The network is one of the key elements of an IoT infrastructure. In view of the vast range of technologies available, finding the one that is best suited to your project can prove challenging. This article presents the main criteria when selecting an IoT network.
The Internet of Things (IoT) incorporates various technologies that enable objects fitted with sensors to share data collected via these sensors on a wireless network. These IoT networks can be grouped into three main families:
PAN (Personal Area Networks)
PAN are networks spanning a very short distance (less than 100 m), which require that the objects or "things" be in immediate proximity to the device intended to link them to the network. Bluetooth, Z-Wave or ZigBee are examples of PAN technologies.
LAN (Local Area Networks)
LAN are medium range networks (100 m to a few km), either domestic or professional. Wi-Fi is the LAN protocol par excellence, however, it requires a gateway in order to connect to the network. DASH7, Weightless-P (present primarily in Asia) are other technologies that can be used for LAN networks.
WAN (Wide Area Networks)
WAN are extensive networks, covering a city or country. On average, their range varies between 5 and 40 km, the record standing at more than 700 km. To achieve this range, they rely on a network of antennae. Within this group, a distinction is made between two sub-families:
LPWAN (Low Power WAN) networks, such as Sigfox or LoRA networks, which are characterised by very low power consumption;
GSM/LTE-type telephone networks, or even those based on the NB-IoT standard.
Choosing the most suitable IoT network: usage-based
The main determining factor when selecting a network is the form of use case. This will enable the definition of the initial selection parameters, namely:
1. The coverage area
The size of the area to be covered will direct you towards one of the three major network families. Its location is also taken into account: LoRa are, for the time being, limited to within national boundaries, whereas an operator such as Sigfox is present in 60 countries.
2. The density of the objects
Are the objects to be connected in close geographical proximity to one another, in which case a network such as Wi-Fi can be used, or are they spread out? In the latter case, LPWAN or GSM networks are preferable, Wi-Fi requiring the installation of gateways on each node of the network.
3. Power consumption
Is it possible to supply the device with power? If this is not the case, it is better to avoid technologies with a high power consumption such as Wi-Fi. LPWAN and Bluetooth Low Energy (BLE) have a much lower power consumption. LPWAN networks can thus function for up to 20 years with the same battery.
4. The size and nature of the data to be transmitted
If large data quantities are involved, as when transmitting video for instance, Wi-Fi and GSM networks are suitable. For small data quantities, BLE over a short distance or LPWAN networks over a long range are more economical and more energy-efficient.
Once the main features of the use case have been established, other criteria will allow you to refine your choice of network. Among these factors are the type of device envisaged, the target users, the planned environment and the various technical and regulatory constraints. The responses given assist you in assessing the following parameters:
The cost: this factor is all the more important if there is large quantity of things to connect or in the case of objects with short expected life span. The chips used in LPWAN networks currently have an entry price of a few Euro cents, which enables the exploration of new forms of use, such as "disposable" connected objects.
Security is taken into account in case of sensitive applications, such as intrusion detection. Certain types of signal, such as GSM, can be easily scrambled, whereas other technologies such as Sigfox cannot. Some networks include data encryption as standard, while for others it is available as an option;
The device environment: the frequencies used by some networks can be blocked by concrete or water. If obstacles are encountered, it may be necessary to repeat the signal using gateways.
Peering with networks: when the device can connect directly to the network, this factor does not pose a problem. However, a gateway must be installed, which adds an additional step and thus increases the level of complexity.
The quantity and size of the messages to be sent: networks using public radio frequencies are subject to restrictions that are dependent on regulators. For Sigfox, for example, this means a limit of 6 messages of up to 12 bytes each per hour, while LoRA networks have an uplink time limit of 30 seconds/day.
The direction of exchange: is the objective simply to retrieve data or does the project require the ability to operate certain pieces of equipment remotely? For two-way exchanges, the required bandwidth is generally greater. Protocols such as LoRa or Wi-Fi are well suited.
The surface area of the chip: GSM chips have a surface area of around 10 mm², while players such as Sigfox offer chips measuring 1 mm², which can be used in very small objects.
The precision of the transmitter signal enables the geolocation of devices. In LoRA networks this precision thus reaches a level of several hundred metres in urban areas, compared to 1km in rural areas.
Service level: for applications requiring a high service level (low latency, message receipt guarantee), GSM/LTE networks are the best choice, however, they are more expensive.
Adherence to a standard: in some instances this can be a requirement in public tenders.
Finally, in certain use cases several technologies can be combined. This allows you, for example, to maximise the coverage area, or to build a resilient infrastructure that is capable of functioning even if one of the networks is unavailable.
Points to remember
The use cases determine the main criteria for the selection of the network.
The coverage area, the density of the object to connect, the power consumption and the nature of the data are the first parameters to be taken into account.