[MVMA] LoRa: Wikipedia

[Chuck Gelm]

Reference:
https://en.wikipedia.org/wiki/LoRa#LoRaWAN
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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]


Features

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 PHY

LoRa uses a *proprietary* spread spectrum modulationthat 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 M = 
2 S F {\displaystyle M=2^{SF}} {\displaystyle M=2^{SF}} possible 
waveforms at the output of the modulator are chirp modulated signals 
over the frequency interval ( f 0 − B / 2 , f 0 + B / 2 {\displaystyle 
f_{0}-B/2,f_{0}+B/2} {\displaystyle f_{0}-B/2,f_{0}+B/2}) with M 
different initial frequencies: the instantaneous frequency is linearly 
increased, and then wrapped to f 0 − B / 2 {\displaystyle f_{0}-B/2} 
{\displaystyle f_{0}-B/2} when it reaches the maximum frequency f 0 + B 
/ 2 {\displaystyle f_{0}+B/2} {\displaystyle f_{0}+B/2}. [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]
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Maximum data rate almost as fast as a 28.8 kbps telephone modem.

It seems that 'long range' means 'Physical range 10km+ in perfect 
conditions.'
Typical range may be up to 2 km.

'LoRa' seems especially suitable for monitoring environment conditions; 
temperature, humidity, fluid level, pressure,...

Is LoRa for one way transmissions?

Is 'chirp spread spectrum (CSS) technology' akin to APRS, one way 
transmissions containing data ?

I did not find any off-the-shelf devices suitable for 2-way networking.

Chuck

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