Shkelzen Cakaj

Rigorous analysis on performance of LEO satellite ground station in urban environment

Since two decades the microsatellites in Low Earth Orbits (LEO) are in use. Low Earth Orbit satellites are used for public and massive communication and for scientific purposes, also. Low Earth Orbits vary with the type of satellites and their primarily purposes. Low Earth Orbit scientific satellites have very wide application, including Earth’ s surveillance and astronomy applications. These satellites provide opportunity for investigations for which existing techniques are either difficult or impossible to be applied. Thus, it is to be expected that such missions in the near future will be more developed especially in the fields where similar experiments can not be done by means on the Earth. So, also the ground stations have to be established in order to communicate with such satellites. The quality of communication depends on the performance of the satellite ground station, also. Before the implementation of the ground station the analyses related to environmental factors have to be considered, especially in urban areas. Rain effects, intermodulation products disturbance, contact time duration at low elevation, are few aspects which are considered in this work related to final decision on design of the ground station. The performance measurement of the ground station based on Sun flux density is described as an experimental method which provides opportunity to check the performance of the ground station.

Migration from PSTN to NGN

Modernization of telecommunication infrastructure of PTK is a Post and Telecommunication of Kosova (PTK) project. This project was initiated to replace most of the switching and access infrastructue of PTK that was very old, up to semi-automatic exchanges. For this project PTK decided to go for the latest switching technology Next Generation Network (NGN). The project consist of replacement of switches in 6 regions with the new access equipment that would use the same Soft Switch installed at central server room in Prishtina, capital of Kosova. The applied aproach by PTK to make a large step by moving from semi-electronic switches to NGN is presented by this paper.

Rain Attenuation at Low Earth Orbiting Satellite Ground Station

The project MOST (micro variability and oscillations of stars) is a Canadian micro satellite space telescope mission. The micro satellite carries a Rumak-Maksutov telescope with an aperture of 15 cm. The size of the satellite is 65 cmtimes65 cmtimes30 cm and the mass is about 65 kg. The goals of the mission are to analyze the inner structure of stars, set a lower limit to the age of the universe and to search for Exoplanets. The project MOST consists of a low Earth orbiting (LEO) satellite and three ground stations, one of them in Vienna. The Vienna ground station system was set up at the Institute for Astronomy of the University of Vienna in cooperation with the Institute of Communications and Radio-Frequency Engineering of the Vienna University of Technology. During the link budget calculations atmospheric attenuation had to be considered. The satellite link operates in 2 GHz band. In this band the ionospheric effects are negligible. This paper presents the methodology applied for rain attenuation calculations

Composite Noise Temperature at Low Earth Orbiting Satellite Ground Station

Noise introduces a fundamental limit on the performance of any communication system. Satellite communication systems are particularly susceptible to noise because of their inherent low received power. During the link budget calculations, noises of the equipment and line loss have to be considered. An alternative, but equivalent way of expressing the noisiness of the equipment and line loss is through noise temperature. The noise temperature which represents noise of all components in satellite receiving system chain is called composite noise temperature. Thus, on this paper the methodology applied for composite noise temperature calculations for satellite links is presented. In order to illustrate these calculations, data of Vienna ground station within MOST project are applied. The project MOST (microvariability and oscillations of stars) is a Canadian micro satellite space telescope mission. The project MOST consists of a low earth orbiting (LEO) satellite and three ground stations, one of them in Vienna. The Vienna ground station system was set up at the Institute for Astronomy of the University of Vienna in cooperation with the Institute of Communications and Radio-Frequency Engineering of the Vienna University of Technology. The satellite link operates on 2 GHz band

Isolation measurement between uplink and downlink antennas at low earth orbiting satellite ground station

The project MOST (micro variability and oscillations of stars) is a Canadian micro satellite space telescope mission. The micro satellite carries a Rumak-Maksutov telescope with an aperture of 15 cm. The size of the satellite is 65 cm times 65 cm times 30 cm and the mass is about 65 kg. The goals of the mission are to analyze the inner structure of stars, set a lower limit to the age of the universe and to search for exoplanets. The project MOST consists of a low earth orbiting (LEO) Satellite and three ground stations, one of them in Vienna. The satellite link operates on 2 GHz band. The separate antennas are used for uplink and downlink in order to achieve better downlink margin. The isolation measurement between uplink and downlink antennas is presented.

Quality of experience (QoE) improvement by video caching implementation

Video streaming through Internet faces different challenges caused by network performance and heterogeneity nature of internet. The larger the distance between end-user and streaming server the stream passes through different networks and causes delays which affect the user quality of experience (QoE). An optimal approach to minimize delays and offer high video quality is Cache implementation. Operators and content providers today are implementing CDN (Content Delivery Networks) using Cache technology to overcome this problem. Cache Servers store the content in order that future requests can be served faster from the cache. The main objective of this paper is to provide analysis of the implemented cache approach and the impact in main QoE parameters.