Enhanced characterization and modeling of A‐MPDU aggregation for IEEE 802.11n WLANs

Abstract

The MAC protocol data unit aggregation (A-MPDU) and Block Acknowledgment (Block Ack) techniques are probably the most relevant 802.11 MAC layer enhancements. In spite of being tremendously studied in the literature, recent research activities have revealed that the available analytical models for those techniques do not capture the impact of the Block Ack window limit on the aggregated frame size. This provokes errors in the estimation of the average aggregation size that raise up to 190% in erroneous environments. Throughout this work, we use Markovian techniques to design a more accurate model for 802.11n MAC layer. Our model reflects the impact of the conventional A-MPDU acknowledgment method on the A-MPDU aggregation size. The accuracy of our model has been validated through ns-3 simulations. A comparison with two analytical models of 802.11n MAC sub-layer has been also carried on. In depth analysis have been conducted to investigate the behavior of A-MPDU aggregation scheme under different channel conditions and its impact on the overall network performance. Assessments have shown that our model is more rigorous than existing models. Besides, we have proved that A-MPDU frame aggregation technique is extremely sensitive to channel conditions variation because of the effect of the Block Ack window limit on the maximum aggregation size. INTRODUCTIONFace to the contemporary trends of applications and developments in actual network technologies like Internet of Things, Fog Computing, VANETs, and 5G networks, the 802.11-based wireless local area networks (WLANs) encounters new challenges. 1,2 Thus many advanced communication techniques have been introduced at the physical (PHY) layer to boost the data rates, such as orthogonal frequency division multiplexing (OFDM), multiple input multiple output (MIMO) technique, beamforming and the use of wider bandwidth. 3,4 However, it has been proved in Reference 5 that the legacy IEEE 802.11 channel access method and the control frame exchange overhead are the major limits to optimize the 802.11-based networks' performance. Therefore the IEEE 802.11n amendment, known also as high throughput (HT) amendment has introduced frame aggregation technique to mitigate to the constraints imposed by the MAC layer specifications and take full benefit from the advanced PHY layer techniques. This technique permits to aggregate many frames as one large frame and to treat them as a single frame during transmission. 2 We distinguish MAC service data unit aggregation (A-MSDU) and MAC protocol data unit aggregation (A-MPDU). The former consists in combining multiple MSDUs of the same 802.11e access category into a single MAC frame (MPDU). Whereas the later is performed at the bottom of the MAC layer, after the insertion of the MAC header and

Framework for Sustainable Wireless Sensor Network Based Environmental Monitoring

“…The general format of a MAC frame is shown in Figure 3. A MAC frame is called MPDU protocols [18]. MAC services are accessed through the MLME SAP.…”

“…The general format of a MAC frame is shown in Figure 3. A MAC frame is called MPDU protocols [18]. The first field in the frame header is the control field.…”

“…The main difference between the two PHYs lies in the frequency band. The 2.4 GHz PHY specifies operation in the ISM band, which is practically available worldwide, while the PHY of the 868/915 MHz band specified operations in the 865 MHz in Europe and 915 MHz in the ISM band in the United States, while mobility between countries is not expected for most network applications [18].…”

“…For example, having low density PHY data in the 868/915 MHz can be occupied for greater sensitivity and coverage areas, thus the number of nodes required to cover a geo-graphical area is reduced, while the upper range transmission in the 2.4 GHz PHY can be used to achieve throughput older and low latency. It is expected that applications are suitable to each PHY and their transmission ranges [18].…”

“…Sustainability 2022, 14, x FOR PEER REVIEW 13 of 29 18. In Figure 17, the red frame is to show the status of network connectivity step by step, the tick appears by itself as soon as the step is completed and the rest uncompleted tasks are not checked.…”