Channel Overlap Issues
Channel overlap refers to interference issues resulting from multiple access points that are all in range of one another and are configured to use similar wavelengths.
- two types
- co-channel interference (CCI)
- each Wi-Fi channel is a collision domain
- where multiple devices use the same channel,
- there is contention
- wireless devices must use CSMA/CA to find opportunities to transmit
- can be measured as a channel utilization percentage
- can be measured from AP or Wi-Fi analyzer
- a channel should exhibit no more than 50% utilization
- adjacent channel interference (ACI)
- occurs when access points are configured to use different but overlapping channels
- e.g., 1 and 3 in the 2.4 GHz band
- slows down the CSMA/CA process
- raises noise levels
- occurs when access points are configured to use different but overlapping channels
- co-channel interference (CCI)
- one design goal of a multi-AP site is
- create clean basic service areas so
- clients can select an AP with the strongest signal easily
- WLAN operates with minimum co-channel interference
- create clean basic service areas so
- 25 MHz spacing should be allowed to avoid channel overlap
- in practice, up to 3 nearby APs using 2.4 GHz bad can have non-overlapping channels
- e.g., channel 1 for AP 1, channel 6 for AP 2, channel 11 for AP 3
- 5 GHz band and Wi-Fi 4/5/6 have more non-overlapping channels
- may be necessary to adjust power level used by an AP on a given channel
- using max power can result in:
- interfering with other cells
- situations where a client can hear the AP but cannot talk to it bc it lacks power