Mean waiting time in the M/H2/s queue: application to mobile communications Systems

In this paper a procedure to approximately calculate the mean waiting time in the M/H2/s queue is presented. The approximation is heuristic although based in the intuitive symmetry between the deterministic and balanced hyperexponential-2 distributions. The three parameters which fully describe the H2 distribution are considered, so the approximation can also be used for the M/G/s queue when the first three moments are known. If only the first two moments of the holding time distribution are known, the estimation can also be applied accepting a lesser accuracy. The estimation proposed is a closed formula extremely easy to compute and the results are very accurate. This features makes it helpful in the design of mobile telecommunication systems with more than one channel and queueing allowed (like trunking Private Mobile Radio PMR systems), where holding time distributions with coefficients of variation higher than one may appear. As a second stage, the possibility of calls owning a certain level of priority is studied. Two service classes are considered according to a non-preemtive priority scheme (also known as Head Of the Line or HOL). This priority feature is often required in mobile telecommunications systems to improve the access delay of some special calls by degrading the delay suffered by the rest. If the proportion of calls owning priority is kept low, the degradation is shared by many calls and then kept small. In this paper a procedure to estimate the mean waiting time in queue for each priority class is presented. This procedure is also very easy to compute. The environment for which the results of this paper are intended suggests medium or heavy overall load and light priority load (priority proportion is kept low). This is the situation under which the accuracy of the proposed method is checked. Although simulations are necessary in the final phase of the design, the procedure presented here is helpful as a first quick insight into the system performance.Peer ReviewedPostprint (published version

Fault Tree Analysis for a Modern Communication System

Wireless communications became one of the most widespread means for transferring information. Speed and reliability in transferring the piece of information are considered one of the most important requirements in communication systems in general. Moreover, Quality and reliability in any system are considered the most important criterion of the efficiency of this system in doing the task it is designed to do and its ability for satisfactory performance for a certain period of time, Therefore, we need fault tree analysis in these systems in order to determine how to detect an error or defect when happening in communication system and what are the possibilities that make this error happens. This research deals with studying TETRA system components, studying the physical layer in theory and practice, as well as studying fault tree analysis in this system, and later benefit from this study in proposing improvements to the structure of the system, which led to improve gain in Link Budget. A simulation and test have been done using MATLAB, where simulation results have shown that the built fault tree is able to detect the system’s work by 82.4%

A New CAC Policy Based on Traffic Characterization in Cellular Networks

The Call Admission Control (CAC) method presented in this paper is based on the statistical properties of the network’s traffic variables. It probabilistically estimates the time until the release of a seized channel: the admission control depends on the computed mean remaining time averaged along all channels at a specific instant and on a time threshold. The policy produces a smooth transition between the QoS metrics, giving the operator the freedom to design the network at the desired QoS point. Another valuable property is that the algorithm is straightforward and fed only by simple teletraffic metrics: distribution and the first and second moments of Channel Holding Time (CHT). Simplicity is important for a CAC method because decisions for accepting or rejecting calls must be computed quickly and frequently.Peer Reviewe

CD-MA-PMR network planning and optimization in İstanbul

Cataloged from PDF version of article.The aim of this work is to design a complete PMR (Professional Mobile Radio) network based on CDMA 450 in Istanbul metropolitan region. Coverage and capacity analysis are performed by the developed simulation software tool. Trade off between several system parameters such as quality of service, user mobility, traffic distribution, data rate and bandwidth are considered to optimize the capacity and coverage of the network. Since, managing system interference by precise power control is a very critical concept for CDMA; forward and reverse link interference analysis, and their effects are also studied. Coverage and handoff areas are shown on the map by the aid of GIS (Geographical Information Systems) tool. System capacity and coverage are presented as the main results of the proposed network.Kızılırmak, Refik ÇağlarM.S

Capacity and spectrum efficiency analysis of an asymmetric PMR system with DAB downlink

Cataloged from PDF version of article.Different trunked Private Mobile Radio (PMR) systems have been designed over the last several decades, all of which have symmetric downlink and uplink channel capacities. Due to this symmetry, those systems may not be spectrally efficient in case of different types of services which are only supported by PMR systems, such as group (acknowledged or unacknowledged) and broadcast calls, either voice or data. In this thesis, a new asymmetric trunked PMR system comprising an OFDM based broadband, wide-area downlink and a narrowband cellular uplink, is proposed to achieve a higher capacity and higher spectral efficiency than current digital trunked PMR systems have. This thesis concentrates on the system capacity analysis of the proposed system associated only with the downlink part for voice communications, as well as the spectrum efficiency comparison of the proposed system with the Terrestrial Trunked Radio (TETRA) system, which is accepted as the spectrally most efficient PMR system. In this study, we study the performance and capacity of the proposed system using Digital Audio Broadcasting (DAB) downlink. In particular, we study the capacity of such a system for voice calls using voice activity detection and statistical multiplexing. Moreover, we show that, the capacity of the system can significantly increase, if the incoming calls, which cannot find an available channel, are allowed to wait a certain amount of time before occupying a channel. The system is shown to have high trunking efficiency since all users are assumed to use the pool of channels available in the wideband downlink. Spectral efficiency of the proposed system and a standard TETRA system are compared using numerical case studies against different traffic loads, cell sizes and number of clusters. The optimum point, with respect to number of clusters, up to which the proposed system is more efficient, is determined. It is shown that for a realistic PMR scenario the proposed system is more efficient up to 5 clusters, i.e. 35 cells, and therefore it can be concluded that the proposed system can be used efficiently in realistic situations.Şengül, ErsinM.S

Performance analysis of handoff resource allocation strategies through the state-dependent rejection scheme

The state-dependent rejection scheme (SRS) provides a common framework for analysing existing handoff schemes and for designing new ones easily. Designing new schemes is made simple by determining the appropriate set of state-dependent probabilities. The Markov analysis of SRS is simple and useful for drawing initial conclusions on handoff strategies. The analysis and simulations carried out here demonstrate the capability of SRS to adapt to different mobility and load scenarios and to achieve good performance while targeting quality of service performance metrics.Peer Reviewe

Priority Communications for Critical Situations on Mobile Networks

[ES] En la actualidad, las redes públicas de comunicación están ampliamente desplegadas en todo el territorio. Como las redes públicas no contemplan un uso priorizado de los recurso, los cuerpos de seguridad tienden a utilizar redes privadas de uso específico. Estas redes privadas satisfacen los requisitos marcados pero, a cambio, los costes de despliegue y mantenimiento son muy elevados, lo cual limita su despliegue y disponibilidad. Además, la interconexión entre distintas redes privadas no siempre es posible, lo que supone un gran problema cuando la emergencia se produce en zonas fronterizas. Estos grandes inconvenientes justifican un estudio minucioso sobre nuevos mecanismos de priorización en la gestión de recursos radio que permitan hacer uso de las redes públicas por parte de los cuerpos de seguridad y emergencias. Para ello se ha analizado el marco tecnológico actual, se ha contactado con distintos cuerpos de seguridad para averiguar los requisitos de comunicación actuales y los deseables. Caracterizado el sistema, se han definido distintos escenarios realistas utilizados en simulación masivas para finalmente demostrar cómo una red pública es capaz de cursar todo el tráfico que actualmente cursa una red privada en una situación de emergencia.[EN] Technical evaluation for enhancement and priorization of calls during a emergency situation over 2G and 3G networksDíaz Sendra, S. (2012). Priority Communications for Critical Situations on Mobile Networks. http://hdl.handle.net/10251/27446.Archivo delegad

Performance Evaluation of H.264/AVC encoded Video over TETRA Enhanced Data Service (TEDS)

Public Safety Systems (PSS) are communication networks oriented towards supporting activities of public safety actors (police, medical, fire-fighters, etc.). TErrestrial Trunked RAdio (TETRA) is a Professional Mobile Radio (PMR) standard designed to meet PSS requirements with specialized voice communication features and reliable, secure communication links. TETRA Release 2 introduces TETRA Enhanced Data Service (TEDS), to support emerging data-intensive applications such as online navigation and tele-medicine by providing higher, scalable data rates. This thesis studies the feasibility of streaming video over a wideband TEDS link using the H.264/AVC codec, a video compression standard that manages to retain high decoded video quality while dramatically reducing streaming bit rate. A bandwidth limiter is used to emulate a link that supports data rates equivalent to those specified in the TEDS standard. Effects of video streaming parameters such as codec rate and play-out buffer size coupled with link-induced delay variation on decoded video quality are investigated. Visual quality is rated using objective quality metrics to quantify results with some measure of reliability. The overall aim is to identify the technical requirements needed to support an acceptable quality of video transmission over TEDS. To this end, we measure decoded video quality in different channel loss conditions, varying video streaming parameters and at different channel bandwidths, plus enhancements such as data traffic prioritisation as defined in the TEDS specification