# An Adaptive Delay-Tolerant Routing Algorithm for Data Transmission in Opportunistic Social Networks
## 4 Simulation
### Analysis of Experimental Results  
#### 4.2.1 Algorithm Performance Comparison between Five Routing Algorithms  
Figure 4 plots the total network energy consumption between five routing algorithms for a various number of nodes. As seen in Figure 4, the total energy consumption is proportional to the number of nodes, which is due to the fact that energy assessment mechanisms weed out nodes whose energy levels are below the average level. Since the increasing number of nodes indicates more relay nodes involved in the data transmission process, the total energy consumption consistently and sharply rises up. As a benchmark protocol, Epidemic shows a highest energy consumption (35,000) as the number of nodes increase from 150 to 400. The flooding model adopted in Epidemic is able to realize the frequent data exchange among nodes and maximize the data grouping, which leads to a relatively high energy consumption. DTCM adopts the fuzzy inference system to evaluate the residual energy of nodes and ensure that the next hop has enough energy to process data information, so the energy consumption under DTCM is the lowest among the five routing algorithms. The implementations of P&F and FCNS do not consider the energy control and are based on a complex structure, so the total energy consumption from them is at a mid-horizon as the number of nodes increase from 150 to 400. The Energy consumption from Spray and Wait is slightly superior to that from Epidemic because of the flooding strategy with the control of the number of data packages.  
Figure 5 shows that the comparison on the average remaining cache for per node among the five routing protocols when given the initial cache space is 35 Mb. As shown from  
Figure 4: Energy consumption comparison between five algorithms with various number of nodes.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Environment Setting** & **Description** \\ \hline Simulator & Opportunistic Network Environment (ONE) \\ Mobility model & HCMM (Health Capability Maturity Model) \\ Number of experiments & 80 (16 groups and 5 time for each group) \\ Communication area (m\({}^{2}\)) & 900 \\ Simulation time (h) & 1–8 \\ Number of nodes & 50, 100, 150, 200, 250, 300, 350, 400 \\ Speed of a node (m/s) & 2–20 \\ Cache of a mobile node (Mb) & 10 (Initial value), 15, 20, 25, 30, 35 \\ Size of a message (Rb) & 100 \\ Energy consumption of single delivery (J) & 10 \\ Total network energy (J) & 48000 \\ Consumption of a transmission (J) & 0.1 \\ Number of data packets carried by a node & 300 \\ Time to live (TTL) (h) & 2 \\ \hline \hline \end{tabular}
\end{table}
Table 3: The common experimental setup for simulation environment.  
protocol (Epidemic), FCNS, and P&F are inferior to DTCM in terms of this evaluation parameter as the number of nodes increase from 50 to 400. This is because Epidemic, FCNS, and P&F fail to judge whether the node has enough cache space to store data grouping and even allows all message carriers to transmit data grouping to any node they encounter. On the contrary, DTCM adopts a type of cache assessment method to analyze the remaining cache spaces of each node and then select the node with the enough cache spaces as the next hop. Moreover, the remaining cache level \(L_{\text{min}}^{c}\) sets a lowest bound for all nodes in the networks, due to which DTCM shows a higher average remaining cache than Spray and wait when the number of nodes increase from 150 to 400. However, when the number of nodes is between 50 to 150, their sparse distribution results in a declines of the frequency of information exchange, and also Spray and Wait has controlled the number of data packages, therefore, the remaining energy consumption from it lower than that from DTCM during this period.