LoRa, LoRaWAN and LORIOT

by Vit Prajzler
August 1st 2015

LoRa

LoRa is an abberviation of "Long Range", which also summarizes the key advantage of this wireless technology.

LoRa is a patented ( EP2763321 from 2013 and US7791415 from 2008 ) spread-spectrum radio modulation developed by Cycleo (Grenoble, France) and acquired by Semtech NASDAQ:SMTC in 2012 .

Thanks to the unique chirp modulation, the wireless link can achieve sensitivity up to -137 dBm and up to 157 dB of link budget. The trade-off is the achievable data rate, which is in the range of kilobits per second. This defines the applicability of the technology - while it is not suited for video streaming, it is well fit to serve the Internet of Things (IoT) and M2M applications.

LoRa can be used over a wide range of frequencies from 137 MHz to 1020 MHz. This includes numerous license-free ISM bands like 169 MHz, 433 MHz, 868 MHz and 915 MHz. This is a key enabler for inexpensive, world-wide deployments and interoperability.

The important aspect of any IoT technology is how it is going to behave once there are millions of devices deployed. The LoRa solution can be labeled CDMA. It is using different spreading factors (chirp data rates) and coding rates to multiplex signals on a single frequency. This not only increases the network capacity, it also allows for dynamic adaptation of device data rates. Devices with a better link to a gateway (due to proximity, lower noise environment, unobstructed line-of-sight) can use higher data rates (up to 11 kbps) and save battery. Devices with poor link quality can increase the link budget by using lower data rates, extending the effective link range to more than 30 km in line-of-sight.

A common misconception is that LoRa chips can only be produced by Semtech ( SX1272 and SX1276 ). While it is correct that Semtech owns the LoRa IP, there are clear signs that the company is willing to license the IP to other chip manufacturers. One of the examples is HopeRF.

In the OSI reference stack model, LoRa would be on the Physical Layer.

LoRaWAN

LoRaWAN is the MAC protocol for high capacity, long range, low power, Internet of Things network of LoRa nodes. It is an open LPWAN standard maintained by the LoRa Alliance. It takes advantage of the LoRa features described above and optimizes battery life and quality of service for the LoRa nodes.

The protocol is fully bi-directional, which allows for reliable message delivery (confirmations). It includes definition of end-to-end encryption for security and data privacy, over-the-air registration of end nodes, and multicast capability.

Thanks to the distributed antenna model and GPS enabled gateways, the network is capable of locating the position of nodes, even when they are mobile.

The standard ensures the interoperability of the various LoRaWAN networks world-wide.

In the OSI reference stack model, LoRaWAN would correspond to the MAC layer.

LORIOT.io

LORIOT.io is a provider of a LoRaWAN Network Server and Application Server software, which is commercially offered through a set of business models.

We provide

  • Software for the supported LoRa gateways
  • Cloud-based LoRaWAN Network Server
  • Programming interface (APIs) for Internet of Things applications to access the end node data
  • Output of end node data to number of 3rd party services

As a gateway owner, you can use our software on your gateways to connect them to our cloud. From then on, all data received by the gateways will be relayed to you through our APIs or 3rd party services.

The network server components fullfils to role of protocol processor. It is a TLS connection end-point for the gateways and the customer applications. It is responsible for processing the incoming end node data according to the LoRaWAN protocol.

The specific roles of LORIOT.io Network Server are

  • Gateway population management
  • Application population management
  • Device population management
  • Collection of billing records
  • Security management
  • Data distribution

LoRaWAN Security and Privacy

Security and privacy is at utmost importance in any IoT solution. The LoRaWAN protocol specifies encryption to assure your data is secure, concretely

  • Per-device AES128 keys
  • Instant regeneration / revocation of device keys
  • Per-packet payload encryption for data privacy
  • Protection against replay attacks
  • Protection against man-in-the-middle attacks

Two sets of cryptographic domains are present in LoRaWAN - the network domain and the application domain.

The network domain is responsible for authentication of the end node data. The authorship is verified through an AES128 secret key shared between the device and the network server.

The application domain is responsible for guarenteeing the privacy of the device data. There is a AES128 secret key shared between the user application and the end node.

LoRa gateways / concentrators

The heart of every LoRa concentrator is a multi-channel LoRa demodulator able to decode all LoRa modulation variants on several frequencies in parallel. A standard LoRa end-device demodulator (LoRa modem like SX1276 or SX1272) can only decode one modulation type on one frequency.

Currently, the widely-used LoRa baseband demodulator is Semtech's SX1301. This chip is integrated in all the LoRa gateways in our current portfolio.

Due to the growing number of gateway manufacturers, it is becoming difficult to pinpoint the differences between the gateways. For a large-scale network operator, the key distinguishing factors should be the radio performance (sensitivity, sending power), the connection of the SX1301 chip to the gateway MCU and the support and distribution of PPS signal.

SX1301 connected over an USB-to-SPI bridge has a longer latency to the MCU than an SX1301 that is directly attached to the MCU's SPI bus. Currently, the only SPI attached SX1301 is in the Kerlink IoT Station, all other gateways use FTDI (or similar) USB-to-SPI bridges.

The availability of PPS signal allows for precise time synchronization over the entire gateway population in a network. It is a key enabler for network-wide beacons, which can be used for time synchronization by the end-devices. PPS distribution and is currently only supported by Kerlink IoT Station, SX1301 reference board and IMST iC880A.