LoRa

What is LoRa technology?

LoRa technology is widely used in the world of the Internet of Things (IoT). It enables the transmission of low-volume data via fixed sensors. The principle of LoRa networks is to transmit data via radio links from low-power sensors, potentially isolated or difficult to access, and operating on batteries for 5 to 10 years.

Functionally, the sensors measure and store their data before transmitting it over the LoRa network. They send their frames to one (or more) gateways (or hubs) that act as relays between a large number of sensors within its coverage area and ad hoc data storage and processing servers. Gateways and servers are interconnected via cellular networks, fiber optics, or copper links, depending on the situation.

In LoRa, bidirectional connections are possible, i.e., sensors to IS and IS to sensors. This feature can be important if firmware updates[1] are required, for example. Although the data rate also depends on the protocol implemented on the LoRa modulation, it should be noted that it does not exceed 150 kbit/s in the upstream direction (sensors to IS), and in the downstream direction (IS to sensors), it is around 50 kbit/s. Although bidirectional, the protocol is optimized for data transmission.

Unlike Sigfox, the number of messages per sensor (both uplink and downlink) is unlimited on LoRa networks. Voice cannot be transmitted over LoRa networks, and the protocol also does not provide handover management, i.e., mobile sensor management.

In terms of coverage, a gateway can receive sensors within a 5km radius in urban areas, and within a 15km radius in rural areas. Buried objects can be received to some extent. Note that indoor coverage is good, but that of the Wize (169 MHz) and NB-IoT networks is better.

What is the difference between LoRa and LoRaWAN?

The terms LoRa and LoRaWAN are sometimes confused, even though they are technically incomparable. As mentioned earlier, LoRa is a signal modulation technology that allows data transmission while respecting a protocol, such as LoRaWAN. This protocol is the main existing LoRa protocol, which was established by the LoRa Alliance with the ambition of standardizing a protocol for exchanging data with connected objects. On LoRa modulation, different protocols can be implemented. For example, Link Labs has developed the Symphony Labs protocol, specifically dedicated to the Americas.

Typically, Link Labs developed the Symphony Labs protocol, specifically dedicated to the Americas. Sensors must be capable of LoRa modulation at the time of transmission (and demodulation at reception), and they apply the LoRaWAN protocol, which sets the rules for communication on the network (in terms of frame format, transmission time, encoding, etc.). The only LoRa chipset manufacturer currently is Semtech, which acquired the Grenoble-based startup Cycléo in 2013, which developed the LoRa standard in 2009. The LoRaWAN protocol governs communication from the sensor to the application server, and LoRa transmission is limited to the low-speed radio communication perimeter (up to the gateway).

Illustrative use case

Thanks to LoRa technology, a company in charge of a city's waste management can determine the fill level of its dumpsters to optimize its truck routes: a full dumpster will be prioritized over one that is not yet full.

How does it work? An ultrasonic fill sensor was installed in each bin. This battery-powered sensor has a transmitter component that sends the fill level value recorded by the ultrasonic sensor at that moment every N minutes. The information, complying with the LoRaWAN protocol rules, is sent via LoRa and received by a gateway. Technically, the gateway returns an acknowledgment of receipt of the frame; otherwise, the sensor would have re-sent the information after a given time. This same gateway collects data from X sensors distributed across its coverage area and retransmits it to the target information system (IS) via 4G (for example).

Complying with the LoRaWAN protocol, the gateway transmits the collected data over the 4G network, which is received and decoded by the network interface of the target IS. The server stores them according to ad hoc rules and makes them available to the business applications that perform the processing for which they were implemented. The application displays the fill rate of the monitored bins on a map so that the city's waste management manager can modify the timing or route of maintenance rounds based on these indicators.

What is the LoRa Alliance?

Founded in 2015, the LoRa Alliance has over 500 members, including institutions, manufacturers, and network operators, and is constantly expanding. The founding members of the LoRa Alliance are IBM, MicroChip, Cisco, Semtech, Bouygues Telecom, Singtel, KPN, Swisscom, Fastnet, and Belgacom. The Alliance's industrial members range from electronic component manufacturers to solution integrators and telecom operators. As of early 2019, the LoRa Alliance had 100 LoRaWAN network operators among its members.

The LoRaWAN standard leverages an open protocol approach led by the LoRa Alliance, which unifies the specification, development, and deployment of the standard, develops certification guides, and ensures interoperability between radio infrastructure providers, core network vendors, and end-device designers and manufacturers. The Alliance is the LoRaWAN product certification authority. LoRaWAN certification ensures interoperability between products (sensors, gateways) and their operational compliance with the standard, and provides increased marketing visibility.

The success of LoRaWAN is primarily based on LoRa modulation, which enables proper demodulation in very poor signal-to-noise ratio conditions.

While the LoRaWAN protocol is open, it is true that Semtech is currently the leading manufacturer of LoRa electronic boards. In 2013, Semtech acquired Cycléo, the French startup that had filed a patent on this technology. However, it appears that Microchip and Murata are producing LoRa chips, and that ST Microelectronics and Renesas have included this promising modulation on their roadmaps.

What are the LoRaWAN product classes?

The LoRaWAN protocol categorizes network equipment into three types:

• Class A: This class has the lowest power consumption. When the device has data to send, it does so unchecked, then opens two successive listening windows for possible messages from the server. The recommended durations are 1 and then 2 seconds. These two windows are the only ones during which the server can send the device the data it has previously stored for it.
• Class B: This class provides a compromise between power consumption and the need for bidirectional communication. These devices open reception windows at scheduled intervals via periodic messages sent by the server.
• Class C: This class has the highest power consumption but allows for unscheduled bidirectional communication. The devices have a permanent listening window.

How is LoRaWAN network management and scalability achieved?

In LoRaWAN, the network server centralizes network management intelligence, including filtering redundant packets, security testing, optimizing acknowledgment sending to the best gateway, managing communication times, etc. Although the LoRaWAN protocol does not allow handover, mobile sensor tracking can still be ensured using the network server. It is also thanks to this network element that LoRa objects can be geolocated through triangulation and through the feedback of frame reception quality information.

A single gateway can concentrate communications with a very large number of sensors. Consequently, scalability is a characteristic property of LoRaWAN networks. This is ensured by the presence of multi-modem multi-port transmitters on the gateways, and by adaptive data rate. Adjusting the data rate amounts to working on the spread spectrum factor, allowing for the simultaneous reception of (orthogonal) signals from different sensors on the same port. Depending on the proximity of a sensor to the gateway, the data rate can be increased to reduce transmission/reception time, and therefore the associated power consumption. This approach aims to optimize communications with sensors that are harder to reach (more distant, or typically buried) by increasing the spread spectrum factor, which reduces data throughput. Furthermore, this feature also allows for optimized sensor battery management.

The method for activating LoRa devices (via the network server) is important. It depends on the capabilities of both the device in question and the network. Over-the-Air Activation (OTAA) is better because it's simpler and more secure. Indeed, in terms of security, keys are exchanged when the device first connects to the network and sends its access request. In ABP mode (Activation by Personalization), the keys must be predefined and encoded on the device beforehand, i.e., at the factory, as well as on the network server.

What are the security measures of the LoRaWAN protocol?
IoT network security is a major concern for stakeholders, which the LoRaWAN standard has natively taken into account in its specifications. First, AES encryption is used, which is based on the principle of exchanging authentication keys between network elements. On the other hand, security management is twofold, comprising a network security layer and an application security layer. The network security layer ensures the authenticity of sensors within the network, i.e., it guarantees the correct origin of the transmitted data. Application layer security ensures that the network operator does not have access to the end user's data.

[1] Sensors must be capable of LoRa modulation upon transmission (and demodulation upon reception), and they typically apply the LoRaWAN protocol, which sets the rules for communication on the network (in terms of frame format, transmission time, encoding, etc.).