Don't you want to move this topic to the forum? I have a hard time
following it. I also think it is helpful for other user to find more
information about it.
https://forum.riot-os.org/
Am 2020-11-30 09:36, schrieb Robert Hartung:
Thanks Benjamin,
as far as I understand RPL MRHOF [0] uses ETX, which is the expected
transmission count, i.e. how many transmissions do you need to transmit
a packet as successful, which can be based on ACKs purely (if you have
unicast communication).
At least back in the Contiki days, the metric wasn't based on LQI at
all [1].
In addition to the LQI definition. There is no guarantee that the LQI
values span over the full range of 0 - 256 and not even evenly spaced.
We had big troubles when using LQI from different radios. A colleague
published the results partially in [2].
I didn't find mrhof for RPL [3] - you said that you found the LQI to
work best? Have you tried in heterogeneous networks with different
radio transceivers and how it behaves?
Best Regards
Robert
[0] https://tools.ietf.org/html/rfc6719
[1]
https://github.com/contiki-os/contiki/blob/master/core/net/rpl/rpl-mrhof.c
[2] https://ieeexplore.ieee.org/document/8510975
[3]
https://github.com/RIOT-OS/RIOT/tree/master/sys/net/gnrc/routing/rpl
Am 28.11.2020 um 14:50 schrieb Benjamin Valentin: On Mon, 23 Nov 2020
11:56:13 +0100
Robert Hartung <hart...@ibr.cs.tu-bs.de> wrote:
just my two cents regarding LQI:
The LQI is very different for different radios. So be aware of that
in heterogeneous networks with different radios! True, the standard
(IEEE 805.15.4-2020) only states
The LQI measurement shall be performed for each received packet. The
minimum and maximum LQI values (0x00 and 0xff) should be associated
with the lowest and highest quality compliant signals detectable by
the receiver, and LQI values in between should be uniformly
distributed between these two limits. At least eight unique values of
LQI shall be used. However, RPL (MR-HOF) uses hysteresis and by default
requires an
improvement of 192 on the whole path before it switches.
So as long as LQI can give a rough estimate of link quality, it should
be good enough. This is not about estimating distance where some sort
of accuracy was required, but just to throw out really bad links.
Best,
Benjamin
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