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VoIP technology becomes more and more profitable and many people prefer this kind of connection instead of classic TDMA telecommunication network. Very helpful is a fact that with voice services becomes another related services like a video, a text or even a file transmission. These services are integrated both into simple software VoIP clients and...
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Voice over IP (VoIP) is a very attractive technology. It is increasingly adopted by enterprises and consumers. VoIP inherits adjacent security issues to IP networks to which are added new specific problems. Spam over IP telephony (SPIT) is expected to become one of the VoIP problems. To resolve it, many anti-SPIT mechanisms are proposed but there a...
In this paper we present a framework for autonomic QoS provisioning for VoIP services. The central role is held by a Measurement Based Admission Control algorithm which incorporates three innovations. First, the mathematical underpin-ing obeys a non-parametric approach, removing the dependency on a priori assumed characteristics of the underlying s...
With the appearance of new Internet services like Voice over IP and IP television, malwares are in the way to update and extend their targets. In this paper, we discuss the emergence of a new generation of malwares attacking VoIP infrastructures and services. Such malwares constitute a real threat to the currently deployed VoIP architectures withou...
Voice over IP (VoIP) is becoming as a common application in wireless local area network. It uses to transfer the voice over Internet Protocol networks. Furthermore, it used over 802.11 standards, it is becoming greatly prevalent, in spite of these features, it stills suffer from many retractions like delay in reaching to destination and packet loss...
Deploying IP telephony or voice over IP (VoIP) is a major and challenging task. This paper describes an analytical approach and tool to assess the readiness of existing IP networks for the deployment of VoIP. The analytical approach utilizes queueing network analysis and investigates two key performance bounds for VoIP: delay and bandwidth. The ana...
Citations
... As a result of the steady growth in VoIP usage, providing reliable services with satisfactory voice quality is now a high priority for Internet and VoIP service providers. A number of factors may affect the service quality of VoIP [1] for example, packet loss, packet delay, network delay variation (also known as "jitter") [2], echo, noise [3], and harmonic and inharmonic distortion [4]. ...
Improving the quality of service in IP networks is a major challenge for real-time voice communications. In particular, packet arrival-delay variation, so-called "jitter," is one of the main factors that degrade the quality of voice in mobile devices with the voice-over Internet protocol (VoIP). To resolve this issue, a receiver-based enhanced timing recovery algorithm combined with active jitter estimation is proposed. The proposed algorithm copes with the effect of transmission jitter by expanding or compressing each packet according to the predicted network delay and variations. Additionally, the active network jitter estimation incorporates rapid detection of delay spikes and reacts to changes in network conditions. Extensive simulations have shown that the proposed algorithm delivers high voice quality by pursuing an optimal trade-off between average buffering delay and packet loss rate.
... The Quality of Service (QoS) is mostly monitored issue by telecommunication operators and vendors. The quality of speech can be affected by many factors such as packet loss, packet delay, jitter, echo, noise [1], harmonic and inharmonic distortion [2], etc. ...
VoIP is one of the most emerging technologies in the area of speech communications. VoIP is widely deployed in fixed line access networks. However, userpsilas requirements on the mobility within communication and on the quality of the speech communications are increasing. Therefore, VoIP technology is more and more integrated into broadband wireless networks with QoS support such as WiMAX. The latest version of WiMAX standard, based on IEEE 802.16e, has implemented a full mobility support. The mobility is allowed due to a handover procedure. IEEE 802.16e specifies only one mandatory handover procedure: hard handover. This handover type is easy to implement, but it increases end-to-end packet delay that is critical for delay sensitive services such as VoIP. This paper evaluates an impact of the handover on the speech quality in VoIP networks.
Many modern systems rely on transparent human-machine interfaces that allow them to fulfill their purpose in a more efficient and unobtrusive way. In order to build an efficient and reliable speech based human-machine interface, being able to determine when to process the incoming signals even in unfavorable environments is a definite requisite. Our Voice Activity Detection (VAD) method proposes a novel way of mixing monaural and microphone array techniques; monaural techniques are mainly focused on providing robusticity, while microphone array techniques complete the system with the capability of detecting source direction from background noise. This is implemented by first applying a cochlear filtering and channel selection to remove noise, and then a series of strict conditions are applied in order to be able to obtain the fundamental frequencies of the sources which is finally used to obtain the VAD masks.
