The impact of multi-rate operation on A-MSDU, A-MPDU and block acknowledgment in greenfield IEEE802.11n wireless LANs

In IEEE 802.11 wireless LANs, stations are able to send data on the channel using different data rates. A station falls back to a lower transmission rate when the channel quality deteriorates. Stations transmitting at a low data rate severely degrade the overall performance of the system and penalize stations transmitting at the full rate. In spite of the many enhancements that have been introduced on the PHY and MAC of the lately standardized IEEE802.11n, this multi-rate performance anomaly has been inherited from the legacy standards and still exists. In this paper we show the impact of this phenomenon on the recently introduced MAC mechanisms of IEEE802.11n such as block acknowledgment, A-MSDU and A-MPDU. Our analysis is completely based on experiments and driver code modifications using certified IEEE802.11n equipments.