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 performance of two frame aggregation schemes, A-MSDU and A-MPDU, is compared with CSMA/CA with RTS/CTS in underwater acoustic physical medium in our simulations.
Furthermore, among the two frame aggregation schemes, A-MPDU achieves higher throughput compared to A-MSDU. It is due to the frame structure and the block acknowledgement mechanism of A-MPDU; therefore, the reliability of the multiple frames being transmitting in the aggregated frame in A-MPDU is higher under lossy underwater acoustic physical medium.
However, under higher offered loads, A-MPDU frame aggregation gains better throughput than A-MSDU and CSMA/CA without frame aggregation.
It illustrates that A-MSDU performs similar to CSMA/CA with no MAC layer frame aggregations while A-MPSU achieves a higher average packet delivery ratio.
However, for higher network sizes, CSMA/CA without frame aggregation results in a higher end-to-end delay than both A-MSDU and A-MPDU frame aggregation schemes.
Among the two frame aggregation schemes that are well defined in IEEE 802.11n amendment, A-MPDU aggregation scheme achieves better results with acoustic channels as compared to A-MSDU aggregation scheme.
Among various other MAC and physical layer enhancements, the two frame aggregation schemes, namely, A-MSDU and A-MPDU, are the key focus of this research on underwater acoustic sensor networks.
To this implemented module, we added the A-MSDU scheme.
A-MSDU scheme is used for voice being more adequate for applications that have small frame size .
Hamid, "An enhanced A-MSDU frame aggregation scheme for 802.11n wireless networks," Wireless Personal Communications, (2011) 1-24.
Simulation parameters Parameter Value DIFS (Data inter frame space) 60 [micro] s SIFS (Short inter frame space) 20 [micro] s PIFS (point inter frame space) 40 [micro] s Slot time 20 [micro] s Propagation delay 1 [micro] s Beacon internal 100ms Delay bound 100ms Priority class 6(VoIP), 5(Video), 0(Data) Mean data rate 64 kbps(VoIP), 375 kbps(Video) Maximum MSDU size 60 bytes(VoIP), 1000 bytes(Video, Data) MAC header 34Bytes Sub-frame header in A-MSDU
14 Bytes PHY Rate 54Mbps ACK, CTS 112 bits + MAC header RTS 160 bits + MAC header Fig.