Per-Stream QoS and Admission Control in Ethernet Passive Optical Networks (EPONs)

Ethernet passive optical networks (EPONs) are designed to deliver services for numerous applications such as voice over Internet protocol, standard and high-definition video, video conferencing (interactive video), and data traffic. Various dynamic bandwidth allocation and intra-optical network unit (ONU) scheduling algorithms have been proposed to enable EPONs to deliver differentiated services for traffic with different quality of service (QoS) requirements. However, none of these protocols and schedulers can guarantee bandwidth for each class of service nor can they protect the QoS level required by admitted real-time traffic streams. In this paper, we propose the first framework for per-stream QoS protection in EPONs using a two-stage admission control (AC) system. The first stage enables the ONU to perform flow admission locally according to the bandwidth availability, and the second stage allows for global AC at the optical line terminal. Appropriate bandwidth allocation algorithms are presented as well. An event-driven simulation model is implemented to study the effectiveness of the proposed schemes in providing and protecting QoS.     

Machine learning-based model of surface tension of liquid metals: a step in designing multicomponent alloys for additive manufacturing

Journal of Materials Science - The surface tension (ST) of metallic alloys is a key property in many processing techniques. Notably, the ST value of liquid metals is crucial in additive...     

A low-power high-performance digital predistorter for wideband power amplifiers

In this paper, we present a low-power high-performance digital predistorter (DPD) for the linearization of wideband RF power amplifiers (PAs). It is based on the novel FIR memory polynomial (FIR-MP) predistorter model, which significantly augments the performance of the conventional memory polynomial predistorter with the use of complex baseband digital FIR filter prior to the memory polynomial. The adjacent channel leakage ratio (ACLR) performance comparison between the conventional MP and the proposed FIR-MP is done based on simulations with multi-carrier modulated signals of 20 and 80 MHz bandwidths. The PA models used for the simulations are extracted from the measurements of a commercial \(1\,\hbox {W}\) GaAs HBT PA. At the ideal system-level simulations, the improvements in ACLR over the conventional MP are 7.2  and 15.6 dB, respectively, for 20 and 80 MHz signals. The choice of selection of various parameters of the predistorter along with the subsequent digital-to-analog converter (DAC) is presented. The impact of fixed-point representation is assessed using ACLR metrics, which shows that a wordlength of 14 bits is sufficient to obtain ACLR beyond \(45\,\hbox {dBc}\) with a margin of \(10\,\hbox {dB}\). The proposed predistorter is synthesized in \(28\,\hbox {nm}\) fully-depleted silicon-on-insulator (FDSOI) CMOS process. It is shown that with a fraction of the power and die area of that of the MP a huge improvement in ACLR is attained. With an overall power consumption of 8.2 and 88.8 mW, respectively, for 20 and 80 MHz signals, the FIR-MP DPD proves to be a suitable candidate for small-cell base station PA linearization.     

UCov: a user‐defined coverage criterion for test case intent verification

The goal of regression testing is to ensure that the behaviour of existing code, believed correct by previous testing, is not altered by new program changes. This paper argues that the primary focus of regression testing should be on code associated with (1) earlier bug fixes and (2) particular application scenarios considered to be important by the developer or tester. Existing coverage criteria do not enable such focus, for example, 100% branch coverage does not guarantee that a given bug fix is exercised or a given application scenario is tested. Therefore, there is a need for a new and complementary coverage criterion in which the user can definea test requirement characterizing a given behaviour to be covered as opposed to choosing from a pool of pre‐defined and generic program elements. This paper proposes this new methodology and calls it UCov, a user‐defined coverage criterion wherein a test requirement is an execution pattern of program elements, and possibly predicates, that a test case must satisfy. The proposed criterion is not meant to replace existing criteria, but to complement them as it focuses the testing on important code patterns that could go untested otherwise. UCov supports test case intent verification. For example, following a bug fix, the testing team may augment the regression suite with the test case that revealed the bug. However, this test case might become obsolete due to code modifications not related to the bug. But if a test requirement characterizing the bug was defined by the user, UCov would determine that test case intent verification failed. The UCov methodology was implemented for the Java platform, was successfully applied onto 10 real‐life case studies and was shown to have advantages over JUnit. The implementation comprises the following tools: (1) TRSpec: allows the user to easily specify complex test requirements; (2) TRCheck: checks whether user‐defined test requirements were satisfied, that is, supports test case intent verification; and (3) TRMigrate: migrates user‐defined test requirements to subsequent versions of a given program. Copyright © 2016 John Wiley & Sons, Ltd.