The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Ramakrishna Janaswamy - One of the best experts on this subject based on the ideXlab platform.
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modeling Radio Transmission loss in curved branched and rough walled tunnels with the adi pe method
IEEE Transactions on Antennas and Propagation, 2010Co-Authors: R Martelly, Ramakrishna JanaswamyAbstract:We discuss the use of the parabolic equation (PE) along with the alternate direction implicit (ADI) method in predicting the loss for three specialized tunnel cases: curved tunnels, branched tunnels, and rough-walled tunnels. This paper builds on previous work which discusses the use of the ADI-PE in modeling Transmission loss in smooth, straight tunnels. For each specialized tunnel case, the ADI-PE formulation is presented along with necessary boundary conditions and tunnel geometry limitations. To complete the study, examples are presented where the ADI-PE numerical results for the curved and rough-walled tunnel are compared to known analytical models and experimental data, and the branched tunnel data is compared to the numerical solutions produced by HFSS.
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an adi pe approach for modeling Radio Transmission loss in tunnels
IEEE Transactions on Antennas and Propagation, 2009Co-Authors: R Martelly, Ramakrishna JanaswamyAbstract:Alternate direction implicit (ADI) method is used to study Radio wave propagation in tunnels using the parabolic equation (PE). We formulate the ADI technique for use in tunnels with rectangular, circular and arched cross sections and with lossy walls. The electrical parameters of the lossy walls are characterized by an equivalent surface impedance. A vector PE is also formulated for use in tunnels with lossy walls. It is shown that the ADI is more computationally efficient than the Crank Nicolson method. However, boundary conditions become more difficult to model. The boundary conditions of the ADI intermediate planes are given the same boundary conditions as the physical plane and the overall accuracy is reduced. Also, when implementing the ADI in tunnels with circular cross sections the order at which the line by line decomposition occurs becomes important. To validate the ADI-PE, we show simulation results for tunnel test cases with known analytical solutions. Furthermore, the ADI-PE is used to simulate real tunnels in order to compare with experimental data. It is shown that the PE models the electric fields most accurately in real tunnels at large distances, where the lower order modes dominate.
R Martelly - One of the best experts on this subject based on the ideXlab platform.
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modeling Radio Transmission loss in curved branched and rough walled tunnels with the adi pe method
IEEE Transactions on Antennas and Propagation, 2010Co-Authors: R Martelly, Ramakrishna JanaswamyAbstract:We discuss the use of the parabolic equation (PE) along with the alternate direction implicit (ADI) method in predicting the loss for three specialized tunnel cases: curved tunnels, branched tunnels, and rough-walled tunnels. This paper builds on previous work which discusses the use of the ADI-PE in modeling Transmission loss in smooth, straight tunnels. For each specialized tunnel case, the ADI-PE formulation is presented along with necessary boundary conditions and tunnel geometry limitations. To complete the study, examples are presented where the ADI-PE numerical results for the curved and rough-walled tunnel are compared to known analytical models and experimental data, and the branched tunnel data is compared to the numerical solutions produced by HFSS.
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an adi pe approach for modeling Radio Transmission loss in tunnels
IEEE Transactions on Antennas and Propagation, 2009Co-Authors: R Martelly, Ramakrishna JanaswamyAbstract:Alternate direction implicit (ADI) method is used to study Radio wave propagation in tunnels using the parabolic equation (PE). We formulate the ADI technique for use in tunnels with rectangular, circular and arched cross sections and with lossy walls. The electrical parameters of the lossy walls are characterized by an equivalent surface impedance. A vector PE is also formulated for use in tunnels with lossy walls. It is shown that the ADI is more computationally efficient than the Crank Nicolson method. However, boundary conditions become more difficult to model. The boundary conditions of the ADI intermediate planes are given the same boundary conditions as the physical plane and the overall accuracy is reduced. Also, when implementing the ADI in tunnels with circular cross sections the order at which the line by line decomposition occurs becomes important. To validate the ADI-PE, we show simulation results for tunnel test cases with known analytical solutions. Furthermore, the ADI-PE is used to simulate real tunnels in order to compare with experimental data. It is shown that the PE models the electric fields most accurately in real tunnels at large distances, where the lower order modes dominate.
Georgios P Koudouridis - One of the best experts on this subject based on the ideXlab platform.
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performance evaluation of multi Radio Transmission diversity qos support for delay sensitive services
Vehicular Technology Conference, 2009Co-Authors: Ali Yaver, Georgios P KoudouridisAbstract:Integration and seamless networking of different wireless technologies is one of the driving scenarios in the contemporary research. In recent years, mobile phones have seen an influx of attractive on-demand multimedia services with strict QoS requirements. This work investigates the QoS for delay sensitive services under the design framework of a heterogeneous network. Multi Radio Transmission Diversity (MRTD), which exploits the benefits of dynamic usage of different access technologies, is tested using simulations for Voice-over-IP on multi-Radio wireless devices. The network technologies in this study include HSDPA on UMTS and IEEE 802.11. By applying various MRTD schemes, gains in performance have been observed in terms of average packet delay, packet loss and goodput as compared to a legacy system which operates under only one network access for a given session. The MRTD schemes have been analyzed for various simulation scenarios characterized by varying traffic load and Radio propagation conditions.
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generic link layer a solution for multi Radio Transmission diversity in communication networks beyond 3g
Vehicular Technology Conference, 2005Co-Authors: Konstantinos Dimou, Georgios P Koudouridis, R Agero, M Bortnik, Reza Karimi, S Kaminski, H Lederer, Joachim SachsAbstract:With the advent of multi-Radio access (MRA), an integration of differentRadio access technologies (RATs) into a heterogeneous Radio access network(RAN) becomes feasible. Such integration allows a user to be at any instantof time served by one or multiple Radio accesses (RAs) concurrently, where anRA constitutes an independent Radio resource, such as a carrier or a channel,implemented by a single RAT. It also allows a user´s service demands to bemapped onto the aggregated network resources in a transparent and efficientway. An approach for the realization of such multi-Radio integrated environmentsis through a unifying generic link layer (GLL) that provides joint Radiolink processing and enables communication between nodes and devices acrossdifferent Radio accesses.Based on the requirements on multi-access, an architecture that supportsMRA is suggested and the functions of GLL that aims at integrating andutilising multiple RATs are defined. We explore the potential for performanceimprovements through novel extensions of the Transmission diversityparadigm which builds on GLL functions that enable multi-Radio access selection.Multi-Radio Transmission diversity (MRTD) is defined as the dynamicselection of Radio access for the Transmission of a user´s data and it can bethought of as consisting of a packet scheduler operating across multiple Radiointerfaces. Different MRTD schemes may be envisaged through combinationsof access re-selection rate, Transmission parallelism and Transmission redundancy.The re-selection rate refers to the rate at which Radio access selectionis performed. It may range from multiple IP packets to one single MACframe. Switched MRTD corresponds to an access selection scheme where auser transmits via one RA at a time, while parallel MRTD corresponds to ascheme where simultaneous Transmissions over multiple RAs are scheduled.Finally, redundancy refers to the Transmission of copies of the same data overmultiple RAs to increase the possibility of correct reception.The benefits of MRTD are investigated by simulation studies on two multiRadiocase scenarios, based on generic RATs and on specific RATs respectively.In the RAT generic scenario, switched MRTD has been evaluated for networktopologies of collocated and non-collocated RAs consisting of macroand pico-cells. In the case of collocated RAs, spectral efficiency is increasedby exploiting diversity in multi-path fading while in non-collocated RAs, thespectral efficiency increase is due to diversity exploitation in both shadowingand multi-path fading. Simulation results show that switched MRTD is mostadvantageous when the RAs provide comparable throughputs. Furthermore,when combined with multi-Radio ARQ, MRTD significantly reduces packetloss and packet Transmission delays. This is also shown in the specific Radioaccesssimulation scenario where a delay sensitive voice service is studied. Inaddition, switched MRTD provides comparable gains to parallel MRTD interms of average packet Transmission delay and packet loss, while using lessRadio resources. In all cases, it is concluded that maximum performance isconditioned on the reporting delays of the channel quality indicator (CQI).Reporting delays of CQI that are half the channel coherence time render sucha complex MRTD mechanism less effective.
H Sasaoka - One of the best experts on this subject based on the ideXlab platform.
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a new multi code high speed mobile Radio Transmission scheme using cyclic modified m sequence
Vehicular Technology Conference, 1997Co-Authors: H Haroshi, K Taira, Yoshihiro Hase, H SasaokaAbstract:This paper proposes a new parallel Transmission scheme using cyclic codes generated from a modified M-sequence, which is biased with constant direct current (DC) on an M-sequence and inserted the guard chips before and after this biased M-sequence. In the proposed system, the orthogonality of the codes is kept not only between parallel Transmission channels but also between direct and delayed waves within guard chips. The bit error rate (BER) performance was evaluated by computer simulations. As a result, the proposed system can transmit several Mbps in the high speed double spike Rayleigh fading channel with better quality in comparison with conventional multi-code CDM Transmission.
Stephan Olariu - One of the best experts on this subject based on the ideXlab platform.
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a probabilistic analysis of link duration in vehicular ad hoc networks
IEEE Transactions on Intelligent Transportation Systems, 2011Co-Authors: Gongjun Yan, Stephan OlariuAbstract:The past decade has witnessed a phenomenal market penetration of wireless communications and a steady increase in the number of mobile users. Unlike wired networks, where communication links are inherently stable, in wireless networks, the lifetime of a link is a random variable whose probability distribution depends on mobility, Transmission range, and various impairments of Radio communications. Because of the very dynamic nature of Vehicular Ad hoc NETworks (VANETs) and the short Transmission range mandated by the Federal Communications Commission (FCC), individual communication links come into existence and vanish unpredictably, making the task of establishing and maintaining routing paths between fast-moving vehicles very challenging. The main contribution of this work is to investigate the probability distribution of the lifetime of individual links in a VANET under the combined assumptions of a realistic Radio Transmission model and a realistic probability distribution model of intervehicle headway distance. Our analytical results were validated and confirmed by extensive simulation.
