# Collaborative Caching for Implementing a Location-Privacy Aware LBS on a MANET
## 6 Performance Evaluation
### Effect of Speed  
The mobility of the nodes significantly affects the performance of the system in MANETs [10; 33]. We analyzed this impact by varying node speeds while maintaining constant node count (400) and cache size (4). Our speed range (2-6 p/s) represents realistic pedestrian movement patterns in urban environments [2].  
An analysis of Tables 5-7 reveals several critical insights:  
1. _Redundancy Dynamics_: System-wide redundancy decreases with increasing speed across all approaches, which is consistent with expected MANET caching behavior [29]. The baseline shows the most dramatic reduction (34% to 21%), while our collaborative approaches maintain more stable, lower redundancy levels (M-LBSv1: 10% to 8%, M-LBSv2: 14% to 8%).
2. _Hit Rate Stability_: Despite increasing mobility, both collaborative approaches maintain high hit rates (M-LBSv1: 0.97 to 0.89, M-LBSv2: 0.97 to 0.89) compared to the higher degradation of the baseline (0.95 to 0.81). This demonstrates the resilience of our cell exit protocols to mobility effects.
3. _Communication Cost_: While increasing speed results in higher communication costs across all systems, our collaborative approaches show more controlled increases,  
\begin{table}
\begin{tabular}{l l l l l l} \hline
**Cache Size** & **ACC** & **NH** & **HR** & **Average RR per Cell** & **CC** \\ \hline
2 & 27,270 & 92,730 & 0.77 & 6\% & 4.68 \\
3 & 16,046 & 103,954 & 0.87 & 10\% & 4.17 \\
4 & 8436 & 111,564 & 0.93 & 10\% & 3.85 \\
5 & 6606 & 113,394 & 0.94 & 11\% & 3.74 \\
6 & 5681 & 114,319 & 0.95 & 12\% & 3.75 \\ \hline \end{tabular}
\end{table}
Table 4: Cache sizes, M-LBSv2.  
Figure 3: Number of LBS accesses when the cache size is varied.  
particularly at higher speeds. This suggests a better adaptability to dynamic network conditions.  
Figure 4 shows that increased node mobility leads to more frequent LBS queries across all systems. However, this performance degradation is significantly less severe in our collaborative approaches with M-LBSv1 and M-LBSv2 maintaining considerably lower LBS access rates even at high speeds. Cell exit protocols effectively maintain data availability within cells despite increased node movement, resulting in enhanced privacy protection through a sustained reduction in LBS dependency. The results validate our protocol design's effectiveness in managing mobility-induced challenges while maintaining privacy protection.  
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Speed** & **ACC** & **NH** & **HR** & **Average RR per Cell** & **CC** \\ \hline
2 & 3814 & 116,186 & 0.97 & 10\% & 2.87 \\
3 & 5989 & 114,011 & 0.95 & 9\% & 3.28 \\
4 & 8087 & 111,913 & 0.93 & 9\% & 3.69 \\
5 & 10,997 & 109,003 & 0.91 & 9\% & 4.25 \\
6 & 13,043 & 106,957 & 0.89 & 8\% & 4.67 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Speed, M-LBSv1.  
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Speed** & **ACC** & **NH** & **HR** & **Average RR per Cell** & **CC** \\ \hline
2 & 4128 & 115,872 & 0.97 & 14\% & 2.77 \\
3 & 6100 & 113,900 & 0.95 & 13\% & 3.34 \\
4 & 8436 & 111,564 & 0.93 & 10\% & 3.85 \\
5 & 11,430 & 108,570 & 0.90 & 9\% & 4.42 \\
6 & 13,092 & 106,908 & 0.89 & 8\% & 4.91 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Speed, M-LBSv2.  
Figure 4: Number of LBS accesses when the speed of the nodes is varied.  
\begin{table}
\begin{tabular}{l l l l l l} \hline \hline
**Speed** & **ACC** & **NH** & **HR** & **Average RR per Cell** & **CC** \\ \hline
2 & 6483 & 113,517 & 0.95 & 34\% & 1.2 \\
3 & 10,461 & 109,539 & 0.91 & 32\% & 1.69 \\
4 & 14,398 & 105,602 & 0.88 & 25\% & 2.16 \\
5 & 19,485 & 100,515 & 0.84 & 23\% & 2.59 \\
6 & 23,148 & 96,852 & 0.81 & 21\% & 2.93 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Speed, baseline.