Quiet… Please

Today I am reviewing RF interference during my self study session. I am paying special attention to co-channel interference and adjacent channel interference.

Hello… Hello…

hearing-30097_640Co-channel interference (CCI) can be a menace to any wireless network. The half-duplex conversations are affected by the nuts and bolts of CSMA-CA, allowing only one radio on the same channel at once.

If many… Or sometimes all, of the AP’s are on the same channel the clients (end users) are going to have a bad time. All of the clients and AP’s are trying to get their chance to communicate, but there is a lot of noise. If we reduce the efficiency of this communication requirement by having a poor channel design, we pay with CCI overhead.

Some vendors support algorithms that are built in to reduce the chances of channel related contention. I am from the camp that if you decide to use an automated radio management, that you still need to get your hands dirty – Make configuration optimizations to reduce the chances of CCI and overall noise issues.

Another channel issue is adjacent channel interference. This is caused by overlapping in the frequency real estate and it will raise your duty cycle and retries causing the end user experience to be poor. This problem is going to corrupt layer 2 data transmissions. CCI is bad, but adjacent channel problems are a nightmare and sometimes you do not have control of the offending devices.

There will always be contention over the air for clients and AP’s to communicate efficiently. Sometimes we inherit a poor design… Sometimes we are unable to design as we want because the customer has restrictions. There is usually non 80211 interference to deal with as well.

superhero-304712_640As wireless footprints and requirements expand, we as engineers have an opportunity to come out looking like a superhero by doing a great survey and making the right design decisions before the install.

Proper channel reuse and a good channel plan is the antidote to the concerns noted above. If you decide to use an automated radio management system to control channel reuse, then remember to roll up your sleeves and make configuration changes that give you more control over the automated changes.


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