Orientation Effects For LOS And NLOS OWC Characterisation Within Small Structures

This paper reports an experimental investigation of the orientation effect towards optical wireless channel parameters within small structures.The experiment has characterised the orientation effect of the line-of-sight (LOS)and non-line-of-sight (NLOS) infrared transmission when using different material and geometrical properties on significant infrared channel parameters.Two measurement setups were used,(1) the straight guiding structures,and (2) bending guiding structures,with three different bending angles (30o,45o and 60o bend).In each of the measurement,the receiver/transmitter is rotated in the steps of 15˚ each time.The results revealed that the characteristic of the channel depends on the physical geometries,the orientation of the transmitter/receiver and also depend on reflection coefficient of the materials.The results are valid for both LOS and NLOS transmission

Free space optical in vehicular networks using rectangular guiding models

This letter introduces Free-Space Optical (FSO) Communication links in vehicular applications using potential guiding structures around a vehicle. An optical wireless communication system simulation is described which delivers received power, bandwidth, root mean square delay spread channel impulse response for purely diffuse and diffuse-specular materials with omnidirectional and directed transmitters. In the former case, a bandwidth of 225 MHz with a power deviation of 25% results at the exit. For the latter, a 75GHz bandwidth is available at best but with a power deviation of over 99% making receiver positioning critical. The impulse response is calculated using a Modified Monte Carlo algorithm taking into account up to 15 reflections. The effect of the pipe bend angle on the path loss is also presented and the simulation is supported with experimental work

NSC98657

Nonlinearity in the response of the optical source responsible in the electrical-to-optical conversion process limits the dynamic range performance in transmitting analog and multilevel digital signals over fiber optic link channels. Fiber-based wireless access schemes provide a unique possibility for digital linearization. We describe a technique for predistorting the dynamic response of the optical source using a Radial Basis Functional Neural Network (RBFNN). The input and output data from the link provide the samples used to train the RBFNN. A simple method employing the Least Squares (LS) algorithm is used to provide an optimization to the predistorter NN. Simulation results demonstrate the simplicity of this method compared to other NN architectures and linearization techniques. This result is used in this paper to demonstrate the feasibility of the technique in providing an adaptive predistortion solution for wireless application