A fragmentation threshold is dynamically determined based on a current transmission rate. A medium access control (MAC) service data unit (MSDU) is received, and it is determined whether a length of the MSDU exceeds the fragmentation threshold. The MSDU is fragmented into multiple MAC protocol data units (MPDUs) when it is determined that the length of the MSDU exceeds the fragmentation threshold, whereas an MPDU that includes the MSDU is generated when it is determined that the length of the MSDU does not exceed the fragmentation threshold.