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airMAX - How to Troubleshoot Poor Throughput


Users will be guided through various features, settings and troubleshooting steps to improve airMAX M and AC throughput when they are experiencing slow network speeds.

NOTES & REQUIREMENTS:This article applies to airMAX M and airMAX AC devices.

Table of Contents

  1. Troubleshooting Steps to Find Cause of Low Throughput
  2. Testing Throughput Correctly
  3. Related Articles

Troubleshooting Steps to Find Cause of Low Throughput

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This section lists a series of configuration elements to check. After each one, you may verify the throughput or wait until completing the five steps before testing for throughput again. Be sure to read the Testing section of this article which explains how to test for throughput effectively.

1. Confirm all devices in the network are running the latest firmware. Find firmware releases in our downloads page, see the Related Articles section below for help on how to select the correct firmware for your device.

2. Make sure Traffic Shaping isn’t enabled. Navigate to the Network tab, and switch to Advanced config mode to confirm that traffic shaping is disabled.

3. Confirm that Max TX Rate is set to Auto in the Wireless tab. Setting the Max TX Rate to anything below 8x (256QAM) will limit the TX performance.

  AC Devices M Devices

Go to the Max TX Data Rate dropdown and select Auto.



M radios operate slightly different than AC for this setting. It is important that Auto is always selected and the highest possible MCS rate selected (Typically MCS 15).



4. Check the Signal to Noise Ratio (SNR) on M devices and Carrier to Interference + Noise Ratio (CINR) on AC devices. If your signal is too low or noise / interference too high, it will reduce your SNR/CINR and overall performance.  Improve the SNR/CINR by increasing signal strength (more TX Output power or gain) or reducing noise / interference. 

5. Make sure all devices in the network are using current wireless encryption options for their wireless security protocol. Both airMAX M and AC radios have hardware acceleration for WPA2-AES which will have no impact on performance. However, airMAX M devices on older firmware could still be using deprecated encryption standards such as WEP, WPA-TKIP or WPA2-TKIP. Any device running these outdated encryption standards will be limited to a Max TX Rate of MCS12, in addition to providing less security. Read more about selecting the best wireless security protocol for your deployment in this article: airMAX - Security Types for airMAX Radio Networks.

6. In cases where noise and interference are low, increasing the channel width will allow for greater throughput capacity. This has the drawback of also increasing your potential for picking up interference from other competing signals, but if you are reaching the limits of your current channel width in a low-noise RF environment then this is a viable way to reach higher speeds and support more clients.

Testing Throughput Correctly

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It is important to isolate where exactly things are slowing down. The method used to test is important: low speeds may not manifest until the entire link is tested from end to end. For example, if one of the radios is only negotiating ethernet at 10Mbps, this will not be visible using the built-in speedtest tool as it only tests between wireless interfaces. Therefore, consider these suggestions when testing:

  • Test each direction separately using the speedtest tool located under the Tools menu. If poor throughput is observed in one direction only, this might indicate interference on the side with low speeds. Use Site Survey and airView to locate possible interfering networks.
  • If low throughput cannot be reproduced when testing wireless to wireless, this might indicate the root cause is on the wired side or after/before the airMAX radios. It is best to rule out all other network devices as a possible bottleneck by using two computers with iPerf3 installed and connected directly to the LAN interface of each radio. See the Related Articles below for more on how to do this.

Related Articles

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airMAX - Testing Throughput with iPerf3

airMAX - Choosing the Correct Device Firmware

airMAX - Security Types for airMAX Radio Networks

airMAX - Improving SNR/CINR

airMAX - Troubleshooting Weak or Fluctuating Signal

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