# 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
### Observability of the Route Feature Values  
We examined how observable RA is and how the route feature values capture changes in route nonuniformity. We conducted video streaming experiments in which total connected time and total disconnected time were measured for different numbers of nodes and different moving speeds. The number of nodes was altered from 3 to 7, and the length of emulation time was varied from 90 to 180 and 270 s. As expressed in Equation (7), the emulation time is the first route establishment time after the emulation program was started plus communication time (total connected time + total disconnected time). We defined the communication to end when the emulation ends. The moving speeds of nodes were varied between 0 m/s and 2 m/s considering that nodes may stand still. The routing protocol used was AODV. The emulation conditions are shown in Table 4. By referring to the holding time of conventional telephone calls, we set the emulation time at about 270 s at the longest. Since, unlike the Internet, a MANET is not an always-on environment, we made the video streaming delivery time shorter than that in the Internet in this experiment. \[ \begin{array}{c}\text{Emulation time = first route establishment time + communication time}\\ \text{(total connected time + total disconnected time)}\end{array}  \tag{7}\]  
An example of a communication pattern in which connections and disconnections occur alternately after the start of emulation is shown in Figure 9. The vertical axis indicates the number of hops from the source node to the destination node during the time in which a connection is set up between them. The width of each bar indicates the time for which a connection is maintained. A section in which the number of hops is \(-1\) indicates the time for which the route is disconnected. The time between the start of emulation and 0.83 s later was the first route establishment time. There were 22 disconnections. Blank sections indicate the time when there was no connection. The length of each bar indicates the number of hops from the source node to the destination node. The number of hops is equal to the number of relay nodes in this paper. If the number of hops is 0, the source node directly communicates with the destination node. We can confirm from Figure 9 that the measurement methods proposed in Section 3.2 are useful for observing connection and disconnection triggers and connected time. The presence of changes in the number of hops indicates that the route nonuniformity of a MANET is observable. \begin{table}
\begin{tabular}{c c} \hline \hline
**Item** & **Value** \\ \hline Emulation time & 90, 180, 270 s \\ Field size & 1 km \(\times\) 1 km \\ Number of nodes & 3, 4, 5, 6, and 7 \\ Wireless communication standard & IEEE802.11g \\ Reception threshold (propagation range) & \(-\)82 dBm (about 500 m) \\ Mobility model & Random waypoint \\ Moving speed & 0 m/s\(\sim\)2 m/s \\ Routing protocol & AODV \\ Video format & H.264/AVC \\ Audio format & AAC \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Emulation conditions. AVC: Advanced Video Coding; AAC: Advanced Audio Coding. Table 5 shows how the route feature values and RA changed when the emulation time and the number of nodes were changed. There were cases where the sum of the total connected time and the total disconnected time was not the same as the emulation time. The difference was the first route establishment time after the emulation started. The table confirms that the total connected time, the total disconnected time, and the number of disconnections can be measured using the measurement method described in Section 3.2. We were able to calculate RA from these observed route feature values as shown in Table 5, and thus verified that RA was observable. It can be seen that RA varied between 71 and 83 under the conditions shown in Table 4.