EU868 TxPower

[mikev]

This comment is a bit confusing to me when read with the one above.
Most of the RSSI's in the tests are changing to 30.
These two are the outliers, and I don't understand from the comments why they're both changing to 20 under opposite circumstances.

Above comment from L315
%% RSSI act as power here we are and based on UPLINK RSSI > -80 we should power downlink at 20

vs. this comment L457
%% RSSI act as power here we are and based on UPLINK RSSI < -80 we should power downlink at 20

Originally posted by @michaeldjeffrey in #710 (comment)

We need to revisit the EU868 maximum tx_power setting in the LoRaWAN library. Historically it has been set to 20, but the maximum allowed is actually 16. Also double-check other Region maximums in the new Regional spec.

Related Issues:
https://www.etsi.org/deliver/etsi_en/300200_300299/30022002/03.02.01_60/en_30022002v030201p.pdf
#304
#355

We noticed while reviewing that this unit test sets packet Region to EU868, but Gateway processing packet is US915 causing confusion.

[mikev]

Fixed in LoRaWAN library
helium/erlang-lorawan@fa7b6fb

[disk91]

A bit surprised to see we use eirp. Btw ok. But the regulation depends on the rx windows

• regulation is 14dBM for RX 1
• Regulation is 27dBm for RX 2

What about the rx2 ? Going always 14dBm will make a regression on the ability to join.

https://www.disk91.com/2017/technology/sigfox/all-what-you-need-to-know-about-regulation-on-rf-868mhz-for-lpwan/

[mikev]

@disk91 - Can you find the exact spec which advises 14dBm for RX 1 and 27dBm for RX 2? The only value in the spec I can find is a max value of 16dBm.

We've used the value 20dBm for quite a while for both EU868 RX1 and RX2

[macpie]

@disk91 We have reviewed the evidence and you are right.

Nevertheless, the regional spec makes no mention of this so we had to dig into the actual EU standard that you provided to see that RX2 is allowed to broadcast at 27dBM.

As we re-wrote the regional code to improve it, we got confused because of some previously file tickets that seemed to tell us otherwise.

• Joining issue on the network - Use of RX2 Windows intead of RX1 for EU868 #363
• Joining issue on the network - use 27dBm on RX2 windows in EU868 #364
• Joining issue on network - Hotspot selection for Join Accept transmission #365

So we really want to make sure that: RX1 = 14dBM and RX2 = 27dBM.

Please confirm that this is the intended behavior and will will fix it.

[disk91]

Check the regulation spec : http://www.arcep.fr/fileadmin/reprise/dossiers/frequences/ERC-REC-70-03E-version02.PDF
Annex 1, Page 6 You will find the band G3 corresponding to the 869.4 to 869.65 where the RX2 windows is. This band is 10% duty cycle and 500mW e.r.p. eq 27dBm

In the LoRaWan Regional settings (RP002-1*.0.3-Final-1.pdf) you can see :
The RX2 receive window uses a fixed frequency and data rate. The default parameters are
869.525 MHz / DR0 (SF12, 125 kHz)

This frequency is inside the band G3

--

To confirm my previous tickets, I propose to:

1. prefer Join Accept and Downlink / Ack on RX2 with 27dBm (869Mhz) when RSSI > -85dBm
2. prefer Join Accept and Downlink/ Ack on RX1 with 14dBm (868Mhz) (=16dBm EIRP) when RSSI < -85dBm

the second option is for when the device is really close to reduce the risk of saturating the device receiver.

[mikev]

Fix to LoRaWAN library
https://github.com/helium/erlang-lorawan/pull/14/files

[mikev]

Fix to Router
#793