LoRa Crash Course by Thomas Telkamp


#1

Hello Everyone

We are proud to announce that Thomas Telkamp (@telkamp), our network architect with over 20 years of experience in large-scale networking, is giving a webinar on November 10. Thomas will provide you with the essential technical information so you can make best use of the product you are about to receive.

Here is the link to the YouTube live event - https://www.youtube.com/watch?v=T3dGLqZrjIQ

To add this event to you calendar, click here

Thanks.


How Spreading Factor influence Time on Air?
Blog on LoRa Encoding Decoding Explanation
Range Calculation (Atmel Application Note)
How Spreading Factor influence Time on Air?
Using a Gateway to catch a downlink, or some other way to determine the link quality?
(Laurens Slats) #2

The LoRa webinar is starting soon, via this link you can find it.

This topic will be used for the QnA session, if the webinar raises any question you can post there here.


#3

IT'S started ... welcome - https://www.youtube.com/watch?v=T3dGLqZrjIQ


(Richard V) #4

Question: The Baracuda Taoglass has a gain of 8dBi; so this antenna is illegal in Europe? as it's higher then 2.15dBi?


#5

same question for this thing: http://webshop.ideetron.nl/Files/3/1000/1211/Attachments/Product/Z170Sc4b903U9HN22I7i5849b2971z6T.pdf


(Richard V) #6

My guess would be, you can substract the loss in the coax cable to the antenna; but then it still would be like 5/6dBi gain left.


#7

Is there a way to use repeaters?


#8

great presentation, thank you thomas!


#9

No there are not illegal.
so long you keep within the regulation limits it is no problem.
it can be used is you use long feeder/coax lengths.

eg : if you feeder/coax loss is about 6dB it is fine ..

Ecoflex15 coax is about 9dB/100Meter @868Mhz.

/joost


(Laurens Slats) #10

The recording of the webinar can be found here.

The slide can be downloaded here. Feel free to use the slides of Thomas wherever needed.


#11

I'd far rather see a high gain antenna then reduce the transmit power so the radiated power is within the limits. That way you get the benefit of better receive signal levels. Is it possible to modify the gateway transmit power with TTN?


(Thomas Telkamp) #12

The latest version of packet forwarder (3.0.0+) has an option to specify "antenna_gain" in the global_conf.json. If you fill in the gain of your antenna here (minus 2.15 dBi for EU, minus 6 dBi for US), the tx power will be limited accordingly.

Be aware though that you might create situations where downlink does not work, and for example devices can't join the network.


#13

why would this asymetric situation really hurt? If I understand the antenna theory right using an antenna with a higher gain does not have real drawbacks. That is when you stay within reasonable limits. So why not just consider the additional range as a kind of gift useful for devices that only transmit?


(Thomas Telkamp) #14

Yes, that's certainly true. But the backend should know about the extra gain, such that it can take that into account when making a downlink decision if there are more gateways. This is currently not possible, but we should put it on the feature list. I'll create an issue for this.


(Andrew Maggio) #15

Thanks @Thomas, great explanation!


#16

I am studying the video, and I am confused about the definition of Spreading Factor.

Here (https://www.youtube.com/watch?v=T3dGLqZrjIQ&feature=youtu.be&t=2122) @Thomas says that SF "indicate how fast the chirps is", and provides this image:

But here (https://www.youtube.com/watch?v=-YNMRZC6v1s) the speed of signal is the Chirp Rate, and SF is the number of bits encoded per symbol.

What I am missing?


(Thomas Telkamp) #17

Nothing! It is both.

The symbol rate (number of chirps per second) is BW/(2^SF). Per symbol you then encode SF bits. Therefor the bitrate is SF*BW/(2^SF).


(menno faber) #18

@laurens

Hello Laurens,

I tried to download the slides of Thomas his webinar form the LoRa Crash course. But the slides don't match the youtube video. Is it possible to add the correct slides?

Thanks


(Laurens Slats) #19

@fab_2solve I'm afraid the slides are no longer available. The slides in my earlier post correspond for the largest part with the video. Hopefully this works for you as well.