Wireless Advanced Settings · Topic 2 of 6
Adaptive Noise Immunity and Tuning Settings
Learn what adaptive noise immunity does on RouterOS wireless interfaces, when to enable it, and how to test the effect on signal, noise and CCQ in a lab.
- 4 min
- Adaptive noise immunity adjusts the receiver to cope with noise.
- The setting is
adaptive-noise-immunitywith the valuesnone,client-modeandap-and-client-mode. - It can lower sensitivity to very weak signals, so it is not always a gain.
What it is
Adaptive noise immunity is a receiver feature that adjusts the radio to cope better with noise.
A wireless receiver must pick a weak wanted signal out of background energy. If the noise is high, the receiver can be confused, and it may lose frames it could have decoded.
With adaptive noise immunity on, the driver changes receiver thresholds as noise conditions change. It is meant for places where interference is steady or varies often.
How it works
You choose where the feature is active, then measure whether it helps.
The setting
The feature is a property of the wireless interface:
/interface wireless set wlan1 adaptive-noise-immunity=ap-and-client-mode
/interface wireless set wlan1 adaptive-noise-immunity=client-mode
/interface wireless set wlan1 adaptive-noise-immunity=none| Value | Meaning |
|---|---|
none | The feature is off |
client-mode | The feature is used when the interface is a client |
ap-and-client-mode | The feature is used in both roles |
It works on cards and drivers that support it. On other cards the setting has no effect.
What it does for you
The radio can raise or lower its sensitivity to match the noise. With very high noise, it can ignore some low energy that is not a real signal. That improves the chance that real frames are decoded.
There is a trade off. Tuning for noise can lower the sensitivity to very weak signals. On a quiet long link, the feature may do more harm than good.
When to use it
Try it in these situations:
- The noise floor is high or changes often.
- Many clients show retries even though the signal looks good.
- The link shares the air with other radio systems.
Avoid it, or compare carefully, where the link depends on picking up very weak signals in a quiet place.
Decide by measurement. Turn the feature on, wait, and compare CCQ and retries with the earlier numbers.
Measuring the effect
A fair test changes one thing and watches the same numbers before and after:
- Note the noise floor,
signal-strength,tx-ccqandrx-ccqfor a test client. - Note the ratio of
hw-framestoframes. - Set
adaptive-noise-immunityand wait for several minutes. - Read the same numbers again and compare.
- Keep the setting only if the numbers are clearly better.
Use the registration table and the monitor command to collect the numbers:
/interface wireless registration-table print stats
/interface wireless monitor wlan1Other tuning settings
Several other advanced settings affect how well a link behaves. These are worth knowing by name:
| Setting | What it influences |
|---|---|
preamble-mode | Whether short or long frame preambles are used. Short is faster, but it is less compatible with old devices |
disconnect-timeout | How long a silent client is kept before it is removed |
max-station-count | How many clients the interface accepts |
multicast-helper | How multicast traffic is converted for the wireless side |
hide-ssid | Whether the SSID is left out of beacons |
Treat each one as a tool for a stated problem, not as a general speed up.
Order of work
When a link has problems, work in this order:
- Fix the physical layer first, such as alignment, cables and antennas.
- Choose a clean frequency with the scan and frequency monitor.
- Check the ack timeout and the distance.
- Only then try the advanced tuning, such as noise immunity and hardware protection.
Advanced settings cannot hide a poor physical link. They can help a good link cope with a difficult place.
Do not copy settings from another site without understanding them. Noise conditions differ, and the best value at one place can hurt at another.
What to remember for the exam
Six facts cover this topic.
- Adaptive noise immunity adjusts the receiver to cope with noise.
- The setting is
adaptive-noise-immunitywith the valuesnone,client-modeandap-and-client-mode. - It can lower sensitivity to very weak signals, so it is not always a gain.
- It works only on cards and drivers that support it.
- Measure the noise floor, CCQ and retries before and after to judge it.
- Fix the physical link and the frequency before you tune advanced settings.
Common mistakes
Four errors are typical.
Turning it on everywhere. On a quiet long link it can reduce the ability to hear weak signals.
Judging by feel. Without before and after numbers you cannot tell if it helped.
Tuning before fixing the basics. Alignment, frequency and timeout come first.
Expecting an effect on every card. Cards without support ignore the setting.
Check yourself
Work through these three questions.
What does adaptive noise immunity do?
It adjusts the receiver so it copes better with noise. This can improve the delivery of real frames on a noisy channel.
What is the trade off of using it?
Tuning for noise can lower the sensitivity to very weak signals. On a quiet long link it can do more harm than good.
How should you decide whether to keep it on?
Compare the noise floor, CCQ and retries before and after, and keep it only if the numbers are clearly better.
Topic 2 of 6 in Wireless Advanced Settings
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