[MVMA] LoRa: Wikipedia

[Tyler Gardner]

From what I understand, LoRa can indeed be thought of as being similar to APRS in many respects.

With my club in Utah, I heard of LoRa being used for high-altitude balloons as an alternative to/in addition to APRS. I also spoke with some club members who were exploring its use for other beacon-type use cases. I believe IoT is the real intended target of LoRa so that devices can report their status.

I haven’t heard of any live, two-way communication, mesh-type use with LoRa.

> On Apr 29, 2021, at 12:06 PM, Chuck Gelm <nc8q-mesh at gelm.net> wrote:
> 
>  Reference:
> https://en.wikipedia.org/wiki/LoRa#LoRaWAN
> -----
> 
> 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 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 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]
> -----
> 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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