Modern Communication Services Research Articles

INFLUENCE OF THE TRANSMISSION RATE OF DIGITAL INFORMATION STREAMS IN VSAT-BASED SATELLITE COMMUNICATION NETWORKS WITH APPROPRIATE SIGNAL-TO-NOISE RATIOS ON THE PROBABILITY OF BIT ERROR

Among the satellite technologies, special attention is paid to the development of satellite communication technologies based on VSAT (Very Small Aperture Terminal). Small ground station VSAT, a terminal with a very small antenna diameter (0.9 … 3.5 m), allows the use of VSAT stations antennas. This makes it possible to significantly reduce the size and cost of ground stations, the power of their transmitters and make their use widespread. VSAT equipment makes it possible to build multiservice networks that provide all modern communication services: Internet access; telephone connection; transmission of audio and video information; reservation of existing communication channels; data collection, monitoring and remote control of industrial facilities, etc. Satellite signals, especially high-frequency bands Ku and Ka, are subject to attenuation during rain, fog, clouds. But this shortcoming is easily overcome when properly designing the network, choosing the technology and location of antennas. The scientific article is devoted to the study of the influence of the speed of digital information transmission in satellite networks based on VSAT – a small satellite ground station, at the appropriate signal-to-noise ratio at the input of the receiver of the subscriber satellite station on the probability of bit error. The technical characteristics of subscriber satellite stations operating in the Ku-frequency band 11/14 GHz with an artificial satellite of the Earth in geostationary orbit are given. The dynamic range of signal power change at the input of the VSAT-based satellite ground receiver at different data rates is determined, which provides a given signal-to-noise ratio and bit error probability in the range of 10-7 – 10-4 for the required communication quality.

SmartCards as Analogous Tools to Operate Tablet Computers for Elderly-A Feasibility Study.

Background: Older adults sometimes shy away from using modern digital communication devices due to lacking experience and fear of failure. Within the present project, SmartCards were developed as analogous means to operate tablet computers for older adults with little previous computer experience. We investigated whether the SmartCards-Tablet-System would (a) increase use of digital communication and (b) affect loneliness, autonomy, cognitive ability and wellbeing of the users. Methods: The suitability and acceptance of the system was evaluated during a three month trial period with seniors in retirement homes, seniors with home assistance care and a waiting control group. Results: Acceptance, duration of use and frequency of use were high in both experimental groups. Cognitive ability significantly improved after three months’ use in both experimental groups. Effects on loneliness, autonomy and wellbeing could not be observed. Discussion: Our results indicate that seniors are very much able and curious to use modern digital devices if the interface and hardware are adjusted to their needs and capabilities without being stigmatizing. The use of modern communication services and the World Wide Web can promote contact of seniors with their (younger) relatives.

Innovative Approach to Sustainable Mobility and Transport Through Big Data From ICT – Pilot Study in Cracow, Poland

New challenges of urban transport are connected to sustainability, the growing urban population globally, life quality and quality of urban environment, reduction of pollution and energy consumption. Sustainable urban mobility is no more dependent only on passenger transport efficiency, but also on transport accessibility of commuting services, acceptable level of comfort, safety and security of urban public transport and many more. Although a huge amount of data are available from modern communication services, the question of how to use those big data efficiently to improve urban mobility is unknown. Positive changes of mobility attitudes and travel behavior of citizens are going slowly, which means that personal motivation do not follow big data availability. This motivation is dependent on quality of public transport offer and services, among which information services are suspected to play a crucial role. Modern ICT methods of transport information delivery are based on Internet and social media, which through commonly used mobile devices are available at every stage of journey. In this article authors try, based on the pilot survey, to check how young Krakow citizens use social media in every day travels and commuting. The overall goal of the author’s study is to answer the question: how to use big data coming from ICT in order to upgrade urban transport sustainability.

An optimized design of optical networks using evolutionary algorithms

Optical networks are key enablers of the modern communication services to handle the increasing bandwidth requests. Virtualization is a feasible technology to response to the users' demands. On the other hand, the cloud computing, as a distinguished use case of the virtualized optical networks, has impacted the IT world. In virtualization of the resources, optimum mapping of the virtual optical networks on the physical infrastructure plays an important role. In this paper, a novel optimized scheme for mapping the virtual optical networks on the physical infrastructure is proposed. A new formulation for Routing and Wavelength Assignment, RWA, problem is presented. A novel encoding method for optical networks is proposed based on categorizing the wavelengths into different groups according to data transmission rate. Then, the Genetic Algorithm, GA, and Binary Particle Swarm Optimization, BPSO, as two popular evolutionary algorithms are implemented to find the optimum map of the virtual optical networks on the physical infrastructure using the proposed encoding method. The optimization constraints and two heuristics, proposed to satisfy them, are detailed. Finally, the simulation results for a physical infrastructure and different virtual optical networks are presented. Results show that the GA outperforms the BPSO in terms of providing optimized solutions with less values of the defined cost function. But the run time required to find the optimum map of the virtual optical networks is more than the BPSO.

Cognitive Radio Systems: Multicarrier Modulation and Power Allocation Challenges

The rapid development of modern communication services results in high data rate requirements from the end user. It is challenging to meet high data rate requirements because of prevailing issues such as spectrum scarcity and spectrum underutilization due to fixed spectrum assignment policy. Cognitive Radio (CR), being the enabler of dynamic spectrum management techniques, has the capability to tackle these issues by proficiently implementing spectrum sharing schemes using Multicarrier Modulation (MCM) techniques. In CR system, where the Primary User (PU) and the Secondary User (SU) co-exist in the same frequency band, mutual interference (i.e., from SU to PU and vice versa) is a limiting factor on the achievable capacity of both the PU and the SU. Power allocation in MCM based CR systems aims to dynamically control the transmit power on each subcarrier of the SU in order to reduce the mutual interference. Furthermore, combining multiple antennas with MCM is regarded as a very attractive solution for the CR communications to effectively enhance data rate without demanding additional bandwidth and transmit power.

La mutation des télécommunications en Allemagne de l'Est

The collapse of the Soviet Empire has provided enormous new opportunities for those Western telcos able to penetrate this promising but difficult market. The Stalinist command economy's neglect of telecommunications created a huge industrial and household demand for modern communication services, but at the same time left organizations and ingrained values hostile to market economies. Several studies illustrate different telco strategies and examine potential success and failures. Among other cases those of Alcatel/SEL and Siemens in East Germany highlight the risks and rewards of Eastern European experiences.

Modern communication services

The authors review current services and envisage what new services could evolve from the existing networks. Aspects covered include new services in existing telephone and data networks, telecopy services, teletex, electronic mail, viewdata, value-added data networks, mobile radio, integrated service digital network, picturephone and video conference, new services in radio broadcasting networks