5G Onyx Spectrum Analyzer

Introduction

In modern 5G networks, RF performance issues such as interference, improper power control, and spectrum anomalies can significantly impact user experience and overall network efficiency. Traditional troubleshooting methods often require expensive external spectrum analyzers, specialized expertise, and time-consuming site visits.

The Spectrum Analyzer feature in the Onyx 5G platform provides real-time, per-RU analysis and visualization of uplink and downlink power characteristics across the RF spectrum. Integrated directly into the Onyx Portal, this tool enables network operators to monitor signal quality, detect interference, and optimize network performance without requiring external test equipment.

The Spectrum Analyzer offers the following analysis plots:

• Average Power – Displays average power distribution across the frequency spectrum to identify interference sources and power anomalies.
• Maximum Power – Displays peak power levels across frequencies to detect transmission spikes and interference patterns.

This application note describes how to configure and use the Spectrum Analyzer, interpret its visualizations, and apply analysis results to real-world RF troubleshooting and network optimization workflows.

Use Cases

The Spectrum Analyzer supports multiple deployment and operational needs. Understanding when to use it helps optimize network performance and troubleshooting efficiency.

• Pre-Deployment Site Survey – Before activating a site, use the Spectrum Analyzer to assess the RF environment and verify spectrum cleanliness. Enable Listen-Only Mode to perform a passive scan without any gNB transmission.

  • Identify existing interference sources in the target frequency band
  • Validate frequency selection and channel planning decisions
  • Document baseline ambient spectrum conditions before the site goes live
• Interference Detection and Analysis – When experiencing unexplained performance degradation, use the Spectrum Analyzer to identify and characterize interference patterns.

  • Detect narrowband interference from adjacent services
  • Identify wideband interference from faulty equipment
  • Correlate interference patterns with time-of-day or specific events
  • Use the Maximum Power plot to distinguish between sustained interference and transient spikes
• Performance Optimization – Monitor signal quality during network optimization activities to validate configuration changes and parameter adjustments.

  • Verify power control algorithms are functioning correctly
  • Assess impact of TDD configuration changes
  • Evaluate spectrum efficiency
• Troubleshooting and Root Cause Analysis – When KPIs indicate degraded performance, use the Spectrum Analyzer to pinpoint the root cause at the physical layer.

  • Diagnose sudden drops in throughput or connection quality
  • Investigate increased retransmission rates
  • Validate antenna system integrity and RF path quality
  • Compare Average Power and Maximum Power plots to distinguish between sustained and intermittent issues
• Compliance and Validation Testing – Support regulatory compliance verification and acceptance testing procedures.

  • Document baseline RF characteristics for compliance records
  • Verify transmit power levels meet specifications
  • Validate frequency mask compliance and adjacent channel leakage

Listen-Only Mode

The Listen-Only Mode configuration determines whether the gNB transmits during signal analysis. Choosing the correct mode before starting analysis is critical — it determines both what the Spectrum Analyzer can measure and whether the network experiences a service interruption.

CAUTION: In multi-RU deployments with Fronthaul Multiplexer (FHM), selecting a specific RU for analysis will cause temporary service interruption to other RUs regardless of the Listen-Only Mode setting. For production networks, schedule analysis during maintenance windows to minimize impact.

Listen-Only Mode Enabled

When the Listen-Only Mode is enabled, the Spectrum Analyzer disables all gNB transmissions and passively listens to the RF spectrum without transmitting.

Listen-Only Mode causes complete service interruption across the entire cell. The gNB stops transmitting entirely, all connected devices are immediately disconnected, and the network becomes completely unavailable for the duration of the analysis interval. This mode is suitable only for pre-deployment site surveys, scheduled maintenance windows, or inactive test sites where service disruption is acceptable.

Listen-Only Mode is specifically designed for pre-deployment site surveys where you need to assess the RF environment before activating the site. This mode is ideal for:

• Verifying spectrum cleanliness and identifying existing interference sources without your own transmissions masking external signals
• Validating frequency selection decisions
• Hunting for intermittent interference sources
• Performing regulatory compliance testing where documenting ambient spectrum conditions without active transmission is required

In Listen-Only mode, downlink traces are not displayed in the analysis plots as the gNB is not transmitting, downlink measurements would only reflect environmental noise and are suppressed.

Uplink traces may show minimal activity from UE devices attempting random-access connections. As devices gradually lose synchronization with the disabled gNB, this activity decreases over time.

Listen-Only Mode Disabled

When Listen-Only Mode is disabled, the Spectrum Analyzer captures RF data while the gNB continues normal transmission and serves active users. This is the default setting and the recommended mode for all production network analysis.

The network continues serving users normally with no service interruption, and real-world operating conditions are maintained throughout the analysis. This mode is ideal for:

• Observing real traffic patterns and resource utilization with active users
• Verifying power control algorithms with connected devices
• Analyzing performance under actual load conditions
• Troubleshooting issues affecting user experience
• Validating configuration changes in production environments where service continuity is essential

Downlink traces show actual gNB transmission power across the channel, including active resource block allocation patterns and real traffic power distribution.

Uplink traces show power from connected UE under active power control, along with real-time user traffic patterns.

Getting Started

This section describes how to enable and launch the Spectrum Analyzer.

Enable/Disable Spectrum Analyzer

The Spectrum Analyzer must be enabled for the Onyx Edge before it can be launched.

NOTE: You can enable/disable the Spectrum Analyzer feature only if you are a GXC Administrator, GXC Partner Administrator, Super Administrator, or an Administrator.

To enable/disable the Spectrum Analyzer feature for an Onyx Edge:

1

In the navigation pane, click Equipment > Onyx Edge (NR+Core) tab or the Onyx Edge tab.

The Equipment page > Onyx Edge (NR+Core) tab or the Onyx Edge tab displays the summary details of all Onyx Edge (NR+Core) configured in the network.

2

For the Onyx Edge that you want to enable/disable the Spectrum Analyzer feature, in the Onyx Edge (n) panel > Actions column, click the corresponding ⋮ (options) icon, then click Edit.

The Edit Onyx Edge (<onyx edge name>) page is displayed.

3

Click the Others tab.

4

Click the Spectrum Analyzer toggle switch to enable/disable Spectrum Analyzer for the Onyx Edge. Default: disabled.

5

To save your edits, in the upper-right corner of the page, click Save Onyx Edge.

Launch Spectrum Analyzer

After enabling the Spectrum Analyzer, you can launch it from the Onyx Edge's details page.

NOTE: You can launch the Spectrum Analyzer only if you are a GXC Administrator, GXC Partner Administrator, Super Administrator, or an Administrator.

To launch the Spectrum Analyzer:

1

In the navigation pane, click Equipment > Onyx Edge (NR+Core) tab or the Onyx Edge tab.

The Equipment page > Onyx Edge (NR+Core) tab or the Onyx Edge tab displays the summary details of all Onyx Edge (NR+Core) configured in the network.

2

For the Onyx Edge that you want to launch Spectrum Analyzer, in the RAN section > Actions column, click the corresponding ⋮ (options) icon, then click Start Spectrum Analyzer.

The Spectrum Analyzer dialog box is displayed.

3

Configure the following details, then click Start.

• Listen-Only Mode – Specify whether the gNB transmits during signal analysis. Default: Disabled.

  When disabled (default), the analyzer captures RF data while the gNB continues serving active users — no service interruption occurs. When enabled, the gNB stops transmitting entirely and the analyzer passively listens to the spectrum. See Listen-Only Mode for full details before making this selection.
• Analysis Interval – Select the duration for which the analyzer should capture and report data. Default: 5 minutes.

NOTE: Longer analysis intervals consume more system resources and storage. Select the minimum interval needed for your analysis objectives.

• Select RU – Select all available RUs or a specific RU to analyze.

NOTE: In multi-RU deployments with FHM, selecting a specific RU will cause service disruption to other RUs, as their transmission gets disabled during analysis.

NOTE: When using Listen-Only mode or in FHM deployments when selecting a specific RU, allow at least 3 minutes between successive Spectrum Analyzer runs. Starting a new analysis within 3 minutes of the previous run will result in an error.

After you start the analysis, the Spectrum Analyzer requires an initial setup period of up to two minutes to gather and process the data and then display the plots.

The Spectrum Analyzer dialog box opens displaying real-time analysis plots.

Analysis Plots

The Spectrum Analyzer provides two complementary plot types, each offering unique insights into RF performance. Understanding how to interpret these plots is essential for effective network analysis and troubleshooting.

• Average Power – Displays average power distribution across the frequency spectrum to identify interference sources and power anomalies.
• Maximum Power – Displays peak power levels across frequencies to detect transmission spikes and interference patterns.

NOTE: All plots refresh automatically every 10 seconds during active analysis.

NOTE: For deployments with FHM and multiple antennas, the Spectrum Analyzer displays data from all configured antennas simultaneously. The interface presents four antenna plots (Antenna 0, Antenna 1, Antenna 2, and Antenna 3) in a 2×2 grid layout, providing comprehensive visibility across the entire antenna array.

NOTE: In Listen-Only mode, downlink traces are not displayed in the analysis plots as the gNB does not transmit, so downlink measurements would only show environmental noise.

Average Power Plot

Displays the average power distribution across the frequency spectrum to highlight interference sources and power anomalies.

Plot Details

• X-Axis: Subcarrier Frequencies (MHz)
• Y-Axis: Average Power (dBm)
• Orange line: Uplink Average Power
• Teal line: Downlink Average Power

What to Look For:

• Flat, consistent levels across subcarriers indicate healthy signal distribution.
• Sharp spikes at specific frequencies suggest interference from external sources or co-channel interference.
• Significant uplink/downlink imbalance may indicate coverage issues or device power control problems.
• Gradual slopes across the band may indicate filter roll-off or edge-of-band effects.
• Elevated noise floor across the entire band may indicate a broadband interference source nearby.

Interpretation Examples:

• Interference – Periodic spikes every X MHz likely indicate adjacent channel interference.
• Investigate – Average power varies significantly over time—check for intermittent interference sources.
• Normal – Symmetrical uplink and downlink traces with a flat noise floor indicate a clean, well-configured channel.

Maximum Power Plot

Displays peak power levels across frequencies to highlight transmission spikes, interference sources, or power anomalies.

Plot Details

• X-Axis: Subcarrier Frequencies (MHz)
• Y-Axis: Maximum Power (dBm)
• Orange line: Uplink Maximum Power
• Teal line: Downlink Maximum Power

What to Look For:

• Peak-to-average ratio – Difference between maximum and average power indicates signal dynamics
• Narrow spikes suggest narrowband interference (e.g., LTE guard bands, other services)
• Broad elevated regions indicate wideband interference or multipath effects
• Symmetry between UL/DL – Asymmetric peaks may indicate one-way interference
• Use the Maximum Power plot alongside the Average Power plot — an anomaly visible in Maximum Power but not Average Power is likely a transient or intermittent event.

Interpretation Examples:

• Investigate – Max power >30 dB above average may indicate interference or device malfunction
• Interference – Single subcarrier with consistently high max power suggests CW (continuous wave) interference
• Normal – Max power only slightly above average power across all subcarriers indicates a stable channel with no significant interference.

Plot Interactions and Control

The Spectrum Analyzer provides the following interactive controls for detailed examination of plot data.

Interactive Tooltips

The Spectrum Analyzer provides real-time data tooltips that display exact measurements when you hover over the plots.

To view precise frequency and power measurements for any point:

1

Move your cursor over any location on the plot.

A tooltip automatically appears showing:

• Frequency value (in MHz, to two decimal places)
• Signal type (Uplink/Downlink, Avg/Max Power)
• Power measurement (in dBm, to three decimal places)

As you move your cursor across a plot, the tooltip follows your cursor, updating continuously to show values at different frequencies. This feature works on all four antenna plots in both Average Power and Maximum Power views.

Using Tooltips for Analysis

Tooltips are particularly useful for:

• Identifying exact power levels at specific frequencies
• Locating interference sources by frequency
• Comparing power levels between uplink and downlink
• Measuring power differences between antennas at the same frequency
• Pinpointing the exact frequency of a narrowband interference source for use in frequency planning or regulatory reporting
• Documenting specific measurements for reports or troubleshooting

Zoom Into Plots

Zoom functionality is available for all plots. Each antenna plot can be zoomed independently, allowing detailed examination of specific frequency regions across different antennas simultaneously.

To zoom in on a specific region of a plot:

1

On the plot, position your cursor at the desired starting frequency.

2

Click and drag horizontally to the left or right to select the frequency range of interest.

3

Release the mouse button to apply the zoom.

The plot zooms into the selected frequency range, adjusting both the X-axis (frequency) and Y-axis (power) scales to show details in that region.

To reset a plot after zooming in:

In the top-right corner of the plot, click (Reset Zoom). The plot immediately returns to the full frequency range view.

NOTE: In multi-antenna deployments, zoom each antenna plot to the same frequency range to compare power levels across antennas at a specific band. This helps identify antenna imbalances or isolated per-antenna interference.

Analysis Completion

Review the plots before closing — once the dialog is closed, the current analysis data is no longer accessible in the portal.

The Spectrum Analyzer stops automatically when the analysis interval specified at launch expires and displays a completion message.

To close the Spectrum Analyzer, click Stop.

Stop Analysis

To stop an analysis session and close the Spectrum Analyzer:

To stop an analysis session and close the Spectrum Analyzer dialog box, click Stop.

The analysis terminates immediately and data collection stops.

NOTE: After stopping an analysis — whether manually or at interval expiry — allow at least 3 minutes before starting a new session when using Listen-Only mode or when a specific RU was selected in an FHM deployment. Starting a new run within 3 minutes will result in an error.

Related Documentation

• 5G Onyx Portal Operations Guide
• 4G & 5G Survey Solution Application Note
• GXC Glossary

Contact GXC

To get in touch with GXC, please visit https://gxc.io/contact-us/.