Files
openairinterface5g/openair1
Robert Schmidt 93b3a5aedb Merge remote-tracking branch 'origin/srs_phy_simulator' into integration_2026_w03 (!3718)
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.
2026-01-13 13:39:32 +01:00
..

This folder contains the software for layer 1 of the OpenAirInterface eNB and UE as well as the unitary simulators

|-- PHY			   // contains all signal processing related to physical layer (used in real-time AND simulation)

General remarks: every directory contains at least defs.h (for declaration of structure and functions), vars.h (for definitions of variables), and extern.h (variables are defined only once in xxx-softmodem.c (for real-time HW operation) or a top-level simulation (in SIMULATION/xxx), if variables are needed in another file, use extern.h)

|   |-- CODING		   // turbo and convolutional (de-)coders, rate-matching, crc generation (implementation of 36-212)
|   |   `-- TESTBENCH      // This contains unitary testbenches for the different channel coders/decoders
|   |-- INIT		   // variables defined in vars.h are initialzed here (memory allocation)
|   |-- LTE_ESTIMATION     // estimation for LTE
|   |-- LTE_REFSIG 	   // reference signals for LTE (sync and pilot sequences) reference signals from 36-211 
|   |-- NR_REFSIG 	   // reference signals for NR (sync and pilot sequences) reference signals from 38-211
|   |-- LTE_TRANSPORT      // these are the top level routines for different transport and physical channels (for example DL-SCH, PSS) implements a subset of 36-211,36-212
|   |-- LTE_UE_TRANSPORT      // these are the top level routines for different transport and physical channels (for example DL-SCH, PSS) implements a subset of 36-211,36-212
|   |-- NR_TRANSPORT      // these are the top level routines for different transport and physical channels (for example DL-SCH, PSS) implements a subset of 38-211,38-212
|   |-- NR_UE_TRANSPORT      // these are the top level routines for different transport and physical channels (for example DL-SCH, PSS) implements a subset of 38-211,38-212
|   |-- NBIoT_TRANSPORT      // these are the top level routines for different transport and physical channels for NB-IoT
|   |-- MODULATION	   // modulation and demodulation includes FFT/SC-FDMA front-end processing from 36-211
|   |-- TOOLS		   // tools like (I)FFT, vector operations, matrix multiplication, etc.
|   |   `-- FFTTEST        // unitary testbench for FFT routines
|   |-- defs.h		  // top level defs.h (includes spec_defs, impl_defs and all defs.h of subdirectories)
|   |-- extern.h
|   |-- impl_defs.h       // non-LTE openair implementation
|   |-- impl_defs_top.h   // general implementaion defs
|   |-- spec_defs.h
|   |-- spec_defs_top.h
|   |-- types.h
|   `-- vars.h		  
|-- SCHED		  // schedules the different LTE eNB functions
|   |-- defs.h
|   |-- extern.h
|   |-- phy_procedures_lte_eNb.c // LTE PHY procedures for eNB (from 36-213) 
|   |-- phy_procedures_lte_common.c  // LTE PHY procedures common for UE and eNB (from 36-213)
|   |-- prach_procedures.c  //LTE PRACH  procedures (from 36-213)
|   |-- ru_procedures.c  //RU  procedures
|   |-- fapi_l1.c  //L1 side of the FAPI interface
|   |-- phy_mac_stub.c  //MAC stub that generates channels when used in phy-test-mode
|   |-- rt_compat.h
|   `-- vars.h
|-- SCHED_UE		  // schedules the different LTE UE functions
|   |-- phy_procedures_lte_ue.c  // LTE PHY procedures for UE (from 36-213)
|   |-- pucch_pc.c // power control for PUCCH
|   |-- pusch_pc.c // power control for PUSCH
|   |-- srs_pc.c // power control for SRS
|-- SCHED_NB_IOT		  // same as above for NB-IOT
|-- SCHED_NR		  // same as above for NR gNB
|-- SCHED_NR_UE		  // same as above for NR UE
|-- SIMULATION		 // contains simulation routines to test PHY
|   |-- LTE_PHY          // LTE simulation testbenches for unitary simulation of transport/physical channels
|   |   |-- pbchsim.c       // PBCH simulation testbench
|   |   |-- pdcchsim.c      // PCFICH/PHICH/PDCCH (DCI) simulation testbench
|   |   |-- dlsim.c         // PDSCH simulation testbench
|   |   |-- ulsim.c         // PUSCH simulation testbench
|   |   |-- pucchsim.c      // PUCCH simulation testbench
|   |-- RF  		    // RF simulation tools
|   |-- ETH_TRANSPORT
|   `-- TOOLS