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The next generation technology of Voice over Internet Protocol (VoIP) allows voice to be delivered over the Internet Protocol based networks. The integration of VoIP and Wireless Local Area Network (WLAN) has become popular. However, WLAN architecture was primarily designed to carry data and not for real-time applications, such as VoIP. Hence, there is a need to enhance the quality of VoIP transmission...
This paper proposes a solution for throughput and stringent delay problems of VoIP in Ad-Hoc mode of IEEE 802.11 WLAN standards. This paper analyses the behaviour different codecs and schemes of WLAN running on VoIP traffic and draws a conclusion on the performance of network based on the criteria of different QOS parameters. Later the suitability of different routing protocols like AODV, DSR, OLSR...
Performance evaluation and analysis of different VoIP over WLAN mobility schemes is essential in order to meet adequate QoS levels in VoWLAN deployments. This paper presents a study of real time voice communication QoS in terms of delay, jitter, throughput and packet loss between three different Wireless Mesh Network mobility schemes in a crowded 802.11 environment. We also discuss the feasibility...
IEEE 802.11 Wireless Local Area Network (WLAN) Physical Layer (PHY) offers multiple data rates. In multi-rate WLANs, 802.11 Medium Access Control (MAC) protocol, Distributed Coordination Function (DCF), essentially provides equal transmission opportunities to each sender host, causing the degradation of system throughput due to some hosts using low rates. In this paper we propose a cross-layer link...
Over the last decade, VoIP has had a fast growth particularly in Small Office Home Office environments overloading the wireless accesses in the last mile. Network Coding schemes have advantageous features for throughput performance but VoIP is a delay critical service requiring fast routing algorithms. In this paper, we design, implement and measure experimental values for a network coding based VoIP...
In VoIP over WLAN (known as VoWLAN) transmission, one of the main problems is that the supported voice channel capacity is relatively low. As an improvement to IEEE 802.11 MAC layer Carrier Sense Multi-Access/Collision Avoidance (CSMA/CA) algorithm, this paper presents Prediction/Collision Avoidance (P/CA) mechanism based on service attribute and cross-layer control. Under this mechanism, there is...
This paper discusses the delay characteristics and packet drop ratio performance of Busy Tone Multiple Access Protocol (BTMAP) for distances up to 48Km in IEEE 802.11 networks. The impact of the Contention Window (CW) is discussed. We note that a larger CW will increase the mean packet delay but decrease the packet drop ratio. Long range also significantly degrades the delay and packet drop ratio...
IEEE 802.11 is world widely established as the most popular protocol for Wireless Local Area Networks (WLANs). Voice over IP (VoIP) applications are widely spread due to their relatively low cost. Applying VoIP traffic on IEEE 802.11 WLANs introduces significant delays in the wireless medium due to the small size of voice packets. In this paper, we develop an analytical model for the IEEE 802.11 Distributed...
The quick market growth and ubiquitous acceptance of VoIP are primarily due to cheap service. VoIP services can be availed in mobile devices at a very low cost by employing IEEE 802.11 to provide last mile coverage. But call capacity is very low in these networks and call jitter occurs if voice quality requirements are not precisely met. We present a VoIP call capacity model for 802.11 networks which...
VoIP offers cheap voice communication which instigated its quick market growth. IEEE 802.11 WLANs offer cheap wireless coverage which can be used to provide VoIP service in mobile devices. But call capacity of such networks is very low compared to wired networks. To increase voice capacity in WLANs incorporation of power capture, increased data rate, and use of multiple channels are of great importance...
VoIP capacity is an important metric as it determines the maximum number of calls that can be supported by a Wireless Local Area Network (WLAN) before call quality degrades. To this end, researchers have conducted extensive simulation and analytical studies to determine the VoIP capacity of different WLANs. These previous works, however, assume stations are always awake during a call. In 2005, the...
The increase in multimedia usage places stringent requirements on wireless network performance in terms of lesser handoff delays. A VOIP client, for example, cannot tolerate a delay larger than 150 ms between the incoming voice packets to ensure a satisfactory interactive service to the user. Of the 150ms, only 50ms is allowed for handoff and the rest should accommodate the transmission delay of the...
Recently, many researchers have investigated the Voice over IP (VoIP) service over Wireless Local Area Networks (WLANs). One of the important challenges is to reduce the handoff delay in WLANs. Especially, the channel scan delay, which takes the largest portion of the WLAN handoff delay, is too long to support the delay-sensitive VoIP service. We propose a selective channel scan based on the pre-collected...
Voice, in the form of VoIP, has emerged as a dominating traffic category in the Internet. VoIP traffic suffers from severe voice quality degradation if the end-to-end delay and loss becomes high. PCF medium access mechanism offers delay bound delivery which is a crucial attribute for delay sensitive applications like VoIP. But due to its unavailability in most commercial products, little analysis...
Capacity and power consumption are two main bottlenecks in the wide deployment of Voice-over-IP (VoIP) over IEEE 802.11 wireless LAN, when mobile terminals are used, the impact on the Voice-over-IP (VoIP) by power consumption becomes more critical. In this paper, we analyze the capacity of VoIP traffic in 802.11 WLAN and do the relevant simulations with and without sleep strategy. We find that capacity...
Wi-Fi phones are becoming extremely popular for implementation of VoIP (or VoWLAN) service. It is well known that voice service is quite critical to delay and delay jitter, therefore it appears important to evaluate VoWLAN service performance. In the research presented below we implemented a typical indoor environment for VoWLAN service using OPNET. Simulation parameters have been carefully selected...
We propose and evaluate the performance of a novel handoff scheme for IEEE 802.11 wireless LANs (WLANs) supporting mobile applications. Because of their wide deployment in public areas, supporting seamless, low-latency, handoffs between pairs of adjacent WLANs becomes a crucial requirement for applications such as voice and video over IP. Handoff latency is an important delay that affects the quality...
IEEE 802.11 based wireless networks are widely deployed in densely populated areas such as university campuses, airports, offices, cafeterias, etc. Their popularity is rising because of their low cost and high bandwidth except that they cover small coverage areas. In order to cover large areas several access points (AP) are required, which makes it disruptive technology. During roaming, the mobile...
Currently, the vertical handover between different technologies presents a real challenge to overcome; the service interruptions during handover pose a real problem to users. In this paper we focus on this problem, and we propose the MSCTP protocol characterized by its multi-homing technique, as vertical handover mechanism between the IEEE 802.16e and the IEEE 802.11e networks, in order to reduce...
Wireless networks, specifically those based on the IEEE 802.11 standard (Wi-Fi), are experiencing rapid growth due to their low cost and high-speed connectivity. To cover larger areas, many AP's are required which need the use of handoff between different AP's. Therefore, handoff latency has become essential issue in wireless LANs. This delay affects the quality of real-time applications like VoIP...
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