Co-Channel Interference
Hidden Node Problem
Figure 4: CCA might cause problems even for far away STAs
The CCA makes 802.11 equipment sensitive to other transmissions. This applies to all RF sig-
nals, not only other 802.11 equipment. If CCA problems occur, it affects the transmission part
of the link between the AP and the handset. If the uplink speech (from the handset) drops, the
problem is near the handset. Check for nearby equipment such as wireless surveillance cam-
eras, Bluetooth gadgets, WiDi devices, ZigBee/Z-wave for HVAC controls, Light controls, and au-
tomation.
Hidden Node Problem
The “Listen before Talk” mechanism, mentioned in
on page 18,
works as long as all STAs in a cell can hear each other. However, when STAs are positioned at
the cell boundaries on opposite sides of the AP, they can not hear each others transmissions.
Therefore if they transmit at the same time, collision is likely to occur at the AP which will not be
able to receive an error free frame from any of the two STAs.
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System Planning, Planning Guide
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