The Internet of things is set to play a vital role in the products of the next generation, connectivity being a major aspect of it. With the increasing demand for battery-operated connected devices, LPWAN is widely used across various IoT segments. LPWAN is a broad term used to denote connectivity technologies which are used in lieu of traditional Wi-Fi and Cellular standards. LPWAN is best known for its use in various applications, including industrial applications, telematics, transportation, asset management, etc., which demand power optimal solutions for transmission of small bits of data over larger distances for several years.
This article discusses the different LPWAN technologies that can be considered for various IoT solutions.
What is LPWAN?
LPWAN (Low Power Wide Area Network) is a popular M2M (machine-to-machine) connectivity technology, designed for low power, battery-operated devices that have relatively low data rate requirements. It provides the increased number of devices connected over an area compared to a traditional network with reduced power consumption, thus making it ideal for modern IoT applications.
LPWAN is a collection of multiple technologies, which serve a similar purpose. In this article, we will be discussing poplar M2M connectivity technologies such as LTE CAT-M, NB-IoT, LoRa, and Sigfox.
LPWAN is designed to connect a large number of IoT devices with the vision of easing human life. The primary design focus of the technology is enhanced battery life for several years, better connectivity and lower cost. Because of these inherent properties, LPWAN is best suited for smart cities, smart metering, real-time location identification, vehicle tracking systems, smart agriculture, and asset tracking use-cases.
LPWAN can be briefly classified into two major categories based on the frequency band at which they operate – one that operates in licensed bands and supported by telecom vendors, and the second one, which operates in un-licensed bands globally.
CAT-M and NB-IoT operate in licensed bands and Sigfox and LoRa operate in unlicensed bands.
CAT-M is the LPWA technology defined for low to medium data rate applications. CAT-M (also termed as CAT-M1) behaves similar to traditional cellular technology by retaining the connection while moving and managing the cell handoffs automatically. However, Release-13 defines the extended range deep penetration of the CAT-M signal compared to earlier specs, thus making it useful for smart cities, large buildings, and basements.
figure 1: Applications of CAT-M
CAT-M is deployed in the existing LTE band and enables the service providers to reuse the existing infrastructure. It provides medium data rate communication of up to 375Kbps with a reduced spectrum bandwidth of 1.4MHz to achieve low power. An added benefit of CAT-M is that it supports VoLTE while promising long battery life. The popular use cases of CAT-M include automotive, asset and vehicle tracking, transportation, connected healthcare, and smart cities.
In North America, AT&T and other networks are working with several manufacturers to provide secure connectivity using this technology.
CAT-M is deployed widely in the USA, Canada, and parts of APAC and Europe.
figure 2: Features of LTE CAT M1
This is the narrowband IoT technology introduced in 3GPP Release-13. It co-exists with GSM and LTE and can share part of the existing infrastructure. It extends the cost and power benefits of CAT-M technology while increasing the range and penetration with a reduced data rate. NB-IoT can be deployed in in-band, guard-band and standalone as required, thus adding more flexibility for the UE (User Equipment). Unlike other LTE technologies, NB-IoT removes the requirement of gateways and communicates directly with the service provider to reduce the cost of infrastructure and maintenance. As per the Release-13, NB-IoT has to re-establish the connection while moving, since automatic cell handoff is not defined. However, the later releases (Release-14+) define the auto handoff feature for NB-IoT, which makes it more useful for automotive and asset tracking.
AT&T has begun the wide deployment of NB-IoT in North America and T-Mobile has nationwide coverage for the same. Meanwhile, Vodafone is driving the NB-IoT growth in Europe, Megaphone and MTS is Russia and China Telecom in China.
NB-IoT is expected to account for 20% of the shipment of connected devices by 2021.
figure 3: Features of NB-IoT
This is a patented low power networking technology by Sigfox. Sigfox network globally works within the ranges from 862 to 928 MHz unlicensed ISM band. Using this unlicensed band enables Sigfox to send data at a very low power and low data rate with the added advantage of lower costs. Network configurations, transmit power and radio specifications differs from country to country based on the local laws and regulations. For the ease of operations, Sigfox has identified 7 geographical zones (RC1 to RC7). Refer to this page for details of the Sigfox RC’s.
SigFox consumes very low power and communicates over a longer distance with numerous devices being part of the network. The current standard of SigFox supports about 140 messages per day with a packet size of 12 octets, making it more suitable for sending small amounts of data infrequently over large distances. Devices in Sigfox’s public network architecture rely on the infrastructure deployed through cities and countries by the local Sigfox operator to communicate. Apart from the public pre-deployed networks, it also supports the private network, where dedicated base stations and devices can be set up and configured, with Sigfox dongles emulating the nodes.
It is widely adopted in Europe, America, and currently, they are cutting their way through APAC and India. By mid-2019, Sigfox had been deployed widely in 60+ countries. Due to the very low cost of the nodes, it has become the first choice for the agriculture and retail market which is looking out for reliable connectivity solutions at an affordable cost.
LoRa is an abbreviation for LongRange, a modern LPWAN technology for a low data rate but long-distance application with the advantage of added security features. This is a non-cellular IoT technology for LoRaWAN, which is not to be confused with LoRa. LoRa is a radio modulation technology and LoRaWAN is a network (protocol) that uses LoRa. The latter being the Chirp Spread Spectrum (CSS) physical layer supported by major silicon companies such as Semtech, ST Micro, Microchip.
Proprietary LoRa wireless RF technology belongs to Semtech which is the driving force behind the LoRa Alliance, where the open LoRaWAN protocol and ecosystem are being defined and developed. The LoRa Alliance has gathered hundreds of members since the time of its inception in 2015.
LoRa, LoRaWAN and Sigfox have become the main non-cellular LPWA ecosystems for various IoT solutions. The LoRaWAN protocol standard provides seamless interoperability among smart ‘things’ without the need for complex local installations, further enabling the Internet of Things. It implements several layers of encryption to ensure the highest security for the whole infrastructure.
A brief comparison of LPWAN Technologies
|Technology vs Properties.||CAT-M||NB-IoT||Sigfox||LoRa|
|License||LTE spectrum license||LTE spectrum license||ISM unlicensed band [Region specific bands]||ISM unlicensed band [Region specific bands]|
|Security||End to end||End to end||Minimal||AES-128|
|Payload size (Bytes)||Limited by IP||1600||12 or 8||243|
Table 1.0: Comparison of LPWAN Technologies
CAT-M, NB-IoT, Sigfox, and LoRa are key technologies for LPWA applications which have enabled several million connected devices already. In the competitive market situations, selecting the right technology is a challenge. While licensed LPWAN is more suitable for the area with the wide deployment of suitable mobile networks, un-licensed LPWAN is preferred for applications involving industrial, warehouse and agriculture applications. At present, LoRa and Sigfox were the early entrants in the market and gradually gained the upper hand in terms of unit cost and battery life wherein NB-IoT is still evolving and is yet to be widely deployed and tested. However, CAT-M has created a unique place for itself, facing fewer challenges in this segment because of its support for a higher data rate.