LoRa

LoRa (from "long range") is a physical proprietary radio communication technique. It is based on spread spectrum modulation techniques derived from chirp spread spectrum (CSS) technology. It was developed by Cycleo, a company of Grenoble, France, and patented in 2014. Cycleo was later acquired by Semtech.

LoRaWAN (wide area network) defines the communication protocol and system architecture. LoRaWAN is an official standard of the International Telecommunication Union (ITU), ITU-T Y.4480. The continued development of the LoRaWAN protocol is managed by the open, non-profit LoRa Alliance, of which Semtech is a founding member.

Together, LoRa and LoRaWAN define a low-power, wide-area (LPWA) networking protocol designed to wirelessly connect battery operated devices to the Internet in regional, national or global networks, and targets key Internet of things (IoT) requirements, such as bi-directional communication, end-to-end security, mobility and localization services. The low power, low bit rate, and IoT use distinguish this type of network from a wireless WAN that is designed to connect users or businesses, and carry more data, using more power. The LoRaWAN data rate ranges from 0.3 kbit/s to 50 kbit/s per channel.

Features
LoRa uses license-free sub-gigahertz radio frequency bands EU868 (863–870/873 MHz) in Europe; AU915/AS923-1 (915–928 MHz) in South America; US915 (902–928 MHz) in North America; IN865 (865–867 MHz) in India; and AS923 (915–928 MHz) in Asia; LoRa enables long-range transmissions with low power consumption. The technology covers the physical layer, while other technologies and protocols such as LoRaWAN (long range wide area network) cover the upper layers. It can achieve data rates between 0.3 kbit/s and 27 kbit/s, depending upon the spreading factor.

LoRa is one of the most popular low-power wireless sensor network technologies for the implementation of the Internet of Things, offering long-range communication compared to technologies such as Zigbee or Bluetooth, but with lower data rates.

LoRa devices have geolocation capabilities used for trilaterating positions of devices via timestamps from gateways.

LoRa PHY
LoRa uses a proprietary spread spectrum modulation that is similar to and a derivative of chirp spread spectrum (CSS) modulation. Each symbol is represented by a cyclic shifted chirp over the frequency interval ($$f_0-B/2,f_0+B/2$$) where $$f_0$$ is the center frequency and $$B$$ the bandwidth of the signal (in Hertz). The spreading factor (SF) is a selectable radio parameter from 5 to 12 and represents the number of bits sent per symbol and in addition determines how much the information is spread over time. There are $$M=2^{\mathrm{SF}}$$ different initial frequencies of the cyclic shifted chirp (the instantaneous frequency is linearly increased and wrapped to $$f_0-B/2$$ when it reaches the maximum frequency $$f_0+B/2$$). The symbol rate is determined by $$R_s = B/2^{\mathrm{SF}}$$. LoRa can trade off data rate for sensitivity (assuming a fixed channel bandwidth $$B$$) by selecting the SF, i.e. the amount of spread used. A lower SF corresponds to a higher data rate but a worse sensitivity, a higher SF implies a better sensitivity but a lower data rate. Compared to lower SF, sending the same amount of data with higher SF needs more transmission time, known as time-on-air. More time-on-air means that the modem is transmitting for a longer time and consuming more energy. Typical LoRa modems support transmit powers up to +22 dBm. However, the regulations of the respective country may additionally limit the allowed transmit power. Higher transmit power results in higher signal power at the receiver and hence a higher link budget, but at the cost of consuming more energy. There are measurement studies of LoRa performance with regard to energy consumption, communication distances, and medium access efficiency. According to the LoRa Development Portal, the range provided by LoRa can be up to 3 mi in urban areas, and up to 10 mi or more in rural areas (line of sight).

In addition, LoRa uses forward error correction coding to improve resilience against interference. LoRa's high range is characterized by high wireless link budgets of around 155 dB to 170 dB. Range extenders for LoRa are called LoRaX.

LoRaWAN
Since LoRa defines the lower, physical, layer, the upper networking layers were lacking. LoRaWAN is a protocol that was developed to define the upper layers of the network. LoRaWAN is a cloud-based medium access control (MAC) layer protocol, but acts mainly as a network layer protocol for managing communication between LPWAN gateways and end-node devices, as a routing protocol maintained by the LoRa Alliance.

LoRaWAN defines the communication protocol and system architecture for the network, while LoRa's physical layer enables the long-range communication link. LoRaWAN is also responsible for managing the communication frequencies, data rate, and power for all devices. Devices in the network are asynchronous and transmit when they have data available to send. Data transmitted by an end-node device is received by multiple gateways, which forward the data packets to a centralized network server. Data is then forwarded to application servers. This technology shows high reliability for the moderate load, however, it has some performance issues with sending acknowledgements.

CSMA for LoRaWAN
In the wireless communication, particularly across the IoT applications, collision avoidance is essential for reliable communication and overall spectral efficiency. Previously, LoRaWAN has relied upon ALOHA as the medium access control (MAC) layer protocol, but to improve this, the LoRa Alliance's Technical Recommendation TR013 introduced CSMA-CA, which does not debilitate LoRa's distinctive modulation advantages such as Spreading Factor orthogonality, and the capability for below noise-floor communication. Employing the CAD based CSMA technique specified in TR013 overcomes the limitations of relying on Received Signal Strength (RSS)-based sensing, which is unable to maintain the two said advantages of LoRa modulation. Therefore, implementing TR013 enhances LoRaWAN's spectrum efficiency and ensures more reliable device communication, including in congested environments. TR013 is based on the LMAC and is the first industry-academia collaboration of LoRa Alliance to have resulted in a Technical Recommendation.

Version history

 * January 2015: 1.0
 * February 2016: 1.0.1
 * July 2016: 1.0.2
 * October 2017: 1.1, adds Class B
 * July 2018: 1.0.3
 * October 2020: 1.0.4

LoRa Alliance
The LoRa Alliance is an open, non-profit association whose stated mission is to support and promote the global adoption of the LoRaWAN standard for massively scaled IoT deployments, as well as deployments in remote or hard-to-reach locations.

Members collaborate in a vibrant ecosystem of device makers, solution providers, system integrators and network operators, delivering interoperability needed to scale IoT across the globe, using  public, private, hybrid, and community networks. Key areas of focus within the Alliance are Smart Agriculture, Smart Buildings, Smart Cities, Smart Industry, Smart Logistics, and Smart Utilities.

Key contributing members of the LoRa Alliance include Actility, Amazon Web Services, Cisco. Everynet, Helium, Kerlink, MachineQ, a Comcast Company, Microsoft, MikroTik, Minol Zenner, Netze BW, Semtech, Senet, STMicroelectronics, TEKTELIC and The Things Industries. In 2018, the LoRa Alliance had over 100 LoRaWAN network operators in over 100 countries; in 2023, there are nearly 200, providing coverage in nearly every country in the world.