AMPDUApplication Message Protocol Data Unit
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In MAC 802.11n, a more efficient frame format developed using the Aggregate MAC Service Data Unit (AMSDU) scheme and the Aggregate MAC Protocol Data Unit (AMPDU) scheme.
Some functions of the AARF-HT algorithm to be tested such as MPDU transmission function using and without using AMPDU, MPDU transmission function using various combination of spatial stream number, Guard Interval size and channel bandwidth size as well as testing controlling the use of 802.11n data rate according to channel condition for resulting in optimal throughput.
MAC AP and STA support AMPDU with a maximum size of 65535 bytes.
The AARF-HT pseudo code algorithm consists of four parts, the initialization part (lines 2-20), the functioning part of the successful transmission of MPDU transmission, without or using AMPDU (lines 23-48), the MPDU/AMPDU delivery failure checking function section (lines 51-70) and parts of the DataTxVector checking function (lines 72-97).
Additionally we also added the nSuccessfuiMpdus (number of successful transmission of MPDU) and maxAMPDU (maximum size of AMPDU) attributes used when a terminal enables AMPDU transmission mode.
Figure 6 shows the AARF-HT rate adaptation simulation results in the IEEE 802.11n WLAN where MPDU transmission is performed without using the AMPDU scheme.
Therefore, each MPDU included in the AMPDU can be acknowledged uniquely and again provides more advantages.
Similar to the A-MSDU frame aggregation, each AMPDU subframe that is destined to the same receiver must be included in the same A-MPDU frame.
The frame corruptions are handled with minimum retransmission overhead in AMPDU scheme compared to A-MSDU because A-MSDU causes retransmission of whole aggregated frame in case of frame corruptions.
In contrast, higher reliability measures taken by AMPDU scheme is capable of providing higher average packet delivery performance.
To investigate the effect of frame aggregation on the quality of voice applications, we modify the implementation of AMPDU module.