IEEE 802.11n 23456789:%; ?@AB @(MAC) CD6A-MSDU(Aggregate-MAC Service Data Unit)EA-MPDU(Aggregate-MAC Protocol Data Unit)FG%HIJ. KLM(, A-MPDU&3G*+;NO$%;P A-MSDUQJ56789RNQ#HIJ. STUA-MPDUV3G*+;NO$WXYA-MPDU Z[MPDU\;V MPDU !\;QJ 6MPDU]^&_>(dummy) MPDU.`ab(delimiter)cV(.d*+efghP 789i%jk#lm%noJ. pXk; qrs%;<%=A-MPDU Z[MPDU\;V MPDU !\;QJ 6]^A-MPDU Z[MPDUV`ab(Ftu2- , ;{*+, 6e|A-MPDU}r~*+%HI~ %&*+, &*+#\;V MPDU !\;QJ 6]^- MSDU*+MSDU%=*+dJ. pX d*+, #;{*+, QJ_6789RNVJ.AbstractIn IEEE 802.11n WLANs(Wireless Local Area Networks), to support high throughput, MAC(Media Access Control) layer adopts A-MSDU(Aggregate-MAC Service Data Unit) and A-MPDU(Aggregate-MAC Protocol Data Unit). Generally, as the A-MPDU uses a selective retransmission capability, A-MPDU provides higher throughput than A-MSDU. However, although A-MPDU uses the selective re-transmission capability, if the size of MPDU within A-MPDU is smaller than the size of minimum MPDU starting spacing, A-MPDU can reduce throughput because of the overhead of retransmission owing to the addition of delimiter, that is a dummy MPDU. Therefore, to overcome the above problem, two-level Aggregation method, where the small MPDU within A-MPDU is replaced by not delimiter but A-MSDU, has been introduced. In the two-level Aggregation method, the existing re-transmission scheme retransmits only A-MPDU, but if the size of retransmission data is smaller than the size of the minimum MPDU starting spacing, the proposed retransmission scheme retransmits the aggregated retransmission data and MSDUs. Therefore, we know that the proposed retransmission scheme have better throughput that the existing retransmission scheme.Keywords: IEEE 802.11n, A-MPDU, A-MSDU, Retransmission, Two-level Aggregation, Throughput (Regular Paper) 20 2, 20153(JBE Vol. 20, No. 2, March 2015)http://dx.doi.org/10.5909/JBE.2015.20.2.300ISSN 2287-9137 (Online) ISSN 1226-7953 (Print)