Performance Analysis of Physical Layer Network Coding for Two-way Relaying over Non-regenerative Communication Satellites

Two-way relaying is one of the major applications of broadband communication satellites, for which an efficient technique is Physical Layer Network Coding (PLNC). Earlier studies have considered satellites employing PLNC with onboard processing. This paper investigates the performance of PLNC over non-regenerative satellites, as a majority of the operational and planned satellites have no onboard processing. Assuming that the channel magnitudes of the two users are equal, two operating conditions are considered with uncoded-QPSK relaying. In the first condition, both users are completely synchronized in phase and transmit power, and in the second condition, phase is not synchronized. The peak power constraint imposed by the satellite amplifier is considered and the error performance bounds are derived for both the conditions. The simulation results for end-to-end Bit Error Rate (BER) and throughput are provided. These results shall enable communication system designers to decide system parameters like power and linearity, and perform tradeoff analysis between different relaying schemes.Comment: 9 pages and 13 figure

Wireless Bidirectional Relaying using Physical Layer Network Coding with Heterogeneous PSK Modulation

In bidirectional relaying using Physical Layer Network Coding (PLNC), it is generally assumed that users employ same modulation schemes in the Multiple Access phase. However, as observed by Zhang et al., it may not be desirable for the users to always use the same modulation schemes, particularly when user-relay channels are not equally strong. Such a scheme is called Heterogeneous PLNC. However, the approach in [1] uses the computationally intensive Closest Neighbour Clustering (CNC) algorithm to find the network coding maps to be applied at the relay. Also, the treatment is specific to certain cases of heterogeneous modulations. In this paper, we show that, when users employ heterogeneous but symmetric PSK modulations, the network coding maps and the mapping regions in the fade state plane can be obtained analytically. Performance results are provided in terms of Relay Error Rate (RER) and Bit Error Rate (BER).Comment: 10 pages, 10 figures and 3 table

Implementing and Characterizing Real-time Broadband RFI Excision for the GMRT Wideband Backend

The Giant Metrewave Radio Telescope (GMRT) is being upgraded to increase the receiver sensitivity. This makes the receiver more susceptible to man-made Radio Frequency Interference (RFI). To improve the receiver performance in presence of RFI, real-time RFI excision (filtering) is incorporated in the GMRT wideband backend (GWB). The RFI filtering system is implemented on FPGA and CPU-GPU platforms to detect and remove broadband and narrowband RFI. The RFI is detected using a threshold-based technique where the threshold is computed using Median Absolute Deviation (MAD) estimator. The filtering is carried out by replacing the RFI samples by either noise samples or constant value or threshold. This paper describes the status of the real-time broadband RFI excision system in the wideband receiver chain of the upgraded GMRT (uGMRT). The test methodology for carrying out various tests to demonstrate the performance of broadband RFI excision at the system level and on radio astronomical imaging experiments are also described.Comment: 7 pages, 7 figure

The Flipped Classroom: Implementing Technology To Aid In College Mathematics Student’s Success

August 2016 there was a call (Braun, Bremser, Duval, Lockwood & White, 2017) for post-secondary instructors to use active learning in their classrooms.  Once such example of active learning is what is called the “flipped” classroom.  This paper presents the need for, and the methodology of the flipped classroom, results of questionnaires on student perceptions, as well as quantitative data on student performance

Quantum Pieri rules for isotropic Grassmannians

We study the three point genus zero Gromov-Witten invariants on the Grassmannians which parametrize non-maximal isotropic subspaces in a vector space equipped with a nondegenerate symmetric or skew-symmetric form. We establish Pieri rules for the classical cohomology and the small quantum cohomology ring of these varieties, which give a combinatorial formula for the product of any Schubert class with certain special Schubert classes. We also give presentations of these rings, with integer coefficients, in terms of special Schubert class generators and relations.Comment: 59 pages, LaTeX, 6 figure

Direct, high resolution, four‐dimensional measurements of the fine scale structure of Sc≫1 molecular mixing in turbulent flows

Results from highly resolved, four‐dimensional measurements of the fine structure of the fully space‐ and time‐varying Sc≫1 conserved scalar field and the associated scalar energy dissipation rate field in a turbulent flow are presented. The resolution achieved in all three spatial dimensions and in time reaches down to the local strain‐limited molecular diffusion scale in the flow, allowing all three components of the instantaneous scalar gradient vector field ∇ζ(x,t) and their time evolution at every point in the data space to be directly evaluated. Results are presented in the form of fine structure maps of the instantaneous dissipation field loge ∇ζ⋅∇ζ(x,t) in several spatially adjacent data planes within an individual three‐dimensional spatial data volume, as well as in several temporally successive data planes from a sequence of such three‐dimensional data volumes. The degree of anisotopy in the underlying scalar gradient field is characterized in terms of the joint distribution β(ϑ,φ) of spherical orientation angles. The probability density of true scalar energy dissipation rates is presented and compared with the distributions that would result from lower‐dimensional measurements of the scalar gradient vector. From this the ‘‘spottiness’’ of the scalar dissipation field is directly quantified by determining the true fraction of the total dissipation that occurs in any given volume fraction of the flow.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70449/2/PFADEB-3-5-1115-1.pd

Fauna edáfica como indicadora de contaminação do solo.

Recentemente, o solo tem se tornado foco de preocupação devido à gradativa contaminação de ambientes terrestres e aquáticos, decorrente do progresso e avanços sócio-econômicos no país. Diante dessa realidade, a demanda por atividades antrópicas menos agressivas ao ambiente é cada vez maior. Os possíveis impactos ambientais, portanto, devem ser monitorados, controlados e remediados, a fim de evitar problemas irreversíveis ao meio ambiente e à sociedade. A ecotoxicologia estuda os efeitos dos poluentes sobre os organismos e a interação destes com o habitat. Para se avaliar o impacto de uma substância no solo, ensaios ecotoxicológicos com metodologia padronizada internacionalmente podem ser realizados com invertebrados edáficos, tais como as minhocas, enquitreídeos e colêmbolos, por serem importantes na decomposição da matéria orgânica do solo. Esses ensaios de laboratório, no entanto, precisam ser adaptados, pois a metodologia padrão se baseia em espécies e condições de clima temperado que não condizem com a realidade do Brasil. Adaptações aos ensaios de efeito agudo (mortalidade), efeito crônico (reprodução) e de fuga (comportamento) têm sido estudados por vários grupos e os resultados têm sido positivos com relação ao uso do substrato com o pó da fibra da casca do côco e utilização de temperaturas maiores que 20ºC. Algumas espécies encontradas no Brasil também têm sido testadas, algumas delas apresentando resultados promissores, outras, com limitações. De modo geral, os métodos para avaliação da contaminação do solo em laboratório têm apresentado avanços, entretanto, mais estudos se fazem necessários para o estabelecimento de espécies nativas recomendadas para cada tipo de ensaio.Resumo expandido