In a first aspect, an aggregated packet (A-MPDU) includes packets (MPDUs) and EC-Blocks (Error Correction Blocks) containing error correction coding information. A transmitter uses a Fountain coding scheme (for example, Raptor or RaptorQ) to generate the error correction coding information from the MPDUs. If a receiver detects an error in a received MPDU, then the receiver uses the error correction coding information from the EC-Blocks to correct the error. In a second novel aspect, a determination is made as to whether a change in error rate is more likely due to collisions or to a low SNR. If the determination is that the change is due to collisions then the MCS index is adjusted to restore a target error rate, whereas if the determination is that the change is due to a low SNR then the number of EC-Blocks per A-MPDU is adjusted to restore the target error rate.