Performance of VoIP in a 802.11 wireless mesh network

Journal of Advances in Information Technology

This study focused on improving the performance of Voice over Internet Protocol (VoIP) over Wireless Mesh Networks (WMN) in an 802.11ac scenario simultaneously using packet compression and packet aggregation. The study employed design science research methodology and developed an algorithm that aims to increase the number of concurrent calls while reducing the impact of jitter, delay, and packet drop. The study is the first of its kind to come up with a combined packet compression and packet aggregation technique for Voice over Internet Protocol Wireless Mesh Networks (VoWMN) in an 802.11ac setting. During simulation tests carried out using ns-3, the algorithm outperformed existing schemes in terms of average delay, jitter, packet loss, and network throughput. The algorithm performed better by 1.4% over compressed packets and by 27.22% over plain VoIP packets in terms of packet loss, and obtained the highest network throughput of 0.16Mbps which was 56.25% more than compressed packets which had the next best throughput. These findings suggest that the proposed algorithm can significantly enhance the performance of VoIP over WMN in an 802.11ac scenario. However, this study did not cover aspects related to security implications when utilizing both aggregation and compression at the same time in VoIP over WMNs. Additionally, it only focused on the 802.11ac scenario. Further research could explore the effectiveness of the proposed algorithm in other scenarios and protocols, and identify the optimal settings for the algorithm. Additional research could explore the use of other techniques, such as error correction and QoS mechanisms, to improve the performance of VoIP over WMN.

IEEE Transactions on Vehicular Technology, 2005

Voice over Internet Protocol (VoIP) over a wireless local area network (WLAN) is poised to become an important Internet application. However, two major technical problems that stand in the way are: 1) low VoIP capacity in WLAN and 2) unacceptable VoIP performance in the presence of coexisting traffic from other applications. With each VoIP stream typically requiring less than 10 kb/s, an 802.11b WLAN operated at 11 Mb/s could in principle support more than 500 VoIP sessions. In actuality, no more than a few sessions can be supported due to various protocol overheads (for GSM 6.10, it is about 12). This paper proposes and investigates a scheme that can improve the VoIP capacity by close to 100% without changing the standard 802.11 CSMA/CA protocol. In addition, we show that VoIP delay and loss performance in WLAN can be compromised severely in the presence of coexisting transmission-control protocol (TCP) traffic, even when the number of VoIP sessions is limited to half its potential capacity. A touted advantage of VoIP over traditional telephony is that it enables the creation of novel applications that integrate voice with data. The inability of VoIP and TCP traffic to coexist harmoniously over the WLAN poses a severe challenge to this vision. Fortunately, the problem can be largely solved by simple solutions that require only changes to the medium-access control (MAC) protocol at the access point. Specifically, in our proposed solutions, the MAC protocol at the wireless end stations does not need to be modified, making the solutions more readily deployable over the existing network infrastructure. Index Terms-Capacity, IEEE 802.11, quality of service (QoS), voice over Internet Protocol (VoIP), wireless local area network (WLAN). I. INTRODUCTION V OICE OVER Internet Protocol (VoIP) is one of the fastest growing Internet applications today [1]. It has two fundamental benefits compared with voice over traditional telephone networks. First, by exploiting advanced voice-compression techniques and bandwidth sharing in packet-switched networks, VoIP can dramatically improve bandwidth efficiency. Second, it facilitates the creation of new services that combine Manuscript

2008 Third International Conference on Broadband Communications, Information Technology & Biomedical Applications, 2008

The deployment of wireless mesh paradigm was meant to extend Internet access without a consideration of delay sensitive applications. Nonetheless, since voice over IP (VoIP) services are rapidly increasing in popularity, IEEE 802.11 based wireless mesh networks are challenged with the provision of guaranteed quality VoIP calls. In this paper, the disquiet on VoIP systems caused by physical (PHY) and medium access control (MAC) anomaly in the current wireless mesh deployment is addressed through a cross-layer scheme. The scheme is aimed at enhancing VoIP call capacity by mitigating PHY and MAC overheads through aggregation of packets of the same next hop. Through simulations, it is shown that the proposed scheme has significant performance improvements while leaving the IEEE 802.11 standard intact.

IEEE Transactions on Mobile Computing, 2009

WLAN has high data rates (e.g., 11 Mbps for 802.11b and 54 Mbps for 802.11g), while voice streams of VoIP typically have low-data-rate requirements (e.g., 29.2 Kbps). One may, therefore, expect WLAN to be able to support a large number of VoIP sessions (e.g., 200 and 900 sessions in 802.11b and 802.11g, respectively). Prior work by one of the authors, however, indicated that 802.11 is extremely inefficient for VoIP transport. Only 12 and 60 VoIP sessions can be supported in an 802.11b and an 802.11g WLAN, respectively. This paper shows that the bad news does not stop there. When there are multiple WLANs in the vicinity of each other-a common situation these days-the already low VoIP capacity can be further eroded in a significant manner. For example, in a 5 Â 5, 25-cell multi-WLAN network, the VoIP capacities for 802.11b and 802.11g are only 1.63 and 10.34 sessions per AP, respectively. This paper investigates several solutions to improve the VoIP capacity. Based on a conflict graph model, we propose a clique-analytical call admission scheme, which increases the VoIP capacity by 52 percent from 1.63 to 2.48 sessions per AP in 802.11b. For 11g, the call admission scheme can also increase the capacity by 37 percent from 10.34 to 14.14 sessions per AP. If all the three orthogonal frequency channels available in 11b and 11g are used to reduce interferences among adjacent WLANs, cliqueanalytical call admission scheme can boost the capacity to 7.39 VoIP sessions per AP in 11b and 44.91 sessions per AP in 11g. Last but not least, this paper expounds for the first time the use of coarse-grained time-division multiple access (CoTDMA) in conjunction with the basic 802.11 CSMA to eliminate the performance-degrading exposed-node and hidden-node problems in 802.11. A two-layer coloring problem (which is distinct from the classical graph coloring problem) is formulated to assign coarse time slots and frequency channels to VoIP sessions, taking into account the intricacies of the carrier-sensing operation of 802.11. We find that CoTDMA can further increase the VoIP capacity in the multi-WLAN scenario by an additional 35 percent, so that 10 and 58 sessions per AP can be supported in 802.11b and 802.11g, respectively.

2008

In this paper we focus on the following question: how routing protocols, working under different channel conditions, can influence the human perceived quality of VoIP calls in a wireless mesh backbone? In order to respond this question, we propose a study case where we analyze two routing approaches in a 802.11 Wireless Mesh Backbone, namely, reactive AODV and proactive OLSR. We calculated the voice speech quality by making use of a reviewed version of ITU-T E-Model proposed in previous work. Results obtained from highly credible stochastic simulation environment, also described in this paper, showed that AODV performs better in very hostile mediums while OLSR presents better results when more friendly mediums take place.

Information, 2017

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 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.

2006

In recent years, there has been a lot of interest in using Wireless Local Area Networks (WLAN) for voice communications with the expanded coverage of hot spots. This paper describes packet aggregation method that increases the throughput of WLAN for voice communication by decreasing the overhead of backoff at the beginning of each packet transmission. Aggregation allows AP to acquire the channel and send its packets inside a multicast packet or back-to-back. Implementation and analysis of frame aggregation show that it improves the performance of voice over IP (VoIP) operating on IEEE 802.11 considerably.

2nd International Conference on New Technologies, Mobility and Security, 2008

Voice over IP (VoIP) over Wireless Mesh Network (WMNs) has become a topic of great interest in both enterprise and research arena. The IEEE 802.11 standard is the most popular Wireless LAN standard for extending the access point (AP) based network. However, it does not provide guaranteed quality for real-time applications such as VoIP. Besides, with the large number of injected flows in WMNs, only a handful of these packets can be supported due to protocol overhead, packet collision and Interferences. In this paper, a link-based aggregation is proposed and its performance improvement is compared with those of fixed aggregation and performance under standard access network. Simulation results show that the proposed aggregation scheme increases the number of supported flow while also reducing end-to-end delay, jitter, and packet loss of VoIP in WMNs.

GLOBECOM 2010, 2010 …, 2010

Voice capacity over IEEE 802.11 networks can be increased with time synchronized medium access, but it is restricted to single hop networks only. We propose a collaborative mechanism that enables client nodes to carry out the time synchronization on ad hoc basis, thereby extends the time synchronized access mechanism over multiple hops, and increases voice capacity considerably. To model real scenario closely, we consider the impact of channel error and employ a Markov chain to determine delay and loss in both medium access and in queue which is then used to derive user perceived voice quality using ITU-T E-model. Our model is then used to determine voice capacity of multichannel, multihop networks. The impact of data rate, interference range, and multiple channels are also analyzed.

Voice over Internet Protocol is a technology that enables to transport voice over Internet Protocol. The growth of this technology is due to the integration of voice and data traffic over wireless infrastructure. The low cost of voice usage on internet and wide spread of wireless technology has an advantage to implement VoIP system in today IP network. This study investigates the performance of VoIP over different IEEE 802.11standard. The focus of the study will be on IEEE 802.11 b/g/n standard. Data related to the performance parameter of the wireless network and the voice quality will be collected. The qualities of voice are analyzed and summarize into a graph between different Wireless LAN physical layer in deployment of WLAN in the future.