The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
SCIS is the State Company for Internet Services in Iraq that works as the main Internet Service Provider (ISP). After 2003 war in Iraq, there is extremely high demand for Internet service due to very long period of sanctions enforced on Iraq. However, satisfying such high demand is a challenging task; as the cost, number of subscribers and Quality of Service (QoS) are important factors that need to...
The purpose of this work is to evaluate the quality of encrypted VoIP calls with different encryption algorithms through OpenVPN software, in order to identify differences in results between encryption algorithms and also differences between non-encrypted and encrypted calls. This evaluation will take into account the MOS (Mean Opinion Score), a method to indicate user satisfaction of voice communication...
This paper, as a case study and tutorial, discusses testing methods for general PLL features and their operating margin. These methods can be applied all for analog-, digital- and PW-PLLs. There are various kinds of on-chip measurement macros which can be applied for the PLL testing, and for the direction toward digitally assisted analog circuit testing, it is shown that a digitally controlled variable...
In this paper, we analyze the effect of time-varying channels to video codec buffer specially for low-delay applications. We derive the sufficient conditions under which an encoder can design a bitstream for any time-varying channel without decoder buffer overflow and underflow. We then apply those conditions to design a bandwidth adaptive rate control in x264 and test it under LTE simulator. Our...
Quality of Service supported multicast has attracted more attentions in the last few years and is regarded as an important communication mechanism for implementing real-time multimedia applications in Next Generation Internet. Considering the difficulty on exact measurement and complete expression of network parameters, an intelligent QoS multicast routing algorithm based on Mind Evolutionary Computation...
A multi-GHz arbitrary timing generator (ATG) design is described and demonstrated in a hardware prototype. The objective of the ATG is to realize ATE hardware that nearly matches the unlimited timing flexibility of software simulation tools. The ATG allows timing edges to be programmed at almost any desired point within the test, with minimal constraints. The delay of every edge can be changed on...
A time-to-digital converter (TDC)-based skew compensation technique is proposed to minimize timing skew between main and pre-emphasis signals of high-speed current mode output driver. Skew between signals of main and pre-emphasis branches of output driver increases jitter. The proposed technique measures and compensates the timing skew to reduce the jitter in the output data. With the compensation...
In this paper, the authors present a proof-of concept demonstrator for an adaptive inter-system-interface gateway between LMR and IP based networks. To underline the flexibility of the proposed solution, a satellite link is utilized to enable the integration of an independent LMR cell or direct connected terminals (MicroSpot) into an existing infrastructure over long distances without the need for...
This paper investigates and compares the performance of the popular VoIP codecs G.711, G.723.1 and G.729A over an IP network based on SIP architecture, using RTP as a transport protocol. This is based on different simulations in order to evaluate the performance of each codec and to find the optimal codec. For this objective this paper analyzes Quality of service (QoS) parameters, principally delay,...
The operating system (OS) Jitter phenomenon has been considered an import and critical factor in high-performance distributed computing. In this paper, we present the results of an experimental study that quantifies the effects of different sources of OS Jitter in the Linux operating system. We use the design of experiments (DOE) method to conduct controlled experiments statistically planned. Different...
The purpose of this research is to design and evaluate a new queue management algorithm effectively controlling the heavy-tailed traffics. Among active queue managements (AQM), Random Early Detection (RED), has been widely used to improve the TCP throughput. The heavy-tailed traffic, however, generates the large fluctuation on the queue causing the degradation of fairness in terms of jitter performance...
Voice communication requires stricter QoS than other types of data communication. Thus, network operations, including the MAC layer protocol, should provide specific voice communication handling to meet voice application requirements. The current MIL-STD-188-220 does not guarantee the QoS of voice communication because of the round robin scheduling mechanism in network access control. Thus, we propose...
Multipath transmission is the important way to increase the efficiency and reliability of network transmission. Along with the development of overlay network, multi-homed host et al, multipath transmission control becomes the hot spot of network transmission technology research gradually. As the base of path choice and switching in multipath transmission, real-time evaluation of path QoS is a key...
This paper presents the results of a simulation-based performance evaluation of a Ka band broadband GEO satellite communication system. The simulation approach is presented, focusing on the modeling of the ground and payload equipment with their RF impairments. The communication system performance are evaluated and presented in terms of the achievable PER, for the Forward, Return and Mesh system communication...
Recently, the rapid development of VoIP has attracted considerable attention. However, VoIP service exposes weakness on voice quality such as delay and jitter. So it is helpful to improve the quality of VoIP service by mitigating time latency and jitter. In this paper, VoIP phone is implemented by open source software components using the Session Initiation Protocol (SIP) based on embedded systems...
Current mirrors are an established technique for reducing memory requirements and run time in Spice-based bus simulations with many simultaneously switching outputs (SSO). Mismatched delayss can reduce accuracy, and a current mirror bus architecture enhanced with a bridge circuit is shown to restore accuracy with mismatched package delays.
To properly operate closed industrial control networks, it is required that communication with nearly constant delay bounds be supported. In [9] the authors introduced FlexTDMA in order to provide this support, and with minimal delay-jitter in an asynchronous network, under unicast communication. In this paper we consider how periodic on-off traffic and frame loss are managed in the presence of network...
Mobile ad hoc networks (MANETs) are notoriously difficult to defend against attack. In this paper we demonstrate that by optimizing a previously reported covert timing channel, it is possible to simultaneously improve the reliability of the channel and create a metric that reliably detects attacks. Using standard methods from information theory, we compute the capacity of the covert channel and show...
This paper aims to introduce the relationships between some Voice over IP Key Performance Indicators (KPIs) and to address them through the background of possible network or platform problems, resulting in KPIs degradation. We present extensions of a generic Quality of Service (QoS) monitoring strategy by describing a variety of correlations between the QoS metrics. For echo correlation for instance,...
The term Hap tic refers to the sense of touch. The feeling has the ability to increase the sense of reality, to excite the user and improve the quality of experience. To carry out this sense through the Internet was, until recently, impracticable due to processing inefficiencies and/or protocol performance in capabilities, such as throughput and jitter constraints. This paper describes a Hap tic system...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.