## 5 Simulations
### Simulation Results for Different File Sizes
Hence, the average credits of the destination nodes raise faster during the period from time 50 to 150, as shown in Figure 11. As a result, SocialCode and SC without DP considerably extend lifetimes of the destination nodes for encouraging them to join the CCD procedure. As mentioned above, when the intermediate node with RCM + CodeOn and FRAME + CodeOn receives a content piece from the destination node, it will increase its credits by one unit, which is paid by this destination one. As the intermediate node with SocialCode and its variety receives a non-duplicate content piece, it has to compensate the sending node credit \(\delta\) due to the guideline in Table 3. Nevertheless, whenever it further forwards its content piece, which is non-duplicate to next intermediate node or innovative to next destination node, SocialCode and SC without DP will \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **File Size** & **10 MB** & **6 MB** & **2 MB** \\ \hline
**Normalized Ratio of File Downloading Delay** & & & \\ \hline
**SocialCode** & & 0.47 & 0.43 & 0.36 \\
**SC without DP** & & 0.57 & 0.56 & 0.49 \\
**FRAME + CodeOn (FRAME)** & & 0.81 & 0.81 & 0.69 \\
**RCM + CodeOn (RCM)** & & 1.00 & 1.00 & 1.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Normalized ratios for average file downloading delays of SocialCode, SC without DP and FRAME + CodeOn (FRAME) over that of RCM + CodeOn (RCM) under three file sizes. raise its credit by \(\delta\) or \(\beta\), respectively, which is paid by next receiver accordingly. Hence, SocialCode and SC without DP achieve more steady values on average credits of the intermediate node than RCM + CodeOn and FRAME + CodeOn do, as shown in Figure 11. On the other hand, because SC without DP does not decide the dynamic priority of each intermediate node, the intermediate node that receives content pieces earlier has higher probability to forward its cached content pieces to nearby ones, which dissipate its credit values faster. Thus, as shown in (a-c) of Figure 11, the intermediate node of SC without DP suffers from lower and less stable average credits than that of SocialCode but its destination node owns higher average credits. Further, the larger the file is, the lower average credits the intermediate node owns but the higher ones the destination node does. Consequently, these results show that the dynamic forwarding priority assignment, proposed in Section 4.3, adopted by SocialCode achieves much fairer content piece forwarding among intermediate nodes than SC without DP does. At last, as shown in Figure 11, RCM + CodeOn and FRAME + CodeOn keep average credits of their overhearing nodes to the value, that is, 50, of the initial credit \(\gamma\) because these nodes do not include in their CCD procedures. Based on the guideline in Table 3, the overhearing node with SocialCode and SC without DP will decrease its credit by \(\alpha\) when it accepts an innovative piece from the destination or intermediate ones. Hence, its credit will decrease to zero rapidly, which is about 150 ms in Figure 11, since it does not earn any credit from nearby nodes by further re-broadcasting the received piece to them. As a result, SocialCode and SC without DP will prohibit the overhearing node from broadcasting its own pieces and receiving any successive piece. This means that SocialCode and SC without DP penalize the overhearing node due to its selfish operation during the CCD procedure.