Many IoT devices send a few bytes a day, run on a battery, and sit far away from any access point. LPWN, or LPWAN, is the family of wireless networks built for that kind of device. This page first defines the term and explains the trade-off behind it. Then it places LPWAN beside the cellular and short range technologies that compete for the same devices.

• What is LPWN/LPWAN ?
• Where does LPWAN sit among IoT networks ?

What is LPWN/LPWAN ?

LPWN stands for Low Power Wireless Network and LPWAN stands for Low Power Wide Area Network. Both one indicate the same technology which has following technical features :

• Low Power : Energy Consumption (Battery Consumption) is very low (Target is to last over 10 years)
• Wirless
• Wide Area of Coverage : There is no clear/explicit number showing how wide it should be, but mostly has the max covergae of a few km of radius or wider

These features pull against each other. A radio reaches further when it puts more energy into each bit, but it saves battery only when it transmits less. LPWAN solves the conflict by giving up data rate. It sends each bit slowly, or in a very narrow band, so each bit carries more energy for the same transmit power. The receiver can then decode a signal that is much weaker than the signal a WiFi or Bluetooth receiver needs.

The price is capacity and latency. A typical LPWAN device sends a few small messages a day, mostly in the uplink. It listens for the downlink only in short windows, and it sleeps the rest of the time. So LPWAN suits meters, sensors and trackers. It does not suit voice, video or any application that needs a quick answer from the network.

• Long range and low power come from a low data rate : each bit is sent with more energy, so a weak signal can still be decoded.
• LPWAN traffic is small and infrequent : a few messages a day, mostly in the uplink, with long sleep periods between them.
• Latency is the cost : an application that needs a fast reply from the network needs a different technology.

Where does LPWAN sit among IoT networks ?

This technology will play important roles in IoT. Many, many different kind of technology will get involved in achieving the full blown IoT network as illustrated below. The part marked in Red is LPWN/LPWAN. The part marked in Purple is usually classified as Cellular Technology. However, these technology meets criteria listed above. So in some sense the purple parts can be classified as LPWN/LPWAN as well.

The diagram groups the IoT radio technologies into three families around a centre.

• Cellular : 2G, 3G, 4G and 5G. Under 4G the diagram shows Cat 0, Cat 1, LTE-M and NB-IoT, and under 5G it shows eMTC and mMTC.
• Short Range Networks : ZigBee, Z-Wave, Thread, Bluetooth and WiFi. These cover a room or a building, not a city.
• LPWN, Low Power Wireless Network : LoRa, SigFox, NWave, Nuel and Weightless. These run in unlicensed spectrum, mostly in sub-GHz bands.

The purple items show where the families overlap. NB-IoT and the 5G items meet the LPWAN criteria, but they use licensed cellular spectrum and the network of a mobile operator. The unlicensed LPWAN technologies need their own gateways instead, or a network run by a dedicated LPWAN operator. That is the real difference between the two groups, more than range or battery life.

One label in the diagram needs care. The diagram places eMTC under 5G, but in 3GPP eMTC is the Release 13 name of LTE-M, so it belongs with LTE-M under 4G. In 5G, mMTC is the usage scenario for a massive number of devices, and 3GPP serves it with NB-IoT and LTE-M. The LoRa and SigFox pages cover two of the unlicensed technologies in more detail.

• Three families compete for IoT devices : cellular, short range networks and LPWN.
• NB-IoT and LTE-M are cellular LPWAN : they meet the LPWAN criteria in licensed spectrum.
• The spectrum decides who runs the network : unlicensed LPWAN needs its own gateways, and cellular LPWAN reuses the mobile network.