LoRa: Non-cellular IoT Technology
Long-Range technology offers comprehensive connectivity while consuming low power and cost. This non-cellular technology operates on different frequency plans and bandwidths across the globe, offering a remarkable range of receiver sensitivity. Know more about the nuances of this technology and its architecture, along with some key names implementing LoRa to transform the future.
Introduction
LoRa is an acronym for Long-Range.
LoRa is a non-cellular Internet-of-things (IoT) technology.
LoRa technology is a low-power wide area network (LPWAN) technology envisioned to meet the ever-increasing need for low-power, long-range, and massive connectivity.
LoRa network operates in the unlicensed sub-GHz band (433, 868, 915 MHz). The frequency plan used in India is 865-867 MHz. There are 8 uplink channels and
LoRa technology follows IEEE 802.15.4 standard.
LoRa is based on Chirp Spread Spectrum (CSS) modulation scheme.
Key Characteristics Of LoRa
LoRa offers attractive features such as long-range, low-power, and low-cost.
Long-range based on Environment (figure on right)
LoRa devices can operate for around 10 years on a single coin cell battery.
However, the catch with LoRa is that it is only suitable for low data-rate applications.
License-free spectrum – to implement the LoRaWAN network, there is no need to pay pricey spectrum license fees.
Deep indoor penetration - LoRa operates on low frequency. Hence, they can support deep indoor coverage and pass through multi-floor buildings.
Low data rate- Data-rate for LoRa ranges from 0.29 kbps (for SF12) to 5.37 kbps (for SF7). LoRa lowers the data rate to improve sensitivity.
LoRa Parameters
ToA (or Packet Duration): The time a transmitter takes to transmit a packet (i.e., all bits of a packet) in the air is called packet duration.
The more the number of bits in a symbol (or packet), the more is the packet duration. Hence, the larger the SF, the larger the transmit ToA (figure below for reference).
ToA Illustration (Source: Lumenci)
Link Budget: Sum of all the gains and losses from the transmitter, through the medium, to the receiver in a communication system.
Receiver Sensitivity: It is the lowest possible power level at which receiver can receive or demodulate the signal. LoRa offers receiver sensitivity ranging from -123 dBm to -137 dBm, depending on SFs. The higher the SF, higher the receiver sensitivity, since if the data is sent slowly, the signal is easier to receive and distinguish from noise (see figures below for reference).
Illustration of Receiver Sensitivity (Source: Lumenci)
Bandwidth: LoRa operates on different frequency plans and bandwidths (among 125 kHz, 250 kHz, and 500 kHz) based on the regions listed below.
LoRa bandwidth depending on different regions (Source: Lumenci)
CSS Modulation
CSS uses chirps (as carrier signal) to modulate the data.
Chirp stands for Compressed High-Intensity Radar Pulse.
Chirp is a signal in which frequency increases (up-chirp) or decreases (down-chirp) with time.
A chirp is often called a sweep signal.
In CSS, spreading is defined by the spreading factor (SF) parameter.
Up-chirp and Down-chirp (Source: Lumenci)
Spreading Factor (SF)
SF value defines the number of bits representing a symbol/chirp. For instance, SF7 defines 7 bits used to represent a symbol/chirp. Regarding signal frequency, SF defines how fast signal frequency changes across the bandwidth of a channel.
In LoRa, the value for SF typically ranges from 7 to 12.
For the lower SF, fewer bits represent a chirp (or symbol). Therefore, more chirps can be sent across the bandwidth of a channel (i.e., a greater number of chirps can be sent per second). Hence lower SF assures a comparatively higher data rate than the data rate assured by its higher SFs.
In terms of signal frequency, for the lower SF, signal frequency increases more rapidly. Such a signal can transfer more data across the bandwidth of a channel (i.e., more chirps can be sent per second). Hence lower SF assures a comparatively higher data rate than the data rate assured by its higher SFs (figures below for reference).
Comparison of lower and higher SFs: The comparison of lower and higher SFs w.r.t different parameters is provided in the table below.
LoRaWAN Architecture
ED: End devices that may transmit their packets to the gateway through the LoRa link.
Gateway: It receives the packets transmitted by EDs and forwards them to the network server through internet connections.
Network server: it is responsible for resource management (viz, spreading factor allocation), and handles the de-duplication of received packets.
Application server: It receives data from the network server, which is then interpreted and displayed
Market Outlook
Potential Applications of LoRa
LoRa technology can be used for various applications that are listed below.
Real-time Implementation Of LoRa Applications
Real-time implementation of LoRa applications (Source: Lumenci)
Real-time Implementation of LoRa applications includes modules, viz., sensors, microcontroller, LoRa transceiver module, LoRa gateway, network server, and application server.
Sensors sense the data from the surrounding environment or object. Different sensors are employed based on different applications.
Microcontroller, which is interfaced with the data pin of sensors, receives sensors data and gives it to the LoRa module (viz., RFM95W module).
LoRa module may transmit their packets to the gateway through the LoRa link.
Gateway then forwards the received packets to the network server through internet connections.
Network server is responsible for SF allocation and handles the de-duplication of received packets. The network server sends the data to the application server through internet connections.
Application server then interprets and displays the received data
Conclusion
LoRa is certainly a key technology that is growing and leading us to provide low-cost, low-power, and long-range solutions to smart devices and making it suitable for use in a wide variety of IoT applications, viz., smart home, smart city, industrial automation, smart meters, smart agriculture, healthcare, etc. This is possible through the support of the CSS modulation scheme, which ensures good receiver sensitivity at the cost of a lower data rate.
Reference
[1] https://josefmtd.com/2018/08/14/lora-modulation-basics-english/
[2] https://lora.readthedocs.io/en/latest/
[3] https://www.youtube.com/watch?v=jHWepP1ZWTk
[4] https://blog.ttulka.com/lora-spreading-factor-explained/
[5] https://sci-hub.se/http:/dx.doi.org/10.1109/TII.2020.3042833
[6] https://www.rfpage.com/applications-future-lora-wan-technology/
[7] https://en.iotvega.com/turnkey_solutions/home/security
[8] https://www.iotforall.com/lorawan-most-common-applications-and-use-cases
[9] https://www.industryarc.com/Report/19424/lora-and-lorawan-devices-market.html
Author
Editorial Team at Lumenci
Through Lumenci blogs and reports, we share important highlights from the latest technological advancements and provide an in-depth understanding of their Intellectual Property (IP). Our goal is to showcase the significance of IP in the ever-evolving world of technology.