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.
fix array lenght errors, k variable wrapping threshold. Make the code smaller and more efficient
generate_nr_prach() has several errors coming from replace int16_t by
c16_t, and also older error in k wrapping at the end of the symbol
the code is also ridiculously complex, wasting memory and cpu time in
intermediate useless buffers and headache usage of memmove()
Update physim timing thresholds in gNB-N300-Timing-Phytest-LDPC
The lower bound for the tests are too tight and any slight improvement
in the timing can result in a test failure. For example, these tests
were failing due to the improvements from the MR !3718
The lower bound for the tests are too tight and any slight improvement in the timing can result in a test failure.
For example, these tests were failing due to the improvements from the MR 3718
- We use the same function at gNB and UE.
- We always use nb_antennas_tx to check the max possible number of ports (which is wrong).
- At gNB, we should use nb_antennas_rx and at the UE, we should use nb_antennas_tx.
The memory alignment is required to use c16multaddVectRealComplex
in SRS channel interpolation. With a change in SRS comb_offset, the
existing algorithm was giving segmentation fault.
The existing srs channel estimation required memory alignment at two
stages. 1. When k = 0 (the first srs subcarrier), 2. When subcarrier <
K_TC (wrapped around after ofdm_symbol_size). Thus two memory alignments
are required leading to complications.
The srs channel estimation is now simplified to do it linearly instead of
wrapping around. This simplified the memory alignment required only when
k = 0.
- Introduce signal energy and noise variance functions
- Combine rotation and OFDM modulation RX as a function
- Harmonize the use of number of antennas across the code
- Rename nr_ue_pusch_common_procedures() to nr_tx_rotation_and_ofdm_mod() to decribe the functionality better
RHEL uses a dedicated cblas include directory. Correctly include this
for the one target PHY_UE that relies on this.
Co-authored-by: Robert Schmidt <robert.schmidt@openairinterface.org>
Rfsimulator beam reception/transmission
A simplified beam switching simulation for rfsimulator. This works
mainly in 1 gNB - N UEs scenarios. This is not a real beamformer with
antenna, channel and propagation model. The way it works is that the
peers inform each other about the beams they transmit in, and on
reception before channel modelling, the beam data is combined based on
preconfigured rx_beam/tx_beam gain matrix.
Usage:
- Add --rfsimulator.enable_beams to enable beam simulation
- Add --rfsimulator.beam_gains .
Example list: 0,-5,-10
Resulting matrix:
[[0, -5, -10] [-5, 0, -5]] [-10, -5, 0]]
- Add --telnetsrv if you want to control the beams manually. The command
in telnet is "rfsimu setbeam <beam_map>", where beam_map is a uint64_t
controling the reception beam and transmission beam. If the
application is switching the beams automatically the beams will be
overwritten as soon as the application chooses to switch beams.
Supports up to 64 concurrent TX and RX beams.
CORESET start multiple of 6 fix
According to the standard any CORESET (except CSET0) would always start
from the first common resource block index which is multiple of 6 in the
BWP. This was not taken into account in the code. The BWP switch CI test
is modified to test a BWP start not multiple of 6.
An exception is the case where rb-Offset-r16 parameter is set, but can't
be used at gNB for FAPI compatibility.
Closes: #1037
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.
Robert Schmidt