fix(nrLDPC_decoder): fix numIter increment
The logs of ./nr_ulsim -n100 -m19 -s12 -S12 -z2 -L4 were showing that sometimes
the decoding of one segment was failing while the CRC check succeeded. This was
happening because the iteration counter numIter was not properly managed so that
when the last iteration was successful to decode the segment still numIter at
the exit was equal to numMaxIter plus 1 so that decoding was considered to have
failed. In other words the last iteration if it occured was always wasted.
This commit offers to solve this problem by simply moving the iteration counter
increment at the end of the iteration loop while remaining careful at fixing the
tests relying on this counter.
Post-Scriptum:
After a first review, we decided to make the counter more standard from a C code
perspective. The counter now counts from 0 to numMaxIter minus 1. If it reaches
numMaxIter, it means that decoding was unsuccessful.
The idea is to make LDPC iteration accounting more standard from a C coding perspective by making two changes:
1. Now the iteration counter starts at 0 for the first iteration and goes up to max_ldpc_iterations - 1 for the last iteration.
If it is equal to max_ldpc_iterations, it means that decoding failed.
2. A chain of useless returns in the UE DLSCH decoding call chain was removed.
The logs of `./nr_ulsim -n100 -m19 -s12 -S12 -z2 -L4` were showing that sometimes the decoding of one segment was failing while the CRC check succeeded.
This was happening because the iteration counter `numIter` was not properly managed so that when the last iteration was successful to decode the segment
still `numIter` at the exit was equal to `numMaxIter` plus 1 so that decoding was considered to have failed.
In other words the last iteration if it occured was always wasted.
This commit offers to solve this problem by simply moving the iteration counter increment at the end of the iteration loop
while remaining careful at fixing the tests relying on this counter.
Use memcpy in nr_prach.c to fill txdata buffer.
Remove global tables related to PRACH generation.
Add new function to compute modulo multiplicative inverse and use it
directly to get inverse instead of LUT.
Removed nr_ru table and compute the values in-place.
In UE, added new flag root_seq_computed in nrUE_config to only compute
the sequence once after new nrUE_config is received.
Long PRACH extends beyond a slot. Changes necessary to mark future slots
that may contain prach in ru, phy and mac functions.
In RU, the PRACH IDFT is done only after receiving last slot and marks
for L1 to start processing. The L1 processes at the last prach slot and
reports to MAC with the first slot index.
In MAC scheduler, the VRB for future slots are also marked as used.
PRACH scheduler is called in advance one frame minus num prach slots.
fix(nrLDPC_coding): timers in DL encoding, fix(ldpctest): Confusion in sizes
Main improvements:
1. fix(ldpctest): Confusion in sizes
IMPORTANT: This fix makes that ldpctest now works with BG2 and K' != K!
(Worth double checking with more cases than I did check with though)
The variable block_length had an ambiguous role and was used as both K and
Kprime. This was leading to arrays with wrong sizes and functions with wrong
arguments. Now there is not anymore block_length but K and Kprime.
Kprime can be set with the command line argument -l.
There was also some problems with array allocation for segments with length
not divisible by 8. A proper sizing with ((size_in_bits + 7) & ~7) / 8 was
used.
A proper masking of the last byte containing payload bits was also added to
keep filler bits to 0 after random initialization.
2. fix(nrLDPC_coding): timers in DL encoding
While timers were available for rate matching and interleaving in the new
interface, these timers were not merged to rate matching and interleaving
timers in nr_dlsch_coding.
The aggregation level search order for PDCCH candidates is modified:
- the search starts from desired_agg_level_index, which is a value from 0 to 4
proportial to pdcch_cl_adjust.
- pdcch_cl_adjust is a value between 0 and 1 that indicates PDCCH channel quality
by averaging HARQ DTX rate. A value of 0 means perfect channel, a value o 1 means
impaired channel.
The variable block_length had an ambiguous role and was used as both K and Kprime.
This was leading to arrays with wrong sizes and functions with wrong arguments.
Now there is not anymore block_length but K and Kprime.
Kprime can be set with the command line argument `-l`.
There was also some problems with array allocation for segments with length not divisible by 8.
A proper sizing with `((size_in_bits + 7) & ~7) / 8` was used.
A proper masking of the last byte containing payload bits was also added to keep filler bits to 0 after random initialization.
The name ldpc8blocks_coding_segment was previously used to avoid any confusion with ldpc8blocks while both were coexisting.
They are not anymore coexisting so it can now be shortened.
While timers were available for rate matching and interleaving in the new interface,
these timers were not merged to rate matching and interleaving timers in nr_dlsch_coding.
Ensure execution of processSlotTX in order in NR UE
Make sure that processSlotTX is executed in slot order.
There is a bug that causes decoding error when processSlotTX is executed
out of order. The root cause is not known at this point, but this change
avoids the bug altogether.
francescomani