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Base station and UEs

As a first step, set the parameters of the radio_interactive.conf on ALL scope nodes (gNB and the two UEs) as those of this file (you can use scp to copy the file, or nano/vim to edit the file). Or, you can use this code below:

cat > /root/radio_api/radio_interactive.conf << EOF
{
  "capture-pkts": "False",
  "colosseumcli": "True",
  "generic-testbed": "False",
  "iperf": "False",
  "users-bs": "3",
  "write-config-parameters": "True",
  "network-slicing": "True",
  "global-scheduling-policy": "0",
  "slice-scheduling-policy": "[0, 0]",
  "tenant-number": "2",
  "slice-allocation": "{0: [0, 8], 1: [9, 16]}",
  "slice-users": "{0: [2], 1: [3]}",
  "custom-ue-slice": "True",
  "force-dl-modulation": "False",
  "heuristic-params": "{'buffer_thresh_bytes': [1000, 2000], 'thr_thresh_mbps': [0.25, 0.75]}",
  "bs-config": "{'dl_freq': 980000000, 'ul_freq': 1020000000, 'n_prb': 50}",
  "ue-config": "{'dl_freq': 980000000, 'ul_freq': 1020000000, 'force_ul_amplitude': 0.9}"
}
EOF

Start the SCOPE Base Station

On one of the two BS terminals we start the SCOPE base station on the first node of the reservation and pass the configuration of the base station through the radio_interactive.conf file located in the ~/radio_api directory. Note that the base station application will only start if this is the first node in the reservation, otherwise a UE application will start. In the SCOPE node, type the following commands which will take care of starting the base station and the core network applications in a tmux session (a cheatsheet for tmux can be found here).

cd radio_api/
python3 scope_start.py --config-file radio_interactive.conf
tmux a

Start the SCOPE UEs

After the BS starts, we can start the UEs. We use the same steps as before. Run the following commands on the terminal of the second and third SRNs of your reservation, under the image scope-with-e2.

cd radio_api/
python3 scope_start.py --config-file radio_interactive.conf
tmux a

Exchange traffic between base station and UEs

Now that we have instantiated a cellular network on Colosseum, we will exchange traffic between BS and UEs.

  1. We will use the ping command to confirm reachability of BS and UEs:
    • Open a terminal on the base station and ping the IP address of the UEs: ping 172.16.0.2 and ping 172.16.0.3
    • Open a terminal on the UEs and ping the IP address of the base station: ping 172.16.0.1
  2. We will use the iperf3 tool to exchange TCP/UDP traffic between base station and UE:
    • Open a terminal on each UE and start an iPerf3 server: iperf3 -s
    • Open two terminals on the BS and start an iPerf cliend for each UE: iperf3 -c 172.16.0.2 and iperf3 -c 172.16.0.3
    • You should see TCP packets being exchanged for 10 seconds. Compare the transmit and receive rates at the base station and UE
    • Now do the same but with UDP (parameter -u in iperf3) and with different source rates (parameter -b in iperf3) and compare the transmit/receive throughput and packet losses (where X is the last octect of the UE IP address):
      • 0.5 Mbps: iperf3 -c 172.16.0.X -u -b 0.5M
      • 2 Mbps: iperf3 -c 172.16.0.X -u -b 2M
      • 5 Mbps: iperf3 -c 172.16.0.X -u -b 5M

Configuring Network Slicing and Scheduling

The slicing configuration specified in the radio_interactive.conf is loaded at the BS start-up time. This is passed in the form of {slice_num: [lowest_allowed_rbg, highest_allowed_rbg], ...}`` (inclusive). E.g., {0: [0, 3], 1: [5, 7]}`` assigns RBGs 0-3 to slice 0 and 5-7 to slice 1. The SCOPE APIs then write the passed configuration on configuration files (e.g., on this file for slice 0), one per each slice. These slicing parameters are periodically reloaded from file. The frequency at which they are reloaded can be modified through the variable line_change_frequency_ms in `../radio_code/srsLTE/srsenb/src/stack/mac/scheduler_metric.cc`, function `dl_metric_rr::sched_users`. In each of these files, slicing is specified as a 0-1 bitstring, where a `0` means the RBG cannot be used, and `1` that if can be used for transmissions. As an example, the string `1111110000000000000000000` would allocate RBGs 0-5 to the slice.

Similarly, the scheduling can be tuned among the round-robin (corresponding to policy 0), waterfilling (1), and proportional fairness (2) scheduling policies. They are written on this file, one entry per slice. This file is also reloaded periodically. If slicing is not used, instead, the global slicing policy can be set in this file.

Data collection for AI training and data analytics

KPIs are periodically (e.g., every 250 ms) written on file in the folder ~/radio_code/scope_config/metrics/csv for the gNB only (an example is shown here directory), one file per user, named <ue_imsi>_metrics.csv, where ue_imsi is the IMSI of the UE. Valid UE IMSI for this exercise should be 001010123456002 and 001010123456003, you can ignore files for which the IMSI value only has 2 or 3 digits. The E2 agent of the O-DU peridically reads user KPIs from these files and sends them to the E2 termination of the near-real-time RIC, and eventually to the xApp.