Adjacent and co-channel interference in crowded public areas (stadium, arenas, shopping malls, airports, etc.) or residential areas (neighbours’ AP, microwave ovens, cordless phones, Bluetooth devices, etc.) should also be considered as another source of interferences. If the Signal to Noise Ratio (SNR) decreases below average, retry attempts ramp up. It is needless to say that non-Wi-Fi interferences are one of the main reasons for corrupting frames.

And, by the time the reply reaches the AP, the signal might be too low for the AP to actually be able to decode the frame, therefore generating a retransmission. Indeed, when the client devices will be farther away from the AP, it will still be able to “hear” the AP quite well however, it won’t have enough power to respond back to the AP. This could appear like a good idea to maximize the coverage area of the AP, however, this can also generate retransmissions. Some network operators set the transmit power of the APs to the maximum. Some retransmissions could be generated when an AP is set to transmit with the highest power available and the client cannot match the same transmit power levels.

Therefore, these frames are likely not to be acknowledged, resulting in re-transmissions. This might be due to not having a proper received signal strength and some frames not being properly decoded in both uplink and downlink communications. Client stations often stubbornly stick to an AP and do not roam to the others.

Wireshark retransmission