## 6 Evaluation and Analysis
### Simulation Results
#### 6.3.4 Parameter Effects on Context-Aware Protocol Set  
This section evaluates the context-aware DR-MAC and context-aware DAAM protocol set (Set 9) under different traffic, node density, and node mobility settings. (A) Effects of Traffic Parameters  
In this section, the number of Aml user nodes (N\({}_{\text{ami}}\)), sensor data publishing frequency (D\({}_{\text{freq}}\)), and sensor data packet size (D\({}_{\text{size}}\)) are varied, as shown in Table 6.  
Figure 19a presents the throughput results. It shows that when D\({}_{\text{freq}}\) increases, the throughput expectedly increases, as more bits are being published by sensors and delivered to VB within a given time. For some, it is interesting to note that the highest throughput with D\({}_{\text{freq}}\) = 10 is even higher than the maximum data rate of 250 kbps specified in Section 6.1. This is because the throughput result is \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline N\({}_{\text{ami}}\) & 25, 50 nodes \\ D\({}_{\text{freq}}\) & 0.5, 1, 2, 5, 10 packets per second \\ D\({}_{\text{size}}\) & 512, 1024 bits \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Traffic parameter settings of protocol set 9. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Performance Metric** & **1 st** & **2 nd** & **3 rd** & **4 th** & **5 th** & **6 th** & **7 th** & **8 th** & **9 th** \\ \hline Throughput & Set 9 & Set 8 & Set 6 & Set 7 & Set 3 & Set 5 & Set 4 & Set 2 & Set 1 \\ PDR & Set 9 & Set 8 & Set 6 & Set 7 & Set 5 & Set 3 & Set 4 & Set 2 & Set 1 \\ End-to-end delay & Set 9 & Set 6 & Set 8 & Set 7 & Set 3 & Set 5 & Set 4 & Set 2 & Set 1 \\ Control frames/packets & Set 3; Set 2; Set 1 & & Set 9; Set 6; Set 8; Set 7, Set 5; Set 4 \\ Energy efficiency & Set 3 & Set 2 & Set 9 & Set 8 & Set 6 & Set 5 & Set 7 & Set 1 & Set 4 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Performance ranking. based on the total number of data bits from all data packets received by the VB divided by the simulation duration. However, our VB is not a single node, but a cooperative group of four co-located sensor nodes that share the responsibility of providing context storage and retrieval services. two or more VB nodes may receive concurrently data packets published by other non-VB sensor nodes, resulting in an overall throughput higher than that for a single node. Similarly, when the packet size (D\({}_{\text{size}}\)) doubles, the throughput increases, but only by approximately 50%. This could be due to some congestion-related packet losses in the network, but the loss is not significant enough to reduce the throughput. However, when N\({}_{\text{ami}}\) increases from 25 to 50 nodes while keeping the packet size constant, throughput decreases despite an increase in the amount of sensor data forwarded to the AmI nodes, _i.e._, intelligent agents. This indicates that a serious congestion has occurred, and the network is more sensitive to an increase in the number of AmI nodes than an increase in the packet size. Figure 19b shows the PDR results. It is observed that reasonable PDR, _i.e._, \(>\)50% can be achieved when the sensor data publishing frequency is \(\leq\)2 packets per second. However, at higher publishing frequency, PDR decreases to below 50% for N\({}_{\text{ami}}\) = 50. Similarly, doubling packet size from 512 to  
Figure 19: **(a)** Throughput; **(b)** PDR; **(c)** End-to-end delay; and **(d)** Energy cost performances under traffic parameter effects. 1024 bits decreases the PDR. However, the PDR is not decreased proportionally by half, but up to 13%, and 20%, for N\({}_{\text{ami}}\) = 25, and N\({}_{\text{ami}}\) = 50, respectively. This may explain why the throughput still increases in Figure 19a when the packet size increases for a given number of AmI nodes. Figure 19c shows the end-to-end delay results, which increase with the publishing frequency.