Which radio technology for your connected objects ? Part 3
Some time ago we tried to answer the following question: which radio technology to choose for the connected objects? based on several criteria. We had therefore compared the performance of different wireless communication protocols LAN (Local Area Network). Today we are going to make the same comparison but for technologies adapted to other uses: LPWAN, Low Power and Wide Area Network.
First, we will present what LPWAN is. Then we will compare the most representative technologies of the existing IoT: LoRaWAN, LTE Cat-M1, NB-IOT and Sigfox. However, this list of radio protocols is not exhaustive, we present today the technologies available to cover LPWAN uses (remote meter reading, environmental monitoring, parking management, waste management etc…).
LPWAN networks are low-power and long-distance network technologies, specifically designed for data exchanges applicable to the IoT domain. The low energy consumption of these technologies allows the deployment of energy autonomous sensors for several years. These technologies are therefore intended for connected objects that communicate poorly and often do not have access to an electrical power source to power them. A distinction is made between non-cellular LPWAN, LoRa and Sigfox networks, and cellular networks such as LTE Cat-M1 and NB-IoT.
The LoraWAN protocol allows any company to deploy LoRa sensors, both on the public network of a telecom operator and on its own private network. Communications are then long range and robust. This bi-directional technology makes it possible to make compromises between the quantity of data to be transmitted, the range, and the energy autonomy.
For example, we will be able to transmit up to 500 51-byte messages per day, depending on the need. It is also possible to control objects by LoRa messages.
Thanks to a technology very well adapted to the constraints of the IoT – low consumption and long range – Sigfox technology provides good coverage in urban areas, especially in underground locations. This unidirectional technology (from the sensor to the network) is very suitable for applications where very little data needs to be sent (limited to 144 messages of 12 bytes per day). We will therefore target uses such as remote reading of water or gas meters, or door opening detectors.
LoRaWAN and Sigfox are optimal for a very low consumption at a low cost. The cost of the NB-IOT and LTE-M components is still much higher than that of the LoRaWAN and Sigfox components (see “LPWAN comparison table” at the bottom of the article).
The NB-IOT, which is currently being deployed, is based on existing 4G networks, accessible under licence and controlled by operators. Today SFR and Orange are deploying a NB-IOT network in France. The radio technology used makes it possible to improve penetration inside buildings or underground compared to 2G/3G/4G coverage. In Asia, there are use cases based on NB-IOT technology for smart agriculture.
The Cat-M1 LTE, also currently being deployed, is a derivative of 4G LTE technology that optimizes the energy consumption of these objects through standby mechanisms. More energy consuming than other LPWANs, it nevertheless allows higher data rates, lower latencies, and makes it possible to transmit photos or voice. (See “LPWAN comparison table” at the bottom of the article). Contrary to other LPWANs, it also makes it possible to address tracking uses in several countries. It is in New Zealand that Vodafone has been testing the deployment of a Cat-M1 LTE network for smart agriculture since 2017. However, roaming agreements between operators are lacking for international applications.
The latter two networks benefit from the extended geographical reach of LoRa and Sigfox technologies, but only LTE-M allows mobility. On the other hand, their consumption is such that the use must be carefully studied to avoid having to change the sensor batteries every 6 months!
Unlike radio technologies such as Wifi, Bluetooth, ZigBee, LPWANs have a very long range, easily reaching a maximum distance of 10 km between objects.
In theory, the NB-IoT protocol allows better ranges compared to other LPWANs. But this is at the expense of consumption since the range is obtained by repetition of the transmitted messages. This artificially increases the chances of picking up a sensor message without really having better sensitivity.
Sigfox and LoRaWAN allow to transport very small quantities of data, their flow rates are low. The NB-IoT protocol operates on the same frequencies as the LTE protocol, but on a narrower band. The data rates are higher, but do not allow an image to be transferred. Unlike other LPWAN technologies, LTE-M1 technology has a high data rate.
If we compare the different technologies according to the theoretical maximum data rate, we can classify them as follows:
Sigfox < LoRa < NB-IOT < LTE-M
The longer the sensor is able to fall asleep without transmitting, the better the autonomy will be. LoRaWAN stands out because it has the advantage of being able to wake up once a day to send a message. Sigfox comes just behind with the possibility to transmit also once a day, but messages that are tripled to maximize the chances of transmission. In NB-IoT and LTE-M, consumption is intrinsically higher despite sleep mechanisms specifically designed to limit it.
Here is a comparison of the energy consumption of the different LPWANs :
LTE-M < NB-IOT< Sigfox < LoRa
For sensors that need to be mobile, the use of LTE-M or LoRaWAN should be preferred. Sigfox messages are not very resistant to rapid environmental changes. The NB-IoT protocol is not intended for the sensor to be mobile. (See “LPWAN comparison table”).
Here’s how we could classify the different technologies according to their mobility:
NB-IoT < Sigfox < LoRa < LTE-M
Sources used for this article
The 5 pillars of an IoT project by Houria Tair // What is NB-IoT ? by Integral system
LTE-M: the characteristics of the network promoted by Orange in France by Le Journal du Net
Which technology to choose to connect objects? by Decideo and Le Journal du Net
LTE-M for connected objects: advantages and technical specifications by Matooma
Private LoRaWAN network by IoT Factory // LoRa Module by muRata
WSSFM10R1 by Partners Sigfox // SARA-R4 series by Ublox