NR UE: add support for multiple RF frontends
This MR adds basic support for multiple RF-frontends at the UE.
There are multiple reasons why we might want this:
1. There might be different antennas needed for different bands (e.g. NTN or
TN antennas). These antennas might be connected to different RF-frontends.
In case of Handover, the UE needs to dynamically switch between these
RF-frontends.
2. Each rf-simulator connection carries baseband I/Q samples. To be able to
perform a handover between two cells at different frequencies, there must
be two rf-simulator connections, as the baseband channels should not
interfere and thus cannot simply be added.
3. When we want to support multiple UE simulation within one instance of
nr-uesoftmodem, and allow multiple cells and probably even handover between
these cells, we need either:
1. dedicated RF-frontends for each simulated UE, or
2. dedicated RF-frontends for each connected cell and dynamically assign
simulated UEs accordingly.
This MR implements what is needed for 1., 2. and 3.1.
This feature shall allow in future to simulate an arbitratry number of UEs connected to an other arbitrary number of cells.
Therefore each RF-frontend (also called RU) needs to be configured for one specific cell.
In case of handover of a UE from one cell to another cell, it needs to switch RUs accordingly (TODO).
There has to be a 1-to-1 mapping between RUs and cells.
Each UE will be assigned to one of the defined cells.
Initially all UEs are assigned to cell 0.
Introduce SRS physical simulator and improvements
This MR consists of two parts:
- Introduces SRS physical simulator to test different configurations of
SRS
- Improvements in the SRS channel estimation (Addressing the comments
from old, unfinished MR !2875)
- rewrite nr_srs_channel_estimation() to loop over rx antennas and
antenna ports to be able to parallelize
- Improvements in timing_advance_offset and timing_advance_offset_nsec
computation
- Introduce SRS multi-symbol channel estimation
- The channel impulse response is estimated from the averaged
channel frequency response over multiple symbols
- The channel frequency estimates are left as they are to be able to
estimate doppler in the future
- Simplify SRS channel estimation to handle memory alignment in the
case of different SRS configurations (eg: comboffset)
To use multiple symbols when running gNB, the following parameters needs
to be edited in the function get_srs_resource()
- srs_res->resourceMapping.startPosition with a range from {0,1,..,5}
corresponds to the start symbol {13, 12, .. 8} with in a slot
- srs_res->resourceMapping.nrofSymbols indicates the number of symbols
{n1, n2, and n4}
Make sure the that start symbol + number of symbols is < 14
The timing results for SRS in develop and srs_phy_simulator are as follows:
Command used: sudo ./nr_ulsim -n1000 -s50 -S50 -R273 -W2 -y2 -z2 -E 1 -P
develop
|__ RX SRS time 124.94 us (1000 trials) (124.94 total [ms])
|__ Generate SRS sequence time 0.05 us (1000 trials) ( 0.05 total [ms])
|__ Get SRS signal time 19.41 us (1000 trials) ( 19.41 total [ms])
|__ SRS channel estimation time 89.11 us (1000 trials) ( 89.11 total [ms])
|__ SRS timing advance estimation time 13.10 us (1000 trials) ( 13.10 total [ms])
|__ SRS report TLV build time 2.80 us (1000 trials) ( 2.80 total [ms])
|__ SRS beam report build time 0.00 us ( 0 trials)
|__ SRS IQ matrix build time 2.73 us (1000 trials)
srs_phy_simulator
|__ RX SRS time 211.93 us (1000 trials) (211.93 total [ms])
|__ Generate SRS sequence time 0.04 us (1000 trials) ( 0.04 total [ms])
|__ Get SRS signal time 19.55 us (1000 trials) ( 19.55 total [ms])
|__ SRS channel estimation time 152.05 us (1000 trials) (152.05 total [ms])
|__ SRS timing advance estimation time 36.67 us (1000 trials) ( 36.67 total [ms])
|__ SRS report TLV build time 2.96 us (1000 trials) ( 2.96 total [ms])
|__ SRS beam report build time 0.00 us ( 0 trials)
|__ SRS IQ matrix build time 2.88 us (1000 trials)
Note that in srs_phy_simulator, to compute timing offset ns, an
oversampling factor of 2 is performed. Also, for peak detection, we
average the channel estimates for every port.
We need the ntn_config when reconfiguring the PHY layer for a new initial sync,
e.g. for calculating the DL Doppler frequency.
As a dedicated scheduled_response dl_config PDU it reaches the PHY layer too late,
as part of the phy_config.config_req it reaches the PHY layer in time with the
other configuration values.
Add symbol timing functions for NR_DL_FRAME_PARMS + optimization for slot timing
counterparts
Add two new functions for calculation symbol timestamp and symbol duration for
NR_DL_FRAME_PARMS. Also includes an optimization focused on removing
inefficiencies related slot-related counterparts.
1. Removed function pointers for functions get_samples_per_slot(),
get_samples_slot_timestamp() and get_slot_from_timestamp() as it does
not offer any advantage. The functions are now called directly from
everywhere.
2. Optimized these functions by removing loops where ever possible.
Add two new functions for calculation symbol timestamp and symbol
duration for NR_DL_FRAME_PARMS. These functions are not using
the existing indirection mechanism via function pointers as this
prevents the compiler from properly optimizing the code.
Hide normal table initialization of Ziggurat generator from outside to
force the usage of randominit() for RNG initialization. In this step,
remove the randominit() seed parameter and only rely on OAI_RNGSEED for
a consistent RNG initialization, as this parameter was used differently
("0" as fixed number or to force a random seed).
Now, only use OAI_RNGSEED env variable to force the usage of a fixed
seed.
Remove schedule response and update L1 threading documentation
This merge requests removes the somewhat superfluous "schedule response"
mechanism. "schedule response" was run after running the scheduler
itself and copied various FAPI messages into a global msgDataTx
structure from which the various TX/RX jobs were triggered. It is not
necessary, though, given that the scheduler is run inside the tx_func()
(running the TX jobs of the L1), and so the scheduler output FAPI
messages can directly be read into a variable of the existing
NR_Sched_Rsp_t type. This allows to delete a couple of hundred lines of
code (while retaining functionality), and simplifies the msgDataTx type
(which is still there to trigger TX job (including the scheduler) from
the ru thread).
In short, prior, there was this call chain:
- tx_func() calls run_scheduler_monolithic() (through fptr
NR_slot_indication())
- get some memory through allocate_sched_response() which has enough
space for NR_Sched_Rsp_t type variable
- call the scheduler and fill the variable
- call nr_schedule_response() (through fptr NR_schedule_response())
which copies into L1: to msgDataTx for TX, to separate structures
for RX
this is changed to
- tx_func() runs one message at a time, hence we can use memory in the
data segment for NR_Sched_Rsp_t. It calls run_scheduler_monolithic()
through the fptr
- pointers into NR_Sched_Rsp_t are passed to the scheduler, which
fills as before
- we return, memory is in its right place and does not need an extra
copy.
Additionally, this merge request updates documentation on threading and
cleans up some unused code along the way.
The next commit will remove msgDataTx. We can therefore not use
msgDataTx to retain the PDSCH/DLSCH variables, and move them to the gNB.
Note that the only reason for NR_gNB_DLSCH_t after this commit is to
hold various large buffers (c, b, f). Future work could be done to
remove this, in which case the array inside PHY_VARS_gNB could be
deleted.
On this occasion, clean up the use of init_DLSCH_struct() and
reset_DLSCH_struct() (renamed destroy_DLSCH_struct()) and centralize
their call in phy_init_nr_gNB()/phy_free_nr_gNB(), and correct
simulators accordingly.
NTN: Fixing variable ULDLduplex issue for NTN bands
- Duplex is assumed to be static but for NTN bands (and also for some non NTN
bands), it is not static.
- Tx-RX Duplex is defined in section 5.4.4 of 38.101-5 (for NTN) specs v1809
- For example: In NTN-OTA testing, the GEO satellite operator configured in
band 256 the DL, UL frequencies with duplex of 185Mhz.
saves about 600MB of memory allocation
Move the definition of PRACH items and the PRACH list to the
defs_nr_commons.h file.
Do not re-write the entire structure in nr_schedule_rx_prach(), as it is
quite large now.
francescomani