Lab 11: OAI NR inter frequency handover

This experiment showcases an example of running handover procedure on top of a 5G Standalone (SA) network using OAI CU/DU/RU 3GPP split with USRP as an RU, OAI CN, FlexRIC as the Near-RT RIC and Quectel model as an COTS UE. Additionally, an instruction to apply handover API via xApp from public xApp SDK repository.

Prerequisites

1. Hardware component requirement:
   • USRP B210
   • A Quectel model - RM5xxN (prefer RM520N-GL)
2. Sections requirement in .yaml:
   • Target CU for DU connection

   annotations:
          extras.t9s.io/cu-name: <target-cu-name>

   • Handover group specification

   cells:
        groups:
            - kind: hog
              name: <cell-group-name>

Introduction

open-ran-ho-inter-oai.yaml

apiVersion: athena.trirematics.io/v1
kind: Network
metadata:
  name: handover
  namespace: trirematics
spec:
  slices:
    -   plmn: "00101"
        dnn: "internet"
        network-mode: "IPv4"
        service-type: eMBB
        differentiator: 0x000000
        ipv4-range: "12.1.1.0/24"
        ipv6-range: "2001:db8:1::/64"
  access:
    -   name: oai-gnb-cu-du
        stack: 5g-sa
        model: oai-ran/cu-du
        radio:
          device: uhd-b200
        identity:
          an-id: 50
        cells:
          -   band: n78
              arfcn: 630048
              bandwidth: 40MHz
              subcarrier-spacing: 30kHz
              tdd-config:
                period: 5ms
                dl-slots: 7
                dl-symbols: 6
                ul-slots: 2
                ul-symbols: 4
              groups:
                -   kind: hog
                    name: handover-group
        controller: flexric.handover
        core-networks:
          - minimal.handover
    -   name: oai-gnb-du
        stack: 5g-sa
        model: oai-ran/du
        radio:
          device: uhd-b200
        identity:
          an-id: 20
        annotations:
          extras.t9s.io/cu-name: "oai-gnb-cu-du"
        cells:
          -   band: n78
              arfcn: 643296
              bandwidth: 40MHz
              subcarrier-spacing: 30kHz
              tdd-config:
                period: 5ms
                dl-slots: 7
                dl-symbols: 6
                ul-slots: 2
                ul-symbols: 4
              groups:
                -   kind: hog
                    name: handover-group
        controller: flexric.handover
        core-networks:
          - minimal.handover
  core:
    -   name: minimal
        stack: 5g-sa
        model: oai-cn/minimal
        identity:
          region: 0
          cn-group: 4
          cn-id: 5
  edge:
    -   name: flexric
        stack: 5g-sa
        model: mosaic5g/flexric
  dns:
    ipv4:
      default: 8.8.8.8
      secondary: 8.8.4.4

Deployment

1. To run up the network

brc install network open-ran-ho-inter-oai.yaml

2. To check the network

brc observe

3. Wait until all the Elements are in the STATUS set to 1/1 Y state.

4. Attach the UE to the network by brc install network open-ran-ue.yaml

open-ran-ue.yaml

apiVersion: athena.trirematics.io/v1
kind: Terminal
metadata:
  name: ue1
  namespace: trirematics
spec:
  vendor: oai
  stack: 5g-sa
  model: terminal/quectel
  target-cores:
    - minimal.handover
  identity:
    imsi: "001010000000001"
    pin: "1234"
    opc: "0xC42449363BBAD02B66D16BC975D77CC1"
    key: "0xfec86ba6eb707ed08905757b1bb44b8f"
    sqn: "0xff9bb4000001"
  slice:
    dnn: internet
    network-mode: IPv4
    service-type: eMBB
    differentiator: 0x000000
  radio:
    bands:
      - n78
      - n77
  readiness-check:
    method: ping
    target: google-ip

Handover via xApp

As provided, xApp SDK supports handover xApp in path /src/usr/python3/ho.py.

# Example of ho.py
import sys
import xapp_usr_sdk as xapp

xapp.init(sys.argv)
nodes = xapp.e2_nodes(xapp.HAND_OVER_USE_CASE_e)
assert(len(nodes) > 0 and len(nodes) < 3 and "Needed at least 1 or 2 E2 nodes to handover")

sum_ue = 0
for idx in range(len(nodes)):
sum_ue += len(nodes[idx].ue_ho)
assert(sum_ue > 0 and "At least one UE needed")

idx = 0 if len(nodes[0].ue_ho) > 0 else 1
n  = nodes[idx].node
ue = nodes[idx].ue_ho[0].ue
ho_pci = nodes[idx].ue_ho[0].nghbr_cell[0].target_pci
ho_ssb = nodes[idx].ue_ho[0].nghbr_cell[0].target_ssb_nr_arfcn

xapp.hand_over(n, ue, ho_pci, ho_ssb)

Simple step by step to interact xApp with the cluster

1. Build the project following README.md file

2. Bind flexric IP with xApp

cd  xapp_sdk/conf/

python3 update_conf.py

# It should show this
# Select the RIC to configure:
#  1) flexric.flexric.handover (10.244.2.46)
# Choice [1-1]: 1
# No entries found for Database.
# Skipping database IP update.
# Config 'xapp.yaml' updated: ip_ric=10.244.2.46, ip_xapp=10.244.0.158

3. Run the xApp

cd build/src/usr/python3

python3 ho.py ../../../conf/xapp.yaml