The LoRa Alliance is an open, non-profit, international alliance of companies and industry stakeholders that share the mission of trying to standardise the deployment of the Low-Power Wide Area Networks (LPWANs) – that are increasingly being deployed around the world to enable Internet-of-Things technology and machine-to-machine communications, “smart cities”, and industrial applications.
Members of the LoRa alliance collaborate with the aim of driving the global success of their LoRaWAN protocol, by sharing knowledge and experience with a view towards interoperability between operators, using a single open global standard for LPWAN connectivity. The Alliance – which is led by IBM, Actility, Semtech and Microchip, formally released the open LoRaWAN R1.0 standard to the public earlier this year.
LoRaWAN is an LPWAN specification intended for wireless, battery-operated IoT “things” with wide-area network connectivity. Its features are specifically aimed at supporting low-cost, secure, mobile and bidirectional communication for wireless IoT applications, with strong energy efficiency and a minimal need for base station deployments.
A LoRa network is already being rolled out by Bouygues Telecom in France, in partnership with Sagemcom, with aims to cover most of the country by the first half of 2016. Some testing and evaluation is already underway with this country-scale LoRaWAN network, and tests are also being conducted locally in Sydney’s North Shore area by the NNN (National Narrowband Network) Company.
LoRaWAN is optimised for strong energy efficiency and support for large networks of up to millions of devices. At the physical layer, the RF hardware is optimised for high efficiency, with data links being maintained over long distances with very low power consumption.
As with some other LPWAN systems such as Taggle, the class-licensed sub-gigahertz ISM bands are used to provide this long-range connectivity – different frequencies depending on which country the technology is deployed in.
This long range and energy efficiency comes at the cost of data rate, though – this technology was never intended for high-bandwidth applications, but it is a perfect fit for lightweight applications such as telemetry from environmental sensors deployed in remote field applications.
LoRaWAN network architecture is typically laid out in a “star-of-stars” topology with multiple endpoints and multiple gateways. In this arrangement each gateway serves as a transparent bridge that relays messages between endpoint devices and a central back-end server. Gateways are connected to the back-end server via familiar IP networks while endpoint “things” use a single-hop lightweight wireless link back to one or more gateway devices.
Wireless communication between the endpoint devices and the gateways is performed in a spread-spectrum manner, employing different frequency channels and data rates. The selection of the data rate is a trade-off between the required transmission range and the acceptable time for the transmission of a message of given size, with typical LoRaWAN data rates ranging from 0.3 kbps to 50 kbps.
This may seem small, but it is sufficient for a lightweight, embedded sensor application that transmits small packets of sensor readings occasionally to the back-end server.
Because of the spread-spectrum approach, communications with different data rates do not interfere with each other, but instead what you have, basically, is a set of “virtual” channels for each transmission at a different data rate. In this manner, the capacity of each gateway is increased, and more endpoint devices are able to be supported by each gateway. This means that the infrastructure cost of rolling out a large-scale LoRaWAN network is reduced.
To maximise both battery life of the endpoint devices and the overall capacity of the network, the LoRaWAN network server is responsible for an adaptive data rate (ADR) scheme that dynamically manages the data rate and the RF power output for each individual endpoint node in the network.
The LoRaWAN standard defines three classes of endpoint nodes – one that allows a small downlink window after each upload, which means that devices don’t have to communicate a scheduled downlink window in cases where the amount of downlink data needed is minimal; or one that allows a scheduled downlink slot at a defined time; or one that listens for downlink messages at any time.
The latter is more flexible, but because it requires the radio receiver to be kept online listening for new downlink messages all the time, this is the most power-inefficient mode compared to the former scenarios where the radio can be powered down. This is another way that the LoRaWAN protocol helps to maintain strong power efficiency in the endpoint devices.
The LoRa Alliance Certified Product program ensures that any LoRa-branded devices on the market are compliant with the standard, are interoperable, and meet regulatory requirements such as the radio frequencies being used. Only LoRa Alliance authorised test houses may perform testing for this program, and the relevant national conformity test reports are supplied by product designers, together with the LoRa Alliance conformity report, to the Alliance’s certification body before the “LoRa Certified Product” status is allowed.
This strict process gives consumers confidence in the LoRa Alliance and in consumer-facing products that carry their brand, meaning that consumers without a technical background can be confident that their products are interoperable, compliant with relevant radio regulations, and can be used in a predictable way alongside other devices and software tools that are built on top of the same open standards.
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LX is an award-winning electronics design company based in Sydney, Australia. LX services include full turnkey design, electronics, hardware, software and firmware design. LX specialises in IoT embedded systems and wireless technologies design.
Published by LX Pty Ltd for itself and the LX Group of companies, including LX Design House, LX Solutions and LX Consulting, LX Innovations.
