May 13, 2019
A Short Introduction to LoRa, LoRaWAN, and The Things Network for IoT Device Communications
The exploding popularity of IoT devices has brought with it new requirements for sending device data which are oftentimes a poor fit for existing technology. Devices deployed in the field require a secure means of transmitting data over long ranges while consuming very little power. The LoRaWAN technology stack has been developed to meet these needs in an open and flexible manner.
What is LoRa?
LoRa (“Long Range”) is a layer 1 and 2 radio network technology developed by Semtech which utilizes a proprietary chirp spread-spectrum (CSS) technology providing long-range communications that are highly resistant to common noise and interference problems found in outdoor environments. The LoRa standard is not open (although independent research has documented large portions of the implementation) and all LoRa radio chipsets are manufactured under license from Semtech.
The radios run on unlicensed ISM bands making for easy local deployment while potentially raising issues with device portability due to different frequency allocations in different parts of the world. With suitable antenna placement, a single device can communicate over 10km. Overall data transmit rates are low and are variable due to signal strength and FCC airtime regulations, but you can expect somewhere on the order of 100 bytes sent every 30 seconds.
LoRa devices can communicate with other LoRa devices within range without encryption and without guaranteed delivery. Using LoRa in this manner provides a fast path to testing capabilities and may be suitable for small-scale deployments in a defined area such as manufacturing or agriculture.
What is LoRaWAN?
LoRaWAN is an open standard providing a layer-3+ stack on top of a LoRa radio network. LoRaWAN offers low-power device communication between edge nodes and central gateways. Device traffic is encrypted via AES and devices can either be pre-provisioned with network access key material or negotiate access automatically when powering on.
LoRaWAN has provisions for coordinating receive and transmit windows for low-power devices along with acknowledged delivery through the use of a coordinating gateway device. The gateway device is a low-cost, unlicensed radio which can forward local device traffic to an Internet-connected server via a secure link. Multiple gateway devices can be deployed in a given area, providing extended coverage and automatically performing data-deduplication of packets received by multiple gateways. With several gateways deployed, a single device can roam between multiple gateways extending the range and coverage of a given installation.
What is The Things Network?
The Things Network is a community-run effort to deploy and manage a shared set of LoRaWAN gateways along with cloud services to support gateways and end-user devices. Interested parties can purchase and deploy gateway devices to connect to The Things Network, providing access to any registered users. Users within range of an existing gateway can sign up at no cost to register their own devices.
Data sent from the device is passed through the gateway to The Things Network cloud service, where the device owner can access the data through an MQTT API. As all traffic is encrypted, gateway operators cannot see device data, but The Things Network can.
The Things Network backend service is entirely open source and can be self-hosted if so desired, but devices will no longer be able to use gateways run by other operators, limiting device range to those gateways operated by and connected to that private backend.
This technology stack provides a low-friction and low-cost framework for mobile device development that is open to everyone without contracts and without monthly payments. This makes LoRaWAN an ideal solution for rapid development and for targeted installations in a defined geography.
It also comes without commitments or service level agreements, so its use may be limited in scope and range without a substantial investment in hosting your own gateway devices. While commercial use is allowed, users expecting contracted network availability may be better suited with commercial IoT network offerings from Sigfox, Helium, or others.
OST has been working alongside the City of Grand Rapids, Start Garden, Simms Electronics, and others pushing forward a municipal LoRaWAN network for community use and development. We have developed hardware and software solutions making meaningful use of this network technology and have gained substantial implementation and architectural experience along the way. If you have questions about how best to deploy your own gateways or devices, please contact us.