Simulation Visualizations

System-level simulations model multinode networks with nodes modeling protocol stack that includes physical (PHY), medium access control (MAC), and radio link control (RLC) layers. You can model NR cells using the 5G Toolbox™ and evaluate the network performance with different MAC scheduling strategies and PHY algorithms. You can also measure metrics like throughput, scheduling fairness, block error rate (BLER), and spectrum efficiency, and use visualization capabilities to analyze the performance of the network.

This topic page explains the visualizations with respect to a sample 5G NR cell consisting of a set of user equipments (UEs) connected to a gNB. These are some of the elements you can customize in a simulation.

Configuration parameters for each layer
Scheduling strategies
PHY layer — Passthrough PHY layer (for faster MAC focused simulations) or real PHY layer
Channel impairments

Visualizations

These run-time visualizations display the network performance metrics.

Cell Performance Metrics

This figure includes four plots that display these uplink (UL) metrics.

UL throughput for each UE and the cell. This value includes both new transmissions and retransmissions.
UL goodput for each UE and the cell. This value includes new transmissions only.
Resource share percentage among the UEs with respect to the total UL resources. This value represents the fairness of UL scheduling.
Pending UL buffer status of the UEs to determine whether the UEs are getting sufficient resources.

UL Cell Performance Metrics

Similar to the UL metrics visualization, this figure includes identical plots that display the downlink (DL) metrics.

DL Cell Performance Metrics

Set the NumMetricsSteps parameter to configure the number of times the plot updates for an entire simulation. These metrics plots update for every metricsStepSize slots, where metricsStepSize is equal to the total slots in the simulation time divided by NumMetricsSteps.

Note

NumMetricsSteps parameter also configures the plot update times for RLC Metrics and Block Error Rate Metrics in an entire simulation.

The peak spectral efficiency value is calculated using the following formula:

$S E p = \frac{v l a y e r s * Q m * f * R \max * \frac{N_{P R B}^{B W_{μ}} * 12}{T_{s}^{μ}} * (1 - O H)}{B W}$

where:

v_layers is the maximum number of layers.
Q_m is the maximum modulation order.
f is the scaling factor and is assumed as 1.
R_max = 948∕1024
$N_{P R B}^{B W_{μ}}$ is the maximum resource block (RB) allocation in the bandwidth with a subcarrier spacing of μ.
$T_{s}^{μ}$ is the average orthogonal frequency division multiplexing (OFDM) symbol duration in a subframe.
OH is the overhead calculated as the average ratio of the number of occupied resource elements (REs) to the total number of REs in effective bandwidth time product. For these metrics visualizations, OH is assumed to be 0.
BW is the UE-supported maximum bandwidth in the given band.

For more information, refer to 3GPP TR 37.910 Section 5.1.1 [1].

The maximum achievable throughput corresponds to the numerator in the above formula and is shown with a dashed line in throughput and goodput plots.

RLC Metrics

These two subplots show the number of bytes transmitted by the RLC layer per logical channel for each UE in the UL and DL direction, respectively. As described in Cell Performance Metrics section, NumMetricsSteps parameter configures the number of times the plot updates for an entire simulation.

Pass a value of 0 or 1 to hNRMetricsVisualizer constructor to toggle the display of the plot before the start of a simulation. A value of 1 enables this metrics plot. A value of 0 disables this metrics plot.

RLC metrics plots showing the number of bytes transmitted by the RLC layer per logical channel for each UE in UL and DL direction

Block Error Rate Metrics

These two subplots show the block error rates (BLER) observed for each UE in the UL and DL direction, respectively. As described in Cell Performance Metrics section, NumMetricsSteps parameter configures the number of times the plot updates for an entire simulation.

PHY metrics displaying the BLER for each cell in UL and DL direction.

Resource Grid Allocation

This 2-D time-frequency grid shows the resource allocation to the UEs on a frame-by-frame basis. The hybrid automatic repeat request (HARQ) process for the physical uplink shared channel (PUSCH) and physical downlink shared channel (PDSCH) assignments is also shown alongside with the radio network temporary identifier (RNTI) of the UEs. New transmissions are shown in black and retransmissions are shown in blue using the HARQ process ID of each UE. Using the HARQ ID, you can map a retransmission assignment to its previously failed transmission.

You can visualize the resource allocations for a selected RB range from the drop down present in the top left of the plot.

The plot is updated for each frame and shows the RB allocation to the UEs in the last complete frame.

Set simParameters.RBVisualization parameter to toggle the display of the plot before the start of a simulation. A value of 1 enables this metrics plot. A value of 0 disables this metrics plot.

Resource grid assignment for UEs alongwith their HARQ process ID.

Channel Quality

This figure shows the channel quality index (CQI) of the UEs in a selected frame number over the PUSCH or PDSCH bandwidth. You can select and visualize the CQI values of 20 RBs at a time from the drop down present in the top left of the plot.

The plot is updated for each frame.

Set simParameters.CQIVisualization parameter to toggle the display of the plot before the start of a simulation. A value of 1 enables this metrics plot. A value of 0 disables this metrics plot.

CQI visualization for a selected frame number for all UEs.

Results

At the end of the simulation, you can compare the achieved value for system performance indicators to their theoretical peak values considering zero overheads.

Performance indicators displayed in this sample result summary are achieved data rate (UL and DL), achieved spectral efficiency (UL and DL), and BLER observed for UEs (DL and UL). The peak values are calculated as per 3GPP TR 37.910 [1].

Peak UL Throughput: 124.42 Mbps. Achieved Cell UL Throughput: 27.44 Mbps
Achieved UL Throughput for each UE: [9.66        9.22        8.12        0.44]
Achieved Cell UL Goodput: 27.44 Mbps
Achieved UL Goodput for each UE: [9.66        9.22        8.12        0.44]
Peak UL spectral efficiency: 24.88 bits/s/Hz.
Achieved UL spectral efficiency for cell: 5.49 bits/s/Hz 

Peak DL Throughput: 62.21 Mbps. Achieved Cell DL Throughput: 36.06 Mbps
Achieved DL Throughput for each UE: [10.73         9.85         9.14         6.34]
Achieved Cell DL Goodput: 36.06 Mbps
Achieved DL Goodput for each UE: [10.73         9.85         9.14         6.34]
Peak DL spectral efficiency: 12.44 bits/s/Hz.
Achieved DL spectral efficiency for cell: 7.21 bits/s/Hz

Block error rate for each UE in the uplink direction: [0  0  0  0]
Block error rate for each UE in the downlink direction: [0  0  0  0]

Post-Simulation

Logs of the simulation are available after the entire simulation is run. You can run the script NRPostSimVisualization to get a quick post-simulation visualization of the logs.

In the post-simulation script, the variable LogReplay provides these options to display Resource Grid Allocation and Channel Quality figures.

Set LogReplay to true for a replay of the simulation logs.
Set LogReplay to false to analyze the details of a particular frame or a particular slot of a frame. In the Resource Grid Allocation window, input the frame number and slot number to visualize the resource assignment of the particular slot, if scheduling type is symbol-based. For slot-based scheduling, enter the frame number to visualize the resource assignment for the entire frame. The frame number entered here controls the frame number for Channel Quality figure too.

References

[1] 3GPP TR 37.910. “Study on self evaluation towards IMT-2020 submission.” 3rd Generation Partnership Project; Technical Specification Group Radio Access Network.