On effectiveness of conditional admission control for IP QoS network services with REM scheme, Journal of Telecommunications and Information Technology, 2002, nr 2

Future IP QoS (quality of service) networks are aiming at differentiating transfer quality of packets belonging to different flows. For this purpose, a set of network services (NS) with different QoS objectives is defined and implemented in the network. To a NS a certain amount of network resources, i.e. dedicated link capacity with associated buffer size, is allocated. Moreover, the resources dedicated for one NS are not available for other NSs. Traditional approach for admission control algorithm corresponding to given NS takes into account current traffic conditions inside considered NS. This can lead to the situation, due to traffic fluctuations, that temporary overloaded NS cannot use the spare bandwidth from underloaded in this time other NSs. This paper describes a conditional admission control algorithm (C-AC), allowing us to admit new packet flow conditionally in the case where no available capacity inside a given NS. For conditionally accepted flow currently unused capacity, dedicated to other NS, is allocated. This can be done only in the case when QoS requirements for both the conditionally accepted flow and the flows in progress are satisfied. The conditions for effective using of C-AC algorithm are discussed in the paper, like characteristics of NS borrowing and lending capacity and their current traffic load. To show potential benefits of the approach, exemplary numerical results are included, corresponding to hypothetical NSs using REM (rate envelope multiplexing) scheme

AQUILA network architecture: first trial experiments, Journal of Telecommunications and Information Technology, 2002, nr 2

The paper presents trial experiments with IP QoS network services (NS) defined and implemented in the AQUILA pilot installation. The AQUILA NSs (premium CBR, premium VBR, premium multimedia and premium mission critical) provide a framework for supporting a variety of applications generating both streaming and elastic traffic. The measurement experiments confirm that AQUILA architecture differentiates the QoS offered to these NSs. The presented numerical results were obtained in the test network installed in the Polish Telecom (Warsaw) consisting of 8 CISCO routers

Scalable quantum photonic devices emitting indistinguishable photons in the telecom C-band

Epitaxial semiconductor quantum dots (QDs) are a promising resource for quantum light generation and the realization of non-linear quantum photonic elements operating at the single-photon level. Their random spatial distribution resulting from their self-organized nature, however, restrains the fabrication yield of quantum devices with the desired functionality. As a solution, the QDs can be imaged and localized, enabling deterministic device fabrication. Due to the significant electronic noise of camera sensors operating in the telecommunication C-band, $1530-1560~\mathrm{nm}$, this technique remained challenging. In this work, we report on the imaging of QDs epitaxially grown on InP with emission wavelengths in the telecom C-band demonstrating a localization accuracy of $80~\mathrm{nm}$. This is enabled by the hybrid integration of QDs in a planar sample geometry with a bottom metallic reflector to enhance the out-of-plane emission. To exemplify our approach, we successfully fabricate circular Bragg grating cavities around single pre-selected QDs with an overall cavity placement uncertainty of $90~\mathrm{nm}$. QD-cavity coupling is demonstrated by a Purcell enhancement up to $\sim5$ with an estimated photon extraction efficiency of $(16.6\pm2.7)\%$ into a numerical aperture of $0.4$. We demonstrate triggered single-photon emission with $g^{(2)}(0)=(3.2\pm0.6)\times10^{-3}$ and record-high photon indistinguishability associated with two-photon interference visibilities of $V = (19.3\pm2.6)\%$ and $V_{\mathrm{PS}} = 99.8^{+0.2}_{-2.6}\%$ without and with temporal postselection, respectively. While the performance of our devices readily enables proof-of-principle experiments in quantum information, further improvements in the yield and coherence may enable the realization of non-linear devices at the single photon level and advanced quantum networks at the telecom wavelength.Comment: 9 pages, 4 figures, Supplemental Material: 20 pages, 18 figure

10 th POLISH TELETRAFFIC SYMPOSIUM PSRT2003 ASSESSMENT OF TOKEN BUCKET PARAMETERS BY ON-LINE TRAFFIC MEASUREMENTS

The paper proposes a method for more precise evaluation of traffic descriptors than a user of QoS oriented packet network is usually able to declare during the pre-connection phase. The recognized approach for traffic characterization is the token bucket mechanism, described by two parameters: token accumulating rate and bucket size. Notice that the values of these parameters constitute a base for evaluation of the effective bandwidth (or an equivalent factor) and, as a consequence, determine the amount of resources the network should dedicate for handling the connection. The typical approach is such that the token bucket parameters are simply declared by the users during the preconnection phase. However, a user usually does not know a priori the correct token bucket parameters and has a tendency rather for over-dimensioning them. As a consequence, the calculated effective bandwidth is greater (sometimes significantly) than it is really required. In order to mitigate this problem, in this paper we propose a method based on the on-line monitoring of traffic, which allows us to obtain the minimum effective bandwidth. The method is investigated for the case the users submit the traffic to the network service aimed for handling non-real time variable bit rate traffic without any losses. In this case, the effective bandwidth value could be calculated e.g. by EMW [3] formula. Apart the theoretical considerations, the numerical results illustrating the effectiveness of the approach are also included

On Effectiveness of Conditional Admission Control for IP QoS network services with REM scheme

differentiating transfer quality of packets belonging to different flows. For this purpose, a set of network services (NS) with different QoS objectives is defined and implemented in the network. To a NS a certain amount of network resources, i.e. dedicated link capacity with associated buffer size, is allocated. Moreover, the resources dedicated for one NS are not available for other NSs. Traditional approach for admission control algorithm corresponding to given NS takes into account current traffic conditions inside considered NS. This can lead to the situation, due to traffic fluctuations, that temporary overloaded NS cannot use the spare bandwidth from underloaded in this time other NSs. This paper describes a conditional admission control algorithm (C-AC), allowing us to admit new packet flow conditionally in the case where no available capacity inside a given NS. For conditionally accepted flow currently unused capacity, dedicated to other NS, is allocated. This can be done only in the case when QoS requirements for both the conditionally accepted flow and the flows in progress are satisfied. The conditions for effective using of C-AC algorithm are discussed in the paper, like characteristics of NS borrowing and lending capacity and their current traffic load. To show potential benefits of the approach, exemplary numerical results are included, corresponding t

Magneto-Optical Characterization of Trions in Symmetric InP-Based Quantum Dots for Quantum Communication Applications

Magneto-optical parameters of trions in novel large and symmetric InP-based quantum dots, uncommon for molecular beam epitaxy-grown nanostructures, with emission in the third telecom window, are measured in Voigt and Faraday configurations of an external magnetic field. The diamagnetic coefficients are found to be in the range of 1.5–4 μeV/T2, and 8–15 μeV/T2, respectively out-of-plane and in-plane of the dots. The determined values of diamagnetic shifts are related to the anisotropy of dot sizes. Trion g-factors are measured to be relatively small, in the range of 0.3–0.7 and 0.5–1.3, in both configurations, respectively. Analysis of single carrier g-factors, based on the formalism of spin-correlated orbital currents, leads to similar values for hole and electron of ~0.25 for Voigt and ge ≈ −5; gh ≈ +6 for Faraday configuration of the magnetic field. Values of g-factors close to zero measured in Voigt configuration make the investigated dots promising for electrical tuning of the g-factor sign, required for schemes of single spin control in qubit applications

Septostomia przedsionkowa w terapii ciężkiego pierwotnego nadciśnienia płucnego - Opis 2 przypadków

Abstract: We present a case of 39-year-old male with symptomatic cardiac tamponade due to neoplastic disease. Because of abdominal symptoms the patient was diagnosed as having acute abdomen and underwent exploratory laparatomy which revealed enlarged liver and ascites. Correct diagnosis was established later by echocardiography and effective pericardiocentesis was performed. Diagnostic difficulties in patients with cardiac tamponade are discussed

Thermal stability of emission from single InGaAs/GaAs quantum dots at the telecom O-band

Single-photon sources are key building blocks in most of the emerging secure telecommunication and quantum information processing schemes. Semiconductor quantum dots (QD) have been proven to be the most prospective candidates. However, their practical use in fiber-based quantum communication depends heavily on the possibility of operation in the telecom bands and at temperatures not requiring extensive cryogenic systems. In this paper we present a temperature-dependent study on single QD emission and single-photon emission from metalorganic vapour-phase epitaxy-grown InGaAs/GaAs QDs emitting in the telecom O-band at 1.3 μm. Micro-photoluminescence studies reveal that trapped holes in the vicinity of a QD act as reservoir of carriers that can be exploited to enhance photoluminescence from trion states observed at elevated temperatures up to at least 80 K. The luminescence quenching is mainly related to the promotion of holes to higher states in the valence band and this aspect must be primarily addressed in order to further increase the thermal stability of emission. Photon autocorrelation measurements yield single-photon emission with a purity of g(2)50K(0)=0.13 up to 50 K. Our results imply that these nanostructures are very promising candidates for single-photon sources at elevated (e.g., Stirling cryocooler compatible) temperatures in the telecom O-band and highlight means for improvements in their performance