openairinterface5g/doc/LDPC_T2_OFFLOAD_SETUP.md

OAI T1/T2 LDPC offload

Table of Contents

[[TOC]]

This documentation aims to provide a tutorial for AMD Xilinx T2 Telco card integration into OAI and its usage.

Prerequisites

Offload of the channel decoding was tested with the T2 card in following setup:

AMD Xilinx T2 card

• bitstream image and PMD driver provided by AccelerComm
• DPDK 20.11.3 with patch from Accelercomm (also tested with DPDK 20.11.7 version)
• tested on RHEL7.9, RHEL9.2, Ubuntu 20.04, Ubuntu 22.04

DPDK setup

• check the presence of the card on the host
  • lspci | grep "Xilinx"
• binding of the device with igb_uio driver
  • ./dpdk-devbind.py -b igb_uio <address of the PCI of the card>
• hugepages setup (10 x 1GB hugepages)
  • ./dpdk-hugepages.py -p 1G --setup 10G

Note: Commands to run from dpdk/usertool folder

Compilation

Deployment of the OAI is precisely described in the following tutorials.

• BUILD
• NR_SA_CN5G_gNB_USRP_COTS_UE_Tutorial

Shared object file libldpc_t2.so is created during the compilation. This object is conditionally compiled. Selection of the library to compile is done using --build-lib ldpc_t2. Example command to build OAI with support for LDPC offload to T2 card is:

./build_oai -P --gNB -w USRP --build-lib "ldpc_t2" --ninja

Required poll mode driver has to be present on the host machine and required DPDK version has to be installed on the host, prior to the build of OAI

nr_ulsim test

Offload of the channel decoding to the AMD Xilinx T2 card is in nr_ulsim specified by -o option. Example command for running nr_ulsim with LDPC decoding offload to the T2 card:

sudo ./nr_ulsim -n100 -s20 -m20 -r273 -o

nr_dlsim test

Offload of the channel encoding to the AMD Xilinx T2 card is in nr_dlsim specified by -c option. Example command for running nr_dlsim with LDPC encoding offload to the T2 card:

sudo ./nr_dlsim -n300 -s30 -R 106 -e 27 -c

OTA and RFSIM test

Offload of the channel encoding and decoding to the AMD Xilinx T2 card is enabled by --ldpc-offload-enable 1 option. Example command for running nr-softmodem with LDPC processing on the T2 card:

./nr-softmodem -O config_file.conf --sa --ldpc-offload-enable 1

LDPC encoding/decoding with CPU/GPU

Available LDPC implementations and loading particular libraries is well described in openair1/PHY/CODING/DOC/LDPCImplementation.md. Default library for LDPC processing is called libldpc.so. Sample command for running nr-softmodem with selected library (in this case we want to replace libldpc.so by libldpc_optim.so library): ./nr-softmodem -O config_file.conf --sa --loader.ldpc.shlibversion _optim

Available options:

• --loader.ldpc.shlibversion _optim8seg
• --loader.ldpc.shlibversion _optim
• --loader.ldpc.shlibversion _orig
• --loader.ldpc.shlibversion _cuda
• --loader.ldpc.shlibversion _cl

Limitations

AMD Xilinx T1 card

• offload of the LDPC decoding implemented only for MCS > 9, decoding of the smaller TBs on the T1 card leads to blocking of the card
• HARQ is not functional with LDPC decoding offload to the T1 card (restricted in the code to avoid blocking of the card)
• LDPC encoding offload not implemented for the T1 card
• not supported in current develop branch, please checkout to 2023.w43

AMD Xilinx T2 card

• offload of the LDPC encoding implemented for MCS > 2
• occasional blocking of the card in decoder function - issue is investigated