Adaptive two-level frame aggregation in IEEE 802.11n WLAN

In order to reduce the overhead of legacy WLANs, the IEEE 802.11n standard defines two aggregation schemes, i.e., A-MSDU and A-MPDU. In general, A-MPDU outperforms A-MSDU due to its selective retransmission capability. However, A-MPDU has a fundamental restriction on the minimum separation in time between the start of two consecutive subframes carried on the same A-MPDU. If such a gap is smaller than the minimum MPDU start spacing of the receiver, the sender should insert additional padding, thus resulting in throughput degradation. The main contribution of this paper is that we provide an adaptive aggregation scheme in which the sender conveys A-MSDUs within A-MPDUs in an adaptive manner, in order to resolve this potential problem in A-MPDU. Our analytical and simulation results demonstrate that the proposed scheme improves throughput performance over A-MPDU and A-MSDU by up to 280% and 19%, respectively.