The code was very unclear and potentially buggy.
This new version is more robust.
We can waste up to 2 bytes because the last header in the MAC PDU
does not contain a length field and when we request data from RLC
we suppose a 3-bytes MAC header. This might be optimized at some
point, but the benefit would be low.
This commit also contains some general cleanup:
- formatting
- variables' types: let's use 'int' instead of trying to be clever
by using small types that may generate bugs if the value is
too big
- remove 'tpc_accumulated' which was globally used for all UEs
and has no purpose other than logging. We may want to rework
a bit the TPC machinery at some point. As the code is today
we may repeatedly send TPC over and over without caring about
the 3GPP limits, in which case no one knows how the UE is
supposed to behave: does it clamp the current max value or does
it accumulate over and over and take the clamped value to compute
its actual power? If we send a reverse TPC (reduce power instead
of increase) does it do it immediately or does it have to decrease
n+1 times if we previously ordered it to increase n times?)
We do not address the problem of prioritizing LCIDs. As of today there
is only one dedicated traffic channel (DTCH), so it's not a problem
at this point.
What has been tested:
- monolithic eNB 5/10/20MHz with one cots UE, TCP/UDP UL/DL. At 20MHz the
machine used was not capable of keeping up, generating lots of Us
and Ls when the throughput reaches 60Mb/s. USRP B210 was used.
eNB should be keep UE context longer than T311 timer after UL failure is detected in layer2.
Configuration file(GENERIC-LTE-EPC) sets T311 to 10s, so eNB keep UE context up to 20s.
Some more fixes for some bad conflict resolutions.
I ran:
git diff 2018.w04 2018.w05
And saw some problems with config_sib2.
There was also something strange in openair2/LAYER2/openair2_proc.c
in the function dump_eNB_l2_stats. Maybe the fix is wrong for
this one. To be checked.
Doing an iperf UDP uplink test, we could reach only 6Mb/s
with very good radio conditions instead of around 8Mb/s.
It turns out the MCS was limited to 16.
With this commit, we are back to a bit more than 8Mb/s
as it used to be.
(This is with a 5MHz bandwidth.)
Cedric Roux