Files
openairinterface5g/openair1
Robert Schmidt ec3642ea05 Merge remote-tracking branch 'origin/srs-delay-comp' into integration_2026_w12 (!3859)
Delay compensation in SRS

Implementation of delay compensation in channel estimation based on SRS.

Testing, for example, with

    sudo ./nr_ulsim -n1 -s50 -S50 -R51 -E 1 -W2 -y2 -z2 -d 10

we obtain the following logs.

LOGs with develop branch:

    [NR_PHY] 	  __lsRe__________lsIm__|____intRe_______intIm__|____noiRe_______noiIm__
    [NR_PHY] (   0)    687	  -198  |     688	  -198  |      -1	    -3
    [NR_PHY] (   1)      0	     0  |     688	  -196  |      -1	    -3
    [NR_PHY] (   2)    687	  -198  |     644	  -272  |      -1	    -1
    [NR_PHY] (   3)      0	     0  |     600	  -346  |      -1	    -1
    [NR_PHY] (   4)    513	  -498  |     556	  -422  |      -1	    -1
    [NR_PHY] (   5)      0	     0  |     512	  -496  |      -1	    -1
    [NR_PHY] (   6)    513	  -498  |     440	  -542  |      -1	     0
    [NR_PHY] (   7)      0	     0  |     370	  -588  |      -1	     0
    [NR_PHY] (   8)    226	  -682  |     298	  -634  |      -1	    -3
    [NR_PHY] (   9)      0	     0  |     228	  -680  |      -1	    -3
    [NR_PHY] (  10)    226	  -682  |     140	  -686  |      -1	    -1
    [NR_PHY] (  11)      0	     0  |      52	  -690  |      -1	    -1

intRe and intIm are the real and imaginary part of the interpolated
channel, respectively. These are the columns that matter. As we can see,
for example, in subcarrier 0 we have (688, -198), then in subcarrier 1
we have (688, -196), which is almost the same, and then in subcarrier 3
we have a jump (644, -272). This MR improves channel estimation by
taking delay into account. If we look at the following logs, we see that
the values vary more consistently from subcarrier to subcarrier.

LOGs with this MR:

    [NR_PHY] 	  __lsRe__________lsIm__|____intRe_______intIm__|____noiRe_______noiIm__
    [NR_PHY] (   0)    487	  -139  |     490	  -111  |      -1	     0
    [NR_PHY] (   1)    487	  -139  |     483	  -138  |      -1	     0
    [NR_PHY] (   2)    487	  -139  |     465	  -197  |       0	     0
    [NR_PHY] (   3)    487	  -139  |     436	  -254  |       0	     0
    [NR_PHY] (   4)    364	  -353  |     402	  -305  |      -1	    -1
    [NR_PHY] (   5)    364	  -353  |     361	  -352  |      -1	    -1
    [NR_PHY] (   6)    364	  -353  |     317	  -392  |      -1	    -1
    [NR_PHY] (   7)    364	  -353  |     269	  -426  |      -1	    -1
    [NR_PHY] (   8)    160	  -481  |     214	  -455  |       0	    -1
    [NR_PHY] (   9)    160	  -481  |     159	  -478  |       0	    -1
    [NR_PHY] (  10)    160	  -481  |      98	  -495  |      -1	     0
    [NR_PHY] (  11)    160	  -481  |      39	  -502  |      -1	     0
2026-03-19 17:41:59 +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