This article deals with the impact of Wireless (Wi-Fi) networks on the perceived quality of voice services. The Quality of Service (QoS) metrics must be monitored in the computer network during the voice data transmission to ensure proper voice service quality the end-user has paid for, especially in the wireless networks. In addition to the QoS, research area called Quality of Experience (QoE) provides metrics and methods for quality evaluation from the end-user’s perspective. This article focuses on a QoE estimation of Voice over IP (VoIP) calls in the wireless networks using network simulator. Results contribute to voice quality estimation based on characteristics of the wireless network and location of a wireless client.
Nowadays, WiFi is mostly operating in 2.4 GHz band, which allows only 3 non-overlapping channels. For deployment in building it could be a problem to repeat only three channels. In this paper we compare standard three channel scheme (channels 1, 6 and 11) with four channel schemes. The most promising scheme is with channels 1, 5, 9 and 13, which involves overlapping channels, but the overlap is minimal and in certain distances (power levels) is possible to use this scheme. The problem could be in some countries which do not allow usage of 13 channels. We also compare other schemes, with overlapping channels, but they have a much lower throughput than scheme with channels 1, 5, 9 and 13.
A management of computer classroom is undoubtedly a diffi cult task for the administrator which has to prepare virtual operating systems for education. It is quite common that lectors need to edit the particular machine during the semester, and that is the case where the main problems can appear. The process of changes deployment is not just very time-consuming but during it a virtual machine inconsistency can appear. The main part of this paper focuses on system process diagrams and its pseudocode. At fi rst, the machine is created on the remote server by lector or administrator. A er a proper approval, the machine is able to be deployed. The lector then specifi es the details about date, time and destinations of the virtual machine deployment. Once these details are approved, the virtual machine will be automatically deployed at the specifi ed time. The automatic deployment includes also an initial confi guration of the virtual machine at remote desktop and its post-install confi guration (hostname, MAC address, etc.). Once all steps are completed, the process will be marked as succeed. We present an automatized solution which provides a possibility how to easily manage computer classroom with virtual operating systems. The proposed solution should deliver a greater fl exibility, more reliability and faster deployment in comparison with the current solution used in our computer classroom. The proposal is also able to manipulate with already deployed machines for easy changes (e.g. so ware updates). The main advantage is the improvement of classroom management process automation.
FEJFAR JIŘÍ ŠŤASTNÝ JIŘÍ, POKORNÝ MARTIN, BALEJ JIŘÍ, ZACH PETR: Analysis of sound data streamed over the network. Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013, LXI, No. 7, pp. 2105-2110
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