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Now-a-days, multi-party conferencing is an essential feature in the VoIP calls among desktop PCs, laptops. The additional voice processing module required for a conferencing when compared to a normal 2-way call is Mixer. Even though some algorithms are available in the literature, they lack in evaluating their performance. In this paper, different types of mixing algorithms are investigated and objective...
The IEEE 802.16/802.16e provides powerful tools in order to achieve different QoS constraints. The MAC layer defined five scheduling service types to provide QoS differentiation for different types of applications. In this paper, we investigate the performance of the scheduling schemes deployed in the OPNET modeler by considering VoIP, video conferencing and non-real-time services. We further investigate...
Voice over Internet Protocol (VoIP) services are susceptible to Internet Protocol (IP) network burstiness causing packets drop and momentary gap in the call. The main objective of this paper is to study the effect of various voice codec schemes on the VoIP Quality of Service (QoS). Popular voice codecs such as G.711, G.729A Conjugate-Structure Algebraic-Code-Excited Linear-Prediction (CS-ACELP), G...
In the increasingly popular Voice over IP (VoIP) application domain, a well known issue relates to the management of available network bandwidth which is usually constrained by uplink capacities as well as access point limitations in the case of wireless connections. An approach that has long been advocated for controlling the admission of new connections based on bandwidth availability is Call Admission...
This paper presents a VoIP traffic model applicable to wireless access transmission media, which is usable for determination of admissible call number threshold value. The main observation is the influence of Voice Activity Detection function and Comfort Noise Generation in particular. The CAC threshold value determination is based on a fluid-flow approach to packet loss evaluation. The well known...
Voice over Internet Protocol is a growing technology that enables voice communication through the Internet. The transmission of audio data over packet switched networks faces lot of difficulties by a variety of network impairments. Such networks are not designed to support real time voice communication because of their variable characteristics. The conversational quality of a VoIP communication is...
Due to low hardware costs, availability of unlicensed spectrums and support of mobility, WLANs have been widely adopted in home, enterprise, hospital, and campus environments. These networks are used for various purposes including VOIP, data services and inventory management. The QoS in WLANs may be degraded due to a number of reasons such as environment changes, hidden terminals, and asymmetric relationships...
The increasing demand for broadband services is causing the cellular network providers to consider for the integration of Wireless LAN with GPRS. WLAN is having higher data rate but low coverage area but GPRS is having lower data rate but with high coverage area. So integrating these two heterogeneous networks will lead to utilization of advantages of both and can increase the system throughput. The...
Today's Internet uses the IP protocol suite that was primarily designed for the transport of data and provides best-effort data delivery. Thus, it does not guarantee the quality of voice transmission that is highly sensitive to error and delay. The situation is even more severe in wireless networks which experience even more distortion and attenuation. Therefore, enhancing the voice traffic quality...
The use of wireless local area networks (WLANs), as well as the proliferation of the use of multimedia applications has grown fast in recent years. Some factors affect the quality of service(QoS) received by the user. The interference is an example. This work presents an empirical study of the QoS parameters of a VoIP application in the presence of an interference network, as well as the relevance...
This paper introduces the system concept and specifications for an enhanced version of the Wireless IP Access System (WIPAS), the Advanced WIPAS, which is a fixed wireless access (FWA) system that provides higher speed and real-time communication for triple play services: broadband IP service, 4class Quality of Service (QoS) especially VoIP services, and multicast HDTV video transmission services...
The continuous growth in both commercial and public network traffic with various quality-of-service (QoS) requirements is calling for better service than the Internet's best effort mechanism. One of the challenging issues is to predict the overall behavior of aggregate network traffic. While network traffic characterization has been studied extensively due to its importance in network scheduling and...
Quality of service support is a major challenge in VoIP. So much research has been devoted recently on maintaining an acceptable quality-of-service (QoS) for the transmission of real-time multimedia streams. In personal communication human speech processing is one of the most important procedure. Because if a low bit-rate codec is used in voice over IP (VoIP) to achieve a high compression ratio, the...
The IEEE 802.16 standard has defined several QoS scheduling types without detailed implementation of the bandwidth scheduling scheme. Since the DL direction is more likely to be bottleneck than the UL direction, in this paper, we propose an improved framework for downlink real-time traffic, which acquire packet information by cross-layer design and dynamic drops the packets according to the network...
Quantifiable quality measures are necessary for VoIP service providers in order to offer services and be sure to keep users for their services. Existing methods used for evaluating the Quality of Experience (QoE) mostly rely on user survey and scores from the user, which are too subjective and need much processing time and cost. This paper proposes a pentagram model for measuring QoE. The model consists...
In this paper, we present different IEEE 802.16e uplink channel access mechanisms that can be used to activate extended real-time polling service (ertPS) voice over IP (VoIP) connections after a silence period. The performance, especially uplink delay, of different resumption mechanisms is compared with each other using simulations. In addition to uplink VoIP delay, we study the uplink resource usage...
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...
Wireless local area networks (WLANs) provide an affordable solution for last mile network access. They also allow for extension of a network by configuring a wireless mesh network (WMN) where it may otherwise be physically infeasible or cost prohibitive to do so. With the increasing use of real-time applications such as video conferencing and Voice over IP (VoIP), networks are stressed to guarantee...
Undergraduate courses for data communications and telecommunications cover services from a network technology perspective more so than they cover network technologies from a service perspective. Thus, critical issues such as interoperability and end-to-end system integration in support of new service and application ideas are left unexplored until post graduation, on-the-job training. Up until now,...
The following topics are dealt with: mobility management; ad hoc networks; routing protocol; resource allocation; cooperative relay MIMO systems; adjacent channel interference cancellation; MANETs; LDPC codes; frequency selective fading channels; mobile services; mobile telemedicine; TCP; public key; time frequency division multiplex; RF front-ends design; asynchronous DS-CDMA; indoor tracking algorithm;...
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