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OAI 7.2 Fronthaul Interface 5G SA Tutorial

Table of Contents

[[TOC]]

Prerequisites

The hardware on which we have tried this tutorial:

Hardware (CPU,RAM) Operating System (kernel) NIC (Vendor,Driver,Firmware)
Intel(R) Xeon(R) Gold 6354 36-Core, 128GB RHEL 9.2 (5.14.0-284.18.1.rt14.303.el9_2.x86_64) Intel X710, i40e, 9.20 0x8000d95e 22.0.9
Intel(R) Xeon(R) Gold 6354 36-Core, 128GB Ubuntu 22.04.3 LTS (5.15.0-1033-realtime) Intel X710, i40e, 9.00 0x8000cfeb 21.5.9
AMD EPYC 9374F 32-Core Processor, 128GB Ubuntu 22.04.2 LTS (5.15.0-1038-realtime) Intel E810 ,ice, 4.00 0x8001184e 1.3236.0

NOTE: These are not minimum hardware requirements. This is the configuration of our servers. The NIC card should support hardware PTP time stamping.

NICs we have tested so far:

Vendor Firmware Version
Intel X710 9.20 0x8000d95e 22.0.9
Intel E810-XXV 4.00 0x8001184e 1.3236.0
E810-C 4.20 0x8001784e 22.0.9
Intel XXV710 6.02 0x80003888

Note: With AMD servers/desktop machines with PCIe 5.0 we have only used E810 cards.

PTP enabled switches and grandmaster clock we have in are lab:

Vendor Software Version
CISCO C93180YC-FX3 10.2(4)
Fibrolan Falcon-RX/812/G 8.0.25.4
Qulsar Qg2 (Grandmaster) 12.1.27

S-Plane synchronization is mandatory. S-plane support is done via ptp4l and phc2sys. Make sure your version matches.

Software Software Version
ptp4l 3.1.1
phc2sys 3.1.1

We have only verified LLS-C3 configuration in our lab, i.e. using an external grandmaster, a switch as a boundary clock, and the gNB/DU and RU. We haven't tested any RU without S-plane. Radio units we are testing/integrating:

Vendor Software Version
VVDN LPRU 03-v3.0.5
LiteON RU 01.00.08/02.00.03
Benetel 650 RAN650-1v1.0.4-dda1bf5
Benetel 550 CAT-A RAN550-1v1.0.4-605a25a

Tested libxran releases:

Vendor
oran_e_maintenance_release_v1.0

Note: The libxran driver of OAI identifies the above version as "5.1.0" (E is fifth letter, then 1.0).

Configure your server

  1. Disable Hyperthreading (HT) in your BIOS. In all our servers HT is always disabled.
  2. We recommend you to start with a fresh installation of OS (either RHEL or Ubuntu). You have to install realtime kernel on your OS (Operating System). Based on your OS you can search how to install realtime kernel.
  3. Install realtime kernel for your OS
  4. Change the boot commands based on the below section. They can be performed either via tuned or via manually building the kernel

CPU allocation

This section is important to read, regardless of the operating system you are using.

Your server could be:

  • One NUMA node (See one NUMA node example): all the processors are sharing a single memory system.
  • Two NUMA nodes (see two NUMA nodes example): processors are grouped in 2 memory systems.
    • Usually the even (ie 0,2,4,...) CPUs are on the 1st socket
    • And the odd (ie (1,3,5,...) CPUs are on the 2nd socket

DPDK, OAI and kernel threads require to be properly allocated to extract maximum real-time performance for your use case.

  1. NOTE: Currently the default OAI 7.2 configuration file requires isolated CPUs 0,2,4 for DPDK/libXRAN, CPU 6 for ru_thread, CPU 8 for L1_rx_thread and CPU 10 for L1_tx_thread. It is preferrable to have all these threads on the same socket.
  2. Allocating CPUs to the OAI nr-softmodem is done using the --thread-pool option. Allocating 4 CPUs is the minimal configuration but we recommend to allocate at least 8 CPUs. And they can be on a different socket as the DPDK threads.
  3. And to avoid kernel preempting these allocated CPUs, it is better to force the kernel to use un-allocated CPUs.

Let summarize for example on a 32-CPU single NUMA node system, regardless of the number of sockets:

Applicative Threads Allocated CPUs
XRAN DPDK usage 0,2,4
OAI ru_thread 6
OAI L1_rx_thread 8
OAI L1_tx_thread 10
OAI nr-softmodem 1,3,5,7,9,11,13,15
kernel 16-31

In below example we have shown the output of /proc/cmdline for two different servers, each of them have different number of NUMA nodes. Be careful in isolating the CPUs in your environment. Apart from CPU allocation there are additional parameters which are important to be present in your boot command.

Modifying the linux command line usually requires to edit string GRUB_CMDLINE_LINUX in /etc/default/grub, run a grub command and reboot the server.

  • Set parameters isolcpus, nohz_full and rcu_nocbs with the list of CPUs to isolate for XRAN.
  • Set parameter kthread_cpus with the list of CPUs to isolate for kernel.

Set the tuned profile to realtime. If the tuned-adm command is not installed then you have to install it. When choosing this profile you have to mention the isolated cpus in /etc/tuned/realtime-variables.conf. By default this profile adds skew_tick=1 isolcpus=managed_irq,domain,<cpu-you-choose> intel_pstate=disable nosoftlockup in the boot command. Make sure you don't add them while changing /etc/default/grub.

tuned-adm profile realtime

Checkout anyway the examples below.

One NUMA Node

Below is the output of /proc/cmdline of a single NUMA node server,

NUMA:
  NUMA node(s):          1
  NUMA node0 CPU(s):     0-31
isolcpus=0-15 nohz_full=0-15 rcu_nocbs=0-15 kthread_cpus=16-31 rcu_nocb_poll nosoftlockup default_hugepagesz=1GB hugepagesz=1G hugepages=20 amd_iommu=on iommu=pt mitigations=off skew_tick=1 selinux=0 enforcing=0 tsc=reliable nmi_watchdog=0 softlockup_panic=0 audit=0 vt.handoff=7

Example taken for AMD EPYC 9374F 32-Core Processor

Two NUMA Nodes

Below is the output of /proc/cmdline of a two NUMA node server,

NUMA:
  NUMA node(s):          2
  NUMA node0 CPU(s):     0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34
  NUMA node1 CPU(s):     1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35

mitigations=off usbcore.autosuspend=-1 intel_iommu=on intel_iommu=pt selinux=0 enforcing=0 nmi_watchdog=0 softlockup_panic=0 audit=0 skew_tick=1 isolcpus=managed_irq,domain,0,2,4,6,8,10,12,14,16 nohz_full=0,2,4,6,8,10,12,14,16 rcu_nocbs=0,2,4,6,8,10,12,14,16 rcu_nocb_poll intel_pstate=disable nosoftlockup cgroup_disable=memory mce=off hugepagesz=1G hugepages=40 hugepagesz=2M hugepages=0 default_hugepagesz=1G isolcpus=managed_irq,domain,0,2,4,6,8,10,12,14 kthread_cpus=18-35 intel_pstate=disable nosoftlockup tsc=reliable

Example taken for Intel(R) Xeon(R) Gold 6354 CPU @ 3.00GHz

Common

Configure your servers to maximum performance mode either via OS or in BIOS. If you want to disable CPU sleep state via OS then use the below command:

# to disable
sudo cpupower idle-set -D 0
#to enable
sudo cpupower idle-set -E

The above information we have gathered either from O-RAN documents or via our own experiments. In case you would like to read the O-RAN documents then here are the links:

  1. O-RAN-SC O-DU Setup Configuration
  2. O-RAN Cloud Platform Reference Designs 2.0,O-RAN.WG6.CLOUD-REF-v02.00,February 2021

PTP configuration

Note: You may run OAI with O-RAN 7.2 Fronthaul without a RU attached (e.g. for benchmarking). In such case, you can skip PTP configuration and go to DPDK section.

  1. You can install linuxptp rpm or debian package. It will install ptp4l and phc2sys.
#RHEL
sudo dnf install linuxptp -y
#Ubuntu
sudo apt install linuxptp -y

Once installed you can use this configuration file for ptp4l (/etc/ptp4l.conf). Here the clock domain is 24 so you can adjust it according to your PTP GM clock domain

[global]
domainNumber            24
slaveOnly               1
time_stamping           hardware
tx_timestamp_timeout    1
logging_level           6
summary_interval        0
#priority1               127

[your_PTP_ENABLED_NIC]
network_transport       L2
hybrid_e2e              0

You need to increase tx_timestamp_timeout to 50 or 100 for Intel E-810. You will see that in the logs of ptp.

Create the configuration file for ptp4l (/etc/sysconfig/ptp4l)

OPTIONS="-f /etc/ptp4l.conf"

Create the configuration file for phc2sys (/etc/sysconfig/phc2sys)

OPTIONS="-a -r -r -n 24"

The service of ptp4l (/usr/lib/systemd/system/ptp4l.service) should be configured as below:

[Unit]
Description=Precision Time Protocol (PTP) service
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
EnvironmentFile=-/etc/sysconfig/ptp4l
ExecStart=/usr/sbin/ptp4l $OPTIONS

[Install]
WantedBy=multi-user.target

and service of phc2sys (/usr/lib/systemd/system/phc2sys.service) should be configured as below:

[Unit]
Description=Synchronize system clock or PTP hardware clock (PHC)
After=ntpdate.service ptp4l.service

[Service]
Type=simple
EnvironmentFile=-/etc/sysconfig/phc2sys
ExecStart=/usr/sbin/phc2sys $OPTIONS

[Install]
WantedBy=multi-user.target

Debugging PTP issues

You can see these steps in case your ptp logs have erorrs or rms reported in ptp4l logs is more than 100ms. Beware that PTP issues may show up only when running OAI and XRAN. If you are using the ptp4l service, have a look back in time in the journal: journalctl -u ptp4l.service -S <hours>:<minutes>:<seconds>

  1. Make sure that you have skew_tick=1 in /proc/cmdline
  2. For Intel E-810 cards set tx_timestamp_timeout to 50 or 100 if there are errors in ptp4l logs
  3. Other time sources than PTP, such as NTP or chrony timesources, should be disabled. Make sure they are enabled as further below.
  4. Make sure you set kthread_cpus=<cpu_list> in /proc/cmdline.
  5. If rms or delay in ptp4l or offset in phc2sys logs remain high then you can try pinning the ptp4l and phc2sys processes to an isolated CPU.
#to check there is NTP enabled or not
timedatectl | grep NTP
#to disable
timedatectl set-ntp false

DPDK (Data Plane Development Kit)

Download DPDK version 20.11.9.

# on debian
sudo apt install wget xz-utils libnuma-dev
# on Fedora/RHEL
sudo dnf install wget xz numactl-devel
cd
wget http://fast.dpdk.org/rel/dpdk-20.11.9.tar.xz

DPDK Compilation and Installation

# Installing meson : it should pull ninja-build and compiler packages
# on debian
sudo apt install meson
# on Fedora/RHEL
sudo dnf install meson
tar xvf dpdk-20.11.9.tar.xz && cd dpdk-stable-20.11.9

meson build
ninja -C build
sudo ninja install -C build

Verify the installation is complete

Check if the LD cache contains the DPDK Shared Objects after update:

sudo ldconfig -v | grep rte_
	librte_fib.so.0.200.2 -> librte_fib.so.0.200.2
	librte_telemetry.so.0.200.2 -> librte_telemetry.so.0.200.2
	librte_compressdev.so.0.200.2 -> librte_compressdev.so.0.200.2
	librte_gro.so.20.0 -> librte_gro.so.20.0.2
	librte_mempool_dpaa.so.20.0 -> librte_mempool_dpaa.so.20.0.2
	librte_distributor.so.20.0 -> librte_distributor.so.20.0.2
	librte_rawdev_dpaa2_cmdif.so.20.0 -> librte_rawdev_dpaa2_cmdif.so.20.0.2
	librte_mempool.so.20.0 -> librte_mempool.so.20.0.2
	librte_pmd_octeontx2_crypto.so.20.0 -> librte_pmd_octeontx2_crypto.so.20.0.2
	librte_common_cpt.so.20.0 -> librte_common_cpt.so.20.0.2
....

You may not have the /usr/local/lib, /usr/local/lib64, or custom DPDK installation paths in the LD_LIBRARY_PATH. In this case, add it as below; if you installed into a custom

sudo echo "/usr/local/lib" > /etc/ld.so.conf.d/local-lib.conf
sudo echo "/usr/local/lib64" >> /etc/ld.so.conf.d/local-lib.conf
sudo ldconfig
sudo ldconfig -v | grep rte_

Check if the PKG-CONFIG tool discovers the libraries:

pkg-config --libs libdpdk --static
Possible output 
-lrte_node -lrte_graph -lrte_bpf -lrte_flow_classify -lrte_pipeline -lrte_table -lrte_port -lrte_fib -lrte_ipsec -lrte_vhost -lrte_stack -lrte_security -lrte_sched -lrte_reorder -lrte_rib -lrte_rawdev -lrte_pdump -lrte_power -lrte_member -lrte_lpm -lrte_latencystats -lrte_kni -lrte_jobstats -lrte_ip_frag -lrte_gso -lrte_gro -lrte_eventdev -lrte_efd -lrte_distributor -lrte_cryptodev -lrte_compressdev -lrte_cfgfile -lrte_bitratestats -lrte_bbdev -lrte_acl -lrte_timer -lrte_hash -lrte_metrics -lrte_cmdline -lrte_pci -lrte_ethdev -lrte_meter -lrte_net -lrte_mbuf -lrte_mempool -lrte_rcu -lrte_ring -lrte_eal -lrte_telemetry -lrte_kvargs -Wl,--whole-archive -lrte_common_cpt -lrte_common_dpaax -lrte_common_iavf -lrte_common_octeontx -lrte_common_octeontx2 -lrte_bus_dpaa -lrte_bus_fslmc -lrte_bus_ifpga -lrte_bus_pci -lrte_bus_vdev -lrte_bus_vmbus -lrte_mempool_bucket -lrte_mempool_dpaa -lrte_mempool_dpaa2 -lrte_mempool_octeontx -lrte_mempool_octeontx2 -lrte_mempool_ring -lrte_mempool_stack -lrte_pmd_af_packet -lrte_pmd_ark -lrte_pmd_atlantic -lrte_pmd_avp -lrte_pmd_axgbe -lrte_pmd_bond -lrte_pmd_bnxt -lrte_pmd_cxgbe -lrte_pmd_dpaa -lrte_pmd_dpaa2 -lrte_pmd_e1000 -lrte_pmd_ena -lrte_pmd_enetc -lrte_pmd_enic -lrte_pmd_failsafe -lrte_pmd_fm10k -lrte_pmd_i40e -lrte_pmd_hinic -lrte_pmd_hns3 -lrte_pmd_iavf -lrte_pmd_ice -lrte_pmd_igc -lrte_pmd_ixgbe -lrte_pmd_kni -lrte_pmd_liquidio -lrte_pmd_memif -lrte_pmd_netvsc -lrte_pmd_nfp -lrte_pmd_null -lrte_pmd_octeontx -lrte_pmd_octeontx2 -lrte_pmd_pfe -lrte_pmd_qede -lrte_pmd_ring -lrte_pmd_sfc -lrte_pmd_softnic -lrte_pmd_tap -lrte_pmd_thunderx -lrte_pmd_vdev_netvsc -lrte_pmd_vhost -lrte_pmd_virtio -lrte_pmd_vmxnet3 -lrte_rawdev_dpaa2_cmdif -lrte_rawdev_dpaa2_qdma -lrte_rawdev_ioat -lrte_rawdev_ntb -lrte_rawdev_octeontx2_dma -lrte_rawdev_octeontx2_ep -lrte_rawdev_skeleton -lrte_pmd_caam_jr -lrte_pmd_dpaa_sec -lrte_pmd_dpaa2_sec -lrte_pmd_nitrox -lrte_pmd_null_crypto -lrte_pmd_octeontx_crypto -lrte_pmd_octeontx2_crypto -lrte_pmd_crypto_scheduler -lrte_pmd_virtio_crypto -lrte_pmd_octeontx_compress -lrte_pmd_qat -lrte_pmd_ifc -lrte_pmd_dpaa_event -lrte_pmd_dpaa2_event -lrte_pmd_octeontx2_event -lrte_pmd_opdl_event -lrte_pmd_skeleton_event -lrte_pmd_sw_event -lrte_pmd_dsw_event -lrte_pmd_octeontx_event -lrte_pmd_bbdev_null -lrte_pmd_bbdev_turbo_sw -lrte_pmd_bbdev_fpga_lte_fec -lrte_pmd_bbdev_fpga_5gnr_fec -Wl,--no-whole-archive -lrte_node -lrte_graph -lrte_bpf -lrte_flow_classify -lrte_pipeline -lrte_table -lrte_port -lrte_fib -lrte_ipsec -lrte_vhost -lrte_stack -lrte_security -lrte_sched -lrte_reorder -lrte_rib -lrte_rawdev -lrte_pdump -lrte_power -lrte_member -lrte_lpm -lrte_latencystats -lrte_kni -lrte_jobstats -lrte_ip_frag -lrte_gso -lrte_gro -lrte_eventdev -lrte_efd -lrte_distributor -lrte_cryptodev -lrte_compressdev -lrte_cfgfile -lrte_bitratestats -lrte_bbdev -lrte_acl -lrte_timer -lrte_hash -lrte_metrics -lrte_cmdline -lrte_pci -lrte_ethdev -lrte_meter -lrte_net -lrte_mbuf -lrte_mempool -lrte_rcu -lrte_ring -lrte_eal -lrte_telemetry -lrte_kvargs -Wl,-Bdynamic -pthread -lm -ldl

If DPDK was installed into /usr/local/lib, /usr/local/lib64, or another custom path, you have to point to the right directory with PKG_CONFIG_PATH, for instance:

export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib64/pkgconfig/
pkg-config --libs libdpdk --static

If you want to de-install this version of DPDK

Go back to the version folder you used to build and install

cd ~/dpdk-stable-20.11.9
sudo ninja deinstall -C build

Build OAI-FHI gNB

Clone OAI code base in a suitable repository, here we are cloning in ~/openairinterface5g directory,

git clone https://gitlab.eurecom.fr/oai/openairinterface5g.git ~/openairinterface5g
cd ~/openairinterface5g/

Build ORAN Fronthaul Interface Library

Download ORAN FHI DU library and checkout the correct version.

git clone https://gerrit.o-ran-sc.org/r/o-du/phy.git ~/phy
cd ~/phy
git checkout oran_e_maintenance_release_v1.0

Apply the patch (available in oai_folder/cmake_targets/tools/oran_fhi_integration_patches/E):

cd ~/phy
git apply ~/openairinterface5g/cmake_targets/tools/oran_fhi_integration_patches/E/oaioran_E.patch

Compile the fronthaul interface library by calling make and the option XRAN_LIB_SO=1 to have it build a shared object. Note that we provide two environment variables RTE_SDK for the path to the source tree of DPDK, and XRAN_DIR to set the path to the fronthaul library.

Note: you need at least gcc-11 and g++-11.

cd ~/phy/fhi_lib/lib
make clean
RTE_SDK=~/dpdk-stable-20.11.9/ XRAN_DIR=~/phy/fhi_lib make XRAN_LIB_SO=1
...
[AR] build/libxran.so
./build/libxran.so

The shared library object ~/phy/fhi_lib/lib/build/libxran.so must be present before proceeding.

Build OAI gNB

You can now proceed building OAI. You build it the same way as for other radios, providing option -t oran_fhlib_5g. Additionally, you need to provide it the location of the FH library: --cmake-opt -Dxran_LOCATION=PATH. Note that since we cannot use ~ here, we resort to $HOME, which is equivalent. Finally, if you needed to define PKG_CONFIG_PATH previously, you need to do so now, too.

# You should have already cloned above
cd ~/openairinterface5g/cmake_targets
# if you installed DPDK in a custom path as described above
export PKG_CONFIG_PATH=$PKG_CONFIG_PATH:/usr/local/lib64/pkgconfig/
./build_oai -I  # if you never installed OAI, use this command once before the next line
./build_oai --gNB --ninja -t oran_fhlib_5g --cmake-opt -Dxran_LOCATION=$HOME/phy/fhi_lib/lib

You can optionally check that everything has been linked properly with

ldd ran_build/build/liboran_fhlib_5g.so
Possible output 
#check if all the libraries are properly linked to liboai_transpro.so
ldd ran_build/build/liboran_fhlib_5g.so
    linux-vdso.so.1 (0x00007fffb459e000)
    librte_node.so.21 => /usr/local/lib64/librte_node.so.21 (0x00007fd358690000)
    librte_graph.so.21 => /usr/local/lib64/librte_graph.so.21 (0x00007fd358685000)
    librte_bpf.so.21 => /usr/local/lib64/librte_bpf.so.21 (0x00007fd358672000)
    librte_flow_classify.so.21 => /usr/local/lib64/librte_flow_classify.so.21 (0x00007fd35866c000)
    librte_pipeline.so.21 => /usr/local/lib64/librte_pipeline.so.21 (0x00007fd35862f000)
    librte_table.so.21 => /usr/local/lib64/librte_table.so.21 (0x00007fd358612000)
    librte_port.so.21 => /usr/local/lib64/librte_port.so.21 (0x00007fd3585f8000)
    librte_fib.so.21 => /usr/local/lib64/librte_fib.so.21 (0x00007fd3585e9000)
...
    libm.so.6 => /lib64/libm.so.6 (0x00007fd357eb1000)
    libnuma.so.1 => /lib64/libnuma.so.1 (0x00007fd357ea1000)
    libc.so.6 => /lib64/libc.so.6 (0x00007fd357c98000)
    /lib64/ld-linux-x86-64.so.2 (0x00007fd3587c7000)
    libelf.so.1 => /lib64/libelf.so.1 (0x00007fd357c7d000)
    libz.so.1 => /lib64/libz.so.1 (0x00007fd357c61000)

Note that you might also call cmake directly instead of using build_oai:

cd ~/openairinterface5g
mkdir build && cd build
cmake .. -GNinja -DOAI_FHI72=ON -Dxran_LOCATION=$HOME/phy/fhi_lib/lib
ninja nr-softmodem oran_fhlib_5g params_libconfig

Configuration

RU and DU configurations have a circular dependency: you have to configure DU MAC address in the RU configuration and the RU MAC address, VLAN and Timing advance parameters in the DU configuration.

Note: You may run OAI with O-RAN 7.2 Fronthaul without a RU attached (e.g. for benchmarking). In such case, skip RU configuration and only configure Network Interfaces, DPDK VFs and OAI configuration by using arbitrary values for RU MAC addresses and VLAN tags.

Configure the RU

Contact the RU vendor and get the configuration manual to understand the below commands. The below configuration only corresponds to the RU firmware version indicated at the start of this document. If your firmware version does not correspond to the indicated version, then please don't try these commands.

NOTE: Please understand all the changes you are doing at the RU, especially if you are manipulating anything related to output power.

Benetel 650

  • Valid only for version RAN650-1v1.0.4-dda1bf5
  • TDD pattern DDDDDDDSUU, 5ms
  • Bandwidth 100MHz
  • MTU 9216 (this is the maximum we can configure on our switch)
  • 4TX4R
  • The OAI configuration file gnb.sa.band78.273prb.fhi72.4x4-benetel650.conf corresponds to below RU configuration.

After switching on the radio or rebooting, wait for the radio bring up to complete, which you can follow using tail -f /tmp/logs/radio_status. Once you will see [INFO] Radio bringup complete, you can configure the RU via editing /etc/ru_config.cfg

cat /etc/ru_config.cfg

mimo_mode=1_2_3_4_4x4
downlink_scaling=0
prach_format=short
compression=static_compressed
lf_prach_compression_enable=true
cplane_per_symbol_workaround=disabled
cuplane_dl_coupling_sectionID=disabled
flexran_prach_workaround=disabled
dl_ul_tuning_special_slot=0xfd00000

Benetel 550

After switching on the radio or rebooting, wait for the radio bring up to complete, which you can follow using tail -f /tmp/logs/radio_status. Once you will see [INFO] Radio bringup complete, you can configure the RU via editing /etc/ru_config.cfg

cat /etc/ru_config.cfg

mimo_mode=1_2_3_4_4x4
downlink_scaling=0
prach_format=short
compression=static_compressed
lf_prach_compression_enable=true
cplane_per_symbol_workaround=disabled
cuplane_dl_coupling_sectionID=disabled
flexran_prach_workaround=disabled
dl_tuning_special_slot=0x13b6

LiteON

  • TDD pattern DDDSU, 2.5ms
  • Bandwidth 100MHz
  • Default MTU is 1500

SSH to the unit as user user. Write enable in the terminal to enter the configuration console; the password should be in the user guide. Use the command show oru-status to check the RU status. The output should be similar to:

# show oru-status 
Sync State  : SYNCHRONIZED
RF State    : Ready
DPD         : Ready

Once the RU is PTP synced, and RF state and DPD are Ready, write configure in the terminal to set:

  • Center frequency
  • Bandwidth
  • Compression Bitwidth
  • TX/RX attenuation

To configure 4TX and 4RX antennas, you have to repeat the below steps after every reboot, so don't restart the RU after entering below commands:

devmem 0x80001014 32 0x00050004
devmem 0x80001018 32 0x00070006
devmem 0x8000201C 32 0x00000001

If you want to set MTU size to 9000 then use the below command:

devmem 0x8000200C 32 0x00000001

VVDN LPRU

  • TDD pattern DDDSU, 2.5ms
  • Bandwidth 100MHz
  • MTU 9216 (this is the maximum we can configure on our switch)
  • The OAI configuration file gnb.sa.band77.273prb.fhi72.4x4-vvdn.conf corresponds to below RU configuration.

Check in the RU user manual how to configure the center frequency. There are multiple ways to do it. We set the center frequency by editing sysrepocfg database. You can use sysrepocfg --edit=vi -d running to do the same. You can edit the startup database to make the center frequency change persistent.

To make any change in the RU, always wait for it to be PTP synced. You can check the sync status via tail -f /var/log/synctimingptp2.log.

To set the RU for 4TX and 4RX antennas with 9 bit compression, you need to create this XML file and apply it.

Login to the ru and create this file as 4x4-config.xml.

<vvdn_config>
    <du_mac_address>YOUR-DU-MAC-ADDR</du_mac_address>
    <cu_plane_vlan>YOUR-RU-VLAN</cu_plane_vlan>  
    <dl_compression_method>1</dl_compression_method>  
    <dl_compression_value>9</dl_compression_value>  
    <ul_compression_method>1</ul_compression_method> 
    <ul_compression_value>9</ul_compression_value>
    <num_prb>273</num_prb>
    <prach_layer0_PCID>4</prach_layer0_PCID>
    <prach_layer1_PCID>5</prach_layer1_PCID>
    <prach_layer2_PCID>6</prach_layer2_PCID>
    <prach_layer3_PCID>7</prach_layer3_PCID>
    <pxsch_layer0_PCID>0</pxsch_layer0_PCID>
    <pxsch_layer1_PCID>1</pxsch_layer1_PCID>
    <pxsch_layer2_PCID>2</pxsch_layer2_PCID>
    <pxsch_layer3_PCID>3</pxsch_layer3_PCID>
</vvdn_config>

Execute the below commands on every restart

xml_parser 4x4-config.xml
## To enable prach compression
mw.l a0010024 1919
## This will show the current configuration
/etc/scripts/lpru_configuration.sh
## Edit the sysrepo to ACTIVATE the carrier when you want to use the RU
sysrepocfg --edit=vi -d running

Configure Network Interfaces and DPDK VFs

The 7.2 fronthaul uses the xran library, which requires DPDK. In this step, we need to configure network interfaces to send data to the RU, and configure DPDK to bind to the corresponding PCI interfaces. More specifically, in the following we use SR-IOV to create multiple virtual functions (VFs) through which Control plane (C plane) and User plane (U plane) traffic will flow. The following commands are not persistant, and have to be repeated after reboot.

In the following, we will use these short hands:

  • physical-interface: Physical network interface through which you can access the RU
  • vlan: VLAN tags as defined in the RU configuration
  • mtu: the MTU as specified by the RU vendor, and supported by the NIC
  • du-c-plane-mac-addr: DU C plane MAC address
  • pci-address-c-plane-vf: PCI bus address of the VF for C plane
  • du-u-plane-mac-addr: DU U plane MAC address
  • pci-address-u-plane-vf: PCI bus address of the VF for U plane

In the configuration file, in option fhi_72.dpdk_devices, the first PCI address is for C-plane and the second for U-plane.

For both the MAC addresses, you might use the MAC addresses which are pre-configured in the RUs (typically 00:11:22:33:44:66, but that is not always the case). Note that if your system has Intel E-810 NIC cards/ICE driver, you have to choose different MAC addresses (valid for above-mentioned kernels). If the RU vendor requires untagged traffic, remove the VLAN tagging in the below command and configure VLAN on the switch as "access VLAN". In case the MTU is different than 1500, you have to update the MTU on the switch interface as well.

First, set maximum ring buffers:

sudo ethtool -g <physical-interface>
sudo ethtool -G <physical-interface> rx 4096     # assumes 4096 is max
sudo ethtool -G <physical-interface> tx 4096     # assumes 4096 is max

Set the maximum MTU in the physical interface:

sudo ifconfig <physical-interface> mtu <mtu>

(Re-)create two VFs, load the Linux "Base Driver for Intel Ethernet Adaptive Virtual Function" (in case you use Intel ethernet card), and set up the VFs.

sudo modprobe iavf
sudo sh -c echo "0" > /sys/class/net/<physical-interface>/device/sriov_numvfs
sudo sh -c echo "2" > /sys/class/net/<physical-interface>/device/sriov_numvfs
sudo ip link set <physical-interface> vf 0 mac <du-c-plane-mac-addr> vlan <vlan> mtu <mtu> spoofchk off
sudo ip link set <physical-interface> vf 1 mac <du-u-plane-mac-addr> vlan <vlan> mtu <mtu> spoofchk off

After running the above commands, the kernel created virtual functions that have been assigned a PCI address under the same device and vendor ID. For instance, use sudo lshw -c network -businfo to get a list of PCI addresses and interface names, locate the PCI address of <physical-interface>, then use lspci | grep Virtual to get all virtual interfaces and use the ones with the same Device/Vendor ID parts (first two numbers).

Example

The machine in this example has an Intel X710 card. The interface in question is eno12409. Running lshw gives:

$ sudo lshw -c network -businfo
Bus info          Device     Class          Description
=======================================================
[...]
pci@0000:31:00.1  eno12409   network        Ethernet Controller X710 for 10GbE SFP+
[...]

We see the PCI address 31:00.1. Listing the virtual interfaces through lspci, we get

$ lspci | grep Virtual
31:06.0 Ethernet controller: Intel Corporation Ethernet Virtual Function 700 Series (rev 02)
31:06.1 Ethernet controller: Intel Corporation Ethernet Virtual Function 700 Series (rev 02)
98:11.0 Ethernet controller: Intel Corporation Ethernet Adaptive Virtual Function (rev 02)
98:11.1 Ethernet controller: Intel Corporation Ethernet Adaptive Virtual Function (rev 02)
98:11.2 Ethernet controller: Intel Corporation Ethernet Adaptive Virtual Function (rev 02)
98:11.3 Ethernet controller: Intel Corporation Ethernet Adaptive Virtual Function (rev 02)
98:11.4 Ethernet controller: Intel Corporation Ethernet Adaptive Virtual Function (rev 02)
98:11.5 Ethernet controller: Intel Corporation Ethernet Adaptive Virtual Function (rev 02)

The hardware card 31:00.1 has two associated virtual functions 31:06.0 and 31:06.1.

Now, unbind any pre-existing DPDK devices, load the "Virtual Function I/O" driver vfio_pci, and bind DPDK to these devices:

sudo /usr/local/bin/dpdk-devbind.py --unbind <pci-address-c-plane-vf>
sudo /usr/local/bin/dpdk-devbind.py --unbind <pci-address-u-plane-vf>
sudo modprobe vfio_pci
sudo /usr/local/bin/dpdk-devbind.py --bind vfio-pci <pci-address-c-plane-vf>
sudo /usr/local/bin/dpdk-devbind.py --bind vfio-pci <pci-address-u-plane-vf>

We recommand to put the above commands into a script file to quickly repeat them.

Example script for Benetel 550-A/650 with Intel X710 on host 
set -x

sudo ethtool -G eno12409 rx 4096
sudo ethtool -G eno12409 tx 4096
sudo ifconfig eno12409 mtu 9216

sudo modprobe -r iavf
sudo modprobe iavf
sudo sh -c 'echo 0 > /sys/class/net/eno12409/device/sriov_numvfs'
sudo sh -c 'echo 2 > /sys/class/net/eno12409/device/sriov_numvfs'
sudo ip link set eno12409 vf 0 mac 00:11:22:33:44:66 vlan 3 qos 0 spoofchk off mtu 9216
sudo ip link set eno12409 vf 1 mac 00:11:22:33:44:67 vlan 3 qos 0 spoofchk off mtu 9216

sudo /usr/local/bin/dpdk-devbind.py --unbind 31:06.0
sudo /usr/local/bin/dpdk-devbind.py --unbind 31:06.1
sudo modprobe vfio-pci
sudo /usr/local/bin/dpdk-devbind.py --bind vfio-pci 31:06.0
sudo /usr/local/bin/dpdk-devbind.py --bind vfio-pci 31:06.1

Configure OAI gNB

Beware in the following section to let in the range of isolated cores the parameters that should be (i.e. L1s.L1_rx_thread_core, L1s.L1_tx_thread_core, RUs.ru_thread_core, fhi_72.io_core and fhi_72.worker_cores)

Sample configuration files for OAI gNB, specific to the manufacturer of the radio unit, are available at:

  1. LITE-ON RU: gnb.sa.band78.273prb.fhi72.4x4-liteon.conf (band n78, 273 PRBs, 3.5GHz center freq, 4x4 antenna configuration with 9 bit I/Q samples (compressed) for PUSCH/PDSCH/PRACH, 2-layer DL MIMO, UL SISO)
  2. Benetel 650 RU: gnb.sa.band78.273prb.fhi72.4x4-benetel650.conf (band n78, 273 PRBs, 3.5GHz center freq, 4x2 antenna configuration with 9 bit I/Q samples (compressed) for PUSCH/PDSCH/PRACH, 2-layer DL MIMO, UL SISO)
  3. VVDN RU: gnb.sa.band77.273prb.fhi72.4x4-vvdn.conf (band n77, 273 PRBs, 4.0GHz center freq, 4x4 antenna configuration with 9 bit I/Q samples (compressed) for PUSCH/PDSCH/PRACH, 2-layer DL MIMO, UL SISO)

Edit the sample OAI gNB configuration file and check following parameters:

  • gNBs section

    • The PLMN section shall match the one defined in the AMF
    • amf_ip_address shall be the correct AMF IP address in your system
    • GNB_IPV4_ADDRESS_FOR_NG_AMF shall match your gNB N2 interface IP address
    • GNB_IPV4_ADDRESS_FOR_NGU shall match your gNB N3 interface IP address
    • prach_ConfigurationIndex
    • prach_msg1_FrequencyStart
    • Adjust the frequency, bandwidth and SSB position

  • L1s section

    • Set an isolated core for L1 thread L1_rx_thread_core, in our environment we are using CPU 8
    • Set an isolated core for L1 thread L1_tx_thread_core, in our environment we are using CPU 10
    • phase_compensation should be set to 0 to disable when it is performed in the RU and set to 1 when it should be performed on the DU side
    • tx_amp_backoff_dB controls the output level of OAI with respect to a full-scale output. The exact value for tx_amp_backoff_dB should be obtained from the O-RU documentation. This documentation typically includes detailed sections on Downlink (DL) signal scaling and gain setup. Warning: Exceeding the recommended power limits may permanently damage the RU.

  • RUs section

    • Set an isolated core for RU thread ru_thread_core, in our environment we are using CPU 6

  • fhi_72 (FrontHaul Interface) section: this config follows the structure that is employed by the xRAN library (xran_fh_init and xran_fh_config structs in the code):

    • dpdk_devices: PCI addresses of NIC VFs binded to the DPDK (not the physical NIC but the VFs, use lspci | grep Virtual)
    • system_core: absolute CPU core ID for DPDK control threads, it should be an isolated core, in our environment we are using CPU 0 (rte_mp_handle, eal-intr-thread, iavf-event-thread)
    • io_core: absolute CPU core ID for XRAN library, it should be an isolated core, in our environment we are using CPU 4
    • worker_cores: array of absolute CPU core IDs for XRAN library, they should be isolated cores, in our environment we are using CPU 2
    • du_addr: DU C- and U-plane MAC-addresses (format UU:VV:WW:XX:YY:ZZ, hexadecimal numbers)
    • ru_addr: RU C- and U-plane MAC-addresses (format UU:VV:WW:XX:YY:ZZ, hexadecimal numbers)
    • mtu: Maximum Transmission Unit for the RU, specified by RU vendor
    • fh_config: parameters that need to match RU parameters
      • timing parameters (starting with T) depend on the RU: Tadv_cp_dl is a single number, the rest pairs of numbers (x, y) specifying minimum and maximum delays
      • ru_config: RU-specific configuration:
        • iq_width: Width of DL/UL IQ samples: if 16, no compression, if <16, applies compression
        • iq_width_prach: Width of PRACH IQ samples: if 16, no compression, if <16, applies compression
      • prach_config: PRACH-specific configuration
        • eAxC_offset: PRACH antenna offset
        • kbar: the PRACH guard interval, provided in RU

Layer mapping (eAxC offsets) happens as follows:

  • For PUSCH/PDSCH, the layers are mapped to [0,1,...,N-1] where N is the respective RX/TX number of antennas.
  • For PRACH, the layers are mapped to [No,No+1,...No+N-1] where No is the fhi_72.fh_config.[0].prach_config.eAxC_offset and N the number of receive antennas.

xRAN SRS reception is not supported.

Start and Operation of OAI gNB

Run the nr-softmodem from the build directory:

cd ~/openairinterface5g/cmake_targets/ran_build/build
sudo ./nr-softmodem -O <configuration file> --sa --thread-pool <list of non isolated cpus>

Warning: Make sure that the configuration file you add after the -O option is adapted to your machine, especially to its isolated cores.

Note: You may run OAI with O-RAN 7.2 Fronthaul without a RU attached (e.g. for benchmarking). In such case, you would generate artificial traffic by replacing the --sa option by the --phy-test option.

You have to set the thread pool option to non-isolated CPUs, since the thread pool is used for L1 processing which should not interfere with DPDK threads. For example if you have two NUMA nodes in your system (for example 18 CPUs per socket) and odd cores are non-isolated, then you can put the thread-pool on 1,3,5,7,9,11,13,15. On the other hand, if you have one NUMA node, you can use either isolated cores or non isolated cores, but make sure that isolated cores are not the ones defined earlier for DPDK/xran.

Once the gNB runs, you should see counters for PDSCH/PUSCH/PRACH per antenna port, as follows (4x2 configuration): 
[NR_PHY]   [o-du 0][rx   24604 pps   24520 kbps  455611][tx  126652 pps  126092 kbps 2250645][Total Msgs_Rcvd 24604]
[NR_PHY]   [o_du0][pusch0   10766 prach0    1536]
[NR_PHY]   [o_du0][pusch1   10766 prach1    1536]

The first line show RX/TX packet counters, i.e., packets received from the RU (RX), and sent to the RU (TX). In the second and third line, it shows the counters for the PUSCH and PRACH ports (2 receive antennas, so two counters each). These numbers should be equal, otherwise it indicates that you don't receive enough packets on either port.

If you see many zeroes, then it means that OAI does not receive packets on the fronthaul from the RU (RX is almost 0, all PUSCH/PRACH counters are 0). 
[NR_PHY]   [o-du 0][rx       2 pps       0 kbps       0][tx 1020100 pps  127488 kbps 4717971][Total Msgs_Rcvd 2]
[NR_PHY]   [o_du0][pusch0       0 prach0       0]
[NR_PHY]   [o_du0][pusch1       0 prach1       0]
[NR_PHY]   [o_du0][pusch2       0 prach2       0]
[NR_PHY]   [o_du0][pusch3       0 prach3       0]

In this case, please make sure that the O-RU has been configured with the right ethernet address of the gNB, and has been activated. You might enable port mirroring at your switch to capture the fronthaul packets: check that you see (1) packets at all (2) they have the right ethernet address (3) the right VLAN tag. Although we did not test this, you might make use of the DPDK packet capture feature

If you see messages about `Received time doesn't correspond to the time we think it is` or `Jump in frame counter`, the S-plane is not working. 
[PHY]   Received Time doesn't correspond to the time we think it is (slot mismatch, received 480.5, expected 475.8)
[PHY]   Received Time doesn't correspond to the time we think it is (frame mismatch, 480.5 , expected 475.5)
[PHY]   Jump in frame counter last_frame 480 => 519, slot 19
[PHY]   Received Time doesn't correspond to the time we think it is (slot mismatch, received 519.19, expected 480.12)
[PHY]   Received Time doesn't correspond to the time we think it is (frame mismatch, 519.19 , expected 480.19)
[PHY]   Received Time doesn't correspond to the time we think it is (slot mismatch, received 520.1, expected 520.0)

You can see that the frame numbers jump around, by 5-40 frames (corresponding to 50-400ms!). This indicates the gNB receives packets on the fronthaul that don't match its internal time, and the synchronization between gNB and RU is not working!

In this case, you should reverify that ptp4l and phc2sys are working, e.g., do not do any jumps (during the last hour). While an occasional jump is not necessarily problematic for the gNB, many such messages mean that the system is not working, and UEs might not be able to attach or reach good performance.

Contact in case of questions

You can ask your question on the mailing lists.

Your email should contain below information:

  • A clear subject in your email.
  • For all the queries there should be [Query] in the subject of the email and for problems there should be [Problem].
  • In case of a problem, add a small description.
  • Do not share any photos unless you want to share a diagram.
  • OAI gNB/DU/CU/CU-CP/CU-UP configuration file in .conf format only.
  • Logs of OAI gNB/DU/CU/CU-CP/CU-UP in .log or .txt format only.
  • RU Vendor and Version.
  • In case your question is related to performance, include a small description of the machine (CPU, RAM and networking card) and diagram of your testing environment.
  • If you have any issues related to PTP or synchronization, then first check the section "Debugging PTP issues". Then share your problem with PTP version you are using, switch details and master clock.
  • Known/open issues are present on GitLab, so keep checking.