Wi-Fi Troubleshooting Guide

Testing Wi-Fi is challenging! There are many variables to consider and no two setups and environments are the same. Here are some tips and tricks for troubleshooting Wi-Fi connectivity or performance issues and improving your Wi-Fi test setup.

Check the antennas

The first step in troubleshooting Wi-Fi connectivity or performance issues is to check the antennas.

QA Cafe provides antennas with all NTA systems. These antennas are specifically chosen to match the capabilities of the installed cards. Whenever possible, use the antennas originally supplied by QA Cafe for your specific NTA. Ensure that all antennas are securely fastened to the RP-SMA connectors on the NTA before attempting any wireless interface tests.

If you are not using the QA Cafe supplied antennas, ensure that the antennas used are rated for the bands being tested. For example, to test in the 2.4 and 5 GHz Wi-Fi bands a dual-band antenna rated for frequencies up to 6 GHz must be used. Likewise, to test in the 2.4, 5, or 6 GHz bands a tri-band antenna rated for frequencies up to 8 GHz must be used. A dual-band antenna should not be used for testing in the Wi-Fi 6 GHz band.

Some NTA versions and systems come with magnetic bases that allow antennas to be positioned remotely for optimal performance. The magnetic antenna bases are optional. For more information, refer to the NTA3000 advanced accessory pack documentation here.

If the Device Under Test (DUT) has external antennas, ensure they are securely attached as well.

Antenna orientation can significantly impact Wi-Fi test behavior and performance. Diversity of orientation is important; avoid having all antennas uniformly aimed. Contact support@qacafe.com with any questions or concerns.

Signals that are hot, hot, hot

Extremely high signal levels can negatively impact Wi-Fi connections and performance.

In some cases, wireless signal levels can be too strong for optimal performance. Monitor signal levels during testing. If the Device Under Test (DUT) and the NTA are very close together, or in a test chamber, consider reducing the wireless radio power levels on the DUT. Changing from “auto” or “high” power to “medium” or even “low” power may improve Wi-Fi reliability and performance.

Note that there are currently no controls within CDRouter to reduce the power level of the NTA’s wireless radios. To easily and uniformly reduce the power levels of the wireless radios in both the DUT and CDRouter, consider purchasing and installing a multi-channel programmable RF attenuator. Simple fixed flat attenuators may also be used but offer much less flexibility and cannot be controlled or modified at all.

If RF attenuators are used, ensure they are rated for the bands being tested. Attenuators should be installed between the NTA RP-SMA connectors and the antennas. Use high-quality coaxial cables with the correct internal and external connectors when installing RF attenuators.

Attenuation values of 10 to 20 dB on all channels should be sufficient for optimal performance in most setups.

Know the DUT’s configuration

The wireless configuration of the DUT is extremely important. Unlike the RF environment, it can be easily controlled, so take advantage of this!

The DUT’s wireless configuration determines how CDRouter’s Wi-Fi clients will behave and what the capabilities and maximum performance of those clients will be. Aside from the RF environment, the DUT’s wireless configuration is the next most important variable to understand and control.

Here are some key parameters to be aware of when configuring wireless on a DUT:

  • Radios: How many independent radios does the DUT have? Is each radio configured with a unique SSID, or is a single SSID shared across all radios? If a shared SSID is used, CDRouter’s clients can be configured to connect to a specific radio or mesh node by specifying the band, using the testvar lanChannel) and/or BSSID, using the testvar lanBSSID of that radio. If testing in open air, avoid connection and congestion issues with the DUT by ensuring all other devices in your environment are configured with unique SSIDs on different channels or turned off.

  • Channels: The IEEE defines several frequency bands for use in Wi-Fi networks. The list of usable channels varies by region. Some channels are dynamic and may only be used if certain conditions are met (DFS). Ensure the DUT uses a valid channel for its region and avoid DFS channels if radar presence is a concern. In most cases, enabling the DUT’s auto-channel selection feature is recommended. Note that CDRouter will operate in DFS channels but does not have test cases for verifying DFS functionality. The default regulatory domain of all systems shipped by QA Cafe is US. To change the regulatory domain, please see this knowledge base article.

  • Wi-Fi Phy Modes: Does the DUT support Wi-Fi 6 (802.11ax)? Wi-Fi 7 (802.11be)? Knowing which modes are supported and enabled on each radio is important as it determines the capabilities and maximum performance of connected clients.

  • Channel Width, Guard Interval (GI), and Spatial Streams: These factors directly correlate to the maximum performance capabilities of connected clients. Reducing the channel width by half reduces the maximum physical layer data rate by half. Likewise, a device with 2 spatial streams will support half the maximum physical layer data rate of a device with 4 spatial streams.

  • Power Levels: In most cases, setting the DUT’s radio power levels to “auto” is recommended. However, in certain situations, it may be necessary to reduce the DUT’s radio power level or add a programmable RF attenuator to the test setup. See the Signals that are hot, hot, hot section for more information.

  • MCS Settings: Modulation Coding Scheme (MCS) encapsulates many Wi-Fi parameters and configuration options into a single index value. The higher the MCS index, the higher the physical layer data rate. If you see MCS index values in the DUT configuration settings, refer to mcsindex.net to understand exactly what they mean.

  • OFDMA, MLO: Advanced Wi-Fi features such as OFDMA and MLO are designed to increase performance and should be transparent in most situations. If in doubt, disable these features on the DUT to see if there is any impact on Wi-Fi functional or performance results.

  • Security Settings: Security modes and settings should be transparent as far as performance testing is concerned. However, connectivity issues may arise due to mismatched security settings or incorrect passwords. CDRouter supports all common wireless security modes and has many advanced configuration options you may want to explore. If testing with WPA or WPA2, be sure to set the testvar wpaKey to the password used by the DUT. If WPA3 is being used, the testvar wpaSaePassword must be used instead.

And remember, the DUT is only one side of the wireless connection. If the DUT supports four spatial streams but the client supports only two, the wireless connection and maximum performance will be limited by the client. It is important to know and understand what the lowest common denominator is.

If wireless connectivity is an issue, focus on the following wireless configuration settings on the DUT:

  1. Radios
  2. Channels
  3. Security Settings

If wireless performance is lower than expected, focus on the following wireless configuration settings instead:

  1. Wi-Fi Phy Modes
  2. Channel Width, Guard Interval (GI), and Spatial Streams
  3. Power Levels
  4. MCS Settings
  5. OFDMA, MLO (and other advanced features)

Note that many DUTs allow radios to be configured independently and that different frequency bands have different maximum data rates. For example, the 6 GHz Wi-Fi band supports channel widths up to 320 MHz, allowing for much higher data rates than the 2.4 GHz band, which only supports channel widths up to 40 MHz.

Consistent CDRouter configs

Your CDRouter configuration must be consistent with the configuration of the DUT. If it isn’t, CDRouter’s LAN clients may not be able to associate or authenticate properly, and performance may not be as high as expected.

Before configuring CDRouter, make sure you understand the DUT’s wireless configuration. At a minimum, you must know the SSID, security mode, and password for the DUT’s Wi-Fi radio. If you are testing a mesh network or are interested in testing over a specific frequency band, you must also know the BSSID, frequency band, or channel of the radio you want CDRouter’s LAN clients to connect to.

For more information and examples of how to configure CDRouter’s wireless LAN interfaces for various modes and security settings, see this knowledge base article.

DUTs that are set for auto channel selection need time to scan the frequency bands and choose an appropriate channel. If you are rebooting the DUT at the start of every test run, add a 120-second delay using the RestartDutDelay testvar to avoid issues with the channel selection process.

Monitor signal levels and statistics

Monitoring Wi-Fi connection statistics is essential when troubleshooting connectivity or performance issues.

Statistics should be monitored on both sides of the connection since only the receiver knows the actual conditions of the RF environment.

CDRouter prints a summary of the association information for each wireless client in the start log. This contains SSID, BSSID, channel, signal, noise, and security information that is useful and important to understand:

 04:37:44.487INFO(lan): Associated (wifi6-ax56)
     ssid="NETGEAR20-6G" bssid=54:07:7d:5f:0e:95 freq/chan=6295/69E signal=-41 dBm noise=-92 dBm
         privacy: 1
         rsn: key-mgmt=SAE pairwise=CCMP-128 group=CCMP-128 mgmt-group=BIP-CMAC-128
              pmkid= caps=PTKSA-RC-0,GTKSA-RC-0,MFPR,MFPC
         wpa: none
         phy: 802.11ax

The DUT should have similar statistics for CDRouter’s connected LAN clients. Additionally, when running wireless performance tests with CDRouter, detailed statistics about the wireless connection are printed for each client, aka “station”, at periodic intervals defined by the perfInterval testvar:

 10:26:34.541INFO(lan): 802.11 station info
     chan-width=320 rx-bitrate=5187.1 tx-bitrate=5764.6
     signal=-30     rx-eht-mcs=12     tx-eht-mcs=13
                    rx-eht-nss=2      tx-eht-nss=2
                    rx-eht-gi=0.8     tx-eht-gi=0.8

These statistics are the heartbeat of the test and indicators of the quality and health of the physical layer connection. CDRouter’s statistics include the following:

  • chan-width: The channel width in MHz. This may be 20, 40, 80, 160, or 320 based on the Wi-Fi phy mode and settings used. The value reported here should match the configuration of the DUT.

  • signal: The receive signal level in dBm, aka RSSI. This article has a great breakdown of how to interpret signal levels, and what is considered good vs bad.

  • noise: The received noise level in dBm. Not all wireless cards support this. If the wireless card used supports it, it will be included in CDRouter’s output. If the wireless card used does not support this, it will be omitted from CDRouter’s output. Noise levels should be significantly less (a more negative number) than signal levels for optimal conditions.

  • tx/rx-bitrate: The transmit or receive bitrate, in Mbps. These values correlate directly to the transmit or receive MCS, NSS and GI which are also reported.

  • tx/rx-eht-mcs: The transmit or receive modulation coding scheme (MCS).

  • tx/rx-eht-nss: The transmit or receive number of spatial streams (NSS).

  • tx/rx-eht-gi: The transmit or receive guard interval (GI).

Understand the wireless statistics and information that is provided by the DUT and CDRouter. Monitor it closely and make sure that it aligns with the configuration of the DUT and CDRouter. If you see fluctuations in performance or connectivity issues, check the statistics and see if the reported MCS or GI are fluctuating as well.

Fluctuations in MCS, GI, etc. at the physical layer may indicate that the RF environment is noisy or congested, or that signal levels are too high or low, and that steps to optimize the environment may be warranted.

When in doubt, upgrade

A new version of CDRouter is released every four weeks and release notes are published on our support site for every release. Upgrading CDRouter is fast and easy using the instructions in our installation and upgrade guide. We recommend keeping your system(s) up to date to ensure that you have access to all new test content, features, functionality, and bug fixes.

We also add new testvars to the configuration file template on a regular basis as new protocols and features are added to CDRouter. If you are using old config files we recommend upgrading them to the latest version using the handy utility documented here. The config upgrade process migrates an existing config to the latest config template and is a great way to stay up to date.

In addition to CDRouter software updates, new NTA operating system images, which we call “golden images” are also released on a regular basis, approximately twice per year. Golden images contain operating system and security updates, new kernels, firmware and drivers, and various other QA Cafe specific OS level enhancements. Golden images have release notes as well. Upgrades require more time and preparation but are still easy and recommended using the instructions here.

Wi-Fi is less efficient than Ethernet

The mcsindex.net site provides a comprehensive table of maximum physical layer data rates for all combinations of Wi-Fi phy mode, channel width, guard interval, and number of spatial streams.

It’s important to remember that the efficiency of Wi-Fi is typically around 65% whereas the efficiency of Ethernet is closer to 95%. This means that the effective throughput, or “goodput”, for a Wi-Fi connection will be much less than the reported physical layer data rate.

For example, assume a Wi-Fi connection has the following characteristics:

Property Value
Phy mode Wi-Fi 7 (802.11be)
Spatial streams 2
Channel width 160 MHz
MCS EHT12
GI 1.6 uS

The reported physical layer data rate will be 2450.0 Mbps. Since Wi-Fi is typically 65% efficient, the expected goodput for this connection will be approximately 1592.5 Mbps and will fluctuate if the GI or MCS change based on the environment and channel conditions.

Compare this to Ethernet where a physical layer data rate of 1000 Mbps for a Fast Ethernet connection will result in an expected goodput of approximately 950 Mbps.

For more information about the theoretical maximum goodput values for Ethernet and Wi-Fi, refer to the CDRouter Performance expansion user guide.

Wired and wireless performance measurements for the NTA3000 are available here.

Summary

  1. Make sure the NTA has suitable antennas securely attached to all RP-SMA connectors.

  2. If measuring the absolute maximum possible Wi-Fi performance throughput in a controlled and consistent way is a key objective, an RF test chamber should be used.

  3. Monitor Wi-Fi signal levels on both the DUT and in CDRouter. Consider adding a programmable RF attenuator if signal levels are very high.

  4. If wireless connectivity is an issue, or if performance is lower than expected, check and verify the DUT’s wireless configuration.

  5. Know and understand the DUT’s wireless configuration and its impact on testing and performance. Optimize the DUT and CDRouter for performance testing if that is a key objective.

Symptom Resolution
Unable to associate with the DUT Step 1: Verify suitable antennas are securely attached to all RP-SMA connectors on the NTA.
Step 2: Verify suitable antennas are securely attached to all connectors on the DUT (if external antennas are provided).
Step 3: Make sure the DUT is located within 10 feet of the NTA.
Step 4: Check the DUT’s wireless radio settings and record the configured SSID(s).
Step 5: Check the CDRouter configuration file and make sure the testvar lanSSID matches one of the SSID values recorded in Step 4.
Step 6: If still unresolved, verify that the NTA wireless interface in use supports the frequency band and channels used by the DUT.
Unable to authenticate with the DUT Step 1: Check the DUT’s wireless security settings and record the security mode and password.
Step 2: Check the CDRouter configuration file and make sure the testvars lanSecurity, wpaMode, and wpaKey or wpaSaePassword match the values recorded in Step 1.
Poor wireless performance Step 1: Verify suitable antennas are securely attached to all RP-SMA connectors on the NTA.
Step 2: Verify suitable antennas are securely attached to all connectors on the DUT (if external antennas are provided).
Step 3: Make sure the DUT is located within 10 feet of the NTA.
Step 4. Check and optimize the DUT’s wireless configuration for performance testing.
Step 5. Optimize the CDRouter configuration for performance testing.
Step 6. Monitor wireless signal, noise, and connection statistics in CDRouter and on the DUT.
Poor wireless performance after optimizing configuration settings Step 1. Optimize the test environment by adding an RF test chamber.
Step 2. Add a programmable RF attenuator if needed.
Other Contact support@qacafe.com for assistance.

Contact support@qacafe.com with any questions. Our support team can also recommend suitable antennas, RF test chambers, and programmable RF attenuators if needed.

Other useful resources

  • NTA3000 data sheet (link) & quick start guide (link)
  • Qualifying Wi-Fi 7 devices webinar (link)
  • Wi-Fi beyond the phy webinar (link)
  • Stability testing series (link)
  • Building an automated test strategy (link)
  • Wi-Fi client scaling (link)
  • Configuring Wi-Fi interfaces in CDRouter (link)
  • FWA testing with CDRouter & Amarisoft (link)
  • mcsindex.net (link)