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Ing. Robert Bešťák, Ph.D.

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Insight into Anomaly Detection and Prediction and Mobile Network Security Enhancement Leveraging K-Means Clustering on Call Detail Records

  • DOI: 10.3390/s24061716
  • Link: https://doi.org/10.3390/s24061716
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The dynamic and evolving nature of mobile networks necessitates a proactive approach to security, one that goes beyond traditional methods and embraces innovative strategies such as anomaly detection and prediction. This study delves into the realm of mobile network security and reliability enhancement through the lens of anomaly detection and prediction, leveraging K-means clustering on call detail records (CDRs). By analyzing CDRs, which encapsulate comprehensive information about call activities, messaging, and data usage, this research aimed to unveil hidden patterns indicative of anomalous behavior within mobile networks and security breaches. We utilized 14 million one-year CDR records. The mobile network used had deployed the latest network generation, 5G, with various sources of network elements. Through a systematic analysis of historical CDR data, this study offers insights into the underlying trends and anomalies prevalent in mobile network traffic. Furthermore, by harnessing the predictive capabilities of the K-means algorithm, the proposed framework facilitates the anticipation of future anomalies based on learned patterns, thereby enhancing proactive security measures. The findings of this research can contribute to the advancement of mobile network security by providing a deeper understanding of anomalous behavior and effective prediction mechanisms. The utilization of K-means clustering on CDR data offers a scalable and efficient approach to anomaly detection, with 96% accuracy, making it well suited for network reliability and security applications in large-scale mobile networks for 5G networks and beyond.

A Study on Disaster Management Databases

  • Authors: Rajasekharan, R., Ing. Robert Bešťák, Ph.D., Dusserre, G.
  • Publication: 2021 International Conference on Military Technologies (ICMT). Praha: IEEE Czechoslovakia Section, 2021. p. 1-6. ISBN 978-1-6654-3724-0.
  • Year: 2021

Augmented reality-based solar system for e-magazine with 3-D audio effect

  • Authors: Martin Sagayam, K., Timothy, A.J., Ho, C.C., Henesey, L.E., Ing. Robert Bešťák, Ph.D.,
  • Publication: International Journal of Simulation and Process Modelling. 2020, 15(6), 524-534. ISSN 1740-2123.
  • Year: 2020
  • DOI: 10.1504/IJSPM.2020.112460
  • Link: https://doi.org/10.1504/IJSPM.2020.112460
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Augmented reality (AR) is the newest technology that can be applied to computer vision, audio, video and other sensor-based input projects into 3D vision. It is the backbone for all specialisation of science, medical and engineering concepts. Currently, the reading and learning method through AR-based approaches are quite highly intensive than the existing methods such as papers, books and magazines. This strategy is more expensive but it is more interactive to the user in understanding the root concepts in an effective manner. This paper explores the experiment on solar system revolution pattern along with 3D audio effect in spatial dimension.

Dependency Between the Distance and International Voice Traffic

  • Authors: Aziz, Z., Ing. Robert Bešťák, Ph.D.,
  • Publication: Ubiquitous Networking. Cham: Springer, 2020. p. 193-204. LNCS. vol. 12293. ISSN 0302-9743. ISBN 978-3-030-58007-0.
  • Year: 2020
  • DOI: 10.1007/978-3-030-58008-7_16
  • Link: https://doi.org/10.1007/978-3-030-58008-7_16
  • Department: Department of Telecommunications Engineering
  • Annotation:
    In this paper, we investigate the international outgoing/incoming voice traffic dependence on the destination based on the three-month Call Detail Records data set analyzes. The distance between countries, more precisely the distance between centroids of countries, is calculated by using the great-circle distance approach. Additionally, the voice traffic parameters are normalized with respect to population of countries to obtained comparable outcome independently of the country population.

Analyzing user mobility using signaling data

  • Authors: Khuder, I., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of 7th International Conference on Military Technologies. Prague: Czechoslovakia Section IEEE, 2019. ISBN 978-1-7281-4593-8.
  • Year: 2019
  • DOI: 10.1109/MILTECHS.2019.8870096
  • Link: https://doi.org/10.1109/MILTECHS.2019.8870096
  • Department: Department of Telecommunications Engineering
  • Annotation:
    In recent years, the monitoring and prediction of users' mobility in a mobile network has become a helpful tool to optimize the network's operation. However, the conventional techniques being used in this regard have several drawbacks, such as their dependence on user/device cooperation in a way or another, or on a specific HW/SW implementation in devices and/or networks. In this paper, we discuss a possible user/device-independent technique which is based on the radio interface signaling messages that result in user mobility data stored in the network. These data can also be used, to a certain extent, in obtaining information about user mobility. Although this technique, known as the Cell-ID location technique, does not provide a precise location, a careful analysis of these data, detecting the occurrence of the "cell oscillation" phenomenon in the mobility data, combined with a good knowledge of the coverage topology, can help detecting the status of the mobile station and improving the location accuracy.

Cells Interrelation in Mobile Networks

  • Authors: Khuder, I., Ing. Robert Bešťák, Ph.D.,
  • Publication: 26th International Science Conference on Computer Networks. Cham: Springer, 2019. p. 242-255. vol. 1039. ISSN 1865-0929. ISBN 978-3-030-21951-2.
  • Year: 2019
  • DOI: 10.1007/978-3-030-21952-9_19
  • Link: https://doi.org/10.1007/978-3-030-21952-9_19
  • Department: Department of Telecommunications Engineering
  • Annotation:
    To better optimize a mobile network, it’s useful to have knowledge about the movement of users in the network. This can relatively easily be done via sending GPS coordinates calculated in a mobile terminal to network. However, this approach is, first of all, quite energy demanding, and secondly user dependent, as a user has to pose a mobile terminal supporting GPS and has to allow the usage of GPS. Another possibility is to make use of signaling data which is an essential and integral part of mobile network operations, plus it’s more or less user independent. By combining the signaling data together with the network coverage map, we can estimate users’ movements in the network. In this paper, we focus on cells interrelation in a network coverage map. We present a simplified cell graphical representation, using a so-called cell-vector, and we analyze the possible use of cell-vector position scenarios to predict whether a pair of cells are neighboring each other or not.

Evaluation of Random Physical Cell Id Assignment to Femtocells Under Dense Cell Deployment

  • Authors: Sedláček, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: Wireless Personal Communications. 2019, 104(2), 753-769. ISSN 0929-6212.
  • Year: 2019
  • DOI: 10.1007/s11277-018-6049-y
  • Link: https://doi.org/10.1007/s11277-018-6049-y
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper discusses femtocell identification aspects in mobile networks such as long-term evolution (LTE) and LTE-advanced. Femtocells, or femto access points (FAPs), are newclass of base stations in addition to existing macro, microcells. Unlike these cells, femtocells implement automatic configuration principles. One of the main parameters in the automatic configuration process is among others an physical cell identifier. By considering two FAP deployment models, we discuss collision and confusion issues, which affect the proper physical cell id allocation. The first model represents a random deployment of FAPs within a (rural) macrocell area, whereas the second one, called dense urban model, constitutes placement of FAPs in a built-up area. The given study serves for the better understanding of interrelations between differently placed FAPs in term of collision and confusion events, and the obtained results can be used as a basis when designing an algorithm for automated assignment of physical cell identifier.

Mobile Voice Traffic Load Characteristics

  • Authors: Aziz, Z., Ing. Robert Bešťák, Ph.D.,
  • Publication: 26th International Science Conference on Computer Networks. Cham: Springer, 2019. p. 193-207. vol. 1039. ISSN 1865-0929. ISBN 978-3-030-21951-2.
  • Year: 2019
  • DOI: 10.1007/978-3-030-21952-9_15
  • Link: https://doi.org/10.1007/978-3-030-21952-9_15
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Knowledge of traffic load evolution in time is essential to properly configure and dimension a mobile network. Moreover, it is a key parameter to indicate the network performance and quality of service. In this paper, we use interarrival time (time between arrivals), waiting time, and service time parameters to investigate outgoing and incoming traffic of an international voice traffic carrier. Both types of traffic are analyzed for the previously mentioned parameters by taking into account short and long-distance international call scenarios. The obtained results follow the expected Poisson and Exponential distributions for these parameters. In addition, the traffic load of neighboring countries shows a long-term stability and consistency.

Multiuser Interference Mitigation using CSK in Indoor Visible Light Communications

  • Authors: Delwar, T.S., Arya, S., Chung, Y.H., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings - 2019 7th International Conference on Green and Human Information Technology. Piscataway, NJ: IEEE, 2019. p. 39-42. ISBN 978-1-7281-0627-4.
  • Year: 2019
  • DOI: 10.1109/ICGHIT.2019.00016
  • Link: https://doi.org/10.1109/ICGHIT.2019.00016
  • Department: Department of Telecommunications Engineering
  • Annotation:
    In this paper, we present a novel multiuser indoor visible light communication (VLC) system based on code shift keying (CSK) modulation. The proposed CSK scheme employs M signaling waveforms each obtained from the circular shift of a single fundamental PN code. In this proposed scheme, the performance is investigated in the presence of jamming and/or interference from other users. In addition, the system performance of CSK is compared with traditional on-off keying (OOK) based system. The simulation results show that the proposed CSK is more reliable than OOK in multiuser systems.

Vectors-based method to deduce neighboring cells in mobile networks

  • Authors: Khuder, I., Ing. Robert Bešťák, Ph.D.,
  • Publication: 2019 International IEEE Conference and Workshop in Óbuda on Electrical and Power Engineering. Institute of Electrical and Electronics Engineers Inc, 2019. p. 35-40. ISBN 978-1-7281-4357-6.
  • Year: 2019
  • DOI: 10.1109/CANDO-EPE47959.2019.9111034
  • Link: https://doi.org/10.1109/CANDO-EPE47959.2019.9111034
  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper discusses the coverage in mobile networks, for which we propose a novel method to deduce neighboring cells, where the number of cells could be very large. The priority for this method is simplicity, so it can be easily implemented and executed in a short processing time, even for a large number of cells. Therefore, the proposed method uses a simple graphical representation of the cells by means of vectors to only maintain the cells’ size and orientation. Although the method is motivated by applications which are related to user-mobility in mobile networks, it might be useful in other applications, where the nearest neighbors search problem is involved, such as in computational geometry and pattern recognition in machine learning.

3D scenery learning on solar system by using marker based augmented reality

  • Authors: Martin Sagayam, K., Ho, C.C., Henesey, L., Ing. Robert Bešťák, Ph.D.,
  • Publication: 4th International Conference of the Virtual and Augmented Reality in Education, VARE 201. Genova: Dime University of Genoa, 2018. p. 139-143. ISBN 978-88-85741-21-8.
  • Year: 2018
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Augmented reality (AR) is the technology that works on computer vision based recognition algorithms to augment sound, video, graphics and other sensor based inputs and real world objects using the camera of your device. AR applications can become the backbone of education industry. Apps are being developed which are embed text, images and videos, as well as the real-world curriculums. With help of AR, travellers can access real-time information of historical places just by pointing their camera viewfinder to subjects. There are two major forms of augmented reality, marker-based AR and markerless AR. A marker based AR works on concept of target recognition. The target can be 3D object, text, image, QR Code or human-face called markers. Whereas marker-less AR, also known as location-based AR, uses GPS of mobile devices to record the device position and displays information relative to that location. Few drawbacks in marker-less AR like house resolution, size variation and time delay can be solved using marker based algorithms such as marker detection, triangle similarity for marker to camera distance and corner detection.

An automatic PCI assignment framework for femtocells in LTE networks

  • Authors: Sedláček, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: Mechatronics 2017. Springer, Cham, 2018. p. 103-110. Advances in Intelligent Systems and Computing. vol. 644. ISSN 2194-5357. ISBN 9783319659596.
  • Year: 2018
  • DOI: 10.1007/978-3-319-65960-2_14
  • Link: https://doi.org/10.1007/978-3-319-65960-2_14
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Evolving mobile networks are requested to transport an increasing data traffic as a result of popularity of online services together with accessibility of modern mobile devices among people. A solution that can help mobile operators to quickly deploy base stations, ensuring great indoor coverage with minimum costs, and providing high data rate capabilities, poses a femtocell concept. As femtocells are expected to be costumer-deployed in great numbers, they have to be effectively managed and configured. Among parameters that should be automatically configured belong a physical cell identifier, called physical cell identity (PCI). However due to limited range of available PCI values and collisions and/or confusions may occur in the network. In this paper, we propose a centralized automatic PCI configuration scheme for femtocell networks that can integrate algorithms and proposals of other authors as well.

Analysis of Call Detail Records of International Voice Traffic in Mobile Networks

  • Authors: Aziz, Z., Ing. Robert Bešťák, Ph.D.,
  • Publication: 10th International Conference on Ubiquitous and Future Networks. USA: IEEE Computer Society, 2018. p. 475-480. ISSN 2165-8536. ISBN 978-1-5386-4646-5.
  • Year: 2018

Self-Organisation Network (SON) Dengan Mekanisme Load Balancing

  • Authors: Ulvan, A., Ulvan, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: Jurnal Rekayasa Elektrika. 2018, 14(3), 152-157. ISSN 1412-4785.
  • Year: 2018
  • DOI: 10.17529/jre.v14i3.9987
  • Link: https://doi.org/10.17529/jre.v14i3.9987
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Load balancing is one of the mechanism used in the self-organization network (SON) to balance the traffic at the overloaded base station with the adjacent low-loaded base station. Load balancing is done by adjusting the handover parameters (metric) to obtain the optimal traffic balance. In this work, the adjusted parameters are the capacity of the cell. Cell capacity is strongly influenced by the bandwidth, modulation type, and the bit rate used by the user. The performance of load balancing was tested by a simulation and network test-bed measurement. The testing results on the Long-Term Evolution Advanced network showed the greater the bandwidth the greater the capacity of the cell. Moreover, the larger type of modulation, the cell capacity will also be greater. On the other hand, the greater bit rate used by the user, then the cell capacity will decrease. The calculation analysis of cell capacity is taken as the basic operation for load balancing procedure. A load balancing process algorithm is introduced to describe the mentioned procedure. The algorithm also considers the ping-pong effect that might occur due to the delay on the handover process.

Survey on the classification of intelligence-based biometric techniques

  • Authors: Martin Sagayam, K., Felix Jacob Edwin, J., Sujith Christopher, J., Reddy, G.V., Ing. Robert Bešťák, Ph.D., Hun, L.C.
  • Publication: Biologically Rationalized Computing Techniques For Image Processing Applications. Dordrecht: Springer Netherlands, 2018. p. 111-132. Lecture Notes in Computational Vision and Biomechanics. vol. 25. ISSN 2212-9391. ISBN 978-3-319-61315-4.
  • Year: 2018
  • DOI: 10.1007/978-3-319-61316-1_6
  • Link: https://doi.org/10.1007/978-3-319-61316-1_6
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Over the past few decades due to the advancement of technology, biometrics has evolved into a key factor of security for societal needs. Biometrics started as a basic ID verification system and has evolved into a major factor of authentication by taking several biological parameters as references. There are certain issues that researchers have yet been facing against hack or overriding. This chapter covers a comparative study of different biometrics and its methods used for safe authentication that improves security management for complicated scenarios.

A Videoconferencing System Based on WebRTC Technology

  • Authors: Ing. Robert Bešťák, Ph.D., Hlaváček, J.
  • Publication: 24th International Conference on Computer Networks. Heidelberg: Springer, 2017. p. 245-255. vol. 718. ISSN 1865-0929. ISBN 978-3-319-59766-9.
  • Year: 2017
  • DOI: 10.1007/978-3-319-59767-6_20
  • Link: https://doi.org/10.1007/978-3-319-59767-6_20
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Last years, videoconferencing systems are rapidly evolving and they are becoming more and more popular as a real time communication tool among users. A technology such as VoIP can be used in conjunction with desktop videoconferencing systems to enable low-cost face-to-face business meetings without a necessity to travel, especially for internationally oriented companies that have offices all around the word. In this paper, we focus on and discuss a videoconferencing platform based on the WebRTC technology. We analyze an impact on the multiplexing server’s CPU load and memory requirements for different number of communicating users while taken into account different HW/SW configurations of end-point devices.

Analysis of Neighbourhood Relations for Femtocell Networks

  • Authors: Sedláček, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: Wireless Personal Communications. 2017, 96(4), 5239-5252. ISSN 0929-6212.
  • Year: 2017
  • DOI: 10.1007/s11277-016-3738-2
  • Link: https://doi.org/10.1007/s11277-016-3738-2
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Nowadays mobile operators are trying to find an economic solution to improve coverage, mainly indoor, and to meet exponentially growing data traffic demands. A cost-effective means to manage these challenges represent small cells, such as metrocells or femtocells. However, in highly populated areas, a large number of these cells can be deployed and can operate in a network. Thus, to enable smooth and simple deployment of small cells, self-organizing concept has to be employed, including an automatic cell identifier assignment mechanism.Due to limited number of available cell identifiers, Physical Cell Identities (PCI), a de-sign of the PCI assignment algorithm is a challenging task, especially in dense small cell environment. In our work, we focus on neighbour relations of densely deployed femtocells because number of neighbouring cells and their relations have direct impact on the PCI assignment algorithm design. Since femtocells are not conventionally deployed by operator but by users, the cells tend to form cell clusters. We investigate these clusters of cells and their structures under different scenarios such as number of cells or radius of cell. Based on our study, the PCI assignment algorithms can be adapted and can be optimised to actual state of a network.

Efficient resource allocation for network-assisted multi-link device-to-device communication

  • Authors: Chithra, R., Ing. Robert Bešťák, Ph.D., Patra, S.K.
  • Publication: International Journal of Communication Systems. 2017, 30(7), 1-16. ISSN 1074-5351.
  • Year: 2017
  • DOI: 10.1002/dac.3169
  • Link: https://doi.org/10.1002/dac.3169
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The network-assisted device-to-device (D2D) communication as an underlay to cellular spectrum has attracted much attention for local area connectivity as a means to improve the cellular spectrum utilization. D2D communication as an underlay to cellular network open up various challenges including appropriate mode selection, spectral utilization, power control and efficient resource allocation. In this article, we study these issues to guarantee the quality-of-service requirements for the users, and a three-step scheme is proposed. The proposed scheme first performs a mode selection procedure to choose the transmission mode of each user equipments (UEs). Then, a clustering scheme is developed to group the links that can share a common resource to improve the spectral efficiency. For the selection of suitable cellular UEs for each cluster whose resource can be shared, a cluster head selection algorithm is also developed. Finally, the expression for maximum number of links that the radio resource of shared UE can support is analytically derived. The performance of the proposed scheme is evaluated using a WINNER II A1 indoor office model. The results show that by proper management, D2D communication can effectively improve the total throughput than conventional cellular communication. From the results, it is clear that the proposed cluster head selection scheme is able to take advantage of both residual power requirement and the power requirement of UEs. Copyright (C) 2016 John Wiley & Sons, Ltd.

Optimization of the low-speed link throughput for voice services

  • Authors: Mazálek, A., Ing. Robert Bešťák, Ph.D., Vránová, Z., Plátěnka, V.
  • Publication: Advances in Military Technology. 2017, 12(1), 61-74. ISSN 1802-2308.
  • Year: 2017
  • DOI: 10.3849/aimt.01171
  • Link: https://doi.org/10.3849/aimt.01171
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The weak point of the field network is represented by E12 low-speed relay links. The situation requires savings of the bandwidth. For this purpose, the necessary bandwidth for voice transmission up to the level of the physical layer has been analyzed. As a suitable solution of network throughput increase, we propose the change of a Voice Payload Size. After finding the optimal Voice Payload Size, tests were carried out to verify the impact of the Voice Payload Size on call quality. A packet loss rate is chosen as a parameter for modelling real traffic. To obtain the expected voice quality, the E-model according to the G.107 Recommendation is applied. The theoretical results are compared with practical measurements, when using the proprietary Cisco Packet Loss Concealment algorithm to evaluate the voice quality. The results obtained have confirmed the suitability of the solution.

Spectrum-less communication by virtualizing the core network of 4G wireless network

  • Authors: Ulvan, A., Ulvan, M., Ing. Robert Bešťák, Ph.D., Septama, H.D.
  • Publication: ARPN Journal of Engineering and Applied Sciences. 2017, 12(2), 365-370. ISSN 1819-6608.
  • Year: 2017
  • Department: Department of Telecommunications Engineering
  • Annotation:
    This research work focuses on the network virtualization, particularly on virtualizing the network elements in LTE-based core network (Evolved Packet Core – EPC). A design of network virtualization is built from the end-user to the core network, which includes all the functionality of the network elements

An Interference Cancellation Scheme for D2D Multi-Link Communication Underlaying Cellular Network

  • Authors: Reghuvaran, C., Ing. Robert Bešťák, Ph.D., Patra, S. K.
  • Publication: Annals of Telecommunications. 2016, 71(1), 47-60. ISSN 0003-4347.
  • Year: 2016

Dynamic Tunnel Switching using Network Functions Virtualization for HA System Failover

  • Authors: Septama, H., Nama, G., Ulvan, A., Ulvan, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: 2015 International Conference on Science in Information Technology (ICSITech). Piscataway, NJ: IEEE, 2016. p. 259-263. ISBN 978-1-4799-8386-5.
  • Year: 2016
  • DOI: 10.1109/ICSITech.2015.7407814
  • Link: https://doi.org/10.1109/ICSITech.2015.7407814
  • Department: Department of Telecommunications Engineering
  • Annotation:
    High Availability (HA) is an ability of the system to operate continuously in desired amount of time. Telephony system, for example, should operate 99.999%, that means the system should have only 5.26 maximum downtime for a year. Provide high available IP based service such as Voice over IP for telephony is difficult since IP is not designed for reliable connection. A lot of research has been conducted to overcome these drawbacks. This paper works by enhancing the failover mechanism of Remus as a high availability solution using server virtualization. This paper proposed network function virtualization in order to create a dynamic tunnel switching between primary and secondary server to the clients gateway. The result shows the jitter level and downtime of modified failover using dynamic tunnel switching did not make the jitter or amount of downtime higher. The server downtime using dynamic tunnel switching were varied between 1.3 - 1.5 second that is still comparable with basic Remus downtime with gratuitous ARP means the proposed idea using network function virtualization works well. This paper extends the ability of failover to adapt the wide area condition.

Distribution of Cell in Mobile Network

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: Advances in Electrical and Electronic Engineering. 2015, 13(4), 331-337. ISSN 1336-1376.
  • Year: 2015

High Available VoIP Server Failover Mechanism in Wide Area Network

  • Authors: Septame, H.D, Ulvan, A., Hlaváček, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: TELKOMNIKA Telecommunication, Computing, Electronics and Control. 2015, 13(2), 739-744. ISSN 1693-6930.
  • Year: 2015

Hungarian Method Based Joint Transmission Mode and Relay Selection in Device-to-Device Communication

  • Authors: Reghuvaran, C., Ing. Robert Bešťák, Ph.D.,
  • Publication: 8th IFIP Wireless and Mobile Networking Conference. Koblenz-Landau: Universität Koblenz-Landau, 2015. p. 261-268. ISBN 978-0-7695-5662-8.
  • Year: 2015
  • DOI: 10.1109/WMNC.2015.33
  • Link: https://doi.org/10.1109/WMNC.2015.33
  • Department: Department of Telecommunications Engineering
  • Annotation:
    In this paper, a transmission mode assignment algorithm based on the Hungarian algorithm is proposed to improve the overall system throughput. The proposed algorithm tries to solve two problems: a suitable transmission mode selection for each scheduled transmissions and a device selection for relaying communication between user equipments in the relay transmission mode.

Increase of Voice Service Performance by Changing Voice Payload Size

  • Authors: Mazálek, A., Ing. Robert Bešťák, Ph.D., Vránová, Z., Plátěnka, V.
  • Publication: Proceedings of the 2014 Networking and Electronic Commerce Research Conference. Dallas, TX: American Telecommunications Systems Management Association Inc., 2014. pp. 151-158. ISBN 978-0-9820958-0-5.
  • Year: 2014

Orthogonal MIMO Precoding Schemes for Device-to-Device Communication in LTE Networks

  • Authors: Reghuvaran, C., Ing. Robert Bešťák, Ph.D., Patra, S. K.
  • Publication: 37th International Conference on Telecommunications and Signal Processing. Brno: VUT v Brně, Fakulta elektrotechniky a komunikačních technologií, 2014. pp. 110-114. ISSN 1805-5435. ISBN 978-80-214-4983-1.
  • Year: 2014
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Direct communications between mobile terminals, also known as Device-to-Device (D2D) communications, is expected to be one of the key features supported by upcoming mobile networks. The D2D communication uses resources of the underlying mobile network which however results in mutual interference between the D2D and base station-to-terminal links. To reduce the mutual interference of these links, we propose a novel orthogonal Multiple Input Multiple Output (MIMO) precoding approach where the orthogonal precoding matrices are assigned to the D2D and base station-to-terminal communication links. The expression for outage probability of the proposed method is also presented in this paper. Numerical results show that our proposition achieves an enhancement of capacity gain in comparison with conventional precoding matrix allocation method and reduction in outage probability in comparison with conventional interference cancellation technique.

The Impact of IPSec Encryption on the Voice Quality

  • Authors: Vránová, Z., Ing. Robert Bešťák, Ph.D., Mazálek, A., Vrsecká, M.
  • Publication: Proceedings of the 2014 Networking and Electronic Commerce Research Conference. Dallas, TX: American Telecommunications Systems Management Association Inc., 2014. pp. 205-212. ISBN 978-0-9820958-0-5.
  • Year: 2014

Virtualisasion of Mobile Core Network by Cloudlet Communication

  • Authors: Ulvan, A., Ing. Robert Bešťák, Ph.D., Olivia, D., Ulvan, M., FordaNama, G.
  • Publication: Proceedings of the 2014 Networking and Electronic Commerce Research Conference. Dallas, TX: American Telecommunications Systems Management Association Inc., 2014. pp. 436-442. ISBN 978-0-9820958-0-5.
  • Year: 2014
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper discusses virtualisation of LTE network. A virtualized platform was developed to measure impact of virtualisation on delay and jitter for two scenarios: registration procedure and VoIP communication.

A New Physical Cell Indetifier Structure in Femtocell Networks

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: The Ninth International Conference onWireless and Mobile Communications. Wilmington: IARIA, 2013. pp. 217-221. ISBN 978-1-61208-284-4.
  • Year: 2013
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper proposes a new Physical Cell Identifier structure in highly dense femtocell environment and discuses possible solutions how to implement the new cluster identifier in today’s mobile networks.

Availability Model for Virtualized Platforms

  • Authors: Hlaváček, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Advances in Electrical and Electronic Engineering. 2013, 11(5), 316-320. ISSN 1336-1376.
  • Year: 2013
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Network virtualization is a method of providing virtual instances of physical networks. Virtualized networks are widely used with virtualized servers, forming a powerful dynamically reconfigurable platform. In this paper we discuss the impact of network virtualization on the overall system availability. We describe a system reflecting the network architecture usually deployed in today's data centres. The proposed system is modelled using Markov chains and fault trees. We compare the availability of virtualized system using standard physique network with the availability of virtualized system using virtualized network. Network virtualization introduces a new software layer to the network architecture. The proposed availability model integrates software failures in addition to the hardware failures. Based on the estimated numerical failure rates, we analyse system's availability.

Cell Identifier Assignment in Two-Tier Femtocell Networks

  • Authors: Oppolzer, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: IEEE 77th Vehicular Technology Conference. New York: IEEE Vehicular Technology Society, 2013. pp. 1-5. ISSN 1550-2252.
  • Year: 2013

Deployment of Femtocells

  • Authors: Sedláček, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: ICMT'13 - Proceedings of the International Conference on Military Technologies. Brno: Univerzita obrany, 2013. pp. 547-552. ISBN 978-80-7231-917-6.
  • Year: 2013
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Key requirement of emerging mobile networks is among others self-configuration or self-optimization of base stations. The paper investigates random placement of femtocell base stations within macrocells of mobile network.

Handover of Relay Stations for Load Balancing in IEEE 802.16

  • DOI: 10.1002/wcm.1103
  • Link: https://doi.org/10.1002/wcm.1103
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The load balancing in wireless networks is a very effective way for maximization of a system throughput. The paper proposes a new load balancing scheme in order to avoid a congestion of base stations (BSs) in IEEE 802.16 standards. While in many technical studies the load balancing is achieved by a handover (HO) of mobile stations (MSs), the novelty of our approach lies in the utilization of the HO of relay stations (RSs). Hence, the algorithm enabling load balancing via RSs is developed and optimized. Furthermore, the paper contemplates the implementation of the proposed mechanism to networks based on IEEE 802.16 standards. The performance of the mechanism is evaluated in terms of achieved system throughput and signaling overhead both at the air interface and over the wired backbone. The obtained results indicate that the load balancing mechanism through the HO of RSs outperforms existing load balancing mechanisms exploiting conventional HO of MSs

Handover Procedure and Decision Strategy in LTE-Based Femtocell Network

  • Authors: Ulvan, A., Ing. Robert Bešťák, Ph.D., Ulvan, M.
  • Publication: Telecommunication Systems. 2013, 52(4) 2733-2748. ISSN 1018-4864.
  • Year: 2013
  • DOI: 10.1007/s11235-011-9599-9
  • Link: https://doi.org/10.1007/s11235-011-9599-9
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Wireless systems have the capability to serve users over broad geographic area without using a costly network infrastructure. However, the main drawback of these systems represents the bandwidth restrictions and coverage. Deployment of femtocell as the emerging promising wireless access technology becomes one of possible solution how to overcome some of the drawbacks. In this paper, we investigate the handover procedure in femtocell network considering, both types of handovers, horizontal and vertical. The 3GPP LTE based handover procedure is analyzed for three scenarios: hand-in, hand-out and inter-FAP. In addition, the reactive handover decision policy, based on the prediction of user movement and the prediction of target-FAP, is proposed as a way to eliminate frequent and unnecessary handovers.

Integrated IMS-Femtocell Testbed

  • Authors: Ulvan, A., Ulvan, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: 36th International Conference on Telecommunications and Signal Processing. Piscataway: IEEE, 2013. p. 100-104. ISSN 1805-5435. ISBN 978-1-4799-0402-0.
  • Year: 2013

Live Replication of Virtualized VoIP Servers

  • Authors: Hlaváček, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: The Eighth International Multi-Conference on Computing in the Global Information Technology. Silicon Valley: International Academy, Research and Industry Association (IARIA), 2013. pp. 277-282. ISBN 978-1-61208-283-7.
  • Year: 2013
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper analyzes a continuous live replication mechanism of Xen hypervisor in the context of virtual machine hosting a Voice over Internet Protocol server processing both signalization and user data.

Optimization of association procedure in WiMAX networks with relay stations

  • DOI: 10.1007/s11235-011-9661-7
  • Link: https://doi.org/10.1007/s11235-011-9661-7
  • Department: Department of Telecommunications Engineering
  • Annotation:
    When a MS enters to the WiMAX network, a network entry procedure has to be performed. The aim of procedure is twofold. Firstly, several connections between the MS and BS are created, i.e. basic, primary and secondary management connections to control data transmissions. Secondly, the MS is admitted into the network. According to the IEEE 802.16 standard, a MS always tries to associate to BS with the highest received signal quality. This method is suitable as long as the MS is directly connected to the network via BS. However by introducing relay stations to the WiMAX architecture, the MS entry procedure needs to be modified. Mainly, the point of attachment influences the network performance. This paper proposes an optimized association procedure which takes into account the use of relays stations in the network. The obtained results show improvement of system performance.

Overlapping Cells in Femtocell Environment

  • Authors: Ing. Robert Bešťák, Ph.D., Sedláček, M.
  • Publication: 6th Joint IFIP Wireless and Mobile Networking Conference (WMNC). Dubai: The Canadian University of Dubai, 2013. pp. 1-5. ISBN 978-1-4673-5614-5.
  • Year: 2013

Physical Cell Identifier Assignment in Dense Femtocell Deployment

  • Authors: Oppolzer, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Broadband Wireless Access Networks for 4G: Theory, Application, and Experimentation. Hershey: IGI Global Disseminator of Knowledge, 2013. p. 366-382. ISBN 978-1-4666-4888-3.
  • Year: 2013
  • DOI: 10.4018/978-1-4666-4888-3.ch019
  • Link: https://doi.org/10.4018/978-1-4666-4888-3.ch019
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The authors deal with a mechanism of Physical Cell Identifier (PCI) assignment for dense femtocell scenarios within LTE/LTE-Advanced networks. After describing the need for femtocells in future Self-Organizing Networks (SONs), the problem is presented. The chapter discusses background information such as related works in this research field and current assignment methods. Subsequently, challenges are defined, and two mechanisms to assign PCIs are proposed. Both the mechanisms are capable of assigning collision-free PCIs and solving any future confusion events that may occur as the network grows in terms of the number of femtocells. To evaluate the algorithms, a model is described and simulation results for two different scenarios are presented.

Probability of Cell Overlapping in Femtocell Environment

  • Authors: Sedláček, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: 36th International Conference on Telecommunications and Signal Processing. Piscataway: IEEE, 2013. pp. 244-248. ISSN 1805-5435. ISBN 978-1-4799-0402-0.
  • Year: 2013

Small Cell Network Topology Comparison

  • Authors: Oppolzer, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Advances in Electrical and Electronic Engineering. 2013, 11(5), 303-308. ISSN 1336-1376.
  • Year: 2013
  • Department: Department of Telecommunications Engineering
  • Annotation:
    One of the essential problems in a mobile network with small cells is that there is only a limited number of Physical Cell Identifiers (PCIs) available. Due to this fact, operators face the inevitable need for reusing PCIs. In our contribution, we are dealing with a PCI assignment to Femtocell Access Points (FAPs) in three different topologies. The first model places FAPs randomly within the network while respecting overlapping defined. The second model places FAPs in a grid without other restrictions. The third model forms a grid as well, although buildings and roads are taken into account and FAPs are always inside buildings. The proposed models are compared and a conclusion is made based on simulation results.

Configuration of Live Migration for VoIP Applications

  • Authors: Hlaváček, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of 15th Mechatronika 2012. Praha: Czech Technical University in Prague, 2012. pp. 187-190. ISBN 978-80-01-04987-7.
  • Year: 2012
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The use of VoIP technologies is still growing: a SIP based client is nowadays integrated even in the Google's smartphone operating system Android. Recent progress in virtualization technology allows the use of virtual machines for real-time applications like VoIP. A continuous live migration of a whole system without breaking down of existing TCP and TLS connections is improving the availability and the hardware fault tolerance. Furthermore, it's transparent for clients without impact on the existing application. One of observed issues is the latency and the jitter added by buffering the network output between two virtual machine replication cycles. This problem can be disregarded for the signalling data, but it needs to be solved for the user data where the jitter must be compensated, otherwise it impairs the voice quality. In this article we present the impact of the live migration on the latency and jitter. We show that the utilisation of continuous live replication without network buffering improves the quality of user experience to the detriment of the data consistency. The impact of network buffering on network characteristics is also shown.

Distributed Physical Cell Identifier Assignment Algorithm in Femtocell Networks

  • Authors: Oppolzer, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Wireless Days 2012. Piscataway: IEEE, 2012. ISBN 978-1-4673-4404-3.
  • Year: 2012
  • DOI: 10.1109/WD.2012.6402878
  • Link: https://doi.org/10.1109/WD.2012.6402878
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Self-configuration ability is the main attribute of LTE/LTE-A femtocell networks. Considering the enormous num-ber of femtocells, the distributed assignment of Physical Cell Identifiers (PCIs) to femtocells, assuring confusion-free and collision-free scenarios, is quite a challenging task. In this paper, we propose a fully distributed algorithm that enables assigning PCIs in a collision-free manner and resolving confusion events based on neighbouring deployment of PCIs. The algorithm is compared with the random algorithm. Effectiveness of proposed algorithm is evaluated by comparing the number of confusions for various femtocell overlapping, PCIs ranges and sizes of neighbourhood area. Simulation results indicate that compared to the random algorithm, the proposed algorithm leads to fewer confusion events and lower network overhead even in dense femtocell environments.

Physical Cell Identifier Assignment in LTE-Advanced Networks

  • Authors: Oppolzer, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of 2012 5th Joint IFIP Wireless and Mobile Networking Conference (WMNC). Piscataway: IEEE, 2012. p. 70-74. ISBN 978-1-4673-2994-1.
  • Year: 2012
  • DOI: 10.1109/WMNC.2012.6416150
  • Link: https://doi.org/10.1109/WMNC.2012.6416150
  • Department: Department of Telecommunications Engineering
  • Annotation:
    In this article, a fully distributed mechanism of Physical Cell Identifier (PCI) assignment within LTE-A networks, where there are more than 504 femtocells deployed under one macrocell, is analysed. We propose a technique that can assign collision-free PCIs and work out any confusion event that may occur in the macrocell. Simulation results based on implementation of the algorithm proposed are presented and discussed. It is shown that the algorithm is capable of solving confusion events in dense femtocell scenarios.

Physicall Cell Identifier Assignment in Dense Home evolved NodeB Deployment

  • Authors: Oppolzer, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: NGMAST 2012. Los Alamitos: IEEE Computer Society Press, 2012. pp. 170-174. ISBN 978-0-7695-4803-6.
  • Year: 2012
  • DOI: 10.1109/NGMAST.2012.48
  • Link: https://doi.org/10.1109/NGMAST.2012.48
  • Department: Department of Telecommunications Engineering
  • Annotation:
    In this article, we are dealing with a mechanism of Physical Cell Identifier (PCI) assignment within LTE/LTE-A networks with more than 504 femtocells under one macrocell. After describing the problem we are concerned with, we propose two mechanisms that are able to assign collision-free PCI correctly and solve any confusion events that may arrive later. We also present simulation results based on our implemented algorithms that we propose to support our claims.

Random Cell Identifiers assigment

  • Authors: Ing. Robert Bešťák, Ph.D., Helou, V.
  • Publication: Advances in Electrical and Electronic Engineering. 2012, 10(4), 195-198. ISSN 1336-1376.
  • Year: 2012
  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper analyses a random based assignment algorithm in LTE systems operating in diverse femtocell scenarios. The performance of the algorithm is evaluated by comparing the number of confusions for various femtocell densities, PCI ranges and knowledge of vicinity.

Assignment of Femtocell Identifiers

  • Authors: Oppolzer, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of the 8th International Conference on Digital Technologies 2011. Žilina: Slovenská elektrotechnická společnost, 2011. pp. 1-4. ISBN 978-80-554-0437-0.
  • Year: 2011
  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper is focused on assignment of femtocell identifiers in Long Term Evolution (LTE) mobile cellular network technology. It describes femtocells in general, principle of identification and potential problems which shall be avoided for network to function properly and reliably. In addition to specification of particular known methods of assignment of identifiers, it devotes also to simulation of distributed method with radio environment scanning.

Overhead of ARQ Mechanism in IEEE 802.16 Networks

  • DOI: 10.1007/s11235-010-9296-0
  • Link: https://doi.org/10.1007/s11235-010-9296-0
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Different techniques for error correction such as automatic repeat request, forward error correction or combination of both methods also known as hybrid automatic repeat request are utilized in today's wireless networks. All these techniques require an implementation of control and management mechanisms to ensure its proper work. These mechanisms increase the management overhead and consume a part of network capacity. It leads to the reduction of data throughput dedicated to users. Besides, the control mechanism can negatively influence a packet delay. This paper proposes three alternatives of automatic repeat request mechanism to minimize the management overhead without a negative impact on the packet delay. Description of all proposed mechanisms, their evaluation and comparison with conventional techniques used in the IEEE 802.16 networks are presented in this paper.

Privacy in Location Based Services

  • Authors: Vláčil, P., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of the 2011 Networking and Electronic Commerce Research Conference. Dallas, TX: American Telecommunications Systems Management Association Inc., 2011. pp. 151-155. ISBN 978-0-9820958-5-0.
  • Year: 2011
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The Location Based Services market, with the boom of new and more capable smart-phones with location awareness, is predicted to rapidly grow. New capabilities and services not only attract new customers but also disclose new problems to be solved. One of the major issues is the protection of the users' location privacy. This paper explores recent advances in privacy in Location Based Services and summarizes techniques proposed to preserver users' privacy. Paper also outlines some of the unresolved interesting problems.

Radio Resources Allocation for Decentrally Controlled Relay Stations

  • DOI: 10.1007/s11276-010-0269-8
  • Link: https://doi.org/10.1007/s11276-010-0269-8
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The crucial point influencing the overall system performance is allocation of appropriate amount of resources to individual relay stations depending on their current needs. We suggest a mechanism that pre-allocates to decentrally controlled relay stations a certain amount of default radio resources while the remaining resources are dynamically shared.

Speech Signal Quality Assessment for Different VoIP Technologies

  • Authors: Vránová, Z., Ing. Robert Bešťák, Ph.D., Ondryhal, V.
  • Publication: ICMT'11 International Conference on Miltary Technologies 2011. Brno: Univerzita obrany, 2011. pp. 1177-1184. ISBN 978-80-7231-788-2.
  • Year: 2011

Testing of transmission channels quality for different types of communication technologies

  • Authors: Ing. Robert Bešťák, Ph.D., Vránova, Z., Ondryhal, V.
  • Publication: Digital Information and Communication Technology and Its Applications. Heidelberg: Springer, 2011. p. 13-23. ISSN 1865-0929. ISBN 978-3-642-21983-2.
  • Year: 2011

Testing of Transmission Channels Quality for Different Types of Communication Technologies.

  • Authors: Ing. Robert Bešťák, Ph.D., Vránova, Z., Ondryhal, V.
  • Publication: Communications in Computer and Information Science. 2011, 2011(166), 13-23. ISSN 1865-0929.
  • Year: 2011

Handover Scenario and Procedure in LTE-based Femtocell Networks

  • Authors: Ulvan, A., Ulvan, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: NexTech 2010. Silicon Valley: International Academy, Research and Industry Association (IARIA), 2010. pp. 213-218. ISBN 978-1-61208-000-0.
  • Year: 2010
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The handover decision policy based on the prediction of user movement is proposed to optimize the handover procedure in LTE-based femtocell networks.

HSUPA Technology Description

  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper deals with the detailed description of enhanced data transmission from the user to the network - High Speed Uplink Packet Access technology in UMTS. There is also given detailed analysis of HSUPA technology. Next paper then describes outputs from the simulation of balancing different parameters in HSUPA.

HSUPA Technology Simulation

  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper deals with outputs of the simulation of balancing different parameters in UMTS network, where HSUPA technology is implemented. It is a direct continuation of the paper "HSUPA Technology Description" where HSUPA supports enhanced data transmission from the user to the network. There are programmed some algorithms occurring in the MAC layer to realize this simulation in Matlab environment, whereas as the fundament states the event driven model. Performance of the wireless connection is depicted, e.g. in dependence on delay, in form of graphs.

Improvements in the Availability of SIP Networks

  • Authors: Hlaváček, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of the 2010 Networking and Electronic Commerce Research Conference. Dallas, TX: American Telecommunications Systems Management Association Inc., 2010. pp. 109-117. ISBN 978-0-9820958-3-6.
  • Year: 2010
  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper analyses the impact of SIP network components on the availability of SIP systems and discusses possibilities for improvements. It describes a redundant network configuration, dynamic routing, failover and some possibilities for improvements in software implementations.

IMS Signalling in LTE-based Femtocell Network

  • Authors: Ulvan, M., Ulvan, A., Ing. Robert Bešťák, Ph.D.,
  • Publication: NexTech 2010. Silicon Valley: International Academy, Research and Industry Association (IARIA), 2010. pp. 157-163. ISBN 978-1-61208-000-0.
  • Year: 2010
  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper investigates IMS signaling in femtocell network based on the 3GPP LTE and provides signaling performance study of the Session Initiation Delay procedure.

Network Entry Procedure in LTE-based Femtocell Network

  • Authors: Ulvan, M., Ulvan, A., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of the 2010 Networking and Electronic Commerce Research Conference. Dallas, TX: American Telecommunications Systems Management Association Inc., 2010. pp. 156-166. ISBN 978-0-9820958-3-6.
  • Year: 2010
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper investigates procedure of network entry of integrated LTE-based femtocell and IMS networks is investigated. The attach procedure in 3GPP LTE-based technology and the SIP registration procedure in IMS are analysed and enhanced for femtocell-IMS network system. The proposed procedure is evaluated by means of signalling flow delays.

Quality of Service Management in the Voice over IP Systems

  • Department: Department of Telecommunications Engineering
  • Annotation:
    This article describes briefly issues caused by the use of the IP protocol in the Voice over IP systems. Furthermore, it discusses the quality of service management in VoIP systems. Resource reservation capabilities defined by H.323 are compared with those defined by SIP and its extensions.

Quality of Service Management in the Voice over IP Systems

  • Department: Department of Telecommunications Engineering
  • Annotation:
    This article describes briefly issues caused by the use of the IP protocol in the Voice over IP systems. Furthermore, it discusses the quality of service management in VoIP systems. Resource reservation capabilities defined by H.323 are compared with those defined by SIP and its extensions.

Software Architectures for High Available Telecommunication Service Platforms

  • Authors: Hlaváček, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Knowledge in Telecommunication Technologies and Optics - KTTO 2010. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2010. pp. 92-95. ISBN 978-80-248-2330-0.
  • Year: 2010
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Today’s mobile networks are built on IP and SIP technologies. Use of these technologies brings cost savings, but the reliability level usual for telecommunication systems can’t be reached without use of availability specific configurations. This paper focuses on software implementation of telecommunication services using SIP. Three different types of applications are investigated: standalone SIP servers, stateless applications controlling SIP servers and stateful control applications. Requirements on context replication are identified for each type of application. Different software solutions improving the availability using context replication are analyzed. Comparison of these architectures is provided and their suitability for different application types is discussed.

The Study of Handover Procedure in LTE-based Femtocell Network

  • Authors: Ulvan, A., Ing. Robert Bešťák, Ph.D., Ulvan, M.
  • Publication: The 3rd Joint IFIP Wireless Mobile Networking Conference (WMNC'2010). Budapest: Budapest University of Technology and Economics, 2010. pp. 24-29. ISBN 978-963-8111-73-9.
  • Year: 2010
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper analyzes handover procedure in LTE femtocell based network where three handover scenarios are considered. Based on the analysis an optimization of handover strategy is proposed

Acquisition of Channel State Information for Routing Purposes in Relay-based WiMAX Networks

  • DOI: 10.1109/ICN.2009.41
  • Link: https://doi.org/10.1109/ICN.2009.41
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper focuses on multi-hop routing mechanism used in relay based WiMAX networks. The proposal how to acquire channel state information (CSI) on relay and access path for de-centrally and centrally controlled relays is presented. Furthermore, on the access path the proposal distinguishes whether the user's terminals are active or inactive in order to save system resources. Based on simulation, the protocol overhead of proposed mechanism for various system configuration and parameters such as nominal channel bandwidth, number of users in the system or reporting period is evaluated. Additionally, an optimum reporting period for the system capacity maximization is determined.

Analysis and Performance Evaluation of IEEE 802.16 Enhanced with Decentrally Controlled Relays

  • Department: Department of Telecommunications Engineering
  • Annotation:
    In order to enhance throughput and to extend coverage of wireless networks based on IEEE 802.16 standards, relay stations may be implemented. This paper primarily focuses on decentrally controlled relays when a relay itself schedules all transmissions for its subordinate stations. Needed system resources are allocated to individual relays by means of already defined scheduling services such as UGS, rtPS or ertPS. The paper analyzes suitability of scheduling services. Studied performance metrics include system throughput, signaling overhead and packet delay depending on offered traffic load. The obtained results indicates that ertPS service considerably outperform UGS or rtPS.

Analysis of Session Establishment Signaling Delay in IP Multimedia Subsystem

  • Authors: Ulvan, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: Wireless and Mobile Networking. Berlin: Springer, 2009. p. 44-55. IFIP Advances in Information and Communication Technology. ISSN 1868-4238. ISBN 978-3-642-03840-2.
  • Year: 2009

Delay Performance of Session Establishment

  • Authors: Ulvan, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: IWSSIP 2009 - 16th International Workshop on Systems, Signals and Image Processing. Chalkida: TEI of Chalkida, 2009. pp. man01. ISBN 978-1-4244-4530-1.
  • Year: 2009

Enhancement of Managed Roaming Procedure in GSM

  • Authors: Vrána, J., Vláčil, P., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of the 5th International Wireless Communications and Mobile Computing Conference. Stoughton: The Printing House Inc., 2009. pp. 547-551. ISBN 978-1-60558-569-7.
  • Year: 2009

Femtocells in 3G Mobile Networks

  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper discusses usage of femtocell and related challenges, such as interferences, frequency spectrum planning, handovers or integration of femtocells into mobile network.

Femtocells Integration into Mobile Networks

IEEE802.16 MAC Management Messages: The Overhead and Efficiency Analysis in Mesh Topology

  • Authors: Ulvan, A., Ulvan, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: 2009 IEEE 9th Malaysia International Conference on Communications. Piscataway: IEEE, 2009. pp. We16-2. ISBN 978-1-4244-5532-4.
  • Year: 2009

Impact of Handover on VoIP Speech Quality in WiMAX Networks

  • Department: Department of Telecommunications Engineering
  • Annotation:
    VoIP is one of the most emerging technologies in the area of speech communications. VoIP is widely deployed in fixed line access networks. However, user's 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.

Implementing Gateway Mobile Location Center

  • Authors: Vláčil, P., Ing. Robert Bešťák, Ph.D.,
  • Publication: TRANSCOM 2009. Žilina: EDIS, 2009. pp. 175-178. ISBN 978-80-554-0039-6.
  • Year: 2009
  • Department: Department of Telecommunications Engineering
  • Annotation:
    This article describes implementation of Gateway Mobile Location Center (GMLC) using C/C++ programming language. GMLC is main part of the GSM network which is controlling Location Based services.

Implementing Mobile Location Protocol

  • Authors: Vláčil, P., Ing. Robert Bešťák, Ph.D.,
  • Publication: TSP - 32nd International Conference on Telecommunications and Signal Processing. Budapest: Asszisztencia Szervező Kft., 2009. ISBN 978-963-06-7716-5.
  • Year: 2009
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Article describes possible implementation of Mobile Location Protocol (MLP) specified by Open Mobile Alliance. Implementation concentrates on providing library that could be easily used by other software projects.

Initialization of Handover Procedure in WiMAX Networks

  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper introduces a new approach in the triggering of handover procedure in WiMAX networks. Mobile WiMAX, based on the IEEE 802.16e standard, supports a several types of handovers and allows full mobility of users. The originating IEEE 802.16j standard introduces new network entities called relay stations. A relay station enables either throughput enhancement in the selected area or enlargement of a coverage area of base station.

New Model for the Service Providers Called Capability Maturity Model Integration for Services

  • Authors: Ing. Robert Bešťák, Ph.D., Hlaváček, J.
  • Publication: Digital Technologies 2009. Žilina: TU v Žilině, 2009. ISBN 978-80-554-0150-8.
  • Year: 2009

Optimization of Frame Structure for WiMAX Multi-hop Networks

  • Authors: Ing. Pavel Mach, Ph.D., Ing. Robert Bešťák, Ph.D.,
  • Publication: Wireless and Mobile Networking. Berlin: Springer, 2009. p. 106-116. IFIP Advances in Information and Communication Technology. ISSN 1868-4238. ISBN 978-3-642-03840-2.
  • Year: 2009
  • DOI: 10.1007/978-3-642-03841-9_10
  • Link: https://doi.org/10.1007/978-3-642-03841-9_10
  • Department: Department of Telecommunications Engineering
  • Annotation:
    To enhance the system throughput and to extend coverage of IEEE 802.16 networks, relay stations can be implemented. If a user station is attached to the base station (BS) through several relays stations (RS), a multi-hop communication occurs. To enable multi-hop communication, the IEEE 802.16j standard proposes two approaches how RSs can be implemented into the network. The first approach groups BSs and several RSs into a multi-frame with repetition of relay zones. In the second approach, the BS schedules several relay zones in one frame. While the first approach causes long packet delays, the second approach has high requirements on RS's processing capabilities. This paper proposes an optimized frame structure that allows using second approach whilst the requirements on RS's processing time are still kept in reasonable range. The obtained simulation results indicate that packet delays in downlink and uplink direction can be significantly reduced.

Parameter Setting of Protocol MAC-hs in HSDPA

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: The Eighth International Conference on Networks (ICN 2009). Los Alamitos: IEEE Computer Society, 2009. pp. 292-296. ISBN 978-1-4244-3470-1.
  • Year: 2009
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The MAC-hs protocol of HSDPA ensures retransmissions of erroneous blocks and in-sequence data delivery to the upper layer. The first function is fulfilled through the HARQ mechanism. The second function is achieved by handling sliding transmitting/receiving window and by numbering of blocks. This paper investigates the MAC-hs performance for different parameters settings such window sizes, number of retransmissions or channel conditions. Simulations show that the parameter setting has to be advisably set up in order to prevent deterioration of performance.

The Analysis of Scanning Time in IEEE802.16m's Handover Procedure Signaling in IP Multimedia Subsystem

  • Authors: Ulvan, A., Ing. Robert Bešťák, Ph.D.,
  • Publication: IWSSIP 2009 - 16th International Workshop on Systems, Signals and Image Processing. Chalkida: TEI of Chalkida, 2009. pp. 198971. ISBN 978-1-4244-4530-1.
  • Year: 2009
  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper investigates the efficiency of scanning process on handover procedure in IEEE802.16m. The performance evaluation is based on current running standard of 802.16e since .16m is still under development. The evaluation is done at both parts of handover procedure i.e. network topology acquisition and handover process. An efficient scanning process is proposed to reduce the scanning time and obtained a minimal handover interruption time.

The Efficiency Performance on Handover's Scanning Process of IEEE802.16m

  • Authors: Ulvan, A., Ing. Robert Bešťák, Ph.D.,
  • Publication: Wireless and Mobile Networking. Berlin: Springer, 2009. p. 321-331. IFIP Advances in Information and Communication Technology. ISSN 1868-4238. ISBN 978-3-642-03840-2.
  • Year: 2009

The Enhancement of Handover Strategy by Mobility Prediction in Broadband Wireless Access

  • Authors: Ulvan, A., Ulvan, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of the 2009 Networking and Electronic Commerce Research Conference (NAEC 2009). Dallas, TX: American Telecommunications Systems Management Association Inc., 2009. pp. 266-276. ISBN 978-0-9820958-2-9.
  • Year: 2009
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper discusses prediction of user's mobility to enhance the handover strategy for broadband wireless access based on IEEE802.16m. Two handover strategies, i.e. proactive and reactive handovers, are proposed.

The Overhead and Efficiency Analysis on WiMAX's MAC Management Message

  • Authors: Ulvan, A., Andrlík, V., Ing. Robert Bešťák, Ph.D.,
  • Publication: Internetworking Indonesia. 2009, 1(1), 3-9. ISSN 1942-9703.
  • Year: 2009
  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper presents the overhead analysis on MAC Management Messages of WiMAX based on IEEE802.16. The efficiency on the MAC layer is derived for Point to Multipoint (PMP) topology. The influence of several parameters (the number of subscriber stations in the network, length of MAC message's tec.) is examined.

The Study of IMS Functionality in Femtocell Environment

  • Authors: Ulvan, M., Ing. Robert Bešťák, Ph.D., Ulvan, A.
  • Publication: 2009 IEEE 9th Malaysia International Conference on Communications. Piscataway: IEEE, 2009. pp. We09-3. ISBN 978-1-4244-5532-4.
  • Year: 2009

Emulation of Wireless Links Using NetEm

  • Authors: Hlaváček, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of VIIIth Conference KTTO 2008. Ostrava: VŠB - Technical University of Ostrava, 2008. pp. 38-42. ISBN 978-80-248-1719-4.
  • Year: 2008
  • Department: Department of Telecommunications Engineering
  • Annotation:
    We describe a new functionality which we added to NetEm in order to improve an insertion of errors in the data flow, which is one of weak points of discussed emulator. Features of NetEm were tested; results of this test are presented and analyzed. Experiments show that NetEm can be useful to emulate wireless links.

Evolution of 3GPP Core Network

Evolution of 3GPP MAC Layer

Evolution of Mobile Networks

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of IWSSIP 2008. Bratislava: Slovak University of Technology, 2008. pp. 29-32. ISBN 978-80-227-2856-0.
  • Year: 2008

Improper implementation of Managed Roaming in GSM

  • Authors: Vláčil, P., Vrána, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Digital Technologies 2008. Žilina: Žilinská universita, Elektrotechnická fakulta, 2008. ISBN 978-80-8070-953-2.
  • Year: 2008
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper investigates the impact of non-standard implementation of Managed roaming procedure in GSM provider networks. This non-standard implementation can cause variety of problems in host networks. The main aim of this paper is to describe one of possible solutions to this problem by using a specific software module. Software module was tested in experimental GSM network.

Improving the Flexibility and Utilisation of Node Association Procedure in Mesh Mode Based on IEEE 802.16e

  • Authors: Ulvan, A., Ulvan, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: ISSM 2008. Jakarta: Institute for Science and Technology Studies (ISTECS), 2008. pp. 152-155. ISSN 0854-8692.
  • Year: 2008
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Regarding the mobility, the node association procedure is critical for network entry as well as network re-entry during handover. In this paper we analysed the scheduling mechanism to improve the utilisation of minislots allocation during the exchange of MAC masssages.

Linux High Resolution Timers in NetEm Emulator

  • Authors: Hlaváček, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: RTT 2008. Bratislava: STU v Bratislave, 2008. ISBN 978-80-227-2939-0.
  • Year: 2008

Mobile IP in Next Generation Intelligent Network

  • Authors: Ulvan, M., Ulvan, A., Ing. Robert Bešťák, Ph.D.,
  • Publication: RTT 2008. Bratislava: STU v Bratislave, 2008. ISBN 978-80-227-2939-0.
  • Year: 2008

Multiple Cell Partitions for Increasing the CDMA-Based Cell Capacity

  • Authors: Ulvan, A., Ribeiro, D., Ing. Robert Bešťák, Ph.D.,
  • Publication: Wireless and Mobile Networking. New York: Springer, 2008. pp. 383-394. ISBN 978-0-387-84838-9.
  • Year: 2008

Optimization of Handover Scanning Procedure in WiMAX Networks with Relay Stations

  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper proposes an optimization of management messages and their exchange during a scanning procedure of mobile station's neighborhood in WiMAX based networks with relay stations.

Optimization of Network Entry Procedure in Relay Based WiMAX Networks

The analysis of IEEE 802.16e MAC Layer Overhead and Efficiency in PMP Topology

  • Authors: Ulvan, A., Andrlík, V., Ing. Robert Bešťák, Ph.D.,
  • Publication: 2008 Fifth International Conference on Wireless and Optical Communications Networks. Piscataway: IEEE, 2008. pp. s14-6. ISBN 978-1-4244-1980-7.
  • Year: 2008
  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper presents an analysis of the IEEE 802.16e MAC overhead. The efficiency on the MAC layer is derived for Point to Multipoint (PMP) topology. Some recommendations to reduce the overhead are put forward.

WiMAX Throughput Evaluation of Conventional Relaying

  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper analyses performance of IEEE 802.16 standard, also known as WiMAX, when relay stations are introduced. Thanks to this feature, coverage area and throughput of the system may be significantly enhanced. The article defines the increase of system capacity of the relay based cell deployment compared to a conventional single hop deployment of the same area size. Further, the parameters that have main impact on the system with relays and its capacity are determined.

WiMAX Throughput Evaluation of Conventional Relaying

Analysing the Flexibility and Utilisation of Node Association MAC Scheduling Mechanism Based on IEEE 802.16e

  • Authors: Ulvan, A., Ing. Robert Bešťák, Ph.D.,
  • Publication: RTT 2007. Žilina: University of Žilina, 2007. pp. 420-424. ISBN 978-80-8070-735-4.
  • Year: 2007

Development of 3rd Generation Mobile Networks

  • Department: Department of Telecommunications Engineering
  • Annotation:
    In order to maintain the future competitiveness of mobile network, standardization bodies already start to work on specifications of future mobile network. This paper provides today's situation and outlines trends in the domain of mobile networks.

Handover in UMTS and WiMAX Networks

HSDPA Technology

Improvements in the Reliability of the Computer-Based Telecommunications Systems

  • Authors: Hlaváček, J., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings CD-ROM of Digital Technologies 2007. Žilina: Slovenská elektrotechnická společnost, 2007. ISBN 978-80-8070-786-6.
  • Year: 2007
  • Department: Department of Telecommunications Engineering
  • Annotation:
    In this work, the design and implementation of reliable network architecture for VoIP systems is presented. An implementation of a double redundant network connection for terminals and servers is described.

Influence of Release Timer on MAC-hs Performance

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: Sixth International Conference on Networking (ICN 2007). Los Alamitos: IEEE Computer Society Press, 2007. pp. 014. ISBN 0-7695-2805-8.
  • Year: 2007
  • Department: Department of Telecommunications Engineering
  • Annotation:
    In this paper, the MAC-hs performance for different MAC-hs window sizes and channel conditions are studied. Simulations show that the parameter setting has to be advisably set up in order to prevent deterioration of the protocol performance.

Long Term Evolution (beyond UMTS)

  • Department: Department of Telecommunications Engineering
  • Annotation:
    In order to maintain the future competitiveness of WCDMA technology, 3GPP organization has started a process of defining the long-term evolution (LTE) for 3G. This paper discusses main features of proposed LTE technology.

Multimedia Broadcast and Multicast Service in UMTS

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: TRANSCOM 2007 - Proceedings, Section 3 - Information and Communication Technologies. Žilina: University of Žilina, 2007. pp. 15-18. ISBN 978-80-8070-693-7.
  • Year: 2007
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The Multimedia Broadcast and Multicast Service (MBMS) is a new feature of mobile networks introduced in 3GPP Release 6. This paper describes basic features of MBMS, layers architecture and required changes in networks architecture.

Network Entry Procedure in WiMAX

Network Entry Procedure in WiMAX

  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper analyses the newest trends in wireless networks with focus on a standard IEEE 802.16-2004. Both, point to multipoint and mesh network topologies are considered. The paper describes the standard association procedures together with the new schemes when considering relay stations in the network architecture.

Performance of IEEE 802.16 with Relay Stations

  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper analyses performance of IEEE 802.16, also known as WiMAX, when relay stations are introduced. Thanks to this feature, coverage and throughput may be significantly enhanced. The article describes MAC frame and its necessary changes for relay utilization and further investigates how the performance of the system is affected.

System MediaFLO

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: RTT 2007. Žilina: University of Žilina, 2007. pp. 32-35. ISBN 978-80-8070-735-4.
  • Year: 2007
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Broadcast and multicast services in mobile networks become more and more popular. Nowadays, there are many systems which can be used for these types of services. In this paper, main features of a new system call MediaFLO is presented.

Technology HSUPA

  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper is focused on a new technology High-Speed Uplink Packet Access, which is implemented into the telecommunication system of third generation Universal Mobile Telecommunications System.

Transmission Performance of Flexible Relay-based Networks on the Purpose of Extending Network Coverage

  • Authors: Ulvan, A., Ing. Robert Bešťák, Ph.D.,
  • Publication: Personal Wireless Communications. New York: Springer, 2007. pp. 99-106. ISSN 1571-5736. ISBN 978-0-387-74158-1.
  • Year: 2007
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper proposes combined distributed/centralized scheduling to improve the utilization of mini-slots allocation during exchange of grant allocation messages.

WiMAX Performance Evaluation

WiMAX Throughput Evaluation of Conventional Relaying

Wireless Systems in Access Networks

  • Department: Department of Telecommunications Engineering
  • Annotation:
    Wireless systems provide an elegant, reliable and economical way of connecting subscribers to Internet. This paper focuses on technologies according to IEEE 802.11 (WiFi) and IEEE 802.16 (WiMAX). Features and employed principles in these technologies are described.

Architecture of IP Multimedia Subsystem

  • Authors: Koukal, M., Ing. Robert Bešťák, Ph.D., Šišma, O.
  • Publication: Proceedings ELMAR 2006. Zadar: Croatian Society Electronics in Marine - ELMAR, 2006. pp. 323-326. ISSN 1334-2630. ISBN 953-7044-03-3.
  • Year: 2006
  • Department: Department of Telecommunications Engineering
  • Annotation:
    The paper describes the IMS architecture and explains its benefits. It focuses on the main IMS system components and briefly summarizes key system functions.

Comparison of Handovers in UMTS and WiMAX

Downlink Enhancement in UMTS

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: Research in Telecommunication Technology 2006 - Proceedings. Brno: Vysoké učení technické v Brně, 2006. pp. 95-99. ISBN 80-214-3243-8.
  • Year: 2006

Enhancements in UMTS Uplink

  • Authors: Koukal, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of the 6th International Conference ELEKTRO 2006. Žilina: EDIS, 2006. pp. 30-33. ISBN 80-8070-544-5.
  • Year: 2006
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Future enhancements to UMTS are driven by the need to improve mobile user experience for real-time and non-real-time multimedia services. This paper discusses proposed enhancements for the uplink direction of UMTS.

Evolution of UMTS

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: Research in Telecommunication Technology 2006 - Proceedings. Brno: Vysoké učení technické v Brně, 2006. pp. 113-117. ISBN 80-214-3243-8.
  • Year: 2006

Implementation of OFDM into Broadband Wireless Networks

Influence of Window Size on MAC-hs Performance

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings ICN 2006 / ICONS 2006 / MCL 2006. Piscataway: IEEE, 2006. pp. 028. ISSN 1063-6382. ISBN 0-7695-2570-9.
  • Year: 2006

Transmission Performance of Flexible Relay-Based Wireless Networks

  • Authors: Ulvan, A., Ing. Robert Bešťák, Ph.D.,
  • Publication: Digital Technologies 2006 - 3rd International Workshop. Žilina: Žilinská universita, Elektrotechnická fakulta, 2006. ISBN 80-8070-637-9.
  • Year: 2006

Wireless Mesh and Relay Networks

ARQ Mechanism in HSDPA

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: TRANSCOM 2005 - Proceedings - Section 3 - Information and Communication Technologies. Žilina: EDIS, 2005. pp. 23-26. ISBN 80-8070-415-5.
  • Year: 2005

ARQ Mechanism in HSDPA

Comparison of Different Versions of IEEE 802.11

  • Authors: Brenn, M., Ing. Robert Bešťák, Ph.D.,
  • Publication: RTT 2005 Proceedings. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2005. ISBN 80-248-0897-8.
  • Year: 2005

Comparison of RLC and TCP Features

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: RTT 2005 Proceedings. Ostrava: VŠB - TUO, FEI, Katedra elektroniky a telekomunikační techniky, 2005. ISBN 80-248-0897-8.
  • Year: 2005

Data Discard in HSDPA

  • Authors: Ing. Robert Bešťák, Ph.D., Vránová, Z.
  • Publication: MoWeIT 2005 - Mobile Computing Meets Knowledge Management. Praha: Česká informatická společnost, 2005. pp. 79-85. ISBN 80-903198-0-7.
  • Year: 2005

Enhancements in Broadband Wireless Access Networks

Modern Forms of Education - Perspectives and Visions

Performance Analysis of MAC-hs Protocol

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: Networking - ICN 2005. Berlin: Springer-Verlag, 2005. pp. 100-108. ISSN 0302-9743. ISBN 3-540-25339-4.
  • Year: 2005

Progressive Broadband Wireless Access Networks

Secure Gateway to the World

UMTS Networks

Learning Management Systems and Their Implementations

Performance of the MAC-hs Protocol in UMTS

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: Proceedings of the IASTED International Conference on Communication Systems and Networks. Calgary: IASTED / Acta Press, 2004. pp. 450-111. ISBN 0-88986-456-X.
  • Year: 2004
  • Department: Department of Telecommunications Engineering
  • Annotation:
    Two main features of the MAC-hs protocol of HSDPA are retransmissions of erroneous blocks and in-sequence data delivery to the above layer. The first functionality is fulfilled through the use of HARQ mechanism. The second function is achieved by using a specific numbering and by managing transmitting/receiving window. We analyze the MAC-hs performance for different sizes of the windows and for different values of a reordering release window timer.

TCP on the UMTS Radio Interface

  • Authors: Ing. Robert Bešťák, Ph.D.,
  • Publication: RTT 2004. Praha: ČVUT FEL, Katedra telekomunikační techniky, 2004. pp. 0108_0029. ISBN 80-01-03063-6.
  • Year: 2004

RLC Bufer Occupancy When Using a TCP Connection Over UMTS

  • Authors: Ing. Robert Bešťák, Ph.D., Godlewski, P., Martins, P.
  • Publication: PIMRC 2002. Piscataway: IEEE, 2002. p. 1161-1165. ISBN 0-7803-7590-4.
  • Year: 2002
  • DOI: 10.1109/PIMRC.2002.1045210
  • Link: https://doi.org/10.1109/PIMRC.2002.1045210
  • Department: Department of Telecommunications Engineering
  • Annotation:
    This paper analyzes a TCP connection over UMTS radio access bearer in RLC acknowledged mode. The stacking of RLC and TCP protocols is highly beneficial for the global system behavior. Protocol mechanisms used by RLC are well adapted to wireless constraints and the ARQ function implemented by RLC hides the wireless channel unreliability to TCP. However, RLC protocol parameters have to be carefully tuned otherwise the TCP performance can degrade due to RLC. One of the factors that can influence the TCP performance is the RLC buffer size. We analyzed some of factors that affect the RLC buffer occupancy and we show that an insufficient buffer size degrades the TCP performance.

Responsible person Ing. Mgr. Radovan Suk