## 5 Performance Evaluation
### Results
Figure 2a,b show that the analytical results corresponding to the saturation network throughput and energy efficiency of all the evaluated mechanisms match the simulation results. In addition, this observation can be made for the rest of the figures presented next. (2) Impact of the MSDU Length  
The saturation throughput and energy efficiency of the evaluated mechanisms with \(\alpha=1\) and \(\alpha=3\) as a function of the MSDU length ranging from 50 bytes to 2250 bytes are shown in Figure 3a and Figure 3b, respectively. Since DCF and PSM show similar saturation performance, the saturation throughput and energy efficiency of DCF and those of PSM are shown together with a single line and marker for the sake of visualization. This is also used for TXOP PSM with \(\alpha=1\) since TXOP PSM performs the same as DCF, with the exception of the saturation energy efficiency of TXOP PSM when \(\alpha=3\) is employed. In what follows, the terms throughput and energy efficiency will be used to refer to the saturation throughput and the saturation energy efficiency, respectively. As it can be seen in Figure 3a, the throughput of the evaluated mechanisms increases as the MSDU length increases since each transmitted data frame includes more information. As in the throughput as a function of the traffic load, DCF, PSM, and TXOP PSM with \(\alpha=3\) outperform these using \(\alpha=1\) for all the MSDU lengths. The throughput improvement ranges from 75% to 24% as the MSDU length increases up to 2250 bytes. This reduction of the throughput improvement is caused by the fact that the longer data frames are the more the data transmission time increases during channel access, thus reducing the influence of the lower channel access overhead enabled by using \(\alpha=3\). For this reason, the increase in energy efficiency for DCF and PSM using \(\alpha=3\) as compared to these with \(\alpha=1\) also ranges from 72% to 22% as the MSDU length increases, as shown in Figure 3b. Figure 3: Saturation throughput and energy efficiency of the evaluated mechanisms with \(\alpha=1\) and \(\alpha=3\) rounds of data transmissions as a function of the MSDU length. (**a**) Saturation throughput. (**b**) Saturation energy efficiency. It can also be seen in Figure 3b that TXOP PSM with \(\alpha=1\) improves the energy efficiency of DCF and PSM for all the MSDU lengths. The reason is that the STAs are not able to microsleep during data transmissions. In addition, TXOP PSM using \(\alpha=3\) achieves energy efficiency increasing at the same rate as that of DCF and PSM until the MSDU length is long enough to enable microsleep operation. This refers to an MSDU length that provides a non-zero microsleep period (\(T_{sl}\)). For TXOP PSM using \(\alpha=3\), this requirement is fulfilled when the MSDU length is above 449 bytes. When the MSDU length increases from such value to 2250 bytes, the energy efficiency of TXOP PSM using \(\alpha=3\) is significantly higher than that of DCF and PSM with an improvement ranging from 39% to 154%. This is due to longer microsleep periods as the MSDU length increases, thus allowing the STAs to sleep for a longer period and save more energy.