ISBN 9783843927314

978-3-8439-2731-4, Reihe Kommunikationstechnik

Mohammed Al-Olofi
Transmission of Ultra-Wideband Radio System over Optical Wireless Links using Intensity Modulation Direct Detection

220 Seiten, Dissertation Universität Duisburg-Essen (2016), Hardcover, A5

Zusammenfassung / Abstract

The use of Impulse Radio-Ultra Wide Band (IR-UWB) introduced low data rate and low-power consumption systems, which are suitable for the sensor networks. Due to the strict regulations on power transmission and frequency use, the range and usage of IR-UWB remain limited. To overcome these limitations, this dissertation proposes a system design on how to replace the radio part of the physical layer (PHY) of an UWB system with optical front-ends, without changing the major features of the standard, including frame structure and modulation.

In the scope of this dissertation, both IR-UWB and optical wireless communication systems are studied. In the IR-UWB part, the design and performances of IR-UWB systems are investigated in different channel scenarios. In optical wireless communication part, the intensity modulation/direct detection (IM/DD) for single carrier and multicarrier modulation schemes are reviewed. Focusing on optical orthogonal frequency division multiplexing (O-OFDM) modulation schemes, a proposed up-sampled clipped (UCO-OFDM) modulation scheme is developed. The UCO-OFDM modulation scheme provides a real nonnegative OFDM signal using simple approach and introduces better BER performances compared to other optical OFDM modulation schemes.

To reach the goal of this dissertation, a transmitter based digital look-up table (LUT) for IR-UWB systems is proposed. This transmitter allows storing IR-UWB pulse samples in the form of binary codewords. The LUT binary output switches the LEDs groups and hence controls transmission power. This parallel switching enables power-efficient optical representation of pulse signal and reduces the nonlinear effects caused by characteristics of LED. The utilization of LUT excludes the necessity of digital to analog converter (DAC) employed in common optical transmitters to perform the electrical-optical conversion.

It has been shown in this dissertation, the transmission of IR-UWB radio signal over an optical wireless link can be achieved assuming fast LEDs with high modulation bandwidth. This proposed idea gives a first step towards the signal transmission of radio-based systems over optical wireless links using intensity modulation/direct detection scheme.