# Real-Time Station Grouping under Dynamic Traffic for IEEE 802.11 ah
## 6 Performance Evaluation and Discussion
### Static Traffic Patterns
#### 6.2.1 Without Hidden Node  
Figure 6 depicts the performance of the evaluation metrics (throughput, latency and packet loss) when there are no hidden nodes in the networks for both the HT and LT scenario. For the HT scenario, Figure 5(a) clearly shows that TAROA scales much better than EDCA/DCF in dense networks in terms of throughout. For traffic load \(T\) = 1.2 Mbps, EDCA/DCF achieves throughput 0.909 \(\pm\) 0.010 Mbps and TAROA gets 0.898 \(\pm\) 0.003 Mbps for 32 stations. However, as the number of stations increases to 1024, throughput of EDCA/DCF dramatically decreases to 0.613 \(\pm\) 0.001 Mbps (i.e., \(-\)32%), and TAROA still achieves 0.832 \(\pm\) 0.010 Mbps (i.e., only \(-\)7%). With traffic load \(T\) = 0.85 Mbps, throughput of EDCA/DCF drops by 25% between 128 and 1024 stations, while there is no significant drop for TAROA. For the lowest traffic load \(T\) = 0.75 Mbps, there is no significant difference between TAROA and EDCA/DCF. Figure 5(b) suggests that the packet loss of TAROA is much less than EDCA/DCF in dense networks, which is quite straightforward since TAROA achieves much higher throughput than EDCA/DCF. For traffic load \(T\) = 1.2 Mbps, packet loss of EDCA/DCF increases from 24.24% \(\pm\) 0.87% to 48.87% \(\pm\) 0.12% when the number of stations increases from 32 to 1024, while packet loss caused by collisions increases from 0.16% \(\pm\) 0.01% to 19.81% \(\pm\) 0.24%. While, for TAROA, packet loss increases from 25.15% \(\pm\) 0.28% to 30.62% \(\pm\) 0.71%. With traffic load \(T\) = 0.85 Mbps, packet loss of EDCA/DCF is 20.51% \(\pm\) 0.62% and 25.26% \(\pm\) 0.10%, respectively, for 512 and 1024 stations, 7.43% \(\pm\) 0.27% and 14.62% \(\pm\) 0.13% packets are lost due to collisions. While only 1.58% \(\pm\) 0.09% and 2.62% \(\pm\) 0.27% packet loss occurs with TAROA. For the lowest traffic load \(T\) = 0.75 Mbps, there is no significant difference between TAROA and EDCA/DCF. When using TAROA, no packet loss due to collisions occurred. In terms of latency, Figure 5(c) shows that TAROA also outperforms EDCA/DCF in most dense networks. The latency can be affected by different aspects, and these factors jointly determine the overall latency. First, fierce channel contention increases the time needed to successfully delivery packets to the AP. Second, in TAROA, RAW schedules stations to contend for the channel only at certain times, which extends the queuing time of packets and in turn increases latency. Especially when the traffic load is low and there is little contention, this results in more packets accumulating in the transmit queue. For medium and high traffic load (i.e., \(T=\{0.85,1.2\}\) Mbps), TAROA usually results in improved latency compared to EDCA/DCF for 256 stations or more, due to high contention in the latter. EDCA/DCF only outperforms TAROA for \(T=1.2\) Mbps and 1024 stations, as EDCA/DCF results in a huge amount of dropped packets, artificially lowering the latency. For low traffic loads (i.e., \(T=0.75\) Mbp), however, EDCA/DCF provides a better latency, due to the slotted nature of RAW. Performance for the LT scenario is depicted in Figure 6d-f, revealing similar conclusions in terms of throughput and packet loss scalability as for HT. For a high load of \(T=0.150\) Mbps, EDCA/DCF throughput drops around to 46% between 32 and 2048 stations, while that of TAROA remains constant around \(0.11\pm 0.0002\) Mbps. The figure, however, also shows that EDCA/DCF scales better for low data rates, as throughput under medium load in the LT scenario only decreases with more than 1024 stations (in contrast to 128 in HT). In this case, throughput drops 23% between 1024 and 2048 stations. In terms of packet loss, for traffic load \(T=0.150\) Mbps and \(T=0.110\) Mbps, TAROA performs better than EDCA/DCF withe more than 128 and 1024 stations, respectively. However, as EDCA/DCF scales better for low data rates and TAROA needs to estimate the traffic load of each station, using TAROA results in more packet loss for traffic load \(T=0.110\) Mbps with less than 1024 stations.