I was thinking at the same corner.
Do we need polarization diversity?
The short answer is no. No one is using it!
What longer answer is – LoRa chirp modulation mitigates this issue.
IMHO – does not solve it only mitigate it.
I was thinking to connect two Lora antennas at 90 degree with two receivers and just move around with one Lora transmitting node – I’m pretty sure that somebody else did such test, Isn’t it?
Do we have such data?
Diversity is benificial in the direction of the receiver and can help a lot in (dense) urban area’s.
By default will the use of two antennas add a gain of 3 dB as aperture gain.
The multipath reflections will add another 7 to 9 dB to the link budget.
So yes diversity will help.
There is one condition that shall be met: The receiver shall be equipped with multiple receivers so each antenna has its own receiver. Than the recived signal shall be conbined using maximum ratio combining.
Until now I have not seen a LoRaWAN receiver capeable of doing this.
Conclusion:
Will diversity help? yes!
Is it availabale? No.
Sectorising ( 3 gateways with a directional antenna) and using high gain antennas is much more benificial.
Sorry for my wrong explanation.
I was aware that full diversity reception/as known in GSM BS/ is not feasible at this moment.
I’ve ment the following setup
Two Rx antennas at the same direction 90 degree polarized.
Two feeding cables
Two receiever connected to antennas – receivers collect packets and RSSI
One mobile transmit node with GPS on it – Hardware is ready/Arduino Atmega 328 SX1278/spi module + GPS+ two yagi antennas/. I’m busy with software and second yagi
At the end I compare and combine the two message streams.
Does it make sense? If yes I can make this measurement and share it.
Any proposals, remarks and concerns are welcome.
To be polarization independent I plan on using a Skew Planar or cloverleaf antenna on my single channel gateway.
I’ve build a Skew Planar antenna, but it wasn’t quite resonant on 868. By touching the antenna on one “leaf” I found out the reflection attenuation (VSWR) improved a lot. So the next experiment is to build a cloverleaf antenna.
As a ham radio operator I have been working lately on a TTN integration to APRS. This is the Automatic Positioning Reporting System that is used amongst radio amateurs to display the GPS data of their mobile rigs or handhelds on e.g. aprs.fi or aprsdirect.com
I have succeeded in creating two RestAPI endpoints so that my GlobalSat tracker is now displaying my position when the lora signal is received by wether a TTN gateway or WirelessThings gateway. If you do a search for ON3ZOE on those websites then : ON3ZOE-1 means received by TTN and ON3ZOE-9 means received by WT
Nice piece of work where loraWAN meets APRS.
73s de on3zoe
Thanks for taking a look and the comments, good to know.
This library is a little old now. I suppose there will be a few libraries to update regarding this.
Im going to start with coffee then;)
The interoperability bit (with SX126X devices) is in itself easy to check.
I did use my link test software, which works on a combination of SX127X or SX126X devices, to carry out checks on certain combinations of sync word and did indeed see receiver sensitivity differences.
OK; well with a SX127x syncword of 0x3F and a SX126X syncword of 0x34F4 the comms works at least, though based on the details Semtech have been prepared to reveal so far, it maybe should not.
Have you carried out a receiver sensitivity check, say comparing just the SX127X comms with a syncword of 0x34 versus 0x3F ?
I have the software tools (for SX126X and SX127X devices) that would allow for me to check the changes in receive sensitivity against particular syncwords and interoperability of course.
I have been involved in Amateur radio projects in the past.