# Route Availability as a Communication Quality Metric of a Mobile Ad Hoc Network
## 5 Evaluation of the RA Calculation Method and Verification of Usefulness of RA
### Usefulness of RA as a QoS Metric  
We conducted experiments to examine how useful RA is as a QoS metric. Specifically, we examined the relationship between RA and conventional QoS metrics: packet loss rate and throughput. We developed emulation scenarios in which the area within which nodes can move, the number of nodes, and the initial locations of nodes were adjusted so that calculated RAs would take values close to the 12 values assumed. Since video quality can be degraded severely by even minor packet loss, we selected an increment of 5 for RA after RA reached 80 so that we could examine QoS metrics in finer granularity. In addition, to check how variations in the number of hops, video quality, and routing protocol affect the relationship between RA and the QoS metrics, we produced, for each RA value, videos with different values for these variables. Thus, a total of 92 scenarios were developed. Furthermore, to be able to vary the quality of transmitted videos, we produced two types of video, each having a different total bit rate and resolution. The video material used was \"Big Buck Bunny\" [21]. Detailed emulation conditions are shown in Table 6 and the codec conditions in Table 7. Although the length of the low-quality video was 10 min, the playing of this video stopped automatically as soon as the emulation time ended in the experiments. \begin{table}
\begin{tabular}{c c} \hline \hline
**Item** & **Value** \\ \hline Emulation time & 180 s \\ Field size & Maximum 2 km \(\times\) 2 km \\ Number of nodes & 4 to 22 \\ Assumed RA & 10, 20, 30, 40, 50, 60, 70, 80, 85, 90, 95, 100 \\ Average number of hops & 2 hops or more; hops or fewer \\ Video quality & High quality, low quality \\ Transport layer & UDP (User Datagram Protocol) \\ Number of scenarios & 92 \\ Wireless communication standard & IEEE 802.11g \\ Reception threshold (propagation range) & \(-\)82 dBm (about 500 m) \\ Transmission rate & About 15 Mbps \\ Mobility model & Random waypoint \\ Moving speed & 0.1 to 2.0 m/s \\ Area within which nodes can move & 500 m \(\times\) 500 m, 600 m \(\times\) 600 m, 750 m \(\times\) 750 m, 1 km \(\times\) 1 km \\ Routing protocol & AODV, OISRV2 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Emulation conditions. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Item** & **Value for High Quality** & **Value for Low Quality** \\ \hline Video format & & H.264/AVC & \\ Audio format & & AAC & \\ Playing time & 180 s & 596 s \\ Profile & & [EMAIL_ADDRESS] & \\ Frame reference distance (Ref Frame) & & 1 frame & \\ Frame rate & & 24 fps & \\ Total bit rate & 3120 kbps & 581 kbps \\ Resolution & 1280 \(\times\) 720 & 416 \(\times\) 240 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Video codec conditions. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Emulation** & **Number of** & **Total Connected** & **Total Disconnected** & **RA (\%)** \\
**Time (s)** & **Nodes** & **Time** & **Time** & **Time** \\ \hline \multirow{5}{*}{180} & 3 & 128 & 51 & 71 \\  & 4 & 130 & 49 & 73 \\  & 5 & 131 & 48 & 73 \\  & 6 & 142 & 37 & 79 \\  & 7 & 146 & 33 & 82 \\ \hline \multirow{5}{*}{270} & 3 & 191 & 78 & 71 \\  & 4 & 185 & 84 & 69 \\ \cline{1-1}  & 5 & 202 & 67 & 75 \\ \cline{1-1}  & 6 & 199 & 70 & 74 \\ \cline{1-1}  & 7 & 196 & 72 & 73 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: _Cont._We examined the relationship between RA and the conventional QoS metrics. The results are shown in Figures 10-12. Approximate straight lines are also shown in each graph. Figure 10 shows the relationship between RA and packet loss rate when the number of hops was varied. Since packet loss rate is affected by both the quality degradation attributable to an adverse radio environment and that attributable to MANET properties, it is not possible to pinpoint the factors that caused packet loss. On the other hand, being a metric of route nonuniformity, RA reflects changes in route quality mainly attributable to MANET properties, i.e., frequent occurrences of disconnections.