Lab 3: 5G Data Plane

This experiment is to deploy a simple 5G Standalone (SA) network using OpenAirInterface (OAI) RF Simulator gNB and OAI minimal 5GC, but this time we modify some of the configurations and see the effect on the throughput.

In this lab, you will need two files:

simple-sa.yaml

apiVersion: athena.trirematics.io/v1
kind: Network
metadata:
    name: eurecom
    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
            stack: 5g-sa
            model: oai-ran/monolithic-gnb
            profiles:
                - t-tracer
            identity:
                an-id: 50
            radio:
                device: rf-sim
            cells:
                -   band: n78
                    arfcn: 641280
                    bandwidth: 40MHz
                    subcarrier-spacing: 30kHz
                    tdd-config:
                        period: 5ms
                        dl-slots: 7
                        dl-symbols: 6
                        ul-slots: 2
                        ul-symbols: 4
            core-networks:
                - minimal.eurecom
    core:
        -   name: minimal
            stack: 5g-sa
            model: oai-cn/minimal
            identity:
                region: 0
                cn-group: 4
                cn-id: 5
    dns:
        ipv4:
            default: 8.8.8.8
            secondary: 8.8.4.4
---
apiVersion: athena.trirematics.io/v1
kind: Terminal
metadata:
    name: ue1
    namespace: trirematics
spec:
    vendor: oai
    stack: 5g-sa
    model: terminal/nr-rfsim
    preferred-access: oai-gnb.eurecom
    target-cores:
        - minimal.eurecom
    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
    readiness-check:
        method: ping
        target: google-ip
        interface-name: oaitun_ue0
---
apiVersion: athena.trirematics.io/v1
kind: Terminal
metadata:
    name: ue2
    namespace: trirematics
spec:
    vendor: oai
    stack: 5g-sa
    model: terminal/nr-rfsim
    preferred-access: oai-gnb.eurecom
    target-cores:
        - minimal.eurecom
    identity:
        imsi: "001010000000002"
        pin: "1234"
        opc: "0xc42449363bbad02b66d16bc975d77cc1"
        key: "0xfec86ba6eb707ed08905757b1bb44b8f"
        sqn: "0xff9bb4000001"
    slice:
        dnn: "internet"
        network-mode: "IPv4"
        service-type: eMBB
        differentiator: 0x000000
    radio:
        bands:
            - n78
    readiness-check:
        method: ping
        target: google-ip
        interface-name: oaitun_ue0

sa-data-plane.yaml

apiVersion: athena.trirematics.io/v1
kind: Network
metadata:
    name: eurecom
    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
            stack: 5g-sa
            model: oai-ran/monolithic-gnb
            identity:
                an-id: 50
            radio:
                device: rf-sim
            annotations:
                extras.trirematics.io/min-rxtx: "6"
            cells:
                -   band: n78
                    arfcn: 641280
                    bandwidth: 40MHz
                    subcarrier-spacing: 30kHz
                    tdd-config:
                        period: 5ms
                        dl-slots: 7
                        dl-symbols: 6
                        ul-slots: 2
                        ul-symbols: 4
            core-networks:
                - minimal.eurecom
    core:
        -   name: minimal
            stack: 5g-sa
            model: oai-cn/minimal
            identity:
                region: 0
                cn-group: 4
                cn-id: 5
    dns:
        ipv4:
            default: 8.8.8.8
            secondary: 8.8.4.4
---
apiVersion: athena.trirematics.io/v1
kind: Terminal
metadata:
    name: ue1
    namespace: trirematics
spec:
    vendor: oai
    stack: 5g-sa
    model: terminal/nr-rfsim
    preferred-access: oai-gnb.eurecom
    target-cores:
        - minimal.eurecom
    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
    readiness-check:
        method: ping
        target: google-ip
        interface-name: oaitun_ue0

TDD Pattern

Modify the YAML file to run the following two TDD pattern setups given in the table below. For each of them, calculate the average DL TCP throughput for the duration of 60 seconds.

#	Period	DL Slots	UL Slots	DL Symbols	UL Symbols	Min Rx-Tx Slots
1	5ms	7	2	6	4	6
2	2.5ms	2	2	6	4	4

💬 Questions

1. Draw a figure to show each of the patterns for the duration of one frame.
2. On your figure, specify how the value of the min Rx-Tx slots is calculated.
3. Calculate the total number of symbols in DL and UL per second for each of the patterns.
4. Calculate the ratio of the DL symbols to the UL symbols for each of the patterns.
5. Calculate the DL throughput as megabits per symbol for each of the patterns and justify why the values should be close to each other.

ARFCN Configuration

Consider the following two cells with the following configuration given in the table below. The first cell is an imaginary neighboring cell to the second cell that we are designing.

#	Band	ARFCN	Bandwidth
1	n78	640000	40MHz
2	n48	642000	40MHz

Deploy a modified version of the simple-sa.yaml file that contains the configuration as cell 2 ONLY (no need to create the first cell). Then measure the DL TCP throughput for the duration of 60 seconds for one of the UEs.

💬 Questions Set 1

1. Draw these two cells on a frequency axis. Mark the frequencies in MHz on the axis and show each cell with an interval.
2. Calculate the center frequency of each cell in MHz.
3. How much of the bandwidth in percentage is overlapping between these two cells, causing interference?

To solve the interference problem, we could take two approaches:

1. Decrease the bandwidth of the second cell to avoid the overlapping.
2. Change the center frequency of the second cell to avoid the overlapping.

First go with the first approach and use a 20MHz bandwidth for the second cell. Then measure the DL TCP throughput again for the duration of 60 seconds for one of the UEs.

💬 Questions Set 2

1. Draw these two cells on a frequency axis like before.
2. Compare the throughput with the previous one and explain the difference.
3. Considering both cells, would you consider the total throughput has been increased or decreased?

For the second option, consider the following three ARFCN numbers:

1. 646000
2. 642667
3. 643000

From these three numbers, only one of them is a valid configuration. Try all the three numbers and extract the gNB logs to see if the gNB is able to start or not. If you managed to connect the UE, measure the DL TCP throughput for the duration of 60 seconds for one of the UEs.

💬 Questions Set 3

1. Calculate the center frequency of each option in MHz.
2. Draw these two cells on a frequency axis like before for each of the options.
3. Compare the throughput with the previous ones and explain the differences.

Multiple UEs

In this exercise, you would modify a network configuration. For this, we suggest you to keep two separate files, stage-1.yaml and stage-2.yaml. Create the stage-1.yaml file from the simple-sa.yaml file by removing the second UE and disabling the t-tracer. Move the second UE configuration to the stage-2.yaml file for later use. Deploy the simple 5G-SA network from the stage-1.yaml file. Wait for the UE to be ready and then start a TCP DL throughput test for the duration of 180 seconds by running the following command in a separate terminal window.

cli test throughput ue1 dl --plot -- gateway --time 180

Open a separate terminal window and roughly after 30 seconds, install the stage-2.yaml file WITHOUT uninstalling the network or stopping the first test. After another 30 seconds, in the second terminal, run a TCP DL throughput test for the second UE for the duration of 30 seconds.

Finally, after another 30 seconds, uninstall the stage-2.yaml file first WITHOUT stopping the first test. Let the first test to finish as well and then take a screenshot of the two plots. Uninstall the stage-1.yaml file too.

💬 Questions

1. Explain the pattern seen in the plot for the first UE.
2. Why adding the second UE has caused the throughput of the first UE to drop, even without any traffic for the second UE?