. Typical Class-C devices are: street lights, devices that need to be updated over-the-air.
In Denmark, the companies Cibicom and SEAS-NVE operate LoRaWan networks, and the open network TheThingsNetwork is also available here.
NB-IoT - Narrow Band - Internet of Things
Narrowband Internet of Things (NB-IoT) was developed by the telecom industry and was launched in June 2016. NB-IoT focuses specifically on indoor coverage, low cost, long battery life and high connection density. NB-IoT uses a subset of the carriers' mobile data standard LTE, but limits the bandwidth to a single narrowband of 200 kHz. In short, NB-IoT runs on existing 2G, 3G and 4G mobile networks. NB-IoT requires a SIM card, fortunately, several operators support eSIM on NB-IoT technology. Think of NB-IoT as a scaled-down mobile phone network that is perfect for IoT devices. In Denmark, NB-IoT solutions are offered by the 3 major telecom companies TDC, Telenor and Telia.
Comparing the three network technologies
There are many parameters you can compare networks based on. We have selected 9 factors that we believe are essential when working with IoT and choosing the right LPWAN technology. The factors are: Scalability, Reach, Coverage, Deployment, Cost, Efficiency, Battery Life, QoS, Payload and Latency.
SCALABILITY
Multi-device support is one of the key features of Sigfox, LoRa and NB-IoT. However, NB-IoT has a clear advantage here as NB-IoT allows up to 100,000 devices per cell compared to 50,000 per cell for Sigfox and LoRa. These figures are theoretical and in practice you should probably expect a lower number.
REACH AND COVERAGE
Sigfox is the technology with the greatest range and coverage. An entire city can be covered by a single base station (due to range > 40 km). In Belgium, a country with a total surface area of approximately 30500 km2 (Denmark ~ 43000km2), the entire country is covered by a Sigfox network with only seven base stations. In contrast, LoRaWAN has a lower range (i.e. range <20km), yet it only requires three base stations to cover an entire city such as Barcelona. NB-IoT has the lowest area and coverage capacity (i.e. range <10 km). NB-IoT primarily focuses on devices installed in locations far from the typical range of mobile networks (e.g. indoor, deep indoor). In addition, the deployment of NB-IoT is limited to LTE base stations. Thus, it is not suitable for rural or suburban areas that do not benefit from LTE coverage.
EXPANSION
The Sigfox and LoRa ecosystems are mature and well on their way to commercialization in different countries and cities. According to The Things Network, today there are LoRaWAN networks in 170 countries worldwide, Sigfox in about 57 countries and NB-IoT in about the same number. A key advantage of the LoRaWAN ecosystem is its flexibility. Unlike Sigfox and NB-IoT, LoRaWAN offers local network deployment, i.e. LAN also using LoRa gateway as public network operation via base stations. In the industrial field, a hybrid operation model could be used to deploy local LoRa networks in factory areas and use the public LoRaWAN network to cover outside areas.
COST-EFFICIENCY
Doing a Total Cost of Owner (TOC) for an entire IoT project would be too extensive, so we focus on the costs directly associated with the different LPWAN networks and their sensors. Table 1 shows the different costs for Sigfox, LoRa and NB-IoT. Overall, Sigfox and LoRa are more cost-effective than NB-IoT.
BATTERY LIFE
Sigfox, LoRa and NB-IoT sensors are in sleep mode most of the time during operation. This reduces energy consumption, so battery life can be measured in years. However, NB-IoT's communication protocol uses more energy than LoRaWAN and Sigfox, partly due to synchronous communication and QoS. This extra energy consumption reduces the lifetime of NB-IoT sensors compared to Sigfox and LoRaWAN. However, all 3 technologies can support long service intervals in terms of battery life.
QoS/SERVICE QUALITY
Sigfox and LoRa use unlicensed radio frequencies and asynchronous communication protocols and are not really designed for QoS. NB-IoT uses licensed frequencies and an LTE-based synchronous protocol, which is optimal for QoS. However, the technology is expensive, with spectrum auctions costing up to 500+ million euros per MHz. NB-IoT is unique with its QoS and if you have applications that need stable and secure communication, NB-IoT is clearly preferable. If your applications do not require this stability, you should consider LoRaWAN or Sigfox.
PAYLOAD
There is a big difference in how large data packets can be sent over the 3 networks. NB-IoT has the largest payload length, i.e. how much data can be sent at a time, of up to 1600 bytes. LoRaWAN allows a maximum of 243 bytes of data, while Sigfox has the lowest payload length of 12 bytes, which limits its utilization on various IoT applications that need to send large data sizes.
LATENCY
Some applications can easily tolerate a slight delay in communication, e.g. a measurement of the water depth in a well can tolerate a delay of several seconds, while other applications need fast response and therefore require low latency. Applications that can tolerate high latency can benefit from using Sigfox or LoRaWAN's class-A equipment. Applications that require low latency are NB-IoT and LoRaWan.
THE SPREAD OF LPWAN TECHNOLOGIES
The website Statista.com (GE) has analyzed the deployment of LPWAN technologies until 2023. In the next 2 years, the number of IoT devices will double, bringing approximately 1.7 billion devices online. LoRaWan and NB-IoT networks are predicted to double in number of devices, while Sigfox will grow somewhat less. This is probably not surprising when you consider the power behind the NB-IoT and LoRaWan systems.
CONCLUSION - how do you choose LPWAN technology for your IoT project?
Basically, there are 5 themes to consider when choosing LPWAN technology for your IoT project.
- IoT device location
Where are the sensors/end-devices located? Their location determines which LPWAN technology is most suitable. Are the devices located indoors in a metropolitan area, is it in remote rural areas, or are the devices mounted on some equipment that moves around over a larger area. Once you have defined where the IoT devices will operate, you have a prerequisite for choosing LPWAN technology. - Data traffic
You need to assess how much and how often data is sent and received. Systems that only send data a few times a day place significantly different demands on the LPWAN network than a system that continuously monitors critical temperatures and sends commands out to the IoT device. - Battery life
How long should the IoT devices be able to operate before they need service/battery replacement? Some sensors/IoT devices may be located in inaccessible places that make service/maintenance a major financial drain on ongoing operations. The technically best solution may not be the most suitable if it requires relatively high maintenance. - Vendor relationship/Vendor-lock-in
Network vendors live on subscriptions and therefore more or less try to lock customers into their system. So you need to weigh up how much the project can tolerate being locked in to a vendor in subsequent operations. Some of the LPWAN technologies are based on open standards, making it relatively easy to switch vendors. - The overall economy of the IoT project
An IoT project typically consists of a development phase and a subsequent operational phase. In the development phase, the biggest costs will be hardware and development hours, while the biggest costs in the operational phase are harder to identify. This is because at the start of the project, you can't predict how much impact the IoT solution will have on your organization. There may be unexpected benefits or costs. That's why it's especially important to work through the IoT project's operational economics when planning a project. When choosing LPWAN technology, it's important to calculate what it costs to send/receive data.
Sources
A comparative study of LPWAN technologies for large-scale IoT deployment - Kais Mekki et al.
https://www.iotforall.com/iot-connectivity-comparison-lora-sigfox-rpma-lpwan-technologies
Evaluation of Energy Consumption of LPWAN Technologies - Husam Rajab et al
LPWAN State of the Art:Trends and Future Directions - Slides - Zaid Ahmad, Shaiful JahariHashim, Fakhrul
Zaman Rokhani, Syed Abdul Rahman Al-Haddad, AduwatiSali, Smart City Conference 2021.
https://lora-developers.semtech.com/uploads/documents/files/LoRa_and_LoRaWAN-A_Tech_OverviewDownloadable.pdf
https://www.thethingsnetwork.org/docs/lorawan/
https://www.sigfox.com/en/coverage
https://www.gsma.com/iot/deployment-map/
Comparison of LPWAN Technologies: Cost Structure and Scalability - Mohammad Istiak Hossain · Jan I. Markendahl
https://www.thethingsnetwork.org/docs/lorawan/classes/
https://www.techplayon.com/lora-long-range-end-device-classifications-class-class-b-class-c/
