LPWAN: LoRaWAN, LoRa & Others

What is LPWAN

A low-power wide-area network (LPWAN) is a type of wireless telecommunication wide area network designed to allow long range communications at a low bit rate among things (connected objects), such as sensors operated on a battery.

LPWAN offers multi-year battery lifetime and is designed for sensors and applications that need to send small amounts of data over long distance a few times per hour from varying environments.

LPWAN has no uniform technical standards. LoRa, SigFox, NB-IoT, Weightless are all typical technologies.

Where does LPWAN Fit

One technology cannot serve all of the projected applications and volumes for IoT.

WiFi and BTLE are widely adopted standards and serve the applications related to communicating personal devices quite well.

Cellular technology is a great fit for applications that need high data throughput and have a power source.

LPWAN offers multi-year battery lifetime and is designed for sensors and applications that need to send small amounts of data over long distances a few times per hour from varying environments.

What is LoRa

LoRa (Long Range) is a patented digital wireless data communication IoT technology developed by Cycleo of Grenoble, France. It was acquired by Semtech in 2012, which holds the IP for LoRa transmission methodology.

LoRa is based on chirp spread spectrum modulation, which maintains the same low power characteristics as FSK modulation but significantly increases the communication range.

Advantage of LoRa

The advantage of LoRa is in the technology’s long range capability. A single gateway or base station can cover entire cities or hundreds of square kilometers. Range highly depends on the environment or obstructions in a given location, but LoRa and LoRaWAN® have a link budget greater than any other standardized communication technology. The link budget, typically given in decibels (dB), is the primary factor in determining the range in a given environment.

What is LoRaWAN®

LoRaWAN® is a media access control (MAC) layer protocol maintained by the LoRa Alliance, a non-profit technology alliance. It is designed to allow low-powered devices to communicate with Internet-connected applications over long range wireless connections. The first LoRaWAN® standard was announced by the LoRa Alliance in June 2015. In 2017 LoRaWAN® specification 1.1 was released.

LoRaWAN® defines the communication protocol and system architecture for the network, while the LoRa physical layer enables the long-range communication link. LoRaWAN® is also responsible for managing the communication frequencies, data rate, and power for all devices.

Advantages and Disadvantages of LoRaWAN®

Advantages:

1) Long Range: LoRa devices can transmit signals over distances from 1km — 10km.
2) Low Power: LoRa end nodes wake up only at a fixed time, which can extend battery life. End node batteries can last for 5-10 years (Class A and Class B devices).
3) Security: data encryption using AES128 between end nodes and network servers/ Data encryption using AES128 at the application level.
4) Network Capability: single LoRa gateway device is designed to take care of thousands of end devices or nodes and easy to extend network capability by increasing gateways.
A LoRaWAN® gateway capability is influenced by these factors:
• Tunnels: different tunnels can receive data from end nodes simultaneously; the greater quantity of tunnels, the more end nodes a gateway can connect to;
• Data size and reporting interval: large data size and reporting interval will reduce the end nodes that a gateway can connect to.
• ADR (Adaptive Data Rate): the distance between end nodes and gateways is closer, the data rate is higher, which can save the bandwidth of gateways.
5) Low Cost: work in free frequencies and no upfront licensing cost to use the technology.
6) Easy Deployment: simple network architecture and easy to deploy by yourself.

Disadvantages

1) Not for large data transmission;
2) Not for continuous monitoring (except Class C devices);
3) Wake up only at a fixed time, so you can’t communicate with end nodes at any time (Class A and Class B devices);
4) The transmission rate is slow and easy to get interference because of using free frequencies.

Network Architecture

LoRaWAN® network architecture is deployed in a star-of-stars topology. The LoRaWAN® networks laid out in a star-of-stars topology have base stations relaying the data between the sensor nodes and the network server.

In a LoRaWAN® network, nodes are not associated with a specific gateway. Instead, data transmitted by a node is typically received by multiple gateways. Each gateway will forward the received packet from the end-node to the cloud-based network server via some backhaul (either cellular, Ethernet, satellite, or Wi-Fi). The intelligence and complexity are pushed to the network server, which manages the network and will filter redundant received packets, perform security checks, schedule acknowledgments through the optimal gateway, and perform adaptive data rate, etc. Whether a node is mobile or moving there is no handover needed from gateway to gateway.

End Nodes

The End Nodes are devices embedded with LoRa chips.

• Sensors (used to detect the changing parameter eg. temperature, humidity, accelerometer, gps)

• Controllers (used to control remote devices, such as lamp)

• Converters (change data format between LoRa and IP data packages)

End nodes serve different applications and have different requirements. The LoRaWAN® specification defines three device types.

• Class A: end nodes transmit whenever they need to and lie dormant during other times. Each end node’s uplink transmission is followed by two short downlink receive windows for downlink communications. So downlink communications from the server at any other time will have to wait until the next scheduled uplink. Class A end nodes are the lowest power which can used in smoke alarm, gas detector, etc.

• Class B: end nodes open extra receive windows for downlink communications periodically. In order for the end-device to open its receive window at the scheduled time, it receives a time-synchronized beacon from the gateway. This allows the server to know when the end-device is listening. Class B can be used in electric meters, water meters, etc.

• Class C: end nodes have almost continuously open receive windows, only closed when transmitting. Class C end nodes are the highest power but no delay and easily controlled which can be used in lamp control, door control, etc.

Gateway

LoRaWAN® gateways (Check out Milesight UG65 LoRaWAN® Gateway) are bridges between end nodes and network server. Gateways can simply convert LoRa data packets received from end nodes to IP packets and transmit them to network servers or cloud, and vice versa. The gateway devices are connected to the Internet via cellular, Wi-Fi, etc. Gateways running an operating system allow users to install their own software, so network server can be integrated into LoRaWAN® gateways.

LoRa Basics™ Station

LoRa Basics™ Station is the next generation of Semtech’s Packet Forwarder with enhanced security and remote configuration capabilities. Instead of using UDP connection, LoRa Basics™ Station uses secure WebSockets to communicate with the network server.

You can find more information here.

Network Server

The network servers filter redundant packets, perform security checks, perform adaptive data rate, manages the network, etc. Then packets are forwarded to application servers. The network servers can be used for both uplink (i.e. sensor to application) or downlink (i.e. application to sensor) communication.

Application Server

The Application servers are software which can process data from network servers and present them as a graph web page or an app

LoRaWAN® Regional

LoRa works in unlicensed frequencies and official regional parameters can be found at LoRa Alliance: https://lora-alliance.org/wp-content/uploads/2020/11/lorawan_regional_parameters_v1.0.2_final_1944_1.pdf
These LoRaWAN® regional specifications do not specify everything either. They only cover a region by specifying the common denominator. For example, the LoRaWAN® regional parameters for Asia only specify a common subset of channels – but there are variations between regulations in Asian countries. Furthermore, each network server operator is free to select additional parameters, such as additional emission channels. We call these parameters Frequency Plans.

Comparison of LoRa, Sigfox and NB-IoT

LoRa, Sigfox and NB-IoT are three of typical LPWAN technologies. Here are comparisons among them:

In conclusion, LoRa technology has moderate data transmission conditions and lowest deployment cost.

Over-the-air Activation (OTAA)

Over-the-Air Activation (OTAA) is the preferred and most secure way to connect with The Things Network. Devices perform a join-procedure with the network, during which a dynamic DevAddr is assigned and security keys are negotiated with the device.

LoRaWAN® defines the communication protocol and system architecture for the network, while the LoRa physical layer enables the long-range communication link. LoRaWAN® is also responsible for managing the communication frequencies, data rate, and power for all devices.

Activation by Personalization (ABP)

In some cases you might need to hardcode the DevAddr as well as the security keys in the device. This means activating a device by personalization (ABP). This strategy might seem simpler because you skip the registration procedure, but it has some downsides related to security.

Activation by Personalization (ABP)

In some cases you might need to hardcode the DevAddr as well as the security keys in the device. This means activating a device by personalization (ABP). This strategy might seem simpler because you skip the registration procedure, but it has some downsides related to security.

What is LTE-M

LTE-M is the abbreviation for LTE Cat-M1 or Long Term Evolution (4G), category M1. This technology is for Internet of Things devices to connect directly to a 4G network, without a gateway and on batteries.

Bottom Line on LTE-M

1. It’s cheaper. Devices can connect to 4G networks with chips that are less expensive to make because they are half-duplex and have a narrower bandwidth.
2. Long Battery Life. Devices can enter a “deep sleep” mode called Power Savings Mode (PSM) or wake up only periodically while connected. That mode is called extended discontinuous reception (eDRX). Read more on eDRX and PSM.
3. Service Costs Less. Because the maximum data rate of LTE-M devices is only about 100 kbit/s, they do not tax the 4G network as much. Carriers can offer service plans that closer to old 2G M2M pricing than 4G pricing.