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.

Requirements

• bitstream image and PMD driver for the T2 card provided by AccelerComm
• DPDK 20.11.9 with patch from Accelercomm: version ACCL_BBDEV_DPDK20.11.3_ldpc_3.1.918.patch
• tested on RHEL7.9, RHEL9.2, Ubuntu 22.04

DPDK setup

DPDK installation

Note: Following instructions are valid for ACCL_BBDEV_DPDK20.11.3_ldpc_3.1.918.patch version, which is compatible with DPDK 20.11.9. Installation steps, which should be followed for older versions of the patch file (for example ACL_BBDEV_DPDK20.11.3_BL_1006_build_1105_dev_branch_MCT_optimisations_1106_physical_std.patch) are present in older version of this documentation, under the tag 2023.w48.

# Get DPDK source code
git clone https://github.com/DPDK/dpdk-stable.git ~/dpdk-stable
cd ~/dpdk-stable
git checkout v20.11.9
git apply ~/ACL_BBDEV_DPDK20.11.3_ldpc_3.1.918.patch

Replace ~/ACL_BBDEV_DPDK20.11.3_ldpc_3.1.918.patch by patch file provided by Accelercomm.

cd ~/dpdk-stable
meson setup build
# meson setup --prefix=/opt/dpdk-t2 build for installation with non-default installation prefix
cd build
ninja
sudo ninja install
sudo ldconfig

DPDK configuration

• load required kernel module

sudo modprobe vfio-pci

• check presence of the card and its PCI addres on the host machine

lspci | grep "Xilinx"

• bind the card with vfio-pci driver

sudo python3 ~/dpdk-stable/usertools/dpdk-devbind.py --bind=vfio-pci 41:00.0

Replace PCI address of the card 41:00.0 by address detected by lspci | grep "Xilinx" command

• hugepages setup (10 x 1GB hugepages)

sudo python3 ~/dpdk-stable/usertools/dpdk-hugepages.py -p 1G --setup 10G

Note: device binding and hugepages setup has to be done after every reboot of the host machine

Modifications in the OAI code

DPDK lib and PMD path specification

If DPDK library was installed into custom path, you have to point to the right directory with PKG_CONFIG_PATH, prior to the OAI build. Sample command to set the DPDK path to /opt/dpdk-t2/lib64/pkgconfig/:

export PKG_CONFIG_PATH=/opt/dpdk-t2/lib64/pkgconfig/:$PKG_CONFIG_PATH

OAI Build

OTA deployment is precisely described in the following tutorial:

• NR_SA_Tutorial_COTS_UE Instead of section 3.2 Build OAI gNB from the tutorial, run following commands:

# Get openairinterface5g source code
git clone https://gitlab.eurecom.fr/oai/openairinterface5g.git ~/openairinterface5g
cd ~/openairinterface5g
git checkout develop

# Install OAI dependencies
cd ~/openairinterface5g/cmake_targets
./build_oai -I

# Build OAI gNB
cd ~/openairinterface5g
source oaienv
cd cmake_targets
./build_oai -w USRP --ninja --gNB -P --build-lib "ldpc_t2" -C

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.

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

Setup of T2-related DPDK EAL parameters

To configure T2-related DPDK Environment Abstraction Layer (EAL) parameters, you can set the following parameters via the command line of PHY simulators or softmodem:

• nrLDPC_coding_t2.dpdk_dev - mandatory parameter, specifies PCI address of the T2 card. PCI address of the T2 card can be detected by lspci | grep "Xilinx" command.
• nrLDPC_coding_t2.dpdk_core_list - mandatory parameter, specifies CPU cores assigned to DPDK for T2 processing. Ensure that the CPU cores specified in nrLDPC_coding_t2.dpdk_core_list are available and not used by other processes to avoid conflicts.
• nrLDPC_coding_t2.dpdk_prefix - DPDK shared data file prefix, by default set to b6.

Note: These parameters can also be provided in a configuration file:

nrLDPC_coding_t2 : {
  dpdk_dev : "41:00.0";
  dpdk_core_list : "14-15";
};

loader : {
  ldpc : {
    shlibversion : "_t2";
  };
};

5G PHY simulators

nr_ulsim test

Offload of the channel decoding to the T2 card is in nr_ulsim specified by --loader.ldpc.shlibversion _t2 option. Example command for running nr_ulsim with LDPC decoding offload to the T2 card:

cd ~/openairinterface5g
source oaienv
cd cmake_targets/ran_build/build
sudo ./nr_ulsim -n100 -s20 -m20 -r273 -R273 --loader.ldpc.shlibversion _t2 --nrLDPC_coding_t2.dpdk_dev 01:00.0 --nrLDPC_coding_t2.dpdk_core_list 0-1

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:

cd ~/openairinterface5g
source oaienv
cd cmake_targets/ran_build/build
sudo ./nr_dlsim -n300 -s30 -R 106 -e 27 --loader.ldpc.shlibversion _t2 --nrLDPC_coding_t2.dpdk_dev 01:00.0 --nrLDPC_coding_t2.dpdk_core_list 0-1

OTA test

Offload of the channel encoding and decoding to the AMD Xilinx T2 card is enabled by --loader.ldpc.shlibversion _t2 option.

Run OAI gNB with USRP B210

cd ~/openairinterface5g
source oaienv
cd cmake_targets/ran_build/build
sudo ./nr-softmodem -O ../../../targets/PROJECTS/GENERIC-NR-5GC/CONF/gnb.sa.band78.fr1.106PRB.usrpb210.conf --loader.ldpc.shlibversion _t2 --nrLDPC_coding_t2.dpdk_dev 01:00.0 --nrLDPC_coding_t2.dpdk_core_list 0-1

Limitations

AMD Xilinx T2 card

• functionality of the LDPC encoding and decoding offload verified in OTA SISO setup with USRP N310 and Quectel RM500Q, blocking of the card reported for MIMO setup (2 layers)

Note: AMD Xilinx T1 Telco card is not supported anymore.