LPWAN communication techniques for the Internet of Things

Recently, the development of wireless communication techniques for the Internet of Things has greatly accelerated. Decreasing prices of communication modules, as well as their increase in functionality, are convincing a growing number of potential recipients to launch new products. Currently, the largest share in the LPWAN communication market is taken by NB-IoT, LTE-M, LoRA and SigFox.

A common feature of all LPWAN communication techniques is the maximum extension of battery life and long range. From devices manufacturer point of view, apart from long battery life, the most important is the availability of the network and its capabilities. The aforementioned types of communication techniques differ from each other in a number of parameters, and hence functionalities.

LTE based communication techniques – NB-IoT and LTE-M

Two of the most popular wireless communication techniques, i.e. NB-IoT and LTE-M, have been standardized by 3GPP in release 13 “LTE Advanced Pro”. 3GPP is a project created in 1998 to standardize the development of the mobile network. These communication techniques are distinguished by a licensed frequency band. The main advantages of using the licensed band are the lack of interference, the ability to send more data at a relatively high speed.

NB-IoT (Narrow Band Internet of Things, aka LTE Cat-NB1) – a secure, reliable and, above all, efficient LPWPA communication technology. NB-IoT has been standardized in 3GPP and hence it is possible to use the existing LTE infrastructure to provide NB-IoT connectivity.
NB-IoT is intended for stationary devices that are registered in the same network cell all the time. The high level of obstacles penetration means that NB-IoT devices can be installed in places that are not easily accessible by radio.

Technology highlights:

  • licensed LTE 700 MHz frequency band – 2100 MHz (depending on the channel)
  • half duplex (alternate data transfer and reception)
  • large delay (1.5 – 10 s)
  • data transfer speed <250 kbps
  • one cell of the network supports 50-10000 devices
  • long range from the BTS (5 km – 50 km) depending on the level of urbanization and natural obstacles
  • very good penetration of obstacles such as walls
  • operates based on the 4G network infrastructure
  • long registration in the network, switching between network cells causes a significant increase in power consumption
  • public network model, usage fees for telecommunications operators
  • standardization around the World (certification, security)
  • the ability to update devices firmware over the network – FOTA (Firmware Over The Air)
  • no SMS and voice support

Examples of applications:

  • stationary sensors for environmental monitoring
  • electricity meters (smart metering)

LTE-M (Long Term Evolution for Machines, aka Cat-M, Cat-M1) – like NB-IoT it works on the existing 4G network and has been standardized in 3GPP Release 13. LTE-M can be used in solutions where NB-IoT does not work, i.e. in transport, where the device quickly changes its location between the cells of the network. Often manufacturers of LTE-M communication modules integrate in their products GNSS module, which may encourage such applications. An additional advantage of LTE-M is VoLTE which enables voice transmission. The parameter that appeals to the detriment of LTE-M in relation to NB-IoT is the relatively worse signal transmission through obstacles.

Technology highlights:

  • licensed LTE 700 MHz frequency band – 2100 MHz (depending on the channel)
  • full duplex or half duplex
  • small delay (10 – 15 ms)
  • data transfer speed <1Mb / s
  • supports voice transfer (VoLTE technology)
  • the ability to update devices firmware over the network
  • fast switching between network cells
  • weaker than NB-IoT permeability through obstacles
  • public network model, usage fees for telecommunications operators
  • standardization around the world (certification, security)

Examples of applications:

  • locating items in transport
  • cold chain temperature monitoring
Countries in which NB-IoT and LTE-M networks are avaiable (as of October 2018)

Countries in which NB-IoT and LTE-M networks are avaiable (as of October 2018)

Unlicensed band based communication techniques – LoRa and Sigfox

Sigfox and LoRa are based on unlicensed frequency bands. This has certain drawbacks – in practice it can lead to overlapping of various signals and the occurrence of disturbances. For this reason, the speed of data transfer is relatively low and amounts to a few dozen kb/s.

Sigfox – communication technology was established in France in 2009 by a company with the same name. While the device is in operation, it is not required to maintain a connection to the cell of the network. When the device sends messages, the data reaches the nearest base station. In principle, the network is to be used by the device sending very small data packets. The network has a light communication protocol and data transfer limits – 140 messages per day, each containing up to 12 bytes of data. A device can receive up to four messages a day in which 8 data bytes can be found. Sigfox, for its part, controls the network, provides network infrastructure and collects fees from operators who mediate in the sale of services.

Technology highlights:

  • unlicensed frequency band (868 MHz – Europe, 915 MHz – USA)
  • no need to maintain connection with the base station
  • data transfer speed <50 kbps
  • data must be sent via the cloud platform provided by Sigfox
  • closed technology, only one network operator (Sigfox), no possibility to build your own network and control it
  • device does not require a SIM card
  • range up to 50 km

Examples of applications:

  • network of environmental sensors
  • monitoring the level of water in water reservoirs

LoRaWan (LoRa) – communication technology developed by a French company called Cycleo (acquired by Semtech in 2012). Currently, development of this technology is coordinated by the LoRa Alliance, a non-profit organization that brings together over 250 member companies. Like Sigfox, it uses a publicly available frequency band. The LoRa network architecture is based on a star topology in which gateways are bridges that provide transmission between end devices and the central servers. Communication with endpoints can be bi-directional, which allows not only receiving messages, but also controlling the operation of devices and updating their software. An additional advantage, in contrast to other popular LPWAN standards of wireless transmission, is the possibility of creating private networks and maintaining full control over them. The maximum range is 15 km in open space.

Technology highlights:

  • unlicensed frequency band (169, 433, 868 MHz – Europe, 915 MHz North America)
  • bidirectional – half duplex (alternate data transfer and reception)
  • data transfer speed <50 kbps
  • open technology, no fees
  • device does not require a SIM card
  • range up to 20 km

Examples of applications:

  • street lighting control
  • control of the crop irrigation system in agriculture
Countries in which LoRa and Sigfox networks are avaiable

Countries in which LoRa and Sigfox networks are avaiable