LoRa (Long Range) is a proprietary low-power wide-area network modulation technique.[1] It is based on spread spectrum modulation techniques derived from chirp spread spectrum (CSS) technology.[2] It was developed by Cycleo of Grenoble, France and acquired by Semtech, the founding member of the LoRa Alliance and it is patented.[3]
LoRa uses license-free sub-gigahertz radio frequency bands like 433 MHz, 868 MHz (Europe), 915 MHz (Australia and North America), 865 MHz to 867 MHz (India) and 923 MHz (Asia). LoRa enables long-range transmissions with low power consumption.[4] 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.[5]
LoRa devices have geolocation capabilities used for trilaterating positions of devices via timestamps from gateways.[6]
LoRa uses a proprietary spread spectrum modulation that is similar to and a derivative of chirp spread spectrum (CSS) modulation. The spread spectrum LoRa modulation is performed by representing each bit of payload information by multiple chirps of information. The rate at which the spread information is sent is referred to as the symbol rate, the ratio between the nominal symbol rate and chirp rate is the spreading factor (SF) and represents the number of symbols sent per bit of information.[2] The result is an M-ary digital modulation, where the possible waveforms at the output of the modulator are chirp modulated signals over the frequency interval () with M different initial frequencies: the instantaneous frequency is linearly increased, and then wrapped to when it reaches the maximum frequency . [7]
LoRa can trade off data rate for sensitivity with a fixed channel bandwidth by selecting the amount of spread used (a selectable radio parameter from 6 to 12). Lower SF means more chirps are sent per second; hence, you can encode more data per second. Higher SF implies fewer chirps per second; hence, there are fewer data to encode per second. Compared to lower SF, sending the same amount of data with higher SF needs more transmission time, known as airtime. More airtime means that the modem is up and running longer and consuming more energy. The benefit of high SF is that more extended airtime gives the receiver more opportunities to sample the signal power which results in better sensitivity.[8]
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.[9]
Since LoRa defines the lower physical layer, the upper networking layers were lacking. LoRaWAN is one of several protocols that were 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 LPWANgateways 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 the LoRa physical layer enables the long-range communication link. LoRaWAN is also responsible for managing the communication frequencies, data rate, and power for all devices.[10] 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.[11] Data is then forwarded to application servers.[12] The technology shows high reliability for the moderate load, however, it has some performance issues related to sending acknowledgements.[13]
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^M. Chiani; A. Elzanaty (2019). "On the LoRa Modulation for IoT: Waveform Properties and Spectral Analysis". IEEE Internet of Things Journal. 6 (5): 772. doi:10.1109/JIOT.2019.2919151. hdl:10754/655888.
^Bankov, D.; Khorov, E.; Lyakhov, A. (November 2016). "On the Limits of LoRaWAN Channel Access". 2016 International Conference on Engineering and Telecommunication (EnT): 10–14. doi:10.1109/ent.2016.011. ISBN978-1-5090-4553-2. S2CID44799707.
^Brad Biddle (7 May 2019). "Linux Foundation is Eating the World". SSRN3377799. Many other organizations formed following this same basic template: incorporation as a mutual benefit non-profit corporation under applicable U.S. state law (with some slight variations of corporate form based on particular state law requirements), and then operation as a tax exempt entity under a provision targeted at “business leagues” and other trade association-style enterprises. This provision, Section 501(c)(6) of Title 26 of the U.S. Code, generally enabled the organizations to avoid paying federal income tax, and often to avoid most state and local taxes as well. Selecting from hundreds of examples, some organizations that follow this model include ... LoRa AllianceCite journal requires |journal= (help)
^Gallivan, Joseph (5 January 2018). "Las Vegas Arrivals". Business Tribune. Retrieved 5 February 2020. The alliance is managed by the VTM Group in Beaverton.... Geoff Mulligan is the Chairman of the LoRa Alliance. He was a presidential innovation Fellow at the National Institute of Standards and Technology (NIST) under the Obama administration.
Lee, Chang-Jae, Ki-Seon Ryu, and Beum-Joon Kim. "Periodic ranging in a wireless access system for mobile station in sleep mode." U.S. Patent No. 7,194,288. 20 March 2007.
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