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.