Internet of Things

Low-Power Wide Area Networks for IoT: A Comparison

February 24, 2024

Low-Power Wide Area Networks for IoT: A Comparison

Introduction

As the Internet of Things (IoT) continues to expand, connecting more devices and enabling new applications, the networking technology that connects these devices becomes increasingly important. Low-power wide area networks (LPWANs) have emerged as a key enabling technology for wireless IoT deployments. In this article, I will provide an in-depth comparison of the major LPWAN technologies – examining their technical capabilities, advantages, disadvantages, and ideal use cases.

The key benefits of LPWANs are their long range, low power consumption, and ability to connect a massive number of devices at low cost. Traditional cellular and WiFi networks are poorly suited for these types of sparse, battery-powered IoT deployments. The leading LPWAN technologies aim to fill this connectivity gap.

I will focus on comparing the four most widely used LPWAN technologies: LoRaWAN, Sigfox, NB-IoT, and LTE-M. By the end of this article, you will have a solid understanding of the strengths and weaknesses of each technology and their target applications.

Overview of LPWAN Technologies

Before diving into the details, here is a high-level overview of the major LPWAN technologies and their key characteristics:

LoRaWAN

Open protocol standard owned by the LoRa Alliance
Uses unlicensed radio spectrum
Long range (2-5 miles/5-10 km) in rural areas
Lower power consumption
Higher flexibility for network deployment
Ideal for private networks

Sigfox

Proprietary technology owned by Sigfox company
Uses unlicensed radio spectrum
Long range (30-50 miles/50-80 km)
Ultra low power and low bandwidth
Operated as public network by Sigfox
Limited flexibility

NB-IoT

Standardized by 3GPP
Uses licensed cellular spectrum
Shorter range (1-10 miles/1-5 km)
Good building penetration
Optimized for low power and low costs
Deployed by mobile operators
High reliability and security

LTE-M

Standardized by 3GPP
Uses licensed cellular spectrum
Enhanced Mobile Broadband (eMBB) capabilities
Higher bandwidth than NB-IoT
Targets applications needing higher data rates
Deployed by mobile operators

This table summarizes the key differences:

In the following sections, I will do a deeper comparison across these technologies on key parameters like architecture, range, bandwidth, battery life, security, and ideal use cases.

Network Architecture

The first area of difference is the network architecture and topology used by each LPWAN technology. This impacts flexibility, scalability, and ease of deployment.

LoRaWAN

LoRaWAN uses a star-of-stars topology in which end devices connect to gateways that relay messages to a central network server. It supports both public and private deployments:

Public networks – End devices connect to gateways owned by a LoRaWAN operator like Senet or Actility. Multiple operators can cover the same area.
Private networks – End devices connect to gateways deployed by a single private organization. The gateways connect to the organization’s LoRaWAN server.

A key advantage of LoRaWAN is flexibility – both public and private networks are possible. Organizations can deploy their own private LoRaWAN network and avoid monthly fees to a public operator.

LoRaWAN also optionally supports a mesh topology where devices can relay messages via intermediate nodes. This extends the range but increases power consumption.

Sigfox

Sigfox uses a simpler star topology – end devices connect directly to Sigfox base stations that relay data to the Sigfox cloud. As it operates as a public network, organizations do not deploy their own infrastructure.

The lack of support for private networks or meshing limits flexibility compared to LoRaWAN. But the network is easier to deploy as Sigfox handles everything.

NB-IoT and LTE-M

NB-IoT and LTE-M leverage the existing LTE architecture used for cellular networks. Devices connect directly to LTE base stations operated by mobile carriers.

As with Sigfox, NB-IoT and LTE-M do not support private deployments. Organizations must use connectivity provided by a mobile operator. But the cellular architecture provides strong coverage, security, and reliability.

Range and Coverage

The next key area of comparison is the range and coverage that can be achieved with each LPWAN technology:

LoRaWAN

LoRaWAN offers 2-5 mile range in rural areas and 0.5-2 miles in urban environments. Range is extended by using lower radio frequencies like 900 MHz.

The use of unlicensed spectrum means LoRaWAN can be deployed in any region without needing spectrum licenses. But range may be limited by regulations on transmit power in the ISM bands.

With LoRaWAN, organizations can densify gateways to optimize coverage for their own campus or private network. The multiple operator model also improves coverage.

Sigfox

Sigfox has the longest range of any LPWAN technology, typically reaching 30-50 miles. This is achieved using ultra narrow band modulation that trades off data rate for sensitivity.

As Sigfox controls the network deployment, coverage is limited to where they have deployed base stations. But the long range means fewer base stations are needed.

NB-IoT

NB-IoT has a short range of 1-10 miles as it operates on mid-band cellular spectrum like 700-900 MHz. But it can leverage existing base stations deployed by mobile operators.

Therefore, NB-IoT offers excellent coverage in urban areas and nationwide footprints in many countries by using existing cellular infrastructure. But range may be limited in remote rural areas.

LTE-M

Similarly, LTE-M leverages existing LTE networks so coverage depends on deployment by mobile operators. Range is estimated between 1-10 miles.

LTE-M has greater bandwidth than NB-IoT which improves range. But NB-IoT may have superior range in extreme rural scenarios given its optimization for range over bandwidth.

Bandwidth and Data Rates

The next key comparison point is network bandwidth and achievable data rates:

LoRaWAN

LoRaWAN offers modest bandwidth of 0.3 kbps to 50 kbps depending on region and duty cycle limits. This is suitable for small periodic sensor messages.

Data rates can be increased for private networks by using more spectrum and deploying dense gateways. LoRaWAN is flexible but higher data rates will impact battery life.

Sigfox

Sigfox has the lowest bandwidth of any LPWAN technology – just 100 bps. This allows ultra long range communication but restricts data to small uplink-only messages. Downlink is very limited.

NB-IoT

NB-IoT offers higher bandwidth of ~200 kbps downlink and ~20 kbps uplink. This is 10x higher than LoRaWAN making it suitable for firmware updates and larger data downloads.

LTE-M

LTE-M provides the highest bandwidth of up to 1 Mbps given its LTE roots. This positions LTE-M more for high bandwidth applications than other LPWANs.

This table summarizes the data rate differences:

Battery Life

As many LPWAN applications involve remote battery-powered devices, battery life is a critical consideration:

LoRaWAN

LoRaWAN offers multi-year battery life – typically 5-10 years with a modest number of messages per day. Lifetimes over 10 years are possible for devices that only send messages every few hours.

The long battery life enables maintenance-free operation. LoRaWAN is highly optimized for low power operation.

Sigfox

Similarly, Sigfox enables lifetimes up to 10+ years given the tiny 100 bps bandwidth and uplink-only operation. Bidirectional communication halves battery life but 5+ year lifetimes are still feasible.

NB-IoT

NB-IoT optimizes for low power operating with 10+ year lifetimes based on power saving features like extended idle mode DRX. Battery life depends on application message frequency.

LTE-M

LTE-M offers the shortest lifetime of the LPWAN technologies – ranging from weeks to several years. The higher bandwidth requires more power.

Security

As IoT applications transmit sensitive data and control messages, security is vital. Here is how the LPWAN technologies compare:

LoRaWAN

LoRaWAN uses AES 128-bit encryption to protect data over-the-air and between network components. Keys are specific to each device preventing spoofing. LoRaWAN security is highly robust but optional for private networks.

Sigfox

Sigfox uses proprietary encryption methods. Details are not published making it hard to evaluate. Sigfox claims security is embedded into the ultra narrow band modulation.

NB-IoT

NB-IoT inherits LTE’s standardized 3GPP security model including encryption, integrity protection, and device authentication. This ensures excellent security given cellular networks transmit banking data.

LTE-M

Similarly, LTE-M leverages LTE security mechanisms like 256-bit encryption. The 3GPP security model provides robust end-to-end security.

Use Cases

Finally, it’s important to compare the ideal use cases for each LPWAN technology based on their technical capabilities:

LoRaWAN

LoRaWAN suits battery-powered sensors that only require low data rates of ~1-50 kbps – for example reading water meters or monitoring soil moisture on farms.

LoRaWAN’s support for private networks makes it suitable for campus or corporate deployments like asset tracking, HVAC monitoring, and smart buildings. Mesh networking enables industrial IoT.

Sigfox

With its tiny messages and uplink-only operation, Sigfox excels at simple remote sensors that need to stream small periodic readings. Examples include leak detectors, smart garbage cans, and railway track monitoring.

NB-IoT

NB-IoT is optimized for affordable and power efficient cellular connectivity. It suits city or nationwide deployments of sensors and meters that need coverage everywhere.

LTE-M

LTE-M supports more bandwidth heavy and latency sensitive applications like asset trackers, voice-enabled devices, and emergency buttons. Its high downlink capacity suits firmware and software updates.

Conclusion

In summary, each LPWAN technology has unique strengths making them suitable for different applications:

LoRaWAN excels at private networks for campus IoT deployments.
Sigfox is ideal for simple uplink-only devices sending tiny messages.
NB-IoT leverages cellular networks for low power wide area connectivity.
LTE-M suits bandwidth heavy devices needing lower latency.

There is no single best LPWAN technology – the optimal choice depends on technical requirements and use case. I hope this article has provided a helpful in-depth comparison of the four major LPWAN options for enabling wireless IoT.