In this article, we will review some of the low power wide area options that are most commonly used, focusing on cellular technologies (Narrowband IoT and LT-M), as well as those WPAN using unlicensed bandwidth, LoRa /LoRaWAN, and Sigfox. We’ll also figure out the differentiation between the technologies of LPWAN and WPAN. Broadcasting technology using higher frequencies can transmit more data and faster bit rates than low-frequency radio. Higher frequencies will demand more power while the travel range is not as far as lower frequencies. In buildings, built-up areas, or areas with other sources of interference, the range is even smaller. Any frequency in a flat, open area will have a wider range than in a built-up area due to less interference. After learning these fundamentals, we’ll also direct you on choosing the right technology for your application, taking into account the power available, the data amount you need to transfer, and the range you want to achieve.
RF-based Internet of Things network
There are many RF-based IoT device communication solutions in the network. For the sake of discussion, we divide them into two categories:
- Short-range technology, or WPAN technologies like Bluetooth, Wi-Fi, Z-Wave, and Zigbee, have short distances, which are with high or low bit rates and is the potential to consume higher or lower power.
- Long range, or low power wide area technology, has low power usage, long distance, and low bit rate.
Wireless Personal Area Network (WPAN)
WPAN technology is limited in scope, but can be extended using mesh topology. Mesh topology is a network implementation by which each device repeatedly sends signals to other devices in the vicinity. As the content below below, you’ll find that the main use cases for WPAN are those who don’t care much on range.
Wi-Fi
Wi-Fi can run at 2.4GHz or 5GHz. Because these frequencies are higher, WIFI data rates are also higher. Each device has a 1:1 relationship with the network router. As we have seen before, the range of communication will be very short due to the high frequency of RF waves. Traditional Wi-Fi devices have higher power requirements, meaning that most available devices need to be powered by mains electricity. Wi-Fi 6 parameter aims to decrease the power consumption of Wi-Fi IoT devices so that IoT devices can use Wi-Fi. However, there’s still a long way for devices using these new specifications to become easily accessible. WI-FI is ideal for situations where mass data need to be transferred instantly. For example: camera equipment that needs to upload 4K video clips.
WI-FI solutions fits the following applications:
- High data rates
- high quality of service (likelihood of message passing)
- Low latency
Wi-Fi solutions are not well suited for the following applications:
- very wide range between devices and routers
- battery-powered devices
Bluetooth
Supports multiple Bluetooth modes. The mode most relevant to the Internet of Things is Bluetooth Low Power (BLE). BLE operates at 2.4GHz, but transmits only a small amount of data. In addition, it also uses FHSS modulation technology to counter interference. BLE Bluetooth 4 implements data transfer at 1Mbps. Bluetooth 5 brings it up to 2Mbps. The BLE range can be increased by Bluetooth Mesh in the way of passing messages between nodes, but you must have a large amounts of nodes to remain connected over a wide range of area.
BLE solutions are most suitable for applications demanding:
- Low power consumption
- High quality service
- Low latency
- Use Bluetooth grid for medium range
BLE solutions are not suitable for:
- Long-term use
Zigbee and Z-Wave
Zigbee operates at 1000MHz and 2.4ghz respectively. The z-wave operates at about 900MHz. Signal will be less affected by interference and is more accessible to get through obstacles with lower frequencies. Lower frequencies results in lower data rates. While Z-Wave and Zigbee are short in scope, the overall reach of the network can be extended with multiple devices in a grid. Zigbee and Z-Wave are ideal for devices with low energy consumption that demand high-quality service and small amounts of data, for example, light switches and temperature sensors in homes.
Zigbee and Z-Wave are best suited for:
- Low power consumption
- High quality service
- Low latency
- Flexible range of multiple devices
Zigbee and Z-Wave are not suitable for:
- Huge amounts of data
- Long-range
Low Power Wide Area Network (LPWAN)
LPWAN technologies can meet the requirements of long-distance and low-power networks. If your network is necessary to cover long distances, or you need to traverse obstacles such as buildings, then an low power wide area solution is a great option for you. The low power wide area solution spans a range of frequencies across licensed and unlicensed bands. In the following sections, we will discuss some of the more popular LPWAN technologies.
Cellular – the difference between LPWAN and WPAN
Cellular networks use licensed bands, typically in the 500MHz to 4GHz range, although 5G technology can use frequencies closer to 100GHz. Initially, cellular networks were born for high-data rate communications, for example, voice calls that are running at higher frequencies to carry larger volumes of data. The higher the frequency, the shorter the distance, so there are now cellular network standards specifically for low-frequency IoT communications to achieve greater distances. There are two key cellular specifications that should be considered for IoT applications.
Both technologies fall under 5G: the Narrow Band IoT
- NB-IoT, sometimes referred to as CAT-M2 or CAT-NB, is a cellular communication category with a narrow frequency channel width. NB-IoT both uses less power than LTE-M with a longer distance.
- LTE-M has higher data rates and lower latency than nB-iot. LTE-M also has the advantage of enabling device mobility over the NB-IoT, so if the device moves during data transmission, it can switch to another base station. Data rates on cellular networks are the most higher among low power wide area solutions, so, the size of packets you can send has been increased.
The frequencies of cellular solutions are permissive, it can reduce interference, and messages can be sent. As a result, cellular technology offers high quality service and low latency. If your use case requires immediate action, such as shutting off a gas valve at a long distance once there’s a leak, then you can take Cellular into consideration.
Cellular networks are typically belong to mobile network providers. By choosing a cellular network for your IoT solution, you can take advantage of the infrastructure already in place based on the coverage of your target area. Nevertheless, cellular IoT specifications are relatively new,that’s why network providers are still setting up their systems as a support. You may also find that the coverage of your network provider is limited and you may choose one or another specification (narrow band IoT or LTE-M) to serve your customers. (Note: it is unlikely that both will be implemented by a given network provider.)
One use case suitable for cellular IoT implementation is electrical metering:
- high data rates and payload length
- high quality of service
- low latency
Sigfox and LoRa
Sigfox and LoRa use unlicensed bands between 433MHz and 928MHz for transmitting low-frequency signals over long range. As we will see, these technologies share some common characteristics. Unlike cellular networks, LoRa networks and Sigfox use a star network topology,which means that broadcast messages can be received and delivered to the cloud by any base station in the specific scope. This increases the chance that the signal will be captured when the device is in the outer range of multiple base stations. Both Sigfox and LoRa can cover longer distances and use less energy than Cellular. Instead, both of them have slower data transfer speeds and more restrictions on the data and frequency. A larger amount of data can be sent per message, broadcast more frequently with LoRa, and get the maximum potential range with Sigfox.
What Sigfox and LoRa have in common:
- long range
- low power consumption
Sigfox
Sigfox was founded in 2010, becoming the first modern low power wide area. Sigfox uses unlicensed bands at frequencies from 862MHz to 928MHz, and uses ultra-narrowband modulation to send 100Hz wide messages. This means that Sigfox devices transmit in random channels over a given operating range, it can be helpful in reducing the possibility of background noise interference. Sigfox can achieve the maximum range of all the technologies we are analyzing, but it will result in low data rates because of the narrowband used. Therefore, a small amount of data must be transmit by each message with less than 12 bytes.
Sigfox users can send no more than six messages per hour from a device to the cloud (upstream) and no more than four messages per day from the cloud to a device (downstream). These limitations mean that Sigfox is ideal for low-power applications that only need to communicate a few simple values per day.
You had to register Sigfox public network now. But it’s ok as, Sigfox allows you to run private instances of your network by offering PAN technology.
- Sigfox’s advantage: Longest range of all low power wide area options.
LoRa uses unlicensed frequency bands between 433MHz and 928MHz based on the region, and uses a proprietary CSS modulation scheme to deliver data over a wider channel bandwidth with narrow bands (125, 250 and 500kHz), in this way, low noise levels and anti-jamming capabilities can be ensured. The modulation scheme can be changed by changing the spread factor to achieve greater distance at the cost of power. LoRaWAN is an open standard protocol that defines the communicate between gateways and devices.
LoRa’s range is larger than Cellular, but smaller than Sigfox. Nevertheless, it’s flexible of packet size limits, and you can transfer more data than you can with Sigfox if the configuration is right. The region you are in and the data rate you want to support decide the maximum package size of a LoRa message. Higher data rates mean shorter ranges because the frequencies are higher.
Many public LoRaWAN network providers are in the market. But you can also set up a private network using your own software and gateway.
Roller has a variety of operations:
- Class A: requires the least power. The device sleeps most of the time and wakes up to send uplink messages when the sensor values change. The window for receiving messages from the server (downstream) is very limited.
- Class B: Also requires very little energy. The device is asleep most of the time, but can wake up on time and report the current reading when the sensor reading changes. The window for receiving messages from the server (downstream) is limited.
- Class C: Requires more power than Class A and B devices, but the device is always listening to the downlink unless broadcasting the uplink. The flexibility of these multi-class operations means a wider range of use cases can be served by LoRaWAN.
Advantages of LoRaWAN:
- It controls the maximum packet size, which is higher than Sigfox.
- Easy to build up a private network that is cost effective.
- Flexible, combinations of devices with different power and delay requirements work together.
Conclusion – the difference between LPWAN and WPAN
Low frequencies have a longer range while carrying less data than high frequencies. WPAN technologies like Wi-Fi, Bluetooth, Zigbee and Z-Wave are with higher frequencies and short of long distance. These options are not ideal for scenarios where distance is important. LPWAN technologies are able to achieve greater range and operate at lower frequencies than WPAN technologies. We have determined that the correct low power wide area technique depends on your use case. Cellular technologies such as NB-IoT and LTE-M are great options for scenarios where cellular coverage and where service, low latency and large amounts of data are more important than power because range is likely to be lower. Sigfox is suitable for situations where you have few data and want to transmit it over long distances with low power consumption. LoRa allows maximum control, configurable ability to send larger volumes of data by simply setting up private networks, and class C supports lower latency.
