Wi-Fi Modules in Dense Deployments Where Throughput Collapses
Wi-Fi throughput collapses in dense deployments when preamble misses and conservative energy detection thresholds trigger retry storms and modulation rate decay.
Hidden Node
Meaning
Communication bottleneck where two devices can communicate with a central access point but cannot hear each other. The hidden node issue leads to packet collisions because neither device can detect that the medium is busy. This situation is common in outdoor environments or buildings with thick walls.
Collision Mechanism
Simultaneous transmissions from two nodes arrive at the access point as garbled noise. Because of the hidden node, the standard carrier sense mechanism fails to prevent the conflict. The access point is unable to decode either message.
This results in repeated retransmissions that further degrade the network efficiency.
Resolution Protocol
Request to Send and Clear to Send exchanges provide a way to reserve the airtime. When a device uses these frames, the hidden node is informed of the upcoming transmission by the access point. This handshake reduces the probability of collisions at the cost of some overhead.
It ensures the medium is clear before the large data payload is sent.
Performance Cost
Total network throughput decreases as the time spent on handshaking increases. However, in environments with a heavy hidden node presence, the gain in reliability outweighs the loss in speed. Network planning and antenna placement aim to minimize these blind spots.