# Evaluation of VoIP QoS Performance in Wireless Mesh Networks
## 3 Experimental Setup
There are two scenarios (First Responders and Platoon) with a waypoint mobility model where the nodes move towards a specific direction with varying mobility speeds. This mobility model is selected since, for example, in an emergency scenario it can happen that an affected area is small and all the first responders move towards that direction. In the case of a platoon, the waypoint mobility simulates the military personnel movement towards a specific direction without major changes in the platoon's formation. In this case, we have considered a platoon line deployment with three squads (left, centered, and right). They move from their initial positions to the final position without changing the platoon's formation using the way-point mobility model. \begin{table}
\begin{tabular}{c c} \hline
**Quality Level** & **MOS** \\ \hline Excellent & 4.3–5.0 \\ Very good & 4.0–4.3 \\ Good & 3.6–4.0 \\ Fair & 3.1–3.6 \\ Poor & 2.6–3.1 \\ Bad & 1.0–2.6 \\ \hline \end{tabular}
\end{table} 
Table 2: MOS rating scale. There is one scenario (First Responders Random Mobility) in which the nodes move using the random waypoint mobility model with a minimum speed of 1.1 m/s and a maximum speed of 1.5 m/s, which simulates pedestrian traffic mobility speed. We have also considered two scenarios (Flooded Village and Isolated Village) with no mobility, where the nodes do not move at all and it is assumed that the mesh nodes are in a fixed installation mode. We have conducted our experiments by combining multiple standards, protocols, and codecs in order to find out how VoIP performance is affected and which combinations would be the best in consideration of specific scenarios. We have limited our research to the choice of two common codecs, namely G.711 and G.729. The G.711 requires higher bandwidth, while G.729 requires lower bandwidth. The routing protocol type for all the scenarios without the IEEE 802.11s standard is AODV, which is a light-weight routing protocol commonly considered in WMNs as protocol of choice in real experiments and focused research activities, as presented in [58; 59; 60; 61; 62]; in [58] a real world evaluation of the AODV is presented in an industrial setup and the rest are AODV usage and its comparison in various mesh network scenarios. For scenarios with IEEE 802.11s, the routing protocol choice is HWMP, which is a built-in path selection protocol as part of the IEEE 802.11s standard [1]. The reason for choosing these two protocols is that AODV operates at the network layer while HWMP operates at the data link layer; HWMP is also called a path selection protocol. The comparison of these two protocols' performance can help us make informed choices in WMNs implementations. As discussed previously, VoIP implementation requires a signaling protocol to work. We have chosen the SIP signaling protocol for our experimental scenarios because of its good performance and low resource usage features, and its commonality of use in VoIP implementations. Node 11 has been configured as the SIP server in all scenarios. In a distributed system such as a WMN, a central VoIP server can create a single point of failure and VoIP calls may not happen if the connectivity to the SIP server is not established. There are solutions like the SIP clustering presented in [63], which could be