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Commonly confused · Wireless & Mobility

Co-Channel vs Adjacent Channel Interference: What's the Difference?

Co-channel interference happens when nearby APs and clients share the same channel and must take turns, wasting airtime. Adjacent channel interference happens when nearby devices use overlapping channels, such as 1 and 3 in 2.4 GHz, so their transmissions corrupt each other.

Co-Channel Interference (CCI)

Full definition
vs

Adjacent Channel Interference (ACI)

Full definition
Co-Channel InterferenceAdjacent Channel Interference
CauseSame channel reused too close togetherPartially overlapping channels nearby
EffectContention; devices defer, throughput dropsCorrupted frames, retransmissions, errors
Protocol handles it?Yes, CSMA/CA coordinates accessNo, signals are seen as noise
SeverityBad but cooperativeUsually worse
FixLower power, better channel reuse plan, more channels (5/6 GHz)Use only non-overlapping channels (1, 6, 11 in 2.4 GHz)
Common inDense deploymentsPoorly planned 2.4 GHz networks
Remember it

Co-channel means waiting in line; adjacent channel means talking over each other.

Exam tip

Questions often show APs on channels 1, 3, and 6 and ask what is wrong (adjacent channel interference). The fix is a 1-6-11 plan in 2.4 GHz.

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