Evaluation of VoIP QoS Performance in Wireless Mesh Networks

Mohammad Meeran, Paul Annus, Muhammad Alam, Yannick Moullec
2017 Information  
The main focus of this research article is the evaluation of selected voice over Internet protocol (VoIP) solutions in wireless mesh network (WMN) scenarios. While WMNs have self-healing, self-forming, and dynamic topology features, they still pose challenges for the implementation of multimedia applications such as voice in various scenarios. Therefore, various solutions to make WMN more suitable for VoIP application have been proposed in the scientific literature. In this work, we have
more » ... ork, we have extensively explored a set of applicable scenarios by conducting experiments by means of a network simulator. The following scenarios were selected as the most representatives for performance evaluation: first responders, flooded village, remote village, and platoon deployment. Each selected scenario has been studied under six sub-scenarios corresponding to various combinations of the IEEE 802.11g, 802.11n, 802.11s, and 802.11e standards; the G.711 and G.729 codecs; and the ad hoc on demand distance vector (AODV) and hybrid wireless mesh protocol (HWMP) routing protocols. The results in terms of quality of service (measured with the mean opinion score rating scale), supported by the analysis of delay, jitter and packet loss, show that 802.11g integration with both VoIP codecs and AODV routing protocol results in better VoIP performance as compared to most other scenarios. In case of 802.11g integration with 802.11s, VoIP performance decreases as compared to the other sub-scenarios without 802.11s. The results also show that 802.11n integration with 802.11e decreases VoIP performance in larger deployments. We conclude the paper with some recommendations in terms of combinations of those standards and protocols with a view to achieve a higher quality of service for the given scenarios. The second type of WMN is the clients mesh. In this type of topology, all the clients form the mesh network; they all participate in the formation of the mesh network backbone and are usually referred to as mesh nodes/points; the type of topology is then called ad hoc, as shown in Figure 1b where the nodes a, b, c, . . . , i form a mesh network without any wireless router or access point's help. This type of network can use the IEEE 802.11 and 802.15 standards. In such types of mesh networks, each mesh node can act as a client, server and router. Each node's role can change based on the type of service offered over the WMN, but the nodes will always have to play either a client or a router role, while the server's role depends on the type of application offered using such network platforms. Ad hoc network with mobile nodes are usually referred to as mobile ad hoc networks (MANETs) [10, 11] . The third type of WMN is a mixture of the first and second types, which comprises a mesh of wireless routers that form the backbone and a mesh of clients that form the access layer of a hierarchical network, as shown in Figure 1c . In this type of network, the nodes can form a mesh network among themselves and the mesh router could be a supportive component of the mesh network to connect mesh nodes to external networks. This type of network is called heterogeneous mesh (HetMesh) [7] and requires the mesh routers to be equipped with dual radio links in order to establish and maintain redundant links with the mesh routers and to service the mesh clients as their gateways to other mesh segments or external networks, e.g., the Internet. Since ad hoc networks increase delay, jitter, and packet loss, VoIP services offerings in such networks are challenging [12, 13] . There are several methods to investigate and measure the performance of VoIP and its service quality. In [14] methods such as mathematical proofs, real implementation and simulation are discussed to evaluate the performance of scenarios that involves multiple variables. The author uses OMNet++ simulation software to measure multiple variables which involves a wide range of parameters across multiple OSI model layers. There exist several network simulators such as OMNet++, NS-2, NS-3, EstiNet, QualNet, OPNET modeler, and JSim [15]; in this research we use the QualNet simulation software in order to evaluate the performance of VoIP in various scenarios using multiple types of parameters for the reasons given below. The QualNet simulation software enables us to conduct experiments that are almost identical to real-life scenarios [16] . It also saves time in configuring, experimenting, collecting data and analyzing multiple scenarios using various parameters. Among several features for configuring VoIP profiles, generating VoIP traffic and evaluating the service performance, the configuration of the "Total VoIP loss probability" percentage parameters enables us to set the estimated VoIP loss probability percentage to mimic a real network scenario. This parameter's setting directly affects the mean opinion score (MOS) rating scale values obtained in simulation results. The MOS rating scale is defined by ITU-T as a 5-point rating scale where 5 is rated as "Excellent", 4 as "Good", 3 as "Fair", 2 as "Poor" and 1 as "Bad" [17] . The motivation behind this research is to provide an insight into VoIP application with recommendations on the best ways to combine standards, protocols and codecs to improve VoIP quality in various scenarios considering ad hoc mesh network implementations using selected IEEE 802.11 standards. Since ad hoc networks are self-formed and do not require any prior setup nor existing infrastructure, this makes it an interesting type of network compared to the first and third types explained above. On the other hand, one of the challenges in this research domain is the applicability of VoIP on wireless mesh networks and how it could be offered with improved service quality. Below we highlight our contributions towards this challenge:
doi:10.3390/info8030088 fatcat:fvjaqbg7kfatbenzvsty2pp7g4