Performance Analysis of the Collision Avoidance Procedure of the Advanced Infrared (AIr) CSMA/CA Protocol for Wireless LANs

Abstract

Slow Light Propagation in a Thin Optical Fiber via Electromagnetically Induced Transparency

We propose a novel configuration that utilizes electromagnetically induced transparency (EIT) to tailor a fiber mode propagating inside a thin optical fiber and coherently control its dispersion properties to drastically reduce the group velocity of the fiber mode. The key to this proposal is: the evanescent-like field of the thin fiber strongly couples with the surrounding active medium, so that the EIT condition is met by the medium. We show how the properties of the fiber mode is modified due to the EIT medium, both numerically and analytically. We demonstrate that the group velocity of the new modified fiber mode can be drastically reduced (approximately 44 m/sec) using the coherently prepared orthohydrogen doped in a matrix of parahydrogen crystal as the EIT medium.Comment: 10 pages in two column RevTex4, 6 Figure

Intuition: Myth or a Decision-making Tool?

Faced with today’s ill-structured business environment of fast-paced change and rising uncertainty, organizations have been searching for management tools that will perform satisfactorily under such ambiguous conditions. In the arena of managerial decision making, one of the approaches being assessed is the use of intuition. Based on our definition of intuition as a non-sequential information-processing mode, which comprises both cognitive and affective elements and results in direct knowing without any use of conscious reasoning, we develop a testable model of integrated analytical and intuitive decision making and propose ways to measure the use of intuition

Coaxial optical couplers

Imperial Users onl

Indoor ambient light noise and its effect on wireless optical links

Knowledge of ambient optical noise is essential for designers of free space optical links, for designing resilient circuits. An experimental characterisation of the most commonly encountered ambient optical radiation is presented. The study includes tungsten filament sources, low and high frequency fluorescent lights, IR headphones, TV remote controls and daylight. Practical means to reduce their influence on the performance of the links are also given. The results are also valuable for setting a standard way of comparing wireless IR links, based on testing their performance under such ambient noise

Modelling and Optimising T<smallletters>iny</smallletters>TP over I<smallletters>r</smallletters>DA Stacks

TinyTP is the IrDA transport layer protocol for indoor infrared communications. For the first time, this paper presents a mathematical model for TinyTP over the IrDA protocol stacks taking into account the presence of bit errors. Based on this model, we carry out a comprehensive optimisation study to improve system performance at the transport layer. Four major parameters are optimised for maximum throughput including TinyTP receiver window, IrLAP window and frame size, as well as IrLAP turnaround time. Equations are derived for the optimum IrLAP window and frame sizes. Numerical results show that the system throughput is significantly improved by implementing the optimised parameters. The major contribution of this work is the modelling of TinyTP including the low-layer protocols and optimisation of the overall throughput by appropriate parameter selection.</p