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Theoretical Investigation of Diﬀerent Diversity Combining Techniques in Cognitive Radio

Agarwal R., Srivastava N., Katiyar H.

Journal of Telecommunications and Information Technology

2018

nr 3

64--69

In this paper, the performance of an energy detector in cognitive radio, using diﬀerent diversity combining techniques, is evaluated. Among many diversity combining techniques, maximal ratio combining (MRC) gives the best results but at the cost of the highest complexity. To design a simpler receiver, it is suggested to use less complex combining techniques, i.e. switched diversity, which provides one of the least complex solutions to combat fading. The paper analyzes two switched diversity schemes, switch examine combining (SEC), and switch examine combining with post examining selection (SECp). A closed form expression determining the probability of detection using MRC, SEC and SECp is derived for various numbers of branches. Detection performance with diﬀerent diversity combining techniques is compared and the complexity trade-oﬀ is observed.

Influence of friction characteristic on the performance of chain CVT drives

Srivastava N., Haque T.

Journal of KONES

2006

Vol. 13, No. 2

405-419

A continuously variable transmission (CVT) is an emerging automotive transmission technology that offers a continuum of gear ratios between desired limits. A chain CVT falls under the category of friction-limited drives as its performance and torque capacity rely significantly on the friction characteristic of the contact patch between the chain and the pulley. The present research focuses on developing models to understand the influence of different friction characteristics on the dynamic performance of a chain CVT drive. Since the friction characteristic of the contact patch may vary in accordance with the loading and design configurations, it is crucial to study the influence of friction characteristic on the performance of a CVT. A detailed planar multibody model of a chain CVT is developed in order to accurately capture the dynamics characterized by the discrete structure of the chain, which causes polygonal excitations in the system. Friction between the chain link and the pulley sheaves is modeled using different mathematical models which account for different loading scenarios. The mathematical models, the computational scheme, and the results corresponding to different loading scenarios are discussed. The results discuss the influence of friction characteristics on the dynamic performance, the axial force requirements, and the torque transmitting capacity of a chain CVT drive.