nr_fill_indication() fills CRC and RX requests, to be sent from L1 to
L2. Before this commit, nr_fill_indication() is called when
- we finally decoded LDPC (or not)
- low signal on PUSCH
This might happen at the same time, i.e., nr_fill_indication() might try
to fill both CRC and RX, in the same list, from different threads. This
can lead to this assertion:
Assertion (crc->rnti == rx->rnti) failed!
In handle_nr_ulsch() ../../../openair2/NR_PHY_INTERFACE/NR_IF_Module.c:190
mis-match between CRC RNTI e071 and RX RNTI 5e3b
e.g., e071 is low energy, and while 5e3b related message are filled in
one thread, e071 is being put into the message structure as well.
At least that is my understanding. I could not actually reproduce this
assertion; to be seen if it still happens.
This commit introduces a separate thread (l1_tx_thread) that processes
gNB DL/TX slots. It receives a message from the ru_thread when a new
slot started, and starts processing.
The DL part of the scheduler is run in the l1_tx_thread. Therefore,
only call UL indication (for scheduler) in UL slots. The UL indication
previously triggered the DL scheduler -- hence, it had to be called in
every slot. Now, since the DL scheduler is moved into the DL thread, we
don't have to call the scheduler in every slot anymore.
The reorder thread is removed, as reordering with this scheme is not
necessary anymore.
The main advantage of this version is that the TX can be scheduled
earlier (sl_ahead). Further, there can no longer be race conditions in
the TX path, since the scheduler/L2, TX L1 processing and the RU tx
function are all execute in the same thread (L1_tX_thread).
Also, the scheduler prepares PRACH/PUSCH/PUCCH FAPI PDUs. As of this
commit, the scheduler runs in the TX processing chain, whereas these
PDUs are destined for RX processing. Thus, too avoid data races,
instead of triggering the RX processing at the same time as TX
processing in the RU thread, this commit changes the code to trigger RX
processing after the scheduler has been run in TX processing to avoid
data races.
Finally, we synchronize RU and L1 threads. This is important for
rfsimulator, since unlike most radios, rfsimulator can run slower or
faster, depending on I/O and CPU (it does not have a stable "tick").
Co-authored-by: kiran <saikiran@iitj.ac.in>
The next commit introduces a separate gNB TX processing thread. To
properly separate DL scheduler (for scheduling decisions) from UL
indication handling (for UL packets), this commit introduces a slot
indication "tick" to run the DL scheduler which will be put into the gNB
TX processing chain instead of the UL indication.
This commit fixes a bug caused by global variables in the gNB_MAC_INST
structure used to transfer MAC scheduler's results to the PHY layer.
When using several threads in the PHY layer, it may happen that the
MAC scheduler is called a second time by the second PHY thread for the
next slot before the content of the global variables in the gNB_MAC_INST
structure used to store the result of the MAC scheduler for the current
slot have been consumed by the first thread, leading to unpredictable
results (all of them certainly wrong).
The solution is to introduce a small memory management module for the
interface between the PHY threads and the MAC scheduler. The MAC
scheduler now fills the data structures passed to it, and not a
global variable anymore. The PHY layer manages the structures and
ensures that no data is overwritten before being fully consumed by
the various threads of the PHY layer.
Some care has to be taken because several PHY threads will access the
same structures at the same time for a given slot (in read mode, so
it's okay). A mechanism of reference counting has thus been introduced.
Only one CC is supported. This restriction should not be too hard
to remove if/when needed. (The code before this commit does not seem
to work for more than one CC anyway.)
After this commit, only the RNTI is used as an identifier in the MAC.
Further, it removes some module_id, but a lot of them remain (the goal
to remove all is still far from us)
This struct is used to store the uplink 5G nFAPI
messages between the proxy and the gNB MAC layer.
The original OAI implementation utilizes a similarly
named variable (UL_info) to store the uplink 5G nFAPI
messages between the PHY and MAC layer. This commit
will utilize the original UL_info variable prior to
calling the handle functions. These changes allow us
to make minimal changes to the nFAPI handle functions
and modifies the NR_UL_Indication parent function instead.
francescomani