openairinterface5g/openair1/PHY/CODING/DOC/LDPCImplementation.md

#LDPC coder/decoder implementation The LDPC coder and decoder are implemented in a shared library, dynamically loaded at run-time using the oai shared library loader. The code loading the LDPC library is in nrLDPC_load.c, in function load_nrLDPClib, which must be called at init time.

Selecting the LDPC library at run time

By default the function int load_nrLDPClib(void) looks for libldpc.so, this default behavior can be changed using the oai loader configuration options in the configuration file or from the command line as shown below:

loading libldpc_optim8seg.so instead of libldpc.so

./nr-softmodem -O libconfig:gnb.band78.tm1.106PRB.usrpx300.conf:dbgl5  --loader.ldpc.shlibversion _optim8seg
.......................
[CONFIG] loader.ldpc.shlibversion set to default value ""
[LIBCONFIG] loader.ldpc: 2/2 parameters successfully set, (1 to default value)
[CONFIG] shlibversion set to  _optim8seg from command line
[CONFIG] loader.ldpc 1 options set from command line
[LOADER] library libldpc_optim8seg.so successfully loaded
........................

Today, this mechanism is not available in the ldpctest phy simulator which doesn't initialize the configuration module. loads libldpc.so and libldpc_orig.so to compare the performance of the two implementations.

###LDPC libraries Libraries implementing the LDPC algorithms must be named libldpc<_version>.so, they must implement two functions: nrLDPC_decod and nrLDPC_encod. The prototypes for these functions is defined in nrLDPC_defs.h.

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